Although no association met genomewide significance, there were clusters of SNPs in PCLO (Figure 2). Notably, 11 of the 200 smallest p-values localized to a 167 kb segment overlapping PCLO. Interest in PCLO was increased given its expression in brain, localization to the presynaptic active zone (71), and involvement in monoamine neurotransmission, a venerable hypothesis of the etiology of MDD (72). Moreover, the third most significant SNP (rs2522833) codes for a non-synonymous amino acid change (ala-4814-ser) in PCLO near its C2A calcium binding domain (73).
