Molecular insights into induced pluripotency mediated by the OCT4, SOX2, KLF and c-MYC gene regulatory network

Human somatic fibroblasts can be reprogrammed to induced pluripotent stem (iPS) cells by exogenic expression of the Yamanaka factors (OCT4, SOX2, KLF4 and MYC) after about 1 month. To gain some insight into the early processes operative in fibroblast reprogramming, we profiled genome-wide transcription levels using Illumina microarrays in the starting donor cells-human foreskin fibroblast (HFF1) cells and at three time points after OSKM transduction (24 h, 48 h, 72 h), as well as two iPS cell lines (iPS2, iPS4) and hES cell lines (H1, H9). We show that within the context of the viral transduction reprogramming protocol, the donor cell response to viral transfection perturbs redox homeostasis, which induces oxidative damage on the donor cells' protein and DNA. This leads to activation of p53, senescence, and apoptosis, greatly reducing the efficiency of reprogramming. Total RNA obtained from HFF1 (human foreskin fibroblast) cells, OSKM-transduced HFF1 cells after 24h, 48h, 72h, undifferentiated hESCs, iPSCs.