Retinoic acid induced expression of Hnf1β and Fzd4 is required for pancreas development in Xenopus laevis

Retinoic acid (RA) is required for pancreas specification in Xenopus and other vertebrates. However, the gene network that is directly induced by RA-signalling in this context remains to be defined. We identified the transcription factor Hnf1β and the Wnt-receptor Fzd4/Fzd4s as direct RA-target genes through RNA-sequencing of in vitro generated pancreatic explants. Functional analyses of Hnf1β and Fzd4/Fzd4s in programmed pancreatic explants and whole embryos revealed their requirement for pancreatic progenitor formation and differentiation. Hnf1β and Fzd4/Fzd4s thus appear to be involved in pre-patterning events of the embryonic endoderm allowing for pancreas formation.