ABSTRACT. Drug abuse continues to be an extremely serious public health problem. While human genome-wide association studies (GWAS) have begun to elucidate genes that influence drug abuse and various traits that are relevant to drug abuse, translation of those results into biological insights remains limited. With the support of a NIDA P50 grant, we are taking a complementary approach in which we study the genetic basis of numerous drug abuse-relevant behavioral traits using genetically heterogeneous rats. We ue selected rats rather than mice beacause our studies focus on complex operant and other procedures that are difficult to perform in mice. We are utilizing a unique rat population: the N/NIH heterogeneous stock (HS), which is derived from 8 deeply sequenced inbred rat strains and has been maintained as an outbred population for more than 80 generations. Because of the extensive number of accumulated generations (and thus chromosomal recombinations) HS rats allow us to implicate very small chromosomal regions in specific behavioral tasks. Drs. Terry Robinson and Shelly Flagel from The University of Michigan focus on the propensity of animals to attribute motivational value (“incentive salience”) to discrete reward cues. Dr. Hao Chen from University of Tennessee Health Sciences Center examines intravenous nicotine self-administration behavior in adolescent rats. Drs. Jerry Richards and Paul Meyer from University at Buffalo, Research Institute on Addictions are studing sensation seeking, impulsivity and cocaine-induced cue preferences. In addition to the projects directly supported by this grant, our center provides core resources and support for multiple additional projects, including two U01 grants led by Olivier George (The Scripps Research Institute) that focus on cocaine and oxycodone self-administration. In order to identify specific genes for specific behaviors, we are integrating data about behavioral, gene expression and known protein coding variants using a systems genetics approach. 1 Department of Psychiatry, University of California San Diego, La Jolla, CA, USA. Funding Support: National Instutute of Drug Abuse P50DA037844.

ABSTRACT. Substance use disorders (SUDs) are highly prevalent and result in significant burden on affected individuals, loved ones and society but few effective treatments exist. Efforts to develop effective therapies have been hampered by gaps in our knowledge about the underlying biological mechanisms that increase risk for SUDs, including genetic causes. Rodent models have proven useful for assessing the genetics of behaviors that predict propensity to use drugs, initial drug response and behaviors that emerge after repeated drug exposure and withdrawal.

Our laboratory is using a relatively new eight-way recombinant inbred mouse population, the Collaborative Cross (CC), which offers increased genetic and phenotypic diversity over traditional inbred mouse strains. We identified two CC strains that are phenotypic outliers novelty-induced locomotion - a trait previously shown to predict addiction-related behaviors. We have extensively characterized the two strains and found divergent behavioral profiles for cocaine-related behaviors including initial locomotor sensitivity to cocaine. We performed genetic mapping in a F2 intercross population derived from the CC strain with low cocaine locomotor activation and identified three significant quantitative trait loci (QTL). We are currently prioritizing candidate genes using a variety of bioinformatic tools and designing strategies to further narrow regions of interest.

Our work highlights the utility of the CC population for studying complex behaviors including those that model SUDs. We believe that this unique mouse population will be useful for identifying genes associated with increased vulnerability and/or resistance to the development of SUDs.

1Department of Genetics, 2Bowles Center for Alcohol Studies, 3Lineberger Comprehensive Cancer Center, 4Department of Psychiatry, 5Division of Pharmacotherapy and Experimental Therapeutics, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC, 6The Jackson Laboratory, Bar Harbor, Maine Research funding provided by grant R01MH100241 from the National Institute of Mental Health and P50 DA039841 from the National Institute on Drug Abuse, National Institutes of Health

ABSTRACT. This work is presented on behalf of the Anorexia Nervosa Genetics Initiative and the Eating Disorders Working Group of the Psychiatric Genomics.

