title: Within-pair differences of DNA methylation levels between monozygotic twins are different between male and female pairs.
abstract: DNA methylation levels will be important for detection of epigenetic effects. However, there are few reports showing sex-related differences in the sensitivity to DNA methylation. To evaluate their sex-related individual differences in the sensitivity to methylation rigorously, we performed a systematic analysis of DNA methylation in monozygotic twins, an optimal model to evaluate them because the genetic backgrounds are the same.
  
  
  
  We examined 30 male and 43 female older monozygotic twin pairs recruited from the registry established by the Center for Twin Research, Osaka University. Their methylation levels were determined using the Infinium HumanMethylation450 BeadChip Kit (Illumina), which interrogated 485577 highly informative CpG sites at the single-nucleotide resolution, and the median methylation level was calculated for each of the 25657 CpG islands. Within-pair differences of methylation levels (WPDMs) were greater in male pairs than female pairs for 86.0 % of autosomal CpG islands, but were higher in female pairs than male pairs for 76.7 % of X chromosomal CpG islands. Mean WPDMs of CpG islands in each autosomal chromosome were significantly higher in male pairs than in female whereas that in X chromosome was significantly higher in female pairs than in male. Multiple comparison indicated that WPDMs in three autosomal and two X-chromosomal CpG islands were significantly greater in male pairs, whereas those in 22 X-chromosomal CpG islands were significantly greater in female pairs.
  
  
  
  Sex-related differences were present in the WPDMs of CpG islands in individuals with the same genetic background. These differences may be associated with the sexual influences in susceptibility of some diseases.
authors: Department of Biomedical Informatics, Osaka University Graduate School of Medicine, Yamadaoka 1-7, Suita, Osaka, 565-0871, Japan. nabe@sahs.med.osaka-u.ac.jp.|Center for Twin Research, Osaka University Graduate School of Medicine, Yamadaoka 1-7, Suita, 565-0871, Osaka, Japan. nabe@sahs.med.osaka-u.ac.jp.
authors: Mikio
authors: M
authors: Watanabe
authors: Center for Twin Research, Osaka University Graduate School of Medicine, Yamadaoka 1-7, Suita, 565-0871, Osaka, Japan.
authors: Chika
authors: C
authors: Honda
authors: Yoshinori
authors: Y
authors: Iwatani
authors: Shiro
authors: S
authors: Yorifuji
authors: Hiroyasu
authors: H
authors: Iso
authors: Kei
authors: K
authors: Kamide
authors: Jun
authors: J
authors: Hatazawa
authors: Shinji
authors: S
authors: Kihara
authors: Norio
authors: N
authors: Sakai
authors: Hiroko
authors: H
authors: Watanabe
authors: Kiyoko
authors: K
authors: Makimoto
authors: Mikio
authors: M
authors: Watanabe
authors: Chika
authors: C
authors: Honda
authors: Department of Biomedical Informatics, Osaka University Graduate School of Medicine, Yamadaoka 1-7, Suita, Osaka, 565-0871, Japan. iwatani@sahs.med.osaka-u.ac.jp.|Center for Twin Research, Osaka University Graduate School of Medicine, Yamadaoka 1-7, Suita, 565-0871, Osaka, Japan. iwatani@sahs.med.osaka-u.ac.jp.
authors: Yoshinori
authors: Y
authors: Iwatani
mesh_terms: D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D005260:Female; D006801:Humans; D008297:Male; D012727:Sex Characteristics; D014430:Twins, Monozygotic / Q000235:genetics*
keywords: Epigenetic change; Individual difference; Methylation; Monozygotic twin