1
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Niedzialkowska E, Truong TM, Eldredge LA, Ali A, Redemann S, Stukenberg PT. Chromosomal passenger complex condensates generate parallel microtubule bundles in vitro. J Biol Chem 2024; 300:105669. [PMID: 38272221 PMCID: PMC10876603 DOI: 10.1016/j.jbc.2024.105669] [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: 09/21/2023] [Revised: 01/02/2024] [Accepted: 01/04/2024] [Indexed: 01/27/2024] Open
Abstract
The mitotic spindle contains many bundles of microtubules (MTs) including midzones and kinetochore fibers, but little is known about how bundled structures are formed. Here, we show that the chromosomal passenger complex (CPC) purified from Escherichia coli undergoes liquid-liquid demixing in vitro. An emergent property of the resultant condensates is to generate parallel MT bundles when incubated with free tubulin and GTP in vitro. We demonstrate that MT bundles emerge from CPC droplets with protruding minus ends that then grow into long and tapered MT structures. During this growth, we found that the CPC in these condensates apparently reorganize to coat and bundle the resulting MT structures. CPC mutants attenuated for liquid-liquid demixing or MT binding prevented the generation of parallel MT bundles in vitro and reduced the number of MTs present at spindle midzones in HeLa cells. Our data demonstrate that an in vitro biochemical activity to produce MT bundles emerges after the concentration of the CPC and provides models for how cells generate parallel-bundled MT structures that are important for the assembly of the mitotic spindle. Moreover, these data suggest that cells contain MT-organizing centers that generate MT bundles that emerge with the opposite polarity from centrosomes.
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Affiliation(s)
- Ewa Niedzialkowska
- Department of Biochemistry and Molecular Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Tan M Truong
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Luke A Eldredge
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Aamir Ali
- Department of Biochemistry and Molecular Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Stefanie Redemann
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia, USA; Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - P Todd Stukenberg
- Department of Biochemistry and Molecular Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA; Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
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2
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Fujii K, Kondo T, Kimura A. Enucleation of the C. elegans embryo revealed dynein-dependent spacing between microtubule asters. Life Sci Alliance 2024; 7:e202302427. [PMID: 37931957 PMCID: PMC10627822 DOI: 10.26508/lsa.202302427] [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: 10/09/2023] [Revised: 10/25/2023] [Accepted: 10/26/2023] [Indexed: 11/08/2023] Open
Abstract
The intracellular positioning of the centrosome, a major microtubule-organizing center, is important for cellular functions. One of the features of centrosome positioning is the spacing between centrosomes; however, the underlying mechanisms are not fully understood. To characterize the spacing activity in Caenorhabditis elegans embryos, a genetic setup was developed to produce enucleated embryos. The centrosome was duplicated multiple times in the enucleated embryo, which enabled us to characterize the chromosome-independent spacing activity between sister and non-sister centrosome pairs. We found that the timely spacing depended on cytoplasmic dynein, and we propose a stoichiometric model of cortical and cytoplasmic pulling forces for the spacing between centrosomes. We also observed dynein-independent but non-muscle myosin II-dependent movement of centrosomes in the later cell cycle phase. The spacing mechanisms revealed in this study are expected to function between centrosomes in general, regardless of the presence of a chromosome/nucleus between them, including centrosome separation and spindle elongation.
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Affiliation(s)
- Ken Fujii
- https://ror.org/0516ah480 Department of Genetics, School of Life Science, Sokendai (Graduate University for Advanced Studies) Mishima, Japan
- https://ror.org/02xg1m795 Cell Architecture Laboratory, National Institute of Genetics, Mishima, Japan
| | - Tomo Kondo
- https://ror.org/02xg1m795 Cell Architecture Laboratory, National Institute of Genetics, Mishima, Japan
| | - Akatsuki Kimura
- https://ror.org/0516ah480 Department of Genetics, School of Life Science, Sokendai (Graduate University for Advanced Studies) Mishima, Japan
- https://ror.org/02xg1m795 Cell Architecture Laboratory, National Institute of Genetics, Mishima, Japan
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3
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Bakshi A, Iturra FE, Alamban A, Rosas-Salvans M, Dumont S, Aydogan MG. Cytoplasmic division cycles without the nucleus and mitotic CDK/cyclin complexes. Cell 2023; 186:4694-4709.e16. [PMID: 37832525 PMCID: PMC10659773 DOI: 10.1016/j.cell.2023.09.010] [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: 06/05/2022] [Revised: 05/11/2023] [Accepted: 09/12/2023] [Indexed: 10/15/2023]
Abstract
Cytoplasmic divisions are thought to rely on nuclear divisions and mitotic signals. We demonstrate in Drosophila embryos that cytoplasm can divide repeatedly without nuclei and mitotic CDK/cyclin complexes. Cdk1 normally slows an otherwise faster cytoplasmic division cycle, coupling it with nuclear divisions, and when uncoupled, cytoplasm starts dividing before mitosis. In developing embryos where CDK/cyclin activity can license mitotic microtubule (MT) organizers like the spindle, cytoplasmic divisions can occur without the centrosome, a principal organizer of interphase MTs. However, centrosomes become essential in the absence of CDK/cyclin activity, implying that the cytoplasm can employ either the centrosome-based interphase or CDK/cyclin-dependent mitotic MTs to facilitate its divisions. Finally, we present evidence that autonomous cytoplasmic divisions occur during unperturbed fly embryogenesis and that they may help extrude mitotically stalled nuclei during blastoderm formation. We postulate that cytoplasmic divisions occur in cycles governed by a yet-to-be-uncovered clock mechanism autonomous from CDK/cyclin complexes.
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Affiliation(s)
- Anand Bakshi
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Fabio Echegaray Iturra
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Andrew Alamban
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA; Biophysics Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Miquel Rosas-Salvans
- Department of Bioengineering and Therapeutic Science, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Sophie Dumont
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA
| | - Mustafa G Aydogan
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA; Biophysics Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA.
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4
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Warecki B, Tao L. Centralspindlin-mediated transport of RhoGEF positions the cleavage plane for cytokinesis. Sci Signal 2023; 16:eadh0601. [PMID: 37402224 PMCID: PMC10501416 DOI: 10.1126/scisignal.adh0601] [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: 02/07/2023] [Accepted: 06/13/2023] [Indexed: 07/06/2023]
Abstract
During cytokinesis, the cell membrane furrows inward along a cleavage plane. The positioning of the cleavage plane is critical to faithful cell division and is determined by the Rho guanine nucleotide exchange factor (RhoGEF)-mediated activation of the small guanosine triphosphatase RhoA and the conserved motor protein complex centralspindlin. Here, we explored whether and how centralspindlin mediates the positioning of RhoGEF. In dividing neuroblasts from Drosophila melanogaster, we observed that immediately before cleavage, first centralspindlin and then RhoGEF localized to the sites where cleavage subsequently initiated. Using in vitro assays with purified Drosophila proteins and stabilized microtubules, we found that centralspindlin directly transported RhoGEF as cargo along single microtubules and sequestered it at microtubule plus-ends for prolonged periods of time. In addition, the binding of RhoGEF to centralspindlin appeared to stimulate centralspindlin motor activity. Thus, the motor activity and microtubule association of centralspindlin can translocate RhoGEF to areas where microtubule plus-ends are abundant, such as at overlapping astral microtubules, to locally activate RhoA and accurately position the cleavage plane during cell division.
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Affiliation(s)
- Brandt Warecki
- Department of Biology, University of Hawai’i at Hilo, HI 96720, USA
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz; Santa Cruz, CA 95064, USA
| | - Li Tao
- Department of Biology, University of Hawai’i at Hilo, HI 96720, USA
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5
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Bellingham-Johnstun K, Tyree ZL, Martinez-Baird J, Thorn A, Laplante C. Actin–Microtubule Crosstalk Imparts Stiffness to the Contractile Ring in Fission Yeast. Cells 2023; 12:cells12060917. [PMID: 36980258 PMCID: PMC10047812 DOI: 10.3390/cells12060917] [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: 03/01/2023] [Revised: 03/10/2023] [Accepted: 03/13/2023] [Indexed: 03/19/2023] Open
Abstract
Actin–microtubule interactions are critical for cell division, yet how these networks of polymers mutually influence their mechanical properties and functions in live cells remains unknown. In fission yeast, the post-anaphase array (PAA) of microtubules assembles in the plane of the contractile ring, and its assembly relies on the Myp2p-dependent recruitment of Mto1p, a component of equatorial microtubule organizing centers (eMTOCs). The general organization of this array of microtubules and the impact on their physical attachment to the contractile ring remain unclear. We found that Myp2p facilitates the recruitment of Mto1p to the inner face of the contractile ring, where the eMTOCs polymerize microtubules without their direct interaction. The PAA microtubules form a dynamic polygon of Ase1p crosslinked microtubules inside the contractile ring. The specific loss of PAA microtubules affects the mechanical properties of the contractile ring of actin by lowering its stiffness. This change in the mechanical properties of the ring has no measurable impact on cytokinesis or on the anchoring of the ring. Our work proposes that the PAA microtubules exploit the contractile ring for their assembly and function during cell division, while the contractile ring may receive no benefit from these interactions.
