1
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Anjur-Dietrich MI, Gomez Hererra V, Farhadifar R, Wu H, Merta H, Bahmanyar S, Shelley MJ, Needleman DJ. Mechanics of spindle orientation in human mitotic cells is determined by pulling forces on astral microtubules and clustering of cortical dynein. Dev Cell 2024; 59:2429-2442.e4. [PMID: 38866013 DOI: 10.1016/j.devcel.2024.05.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 04/03/2024] [Accepted: 05/17/2024] [Indexed: 06/14/2024]
Abstract
The forces that orient the spindle in human cells remain poorly understood due to a lack of direct mechanical measurements in mammalian systems. We use magnetic tweezers to measure the force on human mitotic spindles. Combining the spindle's measured resistance to rotation, the speed at which it rotates after laser ablating astral microtubules, and estimates of the number of ablated microtubules reveals that each microtubule contacting the cell cortex is subject to ∼5 pN of pulling force, suggesting that each is pulled on by an individual dynein motor. We find that the concentration of dynein at the cell cortex and extent of dynein clustering are key determinants of the spindle's resistance to rotation, with little contribution from cytoplasmic viscosity, which we explain using a biophysically based mathematical model. This work reveals how pulling forces on astral microtubules determine the mechanics of spindle orientation and demonstrates the central role of cortical dynein clustering.
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Affiliation(s)
- Maya I Anjur-Dietrich
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
| | - Vicente Gomez Hererra
- Courant Institute of Mathematical Sciences, New York University, New York, NY 10012, USA
| | - Reza Farhadifar
- Center for Computational Biology, Flatiron Institute, New York, NY 10010, USA
| | - Haiyin Wu
- Department of Physics, Harvard University, Cambridge, MA 02138, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Holly Merta
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | - Shirin Bahmanyar
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | - Michael J Shelley
- Courant Institute of Mathematical Sciences, New York University, New York, NY 10012, USA; Center for Computational Biology, Flatiron Institute, New York, NY 10010, USA
| | - Daniel J Needleman
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA; Center for Computational Biology, Flatiron Institute, New York, NY 10010, USA
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2
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Islam A, Manjarrez-González JC, Song X, Gore T, Draviam VM. Search for chromosomal instability aiding variants reveal naturally occurring kinetochore gene variants that perturb chromosome segregation. iScience 2024; 27:109007. [PMID: 38361632 PMCID: PMC10867425 DOI: 10.1016/j.isci.2024.109007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 10/15/2023] [Accepted: 01/19/2024] [Indexed: 02/17/2024] Open
Abstract
Chromosomal instability (CIN) is a hallmark of cancers, and CIN-promoting mutations are not fully understood. Here, we report 141 chromosomal instability aiding variant (CIVa) candidates by assessing the prevalence of loss-of-function (LoF) variants in 135 chromosome segregation genes from over 150,000 humans. Unexpectedly, we observe both heterozygous and homozygous CIVa in Astrin and SKA3, two evolutionarily conserved kinetochore and microtubule-associated proteins essential for chromosome segregation. To stratify harmful versus harmless variants, we combine live-cell microscopy and controlled protein expression. We find the naturally occurring Astrin p.Q1012∗ variant is harmful as it fails to localize normally and induces chromosome misalignment and missegregation, in a dominant negative manner. In contrast, the Astrin p.L7Qfs∗21 variant generates a shorter isoform that localizes and functions normally, and the SKA3 p.Q70Kfs∗7 variant allows wild-type SKA complex localisation and function, revealing distinct resilience mechanisms that render these variants harmless. Thus, we present a scalable framework to predict and stratify naturally occurring CIVa, and provide insight into resilience mechanisms that compensate for naturally occurring CIVa.
