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Abstract
One of the major challenges of bottom-up synthetic biology is rebuilding a minimal cell division machinery. From a reconstitution perspective, the animal cell division apparatus is mechanically the simplest and therefore attractive to rebuild. An actin-based ring produces contractile force to constrict the membrane. By contrast, microbes and plant cells have a cell wall, so division requires concerted membrane constriction and cell wall synthesis. Furthermore, reconstitution of the actin division machinery helps in understanding the physical and molecular mechanisms of cytokinesis in animal cells and thus our own cells. In this review, we describe the state-of-the-art research on reconstitution of minimal actin-mediated cytokinetic machineries. Based on the conceptual requirements that we obtained from the physics of the shape changes involved in cell division, we propose two major routes for building a minimal actin apparatus capable of division. Importantly, we acknowledge both the passive and active roles that the confining lipid membrane can play in synthetic cytokinesis. We conclude this review by identifying the most pressing challenges for future reconstitution work, thereby laying out a roadmap for building a synthetic cell equipped with a minimal actin division machinery.
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2
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Atilgan E, Burgess D, Chang F. Localization of cytokinesis factors to the future cell division site by microtubule-dependent transport. Cytoskeleton (Hoboken) 2012; 69:973-82. [PMID: 23001894 DOI: 10.1002/cm.21068] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Revised: 08/22/2012] [Accepted: 08/23/2012] [Indexed: 02/01/2023]
Abstract
The mechanism by which spindle microtubules (MTs) determine the site of cell division in animal cells is still highly controversial. Putative cytokinesis "signals" have been proposed to be positioned by spindle MTs at equatorial cortical regions to increase cortical contractility and/or at polar regions to decrease contractility [Rappaport, 1986; von Dassow, 2009]. Given the relative paucity of MTs at the future division site, it has not been clear how MTs localize cytokinesis factors there. Here, we test cytokinesis models using computational and experimental approaches. We present a simple lattice-based model in which signal-kinesin complexes move by transient plus-end directed movements on MTs interspersed with occasions of uniform diffusion in the cytoplasm. In simulations, complexes distribute themselves initially at the spindle midzone and then move on astral MTs to accumulate with time at the equatorial cortex. Simulations accurately predict cleavage patterns of cells with different geometries and MT arrangements and elucidate several experimental observations that have defied easy explanation by previous models. We verify this model with experiments on indented sea urchin zygotes showing that cells often divide perpendicular to the spindle at sites distinct from the indentations. These studies support an equatorial stimulation model and provide a simple mechanism explaining how cytokinesis factors localize to the future division site.
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Affiliation(s)
- Erdinc Atilgan
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY 10032, USA
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3
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Argiros H, Henson L, Holguin C, Foe V, Shuster CB. Centralspindlin and chromosomal passenger complex behavior during normal and Rappaport furrow specification in echinoderm embryos. Cytoskeleton (Hoboken) 2012; 69:840-53. [PMID: 22887753 DOI: 10.1002/cm.21061] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2012] [Revised: 07/28/2012] [Accepted: 07/31/2012] [Indexed: 01/25/2023]
Abstract
The chromosomal passenger (CPC) and Centralspindlin complexes are essential for organizing the anaphase central spindle and providing cues that position the cytokinetic furrow between daughter nuclei. However, echinoderm zygotes are also capable of forming "Rappaport furrows" between asters positioned back-to-back without intervening chromosomes. To understand how these complexes contribute to normal and Rappaport furrow formation, we studied the localization patterns of Survivin and mitotic-kinesin-like-protein1 (MKLP1), members respectively of the CPC and the Centralspindlin complex, and the effect of CPC inhibition on cleavage in mono- and binucleate echinoderm zygotes. In zygotes, Survivin initially localized to metaphase chromosomes, upon anaphase onset relocalized to the central spindle and then, together with MKLP1 spread towards the equatorial cortex in an Aurora-dependent manner. Inhibition of Aurora kinase activity resulted in disruption of central spindle organization and furrow regression, although astral microtubule elongation and furrow initiation were normal. In binucleate cells containing two parallel spindles MKLP1 and Survivin localized to the plane of the former metaphase plate, but were not observed in the secondary cleavage plane formed between unrelated spindle poles, except when chromosomes were abnormally present there. However, the secondary furrow was sensitive to Aurora inhibition, indicating that Aurora kinase may still contribute to furrow ingression without chromosomes nearby. Our results provide insights that reconcile classic micromanipulation studies with current molecular understanding of furrow specification in animal cells.
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Affiliation(s)
- Haroula Argiros
- Department of Biology, New Mexico State University, Las Cruces, New Mexico, USA
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4
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Koyama H, Umeda T, Nakamura K, Higuchi T, Kimura A. A high-resolution shape fitting and simulation demonstrated equatorial cell surface softening during cytokinesis and its promotive role in cytokinesis. PLoS One 2012; 7:e31607. [PMID: 22359606 PMCID: PMC3281004 DOI: 10.1371/journal.pone.0031607] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Accepted: 01/10/2012] [Indexed: 11/17/2022] Open
Abstract
Different models for animal cell cytokinesis posit that the stiffness of the equatorial cortex is either increased or decreased relative to the stiffness of the polar cortex. A recent work has suggested that the critical cytokinesis signaling complex centralspindlin may reduce the stiffness of the equatorial cortex by inactivating the small GTPase Rac. To determine if such a reduction occurs and if it depends on centralspindlin, we devised a method to estimate cortical bending stiffness with high spatio-temporal resolution from in vivo cell shapes. Using the early Caenorhabditis elegans embryo as a model, we show that the stiffness of the equatorial cell surface is reduced during cytokinesis, whereas the stiffness of the polar cell surface remains stiff. The equatorial reduction of stiffness was compromised in cells with a mutation in the gene encoding the ZEN-4/kinesin-6 subunit of centralspindlin. Theoretical modeling showed that the absence of the equatorial reduction of stiffness could explain the arrest of furrow ingression in the mutant. By contrast, the equatorial reduction of stiffness was sufficient to generate a cleavage furrow even without the constriction force of the contractile ring. In this regime, the contractile ring had a supportive contribution to furrow ingression. We conclude that stiffness is reduced around the equator in a centralspindlin-dependent manner. In addition, computational modeling suggests that proper regulation of stiffness could be sufficient for cleavage furrow ingression.
