Canada

Cortical astrocytes are highly heterogeneous cells with distinct gene expression profiles, phenotypes, and functions. They are born from neural stem/progenitor cells (NSPCs) during embryonic development starting at E15 and undergo a period of rapid expansion in the first postnatal week. Whether time of astrocyte birth from NSPCs determines their position within the murine cerebral cortex is not known. To determine whether time of birth influences astrocyte distribution in the upper (UL) vs. lower (LL) cortical layers, we permanently labelled ventricular-subventricular zone (V-SVZ) NSPCs and their progeny via in utero electroporation with PiggyBac (PB)-CAG-EGFP at E15, 16, and 17 and sacrificed animals at P21. Immunohistochemistry (IHC) for the astrocyte lineage marker SOX9 was performed and EGFP+SOX9+ or EdU+SOX9+ astrocytes were quantified and compared between UL and LL cortical layers within each timepoint. PB-based labelling of EGFP+SOX9+ astrocytes showed that E15- and E16-born astrocytes were mostly found in the UL at P21; this bias was lost in E17-born astrocytes. As an alternative birth dating method, 5-ethynyl-2&#39;deoxyuridine (EdU) was administered to pregnant mice at E16 and tissue was collected at P3 prior to astrocyte expansion. EdU labelling confirmed that SOX9+ astrocytes born at E16 were mostly found in the UL at P3. Altogether, our results suggest that the distribution of SOX9+ cortical astrocytes is influenced by birth date.

CAN-ACN 2021

Cortical layer distribution of SOX9+ astrocytes from V-SVZ neural stem/progenitor cells depends on time of birth

astrogenesis

development

cortex

Colleagues and Friends:

I am very happy to welcome you to the 14th annual Canadian Neuroscience Meeting, and to the first virtual edition of our meeting. I want to highlight the important work the CAN meeting chair, **Roger Thompson** and co-chair, **Alyson Fournier**, did to put together the great program we are offering this year. Moving to a virtual format required a complete re-design of the program, and both Roger and Alyson did a splendid job in providing us with an appealing and well adapted program for our first virtual event. I wish to thank them for this very important effort.

Highlights of this year’s scientific meeting include invited speakers **Michael Hausser, Franck Polleux, Gwyneth Card, Magdalena Götz**and Brain Prize winner **Huda Zoghbi**. Plenary and parallel symposia, proposed by our members complete our diverse [scientific program.](https://can-acn.org/meeting-2021/program-2021/)

The 2021 Advocacy session, chaired and organized by CAN advocacy committee chair **Karun Singh**, will feature a special lecture and question period with Member of Parliament and past Science Minister **Kirsty Duncan**. This will be followed by a short overview of CAN’s advocacy activities over the last year. We invite you to participate in this session for insight from Dr. Duncan on the workings of Parliament Hill, and to learn more about what CAN has been doing to promote neuroscience research in Canada.

We are also excited to host **Lisa Willis** in the Equity Diversity and Inclusion session, organized by EDI committee chair **Jibran Khokhar**.

A special highlight of our meeting will be the lectures by award-winning young neuroscientists. We are please to host the CAN 2020 Young Investigator Award winner **Mihaela Iordanova**, and CAN 2021 Young Investigator Award winners **Aaron Phillips** and **Tabrez Siddiqui**. Highlights will also include presentation by the top three winners of the CAN-CIHR-INMHA Brain Star Award winners, **Claire Gizowski, Nuria Daviu Abant** and **Lukas Tamayo-Orrego**.

Independently organized satellite symposia complement and complete this exciting program, check them out here: https://can-acn.org/meeting-2021/2021-satellite-symposia/

Some of the most engaging sessions are always the poster sessions featuring the work of our trainees, so make sure to log in to Gather Town during the poster sessions to chat with the presenters.
We hope you enjoy this program, and look forward to welcoming you, virtually.

Shernaz Bamji

President of the Canadian Association for Neuroscience

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/b9aea25343a87d5aac3b9367dc780974.jpg)



Please head to https://can-acn.org/meeting-2021/registration-2021/ to register. 