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Affiliation(s)
- Kimberly Bellingham-Johnstun
- Molecular Biomedical Sciences Department, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607, USA
- Quantitative and Computational Developmental Biology Cluster, North Carolina State University, Raleigh, NC 27607, USA
| | - Zoe L. Tyree
- Molecular Biomedical Sciences Department, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607, USA
- Quantitative and Computational Developmental Biology Cluster, North Carolina State University, Raleigh, NC 27607, USA
| | - Jessica Martinez-Baird
- Molecular Biomedical Sciences Department, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607, USA
- Quantitative and Computational Developmental Biology Cluster, North Carolina State University, Raleigh, NC 27607, USA
| | - Annelise Thorn
- Molecular Biomedical Sciences Department, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607, USA
- Quantitative and Computational Developmental Biology Cluster, North Carolina State University, Raleigh, NC 27607, USA
| | - Caroline Laplante
- Molecular Biomedical Sciences Department, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607, USA
- Quantitative and Computational Developmental Biology Cluster, North Carolina State University, Raleigh, NC 27607, USA
- Correspondence:
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6
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Bellingham-Johnstun K, Tyree ZL, Martinez-Baird J, Thorn A, Laplante C. Actin-microtubule crosstalk imparts stiffness to the contractile ring in fission yeast. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.01.530611. [PMID: 36909652 PMCID: PMC10002727 DOI: 10.1101/2023.03.01.530611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
Abstract
Actin-microtubule interactions are critical for cell division yet how these networks of polymers mutually influence their mechanical properties and functions in live cells remains unknown. In fission yeast, the post-anaphase array (PAA) of microtubules assembles in the plane of the contractile ring and its assembly relies on the Myp2p-dependent recruitment of Mto1p, a component of equatorial microtubule organizing centers (eMTOCs). The general organization of this array of microtubule and the impact on their physical attachment to the contractile ring remain unclear. We found that Myp2p facilitates the recruitment of Mto1p to the inner face of the contractile ring where the eMTOCs polymerize microtubules without their direct interaction. The PAA microtubules form a dynamic polygon of Ase1p crosslinked microtubules inside the contractile ring. The specific loss of PAA microtubules affects the mechanical properties of the contractile ring of actin by lowering its stiffness. This change in the mechanical properties of the ring has no measurable impact on cytokinesis or on the anchoring of the ring. Our work proposes that the PAA microtubules exploit the contractile ring for their assembly and function during cell division while the contractile ring may receive no benefit from these interactions.
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7
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Rani B, Gupta DK, Johansson S, Kamranvar SA. Contribution of integrin adhesion to cytokinetic abscission and genomic integrity. Front Cell Dev Biol 2022; 10:1048717. [PMID: 36578785 PMCID: PMC9791049 DOI: 10.3389/fcell.2022.1048717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 11/28/2022] [Indexed: 12/14/2022] Open
Abstract
Recent research shows that integrin-mediated adhesion contributes to the regulation of cell division at two key steps: the formation of the mitotic spindle at the mitotic entry and the final cytokinetic abscission at the mitotic exit. Failure in either of these processes will have a direct impact on the other in each round of the cell cycle and on the genomic integrity. This review aims to present how integrin signals are involved at these cell cycle stages under normal conditions and some safety mechanisms that may counteract the generation of aneuploid cells in cases of defective integrin signals.
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Affiliation(s)
- Bhavna Rani
- Department of Medical Biochemistry and Microbiology (IMBIM), Biomedical Center, Uppsala University, Uppsala, Sweden
| | - Deepesh K. Gupta
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, United States
| | - Staffan Johansson
- Department of Medical Biochemistry and Microbiology (IMBIM), Biomedical Center, Uppsala University, Uppsala, Sweden,*Correspondence: Staffan Johansson, ; Siamak A. Kamranvar,
| | - Siamak A. Kamranvar
- Department of Medical Biochemistry and Microbiology (IMBIM), Biomedical Center, Uppsala University, Uppsala, Sweden,*Correspondence: Staffan Johansson, ; Siamak A. Kamranvar,
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8
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Najafabadi FR, Leaver M, Grill SW. Orchestrating Non-muscle myosin II filament assembly at the onset of cytokinesis. Mol Biol Cell 2022; 33:ar74. [PMID: 35544301 PMCID: PMC9635286 DOI: 10.1091/mbc.e21-12-0599] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Contractile forces in the actomyosin cortex are required for cellular morphogenesis. This includes the invagination of the cell membrane during division, where filaments of nonmuscle myosin II (NMII) are responsible for generating contractile forces in the cortex. However, how NMII heterohexamers form filaments in vivo is not well understood. To quantify NMII filament assembly dynamics, we imaged the cortex of Caenorhabditis elegans embryos at high spatial resolution around the time of the first division. We show that during the assembly of the cytokinetic ring, the number of NMII filaments in the cortex increases and more NMII motors are assembled into each filament. These dynamics are influenced by two proteins in the RhoA GTPase pathway, the RhoA-dependent kinase LET-502 and the myosin phosphatase MEL-11. We find that these two proteins differentially regulate NMII activity at the anterior and at the division site. We show that the coordinated action of these regulators generates a gradient of free NMII in the cytoplasm driving a net diffusive flux of NMII motors toward the cytokinetic ring. Our work highlights how NMII filament assembly and disassembly dynamics are orchestrated over space and time to facilitate the up-regulation of cortical contractility during cytokinesis.
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Affiliation(s)
| | - Mark Leaver
- Biotechnology Centre, Technische Universität, Tatzberg 47/49, Dresden 01307.,Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, Dresden
| | - Stephan W Grill
- Biotechnology Centre, Technische Universität, Tatzberg 47/49, Dresden 01307.,Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, Dresden.,Excellence Cluster Physics of Life, Technische Universität, Dresden, Germany 01307
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9
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Hirsch SM, Edwards F, Shirasu-Hiza M, Dumont J, Canman JC. Functional midbody assembly in the absence of a central spindle. J Biophys Biochem Cytol 2022; 221:212948. [PMID: 34994802 PMCID: PMC8751756 DOI: 10.1083/jcb.202011085] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 10/13/2021] [Accepted: 12/10/2021] [Indexed: 12/28/2022] Open
Abstract
Contractile ring constriction during cytokinesis is thought to compact central spindle microtubules to form the midbody, an antiparallel microtubule bundle at the intercellular bridge. In Caenorhabditis elegans, central spindle microtubule assembly requires targeting of the CLASP family protein CLS-2 to the kinetochores in metaphase and spindle midzone in anaphase. CLS-2 targeting is mediated by the CENP-F–like HCP-1/2, but their roles in cytokinesis and midbody assembly are not known. We found that although HCP-1 and HCP-2 mostly function cooperatively, HCP-1 plays a more primary role in promoting CLS-2–dependent central spindle microtubule assembly. HCP-1/2 codisrupted embryos did not form central spindles but completed cytokinesis and formed functional midbodies capable of supporting abscission. These central spindle–independent midbodies appeared to form via contractile ring constriction–driven bundling of astral microtubules at the furrow tip. This work suggests that, in the absence of a central spindle, astral microtubules can support midbody assembly and that midbody assembly is more predictive of successful cytokinesis than central spindle assembly.
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Affiliation(s)
- Sophia M Hirsch
- Department of Genetics and Development, Columbia University Medical Center, New York, NY.,Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY
| | - Frances Edwards
- Institut Jacques Monod, Centre national de la recherche scientifique, Université de Paris, Paris, France
| | - Mimi Shirasu-Hiza
- Department of Genetics and Development, Columbia University Medical Center, New York, NY
| | - Julien Dumont
- Institut Jacques Monod, Centre national de la recherche scientifique, Université de Paris, Paris, France
| | - Julie C Canman
- Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY
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10
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Longhini KM, Glotzer M. Aurora A and cortical flows promote polarization and cytokinesis by inducing asymmetric ECT-2 accumulation. eLife 2022; 11:83992. [PMID: 36533896 PMCID: PMC9799973 DOI: 10.7554/elife.83992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 12/12/2022] [Indexed: 12/23/2022] Open
Abstract
In the early Caenorhabditis elegans embryo, cell polarization and cytokinesis are interrelated yet distinct processes. Here, we sought to understand a poorly understood aspect of cleavage furrow positioning. Early C. elegans embryos deficient in the cytokinetic regulator centralspindlin form furrows, due to an inhibitory activity that depends on aster positioning relative to the polar cortices. Here, we show polar relaxation is associated with depletion of cortical ECT-2, a RhoGEF, specifically at the posterior cortex. Asymmetric ECT-2 accumulation requires intact centrosomes, Aurora A (AIR-1), and myosin-dependent cortical flows. Within a localization competent ECT-2 fragment, we identified three putative phospho-acceptor sites in the PH domain of ECT-2 that render ECT-2 responsive to inhibition by AIR-1. During both polarization and cytokinesis, our results suggest that centrosomal AIR-1 breaks symmetry via ECT-2 phosphorylation; this local inhibition of ECT-2 is amplified by myosin-driven flows that generate regional ECT-2 asymmetry. Together, these mechanisms cooperate to induce polarized assembly of cortical myosin, contributing to both embryo polarization and cytokinesis.
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Affiliation(s)
- Katrina M Longhini
- Department of Molecular Genetics and Cell Biology, University of ChicagoChicagoUnited States
| | - Michael Glotzer
- Department of Molecular Genetics and Cell Biology, University of ChicagoChicagoUnited States
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11
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Sugioka K. Symmetry-breaking of animal cytokinesis. Semin Cell Dev Biol 2021; 127:100-109. [PMID: 34955355 DOI: 10.1016/j.semcdb.2021.12.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 12/05/2021] [Accepted: 12/16/2021] [Indexed: 12/24/2022]
Abstract
Cytokinesis is a mechanism that separates dividing cells via constriction of a supramolecular structure, the contractile ring. In animal cells, three modes of symmetry-breaking of cytokinesis result in unilateral cytokinesis, asymmetric cell division, and oriented cell division. Each mode of cytokinesis plays a significant role in tissue patterning and morphogenesis by the mechanisms that control the orientation and position of the contractile ring relative to the body axis. Despite its significance, the mechanisms involved in the symmetry-breaking of cytokinesis remain unclear in many cell types. Classical embryologists have identified that the geometric relationship between the mitotic spindle and cell cortex induces cytokinesis asymmetry; however, emerging evidence suggests that a concerted flow of compressional cell-cortex materials (cortical flow) is a spindle-independent driving force in spatial cytokinesis control. This review provides an overview of both classical and emerging mechanisms of cytokinesis asymmetry and their roles in animal development.
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Affiliation(s)
- Kenji Sugioka
- Life Sciences Institute, The University of British Columbia, Vancouver, BC V6T1Z3, Canada; Department of Zoology, The University of British Columbia, Vancouver, BC V6T1Z3, Canada.
