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McIntosh JR. Anaphase A. Semin Cell Dev Biol 2021; 117:118-126. [PMID: 33781672 DOI: 10.1016/j.semcdb.2021.03.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 03/16/2021] [Accepted: 03/16/2021] [Indexed: 10/21/2022]
Abstract
Anaphase A is the motion of recently separated chromosomes to the spindle pole they face. It is accompanied by the shortening of kinetochore-attached microtubules. The requisite tubulin depolymerization may occur at kinetochores, at poles, or both, depending on the species and/or the time in mitosis. These depolymerization events are local and suggest that cells regulate microtubule dynamics in specific places, presumably by the localization of relevant enzymes and microtubule-associated proteins to specific loci, such as pericentriolar material and outer kinetochores. Motor enzymes can contribute to anaphase A, both by altering microtubule stability and by pushing or pulling microtubules through the cell. The generation of force on chromosomes requires couplings that can both withstand the considerable force that spindles can generate and simultaneously permit tubulin addition and loss. This chapter reviews literature on the molecules that regulate anaphase microtubule dynamics, couple dynamic microtubules to kinetochores and poles, and generate forces for microtubule and chromosome motion.
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Affiliation(s)
- J Richard McIntosh
- Dept. of Molecular, Cellular, and Developmental Biology University of Colorado, Boulder, CO 80309-0347, USA.
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2
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Mechanical Mechanisms of Chromosome Segregation. Cells 2021; 10:cells10020465. [PMID: 33671543 PMCID: PMC7926803 DOI: 10.3390/cells10020465] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/17/2021] [Accepted: 02/19/2021] [Indexed: 12/11/2022] Open
Abstract
Chromosome segregation—the partitioning of genetic material into two daughter cells—is one of the most crucial processes in cell division. In all Eukaryotes, chromosome segregation is driven by the spindle, a microtubule-based, self-organizing subcellular structure. Extensive research performed over the past 150 years has identified numerous commonalities and contrasts between spindles in different systems. In this review, we use simple coarse-grained models to organize and integrate previous studies of chromosome segregation. We discuss sites of force generation in spindles and fundamental mechanical principles that any understanding of chromosome segregation must be based upon. We argue that conserved sites of force generation may interact differently in different spindles, leading to distinct mechanical mechanisms of chromosome segregation. We suggest experiments to determine which mechanical mechanism is operative in a particular spindle under study. Finally, we propose that combining biophysical experiments, coarse-grained theories, and evolutionary genetics will be a productive approach to enhance our understanding of chromosome segregation in the future.
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Danlasky BM, Panzica MT, McNally KP, Vargas E, Bailey C, Li W, Gong T, Fishman ES, Jiang X, McNally FJ. Evidence for anaphase pulling forces during C. elegans meiosis. J Cell Biol 2020; 219:211469. [PMID: 33064834 PMCID: PMC7577052 DOI: 10.1083/jcb.202005179] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 07/20/2020] [Accepted: 09/16/2020] [Indexed: 02/06/2023] Open
Abstract
Anaphase chromosome movement is thought to be mediated by pulling forces generated by end-on attachment of microtubules to the outer face of kinetochores. However, it has been suggested that during C. elegans female meiosis, anaphase is mediated by a kinetochore-independent pushing mechanism with microtubules only attached to the inner face of segregating chromosomes. We found that the kinetochore proteins KNL-1 and KNL-3 are required for preanaphase chromosome stretching, suggesting a role in pulling forces. In the absence of KNL-1,3, pairs of homologous chromosomes did not separate and did not move toward a spindle pole. Instead, each homolog pair moved together with the same spindle pole during anaphase B spindle elongation. Two masses of chromatin thus ended up at opposite spindle poles, giving the appearance of successful anaphase.
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Wang Y, Stear JH, Swain A, Xu X, Bryce NS, Carnell M, Alieva IB, Dugina VB, Cripe TP, Stehn J, Hardeman EC, Gunning PW. Drug Targeting the Actin Cytoskeleton Potentiates the Cytotoxicity of Low Dose Vincristine by Abrogating Actin-Mediated Repair of Spindle Defects. Mol Cancer Res 2020; 18:1074-1087. [PMID: 32269073 DOI: 10.1158/1541-7786.mcr-19-1122] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 03/09/2020] [Accepted: 04/03/2020] [Indexed: 11/16/2022]
Abstract
Antimicrotubule vinca alkaloids are widely used in the clinic but their toxicity is often dose limiting. Strategies that enhance their effectiveness at lower doses are needed. We show that combining vinca alkaloids with compounds that target a specific population of actin filaments containing the cancer-associated tropomyosin Tpm3.1 result in synergy against a broad range of tumor cell types. We discovered that low concentrations of vincristine alone induce supernumerary microtubule asters that form transient multi-polar spindles in early mitosis. Over time these asters can be reconstructed into functional bipolar spindles resulting in cell division and survival. These microtubule asters are organized by the nuclear mitotic apparatus protein (NuMA)-dynein-dynactin complex without involvement of centrosomes. However, anti-Tpm3.1 compounds at nontoxic concentrations inhibit this rescue mechanism resulting in delayed onset of anaphase, formation of multi-polar spindles, and apoptosis during mitosis. These findings indicate that drug targeting actin filaments containing Tpm3.1 potentiates the anticancer activity of low-dose vincristine treatment. IMPLICATIONS: Simultaneously inhibiting Tpm3.1-containing actin filaments and microtubules is a promising strategy to potentiate the anticancer activity of low-dose vincristine.
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Affiliation(s)
- Yao Wang
- Cellular and Genetic Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Jeffrey H Stear
- Cellular and Genetic Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Ashleigh Swain
- Cellular and Genetic Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Xing Xu
- Cellular and Genetic Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Nicole S Bryce
- Cellular and Genetic Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Michael Carnell
- Biomedical Imaging Facility, Mark Wainwright Analytical Center, University of New South Wales, Sydney, New South Wales, Australia
| | - Irina B Alieva
- Department of Electron Microscopy, A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Vera B Dugina
- Department of Mathematical Methods in Biology, A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | | | - Justine Stehn
- Cellular and Genetic Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Edna C Hardeman
- Cellular and Genetic Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Peter W Gunning
- Cellular and Genetic Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.
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O'Toole E, Morphew M, McIntosh JR. Electron tomography reveals aspects of spindle structure important for mechanical stability at metaphase. Mol Biol Cell 2019; 31:184-195. [PMID: 31825721 PMCID: PMC7001478 DOI: 10.1091/mbc.e19-07-0405] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Metaphase spindles exert pole-directed forces on still-connected sister kinetochores. The spindle must counter these forces with extensive forces to prevent spindle collapse. In small spindles, kinetochore microtubules (KMTs) connect directly with the poles, and countering forces are supplied either by interdigitating MTs that form interpolar bundles or by astral MTs connected to the cell cortex. In bigger spindles, particularly those without structured poles, the origin of extensive forces is less obvious. We have used electron tomography of well-preserved metaphase cells to obtain structural evidence about interactions among different classes of MTs in metaphase spindles from Chlamydomonas rheinhardti and two strains of cultured mammalian cells. In all these spindles, KMTs approach close to and cross-bridge with the minus ends of non-KMTs, which form a framework that interdigitates near the spindle equator. Although this structure is not pole-connected, its organization suggests that it can support kinetochore tension. Analogous arrangements of MTs have been seen in even bigger spindles, such as metaphase spindles in Haemanthus endosperm and frog egg extracts. We present and discuss a hypothesis that rationalizes changes in spindle design with spindle size based on the negative exponential distribution of MT lengths in dynamically unstable populations of tubulin polymers.
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Affiliation(s)
- Eileen O'Toole
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Boulder, CO 80309
| | - Mary Morphew
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Boulder, CO 80309
| | - J Richard McIntosh
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Boulder, CO 80309
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Vukušić K, Buđa R, Tolić IM. Force-generating mechanisms of anaphase in human cells. J Cell Sci 2019; 132:132/18/jcs231985. [DOI: 10.1242/jcs.231985] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
ABSTRACT
What forces drive chromosome segregation remains one of the most challenging questions in cell division. Even though the duration of anaphase is short, it is of utmost importance for genome fidelity that no mistakes are made. Seminal studies in model organisms have revealed different mechanisms operating during chromosome segregation in anaphase, but the translation of these mechanisms to human cells is not straightforward. Recent work has shown that kinetochore fiber depolymerization during anaphase A is largely motor independent, whereas spindle elongation during anaphase B is coupled to sliding of interpolar microtubules in human cells. In this Review, we discuss the current knowledge on the mechanisms of force generation by kinetochore, interpolar and astral microtubules. By combining results from numerous studies, we propose a comprehensive picture of the role of individual force-producing and -regulating proteins. Finally, by linking key concepts of anaphase to most recent data, we summarize the contribution of all proposed mechanisms to chromosome segregation and argue that sliding of interpolar microtubules and depolymerization at the kinetochore are the main drivers of chromosome segregation during early anaphase in human cells.
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Affiliation(s)
- Kruno Vukušić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Renata Buđa
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Iva M. Tolić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
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7
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Yu CH, Redemann S, Wu HY, Kiewisz R, Yoo TY, Conway W, Farhadifar R, Müller-Reichert T, Needleman D. Central-spindle microtubules are strongly coupled to chromosomes during both anaphase A and anaphase B. Mol Biol Cell 2019; 30:2503-2514. [PMID: 31339442 PMCID: PMC6743361 DOI: 10.1091/mbc.e19-01-0074] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 07/08/2019] [Accepted: 07/19/2019] [Indexed: 01/05/2023] Open
Abstract
Spindle microtubules, whose dynamics vary over time and at different locations, cooperatively drive chromosome segregation. Measurements of microtubule dynamics and spindle ultrastructure can provide insight into the behaviors of microtubules, helping elucidate the mechanism of chromosome segregation. Much work has focused on the dynamics and organization of kinetochore microtubules, that is, on the region between chromosomes and poles. In comparison, microtubules in the central-spindle region, between segregating chromosomes, have been less thoroughly characterized. Here, we report measurements of the movement of central-spindle microtubules during chromosome segregation in human mitotic spindles and Caenorhabditis elegans mitotic and female meiotic spindles. We found that these central-spindle microtubules slide apart at the same speed as chromosomes, even as chromosomes move toward spindle poles. In these systems, damaging central-spindle microtubules by laser ablation caused an immediate and complete cessation of chromosome motion, suggesting a strong coupling between central-spindle microtubules and chromosomes. Electron tomographic reconstruction revealed that the analyzed anaphase spindles all contain microtubules with both ends between segregating chromosomes. Our results provide new dynamical, functional, and ultrastructural characterizations of central-spindle microtubules during chromosome segregation in diverse spindles and suggest that central-spindle microtubules and chromosomes are strongly coupled in anaphase.
