markers 1-3-5-6-7-8-9-10 or rs1799971-rs524731-rs9479757-rs2075572-rs10485057-rs9322447-rs609148-rs648893. Extracting markers 1-9-10 from this extended haplotype, we have 1-2-2 or A-C-T for rs1799971- rs609148-rs648893. This overlaps with one of the risk haplotypes, A-A-C-C-T for markers rs1799971-rs3823010-rs495491-rs609148-rs648893, identified in the alcoholism study. Given the high comorbidity between alcohol drinking and tobacco smoking, this finding is interesting. Because the 5' end of the gene is not in high LD for those markers we typed in our study, we cannot be certain whether the same risk haplotype underlies the risks for both alcoholism and tobacco smoking. Further studies with more markers at the 5' end of the gene are necessary to clarify this issue.
