1
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do Rosário CF, Zhang Y, Stadnicki J, Ross JL, Wadsworth P. Lateral and longitudinal compaction of PRC1 overlap zones drives stabilization of interzonal microtubules. Mol Biol Cell 2023; 34:ar100. [PMID: 37467037 PMCID: PMC10551706 DOI: 10.1091/mbc.e23-02-0049] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 06/20/2023] [Accepted: 07/04/2023] [Indexed: 07/20/2023] Open
Abstract
During anaphase, antiparallel-overlapping midzone microtubules elongate and form bundles, contributing to chromosome segregation and the location of contractile ring formation. Midzone microtubules are dynamic in early but not late anaphase; however, the kinetics and mechanisms of stabilization are incompletely understood. Using photoactivation of cells expressing PA-EGFP-α-tubulin we find that immediately after anaphase onset, a single highly dynamic population of midzone microtubules is present; as anaphase progresses, both dynamic and stable populations of midzone microtubules coexist. By mid-cytokinesis, only static, non-dynamic microtubules are detected. The velocity of microtubule sliding also decreases as anaphase progresses, becoming undetectable by late anaphase. Following depletion of PRC1, midzone microtubules remain highly dynamic in anaphase and fail to form static arrays in telophase despite furrowing. Cells depleted of Kif4a contain elongated PRC1 overlap zones and fail to form static arrays in telophase. Cells blocked in cytokinesis form short PRC1 overlap zones that do not coalesce laterally; these cells also fail to form static arrays in telophase. Together, our results demonstrate that dynamic turnover and sliding of midzone microtubules is gradually reduced during anaphase and that the final transition to a static array in telophase requires both lateral and longitudinal compaction of PRC1 containing overlap zones.
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Affiliation(s)
- Carline Fermino do Rosário
- Department of Biology, University of Massachusetts Amherst, Amherst MA 01003
- Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst MA 01003
| | - Ying Zhang
- Department of Biology, University of Massachusetts Amherst, Amherst MA 01003
| | - Jennifer Stadnicki
- Department of Biology, University of Massachusetts Amherst, Amherst MA 01003
- Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst MA 01003
| | | | - Patricia Wadsworth
- Department of Biology, University of Massachusetts Amherst, Amherst MA 01003
- Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst MA 01003
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2
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Vukušić K, Tolić IM. Anaphase B: Long-standing models meet new concepts. Semin Cell Dev Biol 2021; 117:127-139. [PMID: 33849764 PMCID: PMC8406420 DOI: 10.1016/j.semcdb.2021.03.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 03/26/2021] [Accepted: 03/28/2021] [Indexed: 12/16/2022]
Abstract
Mitotic cell divisions ensure stable transmission of genetic information from a mother to daughter cells in a series of generations. To ensure this crucial task is accomplished, the cell forms a bipolar structure called the mitotic spindle that divides sister chromatids to the opposite sides of the dividing mother cell. After successful establishment of stable attachments of microtubules to chromosomes and inspection of connections between them, at the heart of mitosis, the cell starts the process of segregation. This spectacular moment in the life of a cell is termed anaphase, and it involves two distinct processes: depolymerization of microtubules bound to chromosomes, which is also known as anaphase A, and elongation of the spindle or anaphase B. Both processes ensure physical separation of disjointed sister chromatids. In this chapter, we review the mechanisms of anaphase B spindle elongation primarily in mammalian systems, combining different pioneering ideas and concepts with more recent findings that shed new light on the force generation and regulation of biochemical modules operating during spindle elongation. Finally, we present a comprehensive model of spindle elongation that includes structural, biophysical, and molecular aspects of anaphase B.
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Affiliation(s)
- Kruno Vukušić
- 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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3
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Vukušić K, Ponjavić I, Buđa R, Risteski P, Tolić IM. Microtubule-sliding modules based on kinesins EG5 and PRC1-dependent KIF4A drive human spindle elongation. Dev Cell 2021; 56:1253-1267.e10. [PMID: 33910056 PMCID: PMC8098747 DOI: 10.1016/j.devcel.2021.04.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 01/03/2021] [Accepted: 04/05/2021] [Indexed: 12/13/2022]
Abstract
Proper chromosome segregation into two future daughter cells requires the mitotic spindle to elongate in anaphase. However, although some candidate proteins are implicated in this process, the molecular mechanism that drives spindle elongation in human cells is unknown. Using combined depletion and inactivation assays together with CRISPR technology to explore redundancy between multiple targets, we discovered that the force-generating mechanism of spindle elongation consists of EG5/kinesin-5 together with the PRC1-dependent motor KIF4A/kinesin-4, with contribution from kinesin-6 and kinesin-8. Disruption of EG5 and KIF4A leads to total failure of chromosome segregation due to blocked spindle elongation, despite poleward chromosome motion. Tubulin photoactivation, stimulated emission depletion (STED), and expansion microscopy show that perturbation of both proteins impairs midzone microtubule sliding without affecting microtubule stability. Thus, two mechanistically distinct sliding modules, one based on a self-sustained and the other on a crosslinker-assisted motor, power the mechanism that drives spindle elongation in human cells.