14th Canadian Neuroscience Meeting from August 23rd-25th

Cortical astrocytes are highly heterogeneous cells with distinct gene expression profiles, phenotypes, and functions. They are born from neural stem/progenitor cells (NSPCs) during embryonic development starting at E15 and undergo a period of rapid expansion in the first postnatal week. Whether time of astrocyte birth from NSPCs determines their position within the murine cerebral cortex is not known. To determine whether time of birth influences astrocyte distribution in the upper (UL) vs. lower (LL) cortical layers, we permanently labelled ventricular-subventricular zone (V-SVZ) NSPCs and their progeny via in utero electroporation with PiggyBac (PB)-CAG-EGFP at E15, 16, and 17 and sacrificed animals at P21. Immunohistochemistry (IHC) for the astrocyte lineage marker SOX9 was performed and EGFP+SOX9+ or EdU+SOX9+ astrocytes were quantified and compared between UL and LL cortical layers within each timepoint. PB-based labelling of EGFP+SOX9+ astrocytes showed that E15- and E16-born astrocytes were mostly found in the UL at P21; this bias was lost in E17-born astrocytes. As an alternative birth dating method, 5-ethynyl-2'deoxyuridine (EdU) was administered to pregnant mice at E16 and tissue was collected at P3 prior to astrocyte expansion. EdU labelling confirmed that SOX9+ astrocytes born at E16 were mostly found in the UL at P3. Altogether, our results suggest that the distribution of SOX9+ cortical astrocytes is influenced by birth date.

poster

Introduction: The COVID-19 pandemic has created a shift in the use of at-home spaces for work, play and research. In the present study we sought to determine if NeuroTrackerX, an anaglyph, at-home version of the three-dimensional multiple object tracking (3D-MOT) software NeuroTracker, produced similar results to the laboratory version that uses active 3D technology. Methods: 20 cognitively healthy adults (10 female, mean age = 68.3 years, SD = 6.75) were recruited for participation as the at-home training group. 20 participants, above 50 years old, who had previously completed at least 8 session of in-lab 3D-MOT, were randomly selected to serve as the in-lab control group. At-home participants were loaned the necessary equipment (e.g. 3D-glasses, computer equipment), and engaged in 10 training sessions over five weeks (2x per week). Results: No demographic differences were observed between the two groups (age, sex, MMSE score). The in-lab control group performed better on the task at session one (p < 0.05), however no differences in session scores (p > 0.05), or learning rates (p > 0.05) were observed between groups over the remaining sessions. Participants in both groups showed significant improvements in task performance across the training sessions (p < 0.001). Conclusions: These results indicate that NeurotrackerX provides a promising in-home option to use for cognitive training in cognitively healthy adults. Future studies are needed to determine if these benefits can also be observed in cognitively-challenged groups who may benefit from this form of cognitive training.

At-home cognitive training during the COVID-19 Pandemic? Validation, utility and lessons for future research

Genetic cell fate manipulation can be used to convert one cell type to another, which facilitates the production of personalized and customized human neurons for basic science applications and disease modeling. Genetic conversions often start with accessible cell types like fibroblasts, which are converted to neurons using multiple lentivirus vectors that encode neurogenic genes, such as Ascl1 and Ngn2; furthermore, for doxycycline (dox) inducibility, another vector is used to deliver a dox-dependent transcriptional regulator (e.g. rtTA or TetR). Such direct cell fate conversion approaches have the advantage of retaining some epigenetic marks, but somatic cells like fibroblasts often grow slowly, and the use of multiple viral vectors decreases conversion efficiencies. To address these limitations, we tested a range of media formulations and found that supplementing serum-based fibroblast media with basic fibroblast growth factor improved growth by 3-fold. We also found that co-expression of Ascl1 and Ngn2 from a single lentivirus vector improved neuronal conversion by approximately 45% compared to the delivery of Ascl1 and Ngn2 on separate vectors. These improvements increase both neuronal conversion efficiency and potential neuronal yield of this fibroblast-to-neuron conversion platform. We are currently developing a self-inactivating "all-in-one" lentivirus, which will express dox-inducible Ascl1-P2A-Ngn2 along with TetR and a selectable marker to isolate pure neuronal populations for studies of human neurobiology and to model disorders of the brain.

