The goal of the proposed research is to discover neurobiological factors underlying alcohol use disorder (AUD). We will identify genes with AUD-related differences in DNA methylation (DNAm) and RNA expression (RNAexp) in two human brain tissues for AUD (dorsolateral prefrontal cortex [DLPFC] and nucleus accumbens [NAc]), map genetic variants underlying these differences, and conduct large-scale association testing of the regulatory genetic variants with AUD. Our proposed study will entail genome-wide testing, along with targeted testing of the growing number of genetic loci associated with alcohol consumption and AUD. Alcohol is the fourth leading cause of preventable morbidity and mortality in the United States. AUD affects more than 16 million U.S. adults and youths and is highly heritable (50%?60%). Genome-wide association study (GWAS) analyses have identified single nucleotide polymorphisms in or near alcohol dehydrogenase and aldehyde dehydrogenase genes and 80+ other genetic loci for alcohol consumption and/or AUD risk. However, their neurobiological effects are largely unknown. Because complex disease-associated variants are widely observed to be enriched for association with DNAm and RNAexp of nearby genes (cis-methylation and expression quantitative trait loci [cis-meQTLs and cis-eQTLs], respectively), we hypothesize that differential gene regulation by AUD will add knowledge of the neurobiology underlying AUD risk and consequences of alcohol exposure and that mapping the underlying cis-meQTLs and cis-eQTLs in DLPFC and NAc, will distinguish these distinct, yet informative, neurobiological signatures. We propose the following specific aims:
Aim 1 : Identify DNAm and RNAexp differences in NAc and DLPFC of AUD cases vs. controls.
Aim 2 : Map QTLs that underlie AUD-related DNAm and RNAexp differences in NAc and DLPFC.
Aim 3 : Test association of eQTLs and meQTLs with AUD risk.
Aim 4 : Functionally characterize alcohol consumption and AUD GWAS loci.
Aims 1, 2, and 4 will leverage multiple `omics data from postmortem human brain tissues from AUD case and control decedents (total N = 220, the largest-to-date postmortem brain collection with AUD status known).
Aim 3 will use existing GWAS samples with AUD defined by DSM-5 (the most up-to-date version of the Diagnostic and Statistical Manual of Mental Disorders): total N = 76,296.
Aim 4 will cycle back to the approaches taken in preceding aims, but it will focus on the 80+ prior GWAS-identified loci. Our integration of epigenomics, transcriptomics, and genomics in human brain and extension into GWAS meta-analysis of AUD will greatly improve the likelihood of meaningful discovery by targeting gene regions and specific variants with high biological relevance, specifically in the brain, while retaining a genome-wide scope.
In the United States, alcohol ranks as the fourth most-preventable cause of death, and alcohol use disorder (AUD) currently affects more than 16 million adults and youths. This study will identify genes that are dysregulated in the brain by AUD and map underlying genetic variants to better understand gene regulatory changes due to AUD risk and changes due to alcohol exposure. Results of this study may identify important neurobiological pathways for AUD and ultimately reduce the burden of alcohol-related health outcomes and fatalities.