1
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Wethekam LC, Moore JK. Tubulin isotype regulation maintains asymmetric requirement for α-tubulin over β-tubulin. J Cell Biol 2023; 222:e202202102. [PMID: 36719400 PMCID: PMC9930134 DOI: 10.1083/jcb.202202102] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 07/19/2022] [Accepted: 11/14/2022] [Indexed: 02/01/2023] Open
Abstract
How cells regulate α- and β-tubulin to meet the demand for αβ-heterodimers and avoid consequences of monomer imbalance is not understood. We investigate the role of gene copy number and how shifting expression of α- or β-tubulin genes impacts tubulin proteostasis and microtubule function in Saccharomyces cerevisiae. We find that α-tubulin gene copy number is important for maintaining excess α-tubulin protein compared to β-tubulin protein. Excess α-tubulin prevents accumulation of super-stoichiometric β-tubulin, which leads to loss of microtubules, formation of non-microtubule assemblies of tubulin, and disrupts cell proliferation. In contrast, sub-stoichiometric β-tubulin or overexpression of α-tubulin has minor effects. We provide evidence that yeast cells equilibrate α-tubulin protein concentration when α-tubulin isotype expression is increased. We propose an asymmetric relationship between α- and β-tubulins, in which α-tubulins are maintained in excess to supply αβ-heterodimers and limit the accumulation of β-tubulin monomers.
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Affiliation(s)
- Linnea C. Wethekam
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Jeffrey K. Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
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2
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Hoff KJ, Neumann AJ, Moore JK. The molecular biology of tubulinopathies: Understanding the impact of variants on tubulin structure and microtubule regulation. Front Cell Neurosci 2022; 16:1023267. [PMID: 36406756 PMCID: PMC9666403 DOI: 10.3389/fncel.2022.1023267] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 09/30/2022] [Indexed: 11/24/2022] Open
Abstract
Heterozygous, missense mutations in both α- and β-tubulin genes have been linked to an array of neurodevelopment disorders, commonly referred to as "tubulinopathies." To date, tubulinopathy mutations have been identified in three β-tubulin isotypes and one α-tubulin isotype. These mutations occur throughout the different genetic domains and protein structures of these tubulin isotypes, and the field is working to address how this molecular-level diversity results in different cellular and tissue-level pathologies. Studies from many groups have focused on elucidating the consequences of individual mutations; however, the field lacks comprehensive models for the molecular etiology of different types of tubulinopathies, presenting a major gap in diagnosis and treatment. This review highlights recent advances in understanding tubulin structural dynamics, the roles microtubule-associated proteins (MAPs) play in microtubule regulation, and how these are inextricably linked. We emphasize the value of investigating interactions between tubulin structures, microtubules, and MAPs to understand and predict the impact of tubulinopathy mutations at the cell and tissue levels. Microtubule regulation is multifaceted and provides a complex set of controls for generating a functional cytoskeleton at the right place and right time during neurodevelopment. Understanding how tubulinopathy mutations disrupt distinct subsets of those controls, and how that ultimately disrupts neurodevelopment, will be important for establishing mechanistic themes among tubulinopathies that may lead to insights in other neurodevelopment disorders and normal neurodevelopment.
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Affiliation(s)
| | | | - Jeffrey K. Moore
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
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3
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White AJ, Harper CS, Rosario EM, Dietz JV, Addis HG, Fox JL, Khalimonchuk O, Lackner LL. Loss of Num1-mediated cortical dynein anchoring negatively impacts respiratory growth. J Cell Sci 2022; 135:jcs259980. [PMID: 36185004 PMCID: PMC9687553 DOI: 10.1242/jcs.259980] [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: 03/02/2022] [Accepted: 09/26/2022] [Indexed: 01/29/2023] Open
Abstract
Num1 is a multifunctional protein that both tethers mitochondria to the plasma membrane and anchors dynein to the cell cortex during nuclear inheritance. Previous work has examined the impact loss of Num1-based mitochondrial tethering has on dynein function in Saccharomyces cerevisiae; here, we elucidate its impact on mitochondrial function. We find that like mitochondria, Num1 is regulated by changes in metabolic state, with the protein levels and cortical distribution of Num1 differing between fermentative and respiratory growth conditions. In cells lacking Num1, we observe a reproducible respiratory growth defect, suggesting a role for Num1 in not only maintaining mitochondrial morphology, but also function. A structure-function approach revealed that, unexpectedly, Num1-mediated cortical dynein anchoring is important for normal growth under respiratory conditions. The severe respiratory growth defect in Δnum1 cells is not specifically due to the canonical functions of dynein in nuclear migration but is dependent on the presence of dynein, as deletion of DYN1 in Δnum1 cells partially rescues respiratory growth. We hypothesize that misregulated dynein present in cells that lack Num1 negatively impacts mitochondrial function resulting in defects in respiratory growth.