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Affiliation(s)
- Che-Hang Yu
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
- Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106
| | - Stefanie Redemann
- Experimental Center, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Center for Membrane and Cell Physiology & Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22903
| | - Hai-Yin Wu
- Department of Physics, Harvard University, Cambridge, MA 02138
| | - Robert Kiewisz
- Experimental Center, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
| | - Tae Yeon Yoo
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138
| | - William Conway
- Department of Physics, Harvard University, Cambridge, MA 02138
| | - Reza Farhadifar
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138
- Center for Computational Biology, Flatiron Institute, Simons Foundation, New York, NY 10010
| | - Thomas Müller-Reichert
- Experimental Center, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
| | - Daniel Needleman
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138
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8
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Context-dependent spindle pole focusing. Essays Biochem 2018; 62:803-813. [PMID: 30429281 DOI: 10.1042/ebc20180034] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 10/12/2018] [Accepted: 10/22/2018] [Indexed: 11/17/2022]
Abstract
The formation of a robust, bi-polar spindle apparatus, capable of accurate chromosome segregation, is a complex process requiring the co-ordinated nucleation, sorting, stabilization and organization of microtubules (MTs). Work over the last 25 years has identified protein complexes that act as functional modules to nucleate spindle MTs at distinct cellular sites such as centrosomes, kinetochores, chromatin and pre-existing MTs themselves. There is clear evidence that the extent to which these different MT nucleating pathways contribute to spindle mass both during mitosis and meiosis differs not only between organisms, but also in different cell types within an organism. This plasticity contributes the robustness of spindle formation; however, whether such plasticity is present in other aspects of spindle formation is less well understood. Here, we review the known roles of the protein complexes responsible for spindle pole focusing, investigating the evidence that these, too, act co-ordinately and differentially, depending on cellular context. We describe relationships between MT minus-end directed motors dynein and HSET/Ncd, depolymerases including katanin and MCAK, and direct minus-end binding proteins such as nuclear-mitotic apparatus protein, ASPM and Patronin/CAMSAP. We further explore the idea that the focused spindle pole acts as a non-membrane bound condensate and suggest that the metaphase spindle pole be treated as a transient organelle with context-dependent requirements for function.
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9
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An Exploration of the Impact of Anticentromere Antibody on Early-Stage Embryo. J Immunol Res 2017; 2017:4809294. [PMID: 29119119 PMCID: PMC5651102 DOI: 10.1155/2017/4809294] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Accepted: 07/16/2017] [Indexed: 11/18/2022] Open
Abstract
Background Previously, we found women with positive anticentromere antibody showed impaired potential of oocyte maturation and embryo cleavage; the possible mechanism behind this phenomenon was still unknown. Objective Thus, the present study aimed to preliminarily explore whether ACA could penetrate into the living embryos and impair their developmental potential via in vitro coculture with mouse embryos. Methods Mouse embryos were collected and used for in vitro culture with polyclonal anticentromere protein A (CENP-A) antibody; then, immunofluorescence assay was performed to determine the penetration of antibody into embryos, and embryo development potential was observed. Results All embryos cultured with anti-CENP-A antibody exhibited immunofluorescence on the nucleus, while none of the embryos from the control groups showed immunofluorescence. Additionally, embryos cultured with anti-CENP-A antibody experienced significant growth impairment compared with controls. Conclusion Mouse embryos may be a direct target for ACA in vitro prior to implantation. However, the precise mechanism needs further clarification.
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Vukušić K, Buđa R, Bosilj A, Milas A, Pavin N, Tolić IM. Microtubule Sliding within the Bridging Fiber Pushes Kinetochore Fibers Apart to Segregate Chromosomes. Dev Cell 2017; 43:11-23.e6. [PMID: 29017027 PMCID: PMC5637169 DOI: 10.1016/j.devcel.2017.09.010] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 07/21/2017] [Accepted: 09/13/2017] [Indexed: 01/06/2023]
Abstract
During cell division, mitotic spindle microtubules segregate chromosomes by exerting forces on kinetochores. What forces drive chromosome segregation in anaphase remains a central question. The current model for anaphase in human cells includes shortening of kinetochore fibers and separation of spindle poles. Both processes require kinetochores to be linked with the poles. Here we show, by combining laser ablation, photoactivation, and theoretical modeling, that kinetochores can separate without any attachment to one spindle pole. This separation requires the bridging fiber, a microtubule bundle that connects sister kinetochore fibers. Bridging fiber microtubules in intact spindles slide apart with kinetochore fibers, indicating strong crosslinks between them. We conclude that sliding of microtubules within the bridging fibers drives pole separation and pushes kinetochore fibers poleward by the friction of passive crosslinks between these fibers. Thus, sliding within the bridging fiber works together with the shortening of kinetochore fibers to segregate chromosomes.
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Affiliation(s)
- Kruno Vukušić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Renata Buđa
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Agneza Bosilj
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia
| | - Ana Milas
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Nenad Pavin
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia.
| | - Iva M Tolić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia.
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Elting MW, Prakash M, Udy DB, Dumont S. Mapping Load-Bearing in the Mammalian Spindle Reveals Local Kinetochore Fiber Anchorage that Provides Mechanical Isolation and Redundancy. Curr Biol 2017; 27:2112-2122.e5. [PMID: 28690110 DOI: 10.1016/j.cub.2017.06.018] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 05/04/2017] [Accepted: 06/08/2017] [Indexed: 11/25/2022]
Abstract
Active forces generated at kinetochores move chromosomes, and the dynamic spindle must robustly anchor kinetochore fibers (k-fibers) to bear this load. The mammalian spindle bears the load of chromosome movement far from poles, but we do not know where and how-physically and molecularly-this load distributes across the spindle. In part, this is because probing spindle mechanics in live cells is difficult. Yet answering this question is key to understanding how the spindle generates and responds to force and performs its diverse mechanical functions. Here, we map load-bearing across the mammalian spindle in space-time and dissect local anchorage mechanics and mechanism. To do so, we laser-ablate single k-fibers at different spindle locations and in different molecular backgrounds and quantify the immediate relaxation of chromosomes, k-fibers, and microtubule speckles. We find that load redistribution is locally confined in all directions: along the first 3-4 μm from kinetochores, scaling with k-fiber length, and laterally within ∼2 μm of k-fiber sides, without detectable load sharing between neighboring k-fibers. A phenomenological model suggests that dense, transient crosslinks to the spindle along k-fibers bear the load of chromosome movement but that these connections do not limit the timescale of spindle reorganization. The microtubule crosslinker NuMA is needed for the local load-bearing observed, whereas Eg5 and PRC1 are not detectably required, suggesting specialization in mechanical function. Together, the data and model suggest that NuMA-mediated crosslinks locally bear load, providing mechanical isolation and redundancy while allowing spindle fluidity. These features are well suited to support robust chromosome segregation.
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Affiliation(s)
- Mary Williard Elting
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Manu Prakash
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Dylan B Udy
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Sophie Dumont
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94143, USA.
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12
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Mechanisms of Chromosome Congression during Mitosis. BIOLOGY 2017; 6:biology6010013. [PMID: 28218637 PMCID: PMC5372006 DOI: 10.3390/biology6010013] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Revised: 01/07/2017] [Accepted: 01/28/2017] [Indexed: 12/13/2022]
Abstract
Chromosome congression during prometaphase culminates with the establishment of a metaphase plate, a hallmark of mitosis in metazoans. Classical views resulting from more than 100 years of research on this topic have attempted to explain chromosome congression based on the balance between opposing pulling and/or pushing forces that reach an equilibrium near the spindle equator. However, in mammalian cells, chromosome bi-orientation and force balance at kinetochores are not required for chromosome congression, whereas the mechanisms of chromosome congression are not necessarily involved in the maintenance of chromosome alignment after congression. Thus, chromosome congression and maintenance of alignment are determined by different principles. Moreover, it is now clear that not all chromosomes use the same mechanism for congressing to the spindle equator. Those chromosomes that are favorably positioned between both poles when the nuclear envelope breaks down use the so-called "direct congression" pathway in which chromosomes align after bi-orientation and the establishment of end-on kinetochore-microtubule attachments. This favors the balanced action of kinetochore pulling forces and polar ejection forces along chromosome arms that drive chromosome oscillatory movements during and after congression. The other pathway, which we call "peripheral congression", is independent of end-on kinetochore microtubule-attachments and relies on the dominant and coordinated action of the kinetochore motors Dynein and Centromere Protein E (CENP-E) that mediate the lateral transport of peripheral chromosomes along microtubules, first towards the poles and subsequently towards the equator. How the opposite polarities of kinetochore motors are regulated in space and time to drive congression of peripheral chromosomes only now starts to be understood. This appears to be regulated by position-dependent phosphorylation of both Dynein and CENP-E and by spindle microtubule diversity by means of tubulin post-translational modifications. This so-called "tubulin code" might work as a navigation system that selectively guides kinetochore motors with opposite polarities along specific spindle microtubule populations, ultimately leading to the congression of peripheral chromosomes. We propose an integrated model of chromosome congression in mammalian cells that depends essentially on the following parameters: (1) chromosome position relative to the spindle poles after nuclear envelope breakdown; (2) establishment of stable end-on kinetochore-microtubule attachments and bi-orientation; (3) coordination between kinetochore- and arm-associated motors; and (4) spatial signatures associated with post-translational modifications of specific spindle microtubule populations. The physiological consequences of abnormal chromosome congression, as well as the therapeutic potential of inhibiting chromosome congression are also discussed.
