Event:

Sox2 positive mouse pituitary cells are somatic stem cells that contribute to the long-term physiological cell turnover of the postnatal pituitary. Meeting the on-going changes in hormone demand throughout life requires continuous remodelling of hormone producing cell populations as well as maintenance of their stem/progenitor pools. Proliferation in the gland is not only provided by stem cells and committed progenitors but additionally by hormone secreting cells.

Using genetic approaches in the mouse pituitary we show that WNT-responsive cells across all lineages are responsible for the majority of turnover during growth phases. Intriguingly the direct contribution of Sox2 positive stem cells is minimal; instead they indirectly promote proliferation of more committed cell types by secretion of factors including WNT ligands. We conclude that Sox2 positive cells can act as niche cells to promote organ expansion, thus identifying a second role for pituitary stem cells during tissue homeostasis.