Gene expression of methylation cycle and related genes in lymphocytes and brain of patients with schizophrenia and non-psychotic controls

Some of the biochemical abnormalities underlying schizophrenia, involve differences in methylation and methylating enzymes, as well as other related target genes. We present results of a study of differences in mRNA expression in peripheral blood lymphocytes (PBLs) and post-mortem brains of chronic schizophrenics (CSZ) and non-psychotic controls (NPC), emphasizing the differential effects of sex and antipsychotic drug treatment on mRNA findings. We studied mRNA expression in lymphocytes of 61 CSZ and 49 NPC subjects using qPCR assays with TaqMan probes to assess levels of DNMT, TET, GABAergic, NR3C1, BDNF mRNAs, and several additional targets identified in a recent RNA sequence analysis. In parallel we studied DNMT1 and GAD67 in samples of brain tissues from 19 CSZ, 26 NPC. In PBLs DNMT1 and DNMT3A mRNA levels were significantly higher in male CSZ vs NPC No significant differences were detected in females. The GAD1, NR3C1 and CNTNAP2 mRNA levels were significantly higher in CSZ than NPC. In CSZ patients treated with clozapine, GAD-1 related, CNTNAP2, and IMPA2 mRNAs were significantly higher than in CSZ subjects not treated with clozapine. Differences between CSZ vs NPC in these mRNAs was primarily attributable to the clozapine treatment. In the brain samples, DNMT1 was significantly higher and GAD67 was significantly lower in CSZ than in NPC, but there were no significant sex differences in diagnostic effects. These findings highlight the importance of considering sex and drug treatment effects in assessing the substantive significance of differences in mRNAs between CSZ and NPC.