One possible source of the variability in prior studies examining the role of the A118G SNP in alcohol effects is a functional interaction between the A118G SNP and dopamine transporter gene (DAT1, gene ID SLC6A3) (Anton et al., 2012). The rationale for focusing on the DA transporter is its role in the regulation of DAergic transmission by clearing DA via uptake from the synaptic cleft. The DAT1 gene is located on chromosome 5q15.3 and contains a 40-base-pair variable number tandem repeat (VNTR) in the 3′ untranslated region (Vandenbergh et al., 1992). A common VNTR polymorphism in DAT1 results in alleles with 10 and with 9 or lesser VNTRs (rs28363170). The 10-repeat allele (A10) is associated with higher DAT1 expression in the striatum than 9- or lesser-repeat alleles (A9), suggesting higher synaptic DA in A9 carriers (Heinz et al., 2000). The A9 has been associated with AUD (Bhaskar et al., 2012), and more severe alcohol-withdrawal symptoms (van der Zwaluw et al., 2009).
