Our earlier work (Ittiwut et al., 2008) identified four regions of strong LD defined by D'>0.8 based on data from a set of 13 SNP markers in 48 AA subjects (Figure 1). We used the htSNP approach in HAPLOVIEW software version 3.32 (available at http://www.broad.mit.edu/mpg/haploview) (Barrett et al., 2005) to identify 6 haplotype tagging (ht) SNPs spanning a 312.6 kb region including GABRG1 and GABRA2. These SNPs, all of which were intronic, had a minor allele frequency (MAF) ≥15%, and included rs1497571, rs10938426, rs10033451, rs567926, rs279869, and rs279837. We will refer to these SNPs as A, D, F, G, J and L after the nomenclature used in our prior report (Ittiwut et al., 2008). SNPs A, D, and F map to GABRG1 and G, J, and L map to GABRA2. Of these, rs279837 (in intron 3 of GABRA2) tagged the 2-SNP LD block composed of that SNP and another synonymous SNP, rs279858, in exon 5 of the same gene. Genotyping was performed using a Taqman genotyping method as described previously (Ittiwut et al., 2008). All genotyping was performed in duplicate;
