Genes controlling pancreas ontogeny.

The pancreas develops from two separate and independent endodermal primordia. The molecular events supporting the early morphological changes that give rise to the formation of the dorsal and ventral pancreatic buds result from coordinated responses to extrinsic and intrinsic signals. The extrinsic signals are involved in processes dictating whether progenitor cells remain as immature or as committed precursors. After specification, the sequential activation of transcription factors determines cell autonomously the commitment and differentiation of these progenitors. During pancreas development, the roles of extrinsic and intrinsic signals are variable, depending on the particular competence of each progenitor cell. We summarize in this review the main events, at the level of gene expression, which are involved in the early stages of pancreas development.