1
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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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2
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Rinaldin M, Kickuth A, Dalton B, Xu Y, Di Talia S, Brugués J. Robust cytoplasmic partitioning by solving an intrinsic cytoskeletal instability. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.12.584684. [PMID: 38559072 PMCID: PMC10980089 DOI: 10.1101/2024.03.12.584684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Early development across vertebrates and insects critically relies on robustly reorganizing the cytoplasm of fertilized eggs into individualized cells. This intricate process is orchestrated by large microtubule structures that traverse the embryo, partitioning the cytoplasm into physically distinct and stable compartments. Despite the robustness of embryonic development, here we uncover an intrinsic instability in cytoplasmic partitioning driven by the microtubule cytoskeleton. We reveal that embryos circumvent this instability through two distinct mechanisms: either by matching the cell cycle duration to the time needed for the instability to unfold or by limiting microtubule nucleation. These regulatory mechanisms give rise to two possible strategies to fill the cytoplasm, which we experimentally demonstrate in zebrafish and Drosophila embryos, respectively. In zebrafish embryos, unstable microtubule waves fill the geometry of the entire embryo from the first division. Conversely, in Drosophila embryos, stable microtubule asters resulting from reduced microtubule nucleation gradually fill the cytoplasm throughout multiple divisions. Our results indicate that the temporal control of microtubule dynamics could have driven the evolutionary emergence of species-specific mechanisms for effective cytoplasmic organization. Furthermore, our study unveils a fundamental synergy between physical instabilities and biological clocks, uncovering universal strategies for rapid, robust, and efficient spatial ordering in biological systems.
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Affiliation(s)
- 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 for 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 for Systems Biology Dresden, 01307 Germany
| | - Benjamin Dalton
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Yitong Xu
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710 USA
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710 USA
| | - 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 for Systems Biology Dresden, 01307 Germany
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3
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de-Carvalho J, Tlili S, Saunders TE, Telley IA. The positioning mechanics of microtubule asters in Drosophila embryo explants. eLife 2024; 12:RP90541. [PMID: 38426416 PMCID: PMC10911390 DOI: 10.7554/elife.90541] [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] [Indexed: 03/02/2024] Open
Abstract
Microtubule asters are essential in localizing the action of microtubules in processes including mitosis and organelle positioning. In large cells, such as the one-cell sea urchin embryo, aster dynamics are dominated by hydrodynamic pulling forces. However, in systems with more densely positioned nuclei such as the early Drosophila embryo, which packs around 6000 nuclei within the syncytium in a crystalline-like order, it is unclear what processes dominate aster dynamics. Here, we take advantage of a cell cycle regulation Drosophila mutant to generate embryos with multiple asters, independent from nuclei. We use an ex vivo assay to further simplify this biological system to explore the forces generated by and between asters. Through live imaging, drug and optical perturbations, and theoretical modeling, we demonstrate that these asters likely generate an effective pushing force over short distances.
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Affiliation(s)
- Jorge de-Carvalho
- Instituto Gulbenkian de Ciência, Fundação Calouste GulbenkianOeirasPortugal
| | - Sham Tlili
- Mechanobiology Institute and Department of Biological Sciences, National University of SingaporeSingaporeSingapore
| | - Timothy E Saunders
- Mechanobiology Institute and Department of Biological Sciences, National University of SingaporeSingaporeSingapore
- Institute of Molecular and Cellular Biology, A*Star, ProteosSingaporeSingapore
- Centre for Mechanochemical Cell Biology, Warwick Medical School, University of WarwickWarwickUnited Kingdom
| | - Ivo A Telley
- Instituto Gulbenkian de Ciência, Fundação Calouste GulbenkianOeirasPortugal
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4
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Goda M, Shribak M, Ikeda Z, Okada N, Tani T, Goshima G, Oldenbourg R, Kimura A. Live-cell imaging under centrifugation characterized the cellular force for nuclear centration in the Caenorhabditis elegans embryo. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.03.574024. [PMID: 38260704 PMCID: PMC10802357 DOI: 10.1101/2024.01.03.574024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Organelles in cells are appropriately positioned, despite crowding in the cytoplasm. However, our understanding of the force required to move large organelles, such as the nucleus, inside the cytoplasm is limited, in part owing to a lack of accurate methods for measurement. We devised a novel method to apply forces to the nucleus of living, wild-type Caenorhabditis elegans embryos to measure the force generated inside the cell. We utilized a centrifuge polarizing microscope (CPM) to apply centrifugal force and orientation-independent differential interference contrast (OI-DIC) microscopy to characterize the mass density of the nucleus and cytoplasm. The cellular forces moving the nucleus toward the cell center increased linearly at ~14 pN/μm depending on the distance from the center. The frictional coefficient was ~1,100 pN s/μm. The measured values were smaller than previously reported estimates for sea urchin embryos. The forces were consistent with the centrosome-organelle mutual pulling model for nuclear centration. Frictional coefficient was reduced when microtubules were shorter or detached from nuclei in mutant embryos, demonstrating the contribution of astral microtubules. Finally, the frictional coefficient was higher than a theoretical estimate, indicating the contribution of uncharacterized properties of the cytoplasm.