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Affiliation(s)
- Kruno Vukušić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Ivana Ponjavić
- 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
| | - Patrik Risteski
- 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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4
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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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5
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Barbosa DJ, Teixeira V, Duro J, Carvalho AX, Gassmann R. Dynein-dynactin segregate meiotic chromosomes in C. elegans spermatocytes. Development 2021; 148:dev.197780. [PMID: 33462114 DOI: 10.1242/dev.197780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 01/05/2021] [Indexed: 11/20/2022]
Abstract
The microtubule motor cytoplasmic dynein 1 (dynein) and its essential activator dynactin have conserved roles in spindle assembly and positioning during female meiosis and mitosis, but their contribution to male meiosis remains poorly understood. Here, we characterize the G33S mutation in the C. elegans dynactin subunit DNC-1, which corresponds to G59S in human p150Glued that causes motor neuron disease. In spermatocytes, dnc-1(G33S) delays spindle assembly and penetrantly inhibits anaphase spindle elongation in meiosis I, which prevents the segregation of homologous chromosomes. By contrast, chromosomes segregate without errors in the early dnc-1(G33S) embryo. Deletion of the DNC-1 N-terminus shows that defective meiosis in dnc-1(G33S) spermatocytes is not due to the inability of DNC-1 to interact with microtubules. Instead, our results suggest that the DNC-1(G33S) protein, which is aggregation prone in vitro, is less stable in spermatocytes than the early embryo, resulting in different phenotypic severity in the two dividing tissues. Thus, the dnc-1(G33S) mutant reveals that dynein-dynactin drive meiotic chromosome segregation in spermatocytes and illustrates that the extent to which protein misfolding leads to loss of function can vary significantly between cell types.
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Affiliation(s)
- Daniel J Barbosa
- Instituto de Investigação e Inovação em Saúde - i3S, Universidade do Porto, 4200-135 Porto, Portugal
| | - Vanessa Teixeira
- Instituto de Investigação e Inovação em Saúde - i3S, Universidade do Porto, 4200-135 Porto, Portugal
| | - Joana Duro
- Instituto de Investigação e Inovação em Saúde - i3S, Universidade do Porto, 4200-135 Porto, Portugal
| | - Ana X Carvalho
- Instituto de Investigação e Inovação em Saúde - i3S, Universidade do Porto, 4200-135 Porto, Portugal
| | - Reto Gassmann
- Instituto de Investigação e Inovação em Saúde - i3S, Universidade do Porto, 4200-135 Porto, Portugal
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6
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So C, Seres KB, Steyer AM, Mönnich E, Clift D, Pejkovska A, Möbius W, Schuh M. A liquid-like spindle domain promotes acentrosomal spindle assembly in mammalian oocytes. Science 2020; 364:364/6447/eaat9557. [PMID: 31249032 DOI: 10.1126/science.aat9557] [Citation(s) in RCA: 100] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 05/02/2019] [Indexed: 12/22/2022]
Abstract
Mammalian oocytes segregate chromosomes with a microtubule spindle that lacks centrosomes, but the mechanisms by which acentrosomal spindles are organized and function are largely unclear. In this study, we identify a conserved subcellular structure in mammalian oocytes that forms by phase separation. This structure, which we term the liquid-like meiotic spindle domain (LISD), permeates the spindle poles and forms dynamic protrusions that extend well beyond the spindle. The LISD selectively concentrates multiple microtubule regulatory factors and allows them to diffuse rapidly within the spindle volume. Disruption of the LISD via different means disperses these factors and leads to severe spindle assembly defects. Our data suggest a model whereby the LISD promotes meiotic spindle assembly by serving as a reservoir that sequesters and mobilizes microtubule regulatory factors in proximity to spindle microtubules.
