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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Valverde JM, Dubra G, Phillips M, Haider A, Elena-Real C, Fournet A, Alghoul E, Chahar D, Andrés-Sanchez N, Paloni M, Bernadó P, van Mierlo G, Vermeulen M, van den Toorn H, Heck AJR, Constantinou A, Barducci A, Ghosh K, Sibille N, Knipscheer P, Krasinska L, Fisher D, Altelaar M. A cyclin-dependent kinase-mediated phosphorylation switch of disordered protein condensation. Nat Commun 2023; 14:6316. [PMID: 37813838 PMCID: PMC10562473 DOI: 10.1038/s41467-023-42049-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 09/28/2023] [Indexed: 10/11/2023] Open
Abstract
Cell cycle transitions result from global changes in protein phosphorylation states triggered by cyclin-dependent kinases (CDKs). To understand how this complexity produces an ordered and rapid cellular reorganisation, we generated a high-resolution map of changing phosphosites throughout unperturbed early cell cycles in single Xenopus embryos, derived the emergent principles through systems biology analysis, and tested them by biophysical modelling and biochemical experiments. We found that most dynamic phosphosites share two key characteristics: they occur on highly disordered proteins that localise to membraneless organelles, and are CDK targets. Furthermore, CDK-mediated multisite phosphorylation can switch homotypic interactions of such proteins between favourable and inhibitory modes for biomolecular condensate formation. These results provide insight into the molecular mechanisms and kinetics of mitotic cellular reorganisation.
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Affiliation(s)
- Juan Manuel Valverde
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Utrecht, 3584 CH, Utrecht, Netherlands
- Netherlands Proteomics Center, Padualaan 8, 3584 CH, Utrecht, Netherlands
| | - Geronimo Dubra
- IGMM, CNRS, University of Montpellier, INSERM, Montpellier, France
- Equipe Labellisée LIGUE 2018, Ligue Nationale Contre le Cancer, Paris, France
| | - Michael Phillips
- Department of Physics and Astronomy, University of Denver, Denver, Co, 80208, USA
| | - Austin Haider
- Department of Molecular and Cellular Biophysics, University of Denver, 80208, Denver, Co, USA
| | | | - Aurélie Fournet
- CBS, CNRS, University of Montpellier, INSERM, Montpellier, France
| | - Emile Alghoul
- IGH, CNRS, University of Montpellier, Montpellier, France
| | - Dhanvantri Chahar
- IGMM, CNRS, University of Montpellier, INSERM, Montpellier, France
- Equipe Labellisée LIGUE 2018, Ligue Nationale Contre le Cancer, Paris, France
| | - Nuria Andrés-Sanchez
- IGMM, CNRS, University of Montpellier, INSERM, Montpellier, France
- Equipe Labellisée LIGUE 2018, Ligue Nationale Contre le Cancer, Paris, France
| | - Matteo Paloni
- Department of Physics and Astronomy, University of Denver, Denver, Co, 80208, USA
| | - Pau Bernadó
- CBS, CNRS, University of Montpellier, INSERM, Montpellier, France
| | - Guido van Mierlo
- Department of Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Oncode Institute, Radboud University Nijmegen, Nijmegen, 6525 GA, The Netherlands
| | - Michiel Vermeulen
- Department of Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Oncode Institute, Radboud University Nijmegen, Nijmegen, 6525 GA, The Netherlands
| | - Henk van den Toorn
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Utrecht, 3584 CH, Utrecht, Netherlands
- Netherlands Proteomics Center, Padualaan 8, 3584 CH, Utrecht, Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Utrecht, 3584 CH, Utrecht, Netherlands
- Netherlands Proteomics Center, Padualaan 8, 3584 CH, Utrecht, Netherlands
| | | | | | - Kingshuk Ghosh
- Department of Physics and Astronomy, University of Denver, Denver, Co, 80208, USA
- Department of Molecular and Cellular Biophysics, University of Denver, 80208, Denver, Co, USA
| | - Nathalie Sibille
- CBS, CNRS, University of Montpellier, INSERM, Montpellier, France
| | - Puck Knipscheer
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Center, Utrecht, 3584 CT, Netherlands
| | - Liliana Krasinska
- IGMM, CNRS, University of Montpellier, INSERM, Montpellier, France
- Equipe Labellisée LIGUE 2018, Ligue Nationale Contre le Cancer, Paris, France
| | - Daniel Fisher
- IGMM, CNRS, University of Montpellier, INSERM, Montpellier, France.
- Equipe Labellisée LIGUE 2018, Ligue Nationale Contre le Cancer, Paris, France.
| | - Maarten Altelaar
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Utrecht, 3584 CH, Utrecht, Netherlands.
- Netherlands Proteomics Center, Padualaan 8, 3584 CH, Utrecht, Netherlands.
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3
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Swider ZT, Michaud A, Leda M, Landino J, Goryachev AB, Bement WM. Cell cycle and developmental control of cortical excitability in Xenopus laevis. Mol Biol Cell 2022; 33:ar73. [PMID: 35594176 PMCID: PMC9635278 DOI: 10.1091/mbc.e22-01-0025] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Interest in cortical excitability—the ability of the cell cortex to generate traveling waves of protein activity—has grown considerably over the past 20 years. Attributing biological functions to cortical excitability requires an understanding of the natural behavior of excitable waves and the ability to accurately quantify wave properties. Here we have investigated and quantified the onset of cortical excitability in Xenopus laevis eggs and embryos and the changes in cortical excitability throughout early development. We found that cortical excitability begins to manifest shortly after egg activation. Further, we identified a close relationship between wave properties—such as wave frequency and amplitude—and cell cycle progression as well as cell size. Finally, we identified quantitative differences between cortical excitability in the cleavage furrow relative to nonfurrow cortical excitability and showed that these wave regimes are mutually exclusive.
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Affiliation(s)
- Zachary T Swider
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-Madison Madison, WI 53706.,Center for Quantitative Cell Imaging, University of Wisconsin-Madison Madison, WI 53706
| | - Ani Michaud
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-Madison Madison, WI 53706.,Center for Quantitative Cell Imaging, University of Wisconsin-Madison Madison, WI 53706
| | - Marcin Leda
- Centre for Synthetic and Systems Biology, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Jennifer Landino
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan-Ann Arbor, Ann Arbor, MI 48109
| | - Andrew B Goryachev
- Centre for Synthetic and Systems Biology, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - William M Bement
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-Madison Madison, WI 53706.,Center for Quantitative Cell Imaging, University of Wisconsin-Madison Madison, WI 53706.,Department of Integrative Biology, University of Wisconsin-Madison Madison, WI 53706
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4
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Xiao S, Tong C, Yang Y, Wu M. Mitotic Cortical Waves Predict Future Division Sites by Encoding Positional and Size Information. Dev Cell 2017; 43:493-506.e3. [DOI: 10.1016/j.devcel.2017.10.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 08/02/2017] [Accepted: 10/22/2017] [Indexed: 10/18/2022]
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5
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Bischof J, Brand CA, Somogyi K, Májer I, Thome S, Mori M, Schwarz US, Lénárt P. A cdk1 gradient guides surface contraction waves in oocytes. Nat Commun 2017; 8:849. [PMID: 29021609 PMCID: PMC5636809 DOI: 10.1038/s41467-017-00979-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 08/09/2017] [Indexed: 11/29/2022] Open
Abstract
Surface contraction waves (SCWs) in oocytes and embryos lead to large-scale shape changes coupled to cell cycle transitions and are spatially coordinated with the cell axis. Here, we show that SCWs in the starfish oocyte are generated by a traveling band of myosin II-driven cortical contractility. At the front of the band, contractility is activated by removal of cdk1 inhibition of the RhoA/RhoA kinase/myosin II signaling module, while at the rear, contractility is switched off by negative feedback originating downstream of RhoA kinase. The SCW's directionality and speed are controlled by a spatiotemporal gradient of cdk1-cyclinB. This gradient is formed by the release of cdk1-cyclinB from the asymmetrically located nucleus, and progressive degradation of cyclinB. By combining quantitative imaging, biochemical and mechanical perturbations with mathematical modeling, we demonstrate that the SCWs result from the spatiotemporal integration of two conserved regulatory modules, cdk1-cyclinB for cell cycle regulation and RhoA/Rok/NMYII for actomyosin contractility.Surface contraction waves (SCWs) are prominent shape changes coupled to cell cycle transitions in oocytes. Here the authors show that SCWs are patterned by the spatiotemporal integration of two conserved modules, cdk1-cyclinB for cell cycle regulation and RhoA/Rok/NMYII for actomyosin contractility.