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Affiliation(s)
- Antoineen J. White
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Clare S. Harper
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Erica M. Rosario
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Jonathan V. Dietz
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, USA
| | - Hannah G. Addis
- Department of Chemistry and Biochemistry, College of Charleston, Charleston, SC 29424, USA
| | - Jennifer L. Fox
- Department of Chemistry and Biochemistry, College of Charleston, Charleston, SC 29424, USA
| | - Oleh Khalimonchuk
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, USA
- Nebraska Redox Biology Center, University of Nebraska, Lincoln, NE 68588, USA
- Fred & Pamela Buffett Cancer Center, Omaha, NE 68198, USA
| | - Laura L. Lackner
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
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4
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Kawano D, Pinter K, Chlebowski M, Petralia RS, Wang YX, Nechiporuk AV, Drerup CM. NudC regulated Lis1 stability is essential for the maintenance of dynamic microtubule ends in axon terminals. iScience 2022; 25:105072. [PMID: 36147950 PMCID: PMC9485903 DOI: 10.1016/j.isci.2022.105072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 07/26/2022] [Accepted: 08/30/2022] [Indexed: 11/28/2022] Open
Abstract
In the axon terminal, microtubule stability is decreased relative to the axon shaft. The dynamic microtubule plus ends found in the axon terminal have many functions, including serving as a docking site for the Cytoplasmic dynein motor. Here, we report an unexplored function of dynein in microtubule regulation in axon terminals: regulation of microtubule stability. Using a forward genetic screen, we identified a mutant with an abnormal axon terminal structure owing to a loss of function mutation in NudC. We show that, in the axon terminal, NudC is a chaperone for the protein Lis1. Decreased Lis1 in nudc axon terminals causes dynein/dynactin accumulation and increased microtubule stability. Microtubule dynamics can be restored by pharmacologically inhibiting dynein, implicating excess dynein motor function in microtubule stabilization. Together, our data support a model in which local NudC-Lis1 modulation of the dynein motor is critical for the regulation of microtubule stability in the axon terminal. NudC, a dynein regulator, is crucial for axon terminal structure NudC mutation leads to a near complete loss of Lis1 protein in axon terminals Lis1 deficits cause accumulation of dynein and cargo in axon terminals Local elevation of dynein increases axon terminal microtubule stability
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Affiliation(s)
- Dane Kawano
- Unit on Neuronal Cell Biology, National Institute of Child Health & Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Katherine Pinter
- Unit on Neuronal Cell Biology, National Institute of Child Health & Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Madison Chlebowski
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Ronald S Petralia
- Advanced Imaging Core, National Institute of Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ya-Xian Wang
- Advanced Imaging Core, National Institute of Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Alex V Nechiporuk
- Department of Cell, Developmental & Cancer Biology, Oregon Health & Science University, Portland, OR 97239, USA
| | - Catherine M Drerup
- Unit on Neuronal Cell Biology, National Institute of Child Health & Human Development, National Institutes of Health, Bethesda, MD 20892, USA.,Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA
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5
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Zucca F, Visintin C, Li J, Gygi SP, Visintin R. APC/CCdc20-mediated degradation of Clb4 prompts astral microtubule stabilization at anaphase onset. J Cell Biol 2022; 222:213563. [PMID: 36269172 PMCID: PMC9595209 DOI: 10.1083/jcb.202203089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 08/12/2022] [Accepted: 10/05/2022] [Indexed: 11/22/2022] Open
Abstract
Key for accurate chromosome partitioning to the offspring is the ability of mitotic spindle microtubules to respond to different molecular signals and remodel their dynamics accordingly. Spindle microtubules are conventionally divided into three classes: kinetochore, interpolar, and astral microtubules (kMTs, iMTs, and aMTs, respectively). Among all, aMT regulation remains elusive. Here, we show that aMT dynamics are tightly regulated. aMTs remain unstable up to metaphase and are stabilized at anaphase onset. This switch in aMT dynamics, important for proper spindle orientation, specifically requires the degradation of the mitotic cyclin Clb4 by the Anaphase Promoting Complex bound to its activator subunit Cdc20 (APC/CCdc20). These data highlight a unique role for mitotic cyclin Clb4 in controlling aMT regulating factors, of which Kip2 is a prime candidate, provide a framework to understand aMT regulation in vertebrates, and uncover mechanistic principles of how the APC/CCdc20 choreographs the timing of late mitotic events by sequentially impacting on the three classes of spindle microtubules.
