High preservation of CpG cytosine methylation patterns at imprinted gene loci in liver and brain of aged mice

• Published in: PloS one Vol. 8; no. 9; p. e73496
• Main Authors: Gravina, Silvia, Dollé, Martijn E T, Wang, Tao, van Steeg, Harry, Hasty, Paul, Hoeijmakers, Jan, Vijg, Jan
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 09.09.2013; Public Library of Science (PLoS)
• Subjects: Age; Aging; Analysis; Animal models; Animal tissues; Animals; Book publishing; Brain; Brain - metabolism; Cancer; Cell division; Cerebral cortex; CpG Islands; Cytosine; Cytosine - metabolism; Deoxyribonucleic acid; DNA; DNA damage; DNA Methylation; DNA Repair; Epigenetics; Experiments; Gene expression; Gene loci; Genes; Genetic Loci; Genetics; Genomes; Genomic Imprinting; Genomics; Genotoxicity; Life span; Liver; Liver - metabolism; Mass spectrometry; Mass spectroscopy; Medicine; Methylation; Mice; Mice, Inbred C57BL; Organs; Patterning; Preservation; Promoter Regions, Genetic; Public health; Pyrimidines; Scientific imaging; Senescence; New York; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0073496

A gradual loss of the correct patterning of 5-methyl cytosine marks in gene promoter regions has been implicated in aging and age-related diseases, most notably cancer. While a number of studies have examined DNA methylation in aging, there is no consensus on the magnitude of the effects, particularly at imprinted loci. Imprinted genes are likely candidate to undergo age-related changes because of their demonstrated plasticity in utero, for example, in response to environmental cues. Here we quantitatively analyzed a total of 100 individual CpG sites in promoter regions of 11 imprinted and non-imprinted genes in liver and cerebral cortex of young and old mice using mass spectrometry. The results indicate a remarkably high preservation of methylation marks during the aging process in both organs. To test if increased genotoxic stress associated with premature aging would destabilize DNA methylation we analyzed two DNA repair defective mouse models showing a host of premature aging symptoms in liver and brain. However, also in these animals, at the end of their life span, we found a similarly high preservation of DNA methylation marks. We conclude that patterns of DNA methylation in gene promoters of imprinted genes are surprisingly stable over time in normal, postmitotic tissues and that the multiple documented changes with age are likely to involve exceptions to this pattern, possibly associated with specific cellular responses to age-related changes other than genotoxic stress.