Canada

Introduction: Intracellular Cl- concentration ([Cl-]i) is high in primary sensory neurons due to the activity of the Na+-K+-Cl- cotransporter 1 (NKCC1), causing greater Cl- accumulation than typically seen in CNS neurons. Consequently, central terminals of primary afferents in the spinal dorsal horn experience depolarization upon activation of GABAA receptors (GABAAR). Thus, regulation of [Cl-]i in these terminals may significantly affect transmitter release. Determining the exact [Cl-]i in C-fiber terminals is pivotal to understand sensory processing. Methods: To image [Cl-]i we used the genetically-encoded ratiometric Cl- sensor, superclomeleon, using 2-photon microscopy in acute spinal cord slices. Superclomeleon was virally transduced selectively in C-fibers in NaV1.8-cre mice. The GABAAR agonist and antagonist muscimol and bicuculline, as well as the NKCC1 antagonist bumetanide, were used to modulate [Cl-]i in afferent terminals in the dorsal horn. NKCC1 mRNA levels in the dorsal root ganglia was evaluated with RNAScope. Results: We found that [Cl-]i in C-fibers was significantly higher in males than females. Bumetanide significantly decreased [Cl-]i in males but not in females. Bicuculline did not significantly affect [Cl-]i in C-fibers indicating a minimal contribution of tonic GABAA signaling to [Cl-]i. NKCC1 mRNA was also significantly lower in females than males, consistent with the functional data. Conclusion: Presynaptic inhibition appears to be under distinct control by GABAergic inhibition between sexes, which should be taken into consideration in future studies.

CAN-ACN 2021

Sex differences in chloride homeostasis of c-fiber primary afferents in the spinal cord dorsal horn

primary afferents

chloride homeostasis

sex difference

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

Mutations in the ATP-dependent chromatin remodeller chromodomain, helicase, DNA binding (CHD) 7 are the primary cause of CHARGE syndrome (CS) and have been associated with autism spectrum disorder (ASD). CHARGE is an acronym for the most characteristic features presented by patients: coloboma of the eye, heart defects, atresia chonae, retardation in growth and development, genital abnormalities, and ear defects. Although not included in the diagnostic criteria CS features often include neurological and behavioural problems such as hyperactivity, seizure, intellectual disability and autism. Little is known about the molecular mechanisms that underlie these neurological symptoms. Further, there is no known treatment yet either for patients with CS or for the neurological symptoms shared between CS and ASD. To investigate this, we generated a novel CRISPR/cas9 zebrafish chd7−/− model. We show that chd7 knockout zebrafish larvae exhibit a small head phenotype, defects in craniofacial cartilage development and display aberrant axonal network development. Further the chd7 mutants have less GABAergic neurons and exhibit a hyperactivity behavioural phenotype. Using an unbiased whole transcriptomic approach, we found that the GABAergic neuron defect was at least in part due to the downregulation of a CHD7 target gene, paqr3b and the subsequent upregulation of the MAPK/ERK signalling pathway, which is also dysregulated in CHD7 mutant human cells. Through a phenotype-based screen in chd7−/− zebrafish and C. elegans, we show that the small molecule ephedrine restores MAPK/ERK signalling and improves both GABAergic defects and behavioural anomalies. This work provides insight into the neuropathogenesis in CS and identifies a promising compound for further preclinical studies.

Chd7 loss of function in zebrafish impairs GABAergic network development through MEK/ERK signalling: CHARGE syndrome and beyond

