Early endodermal expression of the Xenopus Endodermin gene is driven by regulatory sequences containing essential Sox protein-binding elements

Abstract

The Endodermin gene is expressed in the early endoderm and the Spemann organizer of Xenopus embryos. It has previously been shown to be a direct target of the early endodermal transcription factor Xsox17 (Clements et al., 2003, Mech Dev 120:337–348). Here we identify two adjacent control elements in the Endodermin promoter; these drive transcription of the gene in late-gastrula endoderm and contain consensus Sox-binding sites. We have analyzed one element in detail and show that it responds directly to Xsox17 and that the Sox sites are essential for endodermal expression in transgenic embryos. However, flanking regions on both sides are also essential, indicating that Xsox17 acts in concert with several DNA-binding partners.