title: -Back-to-back mechanisms drive actomyosin ring closure during Drosophila embryo cleavage.
abstract: Contraction of actomyosin rings during cytokinesis is typically attributed to actin filaments sliding toward each other via Myosin-2 motor activity. However, rings constrict in some cells in the absence of Myosin-2 activity. Thus, ring closure uses Myosin-2-dependent and -independent mechanisms. But what the Myosin-2-independent mechanisms are, and to what extent they are sufficient to drive closure, remains unclear. During cleavage in Drosophila melanogaster embryos, actomyosin rings constrict in two sequential and mechanistically distinct phases. We show that these phases differ in constriction speed and are genetically and pharmacologically separable. Further, Myosin-2 activity is required for slow constriction in "phase 1" but is largely dispensable for fast constriction in "phase 2," and F-actin disassembly is only required for fast constriction in phase 2. Switching from phase 1 to phase 2 seemingly relies on the spatial organization of F-actin as controlled by Cofilin, Anillin, and Septin. Our work shows that fly embryos present a singular opportunity to compare separable ring constriction mechanisms, with varying Myosin-2 dependencies, in one cell type and in vivo.
authors: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030.
authors: Zenghui
authors: http://orcid.org/0000-0003-4184-7892
authors: Z
authors: Xue
authors: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030 sokac@bcm.edu.
authors: Anna Marie
authors: http://orcid.org/0000-0001-7803-3062
authors: AM
authors: Sokac
mesh_terms: D051339:Actin Depolymerizing Factors / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism*; D000818:Animals; D002970:Cleavage Stage, Ovum / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000196:embryology* / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D007700:Kinetics; D009218:Myosins / Q000378:metabolism
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D029721:Drosophila Proteins; D000205:Actomyosin; D009218:Myosins