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Sequential functioning of the ECT-2 RhoGEF, RHO-1 and CDC-42 establishes cell polarity in Caenorhabditis elegans embryos

Nature Cell Biology volume 8, pages 978–985 (2006)Cite this article

Abstract

During development, the establishment of cell polarity is important for cells to undergo asymmetric cell divisions that give rise to diverse cell types. In C. elegans embryos, cues from the centrosome trigger the cortical flow of an actomyosin network, leading to the formation of anterior–posterior polarity1. However, its precise mechanism is poorly understood. Here, we show that small GTPases have sequential and crucial functions in this process. ECT-2, a potential guanine nucleotide-exchange factor (GEF)2 for RHO-1, was uniformly distributed at the cortex before polarization, but was excluded from the posterior cortex by the polarity cue from the centrosomes. This local exclusion of ECT-2 led to an asymmetric RHO-1 distribution, which generated a cortical flow of the actomyosin that translocated PAR proteins3 and CDC-42 (Refs 4, 5) to the anterior cortex. Polarized CDC-42 was, in turn, involved in maintaining the established anterior-cortical domains. Our results suggest that a local change in the function of ECT-2 and RHO-1 links the centrosomal polarity cue with the polarization of the cell cortex.

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Figure 1: CDC-42, RHO-1 and ECT-2 are required for asymmetric spindle positioning in the one-cell embryo.
Figure 2: RHO-1 and CDC-42 have distinct roles in anterior–posterior polarization.
Figure 3: The centrosome mediates exclusion of cortical ECT-2.
Figure 4: Asymmetric distribution of cortical foci of RHO-1 and CDC-42.
Figure 5: A schematic representation of a model for the establishment of anterior–posterior polarity in the C. elegans one-cell embryo.

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Acknowledgements

We thank N.V. Velarde and F. Piano for kindly providing the strain expressing GFP–moe and for sharing information before publication; F. Matsuzaki for suggestions and thoughtful comments on the manuscript; and G. Seydoux, D. Kiehart, K. Kemphues, A. Audhya and Y. Kohara for their generous gifts of reagents. We also thank Y. Kodama for the initial characterization of the ect-2 gene and all members of our laboratories for helpful discussions. Some of the worm strains used in this study were provided by the Caenorhabditis Genetics Center, which is funded by the National Institutes of Health (NIH) National Center for Research Resources. This work was supported by a Grant-in-Aid for Scientific Research on Priority Areas 'Systems Genomics' (A.S.) and a Grant-in-Aid for Young Scientists B (F.M.) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. F.M. was supported by the Special Postdoctoral Researchers Program of RIKEN.

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  1. Laboratory for Developmental Genomics, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan

    Fumio Motegi & Asako Sugimoto

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  1. Fumio Motegi
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F.M. designed and performed the experiments. F.M. and A.S. performed the data analysis and wrote the paper. A.S. was responsible for project planning and guidance.

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Correspondence to Asako Sugimoto.

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Motegi, F., Sugimoto, A. Sequential functioning of the ECT-2 RhoGEF, RHO-1 and CDC-42 establishes cell polarity in Caenorhabditis elegans embryos. Nat Cell Biol 8, 978–985 (2006). https://doi.org/10.1038/ncb1459

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