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Affiliation(s)
- Johanna Bischof
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Christoph A Brand
- Institute for Theoretical Physics and BioQuant, Heidelberg University, Philosophenweg 19, 69120, Heidelberg, Germany
| | - Kálmán Somogyi
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Imre Májer
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Sarah Thome
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Masashi Mori
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Ulrich S Schwarz
- Institute for Theoretical Physics and BioQuant, Heidelberg University, Philosophenweg 19, 69120, Heidelberg, Germany
| | - Péter Lénárt
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117, Heidelberg, Germany.
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6
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Anderson GA, Gelens L, Baker JC, Ferrell JE. Desynchronizing Embryonic Cell Division Waves Reveals the Robustness of Xenopus laevis Development. Cell Rep 2017; 21:37-46. [PMID: 28978482 PMCID: PMC5679461 DOI: 10.1016/j.celrep.2017.09.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 07/20/2017] [Accepted: 09/04/2017] [Indexed: 11/17/2022] Open
Abstract
The early Xenopus laevis embryo is replete with dynamic spatial waves. One such wave, the cell division wave, emerges from the collective cell division timing of first tens and later hundreds of cells throughout the embryo. Here, we show that cell division waves do not propagate between neighboring cells and do not rely on cell-to-cell coupling to maintain their division timing. Instead, intrinsic variation in division period autonomously and gradually builds these striking patterns of cell division. Disrupting this pattern of division by placing embryos in a temperature gradient resulted in highly asynchronous entry to the midblastula transition and misexpression of the mesodermal marker Xbra. Remarkably, this gene expression defect is corrected during involution, resulting in delayed yet normal Xbra expression and viable embryos. This implies the existence of a previously unknown mechanism for normalizing mesodermal gene expression during involution.
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Affiliation(s)
- Graham A Anderson
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174, USA
| | - Lendert Gelens
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174, USA; Laboratory of Dynamics in Biological Systems, KU Leuven, Department of Cellular and Molecular Medicine, University of Leuven, 3000 Leuven, Belgium; Applied Physics Research Group, Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium.
| | - Julie C Baker
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305-5120, USA
| | - James E Ferrell
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174, USA; Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305-5307, USA.
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7
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Ogura Y, Sasakura Y. Emerging mechanisms regulating mitotic synchrony during animal embryogenesis. Dev Growth Differ 2017; 59:565-579. [DOI: 10.1111/dgd.12391] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2017] [Revised: 07/20/2017] [Accepted: 07/23/2017] [Indexed: 01/21/2023]
Affiliation(s)
- Yosuke Ogura
- Laboratory for Morphogenetic Signaling; RIKEN Center for Developmental Biology; Kobe Japan
| | - Yasunori Sasakura
- Shimoda Marine Research Center; University of Tsukuba; Shizuoka Japan
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8
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Tassan JP, Wühr M, Hatte G, Kubiak J. Asymmetries in Cell Division, Cell Size, and Furrowing in the Xenopus laevis Embryo. Results Probl Cell Differ 2017; 61:243-260. [PMID: 28409308 DOI: 10.1007/978-3-319-53150-2_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Asymmetric cell divisions produce two daughter cells with distinct fate. During embryogenesis, this mechanism is fundamental to build tissues and organs because it generates cell diversity. In adults, it remains crucial to maintain stem cells. The enthusiasm for asymmetric cell division is not only motivated by the beauty of the mechanism and the fundamental questions it raises, but has also very pragmatic reasons. Indeed, misregulation of asymmetric cell divisions is believed to have dramatic consequences potentially leading to pathogenesis such as cancers. In diverse model organisms, asymmetric cell divisions result in two daughter cells, which differ not only by their fate but also in size. This is the case for the early Xenopus laevis embryo, in which the two first embryonic divisions are perpendicular to each other and generate two pairs of blastomeres, which usually differ in size: one pair of blastomeres is smaller than the other. Small blastomeres will produce embryonic dorsal structures, whereas the larger pair will evolve into ventral structures. Here, we present a speculative model on the origin of the asymmetry of this cell division in the Xenopus embryo. We also discuss the apparently coincident asymmetric distribution of cell fate determinants and cell-size asymmetry of the 4-cell stage embryo. Finally, we discuss the asymmetric furrowing during epithelial cell cytokinesis occurring later during Xenopus laevis embryo development.
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Affiliation(s)
- Jean-Pierre Tassan
- , CNRS UMR 6290, Rennes, France. .,Université de Rennes 1, Institut de Génétique et Développement de Rennes, Rennes, France.
| | - Martin Wühr
- Department of Molecular Biology and the Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
| | - Guillaume Hatte
- , CNRS UMR 6290, Rennes, France.,Université de Rennes 1, Institut de Génétique et Développement de Rennes, Rennes, France
| | - Jacek Kubiak
- , CNRS UMR 6290, Rennes, France.,Université de Rennes 1, Institut de Génétique et Développement de Rennes, Rennes, France
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9
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Activator-inhibitor coupling between Rho signalling and actin assembly makes the cell cortex an excitable medium. Nat Cell Biol 2015; 17:1471-83. [PMID: 26479320 PMCID: PMC4849138 DOI: 10.1038/ncb3251] [Citation(s) in RCA: 176] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 09/08/2015] [Indexed: 02/02/2023]
Abstract
Animal cell cytokinesis results from patterned activation of the small GTPase Rho, which directs assembly of actomyosin in the equatorial cortex. Cytokinesis is restricted to a portion of the cell cycle following anaphase onset in which the cortex is responsive to signals from the spindle. We show that shortly after anaphase onset oocytes and embryonic cells of frogs and echinoderms exhibit cortical waves of Rho activity and F-actin polymerization. The waves are modulated by cyclin-dependent kinase 1 (Cdk1) activity and require the Rho GEF (guanine nucleotide exchange factor), Ect2. Surprisingly, during wave propagation, while Rho activity elicits F-actin assembly, F-actin subsequently inactivates Rho. Experimental and modeling results show that waves represent excitable dynamics of a reaction diffusion system with Rho as the activator and F-actin the inhibitor. We propose that cortical excitability explains fundamental features of cytokinesis including its cell cycle regulation.
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10
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Gelens L, Anderson GA, Ferrell JE. Spatial trigger waves: positive feedback gets you a long way. Mol Biol Cell 2015; 25:3486-93. [PMID: 25368427 PMCID: PMC4230609 DOI: 10.1091/mbc.e14-08-1306] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Trigger waves are a recurring biological phenomenon involved in transmitting information quickly and reliably over large distances. Well-characterized examples include action potentials propagating along the axon of a neuron, calcium waves in various tissues, and mitotic waves in Xenopus eggs. Here we use the FitzHugh-Nagumo model, a simple model inspired by the action potential that is widely used in physics and theoretical biology, to examine different types of trigger waves-spatial switches, pulses, and oscillations-and to show how they arise.
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Affiliation(s)
- Lendert Gelens
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174 Applied Physics Research Group, Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium
| | - Graham A Anderson
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174
| | - James E Ferrell
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174
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11
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Gordon R. Google Embryo for Building Quantitative Understanding of an Embryo As It Builds Itself. II. Progress Toward an Embryo Surface Microscope. ACTA ACUST UNITED AC 2015. [DOI: 10.1162/biot_a_00010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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12
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Ishihara K, Nguyen PA, Wühr M, Groen AC, Field CM, Mitchison TJ. Organization of early frog embryos by chemical waves emanating from centrosomes. Philos Trans R Soc Lond B Biol Sci 2015; 369:rstb.2013.0454. [PMID: 25047608 DOI: 10.1098/rstb.2013.0454] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The large cells in early vertebrate development face an extreme physical challenge in organizing their cytoplasm. For example, amphibian embryos have to divide cytoplasm that spans hundreds of micrometres every 30 min according to a precise geometry, a remarkable accomplishment given the extreme difference between molecular and cellular scales in this system. How do the biochemical reactions occurring at the molecular scale lead to this emergent behaviour of the cell as a whole? Based on recent findings, we propose that the centrosome plays a crucial role by initiating two autocatalytic reactions that travel across the large cytoplasm as chemical waves. Waves of mitotic entry and exit propagate out from centrosomes using the Cdk1 oscillator to coordinate the timing of cell division. Waves of microtubule-stimulated microtubule nucleation propagate out to assemble large asters that position spindles for the following mitosis and establish cleavage plane geometry. By initiating these chemical waves, the centrosome rapidly organizes the large cytoplasm during the short embryonic cell cycle, which would be impossible using more conventional mechanisms such as diffusion or nucleation by structural templating. Large embryo cells provide valuable insights to how cells control chemical waves, which may be a general principle for cytoplasmic organization.