1 Center of Excellence for Eating Disorders, Department of Psychiatry, University of North Carolina, Chapel Hill, North Carolina, USA

Anorexia nervosa (AN) is heritable (twin-based estimates ~50-60%) and has the highest mortality rate of any psychiatric disorder. Although the familial component of AN has been well documented, biological mechanisms contributing to AN risk are poorly understood. The objective of this study was to examine the genetic risk factors in the etiology of AN. Using 15,807 AN cases and 50,411 controls from the Anorexia Nervosa Genetics Initiative (ANGI) and the Eating Disorders Working Group of the Psychiatric Genomics Consortium (PGC-ED), we performed a genome-wide association study (GWAS) of 7,696,751 common variants (minor allele frequency > 1%). In addition to identifying six genome-wide significant regions associated with AN risk, we observed high positive genetic correlations between AN and obsessive-compulsive disorder, major depressive disorder, and anxiety, meaning that AN shares a similar genetic architecture with these psychiatric disorders. Additionally, there were strong negative genetic correlations between AN and fasting insulin levels, body fat percentage, and BMI as well as a strong positive genetic correlation between AN and high-density lipoprotein (HDL) cholesterol, suggesting a protective role for AN risk against these unfavorable metabolic traits. Our results replicate and build on the previous PGC-ED GWAS findings (Duncan et al., 2017, Am J Psychiatry) and encourage re-conceptualization of AN as both a psychiatric and metabolic disorder.

Main Funding Support: Klarman Family Foundation, National Institute of Mental Health, Wellcome Trust Case Control Consortium 3, Lundbeck Foundation Initiative for Integrative Psychiatric Research (iPSYCH), QSkin Sun and Health Study, Riksät (Swedish National Quality Register for Eating Disorders), National Institute for Health Research (NIHR) Biomedical Research Centre at South London, Maudsley NHS Foundation Trust and King’s College London.

ABSTRACT. Alaa Koleilat1 Trace Christenson2, Aaron M. Lambert3, Jeffrey L. Bellah 4, Mark A. Masino3, Stephen C. Ekker1, Lisa A. Schimmenti5,6 1Department of Biochemistry and Molecular Biology, Mayo Clinic 2Mayo Clinic Microscopy and Cell Analysis Core, Mayo Clinic 3Department of Neuroscience, University of Minnesota, Twin Cities 4Department of Genetics and Development, Columbia University 5Department of Otorhinolaryngology, Mayo Clinic 6Department of Clinical Genomics, Mayo Clinic

The mariner mutant, a zebrafish model of Usher Syndrome Type 1 (USH1), is caused by homozygous premature stop codon variants in myo7aa and exhibits deafness, abnormal swimming and balance defects. We identified that this model has fewer ribbon vesicles and a smaller ribbon synapse area compared to wildtype. Currently, there are no available pharmacological treatments to improve hearing for patients with USH1. The aim of this study is to rescue the abnormal phenotypes exhibited by the mariner mutant through the use of L-type voltage gated calcium channel agonists. We hypothesize that these compounds will increase intracellular calcium and mediate the release of neurotransmitter filled vesicles at the basolateral end of the hair cell, increasing the probability that hair cell deflection will be coupled to ribbon vesicle release. Wildtype and mariner mutant swimming behavior was measured by the global change in body orientation as a function of time in response to an electric stimulus. Hearing assessments were conducted by administering various tones and recording the presence or absence of a startle response. Lastly, ribbon synapse structures were examined by electron microscopy. Our data supports that treatment with L-type voltage gated calcium channel agonists shifts mariner mutant swimming behavior towards wildtype swimming, improves startle to sound and causes a physiological change at the ribbon synapse. This data represents a significant step towards discovering compounds to treat hearing loss caused by human pathogenic variants in MYO7A.

