ESCs and trophoblast stem (TS) cells are both derived from early embryos, yet these cells have distinct differentiation properties. ESCs can differentiate into all three germ layer cell types, whereas TS cells can only differentiate into placental cells. It has not been determined whether TS cells can be converted into ES-like pluripotent stem (PS) cells. Here, we report that overexpression of a single transcription factor, Oct4, in TS cells is sufficient to reprogram TS cells into a pluripotent state. These Oct4-induced PS (OiPS) cells have the epigenetic characteristics of ESCs, including X chromosome reactivation, elevated H3K27 me3 modifications, and hypomethylation of promoter regions in Oct4 and Nanog genes. Meanwhile, methylation of promoter region in the Elf5 gene occurred during reprogramming of TS cells. The gene expression profile of OiPS cells was very similar to ESCs. Moreover, OiPS cells can differentiate into the three germ layer cell types in vitro and in vivo. More importantly, chimeric mice with germline transmission could be efficiently produced from OiPS cells. Our results demonstrate that one single transcription factor, Oct4, could reprogram the nonembryonic TS cells into PS cells.
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