Besides the CHRNA4, CHRNB2 and CHRNA5/A3/B4 cluster on chromosome 15, which has been investigated intensively, recent evidence from both genome-wide association studies and candidate gene-based association studies has revealed the crucial roles of the CHRNB3-CHRNA6 gene cluster on chromosome 8 in nicotine dependence (ND).
Since both nicotine dependence (ND) and depressive phenotype are complex disorders, we investigated the effects of a significant early life experience, maternal bonding style (MB) and CHRNB2 gene SNPs on smoking-related depression.
These findings suggest that CHRNB2rs4845652 T-allele carriers may be associated with lower levels of ND, and that certain allelic combinations of CHRNA4 and CHRNB2 might be correlated with higher ND levels.
Although CHRNB2 alone was not significantly associated with ND in several previously reported association studies on ND, we found it affects ND through interactions with CHRNA4 and NTRK2.
We found nominally significant (P<0.05) allelic and genotypic association with smoking initiation of SNP rs2072660 and multilocus haplotypes (P<0.007-0.05) in CHRNB2 and nominal (P<0.05) allelic or genotypic association of SNPs in CHRNA7 (rs1909884), CHRNA9 (rs4861065) and CHRNB3 (rs9298629) with nicotine dependence.
We studied six single-nucleotide polymorphisms (SNPs) in the CHRNA4 gene and four SNPs in the CHRNB2 gene with respect to nicotine dependence in a collection of 901 subjects (815 siblings and 86 parents) from 222 nuclear families with multiple nicotine-addicted siblings.
However, sequence variations in CHRNB2 have not been reported, and its role in influencing human smoking behavior and nicotine dependence is not known.