The GPR37 gene is involved in cyclic AMP signaling and in neuroprotection,41 while HSPA2 is a chaperone and was previously shown to have significantly decreased gene expression in the DLPFC and anterior cingulate cortex of MDDs, in a different cohort, compared with controls.42, 43 Meanwhile, two nuclear receptor transcription factors (PPARD and PPARG) involved in neuroprotection, energy homeostasis, inflammation and response to oxidative stress44, 45 were expressed at higher levels in the HIPP of MDD subjects (Figure 3). This evidence concerns the gene PPARD and major depressive disorder.