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Gouveia B, Setru SU, King MR, Hamlin A, Stone HA, Shaevitz JW, Petry S. Acentrosomal spindles assemble from branching microtubule nucleation near chromosomes in Xenopus laevis egg extract. Nat Commun 2023; 14:3696. [PMID: 37344488 DOI: 10.1038/s41467-023-39041-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 05/08/2023] [Indexed: 06/23/2023] Open
Abstract
Microtubules are generated at centrosomes, chromosomes, and within spindles during cell division. Whereas microtubule nucleation at the centrosome is well characterized, much remains unknown about where, when, and how microtubules are nucleated at chromosomes. To address these questions, we reconstitute microtubule nucleation from purified chromosomes in meiotic Xenopus egg extract and find that chromosomes alone can form spindles. We visualize microtubule nucleation near chromosomes using total internal reflection fluorescence microscopy to find that this occurs through branching microtubule nucleation. By inhibiting molecular motors, we find that the organization of the resultant polar branched networks is consistent with a theoretical model where the effectors for branching nucleation are released by chromosomes, forming a concentration gradient that spatially biases branching microtbule nucleation. In the presence of motors, these branched networks are ultimately organized into functional spindles, where the number of emergent spindle poles scales with the number of chromosomes and total chromatin area.
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Affiliation(s)
- Bernardo Gouveia
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Sagar U Setru
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, 08544, USA
| | - Matthew R King
- Department of Molecular Biology, Princeton University, Princeton, NJ, 08544, USA
| | - Aaron Hamlin
- Department of Molecular Biology, Princeton University, Princeton, NJ, 08544, USA
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Joshua W Shaevitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, 08544, USA
- Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ, 08544, USA.
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2
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Ferreira LT, Maiato H. Prometaphase. Semin Cell Dev Biol 2021; 117:52-61. [PMID: 34127384 DOI: 10.1016/j.semcdb.2021.06.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/31/2021] [Accepted: 06/02/2021] [Indexed: 11/28/2022]
Abstract
The establishment of a metaphase plate in which all chromosomes are attached to mitotic spindle microtubules and aligned at the cell equator is required for faithful chromosome segregation in metazoans. The achievement of this configuration relies on the precise coordination between several concurrent mechanisms that start upon nuclear envelope breakdown, mediate chromosome capture at their kinetochores during mitotic spindle assembly and culminate with the congression of all chromosomes to the spindle equator. This period is called 'prometaphase'. Because the nature of chromosome capture by mitotic spindle microtubules is error prone, the cell is provided of error correction mechanisms that sense and correct most erroneous kinetochore-microtubule attachments before committing to separate sister chromatids in anaphase. In this review, aimed for newcomers in the field, more than providing an exhaustive mechanistic coverage of each and every concurrent mechanism taking place during prometaphase, we provide an integrative overview of these processes that ultimately promote the subsequent faithful segregation of chromosomes during mitosis.
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Affiliation(s)
- Luísa T Ferreira
- Chromosome Instability & Dynamics Group, i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Helder Maiato
- Chromosome Instability & Dynamics Group, i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Cell Division Group, Experimental Biology Unit, Department of Biomedicine, Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal.
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3
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Kops GJPL, Gassmann R. Crowning the Kinetochore: The Fibrous Corona in Chromosome Segregation. Trends Cell Biol 2020; 30:653-667. [PMID: 32386879 DOI: 10.1016/j.tcb.2020.04.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 04/08/2020] [Accepted: 04/08/2020] [Indexed: 01/30/2023]
Abstract
The kinetochore is at the heart of chromosome segregation in mitosis and meiosis. Rather than a static linker complex for chromatin and spindle microtubules, it is highly dynamic in composition, size, and shape. While known for decades that it can expand and grow a fibrous meshwork known as the corona, it was until recently unclear what constitutes this 'crown' and what its relevance is for kinetochore function. Here, we highlight recent discoveries in fibrous corona biology, and place them in the context of the processes that orchestrate high-fidelity chromosome segregation.
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Affiliation(s)
- Geert J P L Kops
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Centre Utrecht, Utrecht, 3584, CT, The Netherlands.
| | - Reto Gassmann
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, 4200-135 Porto, Portugal; Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal.
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4
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Tolić IM. Mitotic spindle: kinetochore fibers hold on tight to interpolar bundles. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2018; 47:191-203. [PMID: 28725997 PMCID: PMC5845649 DOI: 10.1007/s00249-017-1244-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 06/30/2017] [Accepted: 07/02/2017] [Indexed: 12/24/2022]
Abstract
When a cell starts to divide, it forms a spindle, a micro-machine made of microtubules, which separates the duplicated chromosomes. The attachment of microtubules to chromosomes is mediated by kinetochores, protein complexes on the chromosome. Spindle microtubules can be divided into three major classes: kinetochore microtubules, which form k-fibers ending at the kinetochore; interpolar microtubules, which extend from the opposite sides of the spindle and interact in the middle; and astral microtubules, which extend towards the cell cortex. Recent work in human cells has shown a close relationship between interpolar and kinetochore microtubules, where interpolar bundles are attached laterally to kinetochore fibers almost all along their length, acting as a bridge between sister k-fibers. Most of the interpolar bundles are attached to a pair of sister kinetochore fibers and vice versa. Thus, the spindle is made of modules consisting of a pair of sister kinetochore fibers and a bundle of interpolar microtubules that connects them. These interpolar bundles, termed bridging fibers, balance the forces acting at kinetochores and support the rounded shape of the spindle during metaphase. This review discusses the structure, function, and formation of kinetochore fibers and interpolar bundles, with an emphasis on how they interact. Their connections have an impact on the force balance in the spindle and on chromosome movement during mitosis because the forces in interpolar bundles are transmitted to kinetochore fibers and hence to kinetochores through these connections.
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Affiliation(s)
- Iva M Tolić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000, Zagreb, Croatia.
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5
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Kapoor TM. Metaphase Spindle Assembly. BIOLOGY 2017; 6:biology6010008. [PMID: 28165376 PMCID: PMC5372001 DOI: 10.3390/biology6010008] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 01/17/2017] [Accepted: 01/19/2017] [Indexed: 01/31/2023]
Abstract
A microtubule-based bipolar spindle is required for error-free chromosome segregation during cell division. In this review I discuss the molecular mechanisms required for the assembly of this dynamic micrometer-scale structure in animal cells.
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Affiliation(s)
- Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, the Rockefeller University, New York, NY 10065, USA.
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6
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Affiliation(s)
- Nenad Pavin
- Department of Physics, Faculty of Science, University of Zagreb, 10000 Zagreb, Croatia;
| | - Iva M. Tolić
- Division of Molecular Biology, Ruđer Bošković Institute, 10000 Zagreb, Croatia;
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7
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Cavazza T, Vernos I. The RanGTP Pathway: From Nucleo-Cytoplasmic Transport to Spindle Assembly and Beyond. Front Cell Dev Biol 2016; 3:82. [PMID: 26793706 PMCID: PMC4707252 DOI: 10.3389/fcell.2015.00082] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 12/07/2015] [Indexed: 01/03/2023] Open
Abstract
The small GTPase Ran regulates the interaction of transport receptors with a number of cellular cargo proteins. The high affinity binding of the GTP-bound form of Ran to import receptors promotes cargo release, whereas its binding to export receptors stabilizes their interaction with the cargo. This basic mechanism linked to the asymmetric distribution of the two nucleotide-bound forms of Ran between the nucleus and the cytoplasm generates a switch like mechanism controlling nucleo-cytoplasmic transport. Since 1999, we have known that after nuclear envelope breakdown (NEBD) Ran and the above transport receptors also provide a local control over the activity of factors driving spindle assembly and regulating other aspects of cell division. The identification and functional characterization of RanGTP mitotic targets is providing novel insights into mechanisms essential for cell division. Here we review our current knowledge on the RanGTP system and its regulation and we focus on the recent advances made through the characterization of its mitotic targets. We then briefly review the novel functions of the pathway that were recently described. Altogether, the RanGTP system has moonlighting functions exerting a spatial control over protein interactions that drive specific functions depending on the cellular context.
