Fig. 4.

Correlation of DNA methylation and gene expression. DNA methylation data of the HumanMethylation27 BeadChip was matched with Affymetrix mRNA expression profiles. As expected, signal intensity in gene expression data revealed higher expression of nonmethylated genes (A). However, differential methylation upon long-term culture (B) or aging (C) was not necessarily reflected in differential gene expression. Six differentially methylated genes that have been analyzed by pyrosequencing were further analysed by quantitative RT-PCR and in this subset hypermethylation coincides with lower gene expression and vice versa (D, E) (all 16 samples, ± SEM).