Although no locus exceeded the genomewide threshold after correction for multiple comparisons, 11 of the top 200 signals localized to a 167 kb region overlapping the gene piccolo (PCLO). The protein product of PCLO localizes to the presynaptic active zone and plays an important role in brain monoaminergic neurotransmission (86), clearly intersecting with a venerable hypothesis of the etiology of mood disorders (87). Moreover, the third most significant association was a common non-synonymous SNP near its critical C2A binding domain in PCLO (88, 89). Although it is an obvious candidate gene, we are not aware of any prior association studies of PCLO and mood disorders (PCLO is in a region of 7q implicated by linkage in autism and one autism association study has been published) (90).