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Affiliation(s)
- Makoto Goda
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA
- Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
- Nagoya University, Nagoya 464-8602, Japan
| | - Michael Shribak
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA
| | - Zenki Ikeda
- National Institute of Genetics, Mishima 411-8540, Japan
- Sokendai (Graduate University for Advanced Studies) Mishima, Mishima 411-8540, Japan
| | | | - Tomomi Tani
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ikeda 563-8577, Japan
| | - Gohta Goshima
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA
- Nagoya University, Nagoya 464-8602, Japan
| | | | - Akatsuki Kimura
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA
- National Institute of Genetics, Mishima 411-8540, Japan
- Sokendai (Graduate University for Advanced Studies) Mishima, Mishima 411-8540, Japan
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5
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Scrofani J, Ruhnow F, Chew WX, Normanno D, Nedelec F, Surrey T, Vernos I. Branched microtubule nucleation and dynein transport organize RanGTP asters in Xenopus laevis egg extract. Mol Biol Cell 2024; 35:ar12. [PMID: 37991893 PMCID: PMC10881172 DOI: 10.1091/mbc.e23-10-0407] [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: 10/24/2023] [Revised: 11/03/2023] [Accepted: 11/07/2023] [Indexed: 11/24/2023] Open
Abstract
Chromosome segregation relies on the correct assembly of a bipolar spindle. Spindle pole self-organization requires dynein-dependent microtubule (MT) transport along other MTs. However, during M-phase RanGTP triggers MT nucleation and branching generating polarized arrays with nonastral organization in which MT minus ends are linked to the sides of other MTs. This raises the question of how branched-MT nucleation and dynein-mediated transport cooperate to organize the spindle poles. Here, we used RanGTP-dependent MT aster formation in Xenopus laevis (X. laevis) egg extract to study the interplay between these two seemingly conflicting organizing principles. Using temporally controlled perturbations of MT nucleation and dynein activity, we found that branched MTs are not static but instead dynamically redistribute over time as poles self-organize. Our experimental data together with computer simulations suggest a model where dynein together with dynactin and NuMA directly pulls and move branched MT minus ends toward other MT minus ends.
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Affiliation(s)
- Jacopo Scrofani
- Quantitative Cell Biology Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
| | - Felix Ruhnow
- Quantitative Cell Biology Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
| | - Wei-Xiang Chew
- Quantitative Cell Biology Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
| | - Davide Normanno
- Quantitative Cell Biology Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
| | - Francois Nedelec
- Sainsbury Laboratory, Cambridge University, Bateman street, CB2 1LR Cambridge, UK
| | - Thomas Surrey
- Quantitative Cell Biology Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
- Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain
- Institución Catalana de Investigación y Estudios Avanzados (ICREA), Pg. Lluis Companys 23, 08010 Barcelona, Spain
| | - Isabelle Vernos
- Quantitative Cell Biology Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
- Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain
- Institución Catalana de Investigación y Estudios Avanzados (ICREA), Pg. Lluis Companys 23, 08010 Barcelona, Spain
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6
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Arjona MI, Najafi J, Minc N. Cytoplasm mechanics and cellular organization. Curr Opin Cell Biol 2023; 85:102278. [PMID: 37979412 DOI: 10.1016/j.ceb.2023.102278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 10/17/2023] [Accepted: 10/18/2023] [Indexed: 11/20/2023]
Abstract
As cells organize spatially or divide, they translocate many micron-scale organelles in their cytoplasm. These include endomembrane vesicles, nuclei, microtubule asters, mitotic spindles, or chromosomes. Organelle motion is powered by cytoskeleton forces but is opposed by viscoelastic forces imparted by the surrounding crowded cytoplasm medium. These resistive forces associated to cytoplasm physcial properties remain generally underappreciated, yet reach significant values to slow down organelle motion or even limit their displacement by springing them back towards their original position. The cytoplasm may also be itself organized in time and space, being for example stiffer or more fluid at certain locations or during particular cell cycle phases. Thus, cytoplasm mechanics may be viewed as a labile module that contributes to organize cells. We here review emerging methods, mechanisms, and concepts to study cytoplasm mechanical properties and their function in organelle positioning, cellular organization and division.