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Affiliation(s)
- Asifa Islam
- School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK
| | | | - Xinhong Song
- School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK
| | - Trupti Gore
- School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK
- London Interdisciplinary Doctoral Program, University College London, London, UK
| | - Viji M. Draviam
- School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK
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3
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Chai B, Efstathiou C, Yue H, Draviam VM. Opportunities and challenges for deep learning in cell dynamics research. Trends Cell Biol 2023:S0962-8924(23)00228-3. [PMID: 38030542 DOI: 10.1016/j.tcb.2023.10.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 09/30/2023] [Accepted: 10/13/2023] [Indexed: 12/01/2023]
Abstract
The growth of artificial intelligence (AI) has led to an increase in the adoption of computer vision and deep learning (DL) techniques for the evaluation of microscopy images and movies. This adoption has not only addressed hurdles in quantitative analysis of dynamic cell biological processes but has also started to support advances in drug development, precision medicine, and genome-phenome mapping. We survey existing AI-based techniques and tools, as well as open-source datasets, with a specific focus on the computational tasks of segmentation, classification, and tracking of cellular and subcellular structures and dynamics. We summarise long-standing challenges in microscopy video analysis from a computational perspective and review emerging research frontiers and innovative applications for DL-guided automation in cell dynamics research.
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Affiliation(s)
- Binghao Chai
- School of Biological and Behavioural Sciences, Queen Mary University of London (QMUL), London E1 4NS, UK
| | - Christoforos Efstathiou
- School of Biological and Behavioural Sciences, Queen Mary University of London (QMUL), London E1 4NS, UK
| | - Haoran Yue
- School of Biological and Behavioural Sciences, Queen Mary University of London (QMUL), London E1 4NS, UK
| | - Viji M Draviam
- School of Biological and Behavioural Sciences, Queen Mary University of London (QMUL), London E1 4NS, UK; The Alan Turing Institute, London NW1 2DB, UK.
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4
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Anjur-Dietrich MI, Hererra VG, Farhadifar R, Wu H, Merta H, Bahmanyar S, Shelley MJ, Needleman DJ. Clustering of cortical dynein regulates the mechanics of spindle orientation in human mitotic cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.11.557210. [PMID: 37745442 PMCID: PMC10515834 DOI: 10.1101/2023.09.11.557210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
The forces which orient the spindle in human cells remain poorly understood due to a lack of direct mechanical measurements in mammalian systems. We use magnetic tweezers to measure the force on human mitotic spindles. Combining the spindle's measured resistance to rotation, the speed it rotates after laser ablating astral microtubules, and estimates of the number of ablated microtubules reveals that each microtubule contacting the cell cortex is subject to ~1 pN of pulling force, suggesting that each is pulled on by an individual dynein motor. We find that the concentration of dynein at the cell cortex and extent of dynein clustering are key determinants of the spindle's resistance to rotation, with little contribution from cytoplasmic viscosity, which we explain using a biophysically based mathematical model. This work reveals how pulling forces on astral microtubules determine the mechanics of spindle orientation and demonstrates the central role of cortical dynein clustering.
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Affiliation(s)
- Maya I. Anjur-Dietrich
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Vicente Gomez Hererra
- Courant Institute of Mathematical Sciences, New York University, New York, NY 10012, USA
| | - Reza Farhadifar
- Center for Computational Biology, Flatiron Institute, New York, NY 10010, USA
| | - Haiyin Wu
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Holly Merta
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | - Shirin Bahmanyar
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | - Michael J. Shelley
- Courant Institute of Mathematical Sciences, New York University, New York, NY 10012, USA
- Center for Computational Biology, Flatiron Institute, New York, NY 10010, USA
| | - Daniel J. Needleman
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
- Center for Computational Biology, Flatiron Institute, New York, NY 10010, USA
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5
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Dang D, Efstathiou C, Sun D, Yue H, Sastry NR, Draviam VM. Deep learning techniques and mathematical modeling allow 3D analysis of mitotic spindle dynamics. J Cell Biol 2023; 222:213913. [PMID: 36880744 PMCID: PMC9998659 DOI: 10.1083/jcb.202111094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 12/03/2022] [Accepted: 01/31/2023] [Indexed: 03/08/2023] Open
Abstract
Time-lapse microscopy movies have transformed the study of subcellular dynamics. However, manual analysis of movies can introduce bias and variability, obscuring important insights. While automation can overcome such limitations, spatial and temporal discontinuities in time-lapse movies render methods such as 3D object segmentation and tracking difficult. Here, we present SpinX, a framework for reconstructing gaps between successive image frames by combining deep learning and mathematical object modeling. By incorporating expert feedback through selective annotations, SpinX identifies subcellular structures, despite confounding neighbor-cell information, non-uniform illumination, and variable fluorophore marker intensities. The automation and continuity introduced here allows the precise 3D tracking and analysis of spindle movements with respect to the cell cortex for the first time. We demonstrate the utility of SpinX using distinct spindle markers, cell lines, microscopes, and drug treatments. In summary, SpinX provides an exciting opportunity to study spindle dynamics in a sophisticated way, creating a framework for step changes in studies using time-lapse microscopy.