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Affiliation(s)
- Keisuke Ishihara
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA Marine Biological Laboratory, Woods Hole, MA, USA
| | - Phuong A Nguyen
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA Marine Biological Laboratory, Woods Hole, MA, USA
| | - Martin Wühr
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA Marine Biological Laboratory, Woods Hole, MA, USA
| | - Aaron C Groen
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA Marine Biological Laboratory, Woods Hole, MA, USA
| | - Christine M Field
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA Marine Biological Laboratory, Woods Hole, MA, USA
| | - Timothy J Mitchison
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA Marine Biological Laboratory, Woods Hole, MA, USA
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13
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Calcium signaling and meiotic exit at fertilization in Xenopus egg. Int J Mol Sci 2014; 15:18659-76. [PMID: 25322156 PMCID: PMC4227238 DOI: 10.3390/ijms151018659] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 10/01/2014] [Accepted: 10/09/2014] [Indexed: 11/16/2022] Open
Abstract
Calcium is a universal messenger that mediates egg activation at fertilization in all sexually reproducing species studied. However, signaling pathways leading to calcium generation and the mechanisms of calcium-induced exit from meiotic arrest vary substantially among species. Here, we review the pathways of calcium signaling and the mechanisms of meiotic exit at fertilization in the eggs of the established developmental model, African clawed frog, Xenopus laevis. We also discuss calcium involvement in the early fertilization-induced events in Xenopus egg, such as membrane depolarization, the increase in intracellular pH, cortical granule exocytosis, cortical contraction, contraction wave, cortical rotation, reformation of the nuclear envelope, sperm chromatin decondensation and sister chromatid segregation.
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14
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Chang JB, Ferrell JE. Mitotic trigger waves and the spatial coordination of the Xenopus cell cycle. Nature 2013; 500:603-7. [PMID: 23863935 PMCID: PMC3758429 DOI: 10.1038/nature12321] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 05/22/2013] [Indexed: 11/09/2022]
Abstract
Despite the large size of the Xenopus laevis egg (approximately 1.2 mm diameter), a fertilized egg rapidly proceeds through mitosis in a spatially coordinated fashion. Mitosis is initiated by a bistable system of regulatory proteins centred on Cdk1 (refs 1, 2), raising the possibility that this spatial coordination could be achieved through trigger waves of Cdk1 activity. Using an extract system that performs cell cycles in vitro, here we show that mitosis does spread through Xenopus cytoplasm via trigger waves, propagating at a linear speed of approximately 60 µm min(-1). Perturbing the feedback loops that give rise to the bistability of Cdk1 changes the speed and dynamics of the waves. Time-lapse imaging of intact eggs argues that trigger waves of Cdk1 activation are responsible for surface contraction waves, ripples in the cell cortex that precede cytokinesis. These findings indicate that Cdk1 trigger waves help ensure the spatiotemporal coordination of mitosis in large eggs. Trigger waves may be an important general mechanism for coordinating biochemical events over large distances.
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Affiliation(s)
- Jeremy B Chang
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, California 94305-5174, USA.
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15
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A mean field Ising model for cortical rotation in amphibian one-cell stage embryos. Biosystems 2012; 109:381-9. [DOI: 10.1016/j.biosystems.2012.05.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 05/11/2012] [Accepted: 05/14/2012] [Indexed: 12/12/2022]
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16
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Baran I, Ganea C, Ungureanu R, Tofolean IT. Signal mass and Ca2+ kinetics in local calcium events: a modeling study. J Mol Model 2011; 18:721-36. [DOI: 10.1007/s00894-011-1104-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 04/20/2011] [Indexed: 10/18/2022]
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17
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Clark AG, Paluch E. Mechanics and regulation of cell shape during the cell cycle. Results Probl Cell Differ 2011; 53:31-73. [PMID: 21630140 DOI: 10.1007/978-3-642-19065-0_3] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Many cell types undergo dramatic changes in shape throughout the cell cycle. For individual cells, a tight control of cell shape is crucial during cell division, but also in interphase, for example during cell migration. Moreover, cell cycle-related cell shape changes have been shown to be important for tissue morphogenesis in a number of developmental contexts. Cell shape is the physical result of cellular mechanical properties and of the forces exerted on the cell. An understanding of the causes and repercussions of cell shape changes thus requires knowledge of both the molecular regulation of cellular mechanics and how specific changes in cell mechanics in turn effect global shape changes. In this chapter, we provide an overview of the current knowledge on the control of cell morphology, both in terms of general cell mechanics and specifically during the cell cycle.
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Affiliation(s)
- Andrew G Clark
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
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18
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Fourrage C, Chevalier S, Houliston E. A highly conserved Poc1 protein characterized in embryos of the hydrozoan Clytia hemisphaerica: localization and functional studies. PLoS One 2010; 5:e13994. [PMID: 21103375 PMCID: PMC2982836 DOI: 10.1371/journal.pone.0013994] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 09/21/2010] [Indexed: 11/18/2022] Open
Abstract
Poc1 (Protein of Centriole 1) proteins are highly conserved WD40 domain-containing centriole components, well characterized in the alga Chlamydomonas, the ciliated protazoan Tetrahymena, the insect Drosophila and in vertebrate cells including Xenopus and zebrafish embryos. Functions and localizations related to the centriole and ciliary axoneme have been demonstrated for Poc1 in a range of species. The vertebrate Poc1 protein has also been reported to show an additional association with mitochondria, including enrichment in the specialized "germ plasm" region of Xenopus oocytes. We have identified and characterized a highly conserved Poc1 protein in the cnidarian Clytia hemisphaerica. Clytia Poc1 mRNA was found to be strongly expressed in eggs and early embryos, showing a punctate perinuclear localization in young oocytes. Fluorescence-tagged Poc1 proteins expressed in developing embryos showed strong localization to centrioles, including basal bodies. Anti-human Poc1 antibodies decorated mitochondria in Clytia, as reported in human cells, but failed to recognise endogenous or fluorescent-tagged Clytia Poc1. Injection of specific morpholino oligonucleotides into Clytia eggs prior to fertilization to repress Poc1 mRNA translation interfered with cell division from the blastula stage, likely corresponding to when neosynthesis normally takes over from maternally supplied protein. Cell cycle lengthening and arrest were observed, phenotypes consistent with an impaired centriolar biogenesis or function. The specificity of the defects could be demonstrated by injection of synthetic Poc1 mRNA, which restored normal development. We conclude that in Clytia embryos, Poc1 has an essentially centriolar localization and function.
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Affiliation(s)
- Cécile Fourrage
- Université Pierre et Marie Curie and CNRS, Developmental Biology Unit, Villefranche-sur-Mer, France
| | - Sandra Chevalier
- Université Pierre et Marie Curie and CNRS, Developmental Biology Unit, Villefranche-sur-Mer, France
| | - Evelyn Houliston
- Université Pierre et Marie Curie and CNRS, Developmental Biology Unit, Villefranche-sur-Mer, France
- * E-mail:
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19
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Cortical and cytoplasmic flows driven by actin microfilaments polarize the cortical ER-mRNA domain along the a–v axis in ascidian oocytes. Dev Biol 2008; 313:682-99. [DOI: 10.1016/j.ydbio.2007.11.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Revised: 10/23/2007] [Accepted: 11/02/2007] [Indexed: 11/22/2022]
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20
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Coffman JA, Denegre JM. Mitochondria, redox signaling and axis specification in metazoan embryos. Dev Biol 2007; 308:266-80. [PMID: 17586486 DOI: 10.1016/j.ydbio.2007.05.042] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 05/30/2007] [Accepted: 05/30/2007] [Indexed: 11/29/2022]
Abstract
Mitochondria are not only the major energy generators of the eukaryotic cell but they are also sources of signals that control gene expression and cell fate. While mitochondria are often asymmetrically distributed in early embryos, little is known about how they contribute to axial patterning. Here we review studies of mitochondrial distribution in metazoan eggs and embryos and the mechanisms of redox signaling, and speculate on the role that mitochondrial anisotropies might play in the developmental specification of cell fate during embryogenesis of sea urchins and other animals.
