Functional analyses and effect of DNA methylation on the EGR1 gene in patients with schizophrenia

EGR1, involved in the regulation of synaptic plasticity, learning, and memory, is considered a candidate gene for schizophrenia. We resequenced the exonic regions of EGR1 in 516 patients with schizophrenia and conducted a reporter gene assay. We found two mutations including a rare mutation (c.-8C>T, rs561524195) and one common SNP (c.308-42C>T, rs11743810). The reporter gene assay showed c.-8C>T mutant did not affect promoter activity. Gene expression analyses showed that the average EGR1 mRNA and protein levels in lymphoblastoid cell lines of schizophrenia in male, but not female, were significantly higher than those in controls. We conducted in vitro DNA methylation reaction, luciferase activity assay, and pyrosequencing to assess DNA methylation of EGR1 expression underlying the pathophysiology of schizophrenia. DNA methylation of the EGR1 promoter region attenuated reporter activity, suggesting that DNA methylation regulates EGR1 expression. There were no statistically significant differences in DNA methylation levels of 17 CpG sites at the EGR1 promoter region between 64 patients with schizophrenia compared with 64 controls. These results suggest that the exonic mutations in EGR1 and DNA methylation regulating EGR1 expression might not be associated with schizophrenia. However, the gender-specific association of elevated EGR1 expression might be involved in the pathophysiology of schizophrenia.