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12
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Thomas A, Gallaud E, Pascal A, Serre L, Arnal I, Richard-Parpaillon L, Savoian MS, Giet R. Peripheral astral microtubules ensure asymmetric furrow positioning in neural stem cells. Cell Rep 2021; 37:109895. [PMID: 34706235 DOI: 10.1016/j.celrep.2021.109895] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 02/26/2021] [Accepted: 10/06/2021] [Indexed: 11/18/2022] Open
Abstract
Neuroblast division is characterized by asymmetric positioning of the cleavage furrow, resulting in a large difference in size between the future daughter cells. In animal cells, furrow placement and assembly are governed by centralspindlin that accumulates at the equatorial cell cortex of the future cleavage site and at the spindle midzone. In neuroblasts, these two centralspindlin populations are spatially and temporally separated. A leading pool is located at the basal cleavage site and a second pool accumulates at the midzone before traveling to the cleavage site. The cortical centralspindlin population requires peripheral astral microtubules and the chromosome passenger complex for efficient recruitment. Loss of this pool does not prevent cytokinesis but enhances centralspindlin signaling at the midzone, leading to equatorial furrow repositioning and decreased size asymmetry. These data show that basal furrow positioning in neuroblasts results from a competition between different centralspindlin pools in which the cortical pool is dominant.
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Affiliation(s)
- Alexandre Thomas
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR17 6290, 35000 Rennes, France
| | - Emmanuel Gallaud
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR17 6290, 35000 Rennes, France
| | - Aude Pascal
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR17 6290, 35000 Rennes, France
| | - Laurence Serre
- Inserm U1216, CEA, CNRS, Grenoble Institut Neurosciences (GIN), Université Grenoble Alpes, 38000 Grenoble, France
| | - Isabelle Arnal
- Inserm U1216, CEA, CNRS, Grenoble Institut Neurosciences (GIN), Université Grenoble Alpes, 38000 Grenoble, France
| | - Laurent Richard-Parpaillon
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR17 6290, 35000 Rennes, France
| | - Matthew Scott Savoian
- School of Fundamental Sciences, Massey University, 4410 Palmerston North, New Zealand
| | - Régis Giet
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR17 6290, 35000 Rennes, France.
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13
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Abstract
During anaphase, a microtubule-containing structure called the midzone forms between the segregating chromosomes. The midzone is composed of an antiparallel array of microtubules and numerous microtubule-associated proteins that contribute to midzone formation and function. In many cells, the midzone is an important source of signals that specify the location of contractile ring assembly and constriction. The midzone also contributes to the events of anaphase by generating forces that impact chromosome segregation and spindle elongation; some midzone components contribute to both processes. The results of recent experiments have increased our understanding of the importance of the midzone, a microtubule array that has often been overlooked. This Journal of Cell Science at a Glance article will review, and illustrate on the accompanying poster, the organization, formation and dynamics of the midzone, and discuss open questions for future research.
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Affiliation(s)
- Patricia Wadsworth
- Department of Biology, Morrill Science Center, University of Massachusetts, 611 N. Pleasant Street, Amherst 01003, USA
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14
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Magliozzi JO, Sears J, Cressey L, Brady M, Opalko HE, Kettenbach AN, Moseley JB. Fission yeast Pak1 phosphorylates anillin-like Mid1 for spatial control of cytokinesis. J Cell Biol 2021; 219:151784. [PMID: 32421151 PMCID: PMC7401808 DOI: 10.1083/jcb.201908017] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 03/09/2020] [Accepted: 04/28/2020] [Indexed: 12/17/2022] Open
Abstract
Protein kinases direct polarized growth by regulating the cytoskeleton in time and space and could play similar roles in cell division. We found that the Cdc42-activated polarity kinase Pak1 colocalizes with the assembling contractile actomyosin ring (CAR) and remains at the division site during septation. Mutations in pak1 led to defects in CAR assembly and genetic interactions with cytokinesis mutants. Through a phosphoproteomic screen, we identified novel Pak1 substrates that function in polarized growth and cytokinesis. For cytokinesis, we found that Pak1 regulates the localization of its substrates Mid1 and Cdc15 to the CAR. Mechanistically, Pak1 phosphorylates the Mid1 N-terminus to promote its association with cortical nodes that act as CAR precursors. Defects in Pak1-Mid1 signaling lead to misplaced and defective division planes, but these phenotypes can be rescued by synthetic tethering of Mid1 to cortical nodes. Our work defines a new signaling mechanism driven by a cell polarity kinase that promotes CAR assembly in the correct time and place.
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Affiliation(s)
- Joseph O Magliozzi
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH
| | - Jack Sears
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH.,Norris Cotton Cancer Center, The Geisel School of Medicine at Dartmouth, Lebanon, NH
| | - Lauren Cressey
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH.,Norris Cotton Cancer Center, The Geisel School of Medicine at Dartmouth, Lebanon, NH
| | - Marielle Brady
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH
| | - Hannah E Opalko
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH
| | - Arminja N Kettenbach
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH.,Norris Cotton Cancer Center, The Geisel School of Medicine at Dartmouth, Lebanon, NH
| | - James B Moseley
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH
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15
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In Vitro Reconstitution of Dynamic Co-organization of Microtubules and Actin Filaments in Emulsion Droplets. Methods Mol Biol 2021. [PMID: 31879898 DOI: 10.1007/978-1-0716-0219-5_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
In vitro (or cell-free) reconstitution is a powerful tool to study the physical basis of cytoskeletal organization in eukaryotic cells. Cytoskeletal reconstitution studies have mostly been done for individual cytoskeleton systems in unconfined 3D or quasi-2D geometries, which lack complexity relative to a cellular environment. To increase the level of complexity, we present a method to study co-organization of two cytoskeletal components, namely microtubules and actin filaments, confined in cell-sized water-in-oil emulsion droplets. We show that centrosome-nucleated dynamic microtubules can be made to interact with actin filaments through a tip-tracking complex consisting of microtubule end-binding proteins and an actin-microtubule cytolinker. In addition to the protocols themselves, we discuss the optimization steps required in order to build these more complex in vitro model systems of cytoskeletal interactions.
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16
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Magliozzi JO, Moseley JB. Connecting cell polarity signals to the cytokinetic machinery in yeast and metazoan cells. Cell Cycle 2021; 20:1-10. [PMID: 33397181 DOI: 10.1080/15384101.2020.1864941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Polarized growth and cytokinesis are two fundamental cellular processes that exist in virtually all cell types. Mechanisms for asymmetric distribution of materials allow for cells to grow in a polarized manner. This gives rise to a variety of cell shapes seen throughout all cell types. Following polarized growth during interphase, dividing cells assemble a cytokinetic ring containing the protein machinery to constrict and separate daughter cells. Here, we discuss how cell polarity signaling pathways act on cytokinesis, with a focus on direct regulation of the contractile actomyosin ring (CAR). Recent studies have exploited phosphoproteomics to identify new connections between cell polarity kinases and CAR proteins. Existing evidence suggests that some polarity kinases guide the local organization of CAR proteins and structures while also contributing to global organization of the division plane within a cell. We provide several examples of this regulation from budding yeast, fission yeast, and metazoan cells. In some cases, kinase-substrate connections point to conserved processes in these different organisms. We point to several examples where future work can indicate the degree of conservation and divergence in the cell division process of these different organisms.
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Affiliation(s)
- Joseph O Magliozzi
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth , Hanover, New Hampshire, USA
| | - James B Moseley
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth , Hanover, New Hampshire, USA
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17
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Gao ZY, Yu F, Jia HX, Ye Z, Yao SJ. ASPM predicts poor prognosis and regulates cell proliferation in bladder cancer. Kaohsiung J Med Sci 2020; 36:1021-1029. [PMID: 32767492 DOI: 10.1002/kjm2.12284] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 05/20/2020] [Accepted: 07/08/2020] [Indexed: 01/05/2023] Open
Abstract
Bladder cancer (BCa) is one of the most common malignancies with high morbidity and mortality worldwide. In recent years, it is of great importance to investigate the molecular etiology associated with of BCa. Abnormal spindle-like microcephaly associated gene (ASPM) is the human orthologous of the Drosophila abnormal spindle (asp) and the most commonly mutated gene of autosomal recessive primary microcephaly. ASPM is overexpressed in several types of cancer cell lines and affects the progression and development of multiple types of cancers. However, its possible role in BCa progression is still unclear. Herein, we demonstrated the possible involvement of ASPM in the progression of BCa. We noticed that high expression of ASPM was positively associated with the poor prognosis. Its knockdown could significantly inhibit the proliferation of BCa cells in vitro and in mice. Therefore, we thought ASPM could act as a promising therapeutic target for BCa.
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Affiliation(s)
- Zhen-Ya Gao
- School of Medicine Xuchang University, Xuchang, China
| | - Fang Yu
- School of Medicine Xuchang University, Xuchang, China
| | - Huan-Xia Jia
- School of Medicine Xuchang University, Xuchang, China
| | - Zhuo Ye
- the First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Shi-Jie Yao
- Department of Urology in Tianjin First Central Hospital, Tianjin, China
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18
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Beaudet D, Pham N, Skaik N, Piekny A. Importin binding mediates the intramolecular regulation of anillin during cytokinesis. Mol Biol Cell 2020; 31:1124-1139. [PMID: 32238082 PMCID: PMC7353161 DOI: 10.1091/mbc.e20-01-0006] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Cytokinesis occurs by the ingression of an actomyosin ring that cleaves a cell into two daughters. This process is tightly controlled to avoid aneuploidy, and we previously showed that active Ran coordinates ring positioning with chromatin. Active Ran is high around chromatin, and forms an inverse gradient to cargo-bound importins. We found that the ring component anillin contains a nuclear localization signal (NLS) that binds to importin and is required for its function during cytokinesis. Here we reveal the mechanism whereby importin binding favors a conformation required for anillin's recruitment to the equatorial cortex. Active RhoA binds to the RhoA-binding domain causing an increase in accessibility of the nearby C2 domain containing the NLS. Importin binding subsequently stabilizes a conformation that favors interactions for cortical recruitment. In addition to revealing a novel mechanism for the importin-mediated regulation of a cortical protein, we also show how importin binding positively regulates protein function.
