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Lemma B, Mitchell NP, Subramanian R, Needleman DJ, Dogic Z. Active Microphase Separation in Mixtures of Microtubules and Tip-Accumulating Molecular Motors. PHYSICAL REVIEW. X 2022; 12:031006. [PMID: 36643940 PMCID: PMC9835929 DOI: 10.1103/physrevx.12.031006] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Mixtures of filaments and molecular motors form active materials with diverse dynamical behaviors that vary based on their constituents' molecular properties. To develop a multiscale of these materials, we map the nonequilibrium phase diagram of microtubules and tip-accumulating kinesin-4 molecular motors. We find that kinesin-4 can drive either global contractions or turbulentlike extensile dynamics, depending on the concentrations of both microtubules and a bundling agent. We also observe a range of spatially heterogeneous nonequilibrium phases, including finite-sized radial asters, 1D wormlike chains, extended 2D bilayers, and system-spanning 3D active foams. Finally, we describe intricate kinetic pathways that yield microphase separated structures and arise from the inherent frustration between the orientational order of filamentous microtubules and the positional order of tip-accumulating molecular motors. Our work reveals a range of novel active states. It also shows that the form of active stresses is not solely dictated by the properties of individual motors and filaments, but is also contingent on the constituent concentrations and spatial arrangement of motors on the filaments.
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Affiliation(s)
- Bezia Lemma
- Physics Department, Harvard University, Cambridge, Massachusetts 02138, USA
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
- Physics Department, University of California, Santa Barbara, California 93106, USA
| | - Noah P. Mitchell
- Physics Department, University of California, Santa Barbara, California 93106, USA
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA
| | - Radhika Subramanian
- Molecular Biology Department, Massachusetts General Hospital Boston, Massachusetts 02114, USA
- Genetics Department, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Daniel J. Needleman
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Molecular and Cellular Biology Department, Harvard University, Cambridge, Massachusetts 02138, USA
- Center for Computational Biology, Flatiron Institute, New York, New York 10010, USA
| | - Zvonimir Dogic
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
- Physics Department, University of California, Santa Barbara, California 93106, USA
- Biomolecular Science and Engineering Department, University of California, Santa Barbara, California 93106, USA
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2
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Ansari S, Yan W, Lamson A, Shelley MJ, Glaser MA, Betterton MD. Active condensation of filaments under spatial confinement. FRONTIERS IN PHYSICS 2022; 10:897255. [PMID: 38116396 PMCID: PMC10730113 DOI: 10.3389/fphy.2022.897255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
Living systems exhibit self-organization, a phenomenon that enables organisms to perform functions essential for life. The interior of living cells is a crowded environment in which the self-assembly of cytoskeletal networks is spatially constrained by membranes and organelles. Cytoskeletal filaments undergo active condensation in the presence of crosslinking motor proteins. In past studies, confinement has been shown to alter the morphology of active condensates. Here, we perform simulations to explore systems of filaments and crosslinking motors in a variety of confining geometries. We simulate spatial confinement imposed by hard spherical, cylindrical, and planar boundaries. These systems exhibit non-equilibrium condensation behavior where crosslinking motors condense a fraction of the overall filament population, leading to coexistence of vapor and condensed states. We find that the confinement lengthscale modifies the dynamics and condensate morphology. With end-pausing crosslinking motors, filaments self-organize into half asters and fully-symmetric asters under spherical confinement, polarity-sorted bilayers and bottle-brush-like states under cylindrical confinement, and flattened asters under planar confinement. The number of crosslinking motors controls the size and shape of condensates, with flattened asters becoming hollow and ring-like for larger motor number. End pausing plays a key role affecting condensate morphology: systems with end-pausing motors evolve into aster-like condensates while those with non-end-pausing crosslinking motor proteins evolve into disordered clusters and polarity-sorted bundles.
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Affiliation(s)
- Saad Ansari
- Department of Physics, University of Colorado Boulder, Colorado, USA
| | - Wen Yan
- Center for Computational Biology, Flatiron Institute, New York, USA
| | - Adam Lamson
- Center for Computational Biology, Flatiron Institute, New York, USA
| | - Michael J. Shelley
- Center for Computational Biology, Flatiron Institute, New York, USA
- Courant Institute, New York University, New York, USA
| | - Matthew A. Glaser
- Department of Physics, University of Colorado Boulder, Colorado, USA
- Center for Computational Biology, Flatiron Institute, New York, USA
| | - Meredith D. Betterton
- Department of Physics, University of Colorado Boulder, Colorado, USA
- Center for Computational Biology, Flatiron Institute, New York, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Colorado, USA
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3
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Extensile to contractile transition in active microtubule-actin composites generates layered asters with programmable lifetimes. Proc Natl Acad Sci U S A 2022; 119:2115895119. [PMID: 35086931 PMCID: PMC8812548 DOI: 10.1073/pnas.2115895119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2021] [Indexed: 12/15/2022] Open
Abstract
We study a reconstituted composite system consisting of an active microtubule network interdigitated with a passive network of entangled F-actin filaments. Increasing the concentration of filamentous actin controls the emergent dynamics, inducing a transition from turbulent-like flows to bulk contractions. At intermediate concentrations, where the active stresses change their symmetry from anisotropic extensile to isotropic contracting, the composite separates into layered asters that coexist with the background turbulent fluid. Contracted onion-like asters have a radially extending microtubule-rich cortex that envelops alternating layers of microtubules and F-actin. These self-regulating structures undergo internal reorganization, which appears to minimize the surface area and maintain the ordered layering, even when undergoing aster merging events. Finally, the layered asters are metastable structures. Their lifetime, which ranges from minutes to hours, is encoded in the material properties of the composite. These results challenge the current models of active matter. They demonstrate self-organized dynamical states and patterns evocative of those observed in the cytoskeleton do not require precise biochemical regulation, but can arise from purely mechanical interactions of actively driven filamentous materials.