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Affiliation(s)
- Chun So
- Department of Meiosis, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - K Bianka Seres
- Department of Meiosis, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.,Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.,Bourn Hall Clinic, Cambridge CB23 2TN, UK
| | - Anna M Steyer
- Electron Microscopy Core Unit, Department of Neurogenetics, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany.,Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37073 Göttingen, Germany
| | - Eike Mönnich
- Department of Meiosis, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Dean Clift
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Anastasija Pejkovska
- Department of Meiosis, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Wiebke Möbius
- Electron Microscopy Core Unit, Department of Neurogenetics, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany.,Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37073 Göttingen, Germany
| | - Melina Schuh
- Department of Meiosis, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany. .,Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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7
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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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8
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Tolić IM. Mitotic spindle: kinetochore fibers hold on tight to interpolar bundles. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2018; 47:191-203. [PMID: 28725997 PMCID: PMC5845649 DOI: 10.1007/s00249-017-1244-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 06/30/2017] [Accepted: 07/02/2017] [Indexed: 12/24/2022]
Abstract
When a cell starts to divide, it forms a spindle, a micro-machine made of microtubules, which separates the duplicated chromosomes. The attachment of microtubules to chromosomes is mediated by kinetochores, protein complexes on the chromosome. Spindle microtubules can be divided into three major classes: kinetochore microtubules, which form k-fibers ending at the kinetochore; interpolar microtubules, which extend from the opposite sides of the spindle and interact in the middle; and astral microtubules, which extend towards the cell cortex. Recent work in human cells has shown a close relationship between interpolar and kinetochore microtubules, where interpolar bundles are attached laterally to kinetochore fibers almost all along their length, acting as a bridge between sister k-fibers. Most of the interpolar bundles are attached to a pair of sister kinetochore fibers and vice versa. Thus, the spindle is made of modules consisting of a pair of sister kinetochore fibers and a bundle of interpolar microtubules that connects them. These interpolar bundles, termed bridging fibers, balance the forces acting at kinetochores and support the rounded shape of the spindle during metaphase. This review discusses the structure, function, and formation of kinetochore fibers and interpolar bundles, with an emphasis on how they interact. Their connections have an impact on the force balance in the spindle and on chromosome movement during mitosis because the forces in interpolar bundles are transmitted to kinetochore fibers and hence to kinetochores through these connections.
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Affiliation(s)
- Iva M Tolić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000, Zagreb, Croatia.
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9
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Vázquez-Diez C, FitzHarris G. Causes and consequences of chromosome segregation error in preimplantation embryos. Reproduction 2018; 155:R63-R76. [DOI: 10.1530/rep-17-0569] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 10/19/2017] [Accepted: 11/06/2017] [Indexed: 01/04/2023]
Abstract
Errors in chromosome segregation are common during the mitotic divisions of preimplantation development in mammalian embryos, giving rise to so-called ‘mosaic’ embryos possessing a mixture of euploid and aneuploid cells. Mosaicism is widely considered to be detrimental to embryo quality and is frequently used as criteria to select embryos for transfer in human fertility clinics. However, despite the clear clinical importance, the underlying defects in cell division that result in mosaic aneuploidy remain elusive. In this review, we summarise recent findings from clinical and animal model studies that provide new insights into the fundamental mechanisms of chromosome segregation in the highly unusual cellular environment of early preimplantation development and consider recent clues as to why errors should commonly occur in this setting. We furthermore discuss recent evidence suggesting that mosaicism is not an irrevocable barrier to a healthy pregnancy. Understanding the causes and biological impacts of mosaic aneuploidy will be pivotal in the development and fine-tuning of clinical embryo selection methods.
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10
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Su KC, Barry Z, Schweizer N, Maiato H, Bathe M, Cheeseman IM. A Regulatory Switch Alters Chromosome Motions at the Metaphase-to-Anaphase Transition. Cell Rep 2017; 17:1728-1738. [PMID: 27829144 PMCID: PMC5130098 DOI: 10.1016/j.celrep.2016.10.046] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 09/09/2016] [Accepted: 10/13/2016] [Indexed: 12/19/2022] Open
Abstract
To achieve chromosome segregation during mitosis, sister chromatids must undergo a dramatic change in their behavior to switch from balanced oscillations at the metaphase plate to directed poleward motion during anaphase. However, the factors that alter chromosome behavior at the metaphase-to-anaphase transition remain incompletely understood. Here, we perform time-lapse imaging to analyze anaphase chromosome dynamics in human cells. Using multiple directed biochemical, genetic, and physical perturbations, our results demonstrate that differences in the global phosphorylation states between metaphase and anaphase are the major determinant of chromosome motion dynamics. Indeed, causing a mitotic phosphorylation state to persist into anaphase produces dramatic metaphase-like oscillations. These induced oscillations depend on both kinetochore-derived and polar ejection forces that oppose poleward motion. Thus, our analysis of anaphase chromosome motion reveals that dephosphorylation of multiple mitotic substrates is required to suppress metaphase chromosome oscillatory motions and achieve directed poleward motion for successful chromosome segregation.
