SOX9 is required for maintenance of the pancreatic progenitor cell pool

TLDR

The maintenance of organ‑specific progenitor cells is poorly understood, but SOX9 marks a mitotically active, Notch‑responsive subset of pancreatic progenitors whose loss causes hypoplasia due to progenitor depletion. We demonstrate that SOX9 is a specific marker and essential maintenance factor for pancreatic progenitors, promoting their proliferation, survival, and undifferentiated state through a Notch‑dependent pathway involving HES1.

Abstract

The factors necessary to maintain organ-specific progenitor cells are poorly understood and yet of extreme clinical importance. Here, we identify the transcription factor SOX9 as the first specific marker and maintenance factor of multipotential progenitors during pancreas organogenesis. In the developing pancreas, SOX9 expression is restricted to a mitotically active, Notch-responsive subset of PDX1 + pluripotent progenitors and is absent from committed endocrine precursors or differentiated cells. Similar to Notch mutations, organ-specific Sox9 inactivation in mice causes severe pancreatic hypoplasia resulting from depletion of the progenitor cell pool. We show that Sox9 maintains pancreatic progenitors by stimulating their proliferation, survival, and persistence in an undifferentiated state. Our finding that SOX9 regulates the Notch-effector HES1 suggests a Notch-dependent mechanism and establishes a possible genetic link between SOX factors and Notch. These findings will be of major significance for the development of in vitro protocols for cell replacement therapies.