Infrequent occurrence of age-dependent changes in CpG island methylation as detected by restriction landmark genome scanning.
Hypermethylation of CpG islands, resulting in the inactivation of tumor suppressor genes, is an early event in the development of some malignancies. Recent studies suggest that this abnormal methylation may be a function of aging. The number of CpG islands that methylate with age is unknown. We used restriction landmark genome scanning (RLGS) to approximate the extent to which CpG islands change methylation status during aging. Comparison of more than 2000 loci in T lymphocytes isolated from newborn, middle age, and elderly people revealed that 29 loci ( approximately 1%) changed methylation status during aging, with 23 increasing methylation, and six decreasing. The same subset also changed methylation status with age in the esophagus, lung, and pancreas, but in variable directions. Virtual genome scanning identified one of these loci as a member of the forkhead family, recently implicated in aging, and another as an EST fragment. The methylation status of both correlated with level of expression. Confirming studies in multiple tissues from normal and DNMT1(+/-) mice demonstrated only one age dependent change in the methylation of more than 2000 loci, occurring in liver and kidney. These results indicate that the methylation status of the majority of CpG islands in both mice and humans is tightly controlled during aging, and that changes are infrequent and in humans confined to a specific subset of genes.
Tra
John
J
Department of Pediatrics and Infectious Diseases, University of Michigan, Ann Arbor, MI 48109, USA.
Kondo
Tadashi
T
Lu
Qianjin
Q
Kuick
Rork
R
Hanash
Samir
S
Richardson
Bruce
B
D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics; D002874:Chromosome Mapping; D018899:CpG Islands / Q000235:genetics*; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000172:deficiency; D019175:DNA Methylation; D015894:Genome, Human; D006579:Heterozygote; D006801:Humans; D007231:Infant, Newborn; D051379:Mice; D018345:Mice, Knockout; D015183:Restriction Mapping; D029701:Saccharomyces cerevisiae Proteins; D013601:T-Lymphocytes / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics
C079592:CDC39 protein, S cerevisiae; D018797:Cell Cycle Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse