BTN3A2 and major depressive disorder: This yielded 25 associated genes consisting mostly of known MDD genes such as NEGR1, BTN3A2, LRFN5 and SCN8A, as well as a number of histone genes located in the same locus as BTN3A2 (Fig. 5b; H2AC13, H2AC15, H2BC14, H2BC15 and H4C13).