Improved methodologies for genetic conversion of human fibroblasts to neurons

State-of-the-art imaging tools rely on a restrained preparation, limiting natural behavior while measuring cellular activity via fluorescence (FL). Recently, advances in wearable microscopy expanded the range of accessible behaviors by allowing imaging of freely behaving animals. However, wearable microscopes to this day are primarily used for brain imaging and have not been adopted for imaging other parts of the body, for example the spinal cord. Furthermore, unfavorable attributes of FL indicators constrain the extent of imaging experiments, including photobleaching, autofluorescence and excitation light scattering noise especially in the parts of the body like the spinal cord due to myelination. All 3 of these issues can be eliminated while offering an increase in the imaging depth by using bioluminescence (BL) instead of the FL. Here we demonstrate our ability of imaging BL calcium indicators through the cranial window in mice as fast as 5 frames per second using redesigned open-source miniscopes. Furthermore, we present an expansion of the miniscope use towards neurovascular imaging in the spinal cord. Spinal neurovascular imaging is accomplished by integrating a custom vertebral implant with miniscope hardware that ensures mechanical stability over time. Such implants allow interchangeable imaging of the brain or spinal cord in free or restrained animals. Altogether, our work expands the imaging toolbox towards better imaging quality via BL indicators and the ability to image across multiple sites throughout the nervous system using wearable miniature microscopes.

Next generation tools for imaging in the cortex and spinal cord

Researchers are expected to manage various responsibilities whilst staying up-to date with developments in their field. This is an arduous and time-consuming task. In Alzheimer's disease research alone, an average of 200 research articles are published every week. Last year we presented our podcast, AMiNDR, as a means of easing the burden on researchers. We offer an accessible audio format channel, sorting research into distinct categories and summarizing its contents. Each episode corresponds to a category or subtheme of research, complete with a bibliography of papers covered. In the year since its launch in June 2020, AMiNDR has published over 160 episodes with accompanying bibliographies. While the podcast has received positive feedback from researchers worldwide, we wonder if it is an effective way of disseminating knowledge and if it is achieving its goal of saving scientists time. To assess the podcast's reach, we tracked followers' growth and engagement across social media platforms and compared AMiNDR's performance with other prominent science communication podcasts with a similar target audience. We also measured the engagement with our podcast and website using Podcast Analytics and Google Analytics. respectively. We supplemented this with a survey to discern listeners' satisfaction with the service, followed-up with optional interviews for feedback. We present the results of this assessment with a list of recommendations for digital knowledge dissemination tools like the AMiNDR podcast. This will help further refine science communication initiatives in Neuroscience.

Are podcasts effective for knowledge dissemination to neuroscientists? Case study: AMiNDR podcast (a month in neurodegenerative disease research)

Recent optogenetic technologies have demonstrated not only light-dependent control of neuronal activity but also the regulation of target molecules by light, suggesting their potential applications to study cellular functions at the molecular level in the brain. Here, we introduce our optogenetic approaches for the non-invasive manipulation of intracellular cAMP processes with light in target neurons of the brain. cAMP is a ubiquitous secondary messenger for intracellular signalling pathways, mediating sensory transduction and neuromodulation. However, cAMP dynamics and related spatiotemporal functions remain elusive in the brain due to limitations of spatiotemporal specificity of pharmacological and genetic approaches to acutely perturb cAMP function. We have optimized and further established genetically encoded light-sensitive cAMP metabolic enzymes to enhance or suppress cAMP levels in living neurons. By expressing the light-sensitive cAMP metabolic enzymes with cAMP fluorescence indicators, we successfully monitored and manipulated cAMP levels of living hippocampal pyramidal neurons in murine hippocampal brain slices with two-photon laser microscopy, validating our optogenetic approaches in the target hippocampal neurons. Furthermore, we incorporated these optogenetic techniques directly in the target hippocampal neurons of freely behaving mice with brain-implanted fiber optic LED devices for light-dependent manipulation of cAMP in the intact brain. We will discuss in vivo optogenetic approaches in combination with murine hippocampus-dependent behavioural tests.

