ABSTRACT. It has been known for over a century that myelin accelerates impulse propagation along axons. However, in recent years it has become clear that myelination in the central nervous system continues throughout life, and that it can be controlled by physiological brain function. Because regulation of the number, distribution, length and thickness of myelin sheaths along axons will all affect conduction timing and thus circuit function, it has been proposed that activity-regulated myelination might represent a fundamental form of nervous system plasticity. Recently we have demonstrated that neuronal activity regulates myelination along specific axons in the larval zebrafish CNS. We are currently investigating the mechanisms by which neuronal activity regulates myelination in vivo, using the power of zebrafish for gene targetting, optogenetics, functional imaging, and in vivo analysis of cell biology. We are also exploiting the suitability of zebrafish for longitudinal live imaging across scales, from molecule to system, to investigate how regulation of myelination affects the function of neural circuits. In one set of approaches we combine live imaging of neurons, myelinated axons, and neural circuits with electrophysiology to investigate how regulation of myelination affects axonal conduction and synaptic communication. In parallel we are asking how CNS myelination regulates population-level activity behaviour using zebrafish imaging based approaches. With this, we hope that zebrafish will help illuminate a poorly understood aspect of neural circuit function.

David Lyons1

1. Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom

ABSTRACT. Early-life adversity (ELA), in particular child abuse, has devastating consequences on psychological development. It is amongst the strongest predictors of psychopathologies, in particular depression, and suicide. While imaging studies suggest that ELA may lead to altered trajectories of brain structural and functional development, the cellular and molecular basis of these changes are unclear. As a protracted form of brain plasticity essential to the functional maturation of the central nervous system, myelination has recently emerged as an interesting candidate to support these changes. Using a combination of molecular and histological approaches in well-characterized post-mortem samples from depressed suicides, our research aims at describing the long-lasting impact of ELA on oligodendrocyte function and myelination. Our main findings suggest that in prefrontal regions of the brain, child abuse lastingly disrupts the epigenetic and transcriptional program of myelination, modifies the balance of oligodendrocyte-lineage cells, and associates with changes in myelin properties of individual fibers. Considering the essential role of myelination in normal brain development, these changes during critical periods may possibly mediate some of the negative mental health outcomes associated with child abuse, in particular increased vulnerability to psychopathology. Beyond myelination, our recent work focuses on glial-glial interactions and oligodendrocyte contribution to extracellular matrix plasticity, one of the multiple aspects of oligodendrocyte functions which may contribute to ELA-associated prefrontal circuits remodeling.

A. Tanti1, Gustavo Turecki1,2, Naguib Mechawar1,2 1McGill Group for Suicide Studies, Douglas Mental Health University Institute, Montreal, QC, Canada. 2McGill University, Dept of Psychiatry, Montreal, QC, Canada. Support: Fonds de Recherche du Québec – Santé; American Foundation for Suicide Prevention; ERA-NET NEURON; Canadian Institutes of Health Research.

ABSTRACT. Environmental and genetic factors interact in the development of anxiety disorders, but the underlying mechanisms remain poorly understood. Additionally, many individuals are resilient to chronic stress-associated psychiatric symptoms. To study the gene-environment interaction in psychosocial stress we used the chronic social defeat stress (CSDS) mouse model in four inbred strains [DBA/2NCrl (D2), 129S2/SvPasCrl, BALB/cAnNCrl, and C57BL/6NCrl (B6)]. To classify mice as stress-susceptible or -resilient we assessed their social avoidance behavior. We found that the behavioral response to stress was strongly moderated by the genetic background. Of the four strains, B6 was the most stress-resilient, while D2 mice were the most stress-susceptible. To examine the transcriptomic response to CSDS, we conducted RNA-seq of these two strains and found significant enrichment of myelin-related genes among the genes differentially expressed between susceptible or resilient mice compared to controls. We also measured myelin thickness by electron microscopy. We detected lower expression levels of myelin-related genes and thinner myelin in the ventral hippocampus of stress-susceptible B6, but not D2, mice. B6 susceptible mice had higher myelin-related gene expression levels and thicker myelin in the bed nucleus of the stria terminalis. In the medial prefrontal cortex, B6 resilient mice had thicker myelin on small axons, while D2 resilient mice had thinner myelin, than controls. Our results suggest myelin plasticity as one of the major brain responses to chronic psychosocial stress. Furthermore, we found brain region dependent variations in this response, and that the behavioral and transcriptomic responses to stress are genetically controlled.

