NANOG is a multidomain homeobox transcription factor which functions to maintain the undifferentiated state of pluripotent stem cells. NANOG expression counteracts the differentiation-promoting signals induced by the extrinsic factors LIF， Stat3 and BMP. Once NANOG expression is downregulated， cell differentiation can proceed. Proteins which regulate NANOG expression include transcription factors Oct4， SOX2， FoxD3， and Tcf3 and tumor suppressor p53.