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Affiliation(s)
- Federico Zucca
- Department of Experimental Oncology, European Institute of Oncology IRCCS, Milan, Italy
| | - Clara Visintin
- Department of Experimental Oncology, European Institute of Oncology IRCCS, Milan, Italy
| | - Jiaming Li
- Department of Cell Biology, Harvard Medical School, Boston, MA
| | - Steven P. Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA
| | - Rosella Visintin
- Department of Experimental Oncology, European Institute of Oncology IRCCS, Milan, Italy,Correspondence to Rosella Visintin:
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6
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Nsamba ET, Bera A, Costanzo M, Boone C, Gupta ML. Tubulin isotypes optimize distinct spindle positioning mechanisms during yeast mitosis. J Cell Biol 2021; 220:212745. [PMID: 34739032 PMCID: PMC8576917 DOI: 10.1083/jcb.202010155] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 09/06/2021] [Accepted: 10/12/2021] [Indexed: 01/13/2023] Open
Abstract
Microtubules are dynamic cytoskeleton filaments that are essential for a wide range of cellular processes. They are polymerized from tubulin, a heterodimer of α- and β-subunits. Most eukaryotic organisms express multiple isotypes of α- and β-tubulin, yet their functional relevance in any organism remains largely obscure. The two α-tubulin isotypes in budding yeast, Tub1 and Tub3, are proposed to be functionally interchangeable, yet their individual functions have not been rigorously interrogated. Here, we develop otherwise isogenic yeast strains expressing single tubulin isotypes at levels comparable to total tubulin in WT cells. Using genome-wide screening, we uncover unique interactions between the isotypes and the two major mitotic spindle positioning mechanisms. We further exploit these cells to demonstrate that Tub1 and Tub3 optimize spindle positioning by differentially recruiting key components of the Dyn1- and Kar9-dependent mechanisms, respectively. Our results provide novel mechanistic insights into how tubulin isotypes allow highly conserved microtubules to function in diverse cellular processes.
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Affiliation(s)
- Emmanuel T Nsamba
- Genetics, Development, and Cell Biology, Iowa State University, Ames, IA
| | - Abesh Bera
- Genetics, Development, and Cell Biology, Iowa State University, Ames, IA
| | - Michael Costanzo
- Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
| | - Charles Boone
- Donnelly Centre, University of Toronto, Toronto, Ontario, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.,Chemical Genomics Research Group, RIKEN Center for Sustainable Resource Sciences, Saitama, Japan
| | - Mohan L Gupta
- Genetics, Development, and Cell Biology, Iowa State University, Ames, IA
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7
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Ecklund KH, Bailey ME, Kossen KA, Dietvorst CK, Asbury CL, Markus SM. The microtubule-associated protein She1 coordinates directional spindle positioning by spatially restricting dynein activity. J Cell Sci 2021; 134:273583. [PMID: 34854468 DOI: 10.1242/jcs.258510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 10/27/2021] [Indexed: 11/20/2022] Open
Abstract
Dynein motors move the mitotic spindle to the cell division plane in many cell types, including in budding yeast, in which dynein is assisted by numerous factors including the microtubule-associated protein (MAP) She1. Evidence suggests that She1 plays a role in polarizing dynein-mediated spindle movements toward the daughter cell; however, how She1 performs this function is unknown. We find that She1 assists dynein in maintaining the spindle in close proximity to the bud neck, such that, at anaphase onset, the chromosomes are segregated to mother and daughter cells. She1 does so by attenuating the initiation of dynein-mediated spindle movements within the mother cell, thus ensuring such movements are polarized toward the daughter cell. Our data indicate that this activity relies on She1 binding to the microtubule-bound conformation of the dynein microtubule-binding domain, and to astral microtubules within mother cells. Our findings reveal how an asymmetrically localized MAP directionally tunes dynein activity by attenuating motor activity in a spatially confined manner.
