The investigation of the histone proteins acetylation and the DNA methylation in monozygotic twins discordant for schizophrenia

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We tried to investigate the relationship between schizophrenia and the epigenetic events such as the methylation of DNA and the acetylation of histone proteins. First, we examined whether the promoter region of dopamine D2 receptor gene (DRD2) was methylated, using the methylation-sensitive restriction enzyme, Hap II, and the methylation-insensitive enzyme, MspI. The subjects were five pairs of monozygotic twins discordant for DSM-IV schizophrenia (all pairs were male, mean age 42.6 years; all twins had been discordant more than ten years). The genome DNA samples were extracted from lymphocytes by the phenol method. After enzyme digestion, polymerase chain reaction (PCR) was performed, and the size of PCR products was determined using polyacrylamide gel electrophoresis. In four out of five pairs, the level of methylation of the DRD2 promoter region was higher in the affected twin than the normal twin. In one pair, the level was nearly equal in both. In this study, we found some evidenc … More e for the relationship between phenotypic difference in monozygotic twins discordant for schizophrenia and DNA methylation. Therefore in future studies we will try to collect more subjects and use other enzymes.Next, we performed SNPs genotyping and gene expression analysis in monozygotic twins discordant for schizophrenia and compared between twins. The subjects were a pair of monozygotic male twins (age:51), one had DSM-IV schizophrenia, undifferentiated type, and the other had a job, was married, and was well-adapted to social life. The samples were genomic DNA and RNA from the subjects. The SNPs were typed using Affymetrix GeneChip Human Mapping 100K Set (50K Xba Array, 50K Hind Array) and the gene expressions were analyzed by Affymetrix Human Genome U133 Plus 2.0 Array. In SNPs genotyping, forty six SNPs had different signal intensity among all 116204 SNPs between twins. Also, we measured the expression level of 12857 genes. As a results, we detected 4 SNPs that had different signal intensity and located near the 5' end or intron of the genes that showed the different gene expression between twins. By sequencing, we confirmed that there were no alterations of DNA sequences in these regions. Therefore, it could be thought that some epigenetic events caused the change of gene expression. We will investigate the associations between the genes including these SNPs and schizophrenia. Less