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13
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Grishchuk EL. Biophysics of Microtubule End Coupling at the Kinetochore. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2017; 56:397-428. [PMID: 28840247 DOI: 10.1007/978-3-319-58592-5_17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The main physiological function of mitotic kinetochores is to provide durable attachment to spindle microtubules, which segregate chromosomes in order to partition them equally between the two daughter cells. Numerous kinetochore components that can bind directly to microtubules have been identified, including ATP-dependent motors and various microtubule-associated proteins with no motor activity. A major challenge facing the field is to explain chromosome motions based on the biochemical and structural properties of these individual kinetochore components and their assemblies. This chapter reviews the molecular mechanisms responsible for the motions associated with dynamic microtubule tips at the single-molecule level, as well as the activities of multimolecular ensembles called couplers. These couplers enable persistent kinetochore motion even under load, but their exact composition and structure remain unknown. Because no natural or artificial macro-machines function in an analogous manner to these molecular nano-devices, understanding their underlying biophysical mechanisms will require conceptual advances.
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Affiliation(s)
- Ekaterina L Grishchuk
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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14
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Nahaboo W, Zouak M, Askjaer P, Delattre M. Chromatids segregate without centrosomes during Caenorhabditis elegans mitosis in a Ran- and CLASP-dependent manner. Mol Biol Cell 2015; 26:2020-9. [PMID: 25833711 PMCID: PMC4472013 DOI: 10.1091/mbc.e14-12-1577] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 03/20/2015] [Indexed: 01/23/2023] Open
Abstract
Laser ablation of centrosomes in one-cell Caenorhabditis elegans embryos shows that chromatids can segregate independently of centrosomes and also independently of the activity of kinetochore microtubules during mitosis. CLASP and RanGTP are required to generate this centrosome-independent force, whereas SPD-1 and BMK-1 act as brakes to oppose it. During mitosis, chromosomes are connected to a microtubule-based spindle. Current models propose that displacement of the spindle poles and/or the activity of kinetochore microtubules generate mechanical forces that segregate sister chromatids. Using laser destruction of the centrosomes during Caenorhabditis elegans mitosis, we show that neither of these mechanisms is necessary to achieve proper chromatid segregation. Our results strongly suggest that an outward force generated by the spindle midzone, independently of centrosomes, is sufficient to segregate chromosomes in mitotic cells. Using mutant and RNAi analysis, we show that the microtubule-bundling protein SPD-1/MAP-65 and BMK-1/kinesin-5 act as a brake opposing the force generated by the spindle midzone. Conversely, we identify a novel role for two microtubule-growth and nucleation agents, Ran and CLASP, in the establishment of the centrosome-independent force during anaphase. Their involvement raises the interesting possibility that microtubule polymerization of midzone microtubules is continuously required to sustain chromosome segregation during mitosis.
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Affiliation(s)
- Wallis Nahaboo
- Laboratory of Molecular Biology of the Cell, University of Lyon 1, CNRS UMR5239, Ecole Normale Supérieure de Lyon, 69007 Lyon, France
| | - Melissa Zouak
- Laboratory of Molecular Biology of the Cell, University of Lyon 1, CNRS UMR5239, Ecole Normale Supérieure de Lyon, 69007 Lyon, France
| | - Peter Askjaer
- Andalusian Centre for Developmental Biology, CSIC-Junta de Andalucia, Universidad Pablo de Olavide, Carretera de Utrera, 41012 Seville, Spain
| | - Marie Delattre
- Laboratory of Molecular Biology of the Cell, University of Lyon 1, CNRS UMR5239, Ecole Normale Supérieure de Lyon, 69007 Lyon, France
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15
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Abstract
During eukaryotic cell division, chromosomes must be precisely partitioned to daughter cells. This relies on a mechanism to move chromosomes in defined directions within the parental cell. While sister chromatids are segregated from one another in mitosis and meiosis II, specific adaptations enable the segregation of homologous chromosomes during meiosis I to reduce ploidy for gamete production. Many of the factors that drive these directed chromosome movements are known, and their molecular mechanism has started to be uncovered. Here we review the mechanisms of eukaryotic chromosome segregation, with a particular emphasis on the modifications that ensure the segregation of homologous chromosomes during meiosis I.
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Affiliation(s)
- Eris Duro
- The Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, United Kingdom
| | - Adèle L Marston
- The Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, United Kingdom
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16
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Ferreira JG, Pereira AL, Maiato H. Microtubule plus-end tracking proteins and their roles in cell division. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2014; 309:59-140. [PMID: 24529722 DOI: 10.1016/b978-0-12-800255-1.00002-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Microtubules are cellular components that are required for a variety of essential processes such as cell motility, mitosis, and intracellular transport. This is possible because of the inherent dynamic properties of microtubules. Many of these properties are tightly regulated by a number of microtubule plus-end-binding proteins or +TIPs. These proteins recognize the distal end of microtubules and are thus in the right context to control microtubule dynamics. In this review, we address how microtubule dynamics are regulated by different +TIP families, focusing on how functionally diverse +TIPs spatially and temporally regulate microtubule dynamics during animal cell division.
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Affiliation(s)
- Jorge G Ferreira
- Chromosome Instability & Dynamics Laboratory, Instituto de Biologia Molecular e Celular, University of Porto, Porto, Portugal; Cell Division Unit, Department of Experimental Biology, University of Porto, Porto, Portugal
| | - Ana L Pereira
- Chromosome Instability & Dynamics Laboratory, Instituto de Biologia Molecular e Celular, University of Porto, Porto, Portugal
| | - Helder Maiato
- Chromosome Instability & Dynamics Laboratory, Instituto de Biologia Molecular e Celular, University of Porto, Porto, Portugal; Cell Division Unit, Department of Experimental Biology, University of Porto, Porto, Portugal.
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17
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Sikirzhytski V, Magidson V, Steinman JB, He J, Le Berre M, Tikhonenko I, Ault JG, McEwen BF, Chen JK, Sui H, Piel M, Kapoor TM, Khodjakov A. Direct kinetochore-spindle pole connections are not required for chromosome segregation. ACTA ACUST UNITED AC 2014; 206:231-43. [PMID: 25023516 PMCID: PMC4107786 DOI: 10.1083/jcb.201401090] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In the absence of continuous K-fiber attachment between each kinetochore and the spindle pole, one or more additional mechanisms dependent on dynein-mediated kinetochore transport exist to ensure proper chromosome segregation during mitosis. Segregation of genetic material occurs when chromosomes move to opposite spindle poles during mitosis. This movement depends on K-fibers, specialized microtubule (MT) bundles attached to the chromosomes′ kinetochores. A long-standing assumption is that continuous K-fibers connect every kinetochore to a spindle pole and the force for chromosome movement is produced at the kinetochore and coupled with MT depolymerization. However, we found that chromosomes still maintained their position at the spindle equator during metaphase and segregated properly during anaphase when one of their K-fibers was severed near the kinetochore with a laser microbeam. We also found that, in normal fully assembled spindles, K-fibers of some chromosomes did not extend to the spindle pole. These K-fibers connected to adjacent K-fibers and/or nonkinetochore MTs. Poleward movement of chromosomes with short K-fibers was uncoupled from MT depolymerization at the kinetochore. Instead, these chromosomes moved by dynein-mediated transport of the entire K-fiber/kinetochore assembly. Thus, at least two distinct parallel mechanisms drive chromosome segregation in mammalian cells.
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Affiliation(s)
| | - Valentin Magidson
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | | | - Jie He
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | | | - Irina Tikhonenko
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | - Jeffrey G Ault
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | - Bruce F McEwen
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | | | - Haixin Sui
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | | | | | - Alexey Khodjakov
- Wadsworth Center, New York State Department of Health, Albany, NY 12201 Rensselaer Polytechnic Institute, Troy, NY 12180
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18
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Zheng Z, Wan Q, Meixiong G, Du Q. Cell cycle-regulated membrane binding of NuMA contributes to efficient anaphase chromosome separation. Mol Biol Cell 2013; 25:606-19. [PMID: 24371089 PMCID: PMC3937087 DOI: 10.1091/mbc.e13-08-0474] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The mitotic apparatus protein NuMA has an intrinsic membrane-targeting mechanism that is regulated by CDK1-mediated phosphorylation, underlies anaphase-specific cortical accumulation of dynein, and contributes to chromosome separation. Accurate and efficient separation of sister chromatids during anaphase is critical for faithful cell division. It has been proposed that cortical dynein–generated pulling forces on astral microtubules contribute to anaphase spindle elongation and chromosome separation. In mammalian cells, however, definitive evidence for the involvement of cortical dynein in chromosome separation is missing. It is believed that dynein is recruited and anchored at the cell cortex during mitosis by the α subunit of heterotrimeric G protein (Gα)/mammalian homologue of Drosophila Partner of Inscuteable/nuclear mitotic apparatus (NuMA) ternary complex. Here we uncover a Gα/LGN-independent lipid- and membrane-binding domain at the C-terminus of NuMA. We show that the membrane binding of NuMA is cell cycle regulated—it is inhibited during prophase and metaphase by cyclin-dependent kinase 1 (CDK1)–mediated phosphorylation and only occurs after anaphase onset when CDK1 activity is down-regulated. Further studies indicate that cell cycle–regulated membrane association of NuMA underlies anaphase-specific enhancement of cortical NuMA and dynein. By replacing endogenous NuMA with membrane-binding-deficient NuMA, we can specifically reduce the cortical accumulation of NuMA and dynein during anaphase and demonstrate that cortical NuMA and dynein contribute to efficient chromosome separation in mammalian cells.
