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Salvador-Garcia D, Jin L, Hensley A, Gölcük M, Gallaud E, Chaaban S, Port F, Vagnoni A, Planelles-Herrero VJ, McClintock MA, Derivery E, Carter AP, Giet R, Gür M, Yildiz A, Bullock SL. A force-sensitive mutation reveals a non-canonical role for dynein in anaphase progression. J Cell Biol 2024; 223:e202310022. [PMID: 38949648 PMCID: PMC11215527 DOI: 10.1083/jcb.202310022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 04/29/2024] [Accepted: 06/18/2024] [Indexed: 07/02/2024] Open
Abstract
The diverse roles of the dynein motor in shaping microtubule networks and cargo transport complicate in vivo analysis of its functions significantly. To address this issue, we have generated a series of missense mutations in Drosophila Dynein heavy chain. We show that mutations associated with human neurological disease cause a range of defects, including impaired cargo trafficking in neurons. We also describe a novel microtubule-binding domain mutation that specifically blocks the metaphase-anaphase transition during mitosis in the embryo. This effect is independent from dynein's canonical role in silencing the spindle assembly checkpoint. Optical trapping of purified dynein complexes reveals that this mutation only compromises motor performance under load, a finding rationalized by the results of all-atom molecular dynamics simulations. We propose that dynein has a novel function in anaphase progression that depends on it operating in a specific load regime. More broadly, our work illustrates how in vivo functions of motors can be dissected by manipulating their mechanical properties.
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Affiliation(s)
- David Salvador-Garcia
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Li Jin
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Andrew Hensley
- Department of Physics, University of California, Berkeley, Berkeley, CA, USA
| | - Mert Gölcük
- School of Mechanical Engineering, Istanbul Technical University, Istanbul, Turkey
| | - Emmanuel Gallaud
- Institut de Génétique et Développement de Rennes, Université de Rennes, Rennes, France
| | - Sami Chaaban
- Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Fillip Port
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Alessio Vagnoni
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | | | - Mark A. McClintock
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Emmanuel Derivery
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Andrew P. Carter
- Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Régis Giet
- Institut de Génétique et Développement de Rennes, Université de Rennes, Rennes, France
| | - Mert Gür
- School of Mechanical Engineering, Istanbul Technical University, Istanbul, Turkey
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ahmet Yildiz
- Department of Physics, University of California, Berkeley, Berkeley, CA, USA
- Department of Molecular and Cellular Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Simon L. Bullock
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
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2
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Salvador-Garcia D, Jin L, Hensley A, Gölcük M, Gallaud E, Chaaban S, Port F, Vagnoni A, Planelles-Herrero VJ, McClintock MA, Derivery E, Carter AP, Giet R, Gür M, Yildiz A, Bullock SL. A force-sensitive mutation reveals a spindle assembly checkpoint-independent role for dynein in anaphase progression. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.03.551815. [PMID: 37577480 PMCID: PMC10418259 DOI: 10.1101/2023.08.03.551815] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
The cytoplasmic dynein-1 (dynein) motor organizes cells by shaping microtubule networks and moving a large variety of cargoes along them. However, dynein's diverse roles complicate in vivo studies of its functions significantly. To address this issue, we have used gene editing to generate a series of missense mutations in Drosophila Dynein heavy chain (Dhc). We find that mutations associated with human neurological disease cause a range of defects in larval and adult flies, including impaired cargo trafficking in neurons. We also describe a novel mutation in the microtubule-binding domain (MTBD) of Dhc that, remarkably, causes metaphase arrest of mitotic spindles in the embryo but does not impair other dynein-dependent processes. We demonstrate that the mitotic arrest is independent of dynein's well-established roles in silencing the spindle assembly checkpoint. In vitro reconstitution and optical trapping assays reveal that the mutation only impairs the performance of dynein under load. In silico all-atom molecular dynamics simulations show that this effect correlates with increased flexibility of the MTBD, as well as an altered orientation of the stalk domain, with respect to the microtubule. Collectively, our data point to a novel role of dynein in anaphase progression that depends on the motor operating in a specific load regime. More broadly, our work illustrates how cytoskeletal transport processes can be dissected in vivo by manipulating mechanical properties of motors.