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Affiliation(s)
- María Isabel Arjona
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France; Equipe Labellisée LIGUE Contre le Cancer, France
| | - Javad Najafi
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France; Equipe Labellisée LIGUE Contre le Cancer, France
| | - Nicolas Minc
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France; Equipe Labellisée LIGUE Contre le Cancer, France.
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7
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Quiogue AR, Sumiyoshi E, Fries A, Chuang CH, Bowerman B. Microtubules oppose cortical actomyosin-driven membrane ingression during C. elegans meiosis I polar body extrusion. PLoS Genet 2023; 19:e1010984. [PMID: 37782660 PMCID: PMC10569601 DOI: 10.1371/journal.pgen.1010984] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 10/12/2023] [Accepted: 09/19/2023] [Indexed: 10/04/2023] Open
Abstract
During C. elegans oocyte meiosis I cytokinesis and polar body extrusion, cortical actomyosin is locally remodeled to assemble a contractile ring that forms within and remains part of a much larger and actively contractile cortical actomyosin network. This network both mediates contractile ring dynamics and generates shallow ingressions throughout the oocyte cortex during polar body extrusion. Based on our analysis of requirements for CLS-2, a member of the CLASP family of proteins that stabilize microtubules, we recently proposed that a balance of actomyosin-mediated tension and microtubule-mediated stiffness limits membrane ingression throughout the oocyte during meiosis I polar body extrusion. Here, using live cell imaging and fluorescent protein fusions, we show that CLS-2 is part of a group of kinetochore proteins, including the scaffold KNL-1 and the kinase BUB-1, that also co-localize during meiosis I to structures called linear elements, which are present within the assembling oocyte spindle and also are distributed throughout the oocyte in proximity to, but appearing to underlie, the actomyosin cortex. We further show that KNL-1 and BUB-1, like CLS-2, promote the proper organization of sub-cortical microtubules and also limit membrane ingression throughout the oocyte. Moreover, nocodazole or taxol treatment to destabilize or stabilize oocyte microtubules leads to, respectively, excess or decreased membrane ingression throughout the oocyte. Furthermore, taxol treatment, and genetic backgrounds that elevate the levels of cortically associated microtubules, both suppress excess membrane ingression in cls-2 mutant oocytes. We propose that linear elements influence the organization of sub-cortical microtubules to generate a stiffness that limits cortical actomyosin-driven membrane ingression throughout the oocyte during meiosis I polar body extrusion. We discuss the possibility that this regulation of sub-cortical microtubule dynamics facilitates actomyosin contractile ring dynamics during C. elegans oocyte meiosis I cell division.
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Affiliation(s)
- Alyssa R. Quiogue
- Institute of Molecular Biology, University of Oregon, Eugen, Oregon, United States of America
| | - Eisuke Sumiyoshi
- Institute of Molecular Biology, University of Oregon, Eugen, Oregon, United States of America
| | - Adam Fries
- Institute of Molecular Biology, University of Oregon, Eugen, Oregon, United States of America
- Imaging Core, Office of the Vice President for Research University of Oregon, Eugene, Oregon, United States of America
| | - Chien-Hui Chuang
- Institute of Molecular Biology, University of Oregon, Eugen, Oregon, United States of America
| | - Bruce Bowerman
- Institute of Molecular Biology, University of Oregon, Eugen, Oregon, United States of America
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8
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Huang WYC, Cheng X, Ferrell JE. Cytoplasmic organization promotes protein diffusion in Xenopus extracts. Nat Commun 2022; 13:5599. [PMID: 36151204 PMCID: PMC9508076 DOI: 10.1038/s41467-022-33339-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 09/12/2022] [Indexed: 11/25/2022] Open
Abstract
The cytoplasm is highly organized. However, the extent to which this organization influences the dynamics of cytoplasmic proteins is not well understood. Here, we use Xenopus laevis egg extracts as a model system to study diffusion dynamics in organized versus disorganized cytoplasm. Such extracts are initially homogenized and disorganized, and self-organize into cell-like units over the course of tens of minutes. Using fluorescence correlation spectroscopy, we observe that as the cytoplasm organizes, protein diffusion speeds up by about a factor of two over a length scale of a few hundred nanometers, eventually approaching the diffusion time measured in organelle-depleted cytosol. Even though the ordered cytoplasm contained organelles and cytoskeletal elements that might interfere with diffusion, the convergence of protein diffusion in the cytoplasm toward that in organelle-depleted cytosol suggests that subcellular organization maximizes protein diffusivity. The effect of organization on diffusion varies with molecular size, with the effects being largest for protein-sized molecules, and with the time scale of the measurement. These results show that cytoplasmic organization promotes the efficient diffusion of protein molecules in a densely packed environment. Cytoplasmic organization is a hallmark of living cells. Here, the authors make use of self-organizing cell extracts to examine how the emergence of large-scale organizations influences the microscopic diffusion of protein molecules in the cytoplasm.