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Affiliation(s)
- Hiroshi Koyama
- Cell Architecture Laboratory, Center for Frontier Research, National Institute of Genetics, Mishima, Japan
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5
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Yu JH, Crevenna AH, Bettenbühl M, Freisinger T, Wedlich-Söldner R. Cortical actin dynamics driven by formins and myosin V. J Cell Sci 2011; 124:1533-41. [PMID: 21486946 DOI: 10.1242/jcs.079038] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cell morphogenesis requires complex and rapid reorganization of the actin cytoskeleton. The budding yeast Saccharomyces cerevisiae is an invaluable model system for studying molecular mechanisms driving actin dynamics. Actin cables in yeast are formin-generated linear actin arrays that serve as tracks for directed intracellular transport by type V myosins. Cables are constantly reorganized throughout the cell cycle but the molecular basis for such dynamics remains poorly understood. By combining total internal reflection microscopy, quantitative image analyses and genetic manipulations we identify kinetically distinct subpopulations of cables that are differentially driven by formins and myosin. Bni1 drives elongation of randomly oriented actin cables in unpolarized cells, whereas both formins Bnr1 and Bni1 mediate slower polymerization of cables in polarized cells. Type V myosin Myo2 surprisingly acts as a motor for translational cable motility along the cell cortex. During polarization, cells change from fast to slow cable dynamics through spatio-temporal regulation of Bni1, Bnr1 and Myo2. In summary, we identify molecular mechanisms for the regulation of cable dynamics and suggest that fast actin reorganization is necessary for fidelity of cell polarization.
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Affiliation(s)
- Jerry H Yu
- AG Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Martinsried, Germany
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6
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Clark AG, Paluch E. Mechanics and regulation of cell shape during the cell cycle. Results Probl Cell Differ 2011; 53:31-73. [PMID: 21630140 DOI: 10.1007/978-3-642-19065-0_3] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Many cell types undergo dramatic changes in shape throughout the cell cycle. For individual cells, a tight control of cell shape is crucial during cell division, but also in interphase, for example during cell migration. Moreover, cell cycle-related cell shape changes have been shown to be important for tissue morphogenesis in a number of developmental contexts. Cell shape is the physical result of cellular mechanical properties and of the forces exerted on the cell. An understanding of the causes and repercussions of cell shape changes thus requires knowledge of both the molecular regulation of cellular mechanics and how specific changes in cell mechanics in turn effect global shape changes. In this chapter, we provide an overview of the current knowledge on the control of cell morphology, both in terms of general cell mechanics and specifically during the cell cycle.
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Affiliation(s)
- Andrew G Clark
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
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7
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von Dassow G. Concurrent cues for cytokinetic furrow induction in animal cells. Trends Cell Biol 2009; 19:165-73. [PMID: 19285868 DOI: 10.1016/j.tcb.2009.01.008] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Revised: 01/19/2009] [Accepted: 01/27/2009] [Indexed: 01/23/2023]
Abstract
Animal cells are deformable, yet live together bound into tissues. Consequently, physical perturbations imposed by neighbors threaten to disrupt the spatial coordination of cell cleavage with chromosome segregation during mitosis. Emerging evidence demonstrates that animal cells integrate multiple positional cues during cleavage-furrow induction, perhaps to facilitate error correction. Classical work indicated that the asters provide the stimulus for furrow induction, but recent results implicate the central spindle at least as much. Similarly, although classical work concluded that the stimulus occurs at the cell equator, new evidence shows that asters modulate cortical contractility outside the equator as well. Meanwhile, a newly revealed distinction between stable and dynamic astral microtubules suggests that these subsets might have complementary effects on furrow induction.
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Affiliation(s)
- George von Dassow
- Oregon Institute of Marine Biology, University of Oregon, Charleston, 97420, USA.
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8
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Yavisheva TM, Shcherbakov SD, Golubeva IS, Sharafutdinov GZ. Interaction of cambial dermal cells (fibroblasts) and epidermis in morphofunctional area of mouse skin. Bull Exp Biol Med 2008; 144:748-53. [PMID: 18683514 DOI: 10.1007/s10517-007-0423-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Epidermis and dermis form an integral morphofunctional area, where cambial cells proliferate and their first-division daughter cells differentiate. An important feature of this area is different rates of the development of daughter cells (fibroblasts) in the dermis and epidermis, which is greater in the epidermis. This asymmetry results in the prevalence of first epidermal daughter cells and, hence, their effect on cambial cells, and then of stromal daughter cells and their effects on cambial cells. The regulator factors of epidermal daughter cells promote unblocking of the major polarity axis of cambial (mother) cell, while stromal cells (fibroblasts) induce their polarization along the major axis and the onset of mitosis. In the dermis and epidermis, division of cambial cells is asymmetric; a prominent role in the formation of mother and daughter cells is given to the basal membrane as an elastic support. Mother and daughter cells form ring-like structures generating electric field that can promote differentiation of the daughter cells.
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Affiliation(s)
- T M Yavisheva
- N. N. Blokhin Cancer Research Center, Russian Academy of Medical Sciences, Moscow
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9
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Webb SE, Li WM, Miller AL. Calcium signalling during the cleavage period of zebrafish development. Philos Trans R Soc Lond B Biol Sci 2008; 363:1363-9. [PMID: 18198156 PMCID: PMC2610124 DOI: 10.1098/rstb.2007.2253] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Imaging studies, using both luminescent and fluorescent Ca(2+)-sensitive reporters, have revealed that during the first few meroblastic cleavages of the large embryos of teleosts, localized elevations of intracellular Ca(2+) accompany positioning, propagation, deepening and apposition of the cleavage furrows. Here, we will review the Ca(2+) transients reported during the cleavage period in these embryos, with reference mainly to that of the zebrafish (Danio rerio). We will also present the latest findings that support the proposal that Ca(2+) transients are an essential feature of embryonic cytokinesis. In addition, the potential upstream triggers and downstream targets of the different cytokinetic Ca(2+) transients will be discussed. Finally, we will present a hypothetical model that summarizes what has been suggested to be the various roles of Ca(2+) signalling during cytokinesis in teleost embryos.
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Affiliation(s)
| | | | - Andrew L Miller
- Department of Biology, The Hong Kong University of Science and TechnologyClear Water Bay, Kowloon, Hong Kong SAR, People's Republic of China
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10
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Abstract
We present a physical mechanism to describe initiation of the contractile ring during cell division. The model couples the membrane curvature with the contractile forces produced by protein clusters attached to the membrane. These protein clusters are mobile on the membrane and possess either an isotropic or an anisotropic spontaneous curvature. Our results show that under these conditions the contraction force gives rise to an instability that corresponds in a closed cellular system to the initiation of the contractile ring. We find a quantization of this process at distinct length-scales, which we compare to available data for different types of eukaryote cells.