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Affiliation(s)
- David Dang
- School of Biological and Behavioural Sciences, Queen Mary University of London , London, UK.,Department of Informatics, King's College London , London, UK
| | | | - Dijue Sun
- School of Biological and Behavioural Sciences, Queen Mary University of London , London, UK
| | - Haoran Yue
- School of Biological and Behavioural Sciences, Queen Mary University of London , London, UK
| | | | - Viji M Draviam
- School of Biological and Behavioural Sciences, Queen Mary University of London , London, UK
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6
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Pasapera AM, Heissler SM, Eto M, Nishimura Y, Fischer RS, Thiam HR, Waterman CM. MARK2 regulates directed cell migration through modulation of myosin II contractility and focal adhesion organization. Curr Biol 2022; 32:2704-2718.e6. [PMID: 35594862 DOI: 10.1016/j.cub.2022.04.088] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 02/23/2022] [Accepted: 04/28/2022] [Indexed: 12/11/2022]
Abstract
Cancer cell migration during metastasis is mediated by a highly polarized cytoskeleton. MARK2 and its invertebrate homolog Par1B are kinases that regulate the microtubule cytoskeleton to mediate polarization of neurons in mammals and embryos in invertebrates. However, the role of MARK2 in cancer cell migration is unclear. Using osteosarcoma cells, we found that in addition to its known localizations on microtubules and the plasma membrane, MARK2 also associates with the actomyosin cytoskeleton and focal adhesions. Cells depleted of MARK proteins demonstrated that MARK2 promotes phosphorylation of both myosin II and the myosin phosphatase targeting subunit MYPT1 to synergistically drive myosin II contractility and stress fiber formation in cells. Studies with isolated proteins showed that MARK2 directly phosphorylates myosin II regulatory light chain, while its effects on MYPT1 phosphorylation are indirect. Using a mutant lacking the membrane-binding domain, we found that membrane association is required for focal adhesion targeting of MARK2, where it specifically enhances cell protrusion by promoting FAK phosphorylation and formation of focal adhesions oriented in the direction of migration to mediate directionally persistent cell motility. Together, our results define MARK2 as a master regulator of the actomyosin and microtubule cytoskeletal systems and focal adhesions to mediate directional cancer cell migration.
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Affiliation(s)
- Ana M Pasapera
- Cell Biology and Physiology Center, National Heart, Lung and Blood Institute, National Institutes of Health, Building 50, South Drive, Room 4537, MSC 8019, Bethesda, MD 20892, USA
| | - Sarah M Heissler
- Cell Biology and Physiology Center, National Heart, Lung and Blood Institute, National Institutes of Health, Building 50, South Drive, Room 4537, MSC 8019, Bethesda, MD 20892, USA; Department of Physiology and Cell Biology, The Ohio State University College of Medicine, 370 W. 9th Avenue, Columbus, OH 43210, USA
| | - Masumi Eto
- Department of Veterinary Medicine, Okayama University of Science, 1-3 Ikoino-oka, Imabari, Ehime 794-8555, Japan
| | - Yukako Nishimura
- Cell Biology and Physiology Center, National Heart, Lung and Blood Institute, National Institutes of Health, Building 50, South Drive, Room 4537, MSC 8019, Bethesda, MD 20892, USA; Division of Developmental Physiology, Institute for Genetic Medicine, Hokkaido University, Kita 15, Nishi 7, Kita-Ku, Sapporo, Hokkaido 060-0815, Japan
| | - Robert S Fischer
- Cell Biology and Physiology Center, National Heart, Lung and Blood Institute, National Institutes of Health, Building 50, South Drive, Room 4537, MSC 8019, Bethesda, MD 20892, USA
| | - Hawa R Thiam
- Cell Biology and Physiology Center, National Heart, Lung and Blood Institute, National Institutes of Health, Building 50, South Drive, Room 4537, MSC 8019, Bethesda, MD 20892, USA
| | - Clare M Waterman
- Cell Biology and Physiology Center, National Heart, Lung and Blood Institute, National Institutes of Health, Building 50, South Drive, Room 4537, MSC 8019, Bethesda, MD 20892, USA.