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Affiliation(s)
- William Y C Huang
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Xianrui Cheng
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, 94305, USA. .,Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA.
| | - James E Ferrell
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, 94305, USA. .,Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA.
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9
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Sami AB, Gatlin JC. Dynein-dependent collection of membranes defines the architecture and position of microtubule asters in isolated, geometrically confined volumes of cell-free extracts. Mol Biol Cell 2022; 33:br20. [PMID: 35976715 DOI: 10.1091/mbc.e22-03-0074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
It is well established that changes in the underlying architecture of the cell's microtubule network can affect organelle organization within the cytoplasm, but it remains unclear whether the spatial arrangement of organelles reciprocally influences the microtubule network. Here we use a combination of cell-free extracts and hydrogel microenclosures to characterize the relationship between membranes and microtubules during microtubule aster centration. We found that initially disperse ER membranes are collected by the aster and compacted near its nucleating center, all while the whole ensemble moves toward the geometric center of its confining enclosure. Once there, aster microtubules adopt a bullseye pattern with a high density annular ring of microtubules surrounding the compacted membrane core of lower microtubule density. Formation of this pattern was inhibited when dynein-dependent transport was perturbed or when membranes were depleted from the extracts. Asters in membrane-depleted extracts were able to move away from the most proximal wall but failed to center in cylindrical enclosures with diameters greater than or equal to 150 µm. Taken as whole, our data suggest that the dynein-dependent transport of membranes buttresses microtubules near the aster center and that this plays an important role in modulating aster architecture and position. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text].
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Affiliation(s)
| | - Jesse C Gatlin
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA.,Cell Division & Organization Group, Marine Biological Laboratory, Woods Hole, MA 02543, USA
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10
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Yamamoto S, Gaillard J, Vianay B, Guerin C, Orhant-Prioux M, Blanchoin L, Théry M. Actin network architecture can ensure robust centering or sensitive decentering of the centrosome. EMBO J 2022; 41:e111631. [PMID: 35916262 PMCID: PMC9574749 DOI: 10.15252/embj.2022111631] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/24/2022] [Accepted: 07/06/2022] [Indexed: 01/17/2023] Open
Abstract
The orientation of cell polarity depends on the position of the centrosome, the main microtubule-organizing center (MTOC). Microtubules (MTs) transmit pushing forces to the MTOC as they grow against the cell periphery. How the actin network regulates these forces remains unclear. Here, in a cell-free assay, we used purified proteins to reconstitute the interaction of a microtubule aster with actin networks of various architectures in cell-sized microwells. In the absence of actin filaments, MTOC positioning was highly sensitive to variations in microtubule length. The presence of a bulk actin network limited microtubule displacement, and MTOCs were held in place. In contrast, the assembly of a branched actin network along the well edges centered the MTOCs by maintaining an isotropic balance of pushing forces. An anisotropic peripheral actin network caused the MTOC to decenter by focusing the pushing forces. Overall, our results show that actin networks can limit the sensitivity of MTOC positioning to microtubule length and enforce robust MTOC centering or decentering depending on the isotropy of its architecture.
