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. Author manuscript; available in PMC: 2013 Sep 1.
Published in final edited form as: Wiley Interdiscip Rev Dev Biol. 2012 Mar 14;1(5):609–628. doi: 10.1002/wdev.44

Figure 1. Pancreatic endoderm patterning and specification.

Figure 1

The portion of the endoderm fated to become dorsal and ventral pancreas is patterned and specified due to the influence of secreted molecules and signalling pathways from adjacent tissues and cells. The influence of FGF and BMP signalling from the cardiac mesoderm and septum transversum mesenchyme, respectively, affect the patterning of ventral pancreatic endoderm. Retinoic acid (RA), SHH, FGF and ACTIVIN signalling from the paraxial mesoderm and notochord allow for patterning of the dorsal pancreatic endoderm. The stage from E9.5 through E12.5 marks the primary transition. During this period, the pancreatic progenitor cells are specified, first wave endocrine cells are present, and epithelial branching morphogenesis begins. The secondary transition occurs after E12.5 and is marked by a major wave of endocrine cell specification and development, as well as further ductal morphogenesis and exocrine lineage differentiation.