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11
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Ca2+ signaling during embryonic cytokinesis in animal systems. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s0167-7306(06)41017-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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12
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Bringmann H, Cowan CR, Kong J, Hyman AA. LET-99, GOA-1/GPA-16, and GPR-1/2 are required for aster-positioned cytokinesis. Curr Biol 2006; 17:185-91. [PMID: 17189697 DOI: 10.1016/j.cub.2006.11.070] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2006] [Revised: 11/08/2006] [Accepted: 11/16/2006] [Indexed: 11/25/2022]
Abstract
At anaphase, the mitotic spindle positions the cytokinesis furrow [1]. Two populations of spindle microtubules are implicated in cytokinesis: radial microtubule arrays called asters and bundled nonkinetochore microtubules called the spindle midzone [2-4]. In C. elegans embryos, these two populations of microtubules provide two consecutive signals that position the cytokinesis furrow: The first signal is positioned midway between the microtubule asters; the second signal is positioned over the spindle midzone [5]. Evidence for two cytokinesis signals came from the identification of molecules that block midzone-positioned cytokinesis [5-7]. However, no molecules that are only required for, and thus define, the molecular pathway of aster-positioned cytokinesis have been identified. With RNAi screening, we identify LET-99 and the heterotrimeric G proteins GOA-1/GPA-16 and their regulator GPR-1/2 [10-12] in aster-positioned cytokinesis. By using mechanical spindle displacement, we show that the anaphase spindle positions cortical LET-99, at the site of the presumptive cytokinesis furrow. LET-99 enrichment at the furrow depends on the G proteins. GPR-1 is locally reduced at the site of cytokinesis-furrow formation by LET-99, which prevents accumulation of GPR-1 at this site. We conclude that LET-99 and the G proteins define a molecular pathway required for aster-positioned cytokinesis.
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Affiliation(s)
- Henrik Bringmann
- Max Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
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13
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Abstract
The mechanism underlying cytokinesis, the final step in cell division, remains one of the major unsolved questions in basic cell biology. Thanks to advances in functional genomics and proteomics, we are now able to assemble a "parts list" of proteins involved in cytokinesis. In this review, we discuss how to relate this parts list to biological mechanism. For easier analysis, we split cytokinesis into discrete steps: cleavage plane specification, rearrangement of microtubule structures, contractile ring assembly, ring ingression, and completion. We report on the advances that have been made to understand these steps and how they can be integrated into a global understanding of cytokinesis. We also discuss the extent to which classic questions have been answered and identify major outstanding questions.
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Affiliation(s)
- Ulrike S Eggert
- Dana-Farber Cancer Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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14
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Darenfed H, Mandato CA. Wound-induced contractile ring: a model for cytokinesis. Biochem Cell Biol 2006; 83:711-20. [PMID: 16333322 DOI: 10.1139/o05-164] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The actomyosin-based contractile ring is required for several biological processes, such as wound healing and cytokinesis of animal cells. Despite progress in defining the roles of this structure in both wound closure and cell division, we still do not fully understand how an actomyosin ring is spatially and temporally assembled, nor do we understand the molecular mechanism of its contraction. Recent results have demonstrated that microtubule-dependent local assembly of F-actin and myosin-II is present in wound closure and is similar to that in cytokinesis in animal cells. Furthermore, signalling factors such as small Rho GTPases have been shown to be involved in the regulation of actin dynamics during both processes. In this review we address recent findings in an attempt to better understand the dynamics of actomyosin contractile rings during wound healing as compared with the final step of animal cell division.
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Affiliation(s)
- Hassina Darenfed
- Department of Anatomy and Cell Biology, Mc Gill University, Montreal, QC, Canada
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15
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Dawes-Hoang RE, Parmar KM, Christiansen AE, Phelps CB, Brand AH, Wieschaus EF. folded gastrulation, cell shape change and the control of myosin localization. Development 2006; 132:4165-78. [PMID: 16123312 DOI: 10.1242/dev.01938] [Citation(s) in RCA: 307] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The global cell movements that shape an embryo are driven by intricate changes to the cytoarchitecture of individual cells. In a developing embryo, these changes are controlled by patterning genes that confer cell identity. However, little is known about how patterning genes influence cytoarchitecture to drive changes in cell shape. In this paper, we analyze the function of the folded gastrulation gene (fog), a known target of the patterning gene twist. Our analysis of fog function therefore illuminates a molecular pathway spanning all the way from patterning gene to physical change in cell shape. We show that secretion of Fog protein is apically polarized, making this the earliest polarized component of a pathway that ultimately drives myosin to the apical side of the cell. We demonstrate that fog is both necessary and sufficient to drive apical myosin localization through a mechanism involving activation of myosin contractility with actin. We determine that this contractility driven form of localization involves RhoGEF2 and the downstream effector Rho kinase. This distinguishes apical myosin localization from basal myosin localization, which we find not to require actinomyosin contractility or FOG/RhoGEF2/Rho-kinase signaling. Furthermore, we demonstrate that once localized apically, myosin continues to contract. The force generated by continued myosin contraction is translated into a flattening and constriction of the cell surface through a tethering of the actinomyosin cytoskeleton to the apical adherens junctions. Our analysis of fog function therefore provides a direct link from patterning to cell shape change.
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Affiliation(s)
- Rachel E Dawes-Hoang
- Department of Molecular Biology, Howard Hughes Medical Institute, Princeton University, NJ 08544, USA.
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16
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Abstract
Remodeling of cell membranes takes place during motile processes such as cell migration and cell division. Defects of proteins involved in membrane dynamics, including clathrin and dynamin, disrupt cytokinesis. To understand the function of clathrin-containing structures (CCS) in cytokinesis, we have expressed a green fluorescent protein (GFP) fusion protein of clathrin light chain a (GFP-clathrin) in NRK epithelial cells and recorded images of dividing cells near the ventral surface with a spinning disk confocal microscope. Punctate GFP-CCS underwent dynamic appearance and disappearance throughout the ventral surface. Following anaphase onset, GFP-CCS between separated chromosomes migrated toward the equator and subsequently disappeared in the equatorial region. Movements outside separating chromosomes were mostly random, similar to what was observed in interphase cells. Directional movements toward the furrow were dependent on both actin filaments and microtubules, while the appearance/disappearance of CCS was dependent on actin filaments but not on microtubules. These results suggest that CCS are involved in remodeling the plasma membrane along the equator during cytokinesis. Clathrin-containing structures may also play a role in transporting signaling or structural components into the cleavage furrow.
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Affiliation(s)
- Anne K Warner
- Department of Physiology, University of Massachusetts Medical School, 377 Plantation Street, Worcester, MA 01605, USA
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17
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Paluch E, Sykes C, Prost J, Bornens M. Dynamic modes of the cortical actomyosin gel during cell locomotion and division. Trends Cell Biol 2005; 16:5-10. [PMID: 16325405 DOI: 10.1016/j.tcb.2005.11.003] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2005] [Revised: 09/08/2005] [Accepted: 11/15/2005] [Indexed: 12/27/2022]
Abstract
Tight regulation of the contractility of the actomyosin cortex is essential for proper cell locomotion and division. Enhanced contractility leads, for example, to aberrations in the positioning of the mitotic spindle or to anomalous migration modes that allow tumor cells to escape anti-dissemination treatments. Spherical membrane protrusions called blebs occasionally appear during cell migration, cell division or apoptosis. We have shown that the cortex ruptures at sites where actomyosin cortical contractility is increased, leading to the formation of blebs. Here, we propose that bleb formation, which releases cortical tension, can be used as a reporter of cortical contractility. We go on to analyze the implications of spontaneous cortical contractile behaviors on cell locomotion and division and we particularly emphasize that variations in actomyosin contractility can account for a variety of migration modes.