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Affiliation(s)
- Tommaso Cavazza
- Cell and Developmental Biology, Centre for Genomic Regulation, The Barcelona Institute of Science and TechnologyBarcelona, Spain; Universitat Pompeu FabraBarcelona, Spain
| | - Isabelle Vernos
- Cell and Developmental Biology, Centre for Genomic Regulation, The Barcelona Institute of Science and TechnologyBarcelona, Spain; Universitat Pompeu FabraBarcelona, Spain; Institució Catalana de Recerca I Estudis AvançatsBarcelona, Spain
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8
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Meunier S, Vernos I. Acentrosomal Microtubule Assembly in Mitosis: The Where, When, and How. Trends Cell Biol 2015; 26:80-87. [PMID: 26475655 DOI: 10.1016/j.tcb.2015.09.001] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 08/31/2015] [Accepted: 09/01/2015] [Indexed: 01/08/2023]
Abstract
In mitosis the cell assembles the bipolar spindle, a microtubule (MT)-based apparatus that segregates the duplicated chromosomes into two daughter cells. Most animal cells enter mitosis with duplicated centrosomes that provide an active source of dynamic MTs. However, it is now established that spindle assembly relies on the nucleation of acentrosomal MTs occurring around the chromosomes after nuclear envelope breakdown, and on pre-existing microtubules. Where chromosome-dependent MT nucleation occurs, when MT amplification takes place and how the two pathways function are still key questions that generate some controversies. We reconcile the data and present an integrated model accounting for acentrosomal microtubule assembly in the dividing cell.
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Affiliation(s)
- Sylvain Meunier
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), Doctor Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Doctor Aiguader 88, 08003 Barcelona, Spain
| | - Isabelle Vernos
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), Doctor Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Doctor Aiguader 88, 08003 Barcelona, Spain; Institució Catalana de Recerca I Estudis Avançats (ICREA), Passeig de Lluis Companys 23, 08010 Barcelona, Spain.
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9
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Pavin N, Tolić-Nørrelykke IM. Swinging a sword: how microtubules search for their targets. SYSTEMS AND SYNTHETIC BIOLOGY 2014; 8:179-86. [PMID: 25136379 PMCID: PMC4127178 DOI: 10.1007/s11693-014-9134-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Accepted: 02/04/2014] [Indexed: 10/25/2022]
Abstract
The cell interior is in constant movement, which is to a large extent determined by microtubules, thin and long filaments that permeate the cytoplasm. To move large objects, microtubules need to connect them to the site of their destination. For example, during cell division, microtubules connect chromosomes with the spindle poles via kinetochores, protein complexes on the chromosomes. A general question is how microtubules, while being bound to one structure, find the target that needs to be connected to this structure. Here we review the mechanisms of how microtubules search for kinetochores, with emphasis on the recently discovered microtubule feature to explore space by pivoting around the spindle pole. In addition to accelerating the search for kinetochores, pivoting helps the microtubules to search for cortical anchors, as well as to self-organize into parallel arrays and asters to target specific regions of the cell. Thus, microtubule pivoting constitutes a mechanism by which they locate targets in different cellular contexts.
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Affiliation(s)
- Nenad Pavin
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička 32, 10000 Zagreb, Croatia
| | - Iva M Tolić-Nørrelykke
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany ; Division of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
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10
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Yao R, Kondoh Y, Natsume Y, Yamanaka H, Inoue M, Toki H, Takagi R, Shimizu T, Yamori T, Osada H, Noda T. A small compound targeting TACC3 revealed its different spatiotemporal contributions for spindle assembly in cancer cells. Oncogene 2013; 33:4242-52. [PMID: 24077290 DOI: 10.1038/onc.2013.382] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 07/17/2013] [Accepted: 08/09/2013] [Indexed: 12/21/2022]
Abstract
The mitotic spindle is assembled by the coordinated action of centrosomes and kinetochore microtubules. An evolutionally conserved protein family, transforming acidic coiled-coil (TACC), has been shown to be involved in this process. In humans, TACC3 is aberrantly expressed in a variety of human cancers, but its biological significance remains to be elucidated. Here, using a novel compound targeting TACC3, spindlactone (SPL), we show that the perturbation of TACC3 selectively inhibited the nucleation of centrosome microtubules in ovarian cancer cells. In contrast to centrosome microtubules, the kinetochore microtubules were robustly assembled, forming ectopic spindle poles that resulted in multipolar spindles. Interestingly, the extensive inhibition of TACC3 partially suppressed the nucleation of kinetochore microtubules. These dose-dependent effects of SPL were consistent with the results observed by the depletion of TACC3 and its binding partner, colonic and hepatic tumor overexpressed gene protein (TOGp). Although these proteins both have roles in the assembly of centrosome and kinetochore microtubules, their contributions were spatiotemporally different. Notably, SPL did not affect spindle assembly in normal cells. Furthermore, the oral administration of SPL significantly suppressed tumor growth in vivo. The unique mechanism of action of SPL not only enables it to be used as a tool to dissect the molecular basis of spindle assembly but also to provide a rationale for the use of TACC3 as a molecular target for cancer treatment. This rationale offers an opportunity to develop new strategies for cancer chemotherapy that overcome the limitations of microtubule toxins and expand their scope and clinical efficacy.
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Affiliation(s)
- R Yao
- Department of Cell Biology, Cancer Institute, The Japanese Foundation for Cancer Research, Tokyo, Japan
| | - Y Kondoh
- Chemical Biology Core Facility, RIKEN Advanced Science Institute, Saitama, Japan
| | - Y Natsume
- Department of Cell Biology, Cancer Institute, The Japanese Foundation for Cancer Research, Tokyo, Japan
| | - H Yamanaka
- Department of Cell Biology, Cancer Institute, The Japanese Foundation for Cancer Research, Tokyo, Japan
| | - M Inoue
- 1] Department of Cell Biology, Cancer Institute, The Japanese Foundation for Cancer Research, Tokyo, Japan [2] Team for the Advanced Development and Evaluation of Human Disease Models, Bioresource Center, RIKEN, Tsukuba, Japan
| | - H Toki
- Team for the Advanced Development and Evaluation of Human Disease Models, Bioresource Center, RIKEN, Tsukuba, Japan
| | - R Takagi
- Chemical Biology Core Facility, RIKEN Advanced Science Institute, Saitama, Japan
| | - T Shimizu
- Chemical Biology Core Facility, RIKEN Advanced Science Institute, Saitama, Japan
| | - T Yamori
- Division of Molecular Pharmacology, Cancer Chemotherapy Center, The Japanese Foundation for Cancer Research, Tokyo, Japan
| | - H Osada
- Chemical Biology Core Facility, RIKEN Advanced Science Institute, Saitama, Japan
| | - T Noda
- 1] Department of Cell Biology, Cancer Institute, The Japanese Foundation for Cancer Research, Tokyo, Japan [2] Team for the Advanced Development and Evaluation of Human Disease Models, Bioresource Center, RIKEN, Tsukuba, Japan
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11
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Schulman VK, Folker ES, Baylies MK. A method for reversible drug delivery to internal tissues of Drosophila embryos. Fly (Austin) 2013; 7:193-203. [PMID: 23846179 DOI: 10.4161/fly.25438] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Drosophila melanogaster is a powerful model organism to elucidate basic cellular mechanisms of development. Indeed, much of our understanding of genetic pathways comes from work in Drosophila. However, mutations in many critical genes cause early embryonic lethality; thus, it is difficult to study the role of proteins that are required for early fundamental processes during later embryonic stages. We have therefore developed a method to reversibly deliver drugs to internal tissues of stage 15-16 Drosophila embryos using a 1:1 combination of D-limonene and heptane (LH). Specifically, delivery of Nocodazole was shown to be effective as evidenced by the significant decrease in microtubule density seen in muscle cells. Following complete depolymerization of the microtubule cytoskeleton, removing the Nocodazole and washing for 10 min was sufficient for the microtubule network to be re-established, indicating that drug delivery is reversible. Additionally, the morphology of LH-treated embryos resembled that of untreated controls, and embryo viability post-treatment with LH was significantly increased compared with previously reported permeabilization techniques. These advances in embryo permeabilization provide a means to disrupt protein function in vivo with high temporally specificity, bypassing the complications associated with genetic disruptions as they relate to the study of late-stage developmental mechanisms.