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Affiliation(s)
- Zhen Zheng
- Institute of Molecular Medicine and Genetics, Georgia Regents University, Augusta, GA 30912 Department of Neurology, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912 Lakeside High School, Evans, GA 30809
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19
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Ying Y, Zhong YP, Zhou CQ, Xu YW, Miao BY, Wang Q, Li J. Preliminary investigation of the impact of anticentromere antibody on oocyte maturation and embryo cleavage. Fertil Steril 2013; 100:1585-9. [PMID: 24044934 DOI: 10.1016/j.fertnstert.2013.07.1998] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 07/24/2013] [Accepted: 07/29/2013] [Indexed: 10/26/2022]
Abstract
OBJECTIVE To explore whether anticentromere antibody (ACA) is the most significant antibody among antinuclear antibodies (ANA), which adversely affect oocyte maturation, embryo cleavage, and pregnancy outcome in women undergoing an intracytoplasmic sperm injection program. DESIGN Retrospective, nested case-control study. SETTING Center for reproductive medicine, university hospital. PATIENT(S) A total of 187 women receiving the first intracytoplasmic sperm injection cycle were enrolled in this study, including 20 women with positive ACA and ANA (ACA[+]/ANA[+] group), 51 women with negative ACA and positive ANA(ACA[-]/ANA[+] group), and 116 patients with negative ACA and ANA (ACA[-]/ANA[-] group). Patients in the three groups were age-matched. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Percentages of germinal vesicle, metaphase I, and metaphase II oocytes, embryo cleavage rate, number of high-quality embryos, and rates of pregnancy and implantation. RESULT(S) The metaphase I oocyte percentage was markedly higher and the metaphase II oocyte percentage and the normal cleavage rate were significantly lower in the ACA[+]/ANA[+] group as compared with the ACA[-]/ANA[+] group. Furthermore, statistically significant differences were found in rates of pregnancy and implantation among the three groups. However, no significant difference was found between any two groups owing to the small sample size, except for a significantly lower implantation rate being found in the ACA[+]/ANA[+] group when compared with the ACA[-]/ANA[-] group. CONCLUSION(S) Our data suggest that ACA may be the essential marker for defective oocytes or embryos in infertile women with any type of ANA.
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Affiliation(s)
- Ying Ying
- Reproductive Medicine Center for The First Affiliated Hospital of Sun Yat-sen University, Key Laboratory of Reproductive Medicine of Guangdong Province, Guangzhou, People's Republic of China
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20
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Kanev I, Mei WN, Mizuno A, DeHaai K, Sanmann J, Hess M, Starr L, Grove J, Dave B, Sanger W. Searching for electrical properties, phenomena and mechanisms in the construction and function of chromosomes. Comput Struct Biotechnol J 2013; 6:e201303007. [PMID: 24688715 PMCID: PMC3962117 DOI: 10.5936/csbj.201303007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 06/09/2013] [Accepted: 06/13/2013] [Indexed: 12/22/2022] Open
Abstract
OUR STUDIES REVEAL PREVIOUSLY UNIDENTIFIED ELECTRICAL PROPERTIES OF CHROMOSOMES: (1) chromosomes are amazingly similar in construction and function to electrical transformers; (2) chromosomes possess in their construction and function, components similar to those of electric generators, conductors, condensers, switches, and other components of electrical circuits; (3) chromosomes demonstrate in nano-scale level electromagnetic interactions, resonance, fusion and other phenomena similar to those described by equations in classical physics. These electrical properties and phenomena provide a possible explanation for unclear and poorly understood mechanisms in clinical genetics including: (a) electrically based mechanisms responsible for breaks, translocations, fusions, and other chromosomal abnormalities associated with cancer, intellectual disability, infertility, pregnancy loss, Down syndrome, and other genetic disorders; (b) electrically based mechanisms involved in crossing over, non-disjunction and other events during meiosis and mitosis; (c) mechanisms demonstrating heterochromatin to be electrically active and genetically important.
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Affiliation(s)
- Ivan Kanev
- Human Genetics Laboratory, Munroe-Meyer Institute for Genetics and Rehabilitation, University of Nebraska Medical Center, Omaha, Nebraska, 68198-5440, USA
| | - Wai-Ning Mei
- Department of physics, University of Nebraska at Omaha, Nebraska, 68182, USA
| | - Akira Mizuno
- Applied Electrostatics Laboratory, Department of Environmental and Life Sciences, Toyohashi University of Technology, Tempaku-cyo, Toyohashi, Aichi, 441-8580, Japan
| | - Kristi DeHaai
- Human Genetics Laboratory, Munroe-Meyer Institute for Genetics and Rehabilitation, University of Nebraska Medical Center, Omaha, Nebraska, 68198-5440, USA
| | - Jennifer Sanmann
- Human Genetics Laboratory, Munroe-Meyer Institute for Genetics and Rehabilitation, University of Nebraska Medical Center, Omaha, Nebraska, 68198-5440, USA
| | - Michelle Hess
- Human Genetics Laboratory, Munroe-Meyer Institute for Genetics and Rehabilitation, University of Nebraska Medical Center, Omaha, Nebraska, 68198-5440, USA
| | - Lois Starr
- Human Genetics Laboratory, Munroe-Meyer Institute for Genetics and Rehabilitation, University of Nebraska Medical Center, Omaha, Nebraska, 68198-5440, USA
| | - Jennifer Grove
- Human Genetics Laboratory, Munroe-Meyer Institute for Genetics and Rehabilitation, University of Nebraska Medical Center, Omaha, Nebraska, 68198-5440, USA
| | - Bhavana Dave
- Human Genetics Laboratory, Munroe-Meyer Institute for Genetics and Rehabilitation, University of Nebraska Medical Center, Omaha, Nebraska, 68198-5440, USA
| | - Warren Sanger
- Human Genetics Laboratory, Munroe-Meyer Institute for Genetics and Rehabilitation, University of Nebraska Medical Center, Omaha, Nebraska, 68198-5440, USA
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21
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Sheykhani R, Shirodkar PV, Forer A. The role of myosin phosphorylation in anaphase chromosome movement. Eur J Cell Biol 2013; 92:175-86. [PMID: 23566798 DOI: 10.1016/j.ejcb.2013.02.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 01/26/2013] [Accepted: 02/22/2013] [Indexed: 11/29/2022] Open
Abstract
This work deals with the role of myosin phosphorylation in anaphase chromosome movement. Y27632 and ML7 block two different pathways for phosphorylation of the myosin regulatory light chain (MRLC). Both stopped or slowed chromosome movement when added to anaphase crane-fly spermatocytes. To confirm that the effects of the pharmacological agents were on the presumed targets, we studied cells stained with antibodies against mono- or bi-phosphorylated myosin. For all chromosomes whose movements were affected by a drug, the corresponding spindle fibres of the affected chromosomes had reduced levels of 1P- and 2P-myosin. Thus the drugs acted on the presumed target and myosin phosphorylation is involved in anaphase force production. Calyculin A, an inhibitor of MRLC dephosphorylation, reversed and accelerated the altered movements caused by Y27632 and ML-7, suggesting that another phosphorylation pathway is involved in phosphorylation of spindle myosin. Staurosporine, a more general phosphorylation inhibitor, also reduced the levels of MRLC phosphorylation and caused anaphase chromosomes to stop or slow. The effects of staurosporine on chromosome movements were not reversed by Calyculin A, confirming that another phosphorylation pathway is involved in phosphorylation of spindle myosin.
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Affiliation(s)
- Rozhan Sheykhani
- Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada
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22
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Gutiérrez-Caballero C, Cebollero LR, Pendás AM. Shugoshins: from protectors of cohesion to versatile adaptors at the centromere. Trends Genet 2012; 28:351-60. [PMID: 22542109 DOI: 10.1016/j.tig.2012.03.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Revised: 03/07/2012] [Accepted: 03/07/2012] [Indexed: 11/20/2022]
Abstract
Sister chromatids are held together by a protein complex named cohesin. Shugoshin proteins protect cohesin from cleavage by separase during meiosis I in eukaryotes and from phosphorylation-mediated removal during mitosis in vertebrates. This protection is crucial for chromosome segregation during mitosis and meiosis. Mechanistically, shugoshins shield cohesin by forming a complex with the phosphatase PP2A, which dephosphorylates cohesin, leading to its retention at centromeres during the onset of meiotic anaphase and vertebrate mitotic prophase I. In addition to this canonical function, shugoshins have evolved novel, species-specific cellular functions, the mechanisms of which remain a subject of intense debate, but are likely to involve spatio-temporally coordinated interactions with the chromosome passenger complex, the spindle checkpoint and the anaphase promoting complex. Here, we compare and contrast these remarkable features of shugoshins in model organisms and humans.
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Affiliation(s)
- Cristina Gutiérrez-Caballero
- Instituto de Biología Molecular y Celular del Cáncer (CSIC-USAL), Campus Miguel de Unamuno, 37007 Salamanca, Spain
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23
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Abstract
Mitosis is the process by which eukaryotic cells organize and segregate their chromosomes in preparation for cell division. It is accomplished by a cellular machine composed largely of microtubules (MTs) and their associated proteins. This article reviews literature on mitosis from a biophysical point of view, drawing attention to the assembly and motility processes required to do this complex job with precision. Work from both the recent and the older literature is integrated into a description of relevant biological events and the experiments that probe their mechanisms. Theoretical work on specific subprocesses is also reviewed. Our goal is to provide a document that will expose biophysicists to the fascination of this quite amazing process and provide them with a good background from which they can pursue their own research interests in the subject.
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24
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Lee MH, Lin L, Equilibrina I, Uchiyama S, Matsunaga S, Fukui K. ASURA (PHB2) Is Required for Kinetochore Assembly and Subsequent Chromosome Congression. Acta Histochem Cytochem 2011; 44:247-58. [PMID: 22282585 PMCID: PMC3263857 DOI: 10.1267/ahc.11033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 08/25/2011] [Indexed: 01/24/2023] Open
Abstract
ASURA (PHB2) knockdown has been known to cause premature loss of sister chromatid cohesion, and disrupt the localization of several outer plate proteins to the kinetochore. As a result, cells are arrested at mitotic phase and chromosomes fail to congress to the metaphase plate. In this study, we further clarified the mechanism underlying ASURA function on chromosome congression. Interestingly, ASURA is not specifically localized at the kinetochore during mitotic phase, unlike other kinetochore proteins which construct the kinetochore. Electron microscopy (EM) observation showed that ASURA is required for proper kinetochore formation. By the partial depletion of ASURA, kinetochore maturation is impaired, and kinetochores showing fibrillar balls without a well-defined outer plates are often observed. Moreover, even when the outer plates of kinetochores are constructed, most showed structures stretched and/or distended from the centromere, which resembled premature kinetochores at prometaphase, indicating that the constructed kinetochore plates are less rigid against tension derived from kinetochore microtubule pulling forces. We concluded that ASURA is an essential protein for complete kinetochore development, although ASURA is not being integrated to the kinetochore. These results highlight the uniqueness of ASURA as a kinetochore protein.
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Affiliation(s)
- Mei Hann Lee
- Department of Biotechnology, Graduate School of Engineering, Osaka University
| | - Linyen Lin
- Research Center for Ultra-High Voltage Electron Microscopy, Osaka University
| | - Ilma Equilibrina
- Department of Biotechnology, Graduate School of Engineering, Osaka University
| | - Susumu Uchiyama
- Department of Biotechnology, Graduate School of Engineering, Osaka University
| | - Sachihiro Matsunaga
- Department of Biotechnology, Graduate School of Engineering, Osaka University
- Present address: Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science
| | - Kiichi Fukui
- Department of Biotechnology, Graduate School of Engineering, Osaka University
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25
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Abstract
The mechanisms that move chromatids poleward during anaphase A have fascinated researchers for decades. There is now growing evidence that this movement is tightly linked to the active depolymerization of both ends of kinetochore-associated microtubules, a mechanism we refer to as "Pacman-Flux." Contemporary data suggest that this is catalyzed by the integration of multiple enzymatic activities including (1) microtubule-end depolymerases housed at the pole or kinetochore, (2) microtubule-severing enzymes used to uncap the ends of kinetochore-associated microtubules, and (3) molecular motors which drive tubulins towards the pole or into kinetochores.
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26
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Maiato H, Lince-Faria M. The perpetual movements of anaphase. Cell Mol Life Sci 2010; 67:2251-69. [PMID: 20306325 PMCID: PMC11115923 DOI: 10.1007/s00018-010-0327-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 02/17/2010] [Indexed: 12/29/2022]
Abstract
One of the most extraordinary events in the lifetime of a cell is the coordinated separation of sister chromatids during cell division. This is truly the essence of the entire mitotic process and the reason for the most profound morphological changes in cytoskeleton and nuclear organization that a cell may ever experience. It all occurs within a very short time window known as "anaphase", as if the cell had spent the rest of its existence getting ready for this moment in an ultimate act of survival. And there is a good reason for this: no space for mistakes. Problems in the distribution of chromosomes during cell division have been correlated with aneuploidy, a common feature observed in cancers and several birth defects, and the main cause of spontaneous abortion in humans. In this paper, we critically review the mechanisms of anaphase chromosome motion that resisted the scrutiny of more than 100 years of research, as part of a tribute to the pioneering work of Miguel Mota.
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Affiliation(s)
- Helder Maiato
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180, Porto, Portugal.
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27
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Abstract
For over a century, scientists have strived to understand the mechanisms that govern the accurate segregation of chromosomes during mitosis. The most intriguing feature of this process, which is particularly prominent in higher eukaryotes, is the complex behaviour exhibited by the chromosomes. This behaviour is based on specific and highly regulated interactions between the chromosomes and spindle microtubules. Recent discoveries, enabled by high-resolution imaging combined with the various genetic, molecular, cell biological and chemical tools, support the idea that establishing and controlling the dynamic interaction between chromosomes and microtubules is a major factor in genomic fidelity.
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28
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Silk AD, Holland AJ, Cleveland DW. Requirements for NuMA in maintenance and establishment of mammalian spindle poles. ACTA ACUST UNITED AC 2009; 184:677-90. [PMID: 19255246 PMCID: PMC2686415 DOI: 10.1083/jcb.200810091] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Microtubules of the mitotic spindle in mammalian somatic cells are focused at spindle poles, a process thought to include direct capture by astral microtubules of kinetochores and/or noncentrosomally nucleated microtubule bundles. By construction and analysis of a conditional loss of mitotic function allele of the nuclear mitotic apparatus (NuMA) protein in mice and cultured primary cells, we demonstrate that NuMA is an essential mitotic component with distinct contributions to the establishment and maintenance of focused spindle poles. When mitotic NuMA function is disrupted, centrosomes provide initial focusing activity, but continued centrosome attachment to spindle fibers under tension is defective, and the maintenance of focused kinetochore fibers at spindle poles throughout mitosis is prevented. Without centrosomes and NuMA, initial establishment of spindle microtubule focusing completely fails. Thus, NuMA is a defining feature of the mammalian spindle pole and functions as an essential tether linking bulk microtubules of the spindle to centrosomes.
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Affiliation(s)
- Alain D Silk
- Ludwig Institute for Cancer Research, Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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29
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Hughes SE, Gilliland WD, Cotitta JL, Takeo S, Collins KA, Hawley RS. Heterochromatic threads connect oscillating chromosomes during prometaphase I in Drosophila oocytes. PLoS Genet 2009; 5:e1000348. [PMID: 19165317 PMCID: PMC2615114 DOI: 10.1371/journal.pgen.1000348] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Accepted: 12/18/2008] [Indexed: 12/04/2022] Open
Abstract
In Drosophila oocytes achiasmate homologs are faithfully segregated to opposite poles at meiosis I via a process referred to as achiasmate homologous segregation. We observed that achiasmate homologs display dynamic movements on the meiotic spindle during mid-prometaphase. An analysis of living prometaphase oocytes revealed both the rejoining of achiasmate X chromosomes initially located on opposite half-spindles and the separation toward opposite poles of two X chromosomes that were initially located on the same half spindle. When the two achiasmate X chromosomes were positioned on opposite halves of the spindle their kinetochores appeared to display proper co-orientation. However, when both Xs were located on the same half spindle their kinetochores appeared to be oriented in the same direction. Thus, the prometaphase movement of achiasmate chromosomes is a congression-like process in which the two homologs undergo both separation and rejoining events that result in the either loss or establishment of proper kinetochore co-orientation. During this period of dynamic chromosome movement, the achiasmate homologs were connected by heterochromatic threads that can span large distances relative to the length of the developing spindle. Additionally, the passenger complex proteins Incenp and Aurora B appeared to localize to these heterochromatic threads. We propose that these threads assist in the rejoining of homologs and the congression of the migrating achiasmate homologs back to the main chromosomal mass prior to metaphase arrest. Proper chromosome segregation is essential during the production of eggs and sperm. Chromosome missegregation during meiosis results in the lethality of the offspring or in children carrying extra copies of a given chromosome (for example, Down syndrome). Recombination results in homologous chromosomes becoming physically interlocked in a manner that is normally sufficient to ensure proper segregation. Chromosomes that fail to undergo recombination require additional mechanisms to ensure their proper segregation. In Drosophila melanogaster oocytes we show that chromosomes that fail to recombine undergo dynamic movements on the meiotic spindle prior to their proper segregation. Although previous studies had shown that non-recombinant chromosomes move to opposite sides of the developing meiotic spindle, we show that these chromosomes can cross the spindle and re-associate with their homologs to attempt reorientation. Additionally, we observed threads connecting separated non-recombinant chromosomes that contained heterochromatic DNA and passenger complex proteins. These threads could assist the non-recombinant chromosomes in locating their homologs during their dynamic movements on the spindle. These chromosome movements and the heterochromatic threads are likely part of the mechanism ensuring proper segregation of nonexchange chromosomes.
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Affiliation(s)
- Stacie E. Hughes
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - William D. Gilliland
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Jeffrey L. Cotitta
- Department of Physiology, University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Satomi Takeo
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Kim A. Collins
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - R. Scott Hawley
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
- Department of Physiology, University of Kansas Medical Center, Kansas City, Kansas, United States of America
- * E-mail:
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30
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Fu G, Ding X, Yuan K, Aikhionbare F, Yao J, Cai X, Jiang K, Yao X. Phosphorylation of human Sgo1 by NEK2A is essential for chromosome congression in mitosis. Cell Res 2007; 17:608-18. [PMID: 17621308 DOI: 10.1038/cr.2007.55] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Chromosome segregation in mitosis is orchestrated by the interaction of the kinetochore with spindle microtubules. Our recent study shows that NEK2A interacts with MAD1 at the kinetochore and possibly functions as a novel integrator of spindle checkpoint signaling. However, it is unclear how NEK2A regulates kinetochore-microtubule attachment in mitosis. Here we show that NEK2A phosphorylates human Sgo1 and such phosphorylation is essential for faithful chromosome congression in mitosis. NEK2A binds directly to HsSgo1 in vitro and co-distributes with HsSgo1 to the kinetochore of mitotic cells. Our in vitro phosphorylation experiment demonstrated that HsSgo1 is a substrate of NEK2A and the phosphorylation sites were mapped to Ser(14) and Ser(507) as judged by the incorporation of (32)P. Although such phosphorylation is not required for assembly of HsSgo1 to the kinetochore, expression of non-phosphorylatable mutant HsSgo1 perturbed chromosome congression and resulted in a dramatic increase in microtubule attachment errors, including syntelic and monotelic attachments. These findings reveal a key role for the NEK2A-mediated phosphorylation of HsSgo1 in orchestrating dynamic kinetochore-microtubule interaction. We propose that NEK2A-mediated phosphorylation of human Sgo1 provides a link between centromeric cohesion and spindle microtubule attachment at the kinetochores.
