passages.id: split_6_test_1242_passage
passages.type: progene_text
passages.text: Fibroblast growth factor ( FGF ) - 4 gene expression in the inner cell mass of the blastocyst and in EC cells requires the combined activity of two transcriptional regulators , Sox2 and Oct-3 , which bind to adjacent sites on the FGF-4 enhancer DNA and synergistically activate transcription .