BACKGROUND Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease with cognitive, behavioral, and psychiatric symptoms, with depression and suicidality present in a large proportion of CTE cases. Pathologically CTE is defined by a distinctive accumulation of hyperphophorylated tau (pTau) predominately involving the frontal and temporal cortices, medial temporal lobe, and brainstem. However, the association between pathology in particular brain regions and psychiatric CTE symptoms is unknown. METHODS AND RESULTS Human postmortem brains from CTE cases and controls were obtained from the VA-BU-CLF Brain Bank. Trained neuropathologists examined each brain for gross and microscopic pathology, and provided semi-quantitative assessments. Regions of interest (including frontal, temporal, limbic, and brainstem structures) were sectioned and stained for pathological markers of interest (e.g. pTau, β-amyloid, α-synuclein, pTDP43, etc). Stained slides were scanned and traced digitally, with staining quantified using a Leica Aperio system. Preliminary analyses suggest alterations in specific cortical, limbic, midbrain, and white matter structures may associate with depressive and suicidal features in CTE. In particular, cortical white matter loss as well as hippocampal and midbrain pathology were associated with psychiatric features. We have also found myelination and inflammation-associated changes in the anterior cingulate cortex of depressed CTE cases. CONCLUSIONS This investigation is the first to explore associations between neuropathology in particular brain regions and specific psychiatric features in CTE. Preliminary results suggest neurodegenerative pathology, loss of white matter, neuroinflammation, and gliosis could underlie psychiatric phenotypes in CTE.

Pathological correlates of psychiatric phenotypes across brain regions in chronic traumatic encephalopathy

**AMajor depressive disorder (depression) involves different mechanisms and brain scales. Altered cortical inhibition is associated with treatment-resistant depression, and reduced dendritic inhibition by somatostatin-expressing (SST) interneurons is a key component of the pathology. Electroencephalography (EEG) is an important source of biomarkers for depression to improve diagnosis and inform personalized treatments. However, whether the effects of reduced SST inhibition on microcircuit activity have signatures detectible in EEG remains unknown. We used detailed models of human cortical layer 2/3 microcircuits with normal or reduced SST inhibition to simulate resting-state activity together with the EEG signals in health and depression. We show that the healthy microcircuit models had emergent properties that reproduced key features of resting-state EEG theta-alpha frequency bands. We found that simulated EEG from depression microcircuits showed a significant increase in theta rhythmic activity and increased broadband power. Neuronal spiking showed a spike preference of EEG peak phase, and did not differ between conditions. We also showed using a realistic head model that the EEG signal biomarkers were mostly localized. Our study thus used detailed computational models to identify EEG biomarkers of reduced SST inhibition in cortical microcircuits in depression, which may serve to improve the diagnosis and stratification of depression subtypes, and in monitoring the effects of pharmacological modulation for treating depression.

Biomarkers of reduced inhibition in human cortical microcircuit signals in depression

Only recently has the scope of parental research expanded beyond maternal contributions to include the paternal sphere. Epidemiological studies have suggested that paternal stress, nutrition, and alcohol consumption, all impact neurobiological and behavioural characteristics in offspring. Given their high prevalence and comorbid use, a severely understudied domain in paternal research includes caffeine, alcohol use, and exercise. In this experiment, sires received seven weeks of regular tap water (placebo) or caffeine and/or ethanol (drug) and were housed in regular static cages (no ex) or cages with running wheels attached (ex). Beginning at P40, offspring were administered RmTBIs or sham injuries, followed by a behavioural test battery designed to assess post concussive symptomology. Post-mortem qRT-PCR was used to assess gene expression in the prefrontal cortex (PFC) and nucleus accumbens (NAc). Paternal experience did not improve or exacerbate RmTBI outcomes. However, female and male offspring displayed unique responses to RmTBI and paternal experience, resulting in sex-dependent changes in physical, behavioural, and molecular outcomes. Injury and paternal exercise drove significant changes in female offspring, whereas male offspring were affected by paternal exercise and drug treatment. Our findings add valuable insight into paternal experience and epigenetic inheritance in offspring. While not directly exacerbating or improving recovery from RmTBI, paternal experience affected male and female offspring in a sexually dimorphic manner.