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Affiliation(s)
- James A Coffman
- Mount Desert Island Biological Laboratory, Salisbury Cove, ME 04672, USA.
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21
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Sardet C, Paix A, Prodon F, Dru P, Chenevert J. From oocyte to 16-cell stage: Cytoplasmic and cortical reorganizations that pattern the ascidian embryo. Dev Dyn 2007; 236:1716-31. [PMID: 17420986 DOI: 10.1002/dvdy.21136] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The dorsoventral and anteroposterior axes of the ascidian embryo are defined before first cleavage by means of a series of reorganizations that reposition cytoplasmic and cortical domains established during oogenesis. These domains situated in the periphery of the oocyte contain developmental determinants and a population of maternal postplasmic/PEM RNAs. One of these RNAs (macho-1) is a determinant for the muscle cells of the tadpole embryo. Oocytes acquire a primary animal-vegetal (a-v) axis during meiotic maturation, when a subcortical mitochondria-rich domain (myoplasm) and a domain rich in cortical endoplasmic reticulum (cER) and maternal postplasmic/PEM RNAs (cER-mRNA domain) become polarized and asymmetrically enriched in the vegetal hemisphere. Fertilization at metaphase of meiosis I initiates a series of dramatic cytoplasmic and cortical reorganizations of the zygote, which occur in two major phases. The first major phase depends on sperm entry which triggers a calcium wave leading in turn to an actomyosin-driven contraction wave. The contraction concentrates the cER-mRNA domain and myoplasm in and around a vegetal/contraction pole. The precise localization of the vegetal/contraction pole depends on both the a-v axis and the location of sperm entry and prefigures the future site of gastrulation and dorsal side of the embryo. The second major phase of reorganization occurs between meiosis completion and first cleavage. Sperm aster microtubules and then cortical microfilaments cause the cER-mRNA domain and myoplasm to reposition toward the posterior of the zygote. The location of the posterior pole depends on the localization of the sperm centrosome/aster attained during the first major phase of reorganization. Both cER-mRNA and myoplasm domains localized in the posterior region are partitioned equally between the first two blastomeres and then asymmetrically over the next two cleavages. At the eight-cell stage the cER-mRNA domain compacts and gives rise to a macroscopic cortical structure called the Centrosome Attracting Body (CAB). The CAB is responsible for a series of unequal divisions in posterior-vegetal blastomeres, and the postplasmic/PEM RNAs it contains are involved in patterning the posterior region of the embryo. In this review, we discuss these multiple events and phases of reorganizations in detail and their relationship to physiological, cell cycle, and cytoskeletal events. We also examine the role of the reorganizations in localizing determinants, postplasmic/PEM RNAs, and PAR polarity proteins in the cortex. Finally, we summarize some of the remaining questions concerning polarization of the ascidian embryo and provide comparisons to a few other species. A large collection of films illustrating the reorganizations can be consulted by clicking on "Film archive: ascidian eggs and embryos" at http://biodev.obs-vlfr.fr/recherche/biomarcell/.
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Affiliation(s)
- Christian Sardet
- BioMarCell group, UMR 7009 Biodev CNRS/ Université Pierre et Marie Curie (Paris VI), Observatoire Océanologique, Villefranche-sur-Mer, France.
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22
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Danilchik MV, Brown EE, Riegert K. Intrinsic chiral properties of the Xenopus egg cortex: an early indicator of left-right asymmetry? Development 2006; 133:4517-26. [PMID: 17050623 DOI: 10.1242/dev.02642] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Vertebrate embryos define an anatomic plane of bilateral symmetry by establishing rudimentary anteroposterior and dorsoventral (DV) axes. A left-right (LR) axis also emerges, presaging eventual morphological asymmetries of the heart and other viscera. In the radially symmetric egg of Xenopus laevis, the earliest steps in DV axis determination are driven by microtubule-dependent localization of maternal components toward the prospective dorsal side. LR axis determination is linked in time to this DV-determining process, but the earliest steps are unclear. Significantly, no cytoskeletal polarization has been identified in early embryos capable of lateral displacement of maternal components. Cleaving Xenopus embryos and parthenogenetically activated eggs treated with 2,3-butanedione monoxime (BDM) undergo a dramatic large-scale torsion, with the cortex of the animal hemisphere shearing in an exclusively counterclockwise direction past the vegetal cortex. Long actin fibers develop in a shear zone paralleling the equator. Drug experiments indicate that the actin is not organized by microtubules, and depends on the reorganization of preexisting f-actin fibers rather than new actin polymerization. The invariant chirality of this drug response suggests a maternally inherited, microfilament-dependent organization within the egg cortex that could play an early role in LR axis determination during the first cell cycle. Consistent with this hypothesis, brief disruption of cortical actin during the first cell cycle randomizes the LR orientation of tadpole heart and gut.
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Affiliation(s)
- Michael V Danilchik
- Department of Integrative Biosciences, Oregon Health and Science University, Portland, OR 97239-3097, USA.
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23
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Chesnel F, Vignaux F, Richard-Parpaillon L, Huguet A, Kubiak JZ. Differences in regulation of the first two M-phases in Xenopus laevis embryo cell-free extracts. Dev Biol 2006; 285:358-75. [PMID: 16087172 DOI: 10.1016/j.ydbio.2005.06.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2004] [Revised: 06/21/2005] [Accepted: 06/23/2005] [Indexed: 11/28/2022]
Abstract
The first embryonic M-phase is special, being the time when paternal and maternal chromosomes mix together for the first time. Reports from a variety of species suggest that the regulation of first M-phase has many particularities; however, no systematic comparative study of the biochemical aspects of first and the following M-phases has been previously undertaken. Here, we ask whether the regulation of the first embryonic M-phase is modified, using Xenopus cell-free extracts. We developed new types of extract specific for the first and the second M-phase obtained either from parthenogenetic or from in vitro fertilized embryos. Analyses of these extracts confirmed that the amplitude of histone H1 kinase activity reflecting CDK1/cyclin B (or MPF for M-phase Promoting Factor) activity is higher and persists longer than during the second M-phase, and that levels of cyclins B1 and B2 are correspondingly higher during the first than the second embryonic M-phase. Inhibition of protein synthesis shortly before M-phase entry reduced mitotic histone H1 kinase amplitude, shortened the period of mitotic phosphorylation of chosen marker proteins, and reduced cyclin B1 and B2 levels, suggesting a role of B-type cyclins in regulating the duration of mitotic events. Moreover, addition of exogenous cyclin B to the extract prior the second mitosis brought forward the activation of mitotic histone H1 kinase but prolonged the duration of this activity. We also confirmed that the inhibitory phosphorylation of CDK1 on tyrosine 15 oscillates between the first two embryonic M-phases, but is clearly more pronounced before the first than the second mitosis, while the MAP kinase ERK2 tended to show greater activation during the first embryonic M-phase but with a similar duration of activation. We conclude that discrete differences exist between the first two M-phases in Xenopus embryo and that higher CDK1/cyclin B activity and B-type cyclin levels could account for the different characteristics of these M-phases.
