Stability of DNA methylation of X-chromosome genes during aging

The stability of DNA methylation during aging was assessed in two groups of young (5-20 years old) and old (85-95 years old) women in DNA from blood leukocytes. Three X-linked genes were investigated. Two, G6PD and GdX, are located on Xq28, on the inactivated portion of the X chromosome: demethylation of specific regions of both genes was shown previously to be directly correlated with gene reactivation. The third, MIC2, is located on the pseudoautosomal region of the X chromosome and escapes X inactivation. The 5' region of the G6PD and GdX genes and the body of the G6PD, GDX, and MIC2 genes were analyzed with specific DNA probes. No age-related changes in methylation pattern were detected. We can conclude therefore that the methylation pattern of the three X-linked genes is stable during aging in female leukocytes and that a high rate of age-related reactivation of X-linked genes may not be a feature of all X-linked loci.