Expression pattern of IAPP and prohormone convertase 1/3 reveals a distinctive set of endocrine cells in the embryonic pancreas

The earliest endocrine cells in the developing pancreas make glucagon and are described as α cells. We show here that these cells express islet amyloid polypeptide and prohormone convertase 1/3 (PC1/3), proteins that are not expressed by mature α cells, but are found in β cells. PC1/3 converts proglucagon to the functionally distinct hormones glucagon-like peptide (GLP)-1 and GLP-2 rather than glucagon. Despite these differences, the early proglucagon-positive cells express, as do mature α cells, the POU domain transcription factor Brn-4, and do not express the β cell factor pdx-1. The early production of atypical peptide hormones by these cells suggests that they could play an important role locally or systemically in the development of the embryo.