The association between beta power and the GABRA2 gene produced the smallest p-value. Because there is stronger prior evidence for this association than the other candidate genes (other than possibly APOE ε4), we elected to follow it up. In order to compare the present results to published findings, it was necessary to impute SNPs in the gene with reference to 1000 Genomes because these SNPs were not on the Illumina genotyping array. This also provided finer coverage of the gene. Results are plotted in the top panel of Figure 15, which indicates that a large segment at the 3′ untranslated region (UTR) and the region immediately flanking it yielded somewhat elevated and relatively homogeneous –log10(p), although none was genome-wide significant. Table 5 shows p-values from the two previous studies of this gene (Edenberg et al., 2004; Lydall et al., 2011) and the present study. Although all SNPs were imputed in our data, with a single exception imputation r2 values uniformly approached 1. Ten SNPs with nominally significant associations (p < .05) in previous studies and the present one are highlighted.
