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XB-ART-5992
Curr Biol December 23, 2002; 12 (24): 2136-41.

Lefty-dependent inhibition of Nodal- and Wnt-responsive organizer gene expression is essential for normal gastrulation.



Abstract
During gastrulation, diffusible "organizer" signals, including members of the TGFbeta Nodal subfamily, pattern dorsal mesoderm and the embryonic axes. Simultaneously, negative regulators of these signals, including the Nodal inhibitor Lefty, an atypical TGFbeta factor, are induced by Nodal. This suggests that Lefty-dependent modulation of organizer signaling might regulate dorsal mesoderm patterning and axial morphogenesis. Here, Xenopus Lefty (Xlefty) function was blocked by injection of anti-Xlefty morpholino oligonucleotides (MO). Xlefty-deficient embryos underwent exogastrulation, an aberrant morphogenetic process not predicted from deregulation of the Nodal pathway alone. In the absence of Xlefty, both Nodal- (Xnr2, gsc, cer, Xbra) and Wnt-responsive (gsc, Xnr3) organizer gene expression expanded away from the dorsal blastopore lip. Conversely, coexpression of Xlefty with Nodal or Wnt reduced the ectopic expression of Nodal- (Xbra) and Wnt-responsive (Xnr3) genes in a dose-dependent manner. Furthermore, Xlefty expression in the ectodermal animal pole inhibited endogenous Nodal- and Wnt-responsive gene expression in distant mesoderm cells, indicating that Xlefty inhibition can spread from its source. We hypothesize that Xlefty negatively regulates the spatial extent of Nodal- and Wnt-responsive gene expression in the organizer and that this Xlefty-dependent inhibition is essential for normal organizer patterning and gastrulation.

PubMed ID: 12498689
Article link: Curr Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: a2m cdx2 cer1 gsc lefty myod1 nodal nodal1 nodal2 nodal3.1 nodal3.2 shh tbxt tgfb1
Morpholinos: lefty MO1 lefty MO2


Article Images: [+] show captions
References :
Solnica-Krezel, Vertebrate development: taming the nodal waves. 2003, Pubmed