Genetic Mapping of Progressive Ethanol Consumption in the Diversity Outbred Mouse

Abstract

Traditional genetic mapping studies using inbred crosses are a powerful tool for identifying chromosomal regions associated with ethanol-related traits, but typically have very large confidence intervals which make identification of specific and potentially causal candidate genes difficult. Diversity Outbred (DO) mice offer the ability to map quantitative trait loci (QTLs) associated with ethanol-drinking behaviors at a high resolution that allows for easier identification of candidate genes. Here, we exposed a population of 636 male DO mice to four weeks of intermittent ethanol access via a three-bottle choice paradigm, identifying 3 significant (Chrs 3, 4, and 12) and 12 suggestive loci for ethanol-drinking behaviors. The confidence intervals for these loci were narrow (1-4 Mbp for significant QTLs). We then further analyzed positional candidate genes using transcriptomics data from prefrontal cortex samples taken from 220 of these animals, as well as human GWAS data and prior gene set data for ethanol or other drugs of abuse. These results represent the highest-resolution genetic mapping of ethanol consumption behaviors in mice to date, providing for the identification of novel loci and candidate genes for progressive ethanol consumption, includingCar8--the lone gene with a significantcis-eQTL in strong linkage disequilibrium with our QTL for last week ethanol consumption on Chr 4.

Identification of Genetic and Genomic Influences on Progressive Ethanol Consumption in Diversity Outbred Mice

“…From our analyses, certain myelin structural genes such as Mbp, Mobp, and Mag were significantly positively correlated with ethanol consumption. Of these, Mbp was a key driver of the orange module, and one of its interacting proteins ( Ticam1 ) showed significant correlation to ethanol consumption or preference [18]. This an interesting finding, as previous studies have shown a reduction in myelin gene expression with ethanol exposure.…”

“…636 DO mice were used for intermittent access ethanol drinking by 3-bottle choice for 11 drinking days over 4 weeks (Figure 1a). As discussed in a previous publication, these mice significantly increased the total amount of ethanol they consumed over the course of the study [18]. Of these, 200 mice were selected for RNAseq analysis, as RNAseq on 636 mice would have been cost prohibitive.…”

“…We have made use of the DO mouse panel with IEA as an animal model of prolonged voluntary ethanol consumption in a genetically diverse population to more accurately reflect mechanisms underlying AUD in the human population. We have recently shown that the IEA drinking paradigm leads to a progressive increase in consumption in DO mice over 4 weeks of drinking, and that variation in specific regions of the genome show significant association to the amount a mouse will consume [18]. Building upon that behavioral genetic analysis, here we have used network analysis methods and expression QTL mapping to characterize the gene expression changes that occur in the prefrontal cortex, the region of the brain responsible for impulse control and other executive functions, after 4 weeks of IEA.…”

“…Our laboratory has recently used the DO mouse population to conduct a behavioral and expression genetics analysis of a model for progressive ethanol consumption using prolonged intermittent voluntary 3-bottle choice drinking. These studies have identified multiple significant and suggestive behavioral quantitative trait loci (QTL) associated with various aspects of ethanol drinking behavior [18].…”

“…Biologically, one of the most notable findings was the abundance of myelin structural and myelin regulatory genes, indicating that regulation of myelination may be a highly conserved PFC response to prolonged ethanol exposure, and that this response is influenced by genetic variation. Regulators of such network responses, which we have identified as candidate genes, may underlie the observed behavioral phenotypes such as escalation of ethanol consumption [18].…”