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Affiliation(s)
- Kari H Ecklund
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Megan E Bailey
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, USA
| | - Kelly A Kossen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Carsten K Dietvorst
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Charles L Asbury
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, USA
| | - Steven M Markus
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA
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8
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Denarier E, Ecklund KH, Berthier G, Favier A, O'Toole ET, Gory-Fauré S, De Macedo L, Delphin C, Andrieux A, Markus SM, Boscheron C. Modeling a disease-correlated tubulin mutation in budding yeast reveals insight into MAP-mediated dynein function. Mol Biol Cell 2021; 32:ar10. [PMID: 34379441 PMCID: PMC8684761 DOI: 10.1091/mbc.e21-05-0237] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mutations in the genes that encode α- and β-tubulin underlie many neurological diseases, most notably malformations in cortical development. In addition to revealing the molecular basis for disease etiology, studying such mutations can provide insight into microtubule function and the role of the large family of microtubule effectors. In this study, we use budding yeast to model one such mutation—Gly436Arg in α-tubulin, which is causative of malformations in cortical development—in order to understand how it impacts microtubule function in a simple eukaryotic system. Using a combination of in vitro and in vivo methodologies, including live cell imaging and electron tomography, we find that the mutant tubulin is incorporated into microtubules, causes a shift in α-tubulin isotype usage, and dramatically enhances dynein activity, which leads to spindle-positioning defects. We find that the basis for the latter phenotype is an impaired interaction between She1—a dynein inhibitor—and the mutant microtubules. In addition to revealing the natural balance of α-tubulin isotype utilization in cells, our results provide evidence of an impaired interaction between microtubules and a dynein regulator as a consequence of a tubulin mutation and sheds light on a mechanism that may be causative of neurodevelopmental diseases.
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Affiliation(s)
- E Denarier
- Univ. Grenoble Alpes, CEA, CNRS, GIN, IBS, Inserm, IRIG, F-38000 Grenoble, France
| | - K H Ecklund
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States
| | - G Berthier
- Univ. Grenoble Alpes, CEA, CNRS, GIN, IBS, Inserm, IRIG, F-38000 Grenoble, France
| | - A Favier
- Univ. Grenoble Alpes, CEA, CNRS, GIN, IBS, Inserm, IRIG, F-38000 Grenoble, France
| | - E T O'Toole
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Boulder, Colorado, United States
| | - S Gory-Fauré
- Univ. Grenoble Alpes, CEA, CNRS, GIN, IBS, Inserm, IRIG, F-38000 Grenoble, France
| | - L De Macedo
- Univ. Grenoble Alpes, CEA, CNRS, GIN, IBS, Inserm, IRIG, F-38000 Grenoble, France
| | - C Delphin
- Univ. Grenoble Alpes, CEA, CNRS, GIN, IBS, Inserm, IRIG, F-38000 Grenoble, France
| | - A Andrieux
- Univ. Grenoble Alpes, CEA, CNRS, GIN, IBS, Inserm, IRIG, F-38000 Grenoble, France
| | - S M Markus
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States
| | - C Boscheron
- Univ. Grenoble Alpes, CEA, CNRS, GIN, IBS, Inserm, IRIG, F-38000 Grenoble, France
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9
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Jain K, Khetan N, Yadav SA, Palani S, Athale CA. Collective dynein transport of the nucleus by pulling on astral microtubules during Saccharomyces cerevisiae mitosis. Yeast 2021; 38:352-366. [PMID: 33547820 DOI: 10.1002/yea.3552] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 01/19/2021] [Accepted: 01/25/2021] [Indexed: 11/06/2022] Open
Abstract
Positioning the nucleus at the bud neck during Saccharomyces cerevisiae mitosis involves pulling forces of cytoplasmic dynein localized in the daughter cell. Although genetic analysis has revealed a complex network positioning the nucleus, quantification of the forces acting on the nucleus and the number of dyneins driving the process has remained difficult. To better understand the collective forces involved in nuclear positioning, we compare a model of dyneins-driven microtubule (MT) pulling, MT pushing, and cytoplasmic drag to experiments. During S. cerevisiae mitosis, MTs interacting with the cortex nucleated by the daughter spindle pole body (SPB) (SPB-D) are longer than the mother SPB (SPB-M), increasing further during spindle elongation in anaphase. Interphasic SPB mobility is effectively diffusive, while the mitotic mobility is directed. By optimizing a computational model of the mobility of the nucleus due to diffusion and MTs pushing at the cell membrane to experiment, we estimate the viscosity governing the drag force on nuclei during positioning. A force balance model of mitotic SPB mobility compared to experimental mobility suggests that even one or two dynein dimers are sufficient to move the nucleus in the bud neck. Using stochastic computer simulations of a budding cell, we find that punctate dynein localization can generate sufficient force to reel in the nucleus to the bud neck. Compared to uniform motor localization, puncta involve fewer motors suggesting a functional role for motor clustering. Stochastic simulations also suggest that a higher number of force generators than predicted by force balance may be required to ensure the robustness of spindle positioning.
