The levels of reprogramming factors influence the induction and maintenance of pluripotency: the case of CD1 mouse strain cells.

The amount of proteins of the regulatory pluripotency network can be determinant for somatic cell reprogramming into induced pluripotent stem cells (iPSCs) as well as for the maintenance of pluripotent stem cells (PSCs). Here, we report a transposon-based reprogramming system (PB-Booster) that allowed high expression levels of a polycistronic transgene containing K O and () and showed increased reprogramming efficiency of fresh mouse embryonic fibroblasts (MEFs) into iPSCs under low, but not under high, expression levels. In contrast, MEFs after 2 passages derived into a similar number of iPSC colonies as fresh MEFs at a high MKOS dose, but this number was reduced at a low MKOS dose.