title: RhoA GTPase inhibition organizes contraction during epithelial morphogenesis.
abstract: During morphogenesis, contraction of the actomyosin cytoskeleton within individual cells drives cell shape changes that fold tissues. Coordination of cytoskeletal contractility is mediated by regulating RhoA GTPase activity. Guanine nucleotide exchange factors (GEFs) activate and GTPase-activating proteins (GAPs) inhibit RhoA activity. Most studies of tissue folding, including apical constriction, have focused on how RhoA is activated by GEFs to promote cell contractility, with little investigation as to how GAPs may be important. Here, we identify a critical role for a RhoA GAP, Cumberland GAP (C-GAP), which coordinates with a RhoA GEF, RhoGEF2, to organize spatiotemporal contractility during Drosophila melanogaster apical constriction. C-GAP spatially restricts RhoA pathway activity to a central position in the apical cortex. RhoGEF2 pulses precede myosin, and C-GAP is required for pulsation, suggesting that contractile pulses result from RhoA activity cycling. Finally, C-GAP expression level influences the transition from reversible to irreversible cell shape change, which defines the onset of tissue shape change. Our data demonstrate that RhoA activity cycling and modulating the ratio of RhoGEF2 to C-GAP are required for tissue folding.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142.
authors.forename: Frank M
authors.initials: FM
authors.lastname: Mason
authors.affiliation: Computational and Systems Biology, Massachusetts Institute of Technology, Cambridge, MA 02142.
authors.forename: Shicong
authors.initials: S
authors.lastname: Xie
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142.
authors.forename: Claudia G
authors.initials: CG
authors.lastname: Vasquez
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142.
authors.forename: Michael
authors.initials: M
authors.lastname: Tworoger
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142 acmartin@mit.edu.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Martin
mesh_terms: D000818:Animals; D016764:Cell Polarity; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000196:embryology* / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism; D009024:Morphogenesis; D009218:Myosins / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors / Q000378:metabolism; D015398:Signal Transduction; D054460:rho-Associated Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D020690:GTPase-Activating Proteins; D034741:RNA, Small Interfering; D064067:Rho Guanine Nucleotide Exchange Factors; C085379:rho GTPase-activating protein; D054460:rho-Associated Kinases; D009218:Myosins; D020742:rhoA GTP-Binding Protein