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Affiliation(s)
- Kunalika Jain
- Division of Biology, IISER Pune, Dr. Homi Bhabha Road, Pune, Maharashtra, 411008, India
| | - Neha Khetan
- Division of Biology, IISER Pune, Dr. Homi Bhabha Road, Pune, Maharashtra, 411008, India
| | - Shivani A Yadav
- Division of Biology, IISER Pune, Dr. Homi Bhabha Road, Pune, Maharashtra, 411008, India
| | - Saravanan Palani
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, UK.,Department of Biochemistry, Indian Institute of Science (IISc), C.V. Raman Road, Bangalore, Karnataka, 560012, India
| | - Chaitanya A Athale
- Division of Biology, IISER Pune, Dr. Homi Bhabha Road, Pune, Maharashtra, 411008, India
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10
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Fourel G, Boscheron C. Tubulin mutations in neurodevelopmental disorders as a tool to decipher microtubule function. FEBS Lett 2020; 594:3409-3438. [PMID: 33064843 DOI: 10.1002/1873-3468.13958] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 09/28/2020] [Accepted: 10/05/2020] [Indexed: 01/08/2023]
Abstract
Malformations of cortical development (MCDs) are a group of severe brain malformations associated with intellectual disability and refractory childhood epilepsy. Human missense heterozygous mutations in the 9 α-tubulin and 10 β-tubulin isoforms forming the heterodimers that assemble into microtubules (MTs) were found to cause MCDs. However, how a single mutated residue in a given tubulin isoform can perturb the entire microtubule population in a neuronal cell remains a crucial question. Here, we examined 85 MCD-associated tubulin mutations occurring in TUBA1A, TUBB2, and TUBB3 and their location in a three-dimensional (3D) microtubule cylinder. Mutations hitting residues exposed on the outer microtubule surface are likely to alter microtubule association with partners, while alteration of intradimer contacts may impair dimer stability and straightness. Other types of mutations are predicted to alter interdimer and lateral contacts, which are responsible for microtubule cohesion, rigidity, and dynamics. MCD-associated tubulin mutations surprisingly fall into all categories, thus providing unexpected insights into how a single mutation may impair microtubule function and elicit dominant effects in neurons.
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11
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Khetan N, Athale CA. Aster swarming by symmetry breaking of cortical dynein transport and coupling kinesins. SOFT MATTER 2020; 16:8554-8564. [PMID: 32840555 DOI: 10.1039/d0sm01086c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Microtubule (MT) radial arrays or asters establish the internal topology of a cell by interacting with organelles and molecular motors. We proceed to understand the general pattern forming potential of aster-motor systems using a computational model of multiple MT asters interacting with motors in cellular confinement. In this model dynein motors are attached to the cell cortex and plus-ended motors resembling kinesin-5 diffuse in the cell interior. The introduction of 'noise' in the form of MT length fluctuations spontaneously results in the emergence of coordinated, achiral vortex-like rotation of asters. The coherence and persistence of rotation require a threshold density of both cortical dyneins and coupling kinesins, while the onset is diffusion-limited with relation to the cortical dynein mobility. The coordinated rotational motion emerges due to the resolution of a 'tug-of-war' of multiple cortical dynein motors bound to MTs of the same aster by 'noise' in the form of MT dynamic instability. This transient symmetry breaking is amplified by local coupling by kinesin-5 complexes. The lack of widespread aster rotation across cell types suggests that biophysical mechanisms that suppress such intrinsic dynamics may have evolved. This model is analogous to more general models of locally coupled self-propelled particles (SPP) that spontaneously undergo collective transport in the presence of 'noise' that have been invoked to explain swarming in birds and fish. However, the aster-motor system is distinct from SPP models with regard to the particle density and 'noise' dependence, providing a set of experimentally testable predictions for a novel sub-cellular pattern forming system.
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Affiliation(s)
- Neha Khetan
- Div. of Biology, IISER Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, India.
| | - Chaitanya A Athale
- Div. of Biology, IISER Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, India.