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Affiliation(s)
- Kuan-Chung Su
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA
| | - Zachary Barry
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Nina Schweizer
- Chromosome Instability and Dynamics Laboratory, Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal; i3S - Instituto de Investigação e Inovação em Saúdem, Universidade do Porto, 4200-135 Porto, Portugal
| | - Helder Maiato
- Chromosome Instability and Dynamics Laboratory, Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal; i3S - Instituto de Investigação e Inovação em Saúdem, Universidade do Porto, 4200-135 Porto, Portugal; Cell Division Unit, Department of Experimental Biology, Faculdade de Medicina, Universidade do Porto, 4200-135 Porto, Portugal
| | - Mark Bathe
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Iain McPherson Cheeseman
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
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11
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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: 69] [Impact Index Per Article: 9.9] [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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12
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Affiliation(s)
- Helder Maiato
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
- Instituto de Investigação e Inovação em Saúde-i3S, Universidade do Porto, Porto, Portugal
- Department of Biomedicine, Faculdade de Medicina, Universidade do Porto, Porto, Portugal
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, USA
| | - Cristina Ferrás
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- Instituto de Investigação e Inovação em Saúde-i3S, Universidade do Porto, Porto, Portugal
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13
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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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14
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Scholey JM, Civelekoglu-Scholey G, Brust-Mascher I. Anaphase B. BIOLOGY 2016; 5:biology5040051. [PMID: 27941648 PMCID: PMC5192431 DOI: 10.3390/biology5040051] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 11/30/2016] [Accepted: 12/01/2016] [Indexed: 11/16/2022]
Abstract
Anaphase B spindle elongation is characterized by the sliding apart of overlapping antiparallel interpolar (ip) microtubules (MTs) as the two opposite spindle poles separate, pulling along disjoined sister chromatids, thereby contributing to chromosome segregation and the propagation of all cellular life. The major biochemical “modules” that cooperate to mediate pole–pole separation include: (i) midzone pushing or (ii) braking by MT crosslinkers, such as kinesin-5 motors, which facilitate or restrict the outward sliding of antiparallel interpolar MTs (ipMTs); (iii) cortical pulling by disassembling astral MTs (aMTs) and/or dynein motors that pull aMTs outwards; (iv) ipMT plus end dynamics, notably net polymerization; and (v) ipMT minus end depolymerization manifest as poleward flux. The differential combination of these modules in different cell types produces diversity in the anaphase B mechanism. Combinations of antagonist modules can create a force balance that maintains the dynamic pre-anaphase B spindle at constant length. Tipping such a force balance at anaphase B onset can initiate and control the rate of spindle elongation. The activities of the basic motor filament components of the anaphase B machinery are controlled by a network of non-motor MT-associated proteins (MAPs), for example the key MT cross-linker, Ase1p/PRC1, and various cell-cycle kinases, phosphatases, and proteases. This review focuses on the molecular mechanisms of anaphase B spindle elongation in eukaryotic cells and briefly mentions bacterial DNA segregation systems that operate by spindle elongation.
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Affiliation(s)
- Jonathan M Scholey
- Department of Molecular and Cell Biology, University of California, Davis, CA 95616, USA.
| | | | - Ingrid Brust-Mascher
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
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15
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Nannas NJ, Higgins DM, Dawe RK. Anaphase asymmetry and dynamic repositioning of the division plane during maize meiosis. J Cell Sci 2016; 129:4014-4024. [PMID: 27609836 DOI: 10.1242/jcs.194860] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 09/05/2016] [Indexed: 01/12/2023] Open
Abstract
The success of an organism is contingent upon its ability to transmit genetic material through meiotic cell division. In plant meiosis I, the process begins in a large spherical cell without physical cues to guide the process. Yet, two microtubule-based structures, the spindle and phragmoplast, divide the chromosomes and the cell with extraordinary accuracy. Using a live-cell system and fluorescently labeled spindles and chromosomes, we found that the process self- corrects as meiosis proceeds. Metaphase spindles frequently initiate division off-center, and in these cases anaphase progression is asymmetric with the two masses of chromosomes traveling unequal distances on the spindle. The asymmetry is compensatory, such that the chromosomes on the side of the spindle that is farthest from the cell cortex travel a longer distance at a faster rate. The phragmoplast forms at an equidistant point between the telophase nuclei rather than at the original spindle mid-zone. This asymmetry in chromosome movement implies a structural difference between the two halves of a bipolar spindle and could allow meiotic cells to dynamically adapt to errors in metaphase and accurately divide the cell volume.
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Affiliation(s)
- Natalie J Nannas
- Department of Plant Biology, University of Georgia, Athens, GA 30605, USA
| | - David M Higgins
- Department of Plant Biology, University of Georgia, Athens, GA 30605, USA
| | - R Kelly Dawe
- Department of Plant Biology, University of Georgia, Athens, GA 30605, USA .,Department of Genetics, University of Georgia, Athens, GA 30605, USA
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16
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Affiliation(s)
- Nenad Pavin
- Department of Physics, Faculty of Science, University of Zagreb, 10000 Zagreb, Croatia;
| | - Iva M. Tolić
- Division of Molecular Biology, Ruđer Bošković Institute, 10000 Zagreb, Croatia;
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17
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Maiato H. Miguel Mota (1922-2016)-the kinetochore engine(er). Chromosome Res 2016; 24:281-3. [PMID: 27106904 DOI: 10.1007/s10577-016-9523-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Accepted: 04/11/2016] [Indexed: 11/25/2022]
Affiliation(s)
- Helder Maiato
- Chromosome Instability & Dynamics Lab., IBMC - Instituto de Biologia Molecular e Celular, i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.
