1
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Connors CQ, Mauro MS, Wiles JT, Countryman AD, Martin SL, Lacroix B, Shirasu-Hiza M, Dumont J, Kasza KE, Davies TR, Canman JC. Germ fate determinants protect germ precursor cell division by reducing septin and anillin levels at the cell division plane. Mol Biol Cell 2024; 35:ar94. [PMID: 38696255 PMCID: PMC11244169 DOI: 10.1091/mbc.e24-02-0096-t] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 04/22/2024] [Accepted: 04/26/2024] [Indexed: 05/04/2024] Open
Abstract
Animal cell cytokinesis, or the physical division of one cell into two, is thought to be driven by constriction of an actomyosin contractile ring at the division plane. The mechanisms underlying cell type-specific differences in cytokinesis remain unknown. Germ cells are totipotent cells that pass genetic information to the next generation. Previously, using formincyk-1(ts) mutant Caenorhabditis elegans 4-cell embryos, we found that the P2 germ precursor cell is protected from cytokinesis failure and can divide with greatly reduced F-actin levels at the cell division plane. Here, we identified two canonical germ fate determinants required for P2-specific cytokinetic protection: PIE-1 and POS-1. Neither has been implicated previously in cytokinesis. These germ fate determinants protect P2 cytokinesis by reducing the accumulation of septinUNC-59 and anillinANI-1 at the division plane, which here act as negative regulators of cytokinesis. These findings may provide insight into the regulation of cytokinesis in other cell types, especially in stem cells with high potency.
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Affiliation(s)
- Caroline Q. Connors
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032
| | - Michael S. Mauro
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032
| | - J. Tristian Wiles
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | | | - Sophia L. Martin
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032
| | - Benjamin Lacroix
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
- Université de Montpellier, CNRS, Centre de Recherche en Biologie Cellulaire de Montpellier, UMR 5237 Montpellier, France
| | - Mimi Shirasu-Hiza
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032
| | - Julien Dumont
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
| | - Karen E. Kasza
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
| | - Timothy R. Davies
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032
- Department of Biosciences, Durham University, Durham DH1 3LE, UK
| | - Julie C. Canman
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032
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2
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Xu Y, Chao A, Rinaldin M, Kickuth A, Brugués J, Di Talia S. The cell cycle oscillator and spindle length set the speed of chromosome separation in Drosophila embryos. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.17.598879. [PMID: 38948726 PMCID: PMC11212860 DOI: 10.1101/2024.06.17.598879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Anaphase is tightly controlled in space and time to ensure proper separation of chromosomes. The mitotic spindle, the self-organized microtubule structure driving chromosome segregation, scales in size with the available cytoplasm. Yet, the relationship between spindle size and chromosome movement remains poorly understood. Here, we address how the movement of chromosomes changes during the cleavage divisions of the Drosophila blastoderm. We show that the speed of chromosome separation gradually decreases during the 4 nuclear divisions of the blastoderm. This reduction in speed is accompanied by a similar reduction in the length of the spindle, thus ensuring that these two quantities are tightly linked. Using a combination of genetic and quantitative imaging approaches, we find that two processes contribute to controlling the speed at which chromosomes move at mitotic exit: the activity of molecular motors important for microtubule depolymerization and the cell cycle oscillator. Specifically, we found that the levels of Klp10A, Klp67A, and Klp59C, three kinesin-like proteins important for microtubule depolymerization, contribute to setting the speed of chromosome separation. This observation is supported by quantification of microtubule dynamics indicating that poleward flux rate scales with the length of the spindle. Perturbations of the cell cycle oscillator using heterozygous mutants of mitotic kinases and phosphatases revealed that the duration of anaphase increases during the blastoderm cycles and is the major regulator of chromosome velocity. Thus, our work suggests a potential link between the biochemical rate of mitotic exit and the forces exerted by the spindle. Collectively, we propose that the cell cycle oscillator and spindle length set the speed of chromosome separation in anaphase.
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Affiliation(s)
- Yitong Xu
- Department of Cell Biology, Duke University Medical Center, Durham NC 27705, USA
| | - Anna Chao
- Department of Cell Biology, Duke University Medical Center, Durham NC 27705, USA
| | - Melissa Rinaldin
- Cluster of Excellence Physics of Life, TU Dresden, Dresden, 01307 Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, 01307 Germany
- Center of Systems Biology, Dresden, 01307 Germany
| | - Alison Kickuth
- Cluster of Excellence Physics of Life, TU Dresden, Dresden, 01307 Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, 01307 Germany
- Center of Systems Biology, Dresden, 01307 Germany
| | - Jan Brugués
- Cluster of Excellence Physics of Life, TU Dresden, Dresden, 01307 Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, 01307 Germany
- Center of Systems Biology, Dresden, 01307 Germany
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham NC 27705, USA
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3
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Rosfelter A, de Labbey G, Chenevert J, Dumollard R, Schaub S, Machaty Z, Besnardeau L, Gonzalez Suarez D, Hebras C, Turlier H, Burgess DR, McDougall A. Reduction of cortical pulling at mitotic entry facilitates aster centration. J Cell Sci 2024; 137:jcs262037. [PMID: 38469748 DOI: 10.1242/jcs.262037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 02/23/2024] [Indexed: 03/13/2024] Open
Abstract
Equal cell division relies upon astral microtubule-based centering mechanisms, yet how the interplay between mitotic entry, cortical force generation and long astral microtubules leads to symmetric cell division is not resolved. We report that a cortically located sperm aster displaying long astral microtubules that penetrate the whole zygote does not undergo centration until mitotic entry. At mitotic entry, we find that microtubule-based cortical pulling is lost. Quantitative measurements of cortical pulling and cytoplasmic pulling together with physical simulations suggested that a wavelike loss of cortical pulling at mitotic entry leads to aster centration based on cytoplasmic pulling. Cortical actin is lost from the cortex at mitotic entry coincident with a fall in cortical tension from ∼300pN/µm to ∼100pN/µm. Following the loss of cortical force generators at mitotic entry, long microtubule-based cytoplasmic pulling is sufficient to displace the aster towards the cell center. These data reveal how mitotic aster centration is coordinated with mitotic entry in chordate zygotes.
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Affiliation(s)
- Anne Rosfelter
- Laboratoire de Biologie du Developpement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, 06230 Villefranche-sur-mer, France
| | - Ghislain de Labbey
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS UMR7241 / INSERM U1050, Université PSL, 75002 Paris, France
| | - Janet Chenevert
- Laboratoire de Biologie du Developpement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, 06230 Villefranche-sur-mer, France
| | - Rémi Dumollard
- Laboratoire de Biologie du Developpement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, 06230 Villefranche-sur-mer, France
| | - Sebastien Schaub
- Laboratoire de Biologie du Developpement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, 06230 Villefranche-sur-mer, France
| | - Zoltan Machaty
- Laboratoire de Biologie du Developpement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, 06230 Villefranche-sur-mer, France
| | - Lydia Besnardeau
- Laboratoire de Biologie du Developpement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, 06230 Villefranche-sur-mer, France
| | - Daniel Gonzalez Suarez
- Laboratoire de Biologie du Developpement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, 06230 Villefranche-sur-mer, France
| | - Céline Hebras
- Laboratoire de Biologie du Developpement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, 06230 Villefranche-sur-mer, France
| | - Hervé Turlier
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS UMR7241 / INSERM U1050, Université PSL, 75002 Paris, France
| | - David R Burgess
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA
| | - Alex McDougall
- Laboratoire de Biologie du Developpement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, 06230 Villefranche-sur-mer, France
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4
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Zimyanin V, Redemann S. Microtubule length correlates with spindle length in C. elegans meiosis. Cytoskeleton (Hoboken) 2024. [PMID: 38450962 DOI: 10.1002/cm.21849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 01/24/2024] [Accepted: 02/21/2024] [Indexed: 03/08/2024]
Abstract
The accurate segregation of chromosomes during female meiosis relies on the precise assembly and function of the meiotic spindle, a dynamic structure primarily composed of microtubules. Despite the crucial role of microtubule dynamics in this process, the relationship between microtubule length and spindle size remains elusive. Leveraging Caenorhabditis elegans as a model system, we combined electron tomography and live imaging to investigate this correlation. Our analysis revealed significant changes in spindle length throughout meiosis, coupled with alterations in microtubule length. Surprisingly, while spindle size decreases during the initial stages of anaphase, the size of antiparallel microtubule overlap decreased as well. Detailed electron tomography shows a positive correlation between microtubule length and spindle size, indicating a role of microtubule length in determining spindle dimensions. Notably, microtubule numbers displayed no significant association with spindle length, highlighting the dominance of microtubule length regulation in spindle size determination. Depletion of the microtubule depolymerase KLP-7 led to elongated metaphase spindles with increased microtubule length, supporting the link between microtubule length and spindle size. These findings underscore the pivotal role of regulating microtubule dynamics, and thus microtubule length, in governing spindle rearrangements during meiotic division, shedding light on fundamental mechanisms dictating spindle architecture.
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Affiliation(s)
- Vitaly Zimyanin
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Stefanie Redemann
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
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5
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Kiyomitsu A, Nishimura T, Hwang SJ, Ansai S, Kanemaki MT, Tanaka M, Kiyomitsu T. Ran-GTP assembles a specialized spindle structure for accurate chromosome segregation in medaka early embryos. Nat Commun 2024; 15:981. [PMID: 38302485 PMCID: PMC10834446 DOI: 10.1038/s41467-024-45251-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Accepted: 01/19/2024] [Indexed: 02/03/2024] Open
Abstract
Despite drastic cellular changes during cleavage, a mitotic spindle assembles in each blastomere to accurately segregate duplicated chromosomes. Mechanisms of mitotic spindle assembly have been extensively studied using small somatic cells. However, mechanisms of spindle assembly in large vertebrate embryos remain little understood. Here, we establish functional assay systems in medaka (Oryzias latipes) embryos by combining CRISPR knock-in with auxin-inducible degron technology. Live imaging reveals several unexpected features of microtubule organization and centrosome positioning that achieve rapid, accurate cleavage. Importantly, Ran-GTP assembles a dense microtubule network at the metaphase spindle center that is essential for chromosome segregation in early embryos. This unique spindle structure is remodeled into a typical short, somatic-like spindle after blastula stages, when Ran-GTP becomes dispensable for chromosome segregation. We propose that despite the presence of centrosomes, the chromosome-derived Ran-GTP pathway has essential roles in functional spindle assembly in large, rapidly dividing vertebrate early embryos, similar to acentrosomal spindle assembly in oocytes.