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Affiliation(s)
- Shohei Yamamoto
- Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Jérémie Gaillard
- Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Benoit Vianay
- Institut de Recherche Saint Louis, UMRS1160-HIPI, CytoMorpho Lab, University of Paris, CEA, INSERM, Paris, France
| | - Christophe Guerin
- Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Magali Orhant-Prioux
- Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Laurent Blanchoin
- Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France.,Institut de Recherche Saint Louis, UMRS1160-HIPI, CytoMorpho Lab, University of Paris, CEA, INSERM, Paris, France
| | - Manuel Théry
- Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France.,Institut de Recherche Saint Louis, UMRS1160-HIPI, CytoMorpho Lab, University of Paris, CEA, INSERM, Paris, France
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11
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Mishra S, Levy DL. Nuclear F-actin and Lamin A antagonistically modulate nuclear shape. J Cell Sci 2022; 135:275607. [PMID: 35665815 PMCID: PMC9377710 DOI: 10.1242/jcs.259692] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 05/28/2022] [Indexed: 12/25/2022] Open
Abstract
Nuclear shape influences cell migration, gene expression and cell cycle progression, and is altered in disease states like laminopathies and cancer. What factors and forces determine nuclear shape? We find that nuclei assembled in Xenopus egg extracts in the presence of dynamic F-actin exhibit a striking bilobed nuclear morphology with distinct membrane compositions in the two lobes and accumulation of F-actin at the inner nuclear envelope. The addition of Lamin A (encoded by lmna), which is absent from Xenopus eggs, results in rounder nuclei, suggesting that opposing nuclear F-actin and Lamin A forces contribute to the regulation of nuclear shape. Nuclear F-actin also promotes altered nuclear shape in Lamin A-knockdown HeLa cells and, in both systems, abnormal nuclear shape is driven by formins and not Arp2/3 or myosin. Although the underlying mechanisms might differ in Xenopus and HeLa cells, we propose that nuclear F-actin filaments nucleated by formins impart outward forces that lead to altered nuclear morphology unless Lamin A is present. Targeting nuclear actin dynamics might represent a novel approach to rescuing disease-associated defects in nuclear shape.
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Affiliation(s)
- Sampada Mishra
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
| | - Daniel L. Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA,Author for correspondence ()
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12
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Lemma B, Mitchell NP, Subramanian R, Needleman DJ, Dogic Z. Active Microphase Separation in Mixtures of Microtubules and Tip-Accumulating Molecular Motors. PHYSICAL REVIEW. X 2022; 12:031006. [PMID: 36643940 PMCID: PMC9835929 DOI: 10.1103/physrevx.12.031006] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Mixtures of filaments and molecular motors form active materials with diverse dynamical behaviors that vary based on their constituents' molecular properties. To develop a multiscale of these materials, we map the nonequilibrium phase diagram of microtubules and tip-accumulating kinesin-4 molecular motors. We find that kinesin-4 can drive either global contractions or turbulentlike extensile dynamics, depending on the concentrations of both microtubules and a bundling agent. We also observe a range of spatially heterogeneous nonequilibrium phases, including finite-sized radial asters, 1D wormlike chains, extended 2D bilayers, and system-spanning 3D active foams. Finally, we describe intricate kinetic pathways that yield microphase separated structures and arise from the inherent frustration between the orientational order of filamentous microtubules and the positional order of tip-accumulating molecular motors. Our work reveals a range of novel active states. It also shows that the form of active stresses is not solely dictated by the properties of individual motors and filaments, but is also contingent on the constituent concentrations and spatial arrangement of motors on the filaments.
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Affiliation(s)
- Bezia Lemma
- Physics Department, Harvard University, Cambridge, Massachusetts 02138, USA
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
- Physics Department, University of California, Santa Barbara, California 93106, USA
| | - Noah P. Mitchell
- Physics Department, University of California, Santa Barbara, California 93106, USA
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA
| | - Radhika Subramanian
- Molecular Biology Department, Massachusetts General Hospital Boston, Massachusetts 02114, USA
- Genetics Department, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Daniel J. Needleman
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Molecular and Cellular Biology Department, Harvard University, Cambridge, Massachusetts 02138, USA
- Center for Computational Biology, Flatiron Institute, New York, New York 10010, USA
| | - Zvonimir Dogic
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
- Physics Department, University of California, Santa Barbara, California 93106, USA
- Biomolecular Science and Engineering Department, University of California, Santa Barbara, California 93106, USA
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13
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Spring-like behavior of cytoplasm holds the mitotic spindle in place. Proc Natl Acad Sci U S A 2022; 119:e2203036119. [PMID: 35324318 PMCID: PMC9169080 DOI: 10.1073/pnas.2203036119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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14
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Contribution of cytoplasm viscoelastic properties to mitotic spindle positioning. Proc Natl Acad Sci U S A 2022; 119:2115593119. [PMID: 35169074 PMCID: PMC8872784 DOI: 10.1073/pnas.2115593119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/28/2021] [Indexed: 11/21/2022] Open
