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Caenorhabditis elegans genes sma-2, sma-3, and sma-4 define a conserved family of transforming growth factor beta
1Waksman Institute, Rutgers University, Piscataway, NJ 08855-0759, USA.
Abstract:
Although transforming growth factor beta (TGF-beta) superfamily ligands play critical roles in diverse developmental processes, how cells transduce signals from these ligands is still poorly understood. Cell surface receptors for these ligands have been identified, but their cytoplasmic targets are unknown. We have identified three Caenorhabditis elegans genes, sma-2, sma-3, and sma-4, that have mutant phenotypes similar to those of the TGF-beta-like receptor gene daf-4, indicating that they are required for daf-4-mediated developmental processes. We show that sma-2 functions in the same cells as daf-4, consistent with a role in transducing signals from the receptor. These three genes define a protein family, the dwarfins, that includes the Mad gene product, which participates in the decapentaplegic TGF-beta-like pathway in Drosophila [Sekelsky, J. J., Newfeld, S. J., Raftery, L. A., Chartoff, E. H. & Gelbart, W. M. (1995) Genetics 139, 1347-1358]. The identification of homologous components of these pathways in distantly related organisms suggests that dwarfins may be universally required for TGF-beta-like signal transduction. In fact, we have isolated highly conserved dwarfins from vertebrates, indicating that these components are not idiosyncratic to invertebrates. These analyses suggest that dwarfins are conserved cytoplasmic signal transducers.
Insights
We identified three Caenorhabditis elegans genes, sma-2, sma-3, and sma-4, essential for transforming growth factor beta (TGF-beta) signaling. These genes, named dwarfins, are conserved cytoplasmic signal transducers in vertebrates.
Area of Science:
- Molecular Biology
- Developmental Biology
- Genetics
Background:
- Transforming growth factor beta (TGF-beta) superfamily ligands are crucial for development.
- Cellular signal transduction mechanisms for TGF-beta ligands remain largely unknown.
- Cytoplasmic targets of TGF-beta receptors have not been identified.
Purpose of the Study:
- Identify novel components involved in TGF-beta signal transduction.
- Investigate the function of newly discovered genes in developmental processes.
- Determine if these components are conserved across species.
Main Methods:
- Genetic analysis of Caenorhabditis elegans mutants with phenotypes similar to TGF-beta receptor mutants.
- Functional studies of identified genes (sma-2, sma-3, sma-4) in relation to TGF-beta signaling pathways.
- Comparative genomics to identify homologous genes in other organisms, including vertebrates.
Main Results:
- Identified three Caenorhabditis elegans genes (sma-2, sma-3, sma-4) essential for TGF-beta-like signaling.
- Demonstrated that sma-2 functions downstream of the TGF-beta receptor daf-4.
- These genes define a conserved protein family, dwarfins, homologous to Drosophila Mad.
- Isolated highly conserved dwarfins from vertebrates.
Conclusions:
- Dwarfins (sma-2, sma-3, sma-4) are key cytoplasmic signal transducers for TGF-beta-like pathways.
- These components are conserved from invertebrates to vertebrates, suggesting a universal role in TGF-beta signaling.
- The discovery of dwarfins provides critical insights into the molecular mechanisms of TGF-beta signal transduction.