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18
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Gerhold AR, Ryan J, Vallée-Trudeau JN, Dorn JF, Labbé JC, Maddox PS. Investigating the regulation of stem and progenitor cell mitotic progression by in situ imaging. Curr Biol 2015; 25:1123-34. [PMID: 25819563 DOI: 10.1016/j.cub.2015.02.054] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 02/15/2015] [Accepted: 02/19/2015] [Indexed: 10/23/2022]
Abstract
Genome stability relies upon efficacious chromosome congression and regulation by the spindle assembly checkpoint (SAC). The study of these fundamental mitotic processes in adult stem and progenitor cells has been limited by the technical challenge of imaging mitosis in these cells in situ. Notably, how broader physiological changes, such as dietary intake or age, affect mitotic progression in stem and/or progenitor cells is largely unknown. Using in situ imaging of C. elegans adult germlines, we describe the mitotic parameters of an adult stem and progenitor cell population in an intact animal. We find that SAC regulation in germline stem and progenitor cells is distinct from that found in early embryonic divisions and is more similar to that of classical tissue culture models. We further show that changes in organismal physiology affect mitotic progression in germline stem and progenitor cells. Reducing dietary intake produces a checkpoint-dependent delay in anaphase onset, and inducing dietary restriction when the checkpoint is impaired increases the incidence of segregation errors in mitotic and meiotic cells. Similarly, developmental aging of the germline stem and progenitor cell population correlates with a decline in the rate of several mitotic processes. These results provide the first in vivo validation of models for SAC regulation developed in tissue culture systems and demonstrate that several fundamental features of mitotic progression in adult stem and progenitor cells are highly sensitive to organismal physiological changes.
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Affiliation(s)
- Abigail R Gerhold
- Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Joël Ryan
- Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Julie-Nathalie Vallée-Trudeau
- Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Jonas F Dorn
- Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Jean-Claude Labbé
- Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada; Department of Pathology and Cell Biology, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada.
| | - Paul S Maddox
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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19
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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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20
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Raaijmakers JA, Medema RH. Function and regulation of dynein in mitotic chromosome segregation. Chromosoma 2014; 123:407-22. [PMID: 24871939 DOI: 10.1007/s00412-014-0468-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 05/08/2014] [Accepted: 05/09/2014] [Indexed: 12/23/2022]
Abstract
Cytoplasmic dynein is a large minus-end-directed microtubule motor complex, involved in many different cellular processes including intracellular trafficking, organelle positioning, and microtubule organization. Furthermore, dynein plays essential roles during cell division where it is implicated in multiple processes including centrosome separation, chromosome movements, spindle organization, spindle positioning, and mitotic checkpoint silencing. How is a single motor able to fulfill this large array of functions and how are these activities temporally and spatially regulated? The answer lies in the unique composition of the dynein motor and in the interactions it makes with multiple regulatory proteins that define the time and place where dynein becomes active. Here, we will focus on the different mitotic processes that dynein is involved in, and how its regulatory proteins act to support dynein. Although dynein is highly conserved amongst eukaryotes (with the exception of plants), there is significant variability in the cellular processes that depend on dynein in different species. In this review, we concentrate on the functions of cytoplasmic dynein in mammals but will also refer to data obtained in other model organisms that have contributed to our understanding of dynein function in higher eukaryotes.
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Affiliation(s)
- J A Raaijmakers
- Department of Cell Biology and Cancer Genomics Center, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam, Netherlands
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21
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Shomper M, Lappa C, FitzHarris G. Kinetochore microtubule establishment is defective in oocytes from aged mice. Cell Cycle 2014; 13:1171-9. [PMID: 24553117 DOI: 10.4161/cc.28046] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Errors in chromosome segregation in mammalian oocytes increase in number with advancing maternal age, and are a major cause of pregnancy loss. Why chromosome segregation errors are more common in oocytes from older females remains poorly understood. In mitosis, accurate chromosome segregation is enabled by attachment of kinetochores to microtubules from appropriate spindle poles, and erroneous attachments increase the likelihood of mis-segregation. Whether attachment errors are responsible for age-related oocyte aneuploidy is unknown. Here we report that oocytes from naturally aged mice exhibit substantially increased chromosome misalignment, and fewer kinetochore pairs that make stable end-on attachments to the appropriate spindle poles compared with younger oocytes. The profile of mis-attachments exhibited is consistent with the types of chromosome segregation error observed in aged oocytes. Loss of chromosome cohesion, which is a feature of oocytes from older females, causes altered kinetochore geometry in meiosis-I. However, this has only a minor impact upon MT attachment, indicating that cohesion loss is not the primary cause of aneuploidy in meiosis-I. In meiosis-II, on the other hand, age-related cohesion loss plays a direct role in errors, since prematurely individualized sister chromatids misalign and misattach to spindle MTs. Thus, whereas cohesion loss leading to precocious sister chromatid separation is a direct cause of errors in meiosis-II, cohesion loss plays a more minor role in the etiology of aneuploidy in meiosis-I. Our data introduce altered MT-kinetochore interactions as a lesion that explains aneuploidy in meiosis-I in older females.
