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Axis determination by inhibition of Wnt signaling in Xenopus
1Department of Microbiology and Molecular Genetics, Harvard Medical School and Molecular Medicine Unit, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215 USA.
Abstract:
The Wnt family of secreted polypeptides participate in a variety of developmental processes in which embryonic polarity is established. To study a role for Wnt ligands in vertebrate axis determination, we interfered with Wnt signaling in the embryo using the extracellular domain of Xenopus Frizzled 8 (ECD8), which blocks Wnt-dependent activation of a target gene in Xenopus ectodermal explants. Expression of ECD8 in ventral blastomeres resulted in formation of secondary axes containing abundant notochord and head structures. These results suggest that Wnt signaling is required to maintain ventral cell fates and has to be suppressed for dorsal development to occur.
Insights
Wnt signaling is crucial for establishing embryonic polarity. Blocking this pathway in Xenopus embryos with ECD8 promoted the development of secondary axes, indicating Wnt suppression is vital for dorsal development.
Area of Science:
- Developmental Biology
- Molecular Biology
- Embryology
Background:
- Wnt proteins are secreted signaling molecules essential for embryonic development.
- Establishing embryonic polarity and axis determination are fundamental processes in embryogenesis.
Purpose of the Study:
- To investigate the role of Wnt ligands in vertebrate axis determination.
- To understand how Wnt signaling influences cell fate during early development.
Main Methods:
- Utilized Xenopus ectodermal explants to study Wnt signaling.
- Interfered with Wnt signaling using the extracellular domain of Xenopus Frizzled 8 (ECD8).
- Analyzed the effects of ECD8 expression on gene activation and embryonic axis formation.
Main Results:
- Expression of ECD8 blocked Wnt-dependent gene activation in explants.
- Introducing ECD8 into ventral blastomeres led to the formation of secondary embryonic axes.
- These secondary axes contained significant notochord and head structures.
Conclusions:
- Wnt signaling is necessary for maintaining ventral cell fates during embryonic development.
- Suppression of Wnt signaling is a prerequisite for dorsal development to occur.
- Wnt pathway regulation is critical for proper vertebrate axis formation.