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Affiliation(s)
- Ai Kiyomitsu
- Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
| | - Toshiya Nishimura
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
- Hokkaido University Fisheries Sciences, 3-1-1, Minato-cho, Hakodate, Hokkaido, 041-8611, Japan
| | - Shiang Jyi Hwang
- Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
| | - Satoshi Ansai
- Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
- Laboratory of Genome Editing Breeding, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Masato T Kanemaki
- Department of Chromosome Science, National Institute of Genetics, Research Organization of Information and Systems (ROIS), and Graduate Institute for Advanced Studies, SOKENDAI, Yata 1111, Mishima, Shizuoka, 411-8540, Japan
- Department of Biological Science, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Minoru Tanaka
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Tomomi Kiyomitsu
- Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan.
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6
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Chenevert J, Robert MLV, Sallé J, Cacchia S, Lorca T, Castro A, McDougall A, Minc N, Castagnetti S, Dumont J, Lacroix B. Measuring Mitotic Spindle and Microtubule Dynamics in Marine Embryos and Non-model Organisms. Methods Mol Biol 2024; 2740:187-210. [PMID: 38393477 DOI: 10.1007/978-1-0716-3557-5_12] [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] [Indexed: 02/25/2024]
Abstract
During eukaryotic cell division a microtubule-based structure, the mitotic spindle, aligns and segregates chromosomes between daughter cells. Understanding how this cellular structure is assembled and coordinated in space and in time requires measuring microtubule dynamics and visualizing spindle assembly with high temporal and spatial resolution. Visualization is often achieved by the introduction and the detection of molecular probes and fluorescence microscopy. Microtubules and mitotic spindles are highly conserved across eukaryotes; however, several technical limitations have restricted these investigations to only a few species. The ability to monitor microtubule and chromosome choreography in a wide range of species is fundamental to reveal conserved mechanisms or unravel unconventional strategies that certain forms of life have developed to ensure faithful partitioning of chromosomes during cell division. Here, we describe a technique based on injection of purified proteins that enables the visualization of microtubules and chromosomes with a high contrast in several divergent marine embryos. We also provide analysis methods and tools to extract microtubule dynamics and monitor spindle assembly. These techniques can be adapted to a wide variety of species in order to measure microtubule dynamics and spindle assembly kinetics when genetic tools are not available or in parallel to the development of such techniques in non-model organisms.
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Affiliation(s)
- Janet Chenevert
- Sorbonne Universités, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Villefranche-sur-mer, France
| | - Morgane L V Robert
- Université de Montpellier, Centre de Recherche en Biologie cellulaire de Montpellier (CRBM), CNRS UMR 5237, Montpellier Cedex 5, France
| | - Jérémy Sallé
- CNRS, Institut Jacques Monod, Université Paris Cité, Paris, France
- Equipe Labellisée Ligue Contre le Cancer, Paris, France
| | - Sébastien Cacchia
- Université de Montpellier, Centre de Recherche en Biologie cellulaire de Montpellier (CRBM), CNRS UMR 5237, Montpellier Cedex 5, France
| | - Thierry Lorca
- Université de Montpellier, Centre de Recherche en Biologie cellulaire de Montpellier (CRBM), CNRS UMR 5237, Montpellier Cedex 5, France
| | - Anna Castro
- Université de Montpellier, Centre de Recherche en Biologie cellulaire de Montpellier (CRBM), CNRS UMR 5237, Montpellier Cedex 5, France
- Programme équipes Labellisées Ligue Contre le Cancer, Paris, France
| | - Alex McDougall
- Sorbonne Universités, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Villefranche-sur-mer, France
| | - Nicolas Minc
- CNRS, Institut Jacques Monod, Université Paris Cité, Paris, France
- Equipe Labellisée Ligue Contre le Cancer, Paris, France
| | - Stefania Castagnetti
- Sorbonne Universités, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Villefranche-sur-mer, France
| | - Julien Dumont
- CNRS, Institut Jacques Monod, Université Paris Cité, Paris, France
| | - Benjamin Lacroix
- Université de Montpellier, Centre de Recherche en Biologie cellulaire de Montpellier (CRBM), CNRS UMR 5237, Montpellier Cedex 5, France.
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7
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Bloomfield M, Cimini D. The fate of extra centrosomes in newly formed tetraploid cells: should I stay, or should I go? Front Cell Dev Biol 2023; 11:1210983. [PMID: 37576603 PMCID: PMC10413984 DOI: 10.3389/fcell.2023.1210983] [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: 04/23/2023] [Accepted: 07/17/2023] [Indexed: 08/15/2023] Open
Abstract
An increase in centrosome number is commonly observed in cancer cells, but the role centrosome amplification plays along with how and when it occurs during cancer development is unclear. One mechanism for generating cancer cells with extra centrosomes is whole genome doubling (WGD), an event that occurs in over 30% of human cancers and is associated with poor survival. Newly formed tetraploid cells can acquire extra centrosomes during WGD, and a generally accepted model proposes that centrosome amplification in tetraploid cells promotes cancer progression by generating aneuploidy and chromosomal instability. Recent findings, however, indicate that newly formed tetraploid cells in vitro lose their extra centrosomes to prevent multipolar cell divisions. Rather than persistent centrosome amplification, this evidence raises the possibility that it may be advantageous for tetraploid cells to initially restore centrosome number homeostasis and for a fraction of the population to reacquire additional centrosomes in the later stages of cancer evolution. In this review, we explore the different evolutionary paths available to newly formed tetraploid cells, their effects on centrosome and chromosome number distribution in daughter cells, and their probabilities of long-term survival. We then discuss the mechanisms that may alter centrosome and chromosome numbers in tetraploid cells and their relevance to cancer progression following WGD.
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Affiliation(s)
- Mathew Bloomfield
- Department of Biological Sciences and Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, United States
| | - Daniela Cimini
- Department of Biological Sciences and Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, United States
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8
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Jain I, Rao M, Tran PT. Reliable and robust control of nucleus centering is contingent on nonequilibrium force patterns. iScience 2023; 26:106665. [PMID: 37182105 PMCID: PMC10173738 DOI: 10.1016/j.isci.2023.106665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 02/23/2023] [Accepted: 04/09/2023] [Indexed: 05/16/2023] Open
Abstract
Cell centers their division apparatus to ensure symmetric cell division, a challenging task when the governing dynamics is stochastic. Using fission yeast, we show that the patterning of nonequilibrium polymerization forces of microtubule (MT) bundles controls the precise localization of spindle pole body (SPB), and hence the division septum, at the onset of mitosis. We define two cellular objectives, reliability, the mean SPB position relative to the geometric center, and robustness, the variance of the SPB position, which are sensitive to genetic perturbations that change cell length, MT bundle number/orientation, and MT dynamics. We show that simultaneous control of reliability and robustness is required to minimize septum positioning error achieved by the wild type (WT). A stochastic model for the MT-based nucleus centering, with parameters measured directly or estimated using Bayesian inference, recapitulates the maximum fidelity of WT. Using this, we perform a sensitivity analysis of the parameters that control nuclear centering.
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Affiliation(s)
- Ishutesh Jain
- Institut Curie, PSL Universite, Sorbonne Universite, CNRS UMR 144, 75005 Paris, France
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences - TIFR, Bangalore 560065, India
| | - Madan Rao
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences - TIFR, Bangalore 560065, India
- Corresponding author
| | - Phong T. Tran
- Institut Curie, PSL Universite, Sorbonne Universite, CNRS UMR 144, 75005 Paris, France
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
- Corresponding author
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9
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Chen P, Levy DL. Regulation of organelle size and organization during development. Semin Cell Dev Biol 2023; 133:53-64. [PMID: 35148938 PMCID: PMC9357868 DOI: 10.1016/j.semcdb.2022.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 01/20/2022] [Accepted: 02/01/2022] [Indexed: 12/11/2022]
Abstract
During early embryogenesis, as cells divide in the developing embryo, the size of intracellular organelles generally decreases to scale with the decrease in overall cell size. Organelle size scaling is thought to be important to establish and maintain proper cellular function, and defective scaling may lead to impaired development and disease. However, how the cell regulates organelle size and organization are largely unanswered questions. In this review, we summarize the process of size scaling at both the cell and organelle levels and discuss recently discovered mechanisms that regulate this process during early embryogenesis. In addition, we describe how some recently developed techniques and Xenopus as an animal model can be used to investigate the underlying mechanisms of size regulation and to uncover the significance of proper organelle size scaling and organization.
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Affiliation(s)
- Pan Chen
- Institute of Biochemistry and Molecular Biology, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, China.
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA.
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10
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Striebel M, Brauns F, Frey E. Length Regulation Drives Self-Organization in Filament-Motor Mixtures. PHYSICAL REVIEW LETTERS 2022; 129:238102. [PMID: 36563230 DOI: 10.1103/physrevlett.129.238102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 10/10/2022] [Indexed: 06/17/2023]
Abstract
Cytoskeletal networks form complex intracellular structures. Here we investigate a minimal model for filament-motor mixtures in which motors act as depolymerases and thereby regulate filament length. Combining agent-based simulations and hydrodynamic equations, we show that resource-limited length regulation drives the formation of filament clusters despite the absence of mechanical interactions between filaments. Even though the orientation of individual remains fixed, collective filament orientation emerges in the clusters, aligned orthogonal to their interfaces.
