PKD2 and depressive symptom measurement: Findings from the present and previous studies converge on several genes considered to play integral roles in depression, particularly VAMP2, CSGALNACT1, and CRHR2, which might be followed by LUZP1, UGCG, UBQLN4, FKBP4, PKD2, CPLX2, and CRHR1. Future well-designed transcriptome studies, integrated functional genomics studies51, and reanalysis/meta-analysis of expression data deposited in the public domain52 should help to further understand gene expression signatures of depression and to establish genes useful in its prediction, diagnosis and treatment.