ON THE ORIGIN OF PANCREATIC ENDOCRINE-CELLS, PROLIFERATION AND NEOPLASTIC TRANSFORMATION

In the adult mouse, pancreatic islets contain four islet cell types: a lpha, beta, delta and pancreatic polypeptide cells that synthesize glu cagon, insulin, somatostatin and pancreatic polypeptide, respectively. The early progenitor cells to the pancreatic islets are multipotentia l and coactivate all the islet-specific genes from the time they first appear. As development proceeds, expression of islet-specific hormone s becomes restricted to the pattern of expression characteristic of ma ture islet cells. The phenotype of mature islet cells, however, is not stable since different environmental stimuli can induce the reappeara nce of embryonal traits in mature beta cells.