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Affiliation(s)
- Maria Shomper
- Cell and Developmental Biology; University College London; London, UK
| | - Christina Lappa
- Cell and Developmental Biology; University College London; London, UK
| | - Greg FitzHarris
- Cell and Developmental Biology; University College London; London, UK
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22
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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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23
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Howe K, FitzHarris G. Recent insights into spindle function in mammalian oocytes and early embryos. Biol Reprod 2013; 89:71. [PMID: 23966320 DOI: 10.1095/biolreprod.113.112151] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Errors in chromosome segregation in oocytes and early embryos lead to embryo aneuploidy, which contributes to early pregnancy loss. At the heart of chromosome segregation is the spindle, a dynamic biomechanical machine fashioned from microtubules, which is tasked with gathering and sorting chromosomes and dispatching them to the daughter cells at the time of cell division. Understanding the causes of segregation error in the oocyte and early embryo will undoubtedly hinge on a thorough understanding of the mechanism of spindle assembly and function in these highly specialized cellular environments. The recent advent of live imaging approaches to observe chromosome segregation in real-time in oocytes and embryos, paired with gene-silencing techniques and specific inhibition for assessing the function of a protein of interest, has led to a substantial advance in our understanding of chromosome segregation in early mammalian development. These studies have uncovered numerous mechanistic differences between oocytes, embryos, and traditional model systems. In addition, a flurry of recent studies using naturally aged mice as the model for human aging have begun to shed light on the increased levels of aneuploidy seen in embryos from older mothers. Here we review these recent developments and consider what has been learned about the causes of chromosome missegregation in early development.
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Affiliation(s)
- Katie Howe
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
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24
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Selective tracking of template DNA strands after induction of mitosis with unreplicated genomes (MUGs) in Drosophila S2 cells. Chromosome Res 2013; 21:329-37. [DOI: 10.1007/s10577-013-9354-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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25
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Hochegger H, Hégarat N, Pereira-Leal JB. Aurora at the pole and equator: overlapping functions of Aurora kinases in the mitotic spindle. Open Biol 2013; 3:120185. [PMID: 23516109 PMCID: PMC3718339 DOI: 10.1098/rsob.120185] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The correct assembly and timely disassembly of the mitotic spindle is crucial for the propagation of the genome during cell division. Aurora kinases play a central role in orchestrating bipolar spindle establishment, chromosome alignment and segregation. In most eukaryotes, ranging from amoebas to humans, Aurora activity appears to be required both at the spindle pole and the kinetochore, and these activities are often split between two different Aurora paralogues, termed Aurora A and B. Polar and equatorial functions of Aurora kinases have generally been considered separately, with Aurora A being mostly involved in centrosome dynamics, whereas Aurora B coordinates kinetochore attachment and cytokinesis. However, double inactivation of both Aurora A and B results in a dramatic synergy that abolishes chromosome segregation. This suggests that these two activities jointly coordinate mitotic progression. Accordingly, recent evidence suggests that Aurora A and B work together in both spindle assembly in metaphase and disassembly in anaphase. Here, we provide an outlook on these shared functions of the Auroras, discuss the evolution of this family of mitotic kinases and speculate why Aurora kinase activity may be required at both ends of the spindle microtubules.
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Affiliation(s)
- Helfrid Hochegger
- Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton, UK.
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26
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Ford JH. Protraction of anaphase B in lymphocyte mitosis with ageing: possible contribution to age-related cancer risk. Mutagenesis 2013; 28:307-14. [PMID: 23435012 DOI: 10.1093/mutage/get004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Ageing is associated with a reduction in the fidelity of cell division as shown by increases in trisomic and polyploid cells; however, to date, the underlying age-specific changes in cell division have not been identified. Understanding these specific changes in cell division could give insight into the aetiology some age-related illnesses, especially cancer. Using blood collected from 72 women aged 18-53 years, this study recorded the frequencies of cells in each of the stages of mitosis in synchronised lymphocyte cultures harvested at controlled temperature without microtubule inhibitors. Factor analysis identified four components that accounted for >67.5% of the variance in the data. The component we named 'Spindle elongation efficiency', which was primarily influenced by the time taken to complete anaphase B, showed a major change with age: women aged ≥36 showed a highly statistically significant protraction of anaphase B compared with those aged ≤35 (t = -2.74, df = 70, P = 0.006) and linear regression showed a logarithmic change in this component with age (R = 0.297, P = 0.011). This phosphorylation-dependent phase of the cycle is responsible for increasing the distance between the two sets of daughter chromosomes and in older subjects the daughter nuclei at telophase were often poorly separated. Inefficient spindle elongation with ageing probably results from decreased cellular energy. Insufficient force at anaphase B might fail to resolve merotelic kinetochore attachments such that lagging at anaphase would be uncorrected and lead to trisomy and polyploidy in daughter cells.
