1
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Tran NV, Montanari MP, Lubenets D, Fischbach LL, Antson H, Okada Y, Ishimoto Y, Tõnissoo T, Shimmi O. α-Spectrin regulates cell shape changes during disassembly of microtubule-driven protrusions in Drosophila wings. MICROPUBLICATION BIOLOGY 2024; 2024:10.17912/micropub.biology.001169. [PMID: 38690064 PMCID: PMC11058509 DOI: 10.17912/micropub.biology.001169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 03/27/2024] [Accepted: 04/11/2024] [Indexed: 05/02/2024]
Abstract
The dynamics of microtubule-mediated protrusions, termed Interplanar Amida Network (IPAN) in Drosophila pupal wing, involve cell shape changes. The molecular mechanisms underlying these processes are yet to be fully understood. This study delineates the stages of cell shape alterations during the disassembly of microtubule protrusions and underscores the pivotal role of α-Spectrin in driving these changes by regulating both the microtubule and actomyosin networks. Our findings also demonstrate that α-Spectrin is required for the apical relaxation of wing epithelia during protrusion disassembly, indicating its substantial contribution to the robustness of 3D tissue morphogenesis.
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Affiliation(s)
- Ngan Vi Tran
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | - Martti P. Montanari
- Institute of Biotechnology, University of Helsinki, Helsinki, Uusimaa, Finland
| | - Dmitri Lubenets
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | | | - Hanna Antson
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | - Yasushi Okada
- The University of Tokyo, Tokyo, Japan
- RIKEN, Wako, Saitama, Japan
| | | | - Tambet Tõnissoo
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | - Osamu Shimmi
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
- Institute of Biotechnology, University of Helsinki, Helsinki, Uusimaa, Finland
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2
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LaFountain JR, Seaman CE, Cohan CS, Oldenbourg R. Sliding of antiparallel microtubules drives bipolarization of monoastral spindles. Cytoskeleton (Hoboken) 2024; 81:167-183. [PMID: 37812128 PMCID: PMC11172411 DOI: 10.1002/cm.21800] [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: 08/02/2023] [Revised: 09/21/2023] [Accepted: 09/23/2023] [Indexed: 10/10/2023]
Abstract
Time-lapse imaging with liquid crystal polarized light (LC-PolScope) and fluorescent speckle microscopy (FSM) enabled this study of spindle microtubules in monoastral spindles that were produced in crane-fly spermatocytes through flattening-induced centrosome displacement. Monoastral spindles are found in several other contexts: after laser ablation of one of a cell's two centrosomes (in the work of Khodjakov et al.), in Drosophila "urchin" mutants (in the works of Heck et al. and of Wilson et al.), in Sciara males (in the works of Fuge and of Metz), and in RNAi variants of Drosophila S2 cells (in the work of Goshima et al.). In all cases, just one pole has a centrosome (the astral pole); the other lacks a centrosome (the anastral pole). Thus, the question: How is the anastral half-spindle, lacking a centrosome, constructed? We learned that monoastral spindles are assembled in two phases: Phase I assembles the astral half-spindle composed of centrosomal microtubules, and Phase II assembles microtubules of the anastral half through extension of new microtubule polymerization outward from the spindle's equatorial mid-zone. That process uses plus ends of existing centrosomal microtubules as guiding templates to assemble anastral microtubules of opposite polarity. Anastral microtubules slide outward with their minus ends leading, thereby establishing proper bipolarity just like in normal biastral spindles that have two centrosomes.
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Affiliation(s)
- James R LaFountain
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, USA
| | - Catherine E Seaman
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, USA
| | - Christopher S Cohan
- Department of Pathology and Anatomy, University at Buffalo, Buffalo, New York, USA
| | - Rudolf Oldenbourg
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, Massachusetts, USA
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3
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Tran NV, Montanari MP, Gui J, Lubenets D, Fischbach LL, Antson H, Huang Y, Brutus E, Okada Y, Ishimoto Y, Tõnissoo T, Shimmi O. Programmed disassembly of a microtubule-based membrane protrusion network coordinates 3D epithelial morphogenesis in Drosophila. EMBO J 2024; 43:568-594. [PMID: 38263333 PMCID: PMC10897427 DOI: 10.1038/s44318-023-00025-w] [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: 03/01/2023] [Revised: 12/14/2023] [Accepted: 12/18/2023] [Indexed: 01/25/2024] Open
Abstract
Comprehensive analysis of cellular dynamics during the process of morphogenesis is fundamental to understanding the principles of animal development. Despite recent advancements in light microscopy, how successive cell shape changes lead to complex three-dimensional tissue morphogenesis is still largely unresolved. Using in vivo live imaging of Drosophila wing development, we have studied unique cellular structures comprising a microtubule-based membrane protrusion network. This network, which we name here the Interplanar Amida Network (IPAN), links the two wing epithelium leaflets. Initially, the IPAN sustains cell-cell contacts between the two layers of the wing epithelium through basal protrusions. Subsequent disassembly of the IPAN involves loss of these contacts, with concomitant degeneration of aligned microtubules. These processes are both autonomously and non-autonomously required for mitosis, leading to coordinated tissue proliferation between two wing epithelia. Our findings further reveal that a microtubule organization switch from non-centrosomal to centrosomal microtubule-organizing centers (MTOCs) at the G2/M transition leads to disassembly of non-centrosomal microtubule-derived IPAN protrusions. These findings exemplify how cell shape change-mediated loss of inter-tissue contacts results in 3D tissue morphogenesis.
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Affiliation(s)
- Ngan Vi Tran
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Martti P Montanari
- Institute of Biotechnology, University of Helsinki, 00014, Helsinki, Finland
| | - Jinghua Gui
- Institute of Biotechnology, University of Helsinki, 00014, Helsinki, Finland
| | - Dmitri Lubenets
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | | | - Hanna Antson
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Yunxian Huang
- Institute of Biotechnology, University of Helsinki, 00014, Helsinki, Finland
| | - Erich Brutus
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Yasushi Okada
- Center for Biosystems Dynamics Research, RIKEN, Osaka, Japan
- Departments of Cell Biology and Physics, University of Tokyo, Tokyo, Japan
| | - Yukitaka Ishimoto
- Department of Machine Intelligence and Systems Engineering, Akita Prefectural University, Akita, 015-0055, Japan
| | - Tambet Tõnissoo
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Osamu Shimmi
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia.
- Institute of Biotechnology, University of Helsinki, 00014, Helsinki, Finland.
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4
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Kraus J, Alfaro-Aco R, Gouveia B, Petry S. Microtubule nucleation for spindle assembly: one molecule at a time. Trends Biochem Sci 2023; 48:761-775. [PMID: 37482516 PMCID: PMC10789498 DOI: 10.1016/j.tibs.2023.06.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 06/01/2023] [Accepted: 06/06/2023] [Indexed: 07/25/2023]
Abstract
The cell orchestrates the dance of chromosome segregation with remarkable speed and fidelity. The mitotic spindle is built from scratch after interphase through microtubule (MT) nucleation, which is dependent on the γ-tubulin ring complex (γ-TuRC), the universal MT template. Although several MT nucleation pathways build the spindle framework, the question of when and how γ-TuRC is targeted to these nucleation sites in the spindle and subsequently activated remains an active area of investigation. Recent advances facilitated the discovery of new MT nucleation effectors and their mechanisms of action. In this review, we illuminate each spindle assembly pathway and subsequently consider how the pathways are merged to build a spindle.
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Affiliation(s)
- Jodi Kraus
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | | | - Bernardo Gouveia
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
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5
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Valdez VA, Neahring L, Petry S, Dumont S. Mechanisms underlying spindle assembly and robustness. Nat Rev Mol Cell Biol 2023; 24:523-542. [PMID: 36977834 PMCID: PMC10642710 DOI: 10.1038/s41580-023-00584-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2023] [Indexed: 03/30/2023]
Abstract
The microtubule-based spindle orchestrates chromosome segregation during cell division. Following more than a century of study, many components and pathways contributing to spindle assembly have been described, but how the spindle robustly assembles remains incompletely understood. This process involves the self-organization of a large number of molecular parts - up to hundreds of thousands in vertebrate cells - whose local interactions give rise to a cellular-scale structure with emergent architecture, mechanics and function. In this Review, we discuss key concepts in our understanding of spindle assembly, focusing on recent advances and the new approaches that enabled them. We describe the pathways that generate the microtubule framework of the spindle by driving microtubule nucleation in a spatially controlled fashion and present recent insights regarding the organization of individual microtubules into structural modules. Finally, we discuss the emergent properties of the spindle that enable robust chromosome segregation.
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Affiliation(s)
| | - Lila Neahring
- Department of Bioengineering & Therapeutic Sciences, UCSF, San Francisco, CA, USA
- Developmental & Stem Cell Biology Graduate Program, UCSF, San Francisco, CA, USA
| | - Sabine Petry
- Molecular Biology, Princeton University, Princeton, NJ, USA.
| | - Sophie Dumont
- Department of Bioengineering & Therapeutic Sciences, UCSF, San Francisco, CA, USA.
- Developmental & Stem Cell Biology Graduate Program, UCSF, San Francisco, CA, USA.
- Department of Biochemistry & Biophysics, UCSF, San Francisco, CA, USA.
- Chan Zuckerberg Biohub, San Francisco, CA, USA.
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6
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Microtubule and Actin Cytoskeletal Dynamics in Male Meiotic Cells of Drosophila melanogaster. Cells 2022; 11:cells11040695. [PMID: 35203341 PMCID: PMC8870657 DOI: 10.3390/cells11040695] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Revised: 02/11/2022] [Accepted: 02/14/2022] [Indexed: 01/12/2023] Open
Abstract
Drosophila dividing spermatocytes offer a highly suitable cell system in which to investigate the coordinated reorganization of microtubule and actin cytoskeleton systems during cell division of animal cells. Like male germ cells of mammals, Drosophila spermatogonia and spermatocytes undergo cleavage furrow ingression during cytokinesis, but abscission does not take place. Thus, clusters of primary and secondary spermatocytes undergo meiotic divisions in synchrony, resulting in cysts of 32 secondary spermatocytes and then 64 spermatids connected by specialized structures called ring canals. The meiotic spindles in Drosophila males are substantially larger than the spindles of mammalian somatic cells and exhibit prominent central spindles and contractile rings during cytokinesis. These characteristics make male meiotic cells particularly amenable to immunofluorescence and live imaging analysis of the spindle microtubules and the actomyosin apparatus during meiotic divisions. Moreover, because the spindle assembly checkpoint is not robust in spermatocytes, Drosophila male meiosis allows investigating of whether gene products required for chromosome segregation play additional roles during cytokinesis. Here, we will review how the research studies on Drosophila male meiotic cells have contributed to our knowledge of the conserved molecular pathways that regulate spindle microtubules and cytokinesis with important implications for the comprehension of cancer and other diseases.
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7
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Villa-Fombuena G, Lobo-Pecellín M, Marín-Menguiano M, Rojas-Ríos P, González-Reyes A. Live imaging of the Drosophila ovarian niche shows spectrosome and centrosome dynamics during asymmetric germline stem cell division. Development 2021; 148:271223. [PMID: 34370012 PMCID: PMC8489027 DOI: 10.1242/dev.199716] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 07/29/2021] [Indexed: 12/02/2022]
Abstract
Drosophila female germline stem cells (GSCs) are found inside the cellular niche at the tip of the ovary. They undergo asymmetric divisions to renew the stem cell lineage and to produce sibling cystoblasts that will in turn enter differentiation. GSCs and cystoblasts contain spectrosomes, membranous structures essential for orientation of the mitotic spindle and that, particularly in GSCs, change shape depending on the cell cycle phase. Using live imaging and a fusion protein of GFP and the spectrosome component Par-1, we follow the complete spectrosome cycle throughout GSC division and quantify the relative duration of the different spectrosome shapes. We also determine that the Par-1 kinase shuttles between the spectrosome and the cytoplasm during mitosis and observe the continuous addition of new material to the GSC and cystoblast spectrosomes. Next, we use the Fly-FUCCI tool to define, in live and fixed tissues, that GSCs have a shorter G1 compared with the G2 phase. The observation of centrosomes in dividing GSCs allowed us to determine that centrosomes separate very early in G1, before centriole duplication. Furthermore, we show that the anterior centrosome associates with the spectrosome only during mitosis and that, upon mitotic spindle assembly, it translocates to the cell cortex, where it remains anchored until centrosome separation. Finally, we demonstrate that the asymmetric division of GSCs is not an intrinsic property of these cells, as the spectrosome of GSC-like cells located outside of the niche can divide symmetrically. Thus, GSCs display unique properties during division, a behaviour influenced by the surrounding niche. Summary: Imaging of live Drosophila germline stem cells in the ovarian niche reveals their asymmetric division and centrosome behaviour, whereas tumorous stem cells divide symmetrically.
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Affiliation(s)
- Gema Villa-Fombuena
- Centro Andaluz de Biología del Desarrollo, CSIC/Universidad Pablo de Olavide/JA, Carretera de Utrera km 1, 41013 Sevilla, Spain
| | - María Lobo-Pecellín
- Centro Andaluz de Biología del Desarrollo, CSIC/Universidad Pablo de Olavide/JA, Carretera de Utrera km 1, 41013 Sevilla, Spain
| | - Miriam Marín-Menguiano
- Centro Andaluz de Biología del Desarrollo, CSIC/Universidad Pablo de Olavide/JA, Carretera de Utrera km 1, 41013 Sevilla, Spain
| | - Patricia Rojas-Ríos
- Centro Andaluz de Biología del Desarrollo, CSIC/Universidad Pablo de Olavide/JA, Carretera de Utrera km 1, 41013 Sevilla, Spain
| | - Acaimo González-Reyes
- Centro Andaluz de Biología del Desarrollo, CSIC/Universidad Pablo de Olavide/JA, Carretera de Utrera km 1, 41013 Sevilla, Spain
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8
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Fingerhut JM, Yamashita YM. mRNA localization mediates maturation of cytoplasmic cilia in Drosophila spermatogenesis. J Cell Biol 2020; 219:e202003084. [PMID: 32706373 PMCID: PMC7480094 DOI: 10.1083/jcb.202003084] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 06/10/2020] [Accepted: 06/15/2020] [Indexed: 01/26/2023] Open
Abstract
Cytoplasmic cilia, a specialized type of cilia in which the axoneme resides within the cytoplasm rather than within the ciliary compartment, are proposed to allow for the efficient assembly of very long cilia. Despite being found diversely in male gametes (e.g., Plasmodium falciparum microgametocytes and human and Drosophila melanogaster sperm), very little is known about cytoplasmic cilia assembly. Here, we show that a novel RNP granule containing the mRNAs for axonemal dynein motor proteins becomes highly polarized to the distal end of the cilia during cytoplasmic ciliogenesis in Drosophila sperm. This allows for the incorporation of these axonemal dyneins into the axoneme directly from the cytoplasm, possibly by localizing translation. We found that this RNP granule contains the proteins Reptin and Pontin, loss of which perturbs granule formation and prevents incorporation of the axonemal dyneins, leading to sterility. We propose that cytoplasmic cilia assembly requires the precise localization of mRNAs encoding key axonemal constituents, allowing these proteins to incorporate efficiently into the axoneme.
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Affiliation(s)
- Jaclyn M. Fingerhut
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI
- Life Sciences Institute, University of Michigan, Ann Arbor, MI
| | - Yukiko M. Yamashita
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI
- Life Sciences Institute, University of Michigan, Ann Arbor, MI
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI
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9
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Sheard KM, Thibault-Sennett SA, Sen A, Shewmaker F, Cox RT. Clueless forms dynamic, insulin-responsive bliss particles sensitive to stress. Dev Biol 2019; 459:149-160. [PMID: 31837288 DOI: 10.1016/j.ydbio.2019.12.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 12/06/2019] [Accepted: 12/07/2019] [Indexed: 12/13/2022]
Abstract
Drosophila Clueless (Clu) is a ribonucleoprotein that directly affects mitochondrial function. Loss of clu causes mitochondrial damage, and Clu associates with proteins on the mitochondrial outer membrane. Clu's subcellular pattern is diffuse throughout the cytoplasm, but Clu also forms large mitochondria-associated particles. Clu particles are reminiscent of ribonucleoprotein particles such as stress granules and processing bodies. Ribonucleoprotein particles play critical roles in the cell by regulating mRNAs spatially and temporally. Here, we show that Clu particles are unique, highly dynamic and rapidly disperse in response to stress in contrast to processing bodies and autophagosomes. In addition, Clu particle formation is dependent on diet as ovaries from starved females no longer contain Clu particles, and insulin signaling is necessary and sufficient for Clu particle formation. Oxidative stress also disperses particles. Since Clu particles are only present under optimal conditions, we have termed them "bliss particles". We also demonstrate that many aspects of Clu function are conserved in the yeast homolog Clu1p. These observations identify Clu particles as stress-sensitive cytoplasmic particles whose absence corresponds with altered cell stress and mitochondrial localization.
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Affiliation(s)
- K M Sheard
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, MD, 20814, USA
| | - S A Thibault-Sennett
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, MD, 20814, USA
| | - A Sen
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, MD, 20814, USA
| | - F Shewmaker
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University, Bethesda, MD, 20814, USA
| | - R T Cox
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, MD, 20814, USA.
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10
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Karabasheva D, Smyth JT. A novel, dynein-independent mechanism focuses the endoplasmic reticulum around spindle poles in dividing Drosophila spermatocytes. Sci Rep 2019; 9:12456. [PMID: 31462700 PMCID: PMC6713755 DOI: 10.1038/s41598-019-48860-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 08/14/2019] [Indexed: 01/04/2023] Open
Abstract
In dividing animal cells the endoplasmic reticulum (ER) concentrates around the poles of the spindle apparatus by associating with astral microtubules (MTs), and this association is essential for proper ER partitioning to progeny cells. The mechanisms that associate the ER with astral MTs are unknown. Because astral MT minus-ends are anchored by centrosomes at spindle poles, we hypothesized that the MT minus-end motor dynein mediates ER concentration around spindle poles. Live in vivo imaging of Drosophila spermatocytes revealed that dynein is required for ER concentration around centrosomes during late interphase. In marked contrast, however, dynein suppression had no effect on ER association with astral MTs and concentration around spindle poles in early M-phase. In fact, there was a sudden onset of ER association with astral MTs in dynein RNAi cells, revealing activation of an M-phase specific mechanism of ER-MT association. ER redistribution to spindle poles also did not require non-claret disjunctional (ncd), the other known Drosophila MT minus-end motor, nor Klp61F, a MT plus-end motor that generates spindle poleward forces. Collectively, our results suggest that a novel, M-phase specific mechanism of ER-MT association that is independent of MT minus-end motors is required for proper ER partitioning in dividing cells.
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Affiliation(s)
- Darya Karabasheva
- Department of Anatomy, Physiology, and Genetics, Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, Bethesda, MD, 20814, USA
| | - Jeremy T Smyth
- Department of Anatomy, Physiology, and Genetics, Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, Bethesda, MD, 20814, USA.
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11
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Molnar C, Heinen JP, Reina J, Llamazares S, Palumbo E, Breschi A, Gay M, Villarreal L, Vilaseca M, Pollarolo G, Gonzalez C. The histone code reader PHD finger protein 7 controls sex-linked disparities in gene expression and malignancy in Drosophila. SCIENCE ADVANCES 2019; 5:eaaw7965. [PMID: 31453329 PMCID: PMC6693905 DOI: 10.1126/sciadv.aaw7965] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 07/11/2019] [Indexed: 05/03/2023]
Abstract
The notable male predominance across many human cancer types remains unexplained. Here, we show that Drosophila l(3)mbt brain tumors are more invasive and develop as malignant neoplasms more often in males than in females. By quantitative proteomics, we have identified a signature of proteins that are differentially expressed between male and female tumor samples. Prominent among them is the conserved chromatin reader PHD finger protein 7 (Phf7). We show that Phf7 depletion reduces sex-dependent differences in gene expression and suppresses the enhanced malignant traits of male tumors. Our results identify potential regulators of sex-linked tumor dimorphism and show that these genes may serve as targets to suppress sex-linked malignant traits.