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Affiliation(s)
| | - Li Jin
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Andrew Hensley
- Department of Physics, University of California at Berkeley, Berkeley, CA 94720, USA
| | - Mert Gölcük
- Department of Mechanical Engineering, Istanbul Technical University, Istanbul, 34437, Turkey
| | - Emmanuel Gallaud
- Institut de Génétique et Développement de Rennes - UMR 6290, Université de Rennes, F-35000 Rennes, France
| | - Sami Chaaban
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Fillip Port
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
- Current address: Division of Signaling and Functional Genomics, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Alessio Vagnoni
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
- Current address: Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, SE5 9RX, UK
| | | | - Mark A. McClintock
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Emmanuel Derivery
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Andrew P. Carter
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Régis Giet
- Institut de Génétique et Développement de Rennes - UMR 6290, Université de Rennes, F-35000 Rennes, France
| | - Mert Gür
- Department of Mechanical Engineering, Istanbul Technical University, Istanbul, 34437, Turkey
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Ahmet Yildiz
- Department of Physics, University of California at Berkeley, Berkeley, CA 94720, USA
- Department of Molecular and Cellular Biology, University of California at Berkeley, Berkeley, CA 94720, USA
| | - Simon L. Bullock
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
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3
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Vaishali, Dimitrova-Paternoga L, Haubrich K, Sun M, Ephrussi A, Hennig J. Validation and classification of RNA binding proteins identified by mRNA interactome capture. RNA (NEW YORK, N.Y.) 2021; 27:1173-1185. [PMID: 34215685 PMCID: PMC8456996 DOI: 10.1261/rna.078700.121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 06/29/2021] [Indexed: 06/13/2023]
Abstract
RNA binding proteins (RBPs) take part in all steps of the RNA life cycle and are often essential for cell viability. Most RBPs have a modular organization and comprise a set of canonical RNA binding domains. However, in recent years a number of high-throughput mRNA interactome studies on yeast, mammalian cell lines, and whole organisms have uncovered a multitude of novel mRNA interacting proteins that lack classical RNA binding domains. Whereas a few have been confirmed to be direct and functionally relevant RNA binders, biochemical and functional validation of RNA binding of most others is lacking. In this study, we used a combination of NMR spectroscopy and biochemical studies to test the RNA binding properties of six putative RBPs. Half of the analyzed proteins showed no interaction, whereas the other half displayed weak chemical shift perturbations upon titration with RNA. One of the candidates we found to interact weakly with RNA in vitro is Drosophila melanogaster end binding protein 1 (EB1), a master regulator of microtubule plus-end dynamics. Further analysis showed that EB1's RNA binding occurs on the same surface as that with which EB1 interacts with microtubules. RNA immunoprecipitation and colocalization experiments suggest that EB1 is a rather nonspecific, opportunistic RNA binder. Our data suggest that care should be taken when embarking on an RNA binding study involving these unconventional, novel RBPs, and we recommend initial and simple in vitro RNA binding experiments.