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Affiliation(s)
- Judith H Ford
- Centre for Rural Health and Community Development, University of South Australia, 101 Currie Street Adelaide, South Australia 5000, Australia.
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27
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Yamagata K, FitzHarris G. 4D imaging reveals a shift in chromosome segregation dynamics during mouse pre-implantation development. Cell Cycle 2012; 12:157-65. [PMID: 23255117 DOI: 10.4161/cc.23052] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cells of the early developing mammalian embryo frequently mis-segregate chromosomes during cell division, causing daughter cells to inherit an erroneous numbers of chromosomes. Why the embryo is so susceptible to errors is unknown, and the mechanisms that embryos employ to accomplish chromosome segregation are poorly understood. Chromosome segregation is performed by the spindle, a fusiform-shaped microtubule-based transient organelle. Here we present a detailed analysis of 4D fluorescence-confocal data sets of live embryos progressing from the one-cell embryo stage through to blastocyst in vitro, providing some of the first mechanistic insights into chromosome segregation in the mammalian embryo. We show that chromosome segregation occurs as a combined result of poleward chromosome motion (anaphase-A) and spindle elongation (anaphase-B), which occur simultaneously at the time of cell division. Unexpectedly, however, regulation of the two anaphase mechanisms changes significantly between the first and second embryonic mitoses. In one-cell embryos, the velocity of anaphase-A chromosome motion and the velocity and overall extent of anaphase-B spindle elongation are significantly constrained compared with later stages. As a result chromosomes are delivered close to the center of the forming two-cell stage blastomeres at the end of the first mitosis. In subsequent divisions, anaphase-B spindle elongation is faster and more extensive, resulting in the delivery of chromosomes to the distal plasma membrane of the newly forming blastomeres. Metaphase spindle length scales with cell size from the two-cell stage onwards, but is substantially shorter in the first mitosis than in the second mitosis, and the duration of mitosis-1 is substantially greater than subsequent divisions. Thus, there is a striking and unexpected shift in the approach to cell division between the first and second mitotic divisions, which likely reflects adaptations to the unique environment within the developing embryo.
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Affiliation(s)
- Kazuo Yamagata
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
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28
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Gay G, Courtheoux T, Reyes C, Tournier S, Gachet Y. A stochastic model of kinetochore-microtubule attachment accurately describes fission yeast chromosome segregation. ACTA ACUST UNITED AC 2012; 196:757-74. [PMID: 22412019 PMCID: PMC3308688 DOI: 10.1083/jcb.201107124] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In fission yeast, erroneous attachments of spindle microtubules to kinetochores are frequent in early mitosis. Most are corrected before anaphase onset by a mechanism involving the protein kinase Aurora B, which destabilizes kinetochore microtubules (ktMTs) in the absence of tension between sister chromatids. In this paper, we describe a minimal mathematical model of fission yeast chromosome segregation based on the stochastic attachment and detachment of ktMTs. The model accurately reproduces the timing of correct chromosome biorientation and segregation seen in fission yeast. Prevention of attachment defects requires both appropriate kinetochore orientation and an Aurora B-like activity. The model also reproduces abnormal chromosome segregation behavior (caused by, for example, inhibition of Aurora B). It predicts that, in metaphase, merotelic attachment is prevented by a kinetochore orientation effect and corrected by an Aurora B-like activity, whereas in anaphase, it is corrected through unbalanced forces applied to the kinetochore. These unbalanced forces are sufficient to prevent aneuploidy.
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Affiliation(s)
- Guillaume Gay
- Laboratoire de biologie cellulaire et moléculaire du contrôle de la proliferation, Université de Toulouse, F-31062 Toulouse, France
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29
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FitzHarris G. Anaphase B precedes anaphase A in the mouse egg. Curr Biol 2012; 22:437-44. [PMID: 22342753 DOI: 10.1016/j.cub.2012.01.041] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 01/14/2012] [Accepted: 01/20/2012] [Indexed: 11/29/2022]
Abstract
Segregation of chromosomes at the time of cell division is achieved by the microtubules and associated molecules of the spindle. Chromosomes attach to kinetochore microtubules (kMTs), which extend from the spindle pole region to kinetochores assembled upon centromeric DNA. In most animal cells studied, chromosome segregation occurs as a result of kMT shortening, which causes chromosomes to move toward the spindle poles (anaphase A). Anaphase A is typically followed by a spindle elongation that further separates the chromosomes (anaphase B). The experiments presented here provide the first detailed analysis of anaphase in a live vertebrate oocyte and show that chromosome segregation is initially driven by a significant spindle elongation (anaphase B), which is followed by a shortening of kMTs to fully segregate the chromosomes (anaphase A). Loss of tension across kMTs at anaphase onset produces a force imbalance, allowing the bipolar motor kinesin-5 to drive early anaphase B spindle elongation and chromosome segregation. Early anaphase B spindle elongation determines the extent of chromosome segregation and the size of the resulting cells. The vertebrate egg therefore employs a novel mode of anaphase wherein spindle elongation caused by loss of k-fiber tension is harnessed to kick-start chromosome segregation prior to anaphase A.
