Cortical flows powered by asymmetrical contraction transport PAR proteins to establish and maintain anterior-posterior polarity in the early C. elegans embryo.
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.
Munro
Edwin
E
Center for Cell Dynamics, Friday Harbor, WA 98250, USA. munroem@u.washington.edu
Nance
Jeremy
J
Priess
James R
JR
D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D017173:Caenorhabditis elegans / Q000196:embryology*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D008164:Luminescent Proteins / Q000378:metabolism; D008297:Male; D008954:Models, Biological; D018995:Myosin Heavy Chains / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism; D034622:RNA Interference; D013094:Spermatozoa / Q000378:metabolism; D013997:Time Factors
D000199:Actins; D029742:Caenorhabditis elegans Proteins; D008164:Luminescent Proteins; C480837:NMY-2 protein, C elegans; D011506:Proteins; C512642:par-6 protein, C elegans; D049452:Green Fluorescent Proteins; D000205:Actomyosin; C097238:PAR-3 protein, C elegans; D017346:Protein Serine-Threonine Kinases; C115015:PKC-3 protein; D011493:Protein Kinase C; D018995:Myosin Heavy Chains