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Affiliation(s)
- Vaishali
- Developmental Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
- Faculty of Biosciences, Heidelberg University, Heidelberg 69120, Germany
| | - Lyudmila Dimitrova-Paternoga
- Developmental Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
- Structural and Computational Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Kevin Haubrich
- Structural and Computational Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Mai Sun
- Genome Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Janosch Hennig
- Structural and Computational Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
- Biochemistry IV, Biophysical Chemistry, University of Bayreuth, 95447 Bayreuth, Germany
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4
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Tao X, Dou Y, Huang G, Sun M, Lu S, Chen D. α-Tubulin Regulates the Fate of Germline Stem Cells in Drosophila Testis. Sci Rep 2021; 11:10644. [PMID: 34017013 PMCID: PMC8138004 DOI: 10.1038/s41598-021-90116-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 05/04/2021] [Indexed: 12/02/2022] Open
Abstract
The Drosophila testis provides an exemplary model for analyzing the extrinsic and intrinsic factors that regulate the fate of stem cell in vivo. Using this model, we show that the Drosophila αTub67C gene (full name αTubulin at 67C), which encodes α4-Tubulin (a type of α-Tubulin), plays a new role in controlling the fate of male germline stem cells (GSC). In this study, we have found that Drosophila α4-Tubulin is required intrinsically and extrinsically for GSCs maintenance. Results from green fluorescent protein (GFP)-transgene reporter assays show that the gene αTub67C is not required for Dpp/Gbb signaling silencing of bam expression, suggesting that αTub67C functions downstream of or parallel to bam, and is independent of Gbb/Dpp-bam signaling pathway. Furthermore, overexpression of αTub67C fails to obviously increase the number of GSC/Gonialblast (GB). Given that the α-tubulin genes are evolutionarily conserved from yeast to human, which triggers us to study the more roles of the gene α-tubulin in other animals in the future.
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Affiliation(s)
- Xiaoqian Tao
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, 241000, China
| | - Yunqiao Dou
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, 241000, China.,Anhui Provincial Key Laboratory of Molecular Enzymology and Mechanism of Major Diseases, College of Life Sciences, Anhui Normal University, Wuhu, 241000, China
| | - Guangyu Huang
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, 241000, China.,Anhui Provincial Key Laboratory of Molecular Enzymology and Mechanism of Major Diseases, College of Life Sciences, Anhui Normal University, Wuhu, 241000, China
| | - Mingzhong Sun
- Anhui Provincial Key Laboratory of Molecular Enzymology and Mechanism of Major Diseases, College of Life Sciences, Anhui Normal University, Wuhu, 241000, China
| | - Shan Lu
- Anhui Provincial Key Laboratory of Molecular Enzymology and Mechanism of Major Diseases, College of Life Sciences, Anhui Normal University, Wuhu, 241000, China
| | - Dongsheng Chen
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, 241000, China. .,Anhui Provincial Key Laboratory of Molecular Enzymology and Mechanism of Major Diseases, College of Life Sciences, Anhui Normal University, Wuhu, 241000, China. .,College of Life Sciences, The Institute of Bioinformatics, Anhui Normal University, Wuhu, 241000, China.
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5
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Blake-Hedges C, Megraw TL. Coordination of Embryogenesis by the Centrosome in Drosophila melanogaster. Results Probl Cell Differ 2019; 67:277-321. [PMID: 31435800 PMCID: PMC11725063 DOI: 10.1007/978-3-030-23173-6_12] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The first 3 h of Drosophila melanogaster embryo development are exemplified by rapid nuclear divisions within a large syncytium, transforming the zygote to the cellular blastoderm after 13 successive cleavage divisions. As the syncytial embryo develops, it relies on centrosomes and cytoskeletal dynamics to transport nuclei, maintain uniform nuclear distribution throughout cleavage cycles, ensure generation of germ cells, and coordinate cellularization. For the sake of this review, we classify six early embryo stages that rely on processes coordinated by the centrosome and its regulation of the cytoskeleton. The first stage features migration of one of the female pronuclei toward the male pronucleus following maturation of the first embryonic centrosomes. Two subsequent stages distribute the nuclei first axially and then radially in the embryo. The remaining three stages involve centrosome-actin dynamics that control cortical plasma membrane morphogenesis. In this review, we highlight the dynamics of the centrosome and its role in controlling the six stages that culminate in the cellularization of the blastoderm embryo.
