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. 2023 May 24;150(10):dev201522. doi: 10.1242/dev.201522

Fig. 4.

Fig. 4.

Schematic of the appearance of epiblast and hypoblast lineages in human blastocysts based on sequential de novo expression of hypoblast markers. At D5, the ICM comprises cells co-expressing OCT4, NANOG, SOX2 and PDGFRA (membrane). At early D6, SOX17 appears in the undefined ICM with PDGFRA, OCT4, SOX2 and NANOG. In parallel, some cells lose PDGFRA and become epiblast (epi) precursors. At late D6, more epiblast cells appear in the ICM and hypoblast precursors emerge, expressing SOX17, FOXA2 and PDGFRA but not NANOG or SOX2. More advanced hypoblast cells beside the blastocoel express GATA4, the last marker to appear. At D7, both lineages are specified and sorted: hypoblast cells beside the blastocoel and the epiblast between the hypoblast and polar TE. Epiblast cells express NANOG, OCT4 and SOX2, whereas PDGFRA, SOX17, FOXA2 and GATA4 mark the hypoblast.