Genetic and Transcriptomic Mechanisms of Progressive Ethanol Consumption in the Diversity Outbred Mouse

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Project Abstract Alcohol use disorder (AUD) poses a global healthcare burden, with significant morbidity and mortality associated with excessive alcohol consumption and effective therapeutic options still lacking. Human genome-wide association studies have recently identified genes potentially modulating alcohol consumption, but pinpointing their mechanisms of action remains difficult. Genetic variance influencing gene expression has been suggested as an additional factor in AUD but remains difficult to study in humans due to confounding environmental factors, difficulty with tissue collection and inability to conduct mechanistic manipulations. Mouse models are an effective substitute; Diversity Outbred (DO) mice from Jackson Labs display a large amount of genetic diversity and small recombination intervals, allowing for precision mapping of quantitative trait loci (QTLs). Recent research in our lab using Diversity Outbred (DO) mice identified marked variability in ethanol consumption, with a pattern of progressive ethanol intake across the DO mice and heritability ranging from 48-62%. Multiple highly significant or suggestive behavioral quantitative trait loci (bQTL) were identified for alcohol consumption phenotypes, along with unique positional candidate genes; however, determination of causal candidates and definition of mechanisms by which specific genes influence ethanol consumption have not been yet been accomplished. We hypothesize that genetic mechanisms of DO mouse ethanol consumption variance are largely driven by cognate differences in gene expression networks across PFC and NAc and that a combined behavioral and expression genetics approach can identify critical molecular mechanisms and candidate genes modulating ethanol consumption. To test this hypothesis, we aim to 1) employ an algorithm to rank candidate genes influencing ethanol consumption using RNA-seq data collected from PFC and NAc samples from DO mice, and functionally characterize gene expression networks associated with ethanol consumption; 2) derive mechanistic causal inferences about individual gene expression patterns and their relationships with ethanol consumption, and estimate direct genetic and individual gene transcript mediation effects using structural equation modeling; and 3) validate causal candidates using viral vector mouse genetic modulation of a candidate gene for ethanol consumption. These studies will provide the applicant with robust and unique training in quantitative genetics, genomic and transcriptomic analyses, and the neurobiology of alcohol, preparing him for a successful career as future independent investigator in the behavioral genetics of alcohol.