Rathletes do not give you wings: How paternal exercise, caffeine, and/or alcohol affects offspring pathophysiology and behaviour following repetitive mild traumatic brain injury (RmTBI)

Background Coronavirus disease 2019 (COVID-19) frequently disturbs the nervous system. However, COVID-19's neurological disease requires a detailed characterization. Furthermore, we do not know what predicts poor neurological outcomes in patients. Previous reports have linked neurological disturbances to COVID-19's increased mortality. Here, we describe the clinical alterations in COVID-19 patients presenting with neurological manifestations and correlate neurological outcomes with disease severity. Methods We retrospectively analyzed clinical, neurological, neuroimaging (CT or MRI scans) and cerebrospinal fluid (CSF) laboratory data from 33 confirmed COVID-19 hospitalized Brazilian patients subjected to CSF sampling as clinically indicated. Findings COVID-19 was associated with a broad spectrum of neurological diseases in mild and severe cases. Headache was the only symptom associated with mild disease. In a bivariate analysis, severe patients had an 18-fold increased risk of presenting neuroimaging alterations. CSF findings do not differ in severe and mild cases. Only four patients presented increased CSF white blood cell counts. CSF levels were high for protein in 12 patients and glucose in six patients. Interpretation These findings strengthen the notion that COVID-19-induced neurological disease is heterogeneous and manifests regardless of patient state. It will be most important to determine the time course of neurological disease and whether it is permanent or alleviated over time so that COVID-19 patients with neurological alterations can be adequately treated.

COVID-19 is associated with a broad spectrum of neurological disease

Loss-of-function variants in the human Zdhhc9 gene are identified in 2% of patients diagnosed with X-linked intellectual disability. These patients exhibit striking reductions in white matter volume and altered microstructure of white matter tracts. To further understand the role of Zdhhc9 in the brain and to elucidate how disrupting Zdhhc9 function contributes to phenotypes observed in patients, we have characterized a Zdhhc9 knockout mouse line. We demonstrate that Zdhhc9 is enriched in oligodendrocytes and is approximately two-fold higher in the corpus callosum than in any other region of the mouse brain. Zdhhc9 knockout mice exhibit significant reduction in myelin/oligodendrocyte associated markers, as well as reductions in the palmitoylation of these proteins, suggesting palmitoylation of myelin proteins may be required for their stability. RNA sequencing of different brain regions from control and Zdhhc9 knockout mice demonstrate differential expression of oligodendrocyte marker genes, suggesting a larger population of immature oligodendrocytes and fewer mature oligodendrocytes in knockout brains. This work provides a new perspective into the role of Zdhhc9 in oligodendrocytes and provides evidence that palmitoylation contributes to the development of white matter.

The role of palmitoylating enzyme, zDHHC9, in intellectual disability

*Bipolar disorder (BD) is characterized by different functional changes in the brain. BD adversely affects human behavior, speech, and cognition. However, the neural basis of BD is still poorly understood. In this study, we apply graph theory analysis to compare functional brain networks features between BD and normal control individuals. Twenty-one individuals in each BD and control groups were participated in this study. Resting state electroencephalography (EEG) was recorded in the resting state condition for each participant in both groups. Then functional brain networks (derived from calculation of lagged coherence between source localized current densities) were compared between groups. Using graph theoretical analysis, we found that BD group exhibited significant reduction in clustering coefficient, global efficiency, largest eigenvalue, and the second smallest eigenvalue in the theta (4-8 Hz) and alpha bands (8-12 Hz). These results suggest that BD is associated with alterations in segregation, integration, synchronizability and robustness of functional brain networks. According to these results, BD group exhibited reduced neural information processing in global brain network scales and specific modules that can be associated with cognitive/behavioral deficits in BD.

