Naive Epiblast Explanation

Cited from the paper "Nanog Is the Gateway to the Pluripotent Ground State"

" After fertilization, mammalian zygotes follow a program of cleavage divisions and elaborate two extraembryonic lineages, trophoblast and hypoblast (Selwood and Johnson, 2006). This preparatory phase of development culminates in creation of the embryo founder tissue, a population of unrestricted pluripotent cells known as the epiblast (Gardner and Beddington, 1988 and Nichols and Smith, 2009). The epiblast proliferates to provide the substrate for axis formation, germlayer specification, and gastrulation. Naive early epiblast cells can be immortalized in culture in the form of embryonic stem (ES) cells (Brook and Gardner, 1997, Evans and Kaufman, 1981 and Martin, 1981). Pluripotent cells can also be created outside the embryo by reprogramming somatic cells, either by fusion with pre-existing pluripotent cells (Miller and Ruddle, 1976, Tada et al., 1997, Tada et al., 2001 and Takagi et al., 1983) or, more compellingly, by transfection with regulatory transcription factors (Takahashi and Yamanaka, 2006)."

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Cited from the paper "Control of ground-state pluripotency by allelic regulation of Nanog"

"The ICM (inner cell mass) of the late blastocyst contains two lineages: the extra-embryonic primitive endoderm, and the ‘ground-state’ pluripotent epiblast^{6, 8}, which gives rise to the embryo. Inner cells expressing Nanog biallelically also express Oct4 but not Gata4, a primitive endoderm marker⁹, and therefore are epiblast cells."