ABSTRACT. CM Nelson1,2, H Lee3, RG Krug3, A Kamilova1, NN Madigan4, KJ Clark3, VA Lennon2,4,5, AJ Windebank4, JR Henley1,6 Following injury, the mammalian spinal cord forms a glial scar and fails to regenerate. In contrast, spinal cord tissue of vertebrate fish regenerates and swimming movements recover. The mechanisms underlying functional regeneration are not fully understood. Here we report that the glucocorticoid pathway regulates functional neural regeneration by directly affecting ependymal glia. Cord transection in larval zebrafish (Danio rerio) causes paralysis and neural cell death, with subsequent ependymal glial proliferation, extension of bipolar glia across the lesion, and neurogenesis. Functional connectivity is restored by axons extending from spared and nascent neurons along trans-lesional glial bridges. Studies in the transgenic SR4G reporter zebrafish reveal downregulation of both the glucocorticoid receptor Nr3c1 and glucocorticoid signaling activity in ependymal glia follow injury. Functional recovery is impaired by dexamethasone (Dex) treatment, which attenuates injury-induced ependymal glial proliferation, bridging, and neural tissue regeneration, and is independent of haematopoietic-derived immune cells. Loss-of-function mutagenesis of nr3c1 reverses functional impairment by Dex. By contrast, in the adult rat, NR3C1 levels and signaling activity in ependymal glia are upregulated following spinal cord transection. The unanticipated negative regulation of neural regeneration by glucocorticoid signaling via a direct effect on ependymal glia calls into question the putative benefit of corticosteroid therapy in early management of spinal cord injury. Indeed, therapeutic down-regulation of CNS glucocorticoid receptors might improve patient outcomes. Departments of 1Neurological Surgery, 2Laboratory Medicine and Pathology, 3Biochemistry and Molecular Biology, 4Neurology, 5Immunology, and 6Physiology and Biomedical Engineering, Mayo Clinic, College of Medicine, Rochester, MN, USA 55905. Present address, AK: Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, TN, USA 37232. Funding Support: NIH-NINDS (USA) R01 NS67311.

ABSTRACT. David G. Ashbrook1, Danny Arends2, Megan K. Mulligan1, Evan G. Williams3, Cathleen Lutz4, Alicia Valenzuela4, Casey Bohl1, Jesse Ingels1, Melinda McCarty1, Arthur Centeno1, Reinmar Hager5, Johan Auwerx6, Saunak Sen7, Lu Lu1, Kelley Harris8, Abraham Palmer9, Yu-yu Ren9, Jonathan K Pritchard10, Andrew G. Clark11, Robert W. Williams1 1. Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, USA 2. Lebenswissenschaftliche Fakultät, Albrecht Daniel Thaer-Institut, Humboldt-Universität zu Berlin, Invalidenstraße 42, Berlin, Germany 3. Department of Biology, Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland 4. Mouse Repository and the Rare and Orphan Disease Center, The Jackson Laboratory, Bar Harbor, ME USA 5. Division of Evolution & Genomic Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester, UK 6. Laboratory of Integrative and Systems Physiology, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland 7. Department of Preventive Medicine, University of Tennessee Health Science Center, Memphis, TN, USA 8. Department of Genome Sciences, School of Medicine, University of Washington, Seattle, WA, USA 9. Institute for Genomic Medicine, Department of Psychiatry, University of California San Diego, La Jolla, CA, USA 10. Department of Genetics, Stanford University, Stanford, CA, USA, 11. Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY.

Abstract The BXD mouse genetic reference population is the most deeply phenotyped mammalian model system, with ~6000 phenotypes in GeneNetwork.org, the repository for BXD family data. GeneNetwork allows examination of complex interactions between gene variants, phenotypes from different biological levels, and environmental factors. The family consists of 152 inbred strains, each of which is a unique mosaic of alleles from the C57Bl/6J and DBA2/J, and segregate for ~4.5 million known sequence variants. Using the current genotype data, it is possible to achieve mapping precision of under ±2.0 Mb over most of the genome. We have carried out 40X sequencing of all BXD strains using a Chromium linked-read barcoding strategy. This deep sequencing of ~40 kb DNA fragments has several uses including: identification of structural variants not reliably detected using short read shotgun sequencing; identification of variants unique to each ‘epoch’ of BXD, derived in the last four decades; identification of rare spontaneous mutations; and production of the first ‘infinite marker maps’, allowing even higher precision mapping of phenotypes. We have confirmed ~4.5 million variants between the DBA/2J and C57BL/6J parents. We have aligned sequences for >50 samples and identified haplotype blocks with greater precision than was possible with microarray-based genotyping. Candidates have been identified for a phenome-wide association study. This family is an excellent resource for testing networks of causal and mechanistic relations among clinical phenotypes and millions of molecular and organismal traits, including metabolic syndrome, infection, addiction, neurodegeneration, and longevity. Full sequencing of all lines will only increase its usefulness.

