Figure 10. Model of Prop1’s role in the transition of stem cells to differentiation.
During normal pituitary development when stem cells transition toward differentiation they exit the cell cycle and express Cyclin E. Our results suggest that for progenitors to differentiate they need to go through an EMT-like process where E-cadherin is down-regulated and the cells lose adhesion. In the absence of Prop1, the expression of genes that can induce EMT, like Zeb2, is reduced, leading to increased cell adhesion and increased expression of tight junction proteins like claudins. Our data suggest that PROP1 is required for progenitors to progress to the transitional stage marked by Cyclin E expression embryonically, and in the absence of Prop1, Sox2 expression is elevated. The failure of progenitors cells to advance to the transitional stage leads to pituitary hormone deficiency and organ dysmorphology.