Pancreatic protein disulfide isomerase (XPDIp) is an early marker for the exocrine lineage of the developing pancreas in Xenopus laevis embryos.

The pancreas develops from dorsal and ventral epithelial extensions at the foregut/midgut boundary in Xenopus embryos. Endocrine and exocrine specification is thought to occur from a pool of uniform precursor cells. While the genetic network controlling endocrine specification and differentiation has been the object of extensive investigations, the corresponding mechanism leading to the exocrine pancreas is much less understood. Here, we report on the identification and characterisation of a novel molecular marker for the early exocrine pancreas in Xenopus embryos. Xenopus pancreatic protein disulfide isomerase is expressed in both dorsal and ventral pancreatic buds. By whole mount in situ hybridization it is detected as early as stage 39 in the exocrine lineage of the developing pancreas; RT-PCR reveals onset of expression as early as stage 35/36.