TCF4 and major depressive disorder: In brief, CACNA1C is a voltage-gated calcium channel gene that was found to associate with schizophrenia, bipolar disorder, Timothy syndrome, and autism, while TCF4, a transcription factor gene, has been implicated in schizophrenia, bipolar disorder, major depressive disorder, post-traumatic stress disorder, and Pitts Hopkins syndrome [12, 13, 19, 20, 27–33] (Methods).