MA Laine1,2,3, K Trontti1,2,3, Z Misiewicz1, E Sokolowska1, N Kulesskaya1,2,3, A Heikkinen1, S Saarnio1, I Balcells1, P Ameslon1, D Greco4, P Mattila5, P Ellonen5, L Paulin4, P Auvinen4, E Jokitalo4, I Hovatta1,2,3

1Molecular and Integrative Biosciences Research Program, University of Helsinki, Finland, 2Department of Psychology and Logopedics, University of Helsinki, Finland, 3SleepWell Research Program, Faculty of Medicine, University of Helsinki, Finland, 4Institute of Biotechnology, University of Helsinki, Finland, 5Finnish Institute of Molecular Medicine, University of Helsinki, Finland. Funding support: European Research Council, ERA-NET NEURON, Sigrid Jusélius Foundation, and the University of Helsinki

ABSTRACT. The etiology of catatonia, an executive ‘psychomotor’ syndrome seen across neuropsychiatric diseases and other medical conditions, has been obscure and its treatment unspecific. To investigate mechanisms involved in the still highly mysterious but frequent phenotype catatonia, we studied myelin mutant mice as experimental models as well as healthy and ill humans. Moreover, we approached specific preventive as well as therapeutic strategies by targeting neuroinflammation via microglia depletion. In a deeply phenotyped schizophrenia sample (N=1095), we uncovered an unexpectedly high prevalence of >25% individuals with catatonic signs. CNP rs2070106-AA, a loss-of-function genotype of a myelin-specific gene, was found associated with catatonia in two independent schizophrenia cohorts, and with white matter hyperintensities in a general population sample. Subtle defects of myelination in mouse mutants not only of Cnp1, but also of Plp1 or Mbp lead to catatonia, coinciding with microgliosis. We therefore hypothesized that neuroinflammation of myelinated tracts might be causative of catatonia and alleviated by depleting microglia. We demonstrate by behavioral phenotyping, MR-spectroscopy, and immunohistochemistry that the inhibitor of CSF1 receptor kinase signaling, PLX5622, can attenuate neuroinflammation and catatonia in Cnp1 mutants. We suggest that catatonic signs and possibly other executive function defects in white matter disease can be efficiently targeted by microglia-directed therapies.

Hannelore Ehrenreich, MD, DVM Clinical Neuroscience, Max Planck Institute of Experimental Medicine, Göttingen, Germany

ABSTRACT. Functional connectivity (FC) networks in human infants have been previously shown to vary in their development, with sensorimotor areas showing more connectivity than association cortex in infancy. However, the developmental trajectory of FC changes between infancy and adulthood and these changes’ potential correspondence to behavioral development are not well-characterized. The objective of this study was therefore to evaluate cortical FC and sensorimotor function in the Thy1-GCaMP6f genetically-encoded calcium indicator (GECI) mouse, using longitudinal mesoscopic calcium imaging and sensorimotor behavioral assays. We hypothesized that performance on Locomotor Activity/exploration and Catwalk assays would improve as development proceeds, in parallel with an increase in homotopic motor cortex FC. Calcium and hemoglobin resting-state data were collected from Thy1-GCaMP6 mice at five developmental timepoints (postnatal day 15 (P15), P22, P28, P35, and P60). Seed-based FC displayed characteristically high correlation for homotopic contralateral regions and passed quality control metrics at all timepoints. We also evaluated the performance of P22 and P60 Thy1-GCaMP6 mice and wildtype littermates in a Locomotor Activity/exploration assay. Our preliminary analyses detected no abnormalities in distance traveled or time in center by the Thy1-GCaMP6 mouse at either developmental timepoint, suggesting typical activity and anxiety-related levels in these mice. We are currently analyzing gait-related metrics such as stride length, duty cycle, and base of support measured on the Catwalk system. Taken together, these neuroimaging and behavioral results will help elucidate the developmental trajectory of FC and sensorimotor function and can provide a reference dataset in our future studies of genetic models of neurodevelopment.