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Affiliation(s)
- Victoria K Schulman
- Program in Developmental Biology; Sloan Kettering Institute; Memorial Sloan-Kettering Cancer Center; New York, NY USA; Department of Cell and Developmental Biology; Weill Cornell Graduate School of Medical Sciences; Cornell University; New York, NY USA
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12
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Mottier-Pavie V, Cenci G, Vernì F, Gatti M, Bonaccorsi S. Phenotypic analysis of misato function reveals roles of noncentrosomal microtubules in Drosophila spindle formation. J Cell Sci 2011; 124:706-17. [PMID: 21285248 DOI: 10.1242/jcs.072348] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mitotic spindle assembly in centrosome-containing cells relies on two main microtubule (MT) nucleation pathways, one based on centrosomes and the other on chromosomes. However, the relative role of these pathways is not well defined. In Drosophila, mutants without centrosomes can form functional anastral spindles and survive to adulthood. Here we show that mutations in the Drosophila misato (mst) gene inhibit kinetochore-driven MT growth, lead to the formation of monopolar spindles and cause larval lethality. In most prophase cells of mst mutant brains, asters are well separated, but collapse with progression of mitosis, suggesting that k-fibers are essential for maintenance of aster separation and spindle bipolarity. Analysis of mst; Sas-4 double mutants showed that mitotic cells lacking both the centrosomes and the mst function form polarized MT arrays that resemble monopolar spindles. MT regrowth experiments after cold exposure revealed that in mst; Sas-4 metaphase cells MTs regrow from several sites, which eventually coalesce to form a single polarized MT array. By contrast, in Sas-4 single mutants, chromosome-driven MT regrowth mostly produced robust bipolar spindles. Collectively, these results indicate that kinetochore-driven MT formation is an essential process for proper spindle assembly in Drosophila somatic cells.
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Affiliation(s)
- Violaine Mottier-Pavie
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Sapienza Università di Roma, Ple. A. Moro 5, 00185 Roma, Italy
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13
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Taylor BF, McNeely SC, Miller HL, States JC. Arsenite-induced mitotic death involves stress response and is independent of tubulin polymerization. Toxicol Appl Pharmacol 2008; 230:235-46. [PMID: 18485433 DOI: 10.1016/j.taap.2008.02.030] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Revised: 02/21/2008] [Accepted: 02/25/2008] [Indexed: 10/22/2022]
Abstract
Arsenite, a known mitotic disruptor, causes cell cycle arrest and cell death at anaphase. The mechanism causing mitotic arrest is highly disputed. We compared arsenite to the spindle poisons nocodazole and paclitaxel. Immunofluorescence analysis of alpha-tubulin in interphase cells demonstrated that, while nocodazole and paclitaxel disrupt microtubule polymerization through destabilization and hyperpolymerization, respectively, microtubules in arsenite-treated cells remain comparable to untreated cells even at supra-therapeutic concentrations. Immunofluorescence analysis of alpha-tubulin in mitotic cells showed spindle formation in arsenite- and paclitaxel-treated cells but not in nocodazole-treated cells. Spindle formation in arsenite-treated cells appeared irregular and multi-polar. gamma-tubulin staining showed that cells treated with nocodazole and therapeutic concentrations of paclitaxel contained two centrosomes. In contrast, most arsenite-treated mitotic cells contained more than two centrosomes, similar to centrosome abnormalities induced by heat shock. Of the three drugs tested, only arsenite treatment increased expression of the inducible isoform of heat shock protein 70 (HSP70i). HSP70 and HSP90 proteins are intimately involved in centrosome regulation and mitotic spindle formation. HSP90 inhibitor 17-DMAG sensitized cells to arsenite treatment and increased arsenite-induced centrosome abnormalities. Combined treatment of 17-DMAG and arsenite resulted in a supra-additive effect on viability, mitotic arrest, and centrosome abnormalities. Thus, arsenite-induced abnormal centrosome amplification and subsequent mitotic arrest is independent of effects on tubulin polymerization and may be due to specific stresses that are protected against by HSP90 and HSP70.
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Affiliation(s)
- B Frazier Taylor
- Department of Pharmacology and Toxicology, Center for Environmental Genomics and Integrative Biology, Center for Genetics and Molecular Medicine, James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
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14
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Tulu US, Fagerstrom C, Ferenz NP, Wadsworth P. Molecular requirements for kinetochore-associated microtubule formation in mammalian cells. Curr Biol 2006; 16:536-41. [PMID: 16527751 PMCID: PMC1500889 DOI: 10.1016/j.cub.2006.01.060] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 01/17/2006] [Accepted: 01/20/2006] [Indexed: 11/30/2022]
Abstract
In centrosome-containing cells, microtubules nucleated at centrosomes are thought to play a major role in spindle assembly. In addition, microtubule formation at kinetochores has also been observed, most recently under physiological conditions in live cells. The relative contributions of microtubule formation at kinetochores and centrosomes to spindle assembly, and their molecular requirements, remain incompletely understood. Using mammalian cells released from nocodazole-induced disassembly, we observed microtubule formation at centrosomes and at Bub1-positive sites on chromosomes. Kinetochore-associated microtubules rapidly coalesced into pole-like structures in a dynein-dependent manner. Microinjection of excess importin-beta or depletion of the Ran-dependent spindle assembly factor, TPX2, blocked kinetochore-associated microtubule formation, enhanced centrosome-associated microtubule formation, but did not prevent chromosome capture by centrosomal microtubules. Depletion of the chromosome passenger protein, survivin, reduced microtubule formation at kinetochores in an MCAK-dependent manner. Microtubule formation in cells depleted of Bub1 or Nuf2 was indistinguishable from that in controls. Our data demonstrate that microtubule assembly at centrosomes and kinetochores is kinetically distinct and differentially regulated. The presence of microtubules at kinetochores provides a mechanism to reconcile the time required for spindle assembly in vivo with that observed in computer simulations of search and capture.