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Affiliation(s)
- Guosheng Fu
- Laboratory of Cellular Dynamics, Hefei National Laboratory, University of Science & Technology of China, Hefei, China
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Raj A, Peskin CS. The influence of chromosome flexibility on chromosome transport during anaphase A. Proc Natl Acad Sci U S A 2006; 103:5349-54. [PMID: 16567616 PMCID: PMC1459358 DOI: 10.1073/pnas.0601215103] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The role of protein flexibility in molecular motor function has previously been studied by considering a Brownian ratchet motor that is connected to its cargo by an elastic spring, with the result that the average velocity of the motor/cargo system is increased by reducing the stiffness of the linkage. Here, we extend this investigation to the case of chromosome transport during anaphase A, in which the relevant flexibility is not primarily in the motor/cargo linkage but rather in the cargo itself, i.e., in the chromosome. We model the motor mechanism as an imperfect Brownian ratchet with a built-in opposing load and the chromosome as a collection of discrete segments linked by an elastic energy function that discretizes the potential energy of an elastic rod. Thermal fluctuations are produced in the model by random forces, as in Brownian dynamics. All of the parameters that characterize the chromosome are known or can be estimated from experimental data, as can all but one of the motor parameters, which is adjusted to give the correct transport velocity of normal-length chromosomes. With the parameters so determined, we then reproduce the experimental finding of Nicklas [Nicklas, R. B. (1965) J. Cell Biol. 25, 119-135] that chromosome speed is essentially independent of chromosome length, even though our model contains no "velocity governor." We find instead that this effect is a consequence of chromosome flexibility, as it disappears when stiffer than normal chromosomes are considered.
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Affiliation(s)
- Arjun Raj
- Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10012
- *To whom correspondence may be addressed. E-mail:
or
| | - Charles S. Peskin
- Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10012
- *To whom correspondence may be addressed. E-mail:
or
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32
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Abstract
Accurate and timely chromosome segregation is a task performed within meiotic and mitotic cells by a specialized force-generating structure--the spindle. This micromachine is constructed from numerous proteins, most notably the filamentous microtubules that form a structural framework for the spindle and also transmit forces through it. Poleward flux is an evolutionarily conserved mechanism used by spindle microtubules both to move chromosomes and to regulate spindle length. Recent studies have identified a microtubule-depolymerizing kinesin as a key force-generating component required for flux. On the basis of these findings, we propose a new model for flux powered by a microtubule-disassembly mechanism positioned at the spindle pole. In addition, we use the flux model to explain the results of spindle manipulation experiments to illustrate the importance of flux for proper chromosome positioning.
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Affiliation(s)
- Gregory C Rogers
- Department of Physiology and Biophysics, 223 Ullmann Building, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Abstract
Proper segregation of chromosomes during cell division is essential for the maintenance of genetic stability. During this process chromosomes must establish stable functional interactions with microtubules through the kinetochore, a specialized protein structure located on the surface of the centromeric heterochromatin. Stable attachment of kinetochores to a number of microtubules results in the formation of a kinetochore fibre that mediates chromosome movement. How the kinetochore fibre is formed and how chromosome motion is produced and regulated remain major questions in cell biology. Here we look at some of the history of research devoted to the study of kinetochore-microtubule interaction and attempt to identify significant advances in the knowledge of the basic processes. Ultrastructural work has provided substantial insights into the structure of the kinetochore and associated microtubules during different stages of mitosis. Also, recent in-vivo studies have probed deep into the dynamics of kinetochore-attached microtubules suggesting possible models for the way in which kinetochores harness the capacity of microtubules to do work and turn it into chromosome motion. Much of the research in recent years suggests that indeed multiple mechanisms are involved in both formation of the k-fibre and chromosome motion. Thus, rather than moving to a unified theory, it has become apparent that most cell types have the capacity to build the spindle using multiple and probably redundant mechanisms.
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Affiliation(s)
- Helder Maiato
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal
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Alsop GB, Zhang D. Microtubules continuously dictate distribution of actin filaments and positioning of cell cleavage in grasshopper spermatocytes. J Cell Sci 2004; 117:1591-602. [PMID: 15020685 DOI: 10.1242/jcs.01007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
We systematically examined the impact of microtubules on distribution of actin filaments and positioning of cell cleavage using micromanipulation to progressively alter the symmetric distribution of spindle microtubules in grasshopper spermatocytes. The initial microtubule asymmetry was induced by placing a single chromosome at one spindle pole using a microneedle, which facilitates regional assembly of spindle microtubules. We augmented chromosome-induced microtubule asymmetry by further removing the aster from the achromosomal pole, producing unichromosome-bearing monopolar spindles. We created the highest spindle asymmetry by cutting early anaphase cells in two, each containing a full set of segregating chromosomes in a half-spindle. We demonstrate that the location of the spindle midzone, distribution of actin filaments, and position of cell cleavage depend on the amount of microtubule asymmetry generated, shifting up to 48.6+/-3.8% away from the spindle equator in cut cells. The positional shift is dynamic, changing incessantly as spindle microtubules reorganize during cytokinesis. These results suggest that microtubules continuously dictate the distribution of actin filaments and positioning of cell cleavage in grasshopper spermatocytes.
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Affiliation(s)
- G Bradley Alsop
- Department of Zoology/Center for Gene Research and Biotechnology, Oregon State University, Corvallis, OR 97331, USA
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35
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Wang H, Hu X, Ding X, Dou Z, Yang Z, Shaw AW, Teng M, Cleveland DW, Goldberg ML, Niu L, Yao X. Human Zwint-1 specifies localization of Zeste White 10 to kinetochores and is essential for mitotic checkpoint signaling. J Biol Chem 2004; 279:54590-8. [PMID: 15485811 DOI: 10.1074/jbc.m407588200] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chromosome segregation in mitosis is orchestrated by dynamic interaction between spindle microtubules and the kinetochore, a multiprotein complex assembled onto centromeric DNA of the chromosome. Here we show that Zwint-1 is required and is sufficient for kinetochore localization of Zeste White 10 (ZW10) in HeLa cells. Zwint-1 specifies the kinetochore association of ZW10 by interacting with its N-terminal domain. Suppression of synthesis of Zwint-1 by small interfering RNA abolishes the localization of ZW10 to the kinetochore, demonstrating the requirement of Zwint-1 for ZW10 kinetochore localization. In addition, depletion of Zwint-1 affects no mitotic arrest but causes aberrant premature chromosome segregation. These Zwint-1-suppressed cells display chromosome bridge phenotype with sister chromatids inter-connected. Moreover, Zwint-1 is required for stable association of CENP-F and dynamitin but not BUB1 with the kinetochore. Finally, our studies show that Zwint-1 is a new component of the mitotic check-point, as cells lacking Zwint-1 fail to arrest in mitosis when exposed to microtubule inhibitors, yielding interphase cells with multinuclei. As ZW10 and Zwint-1 are absent from yeast, we reasoned that metazoans evolved an elaborate spindle checkpoint machinery to ensure faithful chromosome segregation in mitosis.
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Affiliation(s)
- Hongmei Wang
- CAS Key Laboratory for Structure Biology and Hefei National Laboratory for Physical Sciences at Microscale, Hefei 230027, China
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36
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LaFountain JR, Oldenbourg R. Maloriented bivalents have metaphase positions at the spindle equator with more kinetochore microtubules to one pole than to the other. Mol Biol Cell 2004; 15:5346-55. [PMID: 15385630 PMCID: PMC532015 DOI: 10.1091/mbc.e04-06-0524] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
To test the "traction fiber" model for metaphase positioning of bivalents during meiosis, kinetochore fibers of maloriented bivalents, induced during recovery from cold arrest, were analyzed with a liquid crystal polarizing microscope. The measured birefringence retardation of kinetochore fibers is proportional to the number of microtubules in a fiber. Five of the 11 maloriented bivalents analyzed exhibited bipolar malorientations that had at least four times more kinetochore microtubules to one pole than to the other pole, and two had microtubules directed to only one pole. Yet all maloriented bivalents had positions at or near the spindle equator. The traction fiber model predicts such maloriented bivalents should be positioned closer to the pole with more kinetochore microtubules. A metaphase position at the spindle equator, according to the model, requires equal numbers of kinetochore microtubules to both poles. Data from polarizing microscope images were not in accord with those predictions, leading to the conclusion that other factors, in addition to traction forces, must be involved in metaphase positioning in crane-fly spermatocytes. Although the identity of additional factors has not been established, one possibility is that polar ejection forces operate to exert away-from-the-pole forces that could counteract pole-directed traction forces. Another is that kinetochores are "smart," meaning they embody a position-sensitive mechanism that controls their activity.
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Affiliation(s)
- James R LaFountain
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA.
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Zenzes MT, Bielecki R. Nicotine-induced Disturbances of Meiotic Maturation in Cultured Mouse Oocytes: Alterations of Spindle Integrity and Chromosome Alignment. Tob Induc Dis 2004; 2:151-61. [PMID: 19570282 PMCID: PMC2671544 DOI: 10.1186/1617-9625-2-3-151] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
We investigated whether nicotine exposure in vitro of mouse oocytes affects spindle and chromosome function during meiotic maturation (M-I and M-II). Oocytes in germinal vesicle (GV) stage were cultured in nicotine for 8 h or for 16 h, to assess effects in M-I and in metaphase II (M-II). The latter culture setting used the three protocols: 8 h nicotine then 8 h medium (8N + 8M); 16 h nicotine (16N); 8 h medium then 8 h nicotine (8M + 8N). Non-toxic concentrations of nicotine at 1.0, 2.5, 5.0 and 10.0 mmol/L were used. Spindle-chromosome configurations were analyzed with wide-field optical sectioning microscopy. In 8 h cultures, nicotine exposure resulted in dose-related increased proportions of M-I oocytes with defective spindle-chromosome configurations. A dose-related delayed entry into anaphase I was also detected. In 16 h cultures, nicotine exposure for the first 8 h (8N + 8M), or for 16 h (16N), resulted in dose- and time-related increased proportions of oocytes arrested in M-I (10 mmol/L; 8 h: 53.2%, controls 9.6%; 16 h: 87.6%, controls 8.5%). Defects in M-I spindles and chromosomes caused M-I arrest leading to dose-related decreased proportions of oocytes that reached metaphase-II (10 mmol/L 8 h: 46.8%, controls 90.4%;16 h: 12.4%, controls 91.5%). A delayed anaphase-I affected the normal timing of M-II, leading to abnormal oocytes with dispersed chromosomes, or with double spindles and no polar body. Nicotine exposure during the second 8 h (8M + 8N) resulted in dose-related, increased proportions of M-II oocytes with defective spindles and chromosomes (10 mmol/L: 42.9%, controls 2.0%). Nicotine has no adverse effects on GV break down, but induces spindle and chromosome defects compromising oocyte meiotic maturation and development.