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Affiliation(s)
- Cristina Molnar
- IRB Barcelona, BIST, Carrer de Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Jan Peter Heinen
- IRB Barcelona, BIST, Carrer de Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Jose Reina
- IRB Barcelona, BIST, Carrer de Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Salud Llamazares
- IRB Barcelona, BIST, Carrer de Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Emilio Palumbo
- CRG, BIST, Carrer del Dr. Aiguader, 88, 08003 Barcelona, Spain
- UPF, Plaça de la Mercè, 10, 08002 Barcelona, Spain
- IMIM, Carrer del Dr. Aiguader, 88, 08003 Barcelona, Spain
| | | | - Marina Gay
- IRB Barcelona, BIST, Carrer de Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Laura Villarreal
- IRB Barcelona, BIST, Carrer de Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Marta Vilaseca
- IRB Barcelona, BIST, Carrer de Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Giulia Pollarolo
- IRB Barcelona, BIST, Carrer de Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Cayetano Gonzalez
- IRB Barcelona, BIST, Carrer de Baldiri Reixac, 10, 08028 Barcelona, Spain
- ICREA, Passeig Lluís Companys, 08010 Barcelona, Spain
- Corresponding author.
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12
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Finegan TM, Na D, Cammarota C, Skeeters AV, Nádasi TJ, Dawney NS, Fletcher AG, Oakes PW, Bergstralh DT. Tissue tension and not interphase cell shape determines cell division orientation in the Drosophila follicular epithelium. EMBO J 2019; 38:e100072. [PMID: 30478193 PMCID: PMC6356066 DOI: 10.15252/embj.2018100072] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2018] [Revised: 10/26/2018] [Accepted: 11/02/2018] [Indexed: 12/27/2022] Open
Abstract
We investigated the cell behaviors that drive morphogenesis of the Drosophila follicular epithelium during expansion and elongation of early-stage egg chambers. We found that cell division is not required for elongation of the early follicular epithelium, but drives the tissue toward optimal geometric packing. We examined the orientation of cell divisions with respect to the planar tissue axis and found a bias toward the primary direction of tissue expansion. However, interphase cell shapes demonstrate the opposite bias. Hertwig's rule, which holds that cell elongation determines division orientation, is therefore broken in this tissue. This observation cannot be explained by the anisotropic activity of the conserved Pins/Mud spindle-orienting machinery, which controls division orientation in the apical-basal axis and planar division orientation in other epithelial tissues. Rather, cortical tension at the apical surface translates into planar division orientation in a manner dependent on Canoe/Afadin, which links actomyosin to adherens junctions. These findings demonstrate that division orientation in different axes-apical-basal and planar-is controlled by distinct, independent mechanisms in a proliferating epithelium.
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Affiliation(s)
- Tara M Finegan
- Department of Biology, University of Rochester, Rochester, NY, USA
| | - Daxiang Na
- Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, NY, USA
| | - Christian Cammarota
- Department of Physics and Astronomy, University of Rochester, Rochester, NY, USA
| | - Austin V Skeeters
- Department of Physics and Astronomy, University of Rochester, Rochester, NY, USA
| | - Tamás J Nádasi
- Department of Biology, University of Rochester, Rochester, NY, USA
| | - Nicole S Dawney
- Department of Biology, University of Rochester, Rochester, NY, USA
| | - Alexander G Fletcher
- School of Mathematics and Statistics, University of Sheffield, Sheffield, UK
- Bateson Centre, University of Sheffield, Sheffield, UK
| | - Patrick W Oakes
- Department of Biology, University of Rochester, Rochester, NY, USA
- Department of Physics and Astronomy, University of Rochester, Rochester, NY, USA
| | - Dan T Bergstralh
- Department of Biology, University of Rochester, Rochester, NY, USA
- Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, NY, USA
- Department of Physics and Astronomy, University of Rochester, Rochester, NY, USA
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13
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Graziadio L, Palumbo V, Cipressa F, Williams BC, Cenci G, Gatti M, Goldberg ML, Bonaccorsi S. Phenotypic characterization of diamond (dind), a Drosophila gene required for multiple aspects of cell division. Chromosoma 2018; 127:489-504. [PMID: 30120539 DOI: 10.1007/s00412-018-0680-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 08/01/2018] [Accepted: 08/03/2018] [Indexed: 01/04/2023]
Abstract
Many genes are required for the assembly of the mitotic apparatus and for proper chromosome behavior during mitosis and meiosis. A fruitful approach to elucidate the mechanisms underlying cell division is the accurate phenotypic characterization of mutations in these genes. Here, we report the identification and characterization of diamond (dind), an essential Drosophila gene required both for mitosis of larval brain cells and for male meiosis. Larvae homozygous for any of the five EMS-induced mutations die in the third-instar stage and exhibit multiple mitotic defects. Mutant brain cells exhibit poorly condensed chromosomes and frequent chromosome breaks and rearrangements; they also show centriole fragmentation, disorganized mitotic spindles, defective chromosome segregation, endoreduplicated metaphases, and hyperploid and polyploid cells. Comparable phenotypes occur in mutant spermatogonia and spermatocytes. The dind gene encodes a non-conserved protein with no known functional motifs. Although the Dind protein exhibits a rather diffuse localization in both interphase and mitotic cells, fractionation experiments indicate that some Dind is tightly associated with the chromatin. Collectively, these results suggest that loss of Dind affects chromatin organization leading to defects in chromosome condensation and integrity, which in turn affect centriole stability and spindle assembly. However, our results do not exclude the possibility that Dind directly affects some behaviors of the spindle and centrosomes.
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Affiliation(s)
- Lucia Graziadio
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy
| | - Valeria Palumbo
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy
| | - Francesca Cipressa
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy.,Museo storico della fisica e centro di studi e ricerche Enrico Fermi, Rome, Italy
| | - Byron C Williams
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Giovanni Cenci
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy.,Istituto Pasteur Fondazione Cenci Bolognetti, Rome, Italy
| | - Maurizio Gatti
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy.,Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Rome, Italy
| | - Michael L Goldberg
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA.
| | - Silvia Bonaccorsi
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy.
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14
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Chaurasia S, Lehner CF. Dynamics and control of sister kinetochore behavior during the meiotic divisions in Drosophila spermatocytes. PLoS Genet 2018; 14:e1007372. [PMID: 29734336 PMCID: PMC5957430 DOI: 10.1371/journal.pgen.1007372] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 05/17/2018] [Accepted: 04/19/2018] [Indexed: 11/19/2022] Open
Abstract
Sister kinetochores are connected to the same spindle pole during meiosis I and to opposite poles during meiosis II. The molecular mechanisms controlling the distinct behavior of sister kinetochores during the two meiotic divisions are poorly understood. To study kinetochore behavior during meiosis, we have optimized time lapse imaging with Drosophila spermatocytes, enabling kinetochore tracking with high temporal and spatial resolution through both meiotic divisions. The correct bipolar orientation of chromosomes within the spindle proceeds rapidly during both divisions. Stable bi-orientation of the last chromosome is achieved within ten minutes after the onset of kinetochore-microtubule interactions. Our analyses of mnm and tef mutants, where univalents instead of bivalents are present during meiosis I, indicate that the high efficiency of normal bi-orientation depends on pronounced stabilization of kinetochore attachments to spindle microtubules by the mechanical tension generated by spindle forces upon bi-orientation. Except for occasional brief separation episodes, sister kinetochores are so closely associated that they cannot be resolved individually by light microscopy during meiosis I, interkinesis and at the start of meiosis II. Permanent evident separation of sister kinetochores during M II depends on spindle forces resulting from bi-orientation. In mnm and tef mutants, sister kinetochore separation can be observed already during meiosis I in bi-oriented univalents. Interestingly, however, this sister kinetochore separation is delayed until the metaphase to anaphase transition and depends on the Fzy/Cdc20 activator of the anaphase-promoting complex/cyclosome. We propose that univalent bi-orientation in mnm and tef mutants exposes a release of sister kinetochore conjunction that occurs also during normal meiosis I in preparation for bi-orientation of dyads during meiosis II. For production of oocytes and sperm, cells have to complete meiosis which includes two successive divisions. These divisions convert diploid cells with a maternal and a paternal copy of each chromosome into haploid cells with only one copy of each chromosome. Chromosome copy reduction requires regulation of sister kinetochore behavior during the meiotic divisions. Kinetochores are protein networks assembled at the start of divisions within the centromeric region of chromosomes. They provide attachment sites for spindle microtubules which in turn exert poleward pulling forces. During pre-meiotic S phase, each chromosome is duplicated into two closely associated sister chromatids. At the start of the first meiotic division, both sister chromatids together assemble only one functional kinetochore, permitting subsequent separation of paired homologous chromosomes to opposite spindle poles. In contrast, at the onset of the second meiotic division, each sister chromatid organizes its own kinetochore followed by separation of sister chromatids to opposite spindle poles. To analyze when and how sister kinetochores are individualized, we have improved time lapse imaging with Drosophila spermatocytes. Our analyses in normal and genetically altered spermatocytes suggest that the release of sister kinetochore conjunction occurs during the first meiotic division after activation of the anaphase promoting complex/cyclosome.