ABSTRACT. Nicole C. Nelson

Media coverage of animal behavior genetics research often misrepresents the complex etiology of behavioral disorders, typically portraying these disorders as arising from the effects of single genes rather than multiple genetic and environmental causes. This paper explores one mechanism through which these misrepresentations develop: the separation of knowledge about environmental contributors to behavior from knowledge about genetic contributors during the publication process. Using ethnographic research from animal behavior genetics laboratories, I describe how researchers informally acquire knowledge about how environmental factors (noise, smells, other stressors) alter mouse behavior, and how the designation of this knowledge as “methodological” or “tacit” limits its circulation outside of the laboratory. The limited circulation of environmental knowledge, as compared to the much wider circulation of genetic findings, contributes to a distorted public perception of disease etiology. As a counterfactual, I present media coverage of published instances of environmental knowledge (Crabbe, Wahlsten and Dudek’s well-known 1999 paper on mouse behavior and interactions with the laboratory environment), demonstrating that alternative media narratives about behavioral disorders are possible. This research has important implications for the way that animal behavior geneticists communicate their findings publically, suggesting that more effort to circulate environmental knowledge is needed to counterbalance genetic knowledge.

ABSTRACT. Melin MD1, Zhou M1, Sudhof TC1

Essential tremor (ET) is the most common movement disorder, affecting more than 200,000 US citizens each year. However, our understanding of this disease is still very limited, therapies are either invasive or have minimal impact, and we have very few predictive and accurate animal models to study. It has been thought that the primary cause of essential tremor lies in the inferior olivary nucleus, but more recent studies suggest that the cerebellum plays an important role in the tremor phenotype. Previous work in the Sudhof Lab has shown that the knockout of the Synaptotagmin 2 (Syt2) calcium sensor in parvalbumin-positive neurons produces and Essential Tremor-like behavior in mice. Using this novel genetic mouse model we explored which brain region underlies the etiology of essential tremor via spatial and cell type specific knockout of Syt2. Results from this study indicate that the cerebellum plays an active role in generating tremor in this mouse model. Furthermore, we showed that aberrant functioning of the deep cerebellar (fastigial, dentate, and interposed) nuclei contribute to the ET phenotype. The findings from this study indicate that dysfunction of the cerebellum may indeed be responsible for the manifestation of ET, and it validates this Syt2-PV KO mouse as a more accurate model of ET than previous models. Thus this study offers a novel method of studying ET, as well as a window into the possible brain regions and cell type that could be targeted for more effective treatment.

1Department of Molecular and Cellular Physiology, Stanford University. Stanford, California. Funding: Stanford BioX Undergraduate Research Major Grant.

ABSTRACT. Goetjen AM^{1, 2}, Clinton KL², Lieberman R^{2, 3}, & Covault J^1-3

¹University of Connecticut Graduate School Biomedical Sciences PhD Program: Genetics and Developmental Biology; ²UConn Health Department of Psychiatry; ³University of Connecticut Graduate School Biomedical Sciences PhD Program: Neuroscience

Approximately 8.5% of American adults are afflicted by either moderate or severe alcohol use disorder (AUD), defined as excessive alcohol use within the last twelve months that impedes the safety of oneself and others, while being unable to reduce one’s drinking. The Collaborative Study on the Genetics of Alcoholism used linkage analysis to suggest, in European Americans, a significant association between alcohol dependence and a 140kb haplotype block in GABRA2. Synonymous SNP rs279858 tags this haplotype block, and has a minor allele frequency of 0.45. In addition to AUD, rs279858 has been associated with a number of neuropsychiatric phenotypes including comorbid illicit drug use and childhood conduct disorder. Neuro-endophenotypes such as increased activation of the insular cortex and nucleus accumbens in reward anticipation and differential activation of the ventral tegmental area and medial frontal cortex in response to alcohol cues are also associated with this haplotype block. The chr4p12 locus codes for γ1, α2, α4, and β1 GABA receptor subunits; iPSC lines carrying the minor allele at rs279858 have reduced expression not only of GABRA2, but the other three genes within this cluster. Virtual chromatin conformation capture (4C) data supports this hypothesis of cis regulation of GABA gene expression. Identification and characterization of allele-specific variants involved in mediating long-range intrachromosomal interactions in this locus is a step forward in the process of elucidating genetic risk variants for AUD and subsequently developing more-specific therapies for those at increased genetic risk.