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Affiliation(s)
- Maria Teresa Zenzes
- Department of Obstetrics and Gynaecology, Division of Reproductive Sciences, University of Toronto, Toronto, Ontario, Canada.
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38
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Zenzes MT, Bielecki R. Nicotine-induced Disturbances of Meiotic Maturation in Cultured Mouse Oocytes: Alterations of Spindle Integrity and Chromosome Alignment. Tob Induc Dis 2004; 2. [PMCID: PMC2669460 DOI: 10.1186/1617-9625-2-16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
We investigated whether nicotine exposure in vitro of mouse oocytes affects spindle and chromosome function during meiotic maturation (M-I and M-II). Oocytes in germinal vesicle (GV) stage were cultured in nicotine for 8 h or for 16 h, to assess effects in M-I and in metaphase II (M-II). The latter culture setting used the three protocols: 8 h nicotine then 8 h medium (8N + 8M); 16 h nicotine (16N); 8 h medium then 8 h nicotine (8M + 8N). Non-toxic concentrations of nicotine at 1.0, 2.5, 5.0 and 10.0 mmol/L were used. Spindle-chromosome configurations were analyzed with wide-field optical sectioning microscopy. In 8 h cultures, nicotine exposure resulted in dose-related increased proportions of M-I oocytes with defective spindle-chromosome configurations. A dose-related delayed entry into anaphase I was also detected. In 16 h cultures, nicotine exposure for the first 8 h (8N + 8M), or for 16 h (16N), resulted in dose- and time-related increased proportions of oocytes arrested in M-I (10 mmol/L; 8 h: 53.2%, controls 9.6%; 16 h: 87.6%, controls 8.5%). Defects in M-I spindles and chromosomes caused M-I arrest leading to dose-related decreased proportions of oocytes that reached metaphase-II (10 mmol/L 8 h: 46.8%, controls 90.4%;16 h: 12.4%, controls 91.5%). A delayed anaphase-I affected the normal timing of M-II, leading to abnormal oocytes with dispersed chromosomes, or with double spindles and no polar body. Nicotine exposure during the second 8 h (8M + 8N) resulted in dose-related, increased proportions of M-II oocytes with defective spindles and chromosomes (10 mmol/L: 42.9%, controls 2.0%). Nicotine has no adverse effects on GV break down, but induces spindle and chromosome defects compromising oocyte meiotic maturation and development.
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Affiliation(s)
- Maria Teresa Zenzes
- Department of Obstetrics and Gynaecology, Division of Reproductive Sciences, University of Toronto, Toronto, Ontario, Canada,Mount Sinai Hospital, 600 University Ave., Room 876, Toronto, Ontario M5G 1H5, Canada
| | - Ryszard Bielecki
- Department of Obstetrics and Gynaecology, Division of Reproductive Sciences, University of Toronto, Toronto, Ontario, Canada
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39
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Chakravarty A, Howard L, Compton DA. A mechanistic model for the organization of microtubule asters by motor and non-motor proteins in a mammalian mitotic extract. Mol Biol Cell 2004; 15:2116-32. [PMID: 14978218 PMCID: PMC404009 DOI: 10.1091/mbc.e03-08-0579] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Revised: 01/30/2004] [Accepted: 01/30/2004] [Indexed: 11/11/2022] Open
Abstract
We used computer simulation to understand the functional relationships between motor (dynein, HSET, and Eg5) and non-motor (NuMA) proteins involved in microtubule aster organization. The simulation accurately predicted microtubule organization under all combinations of motor and non-motor proteins, provided that microtubule cross-links at minus-ends were dynamic, and dynein and HSET were restricted to cross-linking microtubules in parallel orientation only. A mechanistic model was derived from these data in which a combination of two aggregate properties, Net Minus-end-directed Force and microtubule Cross-linking Orientation Bias, determine microtubule organization. This model uses motor and non-motor proteins, accounts for motor antagonism, and predicts that alterations in microtubule Cross-linking Orientation Bias should compensate for imbalances in motor force during microtubule aster formation. We tested this prediction in the mammalian mitotic extract and, consistent with the model, found that increasing the contribution of microtubule cross-linking by NuMA compensated for the loss of Eg5 motor activity. Thus, this model proposes a precise mechanism of action of each noncentrosomal protein during microtubule aster organization and suggests that microtubule organization in spindles involves both motile forces from motors and static forces from non-motor cross-linking proteins.
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Affiliation(s)
- Arijit Chakravarty
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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40
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Chen W, Zhang D. Kinetochore fibre dynamics outside the context of the spindle during anaphase. Nat Cell Biol 2004; 6:227-31. [PMID: 15039774 DOI: 10.1038/ncb1104] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2003] [Accepted: 01/23/2004] [Indexed: 01/01/2023]
Abstract
Chromosomes move polewards as kinetochore fibres shorten during anaphase. Fibre dynamics and force production have been studied extensively, but little is known about these processes in the absence of the spindle matrix. Here we show that laser-microbeam-severed kinetochore fibres in the cytoplasm of grasshopper spermatocytes maintain a constant length while turning over in a polarized manner. Tubulin incorporates at or near the kinetochore and translocates towards severed ends without shortening the fibre. Consequently, the chromosome cannot move polewards unless the severed fibre reattaches to the pole through microtubules. A potential seclusion artefact has been ruled out, as fibres severed inside spindles behave identically despite being surrounded by the spindle matrix. Our data suggest that kinetochore microtubules constantly treadmill during anaphase in insect cells. Treadmilling is an intrinsic property of microtubules in the kinetochore fibre, independent of the context and attachment of the spindle. The machinery that depolymerizes minus ends of kinetochore microtubules is functional in a non-spindle context. Attachment to the pole, however, is required to cause net kinetochore fibre shortening to generate polewards forces during anaphase.
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Affiliation(s)
- Wei Chen
- Department of Zoology and the Centre for Gene Research and Biotechnology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA
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41
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Lou Y, Yao J, Zereshki A, Dou Z, Ahmed K, Wang H, Hu J, Wang Y, Yao X. NEK2A interacts with MAD1 and possibly functions as a novel integrator of the spindle checkpoint signaling. J Biol Chem 2004; 279:20049-57. [PMID: 14978040 DOI: 10.1074/jbc.m314205200] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chromosome segregation in mitosis is orchestrated by protein kinase signaling cascades. A biochemical cascade named spindle checkpoint ensures the spatial and temporal order of chromosome segregation during mitosis. Here we report that spindle checkpoint protein MAD1 interacts with NEK2A, a human orthologue of the Aspergillus nidulans NIMA kinase. MAD1 interacts with NEK2A in vitro and in vivo via a leucine zipper-containing domain located at the C terminus of MAD1. Like MAD1, NEK2A is localized to HeLa cell kinetochore of mitotic cells. Elimination of NEK2A by small interfering RNA does not arrest cells in mitosis but causes aberrant premature chromosome segregation. NEK2A is required for MAD2 but not MAD1, BUB1, and HEC1 to associate with kinetochores. These NEK2A-eliminated or -suppressed cells display a chromosome bridge phenotype with sister chromatid inter-connected. Moreover, loss of NEK2A impairs mitotic checkpoint signaling in response to spindle damage by nocodazole, which affected mitotic escape and led to generation of cells with multiple nuclei. Our data demonstrate that NEK2A is a kinetochore-associated protein kinase essential for faithful chromosome segregation. We hypothesize that NEK2A links MAD2 molecular dynamics to spindle checkpoint signaling.
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Affiliation(s)
- Yang Lou
- School of Life Sciences, University of Science & Technology of China, Hefei 230027, China
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42
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Abstract
The movements of eukaryotic cell division depend upon the conversion of chemical energy into mechanical work, which in turn involves the actions of motor proteins, molecular transducers that generate force and motion relative cytoskeletal elements. In animal cells, microtubule-based motor proteins of the mitotic apparatus are involved in segregating chromosomes and perhaps in organizing the mitotic apparatus itself, while microfilament-based motors in the contractile ring generate the forces that separate daughter cells during cytokinesis. This review outlines recent advances in our understanding of the roles of molecular motors in mitosis and cytokinesis.
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Affiliation(s)
- K E Sawin
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA 94143, USA
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43
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Gehmlich K, Haren L, Merdes A. Cyclin B degradation leads to NuMA release from dynein/dynactin and from spindle poles. EMBO Rep 2004; 5:97-103. [PMID: 14710193 PMCID: PMC1298957 DOI: 10.1038/sj.embor.7400046] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2003] [Revised: 09/08/2003] [Accepted: 10/10/2003] [Indexed: 11/09/2022] Open
Abstract
The protein NuMA localizes to mitotic spindle poles where it contributes to the organization of microtubules. In this study, we demonstrate that NuMA loses its stable association with the spindle poles after anaphase onset. Using extracts from Xenopus laevis eggs, we show that NuMA is dephosphorylated in anaphase and released from dynein and dynactin. In the presence of a nondegradable form of cyclin B (Delta90), NuMA remains phosphorylated and associated with dynein and dynactin, and remains localized to stable spindle poles that fail to disassemble at the end of mitosis. Inhibition of NuMA or dynein allows completion of mitosis, despite inducing spindle pole abnormalities. We propose that NuMA functions early in mitosis during the formation of spindle poles, but is released from the spindle after anaphase, to allow spindle disassembly and remodelling of the microtubule network.