Abstract
The regulation of mitotic spindle positioning is a key process for tissue architecture, embryo development, and stem cells. To date, most models have assumed that spindles are positioned by forces exerted by polar cytoskeleton networks, like microtubule asters or actomyosin bundles. Here, using in situ magnetic tweezers to apply calibrated forces and torques to mitotic spindles in live dividing sea urchin cells, we found that the viscoelastic properties of the cytoplasm medium in which spindles are embedded can hold spindles in place and move them back if their original position is perturbed. These viscoelastic forces are large and may significantly participate in the force balance that position and orient mitotic spindles in many cell types. Cells are filled with macromolecules and polymer networks that set scale-dependent viscous and elastic properties to the cytoplasm. Although the role of these parameters in molecular diffusion, reaction kinetics, and cellular biochemistry is being increasingly recognized, their contributions to the motion and positioning of larger organelles, such as mitotic spindles for cell division, remain unknown. Here, using magnetic tweezers to displace and rotate mitotic spindles in living embryos, we uncovered that the cytoplasm can impart viscoelastic reactive forces that move spindles, or passive objects with similar size, back to their original positions. These forces are independent of cytoskeletal force generators yet reach hundreds of piconewtons and scale with cytoplasm crowding. Spindle motion shears and fluidizes the cytoplasm, dissipating elastic energy and limiting spindle recoils with functional implications for asymmetric and oriented divisions. These findings suggest that bulk cytoplasm material properties may constitute important control elements for the regulation of division positioning and cellular organization.
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15
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Godard BG, Dumollard R, Heisenberg CP, McDougall A. Combined effect of cell geometry and polarity domains determines the orientation of unequal division. eLife 2021; 10:75639. [PMID: 34889186 PMCID: PMC8691831 DOI: 10.7554/elife.75639] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 12/02/2021] [Indexed: 11/13/2022] Open
Abstract
Cell division orientation is thought to result from a competition between cell geometry and polarity domains controlling the position of the mitotic spindle during mitosis. Depending on the level of cell shape anisotropy or the strength of the polarity domain, one dominates the other and determines the orientation of the spindle. Whether and how such competition is also at work to determine unequal cell division (UCD), producing daughter cells of different size, remains unclear. Here, we show that cell geometry and polarity domains cooperate, rather than compete, in positioning the cleavage plane during UCDs in early ascidian embryos. We found that the UCDs and their orientation at the ascidian third cleavage rely on the spindle tilting in an anisotropic cell shape, and cortical polarity domains exerting different effects on spindle astral microtubules. By systematically varying mitotic cell shape, we could modulate the effect of attractive and repulsive polarity domains and consequently generate predicted daughter cell size asymmetries and position. We therefore propose that the spindle position during UCD is set by the combined activities of cell geometry and polarity domains, where cell geometry modulates the effect of cortical polarity domain(s).
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Affiliation(s)
- Benoit G Godard
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche sur Mer, France.,Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Remi Dumollard
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche sur Mer, France
| | | | - Alex McDougall
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche sur Mer, France
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16
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Deshpande O, Telley IA. Nuclear positioning during development: Pushing, pulling and flowing. Semin Cell Dev Biol 2021; 120:10-21. [PMID: 34642103 DOI: 10.1016/j.semcdb.2021.09.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Revised: 09/29/2021] [Accepted: 09/30/2021] [Indexed: 01/13/2023]
Abstract
The positioning of the nucleus, the central organelle of the cell, is an active and regulated process crucially linked to cell cycle, differentiation, migration, and polarity. Alterations in positioning have been correlated with cell and tissue function deficiency and genetic or chemical manipulation of nuclear position is embryonic lethal. Nuclear positioning is a precursor for symmetric or asymmetric cell division which is accompanied by fate determination of the daughter cells. Nuclear positioning also plays a key role during early embryonic developmental stages in insects, such as Drosophila, where hundreds of nuclei divide without cytokinesis and are distributed within the large syncytial embryo at roughly regular spacing. While the cytoskeletal elements and the linker proteins to the nucleus are fairly well characterised, including some of the force generating elements driving nuclear movement, there is considerable uncertainty about the biophysical mechanism of nuclear positioning, while the field is debating different force models. In this review, we highlight the current body of knowledge, discuss cell context dependent models of nuclear positioning, and outline open questions.
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Affiliation(s)
- Ojas Deshpande
- Instituto Gulbenkian de Ciência (IGC), Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
| | - Ivo A Telley
- Instituto Gulbenkian de Ciência (IGC), Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal.