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Affiliation(s)
- Soumya Chaurasia
- Institute of Molecular Life Sciences (IMLS), University of Zurich, Zurich, Switzerland
| | - Christian F. Lehner
- Institute of Molecular Life Sciences (IMLS), University of Zurich, Zurich, Switzerland
- * E-mail:
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15
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Larsson VJ, Jafferali MH, Vijayaraghavan B, Figueroa RA, Hallberg E. Mitotic spindle assembly and γ-tubulin localisation depend on the integral nuclear membrane protein Samp1. J Cell Sci 2018. [PMID: 29514856 PMCID: PMC5963844 DOI: 10.1242/jcs.211664] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We have investigated a possible role for the inner nuclear membrane protein Samp1 (also known as TMEM201) in the mitotic machinery. Live-cell imaging showed that Samp1a–YFP (Samp1a is the short isoform of Samp1) distributed as filamentous structures in the mitotic spindle, partially colocalising with β-tubulin. Samp1 depletion resulted in an increased frequency of cells with signs of chromosomal mis-segregation and prolonged metaphase, indicating problems with spindle assembly and/or chromosomal alignment. Consistent with this, mitotic spindles in Samp1-depleted cells contained significantly lower levels of β-tubulin and γ-tubulin, phenotypes that were rescued by overexpression of Samp1a–YFP. We found that Samp1 can bind directly to γ-tubulin and that Samp1 co-precipitated with γ-tubulin and the HAUS6 subunit of the Augmin complex in live cells. The levels of HAUS6, in the mitotic spindle also decreased after Samp1 depletion. We show that Samp1 is involved in the recruitment of HAUS6 and γ-tubulin to the mitotic spindle. Samp1 is the first inner nuclear membrane protein shown to have a function in mitotic spindle assembly. Highlighted Article: The transmembrane inner nuclear membrane protein Samp1 has a functional role in recruitment of γ-tubulin to the mitotic spindle and correct spindle assembly.
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Affiliation(s)
- Veronica J Larsson
- Department of Neurochemistry, Stockholm University, SE-106 91 Stockholm, Sweden
| | | | | | - Ricardo A Figueroa
- Department of Neurochemistry, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Einar Hallberg
- Department of Neurochemistry, Stockholm University, SE-106 91 Stockholm, Sweden
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16
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Rossi F, Attolini CSO, Mosquera JL, Gonzalez C. Drosophila Larval Brain Neoplasms Present Tumour-Type Dependent Genome Instability. G3 (BETHESDA, MD.) 2018; 8:1205-1214. [PMID: 29467187 PMCID: PMC5873911 DOI: 10.1534/g3.117.300489] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 02/01/2018] [Indexed: 12/30/2022]
Abstract
Single nucleotide polymorphisms (SNPs) and copy number variants (CNVs) are found at different rates in human cancer. To determine if these genetic lesions appear in Drosophila tumors we have sequenced the genomes of 17 malignant neoplasms caused by mutations in l(3)mbt, brat, aurA, or lgl We have found CNVs and SNPs in all the tumors. Tumor-linked CNVs range between 11 and 80 per sample, affecting between 92 and 1546 coding sequences. CNVs are in average less frequent in l(3)mbt than in brat lines. Nearly half of the CNVs fall within the 10 to 100Kb range, all tumor samples contain CNVs larger that 100 Kb and some have CNVs larger than 1Mb. The rates of tumor-linked SNPs change more than 20-fold depending on the tumor type: at late time points brat, l(3)mbt, and aurA and lgl lines present median values of SNPs/Mb of exome of 0.16, 0.48, and 3.6, respectively. Higher SNP rates are mostly accounted for by C > A transversions, which likely reflect enhanced oxidative stress conditions in the affected tumors. Both CNVs and SNPs turn over rapidly. We found no evidence for selection of a gene signature affected by CNVs or SNPs in the cohort. Altogether, our results show that the rates of CNVs and SNPs, as well as the distribution of CNV sizes in this cohort of Drosophila tumors are well within the range of those reported for human cancer. Genome instability is therefore inherent to Drosophila malignant neoplastic growth at a variable extent that is tumor type dependent.
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Affiliation(s)
- Fabrizio Rossi
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Camille Stephan-Otto Attolini
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Jose Luis Mosquera
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10, 08028 Barcelona, Spain
| | - Cayetano Gonzalez
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10, 08028 Barcelona, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), 08010 Barcelona, Spain
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17
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Wang Z, Oppegard SC, Eddington DT, Cheng J. Effect of localized hypoxia on Drosophila embryo development. PLoS One 2017; 12:e0185267. [PMID: 28934338 PMCID: PMC5608372 DOI: 10.1371/journal.pone.0185267] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Accepted: 09/08/2017] [Indexed: 01/09/2023] Open
Abstract
Environmental stress, such as oxygen deprivation, affects various cellular activities and developmental processes. In this study, we directly investigated Drosophila embryo development in vivo while cultured on a microfluidic device, which imposed an oxygen gradient on the developing embryos. The designed microfluidic device enabled both temporal and spatial control of the local oxygen gradient applied to the live embryos. Time-lapse live cell imaging was used to monitor the morphology and cellular migration patterns as embryos were placed in various geometries relative to the oxygen gradient. Results show that pole cell movement and tail retraction during Drosophila embryogenesis are highly sensitive to oxygen concentrations. Through modeling, we also estimated the oxygen permeability across the Drosophila embryonic layers for the first time using parameters measured on our oxygen control device.
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Affiliation(s)
- Zhinan Wang
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Shawn C. Oppegard
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - David T. Eddington
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Jun Cheng
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
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18
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Lattao R, Kovács L, Glover DM. The Centrioles, Centrosomes, Basal Bodies, and Cilia of Drosophila melanogaster. Genetics 2017; 206:33-53. [PMID: 28476861 PMCID: PMC5419478 DOI: 10.1534/genetics.116.198168] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 03/24/2017] [Indexed: 12/19/2022] Open
Abstract
Centrioles play a key role in the development of the fly. They are needed for the correct formation of centrosomes, the organelles at the poles of the spindle that can persist as microtubule organizing centers (MTOCs) into interphase. The ability to nucleate cytoplasmic microtubules (MTs) is a property of the surrounding pericentriolar material (PCM). The centriole has a dual life, existing not only as the core of the centrosome but also as the basal body, the structure that templates the formation of cilia and flagellae. Thus the structure and functions of the centriole, the centrosome, and the basal body have an impact upon many aspects of development and physiology that can readily be modeled in Drosophila Centrosomes are essential to give organization to the rapidly increasing numbers of nuclei in the syncytial embryo and for the spatially precise execution of cell division in numerous tissues, particularly during male meiosis. Although mitotic cell cycles can take place in the absence of centrosomes, this is an error-prone process that opens up the fly to developmental defects and the potential of tumor formation. Here, we review the structure and functions of the centriole, the centrosome, and the basal body in different tissues and cultured cells of Drosophila melanogaster, highlighting their contributions to different aspects of development and cell division.
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Affiliation(s)
- Ramona Lattao
- Department of Genetics, University of Cambridge, CB2 3EH, United Kingdom
| | - Levente Kovács
- Department of Genetics, University of Cambridge, CB2 3EH, United Kingdom
| | - David M Glover
- Department of Genetics, University of Cambridge, CB2 3EH, United Kingdom
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19
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Microscopy Methods for Analysis of Spindle Dynamics in Meiotic Drosophila Spermatocytes. Methods Mol Biol 2017. [PMID: 28349402 DOI: 10.1007/978-1-4939-6340-9_15] [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
The spindle is a microtubule-based structure whose remodeling is required for partitioning the chromosomes and cytoplasm during meiosis. Characterizing microtubule behavior is fundamental to understanding how these tubulin polymers contribute to successful cell division. Here, a procedure is described for the imaging and analysis of spindle microtubule dynamics in cultures of living Drosophila melanogaster primary spermatocytes expressing tubulin tagged with enhanced green fluorescent protein. It employs time-lapse scanning confocal microscopy and the photobleaching of fiduciary marks onto fluorescently tagged microtubules. These labels are subsequently used to determine the sites and rates of kinetochore fiber growth and shrinkage during metaphase. This method can be readily applied to different microtubule populations, meiotic stages, and genetic backgrounds.
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20
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Amitosis of Polyploid Cells Regenerates Functional Stem Cells in the Drosophila Intestine. Cell Stem Cell 2017; 20:609-620.e6. [PMID: 28343984 DOI: 10.1016/j.stem.2017.02.012] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 12/06/2016] [Accepted: 02/16/2017] [Indexed: 01/06/2023]
Abstract
Organ fitness depends on appropriate maintenance of stem cell populations, and aberrations in functional stem cell numbers are associated with malignancies and aging. Symmetrical division is the best characterized mechanism of stem cell replacement, but other mechanisms could also be deployed, particularly in situations of high stress. Here, we show that after severe depletion, intestinal stem cells (ISCs) in the Drosophila midgut are replaced by spindle-independent ploidy reduction of cells in the enterocyte lineage through a process known as amitosis. Amitosis is also induced by the functional loss of ISCs coupled with tissue demand and in aging flies, underscoring the generality of this mechanism. However, we also found that random homologous chromosome segregation during ploidy reduction can expose deleterious mutations through loss of heterozygosity. Together, our results highlight amitosis as an unappreciated mechanism for restoring stem cell homeostasis, but one with some associated risk in animals carrying mutations.
