CHRNA5 and nicotine dependence: In CHRNA5, we investigated five SNPs, including the non-synonymous coding variant rs16969968, suggested to affect the risk of nicotine dependence by altering the function of α5-containing nAChRs24, as well as three SNPs in the 5′-UTR (rs503464, rs55853698, and rs55781567) and one 22-bp insertion/deletion in the promoter (rs3841324), all suggested to be involved in nicotine dependence by modulating CHRNA5 subunit mRNA levels25–30.