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12
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Nasrin SR, Afrin T, Kabir AMR, Inoue D, Torisawa T, Oiwa K, Sada K, Kakugo A. Regulation of Biomolecular-Motor-Driven Cargo Transport by Microtubules under Mechanical Stress. ACS APPLIED BIO MATERIALS 2020; 3:1875-1883. [DOI: 10.1021/acsabm.9b01010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Syeda Rubaiya Nasrin
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810, Hokkaido, Japan
| | - Tanjina Afrin
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810, Hokkaido, Japan
| | | | - Daisuke Inoue
- Faculty of Science, Hokkaido University, Sapporo 060-0810, Hokkaido, Japan
| | - Takayuki Torisawa
- Cell Architecture Laboratory, Structural Biology Center, National Institute of Genetics, Mishima 411-8540, Japan
- Department of Genetics, SOKENDAI (The Graduate University for Advanced Studies), Mishima 411-8540, Japan
| | - Kazuhiro Oiwa
- Advanced ICT Research Institute, National Institute of Information and Communications Technology, Kobe 651-2492, Hyogo, Japan
| | - Kazuki Sada
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810, Hokkaido, Japan
- Faculty of Science, Hokkaido University, Sapporo 060-0810, Hokkaido, Japan
| | - Akira Kakugo
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810, Hokkaido, Japan
- Faculty of Science, Hokkaido University, Sapporo 060-0810, Hokkaido, Japan
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13
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Estrem C, Moore JK. Help or hindrance: how do microtubule-based forces contribute to genome damage and repair? Curr Genet 2019; 66:303-311. [PMID: 31501990 DOI: 10.1007/s00294-019-01033-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/27/2019] [Accepted: 08/27/2019] [Indexed: 10/26/2022]
Abstract
Forces generated by molecular motors and the cytoskeleton move the nucleus and genome during many cellular processes, including cell migration and division. How these forces impact the genome, and whether cells regulate cytoskeletal forces to preserve genome integrity is unclear. We recently demonstrated that, in budding yeast, mutants that stabilize the microtubule cytoskeleton cause excessive movement of the mitotic spindle and nucleus. We found that increased nuclear movement results in DNA damage and increased time to repair the damage through homology-directed repair. Our results indicate that nuclear movement impairs DNA repair through increased tension on chromosomes and nuclear deformation. However, the previous studies have shown genome mobility, driven by cytoskeleton-based forces, aids in homology-directed DNA repair. This sets up an apparent paradox, where genome mobility may prevent or promote DNA repair. Hence, this review explores how the genome is affected by nuclear movement and how genome mobility could aid or hinder homology-directed repair.
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Affiliation(s)
- Cassi Estrem
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA.
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14
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Aiken J, Moore JK, Bates EA. TUBA1A mutations identified in lissencephaly patients dominantly disrupt neuronal migration and impair dynein activity. Hum Mol Genet 2019; 28:1227-1243. [PMID: 30517687 DOI: 10.1093/hmg/ddy416] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 11/16/2018] [Accepted: 11/27/2018] [Indexed: 02/06/2023] Open
Abstract
The microtubule cytoskeleton supports diverse cellular morphogenesis and migration processes during brain development. Mutations in tubulin genes are associated with severe human brain malformations known as 'tubulinopathies'; however, it is not understood how molecular-level changes in microtubule subunits lead to brain malformations. In this study, we demonstrate that missense mutations affecting arginine at position 402 (R402) of TUBA1A α-tubulin selectively impair dynein motor activity and severely and dominantly disrupt cortical neuronal migration. TUBA1A is the most commonly affected tubulin gene in tubulinopathy patients, and mutations altering R402 account for 30% of all reported TUBA1A mutations. We show for the first time that ectopic expression of TUBA1A-R402C and TUBA1A-R402H patient alleles is sufficient to dominantly disrupt cortical neuronal migration in the developing mouse brain, strongly supporting a causal role in the pathology of brain malformation. To isolate the precise molecular impact of R402 mutations, we generated analogous R402C and R402H mutations in budding yeast α-tubulin, which exhibit a simplified microtubule cytoskeleton. We find that R402 mutant tubulins assemble into microtubules that support normal kinesin motor activity but fail to support the activity of dynein motors. Importantly, the level of dynein impairment scales with the expression level of the mutant in the cell, suggesting a 'poisoning' mechanism in which R402 mutant α-tubulin acts dominantly by populating microtubules with defective binding sites for dynein. Based on our results, we propose a new model for the molecular pathology of tubulinopathies that may also extend to other tubulin-related neuropathies.
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Affiliation(s)
- Jayne Aiken
- Department of Cell and Developmental Biology
| | | | - Emily A Bates
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, USA
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15
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Estrem C, Moore JK. Astral microtubule forces alter nuclear organization and inhibit DNA repair in budding yeast. Mol Biol Cell 2019; 30:2000-2013. [PMID: 31067146 PMCID: PMC6727761 DOI: 10.1091/mbc.e18-12-0808] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Dividing cells must balance the maintenance of genome integrity with the generation of cytoskeletal forces that control chromosome position. In this study, we investigate how forces on astral microtubules impact the genome during cell division by using live-cell imaging of the cytoskeleton, chromatin, and DNA damage repair in budding yeast. Our results demonstrate that dynein-dependent forces on astral microtubules are propagated through the spindle during nuclear migration and when in excess can increase the frequency of double-stranded breaks (DSBs). Under these conditions, we find that homology-directed repair of DSBs is delayed, indicating antagonism between nuclear migration and the mechanism of homology-directed repair. These effects are partially rescued by mutants that weaken pericentric cohesion or mutants that decrease constriction on the nucleus as it moves through the bud neck. We propose that minimizing nuclear movement aids in finding a donor strand for homologous recombination.
