OPRK1 is located on human chromosome 8q11.2. There are four exons within the 22 kb gene (RefSeq NM_000912); the 5′ exon is non-coding (21,23). When we found that non-coding variations in OPRK1 were associated with alcohol dependence (17), we sequenced DNA from individuals with different haplotypes to identify additional variations. We identified a previously unknown insertion/deletion (indel) and examined its effect on the regulation of gene expression. We also tested whether that indel was associated with alcoholism.