A toolbox for the optogenetic control of cAMP in vivo

The neurobiology of depression can increase the risk of developing Alzheimer disease (AD) in later life. The depression-related enzyme monoamine oxidase (MAO) has been implicated in the earliest lesions in the progression of AD. The two isoforms of MAO, e.g. MAO-A and MAO-B, catalyze the degradation of monoaminergic neurotransmitters (e.g. serotonin, dopamine, and noradrenaline) and MAO-mediated neurocytotoxicity may involve hydrogen peroxide (a reaction byproduct). MAO protein expression and catalytic activity often do not correlate and an unrecognized pool of inactive MAO could bias results and give rise to misleading conclusions. Perhaps this explains why MAO inhibition has been only modestly successful in clinical AD populations. It is impossible to differentiate active from inactive MAO protein in cells and tissues. Activity-based probes (ABPs) are probes designed to attach to the catalytic sites of active enzymes. Exploring this concept, our team has synthesized three fluorescent ABPs and using recombinant MAO-A and MAO-B proteins, endogenous (LnCAP cells) and overexpressed (N2a cells) MAO proteins, and confocal microscopy, we demonstrate that these probes bind irreversibly and selectively to MAO-A. This will benefit future live-cell imaging studies. ABPs, especially highly selective candidates, will give us a better understanding of the function of MAO-A and MAO-B in health and could help define a role for MAO in pathology and provide for a stage-specific therapeutic intervention strategy with benefit for clinical depression as well as AD.

Developing selective fluorophore-tagged activity-based probes for live-cell imaging of active monoamine oxidase

Dopamine (DA) connectivity in the prefrontal cortex (PFC) continues to unfold until early adulthood, with dramatic organizational and functional changes occurring during adolescence. This delayed development involves long-distance axonal growth of midbrain DA neurons across the adolescent period and is mediated by the Netrin-1/DCC guidance cue pathway. We examined whether repeated social stress in adolescence dysregulates the Netrin-1/DCC pathway, disrupting PFC DA innervation and cognitive control in adulthood. We used a modified accelerated social defeat stress (ASD) model and segregated mice into resilient (RES) and susceptible (SUS) groups by measuring social avoidance in a social interaction test (SIT) 24h after ASD exposure. ASD in adolescence downregulates DCC expression in DA neurons in SUS and RES groups, but its effects on PFC DA development and behavior differ between phenotypes. ASD-induced molecular, cellular and behavioral changes are not observed following ASD exposure in adulthood. While most (~60%) mice exposed to adolescent ASD show RES, most adult mice show stress SUS. Alterations in dopamine development in adolescence may mediate the established link between genetic variance within the Netrin-1/DCC pathway and psychiatric disorders of neurodevelopmental origin.

Stress in adolescence alters guidance cue pathways and impacts dopamine development

Individual differences in dopamine gene and brain systems influence the responsiveness to environmental variations and affect different types of behaviors (sensitivity to reward, decision-making, eating) over the life course. Robust evidence points to DRD4 gene but neither the characterization of context diversity and dynamics, nor the neurobiological mechanisms involved in metabolic disorders and their co-morbidity with psychiatric conditions (e.g. obesity and ADHD) are understood in sufficient depth. Evidence advancing the theoretical understanding of environmental variation characterization over the life course will first be presented. Second, studies focusing on different genomic approaches to explore the impact of variations of dopamine related genes on the brain responses to both adverse and protective environmental conditions. A recent published study that explored differential susceptibility to positive environments according to the predicted genetically-regulated gene expression of prefrontal cortex DRD4 gene will be presented, evidencing the role of positive environment as a protective factor against the development of eating disorders in children as young as 48 and 60 months of age. To be able to further investigate the role of dopamine on these gene by environment interactions, we will present new data exploring the role of the dopamine transporter gene network through a polygenic approach that reflects variation on the genes co-expressed with DAT1 gene in the PFC and STR in a combined manner. A higher chance of having co-morbidity between mental and cardio-metabolic disorders on the UKBiobank cohort was associated with the interaction between variations in the DAT1 gene network and exposure to early life adversity, confirming our initial hypothesis. Taken together these findings highlight the relevance of a dopamine-related gene network to influence the risk to develop psychiatric conditions associated with exposure to early life adversity. Combining this novel approach to developmental neuropsychology with a more theoretically rich characterization of environmental variation over the life course can guide the elaboration of more efficacious and cost-effective personalized prevention and treatment of complex metabolic and mental health and diseases, targeting individuals that would benefit the most from interventions.

