Selective expression of rat pancreatic genes during embryonic development.

We present the developmental profiles of the mRNAs of 10 selectively expressed pancreatic exocrine genes and of insulin. The mRNA profiles fall into three related classes, but each profile is in some respect unique. The data on gene expression suggest there are four developmental states of the exocrine pancreas: early morphogenesis and low-level gene expression (the protodifferentiated state), the embryonic differentiated state, a modulated state in neonatal animals, and the adult differentiated state. Each state is characterized by distinct ratios of the exocrine mRNAs and presumably involves a distinct regulatory transition. This complex differentiative program must involve multiple regulatory molecules.