NeuroSymposium 2022 | June 17, 2022
Université de MontréalPublished online: June 17, 2022
Variation in subcortical anatomy: relating interspecies differences, heritability, and brain-behavior relationships
2Department of Biological and Biomedical Engineering, McGill University, Montreal, QC, Canada
3Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
4Undergraduate Program in Neuroscience, McGill University, Montreal, QC, Canada
5Krembil Centre for Neuroinformatics, Centre for Addiction and Mental Health, Toronto, ON, Canada
6Department of Psychiatry, McGill University, Montreal, QC, Canada
7Autism Research Centre, University of Cambridge, Cambridge, United Kingdom
8Department of Anthropology and Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, DC, USA
9Department of Comparative Medicine, University of Texas MD Anderson Cancer Center, Bastrop, TX, USA
10Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
11Lifespan Brain Institute of the Children’s Hospital of Philadelphia and Penn Medicine, Philadelphia, PA, USA
12National Institute of Mental Health, United States Department of Health and Human Services, North Bethesda, MD, USA
Corresponding Author: Nadia Blostein, email firstname.lastname@example.org
There has been an immense research focus on the topic of cortical reorganization in human evolution, but much less is known regarding the reorganization of subcortical circuits. Here, by combining advanced image analysis techniques with comparative neuroimaging data, we used surface-based shape measures in the striatum, thalamus and globus pallidus extracted from structural magnetic resonance imaging (MRI) data in order to provide crucial new insights into the relationships between different properties of the subcortex. We systematically mapped interspecies (human-chimpanzee) differences as a proxy for evolutionary changes, the influence of genetics through heritability estimation and latent variables (LVs) of neuroanatomical-behavioral covariance through partial least squares correlation (PLSC) analysis. A key methodological innovation is the investigation of the spatial concordance between the subcortical brain maps generated across these analyses, through the adaptation of the surface-based cortical spin test (Alexander-Bloch et al. 2018). We show that highly heritable morphological measures are significantly expanded across species, in contrast to previous findings in the cortex. The identified morphological-cognitive latent variables were associated with striatal expansion, and affective latent variables were associated with more evolutionarily-conserved areas in the thalamus and globus pallidus, confirming the expectation that regions associated with higher-order cognitive functions are more expanded in humans and regions associated with lower-order limbic functions are more conserved across species. Overall, the purpose of examining fine-grained surface-based shape measures is to better infer the underlying cellular distribution of these structures than volumetric measures could ever convey. Future work should aim to examine how these maps converge with subcortical cytoarchitecture and gene expression.
La relation entre l’altération de l’odorat et la cognition après un traumatisme cranio-cérébral léger
2Centre de recherche de l’Institut Universitaire de Gériatrie de Montréal, Montréal, QC, Canada
3Centre de recherche de l’Hôpital du Sacré-Cœur de Montréal, Montréal, QC, Canada
4Département de psychologie, Université de Montréal, Montréal, QC, Canada
5Département d’anatomie, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
Corresponding Author: Coline Zigrand, email email@example.com
Parmi les nombreuses conséquences engendrées par les traumatismes cranio-cérébraux légers (TCCL), l’altération de l’odorat demeure peu explorée et revêt pourtant un caractère capital. En effet, des travaux récents de notre équipe de recherche ont montré que l’altération de l’odorat pouvait prédire la survenue de certains symptômes tels que les troubles anxieux ou dépressifs chez les patients avec un TCCL. La présente étude investigue la relation entre l’altération de l’odorat et la cognition après un TCCL. Cinquante-trois patients avec un TCCL âgé de 18 à 56 ans ont reçu une évaluation olfactive (test Sniffin’Sticks) et cognitive (Examen cognitif abrégé en traumatologie - EXACT) 2 à 4 semaines après le traumatisme. Les performances cognitives des patients présentant un trouble olfactif ont été comparées à celles de patients sans trouble olfactif. Les résultats ne révèlent pas de différence significative au niveau des performances cognitives entre les patients avec ou sans trouble olfactif. Alors qu’un examen de l’odorat peut être un outil de dépistage pour cibler les symptômes affectifs, les résultats de la présente étude ne suggère pas qu’un examen de l’odorat puisse prédire les symptômes cognitifs après un TCCL.
Functional contribution of midbrain nuclei to locomotor recovery after spinal cord injury
Corresponding Author: Marie Roussel, email firstname.lastname@example.org
Electrical stimulation of the midbrain has been shown to improve locomotor recovery after spinal cord injury (SCI). Are part of this functional region: the cuneiform nucleus (CnF) and the pedunculopontine nucleus (PPN). We have recently shown that activation of glutamatergic CnF neurons initiates and accelerates locomotion, whereas glutamatergic and cholinergic PPN neurons decelerate and stop locomotion in the mouse. We hypothesized that these distinct neuronal populations contribute differently to locomotor recovery after SCI. Transgenic VGluT2-cre mice were injected with AAV to genetically ablate or photostimulate glutamatergic CnF or PPN neurons. Although mice dragged initially their ipsilesional hindlimb, they recovered locomotor functions by the 3rd week post-SCI. 7 weeks post-SCI, genetic ablation of VGluT2+CnF neurons deteriorated motor functions during walking and swimming, whereas ablation of VGlut2+PPN neurons mildly impaired swimming. Short photostimulations of VGluT2+CnF or PPN neurons evoked phase-dependent electromyographic (EMGs) responses in hindlimb muscles during locomotion. Responses decreased at week 1 post-SCI but recovered by week 4 with locomotor recovery. Furthermore, long trains of photostimulations of VGlut2+CnF neurons improved and accelerated the locomotor pattern and rhythm, whereas VGlut2+PPN neurons failed to improve locomotor functions. Although the PPN has been considered as a target in clinical settings, our study argues that glutamatergic neurons of the CnF will be a better neurological target to improve functional locomotor recovery in SCI patients.
l'Olfaction et l'anxiété non pathologique
2Centre de recherche de l'Institut universitaire de gériatrie de Montréal, Montréal, QC, Canada
3Centre de recherche de l'Hôpital du Sacré-Coeur de Montréal, Montréal, QC, Canada
4Département d'Anatomie, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
Corresponding Author: Olivier Fortier-Lebel, email email@example.com
L’anxiété peut avoir une influence sur des tâches cognitives ou sensorielles. Toutefois, peu d’études se sont intéressées à l’influence d’une anxiété non pathologique sur l’olfaction et aucune n’a utilisé les potentiels évoqués olfactifs pour mesurer le fonctionnement olfactif. Il a été proposé que la composante olfactive P3 peut constituer un indicateur de l’engagement émotionnel lors d’une stimulation olfactive. Cette recherche tente d’investiguer s’il existe un lien entre l’anxiété non pathologique et la composante olfactive P3. 35 participants sains entre 18 et 35 ans passeront un questionnaire validé mesurant l’anxiété non pathologique (IASTA) et leur activité cérébrale sera enregistrée durant 40 stimulations olfactives. Les latences et amplitudes de la P3 seront ensuite mesurées. Des corrélations seront effectuées entre ces dernières et les scores d’anxiété. Nous nous attendons à ce que les scores d’anxiété soient corrélés négativement à la latence de la P3 et qu’ils soient corrélés positivement à son amplitude. Pour le moment, nos résultats préliminaires, sur un échantillon de 7 participants (3 hommes) d’un âge moyen de 25 ans (ÉT=3), montrent des tendances corrélationnelles négatives entre l’amplitude de la P3 en Fz et les scores d’anxiété-trait (rs = -0,707, p = 0,050) et d’anxiété situationnelle (rs = -0,699, p = 0,054). Pour les autres mesures d’amplitudes et de latence de la P3 aucune tendance ne se dégage. Cette étude est importante, car elle permet une meilleure compréhension du lien entre l’anxiété et les capacités olfactives. Elle est donc cruciale pour une évaluation adéquate de l’olfaction chez des populations à risque de vivre un haut niveau d’anxiété (p.ex. Trouble Cognitif Léger).
Caractérisation d'un nouveau modèle d'auto-immunité chronique du système nerveux
2Centre de recherche du CHU de Québec - Axe neurosciences, Université Laval, Quebec City, QC, Canada,
3Département de médecine moléculaire, Université Laval, Quebec City, QC, Canada.
Corresponding Author: Reda Fazazi, email firstname.lastname@example.org
La sclérose en plaques (SP) est une maladie auto-immune du système nerveux central (SNC) avec peu de traitements pour les formes progressives chroniques. L'encéphalomyélite auto-immune expérimentale (EAE) est un modèle murin bien établi pour étudier les aspects immunitaires de l'auto-immunité du SNC. Nous avons utilisé les souris transgéniques IgH[MOG] qui ont des lymphocytes B spécifiques au peptide MOG35-55 et l'immunisation avec ce peptide entraîne une réponse obligatoire des lymphocytes T CD4+, permettant une interaction forte des lymphocytes T et B dans ce nouveau modèle. Nous avons immunisé les souris IgH[MOG] et les souris contrôles NOD avec le peptide MOG35-55 . Nous avons ensuite évalué la pathologie des souris selon le score EAE évaluant leur paralysie ascendante. Nous avons ensuite utilisé la cytométrie en flux pour analyser les cellules immunitaires infiltrant le SNC. Finalement. la démyélinisation et l’analyse des cellules immunitaires dans le CNS ont été réalisé par immunofluorescence et immunohistochimie. Les souris IgH[MOG] ont développé une EAE sévère. Les lymphocytes T infiltrant le SNC ont produit des niveaux élevés de cytokines GM-CSF et IL-17 associées aux lymphocytes Th17. Les lymphocytes B infiltrant le SNC de ces souris produisaient plus de cytokines clés pour la différenciation des Th17, tels qu’IL-6, GMCSF et IL-23. En bloquant IL-23, la maladie sévère était considérablement réduite. Finalement, l’apparition de structures lymphoïdes ectopiques (TLOs) dans les méninges des souris IgH[MOG] a été observé avec une agglomération de lymphocytes T et B et de cellules dendritiques. L’EAE sévère des souris IgH[MOG] est du à l’infiltration des lymphocytes Th17 qui est dû à une signalisation cytokinique des lymphocytes B. La production d'IL-23 par les lymphocytes B semble jouer un rôle crucial dans la pathogénicité des lymphocytes T CD4+ s’infiltrant dans le CNS. Les TLOs semblent favoriser la réactivation des lymphocytes Th17 dans le CNS par les lymphocytes B.
Neurostimulation non invasive dans la maladia de Parkinson : études translationnelles chez le primate non humain et les participants en clinique
2Research center of CHU de Québec – Université Laval, neuroscience division, Québec, QC, Canada;
3Faculty of Medicine, Université Laval, Québec, QC, Canada;
4Faculty of Pharmacy, Université Laval, Québec, QC, Canada;
5Department of Rehabilitation, Faculty of medicine, Université Laval, Québec, QC, Canada
Corresponding Author: Estelle Gouriou, email email@example.com
La maladie de Parkinson (MP), seconde maladie neurodégénérative au monde est caractérisée par des symptômes moteurs et cognitifs. Son traitement de référence, la L-Dopa, peut induire avec le temps, des mouvements involontaires invalidants, les dyskinésies (LID). L’amantadine utilisée pour traiter les LID induit des effets secondaires très invalidants. Face à ces inconvénients, l’intérêt est croissant pour les approches non pharmacologiques et non invasives qui normalisent le fonctionnement glutamatergique notamment, du cerveau sans provoquer d’effets secondaires. La stimulation transcrânienne, magnétique ou électrique, peut influencer l’activation des aires cérébrales par inhibition ou facilitation de l'excitabilité de la zone stimulée et influençant les zones qui lui sont connectées. La stimulation magnétique appliquée au niveau des muscles est prometteuse en récupération fonctionnelle. Le projet de doctorat étudie les effets de ces techniques sur la neuroplasticité, les LID et les symptômes moteurs chez le primate non-humain MPTP et chez les personnes vivant avec la MP. Les objectifs chez le patient sont supportés par nos résultats pilotes chez le primate dyskinétique où la stimulation magnétique et électrique ont permis une réduction des LID sans détérioration de l’effet bénéfique de la L-Dopa. Le protocole clinique est en cours, mais les résultats préliminaires présentent des améliorations motrices encourageantes maintenues un mois après l’arrêt des stimulations. L‘étude permettra d’en savoir plus sur la méthodologie la plus adaptée en fonction du bénéfice clinique observé. De plus, l’étude propose une approche personnalisée en fonction du profil clinique propre à chaque personne, ce qui est une avancée significative pour la recherche clinique en maladies neurodégénératives.
Un patron d’altération de la substance blanche spécifique à la maladie de Parkinson
2Banner Sun Health Research Institute, Sun City, AZ, USA,
3CERMEP, Lyon, France,
4Centre de recherche de l'hôpital du Sacré-Cœur de Montréal, Montréal, QC, Canada
Corresponding Author: Sarah Brosse, email firstname.lastname@example.org
Le dysfonctionnement olfactif est un symptôme fréquent de la maladie de Parkinson (MP) qui apparaît dans les premiers stades. C’est donc une voie prometteuse pour le développement d’outils de détection précoce de la MP. Dans ce but, il est important de différencier un trouble de l’odorat associé à la MP d’autres troubles de l’odorat non parkinsoniens (TONP). L’objectif est d’étudier les altérations de la substance blanche dans les troubles de l’odorat associés à la MP. Nous cherchons à examiner l'intégrité des fibres de la substance blanche en utilisant l’IRM de diffusion chez 15 patients atteints de la MP comparativement à 15 patients atteints de TONP et à 15 témoins. Nous avons émis l'hypothèse qu’il existe une altération spécifique des fibres de matière blanche entre les régions chimiosensorielles chez les patients atteints de la MP par rapport aux patients TONP. Trois résultats principaux sont apparus. Premièrement, les personnes ayant la MP ont une anisotropie fractionnelle (fractional anisotropy, FA) plus faible que les sujets contrôles. Deuxièmement, les personnes ayant la MP présentent une FA plus faible que les sujets ayant un TONP. Troisièmement, les personnes ayant un TONP ont une FA similaire à celle des sujets contrôles. Cette étude exploratoire a révélé une altération spécifique des fibres de matière blanche chez les personnes ayant la maladie de Parkinson comparativement aux sujets ayant un trouble de l’odorat non-parkinsonien et aux sujets contrôles.
Investigating the contribution of tau to Huntington’s disease pathology
2Département de Médecine Moléculaire, Université Laval, Québec, QC, Canada,
3Département de Psychiatrie & Neurosciences, Université Laval, Québec, QC, Canada,
4CEA, Institut François Jacob (MIRcen) and CNRS, Laboratory of Neurodegenerative Diseases, Fontenay-aux-Roses, France
Corresponding Author: Shireen Salem, email email@example.com
The tau protein implicated in microtubule stabilization is present in toxic state in several conditions referred to as tauopathies. In Huntington’s disease (HD), it has been reported that hyperphosphorylated tau, neurofibrillary tangles and 4R tau isoforms are increased, suggesting HD may be a secondary tauopathy. We hypothesize that the introduction of tau to cell and animal models of HD leads to an exacerbation of intracellular huntingtin (HTT) aggregation, with consequences on cellular and behavioral functions. Human recombinant tau is introduced to an HD neuronal cell line (StHdh) and various aspects of toxicity are assessed. The uptake of tau is observed by immunocytochemistry, metabolic activity by MTT assay, and HTT aggregation by filter retardation assays. To evaluate the influence of tau on behavioral impairments, 3-month-old wild-type and HD (zQ175) mice received intracerebral stereotaxic injections of tau. Behavioral tests, and post-mortem studies such as western blots and filter retardation assays, are conducted. Tau fibrils decrease the metabolic activity of control and HD cells, while 3R tau increases HTT aggregation in HD cells. In vivo, tau precipitates the appearance of cognitive deficits in zQ175 mice and aggravates motor impairments. These behavioral changes are accompanied by an increased aggregation of mHTT in the hippocampus of zQ175 mice treated with 3R fibrils. Additionally, increased phosphorylation of tau at disease-associated residues is observed in the hippocampus of tau treated WT mice. Tau treatment alters cellular features associated to HD notably decreasing metabolic activities and increasing HTT aggregation within cells and worsens behavioral phenotypes in mice. Ongoing experiments will allow us to link the cellular alterations to the behavioral aspects observed, shedding light on the role of tau in this disease.