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Affiliation(s)
- Caitlyn Blake-Hedges
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA.
| | - Timothy L Megraw
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA
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6
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Yu D, Tan Y, Chakraborty M, Tomchik S, Davis RL. Elongator complex is required for long-term olfactory memory formation in Drosophila. Learn Mem 2018; 25:183-196. [PMID: 29545390 PMCID: PMC5855525 DOI: 10.1101/lm.046557.117] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 01/12/2018] [Indexed: 12/13/2022]
Abstract
The evolutionarily conserved Elongator Complex associates with RNA polymerase II for transcriptional elongation. Elp3 is the catalytic subunit, contains histone acetyltransferase activity, and is associated with neurodegeneration in humans. Elp1 is a scaffolding subunit and when mutated causes familial dysautonomia. Here, we show that elp3 and elp1 are required for aversive long-term olfactory memory in Drosophila RNAi knockdown of elp3 in adult mushroom bodies impairs long-term memory (LTM) without affecting earlier forms of memory. RNAi knockdown with coexpression of elp3 cDNA reverses the impairment. Similarly, RNAi knockdown of elp1 impairs LTM and coexpression of elp1 cDNA reverses this phenotype. The LTM deficit in elp3 and elp1 knockdown flies is accompanied by the abolishment of a LTM trace, which is registered as increased calcium influx in response to the CS+ odor in the α-branch of mushroom body neurons. Coexpression of elp1 or elp3 cDNA rescues the memory trace in parallel with LTM. These data show that the Elongator complex is required in adult mushroom body neurons for long-term behavioral memory and the associated long-term memory trace.
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Affiliation(s)
- Dinghui Yu
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030, USA
| | - Ying Tan
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Molee Chakraborty
- Department of Neuroscience, Scripps Research Institute Florida, Jupiter, Florida 33458, USA
| | - Seth Tomchik
- Department of Neuroscience, Scripps Research Institute Florida, Jupiter, Florida 33458, USA
| | - Ronald L Davis
- Department of Neuroscience, Scripps Research Institute Florida, Jupiter, Florida 33458, USA
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7
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Ververis A, Christodoulou A, Christoforou M, Kamilari C, Lederer CW, Santama N. A novel family of katanin-like 2 protein isoforms (KATNAL2), interacting with nucleotide-binding proteins Nubp1 and Nubp2, are key regulators of different MT-based processes in mammalian cells. Cell Mol Life Sci 2016; 73:163-84. [PMID: 26153462 PMCID: PMC11108477 DOI: 10.1007/s00018-015-1980-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Revised: 06/08/2015] [Accepted: 06/25/2015] [Indexed: 11/30/2022]
Abstract
Katanins are microtubule (MT)-severing AAA proteins with high phylogenetic conservation throughout the eukaryotes. They have been functionally implicated in processes requiring MT remodeling, such as spindle assembly in mitosis and meiosis, assembly/disassembly of flagella and cilia and neuronal morphogenesis. Here, we uncover a novel family of katanin-like 2 proteins (KATNAL2) in mouse, consisting of five alternatively spliced isoforms encoded by the Katnal2 genomic locus. We further demonstrate that in vivo these isoforms are able to interact with themselves, with each other and moreover directly and independently with MRP/MinD-type P-loop NTPases Nubp1 and Nubp2, which are integral components of centrioles, negative regulators of ciliogenesis and implicated in centriole duplication in mammalian cells. We find KATNAL2 localized on interphase MTs, centrioles, mitotic spindle, midbody and the axoneme and basal body of sensory cilia in cultured murine cells. shRNAi of Katnal2 results in inefficient cytokinesis and severe phenotypes of enlarged cells and nuclei, increased numbers of centrioles and the manifestation of aberrant multipolar mitotic spindles, mitotic defects, chromosome bridges, multinuclearity, increased MT acetylation and an altered cell cycle pattern. Silencing or stable overexpression of KATNAL2 isoforms drastically reduces ciliogenesis. In conclusion, KATNAL2s are multitasking enzymes involved in the same cell type in critically important processes affecting cytokinesis, MT dynamics, and ciliogenesis and are also implicated in cell cycle progression.
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Affiliation(s)
- Antonis Ververis
- Department of Biological Sciences, University of Cyprus, University Avenue 1, 1678, Nicosia, Cyprus
| | - Andri Christodoulou
- Department of Biological Sciences, University of Cyprus, University Avenue 1, 1678, Nicosia, Cyprus
| | - Maria Christoforou
- Department of Biological Sciences, University of Cyprus, University Avenue 1, 1678, Nicosia, Cyprus
| | - Christina Kamilari
- Department of Biological Sciences, University of Cyprus, University Avenue 1, 1678, Nicosia, Cyprus
| | | | - Niovi Santama
- Department of Biological Sciences, University of Cyprus, University Avenue 1, 1678, Nicosia, Cyprus.
