VegT induces endoderm by a self-limiting mechanism and by changing the competence of cells to respond to TGF-beta signals.
The maternal determinant VegT is required for both endoderm and mesoderm formation by the Xenopus embryo. An important downstream mediator of VegT action is Xsox17, which has been proposed to be induced in cell-autonomous, then signal-dependent phases. We show that Xsox17 is a direct VegT target, but that direct induction of Xsox17 by VegT is rapidly inhibited. This inhibition is relieved by TGF- beta signalling, to which the future endoderm cell is sensitised by VegT, resulting in the observed dependence on cell contact for maintained Xsox17 expression. We propose that this change in regulation is a consequence of a VegT-induced repressor, inhibiting direct induction of early endoderm markers by VegT, and contributing to the formation of the boundary of the endodermal domain.
Clements
Debbie
D
Department of Biological Sciences, University of Warwick, CV4 7AL, Coventry, UK.
Woodland
Hugh R
HR
D000818:Animals; D004268:DNA-Binding Proteins; D004627:Embryonic Induction; D004707:Endoderm / Q000166:cytology / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006609:High Mobility Group Proteins; D017403:In Situ Hybridization; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D008954:Models, Biological; D011506:Proteins / Q000235:genetics / Q000502:physiology; D055760:SOXF Transcription Factors; D015398:Signal Transduction; D020825:T-Box Domain Proteins / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors; D016212:Transforming Growth Factor beta / Q000502:physiology*; D014981:Xenopus / Q000196:embryology* / Q000235:genetics / Q000502:physiology; D029867:Xenopus Proteins
D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D011506:Proteins; D055760:SOXF Transcription Factors; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C103966:VegT protein, Xenopus; D029867:Xenopus Proteins; C491602:sox17a protein, Xenopus; C491601:sox17b.1 protein, Xenopus