Discovering the transcription factors that define embryonic cell "stemness" is crucial for understanding of how cells become pluripotent and for assisting the search for more widely acceptable means of generating stem cells in vitro. The leukemia inhibitory factor (LIF) plays a major role in self-renewal of embryonic stem (ES) cells via the gp130/Stat3 signaling pathway, and the transcription factor Oct4 functions in the maintenance of pluripotency in blastocyst inner cell mass cells and in primordial germ cells. Overexpression of Oct4 drives ES cells into differentiation, suggesting that other factors may be involved in the maintenance of pluripotency and self-renewal in ES cells. In the May 30 Cell, two papers reveal the discovery of a single molecule that also functions in this capacity in the mouse. Each group cites a third group that has previously reported the same molecule as being expressed selectively in ES cells.

Kaoru Mitsui and colleagues at...

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