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8
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Fahmy K, Akber M, Cai X, Koul A, Hayder A, Baumgartner S. αTubulin 67C and Ncd are essential for establishing a cortical microtubular network and formation of the Bicoid mRNA gradient in Drosophila. PLoS One 2014; 9:e112053. [PMID: 25390693 DOI: 10.1371/journal.pone.0112053] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 10/10/2014] [Indexed: 11/18/2022] Open
Abstract
The Bicoid (Bcd) protein gradient in Drosophila serves as a paradigm for gradient formation in textbooks. To explain the generation of the gradient, the ARTS model, which is based on the observation of a bcd mRNA gradient, proposes that the bcd mRNA, localized at the anterior pole at fertilization, migrates along microtubules (MTs) at the cortex to the posterior to form a bcd mRNA gradient which is translated to form a protein gradient. To fulfil the criteria of the ARTS model, an early cortical MT network is thus a prerequisite. We report hitherto undiscovered MT activities in the early embryo important for bcd mRNA transport: (i) an early and omnidirectional MT network exclusively at the anterior cortex of early nuclear cycle embryos showing activity during metaphase and anaphase only, (ii) long MTs up to 50 µm extending into the yolk at blastoderm stage to enable basal-apical transport. The cortical MT network is not anchored to the actin cytoskeleton. The posterior transport of the mRNA via the cortical MT network critically depends on maternally-expressed αTubulin67C and the minus-end motor Ncd. In either mutant, cortical transport of the bcd mRNA does not take place and the mRNA migrates along another yet undisclosed interior MT network, instead. Our data strongly corroborate the ARTS model and explain the occurrence of the bcd mRNA gradient.
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Affiliation(s)
- Khalid Fahmy
- Department of Experimental Medical Sciences, Lund University, Lund, Sweden
| | - Mira Akber
- Department of Experimental Medical Sciences, Lund University, Lund, Sweden
| | - Xiaoli Cai
- Department of Experimental Medical Sciences, Lund University, Lund, Sweden
| | - Aabid Koul
- Department of Experimental Medical Sciences, Lund University, Lund, Sweden
| | - Awais Hayder
- Department of Experimental Medical Sciences, Lund University, Lund, Sweden
| | - Stefan Baumgartner
- Department of Experimental Medical Sciences, Lund University, Lund, Sweden
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9
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Szikora S, Gaspar I, Szabad J. 'Poking' microtubules bring about nuclear wriggling to position nuclei. J Cell Sci 2012; 126:254-62. [PMID: 23077179 DOI: 10.1242/jcs.114355] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nuclei wriggle in the cells of the follicle epithelium of the Drosophila pre-vitellogenic egg primordia. Although similar phenomena have been reported for a number of cultured cell types and some neurons in the zebrafish embryo, the mechanism and importance of the process have remained unexplained. Wriggling involves successive sudden and random minor turns of the nuclei, approximately three twists per minute with roughly 12° per twist, one of which lasts typically for 14 seconds. Wriggling is generated by the growing microtubules seeded throughout the cell cortex, which, while poking the nuclei, buckle and exert 5-40 piconewtons over ∼16 seconds. While wriggling, the nuclei drift ∼5 µm in a day in the immensely growing follicle cells along the apical-basal axis from the apical to the basal cell region. A >2-fold excess of the microtubules nucleated in the apical cell region, as compared with those seeded in the basal cell cortex, makes the nuclei drift along the apical-basal axis. Nuclear wriggling and positioning appear to be tightly related processes: they cease simultaneously when the nuclei become anchored by the actin cytoskeleton; moreover, colchicine or taxol treatment eliminates both nuclear wriggling and positioning. We propose that the wriggling nuclei reveal a thus far undescribed nuclear positioning mechanism.
