Canada

Astrocytes are involved in diverse and highly specialized functions in the brain. They display morphological and molecular heterogeneity that is reflective of the microenvironments in which they reside. Astrocytes also become reactive in many brain disorders and diseases, and contribute to disease progression. To better understand how astrocytes develop and specialize within brain microenvironments, we transplanted mouse astrocytes into the mouse cortex in the first postnatal week, and assessed their integration in the host brain at various time points. We found that transplanted astrocytes developed complex morphologies typical of cortical protoplasmic astrocytes and displayed tiling arrangements with astrocytes from the host brain. Also, at 110-130 days post-transplantation, transplanted astrocytes expressed the same levels of GLAST/EAAT1, GLT1/EAAT2, and GFAP as astrocytes in the host brain. Similarly, spatial territories covered by transplanted astrocytes displayed the same density of pre-synaptic terminals as territories covered by host brain astrocytes. Finally, transplanted astrocytes developed endfeet with high AQP4 expression that were tightly associated with capillaries, similar to what we observed with astrocytes in the host brain. Our results indicate that transplanted astrocytes successfully integrate and survive long-term within the mouse brain when transplanted in the immature cortex. These findings open the possibility of using transplanted astrocytes to monitor changes in brain activity/function, and potentially as therapeutic tool to tackle brain diseases.

CAN-ACN 2021

Transplanted astrocytes develop, mature, and survive long-term in the mouse cortex

transplantation

astrocytes

development

brain

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://assets.underline.io/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

poster

Ancient medicine drugs containing the alkaloid rhynchophylline (RHY) increase sleep duration and quality in humans. Although treatment with RHY alone has not been tested in humans, rodent studies suggest that it modulates cellular pathways involved in sleep/wake regulation by targeting ion channels and kinases. Interestingly, RHY can inhibit EphA4, and EphA4-/- mice have sleep alterations. We thus studied effects of RHY on sleep and related molecular mechanisms. The electrocorticogram was recorded in male and female mice receiving 50 or 100 mg/kg of RHY (or saline) at light onset and 1h before light offset. Sleep architecture and spectral activity were examined. Additional groups had their brains sampled 3h after each injection to assess changes in the transcriptome with a high spatial resolution. In both sexes, RHY decreases wake and increases NREM sleep during the dark period, and reduces REM sleep during the light period. Moreover, RHY shortens individual bouts of wake and NREM sleep. RHY also enhances activity in low frequencies in wake and modifies the time-course of NREM sleep delta and sigma activity. Preliminary results in females suggest that Rhy affects the expression of genes such as Sgk1 similarly at the beginning of the light and dark periods, while its impact on mitochondrial genes and genes expressed in the hypothalamus appears time-dependent. RHY modifies sleep in manners similar to EphA4-/- mice, but additional effects may suggest EphA4-independent mechanisms. The transcriptomic approach will help defining how RHY impacts wake/sleep regulatory circuits.

The traditional Chinese medicine component Rhynchophylline modifies sleep and the brain spatial transcriptome in mice

It has been established that exposure to drug conditioned stimuli (CS) can enhance memory consolidation, indicating that drug CSs not only produce changes in behaviour, but can also impact cognition. Therefore, it is possible that conditioned memory modulation, like other conditioned responses, will display extinction. The current study used classical and operant conditioning techniques to test this hypothesis in male Sprague-Dawley rats performing an object location (OL) memory task. To establish the CS in Experiment 1, rats were injected with heroin (0, 0.3, 1 mg/kg, S.C.) and immediately placed in operant chambers for 1 hr, once a day for 5 consecutive days. It was found that exposure to the heroin-CS four days after conditioning dose-dependently enhanced object location memory. In addition, when tested after 6 exposures to the CS without receiving heroin, the CSs ability to modulate memory was significantly reduced. In Experiment 2, rats were trained to self-administer heroin (0.05 mg/kg/inf) on a continuous reinforcement schedule for 12 days. It was found that exposure to the heroin-CS four days after training enhanced object location memory, and when tested after 6 exposures to the CS without receiving heroin, the CSs ability to modulate memory was significantly reduced. Taken together, these results support the idea that conditioned memory modulation occurs in parallel with conditioned responses that are mediated by conditioned stimuli.

Extinction of conditioned memory modulation

Maternal immune activation (MIA) in mice can be used to investigate the link between perinatal infection and early-life developmental disorders such as cerebral palsy and autism spectrum disorder. Studies have shown that adult mice exposed to a bacterial or viral immune response during early- to mid-embryonic development display reduced social communication and interaction, and increased repetitive stereotypic behaviour. To date however, few studies have looked at the effects of MIA on early behaviours and developmental milestones in mice. In the current study, pregnant CD-1 dams were injected at embryonic day 11.5 with either lipopolysaccharide (LPS) or polyinosinic:polycytidylic acid (PolyIC) to stimulate aspects of a bacterial or viral immune response, respectively. Offspring were then assessed from post-natal day 2-21 using a modified Fox developmental behavioural test battery to assess reflexive and morphological developmental milestones. Additionally, grooming, homing to maternal bedding, and activity/exploration in the open field were evaluated. Overall, accelerated development and alterations in behaviour were observed in the MIA mice compared to sham-injected controls. These results suggest that MIA results in differential physiological and behavioural characteristics that emerge during early post-natal development, and further highlight the need for research that focuses on the effects of MIA during this developmental period.