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Affiliation(s)
- Daniel Beaudet
- Department of Bioengineering, McGill University, Montreal, QC, Canada, H3A 0G4
| | - Nhat Pham
- Department of Biology, Concordia University, Montreal, QC, Canada, H4B 1R6
| | - Noha Skaik
- Department of Biology, Concordia University, Montreal, QC, Canada, H4B 1R6
| | - Alisa Piekny
- Department of Biology, Concordia University, Montreal, QC, Canada, H4B 1R6
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19
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Bai X, Melesse M, Sorensen Turpin CG, Sloan DE, Chen CY, Wang WC, Lee PY, Simmons JR, Nebenfuehr B, Mitchell D, Klebanow LR, Mattson N, Betzig E, Chen BC, Cheerambathur D, Bembenek JN. Aurora B functions at the apical surface after specialized cytokinesis during morphogenesis in C. elegans. Development 2020; 147:dev.181099. [PMID: 31806662 PMCID: PMC6983721 DOI: 10.1242/dev.181099] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 11/26/2019] [Indexed: 12/18/2022]
Abstract
Although cytokinesis has been intensely studied, the way it is executed during development is not well understood, despite a long-standing appreciation that various aspects of cytokinesis vary across cell and tissue types. To address this, we investigated cytokinesis during the invariant Caenorhabditis elegans embryonic divisions and found several parameters that are altered at different stages in a reproducible manner. During early divisions, furrow ingression asymmetry and midbody inheritance is consistent, suggesting specific regulation of these events. During morphogenesis, we found several unexpected alterations to cytokinesis, including apical midbody migration in polarizing epithelial cells of the gut, pharynx and sensory neurons. Aurora B kinase, which is essential for several aspects of cytokinesis, remains apically localized in each of these tissues after internalization of midbody ring components. Aurora B inactivation disrupts cytokinesis and causes defects in apical structures, even if inactivated post-mitotically. Therefore, we demonstrate that cytokinesis is implemented in a specialized way during epithelial polarization and that Aurora B has a role in the formation of the apical surface.
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Affiliation(s)
- Xiaofei Bai
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Michael Melesse
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | | | - Dillon E. Sloan
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA,Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Chin-Yi Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Wen-Cheng Wang
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Po-Yi Lee
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - James R. Simmons
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Benjamin Nebenfuehr
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Diana Mitchell
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Lindsey R. Klebanow
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Nicholas Mattson
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Eric Betzig
- Janelia Research Campus, HHMI, Ashburn, VA 20147, USA
| | - Bi-Chang Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan,Janelia Research Campus, HHMI, Ashburn, VA 20147, USA
| | - Dhanya Cheerambathur
- Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh, EH9 3BF, UK
| | - Joshua N. Bembenek
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA,Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA,Author for correspondence ()
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20
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Abstract
The notion that graded distributions of signals underlie the spatial organization of biological systems has long been a central pillar in the fields of cell and developmental biology. During morphogenesis, morphogens spread across tissues to guide development of the embryo. Similarly, a variety of dynamic gradients and pattern-forming networks have been discovered that shape subcellular organization. Here we discuss the principles of intracellular pattern formation by these intracellular morphogens and relate them to conceptually similar processes operating at the tissue scale. We will specifically review mechanisms for generating cellular asymmetry and consider how intracellular patterning networks are controlled and adapt to cellular geometry. Finally, we assess the general concept of intracellular gradients as a mechanism for positional control in light of current data, highlighting how the simple readout of fixed concentration thresholds fails to fully capture the complexity of spatial patterning processes occurring inside cells.
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Affiliation(s)
- Lars Hubatsch
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | - Nathan W Goehring
- The Francis Crick Institute, London, United Kingdom; Institute for the Physics of Living Systems, University College London, London, United Kingdom; MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom.
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21
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Pacquelet A, Jousseaume M, Etienne J, Michaux G. Simultaneous Regulation of Cytokinetic Furrow and Nucleus Positions by Cortical Tension Contributes to Proper DNA Segregation during Late Mitosis. Curr Biol 2019; 29:3766-3777.e4. [PMID: 31679940 DOI: 10.1016/j.cub.2019.09.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 08/13/2019] [Accepted: 09/06/2019] [Indexed: 10/25/2022]
Abstract
Coordinating mitotic spindle and cytokinetic furrow positioning is essential to ensure proper DNA segregation. Here, we present a novel mechanism, which corrects DNA segregation defects due to cytokinetic furrow mispositioning during the first division of C. elegans embryos. Correction of DNA segregation defects due to an abnormally anterior cytokinetic furrow relies on the concomitant and opposite displacements of the furrow and of the anterior nucleus toward the posterior and anterior poles of the embryo, respectively. It also coincides with cortical blebbing and an anteriorly directed cytoplasmic flow. Although microtubules contribute to nuclear displacement, relaxation of an excessive tension at the anterior cortex plays a central role in the correction process and simultaneously regulates cytoplasmic flow as well as nuclear and furrow displacements. This work thus reveals the existence of a so-far uncharacterized correction mechanism, which is critical to correct DNA segregation defects due to cytokinetic furrow mispositioning.
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Affiliation(s)
- Anne Pacquelet
- Univ Rennes, CNRS, IGDR (Institut de Génétique et de Développement de Rennes), UMR 6290, 2 Avenue du Professeur Léon Bernard, 35000 Rennes, France.
| | - Matthieu Jousseaume
- Univ Rennes, CNRS, IGDR (Institut de Génétique et de Développement de Rennes), UMR 6290, 2 Avenue du Professeur Léon Bernard, 35000 Rennes, France
| | - Jocelyn Etienne
- Univ Grenoble Alpes, CNRS, LIPhy, 140 Avenue de la Physique, 38402 Saint Martin d'Hères, France
| | - Grégoire Michaux
- Univ Rennes, CNRS, IGDR (Institut de Génétique et de Développement de Rennes), UMR 6290, 2 Avenue du Professeur Léon Bernard, 35000 Rennes, France
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22
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Abstract
The active form of the small GTPase RhoA is necessary and sufficient for formation of a cytokinetic furrow in animal cells. Despite the conceptual simplicity of the process, the molecular mechanisms that control it are intricate and involve redundancy at multiple levels. Here, we discuss our current knowledge of the mechanisms underlying spatiotemporal regulation of RhoA during cytokinesis by upstream activators. The direct upstream activator, the RhoGEF Ect2, requires activation due to autoinhibition. Ect2 is primarily activated by the centralspindlin complex, which contains numerous domains that regulate its subcellular localization, oligomeric state, and Ect2 activation. We review the functions of these domains and how centralspindlin is regulated to ensure correctly timed, equatorial RhoA activation. Highlighting recent evidence, we propose that although centralspindlin does not always prominently accumulate on the plasma membrane, it is the site where it promotes RhoA activation during cytokinesis.
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23
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Verma V, Mogilner A, Maresca TJ. Classical and Emerging Regulatory Mechanisms of Cytokinesis in Animal Cells. BIOLOGY 2019; 8:biology8030055. [PMID: 31357447 PMCID: PMC6784142 DOI: 10.3390/biology8030055] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 07/05/2019] [Accepted: 07/23/2019] [Indexed: 12/12/2022]
Abstract
The primary goal of cytokinesis is to produce two daughter cells, each having a full set of chromosomes. To achieve this, cells assemble a dynamic structure between segregated sister chromatids called the contractile ring, which is made up of filamentous actin, myosin-II, and other regulatory proteins. Constriction of the actomyosin ring generates a cleavage furrow that divides the cytoplasm to produce two daughter cells. Decades of research have identified key regulators and underlying molecular mechanisms; however, many fundamental questions remain unanswered and are still being actively investigated. This review summarizes the key findings, computational modeling, and recent advances in understanding of the molecular mechanisms that control the formation of the cleavage furrow and cytokinesis.
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Affiliation(s)
- Vikash Verma
- Biology Department, University of Massachusetts, Amherst, MA 01003, USA.
| | - Alex Mogilner
- Courant Institute of Mathematical Sciences, New York University, New York, NY 10012, USA
- Department of Biology, New York University, New York, NY 10012, USA
| | - Thomas J Maresca
- Biology Department, University of Massachusetts, Amherst, MA 01003, USA
- Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, MA 01003, USA
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24
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Kondo T, Kimura A. Choice between 1- and 2-furrow cytokinesis in Caenorhabditis elegans embryos with tripolar spindles. Mol Biol Cell 2019; 30:2065-2075. [PMID: 30785847 PMCID: PMC6727771 DOI: 10.1091/mbc.e19-01-0075] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 02/14/2019] [Indexed: 01/08/2023] Open
Abstract
Excessive centrosomes often lead to multipolar spindles, and thus probably to multipolar mitosis and aneuploidy. In Caenorhabditis elegans, ∼70% of the paternal emb-27APC6 mutant embryonic cells contained more than two centrosomes and formed multipolar spindles. However, only ~30% of the cells with tripolar spindles formed two cytokinetic furrows. The rest formed one furrow, similar to normal cells. To investigate the mechanism via which cells avoid forming two cytokinetic furrows even with a tripolar spindle, we conducted live-cell imaging in emb-27APC6 mutant cells. We observed that the chromatids were aligned on only two of the three sides of the tripolar spindle, and the angle of the tripolar spindle relative to the long axis of the cell correlated with the number of cytokinetic furrows. Our numerical modeling showed that the combination of cell shape, cortical pulling forces, and heterogeneity of centrosome size determines whether cells with a tripolar spindle form one or two cytokinetic furrows.
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Affiliation(s)
- Tomo Kondo
- Cell Architecture Laboratory, Department of Chromosome Science, National Institute of Genetics, Yata 1111, Mishima, Shizuoka 411-8540, Japan
| | - Akatsuki Kimura
- Cell Architecture Laboratory, Department of Chromosome Science, National Institute of Genetics, Yata 1111, Mishima, Shizuoka 411-8540, Japan
- Department of Genetics, School of Life Science, The Graduate University for Advanced Studies (Sokendai), Yata 1111, Mishima, Shizuoka 411-8540, Japan
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25
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Kashiwazaki J, Yoneda Y, Mutoh T, Arai R, Yoshida M, Mabuchi I. A unique kinesin-like protein, Klp8, is involved in mitosis and cell morphology through microtubule stabilization. Cytoskeleton (Hoboken) 2019; 76:355-367. [PMID: 31276301 DOI: 10.1002/cm.21551] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 05/23/2019] [Accepted: 07/01/2019] [Indexed: 11/10/2022]
Abstract
Kinesins are microtubule (MT)-based motors involved in various cellular functions including intracellular transport of vesicles and organelles, and dynamics of chromosomes during cell division. The fission yeast Schizosaccharomyces pombe expresses nine kinesin-like proteins (klps). Klp8 is one of them and has not been characterized yet though it has been reported to localize at the division site. Here, we studied function and localization of Klp8 in S. pombe cells. The gene klp8+ was not essential for both viability and cytoskeletal organization. Klp8-YFP was concentrated as medial cortical dots during interphase, and organized into a ring at the division site during mitosis. The Klp8 ring seemed to be localized in the space between the actomyosin contractile ring and the plasma membrane. The Klp8 ring shrank as cytokinesis proceeded. In klp8-deleted (Δ) cells, the speed of spindle elongation during anaphase B was slowed down. Overproduction of Klp8 caused bent or elongated cells, in which MTs were abnormally elongated and less dynamic than those in normal cells. Deletion of klp8+ gene suppressed the delay in mitotic entry in blt1Δ cells. These results suggest that Klp8 is involved in mitosis and cell morphology through MT stabilization.