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7
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Song X, Conti D, Shrestha RL, Braun D, Draviam VM. Counteraction between Astrin-PP1 and Cyclin-B-CDK1 pathways protects chromosome-microtubule attachments independent of biorientation. Nat Commun 2021; 12:7010. [PMID: 34853300 PMCID: PMC8636589 DOI: 10.1038/s41467-021-27131-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 11/02/2021] [Indexed: 02/08/2023] Open
Abstract
Defects in chromosome-microtubule attachment can cause chromosomal instability (CIN), frequently associated with infertility and aggressive cancers. Chromosome-microtubule attachment is mediated by a large macromolecular structure, the kinetochore. Sister kinetochores of each chromosome are pulled by microtubules from opposing spindle-poles, a state called biorientation which prevents chromosome missegregation. Kinetochore-microtubule attachments that lack the opposing-pull are detached by Aurora-B/Ipl1. It is unclear how mono-oriented attachments that precede biorientation are spared despite the lack of opposing-pull. Using an RNAi-screen, we uncover a unique role for the Astrin-SKAP complex in protecting mono-oriented attachments. We provide evidence of domains in the microtubule-end associated protein that sense changes specific to end-on kinetochore-microtubule attachments and assemble an outer-kinetochore crescent to stabilise attachments. We find that Astrin-PP1 and Cyclin-B-CDK1 pathways counteract each other to preserve mono-oriented attachments. Thus, CIN prevention pathways are not only surveying attachment defects but also actively recognising and stabilising mature attachments independent of biorientation. Chromosome instability frequently occurs due to issues with chromosome-microtubule attachments. Here the authors show that the Astrin-PP1 and Cyclin-B-CDK1 pathways counteract each other to protect chromosome-microtubule attachments independent of biorientation.
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Affiliation(s)
- Xinhong Song
- School of Biological and Chemical Sciences, Queen Mary, University of London, London, E1 4NS, UK
| | - Duccio Conti
- School of Biological and Chemical Sciences, Queen Mary, University of London, London, E1 4NS, UK.,Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Straße 11, 44227, Dortmund, Germany
| | - Roshan L Shrestha
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK.,Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Dominique Braun
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK
| | - Viji M Draviam
- School of Biological and Chemical Sciences, Queen Mary, University of London, London, E1 4NS, UK. .,Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK.
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8
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Multinucleation associated DNA damage blocks proliferation in p53-compromised cells. Commun Biol 2021; 4:451. [PMID: 33837239 PMCID: PMC8035210 DOI: 10.1038/s42003-021-01979-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 03/11/2021] [Indexed: 02/06/2023] Open
Abstract
Nuclear atypia is one of the hallmarks of cancers. Here, we perform single-cell tracking studies to determine the immediate and long-term impact of nuclear atypia. Tracking the fate of newborn cells exhibiting nuclear atypia shows that multinucleation, unlike other forms of nuclear atypia, blocks proliferation in p53-compromised cells. Because ~50% of cancers display compromised p53, we explored how multinucleation blocks proliferation. Multinucleation increases 53BP1-decorated nuclear bodies (DNA damage repair platforms), along with a heterogeneous reduction in transcription and protein accumulation across the multi-nucleated compartments. Multinucleation Associated DNA Damage associated with 53BP1-bodies remains unresolved for days, despite an intact NHEJ machinery that repairs laser-induced DNA damage within minutes. Persistent DNA damage, a DNA replication block, and reduced phospho-Rb, reveal a novel replication stress independent cell cycle arrest caused by mitotic lesions. These findings call for segregating protective and prohibitive nuclear atypia to inform therapeutic approaches aimed at limiting tumour heterogeneity. Hart et al. track newborn single cells by live microscopy after inducing a variety of nuclear atypia by CENP-E inhibitor treatment. They find that that multinucleation, unlike other forms of nuclear atypia, blocks proliferation independently of p53 and is associated with persistent 53BP1 DNA damage foci, thus providing insights into the consequences of multinucleation, often observed in disease states.
