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Genes Dev 1997 Dec 01;1123:3265-76. doi: 10.1101/gad.11.23.3265.
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The Xenopus Brachyury promoter is activated by FGF and low concentrations of activin and suppressed by high concentrations of activin and by paired-type homeodomain proteins.

Latinkić BV , Umbhauer M , Neal KA , Lerchner W , Smith JC , Cunliffe V .

The mesoderm of Xenopus laevis arises through an inductive interaction in which signals from the vegetal hemisphere of the embryo act on overlying equatorial cells. One candidate for an endogenous mesoderm-inducing factor is activin, a member of the TGFbeta superfamily. Activin is of particular interest because it induces different mesodermal cell types in a concentration-dependent manner, suggesting that it acts as a morphogen. These concentration-dependent effects are exemplified by the response of Xbra, expression of which is induced in ectodermal tissue by low concentrations of activin but not by high concentrations. Xbra therefore offers an excellent paradigm for studying the way in which a morphogen gradient is interpreted in vertebrate embryos. In this paper we examine the trancriptional regulation of Xbra2, a pseudoallele of Xbra that shows an identical response to activin. Our results indicate that 381 bp 5'' of the Xbra2 transcription start site are sufficient to confer responsiveness both to FGF and, in a concentration-dependent manner, to activin. We present evidence that the suppression of Xbra expression at high concentrations of activin is mediated by paired-type homeobox genes such as goosecoid, Mix.1, and Xotx2.

PubMed ID: 9389657
PMC ID: PMC316753
Article link: Genes Dev

Species referenced: Xenopus laevis
Genes referenced: fgf2 gsc mapk1 mix1 otx2 tbxt tgfb1

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References [+] :
Artinger, Interaction of goosecoid and brachyury in Xenopus mesoderm patterning. 1997, Pubmed, Xenbase