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Affiliation(s)
- Franck Chesnel
- UMR 6061 CNRS, Biology and Genetics of Development, Mitosis and Meiosis Group, IFR140 GFAS, University of Rennes 1, Faculty of Medicine, 2 Ave. Prof. Léon Bernard, CS 34317, 35043 Rennes cedex, France
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24
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Nakamura N, Tokumoto T, Ueno S, Iwao Y. The cytoskeleton-dependent localization of cdc2/cyclin B in blastomere cortex duringXenopus embryonic cell cycle. Mol Reprod Dev 2005; 72:336-45. [PMID: 16097011 DOI: 10.1002/mrd.20348] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In the early development of the frog, Xenopus laevis, blastomeres undergo synchronous divisions at about the 12th cell cycle, followed by asynchronous divisions, which is referred to as mid-blastula transition (MBT). We investigated the distribution of several regulating factors for cell cycles around MBT using immunocytochemistry and confocal fluorescence microscopy. At the 8th cell cycle, most of the cdc2/cyclin B was localized in the cortical cytoplasm throughout the cell cycle, in the centrosomes and the nucleus at interphase and prometaphase, and in the spindles at metaphase and anaphase. Cdc2 was also localized in the chromatins at metaphase and anaphase. Cyclin B1 mRNA was localized in the periphery of the nucleus, but not in the cell cortex. At the 13th cell cycle, the amount of cdc2/cyclin B in the cortical cytoplasm decreased, and the inactive form of cdc2, phosphorylated at tyrosine 15, appeared in the nucleus and the centrosomes at interphase, indicating that the regulation of cdc2 by phosphorylation occurs around MBT. When the blastomeres were treated with nocodazole or latrunculin A at the 8th cell cycle, the amount of cortical cdc2 decreased, but that of cyclin B did not change. The cortical localization of cdc2 is dependent upon both microtubules and microfilaments. Most of the cdc27 was localized in the centrosomes, and in the spindle poles, but no significant difference was observed between the 8th and the 13th cell cycles. It is possible that the cortical MPF activity is regulated by the differential localization between cdc2 and cyclin B.
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Affiliation(s)
- Norihiko Nakamura
- Department of Biological Science, Faculty of Science, Yamaguchi University, Yamaguchi, Japan
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25
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Marrari Y, Rouvière C, Houliston E. Complementary roles for dynein and kinesins in the Xenopus egg cortical rotation. Dev Biol 2004; 271:38-48. [PMID: 15196948 DOI: 10.1016/j.ydbio.2004.03.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2004] [Revised: 03/10/2004] [Accepted: 03/11/2004] [Indexed: 01/01/2023]
Abstract
Aligned vegetal subcortical microtubules in fertilized Xenopus eggs mediate the "cortical rotation", a translocation of the vegetal cortex and of dorsalizing factors toward the egg equator. Kinesin-related protein (KRP) function is essential for the cortical rotation, and dynein has been implicated indirectly; however, the role of neither microtubule motor protein family is understood. We examined the consequence of inhibiting dynein--dynactin-based transport by microinjection of excess dynamitin beneath the vegetal egg surface. Dynamitin introduced before the cortical rotation prevented formation of the subcortical array, blocking microtubule incorporation from deeper regions. In contrast, dynamitin injected after the microtubule array was fully established did not block cortical translocation, unlike inhibitory-KRP antibodies. During an early phase of cortical rotation, when microtubules showed a distinctive wavy organization, dynamitin disrupted microtubule alignment and perturbed cortical movement. These findings indicate that dynein is required for formation and early maintenance of the vegetal microtubule array, while KRPs are largely responsible for displacing the cortex once the microtubule tracks are established. Consistent with this model for the cortical rotation, photobleach analysis revealed both microtubules that translocated with the vegetal cytoplasm relative to the cortex, and ones that moved with the cortex relative to the cytoplasm.
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Affiliation(s)
- Yannick Marrari
- Unité de Biologie du Développement, UMR 7009 CNRS/Université Paris VI, Observatoire Océanologique, 06230 Villefranche sur mer, France
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26
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Terasaki M, Okumura EI, Hinkle B, Kishimoto T. Localization and dynamics of Cdc2-cyclin B during meiotic reinitiation in starfish oocytes. Mol Biol Cell 2003; 14:4685-94. [PMID: 14551249 PMCID: PMC266783 DOI: 10.1091/mbc.e03-04-0249] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The Cdc2-cyclin B kinase has a central role in regulating the onset of M phase. In starfish oocytes, Cdc2-cyclin B begins to be activated approximately 10 min after application of maturation hormone, followed by accumulation in the nucleus then nuclear envelope breakdown. By immunofluorescence and by expressing a green fluorescent (GFP) chimera of cyclin B, we find that cyclin B is present in aggregates in the cytoplasm of immature oocytes. The aggregates disperse at approximately 10 min, suggesting that the dispersal is closely related to the activation of the kinase. Using cyclin B-GFP, the dispersion begins from the region containing the centrosomes. Extractability of Cdc2-cyclin B changes with similar kinetics during maturation. Active Cdc25 phosphatase released Cdc2-cyclin B from the detergent-insoluble fraction independently of its phosphatase activity. Live cell imaging also showed that Cdc2-cyclin B begins to accumulate in the nucleus before changes in nuclear pore permeability, consistent with Cdc2-cyclin B-induced disassembly of the pores.
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Affiliation(s)
- Mark Terasaki
- Department of Physiology, University of Connecticut Health Center, Farmington, Connecticut 06032, USA.
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27
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Abstract
This study examined which component of the egg, the nucleus or cytoplasm, is involved in the timing of the start of gastrulation in the Xenopus embryo, and when it starts to measure time. First, nuclei of cells of 256-cell stage embryos were transplanted to enucleated eggs 60 min after activation. These eggs showed first cleavage 20-30 min later than control eggs fertilized at the same time as the activation of recipient eggs, and started gastrulation 25-35 min later than control embryos (depending on the delay in the first cleavage). Second, eggs whose nuclei were temporarily isolated by the extrusion of the portion containing the nucleus out of the fertilization envelope showed first cleavage 60-90 min later than sibling control eggs, because of delayed introduction of the nucleus from the extruded portion. They started gastrulation 60-90 min later than sibling control embryos (depending on the delay in the first cleavage). The portion inside the envelope underwent two to three rounds of oscillation in cell cycle relevant activities before the first cleavage, while the portion outside underwent the same rounds of cleavage as the inside portion. From the present and previous results it is concluded that the putative timing system for the start of gastrulation in the Xenopus embryo, whether it consists of a single or of multiple clocks, starts measuring time at or around the first cleavage, and that the presence of both the nucleus and the cytoplasm in the same cell and occurrence of mitosis and/or cleavage there are indispensable for the timing system to work, although the role of the cytoplasm is superior to that of the nucleus.
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Affiliation(s)
- Takeshi Itoh
- Department of Biology, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-Machi, Yamagata 990-8560, Japan
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28
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Marrari Y, Clarke EJ, Rouvière C, Houliston E. Analysis of microtubule movement on isolated Xenopus egg cortices provides evidence that the cortical rotation involves dynein as well as Kinesin Related Proteins and is regulated by local microtubule polymerisation. Dev Biol 2003; 257:55-70. [PMID: 12710957 DOI: 10.1016/s0012-1606(03)00057-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In amphibians, the cortical rotation, a translocation of the egg cortex relative to the cytoplasm, specifies the dorsoventral axis. The cortical rotation involves an array of subcortical microtubules whose alignment is mediated by Kinesin-related proteins (KRPs), and stops as M-phase promoting factor (MPF) activation propagates across the egg. To dissect the role of different motor proteins in the cortical rotation and to analyse their regulation, we have developed an open cell assay system involving reactivation of microtubule movement on isolated cortices. Microtubule movements were dependent on ATP and consisted mainly of wriggling and flailing without net displacement, consistent with a tethering of microtubules to the cortex. Reactivated movements were inhibited by anti-KRP and anti-dynein antibodies perfused together but not separately, the KRP antibody alone becoming fixed to the cortex. Neither antibody could inhibit movement in the presence of MPF, indicating that arrest of the cortical rotation is not due to MPF-dependent inhibition of motor molecules. In contrast, D(2)O treatment of live eggs to protect microtubules from progressive depolymerisation prolonged the cortical rotation. We conclude that the cortical rotation probably involves cytoplasmic dynein as well as cortical KRPs and terminates as a result of local MPF-dependent microtubule depolymerisation.
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Affiliation(s)
- Yannick Marrari
- Unité de Biologie du Développement, UMR 7009 CNRS/Université Paris VI, Observatoire Océanologique, 06230, Villefranche-Sur-Mer, France.