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Affiliation(s)
- U Serdar Tulu
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Amherst, Massachusetts 01003, USA
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15
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Lüders J, Patel UK, Stearns T. GCP-WD is a gamma-tubulin targeting factor required for centrosomal and chromatin-mediated microtubule nucleation. Nat Cell Biol 2005; 8:137-47. [PMID: 16378099 DOI: 10.1038/ncb1349] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2005] [Accepted: 11/18/2005] [Indexed: 11/08/2022]
Abstract
The gamma-tubulin ring complex (gammaTuRC) is a large multi-protein complex that is required for microtubule nucleation from the centrosome. Here, we show that the GCP-WD protein (originally named NEDD1) is the orthologue of the Drosophila Dgrip71WD protein, and is a subunit of the human gammaTuRC. GCP-WD has the properties of an attachment factor for the gammaTuRC: depletion or inhibition of GCP-WD results in loss of the gammaTuRC from the centrosome, abolishing centrosomal microtubule nucleation, although the gammaTuRC is intact and able to bind to microtubules. GCP-WD depletion also blocks mitotic chromatin-mediated microtubule nucleation, resulting in failure of spindle assembly. Mitotic phosphorylation of GCP-WD is required for association of gamma-tubulin with the spindle, separately from association with the centrosome. Our results indicate that GCP-WD broadly mediates targeting of the gammaTuRC to sites of microtubule nucleation and to the mitotic spindle, which is essential for spindle formation.
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Affiliation(s)
- Jens Lüders
- Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA
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16
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Rieder CL. Kinetochore fiber formation in animal somatic cells: dueling mechanisms come to a draw. Chromosoma 2005; 114:310-8. [PMID: 16270218 PMCID: PMC2570760 DOI: 10.1007/s00412-005-0028-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Revised: 09/12/2005] [Accepted: 09/12/2005] [Indexed: 01/08/2023]
Abstract
The attachment to and movement of a chromosome on the mitotic spindle are mediated by the formation of a bundle of microtubules (MTs) that tethers the kinetochore on the chromosome to a spindle pole. The origin of these "kinetochore fibers" (K fibers) has been investigated for over 125 years. As noted in 1944 by Schrader [Mitosis, Columbia University Press, New York, 110 pp.], there are three possible ways to form a K fiber: (a) it grows from the pole until it contacts the kinetochore, (b) it grows directly from the kinetochore, or (c) it forms as a result of an interaction between the pole and the chromosome. Since Schrader's time, it has been firmly established that K fibers in centrosome-containing animal somatic cells form as kinetochores capture MTs growing from the spindle pole (route a). It is now similarly clear that in cells lacking centrosomes, including higher plants and many animal oocytes, K fibers "self-assemble" from MTs generated by the chromosomes (route b). Can animal somatic cells form K fibers in the absence of centrosomes by the "self-assembly" pathway? In 2000, the answer to this question was shown to be a resounding "yes." With this result, the next question became whether the presence of a centrosome normally suppresses K fiber self-assembly or if this route works concurrently with centrosome-mediated K-fiber formation. This question, too, has recently been answered: observations on untreated live animal cells expressing green fluorescent protein-tagged tubulin clearly show that kinetochores can nucleate the formation of their associated MTs in a unique manner in the presence of functional centrosomes. The concurrent operation of these two "dueling" routes for forming K fibers in animal cells helps explain why the attachment of kinetochores and the maturation of K fibers occur as quickly as they do on all chromosomes within a cell.
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Affiliation(s)
- Conly L Rieder
- Laboratory of Cell Regulation, Division of Molecular Medicine, Wadsworth Center, New York State Department of Health, 509, Albany, NY 12201-0509, USA.
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Maiato H, DeLuca J, Salmon ED, Earnshaw WC. The dynamic kinetochore-microtubule interface. J Cell Sci 2005; 117:5461-77. [PMID: 15509863 DOI: 10.1242/jcs.01536] [Citation(s) in RCA: 282] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The kinetochore is a control module that both powers and regulates chromosome segregation in mitosis and meiosis. The kinetochore-microtubule interface is remarkably fluid, with the microtubules growing and shrinking at their point of attachment to the kinetochore. Furthermore, the kinetochore itself is highly dynamic, its makeup changing as cells enter mitosis and as it encounters microtubules. Active kinetochores have yet to be isolated or reconstituted, and so the structure remains enigmatic. Nonetheless, recent advances in genetic, bioinformatic and imaging technology mean we are now beginning to understand how kinetochores assemble, bind to microtubules and release them when the connections made are inappropriate, and also how they influence microtubule behaviour. Recent work has begun to elucidate a pathway of kinetochore assembly in animal cells; the work has revealed that many kinetochore components are highly dynamic and that some cycle between kinetochores and spindle poles along microtubules. Further studies of the kinetochore-microtubule interface are illuminating: (1) the role of the Ndc80 complex and components of the Ran-GTPase system in microtubule attachment, force generation and microtubule-dependent inactivation of kinetochore spindle checkpoint activity; (2) the role of chromosomal passenger proteins in the correction of kinetochore attachment errors; and (3) the function of microtubule plus-end tracking proteins, motor depolymerases and other proteins in kinetochore movement on microtubules and movement coupled to microtubule poleward flux.
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Affiliation(s)
- Helder Maiato
- Laboratory of Cell Regulation, NYSDH-Division of Molecular Medicine, Wadsworth Center, Empire State Plaza, PO Box 509, Albany, NY 12201-0509, USA
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Abstract
Proper segregation of chromosomes during cell division is essential for the maintenance of genetic stability. During this process chromosomes must establish stable functional interactions with microtubules through the kinetochore, a specialized protein structure located on the surface of the centromeric heterochromatin. Stable attachment of kinetochores to a number of microtubules results in the formation of a kinetochore fibre that mediates chromosome movement. How the kinetochore fibre is formed and how chromosome motion is produced and regulated remain major questions in cell biology. Here we look at some of the history of research devoted to the study of kinetochore-microtubule interaction and attempt to identify significant advances in the knowledge of the basic processes. Ultrastructural work has provided substantial insights into the structure of the kinetochore and associated microtubules during different stages of mitosis. Also, recent in-vivo studies have probed deep into the dynamics of kinetochore-attached microtubules suggesting possible models for the way in which kinetochores harness the capacity of microtubules to do work and turn it into chromosome motion. Much of the research in recent years suggests that indeed multiple mechanisms are involved in both formation of the k-fibre and chromosome motion. Thus, rather than moving to a unified theory, it has become apparent that most cell types have the capacity to build the spindle using multiple and probably redundant mechanisms.
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Affiliation(s)
- Helder Maiato
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal
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Maiato H, Rieder CL, Khodjakov A. Kinetochore-driven formation of kinetochore fibers contributes to spindle assembly during animal mitosis. ACTA ACUST UNITED AC 2004; 167:831-40. [PMID: 15569709 PMCID: PMC2172442 DOI: 10.1083/jcb.200407090] [Citation(s) in RCA: 247] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is now clear that a centrosome-independent pathway for mitotic spindle assembly exists even in cells that normally possess centrosomes. The question remains, however, whether this pathway only activates when centrosome activity is compromised, or whether it contributes to spindle morphogenesis during a normal mitosis. Here, we show that many of the kinetochore fibers (K-fibers) in centrosomal Drosophila S2 cells are formed by the kinetochores. Initially, kinetochore-formed K-fibers are not oriented toward a spindle pole but, as they grow, their minus ends are captured by astral microtubules (MTs) and transported poleward through a dynein-dependent mechanism. This poleward transport results in chromosome bi-orientation and congression. Furthermore, when individual K-fibers are severed by laser microsurgery, they regrow from the kinetochore outward via MT plus-end polymerization at the kinetochore. Thus, even in the presence of centrosomes, the formation of some K-fibers is initiated by the kinetochores. However, centrosomes facilitate the proper orientation of K-fibers toward spindle poles by integrating them into a common spindle.