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Affiliation(s)
- Moritz Striebel
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstrasse 37, D-80333 Munich, Germany
| | - Fridtjof Brauns
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstrasse 37, D-80333 Munich, Germany
| | - Erwin Frey
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstrasse 37, D-80333 Munich, Germany
- Max Planck School Matter to Life, Hofgartenstraße 8, D-80539 Munich, Germany
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11
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Size regulation of multiple organelles competing for a limiting subunit pool. PLoS Comput Biol 2022; 18:e1010253. [PMID: 35714135 PMCID: PMC9246132 DOI: 10.1371/journal.pcbi.1010253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 06/30/2022] [Accepted: 05/26/2022] [Indexed: 11/20/2022] Open
Abstract
How cells regulate the size of intracellular structures and organelles is a longstanding question. Recent experiments suggest that size control of intracellular structures is achieved through the depletion of a limiting subunit pool in the cytoplasm. While the limiting pool model ensures organelle-to-cell size scaling, it does not provide a mechanism for robust size control of multiple co-existing structures. Here we develop a generalized theory for size-dependent growth of intracellular structures to demonstrate that robust size control of multiple intracellular structures, competing for a limiting subunit pool, is achieved via a negative feedback between the growth rate and the size of the individual structure. This design principle captures size maintenance of a wide variety of subcellular structures, from cytoskeletal filaments to three-dimensional organelles. We identify the feedback motifs for structure size regulation based on known molecular processes, and compare our theory to existing models of size regulation in biological assemblies. Furthermore, we show that positive feedback between structure size and growth rate can lead to bistable size distribution and spontaneous size selection. Organelle size control is essential for the proper physiological functioning of eukaryotic cells, but the underlying mechanisms of size regulation remain poorly understood. By developing a general theory for organelle size control, we show that robust size control of intracellular structures and organelles is achieved via a negative feedback between individual organelle size and their net growth rates. This design principle not only describes size maintenance of single organelles, but also ensures size stability of multiple co-existing organelles that are built from a limiting pool of subunits. Our results delineate the role of limiting pool as a size scaling mechanism rather than a size control mechanism, supporting the idea that negative feedback control of organelle size via depletion of a limiting subunit pool is not sufficient to maintain the size of multiple competing organelles. In the case of positive feedback between organelle size and growth rate, our model reproduces phenomena such as bistability in organelle size distribution and spontaneous emergence of cell polarity.
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12
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Hirsch SM, Edwards F, Shirasu-Hiza M, Dumont J, Canman JC. Functional midbody assembly in the absence of a central spindle. J Biophys Biochem Cytol 2022; 221:212948. [PMID: 34994802 PMCID: PMC8751756 DOI: 10.1083/jcb.202011085] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 10/13/2021] [Accepted: 12/10/2021] [Indexed: 12/28/2022] Open
Abstract
Contractile ring constriction during cytokinesis is thought to compact central spindle microtubules to form the midbody, an antiparallel microtubule bundle at the intercellular bridge. In Caenorhabditis elegans, central spindle microtubule assembly requires targeting of the CLASP family protein CLS-2 to the kinetochores in metaphase and spindle midzone in anaphase. CLS-2 targeting is mediated by the CENP-F–like HCP-1/2, but their roles in cytokinesis and midbody assembly are not known. We found that although HCP-1 and HCP-2 mostly function cooperatively, HCP-1 plays a more primary role in promoting CLS-2–dependent central spindle microtubule assembly. HCP-1/2 codisrupted embryos did not form central spindles but completed cytokinesis and formed functional midbodies capable of supporting abscission. These central spindle–independent midbodies appeared to form via contractile ring constriction–driven bundling of astral microtubules at the furrow tip. This work suggests that, in the absence of a central spindle, astral microtubules can support midbody assembly and that midbody assembly is more predictive of successful cytokinesis than central spindle assembly.
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Affiliation(s)
- Sophia M Hirsch
- Department of Genetics and Development, Columbia University Medical Center, New York, NY.,Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY
| | - Frances Edwards
- Institut Jacques Monod, Centre national de la recherche scientifique, Université de Paris, Paris, France
| | - Mimi Shirasu-Hiza
- Department of Genetics and Development, Columbia University Medical Center, New York, NY
| | - Julien Dumont
- Institut Jacques Monod, Centre national de la recherche scientifique, Université de Paris, Paris, France
| | - Julie C Canman
- Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY
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13
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Microtubule and Actin Cytoskeletal Dynamics in Male Meiotic Cells of Drosophila melanogaster. Cells 2022; 11:cells11040695. [PMID: 35203341 PMCID: PMC8870657 DOI: 10.3390/cells11040695] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Revised: 02/11/2022] [Accepted: 02/14/2022] [Indexed: 01/12/2023] Open
Abstract
Drosophila dividing spermatocytes offer a highly suitable cell system in which to investigate the coordinated reorganization of microtubule and actin cytoskeleton systems during cell division of animal cells. Like male germ cells of mammals, Drosophila spermatogonia and spermatocytes undergo cleavage furrow ingression during cytokinesis, but abscission does not take place. Thus, clusters of primary and secondary spermatocytes undergo meiotic divisions in synchrony, resulting in cysts of 32 secondary spermatocytes and then 64 spermatids connected by specialized structures called ring canals. The meiotic spindles in Drosophila males are substantially larger than the spindles of mammalian somatic cells and exhibit prominent central spindles and contractile rings during cytokinesis. These characteristics make male meiotic cells particularly amenable to immunofluorescence and live imaging analysis of the spindle microtubules and the actomyosin apparatus during meiotic divisions. Moreover, because the spindle assembly checkpoint is not robust in spermatocytes, Drosophila male meiosis allows investigating of whether gene products required for chromosome segregation play additional roles during cytokinesis. Here, we will review how the research studies on Drosophila male meiotic cells have contributed to our knowledge of the conserved molecular pathways that regulate spindle microtubules and cytokinesis with important implications for the comprehension of cancer and other diseases.
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14
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Hornak I, Rieger H. Stochastic model of T Cell repolarization during target elimination (II). Biophys J 2022; 121:1246-1265. [PMID: 35196513 PMCID: PMC9034251 DOI: 10.1016/j.bpj.2022.02.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/08/2021] [Accepted: 02/16/2022] [Indexed: 11/16/2022] Open
Abstract
Cytotoxic T lymphocytes (T cells) and natural killer cells form a tight contact, the immunological synapse (IS), with target cells, where they release their lytic granules containing perforin/granzyme and cytokine-containing vesicles. During this process the cell repolarizes and moves the microtubule organizing center (MTOC) toward the IS. In the first part of our work we developed a computational model for the molecular-motor-driven motion of the microtubule cytoskeleton during T cell polarization and analyzed the effects of cortical-sliding and capture-shrinkage mechanisms. Here we use this model to analyze the dynamics of the MTOC repositioning in situations in which 1) the IS is in an arbitrary position with respect to the initial position of the MTOC and 2) the T cell has two IS at two arbitrary positions. In the case of one IS, we found that the initial position determines which mechanism is dominant and that the time of repositioning does not rise monotonously with the MTOC-IS distance. In the case of two IS, we observe several scenarios that have also been reported experimentally: the MTOC alternates stochastically (but with a well-defined average transition time) between the two IS; it wiggles in between the two IS without transiting to one of the two; or it is at some point pulled to one of the two IS and stays there. Our model allows one to predict which scenario emerges in dependency of the mechanisms in action and the number of dyneins present. We report that the presence of capture-shrinkage mechanism in at least one IS is necessary to assure the transitions in every cell configuration. Moreover, the frequency of transitions does not decrease with the distance between the two IS and is the highest when both mechanisms are present in both IS.
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Affiliation(s)
- Ivan Hornak
- Department of Theoretical Physics, Center for Biophysics, Saarland University, Saarbrücken, Germany.
| | - Heiko Rieger
- Department of Theoretical Physics, Center for Biophysics, Saarland University, Saarbrücken, Germany
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15
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Lacroix B, Dumont J. Spatial and Temporal Scaling of Microtubules and Mitotic Spindles. Cells 2022; 11:cells11020248. [PMID: 35053364 PMCID: PMC8774166 DOI: 10.3390/cells11020248] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/07/2022] [Accepted: 01/09/2022] [Indexed: 02/01/2023] Open
Abstract
During cell division, the mitotic spindle, a macromolecular structure primarily comprised of microtubules, drives chromosome alignment and partitioning between daughter cells. Mitotic spindles can sense cellular dimensions in order to adapt their length and mass to cell size. This scaling capacity is particularly remarkable during early embryo cleavage when cells divide rapidly in the absence of cell growth, thus leading to a reduction of cell volume at each division. Although mitotic spindle size scaling can occur over an order of magnitude in early embryos, in many species the duration of mitosis is relatively short, constant throughout early development and independent of cell size. Therefore, a key challenge for cells during embryo cleavage is not only to assemble a spindle of proper size, but also to do it in an appropriate time window which is compatible with embryo development. How spatial and temporal scaling of the mitotic spindle is achieved and coordinated with the duration of mitosis remains elusive. In this review, we will focus on the mechanisms that support mitotic spindle spatial and temporal scaling over a wide range of cell sizes and cellular contexts. We will present current models and propose alternative mechanisms allowing cells to spatially and temporally coordinate microtubule and mitotic spindle assembly.
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Affiliation(s)
- Benjamin Lacroix
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), CNRS UMR 5237, Université de Montpellier, 1919 Route de Mende, CEDEX 5, 34293 Montpellier, France
- Correspondence:
| | - Julien Dumont
- Université de Paris, CNRS, Institut Jacques Monod, F-75013 Paris, France;
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16
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Cell division geometries as central organizers of early embryo development. Semin Cell Dev Biol 2021; 130:3-11. [PMID: 34419349 DOI: 10.1016/j.semcdb.2021.08.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 08/08/2021] [Indexed: 11/24/2022]
Abstract
Early cellular patterning is a critical step of embryonic development that determines the proper progression of morphogenesis in all metazoans. It relies on a series of rapid reductive divisions occurring simultaneously with the specification of the fate of different subsets of cells. Multiple species developmental strategies emerged in the form of a unique cleavage pattern with stereotyped division geometries. Cleavage geometries have long been associated to the emergence of canonical developmental features such as cell cycle asynchrony, zygotic genome activation and fate specification. Yet, the direct causal role of division positioning on blastomere cell behavior remain partially understood. Oriented and/or asymmetric divisions define blastomere cell sizes, contacts and positions, with potential immediate impact on cellular decisions, lineage specification and morphogenesis. Division positions also instruct daughter cells polarity, mechanics and geometries, thereby influencing subsequent division events, in an emergent interplay that may pattern early embryos independently of firm deterministic genetic programs. We here review the recent literature which helped to delineate mechanisms and functions of division positioning in early embryos.
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17
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Kramer EM, Tayjasanant PA, Cordone B. Scaling Laws for Mitotic Chromosomes. Front Cell Dev Biol 2021; 9:684278. [PMID: 34249936 PMCID: PMC8262490 DOI: 10.3389/fcell.2021.684278] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 05/10/2021] [Indexed: 11/13/2022] Open
Abstract
During mitosis in higher eukaryotes, each chromosome condenses into a pair of rod-shaped chromatids. This process is co-regulated by the activity of several gene families, and the underlying biophysics remains poorly understood. To better understand the factors regulating chromosome condensation, we compiled a database of mitotic chromosome size and DNA content from the tables and figures of >200 published papers. A comparison across vertebrate species shows that chromosome width, length and volume scale with DNA content to the powers ∼1/4, ∼1/2, and ∼1, respectively. Angiosperms (flowering plants) show a similar length scaling, so this result is not specific to vertebrates. Chromosome shape and size thus satisfy two conditions: (1) DNA content per unit volume is approximately constant and (2) the cross-sectional area increases proportionately with chromosome length. Since viscous drag forces during chromosome movement are expected to scale with length, we hypothesize that the cross-section increase is necessary to limit the occurrence of large chromosome elongations that could slow or stall mitosis. Lastly, we note that individual vertebrate karyotypes typically exhibit a wider range of chromosome lengths as compared with angiosperms.