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Affiliation(s)
- Katja Gehmlich
- Wellcome Trust Centre for Cell Biology, ICMB, University of Edinburgh, Edinburgh EH9 3JR, UK
- Present address: Department of Cell Biology, University of Potsdam, Lennéstr. 7a, 14471 Potsdam, Germany
| | - Laurence Haren
- Wellcome Trust Centre for Cell Biology, ICMB, University of Edinburgh, Edinburgh EH9 3JR, UK
- Present address: CNRS-Pierre Fabre, 205 route de Narbonne, 31077 Toulouse, France
| | - Andreas Merdes
- Wellcome Trust Centre for Cell Biology, ICMB, University of Edinburgh, Edinburgh EH9 3JR, UK
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44
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Pearson CG, Maddox PS, Zarzar TR, Salmon ED, Bloom K. Yeast kinetochores do not stabilize Stu2p-dependent spindle microtubule dynamics. Mol Biol Cell 2003; 14:4181-95. [PMID: 14517328 PMCID: PMC207010 DOI: 10.1091/mbc.e03-03-0180] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The interaction of kinetochores with dynamic microtubules during mitosis is essential for proper centromere motility, congression to the metaphase plate, and subsequent anaphase chromosome segregation. Budding yeast has been critical in the discovery of proteins necessary for this interaction. However, the molecular mechanism for microtubule-kinetochore interactions remains poorly understood. Using live cell imaging and mutations affecting microtubule binding proteins and kinetochore function, we identify a regulatory mechanism for spindle microtubule dynamics involving Stu2p and the core kinetochore component, Ndc10p. Depleting cells of the microtubule binding protein Stu2p reduces kinetochore microtubule dynamics. Centromeres remain under tension but lack motility. Thus, normal microtubule dynamics are not required to maintain tension at the centromere. Loss of the kinetochore (ndc10-1, ndc10-2, and ctf13-30) does not drastically affect spindle microtubule turnover, indicating that Stu2p, not the kinetochore, is the foremost governor of microtubule dynamics. Disruption of kinetochore function with ndc10-1 does not affect the decrease in microtubule turnover in stu2 mutants, suggesting that the kinetochore is not required for microtubule stabilization. Remarkably, a partial kinetochore defect (ndc10-2) suppresses the decreased spindle microtubule turnover in the absence of Stu2p. These results indicate that Stu2p and Ndc10p differentially function in controlling kinetochore microtubule dynamics necessary for centromere movements.
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Affiliation(s)
- Chad G Pearson
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280, USA.
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45
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Silverman-Gavrila RV, Forer A. Myosin localization during meiosis I of crane-fly spermatocytes gives indications about its role in division. CELL MOTILITY AND THE CYTOSKELETON 2003; 55:97-113. [PMID: 12740871 DOI: 10.1002/cm.10112] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We showed previously that in crane-fly spermatocytes myosin is required for tubulin flux [Silverman-Gavrila and Forer, 2000a: J Cell Sci 113:597-609], and for normal anaphase chromosome movement and contractile ring contraction [Silverman-Gavrila and Forer, 2001: Cell Motil Cytoskeleton 50:180-197]. Neither the identity nor the distribution of myosin(s) were known. In the present work, we used immunofluorescence and confocal microscopy to study myosin during meiosis-I of crane-fly spermatocytes compared to tubulin, actin, and skeletor, a spindle matrix protein, in order to further understand how myosin might function during cell division. Antibodies to myosin II regulatory light chain and myosin II heavy chain gave similar staining patterns, both dependent on stage: myosin is associated with nuclei, asters, centrosomes, chromosomes, spindle microtubules, midbody microtubules, and contractile rings. Myosin and actin colocalization along kinetochore fibers from prometaphase to anaphase are consistent with suggestions that acto-myosin forces in these stages propel kinetochore fibres poleward and trigger tubulin flux in kinetochore fibres, contributing in this way to poleward chromosome movement. Myosin and actin colocalization at the cell equator in cytokinesis, similar to studies in other cells [e.g., Fujiwara and Pollard, 1978: J Cell Biol 77:182-195], supports a role of actin-myosin interactions in contractile ring function. Myosin and skeletor colocalization in prometaphase spindles is consistent with a role of these proteins in spindle formation. After microtubules or actin were disrupted, myosin remained in spindles and contractile rings, suggesting that the presence of myosin in these structures does not require the continued presence of microtubules or actin. BDM (2,3 butanedione, 2 monoxime) treatment that inhibits chromosome movement and cytokinesis also altered myosin distributions in anaphase spindles and contractile rings, consistent with the physiological effects, suggesting also that myosin needs to be active in order to be properly distributed.
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46
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Sprague BL, Pearson CG, Maddox PS, Bloom KS, Salmon ED, Odde DJ. Mechanisms of microtubule-based kinetochore positioning in the yeast metaphase spindle. Biophys J 2003; 84:3529-46. [PMID: 12770865 PMCID: PMC1302941 DOI: 10.1016/s0006-3495(03)75087-5] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
It has been hypothesized that spatial gradients in kMT dynamic instability facilitate mitotic spindle formation and chromosome movement. To test this hypothesis requires the analysis of kMT dynamics, which have not been resolved at the single kMT level in living cells. The budding yeast spindle offers an attractive system in which to study kMT dynamics because, in contrast to animal cells, there is only one kMT per kinetochore. To visualize metaphase kMT plus-end dynamics in yeast, a strain containing a green fluorescent protein fusion to the kinetochore protein, Cse4, was imaged by fluorescence microscopy. Although individual kinetochores were not resolvable, we found that models of kMT dynamics could be evaluated by simulating the stochastic kMT dynamics and then simulating the fluorescence imaging of kMT plus-end-associated kinetochores. Statistical comparison of model-predicted images to experimentally observed images demonstrated that a pure dynamic instability model for kMT dynamics in the yeast metaphase spindle was unacceptable. However, when a temporally stable spatial gradient in the catastrophe or rescue frequency was added to the model, there was reasonable agreement between the model and the experiment. These results provide the first evidence of temporally stable spatial gradients of kMT catastrophe and/or rescue frequency in living cells.
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Affiliation(s)
- Brian L Sprague
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
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47
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Putkey FR, Cramer T, Morphew MK, Silk AD, Johnson RS, McIntosh JR, Cleveland DW. Unstable kinetochore-microtubule capture and chromosomal instability following deletion of CENP-E. Dev Cell 2002; 3:351-65. [PMID: 12361599 DOI: 10.1016/s1534-5807(02)00255-1] [Citation(s) in RCA: 225] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A selective disruption of the mouse CENP-E gene was generated to test how this kinetochore-associated, kinesin-like protein contributes to chromosome segregation. The removal of CENP-E in primary cells produced spindles in which some metaphase chromosomes lay juxtaposed to a spindle pole, despite the absence of microtubules stably bound to their kinetochores. Most CENP-E-free chromosomes moved to the spindle equator, but their kinetochores bound only half the normal number of microtubules. Deletion of CENP-E in embryos led to early developmental arrest. Selective deletion of CENP-E in liver revealed that tissue regeneration after chemical damage was accompanied by aberrant mitoses marked by chromosome missegregation. CENP-E is thus essential for the maintenance of chromosomal stability through efficient stabilization of microtubule capture at kinetochores.
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Affiliation(s)
- Frances R Putkey
- Ludwig Institute for Cancer Research, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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Gagliardi LJ. Electrostatic force in prometaphase, metaphase, and anaphase-A chromosome motions. ACTA ACUST UNITED AC 2002; 66:011901. [PMID: 12241378 DOI: 10.1103/physreve.66.011901] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2001] [Indexed: 11/07/2022]
Abstract
Primitive cells had to divide using very few biological mechanisms. This work proposes physicochemical mechanisms, based upon nanoscale electrostatics, which explain and unify the motions of chromosomes during prometaphase, metaphase, and anaphase A. In the cytoplasmic medium that exists in biological cells, electrostatic fields are subject to strong attenuation by ionic screening, and therefore decrease rapidly over a distance equal to several Debye lengths. However, the presence of microtubules within cells completely changes the situation. Microtubule dimer subunits are electric dipolar structures, and can act as intermediaries that extend the reach of the electrostatic interaction over cellular distances. Experimental studies have shown that intracellular pH rises to a peak at mitosis, then decreases through cytokinesis. This result, in conjunction with the electric dipole nature of microtubule subunits, is sufficient to explain the dynamics of the above mitotic motions, including their timing and sequencing. The physicochemical mechanisms utilized by primitive eukaryotic cells could provide important clues regarding our understanding of cell division in modern eukaryotic cells.
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Compton DA. In vitro approaches for the study of molecular motors in aster formation. Methods Cell Biol 2002; 67:225-39. [PMID: 11550471 DOI: 10.1016/s0091-679x(01)67016-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Affiliation(s)
- D A Compton
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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LaFountain JR, Oldenbourg R, Cole RW, Rieder CL. Microtubule flux mediates poleward motion of acentric chromosome fragments during meiosis in insect spermatocytes. Mol Biol Cell 2001; 12:4054-65. [PMID: 11739800 PMCID: PMC60775 DOI: 10.1091/mbc.12.12.4054] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We applied a combination of laser microsurgery and quantitative polarization microscopy to study kinetochore-independent forces that act on chromosome arms during meiosis in crane fly spermatocytes. When chromosome arms located within one of the half-spindles during prometa- or metaphase were cut with the laser, the acentric fragments (lacking kinetochores) that were generated moved poleward with velocities similar to those of anaphase chromosomes (approximately 0.5 microm/min). To determine the mechanism underlying this poleward motion of detached arms, we treated spermatocytes with the microtubule-stabilizing drug taxol. Spindles in taxol-treated cells were noticeably short, yet with polarized light, the distribution and densities of microtubules in domains where fragment movement occurred were not different from those in control cells. When acentric fragments were generated in taxol-treated spermatocytes, 22 of 24 fragments failed to exhibit poleward motion, and the two that did move had velocities attenuated by 80% (to approximately 0.1 microm/min). In these cells, taxol did not inhibit the disjunction of chromosomes nor prevent their poleward segregation during anaphase, but the velocity of anaphase was also decreased 80% (approximately 0.1 microm/min) relative to untreated controls. Together, these data reveal that microtubule flux exerts pole-directed forces on chromosome arms during meiosis in crane fly spermatocytes and strongly suggest that the mechanism underlying microtubule flux also is used in the anaphase motion of kinetochores in these cells.
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Affiliation(s)
- J R LaFountain
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA.
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