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4
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Cheng X, Ferrell JE. Spontaneous emergence of cell-like organization in Xenopus egg extracts. Science 2020; 366:631-637. [PMID: 31672897 DOI: 10.1126/science.aav7793] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 09/17/2019] [Indexed: 12/27/2022]
Abstract
Every daughter cell inherits two things from its mother: genetic information and a spatially organized complement of macromolecular complexes and organelles. The extent to which de novo self-organization, as opposed to inheritance of an already organized state, can suffice to yield functional cells is uncertain. We used Xenopus laevis egg extracts to show that homogenized interphase egg cytoplasm self-organizes over the course of ~30 minutes into compartments 300 to 400 micrometers in length that resemble cells. Formation of these cell-like compartments required adenosine triphosphate and microtubule polymerization but did not require added demembranated sperm nuclei with their accompanying centrosomes or actin polymerization. In cycling extracts with added sperm, the compartments underwent multiple cycles of division and reorganization, with mother compartments giving rise to two daughters at the end of each mitotic cycle. These results indicate that the cytoplasm can generate much of the spatial organization and cell cycle function of the early embryo.
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Affiliation(s)
- Xianrui Cheng
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174, USA.
| | - James E Ferrell
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174, USA. .,Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305-5307, USA
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5
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Torisawa T, Kimura A. The Generation of Dynein Networks by Multi-Layered Regulation and Their Implication in Cell Division. Front Cell Dev Biol 2020; 8:22. [PMID: 32083077 PMCID: PMC7004958 DOI: 10.3389/fcell.2020.00022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 01/13/2020] [Indexed: 12/13/2022] Open
Abstract
Cytoplasmic dynein-1 (hereafter referred to as dynein) is a major microtubule-based motor critical for cell division. Dynein is essential for the formation and positioning of the mitotic spindle as well as the transport of various cargos in the cell. A striking feature of dynein is that, despite having a wide variety of functions, the catalytic subunit is coded in a single gene. To perform various cellular activities, there seem to be different types of dynein that share a common catalytic subunit. In this review, we will refer to the different kinds of dynein as “dyneins.” This review attempts to classify the mechanisms underlying the emergence of multiple dyneins into four layers. Inside a cell, multiple dyneins generated through the multi-layered regulations interact with each other to form a network of dyneins. These dynein networks may be responsible for the accurate regulation of cellular activities, including cell division. How these networks function inside a cell, with a focus on the early embryogenesis of Caenorhabditis elegans embryos, is discussed, as well as future directions for the integration of our understanding of molecular layering to understand the totality of dynein’s function in living cells.
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Affiliation(s)
- Takayuki Torisawa
- Cell Architecture Laboratory, National Institute of Genetics, Mishima, Japan.,Department of Genetics, The Graduate University for Advanced Studies, SOKENDAI, Mishima, Japan
| | - Akatsuki Kimura
- Cell Architecture Laboratory, National Institute of Genetics, Mishima, Japan.,Department of Genetics, The Graduate University for Advanced Studies, SOKENDAI, Mishima, Japan
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6
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The multiple functions of kinesin-4 family motor protein KIF4 and its clinical potential. Gene 2018; 678:90-99. [DOI: 10.1016/j.gene.2018.08.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 08/01/2018] [Accepted: 08/02/2018] [Indexed: 02/07/2023]
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7
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Emergent mechanics of actomyosin drive punctuated contractions and shape network morphology in the cell cortex. PLoS Comput Biol 2018; 14:e1006344. [PMID: 30222728 PMCID: PMC6171965 DOI: 10.1371/journal.pcbi.1006344] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 10/04/2018] [Accepted: 07/05/2018] [Indexed: 11/24/2022] Open
Abstract
Filamentous actin (F-actin) and non-muscle myosin II motors drive cell motility and cell shape changes that guide large scale tissue movements during embryonic morphogenesis. To gain a better understanding of the role of actomyosin in vivo, we have developed a two-dimensional (2D) computational model to study emergent phenomena of dynamic unbranched actomyosin arrays in the cell cortex. These phenomena include actomyosin punctuated contractions, or "actin asters" that form within quiescent F-actin networks. Punctuated contractions involve both formation of high intensity aster-like structures and disassembly of those same structures. Our 2D model allows us to explore the kinematics of filament polarity sorting, segregation of motors, and morphology of F-actin arrays that emerge as the model structure and biophysical properties are varied. Our model demonstrates the complex, emergent feedback between filament reorganization and motor transport that generate as well as disassemble actin asters. Since intracellular actomyosin dynamics are thought to be controlled by localization of scaffold proteins that bind F-actin or their myosin motors we also apply our 2D model to recapitulate in vitro studies that have revealed complex patterns of actomyosin that assemble from patterning filaments and motor complexes with microcontact printing. Although we use a minimal representation of filament, motor, and cross-linker biophysics, our model establishes a framework for investigating the role of other actin binding proteins, how they might alter actomyosin dynamics, and makes predictions that can be tested experimentally within live cells as well as within in vitro models. Recent genetic and mechanical studies of embryonic development reveal a critical role for intracellular scaffolds in generating the shape of the embryo and constructing internal organs. In this paper we developed computer simulations of these scaffolds, composed of filamentous actin (F-actin), a rod-like protein polymer, and mini-thick filaments, composed of non-muscle myosin II, forming a two headed spring-like complex of motor proteins that can walk on, and remodel F-actin networks. Using simulations of these dynamic interactions, we can carry out virtual experiments where we change the physics and chemistry of F-actin polymers, their associated myosin motors, and cross-linkers and observe the changes in scaffolds that emerge. For example, by modulating the motor stiffness of the myosin motors in our model we can observe the formation or loss of large aster-like structures. Such fine-grained control over the physical properties of motors or filaments within simulations are not currently possible with biological experiments, even where mutant proteins or small molecule inhibitors can be targeted to specific sites on filaments or motors. Our approach reflects a growing adoption of simulation methods to investigate microscopic features that shape actomyosin arrays and the mesoscale effects of molecular scale processes. We expect predictions from these models will drive more refined experimental approaches to expose the many roles of actomyosin in development.
