association of rare variants in CHRNB3, CHRNA6 or CHRNA5 with nicotine dependence in either population. Therefore, additional common or rare variants in CHRNA5 were not found in our African-American heavy smoker population likely because SNPs in other cholinergic receptor subunits predict risk for nicotine intake levels among different ethnicities (Thorgeirsson et al., 2010; Haller et al., 2012; Saccone et al., 2009b; Chen et al., 2012; Rice et al., 2012) and polymorphisms within other genes, such as CYP2A6, a risk locus for European and Asian population smoking phenotypes (TAG 2010; Thorgeirsson et al., 2010; Liu et al., 2010; Kumasaka et al., 2012), may influence smoking status by affecting nicotine metabolism.
