To evaluate this hypothesis, COGA researchers systematically selected and characterized (i.e., determined the exact nucleotide sequence of) a series of SNPs from GABAA receptor genes located on chromosome 4. The investigators identified several SNPs located in the GABRA2 gene that were associated with alcohol dependence; in the neighboring genes encoding other GABAA receptor components, however, no SNPs related to alcohol dependence were identified (Edenberg et al. 2004). Other researchers have replicated this finding in several independent samples (Covault et al. 2004; Lappalainen et al. 2005; Fehr et al. 2006). These findings indicate that the GABRA2 gene contributes to the development of alcohol dependence.