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29
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Beckhelling C, Chang P, Chevalier S, Ford C, Houliston E. Pre-M phase-promoting factor associates with annulate lamellae in Xenopus oocytes and egg extracts. Mol Biol Cell 2003; 14:1125-37. [PMID: 12631728 PMCID: PMC151584 DOI: 10.1091/mbc.e02-08-0511] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2002] [Revised: 10/21/2002] [Accepted: 11/18/2002] [Indexed: 11/11/2022] Open
Abstract
We have used complementary biochemical and in vivo approaches to study the compartmentalization of M phase-promoting factor (MPF) in prophase Xenopus eggs and oocytes. We first examined the distribution of MPF (Cdc2/CyclinB2) and membranous organelles in high-speed extracts of Xenopus eggs made during mitotic prophase. These extracts were found to lack mitochondria, Golgi membranes, and most endoplasmic reticulum (ER) but to contain the bulk of the pre-MPF pool. This pre-MPF could be pelleted by further centrifugation along with components necessary to activate it. On activation, Cdc2/CyclinB2 moved into the soluble fraction. Electron microscopy and Western blot analysis showed that the pre-MPF pellet contained a specific ER subdomain comprising "annulate lamellae" (AL): stacked ER membranes highly enriched in nuclear pores. Colocalization of pre-MPF with AL was demonstrated by anti-CyclinB2 immunofluorescence in prophase oocytes, in which AL are positioned close to the vegetal surface. Green fluorescent protein-CyclinB2 expressed in oocytes also localized at AL. These data suggest that inactive MPF associates with nuclear envelope components just before activation. This association may explain why nuclei and centrosomes stimulate MPF activation and provide a mechanism for targeting of MPF to some of its key substrates.
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Affiliation(s)
- Clare Beckhelling
- Unité Mixte Recherche 7009, Centre National de la Recherche Scientifique/Université Paris VI, Observatoire Oceanologique de Villefranche sur Mer, 06234, Villefranche sur Mer, France
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30
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Royou A, Sullivan W, Karess R. Cortical recruitment of nonmuscle myosin II in early syncytial Drosophila embryos: its role in nuclear axial expansion and its regulation by Cdc2 activity. J Cell Biol 2002; 158:127-37. [PMID: 12105185 PMCID: PMC2173028 DOI: 10.1083/jcb.200203148] [Citation(s) in RCA: 203] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The nuclei of early syncytial Drosophila embryos migrate dramatically toward the poles. The cellular mechanisms driving this process, called axial expansion, are unclear, but myosin II activity is required. By following regulatory myosin light chain (RLC)-green fluorescent protein dynamics in living embryos, we observed cycles of myosin recruitment to the cortex synchronized with mitotic cycles. Cortical myosin is first seen in a patch at the anterocentral part of the embryo at cycle 4. With each succeeding cycle, the patch expands poleward, dispersing at the beginning of each mitosis and reassembling at the end of telophase. Each cycle of actin and myosin recruitment is accompanied by a cortical contraction. The cortical myosin cycle does not require microtubules but correlates inversely with Cdc2/cyclinB (mitosis-promoting factor) activity. A mutant RLC lacking inhibitory phosphorylation sites was fully functional with no effect on the cortical myosin cycle, indicating that Cdc2 must be modulating myosin activity by some other mechanism. An inhibitor of Rho kinase blocks the cortical myosin recruitment cycles and provokes a concomitant failure of axial expansion. These studies suggest a model in which cycles of myosin-mediated contraction and relaxation, tightly linked to Cdc2 and Rho kinase activity, are directly responsible for the axial expansion of the syncytial nuclei.
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Affiliation(s)
- Anne Royou
- Centre National de la Recherche Scientifique, Centre de Génétique Moléculaire, 91198 Gif-sur-Yvette, France
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31
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Bodart JFL, Gutierrez DV, Nebreda AR, Buckner BD, Resau JR, Duesbery NS. Characterization of MPF and MAPK activities during meiotic maturation of Xenopus tropicalis oocytes. Dev Biol 2002; 245:348-61. [PMID: 11977986 DOI: 10.1006/dbio.2002.0647] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Resumption of meiosis in oocytes of Xenopus tropicalis required translation but not transcription, and was marked by the appearance of a white spot and a dark ring, coincident with entry into metaphase I and the onset of anaphase I, respectively. Cyclin B(2)/p34(cdc2) activity increased prior to the first meiotic division, declined at the onset of anaphase I, and subsequently increased again. The capacity of egg cytoplasm to induce germinal vesicle breakdown (GVBD) was inhibited by cycloheximide, despite the fact that these oocytes contained cyclin B(2)/p34(cdc2) complexes. However, cycloheximide-treated oocytes underwent GVBD following injection of constitutively active mitogen-activated protein kinase (MAPK) kinase 2 (MEK2), p33(Ringo), or Delta 90 cyclin B. MAPK activity increased just prior to the first meiotic division and remained stable thereafter. Although injection of constitutively active MEK2 induced GVBD, treatment with the MEK inhibitors U0126 or anthrax lethal factor delayed GVBD and prevented spindle formation. Interestingly, the ability of egg cytoplasm to induce GVBD was unaffected by the inhibition of MEK activity. Our results indicate that the synthesis of a novel or short-lived protein(s) which acts in a MEK-independent fashion is required in order for egg cytoplasm to induce GVBD in X. tropicalis oocytes.
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Affiliation(s)
- Jean-Francois L Bodart
- Van Andel Research Institute, Laboratory of Developmental Cell Biology, Special Program in Analytical, Cellular, and Molecular Microscopy, 333 Bostwick NE, Grand Rapids, Michigan 49503, USA
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32
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Quaas J, Wylie C. Surface contraction waves (SCWs) in the Xenopus egg are required for the localization of the germ plasm and are dependent upon maternal stores of the kinesin-like protein Xklp1. Dev Biol 2002; 243:272-80. [PMID: 11884036 DOI: 10.1006/dbio.2001.0564] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During the first four cell cycles in Xenopus, islands of germ plasm, initially distributed throughout the vegetal half of the egg cortex, move to the vegetal pole of the egg, fusing with each other as they do so, and form four large cytoplasmic masses. These are inherited by the vegetal cells that will enter the germ line. It has previously been shown that germ plasm islands are embedded in a cortical network of microtubules and that the microtubule motor protein Xklp1 is required for their localization to the vegetal pole [Robb, D., Heasman, J., Raats, J., and Wylie, C. (1996). Cell 87, 823-831]. Here, we show that germ plasm islands fail to localize and fuse in Xklp1-depleted eggs due to the abrogation of the global cytoplasmic movements known as surface contraction waves (SCWs). Thus, SCWs are shown to require a microtubule-based transport system for which Xklp1 is absolutely required, and the SCWs themselves represent a cortical transport system in the egg required for the correct distribution of at least one cytoplasmic determinant of future pattern.
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Affiliation(s)
- Josh Quaas
- University of Minnesota School of Medicine, 420 Delaware Street SE, Minneapolis, MN 55445, USA
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Schnell S, Maini PK, McInerney D, Gavaghan DJ, Houston P. Models for pattern formation in somitogenesis: a marriage of cellular and molecular biology. C R Biol 2002; 325:179-89. [PMID: 12017765 DOI: 10.1016/s1631-0691(01)01418-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Somitogenesis, the process by which a bilaterally symmetric pattern of cell aggregations is laid down in a cranio-caudal sequence in early vertebrate development, provides an excellent model study for the coupling of interactions at the molecular and cellular level. Here, we review some of the key experimental results and theoretical models related to this process. We extend a recent chemical pre-pattern model based on the cell cycle Journal of Theoretical Biology 207 (2000) 305-316, by including cell movement and show that the resultant model exhibits the correct spatio-temporal dynamics of cell aggregation. We also postulate a model to account for the recently observed spatio-temporal dynamics at the molecular level.
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Affiliation(s)
- Santiago Schnell
- Centre for Mathematical Biology, Mathematical Institute, 24-29 St Giles', Oxford OX1 3LB, UK.