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Affiliation(s)
- Jun Kashiwazaki
- Department of Life Science, Gakushuin University, Tokyo, Japan
| | - Yumi Yoneda
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Tadashi Mutoh
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Ritsuko Arai
- Chemical Genetics Laboratory, RIKEN, Wako, Japan
| | - Minoru Yoshida
- Chemical Genetics Laboratory, RIKEN, Wako, Japan.,CREST Research Project, Japan Science and Technology Corporation, Wako, Japan
| | - Issei Mabuchi
- Department of Life Science, Gakushuin University, Tokyo, Japan.,Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
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26
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Gujar MR, Stricker AM, Lundquist EA. RHO-1 and the Rho GEF RHGF-1 interact with UNC-6/Netrin signaling to regulate growth cone protrusion and microtubule organization in Caenorhabditis elegans. PLoS Genet 2019; 15:e1007960. [PMID: 31233487 PMCID: PMC6611649 DOI: 10.1371/journal.pgen.1007960] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 07/05/2019] [Accepted: 05/31/2019] [Indexed: 01/02/2023] Open
Abstract
UNC-6/Netrin is a conserved axon guidance cue that directs growth cone migrations in the dorsal-ventral axis of C. elegans and in the vertebrate spinal cord. UNC-6/Netrin is expressed in ventral cells, and growth cones migrate ventrally toward or dorsally away from UNC-6/Netrin. Recent studies of growth cone behavior during outgrowth in vivo in C. elegans have led to a polarity/protrusion model in directed growth cone migration away from UNC-6/Netrin. In this model, UNC-6/Netrin first polarizes the growth cone via the UNC-5 receptor, leading to dorsally biased protrusion and F-actin accumulation. UNC-6/Netrin then regulates protrusion based on this polarity. The receptor UNC-40/DCC drives protrusion dorsally, away from the UNC-6/Netrin source, and the UNC-5 receptor inhibits protrusion ventrally, near the UNC-6/Netrin source, resulting in dorsal migration. UNC-5 inhibits protrusion in part by excluding microtubules from the growth cone, which are pro-protrusive. Here we report that the RHO-1/RhoA GTPase and its activator GEF RHGF-1 inhibit growth cone protrusion and MT accumulation in growth cones, similar to UNC-5. However, growth cone polarity of protrusion and F-actin were unaffected by RHO-1 and RHGF-1. Thus, RHO-1 signaling acts specifically as a negative regulator of protrusion and MT accumulation, and not polarity. Genetic interactions are consistent with RHO-1 and RHGF-1 acting with UNC-5, as well as with a parallel pathway, to regulate protrusion. The cytoskeletal interacting molecule UNC-33/CRMP was required for RHO-1 activity to inhibit MT accumulation, suggesting that UNC-33/CRMP might act downstream of RHO-1. In sum, these studies describe a new role of RHO-1 and RHGF-1 in regulation of growth cone protrusion by UNC-6/Netrin.
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Affiliation(s)
- Mahekta R. Gujar
- Department of Molecular Biosciences, Program in Molecular, Cellular, and Developmental Biology, University of Kansas, Lawrence, KS, United States of America
| | - Aubrie M. Stricker
- Department of Molecular Biosciences, Program in Molecular, Cellular, and Developmental Biology, University of Kansas, Lawrence, KS, United States of America
| | - Erik A. Lundquist
- Department of Molecular Biosciences, Program in Molecular, Cellular, and Developmental Biology, University of Kansas, Lawrence, KS, United States of America
- * E-mail:
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27
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Pintard L, Bowerman B. Mitotic Cell Division in Caenorhabditis elegans. Genetics 2019; 211:35-73. [PMID: 30626640 PMCID: PMC6325691 DOI: 10.1534/genetics.118.301367] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 10/24/2018] [Indexed: 11/18/2022] Open
Abstract
Mitotic cell divisions increase cell number while faithfully distributing the replicated genome at each division. The Caenorhabditis elegans embryo is a powerful model for eukaryotic cell division. Nearly all of the genes that regulate cell division in C. elegans are conserved across metazoan species, including humans. The C. elegans pathways tend to be streamlined, facilitating dissection of the more redundant human pathways. Here, we summarize the virtues of C. elegans as a model system and review our current understanding of centriole duplication, the acquisition of pericentriolar material by centrioles to form centrosomes, the assembly of kinetochores and the mitotic spindle, chromosome segregation, and cytokinesis.
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Affiliation(s)
- Lionel Pintard
- Equipe labellisée Ligue contre le Cancer, Institut Jacques Monod, Team Cell Cycle and Development UMR7592, Centre National de la Recherche Scientifique - Université Paris Diderot, Sorbonne Paris Cité, 75013 Paris, France
| | - Bruce Bowerman
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403
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28
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Bouvrais H, Chesneau L, Pastezeur S, Fairbrass D, Delattre M, Pécréaux J. Microtubule Feedback and LET-99-Dependent Control of Pulling Forces Ensure Robust Spindle Position. Biophys J 2018; 115:2189-2205. [PMID: 30447992 PMCID: PMC6289040 DOI: 10.1016/j.bpj.2018.10.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 10/03/2018] [Accepted: 10/09/2018] [Indexed: 11/26/2022] Open
Abstract
During asymmetric division of the Caenorhabditis elegans zygote, to properly distribute cell fate determinants, the mitotic spindle is asymmetrically localized by a combination of centering and cortical-pulling microtubule-mediated forces, the dynamics of the latter being regulated by mitotic progression. Here, we show a, to our knowledge, novel and additional regulation of these forces by spindle position itself. For that, we observed the onset of transverse spindle oscillations, which reflects the burst of anaphase pulling forces. After delaying anaphase onset, we found that the position at which the spindle starts to oscillate was unchanged compared to control embryos and uncorrelated to anaphase onset. In mapping the cortical microtubule dynamics, we measured a steep increase in microtubule contact density after the posterior centrosome reached the critical position of 70% of embryo length, strongly suggesting the presence of a positional switch for spindle oscillations. Expanding a previous model based on a force-generator temporal control, we implemented this positional switch and observed that the large increase in microtubule density accounted for the pulling force burst. Thus, we propose that the spindle position influences the cortical availability of microtubules on which the active force generators, controlled by cell cycle progression, can pull. Importantly, we found that this positional control relies on the polarity-dependent LET-99 cortical band, the boundary of which could be probed by microtubules. This dual positional and temporal control well accounted for our observation that the oscillation onset position resists changes in cellular geometry and moderate variations in the active force generator number. Finally, our model suggests that spindle position at mitosis end is more sensitive to the polarity factor LET-99, which restricts the region of active force generators to a posterior-most region, than to microtubule number or force generator number/activity. Overall, we show that robustness in spindle positioning originates in cell mechanics rather than biochemical networks.
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Affiliation(s)
| | | | | | | | - Marie Delattre
- Univ Lyon, ENS de Lyon, Univ Claude Bernard, Laboratory of Biology and Modelling of the Cell, Lyon University, Lyon, France
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29
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Anton KA, Kajita M, Narumi R, Fujita Y, Tada M. Src-transformed cells hijack mitosis to extrude from the epithelium. Nat Commun 2018; 9:4695. [PMID: 30410020 PMCID: PMC6224566 DOI: 10.1038/s41467-018-07163-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 10/15/2018] [Indexed: 12/19/2022] Open
Abstract
At the initial stage of carcinogenesis single mutated cells appear within an epithelium. Mammalian in vitro experiments show that potentially cancerous cells undergo live apical extrusion from normal monolayers. However, the mechanism underlying this process in vivo remains poorly understood. Mosaic expression of the oncogene vSrc in a simple epithelium of the early zebrafish embryo results in extrusion of transformed cells. Here we find that during extrusion components of the cytokinetic ring are recruited to adherens junctions of transformed cells, forming a misoriented pseudo-cytokinetic ring. As the ring constricts, it separates the basal from the apical part of the cell releasing both from the epithelium. This process requires cell cycle progression and occurs immediately after vSrc-transformed cell enters mitosis. To achieve extrusion, vSrc coordinates cell cycle progression, junctional integrity, cell survival and apicobasal polarity. Without vSrc, modulating these cellular processes reconstitutes vSrc-like extrusion, confirming their sufficiency for this process. Potentially cancerous cells undergo live apical extrusion from normal monolayers and vSrc expression induces this in zebrafish epithelia. Here, the authors show that vSrc coordinates cytokinetic ring formation, cell cycle progression, junctional integrity, cell survival and apicobasal polarity to induce extrusion of transformed cells.
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Affiliation(s)
- Katarzyna A Anton
- Department of Cell & Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Mihoko Kajita
- Division of Molecular Oncology, Institute for Genetic Medicine, Hokkaido University Graduate School of Chemical Sciences and Engineering, Sapporo, 060-0815, Japan
| | - Rika Narumi
- Division of Molecular Oncology, Institute for Genetic Medicine, Hokkaido University Graduate School of Chemical Sciences and Engineering, Sapporo, 060-0815, Japan
| | - Yasuyuki Fujita
- Division of Molecular Oncology, Institute for Genetic Medicine, Hokkaido University Graduate School of Chemical Sciences and Engineering, Sapporo, 060-0815, Japan
| | - Masazumi Tada
- Department of Cell & Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK.