RM Rahn1,2, SM Maloney3, LM Brier2, AR Bice2, JP Culver2,4,5, JD Dougherty1,3 1Department of Genetics, 2Department of Radiology, 3Department of Psychiatry, 4Department of Physics, 5Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, MO, USA. Funding Support: The Simons Foundation, NIGMS T32 GM081739-10, NINDS R01 NS090874, NINDS R01NS099429, NHGRI R01 HG008687, NIMH R01 MH107515, NIDA R21 DA041883, NIMH U01 MH109133, NINDS R01 NS104471

ABSTRACT. Winona Booher1, 2, Eliza Elliotte3, Anuradha Prakash4, Marissa Ehringer1, 2

Open-field activity (OFA) is widely viewed as proxy for measuring anxiety behavior in mice. DeFries et al. (1978) bidirectionally selected for OFA that resulted in a 7.8-20 fold difference. Mice with high OFA (high) are considered a model of low anxiety, and mice with low OFA (low) represent a model of high anxiety. The high and low strains of mice also show correlated differences in other anxiety-related behaviors including light-dark box, elevated plus maze, mirror chamber test, and elevated square maze (Henderson et al., 2004). Due to the high correlation of anxiety and alcohol use disorders (AUDs), we have begun to characterize these strains for several alcohol phenotypes. Using a two-bottle choice paradigm, it was revealed that female high mice consume significantly more alcohol than the female low mice. To evaluate acute sensitivity to alcohol, we tested these strains for the loss of righting reflex (LORR). Both male and female high mice regain their righting reflex significantly faster than the male and female low mice, respectively. This increased sensitivity to alcohol’s sedative effects observed in the low mice may explain why the low mice consume less alcohol than the high mice in the two-bottle choice paradigm. In addition, we are currently testing these strains for acute alcohol induced locomotor sensitization and alcohol metabolism. Finally, because the hippocampus may play a role in both anxiety and AUDs, we have collected alcohol naïve brains for hippocampal RNA sequencing to examine differential gene expression between both male and female high and low mice.

1Institute for Behavioral Genetics, University of Colorado, Boulder, CO, USA 2Department of Integrative Physiology, University of Colorado, Boulder, CO, USA 3Hollings University, Roanoke, VA, USA 4Fairview High School, Boulder, CO, USA Supported by the University of Colorado internal funds

ABSTRACT. The gene glyoxalase 1 (Glo1) has been previously implicated in anxiety- and depression-like behaviors in mice, and also in binge-like ethanol consumption. Transgenic mice overexpressing Glo1 show increased ethanol consumption and anxiety- and depression-like behaviors. In contrast, genetic knockdown of Glo1 or pharmacological inhibition of the enzyme leads to lower levels of drinking and lower anxiety- and depression-like behaviors. To further characterize the role of Glo1 in ethanol-related behaviors, we investigated whether genetic or pharmacological manipulations could alter ethanol reward sensitivity and ethanol withdrawal severity. Transgenic mice overexpressing Glo1 and wild type littermates were tested for ethanol conditioned place preference (CPP). Transgenic mice acquired significant CPP after four conditioning trials, whereas wild type mice required eight trials. In a separate experiment with wild type mice, treatment with a GLO1 inhibitor was found to reduce ethanol CPP expression compared to vehicle. Wild type mice treated with a GLO1 inhibitor during ethanol withdrawal showed reduced seizure severity compared to vehicle-treated mice, although seizure severity was still elevated compared to control (non-withdrawal) mice. Vehicle-treated mice had significantly more anxiety-like behavior in an open field test than control mice, and inhibitor treatment completely blocked this effect. These data extend previous work with Glo1 and demonstrate its involvement in ethanol reward and both the physiological and affective effects of ethanol withdrawal. Taken together, these experiments provide further evidence that Glo1 is an important target for ethanol research and may be a potential target for novel pharmacotherapy development.