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Affiliation(s)
- Ewa Paluch
- Laboratoire Physicochimie Curie, UMR168 Institut Curie/CNRS, 11 rue Pierre et Marie Curie, 75231 Paris cedex 05, France.
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18
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Yavisheva TM, Shcherbakov SD, Dubinkin IV. Peculiarities of proliferation of epidermal cambial cells in mouse skin. Bull Exp Biol Med 2005; 140:118-21. [PMID: 16254636 DOI: 10.1007/s10517-005-0426-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The long axis of epidermal cambial cells determining the direction of their division is determined before the beginning of division and is oriented perpendicularly, but not parallel, to the basal membrane, as in other basal cells. As a result, only one of the two newly formed cells adheres to the basal membrane and at the expense of traction forces detaching one cell from the other and elastic force of the basal membrane is formed as a maternal cell and stays in the focus of multiplication. The other cell, turning around under the effect of traction forces perpendicularly to the maternal cell, cardinally changes the direction of its long axis and is polarized parallel to the basal membrane like other cells. This cell becomes the daughter cell, its shape with the "head" and "tail" allows its rapid migration into other rosettes for differentiation.
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Affiliation(s)
- T M Yavisheva
- N. N. Blokhin National Center for Cancer Research, Russian Academy of Medical Sciences, Moscow
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19
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Cervantes MD, Xi X, Vermaak D, Yao MC, Malik HS. The CNA1 histone of the ciliate Tetrahymena thermophila is essential for chromosome segregation in the germline micronucleus. Mol Biol Cell 2005; 17:485-97. [PMID: 16251352 PMCID: PMC1345684 DOI: 10.1091/mbc.e05-07-0698] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Ciliated protozoans present several features of chromosome segregation that are unique among eukaryotes, including their maintenance of two nuclei: a germline micronucleus, which undergoes conventional mitosis and meiosis, and a somatic macronucleus that divides by an amitotic process. To study ciliate chromosome segregation, we have identified the centromeric histone gene in the Tetrahymena thermophila genome (CNA1). CNA1p specifically localizes to peripheral centromeres in the micronucleus but is absent in the macronucleus during vegetative growth. During meiotic prophase of the micronucleus, when chromosomes are stretched to twice the length of the cell, CNA1p is found localized in punctate spots throughout the length of the chromosomes. As conjugation proceeds, CNA1p appears initially diffuse, but quickly reverts to discrete dots in those nuclei destined to become micronuclei, whereas it remains diffuse and is gradually lost in developing macronuclei. In progeny of germline CNA1 knockouts, we see no defects in macronuclear division or viability of the progeny cells immediately following the knockout. However, within a few divisions, progeny show abnormal mitotic segregation of their micronucleus, with most cells eventually losing their micronucleus entirely. This study reveals a strong dependence of the germline micronucleus on centromeric histones for proper chromosome segregation.
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Affiliation(s)
- Marcella D Cervantes
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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20
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Wang YL. The mechanism of cortical ingression during early cytokinesis: thinking beyond the contractile ring hypothesis. Trends Cell Biol 2005; 15:581-8. [PMID: 16209923 DOI: 10.1016/j.tcb.2005.09.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2005] [Revised: 08/22/2005] [Accepted: 09/20/2005] [Indexed: 11/24/2022]
Abstract
Owing to the rapid advances in genomic, proteomic and imaging technologies, the field of cytokinesis has seen rapid advances during the past decade. However, the basic model for the early stage of ingression, known as the contractile ring hypothesis, remains largely unchanged. From recent observations, it is becoming clear that early cytokinesis of animal cells involves a more extensive set of events, both temporally and spatially, than what is encompassed by the original contractile ring hypothesis. Activities relevant to cytokinesis, such as cortical contraction, can initiate well before onset of anaphase. Furthermore, equatorial ingression can involve multiple events in different regions of the cortex, including the establishment of anterior-posterior polarity, the modulation of cortical deformability, the expansion and compression of the cell cortex, and forces directed towards the interior of the cell or away from the equator. In this article (which is part of the Cytokinesis series), I evaluate critically key observations on when, where and how early ingression of animal cells takes place.
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Affiliation(s)
- Yu-li Wang
- University of Massachusetts Medical School, 377 Plantation Street, Suite 327, Worcester, MA 01605, USA.
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21
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D'Avino PP, Savoian MS, Glover DM. Cleavage furrow formation and ingression during animal cytokinesis: a microtubule legacy. J Cell Sci 2005; 118:1549-58. [PMID: 15811947 DOI: 10.1242/jcs.02335] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Cytokinesis ensures the proper partitioning of the nuclear and cytoplasmic contents into independent daughter cells at the end of cell division. Although the metazoan mitotic spindle has been implicated in the placement and advancement of the cleavage furrow, the molecules responsible for these processes have remained elusive. Recent studies have provided insights into the role of different microtubule structures and associated proteins in cleavage furrow positioning and ingression together with the signalling events that regulate the dynamics of the equatorial cell cortex during cytokinesis. We try to unify these findings into a general model of cytokinesis in which both astral and central spindle microtubules have the ability to induce furrowing. We further propose that the evolutionarily conserved centralspindlin complex serves as a master controller of cell cleavage in Drosophila by promoting both furrow formation and ingression. The same mechanism might be conserved in other organisms.
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Affiliation(s)
- Pier Paolo D'Avino
- Cancer Research UK Cell Cycle Genetics Research Group, Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK.
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22
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Luke-Glaser S, Pintard L, Lu C, Mains PE, Peter M. The BTB Protein MEL-26 Promotes Cytokinesis in C. elegans by a CUL-3-Independent Mechanism. Curr Biol 2005; 15:1605-15. [PMID: 16169482 DOI: 10.1016/j.cub.2005.07.068] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2005] [Revised: 07/26/2005] [Accepted: 07/27/2005] [Indexed: 11/17/2022]
Abstract
BACKGROUND The initiation of a cleavage furrow is essential to separate cells during cytokinesis, but little is known about the mechanisms controlling this actin-driven process. Previous studies in C. elegans embryos revealed that inactivation of the CUL-3-based E3 ligase activator rfl-1 results in an aberrant microtubule network, ectopic furrowing during pronuclear migration, and defects during cytokinesis. RESULTS Here, we show that MEL-26, a substrate-specific adaptor of the CUL-3-based E3 ligase, is required for efficient cell separation and cleavage furrow ingression during the C. elegans early mitotic divisions. Loss of MEL-26 function leads to delayed onset and slow ingression of cytokinesis furrows that frequently regress. Conversely, increased levels of MEL-26 in cul-3(RNAi) and rfl-1 mutant embryos cause a hypercontractile cortex, with several simultaneously ingressing furrows during pronuclear migration. MEL-26 accumulates at cleavage furrows and binds the actin-interacting protein POD-1. Importantly, POD-1 is not a substrate of the MEL-26/CUL-3 ligase but is required to localize MEL-26 to the cortex. CONCLUSIONS Our results suggest that MEL-26 not only acts as a substrate-specific adaptor within the MEL-26/CUL-3 complex, but also promotes cytokinesis by a CUL-3- and microtubule-independent mechanism.
