PI4KA and schizophrenia: Interestingly, the PIK4CA gene is well-documented to be highly expressed in the gray matter, with significantly higher levels in the fetal brain than in the adult brain (Nakagawa et al., 1996), suggesting an important role for PIK4CA in neurodevelopment and in neurodevelopment-related mental diseases such as schizophrenia; these findings are in agreement with the neurodevelopmental pathogenesis of schizophrenia (Bassett et al., 2001).