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17
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Abstract
The purpose of this review is to explore self-organizing mechanisms that pattern microtubules (MTs) and spatially organize animal cell cytoplasm, inspired by recent experiments in frog egg extract. We start by reviewing conceptual distinctions between self-organizing and templating mechanisms for subcellular organization. We then discuss self-organizing mechanisms that generate radial MT arrays and cell centers in the absence of centrosomes. These include autocatalytic MT nucleation, transport of minus ends, and nucleation from organelles such as melanosomes and Golgi vesicles that are also dynein cargoes. We then discuss mechanisms that partition the cytoplasm in syncytia, in which multiple nuclei share a common cytoplasm, starting with cytokinesis, when all metazoan cells are transiently syncytial. The cytoplasm of frog eggs is partitioned prior to cytokinesis by two self-organizing modules, protein regulator of cytokinesis 1 (PRC1)-kinesin family member 4A (KIF4A) and chromosome passenger complex (CPC)-KIF20A. Similar modules may partition longer-lasting syncytia, such as early Drosophila embryos. We end by discussing shared mechanisms and principles for the MT-based self-organization of cellular units.
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Affiliation(s)
- Timothy J Mitchison
- Harvard Medical School, Boston, Massachusetts 02115, USA; ,
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA
| | - Christine M Field
- Harvard Medical School, Boston, Massachusetts 02115, USA; ,
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA
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18
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Intertwined and Finely Balanced: Endoplasmic Reticulum Morphology, Dynamics, Function, and Diseases. Cells 2021; 10:cells10092341. [PMID: 34571990 PMCID: PMC8472773 DOI: 10.3390/cells10092341] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 09/02/2021] [Accepted: 09/04/2021] [Indexed: 02/07/2023] Open
Abstract
The endoplasmic reticulum (ER) is an organelle that is responsible for many essential subcellular processes. Interconnected narrow tubules at the periphery and thicker sheet-like regions in the perinuclear region are linked to the nuclear envelope. It is becoming apparent that the complex morphology and dynamics of the ER are linked to its function. Mutations in the proteins involved in regulating ER structure and movement are implicated in many diseases including neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and amyotrophic lateral sclerosis (ALS). The ER is also hijacked by pathogens to promote their replication. Bacteria such as Legionella pneumophila and Chlamydia trachomatis, as well as the Zika virus, bind to ER morphology and dynamics-regulating proteins to exploit the functions of the ER to their advantage. This review covers our understanding of ER morphology, including the functional subdomains and membrane contact sites that the organelle forms. We also focus on ER dynamics and the current efforts to quantify ER motion and discuss the diseases related to ER morphology and dynamics.
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19
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The Cytoskeleton and Its Roles in Self-Organization Phenomena: Insights from Xenopus Egg Extracts. Cells 2021; 10:cells10092197. [PMID: 34571847 PMCID: PMC8465277 DOI: 10.3390/cells10092197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 08/18/2021] [Accepted: 08/21/2021] [Indexed: 01/11/2023] Open
Abstract
Self-organization of and by the cytoskeleton is central to the biology of the cell. Since their introduction in the early 1980s, cytoplasmic extracts derived from the eggs of the African clawed-frog, Xenopus laevis, have flourished as a major experimental system to study the various facets of cytoskeleton-dependent self-organization. Over the years, the many investigations that have used these extracts uniquely benefited from their simplified cell cycle, large experimental volumes, biochemical tractability and cell-free nature. Here, we review the contributions of egg extracts to our understanding of the cytoplasmic aspects of self-organization by the microtubule and the actomyosin cytoskeletons as well as the importance of cytoskeletal filaments in organizing nuclear structure and function.
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20
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Abstract
Understanding the mechanisms of embryonic cell cycles is a central goal of developmental biology, as the regulation of the cell cycle must be closely coordinated with other events during early embryogenesis. Quantitative imaging approaches have recently begun to reveal how the cell cycle oscillator is controlled in space and time, and how it is integrated with mechanical signals to drive morphogenesis. Here, we discuss how the Drosophila embryo has served as an excellent model for addressing the molecular and physical mechanisms of embryonic cell cycles, with comparisons to other model systems to highlight conserved and species-specific mechanisms. We describe how the rapid cleavage divisions characteristic of most metazoan embryos require chemical waves and cytoplasmic flows to coordinate morphogenesis across the large expanse of the embryo. We also outline how, in the late cleavage divisions, the cell cycle is inter-regulated with the activation of gene expression to ensure a reliable maternal-to-zygotic transition. Finally, we discuss how precise transcriptional regulation of the timing of mitosis ensures that tissue morphogenesis and cell proliferation are tightly controlled during gastrulation.
