De novo methylation at intronic CpG islands of Igf2r is associated with decreased expression of antisense RNA in aged mice

Changes in cytosine methylation status of several genes have been implicate d in the aging process. We have examined methylation status of differential ly methylated regions of insulin-like growth factor II: receptor gene durin g mouse senescence. Bisulfite-aided genomic sequencing revealed that methyl ated CpG residues were extended beyond the 3' boundary of de novo methylati on sequence of DMR2 in aged mice. Furthermore, the de novo methylation of D MR2 in aged mice was associated with decreased expression of antisense tran script which recruits DMR2 as a promoter. On the contrary, methylation stat us of DMR1 was well-maintained during senescence. Accordingly, no significa nt changes in expression levels of sense transcripts were observed during t he course of mouse aging. (C) 2000 Academic Press.