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Affiliation(s)
- Eric M Kramer
- Department of Physics, Bard College at Simon's Rock, Great Barrington, MA, United States
| | - P A Tayjasanant
- Department of Physics, Bard College at Simon's Rock, Great Barrington, MA, United States
| | - Bethan Cordone
- Department of Physics, Bard College at Simon's Rock, Great Barrington, MA, United States
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18
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McInally SG, Kondev J, Goode BL. Scaling of subcellular actin structures with cell length through decelerated growth. eLife 2021; 10:68424. [PMID: 34114567 PMCID: PMC8233038 DOI: 10.7554/elife.68424] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 06/10/2021] [Indexed: 12/11/2022] Open
Abstract
How cells tune the size of their subcellular parts to scale with cell size is a fundamental question in cell biology. Until now, most studies on the size control of organelles and other subcellular structures have focused on scaling relationships with cell volume, which can be explained by limiting pool mechanisms. Here, we uncover a distinct scaling relationship with cell length rather than volume, revealed by mathematical modeling and quantitative imaging of yeast actin cables. The extension rate of cables decelerates as they approach the rear of the cell, until cable length matches cell length. Further, the deceleration rate scales with cell length. These observations are quantitatively explained by a ‘balance-point’ model, which stands in contrast to limiting pool mechanisms, and describes a distinct mode of self-assembly that senses the linear dimensions of the cell.
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Affiliation(s)
- Shane G McInally
- Department of Biology, Brandeis University, Waltham, United States.,Department of Physics, Brandeis University, Waltham, United States
| | - Jane Kondev
- Department of Physics, Brandeis University, Waltham, United States
| | - Bruce L Goode
- Department of Biology, Brandeis University, Waltham, United States
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19
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Abstract
Living systems maintain or increase local order by working against the second law of thermodynamics. Thermodynamic consistency is restored as they consume free energy, thereby increasing the net entropy of their environment. Recently introduced estimators for the entropy production rate have provided major insights into the efficiency of important cellular processes. In experiments, however, many degrees of freedom typically remain hidden to the observer, and, in these cases, existing methods are not optimal. Here, by reformulating the problem within an optimization framework, we are able to infer improved bounds on the rate of entropy production from partial measurements of biological systems. Our approach yields provably optimal estimates given certain measurable transition statistics. In contrast to prevailing methods, the improved estimator reveals nonzero entropy production rates even when nonequilibrium processes appear time symmetric and therefore may pretend to obey detailed balance. We demonstrate the broad applicability of this framework by providing improved bounds on the energy consumption rates in a diverse range of biological systems including bacterial flagella motors, growing microtubules, and calcium oscillations within human embryonic kidney cells.
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Affiliation(s)
- Dominic J Skinner
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139
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20
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Gros OJ, Damstra HGJ, Kapitein LC, Akhmanova A, Berger F. Dynein self-organizes while translocating the centrosome in T-cells. Mol Biol Cell 2021; 32:855-868. [PMID: 33689395 PMCID: PMC8108531 DOI: 10.1091/mbc.e20-10-0668] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 02/12/2021] [Accepted: 03/04/2021] [Indexed: 12/16/2022] Open
Abstract
T-cells massively restructure their internal architecture upon reaching an antigen-presenting cell (APC) to form the immunological synapse (IS), a cell-cell interface necessary for efficient elimination of the APC. This reorganization occurs through tight coordination of cytoskeletal processes: actin forms a peripheral ring, and dynein motors translocate the centrosome toward the IS. A recent study proposed that centrosome translocation involves a microtubule (MT) bundle that connects the centrosome perpendicularly to dynein at the synapse center: the "stalk." The synapse center, however, is actin-depleted, while actin was assumed to anchor dynein. We propose that dynein is attached to mobile membrane anchors, and investigate this model with computer simulations. We find that dynein organizes into a cluster in the synapse when translocating the centrosome, aligning MTs into a stalk. By implementing both a MT-capture-shrinkage and a MT-sliding mechanism, we explicitly demonstrate that this organization occurs in both systems. However, results obtained with MT-sliding dynein are more robust and display a stalk morphology consistent with our experimental data obtained with expansion microscopy. Thus, our simulations suggest that actin organization in T-cells during activation defines a specific geometry in which MT-sliding dynein can self-organize into a cluster and cause stalk formation.
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Affiliation(s)
- Oane J Gros
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Hugo G J Damstra
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Lukas C Kapitein
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Anna Akhmanova
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Florian Berger
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
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21
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Spindle scaling mechanisms. Essays Biochem 2021; 64:383-396. [PMID: 32501481 DOI: 10.1042/ebc20190064] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 05/11/2020] [Accepted: 05/12/2020] [Indexed: 02/02/2023]
Abstract
The mitotic spindle robustly scales with cell size in a plethora of different organisms. During development and throughout evolution, the spindle adjusts to cell size in metazoans and yeast in order to ensure faithful chromosome separation. Spindle adjustment to cell size occurs by the scaling of spindle length, spindle shape and the velocity of spindle assembly and elongation. Different mechanisms, depending on spindle structure and organism, account for these scaling relationships. The limited availability of critical spindle components, protein gradients, sequestration of spindle components, or post-translational modification and differential expression levels have been implicated in the regulation of spindle length and the spindle assembly/elongation velocity in a cell size-dependent manner. In this review, we will discuss the phenomenon and mechanisms of spindle length, spindle shape and spindle elongation velocity scaling with cell size.
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22
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Bloomfield M, Chen J, Cimini D. Spindle Architectural Features Must Be Considered Along With Cell Size to Explain the Timing of Mitotic Checkpoint Silencing. Front Physiol 2021; 11:596263. [PMID: 33584330 PMCID: PMC7877541 DOI: 10.3389/fphys.2020.596263] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 12/23/2020] [Indexed: 11/25/2022] Open
Abstract
Mitosis proceeds through a defined series of events that is largely conserved, but the amount of time needed for their completion can vary in different cells and organisms. In many systems, mitotic duration depends on the time required to satisfy and silence the spindle assembly checkpoint (SAC), also known as the mitotic checkpoint. Because SAC silencing involves trafficking SAC molecules among kinetochores, spindle, and cytoplasm, the size and geometry of the spindle relative to cell volume are expected to affect mitotic duration by influencing the timing of SAC silencing. However, the relationship between SAC silencing, cell size, and spindle dimensions is unclear. To investigate this issue, we used four DLD-1 tetraploid (4N) clones characterized by small or large nuclear and cell size. We found that the small 4N clones had longer mitotic durations than the parental DLD-1 cells and that this delay was due to differences in their metaphase duration. Leveraging a previous mathematical model for spatiotemporal regulation of SAC silencing, we show that the difference in metaphase duration, i.e., SAC silencing time, can be explained by the distinct spindle microtubule densities and sizes of the cell, spindle, and spindle poles in the 4N clones. Lastly, we demonstrate that manipulating spindle geometry can alter mitotic and metaphase duration, consistent with a model prediction. Our results suggest that spindle size does not always scale with cell size in mammalian cells and cell size is not sufficient to explain the differences in metaphase duration. Only when a number of spindle architectural features are considered along with cell size can the kinetics of SAC silencing, and hence mitotic duration, in the different clones be explained.
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Affiliation(s)
- Mathew Bloomfield
- Department of Biological Sciences and Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, United States
| | - Jing Chen
- Department of Biological Sciences and Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, United States
| | - Daniela Cimini
- Department of Biological Sciences and Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, United States
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23
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Rieckhoff EM, Berndt F, Elsner M, Golfier S, Decker F, Ishihara K, Brugués J. Spindle Scaling Is Governed by Cell Boundary Regulation of Microtubule Nucleation. Curr Biol 2020; 30:4973-4983.e10. [DOI: 10.1016/j.cub.2020.10.093] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 10/11/2020] [Accepted: 10/29/2020] [Indexed: 02/08/2023]
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24
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Rathbun LI, Aljiboury AA, Bai X, Hall NA, Manikas J, Amack JD, Bembenek JN, Hehnly H. PLK1- and PLK4-Mediated Asymmetric Mitotic Centrosome Size and Positioning in the Early Zebrafish Embryo. Curr Biol 2020; 30:4519-4527.e3. [PMID: 32916112 PMCID: PMC8159022 DOI: 10.1016/j.cub.2020.08.074] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 08/11/2020] [Accepted: 08/21/2020] [Indexed: 12/13/2022]
Abstract
Factors that regulate mitotic spindle positioning remain unclear within the confines of extremely large embryonic cells, such as the early divisions of the vertebrate embryo, Danio rerio (zebrafish). We find that the mitotic centrosome, a structure that assembles the mitotic spindle [1], is notably large in the zebrafish embryo (246.44 ± 11.93 μm2 in a 126.86 ± 0.35 μm diameter cell) compared to a C. elegans embryo (5.78 ± 0.18 μm2 in a 55.83 ± 1.04 μm diameter cell). During embryonic cell divisions, cell size changes rapidly in both C. elegans and zebrafish [2, 3], where mitotic centrosome area scales more closely with changes in cell size compared to changes in spindle length. Embryonic zebrafish spindles contain asymmetrically sized mitotic centrosomes (2.14 ± 0.13-fold difference between the two), with the larger mitotic centrosome placed toward the embryo center in a polo-like kinase (PLK) 1- and PLK4-dependent manner. We propose a model in which uniquely large zebrafish embryonic centrosomes direct spindle placement within disproportionately large cells.