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8
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Rosas-Salvans M, Cavazza T, Espadas G, Sabido E, Vernos I. Proteomic Profiling of Microtubule Self-organization in M-phase. Mol Cell Proteomics 2018; 17:1991-2004. [PMID: 29970457 DOI: 10.1074/mcp.ra118.000745] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 06/11/2018] [Indexed: 01/08/2023] Open
Abstract
Microtubules (MTs) and associated proteins can self-organize into complex structures such as the bipolar spindle, a process in which RanGTP plays a major role. Addition of RanGTP to M-phase Xenopus egg extracts promotes the nucleation and self-organization of MTs into asters and bipolar-like structures in the absence of centrosomes or chromosomes. We show here that the complex proteome of these RanGTP-induced MT assemblies is similar to that of mitotic spindles. Using proteomic profiling we show that MT self-organization in the M-phase cytoplasm involves the non-linear and non-stoichiometric recruitment of proteins from specific functional groups. Our study provides for the first time a temporal understanding of the protein dynamics driving MT self-organization in M-phase.
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Affiliation(s)
- Miquel Rosas-Salvans
- From the ‡Cell and Developmental Biology Programme, Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Tommaso Cavazza
- From the ‡Cell and Developmental Biology Programme, Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Guadalupe Espadas
- **Proteomics Unit, Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain.,§Universitat Pompeu Fabra, Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Eduard Sabido
- **Proteomics Unit, Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain.,§Universitat Pompeu Fabra, Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Isabelle Vernos
- From the ‡Cell and Developmental Biology Programme, Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain; .,§Universitat Pompeu Fabra, Dr. Aiguader 88, 08003 Barcelona, Spain.,‡‡Institució Catalana de Recerca I Estudis Avançats (ICREA), Passeig de Lluis Companys 23, 08010 Barcelona, Spain
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9
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Nguyen PA, Field CM, Mitchison TJ. Prc1E and Kif4A control microtubule organization within and between large Xenopus egg asters. Mol Biol Cell 2017; 29:304-316. [PMID: 29187577 PMCID: PMC5996955 DOI: 10.1091/mbc.e17-09-0540] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 11/13/2017] [Accepted: 11/22/2017] [Indexed: 11/11/2022] Open
Abstract
The cleavage furrow in Xenopus zygotes is positioned by two large microtubule asters that grow out from the poles of the first mitotic spindle. Where these asters meet at the midplane, they assemble a disk-shaped interaction zone consisting of anti-parallel microtubule bundles coated with chromosome passenger complex (CPC) and centralspindlin that instructs the cleavage furrow. Here we investigate the mechanism that keeps the two asters separate and forms a distinct boundary between them, focusing on the conserved cytokinesis midzone proteins Prc1 and Kif4A. Prc1E, the egg orthologue of Prc1, and Kif4A were recruited to anti-parallel bundles at interaction zones between asters in Xenopus egg extracts. Prc1E was required for Kif4A recruitment but not vice versa. Microtubule plus-end growth slowed and terminated preferentially within interaction zones, resulting in a block to interpenetration that depended on both Prc1E and Kif4A. Unexpectedly, Prc1E and Kif4A were also required for radial order of large asters growing in isolation, apparently to compensate for the direction-randomizing influence of nucleation away from centrosomes. We propose that Prc1E and Kif4, together with catastrophe factors, promote "anti-parallel pruning" that enforces radial organization within asters and generates boundaries to microtubule growth between asters.
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Affiliation(s)
- P A Nguyen
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115.,Marine Biological Laboratory, Woods Hole, MA 02543
| | - C M Field
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115.,Marine Biological Laboratory, Woods Hole, MA 02543
| | - T J Mitchison
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115 .,Marine Biological Laboratory, Woods Hole, MA 02543
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10
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Hanley ML, Yoo TY, Sonnett M, Needleman DJ, Mitchison TJ. Chromosomal passenger complex hydrodynamics suggests chaperoning of the inactive state by nucleoplasmin/nucleophosmin. Mol Biol Cell 2017; 28:1444-1456. [PMID: 28404751 PMCID: PMC5449145 DOI: 10.1091/mbc.e16-12-0860] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/27/2017] [Accepted: 04/04/2017] [Indexed: 01/30/2023] Open
Abstract
The chromosomal passenger complex (CPC) is a conserved, essential regulator of cell division. As such, significant anti-cancer drug development efforts have been focused on targeting it, most notably by inhibiting its AURKB kinase subunit. The CPC is activated by AURKB-catalyzed autophosphorylation on multiple subunits, but how this regulates CPC interactions with other mitotic proteins remains unclear. We investigated the hydrodynamic behavior of the CPC in Xenopus laevis egg cytosol using sucrose gradient sedimentation and in HeLa cells using fluorescence correlation spectroscopy. We found that autophosphorylation of the CPC decreases its sedimentation coefficient in egg cytosol and increases its diffusion coefficient in live cells, indicating a decrease in mass. Using immunoprecipitation coupled with mass spectrometry and immunoblots, we discovered that inactive, unphosphorylated CPC interacts with nucleophosmin/nucleoplasmin proteins, which are known to oligomerize into pentamers and decamers. Autophosphorylation of the CPC causes it to dissociate from nucleophosmin/nucleoplasmin. We propose that nucleophosmin/nucleoplasmin complexes serve as chaperones that negatively regulate the CPC and/or stabilize its inactive form, preventing CPC autophosphorylation and recruitment to chromatin and microtubules in mitosis.