Functional brain networks alterations in bipolar disorder: evidence from EEG and Graph theoretical analysis

**AutMultiple sclerosis (MS) is primarily characterized by demyelination within the central nervous system; however, the sustained clinical deficits associated with progressive forms of the disease are correlated with neuronal degeneration and death. Several mechanisms occurring within the MS lesion environment have been associated with axonal damage, including oxidative stress, hypoxic stress and glutamate excitotoxicity. Currently, there are no therapies preventing the neurodegeneration underlying chronic disability in progressive MS. Accordingly, biomarkers of neuronal damage that may suggest novel therapeutic targets and serve as prognostic indicators of disease progression are of great need. microRNAs (miRNA) are small, non-coding RNA molecules that inhibit translation of messenger RNA. They are often secreted from cells within extracellular vesicles (EVs), which are highly stable in circulation and abundant in human blood samples. Here, we use a reductionist in vitro culture system to profile miRNA expression in EVs released from human iPSC-derived neurons challenged with MS-relevant stimuli. We show that iPSC-derived neurons degenerate upon exposure to toxic stimuli and that EV miRNAs can be reproducibly obtained from degenerating neurons for sequencing. We aim to identify regulated EV miRNAs in our in vitro assays which can then be compared to neuronally-derived EVs isolated from MS patient plasma. We hope to identify a conserved miRNA signature that can be used to monitor neurodegeneration and disease progression in MS, while defining new neuroprotective strategies.

Profiling EV microRNAs from degenerating neurons to identify biomarkers for multiple sclerosis

Introduction: Olfactory dysfunction (OD) is a well-established consequence of traumatic brain injury (TBI). Most of the studies reported OD in patients with moderate and severe TBI in the acute phase. However, inconsistent results have been found on OD in patients with mild traumatic brain injury (mTBI). This study aims to investigate olfactory perception in patients with mTBI in the acute phase. Method: We measured olfactory capacities in 53 patients with mTBI between 2 and 4 weeks following their trauma and in 53 healthy controls (HC). More specifically, we administered a well-established olfactory test (Sniffin'Sticks) and we measured odor detection (yes/no paradigm) and odor perception of 4 common odorants (eucalyptol, benzaldehyde, parmesan cheese, geraniol), by using a computer controlled automated odor presentation device (olfactometer). Results: We did not observe any group difference in the Sniffin'Sticks test scores. However, compared to HC, mTBI patients showed more difficulty detecting odors (p= .001) and perceived them as more intense (p= .015). Furthermore, depending on the odorant (interaction odor * group: p= .001), mTBI patients perceived odors as less pleasant than HC. Conclusion: These findings show that patients with mTBI suffer from altered olfactory detection and perception from the first weeks following their trauma. However, well-established olfactory tests such as the Sniffin'Sticks test may not be sufficiently sensitive to these changes. 

Patients with a mild traumatic brain injury: what happens to their sense of smell in the acute phase?

Circadian clocks are ubiquitous throughout tissues and organs in mammals, forming a multioscillatory network that controls daily rhythms in physiology and behavior. A brain region expressing circadian clock genes is the striatum; a basal ganglia structure receiving dopaminergic input plays a major role in motor control. It is composed of distinct populations of medium spiny neurons (MSNs), either expressing Dopamine receptor D1 (DRD1) of the direct (stimulatory) or Dopamine receptor D2 (DRD2) of the indirect (inhibitory) pathway. Components of the dopamine signalling pathway and circadian clock genes mutually influence one other in striatal MSNs, which are key in the role of behaviorial control. Thus, we hypothesize that appropriate motor responses to a selective dopaminergic stimulation of either direct or indirect pathway depends on proper striatal clock function. Experiments were carried out on mice with a conditional knockout (KO) of the core clock gene Bmal1 from MSNs. Under baseline conditions, male and female Bmal1 KO mice display a hyperactive phenotype. To determine whether dopamine signaling was altered in the MSNs, mice were treated with a D1 and D2 receptor agonist and their locomotor activity were recorded in the context of the open field. KOs of both sexes display an attenuated response to the D1 agonist relative to controls, whereas the D2 agonist suppresses activity similarly in KO and control animals of both sexes. Data suggest that disrupted clock function in MSNs influences the locomotor outputs of the basal ganglia, particularly within the direct pathway.

Sex differences in chloride homeostasis of c-fiber primary afferents in the spinal cord dorsal horn

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