Abstract
Redundant gene function frequently hampers investigations of the physiological roles of mammalian proteins. This is the case for Eps8, a receptor tyrosine kinase (RTK) substrate1 that participates in the activation of the Rac-specific guanine nucleotide-exchange function of Sos1 (refs 2–5), thereby regulating actin remodelling by RTKs. EPS8-knockout mice, however, exhibit no evident phenotype2, owing to the redundant function of three other EPS8-related genes6. Here we show that in the nematode Caenorhabditis elegans, only one orthologue of the EPS8 gene exists, which gives rise to two alternatively spliced isoforms, EPS-8A and EPS-8B, differing at their carboxyl termini. In the nematode, eps-8 is essential for embryonic development. Furthermore, EPS-8A, but not EPS-8B, is specifically required for proper apical morphogenesis in the intestinal cells. This latter phenotype could be precisely correlated with a previously unknown actin barbed-end-capping activity, which is present in the C terminus of the EPS-8A isoform. Therefore, nematode genetics allowed not only the unmasking of distinct EPS-8-linked phenotypes, but also the definition of a novel function for this molecule in actin dynamics.
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Acknowledgements
The authors wish to thank the laboratory of Y. Kohara for providing cDNA clones; the Caenorhabditis Genetics Centre, which is funded by the National Institutes of Health National Centre for Research Resources, for some of the strains used in this work; the C. elegans KnockOut Consortium for the eps-8(ok539) allele; and A. Fire for reagents. We thank P. Transidico and C. Giuliani for technical assistance. We also thank J. Hodgkin, A.E. Salcini, M. Innocenti, P. Bazzicalupo and S. Arbucci for helpful discussions. This work was supported by grants from the AIRC (Associazione Italiana per la Ricerca sul Cancro) to P.P.D.F. and G.S.; the Human Science Frontier Program to P.P.D.F., G.S. and M.F.C.; the European Community (VI Framework) to P.P.D.F., R.B. and G.S.; the Italian Ministry of Health to P.P.D.F. and G.S.; the Fondazione Monzino to P.P.D.F.; and the Deutsche Forschungsgemeinschaft, and the Fonds der Chemischen Industrie to R.B. G.C. was supported in part by an EMBO long-term fellowship.
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Croce, A., Cassata, G., Disanza, A. et al. A novel actin barbed-end-capping activity in EPS-8 regulates apical morphogenesis in intestinal cells of Caenorhabditis elegans. Nat Cell Biol 6, 1173–1179 (2004). https://doi.org/10.1038/ncb1198
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DOI: https://doi.org/10.1038/ncb1198
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