Appl1 is essential for the survival of Xenopus pancreas, duodenum, and stomach progenitor cells.

An understanding of the molecular mechanisms governing the survival of organ progenitor cells in vivo is crucial for in vitro tissue regeneration. Here, we have found that Xenopus appl1 and akt2 share a similar embryonic expression pattern, showing characteristic expression in the central nervous system as well as in the pancreas and part of the stomach/duodenum (SD) at tadpole stages of development. Specific knockdown of appl1 in endoderm or inhibition of akt activity did not affect the formation of endodermal organ primordia at tail bud stages of development, but led to a gut-coiling defect, strong apoptosis in endodermal organs, and pancreas and SD hypoplasia or even aplasia at tadpole stages of development. Furthermore, appl1 is required for akt phosphorylation and akt2 in turn can rescue appl1 knockdown phenotypes. Together, our data suggest that appl1-akt signaling is specifically required for the survival of pancreas and SD progenitor cells in Xenopus laevis embryos.