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Affiliation(s)
- Sarah Luke-Glaser
- Institute of Biochemistry, HPM G 8.0, ETH Hönggerberg, 8093 Zürich, Switzerland
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23
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Biron D, Alvarez-Lacalle E, Tlusty T, Moses E. Molecular model of the contractile ring. PHYSICAL REVIEW LETTERS 2005; 95:098102. [PMID: 16197254 DOI: 10.1103/physrevlett.95.098102] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2004] [Indexed: 05/04/2023]
Abstract
We present a model for the actin contractile ring of adherent animal cells. The model suggests that the actin concentration within the ring and consequently the power that the ring exerts both increase during contraction. We demonstrate the crucial role of actin polymerization and depolymerization throughout cytokinesis, and the dominance of viscous dissipation in the dynamics. The physical origin of two phases in cytokinesis dynamics ("biphasic cytokinesis") follows from a limitation on the actin density. The model is consistent with a wide range of measurements of the midzone of dividing animal cells.
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Affiliation(s)
- D Biron
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel
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24
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Bringmann H, Hyman AA. A cytokinesis furrow is positioned by two consecutive signals. Nature 2005; 436:731-4. [PMID: 16079852 DOI: 10.1038/nature03823] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2005] [Accepted: 05/16/2005] [Indexed: 11/10/2022]
Abstract
The position of the cytokinesis furrow in a cell determines the relative sizes of its two daughter cells as well as the distribution of their contents. In animal cells, the position of the cytokinesis furrow is specified by the position of the mitotic spindle. The cytokinesis furrow bisects the spindle midway between the microtubule asters, at the site of the microtubule-based midzone, producing two daughter cells. Experiments in some cell types have suggested that the midzone positions the furrow, but experiments in other cells have suggested that the asters position the furrow. One possibility is that different organisms and cell types use different mechanisms to position the cytokinesis furrow. An alternative possibility is that both asters and the midzone contribute to furrow positioning. Recent work in C. elegans has suggested that centrosome separation and the midzone are implicated in cytokinesis. Here we examine the relative contributions of different parts of the mitotic spindle to positioning of the cytokinesis furrow in the C. elegans zygote. By spatially separating the spindle midzone from one of the asters using an ultraviolet laser, we show that the cytokinesis furrow is first positioned by a signal determined by microtubule asters, and then by a second signal that is derived from the spindle midzone. Thus, the position of the cytokinesis furrow is specified by two consecutive furrowing activities.
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Affiliation(s)
- Henrik Bringmann
- Max Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauer Strasse 108, 01307 Dresden, Germany.
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25
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Benesch S, Polo S, Lai FPL, Anderson KI, Stradal TEB, Wehland J, Rottner K. N-WASP deficiency impairs EGF internalization and actin assembly at clathrin-coated pits. J Cell Sci 2005; 118:3103-15. [PMID: 15985465 DOI: 10.1242/jcs.02444] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
WASP and WAVE family proteins promote actin polymerization by stimulating Arp2/3-complex-dependent filament nucleation. Unlike WAVE proteins, which are known to drive the formation of protrusions such as lamellipodia and membrane ruffles, vertebrate cell functions of WASP or N-WASP are less well established. Recent work demonstrated that clathrin-coated pit invagination can coincide with assembly of actin filaments and with accumulation of N-WASP and Arp2/3 complex, but the relevance of their recruitment has remained poorly defined. We employed two-colour total internal reflection microscopy to study the recruitment and dynamics of various components of the actin polymerization machinery and the epidermal growth factor receptor signalling machinery during clathrin-coated pit internalization in control cells and cells genetically deficient for functional N-WASP. We found that clathrin-coated pit endocytosis coincides with the recruitment of N-WASP, Arp2/3 complex and associated proteins, but not of WAVE family members. Actin accumulation at clathrin-coated pits requires the Arp2/3 complex, since Arp2/3 complex sequestration in the cytosol abolished any detectable actin assembly. The absence of N-WASP caused a significant reduction in the frequencies of actin and Arp2/3 complex accumulations at sites of clathrin-coated pit invagination and vesicle departure. Although N-WASP was not essential for Arp2/3-complex-mediated actin assembly at these sites or for EGF receptor-mediated endocytosis, N-WASP deficiency caused a marked reduction of EGF internalization. We conclude that the assembly of WASP subfamily proteins and associated factors at sites of clathrin-coated pit invagination amplifies actin accumulations at these sites promoting efficient internalization of ligands via clathrin-mediated endocytosis.
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Affiliation(s)
- Stefanie Benesch
- Cytoskeleton Dynamics Group, German Research Centre for Biotechnology (GBF), Mascheroder Weg 1, 38124 Braunschweig, Germany
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26
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Nagata Y, Jones MR, Nguyen HG, McCrann DJ, St Hilaire C, Schreiber BM, Hashimoto A, Inagaki M, Earnshaw WC, Todokoro K, Ravid K. Vascular smooth muscle cell polyploidization involves changes in chromosome passenger proteins and an endomitotic cell cycle. Exp Cell Res 2005; 305:277-91. [PMID: 15817153 DOI: 10.1016/j.yexcr.2004.12.028] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2004] [Revised: 12/18/2004] [Accepted: 12/20/2004] [Indexed: 02/06/2023]
Abstract
Vascular smooth muscle cell polyploidization occurs during normal development and is enhanced under physiologic stress, but the mechanism of this cell cycle has not been explored. We show via time-lapse video imaging and immunofluorescence analyses that primary vascular smooth muscle cells (VSMC) undergo an endomitotic-type cell cycle, including a normal progression through part of mitosis. Mononuclear polyploid cells are generated by defects in sister chromatid separation and/or segregation, and cellular binucleation occurs by reversal of cytokinesis. To obtain further leads to regulators involved, we examined the chromosomal passenger proteins, Aurora B, inner centromere protein and Survivin, and concluded that Aurora B and inner centromere protein are normally colocalized in centromeres, the midzone, and the midbody during mitosis. Survivin, however, is dim and diffused; it does not colocalize with either Aurora B or inner centromere protein in VSMC, which could account for defects in sister chromatid separation and/or segregation and reversal of cytokinesis. In accordance with the reported dependency of Aurora B activity on Survivin, the Aurora B substrate, vimentin, is not phosphorylated during cytokinesis. Finally, the data show that ectopically expressed Survivin inhibits polyploidization in vascular smooth muscle cells. Hence, aberrant chromosome passenger protein activity and endomitosis are associated with VSMC polyploidization.
