Abstract
The association between the D2 dopamine receptor gene (DRD2) Taq1A locus (rs1800497) and alcohol use disorder (AUD) is enduring but the subject of long-standing controversy; meta-analysis of studies across 3 decades shows an association between rs1800497 and AUD, but genome-wide analyses have detected no role for rs1800497 in any phenotype. No evidence has emerged that rs1800497, which is located in ANKK1, perturbs the expression or function of DRD2. To resolve contradictions in previous studies by identifying hidden confounders and assaying for functional effects of rs1800497 and other loci in the DRD2 region. PubMed (882 studies), Embase (1056 studies), and Web of Science (501 studies) databases were searched through August 2018. Three clinical populations-Finnish, Native American, and African American participants-were genotyped for 208 to 277 informative single-nucleotide polymorphisms (SNPs) across the DRD2 region to test the associations of SNPs in this region with AUD. Eligible studies had diagnosis of AUD made by accepted criteria, reliable genotyping methods, sufficient genotype data to calculate odds ratios and 95% CIs, and availability of control allele frequencies or genotype frequencies. After meta-analysis of 62 studies, metaregression was performed to detect between-study heterogeneity and to explore the effects of moderators, including deviations of cases and controls from allele frequencies in large population databases (ExAC and 1000 Genomes). Linkage to AUD and the effect on gene expression of rs1800497 were evaluated in the context of other SNPs in the DRD2 region. Data analysis was performed from August 2018 to March 2019. This study follows the Preferred Reporting Items for Systematic Reviews and Meta-analyses reporting guideline. The effects of rs1800497 and other SNPs in the DRD2 region on gene expression were measured in human postmortem brain samples via differential allelic expression and evaluated in other tissues via publicly available expression quantitative locus data. A total of 62 studies of DRD2 and AUD with 16 294 participants were meta-analyzed. The rs1800497 SNP was associated with AUD (odds ratio, 1.23; 95% CI, 1.14-1.31; P < .001). However, the association was attributable to spuriously low allele frequencies in controls in positive studies, which also accounted for some between-study heterogeneity (I2 = 43%; 95% CI, 23%-58%; Q61 = 107.20). Differential allelic expression of human postmortem brain and analysis of expression quantitative loci in public data revealed that a cis-acting locus or loci perturb the DRD2 transcript level; however, rs1800497 does not and is not in strong disequilibrium with such a locus. Across the DRD2 region, other SNPs are more strongly associated with AUD than rs1800497, although no DRD2 SNP was significantly associated in these 3 clinical samples. In this meta-analysis, the significant association of DRD2 with AUD was reassessed. The DRD2 association was attributable to anomalously low control allele frequencies, not function, in positive studies. For genetic studies, statistical replication is not verification.
Highlights
Whether the dopamine D2 receptor gene (DRD2) is associated with alcohol use disorder (AUD) and other behavioral phenotypes is a long-standing controversy
The rs1800497 singlenucleotide polymorphisms (SNPs) was associated with AUD
This discussion is driven by the role of 1 single-nucleotide polymorphism (SNP), rs1800497, which is located in a nearby gene, ANKK1
Summary
Whether the dopamine D2 receptor gene (DRD2) is associated with alcohol use disorder (AUD) and other behavioral phenotypes is a long-standing controversy. This discussion is driven by the role of 1 single-nucleotide polymorphism (SNP), rs1800497, which is located in a nearby gene, ANKK1. This SNP, from among hundreds known in the DRD2 region, was assayable as a restriction fragment– length polymorphism (RFLP) in 1990, when the association of DRD2 and other genes with alcoholism was first examined.[1]. Studies were still sparse, the possibilities that rs1800497 T allele frequencies were spuriously low and that the association might be attributable to population variation in allele frequencies were advanced by Gelernter et al,[14] and consistent with this idea, studies conducted in well-defined populations, such as Finnish participants[14,15] and Native American participants,[15] were negative
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