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Affiliation(s)
- Greg FitzHarris
- University College London Institute for Women's Health, 86-96 Chenies Mews, London WC1E 6HX, UK.
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30
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Hégarat N, Smith E, Nayak G, Takeda S, Eyers PA, Hochegger H. Aurora A and Aurora B jointly coordinate chromosome segregation and anaphase microtubule dynamics. ACTA ACUST UNITED AC 2011; 195:1103-13. [PMID: 22184196 PMCID: PMC3246887 DOI: 10.1083/jcb.201105058] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
We established a conditional deletion of Aurora A kinase (AurA) in Cdk1 analogue-sensitive DT40 cells to analyze AurA knockout phenotypes after Cdk1 activation. In the absence of AurA, cells form bipolar spindles but fail to properly align their chromosomes and exit mitosis with segregation errors. The resulting daughter cells exhibit a variety of phenotypes and are highly aneuploid. Aurora B kinase (AurB)-inhibited cells show a similar chromosome alignment problem and cytokinesis defects, resulting in binucleate daughter cells. Conversely, cells lacking AurA and AurB activity exit mitosis without anaphase, forming polyploid daughter cells with a single nucleus. Strikingly, inhibition of both AurA and AurB results in a failure to depolymerize spindle microtubules (MTs) in anaphase after Cdk1 inactivation. These results suggest an essential combined function of AurA and AurB in chromosome segregation and anaphase MT dynamics.
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Affiliation(s)
- Nadia Hégarat
- Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, England, UK
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31
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LaFountain JR, Cohan CS, Oldenbourg R. Functional states of kinetochores revealed by laser microsurgery and fluorescent speckle microscopy. Mol Biol Cell 2011; 22:4801-8. [PMID: 22031294 PMCID: PMC3237623 DOI: 10.1091/mbc.e11-06-0494] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The impact of mechanical forces on kinetochore motility was investigated using laser microsurgery and fluorescent speckle microscopy on kinetochores and associated microtubules during anaphase in crane fly spermatocytes. Kinetochores detached from their chromosomes moved at twice their normal speed, entering a motile state identified as “park.” The impact of mechanical forces on kinetochore motility was investigated using laser microsurgery to detach kinetochores with associated chromatin (K fragment) from meiotic chromosomes in spermatocytes from the crane fly Nephrotoma suturalis. In spermatocytes, elastic tethers connect telomeres of homologues during anaphase A of meiosis I, thus preventing complete disjunction until mid- to late anaphase A. K fragments liberated from tethered arms moved at twice the normal velocity toward their connected poles. To assess functional states of detached and control kinetochores, we loaded cells with fluorescently labeled tubulin for fluorescent speckle microscopy on kinetochore microtubules. Control kinetochores added fluorescent speckles at the kinetochore during anaphase A, whereas kinetochores of K fragments generally did not. In cases in which speckles reappeared in K-fragment K fibers, speckles and K fragments moved poleward at similar velocities. Thus detached kinetochores convert from their normal polymerization (reverse pac-man) state to a different state, in which polymerization is not evident. We suggest that the converted state is “park,” in which kinetochores are anchored to plus ends of kinetochore microtubules that shorten exclusively at their polar ends.
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Affiliation(s)
- James R LaFountain
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA.
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32
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Abstract
The kinetochore is the protein machine built at the centromere that integrates mechanical force and chemical energy from dynamic microtubules into directed chromosome motion. The kinetochore also provides a powerful signaling function that is able to alter the properties of the spindle checkpoint and initiate a signal transduction cascade that leads to inhibition of the anaphase promoting complex and cell cycle arrest. Together, the kinetochore accomplishes the feat of chromosome segregation with unparalleled accuracy. Errors in segregation lead to Down's syndrome, the most frequent inherited birth defect, pregnancy loss, and cancer. Over a century after the discovery of the kinetochore, an architectural map comprising greater than 100 proteins is emerging. Understanding the architecture and physical biology of the key components provides new insights into how this fascinating machine moves genomes.
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Affiliation(s)
- Kerry Bloom
- Department of Biology, University of North Carolina at Chapel Hill, NC 27599-3280, USA.
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33
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Matos I, Maiato H. Prevention and Correction Mechanisms behind Anaphase Synchrony: Implications for the Genesis of Aneuploidy. Cytogenet Genome Res 2011; 133:243-53. [DOI: 10.1159/000323803] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
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34
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