A functional polymorphism, rs6280, in DRD3 is significantly associated with nicotine dependence in European-American smokers.

Nicotine enhances reward functions in the mesocorticolimbic dopamine system in general and the nucleus accumbens in particular. The genes encoding dopamine receptors are thus plausible candidates for involvement in nicotine dependence (ND). We investigated 13 single nucleotide polymorphisms (SNPs) spanning a region of the dopamine D(3) receptor gene (DRD3) to determine whether DRD3 is associated with ND. We studied a set of 2,037 subjects in 602 nuclear families representing two distinct American populations using three ND measures, namely, smoking quantity (SQ), the Heaviness of Smoking Index (HSI), and the Fagerström Test for ND (FTND). In the family based association study, we found that SNP rs6280 showed a strong association with ND in European-Americans (EAs) and the pooled sample, whereas SNPs rs1486012 and rs963468 had weak associations with ND in African-Americans (AAs) and the pooled sample. Further haplotype analysis with all contiguous 3-SNP groups revealed relatively weak evidence for association of DRD3 with ND in the EA and pooled samples. The results indicate that DRD3 is significantly associated with ND in EAs, and that rs6280, a functional polymorphism causing an amino acid change of serine to glycine (Ser9Gly) in the N-terminal extracellular domain of the D(3) receptor, likely is causative of the association between DRD3 and ND.