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Affiliation(s)
- Yuka Nagata
- Recognition and Formation, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Japan
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27
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Murthy K, Wadsworth P. Myosin-II-Dependent Localization and Dynamics of F-Actin during Cytokinesis. Curr Biol 2005; 15:724-31. [PMID: 15854904 DOI: 10.1016/j.cub.2005.02.055] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Revised: 02/11/2005] [Accepted: 02/14/2005] [Indexed: 11/24/2022]
Abstract
BACKGROUND The assembly of an F-actin- and myosin-II-containing contractile ring (CR) is required for cytokinesis in eukaryotic cells. Interactions between myosin II and actin in the ring are believed to generate the force that constricts the cell into two daughters. The mechanism(s) that contribute to the spatially and temporally regulated assembly and disassembly of the CR at the cell equator are poorly understood. RESULTS We generated an LLCPK1 epithelial cell line that stably expresses GFP-actin. Live confocal imaging showed accumulation of GFP-actin in the equatorial cortex from late anaphase through cytokinesis. Fluorescence recovery after photobleaching (FRAP) experiments showed that actin in the CR is highly dynamic (t(1/2) = 26 s). In some cells, movement of GFP-actin toward the equatorial region was observed and contributed to FRAP. Blocking actin dynamic turnover with jasplakinolide demonstrates that dynamic actin is required for CR formation and cytokinesis. To test the role of myosin II in actin turnover and transport during CR formation, we inhibited myosin light-chain kinase with ML7 and myosin II ATPase activity with blebbistatin. Inhibition of myosin light-chain phosphorylation resulted in clearance of GFP-actin from the equatorial region, a reduction in myosin II in the furrow, and inhibition of cytokinesis. Treatment with blebbistatin did not block CR formation but reduced FRAP of GFP-actin and prevented completion of cytokinesis. CONCLUSIONS These results demonstrate that the majority of actin in the CR is highly dynamic and establish novel roles for myosin II in the retention and dynamic turnover of actin in the CR.
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Affiliation(s)
- Kausalya Murthy
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, 01003, USA
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28
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Bao J, Jana SS, Adelstein RS. Vertebrate nonmuscle myosin II isoforms rescue small interfering RNA-induced defects in COS-7 cell cytokinesis. J Biol Chem 2005; 280:19594-9. [PMID: 15774463 DOI: 10.1074/jbc.m501573200] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RNA interference (RNAi) treatment of monkey COS-7 cells, a cell line that lacks nonmuscle myosin heavy chain II-A (NMHC II-A) but contains NMHC II-B and II-C, was used to investigate the participation of NMHC isoforms in cytokinesis. We specifically suppressed the expression of NMHC II-B or II-C using 21 nucleotide small interfering RNA (siRNA) duplexes. Down-regulation of NMHC II-B protein expression to 10.2 +/- 0.7% inhibited COS-7 cell proliferation by 50% in the RNAi-treated cells compared with control cells. Moreover, whereas 8.7 +/- 1.0% of control cells were multinucleated, 62.4 +/- 8.8% of the NMHC II-B RNAi-treated cells were multinucleated 72 h after transfection. The RNAi-treated cells had increased surface areas and, unlike control cells, lacked actin stress fibers. Treatment of the COS-7 cells with NMHC II-C siRNA decreased NMHC II-C expression to 5.2 +/- 0.1% compared with the endogenous content of II-C; however, down-regulation of NMHC II-C did not cause increased multinucleation. Immunoblot analysis using a pan-myosin antibody showed that the content of NMHC II-C was less than one-twentieth the amount of NMHC II-B, thereby explaining the lack of response to II-C siRNA. Introducing green fluorescent protein (GFP)-tagged NMHC II isoforms into II-B siRNA-treated cells resulted in reduction of multinucleation from 62.4 +/- 8.8% to 17.8 +/- 2.2% using GFP-NMHC II-B, to 29.8 +/- 7.4% using GFP-NMHC II-A, and to 34.1 +/- 8.6% using NMHC II-C-GFP. These studies have shown that expression of endogenous NMHC II-C in COS-7 cells is insufficient for normal cytokinesis and that exogenous NMHC II-A and NMHC II-C can, at least partially, rescue the defect in cytokinesis due to the loss of NMHC II-B.
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Affiliation(s)
- Jianjun Bao
- Laboratory of Molecular Cardiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA
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29
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Oceguera-Yanez F, Kimura K, Yasuda S, Higashida C, Kitamura T, Hiraoka Y, Haraguchi T, Narumiya S. Ect2 and MgcRacGAP regulate the activation and function of Cdc42 in mitosis. ACTA ACUST UNITED AC 2005; 168:221-32. [PMID: 15642749 PMCID: PMC2171585 DOI: 10.1083/jcb.200408085] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although Rho regulates cytokinesis, little was known about the functions in mitosis of Cdc42 and Rac. We recently suggested that Cdc42 works in metaphase by regulating bi-orient attachment of spindle microtubules to kinetochores. We now confirm the role of Cdc42 by RNA interference and identify the mechanisms for activation and down-regulation of Cdc42. Using a pull-down assay, we found that the level of GTP-Cdc42 elevates in metaphase, whereas the level of GTP-Rac does not change significantly in mitosis. Overexpression of dominant-negative mutants of Ect2 and MgcRacGAP, a Rho GTPase guanine nucleotide exchange factor and GTPase activating protein, respectively, or depletion of Ect2 by RNA interference suppresses this change of GTP-Cdc42 in mitosis. Depletion of Ect2 also impairs microtubule attachment to kinetochores and causes prometaphase delay and abnormal chromosomal segregation, as does depletion of Cdc42 or expression of the Ect2 and MgcRacGAP mutants. These results suggest that Ect2 and MgcRacGAP regulate the activation and function of Cdc42 in mitosis.
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Affiliation(s)
- Fabian Oceguera-Yanez
- Department of Pharmacology, Kyoto University Faculty of Medicine, Kyoto 606-8501, Japan
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30
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Maiato H, Sampaio P, Sunkel CE. Microtubule-associated proteins and their essential roles during mitosis. ACTA ACUST UNITED AC 2005; 241:53-153. [PMID: 15548419 DOI: 10.1016/s0074-7696(04)41002-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Microtubules play essential roles during mitosis, including chromosome capture, congression, and segregation. In addition, microtubules are also required for successful cytokinesis. At the heart of these processes is the ability of microtubules to do work, a property that derives from their intrinsic dynamic behavior. However, if microtubule dynamics were not properly regulated, it is certain that microtubules alone could not accomplish any of these tasks. In vivo, the regulation of microtubule dynamics is the responsibility of microtubule-associated proteins. Among these, we can distinguish several classes according to their function: (1) promotion and stabilization of microtubule polymerization, (2) destabilization or severance of microtubules, (3) functioning as linkers between various structures, or (4) motility-related functions. Here we discuss how the various properties of microtubule-associated proteins can be used to assemble an efficient mitotic apparatus capable of ensuring the bona fide transmission of the genetic information in animal cells.