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Affiliation(s)
- Helder Maiato
- Wadsworth Center, New York State Department of Health, Albany 12201, USA
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20
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Kline-Smith SL, Khodjakov A, Hergert P, Walczak CE. Depletion of centromeric MCAK leads to chromosome congression and segregation defects due to improper kinetochore attachments. Mol Biol Cell 2003; 15:1146-59. [PMID: 14699064 PMCID: PMC363095 DOI: 10.1091/mbc.e03-08-0581] [Citation(s) in RCA: 228] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The complex behavior of chromosomes during mitosis is accomplished by precise binding and highly regulated polymerization dynamics of kinetochore microtubules. Previous studies have implicated Kin Is, unique kinesins that depolymerize microtubules, in regulating chromosome positioning. We have characterized the immunofluorescence localization of centromere-bound MCAK and found that MCAK localized to inner kinetochores during prophase but was predominantly centromeric by metaphase. Interestingly, MCAK accumulated at leading kinetochores during congression but not during segregation. We tested the consequences of MCAK disruption by injecting a centromere dominant-negative protein into prophase cells. Depletion of centromeric MCAK led to reduced centromere stretch, delayed chromosome congression, alignment defects, and severe missegregation of chromosomes. Rates of chromosome movement were unchanged, suggesting that the primary role of MCAK is not to move chromosomes. Furthermore, we found that disruption of MCAK leads to multiple kinetochore-microtubule attachment defects, including merotelic, syntelic, and combined merotelic-syntelic attachments. These findings reveal an essential role for Kin Is in prevention and/or correction of improper kinetochore-microtubule attachments.
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Affiliation(s)
- Susan L Kline-Smith
- Departments of Anatomy and Cell Biology, Indiana University Medical Sciences Program, Bloomington, Indiana 47405, USA
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Cimini D, Moree B, Canman JC, Salmon ED. Merotelic kinetochore orientation occurs frequently during early mitosis in mammalian tissue cells and error correction is achieved by two different mechanisms. J Cell Sci 2003; 116:4213-25. [PMID: 12953065 DOI: 10.1242/jcs.00716] [Citation(s) in RCA: 192] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Merotelic kinetochore orientation is an error that occurs when a single kinetochore becomes attached to microtubules from two spindle poles rather than just to one pole. We obtained the first evidence that merotelic kinetochore orientation occurs very frequently during early mitosis in mammalian tissue cells and that two different correction mechanisms are critical for accurate chromosome segregation in cells possessing bipolar spindles and unperturbed chromosomes. Our data show that about 30% of prometaphase PtK1 cells possess one or more merotelically oriented kinetochores. This frequency is increased to over 90% in cells recovering from a nocodazole-induced mitotic block. A delay in establishing spindle bipolarity is responsible for the high frequency of merotelic orientations seen in cells recovering from nocodazole, but not in untreated cells. The frequency of anaphase cells with merotelically oriented lagging chromosomes is 1% in untreated cells and 18% in cells recovering from nocodazole. Prolonging metaphase by 2 hours reduced the frequency of anaphase cells with lagging chromosomes both for untreated and for nocodazole-treated cells. Surprisingly, anaphase lagging chromosomes represented a very small fraction of merotelic kinetochore orientations present in late metaphase. Our data indicate that two correction mechanisms operate to prevent chromosome missegregation due to merotelic kinetochore orientation. The first, a pre-anaphase correction mechanism increases the ratio of kinetochore microtubules attached to the correct versus incorrect pole and might eventually result in kinetochore reorientation before anaphase onset. The increase in microtubule ratio to opposite poles is the groundwork for a second mechanism, active in anaphase, that promotes the segregation of merotelically oriented chromosomes to the correct pole.
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Affiliation(s)
- Daniela Cimini
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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Peterson JR, Mitchison TJ. Small molecules, big impact: a history of chemical inhibitors and the cytoskeleton. CHEMISTRY & BIOLOGY 2002; 9:1275-85. [PMID: 12498880 DOI: 10.1016/s1074-5521(02)00284-3] [Citation(s) in RCA: 258] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Chemical inhibitors, whether natural products or synthetic, have had an enormous impact on the study of the eukaryotic cytoskeleton. Here we review the history of some of the most widely used cytoskeletal poisons and their influence on our understanding of cytoskeletal functions. We then highlight several new inhibitors and the targeted screens used to identify them and discuss why this approach has been successful.
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Affiliation(s)
- Jeffrey R Peterson
- Department of Cell Biology and Institute of Chemistry and Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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Abstract
In all eukaryotes, a microtubule-based structure known as the spindle is responsible for accurate chromosome segregation during cell division. Spindle assembly and function require localized regulation of microtubule dynamics and the activity of a variety of microtubule-based motor proteins. Recent work has begun to uncover the molecular mechanisms that underpin this process. Here we describe the structural and dynamic properties of the spindle, and introduce the current concepts regarding how a bipolar spindle is assembled and how it functions to segregate chromosomes.
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Affiliation(s)
- T Wittmann
- Department of Cell Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
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24
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Andrade-Monteiro CD, Martinez-Rossi NM. The nucleation of microtubules in Aspergillus nidulans germlings. Genet Mol Biol 1999. [DOI: 10.1590/s1415-47571999000300004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Microtubules are filaments composed of dimers of alpha- and beta-tubulins, which have a variety of functions in living cells. In fungi, the spindle pole bodies usually have been considered to be microtubule-organizing centers. We used the antimicrotubule drug Benomyl in block/release experiments to depolymerize and repolymerize microtubules in Aspergillus nidulans germlings to learn more about the microtubule nucleation process in this filamentous fungus. Twenty seconds after release from Benomyl short microtubules were formed from several bright (immunofluorescent) dots distributed along the germlings, suggesting that microtubule nucleation is randomly distributed in A. nidulans germlings. Since nuclear movement is dependent on microtubules in A. nidulans we analyzed whether mutants defective in nuclear distribution along the growing hyphae (nud mutants) have some obvious microtubule defect. Cytoplasmic, astral and spindle microtubules were present and appeared to be normal in all nud mutants. However, significant changes in the percentage of short versus long mitotic spindles were observed in nud mutants. This suggests that some of the nuclei of nud mutants do not reach the late stage of cell division at normal temperatures.
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25
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Abstract
Assembly of mitotic and meiotic spindles into an elliptical bipolar shape is an example of morphogenetic processes that involve local chromosomal regulation of microtubule dynamics for proper spatial microtubule assembly. Global microtubule dynamics during the cell cycle and local microtubule dynamics during spindle assembly are regulated by a balance between microtubule stabilizing and destabilizing factors. How a chromosome-induced phosphorylation gradient may be generated and modulate spindle microtubule assembly through balanced regulation of the activity of microtubule-associated proteins and Stathmin/Op 18 is analyzed.
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Affiliation(s)
- S S Andersen
- University of California, San Diego, La Jolla, CA92093-0357, USA.