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Affiliation(s)
- Lindsay I Rathbun
- Syracuse University, Department of Biology, 107 College Place, Syracuse, NY 13244, USA
| | - Abrar A Aljiboury
- Syracuse University, Department of Biology, 107 College Place, Syracuse, NY 13244, USA
| | - Xiaofei Bai
- University of Tennessee, Department of Biochemistry, Cellular and Molecular Biology, 1311 Cumberland Avenue, Knoxville, TN 37916, USA
| | - Nicole A Hall
- Syracuse University, Department of Biology, 107 College Place, Syracuse, NY 13244, USA
| | - Julie Manikas
- Syracuse University, Department of Biology, 107 College Place, Syracuse, NY 13244, USA
| | - Jeffrey D Amack
- SUNY Upstate Medical School, Department of Cell and Developmental Biology, 766 Irving Avenue, Syracuse, NY 13210, USA
| | - Joshua N Bembenek
- University of Tennessee, Department of Biochemistry, Cellular and Molecular Biology, 1311 Cumberland Avenue, Knoxville, TN 37916, USA; University of Michigan Medical School, Department of Molecular, Cellular, Developmental Biology, 1105 North University Avenue, Ann Arbor, MI 48109-1085, USA
| | - Heidi Hehnly
- Syracuse University, Department of Biology, 107 College Place, Syracuse, NY 13244, USA.
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25
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Abstract
As cells grow, the size and number of their internal organelles increase in order to keep up with increased metabolic requirements. Abnormal size of organelles is a hallmark of cancer and an important aspect of diagnosis in cytopathology. Most organelles vary in either size or number, or both, as a function of cell size, but the mechanisms that create this variation remain unclear. In some cases, organelle size appears to scale with cell size through processes of relative growth, but in others the size may be set by either active measurement systems or genetic programs that instruct organelle biosynthetic activities to create organelles of a size appropriate to a given cell type.
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Affiliation(s)
- Wallace F Marshall
- Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143, USA;
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26
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Farhadifar R, Yu CH, Fabig G, Wu HY, Stein DB, Rockman M, Müller-Reichert T, Shelley MJ, Needleman DJ. Stoichiometric interactions explain spindle dynamics and scaling across 100 million years of nematode evolution. eLife 2020; 9:e55877. [PMID: 32966209 PMCID: PMC7511230 DOI: 10.7554/elife.55877] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Accepted: 08/31/2020] [Indexed: 01/17/2023] Open
Abstract
The spindle shows remarkable diversity, and changes in an integrated fashion, as cells vary over evolution. Here, we provide a mechanistic explanation for variations in the first mitotic spindle in nematodes. We used a combination of quantitative genetics and biophysics to rule out broad classes of models of the regulation of spindle length and dynamics, and to establish the importance of a balance of cortical pulling forces acting in different directions. These experiments led us to construct a model of cortical pulling forces in which the stoichiometric interactions of microtubules and force generators (each force generator can bind only one microtubule), is key to explaining the dynamics of spindle positioning and elongation, and spindle final length and scaling with cell size. This model accounts for variations in all the spindle traits we studied here, both within species and across nematode species spanning over 100 million years of evolution.
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Affiliation(s)
- Reza Farhadifar
- Department of Molecular and Cellular Biology and School of Engineering and Applied Sciences, Harvard UniversityCambridgeUnited States
- Center for Computational Biology, Flatiron InstituteNew YorkUnited States
| | - Che-Hang Yu
- Department of Molecular and Cellular Biology and School of Engineering and Applied Sciences, Harvard UniversityCambridgeUnited States
| | - Gunar Fabig
- Experimental Center, Faculty of Medicine Carl Gustav CarusDresdenGermany
| | - Hai-Yin Wu
- Department of Molecular and Cellular Biology and School of Engineering and Applied Sciences, Harvard UniversityCambridgeUnited States
| | - David B Stein
- Center for Computational Biology, Flatiron InstituteNew YorkUnited States
| | - Matthew Rockman
- Department of Biology and Center for Genomics & Systems Biology, New York UniversityNew YorkUnited States
| | | | - Michael J Shelley
- Center for Computational Biology, Flatiron InstituteNew YorkUnited States
- Courant Institute, New York UniversityNew YorkUnited States
| | - Daniel J Needleman
- Department of Molecular and Cellular Biology and School of Engineering and Applied Sciences, Harvard UniversityCambridgeUnited States
- Center for Computational Biology, Flatiron InstituteNew YorkUnited States
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27
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Ong JY, Torres JZ. Phase Separation in Cell Division. Mol Cell 2020; 80:9-20. [PMID: 32860741 DOI: 10.1016/j.molcel.2020.08.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 07/10/2020] [Accepted: 08/07/2020] [Indexed: 02/08/2023]
Abstract
Cell division requires the assembly and organization of a microtubule spindle for the proper separation of chromosomes in mitosis and meiosis. Phase separation is an emerging paradigm for understanding spatial and temporal regulation of a variety of cellular processes, including cell division. Phase-separated condensates have been recently discovered at many structures during cell division as a possible mechanism for properly localizing, organizing, and activating proteins involved in cell division. Here, we review how these condensates play roles in regulating microtubule density and organization and spindle assembly and function and in activating some of the key players in cell division. We conclude with perspectives on areas of future research for this exciting and rapidly advancing field.
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Affiliation(s)
- Joseph Y Ong
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Jorge Z Torres
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA; Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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28
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Mukherjee RN, Sallé J, Dmitrieff S, Nelson KM, Oakey J, Minc N, Levy DL. The Perinuclear ER Scales Nuclear Size Independently of Cell Size in Early Embryos. Dev Cell 2020; 54:395-409.e7. [PMID: 32473090 PMCID: PMC7423768 DOI: 10.1016/j.devcel.2020.05.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 03/26/2020] [Accepted: 05/05/2020] [Indexed: 01/15/2023]
Abstract
Nuclear size plays pivotal roles in gene expression, embryo development, and disease. A central hypothesis in organisms ranging from yeast to vertebrates is that nuclear size scales to cell size. This implies that nuclei may reach steady-state sizes set by limiting cytoplasmic pools of size-regulating components. By monitoring nuclear dynamics in early sea urchin embryos, we found that nuclei undergo substantial growth in each interphase, reaching a maximal size prior to mitosis that declined steadily over the course of development. Manipulations of cytoplasmic volume through multiple chemical and physical means ruled out cell size as a major determinant of nuclear size and growth. Rather, our data suggest that the perinuclear endoplasmic reticulum, accumulated through dynein activity, serves as a limiting membrane pool that sets nuclear surface growth rate. Partitioning of this local pool at each cell division modulates nuclear growth kinetics and dictates size scaling throughout early development.
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Affiliation(s)
| | - Jérémy Sallé
- Université de Paris, Centre National de la Recherche Scientifique, Institut Jacques Monod, F-75006, Paris, France
| | - Serge Dmitrieff
- Université de Paris, Centre National de la Recherche Scientifique, Institut Jacques Monod, F-75006, Paris, France
| | - Katherine M Nelson
- Department of Chemical Engineering, University of Wyoming, Laramie, WY 82071, USA
| | - John Oakey
- Department of Chemical Engineering, University of Wyoming, Laramie, WY 82071, USA
| | - Nicolas Minc
- Université de Paris, Centre National de la Recherche Scientifique, Institut Jacques Monod, F-75006, Paris, France.
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA.
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29
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Guilloux G, Gibeaux R. Mechanisms of spindle assembly and size control. Biol Cell 2020; 112:369-382. [PMID: 32762076 DOI: 10.1111/boc.202000065] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 08/03/2020] [Accepted: 08/03/2020] [Indexed: 01/09/2023]
Abstract
The spindle is crucial for cell division by allowing the faithful segregation of replicated chromosomes to daughter cells. Proper segregation is ensured only if microtubules (MTs) and hundreds of other associated factors interact to assemble this complex structure with the appropriate architecture and size. In this review, we describe the latest view of spindle organisation as well as the molecular gradients and mechanisms underlying MT nucleation and spindle assembly. We then discuss the overlapping physical and molecular constraints that dictate spindle morphology, concluding with a focus on spindle size regulation.
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Affiliation(s)
- Gabriel Guilloux
- Univ Rennes, CNRS, IGDR [(Institute of Genetics and Development of Rennes)] - UMR 6290, F-35000 Rennes, France
| | - Romain Gibeaux
- Univ Rennes, CNRS, IGDR [(Institute of Genetics and Development of Rennes)] - UMR 6290, F-35000 Rennes, France
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30
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Nazockdast E, Redemann S. Mechanics of the spindle apparatus. Semin Cell Dev Biol 2020; 107:91-102. [PMID: 32747191 DOI: 10.1016/j.semcdb.2020.06.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 06/02/2020] [Accepted: 06/30/2020] [Indexed: 12/01/2022]
Abstract
During mitosis microtubules self-organize to form a bipolar mitotic spindle structure, which positions the sister chromatids on the spindle mid-plane and separates them afterwards. Previous studies have identified many spindle associated proteins. Yet, we do not fully understand how these nanoscopic proteins lead to force generation through interactions of individual microtubules, motor proteins and chromosomes, and how a large number of these local interactions ultimately determine the structure and mechanics of the spindle in micron scale. Here we review the current understanding and open questions related to the structure and mechanics of the mitotic spindle. We then discuss how a combination of electron microscopy and computational modeling can be used to tackle some of these open questions.
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Affiliation(s)
- Ehssan Nazockdast
- Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3250, USA.
| | - Stefanie Redemann
- Center for Membrane and Cell Physiology & Department of Molecular Physiology and Biological Physics, University of Virginia, School of Medicine, Charlottesville, VA, USA.
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31
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Chatterjee S, Sarkar A, Zhu J, Khodjakov A, Mogilner A, Paul R. Mechanics of Multicentrosomal Clustering in Bipolar Mitotic Spindles. Biophys J 2020; 119:434-447. [PMID: 32610087 DOI: 10.1016/j.bpj.2020.06.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 04/06/2020] [Accepted: 06/04/2020] [Indexed: 12/27/2022] Open
Abstract
To segregate chromosomes in mitosis, cells assemble a mitotic spindle, a molecular machine with centrosomes at two opposing cell poles and chromosomes at the equator. Microtubules and molecular motors connect the poles to kinetochores, specialized protein assemblies on the centromere regions of the chromosomes. Bipolarity of the spindle is crucial for the proper cell division, and two centrosomes in animal cells naturally become two spindle poles. Cancer cells are often multicentrosomal, yet they are able to assemble bipolar spindles by clustering centrosomes into two spindle poles. Mechanisms of this clustering are debated. In this study, we computationally screen effective forces between 1) centrosomes, 2) centrosomes and kinetochores, 3) centrosomes and chromosome arms, and 4) centrosomes and cell cortex to understand mechanics that determines three-dimensional spindle architecture. To do this, we use the stochastic Monte Carlo search for stable mechanical equilibria in the effective energy landscape of the spindle. We find that the following conditions have to be met to robustly assemble the bipolar spindle in a multicentrosomal cell: 1) the strengths of centrosomes' attraction to each other and to the cell cortex have to be proportional to each other and 2) the strengths of centrosomes' attraction to kinetochores and repulsion from the chromosome arms have to be proportional to each other. We also find that three other spindle configurations emerge if these conditions are not met: 1) collapsed, 2) monopolar, and 3) multipolar spindles, and the computational screen reveals mechanical conditions for these abnormal spindles.