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9
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Burakov AV, Nadezhdina ES. Centering and Shifting of Centrosomes in Cells. Cells 2020; 9:E1351. [PMID: 32485978 PMCID: PMC7348834 DOI: 10.3390/cells9061351] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 05/24/2020] [Accepted: 05/27/2020] [Indexed: 12/16/2022] Open
Abstract
Centrosomes have a nonrandom localization in the cells: either they occupy the centroid of the zone free of the actomyosin cortex or they are shifted to the edge of the cell, where their presence is justified from a functional point of view, for example, to organize additional microtubules or primary cilia. This review discusses centrosome placement options in cultured and in situ cells. It has been proven that the central arrangement of centrosomes is due mainly to the pulling microtubules forces developed by dynein located on the cell cortex and intracellular vesicles. The pushing forces from dynamic microtubules and actomyosin also contribute, although the molecular mechanisms of their action have not yet been elucidated. Centrosomal displacement is caused by external cues, depending on signaling, and is drawn through the redistribution of dynein, the asymmetrization of microtubules through the capture of their plus ends, and the redistribution of actomyosin, which, in turn, is associated with basal-apical cell polarization.
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Affiliation(s)
- Anton V. Burakov
- A. N. Belozersky Institute of Physico-Chemical Biology, M. V. Lomonosov Moscow State University, 119991 Moscow, Russia;
| | - Elena S. Nadezhdina
- Institute of Protein Research of Russian Academy of Science, Pushchino, 142290 Moscow Region, Russia
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10
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Stiff T, Echegaray-Iturra FR, Pink HJ, Herbert A, Reyes-Aldasoro CC, Hochegger H. Prophase-Specific Perinuclear Actin Coordinates Centrosome Separation and Positioning to Ensure Accurate Chromosome Segregation. Cell Rep 2020; 31:107681. [PMID: 32460023 PMCID: PMC7262599 DOI: 10.1016/j.celrep.2020.107681] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 02/11/2020] [Accepted: 05/01/2020] [Indexed: 12/30/2022] Open
Abstract
Centrosome separation in late G2/ early prophase requires precise spatial coordination that is determined by a balance of forces promoting and antagonizing separation. The major effector of centrosome separation is the kinesin Eg5. However, the identity and regulation of Eg5-antagonizing forces is less well characterized. By manipulating candidate components, we find that centrosome separation is reversible and that separated centrosomes congress toward a central position underneath the flat nucleus. This positioning mechanism requires microtubule polymerization, as well as actin polymerization. We identify perinuclear actin structures that form in late G2/early prophase and interact with microtubules emanating from the centrosomes. Disrupting these structures by breaking the interactions of the linker of nucleoskeleton and cytoskeleton (LINC) complex with perinuclear actin filaments abrogates this centrosome positioning mechanism and causes an increase in subsequent chromosome segregation errors. Our results demonstrate how geometrical cues from the cell nucleus coordinate the orientation of the emanating spindle poles before nuclear envelope breakdown.
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Affiliation(s)
- Tom Stiff
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN19RQ, UK
| | - Fabio R Echegaray-Iturra
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN19RQ, UK
| | - Harry J Pink
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN19RQ, UK
| | - Alex Herbert
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN19RQ, UK
| | | | - Helfrid Hochegger
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN19RQ, UK.
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11
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Conti D, Gul P, Islam A, Martín-Durán JM, Pickersgill RW, Draviam VM. Kinetochores attached to microtubule-ends are stabilised by Astrin bound PP1 to ensure proper chromosome segregation. eLife 2019; 8:49325. [PMID: 31808746 PMCID: PMC6930079 DOI: 10.7554/elife.49325] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 12/01/2019] [Indexed: 12/12/2022] Open
Abstract
Microtubules segregate chromosomes by attaching to macromolecular kinetochores. Only microtubule-end attached kinetochores can be pulled apart; how these end-on attachments are selectively recognised and stabilised is not known. Using the kinetochore and microtubule-associated protein, Astrin, as a molecular probe, we show that end-on attachments are rapidly stabilised by spatially-restricted delivery of PP1 near the C-terminus of Ndc80, a core kinetochore-microtubule linker. PP1 is delivered by the evolutionarily conserved tail of Astrin and this promotes Astrin’s own enrichment creating a highly-responsive positive feedback, independent of biorientation. Abrogating Astrin:PP1-delivery disrupts attachment stability, which is not rescued by inhibiting Aurora-B, an attachment destabiliser, but is reversed by artificially tethering PP1 near the C-terminus of Ndc80. Constitutive Astrin:PP1-delivery disrupts chromosome congression and segregation, revealing a dynamic mechanism for stabilising attachments. Thus, Astrin-PP1 mediates a dynamic ‘lock’ that selectively and rapidly stabilises end-on attachments, independent of biorientation, and ensures proper chromosome segregation.