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Affiliation(s)
- Mariah L Hanley
- Department of Systems Biology, Harvard Medical School, Boston, MA 02114-5701.,Department of Chemistry, Harvard University, Cambridge, MA 02138-2902
| | - Tae Yeon Yoo
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138-2902
| | - Matthew Sonnett
- Department of Systems Biology, Harvard Medical School, Boston, MA 02114-5701
| | - Daniel J Needleman
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138-2902.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138-2902
| | - Timothy J Mitchison
- Department of Systems Biology, Harvard Medical School, Boston, MA 02114-5701
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11
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Spatial confinement of active microtubule networks induces large-scale rotational cytoplasmic flow. Proc Natl Acad Sci U S A 2017; 114:2922-2927. [PMID: 28265076 DOI: 10.1073/pnas.1616001114] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Collective behaviors of motile units through hydrodynamic interactions induce directed fluid flow on a larger length scale than individual units. In cells, active cytoskeletal systems composed of polar filaments and molecular motors drive fluid flow, a process known as cytoplasmic streaming. The motor-driven elongation of microtubule bundles generates turbulent-like flow in purified systems; however, it remains unclear whether and how microtubule bundles induce large-scale directed flow like the cytoplasmic streaming observed in cells. Here, we adopted Xenopus egg extracts as a model system of the cytoplasm and found that microtubule bundle elongation induces directed flow for which the length scale and timescale depend on the existence of geometrical constraints. At the lower activity of dynein, kinesins bundle and slide microtubules, organizing extensile microtubule bundles. In bulk extracts, the extensile bundles connected with each other and formed a random network, and vortex flows with a length scale comparable to the bundle length continually emerged and persisted for 1 min at multiple places. When the extracts were encapsulated in droplets, the extensile bundles pushed the droplet boundary. This pushing force initiated symmetry breaking of the randomly oriented bundle network, leading to bundles aligning into a rotating vortex structure. This vortex induced rotational cytoplasmic flows on the length scale and timescale that were 10- to 100-fold longer than the vortex flows emerging in bulk extracts. Our results suggest that microtubule systems use not only hydrodynamic interactions but also mechanical interactions to induce large-scale temporally stable cytoplasmic flow.
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12
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Gache V, Gomes ER, Cadot B. Microtubule motors involved in nuclear movement during skeletal muscle differentiation. Mol Biol Cell 2017; 28:865-874. [PMID: 28179457 PMCID: PMC5385935 DOI: 10.1091/mbc.e16-06-0405] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 02/01/2017] [Accepted: 02/01/2017] [Indexed: 12/22/2022] Open
Abstract
Nuclear mispositioning in muscle is often associated with muscular diseases, but little is known about the mechanisms governing nuclear motion in these cells. A screen is presented for molecular motors involved in moving nuclei during myofiber differentiation. Nuclear positioning is a determining event in several cellular processes, such as fertilization, cell migration, and cell differentiation. The structure and function of muscle cells, which contain hundreds of nuclei, have been shown to rely in part on proper nuclear positioning. Remarkably, in the course of muscle differentiation, nuclear movements along the myotube axis might represent the event required for the even positioning of nuclei in the mature myofiber. Here we analyze nuclear behavior, time in motion, speed, and alignment during myotube differentiation and temporal interference of cytoskeletal microtubule-related motors. Using specific inhibitors, we find that nuclear movement and alignment are microtubule dependent, with 19 microtubule motor proteins implicated in at least one nuclear behavior. We further focus on Kif1c, Kif5b, kif9, kif21b, and Kif1a, which affect nuclear alignment. These results emphasize the different roles of molecular motors in particular mechanisms.
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Affiliation(s)
- V Gache
- Center of Research in Myology, INSERM UPMC UMR974, Centre National de la Recherche Scientifique, FRE3617, 75013 Paris, France
| | - E R Gomes
- Center of Research in Myology, INSERM UPMC UMR974, Centre National de la Recherche Scientifique, FRE3617, 75013 Paris, France .,Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, 1649-028 Lisbon, Portugal
| | - B Cadot
- Center of Research in Myology, INSERM UPMC UMR974, Centre National de la Recherche Scientifique, FRE3617, 75013 Paris, France
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13
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Abstract
Progression through the meiotic cell cycle must be strictly regulated in oocytes to generate viable embryos and offspring. During mitosis, the kinesin motor protein Kif4 is indispensable for chromosome condensation and separation, midzone formation and cytokinesis. Additionally, the bioactivity of Kif4 is dependent on phosphorylation via Aurora Kinase B and Cdk1, which regulate Kif4 function throughout mitosis. Here, we examine the role of Kif4 in mammalian oocyte meiosis. Kif4 localized in the cytoplasm throughout meiosis I and II, but was also observed to have a dynamic subcellular distribution, associating with both microtubules and kinetochores at different stages of development. Co-localization and proximity ligation assays revealed that the kinetochore proteins, CENP-C and Ndc80, are potential Kif4 interacting proteins. Functional analysis of Kif4 in oocytes via antisense knock-down demonstrated that this protein was not essential for meiosis I completion. However, Kif4 depleted oocytes displayed enlarged polar bodies and abnormal metaphase II spindles, indicating an essential role for this protein for correct asymmetric cell division in meiosis I. Further investigation of the phosphoregulation of meiotic Kif4 revealed that Aurora Kinase and Cdk activity is critical for Kif4 kinetochore localization and interaction with Ndc80 and CENP-C. Finally, Kif4 protein but not gene expression was found to be upregulated with age, suggesting a role for this protein in the decline of oocyte quality with age.