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21
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Bergstralh DT, Lovegrove HE, Kujawiak I, Dawney NS, Zhu J, Cooper S, Zhang R, St Johnston D. Pins is not required for spindle orientation in the Drosophila wing disc. Development 2016; 143:2573-81. [PMID: 27287805 PMCID: PMC4958339 DOI: 10.1242/dev.135475] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 06/01/2016] [Indexed: 02/03/2023]
Abstract
In animal cells, mitotic spindles are oriented by the dynein/dynactin motor complex, which exerts a pulling force on astral microtubules. Dynein/dynactin localization depends on Mud/NUMA, which is typically recruited to the cortex by Pins/LGN. In Drosophila neuroblasts, the Inscuteable/Baz/Par-6/aPKC complex recruits Pins apically to induce vertical spindle orientation, whereas in epithelial cells Dlg recruits Pins laterally to orient the spindle horizontally. Here we investigate division orientation in the Drosophila imaginal wing disc epithelium. Live imaging reveals that spindle angles vary widely during prometaphase and metaphase, and therefore do not reliably predict division orientation. This finding prompted us to re-examine mutants that have been reported to disrupt division orientation in this tissue. Loss of Mud misorients divisions, but Inscuteable expression and aPKC, dlg and pins mutants have no effect. Furthermore, Mud localizes to the apical-lateral cortex of the wing epithelium independently of both Pins and cell cycle stage. Thus, Pins is not required in the wing disc because there are parallel mechanisms for Mud localization and hence spindle orientation, making it a more robust system than in other epithelia. Highlighted article: Mud (Drosophila NuMA), a crucial spindle orientation factor, does not require its binding partner Pins (Drosophila LGN) to localize or function in the Drosophila imaginal wing disc.
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Affiliation(s)
- Dan T Bergstralh
- The Gurdon Institute and the Department of Genetics, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Holly E Lovegrove
- The Gurdon Institute and the Department of Genetics, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Izabela Kujawiak
- The Gurdon Institute and the Department of Genetics, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Nicole S Dawney
- The Gurdon Institute and the Department of Genetics, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Jinwei Zhu
- National Center for Protein Science Shanghai, Shanghai Institute of Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Samantha Cooper
- The Gurdon Institute and the Department of Genetics, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Rongguang Zhang
- National Center for Protein Science Shanghai, Shanghai Institute of Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Daniel St Johnston
- The Gurdon Institute and the Department of Genetics, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
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22
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Savoian MS. Using Photobleaching to Measure Spindle Microtubule Dynamics in Primary Cultures of Dividing Drosophila Meiotic Spermatocytes. J Biomol Tech 2016; 26:66-73. [PMID: 25802491 DOI: 10.7171/jbt.15-2602-004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In dividing animal cells, a microtubule (MT)-based bipolar spindle governs chromosome movement. Current models propose that the spindle facilitates and/or generates translocating forces by regionally depolymerizing the kinetochore fibers (k-fibers) that bind each chromosome. It is unclear how conserved these sites and the resultant chromosome-moving mechanisms are between different dividing cell types because of the technical challenges of quantitatively studying MTs in many specimens. In particular, our knowledge of MT kinetics during the sperm-producing male meiotic divisions remains in its infancy. In this study, I use an easy-to-implement photobleaching-based assay for measuring spindle MT dynamics in primary cultures of meiotic spermatocytes isolated from the fruit fly Drosophila melanogaster. By use of standard scanning confocal microscopy features, fiducial marks were photobleached on fluorescent protein (FP)-tagged MTs. These were followed by time-lapse imaging during different division stages, and their displacement rates were calculated using public domain software. I find that k-fibers continually shorten at their poles during metaphase and anaphase A through the process of MT flux. Anaphase chromosome movement is complemented by Pac-Man, the shortening of the k-fiber at its chromosomal interface. Thus, Drosophila spermatocytes share the sites of spindle dynamism and mechanisms of chromosome movement with mitotic cells. The data reveal the applicability of the photobleaching assay for measuring MT dynamics in primary cultures. This approach can be readily applied to other systems.
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Affiliation(s)
- Matthew S Savoian
- Massey University, Institute of Fundamental Sciences, Palmerston North, New Zealand
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23
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Abstract
Life depends on cell proliferation and the accurate segregation of chromosomes, which are mediated by the microtubule (MT)-based mitotic spindle and ∼200 essential MT-associated proteins. Yet, a mechanistic understanding of how the mitotic spindle is assembled and achieves chromosome segregation is still missing. This is mostly due to the density of MTs in the spindle, which presumably precludes their direct observation. Recent insight has been gained into the molecular building plan of the metaphase spindle using bulk and single-molecule measurements combined with computational modeling. MT nucleation was uncovered as a key principle of spindle assembly, and mechanistic details about MT nucleation pathways and their coordination are starting to be revealed. Lastly, advances in studying spindle assembly can be applied to address the molecular mechanisms of how the spindle segregates chromosomes.
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Affiliation(s)
- Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544-1014;
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24
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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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25
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Lerit DA, Jordan HA, Poulton JS, Fagerstrom CJ, Galletta BJ, Peifer M, Rusan NM. Interphase centrosome organization by the PLP-Cnn scaffold is required for centrosome function. J Cell Biol 2015; 210:79-97. [PMID: 26150390 PMCID: PMC4494003 DOI: 10.1083/jcb.201503117] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cnn and PLP directly interact at two defined sites to coordinate the cell cycle–dependent rearrangement and scaffolding activity of the centrosome to permit normal centrosome organization, cell division, and embryonic viability. Pericentriolar material (PCM) mediates the microtubule (MT) nucleation and anchoring activity of centrosomes. A scaffold organized by Centrosomin (Cnn) serves to ensure proper PCM architecture and functional changes in centrosome activity with each cell cycle. Here, we investigate the mechanisms that spatially restrict and temporally coordinate centrosome scaffold formation. Focusing on the mitotic-to-interphase transition in Drosophila melanogaster embryos, we show that the elaboration of the interphase Cnn scaffold defines a major structural rearrangement of the centrosome. We identify an unprecedented role for Pericentrin-like protein (PLP), which localizes to the tips of extended Cnn flares, to maintain robust interphase centrosome activity and promote the formation of interphase MT asters required for normal nuclear spacing, centrosome segregation, and compartmentalization of the syncytial embryo. Our data reveal that Cnn and PLP directly interact at two defined sites to coordinate the cell cycle–dependent rearrangement and scaffolding activity of the centrosome to permit normal centrosome organization, cell division, and embryonic viability.
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Affiliation(s)
- Dorothy A Lerit
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Holly A Jordan
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - John S Poulton
- Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Carey J Fagerstrom
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Brian J Galletta
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Mark Peifer
- Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Nasser M Rusan
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
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26
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Abstract
This protocol describes a method to allograft Drosophila larval tissue into adult fly hosts that can be used to assay the tumorigenic potential of mutant tissues. The tissue of interest is dissected, loaded into a fine glass needle and implanted into a host. Upon implantation, nontransformed tissues do not overgrow beyond their normal size, but malignant tumors grow without limit, are invasive and kill the host. By using this method, Drosophila malignant tumors can be transplanted repeatedly, for years, and therefore they can be aged beyond the short life span of flies. Because several hosts can be implanted using different pieces from a single tumor, the method also allows the tumor mass to be increased to facilitate further studies that may require large amounts of tissue (i.e., genomics, proteomics and so on). This method also provides an operational definition of hyperplastic, benign and malignant growth. The injection procedure itself requires only ∼1 d. Tumor development can then be monitored until the death of the implanted hosts.
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27
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González C, Sedwick C. Cayetano González: mothers, daughters, stemness, and cancer. ACTA ACUST UNITED AC 2015; 208:254-5. [PMID: 25646082 PMCID: PMC4315249 DOI: 10.1083/jcb.2083pi] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
González studies centrosomal inheritance, asymmetric cell division, and cancer.
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28
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Savoian MS, Glover DM. Differing requirements for Augmin in male meiotic and mitotic spindle formation in Drosophila. Open Biol 2015; 4:140047. [PMID: 24829288 PMCID: PMC4042853 DOI: 10.1098/rsob.140047] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Animal cells divide using a microtubule-based, bipolar spindle. Both somatic, mitotic cells and sperm-producing male meiotic spermatocytes use centrosome-dependent and acentrosomal spindle-forming mechanisms. Here, we characterize the largely undefined, centrosome-independent spindle formation pathway used during male meiosis. Our live and fixed cell analyses of Drosophila spermatocytes reveal that acentrosomal microtubules are nucleated at kinetochores and in the vicinity of chromatin and that together these assemble into functional spindles. Mutational studies indicate that γ-tubulin and its extra-centrosomal targeting complex, Augmin, are vital for this process. In addition, Augmin facilitates efficient spindle assembly in the presence of centrosomes. In contrast to the pronounced recruitment of Augmin on spindles in other cell types, the complex is absent from those of spermatocytes but does accumulate on kinetochores. Polo kinase facilitates this kinetochore recruitment while inhibiting Augmin's spindle association, and this in turn dictates γ-tubulin distribution and spindle density. Polo's negative regulation of Augmin in male meiosis contrasts with its requirement in loading Augmin along mitotic spindles in somatic Drosophila cells. Together our data identify a novel mechanism of acentrosomal spindle formation in spermatocytes and reveal its divergence from that used in mitotic cells.
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Affiliation(s)
- Matthew S Savoian
- Department of Genetics, University of Cambridge, Downing Site, Cambridge CB2 3EH, UK
| | - David M Glover
- Department of Genetics, University of Cambridge, Downing Site, Cambridge CB2 3EH, UK
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Januschke J, Näthke I. Stem cell decisions: a twist of fate or a niche market? Semin Cell Dev Biol 2014; 34:116-23. [PMID: 24613913 PMCID: PMC4169664 DOI: 10.1016/j.semcdb.2014.02.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 02/24/2014] [Accepted: 02/26/2014] [Indexed: 12/28/2022]
Abstract
Extrinsic and intrinsic cues that impact on stem cell biology. The importance to establish methods that allow to compare spindle orientation measurements. Mechanisms of centrosome segregation in asymmetrically dividing cells.
Establishing and maintaining cell fate in the right place at the right time is a key requirement for normal tissue maintenance. Stem cells are at the core of this process. Understanding how stem cells balance self-renewal and production of differentiating cells is key for understanding the defects that underpin many diseases. Both, external cues from the environment and cell intrinsic mechanisms can control the outcome of stem cell division. The role of the orientation of stem cell division has emerged as an important mechanism for specifying cell fate decisions. Although, the alignment of cell divisions can dependent on spatial cues from the environment, maintaining stemness is not always linked to positioning of stem cells in a particular microenvironment or `niche'. Alternate mechanisms that could contribute to cellular memory include differential segregation of centrosomes in asymmetrically dividing cells.