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Chen J, Castelvecchi GD, Li-Villarreal N, Raught B, Krezel AM, McNeill H, Solnica-Krezel L. Atypical Cadherin Dachsous1b Interacts with Ttc28 and Aurora B to Control Microtubule Dynamics in Embryonic Cleavages. Dev Cell 2018; 45:376-391.e5. [PMID: 29738714 PMCID: PMC5983389 DOI: 10.1016/j.devcel.2018.04.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 02/22/2018] [Accepted: 04/09/2018] [Indexed: 01/15/2023]
Abstract
Atypical cadherin Dachsous (Dchs) is a conserved regulator of planar cell polarity, morphogenesis, and tissue growth during animal development. Dchs functions in part by regulating microtubules by unknown molecular mechanisms. Here we show that maternal zygotic (MZ) dchs1b zebrafish mutants exhibit cleavage furrow progression defects and impaired midzone microtubule assembly associated with decreased microtubule turnover. Mechanistically, Dchs1b interacts via a conserved motif in its intracellular domain with the tetratricopeptide motifs of Ttc28 and regulates its subcellular distribution. Excess Ttc28 impairs cleavages and decreases microtubule turnover, while ttc28 inactivation increases turnover. Moreover, ttc28 deficiency in dchs1b mutants suppresses the microtubule dynamics and midzone microtubule assembly defects. Dchs1b also binds to Aurora B, a known regulator of cleavages and microtubules. Embryonic cleavages in MZdchs1b mutants exhibit increased, and in MZttc28 mutants decreased, sensitivity to Aurora B inhibition. Thus, Dchs1b regulates microtubule dynamics and embryonic cleavages by interacting with Ttc28 and Aurora B.
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Affiliation(s)
- Jiakun Chen
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Gina D Castelvecchi
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Nanbing Li-Villarreal
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Brian Raught
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, Canada
| | - Andrzej M Krezel
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Helen McNeill
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Molecular Genetics, University of Toronto, Toronto, Canada; Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Lilianna Solnica-Krezel
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Lim TC, Hatano T, Kamnev A, Balasubramanian MK, Chew TG. Equatorial Assembly of the Cell-Division Actomyosin Ring in the Absence of Cytokinetic Spatial Cues. Curr Biol 2018; 28:955-962.e3. [PMID: 29502950 PMCID: PMC5863765 DOI: 10.1016/j.cub.2018.01.088] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 12/18/2017] [Accepted: 01/31/2018] [Indexed: 11/30/2022]
Abstract
The position of the division site dictates the size and fate of daughter cells in many organisms. In animal cells, division-site placement involves overlapping mechanisms, including signaling from the central spindle microtubules, astral microtubules, and spindle poles and through polar contractions [1, 2, 3]. In fission yeast, division-site positioning requires overlapping mechanisms involving the anillin-related protein Mid1 and the tip complex (comprising the Kelch-repeat protein Tea1, the Dyrk-kinase Pom1, and the SH3-domain protein Tea4) [4, 5, 6, 7, 8, 9, 10, 11]. In addition to these factors, cell shape has also been shown to participate in the maintenance of the position of the actomyosin ring [12, 13, 14]. The first principles guiding actomyosin ring placement, however, have not been elucidated in any organism. Because actomyosin ring positioning, ring assembly, and cell morphogenesis are genetically separable in fission yeast, we have used it to derive actomyosin ring placement mechanisms from first principles. We report that, during ring assembly in the absence of cytokinetic cues (anillin-related Mid1 and tip-complex proteins), actin bundles follow the path of least curvature and assemble actomyosin rings in an equatorial position in spherical protoplasts and along the long axis in cylindrical cells and compressed protoplasts. The equatorial position of rings is abolished upon treatment of protoplasts with an actin-severing compound or by slowing down actin polymerization. We propose that the physical properties of actin filaments/bundles play key roles in actomyosin ring assembly and positioning, and that key cytokinetic molecules may modulate the length of actin filaments to promote ring assembly along the short axis. Spheroplasts lacking cytokinetic spatial cues assemble equatorial actomyosin rings An actin-severing compound abolishes equatorial ring assembly in spheroplasts Actin bundles favor the path of least curvature in the absence of cytokinetic cues
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Affiliation(s)
- Tzer Chyn Lim
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry, West Midlands CV4 7AL, UK
| | - Tomoyuki Hatano
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry, West Midlands CV4 7AL, UK
| | - Anton Kamnev
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry, West Midlands CV4 7AL, UK
| | - Mohan K Balasubramanian
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry, West Midlands CV4 7AL, UK.
| | - Ting Gang Chew
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry, West Midlands CV4 7AL, UK.
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Li J, Jiang H. Regulating positioning and orientation of mitotic spindles via cell size and shape. Phys Rev E 2018; 97:012407. [PMID: 29448469 DOI: 10.1103/physreve.97.012407] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Indexed: 06/08/2023]
Abstract
Proper location of the mitotic spindle is critical for chromosome segregation and the selection of the cell division plane. However, how mitotic spindles sense cell size and shape to regulate their own position and orientation is still largely unclear. To investigate this question systematically, we used a general model by considering chromosomes, microtubule dynamics, and forces of various molecular motors. Our results show that in cells of various sizes and shapes, spindles can always be centered and oriented along the long axis robustly in the absence of other specified mechanisms. We found that the characteristic time of positioning and orientation processes increases with cell size. Spindles sense the cell size mainly by the cortical force in small cells and by the cytoplasmic force in large cells. In addition to the cell size, the cell shape mainly influences the orientation process. We found that more slender cells have a faster orientation process, and the final orientation is not necessarily along the longest axis but is determined by the radial profile and the symmetry of the cell shape. Finally, our model also reproduces the separation and repositioning of the spindle poles during the anaphase. Therefore, our work provides a general tool for studying the mitotic spindle across the whole mitotic phase.
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Affiliation(s)
- Jingchen Li
- Department of Modern Mechanics, CAS Key Laboratory of Mechanical Behavior and Design of Materials, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Hongyuan Jiang
- Department of Modern Mechanics, CAS Key Laboratory of Mechanical Behavior and Design of Materials, University of Science and Technology of China, Hefei, Anhui 230027, China
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Abstract
Laser ablation is a powerful tool to study forces within biological systems. This technique has been extensively used to study mitotic spindle formation and chromosome segregation. This chapter describes laser ablation of microtubule-chromosome attachments coupled to fluorescence live microscopy and quantitative analysis of individual chromosome movement after microtubule severing. This method allows to gain insight into the organization and dynamics of the meiotic spindle and chromosomes in metaphase I mouse oocytes.
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Abstract
During the process of neurogenesis, the stem cell committed to the neuronal cell fate starts a series of molecular and morphological changes. The understanding of the physio-pathology of mechanisms controlling the molecular and morphological changes occurring during neuronal differentiation is fundamental to the development of effective therapies for many neurologic diseases. Unfortunately, our knowledge of the biological events occurring in the cell during neuronal differentiation is still poor. In this study, we focus preliminarily on the relevance of the cytoskeletal rearrangements, which earlier drive the morphology of the neuronal precursors, and later the migrating/mature neurons. In fact, neuritogenesis, neurite branching, outgrowth and retraction are seminal to the development of a fully functional nervous system. With this in mind, we highlight the importance of iPSC technology to study the processes of cytoskeletal-driven morphological changes during neuronal differentiation.
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Abstract
Cytokinesis in metazoan cells is mediated by an actomyosin-based contractile ring that assembles in response to activation of the small GTPase RhoA. The guanine nucleotide exchange factor that activates RhoA during cytokinesis, ECT-2, is highly regulated. In most metazoan cells, with the notable exception of the early
Caenorhabditis elegans embryo, RhoA activation and furrow ingression require the centralspindlin complex. This exception is due to the existence of a parallel pathway for RhoA activation in
C. elegans. Centralspindlin contains CYK-4 which contains a predicted Rho family GTPase-activating protein (GAP) domain. The function of this domain has been the subject of considerable debate. Some publications suggest that the GAP domain promotes RhoA activation (for example, Zhang and Glotzer, 2015; Loria, Longhini and Glotzer, 2012), whereas others suggest that it functions to inactivate the GTPase Rac1 (for example, Zhuravlev
et al., 2017). Here, we review the mechanisms underlying RhoA activation during cytokinesis, primarily focusing on data in
C. elegans. We highlight the importance of considering the parallel pathway for RhoA activation and detailed analyses of
cyk-4 mutant phenotypes when evaluating the role of the GAP domain of CYK-4.
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Affiliation(s)
| | - Michael Glotzer
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois, USA
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Beaudet D, Akhshi T, Phillipp J, Law C, Piekny A. Active Ran regulates anillin function during cytokinesis. Mol Biol Cell 2017; 28:3517-3531. [PMID: 28931593 PMCID: PMC5683762 DOI: 10.1091/mbc.e17-04-0253] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 09/06/2017] [Accepted: 09/13/2017] [Indexed: 11/11/2022] Open
Abstract
We describe a novel mechanism by which active Ran regulates anillin during cytokinesis. Anillin is highly conserved and coordinates RhoA, actomyosin, microtubules, and the membrane for cytokinesis in mammalian cells. This study implicates Ran-GTP in influencing cortical contractility during anaphase by regulating anillin function. Cytokinesis cleaves a cell into two daughters at the end of mitosis, and must be spatially coordinated with chromosome segregation to prevent aneuploidy. The dogma is that the mitotic spindle governs the assembly and constriction of an actomyosin ring. Here, we reveal a function for active Ran in spatially restricting the ring. Our model is that during anaphase, “free” importins, whose gradient inversely correlates with active Ran and chromatin position, function as a molecular ruler for the recruitment and localization of anillin, a contractile protein and a crucial regulator of cytokinesis. We found that decreasing Ran-GTP levels or tethering active Ran to the equatorial membrane affects anillin’s localization and causes cytokinesis phenotypes. Anillin contains a conserved nuclear localization signal (NLS) at its C-terminus that binds to importin-β and is required for cortical polarity and cytokinesis. Mutating the NLS decreases anillin’s cortical affinity, causing it to be more dominantly regulated by microtubules. Anillin contains a RhoA-GTP binding domain, which autoinhibits the NLS and the neighboring microtubule-binding domain, and RhoA-GTP binding may relieve this inhibition during mitosis. Retention of the C-terminal NLS in anillin homologues suggests that this is a conserved mechanism for controlling anillin function.