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Affiliation(s)
- Cassi Estrem
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045
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16
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Denarier E, Brousse C, Sissoko A, Andrieux A, Boscheron C. A neurodevelopmental TUBB2B β-tubulin mutation impairs Bim1 (yeast EB1)-dependent spindle positioning. Biol Open 2019; 8:bio.038620. [PMID: 30674462 PMCID: PMC6361202 DOI: 10.1242/bio.038620] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Malformations of the human cerebral cortex can be caused by mutations in tubulins that associate to compose microtubules. Cerebral cortical folding relies on neuronal migration and on progenitor proliferation partly dictated by microtubule-dependent mitotic spindle positioning. A single amino acid change, F265L, in the conserved TUBB2B β-tubulin gene has been identified in patients with abnormal cortex formation. A caveat for studying this mutation in mammalian cells is that nine genes encode β-tubulin in human. Here, we generate a yeast strain expressing F265L tubulin mutant as the sole source of β-tubulin. The F265L mutation does not preclude expression of a stable β-tubulin protein which is incorporated into microtubules. However, impaired cell growth was observed at high temperatures along with altered microtubule dynamics and stability. In addition, F265L mutation produces a highly specific mitotic spindle positioning defect related to Bim1 (yeast EB1) dysfunction. Indeed, F265L cells display an abnormal Bim1 recruitment profile at microtubule plus-ends. These results indicate that the F265L β-tubulin mutation affects microtubule plus-end complexes known to be important for microtubule dynamics and for microtubule function during mitotic spindle positioning.
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Affiliation(s)
- Eric Denarier
- Univ. Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, F-38000, Grenoble, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38000, Grenoble, France.,Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Biosciences and Biotechnology Institute of Grenoble, Grenoble, France
| | - Carine Brousse
- Institut National de la Transfusion Sanguine (INTS), F-75015 Paris, France
| | | | - Annie Andrieux
- Univ. Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, F-38000, Grenoble, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38000, Grenoble, France.,Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Biosciences and Biotechnology Institute of Grenoble, Grenoble, France
| | - Cécile Boscheron
- Univ. Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, F-38000, Grenoble, France .,Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38000, Grenoble, France.,Institut de Biologie Structurale (IBS) , F-38000 Grenoble, France
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17
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Bergman ZJ, Wong J, Drubin DG, Barnes G. Microtubule dynamics regulation reconstituted in budding yeast lysates. J Cell Sci 2018; 132:jcs.219386. [PMID: 30185524 DOI: 10.1242/jcs.219386] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 08/23/2018] [Indexed: 01/14/2023] Open
Abstract
Microtubules (MTs) are important for cellular structure, transport of cargoes and segregation of chromosomes and organelles during mitosis. The stochastic growth and shrinkage of MTs, known as dynamic instability, is necessary for these functions. Previous studies to determine how individual MT-associated proteins (MAPs) affect MT dynamics have been performed either through in vivo studies, which provide limited opportunity for observation of individual MTs or manipulation of conditions, or in vitro studies, which focus either on purified proteins, and therefore lack cellular complexity, or on cell extracts made from genetically intractable organisms. In order to investigate the ensemble activities of all MAPs on MT dynamics using lysates made from a genetically tractable organism, we developed a cell-free assay for budding yeast lysates using total internal reflection fluorescence (TIRF) microscopy. Lysates were prepared from yeast strains expressing GFP-tubulin. MT polymerization from pre-assembled MT seeds adhered to a coverslip was observed in real time. Through use of cell division cycle (cdc) and MT depolymerase mutants, we found that MT polymerization and dynamic instability are dependent on the cell cycle state and the activities of specific MAPs.