Surgical menopause does not impact brain anatomy
2Rotman Research Institute at Baycrest, Toronto, ON, Canada
3Department of Psychology, University of Toronto, Toronto, ON, Canada
4Department of Biological and Biomedical Engineering, McGill University, Montreal, QC, Canada
Corresponding Author: Manuela Costantino, email firstname.lastname@example.org
Surgically induced menopause through bilateral removal of the ovaries is associated with a rapid drop in the production of ovarian hormones. Previous studies have found an association between this transition and changes in brain anatomy, cognition and neurodegenerative disease incidence and hormone replacement therapy (HRT) has been suggested as a preventative measure. However, most of these studies have small sample sizes and don't completely account for age, which is a strong correlate of menopausal status. Structural MRI scans from women in the UK Biobank were processed using CIVET 2.1.0 and manually quality controlled. We extracted measures of vertex-wise cortical thickness (CT), total brain volume (TBV), grey matter volume (GMV) and white matter volume (WMV). We used linear models to examine the relationship between these measures and surgical menopause status in age-matched groups (N=551), age at menopause, time since menopause and use of HRT (N=978). Age was included as a covariate. The linear models between vertex-wise CT and age at menopause, time since menopause, HRT use and menopausal status were found to be insignificant at 15% FDR. There is a small yet significant relationship between surgical menopause status and increased GMV and TBV but it does not survive Bonferroni correction. Age at menopause, time since menopause and use of HRT were not significantly linked to brain morphometry. Thus, the surgical menopause transition does not have a notable effect of cortical anatomy in this cohort. Further studies are needed in order to assess its impact on cognition, disease incidence and subcortical anatomy.
TDP-43 and SOD1 role in pathogenesis transmitted by ALS patients CSF
Corresponding Author: Amélie Poulin-Brière, email email@example.com
The majority of amyotrophic lateral sclerosis (ALS) cases (~90%) are considered sporadic (sALS) and their etiology still remains unknown. However, a TDP-43 proteinopathy is observed in more than 95% of ALS cases, suggesting that TDP-43 could play a role in neurodegeneration. Our hypothesis is that the pathogenic effect of sALS patients CSF, previously observed, is in part due to the presence of misfolded TDP-43 and SOD1, which can spread prion-like proteinopathy to healthy cells. Human TDP-43 WT transgenic mice (hTDP-43WT) are infused intracerebroventricularly (ICV) with sALS patients CSF. Mice are treated with a full-length antibody directed against the RRM1 domain of TDP-43, named E6, administered by intrathecal (IT) injection or ICV infusion. Effects on cognitive and motor functions as well as on pathological changes in tissues are analysed. E6 immunotherapy decreased TDP-43 mislocalisation and improved motor and cognitive functions. Immunofluorescence analysis showed an increased nuclear/cytoplasmic ratio of TDP-43 in lumbar motor neurons of IT E6 treated mice compared to control. Gait analysis revealed an increased stride length in both IT and ICV E6 treated mice compared to control. Novel object recognition test showed an increased interaction time with the novel object in ICV E6 treated mice compared to controls. Neuromuscular junctions and muscle fibres calibre are under evaluation. Immunotherapy against TDP-43 provided promising results. We now propose to study the long-term effects of CSF infusion on disease progression after its delivery. These studies will provide new insights on disease mechanisms and will serve to advance the development of new treatments to halt the disease propagation.
Neurovascular biology underlying pro-resilient effects of preventative strategies against chronic stress
2CERVO Brain Research Center, Québec, QC, Canada
Corresponding Author: Sam Paton, email firstname.lastname@example.org
Chronic stress is a risk factor for major depressive disorder (MDD), a leading cause of disease worldwide. Stress-related peripheral inflammation damages the blood brain barrier (BBB) leading to neuroinflammation, depressive behaviours, and cognitive deficits. In mice, access to enriched environment (EE) or physical exercise (PE) promotes stress resilience, but underlying biological mechanisms remain unclear. We hypothesize that EE and PE enhance stress resilience in mice by promoting molecular adaptations associated with BBB integrity. Male C57/Bl6 mice underwent ten days of chronic social defeat stress (CSDS) with free access to a house, nesting material, and toy (EE) or running wheel (PE). A social interaction test determined stress susceptible (SS) or resilient (RES) phenotype, and tissue was collected from brain regions involved in stress responses for qRT-PCR and immunofluorescence staining along with blood serum for cytokine profiling. Results were compared to previous standard CSDS cohorts from our lab. As expected, access to both EE and PE attenuated stress-induced behavioural deficits. Interestingly, for both protective conditions stress exposure was associated with upregulation of genes and proteins associated with BBB integrity, contrasting the loss observed in standard CSDS. Finally, analysis of circulating cytokines revealed potential immunological mediators of the pro-resilient effects conferred by EE and PE. This project will help understand environmental contributions to the pathophysiology of depression and better define the relationship between mental health status and the neurovasculature.
PDGF-D promotes neurovascular repair after stroke via stimulation of the pro-angiogenic properties of pericytes
Corresponding Author: Maxime Bernard, email email@example.com
Stroke is one of the leading causes of death and disability in the world. Unfortunately, still no disease-modifying therapy exists. Brain pericytes are specialized multitasking cells that play a key role in generating critical neurovascular functions, including vascular stabilization and maintenance. Due to their multitasking properties, pericytes constitute a promising target for the development of new therapeutic interventions after stroke. For this purpose, C57BL6 mice were subjected to ischemic stroke using middle cerebral artery occlusion (MCAo). Mice were treated in the subacute phase via the intranasal route with siRNA or recombinant active peptide of platelet-derived growth factor (PDGF)-D, a newly identified PDGF isoform that specifically activates PDGFRβ in pericytes to assess brain damage. Moreover, human primary brain pericytes exposed to ischemic-like conditions in vitro were used to decipher the mechanisms underlying role of PDGF-D effects. The endogenous PDGF-D is transiently increased in the brain after stroke. Reduction of PDGF-D expression using siRNA delivered via the intranasal route exacerbated brain damage after stroke. The intranasal infusion of PDGF-D reduced brain atrophy and neuronal loss associated with stroke and increased the vascularization of the injured tissue. Interestingly, PDGF-D promoted the coverage of pericytes at the lesion site via attenuation of apoptosis. These changes were accompanied by an improved neurological recovery. Our results suggest that PDGF-D plays an important role in promoting the pro-angiogenic functions of pericytes upon ischemic stroke. The overall results thus suggest that pericytes are an interesting target for the development of new therapies for stroke.
White matter hyperintensities and brain vasculature: impact of weight loss following bariatric surgery
2École de nutrition, Université Laval, Québec, QC, Canada,
3Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada,
4Institut de recherche Douglas, Université McGill, Verdun, QC, Canada,
5École de psychologie, Université Laval, Québec, QC, Canada,
6Département de chirurgie bariatrique, Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, QC, Canada,
7Département de radiologie diagnostique, Université de Sherbrooke, Sherbrooke, QC, Canada. * co-last author
Corresponding Author: Justine Daoust, email firstname.lastname@example.org
Obesity is associated with structural brain alterations, which may mediate the link between obesity and cognitive impairment. It is unclear which mechanisms are implicated and if these brain changes can be reversed by weight-loss intervention. The objective of the study is to characterize changes in lesions of vascular nature assessed by white matter hyperintensities (WMH) and changes in the volume of cerebral arteries 4 months after weight-loss induced by bariatric surgery (BS). We are currently recruiting participants with severe obesity (BMI=41.8±3.3 kg/m2, age=43.9±6.8 years, n=12) scheduled to undergo BS. Prior to and 4 months after surgery, MRI measurements were acquired to assess WMH volume (reflecting the size of the area of damage), WMH intensity (reflecting the severity of damage in the same area) and the mean arterial volume of main cerebral arteries. We used linear mixed-effect models controlling for age and education. The mean total weight loss was 19.2% ± 4.6% after 4 months (t=16.05, p˂0.001). Our preliminary results show significant reductions in WMH volume (t=-2.10, p=0.049) and WMH intensity (t=-2.71, p=0.013) 4 months after BS, suggesting resorption in cerebrovascular damage’s size and severity. We also found significant increases in mean arterial volume 4 months following BS (t=3.05, p=0.01). Higher mean arterial volume was significantly associated with lower WMH volume at 4 months (t=-3.35, p=0.008, n=10). These preliminary results suggest an improvement in lesions of vascular nature after weight-loss induced by BS. The increase in cerebral vasculature following weight loss could be a key factor in this improvement. Showing a reversal of brain abnormalities associated with obesity after BS will have strong implications for clinical practice.
A lateral head impact model for mouse studies on hypothalamic dysfunction associated with traumatic brain injury
Corresponding Author: Julie O'Reilly, email email@example.com
The development of central autonomic and endocrine deficits after traumatic brain injury (TBI) is believed to involve hypothalamic dysfunction, but the underlying mechanisms are unknown. We developed a model of lateral head injury to study TBI-related dysautonomias in mice. Mice were lightly anesthetized with isoflurane and subjected to TBI using a Gothenburg Impactor (Collision Analysis Inc). This instrument was used to deliver a reproducible, calibrated blow to the side of the head of mice via a 50 g projectile launched at predetermined velocities (v). Mice treated the same way but without the head impact served as controls (shams). TBI caused increased righting times proportional to impact velocity. At v = 9 m/s, no mortality, skull fracture or external bleeding was observed and grimace scale score 3 hours following TBI was 0. During the 7 days that followed TBI, mice displayed a 10% decrease in body weight. Immunohistochemistry analysis revealed marked activation of c-Fos in several neuronal populations of the paraventricular hypothalamus including vasopressin and oxytocin neurons. This model may be useful for studies on hypothalamic dysfunction associated with TBI.
Drug screen analysis in Restless Legs Syndrome worm model
2Montreal Neurological Institute, McGill University, Montréal, QC, Canada,
3Centre de recherche du Centre hospitalier de l'Université de Montréal (CRCHUM), Montréal, QC, Canada,
4Department of Human Genetics, McGill University, Montréal, QC, Canada,
5Department of Neurology and Neurosurgery, McGill University, Montréal, QC, Canada.
Corresponding Author: Rachel De Barros Oliveira , email firstname.lastname@example.org
Restless leg syndrome (RLS) is a chronic sleep-related sensorimotor disorder characterized by a strong impulse to move the legs to relieve uncomfortable sensations. A GWAS in 2000 has identified an association between RLS and three genomic regions. One of the regions was the intronic variants in the homeobox gene MEIS1. MEIS1 is a gene that increases the risk of developing RLS by 50% and has an association with iron homeostasis and dopaminergic system. In C. elegans, the ortholog for MEIS1 is unc-62. It was shown to be expressed in different tissues (hypodermis, intestine, and nervous system) and exhibit a strong impaired movement phenotype. Because of the phenotypical difference between unc-62 worms and their control N2, this strain was a perfect candidate to perform an unbiased drug screen analysis with almost 4,000 compounds. The drug screen was performed using the WMicrotrackerTM ONE (Phylumtech) with standard parameters for C. elegans. With more than 100 hits, we are now proceeding to confirm the results in a second drug screen and then we will analyze the best candidates on plates. Our study aims to use a simple and strong genetic model (Caenorhabditis elegans) to understand the neurobiology of RLS. This approach can give us new targets, that can be confirmed in more complex models and used for treatments in the future.
Rôle des hormones gonadiques et du traitement par le dutastéride sur l'axe microbiote-intestin-cerveau dans un modèle murin mâle et femelle de la maladie de Parkinson
2Faculté de Pharmacie, Université Laval, Quebec, QC, Canada,
3IBIS, Québec, QC, Canada,
4Centre de recherche de l’IUCPQ, INAF, Québec, QC, Canada.
Corresponding Author: Denis Soulet, email email@example.com
La prévalence et l'incidence de la maladie de Parkinson (MP) sont plus élevées chez les hommes que chez les femmes, suggérant un rôle possible des hormones sexuelles dans la neuroprotection. Le dutastéride (DUT), un inhibiteur de la 5α-réductase (5αR) utilisé chez les hommes, a montré des effets neuroprotecteurs dans un modèle de souris mâle de MP. Le DUT pourrait agir indirectement en augmentant les niveaux endogènes d'hormones gonadiques féminines (HGF) par inhibition de l'enzyme 5αR. Nous voulons étudier l'impact du DUT et des hormones sexuelles dans la MP au niveau central et périphérique. Quatre groupes de souris, mâles ou femelles, ont été gonadectomisés (GDX), pour modéliser l’andropause et la ménopause, ou opérés de manière fictive (SHAM). Ils ont reçu du DUT ou un véhicule pendant 10 jours. Au 5ème jour de traitement avec le DUT, les souris ont reçu du MPTP (1-méthyl-4-phényl-1,2,3,6-tétrahydropyridine) pour modéliser la MP ou de la saline. Le MPTP a causé une perte de dopamine et une activation astrocytaire dans tous les groupes sauf chez les femelles SHAM et, chez les mâles SHAM, le DUT a eu un effet protecteur. Avec une analyse morphologique 3D des microglies, nous avons observé une activation microgliale causée par le MPTP chez les mâles SHAM et GDX uniquement. Une analyse de la composition du microbiote intestinal montre des différences en fonction du sexe et des GDX. Nous montrons un effet protecteur des HGF dans ce modèle de MP pour la dopamine et les astrocytes ainsi qu’une protection intéressante du DUT chez les mâles SHAM. L’activation microgliale ne semble elle pas avoir une réponse dépendante de ces HGF mais bien du sexe biologique de l’animal.
Impact of alpha-synuclein aggregation on the protein degradation systems and its implication in Parkinson’s Disease pathogenesis
Corresponding Author: Walid Idi, email firstname.lastname@example.org
In Parkinson Disease (PD), the aggregation of a misfolded proteins called alpha-synuclein (a-syn) represents one of the major pathological hallmarks. However, how these aggregates disturb neuronal homeostasis leading to neurodegeneration remains elusive. Several studies shown a correlation between alterations of the degradation systems (autophagic or proteasomal), implicated in the protein quality control, and a-syn aggregation. It’s relevant to know how an alteration of the degradation systems is involved in the pathogenesis of PD. To study the effect of a-syn aggregation, the LIPA (Light-Inducible Protein Aggregation) system recently developed by our laboratory is used (Bérard et al., 2022). This system is based on the aggregation capacity of the CRY2 protein, which aggregates when exposed to blue light. Associated with a-syn and thus constituting the LIPA-Syn system, it allows to optogenetically control and observe in real time the aggregation of a-syn and its effects on the degradation systems Using this model, we were able to observe for the first time the effect of LIPA-induced aggregates on the proteasome and autophagy systems by using specific markers (Menéndez-Benito et al., 2005; Larsen et al., 2010). Moreover, we also get interested in the inhibition of these systems and the effect on the aggregation. Interestingly, we found that both systems seem involved but in a different manner and with a different kinetic. Our observations will allow us to better understand the vulnerability of degradation systems and their role in Parkinson's disease pathogenesis. In order to potentially consider pharmacological manipulation of these systems, with the aim of limiting a-syn aggregation and the impact on cellular homeostasis.
