Actin-myosin network reorganization breaks symmetry at the cell rear to spontaneously initiate polarized cell motility.
We have analyzed the spontaneous symmetry breaking and initiation of actin-based motility in keratocytes (fish epithelial cells). In stationary keratocytes, the actin network flow was inwards and radially symmetric. Immediately before motility initiation, the actin network flow increased at the prospective cell rear and reoriented in the perinuclear region, aligning with the prospective axis of movement. Changes in actin network flow at the cell front were detectable only after cell polarization. Inhibition of myosin II or Rho kinase disrupted actin network organization and flow in the perinuclear region and decreased the motility initiation frequency, whereas increasing myosin II activity with calyculin A increased the motility initiation frequency. Local stimulation of myosin activity in stationary cells by the local application of calyculin A induced directed motility initiation away from the site of stimulation. Together, these results indicate that large-scale actin-myosin network reorganization and contractility at the cell rear initiate spontaneous symmetry breaking and polarized motility of keratocytes.
Yam
Patricia T
PT
Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA.
Wilson
Cyrus A
CA
Ji
Lin
L
Hebert
Benedict
B
Barnhart
Erin L
EL
Dye
Natalie A
NA
Wiseman
Paul W
PW
Danuser
Gaudenz
G
Theriot
Julie A
JA
D000199:Actins / Q000378:metabolism*; D000818:Animals; D002465:Cell Movement / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D016764:Cell Polarity / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D005399:Fishes; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008387:Marine Toxins; D008954:Models, Biological; D009218:Myosins / Q000378:metabolism*; D010080:Oxazoles / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D014981:Xenopus; D054460:rho-Associated Kinases
D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins; D008387:Marine Toxins; D010080:Oxazoles; C059041:calyculin A; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D009218:Myosins