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Carré D, Djediat C, Sardet C. Formation of a large Vasa-positive germ granule and its inheritance by germ cells in the enigmatic Chaetognaths. Development 2002; 129:661-70. [PMID: 11830567 DOI: 10.1242/dev.129.3.661] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Chaetognaths (arrow worms) are abundant hermaphrodite marine organisms whose phylogenetic position amongst protostomes and deuterostomes is still debated. Ancient histological observations dating from a century ago described the presence in eggs of a large granule, presumed to be a germ plasm, and its probable inheritance in four primary germ cells (PGCs). Using videomicroscopy, electron microscopy and immunocytochemistry (labelling with anti-Vasa antibodies) we have followed the cycle of aggregation and dispersion of germ plasm and nuage material in eggs, embryos, PGCs and oocytes in several species of benthic (Spadella) and planctonic (Sagitta) chaetognaths. In these animals, germ cells and gametes can be observed in vivo throughout the 1-2 month life cycle.After describing internal fertilization in live animals we show that the single large (15 μm diameter) germ granule forms by a spiralling aggregation movement of small germ islands situated in the vegetal cortex at the time of first mitosis. We also demonstrate that the granule forms autonomously in unfertilized activated eggs or fertilized egg fragments. Once formed, the germ granule first associates with the cleavage furrow and is segregated into one of the first two blastomeres. The germ granule is then translocated from the cortex to the mitotic spindle during 3rd cleavage and remains in the single most-vegetal blastomere until the 32-cell stage. At the 64-cell stage the germ granule is partitioned as nuage material into two founder PGCs and further partitioned into four PGCs situated at the tip of the archenteron during gastrulation. These four PGCs migrate without dividing to reach the transverse septum, then proliferate and differentiate into oocytes and spermatocytes of two ovaries and two testes. We noted that germ plasm and nuage material were associated with mitochondria, the nucleus, the spindle and the centrosome during some stages of development and differentiation of the germ line. Finally, we demonstrate that a Vasa-like protein is present in the germ granule, in PGCs and in the electron-dense material associated with the germinal vesicle of oocytes. These features stress the conservation of cellular and molecular mechanisms involved in germ cell determination.Movies available on-line
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Affiliation(s)
- Danièle Carré
- Bio Mar Cell, Laboratoire de Biologie du Développement, UMR7009 CNRS / UPMC, Station Zoologique, Observatoire Océanologique, 06234 Villefranche-sur-mer cedex, France
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Kuroda S, Satoh T, Shinagawa A. Involvement of a urethane-sensitive system in timing the onset of gastrulation in Xenopus laevis embryos. Dev Growth Differ 2001; 43:401-13. [PMID: 11473547 DOI: 10.1046/j.1440-169x.2001.00585.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This paper describes success in delaying the onset of gastrulation in Xenopus laevis embryos without damage to their subsequent development by temporarily arresting cleavage with urethane. Exposure of X. laevis embryos to 150 mM urethane before gastrulation resulted in cleavage arrest and its removal led to cleavage resumption. During cleavage arrest, cyclic activities including nuclear replication and the M-phase-promoting factor cycle continued, although their duration was lengthened to nearly 1.8-fold that of the controls. Because of a 30-min time lag from removal of urethane to resumption of cleavage, as well as the retardation of cyclic activities during cleavage arrest, the development of embryos after a 60-min exposure to urethane lagged two cell cycles behind that of control embryos. Here, the two cell cycle delay is equivalent to 50 min at 22-23 degrees C. The start of gastrulation in exposed embryos was accordingly delayed about 50 min, although the delay in mid-blastula transition was as little as 20-25 min. Consistent results were obtained in embryos exposed to urethane for 90 or 120 min and those exposed to procaine or NH4Cl for 60 min. Although these results imply that delay in the start of gastrulation in exposed embryos is ascribed simply to delay in their development raised by cleavage arrest, at the same time they suggest that the onset of gastrulation is timed by systems sensitive to urethane, procaine and NH4Cl in X. laevis embryos.
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Affiliation(s)
- S Kuroda
- Department of Biology, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-Machi, Yamagata 990-8560, Japan
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Terasaki M, Campagnola P, Rolls MM, Stein PA, Ellenberg J, Hinkle B, Slepchenko B. A new model for nuclear envelope breakdown. Mol Biol Cell 2001; 12:503-10. [PMID: 11179431 PMCID: PMC30959 DOI: 10.1091/mbc.12.2.503] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2000] [Revised: 11/29/2000] [Accepted: 12/01/2000] [Indexed: 11/11/2022] Open
Abstract
Nuclear envelope breakdown was investigated during meiotic maturation of starfish oocytes. Fluorescent 70-kDa dextran entry, as monitored by confocal microscopy, consists of two phases, a slow uniform increase and then a massive wave. From quantitative analysis of the first phase of dextran entry, and from imaging of green fluorescent protein chimeras, we conclude that nuclear pore disassembly begins several minutes before nuclear envelope breakdown. The best fit for the second phase of entry is with a spreading disruption of the membrane permeability barrier determined by three-dimensional computer simulations of diffusion. We propose a new model for the mechanism of nuclear envelope breakdown in which disassembly of the nuclear pores leads to a fenestration of the nuclear envelope double membrane.
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Affiliation(s)
- M Terasaki
- Department of Physiology, University of Connecticut Health Center, Farmington, 06032, USA.
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Pérez-Mongiovi D, Beckhelling C, Chang P, Ford CC, Houliston E. Nuclei and microtubule asters stimulate maturation/M phase promoting factor (MPF) activation in Xenopus eggs and egg cytoplasmic extracts. J Cell Biol 2000; 150:963-74. [PMID: 10973988 PMCID: PMC2175258 DOI: 10.1083/jcb.150.5.963] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2000] [Accepted: 07/07/2000] [Indexed: 11/22/2022] Open
Abstract
Although maturation/M phase promoting factor (MPF) can activate autonomously in Xenopus egg cytoplasm, indirect evidence suggests that nuclei and centrosomes may focus activation within the cell. We have dissected the contribution of these structures to MPF activation in fertilized eggs and in egg fragments containing different combinations of nuclei, centrosomes, and microtubules by following the behavior of Cdc2 (the kinase component of MPF), the regulatory subunit cyclin B, and the activating phosphatase Cdc25. The absence of the entire nucleus-centrosome complex resulted in a marked delay in MPF activation, whereas the absence of the centrosome alone caused a lesser delay. Nocodazole treatment to depolymerize microtubules through first interphase had an effect equivalent to removing the centrosome. Furthermore, microinjection of isolated centrosomes into anucleate eggs promoted MPF activation and advanced the onset of surface contraction waves, which are close indicators of MPF activation and could be triggered by ectopic MPF injection. Finally, we were able to demonstrate stimulation of MPF activation by the nucleus-centriole complex in vitro, as low concentrations of isolated sperm nuclei advanced MPF activation in cycling cytoplasmic extracts. Together these results indicate that nuclei and microtubule asters can independently stimulate MPF activation and that they cooperate to enhance activation locally.
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Affiliation(s)
- Daniel Pérez-Mongiovi
- UMR 7009, Centre National de la Recherche Scientifique/Université Paris VI, Station Zoologique, 06230 Villefranche-sur-mer, France
| | - Clare Beckhelling
- UMR 7009, Centre National de la Recherche Scientifique/Université Paris VI, Station Zoologique, 06230 Villefranche-sur-mer, France
- School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG, United Kingdom
| | - Patrick Chang
- UMR 7009, Centre National de la Recherche Scientifique/Université Paris VI, Station Zoologique, 06230 Villefranche-sur-mer, France
| | - Christopher C. Ford
- School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG, United Kingdom
| | - Evelyn Houliston
- UMR 7009, Centre National de la Recherche Scientifique/Université Paris VI, Station Zoologique, 06230 Villefranche-sur-mer, France
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Beckhelling C, Penny C, Clyde S, Ford C. Timing of calcium and protein synthesis requirements for the first mitotic cell cycle in fertilised Xenopus eggs. J Cell Sci 1999; 112 ( Pt 22):3975-84. [PMID: 10547358 DOI: 10.1242/jcs.112.22.3975] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mitosis is governed by the activity of the M-phase promoting factor (MPF). In some systems, particularly early embryos, transient increases in calcium concentration have been shown to be necessary for mitosis and regulate its timing. By microinjection of the calcium buffer, dibromoBAPTA, into fertilised Xenopus eggs, we have assessed whether calcium events are required to initiate MPF activation and inactivation. Since initial experiments showed that this buffer inhibited protein synthesis, we measured when mitosis and cleavage became independent of translation. We found that, after a period of protein synthesis essential for cleavage, there was a phase during which continued translation affected the timing of cleavage, but was not essential for its occurrence. Measurement of MPF activity in single embryos injected with calcium buffer at different times in the first cell cycle, showed that there were two sensitive periods. The first period of sensitivity blocked MPF activation and coincided with the time at which cleavage became completely independent of protein synthesis. The second sensitive period occurred just before histone kinase activity peaked, and was necessary for kinase inactivation. Preventing inactivation in this way arrested egg extracts in mitosis. These results support the view that transient increases in free calcium concentration contribute to mitotic progression by first triggering MPF activation and subsequently, with elevated MPF activity, inducing its inactivation.
