Association Study Of COMT Gene Methylation And Schizophrenia

ObjectiveBisulfite Genomic Sequencing,the gold standard method,was used in this quantitative study of DNA methylation on untranslated region in COMT(the catechol-O-nethyltransferase) from schizophrenic patients’ and normal controls’ peripheral blood. Then compared the epigenetic COMT methylation modification of two groups and applied cognition tests including event-related potentials P300 and wechsler memory scale on schizophrenic patients to explore the role of COMT methylation in peripheral blood in schizophrenia and the cognitive deficits endophenotype. Positive and Negative Syndrome Scale was also used to evaluate clinical symptoms of first onset patients, in order to reveal the correlation between COMT methylation and clinical symptoms in patients with schizophrenia. We aimed at preliminary exploration on the feasibility of COMT methylation as epigenetic markers of disease diagnosis.Methods1. According to the inclusion criteria, 120 outpatients or inpatients with schizophrenia treated in Ningbo Kangning Hospital from July 2013 to December 2014 were selected as case group. 35 of the 120 selected schizophrenia patients did not use any Antipsychotics before were choosen as first onset group. Subsequently, 120 healthy volunteers matched with the case group in gender, age, educational level, smoking and alcohol consumption were selected as control group.2. 4ml peripheral blood of each participants was extracted for genomic DNA. After bisulfite conversion of DNA, bisulfite pyrosequencing methord was used to detect the methylation of CpG sites on two sequences of COMT gene untranslated region.3. After the blood examination, case group respectively accepted P300 and WMS test under calm state. Their serum homocysteine levels were measured at the same time; Moreover, the first onset group accepted PANSS scale assessment before treatment.4. SPSS13.0 software was used in this study. Ststistical method of t test, single variance analysis, rank sum test, chi-square test and correlation analysis were applied to all data. All the experimental data were presented as mean ± standard deviation.Results1. The seven sites on COMT gene CpG island showwed low correlation, and were hypomethylated. The three sites outside CpG island showwed high correlation, and were hypermethlated.2. The methylation of CpG1 and CpG3 on CpG island in case group were lower than those in healthy controls. Similar results were found in male population. While no significant differences of methylation were found in those sites between female patients and healthy controls.3. The methylation of all three sites outside CpG island and even their average methylation(CpG123) in case group were higher than those in control group. Similar results were found in male population. While in Females, only the methylation of CpG3 in patients was higher than that in health.4. Male patients with different family history, history of trauma, onset form, diagnosis type, smoking and drinking history showed no statistically difference in the methylation of CpG1 and CpG3 on CpG island. No correlation was found between age, age of onset, course of disease, homocysteine levels, P300, WMS score and the methylation of CpG1 and CpG3.5. Male patients with different family history, history of trauma, onset form, diagnosis type, smoking and drinking history showed no statistically difference in the methylation of CpG123 outside CpG island. No correlation was found between age, age of onset, course of disease, homocysteine levels, P300, WMS score and the methylation of CpG123.6. Female patients with different family history, history of trauma, onset form, diagnosis type showed no statistically difference in the methylation of CpG3 outside CpG island. No correlation was found yet between age, age of onset, course of disease,homocysteine levels, P300, WMS score and the methylation of CpG3.7. On COMT CpG island, the methylation of CpG1 in first onset male patients was unrelated with PANSS scores, but there was negative correlation between the methylation of CpG3 and both PANSS total score and general psychopathology score.8. Outside COMT CpG island, there was a negative correlation between the methylation of CpG123 and PANSS positive score in first onset male patients and a negative correlation between methylation of CpG3 and PANSS negative score in first onset female patients.Conclussion1. On COMT gene untranslated region, CpG sites on CpG island were hypomethylated, while CpG sites outside CpG island were hypermethylated. Methylation of different CpG sites on COMT may exist opposite effects on the regulation of gene expression.2. Sex has a significant effect on COMT methylation. Methylation modification may be more important in male patients. In males, the methylation of CpG1 and CpG3 on CpG island and three CpG sites outside CpG island may be involved in the etiology of schizophrenia. While in females, only the methylation of CpG3 outside CpG island play an important role in disease. The methylation of these CpG sites may act as epigenetic markers for disease diagnosis.3. Schizophrenia patients showed long P300 latency and low WMS score. But there was no relationship between such cognitive impairments and the methylation of the statistically significant CpG sites in patients.4. The methylation of CpG3 on CpG island could reflect the severity of general psychiatric symptoms in male patients. Three sites outside CpG island in male patients and CpG3 outsede CpG island in female patients may be involved in the feedback regulation of neurotransmitter dsysfunction.