Pathological and MRI investigations of COA8 cytochrome c oxidase deficiency
2Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada;
3Centre Hospitalier Universitaire de Québec-Université Laval, Québec City, QC, Canada;
4Department of Pediatric Neurology, Emma Children’s Hospital, Amsterdam University Medical Center, Amsterdam, Netherlands;
5Amsterdam Neuroscience, Amsterdam University Medical Center, Amsterdam, Netherlands;
6Center for Pediatric Genomic Medicine, Children’s Mercy Hospital and School of Medicine, University of Missouri-Kansas City, Kansas City, MO, USA;
7Department of Medical Biology, Centre Hospitalier Universitaire de Québec, Hôpital de l’Enfant-Jésus, Québec City, QC, Canada;
8Division of Anatomic Pathology and Neuropathology, Centre Hospitalier Universitaire de Québec, Hôpital de l’Enfant-Jésus, Québec City, QC, Canada;
11Division of Medical Genetics, Department of Specialized Medicine, McGill University Health Centre, Montreal, QC, Canada
Corresponding Author: Alexandra Chapleau, email email@example.com
COA8 cytochrome c oxidase (COX) deficiency is a recently described rare cavitating leukoencephalopathy caused by biallelic variants in the COA8 gene. COA8 is an enzyme involved in COX biogenesis and is suspected to play a role protecting the complex from oxidative stress induced degradation. Clinically, COA8 COX deficiency presents heterogeneously and usually follows a bi-phasic clinical course with a period of acute onset and regression, followed by stabilization, and in some cases, even subtle improvement. Retrospective medical records review, including analysis of brain MRIs and autopsy pathological examination, was performed for a deceased patient with a COX deficiency caused by a homozygous 2.5 kilobase pair deletion in COA8. A 4-year-old boy, previously healthy, presented with rapid neurological deterioration resulting in death weeks after onset. Brain MRI revealed a distinctive pattern of cavitating leukodystrophy predominantly involving the posterior cerebral white matter and splenium of the corpus callosum. Follow up MRI one month later showed some improvement. Brain pathology displayed overall white matter destruction with gliosis and infiltration by macrophages. There was preservation of astrocytes around blood vessels and axons around the zones of demyelination. We present the first brain pathological examination of COA8 COX deficiency and provide further characterization of the clinical and MRI phenotype. Integration of the clinical, radiological and pathological data can help guide diagnosis as well as improve understanding of disease mechanisms.
A light-inducible protein clustering system for in vivo analysis of α-synuclein aggregation in Parkinson disease
2Department of Molecular Medicine, Faculty of Medicine, Université Laval, Quebec City, QC, Canada.
3CERVO Brain Research Centre, Quebec City, QC, Canada.
4Department of Psychiatry and Neurosciences, Faculty of Medicine, Université Laval, Quebec City, QC, Canada
5Faculty of Pharmacy, Université Laval, Quebec City, Canada.
6McGill Parkinson Program and Neurodegenerative Diseases Group, Montreal Neurological Institute, McGill University, Montreal, QC, Canada.
7Department of Electrical, Computer, and Energy Engineering, University of Colorado, Boulder, CO, USA.
8School of Electrical Engineering Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea.
9Division of Medical Sciences, University of Victoria, Victoria, BC, Canada.
Corresponding Author: Morgan Bérard, email firstname.lastname@example.org
α-synuclein (α-syn) aggregation into insoluble deposits, referred to as Lewy bodies (LBs) is the paramount pathological hallmark of Parkinson’s disease (PD) and related α-synucleinopathies. However, how these aggregates affect neuronal homeostasis leading to neurodegeneration remains elusive. This gap in knowledge is mainly due to the lack of proper cellular and animal models to undertake such investigations. We used a gene therapy approach, based on the use of adeno-associated virus (AAV), to overexpress our LIPA system directly into the brains of naive mice. For the delivery of the blue light necessary for the induction of the aggregation and propagation of α-syn, we used implantable micro-devices developed by Amuza Inc. We report on the development of a light-inducible protein aggregation (LIPA) system that enables real-time induction of α-syn inclusion formation with remarkable spatial and temporal resolution in living cells. We demonstrate that LIPA-α-syn inclusions faithfully mimic key biochemical and ultrastructural features, as well as the seeding capacity of authentic LBs. In vivo, LIPA-α-syn aggregates compromised the nigrostriatal transmission, induced dopaminergic neuronal loss and PD-like behavioral impairment Our system provides a novel, dependable and invaluable tool to generate, visualize and dissect the role of protein aggregates in PD and possibly other neurodegenerative disorders.
A rare syndrome characterized by mega-corpus callosum, polymicrogyria, and psychomotor retardation
2Department of Radiology, Antonio Prudente Hospital, Fortaleza, CE, Brazil
3Pontifical Catholic University of Goias, Goiania, GO, Brazil
Corresponding Author: Antonio Gomes Lima Junior, email email@example.com
The megalencephaly-polymicrogyria-mega-corpus-callosum (MEG-PMG-Mega CC) syndrome is an extremely rare entity initially described in 1998 by Göhlich-Ratmann et al. It is and is characterized through magnetic resonance imaging findings previously mentioned associated with a deficit in psychomotor development. Reports of subsequent cases, although in minimal quantity, were important to confirm some pathognomonic alterations in this syndrome. The present study aims to reinforce the pathognomonic findings previously described in the literature and contribute to future research initiatives. Case Report and Literature Review. Case report of an 11-year-old male patient, that presented with a complaint of cerebral palsy since birth. He had difficulty walking, as well as a significant delay in speech development and important hearing impairment. A magnetic resonance imaging study of the skull was performed for neurological evaluation, it revealed the pathognomonic findings of megalencephaly, polymicrogyria, and mega corpus callosum, which characterized the MEG-PMG-Mega CC syndrome. The MRI findings of MEG-PMG-Mega CC associated with the psychomotor retardation were compatible with the classical description of Göhlich-Ratmann et al. Subsequent studies reported that radiological detection of megalencephaly was not mandatory. Thickening of the corpus callosum, however, had already been described in other pathologies: Cohen's Syndrome and Neurofibromatosis 1. The patient normal cranial dimensions corroborate with recent hypothesis that the MEG-PMG-Megga CC are pathognomonic of this syndrome whereas cranial dimensions are not as significant. Although having scarce literature, all cases reported share similar characteristics, such as the mega corpus callosum, cortical migration abnormalities, and delayed psychomotor development. Therefore, it can be inferred that these three findings are unique to this syndrome, while other associated anatomical abnormalities may be related to a spectrum of this rare syndrome.
Characterizing the role of Polr3a, Polr3b and Polr1c in oligodendrocyte lineage development
2Child Health and Human Development Program, Research Institute of the McGill University Health Center, Montreal, QC, Canada
3Department of Pediatrics, McGill University, Montreal, QC, Canada
4Department of Human Genetics, McGill University, Montreal, QC, Canada
5Department Specialized Medicine, Division of Medical Genetics, McGill University Health Center, Montreal, QC, Canada
Corresponding Author: Julia Macintosh, email firstname.lastname@example.org
RNA polymerase III-related hypomyelinating leukodystrophy (POLR3-HLD) is a genetic white matter disorder characterized by insufficient myelin deposition in development. Myelin, produced by oligodendrocytes (OLs) in the central nervous system, insulates axons, enabling efficient propagation of action potentials. POLR3-HLD is caused by biallelic pathogenic variants in genes encoding subunits of RNA polymerase III (Pol III), a ubiquitous enzymatic complex. It is unclear how OLs are particularly affected by altered Pol III to explain the devastating hypomyelination seen in POLR3-HLD. Oligodendrocyte precursor cells (OPCs) undergo a complex developmental process to become OLs. Therefore, we hypothesized that reduced Pol III activity would lead to defective OL-lineage development, either in the 1) migration and proliferation of OPCs, 2) maturation of OPCs into OLs or 3) myelination by OLs. To investigate this, primary mouse OPCs transfected with siRNA targeting Polr3a, Polr3b or Polr1c were subjected to various in vitro assays. Our preliminary data shows that reducing Pol III activity leads to a maturation defect, with siRNA-treated OLs demonstrating reduced morphological complexity and decreased expression of late-stage OL markers. Staining for apoptotic markers suggests these cells remain alive. Moreover, analysis of the OPC stage demonstrated a higher proportion of cells in S-phase, suggestive of abnormal proliferation, while migration was unaffected. Myelination assays are in progress to see how this altered oligodendrogenesis might impact myelination. Our early results suggest that Pol III is required for normal OL development and sheds light on the mechanisms of myelination failure in POLR3-HLD.
Investigating the impact of tau deletion in a Huntington's disease mouse model
2Département de Psychiatrie & Neurosciences, Université Laval, Québec, QC, Canada.
Corresponding Author: Eva LEPINAY, email email@example.com
In recent years, accumulating evidence has suggested that tau protein also contributes to Huntington’s disease (HD) pathology. Studies have reported that (i) tau aggregates form within brain structures in HD patients, (ii) motor behavior is improved with a tau deletion in a transgenic HD mouse model and therefore that (iii) HD could be a secondary tauopathy. We hypothesized that tau protein is involved in the development of behavioral and neuropathological phenotypes associated to HD. zQ175 mice were crossed with tau knockout (mTKO) mice and behavioural tests, including the Barnes maze, open field, rotarod and narrow beam, were performed at 3, 6, 9 and 12 months of age to assess anxiety, cognitive and motor deficits in relation to the presence or absence of tau. Post-mortem analyses, which have just begun, include the quantification of soluble HTT, mHTT and aggregates, elements of the neuroinflammatory response, the microtubule organization and cell degeneration. Preliminary results obtained in the zQ175/mTKO model suggest a precipitation of motor deficits - by the narrow beam test - and cognitive deficits - by the Barnes maze test - of tau-deleted zQ175 mice. In addition, the open field and rotarod revealed worsening motor and cognitive deficits in zQ175/mTKO mice. Our preliminary observations suggest that the absence of tau triggers the precipitation and exacerbation of cognitive and motor deficits in zQ175/mTKO mice. Ongoing post-mortem analyses as well as in vitro studies will shed light on the role of tau in HD.
Interplay between the endolysosomal system and protein aggregation in the pathogenesis of Parkinson’s disease
2Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
Corresponding Author: Maxime Teixeira, email firstname.lastname@example.org
While progress has been made in understanding the neurodegenerative mechanisms that lead to cell death in Parkinson’s disease (PD), early causal pathogenic events are not clear. Converging findings point at endolysosomal system (ELS) dysfunction as the early mechanism and key pathway affected in PD. However, the exact mechanism by which alpha-synuclein aggregates, also called Lewy Bodies (LBs), disrupt the ELS remain elusive. To answer this question, we created a new optogenetic-based model of PD that allows for the real-time induction of α-syn aggregates under the blue light control (LIPA system), that mimics all cardinal LBs features. Using that system, we investigated the interactions between our aggregates and the ELS combining STED and transmission electron microscopy (TEM) overtime. Then, we used live-cell microscopy to decipher how alpha-synuclein interacts with the ELS at the very first steps of aggregation. Those high-resolution techniques allowed us to show that alpha-synuclein aggregates and trafficking vesicles are forming a quick and robust colocalization. Interestingly, early endosomes and lysosomes were specifically interacting with alpha-synuclein. Moreover, we showed that the aggregates are composed of multiple vesicles and distorted organelles. Our live-cell microscopy data revealed that the alpha-synuclein, at the initiation of the aggregation, quickly bind to the membrane of specific vesicles forming a dynamic complex that will further lead to the formation of bigger aggregates Those results allowed us to observe and to better understand how is mediated alpha-synuclein aggregation in the context of PD, suggesting that the ELS play a key role in alpha-synuclein aggregation. Deciphering that complex interaction could pave the road to a better comprehension of the disease and lead to new therapeutic strategies.
Role de domaine intracellulaire dans la plasicité synaptique et maladie d'Alzheimer
2Centre de Recherche, Centre Hospitalier Universitaire Sainte-Justine, Montréal, QC, Canada
Corresponding Author: Jannic Boehm, email email@example.com
Deux formes importantes de plasticité synaptique sont la potentialisation à long terme (LTP) et la dépression à long terme (LTD). Aujourd'hui, nous savons que ces processus sont les mécanismes cellulaires qui sous-tendent la formation de la mémoire. L'induction de la plasticité synaptique est contrôlée par l'activation de voies de signalisation spécifiques. Il est devenu évident ces dernières années que certaines molécules clés peuvent influencer et modifier l'induction de la plasticité synaptique, c'est-à-dire qu'elles peuvent changer et contrôler si la LTP ou plutôt la LTD est induite, un phénomène appelé métaplasticité. - Pour les expériences proposées, j'utilise des cultures de tranches d'hippocampe organotypiques de souris âgées de 6 jours. Dans les cultures en tranches, j'exprime une protéine APP chimérique, où le domaine Aβ a été remplacé par le domaine homologue d'APLP2. L'expression de cette construction facilite la dépression synaptique causée par 10 nM A-bêta L'objectif de ma thèse est maintenant d'analyser le mécanisme moléculaire sous-jacent et la cascade de signalisation qui conduisent à des changements dans la métaplasticité et par extension à la formation de la mémoire. De plus, étant donné que Aβ et le domaine intracellulaire de l'APP sont produits en même temps par clivage de l'APP, j'analyserai s'ils travaillent main dans la main, c'est-à-dire s'ils ont un effet synergique sur la régulation de la métaplasticité Les résultats de ce projet mettront en lumière le rôle sous-étudié de la protéine précurseur de l'amyloïde dans la physiologie synaptique. Plus précisément, mon programme de recherche combinera pour la première fois les deux produits de clivage APP, A-beta et APP-ICD, en analysant leur effet combiné sur la plasticité synaptique. Étant donné que l'APP est impliquée dans une multitude de processus neurodéveloppementaux, mon projet élucidera les voies neurodéveloppementales complexes qui conduisent à des changements dans de la dépression synaptique et de la perte de synapse au cours de la maladie d'Alzheimer
Identification of Dickkopf-1 as a potent repressor of subacute repair and chronic recovery associated with anxiety-like behavior upon stroke
Corresponding Author: Menet Romain, email firstname.lastname@example.org
Stroke constitutes a major cause of death and disability in Canada. It is caused by the sudden obstruction of the cerebral blood flow. Our group has previously demonstrated that the canonical Wnt pathway, which plays key roles in controlling neurovascular functions, is deregulated after stroke. Interestingly, Dickkopf-1 (DKK1), an endogenous inhibitor of the pathway, has been shown to be regulated by ischemic stressors and vascular risk factors, correlating with stroke prognosis in patients. Although DKK1 systemic levels are elevated in stroke patients, its pathological role remains unknown. Our study aims to elucidate the role of DKK1 in stroke pathobiology and therapy. For this purpose, inducible transgenic mice allowing temporal regulation of DKK1 expression (iDKK1 mice) were used. Mice were subjected to ischemic stroke using middle cerebral artery occlusion (MCAo). Furthermore, pharmacological approaches were used to neutralize the biological effects of DKK1 after stroke to explore the impact on neurovascular repair. Early DKK1 induction exacerbated infarct and oedema sizes as well as aggravated motor deficits after stroke. DKK1 induction was associated with neuronal degeneration, while preventing neurogenesis, neuronal maturation, and neovascularization. These results were accompanied with an impaired cerebral blood flow and synaptic plasticity. Delayed DKK1 induction attenuated long-term post-stroke restorative processes and impaired motor recovery, while causing anxiety-like behavior. These changes were accompanied with a chronic neuroinflammatory responses at the lesion site. Finally, the pharmacological neutralization of DKK1 improved structural and neurological recovery after stroke. Our results indicate that DKK1 plays a key role in stroke pathobiology and its neutralization constitutes a clinically relevant approach to promote neurovascular repair after stroke.
