SOX9 and major depressive disorder: By overlapping the 12 DRGMDD with the 48 DRLMDD, six key DRGs (termed key-DRGMDD that included FOSL1, SRF, JUN, TFAP4, SOX9, and HLF) and 16 TF2target DCLs (termed key-DRLMDD) appear to be the key differential factors in MDD (Figure 2).