A.M. Barkley-Levenson1, A. Page1, A. Lee1, A.A. Palmer1 1Department of Psychiatry, University of California - San Diego, La Jolla, CA, 92093

ABSTRACT. Opioid dependence is a heritable substance use disorder that has reached epidemic proportions within the US, however its genetic etiology is poorly understood. Murine forward genetics can identify novel genetic factors and biological pathways relevant to the human condition, and could lead to improved therapeutics. To facilitate gene mapping of opioid addiction traits in Reduced Complexity Crosses (RCCs), we phenotyped two closely related inbred mouse substrains, BALB/cJ and BALB/cByJ, for behavioral responses to the mu opioid receptor agonist oxycodone (OXY). BALB/cJ and BALB/cByJ mice were segregated from a colony of BALB/c mice at generation F36 in 1935 and are nearly 100% isogenic. Low genetic diversity combined with high phenotypic diversity facilitates gene mapping. To capture behaviors associated with various stages of the opioid addiction process, we used our multistage addiction assessment protocol (MSAAP) to examine OXY-induced locomotion, drug-free and state-dependent conditioned place preference (CPP), acute antinociception EC50s and EC50 shifts (tolerance), spontaneous emotional/affective withdrawal, body weight loss, and protracted withdrawal. We found differences in state dependent CPP, OXY induced analgesia, acute emotional/affective withdrawal, and body weight loss in response to OXY. Together, the increased state dependent OXY-CPP and spontaneous OXY withdrawal paired with increased antinociceptive potency and increased OXY-induced weight loss suggest BALB/cJ mice are generally more sensitive to the behavioral and physiological effects of OXY than BALB/cByJ mice. Future studies will employ a systems genetic approach combining behavioral QTL, expression QTL, and single cell RNA-sequencing to identify the genetic basis and molecular mechanisms underlying genetic differences in OXY phenotypes.

Jacob A. Beierle 1,2,3, Emily Yao1, Julia Scotellaro 1, Camron D. Bryant 1

1. Laboratory of Addiction Genetics, Department of Pharmacology and Experimental Therapeutics and Psychiatry, Boston University School of Medicine 2. Transformative Training Program in Addiction Science, Boston University School of Medicine 3. T32 Biomolecular Pharmacology Training Program, Boston University School of Medicine

ABSTRACT. Cognitive deficits are a major symptom of nicotine withdrawal. These deficits are heritable, yet the genetic basis is unknown. Our lab has developed a mouse model of nicotine withdrawal deficits in learning, using chronic nicotine exposure and fear conditioning. Here, we aimed to utilize a systems genetics approach to characterize inbred strain differences and identify genetic variants underlying nicotine withdrawal deficits in learning. Thus far, male mice (n=4-13 per strain per treatment) from 21 inbred strains (C57BL/6J, BALB/cJ, CBA/J, FVB/NJ, NOD/ShiLtJ, A/J, C3H/HeJ, DBA/2J, AKR/J, DBA/1J, 129S1/SvlmJ, SJL/J, SWR/J, LP/J, BTBR T+ ltpr3tf/J, NZB/BINJ, SM/J, MA/MyJ, 129S4/SvJaeJ, 129S8/SvEvNimrJ,129-Elite) received either chronic saline or nicotine (12.6 or 18 mg/kg per day for 12 days), and then were tested for hippocampus-dependent learning deficits using contextual fear conditioning. We have replicated a previously observed deficit in the C57BL/6J and identified SJL/J as exhibiting enhanced learning during withdrawal from chronic nicotine. Additionally, we are utilizing the BXD panel to identify genetic variants underlying these differences. Male and female mice (n=6-11 per sex per strain, 31 strains) were tested for contextual fear conditioning after receiving either chronic saline or nicotine (6.3 mg/kg per day for 12 days). Quantitative trait locus (QTL) mapping analyses using GeneNetwork identified a significant QTL on chromosome 4 (82.4 Mb, LRS =23.74, p<0.05). Utilizing publicly available hippocampal gene expression data from naive animals, we identified 4 positional candidates (Ptprd, Tyrp1, 2310067E19Rik, Nfib). To expand upon these positional candidates and identify hippocampal transcriptome changes associated with nicotine withdrawal, we will soon complete mRNA-sequencing in the BXD lines exhibiting extreme phenotypic variation.

