Practice question

Pluripotency in embryonic stem cells depends on a core transcriptional circuit centered on Oct4, Sox2, and Nanog. Oct4, a POU domain transcription factor, activates self-renewal genes and represses differentiation drivers such as Cdx2 and Gata6. Its dosage is critical; too low triggers trophectoderm differentiation, too high pushes toward primitive endoderm and mesoderm. Oct4 collaborates with LIF-STAT3 and FGF signaling to sustain open chromatin and prevent lineage commitment. Loss of Oct4 leads to rapid differentiation, making it indispensable for maintaining the undifferentiated, unlimited proliferative state of embryonic stem cells.