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Affiliation(s)
- C Beckhelling
- Biology Building, School of Biological Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
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Shuster CB, Burgess DR. Parameters that specify the timing of cytokinesis. J Cell Biol 1999; 146:981-92. [PMID: 10477753 PMCID: PMC2169486 DOI: 10.1083/jcb.146.5.981] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/1999] [Accepted: 08/05/1999] [Indexed: 11/22/2022] Open
Abstract
One model for the timing of cytokinesis is based on findings that p34(cdc2) can phosphorylate myosin regulatory light chain (LC20) on inhibitory sites (serines 1 and 2) in vitro (Satterwhite, L.L., M.H. Lohka, K.L. Wilson, T.Y. Scherson, L.J. Cisek, J.L. Corden, and T.D. Pollard. 1992. J. Cell Biol. 118:595-605), and this inhibition is proposed to delay cytokinesis until p34(cdc2) activity falls at anaphase. We have characterized previously several kinase activities associated with the isolated cortical cytoskeleton of dividing sea urchin embryos (Walker, G.R., C.B. Shuster, and D.R. Burgess. 1997. J. Cell Sci. 110:1373-1386). Among these kinases and substrates is p34(cdc2) and LC20. In comparison with whole cell activity, cortical H1 kinase activity is delayed, with maximum levels in cortices prepared from late anaphase/telophase embryos. To determine whether cortical-associated p34(cdc2) influences cortical myosin II activity during cytokinesis, we labeled eggs in vivo with [(32)P]orthophosphate, prepared cortices, and mapped LC20 phosphorylation through the first cell division. We found no evidence of serine 1,2 phosphorylation at any time during mitosis on LC20 from cortically associated myosin. Instead, we observed a sharp rise in serine 19 phosphorylation during anaphase and telophase, consistent with an activating phosphorylation by myosin light chain kinase. However, serine 1,2 phosphorylation was detected on light chains from detergent-soluble myosin II. Furthermore, cells arrested in mitosis by microinjection of nondegradable cyclin B could be induced to form cleavage furrows if the spindle poles were physically placed in close proximity to the cortex. These results suggest that factors independent of myosin II inactivation, such as the delivery of the cleavage stimulus to the cortex, determine the timing of cytokinesis.
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Affiliation(s)
- Charles B. Shuster
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
- Mount Desert Island Biological Laboratory, Salisbury, Maine 04672
| | - David R. Burgess
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467
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40
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Abstract
The division of the Xenopus oocyte cortex into structurally and functionally distinct "animal" and "vegetal" regions during oogenesis provides the basis of the organisation of the early embryo. The vegetal region of the cortex accumulates specific maternal mRNAs that specify the development of the endoderm and mesoderm, as well as functionally-defined "determinants" of dorso-anterior development, and recognisable "germ plasm" determinants that segregate into primary germ cells. These localised elements on the vegetal cortex underlie both the primary animal-vegetal polarity of the egg and the organisation of the developing embryo. The animal cortex meanwhile becomes specialised for the events associated with fertilisation: sperm entry, calcium release into the cytoplasm, cortical granule exocytosis, and polarised cortical contraction. Cortical and subcortical reorganisations associated with meiotic maturation, fertilisation, cortical rotation, and the first mitotic cleavage divisions redistribute the vegetal cortical determinants, contributing to the specification of dorso-anterior axis and segregation of the germ line. In this article we consider what is known about the changing organisation of the oocyte and egg cortex in relation to the mechanisms of determinant localisation, anchorage, and redistribution, and show novel ultrastructural views of cortices isolated at different stages and processed by the rapid-freeze deep-etch method. Cortical organisation involves interactions between the different cytoskeletal filament systems and internal membranes. Associated proteins and cytoplasmic signals probably modulate these interactions in stage-specific ways, leaving much to be understood.
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Affiliation(s)
- P Chang
- Unité de Biologie Cellulaire Marine (UMR. 643 CNRS-Université Paris VI), Station Zoologique, Villefranche-sur-mer, France
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41
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Abstract
Cytokinesis is a crucial but poorly understood process of cell proliferation. Recently, molecular genetic analyses of fungal cytokinesis have led to an appreciation of contractile mechanisms in simple eukaryotes, and studies in animal and plant cells have led to new insights into the role of microtubules in the cleavage process. These findings suggest that fundamental mechanisms of cytokinesis may be highly conserved among eukaryotic organisms.
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Affiliation(s)
- C Field
- Department of Cell Biology Harvard Medical School 240 Longwood Avenue Boston MA 02115 USA
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Cha BJ, Gard DL. XMAP230 is required for the organization of cortical microtubules and patterning of the dorsoventral axis in fertilized Xenopus eggs. Dev Biol 1999; 205:275-86. [PMID: 9917363 DOI: 10.1006/dbio.1998.9123] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The dorsoventral axis of Xenopus embryos is specified by a rotation of the egg cortex relative to the underlying yolky cytoplasm. This cortical rotation, which occurs during the first cell cycle after fertilization, is dependent upon an array of parallel microtubules in the subcortical cytoplasm. We have used confocal immunofluorescent microscopy and microinjection of affinity-purified anti-XMAP230 antibody to address the role of XMAP230, one of three high-molecular-weight microtubule-associated proteins (MAPs) in Xenopus eggs, in the assembly and organization of the cortical microtubule array and specification of the dorsoventral axis. Confocal immunofluorescence microscopy revealed that XMAP230 was associated with cortical microtubules shortly after their appearance in the subcortical cytoplasm. XMAP230 staining became more prominent as microtubules were aligned and bundled during the cortical rotation. Loss of XMAP230 appeared to precede disassembly of cortical microtubules at the end of the first cell cycle. Deeper within the cytoplasm, XMAP230 was associated with microtubules early in the assembly of the sperm aster. However, later in the first cell cycle, XMAP230 was associated with microtubules (MTs) of the first mitotic spindle, spindle asters, and the cortical MTs, but not with microtubule remnants of the sperm aster. Microinjection of anti-XMAP230 antibody locally disrupted the assembly and organization of microtubules in the cortex of activated or fertilized eggs and resulted in defects in the dorsoventral patterning of embryos. These results indicate that the assembly and/or organization of cortical microtubules in fertilized Xenopus eggs and subsequent specification of the dorsoventral axis are dependent upon XMAP230.
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Affiliation(s)
- B J Cha
- Department of Biology, University of Utah, Salt Lake City, 84112, USA
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43
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Abstract
Most long distance calcium signals are believed to take the form of actively propagated calcium waves. In 1991, when this proposal was first advanced, all such waves were thought to belong to one class, for which fertilization waves were the prototype. Moreover, the speeds of such waves were found to be conserved at about 10 microns/s for primary fertilization waves and 30 microns/s for waves through fully active systems at 20 degrees C. In 1993, preliminary evidence for a second class of such waves was published and the prototype for these were ones which drive cell cleavage. These move at only about 1 micron/s at 20 degrees C and were, therefore, called slow calcium waves as opposed to the fast ones first considered. Here we compile compelling evidence that slow waves comprise a second distinct class of actively propagated calcium waves. This is based on 30 papers which yield evidence of slow calcium waves in organisms ranging from Dictyostelium to mammals and phenomena ranging from the surface contraction waves seen long ago in axolotl eggs to embryonic cleavage and mitotic waves and to ones recently seen to accompany primary neural induction in axolotls. Ultraslow and ultrafast calcium waves are also considered.
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Affiliation(s)
- L F Jaffe
- Calcium Imaging Laboratory, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
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