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Affiliation(s)
- Daniel Beaudet
- Department of Biology, Concordia University, Montreal, QC H4B 1R6, Canada
| | - Tara Akhshi
- Program in Cell Biology, the Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Julia Phillipp
- Department of Biology, Concordia University, Montreal, QC H4B 1R6, Canada
| | - Christopher Law
- Centre for Microscopy and Cellular Imaging, Concordia University, Montreal, QC H4B 1R6, Canada
| | - Alisa Piekny
- Program in Cell Biology, the Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
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Price KL, Rose LS. LET-99 functions in the astral furrowing pathway, where it is required for myosin enrichment in the contractile ring. Mol Biol Cell 2017; 28:2360-2373. [PMID: 28701343 PMCID: PMC5576900 DOI: 10.1091/mbc.e16-12-0874] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 06/16/2017] [Accepted: 06/27/2017] [Indexed: 11/11/2022] Open
Abstract
LET-99 is required for furrowing during cytokinesis in both symmetrically and asymmetrically dividing cells. This function is distinct from the role of LET-99 in spindle positioning with Gα signaling. LET-99 is localized to the furrow, where it acts to promote myosin enrichment. The anaphase spindle determines the position of the cytokinesis furrow, such that the contractile ring assembles in an equatorial zone between the two spindle poles. Contractile ring formation is mediated by RhoA activation at the equator by the centralspindlin complex and midzone microtubules. Astral microtubules also inhibit RhoA accumulation at the poles. In the Caenorhabditis elegans one-cell embryo, the astral microtubule–dependent pathway requires anillin, NOP-1, and LET-99. LET-99 is well characterized for generating the asymmetric cortical localization of the Gα-dependent force-generating complex that positions the spindle during asymmetric division. However, whether the role of LET-99 in cytokinesis is specific to asymmetric division and whether it acts through Gα to promote furrowing are unclear. Here we show that LET-99 contributes to furrowing in both asymmetrically and symmetrically dividing cells, independent of its function in spindle positioning and Gα regulation. LET-99 acts in a pathway parallel to anillin and is required for myosin enrichment into the contractile ring. These and other results suggest a positive feedback model in which LET-99 localizes to the presumptive cleavage furrow in response to the spindle and myosin. Once positioned there, LET-99 enhances myosin accumulation to promote furrowing in both symmetrically and asymmetrically dividing cells.
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Affiliation(s)
- Kari L Price
- Department of Molecular and Cellular Biology and Biochemistry, Molecular, Cellular and Developmental Biology Graduate Program, University of California, Davis, Davis, CA 95616
| | - Lesilee S Rose
- Department of Molecular and Cellular Biology and Biochemistry, Molecular, Cellular and Developmental Biology Graduate Program, University of California, Davis, Davis, CA 95616
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Flynn JR, McNally FJ. A casein kinase 1 prevents expulsion of the oocyte meiotic spindle into a polar body by regulating cortical contractility. Mol Biol Cell 2017; 28:2410-2419. [PMID: 28701347 PMCID: PMC5576904 DOI: 10.1091/mbc.e17-01-0056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 05/25/2017] [Accepted: 07/05/2017] [Indexed: 01/20/2023] Open
Abstract
During female meiosis, haploid eggs are generated from diploid oocytes. This reduction in chromosome number occurs through two highly asymmetric cell divisions, resulting in one large egg and two small polar bodies. Unlike mitosis, where an actomyosin contractile ring forms between the sets of segregating chromosomes, the meiotic contractile ring forms on the cortex adjacent to one spindle pole, then ingresses down the length of the spindle to position itself at the exact midpoint between the two sets of segregating chromosomes. Depletion of casein kinase 1 gamma (CSNK-1) in Caenorhabditis elegans led to the formation of large polar bodies that contain all maternal DNA, because the contractile ring ingressed past the spindle midpoint. Depletion of CSNK-1 also resulted in the formation of deep membrane invaginations during meiosis, suggesting an effect on cortical myosin. Both myosin and anillin assemble into dynamic rho-dependent cortical patches that rapidly disassemble in wild-type embryos. CSNK-1 was required for disassembly of both myosin patches and anillin patches. Disassembly of anillin patches was myosin independent, suggesting that CSNK-1 prevents expulsion of the entire meiotic spindle into a polar body by negatively regulating the rho pathway rather than through direct inhibition of myosin.
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Affiliation(s)
- Jonathan R Flynn
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
| | - Francis J McNally
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
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Buđa R, Vukušić K, Tolić IM. Dissection and characterization of microtubule bundles in the mitotic spindle using femtosecond laser ablation. Methods Cell Biol 2017; 139:81-101. [PMID: 28215341 DOI: 10.1016/bs.mcb.2016.11.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The mitotic spindle is a highly organized and dynamic structure required for segregation of the genetic material into two daughter cells. Although most of the individual players involved in building the spindle have been characterized in vitro, a general understanding of how all of the spindle players act together in vivo is still missing. Hence, in recent years, experiments have focused on introducing mechanical perturbations of the spindle on a micron scale, thereby providing insight into its function and organization, as well as into forces acting in the spindle. Among different types of mechanical perturbations, optical ones are more flexible, less invasive, and more precise than other approaches. In this chapter, we describe a detailed protocol for cutting the microtubule bundles in human cells using a near-infrared femtosecond laser. This type of laser microsurgery provides the ability to precisely sever a single microtubule bundle while preserving spindle integrity and dynamics. Furthermore, we describe quantitative measurements obtained from the response of a severed microtubule bundle to laser ablation, which reveal the structure and function of individual parts of the spindle, such as the bridging fiber connecting sister k-fibers. Finally, the method described here can be easily combined with other quantitative techniques to address the complexity of the spindle.
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Affiliation(s)
- R Buđa
- Ruđer Bošković Institute, Zagreb, Croatia
| | - K Vukušić
- Ruđer Bošković Institute, Zagreb, Croatia
| | - I M Tolić
- Ruđer Bošković Institute, Zagreb, Croatia
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Dudka D, Meraldi P. Symmetry Does not Come for Free: Cellular Mechanisms to Achieve a Symmetric Cell Division. Results Probl Cell Differ 2017; 61:301-321. [PMID: 28409311 DOI: 10.1007/978-3-319-53150-2_14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
During mitosis cells can divide symmetrically to proliferate or asymmetrically to generate tissue diversity. While the mechanisms that ensure asymmetric cell division have been extensively studied, it is often assumed that a symmetric cell division is the default outcome of mitosis. Recent studies, however, imply that the symmetric nature of cell division is actively controlled, as they reveal numerous mechanisms that ensure the formation of equal-sized daughter cells as cells progress through cell division. Here we review our current knowledge of these mechanisms and highlight possible key questions in the field.
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Affiliation(s)
- Damian Dudka
- Medical Faculty, Department of Physiology and Metabolism, University of Geneva, 1211, Geneva 4, Switzerland
| | - Patrick Meraldi
- Medical Faculty, Department of Physiology and Metabolism, University of Geneva, 1211, Geneva 4, Switzerland.
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Pacquelet A. Asymmetric Cell Division in the One-Cell C. elegans Embryo: Multiple Steps to Generate Cell Size Asymmetry. Results Probl Cell Differ 2017; 61:115-140. [PMID: 28409302 DOI: 10.1007/978-3-319-53150-2_5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The first division of the one-cell C. elegans embryo has been a fundamental model in deciphering the mechanisms underlying asymmetric cell division. Polarization of the one-cell zygote is induced by a signal from the sperm centrosome and results in the asymmetric distribution of PAR proteins. Multiple mechanisms then maintain PAR polarity until the end of the first division. Once asymmetrically localized, PAR proteins control several essential aspects of asymmetric division, including the position of the mitotic spindle along the polarity axis. Coordination of the spindle and cytokinetic furrow positions is the next essential step to ensure proper asymmetric division. In this chapter, I review the different mechanisms underlying these successive steps of asymmetric division. Work from the last 30 years has revealed the existence of multiple and redundant regulatory pathways which ensure division robustness. Besides the essential role of PAR proteins, this work also emphasizes the importance of both microtubules and actomyosin throughout the different steps of asymmetric division.
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Affiliation(s)
- Anne Pacquelet
- CNRS, UMR6290, Rennes, France. .,Université de Rennes 1, Institut de Génétique et Développement de Rennes, Rennes, France. .,CNRS UMR6290-IGDR, 2 avenue du Professeur Léon Bernard, 35043, Rennes Cedex, France.
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Kim H, Johnson JM, Lera RF, Brahma S, Burkard ME. Anillin Phosphorylation Controls Timely Membrane Association and Successful Cytokinesis. PLoS Genet 2017; 13:e1006511. [PMID: 28081137 PMCID: PMC5230765 DOI: 10.1371/journal.pgen.1006511] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Accepted: 11/29/2016] [Indexed: 12/15/2022] Open
Abstract
During cytokinesis, a contractile ring generates the constricting force to divide a cell into two daughters. This ring is composed of filamentous actin and the motor protein myosin, along with additional structural and regulatory proteins, including anillin. Anillin is a required scaffold protein that links the actomyosin ring to membrane and its organizer, RhoA. However, the molecular basis for timely action of anillin at cytokinesis remains obscure. Here, we find that phosphorylation regulates efficient recruitment of human anillin to the equatorial membrane. Anillin is highly phosphorylated in mitosis, and is a substrate for mitotic kinases. We surveyed function of 46 residues on anillin previously found to be phosphorylated in human cells to identify those required for cytokinesis. Among these sites, we identified S635 as a key site mediating cytokinesis. Preventing S635 phosphorylation adjacent to the AH domain disrupts anillin concentration at the equatorial cortex at anaphase, whereas a phosphomimetic mutant, S635D, partially restores this localization. Time-lapse videomicroscopy reveals impaired recruitment of S635A anillin to equatorial membrane and a transient unstable furrow followed by ultimate failure in cytokinesis. A phosphospecific antibody confirms phosphorylation at S635 in late cytokinesis, although it does not detect phosphorylation in early cytokinesis, possibly due to adjacent Y634 phosphorylation. Together, these findings reveal that anillin recruitment to the equatorial cortex at anaphase onset is enhanced by phosphorylation and promotes successful cytokinesis.