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Affiliation(s)
- Jens Januschke
- Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
| | - Inke Näthke
- Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
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30
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LaFountain JR, Oldenbourg R. Kinetochore-driven outgrowth of microtubules is a central contributor to kinetochore fiber maturation in crane-fly spermatocytes. Mol Biol Cell 2014; 25:1437-45. [PMID: 24574457 PMCID: PMC4004593 DOI: 10.1091/mbc.e14-01-0008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
During meiosis I in crane-fly spermatocytes, the increase in microtubule density in K-fibers clearly originates at the kinetochore. The increased density first appears at the kinetochore, then elongates toward the pole, probably by addition of tubulin at microtubule plus ends anchored in the kinetochore. We use liquid crystal polarized light imaging to record the life histories of single kinetochore (K-) fibers in living crane-fly spermatocytes, from their origins as nascent K-fibers in early prometaphase to their fully matured form at metaphase, just before anaphase onset. Increased image brightness due to increased retardance reveals where microtubules are added during K-fiber formation. Analysis of experimentally generated bipolar spindles with only one centrosome, as well as of regular, bicentrosomal spindles, reveals that microtubule addition occurs at the kinetochore-proximal ends of K-fibers, and added polymer expands poleward, giving rise to the robust K-fibers of metaphase cells. These results are not compatible with a model for K-fiber formation in which microtubules are added to nascent fibers solely by repetitive “search and capture” of centrosomal microtubule plus ends. Our interpretation is that capture of centrosomal microtubules—when deployed—is limited to early stages in establishment of nascent K-fibers, which then mature through kinetochore-driven outgrowth. When kinetochore capture of centrosomal microtubules is not used, the polar ends of K-fibers grow outward from their kinetochores and usually converge to make a centrosome-free pole.
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Affiliation(s)
- James R LaFountain
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260 Cellular Dynamics Program, Marine Biological Laboratory, Woods Hole, MA 02543 Physics Department, Brown University, Providence, RI 02912
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Sitaram P, Hainline SG, Lee LA. Cytological analysis of spermatogenesis: live and fixed preparations of Drosophila testes. J Vis Exp 2014:e51058. [PMID: 24473184 DOI: 10.3791/51058] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Drosophila melanogaster is a powerful model system that has been widely used to elucidate a variety of biological processes. For example, studies of both the female and male germ lines of Drosophila have contributed greatly to the current understanding of meiosis as well as stem cell biology. Excellent protocols are available in the literature for the isolation and imaging of Drosophila ovaries and testes(3-12). Herein, methods for the dissection and preparation of Drosophila testes for microscopic analysis are described with an accompanying video demonstration. A protocol for isolating testes from the abdomen of adult males and preparing slides of live tissue for analysis by phase-contrast microscopy as well as a protocol for fixing and immunostaining testes for analysis by fluorescence microscopy are presented. These techniques can be applied in the characterization of Drosophila mutants that exhibit defects in spermatogenesis as well as in the visualization of subcellular localizations of proteins.
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Affiliation(s)
- Poojitha Sitaram
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center
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32
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The microcephaly protein Asp regulates neuroepithelium morphogenesis by controlling the spatial distribution of myosin II. Nat Cell Biol 2013; 15:1294-306. [PMID: 24142104 DOI: 10.1038/ncb2858] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 09/09/2013] [Indexed: 12/16/2022]
Abstract
Mutations in ASPM are the most frequent cause of microcephaly, a disorder characterized by reduced brain size at birth. ASPM is recognized as a major regulator of brain size, yet its role during neural development remains poorly understood. Moreover, the role of ASPM proteins in invertebrate brain morphogenesis has never been investigated. Here, we characterized the function of the Drosophila ASPM orthologue, Asp, and found that asp mutants present severe defects in brain size and neuroepithelium morphogenesis. We show that size reduction depends on the mitotic function of Asp, whereas regulation of tissue shape depends on an uncharacterized function. Asp interacts with myosin II regulating its polarized distribution along the apico-basal axis. In the absence of Asp, mislocalization of myosin II results in interkinetic nuclear migration and tissue architecture defects. We propose that Asp regulates neuroepithelium morphogenesis through myosin-II-mediated structural and mechanical processes to maintain force balance and tissue cohesiveness.
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Volpi S, Bongiorni S, Fabbretti F, Wakimoto BT, Prantera G. Drosophila rae1 is required for male meiosis and spermatogenesis. J Cell Sci 2013; 126:3541-51. [PMID: 23788425 DOI: 10.1242/jcs.111328] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Previous studies of RAE1, a conserved WD40 protein, in Schizosaccharomyces pombe and mouse revealed a role in mRNA export and cell cycle progression in mitotic cells. Studies of RAE1 in Drosophila showed that the protein localizes to the nuclear envelope and is required for progression through the G1 phase of the cell cycle but not RNA export in tissue culture cells. Drosophila RAE1 also plays an essential developmental role, as it is required for viability and synaptic growth regulation as a component of an E3 ubiquitin ligase complex. Here we describe characterization of a new Drosophila rae1 mutant that is viable but results in male sterility. The mutant showed striking defects in primary spermatocyte nuclear integrity, meiotic chromosome condensation, segregation, and spindle morphology. These defects led to a failure to complete meiosis but allowed several aspects of spermatid differentiation to proceed, including axoneme formation and elongation. A GFP-RAE1 fusion protein that rescued most of the cytological defects showed a dynamic localization to the nuclear envelope, chromatin and other structures depending on the stage of spermatogenesis. A role for RAE1 in male meiosis, as well as mitotic cells, was also indicated by the defects induced by expression of rae1-RNAi. These studies in Drosophila provide the first evidence for an essential meiotic role of RAE1, and thus define RAE1 as a protein required for both meiotic and mitotic cell cycles.
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Affiliation(s)
- Silvia Volpi
- Department of Ecology and Biology, University of Tuscia, Viterbo, Italy
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34
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Centrobin controls mother-daughter centriole asymmetry in Drosophila neuroblasts. Nat Cell Biol 2013; 15:241-8. [PMID: 23354166 DOI: 10.1038/ncb2671] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 12/07/2012] [Indexed: 12/23/2022]
Abstract
During interphase in Drosophila neuroblasts, the Centrobin (CNB)-positive daughter centriole retains pericentriolar material (PCM) and organizes an aster that is a key determinant of the orientation of cell division. Here we show that daughter centrioles depleted of CNB cannot fulfil this function whereas mother centrioles that carry ectopic CNB can. CNB co-precipitates with a set of centrosomal proteins that include γ-TUB, ANA2, CNN, SAS-4, ASL, DGRIP71, POLO and SAS-6. Following chemical inhibition of POLO or removal of three POLO phosphorylation sites present in CNB, the interphase microtubule aster is lost. These results demonstrate that centriolar CNB localization is both necessary and sufficient to enable centrioles to retain PCM and organize the interphase aster in Drosophila neuroblasts. They also reveal an interphase function for POLO in this process that seems to have co-opted part of the protein network involved in mitotic centrosome maturation.
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35
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Sitaram P, Anderson MA, Jodoin JN, Lee E, Lee LA. Regulation of dynein localization and centrosome positioning by Lis-1 and asunder during Drosophila spermatogenesis. Development 2012; 139:2945-54. [PMID: 22764052 DOI: 10.1242/dev.077511] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Dynein, a microtubule motor complex, plays crucial roles in cell-cycle progression in many systems. The LIS1 accessory protein directly binds dynein, although its precise role in regulating dynein remains unclear. Mutation of human LIS1 causes lissencephaly, a developmental brain disorder. To gain insight into the in vivo functions of LIS1, we characterized a male-sterile allele of the Drosophila homolog of human LIS1. We found that centrosomes do not properly detach from the cell cortex at the onset of meiosis in most Lis-1 spermatocytes; centrosomes that do break cortical associations fail to attach to the nucleus. In Lis-1 spermatids, we observed loss of attachments between the nucleus, basal body and mitochondria. The localization pattern of LIS-1 protein throughout Drosophila spermatogenesis mirrors that of dynein. We show that dynein recruitment to the nuclear surface and spindle poles is severely reduced in Lis-1 male germ cells. We propose that Lis-1 spermatogenesis phenotypes are due to loss of dynein regulation, as we observed similar phenotypes in flies null for Tctex-1, a dynein light chain. We have previously identified asunder (asun) as another regulator of dynein localization and centrosome positioning during Drosophila spermatogenesis. We now report that Lis-1 is a strong dominant enhancer of asun and that localization of LIS-1 in male germ cells is ASUN dependent. We found that Drosophila LIS-1 and ASUN colocalize and coimmunoprecipitate from transfected cells, suggesting that they function within a common complex. We present a model in which Lis-1 and asun cooperate to regulate dynein localization and centrosome positioning during Drosophila spermatogenesis.
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Affiliation(s)
- Poojitha Sitaram
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, U-4225 Medical Research Building III, 465 21st Avenue South, Nashville, TN 37232-8240, USA
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Meunier S, Vernos I. Microtubule assembly during mitosis - from distinct origins to distinct functions? J Cell Sci 2012; 125:2805-14. [PMID: 22736044 DOI: 10.1242/jcs.092429] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The mitotic spindle is structurally and functionally defined by its main component, the microtubules (MTs). The MTs making up the spindle have various functions, organization and dynamics: astral MTs emanate from the centrosome and reach the cell cortex, and thus have a major role in spindle positioning; interpolar MTs are the main constituent of the spindle and are key for the establishment of spindle bipolarity, chromosome congression and central spindle assembly; and kinetochore-fibers are MT bundles that connect the kinetochores with the spindle poles and segregate the sister chromatids during anaphase. The duplicated centrosomes were long thought to be the origin of all of these MTs. However, in the last decade, a number of studies have contributed to the identification of non-centrosomal pathways that drive MT assembly in dividing cells. These pathways are now known to be essential for successful spindle assembly and to participate in various processes such as K-fiber formation and central spindle assembly. In this Commentary, we review the recent advances in the field and discuss how different MT assembly pathways might cooperate to successfully form the mitotic spindle.