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26
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Hanke-Bücker G, Hauser M. Nuclear phenomena during conjugation of the suctorian Heliophrya erhardi. Eur J Protistol 1996. [DOI: 10.1016/s0932-4739(96)80005-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Fuller CM, Bridges RJ, Benos DJ. Forskolin- but not ionomycin-evoked Cl- secretion in colonic epithelia depends on intact microtubules. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 266:C661-8. [PMID: 8166229 DOI: 10.1152/ajpcell.1994.266.3.c661] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Several transport proteins are known to be trafficked to the cell membrane in response to appropriate secretagogues. In several cases, the response has been shown to be dependent on the cytoskeleton. We tested the hypothesis that the forskolin- and/or ionomycin-sensitive Cl- secretory response in colonic epithelia is dependent on an intact cytoskeleton. Using 125I- efflux as an assay for Cl- transport in the colonic epithelial cell line T84, we found that preincubation of the tissue for 3 h with either of two inhibitors of microtubule polymerization, nocodazole or colchicine, disrupted the cellular tubulin architecture and also reduced the forskolin- but not the ionomycin-evoked I- efflux. In contrast, brief exposure (4 min) to nocodazole was without effect on the forskolin-sensitive efflux, suggesting that the drug is not acting to block the stimulus-response pathway. An inactive structural analogue of colchicine, beta-lumicolchicine, had no inhibitory effect on either the forskolin-sensitive efflux or on microtubular structure. In a second model of Cl- secretion, the stripped rat colon, both colchicine and nocodazole reduced the forskolin-dependent short-circuit current by an average of 30-40%, suggesting a similar mechanism for insertion of Cl- channels into the plasma membrane. These findings suggest that the Cl- secretory response is dependent on microtubules and has a physiological role in the adenosine 3',5'-cyclic monophosphate-dependent, but not the Ca(2+)-dependent, Cl- secretion in colonic epithelia.
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Affiliation(s)
- C M Fuller
- Department of Physiology and Biophysics, University of Alabama at Birmingham 35294
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28
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Ley SC, Verbi W, Pappin DJ, Druker B, Davies AA, Crumpton MJ. Tyrosine phosphorylation of alpha tubulin in human T lymphocytes. Eur J Immunol 1994; 24:99-106. [PMID: 7517366 DOI: 10.1002/eji.1830240116] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
N-terminal sequencing of the 55- and 50-kDa polypeptides affinity purified on a phosphotyrosine monoclonal antibody column from activated Jurkat T cells identified alpha and beta tubulin. Two-dimensional gel analysis indicated that alpha tubulin was directly phosphorylated on tyrosine. beta Tubulin was not detectably tyrosine phosphorylated but was precipitated by anti-phosphotyrosine (PTyr) antibody by virtue of its association with the alpha subunit as a heterodimer. Phosphotyrosyl alpha tubulin was not incorporated into intact microtubules and was all in the unpolymerized soluble fraction. These results suggest that tyrosine phosphorylation of alpha tubulin may inhibit the ability of this subunit to polymerize into microtubules. Stimulation of Jurkat T cells via T cell receptor increased the amount of tubulin precipitated by the anti-PTyr antibody. These data raise the possibility that the polymerization of tubulin heterodimers may be regulated by phosphorylation on tyrosine during T cell activation.
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Affiliation(s)
- S C Ley
- Cellular Immunology, National Institute for Medical Research, London, GB
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Rieder CL. Formation of the astral mitotic spindle: ultrastructural basis for the centrosome-kinetochore interaction. ELECTRON MICROSCOPY REVIEWS 1990; 3:269-300. [PMID: 2103345 DOI: 10.1016/0892-0354(90)90005-d] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The formation of the astral mitotic spindle is initiated at the time of nuclear envelope breakdown from an interaction between the replicated spindle poles (i.e. centrosomes) and the chromosomes. As a result of this interaction bundles of microtubules are generated which firmly attach the kinetochores on each chromosome to opposite spindle poles. Since these kinetochore fibers are also involved in moving the chromosomes, the mechanism by which they are formed is of paramount importance to understanding the etiology of force production within the spindle. As a prelude to outlining such a mechanism, the dynamics of spindle formation and chromosome behavior are examined in the living cell. Next, the properties of centrosomes and kinetochores are reviewed with particular emphasis on the structural and functional changes that occur within these organelles as the cell transits from interphase to mitosis. Finally, a number of recent observations relevant to the mechanism by which these organelles interact are detailed and discussed. From these diverse data it can be concluded that kinetochore fiber microtubules are derived from dynamically unstable astral microtubules that grow into, or grow by and then interact laterally with, the kinetochore. Moreover, the data clearly demonstrate that the interaction of a single astral microtubule with one of the kinetochores on an unattached chromosome is sufficient to attach the chromosome to the spindle, orient it towards a pole, and initiate poleward motion. As the chromosomes move into the region of the forming spindle more astral microtubules become incorporated into the nascent kinetochore fibers and chromosome velocity decreases dramatically. During this time the distribution of spindle microtubules changes from two overlapping radial arrays to the fusiform array characteristic of metaphase cells.
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Affiliation(s)
- C L Rieder
- Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509
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31
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Geuens G, Hill AM, Levilliers N, Adoutte A, DeBrabander M. Microtubule dynamics investigated by microinjection of Paramecium axonemal tubulin: lack of nucleation but proximal assembly of microtubules at the kinetochore during prometaphase. J Biophys Biochem Cytol 1989; 108:939-53. [PMID: 2646309 PMCID: PMC2115398 DOI: 10.1083/jcb.108.3.939] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Microtubule (MT) dynamics in PtK2 cells have been investigated using in vivo injection of unmodified Paramecium ciliary tubulin and time-lapse fixation. The sites of incorporation of the axonemal tubulin were localized using a specific antibody which does not react with vertebrate cytoplasmic tubulin (Adoutte, A., M. Claisse, R. Maunoury, and J. Beisson. 1985. J. Mol. Evol. 22:220-229), followed by immunogold labeling, Nanovid microscopy, and ultrastructural observation of the same cells. We confirm data from microinjection of labeled tubulins in other cell types (Soltys, B. J., and G. G. Borisy. 1985. J. Cell Biol. 100:1682-1689; Mitchison, T., L. Evans, E. Schulze, and M. Kirschner. 1986. Cell. 45:515-527; Schulze, E., and M. Kirschner. 1986. J. Cell Biol. 102:1020-1031). In agreement with the dynamic instability model (Mitchison, T., and M. Kirschner. 1984. Nature (Lond.). 312:237-242), during interphase, fast (2.6 microns/min) distal growth of MTs occurs, together with new centrosomal nucleation. Most of the cytoplasmic MT complex is replaced within 15-30 min. During mitosis, astral MTs display the same pattern of renewal, but the turnover of the MT system is much faster (approximately 6 min). We have concentrated on the construction of the kinetochore fibers during prometaphase and observe that (a) incorporation of tubulin in the vicinity of the kinetochores is not seen during prophase and early prometaphase as long as the kinetochores are not yet connected to a pole by MTs; (b) proximal time-dependent incorporation occurs only into preexisting kinetochore MTs emanating from centrosomes. Consequently, in undisturbed prometaphase cells, the kinetochores probably do not act as independent nucleation sites. This confirms a model in which, at prometaphase, fast probing centrosomal MTs are grabbed by the kinetochores, where tubulin incorporation then takes place.