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Affiliation(s)
| | - Apurba Sarkar
- Indian Association for the Cultivation of Science, Kolkata, India
| | - Jie Zhu
- Gerber Technology, Tolland, Connecticut
| | - Alexei Khodjakov
- Wadsworth Center, New York State Department of Health, Albany, New York; Rensselaer Polytechnic Institute, Troy, New York
| | - Alex Mogilner
- Courant Institute and Department of Biology, New York University, New York, New York.
| | - Raja Paul
- Indian Association for the Cultivation of Science, Kolkata, India.
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32
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Active forces shape the metaphase spindle through a mechanical instability. Proc Natl Acad Sci U S A 2020; 117:16154-16159. [PMID: 32601228 DOI: 10.1073/pnas.2002446117] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The metaphase spindle is a dynamic structure orchestrating chromosome segregation during cell division. Recently, soft matter approaches have shown that the spindle behaves as an active liquid crystal. Still, it remains unclear how active force generation contributes to its characteristic spindle-like shape. Here we combine theory and experiments to show that molecular motor-driven forces shape the structure through a barreling-type instability. We test our physical model by titrating dynein activity in Xenopus egg extract spindles and quantifying the shape and microtubule orientation. We conclude that spindles are shaped by the interplay between surface tension, nematic elasticity, and motor-driven active forces. Our study reveals how motor proteins can mold liquid crystalline droplets and has implications for the design of active soft materials.
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33
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Abstract
The size of the intracellular structure that encloses genomic DNA - known as the nucleus in eukaryotes and nucleoid in prokaryotes - is believed to scale according to cell size and genomic content inside them across the tree of life. However, an actual scaling relationship remains largely unexplored across eukaryotic species. Here, I collected a large dataset of nuclear and cell volumes in diverse species across different phyla, including some prokaryotes, from the published literature and assessed the scaling relationship. Although entire inter-species data showed that nuclear volume correlates with cell volume, the quantitative scaling property exhibited differences among prokaryotes, unicellular eukaryotes and multicellular eukaryotes. Additionally, the nuclear volume correlates with genomic content inside the nucleus of multicellular eukaryotes but not of prokaryotes and unicellular eukaryotes. In this Hypothesis, I, thus, propose that the basic concept of nuclear-size scaling is conserved across eukaryotes; however, structural and mechanical properties of nuclear membranes and chromatin can result in different scaling relationships of nuclear volume to cell volume and genomic content among species. In particular, eukaryote-specific properties of the nuclear membrane may contribute to the extreme flexibility of nuclear size with regard to DNA density inside the nucleus.
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Affiliation(s)
- Yuki Hara
- Evolutionary Cell Biology Laboratory, Faculty of Science, Yamaguchi University, Yoshida 1677-1, Yamaguchi city 753-8512, Japan
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34
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Geisterfer ZM, Zhu DY, Mitchison TJ, Oakey J, Gatlin JC. Microtubule Growth Rates Are Sensitive to Global and Local Changes in Microtubule Plus-End Density. Curr Biol 2020; 30:3016-3023.e3. [PMID: 32531285 DOI: 10.1016/j.cub.2020.05.056] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Revised: 04/14/2020] [Accepted: 05/18/2020] [Indexed: 01/02/2023]
Abstract
The microtubule cytoskeleton plays critically important roles in numerous cellular functions in eukaryotes, and it does so across a functionally diverse and morphologically disparate range of cell types [1]. In these roles, microtubule assemblies must adopt distinct morphologies and physical dimensions to perform specific functions [2-5]. As such, these macromolecular assemblies-as well as the dynamics of the individual microtubule polymers from which they are made-must scale and change in accordance with cell size, geometry, and function. Microtubules in cells typically assemble to a steady state in mass, leaving enough of their tubulin subunits soluble to allow rapid growth and turnover. This suggests some negative feedback that limits the extent of assembly, for example, decrease in growth rate, or increase in catastrophe rate, as the soluble subunit pool decreases. Although these ideas have informed the field for decades, they have not been observed experimentally. Here, we describe the application of an experimental approach that combines cell-free extracts with photo-patterned hydrogel micro-enclosures as a means to investigate microtubule dynamics in cytoplasmic volumes of defined size and shape. Our measurements reveal a negative correlation between microtubule plus-end density and microtubule growth rates and suggest that these rates are sensitive to the presence of nearby growing ends.
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Affiliation(s)
- Zachary M Geisterfer
- Department of Molecular Biology, University of Wyoming, 1000 E. University Avenue, Laramie, WY 82070, USA.
| | - Daniel Y Zhu
- Department of Molecular Biology, University of Wyoming, 1000 E. University Avenue, Laramie, WY 82070, USA
| | - Timothy J Mitchison
- Department of Systems Biology, Harvard Medical School, 25 Shattuck Street, Boston, MA 02115, USA; Marine Biological Laboratory, Cell Division and Organization Group, 7 MBL Street, Woods Hole, MA 02543, USA
| | - John Oakey
- Marine Biological Laboratory, Cell Division and Organization Group, 7 MBL Street, Woods Hole, MA 02543, USA; Department of Chemical Engineering, University of Wyoming, 1000 E. University Avenue, Laramie, WY 82070, USA
| | - Jesse C Gatlin
- Department of Molecular Biology, University of Wyoming, 1000 E. University Avenue, Laramie, WY 82070, USA; Marine Biological Laboratory, Cell Division and Organization Group, 7 MBL Street, Woods Hole, MA 02543, USA.
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35
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Levy DL. Cell Biology: Tubulin Contributes to Spindle Size Scaling. Curr Biol 2020; 30:R637-R639. [PMID: 32516610 DOI: 10.1016/j.cub.2020.04.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sizes of intracellular structures are important for function, yet mechanisms underlying subcellular size control are largely unexplored. A new study reveals how differences in tubulin populations between two related Xenopus frog species influence microtubule dynamics and spindle length.
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Affiliation(s)
- Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA.
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36
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Hirst WG, Biswas A, Mahalingan KK, Reber S. Differences in Intrinsic Tubulin Dynamic Properties Contribute to Spindle Length Control in Xenopus Species. Curr Biol 2020; 30:2184-2190.e5. [PMID: 32386526 DOI: 10.1016/j.cub.2020.03.067] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 02/13/2020] [Accepted: 03/26/2020] [Indexed: 01/21/2023]
Abstract
The function of cellular organelles relates not only to their molecular composition but also to their size. However, how the size of dynamic mesoscale structures is established and maintained remains poorly understood [1-3]. Mitotic spindle length, for example, varies several-fold among cell types and among different organisms [4]. Although most studies on spindle size control focus on changes in proteins that regulate microtubule dynamics [5-8], the contribution of the spindle's main building block, the αβ-tubulin heterodimer, has yet to be studied. Apart from microtubule-associated proteins and motors, two factors have been shown to contribute to the heterogeneity of microtubule dynamics: tubulin isoform composition [9, 10] and post-translational modifications [11]. In the past, studying the contribution of tubulin and microtubules to spindle assembly has been limited by the fact that physiologically relevant tubulins were not available. Here, we show that tubulins purified from two closely related frogs, Xenopus laevis and Xenopus tropicalis, have surprisingly different microtubule dynamics in vitro. X. laevis microtubules combine very fast growth and infrequent catastrophes. In contrast, X. tropicalis microtubules grow slower and catastrophe more frequently. We show that spindle length and microtubule mass can be controlled by titrating the ratios of the tubulins from the two frog species. Furthermore, we combine our in vitro reconstitution assay and egg extract experiments with computational modeling to show that differences in intrinsic properties of different tubulins contribute to the control of microtubule mass and therefore set steady-state spindle length.
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Affiliation(s)
- William G Hirst
- IRI Life Sciences, Humboldt-Universität zu Berlin, 10115 Berlin, Germany; Research School of Biology, The Australian National University, Canberra, ACT 2600, Australia; Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Abin Biswas
- IRI Life Sciences, Humboldt-Universität zu Berlin, 10115 Berlin, Germany; Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | | | - Simone Reber
- IRI Life Sciences, Humboldt-Universität zu Berlin, 10115 Berlin, Germany; Marine Biological Laboratory, Woods Hole, MA 02543, USA; University of Applied Sciences Berlin, 13353 Berlin, Germany.
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37
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The Spindle Assembly Checkpoint Functions during Early Development in Non-Chordate Embryos. Cells 2020; 9:cells9051087. [PMID: 32354040 PMCID: PMC7290841 DOI: 10.3390/cells9051087] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 04/22/2020] [Accepted: 04/24/2020] [Indexed: 12/14/2022] Open
Abstract
In eukaryotic cells, a spindle assembly checkpoint (SAC) ensures accurate chromosome segregation, by monitoring proper attachment of chromosomes to spindle microtubules and delaying mitotic progression if connections are erroneous or absent. The SAC is thought to be relaxed during early embryonic development. Here, we evaluate the checkpoint response to lack of kinetochore-spindle microtubule interactions in early embryos of diverse animal species. Our analysis shows that there are two classes of embryos, either proficient or deficient for SAC activation during cleavage. Sea urchins, mussels, and jellyfish embryos show a prolonged delay in mitotic progression in the absence of spindle microtubules from the first cleavage division, while ascidian and amphioxus embryos, like those of Xenopus and zebrafish, continue mitotic cycling without delay. SAC competence during early development shows no correlation with cell size, chromosome number, or kinetochore to cell volume ratio. We show that SAC proteins Mad1, Mad2, and Mps1 lack the ability to recognize unattached kinetochores in ascidian embryos, indicating that SAC signaling is not diluted but rather actively silenced during early chordate development.
