Symmetry breaking and polarization of the C. elegans zygote by the polarity protein PAR-2

Development. 2010 May;137(10):1669-77. doi: 10.1242/dev.045823. Epub 2010 Apr 14.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Amino Acid Sequence
  • Animals
  • Animals, Genetically Modified
  • Body Patterning / genetics*
  • Caenorhabditis elegans / embryology
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism
  • Caenorhabditis elegans Proteins / physiology*
  • Cell Polarity / genetics*
  • Embryo, Nonmammalian
  • Genes, Helminth / physiology
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Guanine Nucleotide Exchange Factors / genetics
  • Molecular Sequence Data
  • Sequence Homology, Amino Acid
  • Signal Transduction / genetics
  • Signal Transduction / physiology
  • Zygote / growth & development*
  • Zygote / metabolism
  • Zygote / physiology


  • Caenorhabditis elegans Proteins
  • Ect-2 protein, C elegans
  • Guanine Nucleotide Exchange Factors
  • par-2 protein, C elegans
  • Green Fluorescent Proteins