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Affiliation(s)
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27705, USA
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21
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Ishihara K, Decker F, Caldas P, Pelletier JF, Loose M, Brugués J, Mitchison TJ. Spatial variation of microtubule depolymerization in large asters. Mol Biol Cell 2021; 32:869-879. [PMID: 33439671 PMCID: PMC8108532 DOI: 10.1091/mbc.e20-11-0723] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Microtubule plus-end depolymerization rate is a potentially important target of physiological regulation, but it has been challenging to measure, so its role in spatial organization is poorly understood. Here we apply a method for tracking plus ends based on time difference imaging to measure depolymerization rates in large interphase asters growing in Xenopus egg extract. We observed strong spatial regulation of depolymerization rates, which were higher in the aster interior compared with the periphery, and much less regulation of polymerization or catastrophe rates. We interpret these data in terms of a limiting component model, where aster growth results in lower levels of soluble tubulin and microtubule-associated proteins (MAPs) in the interior cytosol compared with that at the periphery. The steady-state polymer fraction of tubulin was ∼30%, so tubulin is not strongly depleted in the aster interior. We propose that the limiting component for microtubule assembly is a MAP that inhibits depolymerization, and that egg asters are tuned to low microtubule density.
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Affiliation(s)
- Keisuke Ishihara
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, 01307 Dresden, Germany.,Center for Systems Biology Dresden, 01307 Dresden, Germany.,Cluster of Excellence Physics of Life, TU Dresden, 01307 Dresden, Germany
| | - Franziska Decker
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, 01307 Dresden, Germany.,Center for Systems Biology Dresden, 01307 Dresden, Germany.,Cluster of Excellence Physics of Life, TU Dresden, 01307 Dresden, Germany
| | - Paulo Caldas
- Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria
| | - James F Pelletier
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115.,Cell Division Group, Marine Biological Laboratory, Woods Hole, MA 02543.,Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Martin Loose
- Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria
| | - Jan Brugués
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, 01307 Dresden, Germany.,Center for Systems Biology Dresden, 01307 Dresden, Germany.,Cluster of Excellence Physics of Life, TU Dresden, 01307 Dresden, Germany
| | - Timothy J Mitchison
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115.,Cell Division Group, Marine Biological Laboratory, Woods Hole, MA 02543
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22
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Sulerud T, Sami AB, Li G, Kloxin A, Oakey J, Gatlin J. Microtubule-dependent pushing forces contribute to long-distance aster movement and centration in Xenopus laevis egg extracts. Mol Biol Cell 2020; 31:2791-2802. [PMID: 33026931 PMCID: PMC7851858 DOI: 10.1091/mbc.e20-01-0088] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
During interphase of the eukaryotic cell cycle, the microtubule (MT) cytoskeleton serves as both a supportive scaffold for organelles and an arborized system of tracks for intracellular transport. At the onset of mitosis, the position of the astral MT network, specifically its center, determines the eventual location of the spindle apparatus and ultimately the cytokinetic furrow. Positioning of the MT aster often results in its movement to the center of a cell, even in large blastomeres hundreds of microns in diameter. This translocation requires positioning forces, yet how these forces are generated and then integrated within cells of various sizes and geometries remains an open question. Here we describe a method that combines microfluidics, hydrogels, and Xenopus laevis egg extract to investigate the mechanics of aster movement and centration. We determined that asters were able to find the center of artificial channels and annular cylinders, even when cytoplasmic dynein-dependent pulling mechanisms were inhibited. Characterization of aster movement away from V-shaped hydrogel barriers provided additional evidence for a MT-based pushing mechanism. Importantly, the distance over which this mechanism seemed to operate was longer than that predicted by radial aster growth models, agreeing with recent models of a more complex MT network architecture within the aster.
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Affiliation(s)
- Taylor Sulerud
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071.,Cell Organization and Division Group, Marine Biological Laboratory, Woods Hole, MA 02543
| | | | - Guihe Li
- Department of Chemical Engineering, University of Wyoming, Laramie, WY 82071
| | - April Kloxin
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716
| | - John Oakey
- Department of Chemical Engineering, University of Wyoming, Laramie, WY 82071.,Cell Organization and Division Group, Marine Biological Laboratory, Woods Hole, MA 02543
| | - Jesse Gatlin
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071.,Cell Organization and Division Group, Marine Biological Laboratory, Woods Hole, MA 02543
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