The analysis of significant MF from GO showed that MDD-associated genes mainly function as enzyme binding (GO:0019899) (n = 11, e.g., AKT, CREB1, CAT, SORT1, TGFB1, YWHAE), as receptors (e.g., glutamate receptor (GRM) family or receptor subunits (GO:0008066, GO:0004970, GO:0001642) (GRIA, GRIN, GRIK) or are involved in transportation (GO:0022857) such as SLC6A family. The gene discussed is GRIK4; the disease is major depressive disorder.