title: Apical domain polarization localizes actin-myosin activity to drive ratchet-like apical constriction.
abstract: Apical constriction promotes epithelia folding, which changes tissue architecture. During Drosophila gastrulation, mesoderm cells exhibit repeated contractile pulses that are stabilized such that cells apically constrict like a ratchet. The transcription factor Twist is required to stabilize cell shape. However, it is unknown how Twist spatially coordinates downstream signals to prevent cell relaxation. We find that during constriction, Rho-associated kinase (Rok) is polarized to the middle of the apical domain (medioapical cortex), separate from adherens junctions. Rok recruits or stabilizes medioapical myosin II (Myo-II), which contracts dynamic medioapical actin cables. The formin Diaphanous mediates apical actin assembly to suppress medioapical E-cadherin localization and form stable connections between the medioapical contractile network and adherens junctions. Twist is not required for apical Rok recruitment, but instead polarizes Rok medioapically. Therefore, Twist establishes radial cell polarity of Rok/Myo-II and E-cadherin and promotes medioapical actin assembly in mesoderm cells to stabilize cell shape fluctuations.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA.
authors.forename: Frank M
authors.initials: FM
authors.lastname: Mason
authors.forename: Michael
authors.initials: M
authors.lastname: Tworoger
authors.forename: Adam C
authors.initials: AC
authors.lastname: Martin
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D016764:Cell Polarity / Q000502:physiology*; D048430:Cell Shape; D004330:Drosophila / Q000166:cytology* / Q000196:embryology*; D029721:Drosophila Proteins / Q000378:metabolism; D007294:Inositol / Q000031:analogs & derivatives / Q000378:metabolism; D007365:Intercellular Junctions; D009218:Myosins / Q000378:metabolism*; D015398:Signal Transduction; D051879:Twist-Related Protein 1 / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D000199:Actins; D029721:Drosophila Proteins; C497753:Twi protein, Drosophila; D051879:Twist-Related Protein 1; C002183:inosose; D007294:Inositol; D054460:rho-Associated Kinases; D009218:Myosins; C511153:Rho1 protein, Drosophila; D020741:rho GTP-Binding Proteins