DAO and schizophrenia: We first examined the methylation status of the gene encoding the D-Ser degrading enzyme, DAO, in the hippocampus (HIPP) and dorsolateral prefrontal cortex (DLPFC) from non-psychiatric subjects (CTRL; n = 20) and schizophrenia patients (SCZ; n = 20), as well as in the cerebellum (CB; 10 CTRL and 9 SCZ).