Pancreatic polypeptide progenitor cells are immature precursors of the PP producing endocrine cell type. These progenitors are committed to the PP lineage and express early markers, but do not secrete the ploypeptide hormone. Although pancreatic polypeptide mRNA is detected from E10.5, presumably in the PP progenitor cells, the hormone secreting pancreatic polypeptide cells are the latest to mature in the developing pancreas and can only be detected from E16.5.
In the pancreas the differentiation of endocrine cells is non-synchronous and lasts from the secondary transition period (which is the major time of endocrine cell differentiation) to the postnatal period.
EMBRYONIC DEVELOPMENT & STEM CELL COMPENDIUM