The effects of maternal immune activation on early developmental milestones and behaviour in outbred CD-1 mice.

Background: Multiple sclerosis (MS) is characterised by widespread damage of the central nervous system that includes alterations in normal-appearing white matter (NAWM) and demyelinating white matter (WM) lesions. Neurite Orientation Dispersion and Density Imaging (NODDI) has been proposed to provide a precise characterisation of WM microstructure. NODDI maps can be calculated for neurite density index (NDI), orientation dispersion index (ODI), which estimate orientation dispersion and neurite density. Although NODDI has not been widely applied in MS, this technique is promising in investigating the complexity of MS pathology, being more specific than diffusion tensor imaging (DTI) in capturing microstructural alterations.Aims: We conducted a meta-analysis of studies using NODDI metrics to assess brain microstructural changes and neuroaxonal pathology in WM lesions and NAWM in patients with MS.Methods: Three reviewers conducted the literature search of four electronic databases (Medline, Embase, Scopus, and PubMed). We performed a random-effect meta-analysis. The extent of between-study heterogeneity was assessed with the I2 statistic. Funnel plots and Egger's tests were used to assess publication bias.Result: We identified 7 studies analysing 374 participants (202 MS, 172 controls). NDI in WM lesions and NAWM were significantly reduced compared to healthy WM. The standardised mean difference was -3.08 (95%CI -4.22 to (-1.95), p=<0.00001, I2=88%) and -0.70 (95%CI -0.99 to (-0.40), p=<0.00001, I2=35%) respectively. There was no statistically significant difference of ODI in MS WM lesions and NAWM compared to healthy controls. The standardised mean difference was -0.44 (95%CI -1.60 to (-0.71), p=0.45, I2=95%) for WM lesions and -0.46 (95%CI -2.07 to (-1.15), p=0.58,

Investigating microstructural changes in white matter in multiple sclerosis: A systematic review and individual participant data meta-analysis of neurite orientation dispersion and density imaging

Microglia are functionally dynamic brain immune cells known to adapt their morphology depending on their environment. These context-dependent morphologies are extensively measured to inform changes in function. However, current manual morphological analyses, while informative, are often time-consuming and fail to detect subtle differences in cell architecture. To solve these limitations, we tested the sensitivity of an open-source quantitative method to measure microglial morphology called Fractal Analysis, adapted into a manual analysis of cell perimeter and area. Using the automated FracLac Plugin (ImageJ), we calculated the fractal dimension (FD) and lacunarity (LA), complementary indices, of two sets of immunohistochemical stainings (fluorescent and non-fluorescent) of hippocampal microglia and infiltrating bone marrow-derived macrophages (BMDM) from healthy postnatal mice. By creating a macro, we were able to combine our manual methodology to the fractal analysis, and find that FD and LA were more sensitive to changes in morphology than measurements of area and perimeter. In our dataset, FD and LA were both significantly increased in microglia compared to BMDM, while only LA was significantly higher in microglia among the ventral compared to the dorsal part of the hippocampus, possibly indicating increased process ramification. The detection of these differences in healthy tissue emphasizes the diverse regional morphology of microglia compared with infiltrating immune cells, but also the sensitivity of this automated methodology to detect subtle morphological changes.

Testing available quantitative methods to analyze brain immune cell morphology

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 have addressed this limitation by developing a light-inducible protein aggregation system (LIPA). This application is based on the use of a mutant form of the Arabidopsis thaliana photoreceptor cryptochrome 2 (CRY2), which when stimulated with blue light, mutant CRY2 undergoes rapid, reversible and robust protein clustering or aggregation. The use of this application allows for real-time induction of α-syn inclusions formation with remarkable spatial and temporal resolution in both cell culture and in vivo paradigms. 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. 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.

Optogenetic-mediated spatiotemporal control of α-synuclein aggregation mimics Lewy body formation and triggers neurodegeneration

Brain development and function are exceptionally reliant on the adequate development and maintenance of vascular networks. As such, early impairments in vascular health can lead to neurodevelopmental defects. Despite a wealth of knowledge on neuronal mechanisms of autism spectrum disorders (ASD), very few studies have considered the role played by the brain vasculature in ASD. ASD are viewed as neurodevelopmental conditions associated with genetic origins such as the common 16p11.2 deletion which leads to haploinsufficiency of 27 conserved genes. We undertook an extensive study to investigate the cerebrovascular contributions to ASD and revealed that 16p11.2 deletion induced endothelial-dependent structural and functional neurovascular abnormalities, establishing a novel vascular link to ASD. While this study associated dysfunctional endothelial cells (ECs) with 16p11.2 deletion syndrome, the endothelial aspects leading to these dysfunctions remain to be elucidated. We are using an untargeted metabolomics approach, as well as assessing mitochondrial function, to decipher core features of brain ECs isolated from a mouse model of 16p11.2 deletion syndrome. We identified an energetic failure in 16p11.2 deficient ECs compared to WT ECs, as shown by altered concentration of high energy metabolites involved in the Krebs cycle as well as in energy supply. This research program will provide new insight into key players in ASD pathogenesis, which is an essential pre-requisite for the development of transformative therapeutic strategies.