Functional connectivity of the motor network in children with spinal muscular atrophy
2Alberta Children's Hospital Research Institute, Calgary, AB, Canada
3Hotchkiss Brain Institute, Calgary, AB, Canada
4Advances in Brain & Child Development Research Laboratory, Montreal, QC, Canada
5Department of Pediatrics and Neurology & Neurosurgery, McGill University, Montreal, QC, Canada
Corresponding Author: Nancy Mugisha, email Nancy Mugisha
Spinal Muscular Atrophy (SMA) is a motor neuron disease caused by depletion of the survival motor neuron protein (SMN). The effects of this early motor unit dysfunction on brain development and connectivity remain largely unknown. Discovering new pathways to augment motor outcomes in SMA patients has a high potential for future impact as co-intervention to disease modifying therapies facilitating long-term survival. We conducted a case-control study of rs-fMRI in a pediatric cohort of patients with SMA and age- and sex-matched typically developing peers. We used both seed-to-voxel and ROI-based connectivity analyses to explore differences in key motor regions and networks including bilateral pre- and post-central gyri, supplementary motor area, superior sensorimotor network, lateral sensorimotor network, basal ganglia (pallidum, caudate, putamen) and thalamus. We compared 8 children with SMA (mean age: 9.26 ± 1.34) and 8 matched controls (mean age: 9.8 ± 1.64 ). Group analyses suggested higher and lower functional connectivity in cortical motor regions and lower functional connectivity in the basal ganglia in the SMA group. We demonstrate potential alterations in resting-state brain connectivity of key motor regions in children with SMA with implications that open new pathways for therapeutic approaches to optimize motor learning and function.
The fibroblast growth factor 21 (FGF21) improves metabolic and cognitive determinants in a mouse model of AD
2Neuroscience Axis, CHU de Québec-Université Laval, Québec, QC, Canada
3Department of Diabetes and Obesity Biology, Novo Nordisk A/S, Denmark
Corresponding Author: Josue Valentin, email email@example.com
Alzheimer’s disease is an incurable form of dementia that is recognized to have a strong metabolic component. This opens the possibility to target metabolic deficits as therapeutic strategies for AD. FGF21 is a hormone with important metabolic effects that is being tested in clinical trials for diabetes and obesity. There is evidence showing that FGF21 can also act on the CNS and modulate brain functions, but such mechanisms are less understood. We used a transgenic mouse model of AD (3xTgAD) that develops tau and amyloid pathologies over time. Mice were fed either a CD (5% w/w) or a HFD (35% w/w) for 9 months and received rhFGF21 (1 mg/kg/day, osmotic minipump) or vehicle from 15 to 16 months of age. Metabolic and cognitive tests were performed during the last week of treatment and protein analysis in the hippocampus and liver were performed post-mortem. FGF21 administration profoundly improved metabolic determinants in NonTg and 3xTgAD, including decreased levels of fasting glucose and insulin, and improved glucose tolerance. The novel object recognition test (NOR) and Dark-light box test (DLB) revealed that FGF21 improved anxiety and memory in 3xTgAD mice. Moreover, tau phosphorylation was not affected in the hippocampus while the Aβ42/ Aβ40 ratio was reduced female 3xTgAD mice. FGF21 increased FGFR1 phosphorylation in the liver, but not in the brain. FGF21 is an important metabolic regulator. The effects on cognitive endpoints observed here suggest that FGF21 can also present a therapeutic potential for CNS diseases, such as AD. Whether its impact on the brain is direct or indirect through the periphery remains to be determined.
Fishing for new genetic causes of rare epileptic syndromes
Corresponding Author: Katarzyna Ochenkowska, email firstname.lastname@example.org
More than a half of the children with IS (infantile spasms) will later develop other types of seizures such as Lennox-Gastaut syndrome (LGS), characterized by multiple seizure types and cognitive dysfunction, refractory to anti-epileptic medicines. With poor prognosis (5% mortality in childhood, persistent seizures into adulthood in 85% of the cases) and still unknown origin in a quarter of the cases, there is a need to identify new IS/LGS-causing genes and to functionally validate their pathogenicity in appropriate in vivo models. Recently, two new variants in the THAP12 gene have been identified by whole-exome sequencing in two siblings with idiopathic IS and LGS. Since no other disease-causing mutations in THAP12 have ever been referenced, the causative role of THAP12 mutations in causing IS/LGS still needs to be demonstrated. We have access to skin-derived fibroblasts for both probands and their unaffected parents. Using immunofluorescence, we will check the subcellular localization of THAP12 in probands versus unaffected parents by immunofluorescence and confocal imagine. It is known that THAP12 expression is restricted to the nucleoplasm and we will check if mutations in THAP12 change this pattern. We will also check if the level of expression of THAP12, at the level of the transcript (using RTqPCR) and of the protein (by western blot on total or subfraction protein extracts) is affected in the probands’ cells. We will functionally test the effect of THAP12 LoF in vivo using zebrafish and confirm that it leads to neurodevelopmental defects. Since the beginning of this project in July 2021, we established a stable THAP12-KO line. We checked differences in the behavior in the light-dark cycle by locomotor tracking recording. We observed that THAP12 mutants display a significant hypoactivity during light periods, and dark time hyperactivity compared to WT siblings. This data is consistent with other severe epileptic encephalopathy fish models, making these results relevant to LGS. We treated larvae with PTZ(proconvulsant) and noticed that mutants are more sensitive to low doses of the compound. This result suggests an imbalance in the excitatory/inhibitory (E/I) balance brain circuits. Furthermore, we performed liquid chromatography/mass spectrometry analysis (LC/MS) to investigate if there are any differences in neurotransmitters level in mutant larvae. We showed that there is significantly more glutamate in samples obtained from mutant compared to WT, confirming the E/I imbalance at the neurotransmitter level. We outcrossed the THAP12 line with transgenic fluorescent reporter lines and we showed that the brain of mutant larvae is significantly smaller compared to WT siblings with disorganized neural structure This research project will allow inferring a pathogenic role of THAP12 mutation and therefore help confirming a definite genetic diagnosis for our patients. More broadly, it can unravel a novel gene involved in LGS that could be further included in infantile epilepsy genetic testing panels. This project will generate useful in vivo genetic models to (1) further investigate the role of THAP12 in neurodevelopment and (2) that will be useful for the development of further therapeutic approaches. This project has the potential to push LGS research forward with a big leap (identifying a novel genetic cause), rather than by smaller incremental steps.
Developing zebrafish genetic models for precision medicine in epilepsy
2Department of Neuroscience, Université de Montréal, Montreal, QC, Canada
Corresponding Author: Éric Samarut [1,2], email email@example.com
Epilepsy is a widespread neurological disorder characterized by recurrent seizures that affect more than 50 million individuals worldwide. Although 28 Anti-Epileptic Drugs (AEDs) are available, treatment response is often unpredictable. A recent study showed that an inappropriate first medication can affect the efficacy of further treatments. Therefore, our objective is to generate a patient-specific zebrafish model using Cre-Lox recombination and to identify which AED works the best for a specific patient using a customized zebrafish genetic avatar (one patient = one genetic variant = one genetic zebrafish avatar). We are using a transgenic approach Cre-lox recombination, particularly we are focussing on specific LoxP sites namely Lox66, Lox71, and LoxP-Lox2272 allowing stable and irreversible recombination events. LoxP sites were inserted at the 5’UTR of zebrafish gabra1, an epilepsy-causing gene with a large spectrum of phenotypes in patients. Using CRISPR/CAS9 homologous recombination stable transgenic zebrafish lines carrying Lox71 and LoxP-Lox2272 sites at the 5’UTR will be generated. We will generate these lines by co-injecting into one-cell zebrafish embryos (i) a DNA template encoding specific Lox sites surrounded by short homologous arms, (ii) a specific guide RNA targeting the 5’UTR of gabra1 gene, and (iii) an mRNA encoding Cas9 endonuclease. Once these lines are established, we plan to recombine the Lox71 site and LoxP-Lox2272 site with different patient-specific cDNAs encoding the precise GABRA1 variant of a particular epileptic patient specific variants identified by our collaborator's. We have generated stable transgenic lines of Tg[gabra1_Lox71] further we will try the preliminary recombination events. For the second strategy, we have isolated a founder fish with Tg [gabra1_LoxP_Lox2272], thus ensuring the feasibility of the project. It is anticipated that the establishment of the line Tg[gabra1_LoxP_Lox2272] by CRISPR/CAS9 will take about 10-12 months. However, once the parent line is established, we estimate that we could recombine and test up to 80 patient cDNAs per year (2 weeks to test 28 AEDs per cDNA, 4 cDNAs tested per round). In conclusion, we believe that this research program will pave the way for a deeper understanding of the genotype- phenotype-treatment-responsiveness correlation in epilepsy. Moreover, our findings will have a direct impact on patients by saving their precious time by deciphering which anti-epileptic drug (AED) is the most suitable for them.
Fenestrated actin cortex of rat supraoptic nucleus magnocellular neurosecretory cells
Corresponding Author: Anzala Murtaz, email Anzala.firstname.lastname@example.org
Osmosensory transduction (OT) is a mechanical process where dn-Trpv1 channels are activated by a “push” force from microtubules during hypertonicity-induced cell shrinkage in osmosensory neurons such as the magnocellular neurosecretory neurons (MNCs) of the rat supraoptic nucleus (SON). These neurons also feature a thick actin cortex (~1 µm) which is also essential for OT but how exactly so and whether specific features promote this process is unknown. All experiments were done on acutely isolated MNCs. Proximity ligation assay (PLA) generates detectable signals when proteins of interest are in close proximity (40 nm). PLA was used with anti TRPV1, α-tubulin, and β-actin antibodies. We used super-resolution fluorescence microscopy with a FV 3000 Olympus confocal microscope (FV-OSR; 120 nm xy resolution) and image deconvolution (CellSens software, Olympus Canada Ltd) to obtain high-resolution images of the MNC actin cytoskeleton. Intensity analysis of MNC perimeter revealed “gaps” of reduced fluorescence and thus less f-actin of ~0.5 µm. PLA confirmed previously known microtubule-Trpv1 channel interactions (Prager-Khoutorsky et al., 2014). Specifically, we observed ~10-100 interaction sites per cell (n=30; 6 preparations), mainly discrete puncta scattered on the cell surface. In contrast, no interaction sites were detected when PLA was performed using antibodies directed against actin and trpv1 (n=20, 2 preparations). In conclusion, this study reveals that the submembrane actin cortex of MNCs is fenestrated and actin does not interact with Trpv1 channels.
In-vivo evaluation peripheral nerve regeneration - The rabbit model
2Department of Surgery, Faculty of Medicine, Université Laval, Québec, QC, Canada
Corresponding Author: Alexane Thibodeau, email email@example.com
Peripheral nerve injuries have a significant impact on a patient’s quality of life. Researchers around the world are developing innovative techniques to repair large nerve deficits (>3cm). The rat model is the first choice for in-vivo testing. Unfortunately, the use of rat data alone may lead to poor results. There is a need to use larger animals to study critical human gaps. Our objective is to describe an effective evaluation methodology for rabbit peripheral nerve regeneration. Autograft were implanted in New Zealand rabbits for 36 weeks to repair a 4 cm fibular nerve defect. Electrodiagnostic testing and functional assessment are among the most reliable and accurate methods for peripheral nerve repair evaluation. The nerve conduction of the fibular nerve in rabbit was evaluated every three weeks under light anesthesia as the same time an electromyogram (EMG) was recorded. The Toe Spread Index (TSI) was used to monitor the functional outcome. Nerve conduction analysis in the tibialis anterior muscle showed that the nerve conduction recovery began around the 18th week. The EMG of the tibialis muscle showed a resting electrical activity return with multiple polyphasic activities (I.e., reinnervation in progress) around the 24th week. Unrepaired rabbits maintain an anarchic activity profile showing an absence of innervation throughout the experiment. After 36 weeks, an improvement of the TSI showed a partial motor function recovery in rabbit (p<0.05). Electrodiagnostic testing is a fast, objective, and reliable technique to evaluate the fibular nerve regeneration in rabbit. It is a noninvasive method and associated with very few minor complications. Furthermore, this study reinforces the idea that the fibular nerve is a good animal model for the study of nerve injuries.
Dynamic regulation of the microglial transcriptional landscape during neuroinflammatory response
Corresponding Author: David Gosselin, email David.Gosselin@crchudequebec.ulaval.ca
Various medical conditions can trigger a neuroinflammatory response, from neurodegenerative diseases like multiple sclerosis (MS) to systemic infection. Such a response is orchestrated by microglia, the resident macrophage of the brain parenchyma. Notably, microglia are polarized upon activation of surface receptors which leads to the binding of transcription factors to genomic regulatory elements, promoting transcription of target genes. However, the transcriptional and regulatory landscape of microglia across neuroinflammation remains under-characterized, especially in vivo. To address this issue, we induced a systemic inflammatory response in mice with bacterial lipopolysaccharide (LPS) to induce neuroinflammation. We then extracted microglia at various timepoints following LPS challenge and used various massively parallel sequencing methods (i.e., RNA-seq, ChIP-seq, ATAC-seq) to detect differential events in the transcriptome and epigenome. Our RNA-seq analyses revealed that multiple waves of transcription are activated at different stages of neuroinflammatory response. In addition, epigenomic features across the genome showed dynamic shifts. Upon integrating this data with the cuprizone demyelination model, we found that some gene programs are common to both conditions while others operate in a context-dependent manner. This differential response was linked to involvement of distinct transcription factors for both LPS (e.g., Nf-κB) and cuprizone (e.g., Usf/Mitf). Our results demonstrate that microglia’s transcriptomic and regulatory landscape can rapidly shift during neuroinflammation and is highly dependent on the immune context driving the response.
CD4+ T cells rescue the infiltration of CD8+ T cells to CNS in autoimmune mouse model of CD8+ T cell adoptive transfer
2Department of Molecular Medicine, Faculty of Medicine, Université Laval, Quebec City, QC, Canada
Corresponding Author: Dr. Manu Rangachari, email Manu.Rangachari@crchudequebec.ulaval.ca
Both CD4+ and CD8+ T cells play critical roles in the immunopathogenesis of MS. We recently demonstrated that in vitro-differentiated 1C6 T cell receptor transgenic CD4 Th1 and Th17 cells can induce a progressive form of experimental autoimmune encephalomyelitis (EAE) upon adoptive transfer to NOD.Scid recipient mice. In this study, we assessed whether the same is true for 1C6 CD8+ T cells Naive 1C6 CD8+ T cells were cultured under Tc1 or Tc17 differentiation conditions for 5 days and 5 million cells/NOD.Scid recipient mice were adoptive transferred on day 5. In vivo blockade of CD4+ T cells was done by intraperitoneal injection of anti-CD4 antibody. 1C6 Tc1 and Tc17 cells (5x106 per recipient) induced progressive EAE upon adoptive transfer. However, disease of increased severity was seen upon co-transfer of Th1+Tc1 (2.5x106 of each per recipient). Intriguingly, ex vivo analysis of the spleens and CNS of Tc1-alone or Tc17-alone recipients revealed the presence of CD4+ T cells. Co-transfer of Th1+Tc1 cells induce highly severe disease. In vivo blockade of CD4 reduced not only the presence of CD4+ T cells in the CNS of Tc17 alone recipients, but also the presence of CD8+ T cells.
Sleep disturbances and Alzheimer's disease pathology in at-risk cognitively unimpaired older adults
2Douglas Mental Health University Institute, Verdun, QC, Canada
3Department of Psychology, Université de Montréal, Montreal, QC, Canada
Corresponding Author: Bery Mohammediyan, email firstname.lastname@example.org
Evidence suggests an association between sleep and Alzheimer’s disease (AD) pathology, amyloid-β (Aβ) and tau. It remains unclear whether this association between sleep and AD pathology is present during the preclinical phases of AD, and if this association holds across time. The objective of the study was to explore whether sleep is associated with AD pathology in cognitively unimpaired individuals with a family history of sporadic AD dementia, and whether this association holds over time. We included 125 participants who underwent Aβ and tau positron emission tomography (PET). Each participant completed the Pittsburgh Sleep Quality Index (PSQI) 2-3 times during 2017-2019. The PSQI is a self-reported questionnaire where a score ≥5 reflects poor sleep. Participants wore an actigraph for seven days during 1-2 time points, which allows us to assess participants sleep duration, and whether they were nappers. For our analysis, we used linear and linear mixed effect models. We found that increased tau in the entorhinal cortex was associated with subjective poorer sleep quality cross-sectionally and longitudinally (p=.01, p=.01, respectively). We found no association between sleep duration measured with actigraphy, and Aβ and tau levels at baseline. We found that increased amyloid in the global brain was associated with napping (p=.03, p=.04, respectively). These results suggest that poorer sleep quality observed early in the course of the disease is associated with AD pathology. Poorer sleep quality that worsens over time might represent a risk factor of AD, a consequence of the pathology, or both.
