Despite its consistent association in AAs, rs9829896 was not associated with drug abuse in EAs. Several other examples of ancestry-specific genetic associations have been reported for complex diseases.(Keebler et al., 2009; Namjou et al., 2013; Torgerson et al., 2011) Heterogeneous SNP associations across ancestry groups may reflect differing allele frequencies and effect sizes, varied linkage disequilibrium patterns with causal variants, modifying genetic backgrounds, or environmental exposures. Our findings implicated rs9829896 as both a cis- and trans-eQTL, altering gene expression levels in AAs but not in EAs. Prior comparisons across the diverse HapMap populations showed that cis-eQTL associations are often shared across ancestry groups but that the majority of cis-eQTL associations are specific to only one ancestry group.(Stranger et al., 2012) It is plausible that the ancestry-specific SNP association results observed between rs9829896 and drug abuse were driven by cis- and trans-eQTL effects that differ between AAs and EAs.
