Fig. 2.

Pyrosequencing of differentially methylated CpGs. For six CpG sites differential methylation of the HumanMethylation27 BeadChip (open circles) was validated by pyrosequencing (filled circles) (all 16 samples, ± SEM). Overall, methylation levels were lower in pyrosequencing but there was a striking correlation in differential methylation between the two methods for long-term culture (A) and aging (B). This differential methylation was also observed in CpGs in close vicinity to the analyzed CpG site represented on the microarray (blue box; C, D). The percentage of methylation at each CpG site is indicated in black.