Myosin-IXA regulates collective epithelial cell migration by targeting RhoGAP activity to cell-cell junctions.
BACKGROUND
Epithelial tissues undergo extensive collective movements during morphogenesis, repair, and renewal. Collective epithelial cell migration requires the intercellular coordination of cell-cell adhesions and the establishment of anterior-posterior polarity, while maintaining apical-basal polarity, but how this is achieved at the molecular level is not well understood.


RESULTS
Using an RNA interference-based screen to identify Rho family GTPase regulators required for the collective migration of human bronchial epithelial cells, we identified myosin-IXA (gene name: Myo9a). Depletion of myosin-IXA, a RhoGAP and actin motor protein, in collectively migrating cells led to altered organization of the actin cytoskeleton and tension-dependent disruption of cell-cell adhesions, followed by an inability to form new adhesions resulting in cell scattering. Closer examination revealed that myosin-IXA is required during the formation of junction-associated actin bundles soon after cell-cell contact. Structure-function analysis of myosin-IXA revealed that the motor domain is necessary and sufficient for binding to actin filaments, whereas expression of the RhoGAP domain partially rescued the cell scattering phenotype induced by myosin-IXA depletion. Finally, a fluorescence resonance energy transfer biosensor revealed a significant increase in Rho activity at nascent cell-cell contacts in myosin-IXA depleted cells compared to controls.


CONCLUSIONS
We propose that myosin-IXA locally regulates Rho and the assembly of thin actin bundles associated with nascent cell-cell adhesions and that this is required to sustain the collective migration of epithelial cells.
Cell Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA. omelchet@mskcc.org
Tatiana
T
Omelchenko
Alan
A
Hall
D008841:Actin Cytoskeleton / Q000378:metabolism*; D022005:Adherens Junctions / Q000378:metabolism*; D002448:Cell Adhesion; D002454:Cell Differentiation; D002460:Cell Line; D002465:Cell Movement; D004847:Epithelial Cells / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D008858:Microscopy, Phase-Contrast; D009218:Myosins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism; D020743:rhoB GTP-Binding Protein / Q000378:metabolism
C120896:MYO9A protein, human; D034741:RNA, Small Interfering; C066737:RHOA protein, human; D009218:Myosins; D020764:cdc42 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein