1
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Roles for focal adhesion kinase (FAK) in blastomere abscission and vesicle trafficking during cleavage in the sea urchin embryo. Mech Dev 2013; 130:290-303. [PMID: 23313141 DOI: 10.1016/j.mod.2012.12.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 12/23/2012] [Accepted: 12/27/2012] [Indexed: 11/23/2022]
Abstract
Is focal adhesion kinase (FAK) needed for embryonic cleavage? We find that FAK is expressed during early cleavage divisions of sea urchin embryos as determined by polyclonal antibodies to the Lytechinus variegatus protein. FAK is absent in eggs and zygotes and then cycles in abundance during the first cleavages after fertilization. It is maximal at anaphase, similar to the destruction and synthesis of cyclin proteins. To investigate whether FAK is needed during early cleavage, we interfered with its function by microinjecting eggs with anti-FAK antibodies or with FAK antisense morpholino oligonucleotides. Both treatments led to regression of the cleavage furrow. FAK knockdown with antibodies or morpholino oligonucleotides also resulted in an over-accumulation of endocytic vesicles. Thus, FAK could be restricting endocytosis or increasing exocytosis in localized areas important for abscission. FAK appears to be necessary for successful cleavage. These results are the first to document a functional role for FAK during embryonic cleavage.
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2
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Cabernard C. Cytokinesis in Drosophila melanogaster. Cytoskeleton (Hoboken) 2012; 69:791-809. [PMID: 22888045 DOI: 10.1002/cm.21060] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 07/31/2012] [Indexed: 12/22/2022]
Abstract
Cytokinesis is the process that physically separates two sibling cells, ensuring the proper partitioning of the nuclear and cytoplasmic contents at the end of cell division. Cytokinesis requires a fine-tuned molecular machinery that has to be assembled with high spatiotemporal precision. Drosophila melanogaster is an ideal model system to investigate this cellular process. Genetic screens performed in spermatocytes, neuroblasts, and Schneider cells revealed numerous evolutionary conserved components. These genetically amenable systems have proven to be very useful to further elucidate the cellular and molecular mechanism of cytokinesis, significantly contributing to our current understanding of this important cellular process. As in other organisms, cytokinesis is largely dependent on the mitotic spindle, providing positional cues for cleavage furrow placement and progression. However, spindle-independent mechanisms could also be important during special cases of cytokinesis, such as asymmetric cell division. Thus, powerful fly genetics combined with single-cell analysis, live imaging, and biochemical assays will continue to provide important insights into the mechanism of cytokinesis.
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3
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Centralspindlin and α-catenin regulate Rho signalling at the epithelial zonula adherens. Nat Cell Biol 2012; 14:818-828. [PMID: 22750944 DOI: 10.1038/ncb2532] [Citation(s) in RCA: 203] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 05/25/2012] [Indexed: 12/17/2022]
Abstract
The biological impact of Rho depends critically on the precise subcellular localization of its active, GTP-loaded form. This can potentially be determined by the balance between molecules that promote nucleotide exchange or GTP hydrolysis. However, how these activities may be coordinated is poorly understood. We now report a molecular pathway that achieves exactly this coordination at the epithelial zonula adherens. We identify an extramitotic activity of the centralspindlin complex, better understood as a cytokinetic regulator, which localizes to the interphase zonula adherens by interacting with the cadherin-associated protein, α-catenin. Centralspindlin recruits the RhoGEF, ECT2, to activate Rho and support junctional integrity through myosin IIA. Centralspindlin also inhibits the junctional localization of p190 B RhoGAP, which can inactivate Rho. Thus, a conserved molecular ensemble that governs Rho activation during cytokinesis is used in interphase cells to control the Rho GTPase cycle at the zonula adherens.
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4
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Chang YC, Chen YJ, Wu CH, Wu YC, Yen TC, Ouyang P. Characterization of centrosomal proteins Cep55 and pericentrin in intercellular bridges of mouse testes. J Cell Biochem 2010; 109:1274-85. [PMID: 20186884 DOI: 10.1002/jcb.22517] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Centrosomal protein 55 (Cep55), located in the centrosome in interphase cells and recruited to the midbody during cytokinesis, is essential for completion of cell abscission. Northern blot previously showed that a high level of Cep55 is predominantly expressed in the testis. In the present study, we examined the spatial and temporal expression patterns of Cep55 during mouse testis maturation. We found that Cep55, together with pericentrin, another centrosomal protein, were localized to the intercellular bridges (IBs) interconnecting spermatogenic cells in a syncytium. The IBs were elaborated as a double ring structure formed by an inner ring decorated by Cep55 or pericentrin and an outer ring of mitotic kinesin-like protein 1 (MKLP1) in the male germ cell in early postnatal stages and adulthood. In addition, Cep55 and pericentrin were also localized to the acrosome region and flagellum neck and middle piece in elongated spermatids, respectively. These results suggest that Cep55 and pericentrin are required for the stable bridge between germ cells during spermatogenesis and spermiogenesis.
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Affiliation(s)
- Yu-Chen Chang
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan, ROC
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5
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von Dassow G, Verbrugghe KJC, Miller AL, Sider JR, Bement WM. Action at a distance during cytokinesis. J Cell Biol 2009; 187:831-45. [PMID: 20008563 PMCID: PMC2806324 DOI: 10.1083/jcb.200907090] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Accepted: 11/16/2009] [Indexed: 01/12/2023] Open
Abstract
Animal cells decide where to build the cytokinetic apparatus by sensing the position of the mitotic spindle. Reflecting a long-standing presumption that a furrow-inducing stimulus travels from spindle to cortex via microtubules, debate continues about which microtubules, and in what geometry, are essential for accurate cytokinesis. We used live imaging in urchin and frog embryos to evaluate the relationship between microtubule organization and cytokinetic furrow position. In normal cells, the cytokinetic apparatus forms in a region of lower cortical microtubule density. Remarkably, cells depleted of astral microtubules conduct accurate, complete cytokinesis. Conversely, in anucleate cells, asters alone can support furrow induction without a spindle, but only when sufficiently separated. Ablation of a single centrosome displaces furrows away from the remaining centrosome; ablation of both centrosomes causes broad, inefficient furrowing. We conclude that the asters confer accuracy and precision to a primary furrow-inducing signal that can reach the cell surface from the spindle without transport on microtubules.
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Affiliation(s)
- George von Dassow
- Center for Cell Dynamics, Friday Harbor Laboratories, University of Washington, Seattle, WA 98250, USA.
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6
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Chen W, Foss M, Tseng KF, Zhang D. Redundant mechanisms recruit actin into the contractile ring in silkworm spermatocytes. PLoS Biol 2008; 6:e209. [PMID: 18767903 PMCID: PMC2528054 DOI: 10.1371/journal.pbio.0060209] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Accepted: 07/17/2008] [Indexed: 11/24/2022] Open
Abstract
Cytokinesis is powered by the contraction of actomyosin filaments within the newly assembled contractile ring. Microtubules are a spindle component that is essential for the induction of cytokinesis. This induction could use central spindle and/or astral microtubules to stimulate cortical contraction around the spindle equator (equatorial stimulation). Alternatively, or in addition, induction could rely on astral microtubules to relax the polar cortex (polar relaxation). To investigate the relationship between microtubules, cortical stiffness, and contractile ring assembly, we used different configurations of microtubules to manipulate the distribution of actin in living silkworm spermatocytes. Mechanically repositioned, noninterdigitating microtubules can induce redistribution of actin at any region of the cortex by locally excluding cortical actin filaments. This cortical flow of actin promotes regional relaxation while increasing tension elsewhere (normally at the equatorial cortex). In contrast, repositioned interdigitating microtubule bundles use a novel mechanism to induce local stimulation of contractility anywhere within the cortex; at the antiparallel plus ends of central spindle microtubules, actin aggregates are rapidly assembled de novo and transported laterally to the equatorial cortex. Relaxation depends on microtubule dynamics but not on RhoA activity, whereas stimulation depends on RhoA activity but is largely independent of microtubule dynamics. We conclude that polar relaxation and equatorial stimulation mechanisms redundantly supply actin for contractile ring assembly, thus increasing the fidelity of cleavage. In animal cells, the last step of cell division, or cytokinesis, requires the action of a contractile ring—composed largely of actin and myosin filaments—that cleaves the cell in two. Before the cell divides, it first duplicates its genome and separates the chromosomes into the two newly forming daughter cells, a task carried out by a structure called the spindle apparatus, which is composed mostly of long polymers called microtubules. The site of cleavage must occur between the segregating chromosomes—at the spindle equator—to ensure that each cell receives the proper number of chromosomes. In addition to separating the chromosomes, microtubules are also essential for inducing cytokinesis—but how they do this is controversial. For example, the “polar relaxation” hypothesis proposes that the astral microtubules, which radiate outward, cause contractile elements to flow from the polar cortex toward the equator, resulting in furrowing. In contrast, the “equatorial stimulation” hypothesis proposes that the spindle microtubules directly stimulate cleavage exclusively at the equator. Using a novel approach, we demonstrate that both mechanisms are in fact functioning together to recruit actin filaments to the nascent ring, providing redundancy that increases fidelity. Specifically, we were able to mechanically alter the distribution of actin filaments in living, dividing cells by using a microscopic needle to manipulate microtubules while perturbing the cytoskeleton with chemical compounds. Our high-resolution microscopy data advance the understanding of both proposed mechanisms. We also documented a novel, microtubule-based mechanism for transporting actin aggregates to the equatorial cortex. These results help to resolve a long-standing dispute concerning this fundamental cellular process. How is actin recruited to assemble a contractile ring during cytokinesis? Combining micromanipulation with pharmacological perturbation, this comprehensive study elegantly documents the contributions of two complementary mechanisms within one cell.
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Affiliation(s)
- Wei Chen
- Department of Zoology, Oregon State University, Corvallis, Oregon, United States of America
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, Oregon, United States of America
| | - Margit Foss
- Department of Zoology, Oregon State University, Corvallis, Oregon, United States of America
| | - Kuo-Fu Tseng
- Department of Zoology, Oregon State University, Corvallis, Oregon, United States of America
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, Oregon, United States of America
| | - Dahong Zhang
- Department of Zoology, Oregon State University, Corvallis, Oregon, United States of America
- Center for Genome Research and Biocomputing (CGRB), Oregon State University, Corvallis, Oregon, United States of America
- * To whom correspondence should be addressed. E-mail:
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7
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Glover DM, Capalbo L, D'Avino PP, Gatt MK, Savoian MS, Takeda T. Girds 'n' cleeks o' cytokinesis: microtubule sticks and contractile hoops in cell division. Biochem Soc Trans 2008; 36:400-4. [PMID: 18481968 DOI: 10.1042/bst0360400] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Microtubules maintain an intimate relationship with the rings of anillin, septins and actomyosin filaments throughout cytokinesis. In Drosophila, peripheral microtubules emanating from the spindle poles contact the equatorial cell cortex to deliver the signal that initiates formation of the cytokinetic furrow. Mutations that affect microtubule stability lead to ectopic furrowing because peripheral microtubules contact inappropriate cortical sites. The PAV-KLP (Pavarotti-kinesin-like protein)/RacGAP50C (where GAP is GTPase-activating protein) centralspindlin complex moves towards the plus ends of microtubules to reach the cell equator. When RacGAP50C is tethered to the cell membrane, furrowing initiates at multiple non-equatorial sites, indicating that mis-localization of this single molecule is sufficient to promote furrowing. Furrow formation and ingression requires RhoA activation by the RhoGEF (guanine-nucleotide-exchange factor) Pebble, which interacts with RacGAP50C. RacGAP50C also binds anillin, which associates with actin, myosin and septins. Thus RacGAP50C plays a pivotal role during furrow formation by activating RhoA and linking the peripheral microtubules with the nascent rings through its interaction with anillin.
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Affiliation(s)
- David M Glover
- Cancer Research U.K. Cell Cycle Genetics Research Group, University of Cambridge, Department of Genetics, Downing Street, Cambridge CB2 3EH, UK.
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8
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D'Avino PP, Takeda T, Capalbo L, Zhang W, Lilley KS, Laue ED, Glover DM. Interaction between Anillin and RacGAP50C connects the actomyosin contractile ring with spindle microtubules at the cell division site. J Cell Sci 2008; 121:1151-8. [PMID: 18349071 DOI: 10.1242/jcs.026716] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Anillin, one of the first factors recruited to the cleavage site during cytokinesis, interacts with actin, myosin II and septins, and is essential for proper organization of the actomyosin contractile ring. We employed affinity-purification methodology coupled with mass spectrometry to identify Anillin-interacting molecules in Drosophila cells. We isolated several actin and myosin proteins, three of the five Drosophila septins and RacGAP50C (Tum), a component of the centralspindlin complex. Using drug and RNA interference (RNAi) treatments we established that F-actin is essential for Anillin cortical localization in prometaphase but not for its accumulation at the cleavage furrow after anaphase onset. Moreover, septins were not recruited to the cleavage site in cells in which Anillin was knocked down by RNAi, but localized to central-spindle microtubules, suggesting that septins travel along microtubules to interact with Anillin at the furrow. Finally, we demonstrate that RacGAP50C is necessary for Anillin accumulation at the furrow and that the two proteins colocalize in vivo and interact in vitro. Thus, in addition to its role in activating RhoA signalling, RacGAP50C also controls the proper assembly of the actomyosin ring by interacting with Anillin at the cleavage furrow.
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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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9
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Caldwell CM, Green RA, Kaplan KB. APC mutations lead to cytokinetic failures in vitro and tetraploid genotypes in Min mice. ACTA ACUST UNITED AC 2007; 178:1109-20. [PMID: 17893240 PMCID: PMC2064647 DOI: 10.1083/jcb.200703186] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Previous research has proposed that genomic instability contributes to cancer progression, with its initiation linked to tetraploid cell formation (Duesberg, P., and R. Li. 2003. Cell Cycle. 2:202-210; Ganem, N.J., Z. Storchova, and D. Pellman. 2007. Curr. Opin. Genet. Dev. 17:157-162). However, there is little direct evidence linking cancer-causing mutations with such events, and it remains controversial whether genomic instability is a cause or an effect of cancer. In this study, we show that adenomatous polyposis coli (APC) mutations found in human colorectal cancers dominantly inhibit cytokinesis by preventing mitotic spindle anchoring at the anaphase cortex and, thus, blocking initiation of the cytokinetic furrow. We find that dividing crypt cells in the small intestines of APC(Min/+) mice exhibit similar mitotic defects, including misoriented spindles and misaligned chromosomes. These defects are observed in normal crypt cells with wild-type levels of beta-catenin and, importantly, are associated with tetraploid genotypes. We provide direct evidence that the dominant activity of APC mutants induces aneuploidy in vivo. Our data support a model whereby tetraploid cells represent a first step in the onset of genomic instability and colorectal cancer.
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Affiliation(s)
- Christine M Caldwell
- Section of Molecular and Cell Biology, University of California, Davis, Davis, CA 95616, USA
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10
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Yüce O, Piekny A, Glotzer M. An ECT2-centralspindlin complex regulates the localization and function of RhoA. ACTA ACUST UNITED AC 2007; 170:571-82. [PMID: 16103226 PMCID: PMC2171506 DOI: 10.1083/jcb.200501097] [Citation(s) in RCA: 374] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In anaphase, the spindle dictates the site of contractile ring assembly. Assembly and ingression of the contractile ring involves activation of myosin-II and actin polymerization, which are triggered by the GTPase RhoA. In many cells, the central spindle affects division plane positioning via unknown molecular mechanisms. Here, we dissect furrow formation in human cells and show that the RhoGEF ECT2 is required for cortical localization of RhoA and contractile ring assembly. ECT2 concentrates on the central spindle by binding to centralspindlin. Depletion of the centralspindlin component MKLP1 prevents central spindle localization of ECT2; however, RhoA, F-actin, and myosin still accumulate on the equatorial cell cortex. Depletion of the other centralspindlin component, CYK-4/MgcRacGAP, prevents cortical accumulation of RhoA, F-actin, and myosin. CYK-4 and ECT2 interact, and this interaction is cell cycle regulated via ECT2 phosphorylation. Thus, central spindle localization of ECT2 assists division plane positioning and the CYK-4 subunit of centralspindlin acts upstream of RhoA to promote furrow assembly.
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Affiliation(s)
- Ozlem Yüce
- Research Institute of Molecular Pathology, 1030, Vienna, Austria
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11
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D'Avino PP, Savoian MS, Capalbo L, Glover DM. RacGAP50C is sufficient to signal cleavage furrow formation during cytokinesis. J Cell Sci 2006; 119:4402-8. [PMID: 17032738 DOI: 10.1242/jcs.03210] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Several studies indicate that spindle microtubules determine the position of the cleavage plane at the end of cell division, but their exact role in triggering the formation and ingression of the cleavage furrow is still unclear. Here we show that in Drosophila depletion of either the GAP (GTPase-activating protein) or the kinesin-like subunit of the evolutionary conserved centralspindlin complex prevents furrowing without affecting the association of astral microtubules with the cell cortex. Moreover, time-lapse imaging indicates that astral microtubules serve to deliver the centralspindlin complex to the equatorial cortex just before furrow formation. However, when the GAP-signaling component was mislocalized around the entire cortex using a membrane-tethering motif, this caused ectopic furrowing even in the absence of its motor partner. Thus, the GAP component of centralspindlin is both necessary and sufficient for furrow formation and ingression and astral microtubules provide a route for its delivery to the cleavage site.
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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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12
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Zavortink M, Contreras N, Addy T, Bejsovec A, Saint R. Tum/RacGAP50C provides a critical link between anaphase microtubules and the assembly of the contractile ring in Drosophila melanogaster. J Cell Sci 2006; 118:5381-92. [PMID: 16280552 DOI: 10.1242/jcs.02652] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A central question in understanding cytokinesis is how the cleavage plane is positioned. Although the positioning signal is likely to be transmitted via the anaphase microtubule array to the cell cortex, exactly how the microtubule array determines the site of contractile ring formation remains unresolved. By analysing tum/RacGAP50C mutant Drosophila embryos we show that cells lacking Tum do not form furrows and fail to localise the key cytokinetic components Pebble (a RhoGEF), Aurora B kinase, Diaphanous, Pav-KLP and Anillin. The GAP activity of Tum is required for cytokinesis: in its absence cytokinesis fails early even though Tum is present on microtubules at the cell equator where the furrow should form. Disruption of the Pebble-interacting domain leaves Tum localised to the cell equator on cortically associated microtubules, again with no evidence of furrowing. These data support a model in which Tum/RacGAP, via its interaction with Pbl, provides a critical link between the anaphase microtubule spindle and cytokinetic furrow formation in Drosophila cells.
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Affiliation(s)
- Michael Zavortink
- ARC Special Research Centre for the Molecular Genetics of Development and Molecular Genetics and Evolution Group, Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia
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13
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Nishimura Y, Yonemura S. Centralspindlin regulates ECT2 and RhoA accumulation at the equatorial cortex during cytokinesis. J Cell Sci 2006; 119:104-14. [PMID: 16352658 DOI: 10.1242/jcs.02737] [Citation(s) in RCA: 204] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
During determination of the cell division plane, an actomyosin contractile ring is induced at the equatorial cell cortex by signals from the mitotic apparatus and contracts to cause cleavage furrow progression. Although the small GTPase RhoA is known to regulate the progression, probably by controlling actin filament assembly and enhancing actomyosin interaction, any involvement of RhoA in division plane determination is unknown. In this study, using a trichloroacetic acid (TCA) fixation protocol we recently developed, we show that RhoA accumulates at the equatorial cortex before furrow initiation and continues to concentrate at the cleavage furrow during cytokinesis. We also demonstrate that both Rho activity and microtubule organization are required for RhoA localization and proper furrowing. Selective disruption of microtubule organization revealed that both astral and central spindle microtubules can recruit RhoA at the equatorial cortex. We find that centralspindlin and ECT2 are required for RhoA localization and furrowing. Centralspindlin is localized both to central spindle microtubules and at the tips of astral microtubules near the equatorial cortex and recruits ECT2. Positional information for division plane determination from microtubules is transmitted to the cell cortex to organize actin cytoskeleton through a mechanism involving these proteins.