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38
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Goupil A, Nano M, Letort G, Gemble S, Edwards F, Goundiam O, Gogendeau D, Pennetier C, Basto R. Chromosomes function as a barrier to mitotic spindle bipolarity in polyploid cells. J Cell Biol 2020; 219:133854. [PMID: 32328633 PMCID: PMC7147111 DOI: 10.1083/jcb.201908006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 12/13/2019] [Accepted: 01/24/2020] [Indexed: 01/22/2023] Open
Abstract
Ploidy variations such as genome doubling are frequent in human tumors and have been associated with genetic instability favoring tumor progression. How polyploid cells deal with increased centrosome numbers and DNA content remains unknown. Using Drosophila neuroblasts and human cancer cells to study mitotic spindle assembly in polyploid cells, we found that most polyploid cells divide in a multipolar manner. We show that even if an initial centrosome clustering step can occur at mitotic entry, the establishment of kinetochore-microtubule attachments leads to spatial chromosome configurations, whereby the final coalescence of supernumerary poles into a bipolar array is inhibited. Using in silico approaches and various spindle and DNA perturbations, we show that chromosomes act as a physical barrier blocking spindle pole coalescence and bipolarity. Importantly, microtubule stabilization suppressed multipolarity by improving both centrosome clustering and pole coalescence. This work identifies inhibitors of bipolar division in polyploid cells and provides a rationale to understand chromosome instability typical of polyploid cancer cells.
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Affiliation(s)
- Alix Goupil
- Institut Curie, Paris Science et Lettres Research University, Centre National de la Recherche Scientifique, Unité Mixte de Recherche UMR144, Biology of Centrosomes and Genetic Instability Laboratory, Paris, France
| | - Maddalena Nano
- Institut Curie, Paris Science et Lettres Research University, Centre National de la Recherche Scientifique, Unité Mixte de Recherche UMR144, Biology of Centrosomes and Genetic Instability Laboratory, Paris, France
| | - Gaëlle Letort
- Center for Interdisciplinary Research in Biology, Collège de France, UMR7241/U1050, Paris, France
| | - Simon Gemble
- Institut Curie, Paris Science et Lettres Research University, Centre National de la Recherche Scientifique, Unité Mixte de Recherche UMR144, Biology of Centrosomes and Genetic Instability Laboratory, Paris, France
| | - Frances Edwards
- Institut Curie, Paris Science et Lettres Research University, Centre National de la Recherche Scientifique, Unité Mixte de Recherche UMR144, Biology of Centrosomes and Genetic Instability Laboratory, Paris, France
| | - Oumou Goundiam
- Institut Curie, Paris Science et Lettres Research University, Centre National de la Recherche Scientifique, Unité Mixte de Recherche UMR144, Biology of Centrosomes and Genetic Instability Laboratory, Paris, France.,Department of Translational Research, Institut Curie, PSL University, Paris, France
| | - Delphine Gogendeau
- Institut Curie, Paris Science et Lettres Research University, Centre National de la Recherche Scientifique, Unité Mixte de Recherche UMR144, Biology of Centrosomes and Genetic Instability Laboratory, Paris, France
| | - Carole Pennetier
- Institut Curie, Paris Science et Lettres Research University, Centre National de la Recherche Scientifique, Unité Mixte de Recherche UMR144, Biology of Centrosomes and Genetic Instability Laboratory, Paris, France
| | - Renata Basto
- Institut Curie, Paris Science et Lettres Research University, Centre National de la Recherche Scientifique, Unité Mixte de Recherche UMR144, Biology of Centrosomes and Genetic Instability Laboratory, Paris, France
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39
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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: 90] [Impact Index Per Article: 22.5] [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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40
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Edelmaier C, Lamson AR, Gergely ZR, Ansari S, Blackwell R, McIntosh JR, Glaser MA, Betterton MD. Mechanisms of chromosome biorientation and bipolar spindle assembly analyzed by computational modeling. eLife 2020; 9:48787. [PMID: 32053104 PMCID: PMC7311174 DOI: 10.7554/elife.48787] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 02/12/2020] [Indexed: 01/19/2023] Open
Abstract
The essential functions required for mitotic spindle assembly and chromosome biorientation and segregation are not fully understood, despite extensive study. To illuminate the combinations of ingredients most important to align and segregate chromosomes and simultaneously assemble a bipolar spindle, we developed a computational model of fission-yeast mitosis. Robust chromosome biorientation requires progressive restriction of attachment geometry, destabilization of misaligned attachments, and attachment force dependence. Large spindle length fluctuations can occur when the kinetochore-microtubule attachment lifetime is long. The primary spindle force generators are kinesin-5 motors and crosslinkers in early mitosis, while interkinetochore stretch becomes important after biorientation. The same mechanisms that contribute to persistent biorientation lead to segregation of chromosomes to the poles after anaphase onset. This model therefore provides a framework to interrogate key requirements for robust chromosome biorientation, spindle length regulation, and force generation in the spindle. Before a cell divides, it must make a copy of its genetic material and then promptly split in two. This process, called mitosis, is coordinated by many different molecular machines. The DNA is copied, then the duplicated chromosomes line up at the middle of the cell. Next, an apparatus called the mitotic spindle latches onto the chromosomes before pulling them apart. The mitotic spindle is a bundle of long, thin filaments called microtubules. It attaches to chromosomes at the kinetochore, the point where two copied chromosomes are cinched together in their middle. Proper cell division is vital for the healthy growth of all organisms, big and small, and yet some parts of the process remain poorly understood despite extensive study. Specifically, there is more to learn about how the mitotic spindle self-assembles, and how microtubules and kinetochores work together to correctly orient and segregate chromosomes into two sister cells. These nanoscale processes are happening a hundred times a minute, so computer simulations are a good way to test what we know. Edelmaier et al. developed a computer model to simulate cell division in fission yeast, a species of yeast often used to study fundamental processes in the cell. The model simulates how the mitotic spindle assembles, how its microtubules attach to the kinetochore and the force required to pull two sister chromosomes apart. Building the simulation involved modelling interactions between the mitotic spindle and kinetochore, their movement and forces applied. To test its accuracy, model simulations were compared to recordings of the mitotic spindle – including its length, structure and position – imaged from dividing yeast cells. Running the simulation, Edelmaier et al. found that several key effects are essential for the proper movement of chromosomes in mitosis. This includes holding chromosomes in the correct orientation as the mitotic spindle assembles and controlling the relative position of microtubules as they attach to the kinetochore. Misaligned attachments must also be readily deconstructed and corrected to prevent any errors. The simulations also showed that kinetochores must begin to exert more force (to separate the chromosomes) once the mitotic spindle is attached correctly. Altogether, these findings improve the current understanding of how the mitotic spindle and its counterparts control cell division. Errors in chromosome segregation are associated with birth defects and cancer in humans, and this new simulation could potentially now be used to help make predictions about how to correct mistakes in the process.
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Affiliation(s)
| | - Adam R Lamson
- Department of Physics, University of Colorado Boulder, Boulder, United States
| | - Zachary R Gergely
- Department of Physics, University of Colorado Boulder, Boulder, United States.,Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, United States
| | - Saad Ansari
- Department of Physics, University of Colorado Boulder, Boulder, United States
| | - Robert Blackwell
- Department of Physics, University of Colorado Boulder, Boulder, United States
| | - J Richard McIntosh
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, United States
| | - Matthew A Glaser
- Department of Physics, University of Colorado Boulder, Boulder, United States
| | - Meredith D Betterton
- Department of Physics, University of Colorado Boulder, Boulder, United States.,Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, United States
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41
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Wesley CC, Mishra S, Levy DL. Organelle size scaling over embryonic development. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2020; 9:e376. [PMID: 32003549 DOI: 10.1002/wdev.376] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 12/19/2019] [Accepted: 01/08/2020] [Indexed: 12/13/2022]
Abstract
Cell division without growth results in progressive cell size reductions during early embryonic development. How do the sizes of intracellular structures and organelles scale with cell size and what are the functional implications of such scaling relationships? Model organisms, in particular Caenorhabditis elegans worms, Drosophila melanogaster flies, Xenopus laevis frogs, and Mus musculus mice, have provided insights into developmental size scaling of the nucleus, mitotic spindle, and chromosomes. Nuclear size is regulated by nucleocytoplasmic transport, nuclear envelope proteins, and the cytoskeleton. Regulators of microtubule dynamics and chromatin compaction modulate spindle and mitotic chromosome size scaling, respectively. Developmental scaling relationships for membrane-bound organelles, like the endoplasmic reticulum, Golgi, mitochondria, and lysosomes, have been less studied, although new imaging approaches promise to rectify this deficiency. While models that invoke limiting components and dynamic regulation of assembly and disassembly can account for some size scaling relationships in early embryos, it will be exciting to investigate the contribution of newer concepts in cell biology such as phase separation and interorganellar contacts. With a growing understanding of the underlying mechanisms of organelle size scaling, future studies promise to uncover the significance of proper scaling for cell function and embryonic development, as well as how aberrant scaling contributes to disease. This article is categorized under: Establishment of Spatial and Temporal Patterns > Regulation of Size, Proportion, and Timing Early Embryonic Development > Fertilization to Gastrulation Comparative Development and Evolution > Model Systems.
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Affiliation(s)
- Chase C Wesley
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming
| | - Sampada Mishra
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming
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42
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Winkley K, Ward S, Reeves W, Veeman M. Iterative and Complex Asymmetric Divisions Control Cell Volume Differences in Ciona Notochord Tapering. Curr Biol 2019; 29:3466-3477.e4. [PMID: 31607534 DOI: 10.1016/j.cub.2019.08.056] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/29/2019] [Accepted: 08/21/2019] [Indexed: 12/12/2022]
Abstract
The notochord of the invertebrate chordate Ciona forms a tapered rod at tailbud stages consisting of only 40 cylindrical cells in a single-file column. This tapered shape involves differences in notochord cell volume along the anterior-posterior axis. Here, we quantify sibling cell volume asymmetry throughout the developing notochord and find that there are distinctive patterns of unequal cleavage in all 4 bilateral pairs of A-line primary notochord founder cells and also in the B-line-derived secondary notochord founder cells. A quantitative model confirms that the observed patterns of unequal cleavage are sufficient to explain all the anterior-posterior variation in notochord cell volume. Many examples are known of cells that divide asymmetrically to give daughter cells of different size and fate. Here, by contrast, a series of subtle but iterative and finely patterned asymmetric divisions controls the shape of an entire organ. Quantitative 3D analysis of cell shape and spindle positioning allows us to infer multiple cellular mechanisms driving these unequal cleavages, including polarized displacements of the mitotic spindle, contributions from the shape of the mother cell, and late changes occurring between anaphase and abscission that potentially involve differential cortical contractility. We infer differential use of these mechanisms between different notochord blastomeres and also between different rounds of cell division. These results demonstrate a new role for asymmetric division in directly shaping a developing organ and point toward complex underlying mechanisms.
