Practice question

Pluripotency of inner cell mass and embryonic stem cells is maintained by core transcriptional network centered on Oct4, Sox2 and Nanog. These factors co-occupy enhancers of self-renewal genes while repressing lineage-specific differentiation genes via chromatin remodeling. Oct4 and Sox2 form heterodimer activating Nanog promoter, and all three autoregulate and cross-regulate each other creating robust circuit. Stat3 downstream of LIF supports mouse pluripotency but alone insufficient. Nanog alone cannot sustain, nor can FoxA2/Gata6 which actually promote primitive endoderm differentiation, opposing pluripotent state and triggering exit toward differentiated lineages.