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Affiliation(s)
- Sylvain Meunier
- Microtubule Function and Cell Division group, Cell and Developmental Biology Program, Centre for Genomic Regulation (CRG) and UPF, Dr. Aiguader 88, 08003 Barcelona, Spain
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37
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Synergism between altered cortical polarity and the PI3K/TOR pathway in the suppression of tumour growth. EMBO Rep 2012; 13:157-62. [PMID: 22173033 DOI: 10.1038/embor.2011.230] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 11/07/2011] [Accepted: 11/08/2011] [Indexed: 12/13/2022] Open
Abstract
Loss of function of pins (partner of inscuteable) partially disrupts neuroblast (NB) polarity and asymmetric division, results in fewer and smaller NBs and inhibits Drosophila larval brain growth. Food deprivation also inhibits growth. However, we find that the combination of loss of function of pins and dietary restriction results in loss of NB asymmetry, overproliferation of Miranda-expressing cells, brain overgrowth and increased frequency of tumour growth on allograft transplantation. The same effects are observed in well-fed pins larvae that are mutant for pi3k (phosphatidylinositol 3-kinase) or exposed to the TOR inhibitor rapamycin. Thus, pathways that are sensitive to food deprivation and dependent on PI3K and TOR are essential to suppress tumour growth in Drosophila larval brains with compromised pins function. These results highlight an unexpected crosstalk whereby the normally growth-promoting, nutrient-sensing PI3K/TOR pathway suppresses tumour formation in neural stem cells with compromised cell polarity.
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38
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Kitazawa D, Yamaguchi M, Mori H, Inoue YH. COPI-mediated membrane trafficking is required for cytokinesis in Drosophila male meiotic divisions. J Cell Sci 2012; 125:3649-60. [DOI: 10.1242/jcs.103317] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The coatomer protein complex, COPI, mediates retrograde vesicle transport from the Golgi apparatus to the ER. Here, we investigated the meiotic phenotype of Drosophila spermatocytes expressing dsRNA of 52 genes encoding membrane trafficking-related factors. We identified COPI as an essential factor for male meiosis. In Drosophila male meiotic divisions, COPI is localized in the ER-Golgi intermediate compartment of tER-Golgi units scattered throughout the spermatocyte cytoplasm. Prior to chromosome segregation, the vesicles assemble at the spindle pole periphery through a poleward movement, mediated by minus-ended motor dynein along astral microtubules. At the end of each meiotic division, COPI-containing vesicles are equally partitioned between 2 daughter cells. Our present data strongly suggest that spermatocytes possess a regulatory mechanism, to fulfill equal inheritance of several types of membrane vesicles. Using testis-specific knockdown of COPI subunits or small GTPase Arf, or mutations of the γCOP gene, we examined the role of COPI in male meiosis. COPI depletion resulted in the failure of cytokinesis, through disrupted accumulation of essential proteins and lipid components at the cleavage furrow region. Furthermore, it caused a reduction in the number of overlapping central spindle microtubules, which are essential for cytokinesis. Drosophila spermatocytes construct ER-based intracellular structures associated with astral and spindle microtubules. COPI depletion resulted in severe disruption of these ER-based structures. Thus, we propose that COPI plays an important role in Drosophila male meiosis, not only through vesicle transport to the cleavage furrow region, but also via the formation of ER-based structures.
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39
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Duncan T, Wakefield JG. 50 ways to build a spindle: the complexity of microtubule generation during mitosis. Chromosome Res 2011; 19:321-33. [PMID: 21484448 DOI: 10.1007/s10577-011-9205-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The accurate segregation of duplicated chromosomes, essential for the development and viability of a eukaryotic organism, requires the formation of a robust microtubule (MT)-based spindle apparatus. Entry into mitosis or meiosis precipitates a cascade of signalling events which result in the activation of pathways responsible for a dramatic reorganisation of the MT cytoskeleton: through changes in the properties of MT-associated proteins, local concentrations of free tubulin dimer and through enhanced MT nucleation. The latter is generally thought to be driven by localisation and activation of γ-tubulin-containing complexes (γ-TuSC and γ-TuRC) at specific subcellular locations. For example, upon entering mitosis, animal cells concentrate γ-tubulin at centrosomes to tenfold the normal level during interphase, resulting in an aster-driven search and capture of chromosomes and bipolar mitotic spindle formation. Thus, in these cells, centrosomes have traditionally been perceived as the primary microtubule organising centre during spindle formation. However, studies in meiotic cells, plants and cell-free extracts have revealed the existence of complementary mechanisms of spindle formation, mitotic chromatin, kinetochores and nucleation from existing MTs or the cytoplasm can all contribute to a bipolar spindle apparatus. Here, we outline the individual known mechanisms responsible for spindle formation and formulate ideas regarding the relationship between them in assembling a functional spindle apparatus.
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Affiliation(s)
- Tommy Duncan
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
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40
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Cheng J, Tiyaboonchai A, Yamashita YM, Hunt AJ. Asymmetric division of cyst stem cells in Drosophila testis is ensured by anaphase spindle repositioning. Development 2011; 138:831-7. [PMID: 21303845 DOI: 10.1242/dev.057901] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Many stem cells divide asymmetrically to balance self-renewal and differentiation. In Drosophila testes, two stem cell populations, germline stem cells (GSCs) and somatic cyst stem cells (CySCs), cohere and regulate one another. Here, we report that CySCs divide asymmetrically through repositioning the mitotic spindle around anaphase. CySC spindle repositioning requires functional centrosomes, Dynein and the actin-membrane linker Moesin. Anaphase spindle repositioning is required to achieve high-fidelity asymmetric divisions in CySCs, thus maintaining both GSC and CySC numbers. We propose that dynamic spindle repositioning allows CySCs to divide asymmetrically while accommodating the structure of the GSCs they encapsulate.
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Affiliation(s)
- Jun Cheng
- Department of Biomedical Engineering, Center for Ultrafast Optical Science, 1101 Beal Ave., Ann Arbor, MI 48109, USA
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41
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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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42
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Riparbelli MG, Callaini G. Male gametogenesis without centrioles. Dev Biol 2010; 349:427-39. [PMID: 20974123 DOI: 10.1016/j.ydbio.2010.10.021] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 10/05/2010] [Accepted: 10/15/2010] [Indexed: 01/08/2023]
Abstract
The orientation of the mitotic spindle plays a central role in specifying stem cell-renewal by enabling interaction of the daughter cells with external cues: the daughter cell closest to the hub region is instructed to self-renew, whereas the distal one starts to differentiate. Here, we have analyzed male gametogenesis in DSas-4 Drosophila mutants and we have reported that spindle alignment and asymmetric divisions are properly executed in male germline stem cells that lack centrioles. Spermatogonial divisions also correctly proceed in the absence of centrioles, giving rise to cysts of 16 primary spermatocytes. By contrast, abnormal meiotic spindles assemble in primary spermatocytes. These results point to different requirements for centrioles during male gametogenesis of Drosophila. Spindle formation during germ cell mitosis may be successfully supported by an acentrosomal pathway that is inadequate to warrant the proper execution of meiosis.
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43
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Bergner LM, Hickman FE, Wood KH, Wakeman CM, Stone HH, Campbell TJ, Lightcap SB, Favors SM, Aldridge AC, Hales KG. A novel predicted bromodomain-related protein affects coordination between meiosis and spermiogenesis in Drosophila and is required for male meiotic cytokinesis. DNA Cell Biol 2010; 29:487-98. [PMID: 20491580 DOI: 10.1089/dna.2009.0989] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Temporal coordination of meiosis with spermatid morphogenesis is crucial for successful generation of mature sperm cells. We identified a recessive male sterile Drosophila melanogaster mutant, mitoshell, in which events of spermatid morphogenesis are initiated too early, before meiotic onset. Premature mitochondrial aggregation and fusion lead to an aberrant mitochondrial shell around premeiotic nuclei. Despite successful meiotic karyokinesis, improper mitochondrial localization in mitoshell testes is associated with defective astral central spindles and a lack of contractile rings, leading to meiotic cytokinesis failure. We mapped and cloned the mitoshell gene and found that it encodes a novel protein with a bromodomain-related region. It is conserved in some insect lineages. Bromodomains typically bind to histone acetyl-lysine residues and therefore are often associated with chromatin. The Mitoshell bromodomain-related region is predicted to have an alpha helical structure similar to that of bromodomains, but not all the crucial residues in the ligand-binding loops are conserved. We speculate that Mitoshell may participate in transcriptional regulation of spermatogenesis-specific genes, though perhaps with different ligand specificity compared to traditional bromodomains.
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Affiliation(s)
- Laura M Bergner
- Department of Biology, Davidson College , Davidson, NC 28035, USA
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44
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Kracklauer MP, Wiora HM, Deery WJ, Chen X, Bolival B, Romanowicz D, Simonette RA, Fuller MT, Fischer JA, Beckingham KM. The Drosophila SUN protein Spag4 cooperates with the coiled-coil protein Yuri Gagarin to maintain association of the basal body and spermatid nucleus. J Cell Sci 2010; 123:2763-72. [PMID: 20647369 DOI: 10.1242/jcs.066589] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Maintaining the proximity of centrosomes to nuclei is important in several cellular contexts, and LINC complexes formed by SUN and KASH proteins are crucial in this process. Here, we characterize the presumed Drosophila ortholog of the mammalian SUN protein, sperm-associated antigen 4 (Spag4, previously named Giacomo), and demonstrate that Spag4 is required for centriole and nuclear attachment during spermatogenesis. Production of spag4 mRNA is limited to the testis, and Spag4 protein shows a dynamic pattern of association with the germline nuclei, including a concentration of protein at the site of attachment of the single spermatid centriole. In the absence of Spag4, nuclei and centrioles or basal bodies (BBs) dissociate from each other after meiosis. This role of Spag4 in centriolar attachment does not involve either of the two KASH proteins of the Drosophila genome (Klarsicht and MSP-300), but does require the coiled-coil protein Yuri Gagarin. Yuri shows an identical pattern of localization at the nuclear surface to Spag4 during spermatogenesis, and epistasis studies show that the activities of Yuri and dynein-dynactin are downstream of spag4 in this centriole attachment pathway. The later defects in spermatogenesis seen for yuri and spag4 mutants are similar, suggesting they could be secondary to initial disruption of events at the nuclear surface.