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Affiliation(s)
- Hyunjung Kim
- University of Wisconsin Carbone Cancer Center and Department of Medicine, Hematology/Oncology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - James M. Johnson
- University of Wisconsin Carbone Cancer Center and Department of Medicine, Hematology/Oncology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Robert F. Lera
- University of Wisconsin Carbone Cancer Center and Department of Medicine, Hematology/Oncology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Sarang Brahma
- University of Wisconsin Carbone Cancer Center and Department of Medicine, Hematology/Oncology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Mark E. Burkard
- University of Wisconsin Carbone Cancer Center and Department of Medicine, Hematology/Oncology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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44
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Kotýnková K, Su KC, West SC, Petronczki M. Plasma Membrane Association but Not Midzone Recruitment of RhoGEF ECT2 Is Essential for Cytokinesis. Cell Rep 2016; 17:2672-2686. [PMID: 27926870 PMCID: PMC5177604 DOI: 10.1016/j.celrep.2016.11.029] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Revised: 08/29/2016] [Accepted: 11/07/2016] [Indexed: 11/27/2022] Open
Abstract
Cytokinesis, the final step of cell division, begins with the formation of a cleavage furrow. How the mitotic spindle specifies the furrow at the equator in animal cells remains unknown. Current models propose that the concentration of the RhoGEF ECT2 at the spindle midzone and the equatorial plasma membrane directs furrow formation. Using chemical genetic and optogenetic tools, we demonstrate that the association of ECT2 with the plasma membrane during anaphase is required and sufficient for cytokinesis. Local membrane targeting of ECT2 leads to unilateral furrowing, highlighting the importance of local ECT2 activity. ECT2 mutations that prevent centralspindlin binding compromise concentration of ECT2 at the midzone and equatorial membrane but sustain cytokinesis. While the association of ECT2 with the plasma membrane is essential for cytokinesis, our data suggest that ECT2 recruitment to the spindle midzone is insufficient to account for equatorial furrowing and may act redundantly with yet-uncharacterized signals.
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Affiliation(s)
- Kristýna Kotýnková
- Cell Division and Aneuploidy Laboratory, Cancer Research UK London Research Institute, Clare Hall Laboratories, Blanche Lane, South Mimms, Herts EN6 3LD, UK; DNA Recombination and Repair Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Kuan-Chung Su
- Cell Division and Aneuploidy Laboratory, Cancer Research UK London Research Institute, Clare Hall Laboratories, Blanche Lane, South Mimms, Herts EN6 3LD, UK; Whitehead Institute and Department of Biology, MIT, 9 Cambridge Center, Cambridge, MA 02142, USA
| | - Stephen C West
- DNA Recombination and Repair Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Mark Petronczki
- Cell Division and Aneuploidy Laboratory, Cancer Research UK London Research Institute, Clare Hall Laboratories, Blanche Lane, South Mimms, Herts EN6 3LD, UK; Boehringer Ingelheim RCV, Dr.-Boehringer-Gasse 5-11, 1121 Vienna, Austria.
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Pillitteri LJ, Guo X, Dong J. Asymmetric cell division in plants: mechanisms of symmetry breaking and cell fate determination. Cell Mol Life Sci 2016; 73:4213-4229. [PMID: 27286799 PMCID: PMC5522748 DOI: 10.1007/s00018-016-2290-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 06/02/2016] [Accepted: 06/02/2016] [Indexed: 02/07/2023]
Abstract
Asymmetric cell division is a fundamental mechanism that generates cell diversity while maintaining self-renewing stem cell populations in multicellular organisms. Both intrinsic and extrinsic mechanisms underpin symmetry breaking and differential daughter cell fate determination in animals and plants. The emerging picture suggests that plants deal with the problem of symmetry breaking using unique cell polarity proteins, mobile transcription factors, and cell wall components to influence asymmetric divisions and cell fate. There is a clear role for altered auxin distribution and signaling in distinguishing two daughter cells and an emerging role for epigenetic modifications through chromatin remodelers and DNA methylation in plant cell differentiation. The importance of asymmetric cell division in determining final plant form provides the impetus for its study in the areas of both basic and applied science.
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Affiliation(s)
- Lynn Jo Pillitteri
- Department of Biology, Western Washington University, Bellingham, WA, 98225, USA
| | - Xiaoyu Guo
- Waksman Institute of Microbiology, Rutgers the State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Juan Dong
- Waksman Institute of Microbiology, Rutgers the State University of New Jersey, Piscataway, NJ, 08854, USA.
- Department of Plant Biology and Pathology, Rutgers the State University of New Jersey, New Brunswick, NJ, 08901, USA.
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Abstract
Centrosomes are complex structures, which are embedded into the opposite poles of the mitotic spindle of most animals, acting as microtubule organizing centres. Surprisingly, in several biological systems, such as flies, chicken, or human cells, centrosomes are not essential for cell division. Nonetheless, they ensure faithful chromosome segregation. Moreover, mis-functioning centrosomes can act in a dominant-negative manner, resulting in erroneous mitotic progression. Here, I review the mechanisms by which centrosomes contribute to proper spindle organization and faithful chromosome segregation under physiological conditions and discuss how errors in centrosome function impair transmission of the genomic material in a pathological setting.
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Gnazzo MM, Uhlemann EME, Villarreal AR, Shirayama M, Dominguez EG, Skop AR. The RNA-binding protein ATX-2 regulates cytokinesis through PAR-5 and ZEN-4. Mol Biol Cell 2016; 27:3052-3064. [PMID: 27559134 PMCID: PMC5063614 DOI: 10.1091/mbc.e16-04-0219] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 08/17/2016] [Indexed: 12/15/2022] Open
Abstract
The mechanisms that mediate the temporal and spatial recruitment of cell division factors to the spindle midzone and midbody remain unclear. Cell division is regulated by the conserved RNA-binding protein, ATX-2/Ataxin-2, which facilitates the targeting of ZEN-4 to the spindle midzone by mediating PAR-5. The spindle midzone harbors both microtubules and proteins necessary for furrow formation and the completion of cytokinesis. However, the mechanisms that mediate the temporal and spatial recruitment of cell division factors to the spindle midzone and midbody remain unclear. Here we describe a mechanism governed by the conserved RNA-binding protein ATX-2/Ataxin-2, which targets and maintains ZEN-4 at the spindle midzone. ATX-2 does this by regulating the amount of PAR-5 at mitotic structures, particularly the spindle, centrosomes, and midbody. Preventing ATX-2 function leads to elevated levels of PAR-5, enhanced chromatin and centrosome localization of PAR-5–GFP, and ultimately a reduction of ZEN-4–GFP at the spindle midzone. Codepletion of ATX-2 and PAR-5 rescued the localization of ZEN-4 at the spindle midzone, indicating that ATX-2 mediates the localization of ZEN-4 upstream of PAR-5. We provide the first direct evidence that ATX-2 is necessary for cytokinesis and suggest a model in which ATX-2 facilitates the targeting of ZEN-4 to the spindle midzone by mediating the posttranscriptional regulation of PAR-5.
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Affiliation(s)
- Megan M Gnazzo
- Laboratory of Genetics and Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706
| | - Eva-Maria E Uhlemann
- Laboratory of Genetics and Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706
| | - Alex R Villarreal
- Laboratory of Genetics and Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706
| | - Masaki Shirayama
- Program in Molecular Medicine, RNA Therapeutics Institute, and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA 01605
| | - Eddie G Dominguez
- Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705
| | - Ahna R Skop
- Laboratory of Genetics and Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706
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Juanes MA, Piatti S. The final cut: cell polarity meets cytokinesis at the bud neck in S. cerevisiae. Cell Mol Life Sci 2016; 73:3115-36. [PMID: 27085703 PMCID: PMC4951512 DOI: 10.1007/s00018-016-2220-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 03/22/2016] [Accepted: 04/05/2016] [Indexed: 02/07/2023]
Abstract
Cell division is a fundamental but complex process that gives rise to two daughter cells. It includes an ordered set of events, altogether called "the cell cycle", that culminate with cytokinesis, the final stage of mitosis leading to the physical separation of the two daughter cells. Symmetric cell division equally partitions cellular components between the two daughter cells, which are therefore identical to one another and often share the same fate. In many cases, however, cell division is asymmetrical and generates two daughter cells that differ in specific protein inheritance, cell size, or developmental potential. The budding yeast Saccharomyces cerevisiae has proven to be an excellent system to investigate the molecular mechanisms governing asymmetric cell division and cytokinesis. Budding yeast is highly polarized during the cell cycle and divides asymmetrically, producing two cells with distinct sizes and fates. Many components of the machinery establishing cell polarization during budding are relocalized to the division site (i.e., the bud neck) for cytokinesis. In this review we recapitulate how budding yeast cells undergo polarized processes at the bud neck for cell division.
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Affiliation(s)
- Maria Angeles Juanes
- Centre de Recherche en Biologie Cellulaire de Montpellier, 1919 Route de Mende, 34293, Montpellier, France
- Brandeis University, 415 South Street, Waltham, MA, 02454, USA
| | - Simonetta Piatti
- Centre de Recherche en Biologie Cellulaire de Montpellier, 1919 Route de Mende, 34293, Montpellier, France.
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Smith MB, Chaigne A, Paluch EK. An active contour ImageJ plugin to monitor daughter cell size in 3D during cytokinesis. Methods Cell Biol 2016; 137:323-340. [PMID: 28065314 DOI: 10.1016/bs.mcb.2016.05.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Controlling relative daughter cell size is key during cytokinesis. Uncontrolled size asymmetries can lead to aneuploidy and division failure. At the same time, precisely regulated size asymmetries are of crucial importance in many divisions during embryonic development. Therefore, being able to monitor daughter cell size is important in cytokinesis studies. However, freely available tools allowing to effectively measure the size of daughter cells in three dimensions during cytokinesis are missing. Here, we describe an open-access plugin for ImageJ or Fiji based on an active contour surface representation of the cells. Our method provides a user-friendly and accurate way to monitor the size of the two daughter cells throughout cytokinesis.
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Affiliation(s)
- M B Smith
- MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - A Chaigne
- MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - E K Paluch
- MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
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50
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Abstract
Following up on a chapter on the Correlative Light and Electron Microscopy of Early Caenorhabditis elegans Embryos in Mitosis (MCB 79, 101-119), we present an adaptation of our established protocol for the ultrastructural analysis of either permeabilized or injected embryonic systems. We prepared both drug-treated early C. elegans embryos and fluorescently labeled sea urchin embryos of Lytechinus pictus for ultrastructural studies on animal cytokinesis. Here we focus on the initial preparation steps of postmitotic embryos for high-pressure freezing and subsequent electron microscopy with an emphasis on electron tomography. The advantages and limitations of our extended protocol will be discussed.
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