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Affiliation(s)
- Konner Winkley
- Division of Biology, Kansas State University, 1717 Claflin Road, Manhattan, KS 66506, USA
| | - Spencer Ward
- Division of Biology, Kansas State University, 1717 Claflin Road, Manhattan, KS 66506, USA
| | - Wendy Reeves
- Division of Biology, Kansas State University, 1717 Claflin Road, Manhattan, KS 66506, USA
| | - Michael Veeman
- Division of Biology, Kansas State University, 1717 Claflin Road, Manhattan, KS 66506, USA.
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43
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Redemann S, Fürthauer S, Shelley M, Müller-Reichert T. Current approaches for the analysis of spindle organization. Curr Opin Struct Biol 2019; 58:269-277. [DOI: 10.1016/j.sbi.2019.05.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 05/28/2019] [Accepted: 05/29/2019] [Indexed: 01/06/2023]
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44
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Rieckhoff EM, Ishihara K, Brugués J. How to tune spindle size relative to cell size? Curr Opin Cell Biol 2019; 60:139-144. [PMID: 31377657 DOI: 10.1016/j.ceb.2019.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 06/17/2019] [Accepted: 06/17/2019] [Indexed: 12/20/2022]
Abstract
Cells need to regulate the size and shape of their organelles for proper function. For example, the mitotic spindle adapts its size to changes in cell size over several orders of magnitude, but we lack a mechanistic understanding of how this is achieved. Here, we review our current knowledge of how small and large spindles assemble and ask which microtubule-based biophysical processes (nucleation, polymerization dynamics, transport) may be responsible for spindle size regulation. Finally, we review possible cell-scale mechanisms that put spindle size under the regulation of cell size.
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Affiliation(s)
- Elisa Maria Rieckhoff
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, Germany; Center for Systems Biology Dresden, Dresden, Germany; Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany
| | - Keisuke Ishihara
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, Germany; Center for Systems Biology Dresden, Dresden, Germany; Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany
| | - Jan Brugués
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, Germany; Center for Systems Biology Dresden, Dresden, Germany; Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany.
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45
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Abstract
Cell division is a highly regulated and carefully orchestrated process. Understanding the mechanisms that promote proper cell division is an important step toward unraveling important questions in cell biology and human health. Early studies seeking to dissect the mechanisms of cell division used classical genetics approaches to identify genes involved in mitosis and deployed biochemical approaches to isolate and identify proteins critical for cell division. These studies underscored that post-translational modifications and cyclin-kinase complexes play roles at the heart of the cell division program. Modern approaches for examining the mechanisms of cell division, including the use of high-throughput methods to study the effects of RNAi, cDNA, and chemical libraries, have evolved to encompass a larger biological and chemical space. Here, we outline some of the classical studies that established a foundation for the field and provide an overview of recent approaches that have advanced the study of cell division.
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Affiliation(s)
- Joseph Y Ong
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095
| | - Jorge Z Torres
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095 .,The Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, California 90095.,Molecular Biology Institute, UCLA, Los Angeles, California 90095
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46
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The quantification and regulation of microtubule dynamics in the mitotic spindle. Curr Opin Cell Biol 2019; 60:36-43. [PMID: 31108428 DOI: 10.1016/j.ceb.2019.03.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 03/20/2019] [Accepted: 03/30/2019] [Indexed: 12/18/2022]
Abstract
Microtubules play essential roles in cellular organization, cargo transport, and chromosome segregation during cell division. During mitosis microtubules form a macromolecular structure known as the mitotic spindle that is responsible for the accurate segregation of chromosomes between the two daughter cells. This is accomplished thanks to finely tuned control of microtubule dynamics. Even small changes in microtubule dynamics during spindle formation and/or operation may lead to chromosome mis-segregation, chromosome instability and aneuploidy. These three events are directly correlated with human diseases like cancer and developmental defects. Precise measurements of microtubule dynamics in the spindle will allow us to discover new molecules involved in regulating microtubule dynamics and enable a deeper understanding of the mechanisms that underlie mitosis and cancer emergence and development. Moreover, many chemotherapeutic agents for cancer treatment are targeted to microtubules, so continued investigation of their dynamics with utmost precision will facilitate the development of new drugs. Measuring microtubule dynamics in the spindle has been a difficult task until recently. With the development of new and gentler microscopic techniques, and new computer programs, we can perform better and more accurate measurements of microtubule dynamics during mitosis.
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47
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Abstract
Individual cell types have characteristic sizes, suggesting that size sensing mechanisms may coordinate transcription, translation, and metabolism with cell growth rates. Two types of size-sensing mechanisms have been proposed: spatial sensing of the location or dimensions of a signal, subcellular structure or organelle; or titration-based sensing of the intracellular concentrations of key regulators. Here we propose that size sensing in animal cells combines both titration and spatial sensing elements in a dynamic mechanism whereby microtubule motor-dependent localization of RNA encoding importin β1 and mTOR, coupled with regulated local protein synthesis, enable cytoskeleton length sensing for cell growth regulation.
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Affiliation(s)
- Ida Rishal
- Department of Biomolecular Sciences, Weizmann Institute of Science, 76100, Rehovot, Israel
| | - Mike Fainzilber
- Department of Biomolecular Sciences, Weizmann Institute of Science, 76100, Rehovot, Israel.
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48
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Letort G, Bennabi I, Dmitrieff S, Nedelec F, Verlhac MH, Terret ME. A computational model of the early stages of acentriolar meiotic spindle assembly. Mol Biol Cell 2019; 30:863-875. [PMID: 30650011 PMCID: PMC6589792 DOI: 10.1091/mbc.e18-10-0644] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 12/18/2018] [Accepted: 01/09/2019] [Indexed: 11/11/2022] Open
Abstract
The mitotic spindle is an ensemble of microtubules responsible for the repartition of the chromosomal content between the two daughter cells during division. In metazoans, spindle assembly is a gradual process involving dynamic microtubules and recruitment of numerous associated proteins and motors. During mitosis, centrosomes organize and nucleate the majority of spindle microtubules. In contrast, oocytes lack canonical centrosomes but are still able to form bipolar spindles, starting from an initial ball that self-organizes in several hours. Interfering with early steps of meiotic spindle assembly can lead to erroneous chromosome segregation. Although not fully elucidated, this process is known to rely on antagonistic activities of plus end- and minus end-directed motors. We developed a model of early meiotic spindle assembly in mouse oocytes, including key factors such as microtubule dynamics and chromosome movement. We explored how the balance between plus end- and minus end-directed motors, as well as the influence of microtubule nucleation, impacts spindle morphology. In a refined model, we added spatial regulation of microtubule stability and minus-end clustering. We could reproduce the features of early stages of spindle assembly from 12 different experimental perturbations and predict eight additional perturbations. With its ability to characterize and predict chromosome individualization, this model can help deepen our understanding of spindle assembly.
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Affiliation(s)
- Gaelle Letort
- CIRB, Collège de France, UMR7241/U1050, F-75005 Paris, France
| | - Isma Bennabi
- CIRB, Collège de France, UMR7241/U1050, F-75005 Paris, France
| | - Serge Dmitrieff
- Institut Jacques Monod, UMR7592 and Université Paris-Diderot, F-75205 Paris, France
| | - François Nedelec
- Centre de Recherche Interdisciplinaire, F-75004 Paris, France
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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49
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Krüger LK, Sanchez JL, Paoletti A, Tran PT. Kinesin-6 regulates cell-size-dependent spindle elongation velocity to keep mitosis duration constant in fission yeast. eLife 2019; 8:42182. [PMID: 30806623 PMCID: PMC6391065 DOI: 10.7554/elife.42182] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 02/13/2019] [Indexed: 01/01/2023] Open
Abstract
The length of the mitotic spindle scales with cell size in a wide range of organisms during embryonic development. Interestingly, in C. elegans embryos, this goes along with temporal regulation: larger cells speed up spindle assembly and elongation. We demonstrate that, similarly in fission yeast, spindle length and spindle dynamics adjust to cell size, which allows to keep mitosis duration constant. Since prolongation of mitosis was shown to affect cell viability, this may resemble a mechanism to regulate mitosis duration. We further reveal how the velocity of spindle elongation is regulated: coupled to cell size, the amount of kinesin-6 Klp9 molecules increases, resulting in an acceleration of spindle elongation in anaphase B. In addition, the number of Klp9 binding sites to microtubules increases overproportionally to Klp9 molecules, suggesting that molecular crowding inversely correlates to cell size and might have an impact on spindle elongation velocity control.
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Affiliation(s)
| | | | - Anne Paoletti
- Institut Curie, PSL Research University, CNRS, UMR 144, Paris, France
| | - Phong Thanh Tran
- Institut Curie, PSL Research University, CNRS, UMR 144, Paris, France.,Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, United States
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50
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Ravichandran A, Duman Ö, Hoore M, Saggiorato G, Vliegenthart GA, Auth T, Gompper G. Chronology of motor-mediated microtubule streaming. eLife 2019; 8:e39694. [PMID: 30601119 PMCID: PMC6338466 DOI: 10.7554/elife.39694] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 12/28/2018] [Indexed: 12/19/2022] Open
Abstract
We introduce a filament-based simulation model for coarse-grained, effective motor-mediated interaction between microtubule pairs to study the time-scales that compose cytoplasmic streaming. We characterise microtubule dynamics in two-dimensional systems by chronologically arranging five distinct processes of varying duration that make up streaming, from microtubule pairs to collective dynamics. The structures found were polarity sorted due to the propulsion of antialigned microtubules. This also gave rise to the formation of large polar-aligned domains, and streaming at the domain boundaries. Correlation functions, mean squared displacements, and velocity distributions reveal a cascade of processes ultimately leading to microtubule streaming and advection, spanning multiple microtubule lengths. The characteristic times for the processes extend over three orders of magnitude from fast single-microtubule processes to slow collective processes. Our approach can be used to directly test the importance of molecular components, such as motors and crosslinking proteins between microtubules, on the collective dynamics at cellular scale.
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Affiliation(s)
- Arvind Ravichandran
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Özer Duman
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Masoud Hoore
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Guglielmo Saggiorato
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Gerard A Vliegenthart
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Thorsten Auth
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Gerhard Gompper
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
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