OR4K2 and bipolar disorder: Obvious physiological relevance of these results was observed in the susceptible genes identified for bipolar disorder, including INPP5B (MIM, 147264), POU3F1 (MIM, 602479), MTF1 (MIM, 600172), CCDC91 (coiled-coil domain containing 91), KCNQ5 (MIM 607357) and Olfactory receptors (OR4K5, OR4K2, OR4M1, OR4K1, OR4N2, OR4K14, OR4K13; 14q11.2).