Longitudinal : Effects of dosage and anticholinergic burden of antipsychotics on hippocampal volume and verbal memory in first episode psychosis
2Montreal Neurological Institute-Hospital, McGill University, Montreal, QC, Canada,
3Department of Radiology, University of California San Diego, La Jolla, CA, USA
Corresponding Author: Agnes Belkacem, email email@example.com
Antipsychotics are widely used for the treatment of first-episode psychosis. Results suggest that high dosage and anticholinergic burden may contribute to verbal memory deficits and reduced hippocampal volumes. We therefore sought to examine changes in verbal memory performance and hippocampal volumes in patients compared with controls. We hypothesized that patients would have poorer verbal memory and reduced hippocampal volumes compared to controls and medication burden to be negatively associated with verbal memory and hippocampal volume. First-Episode Psychosis patients, followed by the PEPP-Montreal clinic (n = 74), and non-clinical controls (n = 53) completed a 3T MRI scan and a neurocognitive evaluation (CogState) at 3, 9, 12 and 18 months after admission. Generalized Estimating Equations (GEE) analysis revealed a significant group and time effect for verbal memory performance, for the right CA1 and left dentate gyrus subfield. Significant negative correlations were found between antipsychotic dosage and left CA1, left dentage gyrus, left fimbria and left hippocampus subfields volumes change over time. A significant negative correlation was found between anticholinergic burden and verbal memory performance change over time. As the relationship between antipsychotic treatment, brain volume and cognitive deficits remains poorly understood, this study could provide better insight into the long-term effect of antipsychotics. Given that cognitive deficits and appear in the early stages of psychosis, our results highlight the need to consider anticholinergic burden when prescribing medications.
Prevalence of risk and diagnosis of obstructive sleep apnea in neurological diseases in older adults: A Canadian longitudinal study of aging.
2Translational Research in Respiratory Diseases, Research Institute of the McGill University Health Centre, Montreal, QC, Canada
3Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, QC, Canada
4Mount Sinai Hospital Center, Montreal, QC, Canada
5Department of Neurology and Neurosurgery, McGill University, Montreal General Hospital, Montreal, QC, Canada
6Department of Medicine and Department of Epidemiology, Biostatistics & Occupational Health, McGill University Health Centre, Montreal, QC, Canada
7Research Center, CIUSSS Nord-de-l'Ile-de-Montreal, Montreal, QC, Canada
8Respiratory Division and Sleep Laboratory, McGill University Health Centre, Montreal, QC, Canada
Corresponding Author: Teresa Gomes, email firstname.lastname@example.org
Obstructive sleep apnea (OSA) is a frequent comorbidity in Parkinson’s disease (PD) Alzheimer’s disease (AD) and stroke in clinical populations and is believed to exacerbate neurodegeneration. This study aimed to determine the prevalence of high risk of OSA using different self-reported questionnaires and of self-reported OSA diagnosis, in individuals with PD, AD, stroke compared with the general population (GP) of older individuals. Using data from the Canadian Longitudinal Study on Aging (CLSA) comprehensive cohort, we examined the prevalence of OSA, assessed with different OSA questionnaires: STOP (Snoring, Tiredness, Observed apneas, high blood Pressure) >2, STOP-BAG (STOP, BMI, Age, Gender) >3, STOP-B28 (STOP, BMI) >2 and GOAL (Gender, Obesity, Age, Loud snoring) >2. Logistic regression was performed to obtain odd ratios for high risk of OSA, adjusted for age, sex and BMI, in neurological conditions vs. the GP. In all groups, a positive GOAL was the most prevalent, while STOP had the lowest prevalence of all questionnaires. Compared with the GP, individuals with stroke had increased odds of high OSA risk for each screening questionnaire. Individuals with PD were more likely to have a positive STOP-BAG and GOAL, and those with AD a positive STOP-B28 and GOAL, compared with the GP. OSA was self-reported in a lower proportion compare to the screening tools. Different screening questionnaires present a variation of prevalence of high risk of OSA in older adults with and without neurological disorders. Self-reported OSA diagnosis is underrecognized in older adults. Given the role of OSA in neurodegeneration, strategies should be implemented to improve awareness and diagnosis of OSA in older Canadians.
Endogenous cerebellin 1 protects cerebellar granule cells from amyloid-β oligomers deposition
2Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
3Department of Molecular Biology, University of Montreal, Montreal, QC, Canada
4Department of Neuroscience, University of Montreal, Montreal, QC, Canada
5Department of Medicine, University of Montreal, Montreal, QC, Canada
6Department of Medicine, Division of Experimental Medicine, McGill University, Montreal, QC, Canada
Corresponding Author: Nicolas Chofflet, email email@example.com
Amyloid-β (Aβ) is a key molecule involved in the pathogenesis of Alzheimer’s disease (AD), the most common neurodegenerative disease. Earlier researches have shown that the cerebellum is relatively spared from amyloid deposition compared to other brain regions. We have previously shown that AbO binds to NRX isoforms with alternative splicing site 4 (S4), which Cbln1 also bind to. Thus, we hypothesize that Cbln1 prevents AβO accumulation in the cerebellum by blocking NRXs-AβO interaction. To probe the effect of Cbln1 on NRXs-AβOs interaction, we are using cell surface binding assays in which we applied soluble Cbln1 and AβO proteins on NRX-expressing COS7 cells. To determine whether endogenous Cbln1 can suppress NRXs-AβOs interaction, we treated primary cerebellar neuronal cultures from Cbln1 knockout (KO) mice and WT littermates with AβO protein. Immunostaining and fluorescence microscopy are used as a read out in both assays. Our results revealed that application of Cbln1 completely abolished the binding of AβOs to NRX, but AβO application did not disrupt NRX-Cbln1 binding, suggesting that NRX-Cbln1 complex is resistant to AβOs. Furthermore, AβO treatment in Cbln1 KO cerebellar neurons showed a significant increase of AβO deposition on axons compared to wild-type neurons, and this increase was cancelled by exogenously-applied Cbln1 recombinant proteins, suggesting that endogenous Cbln1 could protect cerebellar neurons from AβOs. Our work revealed that Cbln1 prevents AβOs binding on cerebellar granule cell axons through suppression of NRX-AβO interaction. This study may uncover novel mechanisms explaining selective cerebellar resistance in AD. We are currently assessing whether ablation of Cbln1 leads to increased AβO deposition and pathology in AD model mouse cerebellum.
Exploration of signal-based measures of white matter hyperintensity severity
2Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
3Department of Psychiatry, McGill University, Montreal, QC, Canada
4Department of Biomedical Engineering, McGill University, Montreal, QC, Canada
5McConnell Brain Imaging Center, Montreal Neurological Institute, Montreal, QC, Canada
6Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
Corresponding Author: Olivier Parent, email firstname.lastname@example.org
White matter hyperintensities (WMH), as detected on magnetic resonance imaging (MRI), can be caused by varied microstructural alterations (e.g., oedema and demyelination). However, most studies quantify WMH severity only based on the volume of the lesion. We explore if signal-based measures of WMH severity could be sensitive to microstructural alterations in a cohort spanning the Alzheimer’s Disease (AD) spectrum, with the rationale that clinically relevant signal-based measures will be associated with atrophy and cognition. Multiple MRI sequences (T1w, T2w, fluid-attenuated inversion recovery [FLAIR], quantitative T1, T2*) and cognitive measures were acquired on a total of 118 participants categorized as healthy controls, familial history of AD, mild cognitive impairment, or AD. WMHs were automatically segmented using a validated tool, and the median signal of all MRI sequences inside WMHs was calculated. Cortical Thickness (CT) was estimated with CIVET, and data-driven patterns of CT covariance were detected using non-negative matrix decomposition. In univariate analyses controlling for age and sex, our results show significant associations between T2* and medial temporal lobe CT, Montreal Cognitive Assessment scores, and group differences. In multivariate partial-least squares (PLS) analyses, our results show that T2* is the WMH signal-based measure contributing the most to the pattern of brain variables (atrophy and WMH characteristics) that is related to a pattern of age, visuospatial memory, and language functioning. In sum, T2* signal inside WMHs is associated with cortical atrophy, cognition and AD status, and could be sensitive to clinically-relevant microstructural alterations, thus offering additional information in assessing the WMH burden. Our results warrant the investigation of the sources of T2* signal inside WMHs.
Pharmacological inhibition of Polo-like kinase 2 activity modulates Alzheimer’s disease pathology in a sex-dependent manner
Corresponding Author: Laura Martínez-Drudis, email email@example.com
Phosphorylation plays an important role in the aggregation and toxicity of amyloid beta (Aβ) and Tau, the major neuropathological hallmarks of Alzheimer´s disease (AD). The accumulation of Polo-like kinase 2 (PLK2) in the brain of patients and animal models of AD suggests that PLK2 might play a role in AD pathogenesis. Here, we examined the effect of PLK2 pharmacological inhibition on Aβ and Tau accumulation and toxicity in cells and transgenic mouse models of AD. First, we used co-transfected HEK293T cells to examine the effect of PLK2 overexpression and its inhibition on the amyloid precursor protein (APP) and Tau protein and phosphorylation levels by immunoblotting. Furthermore, we examined the effect of treatment with PLK2 pharmacological inhibitor #37 (PLK2i #37), in two transgenic mouse models of AD, namely 3xTg-AD and APP-PS1 mice, at the behavioral, biochemical and histological levels. Our cell culture results confirmed that PLK2 overexpression modulates APP and Tau protein and phosphorylation levels in a kinase activity dependent manner. In vivo, treatment with PLK2i #37 reduced some neuropathological aspects of AD in 3xTg-AD and APP-PS1 males. Surprisingly, treated females showed an exacerbation of Aβ and Tau pathologies. Overall, our findings indicate that PLK2 pharmacological inhibition alters key components of AD neuropathology in a sex-dependent manner and highlight the importance of sex-specific stratification when assessing AD therapeutic strategies.
Functional role of NaX channels in the magnocellular neurosecretory cells of the supraoptic nucleus of rats
2Department of Physiology, Biophysics and Neurosciences, Centre for Research and Advance Studies, Mexico
Corresponding Author: Sandra Salgado , email firstname.lastname@example.org
Body fluids are continuously monitored to regulate the electrolyte-water balance. The central monitoring of this process occurs at the circumventricular organs which lack blood-brain-barrier. Neurons in these structures are in contact with peripheral blood and cerebrospinal fluid, and they project to the magnocellular neurosecretory cells (MNCs) in the supraoptic (SON) and paraventricular nuclei (PVN). We hypothesized that MNCs can detect the extracellular sodium concentration ([Na+]o) through the sodium channel NaX. Although this channel is somewhat homologous to voltage-gated sodium channels (VGSCs), it differs from the other family members, including in key regions for voltage sensing and inactivation. Moreover, NaX channels are tetrodotoxin-resistant. Voltage and current-clamp recordings were obtained at the whole-cell configuration from identified MNCs VP and OT. In all slice experiments involving high Na+ stimulation, a period of 3 minutes of stable baseline activity was followed by bath application of hypernatremic ACSF. By using an AVV, we knockdown the NaX expression on the SON and we did the analysis of neuronal activity using c-fos. We demonstrated that both vasopressin and oxytocin, MNCs express NaX channels. Functionally, MNCs respond to a hypernatremic-isoosmotic stimulus with a depolarisation that increases their firing rate. This depolarisation temporally correlates with an inward current whose reversal potential corresponds to the equilibrium potential for sodium. In addition, the NaX current magnitude was dependent of the [Na+]o . The NaX current was isolated by blocking other sodium permeability pathways that are present in MNCs, such as VGSCs, epithelial sodium channels (ENaCs) and TRPV1 channels. Finally, we demonstrated that virally-mediated knockdown of NaX channels in MNCs reduced their electrophysiological response to physiological stimulus (hyperosmotic-hypernatremic) in vitro, as well as the sodium-mediated increase in c-fos expression in vivo. The present study indicates that MNCs of the rat SON are intrinsic detectors of [Na+]. We demonstrated in slices and isolated cells, that increases in [Na+] evoke a depolarisation that results from a Na+ inward current which increases the firing rate. In addition, we showed NaX is not expressed in astrocytes, and that astrocytes are not required for the Na-induced response. Finally, we demonstrated, in vivo and in vitro, that knockdown of NaX channels on MNCs decreased the response to a high Na+ stimulus.
Neuron-specific alterations in organelle function and trafficking in VPS35[D620N] patient dopaminergic neurons and mouse cortical neurons
Corresponding Author: Yuting Zhang, email email@example.com
VPS35 is important for endolysosomal and mitochondrial homeostasis, two extremely interdependent pathways. The PD-linked D620N variant shows altered interaction with proteins that regulate both processes. Impaired mitochondrial network morphology, respiratory function, and endolysosomal clearance have been reported in D620N mutant systems, but results are contradictory. It is unclear whether dysfunction in endolysosomes and mitochondria arise concurrently due to mutation effects on key interactions, or if one or other pathway is altered downstream of the other. hiPSC-derived neuronal neuronal culture, mouse primary culture, immunofluorescence, live-imaging, CRISPR-generated VPS35 knock-out COS7 cells and rescue by transfection of GFP-tagged VPS35 (WT and D620N) constructs VPS35 patient-derived neurons exhibit fewer and fragmented mitochondria, as well as altered colocalization between VPS35 and the mitochondrial fission protein DRP1. In COS7 cells, VPS35 knock-out cells show a subtly fragmented mitochondria network, which was ameliorated by expression of GFP-VPS35-WT but not GFP-VPS35-D620. VPS35 knock-out COS7 cells also showed increased localization of DRP1 to mitochondrial tubules which was increased by both GFP-VPS35-WT and GFP-VPS35-D620N expression. GFP-VPS35-D620N exhibited reduced colocalization with DRP1 when compared to GFP-VPS35-WT. In neurons, function and even morphology of endolysosomes and mitochondrion vary based on the neuronal compartment that they are localized to. Therefore, it is important to consider the spatial profile of these organelles in order to understand retromer dysfunction caused by the D620N variant in neurons.
Insulin promotes RGC dendrite regeneration through ribosomal protein S6 kinase activation leading to restoration of neuronal function in glaucoma
Corresponding Author: Sana El Hajji, email firstname.lastname@example.org
We previously demonstrated that insulin promotes RGC dendrite regeneration through activation of the mTOR pathway. However, the precise mechanisms of insulin-mediated regeneration and the effect of insulin on vision restoration are not well understood. Here, we asked: 1) what are the mTOR downstream effectors responsible for insulin-induced dendritic regrowth? 2) does insulin restore RGC function and visual responses in glaucoma? Ocular hypertension (OHT) was induced by injection of magnetic microbeads in Thy1-YFP mice. Daily insulin or saline eye drops started at 2-weeks of OHT, dendrites were imaged and reconstructed 1 or 4 weeks later. The role of the mTORC1 downstream effectors, S6K and 4EBP1, was assessed by loss of function using targeted siRNAs. RGC survival and function were evaluated using: RBPMS-positive neurons counting, single-RGC calcium dynamics using live-imaging in Thy1-GCaMP6f transgenic mice, and optomotor assays. Insulin promoted a substantial increase in RGC dendritic length and complexity in glaucomatous eyes (p<0.001). siRNA-based knockdown of S6K impaired insulin-mediated RGC dendrite regeneration, while 4EBP1 silencing had no effect. Intriguingly, S6K increased mTORC2 activity through phosphorylation of mSIN1 enhancing RGC dendrite regeneration. Insulin promoted robust RGC survival at 3 and 6 weeks of OHT induction relative to saline (p<0.001). Importantly, insulin restored light-evoked RGC calcium dynamics (p<0.01) and improved visual acuity (p<0.01) in glaucoma Our data show that S6K is a key signaling component required for insulin-mediated RGC dendrite regeneration, an effect that is enhanced by cross-talk with mTORC2 through mSIN1 activation. Importantly, insulin prevents RGC loss while restoring light-evoked responses and visual acuity. These findings support a critical role for insulin as a pro-regenerative therapy and identify downstream targets to restore RGC connectivity and function in glaucoma.
