The 15q24 region on chromosome 15 includes the genes (CHRNA5-CHRNA3-CHRNB4) that encode the α5, α3, and β4 nAChR subunits, which are in strong linkage disequilibrium (LD) with each other. Several recent GWAS and pathway-based studies have identified SNPs in the CHRNA5-CHRNA3-CHRNB4 gene cluster as associated with heaviness of smoking and/or nicotine dependence (Berrettini et al. 2008; Bierut et al. 2007; Caporaso et al. 2009; Saccone et al. 2007; TAG 2010; Thorgeirsson and Stefansson 2008).