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Affiliation(s)
- Duccio Conti
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Parveen Gul
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - Asifa Islam
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - José M Martín-Durán
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - Richard W Pickersgill
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - Viji M Draviam
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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12
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Hart M, Zulkipli I, Shrestha RL, Dang D, Conti D, Gul P, Kujawiak I, Draviam VM. MARK2/Par1b kinase present at centrosomes and retraction fibres corrects spindle off-centring induced by actin disassembly. Open Biol 2019; 9:180263. [PMID: 31238822 PMCID: PMC6597755 DOI: 10.1098/rsob.180263] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Tissue maintenance and development requires a directed plane of cell division. While it is clear that the division plane can be determined by retraction fibres that guide spindle movements, the precise molecular components of retraction fibres that control spindle movements remain unclear. We report MARK2/Par1b kinase as a novel component of actin-rich retraction fibres. A kinase-dead mutant of MARK2 reveals MARK2's ability to monitor subcellular actin status during interphase. During mitosis, MARK2's localization at actin-rich retraction fibres, but not the rest of the cortical membrane or centrosome, is dependent on its activity, highlighting a specialized spatial regulation of MARK2. By subtly perturbing the actin cytoskeleton, we reveal MARK2's role in correcting mitotic spindle off-centring induced by actin disassembly. We propose that MARK2 provides a molecular framework to integrate cortical signals and cytoskeletal changes in mitosis and interphase.
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Affiliation(s)
- Madeleine Hart
- 1 School of Biological and Chemical Sciences, Queen Mary University of London , London , UK
| | - Ihsan Zulkipli
- 2 Department of Genetics, University of Cambridge , Cambridge , UK
| | | | - David Dang
- 1 School of Biological and Chemical Sciences, Queen Mary University of London , London , UK.,3 Department of Informatics, King's College, London , London , UK
| | - Duccio Conti
- 1 School of Biological and Chemical Sciences, Queen Mary University of London , London , UK
| | - Parveen Gul
- 1 School of Biological and Chemical Sciences, Queen Mary University of London , London , UK
| | - Izabela Kujawiak
- 2 Department of Genetics, University of Cambridge , Cambridge , UK
| | - Viji M Draviam
- 1 School of Biological and Chemical Sciences, Queen Mary University of London , London , UK
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13
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Zhu Y, Tan W, Lee WL. An in vitro Microscopy-based Assay for Microtubule-binding and Microtubule-crosslinking by Budding Yeast Microtubule-associated Protein. Bio Protoc 2018; 8:e3110. [PMID: 30733975 DOI: 10.21769/bioprotoc.3110] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In this protocol, we describe a simple microscopy-based method to assess the interaction of a microtubule-associated protein (MAP) with microtubules. The interaction between MAP and microtubules is typically assessed by a co-sedimentation assay, which measures the amount of MAP that co-pellets with microtubules by centrifugation, followed by SDS-PAGE analysis of the supernatant and pellet fractions. However, MAPs that form large oligomers tend to pellet on their own during the centrifugation step, making it difficult to assess co-sedimentation. Here we describe a microscopy-based assay that measures microtubule binding by direct visualization using fluorescently-labeled MAP, solving the limitations of the co-sedimentation assay. Additionally, we recently reported quantification of microtubule bundling by measuring the thickness of individual microtubule structures observed in the microscopy-based assay, making the protocol more advantageous than the traditional microtubule co-pelleting assay.
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Affiliation(s)
- Yili Zhu
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Weimin Tan
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Wei-Lih Lee
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
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