The role of dopamine on the link between early life environment and lifecourse eating behavior and co-morbidity between metabolic and psychiatric disorders: Context characterization and biologically-informed genomic approaches

The resting perfusion of blood to the brain is immense and essential for proper function yet we have little understanding of how the brain regulates its basal blood supply. Astrocyte-mediated neurovascular coupling has conventionally been examined in the context of transient neuronally-evoked calcium (Ca2+) events triggering phasic changes in arteriole diameter to control blood flow. However, our group recently demonstrated that "resting" astrocyte Ca2+ levels control tonic, neural activity independent, brain blood flow. It was unclear if or how fluctuations in resting astrocyte Ca2+ regulated vascular tone in vivo. Using two-photon fluorescence imaging, astrocyte patch-clamp, pharmacology, chemogenetics and cre-lox gene knockdown in acute cortical brain slices and in vivo, we showed that increases in arteriole tone (vasoconstriction) caused a sustained elevation in the astrocyte endfoot Ca2+ level. Pharmacology suggested that a TRPV4-mediated Ca2+ influx initiated a Ca2+-dependent COX-1 pathway in endfeet that triggered the release of prostaglandin vasodilators. The role of endfoot COX-1 was further demonstrated with astrocyte specific cre-lox knockdown of the COX-1 gene PTGS1. Furthermore, chemogenetic control of arteriole constriction was sufficient to engage this pathway. While in brain slices this pathway appeared to be a static effect on arteriole tone, in awake mice in vivo, we found this pathway was involved in vasomotion - a pulsatile phenomenon of vascular contraction and relaxation occurring at ~0.1Hz which is important for the basal perfusion of tissue. Using an astrocyte selective AAV to overexpress a Ca2+ extrusion pump called CalEx, which clamps astrocyte free Ca2+ at a lower level and prevents increases, this largely abolished vasomotion compared to control virus. Our data demonstrated that bidirectional communication between astrocyte endfeet and arterioles is important for setting basal arteriole tone and vasomotion in vivo, which is likely an essential process for optimizing cerebral perfusion of oxygenated blood.

Bidirectional communication between astrocytes and arterioles controls vasomotion

BACKGROUND AND AIM Several functions, motor or sensory, rely on the ability of neurons to modify their discharge pattern to faithfully encode the characteristics of a sensory stimulus or to reflect a rhythmic motor control for example. Changes in firing pattern often involve particular ion channels and are intimately related to the function of the circuit. Astrocytes are increasingly recognized as key regulators of neural activity, through release of gliotransmitters. An increasing number of studies have documented how they affect synaptic and network functions. However, their contribution to neuronal computations is still poorly understood. METHODS: Whole cell patch recordings of neurons and astrocytes was combined to Ca2+-imaging and optogenetic manipulations in either brainstem or cortical slices from rats and transgenic mice. RESULTS: Here I will describe a mechanism first identified in a brainstem trigeminal circuit where neuronal firing pattern depends on particular Na+ channels sensitive to the extracellular Ca2 + concentration which is regulated by astrocytes through release of the calcium-binding protein, S100ß. The same mechanism also contribute to inputs integration and influences the input-output function of cortical layer 5 pyramidal neurons, and of primary afferents neurons. I will also describe how astrocytic coupling define functional domains and determines synchronization and coordination of neuronal firing within these domains. CONCLUSIONS Neuron-glia interactions are most often thought to occur at or near synapses. Our results suggest that astrocytes control neural activity by acting directly on or near the neuronal ionic channels, a largely unexplored form of communication between astrocytes and neurons. The S100β-dependent mechanism adds up to the previously reported conventional gliotransmitters such as glutamate, GABA, and ATP. Beyond increasing our understanding of how astrocytes contribute to neuronal computations an important value of our findings resides in the increased understanding of the role of S100β which is abnormally regulated after trauma and in many neurological disorders including epilepsy, depression, Parkinson's and Alzheimer's diseases. We propose that abnormal S100β control may have a wide impact by leading to abnormal extracellular ionic environment, abnormal neural activities, and thus pathological states.

Cortical layer distribution of SOX9+ astrocytes from V-SVZ neural stem/progenitor cells depends on time of birth

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