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Affiliation(s)
- G Geuens
- Department of Cellular Biology and Pathology, Janssen Research Foundation, Beerse, Belgium
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Sweet SC, Rogers CM, Welsh MJ. Calmodulin is associated with microtubules forming in PTK1 cells upon release from nocodazole treatment. CELL MOTILITY AND THE CYTOSKELETON 1989; 12:113-22. [PMID: 2713899 DOI: 10.1002/cm.970120206] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
To investigate the association of calmodulin (CaM) with microtubules (MTs) in the mitotic apparatus (MA), the distributions of CaM and tubulin were examined in cells in which the normal spindle organization had been altered. A fluorescent CaM conjugate with tetramethylrhodamine isothiocyanate (CaM-TRITC) and a dichlorotriazinyl aminofluorescein conjugate with tubulin (tubulin-DTAF) were injected into cells that had been treated with the MT inhibitor nocodazole. With moderate nocodazole concentration (0.3 micrograms/ml, 37 degrees C, 4 h) in live cells, CaM-TRITC and tubulin-DTAF concentrated identically on or near the centrosomes and kinetochores. In serial sections of these cells, small MT segments were observed by transmission electron microscopy (TEM) in the regions where fluorescent protein had concentrated. When a higher drug concentration was used (3.0 micrograms/ml, 37 degrees C, 4 h), no regions of CaM-TRITC or tubulin-DTAF localization were observed, and no MTs were observed when serial sections were examined by TEM. However, following release from the high-concentration nocodazole block, CaM-TRITC colocalized with newly formed MTs at the kinetochores and centrosomes. Later in the recovery period, when chromosome-to-pole fibers had formed, CaM association with kinetochores diminished, ultimately attaining its normal pole-proximal association with kinetochore MTs in cells that progressed through mitosis. We interpret these observations as supporting the hypothesis that in the MA, CaM attains a physical association with kinetochore MTs and suggest that CaM-associated MTs may be inherently more stable.
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Affiliation(s)
- S C Sweet
- Department of Anatomy and Cell Biology, University of Michigan Medical School, Ann Arbor 48109-0616
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33
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Chromosomes and Kinetochores do More in Mitosis than Previously Thought. CHROMOSOME STRUCTURE AND FUNCTION 1988. [DOI: 10.1007/978-1-4613-1037-2_2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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Kaiser J, Went DF. Early embryonic development of the dipteran insect Heteropeza pygmaea in the presence of cytoskeleton-affecting drugs. ACTA ACUST UNITED AC 1987; 196:356-366. [PMID: 28305635 DOI: 10.1007/bf00375772] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/1986] [Accepted: 03/16/1987] [Indexed: 10/26/2022]
Abstract
Embryos of the paedogenetically reproducing gall midge Heteropeza pygmaea develop floating in the haemocoel of a so-called mother larva. The egg membranes remain permeable and the embryos increase in size during embryonic development by taking up nutrients from the haemolymph. Such embryos can be cultured in vitro, i.e. in haemolymph drops obtained from mother larvae. We tested the effects of several drugs known to interact with cytoskeletal elements on different stages of embryonic development, including cleavage and gastrulation. The drugs were added to the in vitro cultures and the effects were studied with time-lapse cine-micrography. Colchicine and vinblastine blocked cleaving eggs in metaphase stage and arrested yolk globule oscillation. In spite of such a block blastoderms once formed continued development through germ band formation and extension and also increased in size. Cytochalasin B did not affect the stage of cleavage; however, it inhibited gastrulation and subsequent morphogenetic processes and also prevented size increase. We conclude that (1) the functioning of microtubules is needed for yolk globule oscillation during cleavage interphases but not for the gastrulation processes subsequent to blastoderm formation and (2) microfilaments do not play an important role in cleavage, at least not for the orderly succession of the cleavage divisions, but are essential for the morphogenetic movements associated with gastrulation. We suggest that during cleavage a limited stock of microtubules and their precursors is responsible for both transport of chromosomes during mitoses and translocation of organelles during interphase. Yolk oscillation seems to be a secondary effect and of minor or no importance for the normal course of embryonic development.
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Affiliation(s)
- Johannes Kaiser
- Department of Entomology, Swiss Federal Institute of Technology Zurich, CH-8092, Zurich
| | - Dirk F Went
- Institute of Animal Science, Swiss Federal Institute of Technology Zurich, CH-8092, Zurich, Switzerland
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35
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Hugon JS, Bennett G, Pothier P, Ngoma Z. Loss of microtubules and alteration of glycoprotein migration in organ cultures of mouse intestine exposed to nocodazole or colchicine. Cell Tissue Res 1987; 248:653-62. [PMID: 3607853 DOI: 10.1007/bf00216496] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Explants from mouse jejunum were cultured for 3-7 h in the absence (control) or presence of colchicine (100 micrograms/ml) or nocodazole (10 micrograms/ml). In recovery experiments, explants were cultured in fresh medium for an additional period. To label glycoproteins, 3H-fucose was added during the last 3 or 6 h of the initial culture or recovery period. Subcellular fractionation studies revealed that colchicine and nocodazole inhibited migration of labelled glycoproteins to the brush border (P2) by 40-45%. Radioautographic studies of absorptive cells showed that colchicine and nocodazole inhibited labelling of the microvillous border by 67% and 87%, while labelling of the basolateral plasma membrane increased by 114% and 275%. Immunocytochemical studies revealed that both colchicine and nocodazole caused the virtual disappearance of the microtubular network in the absorptive cells. It is possible that some glycoproteins normally destined for the microvillous border are rerouted to the basolateral membrane. The observed loss of microtubules after drug treatment suggests that microtubules may play a role in the intracellular migration of membrane glycoproteins. Additional support for this concept is provided by the fact that in recovery experiments the distribution of label returned to control values after the microtubular network became re-established.
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Gaertig J, Seyfert HM, Kaczanowski A. Post-meiotic DNA synthesis in nocodazole-blocked nuclei during conjugation of Tetrahymena thermophila. Induction of polyploidy in the micronucleus. Exp Cell Res 1986; 164:562-7. [PMID: 3709684 DOI: 10.1016/0014-4827(86)90055-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The formation of single, polyploid micronuclei was induced during conjugation of Tetrahymena thermophila with Nocodazole (ND) according to Kaczanowski et al. The increase in DNA content in these nuclei was measured cytophotometrically in conjugating pairs continuously exposed to the drug. ND-treated micronuclei ('restitution nuclei') undergo two complete rounds of DNA replication and enter the third at the time of pair separation. The DNA content of these micronuclei in late pairs was in the range 16-30C (mean 20C). This amount was similar to the sum of the DNA content of all post-meiotic products during normal conjugation at about the same stage. Thus the increase in DNA content in 'restitution' nuclei reflects some intrinsic ability of nuclei in pairing cells to replicate DNA independently of nuclear division.
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Carlier H, Bernard A, Hugon JS. Effect of monensin and nocodazole on the intestinal lipid esterification in mouse jejunal organ culture. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1986; 84:655-9. [PMID: 2875830 DOI: 10.1016/0300-9629(86)90381-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The ability of mouse jejunal explants to esterify a lipid emulsion containing oleic acid, palmitic acid and monopalmitin has been studied in different in vitro experimental conditions. The incubating lipid solution must have a minimum volume for obtaining optimal triglyceride esterification by the cultured intestinal mucosa. In our incubating conditions the exchange of oleic for palmitic acid does not significantly modify the amount of lipids esterified by the explants in 15 min. Monensin or nocodazole, added to the culture medium of intestinal explants for 3 hr, significantly change the amount of lipids esterified and secreted. The inhibition observed after nocodazole treatment disappears, however, when the explants are rinsed and the culture is allowed to continue for an additional 3 hr in a drug-free medium. These results suggest that the regulation of lipid metabolism can be studied in organ culture.