ABSTRACT. Developing therapeutics to address cognitive symptoms in Alzheimer’s disease (AD) remains a priority. However, non-cognitive symptoms significantly impact quality of life for patients and caregivers. Our recent work suggests that genetic mechanisms underlying cognitive decline are distinct from non-cognitive symptoms (e.g. decline in muscle strength). Understanding underlying causes of non-cognitive symptoms in AD is important, as these will likely require therapeutic attention. Here we use a mouse genetic reference panel that better models AD in humans to identify genetic mechanisms regulating grip strength--a measure of frailty that is associated with aging and increased risk of AD in humans. Decline in grip strength was measured from 6 to 14m in a genetically diverse panel of AD transgenic mice, and their age-matched nontransgenic controls (Ntg). Both AD and Ntg mice showed age-related decline in grip strength; however, the magnitude of decline was dependent on background strain (n=25 strains). Quantitative trait loci (QTL) mapping identified a locus on mouse chromosome 12 (Chr12: 57.8-65.0Mb) associated with variation in grip strength in the AD population that differed from Ntg controls (Chr6: 17.5-28.2Mb). These data suggest genetic modifiers of motor function may differ in the AD versus normal aging, which was supported by weak correlation between grip strength in AD vs. Ntg strains (r 2=0.14, p=0.08). Combined with ongoing work, we demonstrate that genetic mechanisms modulating cognitive and motor-related decline in AD are distinct. We are using existing gene expression data and variant prediction to identify positional candidates for validation and potential therapeutic targets. 1. The Jackson Laboratory, Bar Harbor, Maine, USA 2. University of Tennessee Health Science Center, Memphis, TN. Funding Support: NIA 1 R01 AG057914-01 to C.C.K., NIA 1 R01 AG054180-01A1 to C.C.K

ABSTRACT. Ja-Hyun Baik Molecular Neurobiology Laboratory, Dept. of Life Sciences, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, South Korea

Impulsive behavior—the tendency to act in premature, risky, or inappropriate ways, without consideration of the consequences—is often associated with psychiatric conditions such as drug addiction, as well as eating and personality disorders. Because of the complex aspects of impulsivity, neural correlates of impulsivity have not been well characterized yet despite its clinical and social importance. Increasing evidence from both human and animal studies suggests the importance of dopaminergic regulation in the pathophysiology of impulsive behavior. We now show that the absence of the D2 dopamine receptor (D2R) increases impulsive behavior in mice, whereas restoration of D2R expression specifically in the central amygdala (CeA) of D2R knockout mice normalizes their enhanced impulsivity. I will present recent findings obtained in our laboratory in the analysis of the role of D2R for the control of impulsive behavior using genetic, anatomical and optogenetic manipulations. Our identification of the key contribution of D2R-expressing neurons in the brain circuit to the control of impulsive behavior may provide a basis for the development of new approaches to the management of neuropsychiatric disorders associated with impulsivity.

[This work was supported by the Brain Research Program (2013M3C7A1056101), Bio & Medical Technology Development Program (2016M3A9D5A01952412), Mid-Career Researcher Program (2017R1A2B4008875) of the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT, & Future Planning of the Republic of Korea and by a Korea University grant.]

