Human embryonic stem cells with biological and epigenetic characteristics similar to those of mouse ESCs

Human and mouse embryonic stem cells (ESCs) are derived from blastocyst stage embryos but have very different biological properties, and molecular analyses suggest that the pluripotent state of human ESCs isolated so far corresponds to that of mouse derived epiblast stem cells (EpiSCs). Here we rewire the identity of conventional human ESCs into a more immature state that extensively shares defining features with pluripotent mouse ESCs. This was achieved by exogenous induction of Oct4, Klf4 and Klf2 factors combined with LIF and inhibitors of glycogen synthase kinase 3 (GSK3) and mitogen-activated protein kinase (ERK) pathway. Forskolin, a protein kinase A pathway agonist that induces Klf4 and Klf2 expression, can transiently substitute for the requirement for ectopib transgene expression. In contrast to conventional human ESCs, these epigenetically converted cells have growth properties, an X chromosome activation state (XaXa), a gene expression profile, and signaling pathway dependence that are highly similar to that of mouse ESCs. Finally, the same growth conditions allow the derivation of human induced pluripotent stem (iPS) cells with similar properties as mouse iPS cells. The generation of “naïve” human ESCs will allow the molecular dissection of a previously undefined pluripotent state in humans, and may open up new opportunities for patient-specific, disease-relevant research.