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Affiliation(s)
- Szilard Szikora
- Department of Biology, University of Szeged, H-6720 Szeged, Hungary
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10
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Gaspar I, Szabad J. Glu415 in the alpha-tubulins plays a key role in stabilizing the microtubule-ADP-kinesin complexes. J Cell Sci 2009; 122:2857-65. [PMID: 19622631 DOI: 10.1242/jcs.050252] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Kavar(21g), a dominant female-sterile mutation of Drosophila, identifies the alphaTubulin67C gene that encodes alpha4-tubulin, the maternally provided alpha-tubulin isoform. Although alpha4-tubulin is synthesized during oogenesis, its function is required only in the early cleavage embryos. However, once present in the developing oocyte, much of the alpha4-tubulin and the Kavar(21g)-encoded E426K-alpha4-tubulin molecules become incorporated into the microtubules. We analyzed ooplasmic streaming and lipid-droplet transport, with confocal reflection microscopy, in the developing egg primordia in the presence and absence of alpha4-tubulin and E426K-alpha4-tubulin and learnt that the E426K-alpha4-tubulin molecules eliminate ooplasmic streaming and alter lipid-droplet transport. Apparently, Glu426 is involved in stabilization of the microtubule-kinesin complexes when the kinesins are in the most labile, ADP-bound state. Replacement of Glu426 by Lys results in frequent detachments of the kinesins from the microtubules leading to reduced transport efficiency and death of the embryos derived from the Kavar(21g)-carrying females. Glu426 is a component of the twelfth alpha-helix, which is the landing and binding platform for the mechanoenzymes. Since the twelfth alpha-helix is highly conserved in the alpha-tubulin family, Glu415, which corresponds to Glu426 in the constitutively expressed alpha-tubulins, seems be a key component of microtubule-kinesin interaction and thus the microtubule-based transport.
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Affiliation(s)
- Imre Gaspar
- University of Szeged, Faculty of Medicine, Department of Biology, Szeged, Hungary
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11
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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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12
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Gáspár I, Szabad J. In vivo analysis of MT-based vesicle transport by confocal reflection microscopy. ACTA ACUST UNITED AC 2009; 66:68-79. [DOI: 10.1002/cm.20334] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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13
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Affiliation(s)
- Arthur Forer
- Biology Department, York University, Toronto, Canada
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14
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Zhang J, Megraw TL. Proper recruitment of gamma-tubulin and D-TACC/Msps to embryonic Drosophila centrosomes requires Centrosomin Motif 1. Mol Biol Cell 2007; 18:4037-49. [PMID: 17671162 PMCID: PMC1995719 DOI: 10.1091/mbc.e07-05-0474] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Centrosomes are microtubule-organizing centers and play a dominant role in assembly of the microtubule spindle apparatus at mitosis. Although the individual binding steps in centrosome maturation are largely unknown, Centrosomin (Cnn) is an essential mitotic centrosome component required for assembly of all other known pericentriolar matrix (PCM) proteins to achieve microtubule-organizing activity at mitosis in Drosophila. We have identified a conserved motif (Motif 1) near the amino terminus of Cnn that is essential for its function in vivo. Cnn Motif 1 is necessary for proper recruitment of gamma-tubulin, D-TACC (the homolog of vertebrate transforming acidic coiled-coil proteins [TACC]), and Minispindles (Msps) to embryonic centrosomes but is not required for assembly of other centrosome components including Aurora A kinase and CP60. Centrosome separation and centrosomal satellite formation are severely disrupted in Cnn Motif 1 mutant embryos. However, actin organization into pseudocleavage furrows, though aberrant, remains partially intact. These data show that Motif 1 is necessary for some but not all of the activities conferred on centrosome function by intact Cnn.
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Affiliation(s)
- Jiuli Zhang
- Department of Pharmacology and The Cecil and Ida Green Center for Reproductive Biology Sciences, The University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9051
| | - Timothy L. Megraw
- Department of Pharmacology and The Cecil and Ida Green Center for Reproductive Biology Sciences, The University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9051
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