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Rasl11b knock down in zebrafish suppresses one-eyed-pinhead mutant phenotype
Guillaume Pézeron1, Guillaume Lambert, Thomas Dickmeis
1INSERM, U784, Paris, France.
Abstract:
The EGF-CFC factor Oep/Cripto1/Frl1 has been implicated in embryogenesis and several human cancers. During vertebrate development, Oep/Cripto1/Frl1 has been shown to act as an essential coreceptor in the TGFbeta/Nodal pathway, which is crucial for germ layer formation. Although studies in cell cultures suggest that Oep/Cripto1/Frl1 is also implicated in other pathways, in vivo it is solely regarded as a Nodal coreceptor. We have found that Rasl11b, a small GTPase belonging to a Ras subfamily of putative tumor suppressor genes, modulates Oep function in zebrafish independently of the Nodal pathway. rasl11b down regulation partially rescues endodermal and prechordal plate defects of zygotic oep(-/-) mutants (Zoep). Rasl11b inhibitory action was only observed in oep-deficient backgrounds, suggesting that normal oep expression prevents Rasl11b function. Surprisingly, rasl11b down regulation does not rescue mesendodermal defects in other Nodal pathway mutants, nor does it influence the phosphorylation state of the downstream effector Smad2. Thus, Rasl11b modifies the effect of Oep on mesendoderm development independently of the main known Oep output: the Nodal signaling pathway. This data suggests a new branch of Oep signaling that has implications for germ layer development, as well as for studies of Oep/Frl1/Cripto1 dysfunction, such as that found in tumors.
Insights
The EGF-CFC factor Oep modulates zebrafish development via Rasl11b, independent of the Nodal pathway. This discovery reveals a new signaling branch for Oep, impacting germ layer formation and cancer research.
Area of Science:
- Developmental Biology
- Molecular Signaling
- Genetics
Background:
- The EGF-CFC factor Oep/Cripto1/Frl1 is vital for vertebrate embryogenesis, acting as a coreceptor in the TGFbeta/Nodal pathway for germ layer formation.
- While cell culture studies suggest broader roles, in vivo research has primarily linked Oep to Nodal signaling.
Purpose of the Study:
- To investigate potential Nodal-independent functions of Oep/Cripto1/Frl1 in vivo.
- To explore the role of the small GTPase Rasl11b in modulating Oep function during zebrafish development.
Main Methods:
- Utilized zebrafish (Danio rerio) as a model organism.
- Employed genetic manipulation techniques to downregulate rasl11b in oep(-/-) mutant zebrafish.
- Assessed developmental defects in endoderm and prechordal plate formation.
- Evaluated the impact on Nodal pathway activity by examining Smad2 phosphorylation.
Main Results:
- Downregulation of Rasl11b partially rescued endodermal and prechordal plate defects in zygotic oep(-/-) mutants (Zoep).
- Rasl11b's inhibitory effect on Oep function was only apparent in oep-deficient backgrounds.
- Rasl11b modulation of Oep did not rescue mesendodermal defects in other Nodal pathway mutants and did not affect Smad2 phosphorylation.
- This indicates Rasl11b influences Oep's role in mesendoderm development independently of the Nodal pathway.
Conclusions:
- Rasl11b modulates Oep function in zebrafish development through a mechanism distinct from the Nodal signaling pathway.
- This finding uncovers a novel signaling pathway for Oep, with implications for understanding germ layer development.
- The study opens new avenues for investigating Oep/Frl1/Cripto1 dysfunction in diseases like cancer.