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Affiliation(s)
- Hélder Maiato
- Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal
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31
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Hinchcliffe EH. Using long-term time-lapse imaging of mammalian cell cycle progression for laboratory instruction and analysis. CELL BIOLOGY EDUCATION 2005; 4:284-90. [PMID: 16353401 PMCID: PMC1305890 DOI: 10.1187/cbe.05-02-0064] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Accepted: 06/14/2005] [Indexed: 11/20/2022]
Affiliation(s)
- Edward H Hinchcliffe
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
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32
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Sakaida T, Inomata S, Shinagawa A. Asters play only a dispensable role in the induction of the cleavage furrow in the blastomeres of early Xenopus embryos. Dev Growth Differ 2004; 46:371-81. [PMID: 15367205 DOI: 10.1111/j.1440-169x.2004.00754.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Kuroda et al. (2001) of our laboratory have previously revealed that exposure of early Xenopus embryos to 150 mm urethane results in complete suppression of formation of the asters and the cleavage furrow, as well as significant reduction of the size of the spindle in the blastomeres, allowing only 1 or 2 cycles of mitosis but not cytokinesis. In the course of closer examination of the effect of urethane on the cleavage of blastomeres of early Xenopus embryos, we unexpectedly discovered that exposure of early Xenopus embryos to 75 mm urethane did not prevent cell division at all, though asters were not detected in the blastomeres. Instead, they contained a spindle that appeared rather normal. They also formed the diastema, a thin yolk-free structure, which is considered to play an essential role in the induction of the cleavage furrow. Essentially the same results were obtained in the exposure of embryos to vinblastine, a well-known microtubule inhibitor: exposure of embryos to 20 micro g/mL vinblastine resulted in complete suppression of cleavage of the blastomeres, where formation of both the spindle and asters were perfectly suppressed. By contrast, exposure of embryos to 5 microg/mL vinblastine did not prevent cleavage in the blastomeres though asters were not detected, whereas the rather normal spindle was formed. Thus, there was a close correlation between the formation of the normal spindle, not asters, and that of the cell division furrow and the diastema in the blastomeres of early Xenopus embryos. We suggest that while the spindle plays an essential role, asters are likely to play only a dispensable role in the induction of the cleavage furrow in even very large cells like the blastomeres of early Xenopus embryos.
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Affiliation(s)
- Tomoyuki Sakaida
- Department of Biology, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-Machi, Yamagata 990-8560, Japan
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33
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Vasiliev JM, Omelchenko T, Gelfand IM, Feder HH, Bonder EM. Rho overexpression leads to mitosis-associated detachment of cells from epithelial sheets: a link to the mechanism of cancer dissemination. Proc Natl Acad Sci U S A 2004; 101:12526-30. [PMID: 15304643 PMCID: PMC515091 DOI: 10.1073/pnas.0404723101] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Dissemination of neoplastic cells from the primary tumor (invasion and metastasis) is a fundamentally dangerous step in multistage carcinogenesis. Recent evidence suggests that Rho GTPase-mediated signaling is linked to dissemination of cells from several different types of human tumors. The Rho family of proteins is typically associated with the regulation of cytoskeletal activity, including actin assembly, microtubule dynamics, and myosin II-dependent contractility of the actin-rich cortex. We examined the effect of overexpression of constitutively active RhoA on islands and monolayers of epithelial cells. Although newly plated cells initially formed small spread islands, there was also a significant population of cells that detached from the substrate, floated in the medium, and then could reattach to the substrate to form new colonies. Detachment of cells from transfected epithelial islands or monolayers occurred in correlation to the plane of cytokinesis after misorientation of the mitotic spindle axis. We suggest that these alterations result from Rho-induced increase of contractility of the cortex of dividing cells, which, during cytokinesis, produces a cell that has budded out of an existing layer of cells. Cell division-mediated detachment of cells from tissue structures may be an important mechanism of tumor dissemination and metastasis.
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Affiliation(s)
- J M Vasiliev
- Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia
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34
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Saul D, Fabian L, Forer A, Brill JA. Continuous phosphatidylinositol metabolism is required for cleavage of crane fly spermatocytes. J Cell Sci 2004; 117:3887-96. [PMID: 15265984 DOI: 10.1242/jcs.01236] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Successful cleavage of animal cells requires co-ordinated regulation of the actomyosin contractile ring and cleavage furrow ingression. Data from a variety of systems implicate phosphoinositol lipids and calcium release as potential regulators of this fundamental process. Here we examine the requirement for various steps of the phosphatidylinositol (PtdIns) cycle in dividing crane fly (Nephrotoma suturalis) spermatocytes. PtdIns cycle inhibitors were added to living cells after cleavage furrows formed and began to ingress. Inhibitors known to block PtdIns recycling (lithium), PtdIns phosphorylation (wortmannin, LY294002) or phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] hydrolysis [U73122 (U7)] all stopped or slowed furrowing. The effect of these drugs on cytokinesis was quite rapid (within 0-4 minutes), so continuous metabolism of PtdIns appears to be required for continued cleavage furrow ingression. U7 caused cleavage furrow regression concomitant with depletion of F-actin from the contractile ring, whereas the other inhibitors caused neither regression nor depletion of F-actin. That U7 depletes furrow-associated actin seems counterintuitive, as inhibition of phospholipase C would be expected to increase cellular levels of PtdIns(4,5)P2 and hence increase actin polymerization. Our confocal images suggest, however, that F-actin might accumulate at the poles of U7-treated cells, consistent with the idea that PtdIns(4,5)P2 hydrolysis may be required for actin filaments formed at the poles to participate in contractile ring assembly at the furrow.