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14
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Hasley A, Chavez S, Danilchik M, Wühr M, Pelegri F. Vertebrate Embryonic Cleavage Pattern Determination. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 953:117-171. [PMID: 27975272 PMCID: PMC6500441 DOI: 10.1007/978-3-319-46095-6_4] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The pattern of the earliest cell divisions in a vertebrate embryo lays the groundwork for later developmental events such as gastrulation, organogenesis, and overall body plan establishment. Understanding these early cleavage patterns and the mechanisms that create them is thus crucial for the study of vertebrate development. This chapter describes the early cleavage stages for species representing ray-finned fish, amphibians, birds, reptiles, mammals, and proto-vertebrate ascidians and summarizes current understanding of the mechanisms that govern these patterns. The nearly universal influence of cell shape on orientation and positioning of spindles and cleavage furrows and the mechanisms that mediate this influence are discussed. We discuss in particular models of aster and spindle centering and orientation in large embryonic blastomeres that rely on asymmetric internal pulling forces generated by the cleavage furrow for the previous cell cycle. Also explored are mechanisms that integrate cell division given the limited supply of cellular building blocks in the egg and several-fold changes of cell size during early development, as well as cytoskeletal specializations specific to early blastomeres including processes leading to blastomere cohesion. Finally, we discuss evolutionary conclusions beginning to emerge from the contemporary analysis of the phylogenetic distributions of cleavage patterns. In sum, this chapter seeks to summarize our current understanding of vertebrate early embryonic cleavage patterns and their control and evolution.
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Affiliation(s)
- Andrew Hasley
- Laboratory of Genetics, University of Wisconsin-Madison, Genetics/Biotech Addition, Room 2424, 425-G Henry Mall, Madison, WI, 53706, USA
| | - Shawn Chavez
- Division of Reproductive & Developmental Sciences, Oregon National Primate Research Center, Department of Physiology & Pharmacology, Oregon Heath & Science University, 505 NW 185th Avenue, Beaverton, OR, 97006, USA
- Division of Reproductive & Developmental Sciences, Oregon National Primate Research Center, Department of Obstetrics & Gynecology, Oregon Heath & Science University, 505 NW 185th Avenue, Beaverton, OR, 97006, USA
| | - Michael Danilchik
- Department of Integrative Biosciences, L499, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA
| | - Martin Wühr
- Department of Molecular Biology & The Lewis-Sigler Institute for Integrative Genomics, Princeton University, Icahn Laboratory, Washington Road, Princeton, NJ, 08544, USA
| | - Francisco Pelegri
- Laboratory of Genetics, University of Wisconsin-Madison, Genetics/Biotech Addition, Room 2424, 425-G Henry Mall, Madison, WI, 53706, USA.
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15
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Mishima M. Centralspindlin in Rappaport’s cleavage signaling. Semin Cell Dev Biol 2016; 53:45-56. [DOI: 10.1016/j.semcdb.2016.03.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 03/02/2016] [Indexed: 02/07/2023]
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16
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Henson JH, Buckley MW, Yeterian M, Weeks RM, Simerly CR, Shuster CB. Central Spindle Self-Organization and Cytokinesis in Artificially Activated Sea Urchin Eggs. THE BIOLOGICAL BULLETIN 2016; 230:85-95. [PMID: 27132131 DOI: 10.1086/bblv230n2p85] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The ability of microtubules of the mitotic apparatus to control the positioning and initiation of the cleavage furrow during cytokinesis was first established from studies on early echinoderm embryos. However, the identity of the microtubule population that imparts cytokinetic signaling is unclear. The two main--and not necessarily mutually exclusive--candidates are the central spindle and the astral rays. In the present study, we examined cytokinesis in ammonia-activated sea urchin eggs, which lack paternally derived centrosomes and undergo mitosis mediated by unusual anastral, bipolar mini-spindles. Live cell imaging and immunolabeling for microtubules and the centralspindlin constituent and kinesin-related protein, MKLP1, demonstrated that furrowing in ammonia-activated eggs was associated with aligned arrays of centralspindlin-linked, opposed bundles of antiparallel microtubules. These autonomous, zipper-like arrays were not associated with a mitotic apparatus, but did possess characteristics similar to the central spindle region of control, fertilized embryos. Our results highlight the self-organizing nature of the central spindle region and its ability to induce cytokinesis-like furrowing, even in the absence of a complete mitotic apparatus.