Metabolic defects in brain endothelial cells from 16p11.2 deletion autism mice

Adult hippocampal neurogenesis (AHN) is the process that generates neurons from neural progenitor cells (NPCs) in the adult hippocampus. AHN is important for proper learning, memory, cognition, and mood regulation but is severely decreased in memory and mood disorders. Understanding how AHN is regulated may lead to treatments for these conditions. AHN entails multiple cell stages involving NPC proliferation and differentiation, followed by neuron maturation. The transition of these cell stages is regulated by expression of specific transcription factors. We found that the transcription factor capicua (CIC) is expressed in NPCs but is downregulated during NPC differentiation. Contrastingly, CIC is upregulated during neuron maturation. Such expression changes suggest CIC might play a role in AHN. Here we find that deleting CIC in the hippocampus, including the adult hippocampal neuronal lineage, results in reduced NPCs due to increased differentiation into immature neurons. These immature neurons have impaired dendrite complexity and abnormal migration, with delayed progression to fully matured granule neurons. Together, our results show that CIC plays a critical role in NPC differentiation and neuron maturation in AHN. Our study identifies a previously unknown role for CIC in AHN. Given that decreased AHN is associated with mood and memory disorders, future investigations into the genes and pathways that CIC regulates may reveal crucial molecular inroads and therapeutic entry points into these conditions.

Capicua is required for the regulation of adult hippocampal neurogenesis

The adult brain has a remarkable capacity to produce new cells that migrate and integrate into pre-existing neuronal circuits throughout the lifespan of animals. Adult neural stem cells (NSCs) in subventricular zone (SVZ) are a largely quiescent population and their activation and proliferation is modulated by a number of physical and chemical cues from different sources. However, the mechanisms that integrate those signals and regulate quiescent/proliferative (Q/A) states transition are poorly understood. In this study, using ex-vivo calcium imaging, we revealed the universal Ca2+ signature that characterize activated (aNSCs) and quiescent (qNSCs) NSCs states. We showed that qNSCs are characterized by higher frequency of Ca2+ fluctuations and lower intracellular Ca2+ level, compared to aNSCs. This different Ca2+ dynamics were regulated by intracellular IP3-sensitive Ca2+ stores. Pharmacological inhibition of IP3-sensitive stores decreased the frequency of Ca2+ fluctuations and increased intracellular Ca2+ level of qNSCs. Similarly, CRISPR-Cas9 mediated deletion of Itpr2, specifically in SVZ NSCs resulted in the same characteristic differences in the Ca2+ dynamics. Importantly, these changes were accompanied with increase in proliferation indicating a causal relationship between internal store-dependent Ca2+ dynamics and NSCs Q/A transition. We also showed that anti-proliferative pathways are keeping NSCs quiescent by modulating calcium dynamics. For instance, pharmacological inhibition of the melatonin signaling pathway activates NSCs by reducing the frequency of Ca2+ fluctuations and increasing intracellular Ca2+ levels. Altogether, our data suggest that Ca2+ signaling in NSCs may integrate and decode different signals to regulate NSCs Q/A transition.

Quiescent and proliferative states of adult neural stem cells are characterized by different Ca2+ dynamics and steady-state intracellular levels

Haploinsufficiency of Syngap1 gene encoding the Synaptic Ras- GTPase Activating protein is associated with intellectual disability, autism spectrum disorder and epilepsy. Haploinsufficiency of Syngap1 leads to alterations in synaptic plasticity, behavioral abnormalities and cognitive deficits in mouse models. In particular, several studies have shown that Syngap1 regulates the time course of the maturation of dendritic spines and glutamatergic synapses in excitatory neurons; In contrast, the role of Syngap1 in inhibitory, GABAergic neurons is relatively uncharted. GABAergic neurons are a diverse class of neurons with different morphology, connectivity and physiological properties. They play an important role in neural circuit development and plasticity. Parvalbumin (PV)-expressing interneurons, one of the major classes of cortical GABAergic interneurons, form synapses onto the soma and proximal dendrites of pyramidal cells and are involved in the synchronization of the firing rate of pyramidal cell populations. Our aim is to study the role of Syngap1 in PV cell development In vivo, in establishing balanced synaptic connectivity and proper network in contributing to the behavioral endophenotype and cognition in mouse model by techniques like immunolabelling the synapses and behavioral studies. Preliminary data suggest that alteration in synaptic connectivity of PV cells in different cortical regions do contribute to observed overall behavioral and cognitive deficits. A better understanding of the role of Syngap1 in GABAergic cell development may shed light on the involvement of GABAergic circuit alterations in the cognitive deficits caused by Syngap1 haploinsufficiency in humans.

Transplanted astrocytes develop, mature, and survive long-term in the mouse cortex

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The traditional Chinese medicine component Rhynchophylline modifies sleep and the brain spatial transcriptome in mice

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