Coordination of engineered factors with TET1/2 promotes early stage epigenetic modification during somatic cell reprogramming
Somatic cell reprogramming towards induced pluripotent stem cells (iPSCs) holds great promise in future regenerative medicine, however, the reprogramming process mediated by the traditional defined factors (OSNK) is slow and extremely inefficient. Here we show that a combination of modified reprogramming factors (OySyNyK), in which the transactivation domain of the Yes-associated protein is fused to OCT4, SOX2 and NANOG respectively, could be used to establish a highly efficient and rapid reprogramming system for iPSC generation. We show that the efficiency of OySyNyK-induced iPSCs was up to 100-fold higher than that of induction by traditional OSNK. Moreover we show that the reprogramming by OySyNyK is very rapid (initiated at 24 h versus 5 d by OSNK). Compared with OSNK, we found that OySyNyK factors significantly increased the expression of Tet1/2 at the early stage, which will interact with OSNK factors, and co-occupy pluripotency loci in the genome for somatic cell reprogramming. Our studies not only establish a rapid and highly efficient iPSC reprogramming system, but also uncover a novel mechanism by which OSNK factors coordinate with TET proteins to regulate 5hmC-mediated epigenetic control, thereby promoting somatic cell reprogramming. Overall design: We examined DNA hydroxymethylation progression of reprogramming intermediates. To this end, we profiled the genome-wide 5hmC distribution in MEFs, the reprogramming intermediates at different stages induced by either the OSNK or OySyNyK methods, and iPSCs using the chemical capture approach