Compromised stress granule response in the CNS of TDP-43 M337V mice
2Department of Neuroscience, Université de Montreal, Montreal, QC, Canada
3Department of Biochemistry, Université de Montreal, Montreal, QC, Canada
4Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, United Kingdom
Corresponding Author: Alicia Dubinski, email email@example.com
Responding effectively to external stress is crucial for neurons. Defective stress granule dynamics have been hypothesized as one of the pathways that renders motor neurons in amyotrophic lateral sclerosis (ALS) more prone to early death. Specifically, it is thought that stress granules seed the cytoplasmic TDP-43 inclusions that are observed in the neurons of most ALS patients and 50% of frontotemporal dementia (FTD) patients. In this study, we tested this hypothesis in the mammalian nervous system. Using two genetic ALS mouse models as well as aging mice, we established an in vivo heat stress paradigm in mice that effectively triggers the eIF2alpha pathway and the formation of stress granules in the CNS. In non-transgenic mice, we report an age-dependent decline in the formation of heat-induced stress granules, with 18-month-old animals showing a significant impairment. While neuronal stress granules were robustly observed in non-transgenic mice and SOD1 G93A mice, they were largely absent in aged matched TDP-43 M337V animals. Lastly, while TDP-43 was not localized to stress granules, we observed complete nuclear depletion of TDP-43 in a subset of neurons, with the highest proportion being in the TDP-43 M337V mice. Overall, our results indicate that mutant TDP-43 expression is associated with defective stress granule assembly and increased TDP-43 nuclear depletion in the mammalian nervous system, which could be relevant to ALS/FTD pathogenesis.
rAAV–CRISPRa gene therapy corrects Rai1 haploinsufficiency and alleviates multiple disease features in a mouse model of Smith–Magenis syndrome
2Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montréal, QC, Canada
Corresponding Author: Dr. Wei–Hsiang Huang, email firstname.lastname@example.org
Smith-Magenis Syndrome (SMS) is a neurogenetic disorder characterized by excessive weight gain and autistic features. SMS is caused by haploinsufficiency in retinoic acid-induced 1 (Rai1), which encodes a brain enriched transcription factor and is a dosage-sensitive gene expressed in many tissues and highly conserved among species. However, curative treatments for SMS do not exist. We identified a single guide RNA (sgRNA) that when coupled with a single vector recombinant adeno–associated virus (rAAV)–CRISPR activation (CRISPRa) system, can sufficiently increase mouse neuronal Rai1 expression. Given a central role of paraventricular nucleus of hypothalamus (PVH) neurons in SMS pathogenesis, we tested if SMS-like neurobehavioral and obesity features in mice can be rescued by delivering the rAAV–CRISPRa system into the PVH during adolescent stage. By identifying a sgRNA that targets Rai1 proximal promoter and stimulates Rai1 expression in vitro, we found that PVH–specific rAAV–CRISPRa therapy successfully increased endogenous Rai1 expression from the remaining intact allele and effectively rescued the excessive repetitive behavior in SMS mice. This treatment also delayed the onset of obesity and partially reduced excessive weight gain in SMS mice by reducing food intake. Our work provides evidence that localized gene–regulatory therapy reverses Rai1 haploinsufficiency and improved multiple disease features in a preclinical mouse model of SMS. If successful, this project will reveal the therapeutic potential of the remaining functional copy of Rai1 in the PVH of SMS mice and provide critical preclinical evidence to facilitate the development of SMS therapy.
Exploration du connectome moteur de la formation réticulée médullaire par apprentissage automatisé
2Department of Psychiatry and Neuroscience, Faculty of Medicine, Université Laval, Québec, QC, Canada
Corresponding Author: Frédéric Bretzner, email email@example.com
D’anciennes études ont rapporté que les populations réticulospinales projetteraient de façon divergente sur la moelle épinière, des récentes études génétiques chez la souris montrent une ségrégation des populations en fonction de leur projection spinale. Nous émettons l’hypothèse que les populations réticulospinales s’organisent topographiquement en groupes de neurones contrôlant spécifiquement le membre antérieur ou postérieur via le circuit spinal cervical ou via le circuit spinal lombaire et un 3ème contrôlant simultanément le circuit cervical et lombaire. Des souris VGluT2-cre adultes ont reçu une injection d’un AAV-DiO-mCherry dans le segment lombaire droit et une injection d’un AAV-Flex-eGFP dans le segment cervical gauche. Dans une autre expérience, les souris ont été injectées avec ces deux virus dans le segment lombaire gauche et droit. Trois semaines plus tard, les tissus nerveux ont été coupé et des images ont été prises par microscopie. Les neurones marqués ont été identifiés à l’aide d’un logiciel d’apprentissage automatisé. Nos résultats nous permettent de cartographier les populations glutamatergiques du GI en fonction de leur projection dans la moelle épinière. En conclusion, nous avons développé une méthode pertinente permettant une analyse avancée de la distribution et de l’organisation topographique des neurones réticulospinaux glutamatergiques au niveau du tronc cérébral et en particulier des neurones glutamatergiques impliqués dans le contrôle moteur et locomoteur.
Improvement of wrist motricity in thalamic stroke: combination of repetitive peripheral magnetic stimulation (rPMS) and virtual reality-based rehabilitation
2Faculté de Médecine, Université Laval, Québec, QC, Canada
3Département de réadaptation, Université Laval, Québec, QC, Canada
Corresponding Author: Uziel Miguel Rayas Hernandez, email firstname.lastname@example.org
People with thalamic stroke hardly respond to physical/occupational therapy. Virtual reality-based rehabilitation using the RAPAEL smart glove (Neofect, Germany ©) could improve the gains. However, patient fatigue is a concern against virtual therapy regimens needed (1h per day). rPMS of paretic muscles influences the primary motor cortex (M1) plasticity and can improve the function in cortical stroke. It is thus questioned whether the combination rPMS + RAPAEL-virtual-therapy could immediately trigger functional changes in thalamic stroke. A man with spastic hemiparesis (73 years-old, right-hemispheric stroke 5 years ago, right-handed) was tested in 8 sessions: rPMS only (S1), combo rPMS-RAPAEL (S2-S6), follow-ups post-S6 (1 week, 1 month). Wrist flexion-extension, wrist flexors resistance to stretch, grip strength and corticospinal excitability (by magnetic stimulation of M1) were tested at pre/post-S1, pre/post-S2, post-S6 and follow-ups. At S2-to-S6, directly after rPMS, the participant wearing the smart glove was involved in 10-min serious games entraining wrist flexion-extension. rPMS alone significantly decreased wrist flexors resistance to stretch, increased wrist range of motion (ROM) with gravity eliminated (neutral position) and increased grip strength. The combo rPMS + RAPAEL-training (S2-to-S6) further improved these outcomes and increased wrist ROM against gravity (S2-to-S6). These changes were paralleled by corticospinal changes and correlations detected a link between motor improvements and M1 plasticity. Changes were still present at one week and one month after the last rPMS+RAPAEL session. Rapid significant wrist motor improvement in chronic thalamic stroke and persistence over a month are original findings. The virtual therapy using RAPAEL smart glove may have oriented and potentiated/lengthened the after-effects of rPMS on the circuits recruited by movement training. This should be replicated in larger stroke groups.
Age-dependent changes of the morphofunctional integrity of the human neuromuscular junction.
2Groupe de Recherche sur la Signalisation Neurale et la Circuiterie, Université de Montréal, Montreal, QC, Canada;
3Département des Sciences de l’Activité Physique, Université du Québec à Montréal, Montreal, QC, Canada;
4Département de Recherche en Activité Physique Adaptée, Université du Québec à Montréal, Montreal, QC, Canada;
5Centre de recherche de l’Institut Universitaire de Gériatrie de Montréal, Université de Montréal, Montreal, QC, Canada;
6McGill University Health Centre, Research Institute and Geriatric Medicine, Faculty of Medecine, McGill University, Montreal, QC, Canada;
7Centre Interdisciplinaire de Recherche sur le Cerveau et l’Apprentissage, Université de Montréal, Montreal, QC, Canada
Corresponding Author: Sandrine Marchand, email email@example.com
Several changes occur in normal aging contributing to a loss of skeletal muscle mass and function. A key factor contributing to muscle changes is the alterations of neuromuscular junctions (NMJ). NMJs are tripartite synapses composed of a presynaptic nerve terminal, postsynaptic fiber and perisynaptic Schwann cells (PSCs). However, the human NMJ remains largely understudied We used an adapted needle biopsy method to study the morphofunctional alterations in aging. The cohort was composed of 4 young (18-30 years) and 5 older adults (over 55 years). Several physiological measurements (physical activity level, muscle strength, etc.) were assessed prior to the biopsy. Biopsy samples were stained by immunohistochemistry for the nerve terminal (NFM/SV2), postsynaptic nAChRs (α-btx), PSCs (s100β) and fiber type (MHC I) and imaged using confocal microscopy. Human NMJs have a very distinct organisation compared to rodent NMJs, especially regarding postsynaptic and PSCs morphology. Comparative analyses revealed that the NMJ structure remained had an higher instability in aging. Indeed, a larger number of denervated NMJs and lower glial coverage were observed in older individuals. These data were correlated with the participants’ physiological data to identify which NMJ parameters better reflect the physiological state of each individual Taken altogether, aging leads to alterations of the NMJs which correlates with altered neuromuscular function. Our results will provide a better understanding of neuromuscular aging and develop better therapeutic approaches to limit muscle weakening in aging.
Determining the in-vivo roles of TRKC-PTPσ interaction in synapse development
2Molecular Biology program, Faculty of Medicine, Université de Montréal, Montreal,QC, Canada
3Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
4Division of Experimental Medicine, McGill University, Montreal, QC, Canada
Corresponding Author: Husam Khaled, email firstname.lastname@example.org
Synaptic organizing complexes are trans-synaptic adhesion molecules that can promote pre- and post-synaptic differentiation necessary for normal synapse development. Dr. Takahashi’s lab has previously identified TrkC-PTPσ as a novel synaptic organizing complex, which through in vitro data was shown to promote only excitatory synapse development. The genes coding for TrkC and PTPσ are genetically associated with anxiety disorders and autism respectively. It is not well understood how this complex regulates excitatory synapse development in vivo. We have generated a mutant mouse line that completely abolishes TrkC-PTPσ interaction. Using this line, I am working on characterizing the biochemical and structural phenotypes of excitatory synapses in the mutant mice, as well as determine the role of this interaction and its effect on the synapse. Eventually, I would also like to determine the behavioural phenotypes in these mice. We have validated through co-immunoprecipitation the complete loss of interaction between TrkC and PTPσ in mutant mice. Our immunohistochemistry data show that TrkC is most strongly expressed in the hippocampal brain region. In contrast to the previously published in vitro data, the loss of this interaction in vivo does not lead to excitatory synapse loss. However, our preliminary data show the expression of other proteins may indicate some synapse function changes in these mutant mice. My project will shed light on the role of this complex in excitatory synapse development and function in vivo and how its impairment can lead to cognitive dysfunction, as well as enable the development of novel therapeutic strategies.
Intraindividual stability of gene expression and immune repertoire throughout the cryopreservation process.
2Universite de Montreal - CHUM, Neurology, Montreal, QC, Canada
Corresponding Author: Rose-Marie Rébillard, email email@example.com
Biobanking of patient material has become instrumental in both fundamental and clinical research. The availability of cryopreserved peripheral blood mononuclear cells (PBMC) greatly simplifies experimental design and effectively reduces intraexperimental batch effects as all samples can be processed in a short lapse of time. The use of cryopreserved PBMCs holds great potential for the identification of disease predictors in multiple sclerosis (MS), but it is essential to confirm the intraindividual stability of gene expression, immunophenotype, and immune repertoire throughout the cryopreservation process. Our goal is to assess the stability of gene expression and T cell repertoire of fresh versus frozen PBMC samples from MS patients and healthy control. Single-cell RNA Sequencing (scRNA-Seq) using 10X Genomics technologies was used to perform an in-depth characterization of the transcriptome and the T cell repertoire of PBMCs from 2 untreated relapsing-remitting MS patients and 2 healthy controls. For each subject, a fraction of the PBMC sample was processed immediately and the rest was frozen in liquid nitrogen for processing after two timepoints of cryopreservation; 2 days and 10 months. Our correlation analysis showed that the gene expression is highly preserved through cryopreservation with a R of 0.99 and a p value of < 0,0001 in each paired comparison for each donor. Moreover, clustering of the samples based on the most variable genes showed perfect segregation of samples belonging to the same individual. Clonality and diversity of the T cell repertoire, as well as the proportion of clusters based on the sequence of the T cell receptor sequence, were also highly preserved. Our data demonstrates a highly preserved PBMC profile at the transcriptome level over cryopreservation time, confirming that biobanked PBMCs are suitable for projects using scRNA-seq on large cohorts.
Investigating a dysregulated immune response in the gut underlying early Parkinson’s disease symptoms in a prodromal model
2Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
3Department of Pharmacology and Physiology, Deptartment of Neurosciences, Université de Montreal, Montreal, QC, Canada
4Department of Pathology and Cell Biology, Université de Montreal, Montreal, QC, Canada
Corresponding Author: Sherilyn Junelle Recinto, email firstname.lastname@example.org
Parkinson’s disease (PD) is characterized by Lewy pathology and progressive loss of dopaminergic neurons in the substantia nigra pars compacta of the brain, leading to motor impairments. Decades prior to clinical diagnosis, PD patients often already manifest various autonomic dysfunctions, including constipation. However, little is known about the mechanisms at play during the evolution of disease partly due to the lack of PD models able to recapitulate the protracted nature of neurodegeneration originating in the gut. To this end, we aim to further characterize a mouse model, where our collaborators showed that intestinal infection triggers PD-like motor impairment in PTEN-induced kinase 1 (Pink1)-deficient mice. We performed spatiotemporal analyses across the gut-immune-brain axis using immunohistochemistry, flow cytometry, and single cell RNA sequencing in Pink1-deficient and WT mice following bacterial infection in the gut. Our preliminary data suggests that Pink1-deficient mice, prior to onset of motor symptoms and following gut infection, displayed constipation and excessive intestinal inflammation pointing to a dysregulation in the innate immune response, as drivers of early disease. Whether these observations are mechanistically related and result in the eventual loss of dopaminergic neurons in the gut are currently under investigation. Taken together, we suggest that bacterial infection in the gut first engenders an impaired innate immune response that may induce peripheral neuronal damage, and consequently underlies constipation, after which pathology propagates to the brain instigating motor deficits in response to repeated infections.
Coping with the pandemic: Perceptions of caregivers of youth with neurodevelopmental disabilities on the impact of COVID-19
2School of Physical and Occupational Therapy, McGill University, Montreal, QC, Canada.
Corresponding Author: Anna Katalifos, email email@example.com
Youths with neurodevelopmental disabilities (NDDs) and their caregivers have experienced high levels of mental health complications during the COVID-19 pandemic (Summers et al., 2021). Canadian governments have published public service strategies to address these challenges. Nonetheless, evidence suggests that Canadian caregivers of youth with NDDs struggle to cope during the pandemic, notably experiencing a lack of supports and managing the worsening of the child’s symptoms in isolation (Gonzalez et al., 2021). The objective of this study is to describe caregiver barriers and facilitators to coping during the pandemic. The data sources consisted of open-ended question responses completed by Canadian caregivers of youth with NDDs (n=573) in the WHO Global Report Survey on Developmental Delays, Disorders, and Disabilities. We conducted a thematic analysis involving inductive and deductive coding to interpret qualitative data using NVivo software. Participants reflected on what made it hard or easier for them to cope during the pandemic. The predominant barriers to coping were mental health complications experienced by both caregivers and their youth. Caregiver stressors were related to the loss of public services, working from home while caregiving, online schooling, and heightened family conflict. Alternatively, parents pointed to virtual media entertainment, more time spent with family, and maintaining hygiene within the home as facilitators for coping. Decision-makers should take into consideration what youth with disabilities and their families value while coping during a global health emergency. The identified facilitators and barriers are promising avenues for future research into fostering resilience and tailoring support for families of youth with NDDs during adversity.