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Affiliation(s)
- John H Henson
- Department of Biology, Dickinson College, Carlisle, Pennsylvania 17013; Marine Biological Laboratory, Woods Hole, Massachusetts 02543;
| | - Mary W Buckley
- Department of Biology, Dickinson College, Carlisle, Pennsylvania 17013
| | - Mesrob Yeterian
- Department of Biology, Dickinson College, Carlisle, Pennsylvania 17013
| | - Richard M Weeks
- Department of Biology, Dickinson College, Carlisle, Pennsylvania 17013
| | - Calvin R Simerly
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213; and
| | - Charles B Shuster
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543; Department of Biology, New Mexico State University, Las Cruces, New Mexico 88003
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Foster PJ, Fürthauer S, Shelley MJ, Needleman DJ. Active contraction of microtubule networks. eLife 2015; 4. [PMID: 26701905 PMCID: PMC4764591 DOI: 10.7554/elife.10837] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 12/20/2015] [Indexed: 01/08/2023] Open
Abstract
Many cellular processes are driven by cytoskeletal assemblies. It remains unclear how cytoskeletal filaments and motor proteins organize into cellular scale structures and how molecular properties of cytoskeletal components affect the large-scale behaviors of these systems. Here, we investigate the self-organization of stabilized microtubules in Xenopus oocyte extracts and find that they can form macroscopic networks that spontaneously contract. We propose that these contractions are driven by the clustering of microtubule minus ends by dynein. Based on this idea, we construct an active fluid theory of network contractions, which predicts a dependence of the timescale of contraction on initial network geometry, a development of density inhomogeneities during contraction, a constant final network density, and a strong influence of dynein inhibition on the rate of contraction, all in quantitative agreement with experiments. These results demonstrate that the motor-driven clustering of filament ends is a generic mechanism leading to contraction.
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Affiliation(s)
- Peter J Foster
- John A. Paulson School of Engineering and Applied Sciences, FAS Center for Systems Biology, Harvard University, Cambridge, United States
| | - Sebastian Fürthauer
- Courant Institute of Mathematical Science, New York University, New York, United States.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Michael J Shelley
- Courant Institute of Mathematical Science, New York University, New York, United States
| | - Daniel J Needleman
- John A. Paulson School of Engineering and Applied Sciences, FAS Center for Systems Biology, Harvard University, Cambridge, United States.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
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18
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Reboutier D, Benaud C, Prigent C. Aurora A's Functions During Mitotic Exit: The Guess Who Game. Front Oncol 2015; 5:290. [PMID: 26734572 PMCID: PMC4685928 DOI: 10.3389/fonc.2015.00290] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 12/07/2015] [Indexed: 11/24/2022] Open
Abstract
Until recently, the knowledge of Aurora A kinase functions during mitosis was limited to pre-metaphase events, particularly centrosome maturation, G2/M transition, and mitotic spindle assembly. However, an involvement of Aurora A in post-metaphase events was also suspected, but not clearly demonstrated due to the technical difficulty to perform the appropriate experiments. Recent developments of both an analog-specific version of Aurora A and small molecule inhibitors have led to the first demonstration that Aurora A is required for the early steps of cytokinesis. As in pre-metaphase, Aurora A plays diverse functions during anaphase, essentially participating in astral microtubules dynamics and central spindle assembly and functioning. The present review describes the experimental systems used to decipher new functions of Aurora A during late mitosis and situate these functions into the context of cytokinesis mechanisms.
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Affiliation(s)
- David Reboutier
- Unité Mixte de Recherche 6290, Équipe labellisée Ligue, Centre National de la Recherche Scientifique, Rennes, France; Institut de Génétique et Développement de Rennes, Université Rennes 1, Rennes, France
| | - Christelle Benaud
- Unité Mixte de Recherche 6290, Équipe labellisée Ligue, Centre National de la Recherche Scientifique, Rennes, France; Institut de Génétique et Développement de Rennes, Université Rennes 1, Rennes, France
| | - Claude Prigent
- Unité Mixte de Recherche 6290, Équipe labellisée Ligue, Centre National de la Recherche Scientifique, Rennes, France; Institut de Génétique et Développement de Rennes, Université Rennes 1, Rennes, France
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19
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White D, Vries G, Martin J, Dawes A. Microtubule patterning in the presence of moving motor proteins. J Theor Biol 2015; 382:81-90. [DOI: 10.1016/j.jtbi.2015.06.040] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 10/31/2014] [Accepted: 06/24/2015] [Indexed: 10/23/2022]
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20
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Field CM, Groen AC, Nguyen PA, Mitchison TJ. Spindle-to-cortex communication in cleaving, polyspermic Xenopus eggs. Mol Biol Cell 2015; 26:3628-40. [PMID: 26310438 PMCID: PMC4603933 DOI: 10.1091/mbc.e15-04-0233] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 08/18/2015] [Indexed: 12/01/2022] Open
Abstract
Polyspermic Xenopus eggs and a cytokinesis extract system were used to investigate spindle-to-cortex communication, which positions cleavage furrows. Chromosome passenger complex recruitment to microtubule bundles between asters plays a key role and is positively influenced by microtubule stabilization and proximity to chromatin. Mitotic spindles specify cleavage planes in early embryos by communicating their position and orientation to the cell cortex using microtubule asters that grow out from the spindle poles during anaphase. Chromatin also plays a poorly understood role. Polyspermic fertilization provides a natural experiment in which aster pairs from the same spindle (sister asters) have chromatin between them, whereas asters pairs from different spindles (nonsisters) do not. In frogs, only sister aster pairs induce furrows. We found that only sister asters recruited two conserved furrow-inducing signaling complexes, chromosome passenger complex (CPC) and Centralspindlin, to a plane between them. This explains why only sister pairs induce furrows. We then investigated factors that influenced CPC recruitment to microtubule bundles in intact eggs and a cytokinesis extract system. We found that microtubule stabilization, optimal starting distance between asters, and proximity to chromatin all favored CPC recruitment. We propose a model in which proximity to chromatin biases initial CPC recruitment to microtubule bundles between asters from the same spindle. Next a positive feedback between CPC recruitment and microtubule stabilization promotes lateral growth of a plane of CPC-positive microtubule bundles out to the cortex to position the furrow.
