title: Symmetry breaking and polarization of the C. elegans zygote by the polarity protein PAR-2.
abstract: Polarization of the C. elegans zygote is initiated by ECT-2-dependent cortical flows, which mobilize the anterior PAR proteins (PAR-3, PAR-6 and PKC-3) away from the future posterior end of the embryo marked by the sperm centrosome. Here, we demonstrate the existence of a second, parallel and redundant pathway that can polarize the zygote in the absence of ECT-2-dependent cortical flows. This second pathway depends on the polarity protein PAR-2. We show that PAR-2 localizes to the cortex nearest the sperm centrosome even in the absence of cortical flows. Once on the cortex, PAR-2 antagonizes PAR-3-dependent recruitment of myosin, creating myosin flows that transport the anterior PAR complex away from PAR-2 in a positive-feedback loop. We propose that polarity in the C. elegans zygote is initiated by redundant ECT-2- and PAR-2-dependent mechanisms that lower PAR-3 levels locally, triggering a positive-feedback loop that polarizes the entire cortex.
authors.affiliation: Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Center for Cell Dynamics, Johns Hopkins School of Medicine, PCTB 706, Baltimore, MD 21205, USA.
authors.forename: Seth
authors.initials: S
authors.lastname: Zonies
authors.forename: Fumio
authors.initials: F
authors.lastname: Motegi
authors.forename: Yingsong
authors.initials: Y
authors.lastname: Hao
authors.forename: Geraldine
authors.initials: G
authors.lastname: Seydoux
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics*; D017173:Caenorhabditis elegans / Q000196:embryology / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016764:Cell Polarity / Q000235:genetics*; D004625:Embryo, Nonmammalian; D017238:Genes, Helminth / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D015053:Zygote / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology
chemical_list: D029742:Caenorhabditis elegans Proteins; C507872:Ect-2 protein, C elegans; D020662:Guanine Nucleotide Exchange Factors; C087977:par-2 protein, C elegans; D049452:Green Fluorescent Proteins
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