ABSTRACT. Luc Maroteaux1, Stéphane Doly1, Emily Quentin1, Arnauld Belmer1

A functional stop codon in the human 5-HT2B-receptor gene (HTR2B) releases impulsive behavior. Similarly, Htr2B knockout (Htr2B−/−) mice displayed more impulsive choice, sought novelty, and were more active after receiving a D1 dopamine receptor agonist, fully consistent with a role of serotonin (5-HT) in the rewarding effects of psychostimulant. Long-term inactivation (chronic pharmacological blockade or genetic ablation) of the 5-HT2B receptor is required for novelty- and cocaine-induced hyperlocomotion, while acute pharmacologic inhibition had no effect. Interestingly, in cocaine-injected Htr2B-/- mice, reduced release of DA blunts activation of medium spiny neurons of the NAcc shell, without modification of reactivity of the dorsal striatum. We also observed that 100% of the retrogradly labeled DA neurons from NAcc to VTA do express 5-HT2B receptors that modulate their activity by controlling firing rate. Local recombination of Htr2B gene in DA neurons recapitulates novelty- and cocaine-induced hyperlocomotion seen in Htr2B-/- mice or chronic antagonist-treated mice. A delay appears thus necessary to allow neuroadaptations responsible for these apparent paradoxical responses, the increased cocaine response being only an indirect consequence of the reduced DA tone observed in NAcc and downstream adaptation. Our findings in mice provide evidence for a role for the 5-HT2B receptor in mesolimbic pathways, with a lack of 5-HT2B receptor representing a source of permanent 5-HT-dependent DAergic system hypofunction in NAcc. This functional deficit may represent a susceptibility factor for both impulsive and addictive behavior; two behaviors that have been tightly interwoven, and may explain both the impulsivity and cocaine vulnerability of Htr2B−/− mice.

1INSERM, U839, Institut du Fer à Moulin, 17 rue du du Fer à Moulin 75005 Paris, France. Funding Support: Fondation pour la Recherche sur le Cerveau, the Fondation de France, the Fondation pour la Recherche Médicale "Equipe FRM DEQ2014039529", the French Ministry of Research (Agence Nationale pour la Recherche ANR-12-BSV1-0015-01 and the Investissements d'Avenir programme ANR-11-IDEX-0004-02).

ABSTRACT. KA Cunningham,1 FG Moeller,2 Ed Boone3, Qin Wang,3 NC Anastasio1

1Center for Addiction Research and Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas, USA; 2Institute of Drug and Alcohol Studies, and Department of Psychiatry, Virginia Commonwealth University, Richmond, Virginia, USA; 3Institute of Drug and Alcohol Studies, and Department of Statistics, Virginia Commonwealth University, Richmond, Virginia, USA

Cocaine use disorder (CUD) remains a disturbing chronic health problem as well as an individual and societal burden in the United States. A 61% increase in adults initiating cocaine use (2013-2015) coupled with the highest cocaine overdoses reported since 2006 reveal alarming trends (www.samhsa.gov/data/sites/default/files/report_2736/ShortReport-2736.html). A hallmark of CUD is “continued drug use despite adverse consequences,” which aligns with the definition of impulsivity, a predisposition toward rapid unplanned reactions to stimuli without regard to negative consequences. Impulsivity is interlocked with cue reactivity which is defined as the attentional orientation toward drug-associated stimuli that predict reward in humans and rodents. We report translational studies employing gene-mediated viral vector targeting strategies in rodents and analyses of structural and effective connectivity in fMRI studies in humans that interrogate the neurocircuitry engaged in impulsive action and the response bias toward cocaine-associated cues. Our data support the contention that medial prefrontal cortex (mPFC)  nucleus accumbens shell (NAcSh) circuitry in rodents and the anterior cingulate cortex in humans are brain circuits involved in the overlap of impulsive action and cocaine cue reactivity. Furthermore, we have uncovered that impulsive action and cue reactivity are mechanistically-linked to disrupted serotonin (5-HT) signaling through a 5-HT2A receptor (5-HT2AR) and 5-HT2CR interaction within this circuitry. Employing integrative Bayesian Analyses of Neuroimaging-Genetics methods, we recently demonstrated that single nucleotide polymorphisms (SNPs) of the HTR2A and HTR2C are interrelated with cocaine use, impulsivity, and altered brain structural and functional connectivity on fMRI in humans. This interaction may be relevant to our discovery that CUD subjects carrying the same HTR2C SNP exhibit the highest cue reactivity. Given the importance of cue reactivity and impulsivity in the risk for relapse in CUD, the outcomes of these studies contribute a greater appreciation of the serotonergic neurocircuitry underlying these constructs and suggest new concepts in the treatment of CUD.

