KCNQ3 and major depressive disorder: By restriction enzyme assay the c.1720C > T (p.P574S) variant in KCNQ3 was identified in two additional ASD patients (patient C and D) (Figure 2B) and was confirmed in patient B. Patient C inherited the variant from the mother who suffers from major depression and patient D inherited the variant from the father who does not suffer from any psychiatric- or neurological disorders (Figure 2B).