Profiling the alcohol-naive primate cortex to understand the functional role of epigenetics in predisposing the brain to risky alcohol use

PROJECT SUMMARY Among the six percent of active ethanol drinkers who develop an alcohol use disorder (AUD), there is great variability in etiology and relapse rates. Early and accurate identification of individuals at risk of developing an AUD would facilitate effective deployment of personalized interventions. Recent evidence demonstrates that individuals with low cognitive flexibility and a predisposition towards habitual behaviors are at an increased risk for future heavy drinking. However, the underlying molecular mechanisms driving these differences in cognition and the accompanying higher risk for drinking remain unknown. Growing evidence suggests that an epigenetic signature, either inherited or acquired in life, predisposes individuals to risky addictive behaviors. However, cross-sectional studies cannot reliably identify this pre-existing risk and distinguish it from an induced effect of chronic alcohol use. Attempts to identify biomarkers of AUD have focused on easy-access tissues, specifically peripheral blood. While these studies are important, their ability to inform on the specific molecular mechanisms in the brain are limited. To overcome this limitation, we conducted a longitudinal genome-wide DNA methylation (GW-DNAm) analysis of the rhesus macaque dorsolateral prefrontal cortex area 46 (dlPFC-A46) collected before alcohol use. The dlPFC is a component of the executive network and is critical for cognitive function and decision making. With alcohol-naïve dlPFC-A46 samples from 11 male macaques, we identified 3,539 differentially methylated regions (DMRs) that were associated with future ethanol drinking levels (following 12 months of drinking). The genes mapped by these DMRs are enriched in neurogenesis, neuronal differentiation, axonogenesis, synaptic plasticity and glutamatergic neurotransmission. These results suggest that, in an alcohol-naïve state, the variability in DNAm signatures represents a vulnerable neural state primed for future problematic drinking. In this application, we seek to identify more robust molecular signatures that explain pre-existing risk for excessive alcohol consumption by increasing the sample size (n = 54), completing cell-sorting to reduce noise from cellular heterogeneity, and including both males and females. Furthermore, we will include functional studies to better understand the regulatory function of these DMRs and evaluate their impact on gene expression in different cell type populations. This proposal will elucidate, for the first time, the pre-existing neural molecular signatures priming the brain of alcohol-naïve individuals for future risk of excessive alcohol consumption. To increase translatability, we will characterize the methylomics and metabolomics of blood samples collected from the same subjects. In totality, this work will translate behavioral phenotypes into neural markers of risk for AUD and hold promise for parallel discoveries in risk for other disorders involving impaired cognitive flexibility.