10−35), and that predominantly were not expressed in H1 cells but were transcribed at a low level in ADS-iPSCs (Supplementary Table 5). Focusing subsequent analysis on the 22 non-CG mega-DMRs hypomethylated in the ADS-iPSC line compared to the H1 line, we discovered that non-CG mega-DMR localization was strongly biased towards close proximity to centromeres and telomeres (Fig. 5a; Poisson P value = 1 × 10−12), indicating that somatic cell reprogramming may be susceptible to DNA methylation abnormalities in these chromosomal regions. We did not find evidence that the retroviral insertions used to introduce the pluripotency factors in ADS-iPSCs was associated with the altered reprogramming of DNA methylation (Supplementary Fig. 16 and Supplementary Table 6).