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Affiliation(s)
- Martin P Kracklauer
- Institute for Cell and Molecular Biology and Section of Cell and Developmental Biology, The University of Texas at Austin, Austin, TX 78712, USA
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Müller-Reichert T, Greenan G, O’Toole E, Srayko M. The elegans of spindle assembly. Cell Mol Life Sci 2010; 67:2195-213. [PMID: 20339898 PMCID: PMC2883083 DOI: 10.1007/s00018-010-0324-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 02/17/2010] [Indexed: 11/26/2022]
Abstract
The Caenorhabditis elegans one-cell embryo is a powerful system in which to study microtubule organization because this large cell assembles both meiotic and mitotic spindles within the same cytoplasm over the course of 1 h in a stereotypical manner. The fertilized oocyte assembles two consecutive acentrosomal meiotic spindles that function to reduce the replicated maternal diploid set of chromosomes to a single-copy haploid set. The resulting maternal DNA then unites with the paternal DNA to form a zygotic diploid complement, around which a centrosome-based mitotic spindle forms. The early C. elegans embryo is amenable to live-cell imaging and electron tomography, permitting a detailed structural comparison of the meiotic and mitotic modes of spindle assembly.
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Affiliation(s)
| | - Garrett Greenan
- Max Planck Institute of Molecular Cell Biology and Genetics (MPICBG), Pfotenhauerstr. 108, 01307 Dresden, Germany
| | - Eileen O’Toole
- Boulder Laboratory for 3D Electron Microscopy of Cells, University of Colorado, Boulder, CO 80309 USA
| | - Martin Srayko
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9 Canada
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Debec A, Sullivan W, Bettencourt-Dias M. Centrioles: active players or passengers during mitosis? Cell Mol Life Sci 2010; 67:2173-94. [PMID: 20300952 PMCID: PMC2883084 DOI: 10.1007/s00018-010-0323-9] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 02/17/2010] [Indexed: 12/31/2022]
Abstract
Centrioles are cylinders made of nine microtubule (MT) triplets present in many eukaryotes. Early studies, where centrosomes were seen at the poles of the mitotic spindle led to their coining as "the organ for cell division". However, a variety of subsequent observational and functional studies showed that centrosomes might not always be essential for mitosis. Here we review the arguments in this debate. We describe the centriole structure and its distribution in the eukaryotic tree of life and clarify its role in the organization of the centrosome and cilia, with an historical perspective. An important aspect of the debate addressed in this review is how centrioles are inherited and the role of the spindle in this process. In particular, germline inheritance of centrosomes, such as their de novo formation in parthenogenetic species, poses many interesting questions. We finish by discussing the most likely functions of centrioles and laying out new research avenues.
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Affiliation(s)
- Alain Debec
- Polarity and Morphogenesis Group, Jacques Monod Institute, University Paris Diderot, UPMC Univ Paris 6, Bâtiment Buffon, 15 rue Hélène Brion, 75205, Paris Cedex 13, France.
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The Nup107-160 complex and gamma-TuRC regulate microtubule polymerization at kinetochores. Nat Cell Biol 2010; 12:164-9. [PMID: 20081840 PMCID: PMC2859955 DOI: 10.1038/ncb2016] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2009] [Accepted: 12/12/2009] [Indexed: 01/06/2023]
Abstract
The metazoan nuclear pore complex (NPC) disassembles during mitosis, and many of its constituents distribute onto spindles and kinetochores, including the Nup107-160 sub-complex1,2. We have found that Nup107-160 interacts with the γ-tubulin ring complex (γ-TuRC), an essential and conserved microtubule (MT) nucleator3,4, and recruits γ-TuRC to unattached kinetochores. Unattached kinetochores nucleate MTs in a manner that is regulated by the Ran GTPase5; such MTs contribute to the formation of kinetochore fibers (k-fibers)6, MT bundles connecting kinetochores to spindle poles. Our data indicate that Nup107-160 and γ-TuRC act cooperatively to promote spindle assembly through MTs nucleation at kinetochores: HeLa cells lacking Nup107-160 or γ-TuRC were profoundly deficient in kinetochore-associated MT nucleation. Moreover, co-precipitated Nup107-160/γ-TuRC complexes nucleate MT formation in assays using purified tubulin. While Ran did not regulate MTs nucleation by γ-TuRC alone, Nup107-160/γ-TuRC complexes required Ran-GTP for MT nucleation. Our observations collectively show that Nup107-160 promotes spindle assembly through Ran-GTP-regulated nucleation of MT by γ-TuRC at kinetochores, and reveal a novel relationship between nucleoporins and the MT cytoskeleton.
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Ninov N, Manjón C, Martín-Blanco E. Dynamic control of cell cycle and growth coupling by ecdysone, EGFR, and PI3K signaling in Drosophila histoblasts. PLoS Biol 2009; 7:e1000079. [PMID: 19355788 PMCID: PMC2672598 DOI: 10.1371/journal.pbio.1000079] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Accepted: 02/20/2009] [Indexed: 11/19/2022] Open
Abstract
Regulation of cell proliferation has been extensively studied in cultured cell systems that are characterized by coordinated growth and cell-cycle progression and relatively uniform cell size distribution. During the development of multicellular organisms, however, growth and division can be temporally uncoupled, and the signaling pathways that regulate these growth programs are poorly understood. A good model for analyzing proliferation control in such systems is the morphogenesis of the Drosophila adult abdominal epidermis by histoblasts. These cells undergo a series of temporally regulated transitions during which neither cell size nor division rate is constant. The proliferation of histoblasts during metamorphosis is uniquely amenable to clonal analysis in combination with live imaging. Thereby, we show that abdominal histoblasts, which grow while in G2 arrest during larval stages, enter a proliferative stage in the pupal period that is initiated by ecdysone-dependent string/Cdc25 phosphatase transcription. The proliferating histoblasts have preaccumulated stores of Cyclin E, which trigger an immediate S phase onset after mitosis. These rapid cell cycles lack a G1 phase and result in a progressive reduction of cell size. Eventually, the histoblasts proceed to a stage of slower proliferation that, in contrast to the preceding, depends on epidermal growth factor receptor (EGFR) signaling for progression through the G2/M transition and on insulin receptor/PI3K-mediated signaling for growth. These results uncover the developmentally programmed changes coupling the growth and proliferation of the histoblasts that form the abdominal epidermis of Drosophila. Histoblasts proceed through three distinct stages: growth without division, division without growth, and growth-coupled proliferation. Our identification of the signaling pathways and cell-cycle regulators that control these programs illustrates the power of in vivo time-lapse analyses after clone induction. It sets the stage for the comprehensive understanding of the coordination of cell growth and cell-cycle progression in complex multicellular eukaryotes. A fundamental issue in biology is the question of how the rate of cell division is coupled to cell growth. Coordination of these processes has been studied extensively in cultured cell systems but to a much lesser extent in intact organisms. To study this phenomenon in a physiological setting, we developed a methodology to observe and manipulate cell division and growth in a population of Drosophila abdominal cells called histoblasts. The various developmental stages of histoblast morphogenesis include exit from cell-cycle arrest, initially rapid growth in the absence of cell division, and subsequent coupling of proliferation and growth. We identified several critical developmental signaling pathways (including signaling via ecdysone, the EGF receptor, and PI 3-kinase) that regulate and coordinate cell growth and division cycles during these different types of cell-cycle phenomena. We propose that the internal logic of the Drosophila histoblast system may serve as a basic framework for understanding not only how coordinated cell growth and division operate in a number of other developmental contexts, but also how misregulation of cell growth and division occurs in contexts such as cancer cell populations. Integration of the ecdysone, EGF receptor, and PI 3-kinase signaling pathways determines the relative rates of growth and cell division duringDrosophila abdominal cell morphogenesis.
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Wainman A, Creque J, Williams B, Williams EV, Bonaccorsi S, Gatti M, Goldberg ML. Roles of the Drosophila NudE protein in kinetochore function and centrosome migration. J Cell Sci 2009; 122:1747-58. [PMID: 19417004 DOI: 10.1242/jcs.041798] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We examined the distribution of the dynein-associated protein NudE in Drosophila larval brain neuroblasts and spermatocytes, and analyzed the phenotypic consequences of a nudE null mutation. NudE can associate with kinetochores, spindles and the nuclear envelope. In nudE mutant brain mitotic cells, centrosomes are often detached from the poles. Moreover, the centrosomes of mutant primary spermatocytes do not migrate from the cell cortex to the nuclear envelope, establishing a new role for NudE. In mutant neuroblasts, chromosomes fail to congress to a tight metaphase plate, and cell division arrests because of spindle assembly checkpoint (SAC) activation. The targeting of NudE to mitotic kinetochores requires the dynein-interacting protein Lis1, and surprisingly Cenp-meta, a Drosophila CENP-E homolog. NudE is non-essential for the targeting of all mitotic kinetochore components tested. However, in the absence of NudE, the 'shedding' of proteins off the kinetochore is abrogated and the SAC cannot be turned off, implying that NudE regulates dynein function at the kinetochore.
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Affiliation(s)
- Alan Wainman
- Instituto Pasteur Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Sapienza, Università di Roma, 00185 Rome, Italy
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Delattre M, Félix MA. The evolutionary context of robust and redundant cell biological mechanisms. Bioessays 2009; 31:537-45. [DOI: 10.1002/bies.200800215] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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