ABSTRACT. Hong SI1, Starski P1, Choi S1, Kang S1, Choi DS1.

Adenosine A2A receptor (A2AR) is abundantly expressed in the striatopallidal neurons in the striatum and has been implicated in increased alcohol drinking through enhancement of goal-directed behaviors and impulsivity. Using mice that were exposed to differential reward of low rate (DRL) schedules during Pavlovian conditioning, second-order schedule discrimination, and the 5-choice serial reaction time task (5-CSRTT), we demonstrate that deficits of A2AR function promote impulsive responses. In a binge-drinking paradigm, mice were exposed to vaporized ethanol for 4 h in every 4th day displayed increased premature responses during the challenge tests, suggesting that binge alcohol consumption increase impulsivity through dampening A2AR. Next, we investigated whether the A2AR in the dorsomedial striatum (DMS) contributes to goal-directed behavior in mice exposed to vaporized ethanol for 16 h per day during 4 days. Our results show that ethanol-exposed mice elicited anxiety-like behavior in elevated plus maze test without affecting working memory in y-maze test. During acquisition of instrumental behavior training in C57BL/6J mice, CGS21680 (0.3 mg/kg, i.p.), A2AR agonist, and optogenetic stimulation of A2AR-expressing neurons in the DMS abolished goal-directed behavior in response to 10% ethanol, whereas ZM241385 (20 mg/kg, i.p.), A2AR antagonist, did not impede goal-directed behavior under valued condition. Interestingly, A2AR activation prevented voluntary ethanol consumption in operant chamber even after 24 h following CGS21680 (0.3 mg/kg, i.p.) injection. Taken together, our results demonstrate that the DMS A2AR regulates impulsivity, goal-directed and alcohol seeking behaviors.

1Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, Minnesota, 55905, USA. Funding Support: the Samuel C. Johnson for Genomics of Addiction Program at Mayo Clinic, the Ulm Foundation, and National Institute on Alcohol Abuse and Alcoholism (AA018779).

ABSTRACT. Progressive supranuclear palsy (PSP) is a common and incurable neurodegenerative disease associated with prominent motor, oculomotor and cognitive-behavioral deficits, and a poor prognosis for functional independence and survival. The pathology of PSP is characterized by neuronal loss and accumulation of abnormal aggregates of the 4-repeat isoform of the microtubule-associated protein tau (4R-tau), which is strongly implicated in pathogenesis by convergent lines of genetic evidence. Phenotype-based drug discovery has previously identified many first-in-class drugs and is particularly applicable when therapeutic targets are unclear. Our current work is directed towards developing effective treatments for PSP and related tauopathies, by exploiting the potential of zebrafish genetics and high-throughput automated neurobehavioral phenotyping to identify chemical modifiers of pathogenesis, unbiased by preconceptions about mechanism of action. We developed a zebrafish tauopathy model that replicates many features of PSP including: impaired survival; neurobehavioral deficits; oculomotor abnormalities; somatodendritic accumulation of hyperphosphorylated 4R-tau; and neurodegeneration. Using automated neurobehavioral profiling to detect phenotypic rescue, we recently completed a pilot chemical modifier screen, identifying several small molecules that rescue the neurobehavioral phenotype of the zebrafish tau model. Validation of these ‘hit’ compounds and verification of their targets is ongoing, but preliminary studies suggest unexpected modes of action, thereby justifying a phenotype-driven approach. We conclude that automated behavioral phenotyping to detect chemical rescue in genetic disease models in vivo may have general application in drug discovery for neurological disease. The zebrafish tauopathy model will also be useful for evaluating the functional effects of putative genetic PSP modifiers identified in GWAS studies.