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Affiliation(s)
- Christine M Field
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115; Marine Biological Laboratory, Woods Hole, MA 02143
| | - Aaron C Groen
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115; Marine Biological Laboratory, Woods Hole, MA 02143
| | - Phuong A Nguyen
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115; Marine Biological Laboratory, Woods Hole, MA 02143
| | - Timothy J Mitchison
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115; Marine Biological Laboratory, Woods Hole, MA 02143
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21
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Wang H, Brust-Mascher I, Scholey JM. The microtubule cross-linker Feo controls the midzone stability, motor composition, and elongation of the anaphase B spindle in Drosophila embryos. Mol Biol Cell 2015; 26:1452-62. [PMID: 25694445 PMCID: PMC4395126 DOI: 10.1091/mbc.e14-12-1631] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/13/2015] [Indexed: 01/19/2023] Open
Abstract
The antiparallel MT-MT cross-linking nonmotor MAP, Feo, controls the organization, stability, and motor composition of the Drosophila embryo anaphase B spindle midzone, thereby facilitating the kinesin-5-driven sliding filament mechanism underlying proper anaphase B spindle elongation and chromosome segregation. Chromosome segregation during anaphase depends on chromosome-to-pole motility and pole-to-pole separation. We propose that in Drosophila embryos, the latter process (anaphase B) depends on a persistent kinesin-5–generated interpolar (ip) microtubule (MT) sliding filament mechanism that “engages” to push apart the spindle poles when poleward flux is turned off. Here we investigated the contribution of the midzonal, antiparallel MT-cross-linking nonmotor MAP, Feo, to this “slide-and-flux-or-elongate” mechanism. Whereas Feo homologues in other systems enhance the midzone localization of the MT-MT cross-linking motors kinesin-4, -5 and -6, the midzone localization of these motors is respectively enhanced, reduced, and unaffected by Feo. Strikingly, kinesin-5 localizes all along ipMTs of the anaphase B spindle in the presence of Feo, including at the midzone, but the antibody-induced dissociation of Feo increases kinesin-5 association with the midzone, which becomes abnormally narrow, leading to impaired anaphase B and incomplete chromosome segregation. Thus, although Feo and kinesin-5 both preferentially cross-link MTs into antiparallel polarity patterns, kinesin-5 cannot substitute for loss of Feo function. We propose that Feo controls the organization, stability, and motor composition of antiparallel ipMTs at the midzone, thereby facilitating the kinesin-5–driven sliding filament mechanism underlying proper anaphase B spindle elongation and chromosome segregation.
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Affiliation(s)
- Haifeng Wang
- Department of Molecular and Cell Biology, University of California at Davis, Davis, CA 95616
| | - Ingrid Brust-Mascher
- Department of Molecular and Cell Biology, University of California at Davis, Davis, CA 95616
| | - Jonathan M Scholey
- Department of Molecular and Cell Biology, University of California at Davis, Davis, CA 95616
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22
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Nguyen PA, Groen AC, Loose M, Ishihara K, Wühr M, Field CM, Mitchison TJ. Spatial organization of cytokinesis signaling reconstituted in a cell-free system. Science 2014; 346:244-7. [PMID: 25301629 DOI: 10.1126/science.1256773] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
During animal cell division, the cleavage furrow is positioned by microtubules that signal to the actin cortex at the cell midplane. We developed a cell-free system to recapitulate cytokinesis signaling using cytoplasmic extract from Xenopus eggs. Microtubules grew out as asters from artificial centrosomes and met to organize antiparallel overlap zones. These zones blocked the interpenetration of neighboring asters and recruited cytokinesis midzone proteins, including the chromosomal passenger complex (CPC) and centralspindlin. The CPC was transported to overlap zones, which required two motor proteins, Kif4A and a Kif20A paralog. Using supported lipid bilayers to mimic the plasma membrane, we observed the recruitment of cleavage furrow markers, including an active RhoA reporter, at microtubule overlaps. This system opens further approaches to understanding the biophysics of cytokinesis signaling.
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Affiliation(s)
- Phuong A Nguyen
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA. Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Aaron C Groen
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA. Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Martin Loose
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Keisuke Ishihara
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA. Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Martin Wühr
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Christine M Field
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA. Marine Biological Laboratory, Woods Hole, MA 02543, USA.
| | - Timothy J Mitchison
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA. Marine Biological Laboratory, Woods Hole, MA 02543, USA
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23
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Forth S, Hsia KC, Shimamoto Y, Kapoor TM. Asymmetric friction of nonmotor MAPs can lead to their directional motion in active microtubule networks. Cell 2014; 157:420-432. [PMID: 24725408 DOI: 10.1016/j.cell.2014.02.018] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 11/25/2013] [Accepted: 02/03/2014] [Indexed: 01/13/2023]
Abstract
Diverse cellular processes require microtubules to be organized into distinct structures, such as asters or bundles. Within these dynamic motifs, microtubule-associated proteins (MAPs) are frequently under load, but how force modulates these proteins' function is poorly understood. Here, we combine optical trapping with TIRF-based microscopy to measure the force dependence of microtubule interaction for three nonmotor MAPs (NuMA, PRC1, and EB1) required for cell division. We find that frictional forces increase nonlinearly with MAP velocity across microtubules and depend on filament polarity, with NuMA's friction being lower when moving toward minus ends, EB1's lower toward plus ends, and PRC1's exhibiting no directional preference. Mathematical models predict, and experiments confirm, that MAPs with asymmetric friction can move directionally within actively moving microtubule pairs they crosslink. Our findings reveal how nonmotor MAPs can generate frictional resistance in dynamic cytoskeletal networks via micromechanical adaptations whose anisotropy may be optimized for MAP localization and function within cellular structures.