L.R. Goldberg1, S.M. Mooney-Leber1, M.G. Kutlu1, D. Zeid1, G. Peltz2, T.J. Gould1 1Department of Biobehavioral Health, Penn State University, University Park, PA, USA 2Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University School of Medicine

ABSTRACT. Although mice carrying engineered mutations have provided a wealth of insights into the molecular and physiological mechanisms of behaviour, each of these studies have typically reported a single mutant and because different laboratories use non-standardized protocols there is an absence of quantitative data enabling comparison of phenotypes and metaanalyses. We have studied 58 lines of mice using a standardized pipeline in a single facility and generated a resource including behavioural measures in five apparatus that generated innate and learned responses; hippocampus slice electrophysiology using multielectrode arrays; and hippocampus transcriptome data. The targeted genes encode different classes of proteins in the postsynaptic proteome of excitatory synapses. These data reveal unexpected findings leading to a novel model for the synaptic basis of innate and learned behaviour.

ABSTRACT. The beginnings for providing a deep understanding of the brain in development and disease is at the genome. Moving outward there are networks of genes that are expressed at specific times and in specific cells that orchestrate neurodevelopment. The focus of this presentation is on the richness of the FANTOM5 transcriptome dataset to identify both coding and non-coding elements in mouse cerebellar development, as a proxy for the larger brain and in the context studies to identify genes involved in neurodevelopmental disorders. Novel long non-coding RNAs and enhancers RNAs are identified that could regulate gene expression. And genes novel to cerebellar development have been identified through bioinformatic mining of these data. We look forward to moving this data to the human to help identify the gene-based etiology of neurodevelopmental disabilities.

Dan Goldowitz Centre for Molecular Medicine and Therapeutics, Dept of Medical Genetics, Univ British Columbia

ABSTRACT. A major challenge facing Autism Spectrum Disorder (ASD) is the large and growing number of genes and gene variants of unknown functional significance. Here, we used Caenorhabditis elegans to systematically functionally characterize ASD-associated genes in vivo. Using our custom machine vision system we quantified 26 phenotypes spanning morphology, locomotion, sensitivity, and habituation learning in 87 strains each carrying a mutation in an ortholog of an ASD-associated gene. We identified hundreds of novel genotype-phenotype relationships ranging from severe developmental delays and uncoordinated movement to subtle deficits in sensory and learning behaviours. We clustered genes by similarity in phenomic profiles and used epistasis analysis to uncover parallel and convergent networks centered on CHD8●chd-7 and NLGN3●nlg-1 that underlie hypersensitivity and impaired habituation. We then leveraged our data for in vivo functional assays to gauge missense variant effect. Expression of human NLGN3 in nlg-1 mutant C. elegans rescued their hypersensitivity and habituation impairments, confirming functional conservation. We then tested the rescuing ability of all ASD-associated neuroligin variants, revealing varied partial loss-of-function despite proper localization. Finally, we used CRISPR-Cas9 Auxin Inducible Degradation to determine if phenotypic abnormalities caused by developmental loss of nlg-1 can be reversed by adult expression. This work charts the phenotypic landscape of ASD-associated genes, offers novel in vivo variant functional assays, and therapeutic targets for ASD

Troy McDiarmid1, Manuel Belmadani2, Joseph Liang1, Fabian Meili1, Kota Mizumoto3, Kurt Haas1, Paul Pavlidis1,2, Catharine Rankin1

1Djavad Mowfaghian Centre for Brian Health, University of British Columbia, 2211 Wesbrook Mall, Vancouver, BC, V6T 2B5. Department of Psychiatry and Centre for Brain Health, Michael Smith labs, UBC, Vancouver BC, Department of Biology, Life Sciences Centre, 2406-2350 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3. Funding: CIHR Project Grant to CHR, SFARI grant to CHR, KH and PP.

