Cortical flows powered by asymmetrical contraction transport PAR proteins to establish and maintain anterior-posterior polarity in the early C. elegans embryo

Dev Cell. 2004 Sep;7(3):413-24. doi: 10.1016/j.devcel.2004.08.001.


The C. elegans PAR proteins PAR-3, PAR-6, and PKC-3 are asymmetrically localized and have essential roles in cell polarity. We show that the one-cell C. elegans embryo contains a dynamic and contractile actomyosin network that appears to be destabilized near the point of sperm entry. This asymmetry initiates a flow of cortical nonmuscle myosin (NMY-2) and F-actin toward the opposite, future anterior, pole. PAR-3, PAR-6, and PKC-3, as well as non-PAR proteins that associate with the cytoskeleton, appear to be transported to the anterior by this cortical flow. In turn, PAR-3, PAR-6, and PKC-3 modulate cortical actomyosin dynamics and promote cortical flow. PAR-2, which localizes to the posterior cortex, inhibits NMY-2 from accumulating at the posterior cortex during flow, thus maintaining asymmetry by preventing inappropriate, posterior-directed flows. Similar actomyosin flows accompany the establishment of PAR asymmetries that form after the one-cell stage, suggesting that actomyosin-mediated cortical flows have a general role in PAR asymmetry.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / metabolism
  • Actomyosin / metabolism
  • Animals
  • Biological Transport
  • Caenorhabditis elegans / embryology*
  • Caenorhabditis elegans Proteins / metabolism
  • Embryo, Nonmammalian / physiology
  • Gene Expression Regulation, Developmental*
  • Green Fluorescent Proteins
  • Immunohistochemistry
  • Luminescent Proteins / metabolism
  • Male
  • Models, Biological
  • Myosin Heavy Chains / metabolism
  • Protein Kinase C / metabolism
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases
  • Proteins / metabolism
  • RNA Interference
  • Spermatozoa / metabolism
  • Time Factors


  • Actins
  • Caenorhabditis elegans Proteins
  • Luminescent Proteins
  • NMY-2 protein, C elegans
  • Proteins
  • par-6 protein, C elegans
  • Green Fluorescent Proteins
  • Actomyosin
  • PAR-3 protein, C elegans
  • Protein-Serine-Threonine Kinases
  • PKC-3 protein
  • Protein Kinase C
  • Myosin Heavy Chains