CACNA1C and bipolar disorder: Of interest, the VRK2 region (2p16.1) was identified in the previous sample after including a large schizophrenia replication sample [30], and the ITIH4 region (3p21.1), ANK3 (10q21) and CACNA1C (12p13.3) were discovered previously in the same, combined schizophrenia and bipolar disorder sample [13], [14].