Loss of Rai1 enhances hippocampal excitability and epileptogenesis in mouse models of Smith-Magenis syndrome
2Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montréal, QC, Canada
3Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
4Department of Biology, Stanford University, Stanford, CA, USA
5Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
Corresponding Author: Wei-Hsiang Huang, email firstname.lastname@example.org
Hyperexcitability of the brain circuit is a common feature of autism spectrum disorders (ASDs). Genetic deletion of retinoic acid induced 1 (RAI1) causes Smith-Magenis syndrome (SMS), a syndromic ASD associated with intellectual disability, autistic features, maladaptive behaviors, overt seizures, and abnormal electroencephalogram (EEG) patterns. The molecular and neural mechanism underlying abnormal brain activity in SMS remain unclear. Kainic Acid-induced seizure model is conduced in neuron and cell type specific Rai1 knock out mice. iDISCO, EEG, field potential recording, and whole-cell recording are applied for examine neuronal activity. Here we show that pan-neural Rai1 deletion results in increased seizure susceptibility in mice. Brain-wide mapping of neuronal activity pinpointed that selective cell types within the limbic system including the hippocampal dentate gyrus granule cells (dGCs) are hyperactivated by chemoconvulsant administration or sensory experience in Rai1-deficient brains. Rai1 deletion increased dGC neuronal population spikes ex vivo and prolonged time spent in seizure state in vivo. Glutamatergic but not gamma-aminobutyric acidergic (GABAergic) specific Rai1 deletion was responsible for increased seizure susceptibility in vivo. Specifically, deleting Rai1 from the Emx1Cre–lineage forebrain glutamatergic neurons resulted in increased excitatory synaptic transmission and increased intrinsic dGC excitability. Our work uncovers the mechanism of hyperexcitability in SMS by identifying Rai1 as a novel regulator of dGC intrinsic excitability.
Characterization of the interaction between pathological α-synuclein and synaptic cell adhesion molecule neurexins
2Department of Medicine, Université de Montréal, Montréal, QC, Canada
3Integrated program in Neuroscience, McGill University, Montréal, QC, Canada
4Montreal Neurological Institute, McGill University, Montréal, QC, Canada
5Department of Chemistry, Université du Québec à Montréal, Montréal, QC, Canada;
6Division of Experimental Medicine, McGill University, Montréal, QC, Canada
Corresponding Author: Nicolas Chofflet, email Nicolas.email@example.com
Synucleinopathies are a group of neurodegenerative diseases that imply the misfolding and aggregation of alpha-synuclein (α-syn), Additionally, α-syn is able to spread between cells in a prion-like manner. Although the responsible mechanisms for this process are still unclear, our screening of synaptic membrane proteins has revealed neurexin (NRX) family members, an important family of synaptic cell adhesion molecules, as strong ligands for α-syn aggregates. We hypothesized that NRXs participate in the trans-synaptic propagation of α-syn. Using cos7 or primary hippocampal neuron culture transfected with neurexin constructs, α-syn preformed fibrils (SynPFF) are extracellularly applied and their binding capability is analyzed through fluorescent microscopy. Our cell-based and cell-free binding assays both revealed a dissociation constant in the nanomolar range (~500nM). Finally, we showed that α-syn specifically interacts with the β-isoforms of NRXs (NRXβ) through their unique histidine rich domain. We are currently assessing whether and how NRXβ mediate α-syn internalization and propagation in vitro using biotin surface labelling and colocalization experiments as well as the monitoring of the phosphorylated α-syn accumulation in neuron culture. Those data will help to identify whether and how NRXs are involved in SynPFF propagation between neurons, thus supporting the trans-synaptic hypothesis. In vivo studies using mutant mice lacking the HRD will be also performed to evaluate the role of NRX in synucleinopathy development.
Pattern of cognitive impairment among Parkinson’s disease patients with subjective cognitive complaints
Corresponding Author: Alexander Bailey, email firstname.lastname@example.org
Subjective cognitive complaints (SCCs), the sensation that one’s cognitive abilities do not feel the same as they used to (i.e., feeling more forgetful), are common symptoms in Parkinson’s disease (PD). While a recent study found that later cognitive decline in PD can be predicted based on the presence of SCCs, not all areas of cognition are affected early in PD. Additionally, patients’ sense of decline may be more sensitive to deficits in certain cognitive domains. Using data collected from the Quebec Parkinson Network, we seek to examine whether impairments in different cognitive domains are differentially associated with the presence of SCCs among PD patients (currently, n=66) without mild cognitive impairment (MoCA>25). Participants underwent neuropsychological testing during an “On” dopaminergic state. Our analyses consist of composite scores of cognitive domains such as attention (e.g., Trail Making Test A), executive function (e.g., Stroop Interference), and memory (e.g., Hopkins Verbal Learning Test–Revised). Our preliminary results suggest that PD patients with SCCs (namely, exhibiting slight, mild, and moderate levels of complaint) performed worse than PD patients without SCCs in domains of attention (p =.018) and executive function (p =.0074). Using logistic regressions to model the relationship between cognitive domain performance and SCC presence – controlling for confounds on other domains of function, demographic factors, and disease duration – only deficits in executive function were associated with SCC presence (p =.0019). Our results suggest that the earliest impact of PD neurodegeneration is on executive function, possibly related to changes in dopaminergic and noradrenergic transmission, which are known to occur early in the disease. Our findings may also reflect greater sensitivity to executive function changes, compared to other domains of function.
Symptomatic neonatal seizure management and postneonatal epilepsy : A retrospective single center study
Corresponding Author: Alejandra Martinez, email email@example.com
Seizures are the most common sign of neurological injury in the neonatal period. While seizures themselves may have consequences on brain development, the prescribed antiseizure medications (ASM) may also contribute to detrimental neurodevelopmental outcomes. The objective of this study was to evaluate the impact implementing a neonatal seizure treatment protocol, the factors influencing ASM maintenance at discharge and the influence of ASM duration and other clinical factors on risk of seizure recurrence. Retrospective chart review of term newborns born between 2013 and March 2021 with acute symptomatic seizures presenting before 44 weeks post-menstrual age. The algorithm to guide treatment of neonatal seizures at Sainte-Justine-Hospital was put in place in July 2016. Findings analyzed using Student T-test and Fisher exact test. Of 135 term newborns with acute symptomatic seizures, 97 had HIE (72%). ASM continuation at discharge was not associated with seizure recurrence and postneonatal epilepsy. Seizure burden (p<0.001, OR8.13, [3.33-19.82]), EEG/aEEG seizure (p<0.001, OR 10.58, [4.73-23.67]) and ≥ 3 ASMs to control acute seizure (p<0.001, OR 4.33, [1.89-9.92]) associated with ASM continuation at discharge. Only abnormal neurological exam (p=0.003, OR 6.3, [1.85-21.47]) at discharge was associated with post neonatal epilepsy. The protocol did not significantly change ASM prescriptions habits during NICU stay and at discharge. In our cohort, clinical variables associated with continuation of ASM at discharge were not the ones associated to postneonatal epilepsy. No association was found between ASM maintenance at discharge and postneonatal epilepsy. Highlights the importance of re-evaluating ASM use before discharge and discontinuing ASMs when no longer necessary.
Re-examining adult hippocampal neurogenesis in the human brain
2Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
3Department of Psychiatry, McGill University, Montreal, QC, Canada
4Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada
Corresponding Author: Sophie Simard, email firstname.lastname@example.org
Neurogenesis is a phenomenon where new neurons are generated from neural precursor cells. The existence of neurogenesis in the adult human hippocampus was first suggested approximately twenty years ago. In recent years, however, the existence of adult hippocampal neurogenesis (AHN) in humans has been widely debated. Here, using novel approaches, we aim to determine whether AHN does indeed occur in humans. We used the 10X Genomics Visium Spatial Gene Expression technology on sections from frozen hippocampal samples (Douglas-Bell Canada Brain Bank) from young and middle-aged male adults. To identify the specific cell-types involved in neurogenesis in the subgranular zone (SGZ) of the dentate gyrus (DG), we also performed RNAscope (Advanced Cell Diagnostics) on sections from frozen-fixed DG samples from middle-aged male adults with probes directed against neurogenic markers. Our preliminary results from the Visium platform show expression of different neurogenic markers, including DCX and NCAM1, proxy markers of immature granule neurons, in spots contained in the cluster corresponding to the SGZ. With RNAscope, we identified DCX and NCAM1 expression in the SGZ in both SLC17A7+ cells and GAD1+ cells, suggesting that DCX and NCAM1 expression in this region may not be specific to immature granule cells. These preliminary findings are in agreement with the recent literature suggesting that DCX and NCAM1, although present in the SGZ, are potentially insufficient to define immature granule neurons in the adult human DG.
A study of human mutations in the gene encoding the tyrosine kinase receptor EPHB2.
2Integrated Program in Neuroscience, McGill University, Montréal, QC, Canada
3Oxford University, Oxford, UK
4IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
5Amsterdam UMC, Amsterdam, Netherlands
6University of Bergen, Bergen, Norway
7St George’s University of London, London, UK
8Instituto de Neurociencias, Alicante, Spain
9University Hospital Essen, Essen, Germany
Corresponding Author: Artur Kania, email email@example.com
Aberrant neural development often results in neurological disorders affecting nervous system function and may even be fatal. In the nervous system, contact-mediated cell to cell signaling between Erythropoietin-producing hepatoma receptor tyrosine kinases (Eph RTKs) and Eph-receptor interacting ligands (Ephrins), so-called the Ephrin-Eph signaling, regulates axon guidance and synaptic function. Dysfunction of EphB2 has been shown to generate neurodevelopmental defects in animal models. However, the link between neuropathology and human EPHB2 mutations remains tenuous. We use multidisciplinary approach combining human genetics, structure biology, and molecular/cellular biology. Based on clinical profiles of patients with mutations in EPHB2 gene, we categorize symptoms of patients and analyze the extent of diseases. By analyzing structural impacts of each mutation on EphB2 protein and using computational prediction, we develop hypothetical models of etiology in mutations. Lastly, we verify our hypotheses using molecular/cellular experimental techniques as well as in vivo experiments in model mice. Our data show that mutations in the gene encoding EPHB2 disrupt proper EphB2 functions such as ephrin binding, surface targeting, endocytosis, and phosphorylation. Consistently, structure analysis on EPHB2 mutations suggests that our mutations cause conformational change and instability, resulting in defective EphB2 functions. Our results suggest that mutations in the gene encoding the human EphB2 receptor could be a risk factor for abnormal development of corpus callosum in humans.
The effects of MDMA on fluid balance in rats
2Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montréal, QC, Canada
Corresponding Author: Joshua Wyrosdic , email Joshua.Wyrosdic@mail.mcgill.ca
Thirst is one of the primordial emotions experienced by humans, and animals. Excessive thirst causing inappropriately high-water intake (polydipsia) coupled to excessive vasopressin release can lead to dilutional hyponatremia. This life-threatening condition that causes rapid swelling of the brain is commonly encountered in critical care medicine. For example, it occurs commonly following heart attacks, traumatic brain injury, and notably following ingestion of the common street drug MDMA. To investigate the neurophysiological mechanisms underlying these effects horizontal brain slices obtained from AVP-eGFP transgenic rats were prepared at a specific angle to preserve circuitry important for the regulation of thirst and vasopressin release. Whole cell current clamp, and voltage clamp recordings from identified vasopressin neurons revealed that a bath application of MDMA causes an excitatory response; mediated in part by membrane depolarization. These results suggest that MDMA can act directly on neurons controlling fluid balance and could underly the emergence of MDMA-induced hyponatremia Findings could not only aid in MDMA associated hyponatremia but could also provide the foundation clinically for fluid regulation during MDMA assisted psychotherapy.
How tuberous sclerosis causes brain circuit miswiring through molecular and neural changes
Corresponding Author: Dr. Wei-Hsiang Huang, email firstname.lastname@example.org
Tuberous Sclerosis Complex (TSC) is a rare genetically defined neurodevelopmental disorder caused by a mutation in one of two TSC genes (Tsc1 or Tsc2), making the gene defective and cause greater mTOR signaling. Tsc2 will be the focus since patients experience more severe intellectual and behavioral impairment. A consistent finding in TSC patients is hyperactivation of mTOR signaling. This likely generates changes in neuronal properties and improper fiber growth contributing to seizures and intellectual disabilities. Genetically engineered mice containing a fluorescent protein to label granule cells will be used to analyze their various aspects and their environment, including effects of Tsc2 on cell activity, mTOR signaling, and fiber growth. The intellectual and behavioral effects will also be examined by performing behavior/learning tests in mice. The same aspects will then be re-examined after a Rapamycin treatment, a drug known to reverse the effects Tsc2 has on mTOR signaling. The preliminary data found that dGC-specific Tsc2 deletion induces TSC-like phenotypes. This includes significantly increased c-fos and pS6 signals, demonstrating an elevated cellular activity and mTOR hyperactivation. For morphology, cellular tracing is expected to demonstrate abnormalities such as: increased axon length and cross-sectional area, ectopic axonal growth, increased synaptic bouton volume and density, and increased dendritic arborization. For behavior, the knockout mice are expected to perform poorer in both the sociability and learning/memory tests. The study will characterize the cellular, morphological, and behavioral effects of adult born dGC-specific Tsc2 deletion and determine the reversibility of each phenotype by rapamycin. This creates an opportunity to better characterize the properties and uncover the causes behind hyper-excitable neuronal membranes in brain regions of various epilepsy models.
Modulation des comportements d'anxiété par les afférences sérotoninergiques du raphé à l'hippocampe ventral chez les femelles
2Département de Neurosciences, Université de Montréal, Montréal, QC, Canada
Corresponding Author: Bénédicte Amilhon, email email@example.com
L’hippocampe est une région cérébrale qui présente une grande hétérogénéité fonctionnelle. L'hippocampe dorsal (dHP; postérieur chez l'homme) a un rôle central dans la mémoire spatiale, tandis que l'hippocampe ventral (vHP; antérieur) est associé à la mémoire émotionnelle, ainsi que la régulation de l’expression des comportements d’anxiété et de dépression. Les neurones sérotoninergiques (5-HT), situés dans les noyaux du raphé, envoient des projections denses à l’HPv qui sont essentielles à la régulation de ces processus émotionnels. Des résultats obtenus par notre laboratoire montrent que l’activation optogénétique des neurones 5-HT du raphé qui projettent à l’HPv influence le niveau d’anxiété des souris femelles, mais pas des mâles. En se basant sur ces résultats, l’objectif de mon projet est d’explorer les causes de ce dimorphisme sexuel de la voie raphé-HPv dans l’anxiété. J’analyserai l’expression du marqueur d’activation c-fos après un test d’anxiété, avec ou sans activation optogénétique de la voie 5-HT raphé-HPv. Notre hypothèse est qu’il existe une différence mâle-femelle dans l’excitabilité des neurones 5-HT projetant à l’HPv. Les résultats obtenus permettront de mettre en lumière i) l’expression de c-fos dans les neurones 5-HT qui projettent à l’HPv en conditions basales (eYFP) chez les mâles et femelles et ii) la différence dans l’expression de c-fos après activation optogénétique de notre population d’intérêt chez les mâles et femelles. Ce travail permettra de mieux comprendre les mécanismes qui sous-tendent le rôle de la voie 5-HT raphé-HPv dans la modulation différentielle des comportements d’anxiété selon le sexe.