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Affiliation(s)
- Zane J Bergman
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Jonathan Wong
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - David G Drubin
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Georjana Barnes
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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18
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Omer S, Greenberg SR, Lee WL. Cortical dynein pulling mechanism is regulated by differentially targeted attachment molecule Num1. eLife 2018; 7:36745. [PMID: 30084355 PMCID: PMC6080947 DOI: 10.7554/elife.36745] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Accepted: 07/05/2018] [Indexed: 12/17/2022] Open
Abstract
Cortical dynein generates pulling forces via microtubule (MT) end capture-shrinkage and lateral MT sliding mechanisms. In Saccharomyces cerevisiae, the dynein attachment molecule Num1 interacts with endoplasmic reticulum (ER) and mitochondria to facilitate spindle positioning across the mother-bud neck, but direct evidence for how these cortical contacts regulate dynein-dependent pulling forces is lacking. We show that loss of Scs2/Scs22, ER tethering proteins, resulted in defective Num1 distribution and loss of dynein-dependent MT sliding, the hallmark of dynein function. Cells lacking Scs2/Scs22 performed spindle positioning via MT end capture-shrinkage mechanism, requiring dynein anchorage to an ER- and mitochondria-independent population of Num1, dynein motor activity, and CAP-Gly domain of dynactin Nip100/p150Glued subunit. Additionally, a CAAX-targeted Num1 rescued loss of lateral patches and MT sliding in the absence of Scs2/Scs22. These results reveal distinct populations of Num1 and underline the importance of their spatial distribution as a critical factor for regulating dynein pulling force. Cells must divide so that organisms can grow, repair damaged tissues or reproduce. Before dividing, a cell creates two identical copies of its genetic information – one for each daughter. A molecular machine known as the mitotic spindle then moves each set of genetic material to where it will be needed when the daughter cells form. For the process to work properly, however, a motor protein known as dynein must correctly position the spindle by pulling it into place from the outskirts of the cell. When a baker’s yeast cell divides, it first forms a ‘bump’, which grows into a bud that will ultimately become another yeast. The spindle needs to be precisely placed at the midpoint between the original cell and the bud, so the genetic material can get into the future daughter cell. To do so, dynein travels to the bud, where a protein called Num1 helps it attach to the periphery and pull the filaments of the mitotic spindle (known as microtubules) to the correct position. Num1 also attaches to other cellular structures in the bud, including one known as the endoplasmic reticulum. It was unclear how this connection changes where dynein is located, and how it can pull on the spindle. To study this, Omer et al. labeled Num1, dynein and microtubules with fluorescent markers so they could be followed in living baker’s yeast using time-lapse microscopy. Mutant yeast strains were also used to disrupt how these proteins associate, which helps to tease out their roles. The experiments show that there are several populations of Num1 in the bud. One associates with the endoplasmic reticulum, and it helps dynein grab the side of a microtubule and make it slide into the bud. The other does not attach to the reticulum, but instead is located at the very tip of the bud. There, it makes dynein capture the end of the microtubule; this destabilizes the filament, which starts to shorten. As the microtubule shrinks, the spindle is pulled closer to the bud’s tip, which aligns it in the right position. The yeast cells thus need Num1 in both locations to fine-tune the pulling activity of dynein, and the spindle’s final positioning. In the human body, not all divisions create two identical cells; for example, the daughters of stem cells can have different fates. This is due to a precise asymmetric division which dynein partly controls. The results by Omer et al. could help to unravel this mechanism.
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Affiliation(s)
- Safia Omer
- Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, United States
| | - Samuel R Greenberg
- Department of Biological Sciences, Dartmouth College, Hanover, United States
| | - Wei-Lih Lee
- Department of Biological Sciences, Dartmouth College, Hanover, United States
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19
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Xiang X. Nuclear movement in fungi. Semin Cell Dev Biol 2017; 82:3-16. [PMID: 29241689 DOI: 10.1016/j.semcdb.2017.10.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 10/17/2017] [Accepted: 10/23/2017] [Indexed: 12/22/2022]
Abstract
Nuclear movement within a cell occurs in a variety of eukaryotic organisms including yeasts and filamentous fungi. Fungal molecular genetic studies identified the minus-end-directed microtubule motor cytoplasmic dynein as a critical protein for nuclear movement or orientation of the mitotic spindle contained in the nucleus. Studies in the budding yeast first indicated that dynein anchored at the cortex via its anchoring protein Num1 exerts pulling force on an astral microtubule to orient the anaphase spindle across the mother-daughter axis before nuclear division. Prior to anaphase, myosin V interacts with the plus end of an astral microtubule via Kar9-Bim1/EB1 and pulls the plus end along the actin cables to move the nucleus/spindle close to the bud neck. In addition, pushing or pulling forces generated from cortex-linked polymerization or depolymerization of microtubules drive nuclear movements in yeasts and possibly also in filamentous fungi. In filamentous fungi, multiple nuclei within a hyphal segment undergo dynein-dependent back-and-forth movements and their positioning is also influenced by cytoplasmic streaming toward the hyphal tip. In addition, nuclear movement occurs at various stages of fungal development and fungal infection of plant tissues. This review discusses our current understanding on the mechanisms of nuclear movement in fungal organisms, the importance of nuclear positioning and the regulatory strategies that ensure the proper positioning of nucleus/spindle.
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Affiliation(s)
- Xin Xiang
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences - F. Edward Hébert School of Medicine, Bethesda, MD, USA.
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