DNA methylation differences between Newborns and Nonagenarians [PBMNC]

Human aging implies many phenotypic modifications and an increased susceptibility to many common diseases, phenomena that cannot be fully explained by the constrained genetic setting. An alternative pathway that could explain the age-associated alterations is epigenetic drifts. To address this issue, we performed Whole Genome Bisulfite Sequencing (WGBS) of a newborn and of a centenarian. The centenarian DNA exhibited a significant loss in DNA methylation and a poor correlation in the methylation status of neighboring CpGs throughout the genome. From a gene-regulatory region standpoint, we observed that the DNA hypomethylation events occurred mainly at CpG-poor promoters and in tissue-specific genes, whereas a greater level of DNA methylation was observed in CpG island promoters. Most importantly, we extended the study to a larger cohort of newborn and nonagenarian samples using a 450,000 CpG-site DNA methylation microarray. The 450K DNA methylation approach enabled validation of the WGBS data and revealed additional age-related DNA methylation events. Interestingly, we also observed the DNA methylation fingerprint characteristic of a healthy aged cell in samples from patients with premature-aging disorders such as Hutchinson-Gilford progeria and Werner syndrome. Overall, we suggest that defects in the physiological DNA methylation profile contribute to the process of human aging. As the disease associated cells were immortalized B cells, the effect of EBV immortalization was determined in advance to the study using immortalized and naive B cells.