Increased insoluble Filamin A concentrations in post-mortem brain tissue during mid-stage Alzheimer’s disease
2Centre de recherche du Centre hospitalier de l'Université de Montréal, Montréal, QC, Canada
3Montreal Neurological Institute, Montréal, QC, Canada
4Faculté de pharmacie de l’Université Laval, Québec, QC, Canada
5Centre de recherche du Centre hospitalier de l'Université Laval, Québec, QC, Canada
6Département de neurosciences Université de Montréal, Montréal, QC, Canada
7Rush Alzheimer’s Disease Center, Chicago, IL, USA
Corresponding Author: Étienne Aumont, email firstname.lastname@example.org
While Alzheimer’s disease (AD) is principally characterized by Amyloid β (Aβ) and tau aggregation, other proteins interact with the toxic processes leading to this accumulation. One such protein, filamin A (FLNA) is an essential component of Aβ42-induced neuroinflammation and tau hyperphosphorylation. FLNA is known to colocalize with tau fibrils. We aimed to investigate the cross-sectional course followed by FLNA deposition through the stages of AD in the post-mortem brain. From parietal cortex extracts of 57 subjects from the Religious Order Study, we quantified insoluble Aβ42 by ELISA, total insoluble tau, insoluble phosphorylated tau and insoluble FLNA normalized on sample weight by Western blot, and neuritic plaque density by immunofluorescence. AD progression was based on clinical diagnosis and the ABC scoring method combining Thal, Braak and the CERAD staging. We correlated FLNA with Aβ42, tau and neuritic plaque quantifications as well as with AD stages. We found significant positive correlations between FLNA concentrations and ABC scores, Aβ42 levels, neuritic plaques and Thal stages. FLNA concentrations were significantly higher during intermediary stages of AD, at Thal stage 3, CERAD stage 2 and intermediate ABC score. FLNA increase was most pronounced in the mild cognitively impaired (MCI) with AD neuropathology (ABC score either intermediate or high) (sensitivity: .727, specificity: .875, AUC: .852). We found that the increased insoluble FLNA concentrations in AD-wrought post-mortem brains may occur at an intermediary stage which coincides with the appearance of cognitive symptoms. As such, it may be a key event in the transition from preclinical to prodromal AD .
Potential rescue effects of SorCS1, a novel Amyloid beta competitor, in synaptic and cognitive defects in Alzheimer’s disease model mouse
2Synapse Development and Plasticity Research Unit, Institute de Recherches Cliniques de Montréal (IRCM), Montreal, QC, Canada,
3Intergrated Program in Neuroscience, McGill University, Montreal, QC, Canada
Corresponding Author: Hideto Takahashi, email Hideto.Takahashi@ircm.qc.ca
Soluble amyloid-β oligomers (AβOs) cause synapse dysfunction, cognitive impairment and learning/memory deficits in Alzheimer's disease (AD). We found that AβOs bind to neurexin and it causes synaptic dysfunction. A recent study has demonstrated that SorCS1, a key regulator of intracellular protein trafficking, regulates NRX1β surface expression. Here, we hypothesize that SorCS1 stabilizes synaptic NRX1β through competitive inhibition of AβO-NRXβ interaction and rescue AβO-induced synaptic dysfunction and learning/memory deficits in AD model mice. To analyze in vivo roles of SorCS1, we generated a forebrain-specific inducible SorCS1 transgenic mice. By crossing the SorCS1 Tg mice with 5xFAD, an AD mice model overproducing AβOs, we designed four genetic groups: non-AD control, non-AD with SorCS1 overexpression (OE) group, AD mice model group, and AD with SorCS1 OE group as a rescue model. I will conduct biochemical, histological and behavioral analyses to determine whether SorCS1 ameliorates synaptic impairment and learning/memory deficits. We recently confirmed that SorCS1 binds to NRX1β competitively with AβOs, and SorCS1 rescues AβO-mediated impairment of NRX function in axon and synaptic impairments. As a preliminary study, we also conducted Western blot assay using total cortical lysates of above-mentioned mouse groups and obtained a preliminary data showing that the expression of APP and Aβ spieces are decreased in AD with SorCS1 OE group. We anticipate that in vivo SorcS1 overexpression could rescue synaptic dysfunction through competing AβO-NRX interaction and also suppress amyloid pathology through reducing the expression of APP and Aβ species in AD model mice, resulting in the improvement of their learning and memory deficits.
Intravenous injection of AAV encoding scFv antibody to target TDP-43 proteinopathy
2Department of Psychiatry and Neuroscience, Université Laval, Québec City, QC, Canada.
Corresponding Author: Anna A. Chami, email email@example.com
Abnormal cytoplasmic aggregates of TDP-43 (TAR DNA-binding protein 43) are a pathological hallmark of degenerating neurons in many neurodegenerative disorders, including Amyotrophic Lateral Sclerosis (ALS), Frontotemporal Dementia (FTD), Alzheimer’s disease. To target TDP-43 and reduce its pathology, we developed an AAV (Adeno-Associated Virus) vector encoding a single chain antibody (scFv) against TDP-43. Our lab reported that this AAV-mediated delivery intrathecal of the scFv can be used to mitigate TDP-43 pathology in ALS mouse models. Here, we propose to further validate the antibody approach in mitigating pathology and cognitive defects in new mouse models with robust TDP-43 pathology and the use of scFv-encoding AAV vector bearing a recombinant capsid designed to achieve efficient neuronal transduction after injection directly into blood circulation. With this improved AAV vector and an injection directly into blood circulation, it is possible to reach and transduced neurons over a large portion of the nervous system. After producing the AAV vector pseudotyped with the PHP.eB capsid encoding the scFv, we performed an intravenous bilateral administraton in the retro-orbital sinus of C57Bl6 mice. After three weeks, we observed a widespread neuronal expression in the brain and the spinal cord. It is our hope that such AAV-delivery of scFv antibodies will succeed in TDP-43 proteinopathy. A single intravenous administration of AAV vector to achieve sustained production in neurons of therapeutic antibody mitigating TDP-43 proteinopathy is an appealing strategy for treatment of neurodegenerative diseases.
Temporal dissection of Rai1 function reveals brain-derived neurotrophic factor as a potential therapeutic target for Smith-Magenis syndrome.
Corresponding Author: Wei-Hsiang Huang, email wei-hsiang.huang at mcgill.ca
Smith-Magenis syndrome (SMS) is an incurable neurodevelopmental disorder associated with severe hyperphagia, obesity, and autism. SMS is caused by haploinsufficiency of Retinoic acid induced 1 (Rai1)., a transcription factor widely expressed in the brain to regulate the expression of hundreds of genes involved in neurotransmission. The temporal- and spatial- function of Rai1 remains poorly understood. Using advanced mouse genetic models, we addressed three key questions. (1) Given the early onset of SMS symptoms, is Rai1 expression only required in early development stage or throughout life? (2) Whether Rai1 deficiency within a specific hypothalamic region, the paraventricular nucleus of hypothalamus (PVH) is sufficient to cause hyperphagia and obesity? (3) Can we treat SMS by targeting one of many Rai1downstream pathways? We found that delayed Rai1 deletion at 3 or 8 weeks of age had no effect on neurobehavioral functions but resulted in adult-onset obesity and decreased expression of Bdnf in the hypothalamus. Deleting Rai1 specifically from the PVH by AAV mediated cre injection in Rai1 floxed mice is sufficient to induce obesity in mice. Remarkably, genetic overexpression of human Bdnf in Rai1 heterozygous mice reversed SMS-like obesity, hyperphagia, metabolic syndrome-like features, and hypo-sociability. Temporal and spatial analyses of Rai1 function in vivo, uncovered an unexpected role for Rai1 in maintaining energy homeostasis in the postnatal brain, specifically by the PVH neurons. The continuous requirement of Rai1 in the adult brain suggests that therapies targeting Rai1 must be maintained throughout life. Furthermore, this is the first study to (1) fully rescue all SMS-like features in mice and (2) show that restoring one of hundreds of Rai1 downstream genes was sufficient to modify disease progression.
Contribution of glutamatergic neurons of the gigantocellular reticular nucleus (Gi) to functional locomotor and postural recovery after spinal cord injury (SCI)
2Faculty of Medicine, Departement of Psychiaty and Neuroscience, Universite Laval, Québec, QC, Canada
Corresponding Author: Louis Baillot, email firstname.lastname@example.org
The gigantocellular reticular nucleus, located in the medullary reticular formation, is implicated in locomotor control. The aim of this project was to evaluate the contribution of glutamatergic Gi neurons in the motor control of the neck, trunk, fore- and hindlimbs in freely behaving mice before and after spinal cord injury. 15 VGlut2-cre mice were injected unilaterally in the Gi with an adeno-associated virus (AAV2/9), allowing the expression of channelrhodopsin-2 (ChR2) in glutamatergic neurons. Mice were implanted with an optical fiber above the Gi to photoactivate ChR2 expressing glutamatergic neurons. Kinematic analyses were performed during treadmill locomotion upon trains of photostimulation (10ms pulse duration at 50 Hz for 500ms) before and after a lateral thoracic hemisection at T9-T10. Before SCI, photostimulations evoked head-turnings in half of mice (7/15), trunk flexions in half of mice (8/15), locomotor arrests in half of mice (7/15), and accelerations in 20% of mice (3/15). Although photostimulations maintained head-turnings in half of mice 7 weeks after SCI, they failed to evoke trunk or limb flexions but they induced locomotor stops in nearly 90% of mice (14/15). Taken together, our results suggest a functional reorganization of glutamatergic Gi neurons in motor control after SCI.
Investigating blood brain barrier damage and immune cell entry post Citrobacter rodentium infection in PINK1 KO mice
2Department of Neurology and Neurosurgery, Montreal Neurological Institute , McGill University, Montreal, QC, Canada
3Department of Neuroscience and Neurology, Montreal Neurological Institute , McGill University, Montreal, QC, Canada
4Douglas Research Centre, McGill University, Verdun, QC, Canada
5Department of Microbiology and Immunology, McGill Life Sciences Complex, Bellini Pavilion, McGill University, Montreal, QC, Canada
Corresponding Author: Dr. Louis-Eric Trudeau, email email@example.com
Research in the past decade established a strong link between immune system activation and the development of Parkinson’s Disease (PD). In a recent study, we showed that repeated gastrointestinal infection with Citrobacter rodentium can lead to PD-like symptoms in Pink1 KO mice. Here, we aimed to test the hypothesis that entry of CD8+ T cells in brain in this model could occur because of increased blood brain barrier (BBB) permeability induced by inflammatory mediators. Pink1 WT and KO mice were infected with Citrobacter rodentium and at days 13 and 26 post infection, we conducted gadolinium-enhanced MR imaging to identify any signs of BBB permeability. We also quantified expression of endothelial tight junction proteins and dopamine metabolites along with investigating systemic inflammatory mediators. A panel of cytokines and chemokines were quantified from serum using a cytometric bead array. Our preliminary MRI data show a tendency for increased gadolinium entry in Pink1 KO mice at day 26 post infection, as compared to uninfected KO mice and infected WT mice. A regional analysis revealed increased BBB permeability in the striatum. We also observed up-regulation of systemic pro-inflammatory cyto-chemokines in the infected mice. However, no changes in the endothelial tight junction proteins were found. These results support the hypothesis that increased immune cell entry in the brain after gastro-intestinal infection results, at least in part from vasculature perturbation. The links between immune cell entry in the brain and BBB permeability changes are presently being invested.
Understanding the role of vasoactive intestinal peptide (VIP) interneurons in the medial entorhinal cortex (MEC) - a characterization of its various properties.
2Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
Corresponding Author: Mark P Brandon, email firstname.lastname@example.org
Interneurons play a crucial role in the balance of excitation and inhibition (E/I) in all structures. This E/I balance in MEC is important for spatial navigation and memory. In some structures, VIP cells inhibit interneurons and excitatory cells and provide a mechanism to maintain the E/I balance. The role of various cells in the MEC has been previously investigated; however, the role of VIP interneurons to maintain this E/I balance and its role in memory remains elusive. To investigate the role of VIP interneurons in the MEC, we first characterized the electrophysiological and morphological properties of VIP cells using in vitro whole-cell patch-clamp recordings in VIPcre/tdTom mice. In addition to this, we also look into the potential role of VIP cells in memory using the detection of immediate early genes such as cfos induced after a novel object location task to evaluate the involvement of this cell population in memory. We observed gradients in the electrophysiological properties of VIP cells that differ across laminae and along the dorsal-ventral axis of the MEC. We also observed that VIP cells have distinct morphological features across laminae. Our preliminary results from our behavioral experiments also indicate that VIP cells are activated in the novel object location task and that these cells show higher Cfos expression in the dissimilar paradigm of the novel object location. Together, these results characterize the electrophysiological and morphological properties of VIP cells in the MEC. We also observe a gradient in the electrophysiological properties along the dorsal-ventral axis of MEC and differences in certain passive and active membrane properties between VIP cells located in the superficial and deep MEC. Our preliminary results from our behavioural studies also indicates that VIP activation could be required for memory.
Neuronal preferences in the mouse primary visual cortex
Corresponding Author: Hifza Randhawa, email email@example.com
We can study what types of qualities V1 neurons extract from visual information, through an assessment of the change in the average firing of a group of neurons or single-cell coding. For example, a study (Kondo, et. al, 2016) found that neurons with similar orientation preferences were clustered in minicolumns for a short length. This experiment further assesses the characteristics preferred by single neurons in V1, probing the question of whether there exists a map of preferred stimulus characteristics in V1. A convoluted neural network was utilized to create images from 4096-dimension vectors, where each element in the vector represents a “gene” associated with the image. The images that produced the highest responses entered the next generation unchanged, while other images were mutated or recombined.The process was done multiple times, with the network feeding back on itself to produce the most optimal images for neural activation, thus constituting a closed-loop. A one-way ANOVA was run to see whether there existed any statistically significant difference between the following four groups: the average neuropil-corrected fluorescence trace to the optimal images in the first generation, the average neuropil-corrected fluorescence trace to the reference images in the first generation, the average neuropil-corrected fluorescence trace to the optimal images in the last generation, and the average neuropil-corrected fluorescence trace to the reference images in the last generation. No significant difference was found. These results may be due to the neuron changing its tuning preference. Experiments conducted by Jeon et.al demonstrate that 43% of neurons in the mouse primary visual cortex, changed aspects of their tuning preference daily. The results may also be due to hemodynamics interfering with GCaMP absorbance.
NMDA receptor regulation of glioblastoma tumour growth and cell invasion modelled with spheroids
2Département de Médecine, Université de Montréal, Montréal, QC, Canada
Corresponding Author: Nicolas Paradis-Isler, email firstname.lastname@example.org
Glioblastoma multiforme is the deadliest and most frequent primary brain cancer. Glutamate, a neurotransmitter in normal neurological function, is also involved in intercellular signalling with and between glioblastoma cells. Activation of NMDA receptors on glioblastoma cells by glutamate is thought to promote cell survival, proliferation, and migration. Supporting evidence has, however, until now been mostly limited to observations made in 2D cell cultures, devoid of important characteristics of the tumour microenvironment. To study glutamate signalling in glioblastoma cells in a microenvironment resembling tumours, we generate spheroids, compact 3D structures, with different human glioblastoma cell lines. To characterize glioblastoma cell invasion and model peritumoral tissue, we embed the spheroids in bio mimicking scaffolds. To analyze the contribution of NMDA receptor activity on glioblastoma cells to glutamate-dependent tumour growth and cell invasion , we target NMDA receptors with specific agonists and antagonists. Glioblastoma spheroids generated with different cell lines exhibit different sensitivities and growth patterns in response to glutamate. We also observe cell line-dependent relationships between NMDA receptor activity and glioblastoma spheroid growth. Furthermore, we find that scaffold characteristics modulate responses to NMDA receptor agonism and antagonism. Our results bring further support for the important role of glutamate signalling in glioblastoma tumour growth. More importantly, our findings underline the therapeutic potential of targeting NMDA receptors, in combination with other treatments, to slow glioblastoma progression and prevent tumour recurrence.
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