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De Brabander M, Geuens G, Nuydens R, Willebrords R, Aerts F, De Mey J. Microtubule dynamics during the cell cycle: the effects of taxol and nocodazole on the microtubule system of Pt K2 cells at different stages of the mitotic cycle. INTERNATIONAL REVIEW OF CYTOLOGY 1986; 101:215-74. [PMID: 2870994 DOI: 10.1016/s0074-7696(08)60250-8] [Citation(s) in RCA: 108] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Mitchison TJ, Kirschner MW. Properties of the kinetochore in vitro. I. Microtubule nucleation and tubulin binding. J Cell Biol 1985; 101:755-65. [PMID: 4030893 PMCID: PMC2113742 DOI: 10.1083/jcb.101.3.755] [Citation(s) in RCA: 114] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We have isolated chromosomes from Chinese hamster ovary cells arrested in mitosis with vinblastine and examined the interactions of their kinetochores with purified tubulin in vitro. The kinetochores nucleate microtubule (MT) growth with complex kinetics. After an initial lag phase, MTs are continuously nucleated with both plus and minus ends distally localized. This mixed polarity seems inconsistent with the formation of an ordered, homopolar kinetochore fiber in vivo. As isolated from vinblastine-arrested cells, kinetochores contain no bound tubulin. The kinetochores of chromosomes isolated from colcemid-arrested cells or of chromosomes incubated with tubulin in vitro are brightly stained after anti-tubulin immunofluorescence. This bound tubulin is probably not in the form of MTs. It is localized to the corona region by immunoelectron microscopy, where it may play a role in MT nucleation in vitro.
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Mitchison TJ, Kirschner MW. Properties of the kinetochore in vitro. II. Microtubule capture and ATP-dependent translocation. J Cell Biol 1985; 101:766-77. [PMID: 4030894 PMCID: PMC2113737 DOI: 10.1083/jcb.101.3.766] [Citation(s) in RCA: 202] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We have studied the interaction of preformed microtubules (MTs) with the kinetochores of isolated chromosomes. This reaction, which we call MT capture, results in MTs becoming tightly bound to the kinetochore, with their ends capped against depolymerization. These observations, combined with MT dynamic instability, suggest a model for spindle morphogenesis. In addition, ATP appears to mobilize dynamic processes at captured MT ends. We used biotin-labeled MT seeds to follow assembly dynamics at the kinetochore. In the presence of ATP and unlabeled tubulin, labeled MT segments translocate away from the kinetochore by polymerization of subunits at the attached end. We have termed this reaction proximal assembly. Further studies demonstrated that translocation could be uncoupled from MT assembly. We suggest that the kinetochore contains an ATPase activity that walks along the MT lattice toward the plus end. This activity may be responsible for the movement of chromosomes away from the pole in prometaphase.
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Kaczanowski A, Gaertig J, Kubiak J. Effect of the antitubulin drug nocodazole on meiosis and postmeiotic development in Tetrahymena thermophila. Induction of achiasmatic meiosis. Exp Cell Res 1985; 158:244-56. [PMID: 3996478 DOI: 10.1016/0014-4827(85)90447-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nocodazole (ND), a potent antitubulin drug, can be used to dissect the steps of meiosis in Tetrahymena, presumably by interfering with the assembly of microtubules. Its effects depend upon the time during conjugation at which the drug is applied. When applied prior to the elongation of the micronucleus into the characteristic 'crescent' configuration, no crescent is formed and the chromosomes of prepachytene and pachytene condense into spherical nuclei. If ND is applied after micronuclear elongation has begun, but before it is fully elongated, the chromosomes fail to synapse and appear in metaphase I as unpaired monovalents. In contrast, the metaphase I chromosomes appear as bivalents when ND is applied later, during or after the crescent has reached its maximum elongation. Still later, application of ND inhibits chromosome movements during anaphase and telophase of either meiotic division, but does not prevent separation of kinetochores. In some of the blocked restitutive nuclei an additional round of chromosome replication occurs, corresponding to the third pregamic division in normal conjugation. The hyperploid micronuclei produced by such treatment may be useful in certain genetic manipulations and in studying the regulation of nuclear DNA content.
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Sluder G, Rieder CL. Experimental separation of pronuclei in fertilized sea urchin eggs: chromosomes do not organize a spindle in the absence of centrosomes. J Cell Biol 1985; 100:897-903. [PMID: 3972900 PMCID: PMC2113528 DOI: 10.1083/jcb.100.3.897] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We tested the ability of chromosomes in a mitotic cytoplasm to organize a bipolar spindle in the absence of centrosomes. Sea urchin eggs were treated with 5 X 10(-6) colcemid for 7-9 min before fertilization to block future microtubule assembly. Fertilization events were normal except that a sperm aster was not formed and the pronuclei remained up to 70 microns apart. After nuclear envelope breakdown, individual eggs were irradiated with 366-nm light to inactivate photochemically the colcemid. A functional haploid bipolar spindle was immediately assembled in association with the male chromosomes. In contrast to the male pronucleus, the female pronucleus in most of these eggs remained as a small nonbirefringent hyaline area throughout mitosis. High-voltage electron microscopy of serial semithick sections from individual eggs, previously followed in vivo, revealed that the female chromosomes were randomly distributed within the remnants of the nuclear envelope. No microtubules were found in these pronuclear areas even though the chromosomes were well-condensed and had prominent kinetochores with well-developed coronas. In the remaining eggs, a weakly birefringent monaster was assembled in the female pronuclear area. These observations demonstrate that chromosomes in a mitotic cytoplasm cannot organize a bipolar spindle in the absence of a spindle pole or even in the presence of a monaster. In fact, chromosomes do not even assemble kinetochore microtubules in the absence of a spindle pole, and kinetochore microtubules form only on kinetochores facing the pole when a monaster is present. This study also provides direct experimental proof for the longstanding paradigm that the sperm provides the centrosomes used in the development of the sea urchin zygote.
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De Brabander M, Aerts F, De Mey J, Geuens G, Moeremans M, Nuydens R, Willebrords R. Microtubule dynamics and the mitotic cycle: a model. BASIC LIFE SCIENCES 1985; 36:269-78. [PMID: 3913416 DOI: 10.1007/978-1-4613-2127-9_17] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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McIntosh J. Mechanisms of mitosis. Trends Biochem Sci 1984. [DOI: 10.1016/0968-0004(84)90138-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Otto JJ, Schroeder TE. Microtubule arrays in the cortex and near the germinal vesicle of immature starfish oocytes. Dev Biol 1984; 101:274-81. [PMID: 6363161 DOI: 10.1016/0012-1606(84)90141-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
An extensive array of long, crisscrossing microtubules has been discovered in the cortex of oocytes of the starfish Pisaster ochraceus. The microtubules were visualized in cortex preparations by indirect immunofluorescence microscopy using antibodies to tubulin. The cortical array of microtubules is present in all oocytes before and for about 30 min after the application of 1-methyladenine, the hormone that induces oocyte maturation. The presence of microtubules was confirmed by electron microscopy. The microtubules in this array are depolymerized when oocytes are treated with colchicine or nocodozole and are augmented when oocytes are treated with taxol. Dihydrocytochalasin B treatment of the oocytes causes the microtubules to aggregate, presumably by altering a microfilament network also found in the cortex. The distribution of microtubules was also explored in whole oocytes stained with antitubulin. One or two aster-like structures were observed adjacent to the germinal vesicle of each oocyte.
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Rieder CL. The formation, structure, and composition of the mammalian kinetochore and kinetochore fiber. INTERNATIONAL REVIEW OF CYTOLOGY 1982; 79:1-58. [PMID: 6185450 DOI: 10.1016/s0074-7696(08)61672-1] [Citation(s) in RCA: 349] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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