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Affiliation(s)
- Daniel Saul
- Department of Biology, York University, 4700 Keele Street, Toronto, Ontario, M3J 1P3, Canada
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35
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Hunding A. Microtubule Dynamics may Embody a Stationary Bipolarity Forming Mechanism Related to the Prokaryotic Division Site Mechanism (Pole-to-Pole Oscillations). J Biol Phys 2004; 30:325-44. [PMID: 23345876 PMCID: PMC3456318 DOI: 10.1007/s10867-004-3387-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Cell division mechanisms in eukaryotes and prokaryotes have until recently been seen as being widely different. However, pole-to-pole oscillations of proteins like MinE in prokaryotes are now known to determine the division plane. These protein waves arise through spontaneous pattern forming reaction-diffusion mechanisms, based on cooperative binding of the proteins to a quasistationary matrix (like the cell membrane or DNA). Rather than waves, stationary bipolar pattern formation may arise as well. Some of the involved proteins have eukaryotic homologs (e.g. FtsZ and tubulin), pointing to a possible ancient shared mechanism. Tubulin polymerizes to microtubules in the spindle. Mitotic microtubules are in a highly dynamical state, frequently undergoing rapid shortening (catastrophe), and fragments formed from the microtubule ends are inferred to enhance the destabilization. Here, we show that cooperative binding of such fragments to microtubules may set up a similar pattern forming mechanism as seen in prokaryotes. The result is a spontaneously formed, well controllable, bipolar state of microtubule dynamics in the cell, which may contribute to defining the bipolar spindle.
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Affiliation(s)
- A. Hunding
- Chemistry Laboratory III, Department of Chemistry C116, H. C. Ørsted Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
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36
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37
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Takeda K, Kishi H, Ma X, Yu ZX, Adelstein RS. Ablation and mutation of nonmuscle myosin heavy chain II-B results in a defect in cardiac myocyte cytokinesis. Circ Res 2003; 93:330-7. [PMID: 12893741 DOI: 10.1161/01.res.0000089256.00309.cb] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We have identified a novel form of cardiac myocyte enlargement in nonmuscle myosin heavy chain II-B (NMHC II-B) ablated mice, based on a partial failure in cytokinesis. In contrast to most cells, cardiac myocytes lack NMHC II-A, and ablation of NMHC II-B results in a heart with 70% fewer myocytes at embryonic day 14.5 (E14.5) than control mice (B+/B- and B+/B+). In addition, B-/B- cardiac myocytes show a marked increase in binucleation at E12.5, reflecting the occurrence of karyokinesis in the absence of cytokinesis. An increase in binucleation and cell size is also found in hypomorphic, homozygous mice harboring a single amino acid mutation (R709C) in the gene encoding NMHC II-B. The nonmyocytes in B-/B- hearts and homozygous mutant hearts, all of which contain NMHC II-A, do not show either of these abnormalities. B-/B- cardiac myocytes at E14.5 show a decreased bromodeoxyuridine (BrdU) labeling index compared with controls, consistent with the decrease in myocyte proliferation. This decreased BrdU labeling is not seen in nonmyocyte cells in the heart. In addition to these changes, both B-/B- mice as well as homozygous mutated mice show an increase in cyclin D2 and D3 reflecting an abnormality in earlier steps in the cell cycle. Whereas cardiac myocytes completely ablated for NMHC II-B show enlargement and binucleation, mice expressing as little as 6% of the normal amount of wild-type NMHC II-B in the heart do not show these abnormalities.
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Affiliation(s)
- Kazuyo Takeda
- Laboratory of Molecular Cardiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Md 20892-1762, USA
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38
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Abstract
Recent studies have provided evidence that, during cytokinesis, activation of the Pbl-Rho1 pathway by a protein complex located at the spindle midzone, and inhibition of this pathway by two mitotic cyclins, may be major contributing factors controlling the place and timing of the cleavage furrow.
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Affiliation(s)
- Cayetano Gonzalez
- European Molecular Biology Laboratory, Cell Biology and Biophysics Programme, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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39
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Abstract
In creating the mitotic spindle and the contractile ring, natural selection has engineered fascinating precision machines whose movements depend upon forces generated by ensembles of cytoskeletal proteins. These machines segregate chromosomes and divide the cell with high fidelity. Current research on the mechanisms and regulation of spindle morphogenesis, chromosome motility and cytokinesis emphasizes how ensembles of dynamic cytoskeletal polymers and multiple motors cooperate to generate the forces that guide the cell through mitosis and cytokinesis.
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Affiliation(s)
- Jonathan M Scholey
- Laboratory of Cell and Computational Biology, Center for Genetics and Development, University of California, Davis, California 95616, USA.
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40
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Abstract
BACKGROUND Cytokinesis occurs just as chromosomes complete segregation and reform nuclei. It has been proposed that cyclin/Cdk kinase inhibits cytokinesis until exit from mitosis; however, the timer of cytokinesis has not been experimentally defined. Whereas expression of a stable version of Drosophila cyclin B blocks cytokinesis along with numerous events of mitotic exit, stable cyclin B3 allows cytokinesis even though it blocks late events of mitotic exit. We examined the interface between mitotic cyclin destruction and the timing of cytokinesis. RESULTS In embryonic mitosis 14, the cytokinesis furrow appeared 60 s after the metaphase/anaphase transition and closed 90 s later during telophase. In cyclin B or cyclin B3 mutant cells, the cytokinesis furrow appeared at an earlier stage of mitosis. Expression of stable cyclin B3 delayed and prolonged furrow invagination; nonetheless, cytokinesis completed during the extended mitosis. Reduced function of Pebble, a Rho GEF required for cytokinesis, also delayed and slowed furrow invagination, but incomplete furrows were aborted at the time of mitotic exit. In functional and genetic tests, cyclin B and cyclin B3 inhibited Pebble contributions to cytokinesis. CONCLUSIONS Temporal coordination of mitotic events involves inhibition of cytokinesis by cyclin B and cyclin B3 and punctual relief of the inhibition by destruction of these cyclins. Both cyclins inhibit Pebble-dependent activation of cytokinesis, whereas cyclin B can inhibit cytokinesis by additional modes. Stable cyclin B3 also blocks the later return to interphase that otherwise appears to impose a deadline for the completion of cytokinesis.
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Murata-Hori M, Wang YL. Both midzone and astral microtubules are involved in the delivery of cytokinesis signals: insights from the mobility of aurora B. J Cell Biol 2002; 159:45-53. [PMID: 12370248 PMCID: PMC2173485 DOI: 10.1083/jcb.200207014] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
To address the mechanism that coordinates cytokinesis with mitosis, we have studied the dynamics of aurora B, a chromosomal passenger protein involved in signaling cytokinesis. Photobleaching analyses indicated dynamic exchange of aurora B between a centromeric and a cytoplasmic pool before anaphase onset, and stable associations with microtubules after anaphase onset. Bleaching near centromeres upon anaphase onset affected the subsequent appearance of fluorescence along midzone microtubules, but not that near the lateral equatorial cortex, suggesting that there were centromeric-dependent and -independent pathways that transported aurora B to the equator. The former delivered centromeric aurora B along midzone microtubules, whereas the latter delivered cytoplasmic aurora B along astral microtubules. We suggest that cultured cells use midzone microtubules as the primary signaling pathway for cytokinesis, whereas embryos, with their stockpile of cytoplasmic proteins and large sizes, rely primarily on astral microtubules.
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Affiliation(s)
- Maki Murata-Hori
- University of Massachusetts Medical School, Worcester, MA 01605, USA
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