In addition to chromosome 7p12 and chromosome 4q32, we followed up another four SNPs using a GoldenGate custom array (Illumina, San Diego, California) in 2553 replication subjects. After quality control, 1658 EAs (134 PTSD cases) and 744 AAs (89 PTSD cases) with known PTSD diagnosis were included in the replication analyses. The first SNP, rs2272651, was located in the seventh intron of NDRG1 and the second SNP, rs2779551, was located in the fourth intron of GABBR2. These two SNPs were the eighth and ninth most significant in the GWAS results for EAs and were selected because they map to obvious candidate loci. Neither of these SNPs was significantly associated with PTSD in the 1658 EA subject replication sample (Table 2). We also tested two SNPs with the most significant p values in the GWAS results of AAs: rs7014900, which is about 842 kilobase away from the nearest gene TRPS1, and rs13006863, which is located in the 14th intron of SLC4A5. Likewise, neither of them was replicated in the 744 AAs (Table 3).