ABSTRACT. The synaptic proteome is widely believed to be the molecular machine that underpins the core functions of neurons – the integration and transfer of information from one cell to another. Perhaps unsurprisingly it is enriched for proteins whose genes are linked to a wide range of human neurological conditions. However GWAS datasets from these conditions map less clearly onto the synaptic proteome often with weak or no significant enrichment. The synaptic proteome can be subdivided, on the basis of network topology into clusters that each have enriched functional associations. We hypothesised that these topological communities form natural groups for gene set analysis and contain information not only about protein encoding genes with a mechanistic association with the phenotype but also with interaction partners whose role is important but less direct. We combined 30 published synaptic proteomic studies from 2000 to date to obtain a list of 6500 molecules. We retrieved protein-protein interactions (PPIs) for combined list and built the most complete up-to-date PPI networks for presynaptic and postsynaptic compartments. We then divided this proteome up into sub-communities on the basis of network topology. We analysed three large Genome Wide Associations Studies of genetic associations with human cognitive ability, educational attainment and human diseases including autism and neurodevelopmental disorders. We find closely interacting sub-communities within the synaptic proteome that are very highly enriched for genetic associations with a range of phenotypes and disorders. These sub-communities likely indicate molecular pathways that span complex traits and disease

ABSTRACT. Autism spectrum disorder (ASD) is a heterogeneous group of neurodevelopmental disorders that affects boys four times more frequently than girls. In addition to the clinically characterized deficits in social interaction and communication, a number of other conditions – including attention deficit/hyperactivity disorder, learning disorders, and seizures – frequently co-occur with ASD. While it has been proposed that developmental dysregulation of the locus coeruleus-norepinephrine (LC-NE) system underlies some of the behavioral deficits associated with these conditions, supporting evidence is lacking. Unfortunately, current strategies aimed at testing this developmental hypothesis are restricted to manipulation of the adult LC-NE system, due to the difficulty of targeting the developing LC without affecting other central and peripheral NE neurons. To circumvent this problem, we exploited our finding that LC-NE neurons are uniquely defined by embryonic expression of the transcription factor Engrailed 1 (En1) and later expression of dopamine β-hydroxylase (Dbh), the enzyme required to convert dopamine to NE. We generated a conditional knockout allele of Dbh and crossed it with En1cre to selectively eliminate NE synthesis in LC neurons during embryonic development (LC-NE mutants). Unlike the full Dbh knockout, which is embryonic lethal, LC-NE mutants survive to adulthood, allowing us to evaluate the consequences of embryonic disruption of LC-NE on adult behavior. We subjected LC-NE mutants and littermate controls to a battery of behavioral tests to assess sociability, general activity, and learning. We found that male, but not female, LC-NE mutants exhibit reduced sociability, as well as hyperactivity, impaired contextual learning and increased incidence of seizures. Surprisingly, results from mass spectrometry revealed that only female LC-NE mutants have elevated dopamine levels in the cortex consequent to Dbh loss. These data suggest that the behavioral phenotypes observed in male mutants are likely due to loss of LC-NE, and that elevated dopamine in females may compensate for NE loss. Taken together, our data demonstrate that LC-NE mutants exhibit several behavioral deficits observed in ASD and associated disorders, providing a new experimental system to investigate how developmental dysregulation of LC-NE drives these sex-specific phenotypes. 1Neurobiology Laboratory, 2Neurobehavioral Core, National Institute of Environmental Health Sciences, National Institutes of Health, Dept. of Health and Human Services, Research Triangle Park, NC, USA. 3Mouse Behavioral Phenotyping Core, CIDD, University of North Carolina-Chapel Hill

I Evsyukova1, N Plummer1, KG Smith1, JM Strauss1,2, N Riddick3, S Moy3, JD Cushman1,2, P Jensen1

ABSTRACT. The synaptic connectome of C. elegans has been mapped completely, and efforts are ongoing to map the connectomes of other animals. However, chemical synapses represent only one of several types of signaling interactions upon which the nervous system depends. In particular, neuromodulatory interactions involving monoamines, neuropeptides, or classical neurotransmitters are widespread in all nervous systems, and these interactions often occur extrasynaptically between neurons unconnected by wired synapses. In the nematode C. elegans, it is feasible to map these neuromodulatory networks comprehensively and at a single-cell level and examine in detail how wired and wireless signaling interact in the context of the connectome. In this talk, I will describe what we have learned about the functional organisation of neuromodulatory circuitry involved in the control of behavioural states such as arousal, as well as our ongoing efforts to comprehensively map extrasynaptic connectome networks in the worm. In addition, I will discuss our identification of new ionotropic receptors for monoamines and other neuromodulators, which may represent novel targets for anti-parasitic drugs.

William Schafer, Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK