ERBB4 and schizophrenia: GNMT catalyzes the synthesis of sarcosine from glycine using S-adenosylmethionine as the methyl-donor in one carbon metabolic pathway, and Gnmt−/− mice have shown dysregulation of DNA methyltransferases (DNMT1 and Dnmt3a), ErbB (Nrg1 and ErbB4), and mTOR (Akt2, S6, S6k1, and S6k2) in the cortex, as well as abnormal behaviors associated with schizophrenia (Yang et al., 2012).