title: Sequential functioning of the ECT-2 RhoGEF, RHO-1 and CDC-42 establishes cell polarity in Caenorhabditis elegans embryos.
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 polarity. 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) 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 proteins 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.
authors.affiliation: Laboratory for Developmental Genomics, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Motegi
authors.forename: Asako
authors.initials: A
authors.lastname: Sugimoto
mesh_terms: D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology*; D018385:Centrosome / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism / Q000502:physiology*; D021381:Protein Transport; D064067:Rho Guanine Nucleotide Exchange Factors; D008941:Spindle Apparatus / Q000502:physiology; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000378:metabolism / Q000502:physiology*
chemical_list: D029742:Caenorhabditis elegans Proteins; C507872:Ect-2 protein, C elegans; D020662:Guanine Nucleotide Exchange Factors; D064067:Rho Guanine Nucleotide Exchange Factors; D000205:Actomyosin; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins