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A post-mid-blastula transition requirement for TGFbeta signaling in early endodermal specification.
1Department of Vertebrate Molecular Embryology, Box 32, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Mechanisms of Development
|January 21, 2000
Summary
Maternal VegT and TGFbeta signaling cooperate to determine Xenopus endoderm cell fate. This process requires continuous extracellular signaling before the mid-blastula transition (MBT) for endoderm development.
Area of Science:
- Developmental Biology
- Cell Signaling
- Molecular Biology
Background:
- Endodermal cell fate determination in Xenopus is a gradual process.
- Cell-cell interactions are crucial for endoderm specification.
- Extracellular signaling plays a vital role before endoderm determination.
Purpose of the Study:
- To investigate the role of extracellular signaling in endoderm determination.
- To elucidate the interplay between VegT and TGFbeta pathways in endoderm specification.
- To identify specific signaling molecules involved in early endoderm development.
Main Methods:
- Cell dissociation assays were performed.
- Rescue experiments with signaling molecules (Activin, Vg1, BMP2, FGF) were conducted.
- In vivo experiments using dominant-negative receptors and vegetal explants were utilized.
Main Results:
- Activin and Vg1, but not BMP2 or FGF, rescued endodermal marker expression in dissociated cells at MBT.
- Removal of exogenous activin or Vg1 before MBT reduced endodermal gene expression.
- Blocking activin-like signaling in vivo reduced endodermal markers; VegT requires TGFbeta for endoderm induction.
Conclusions:
- TGFbeta signaling is activated by maternal VegT to participate in endoderm determination.
- VegT functions in parallel with the TGFbeta pathway.
- Maternal VegT initiates zygotic TGFbeta signaling, then collaborates with it for endoderm fate determination.