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Affiliation(s)
- Scott Forth
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Kuo-Chiang Hsia
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Yuta Shimamoto
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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24
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Head DA, Briels WJ, Gompper G. Nonequilibrium structure and dynamics in a microscopic model of thin-film active gels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:032705. [PMID: 24730872 DOI: 10.1103/physreve.89.032705] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Indexed: 06/03/2023]
Abstract
In the presence of adenosine triphosphate, molecular motors generate active force dipoles that drive suspensions of protein filaments far from thermodynamic equilibrium, leading to exotic dynamics and pattern formation. Microscopic modeling can help to quantify the relationship between individual motors plus filaments to organization and dynamics on molecular and supramolecular length scales. Here, we present results of extensive numerical simulations of active gels where the motors and filaments are confined between two infinite parallel plates. Thermal fluctuations and excluded-volume interactions between filaments are included. A systematic variation of rates for motor motion, attachment, and detachment, including a differential detachment rate from filament ends, reveals a range of nonequilibrium behavior. Strong motor binding produces structured filament aggregates that we refer to as asters, bundles, or layers, whose stability depends on motor speed and differential end detachment. The gross features of the dependence of the observed structures on the motor rate and the filament concentration can be captured by a simple one-filament model. Loosely bound aggregates exhibit superdiffusive mass transport, where filament translocation scales with lag time with nonunique exponents that depend on motor kinetics. An empirical data collapse of filament speed as a function of motor speed and end detachment is found, suggesting a dimensional reduction of the relevant parameter space. We conclude by discussing the perspectives of microscopic modeling in the field of active gels.
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Affiliation(s)
- D A Head
- School of Computing, Leeds University, Leeds LS2 9JT, United Kingdom
| | - W J Briels
- Computational Biophysics, University of Twente, 7500 AE Enschede, The Netherlands
| | - Gerhard Gompper
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany
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25
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Wang S, Romano FB, Field CM, Mitchison TJ, Rapoport TA. Multiple mechanisms determine ER network morphology during the cell cycle in Xenopus egg extracts. ACTA ACUST UNITED AC 2013; 203:801-14. [PMID: 24297752 PMCID: PMC3857478 DOI: 10.1083/jcb.201308001] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Fusion of ER membranes by atlastin and interaction of ER with growing microtubule ends and dynein cooperate to generate distinct ER morphologies during the cell cycle. In metazoans the endoplasmic reticulum (ER) changes during the cell cycle, with the nuclear envelope (NE) disassembling and reassembling during mitosis and the peripheral ER undergoing extensive remodeling. Here we address how ER morphology is generated during the cell cycle using crude and fractionated Xenopus laevis egg extracts. We show that in interphase the ER is concentrated at the microtubule (MT)-organizing center by dynein and is spread by outward extension of ER tubules through their association with plus ends of growing MTs. Fusion of membranes into an ER network is dependent on the guanosine triphosphatase atlastin (ATL). NE assembly requires fusion by both ATL and ER-soluble N-ethyl-maleimide–sensitive factor adaptor protein receptors. In mitotic extracts, the ER converts into a network of sheets connected by ER tubules and loses most of its interactions with MTs. Together, these results indicate that fusion of ER membranes by ATL and interaction of ER with growing MT ends and dynein cooperate to generate distinct ER morphologies during the cell cycle.
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Affiliation(s)
- Songyu Wang
- Department of Cell Biology and Howard Hughes Medical Institute and 2 Department of Systems Biology, Harvard Medical School, Boston, MA 02115
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26
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Meadows JC, Graumann K, Platani M, Schweizer N, Shimi T, Vagnarelli P, Gatlin JC. Meeting report: mitosis and nuclear structure. J Cell Sci 2013; 126:5087-90. [PMID: 24244037 DOI: 10.1242/jcs.142950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Company of Biologists Workshop entitled 'Mitosis and Nuclear Structure' was held at Wiston House, West Sussex in June 2013. It provided a unique and timely opportunity for leading experts from different fields to discuss not only their own work but also its broader context. Here we present the proceedings of this meeting and several major themes that emerged from the crosstalk between the two, as it turns out, not so disparate fields of mitosis and nuclear structure. Co-chaired by Katherine Wilson (Johns Hopkins School of Medicine, Baltimore, MD), Timothy Mitchison (Harvard University, Cambridge, MA) and Michael Rout (Rockefeller University, New York, NY), this workshop brought together a small group of scientists from a range of disciplines to discuss recent advances and connections between the areas of mitosis and nuclear structure research. Several early-career researchers (students, postdoctoral researchers, junior faculty) participated along with 20 senior scientists, including the venerable and affable Nobel Laureate Tim Hunt. Participants were encouraged to embrace unconventional thinking in the 'scientific sandbox' created by this unusual combination of researchers in the inspiring, isolated setting of the 16th-century Wiston House.
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Affiliation(s)
- John C Meadows
- Division of Biomedical Cell Biology, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
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