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Affiliation(s)
- Yukako Nishimura
- Laboratory for Cellular Morphogenesis, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan
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14
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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: 153] [Impact Index Per Article: 7.7] [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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15
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Zhao WM, Fang G. MgcRacGAP controls the assembly of the contractile ring and the initiation of cytokinesis. Proc Natl Acad Sci U S A 2005; 102:13158-63. [PMID: 16129829 PMCID: PMC1201590 DOI: 10.1073/pnas.0504145102] [Citation(s) in RCA: 162] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Initiation of cytokinesis requires the establishment of the cleavage plane, the assembly of the contractile ring, and the ingression of the cleavage furrow. MgcRacGAP, a GTPase-activating protein for RhoA, is required for cytokinesis, but the mechanism of its action remains unknown. We report here that MgcRacGAP is required for the assembly of anillin and myosin into the contractile ring. In addition, MgcRacGAP is required for the localized activation of myosin through the RhoA-mediated phosphorylation of the myosin regulatory light chain. Cells with MgcRacGAP RNA interference (RNAi) failed cytokinesis without any ingression of the cleavage furrow. Paradoxically, MgcRacGAP, a GTPase-activating protein, associates during cytokinesis with ECT2, a guanine nucleotide exchange factor for RhoA, and the localization of ECT2 to both the central spindle and the contractile ring depends on MgcRacGAP. Knockdown of ECT2 phenocopies that of MgcRacGAP. We conclude that MgcRacGAP controls the initiation of cytokinesis by regulating ECT2, which in turn induces the assembly of the contractile ring and triggers the ingression of the cleavage furrow.
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Affiliation(s)
- Wei-meng Zhao
- Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA
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16
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Yoshizaki H, Aoki K, Mochizuki N, Matsuda M. [Dynamics of Rho-family G proteins as visualized with FRET-based probes]. Nihon Yakurigaku Zasshi 2005; 126:135-41. [PMID: 16205017 DOI: 10.1254/fpj.126.135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
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17
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Pielak RM, Hawkins C, Pyie A, Bautista J, Lee KG, Cohen WD. Polar body formation in Spisula oocytes: function of the peripheral aster. THE BIOLOGICAL BULLETIN 2005; 209:21-30. [PMID: 16110091 DOI: 10.2307/3593139] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Activated Spisula oocytes proceed through meiotic stages rapidly and in near synchrony, providing an excellent system for analyzing polar body formation. Our previous studies suggested that cortical spreading of the metaphase peripheral aster determines spatial features of the cortical F-actin ring that is generated prior to extrusion of the polar body. We tested this hypothesis by experimentally altering the number and cortical contact patterns of peripheral asters. Such alteration was achieved by (a) lovastatin-induced arrest at metaphase I, with and without hexylene glycol modification, followed by washout; and (b) cytochalasin-D inhibition of extrusion of the first polar body, with washout before extrusion of the second polar body. Both methods induced simultaneous formation of two or more cortically spreading asters, correlated with subsequent formation of double, or even triple, overlapping F-actin rings during anaphase. Regardless of pattern, ring F-actin was deposited near regions of greatest astral microtubule density, indicating that microtubules provided a positive stimulus to which the cortex responded indiscriminately. These results strongly support the proposed causal relationship between peripheral aster spreading and biogenesis of the F-actin ring involved in polar body formation.
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Affiliation(s)
- Rafal M Pielak
- Department of Biological Sciences, Hunter College, New York, New York, USA
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18
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Bejsovec A, Lecuit T, Modolell J. The fly Olympics: faster, higher and stronger answers to developmental questions. Conference on the Molecular and Developmental Biology of Drosophila. EMBO Rep 2004; 5:1037-40. [PMID: 15486566 PMCID: PMC1299169 DOI: 10.1038/sj.embor.7400274] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2004] [Accepted: 08/27/2004] [Indexed: 11/09/2022] Open
Affiliation(s)
- Amy Bejsovec
- Department of Biology, Duke University, Durham, North Carolina 27708, USA.
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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: 0.0] [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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Mitotic Kinesin Inhibitors as Novel Anti-cancer Agents. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 2004. [DOI: 10.1016/s0065-7743(04)39014-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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