Several association studies have implicated genes encoding GABA-A subunits in the risk for AD. GABRA2, which encodes the α2 subunit, has been the most widely studied, with the majority of studies (Covalt et al., 2004; Drgon et al., 2006; Edenberg et al., 2004; Lappalainen et al., 2005, Enoch et al., 2006; Fehr et al., 2006; Matthews et al., 2007; Soyka et al., 2008), providing evidence that markers located at the 3′ region of the gene are associated to the risk for AD. GABRA2 maps to the GABA gene cluster on human chromosome 4 (4p12-p13), which also includes GABRG1, GABRB1 and GABRB4, genes that encode the γ1, β1 and β4 subunits of GABA-A, respectively (Buckle et al., 1989; Kirkness et al., 1991; McLean et al., 1995; Wilcox et al., 1992). No functional variant has yet been found in the GABRA2 gene that could account for the association. The previously reported associations between GABRA2 and AD could be attributable in part to the adjacent gene, GABRG1, which is located 90kb distant in the 3′ direction, and is in strong LD with GABRA2
