Cross-species co-analysis of prefrontal cortex chronic ethanol transcriptome responses in mice and monkeys

Despite recent extensive genomic and genetic studies on behavioral responses to ethanol, relatively few new therapeutic targets for the treatment of alcohol use disorder have been validated. Here we describe a cross-species genomic approach focused on identifying gene networks associated with chronic ethanol consumption. To identify brain mechanisms underlying a chronic ethanol consumption phenotype highly relevant to human alcohol use disorder, and to elucidate potential future therapeutic targets, we conducted a genomic study in a nonhuman primate model of chronic open-access ethanol consumption. Microarray analysis of RNA expression in anterior cingulate and subgenual cortices from rhesus macaques was performed across multiple cohorts of animals. Gene networks correlating with ethanol consumption or showing enrichment for ethanol-regulated genes were identified, as were major ethanol-related hub genes within these networks. A subsequent consensus module analysis was used to co-analyze monkey data with expression data from a chronic intermittent ethanol vapor-exposure and consumption model in C57BL/6J mice. Ethanol-related gene networks conserved between primates and rodents were enriched for genes involved discrete biological functions, including; myelination, synaptic transmission, chromatin modification, Golgi apparatus function, translation, cellular respiration, and RNA processing. The myelin-related network, in particular, showed strong correlations with ethanol consumption behavior and displayed marked network reorganization between control and ethanol-drinking animals. Further bioinformatics analysis revealed that these networks also showed highly significant overlap with other ethanol-regulated gene sets. Altogether, these studies provide robust primate and rodent cross-species validation of gene networks associated with chronic ethanol consumption. Our results also suggest potential novel focal points for future therapeutic interventions in alcohol use disorder. Tissue samples of monkey anterior cingulate and subgenual cortex (Brodmann areas 24, 25, and 32) from 43 (32 ethanol drinking, 11 control) adult male rhesus macaques (Macaca mulatta), aged 5 to 11 years, were used in this study. These animals, individually housed at the Oregon National Primate Research Center, were induced to drink ethanol by schedule-induced polydipsia per previously published methods (Grant et al. 2008, Helms, Park, and Grant 2014), and were then allowed 22 hours per day of ad libitum access to water and 4% (w/v) ethanol in water for a period of one year. Control animals were given daily maltose dextran solution (calorically matched to an ethanol drinker) and had access to water during all portions of the experiment.