Alcohol use disorders (AUDs) affect approximately 8.5% of the United States population. Risk of developing an AUD is influenced by both genetic and environmental factors, with heritability estimated to be between 50 and 60%. While several genetic variants have been associated with increased risk of developing an AUD, little is known about the biological mechanisms linking such variants to the pathophysiology of AUD. One of the most commonly-examined single-nucleotide polymorphisms (SNPs) associated with increased genetic risk of developing an AUD is rs279858, a synonymous SNP located in exon 5 of GABRA2. This tag-SNP serves as a bookmark for a 140 kilobase (kb) haplotype block containing a number of SNPs that are in high linkage disequilibrium (LD) and are associated with increased genetic risk for developing an AUD. The absence of a linked coding variant suggests that AUD-associated risk in this region due to an unidentified functional non- coding variant that influences developmentally-regulated gene expression of GABRA2 or nearby genes. Using induced pluripotent stem cell (iPSC)-derived neurons, it has been reported that decreased expression of GABRA2 on chromosome 4p12 as well as that of the GABRA4 and GABRB1 subunit genes 500kb distal to GABRA2 is correlated with the rs279858 risk C-allele, as compared to iPSC-derived neurons that are homozygous for the non-risk-associated allele. Furthermore, promoter methylation analysis suggests that in CC lines, long-range intrachromosomal interactions may bring enhancer elements into close physical proximity to GABRA2 and subsequently alter the transcription of the chr4p12 GABA gene cluster, as compared to a more-localized mechanism of transcriptional control in TT homozygotes. The goal of this project is to define the elements of the long-range interactions that appear to influence transcription from this region, to better understand the proximal genetic effects of this AUD-associated variation and thereby stimulate further understanding of how it may relate to risk of developing AUD.
Alcohol use disorder is a chronic neuropsychiatric disorder with limited treatment options currently available. High prevalence of this disorder in the U.S. population presents a significant financial, emotional, and physical burden on patients, their families, and society. Early detection of individuals at increased genetic risk for developing AUD could lead to more-individualized treatment options.
