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Craig EM, Oprea F, Alam S, Grodsky A, Miller KE. A simple active fluid model unites cytokinesis, cell crawling, and axonal outgrowth. Front Cell Dev Biol 2024; 12:1491429. [PMID: 39483337 PMCID: PMC11524947 DOI: 10.3389/fcell.2024.1491429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2024] [Accepted: 10/04/2024] [Indexed: 11/03/2024] Open
Abstract
While the structural organization and molecular biology of neurons are well characterized, the physical process of axonal elongation remains elusive. The classic view posited elongation occurs through the deposition of cytoskeletal elements in the growth cone at the tip of a stationary array of microtubules. Yet, recent studies reveal axonal microtubules and docked organelles flow forward in bulk in the elongating axons of Aplysia, chick sensory, rat hippocampal, and Drosophila neurons. Noting that the morphology, molecular components, and subcellular flow patterns of growth cones strongly resemble the leading edge of migrating cells and the polar regions of dividing cells, our working hypothesis is that axonal elongation utilizes the same physical mechanisms that drive cell crawling and cell division. As a test of that hypothesis, here we take experimental data sets of sub-cellular flow patterns in cells undergoing cytokinesis, mesenchymal migration, amoeboid migration, neuronal migration, and axonal elongation. We then apply active fluid theory to develop a biophysical model that describes the different sub-cellular flow profiles across these forms of motility and how this generates cell motility under low Reynolds numbers. The modeling suggests that mechanisms for generating motion are shared across these processes, and differences arise through modifications of sub-cellular adhesion patterns and the profiles of internal force generation. Collectively, this work suggests that ameboid and mesenchymal cell crawling may have arisen from processes that first developed to support cell division, that growth cone motility and cell crawling are closely related, and that neuronal migration and axonal elongation are fundamentally similar, differing primarily in the motion and strength of adhesion under the cell body.
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Affiliation(s)
- Erin M. Craig
- Central Washington University, Department of Physics, Ellensburg, WA, United States
| | - Francesca Oprea
- Department of Integrative Biology, Michigan State University, East Lansing, MI, United States
| | - Sajid Alam
- Department of Integrative Biology, Michigan State University, East Lansing, MI, United States
| | - Ania Grodsky
- Department of Integrative Biology, Michigan State University, East Lansing, MI, United States
| | - Kyle E. Miller
- Department of Integrative Biology, Michigan State University, East Lansing, MI, United States
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2
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Craig EM, Oprea F, Alam S, Grodsky A, Miller KE. A simple active fluid model unites cytokinesis, cell crawling, and axonal outgrowth. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.22.595337. [PMID: 38826455 PMCID: PMC11142150 DOI: 10.1101/2024.05.22.595337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Axonal outgrowth, cell crawling, and cytokinesis utilize actomyosin, microtubule-based motors, cytoskeletal dynamics, and substrate adhesions to produce traction forces and bulk cellular motion. While it has long been appreciated that growth cones resemble crawling cells and that the mechanisms that drive cytokinesis help power cell crawling, they are typically viewed as unique processes. To better understand the relationship between these modes of motility, here, we developed a unified active fluid model of cytokinesis, amoeboid migration, mesenchymal migration, neuronal migration, and axonal outgrowth in terms of cytoskeletal flow, adhesions, viscosity, and force generation. Using numerical modeling, we fit subcellular velocity profiles of the motions of cytoskeletal structures and docked organelles from previously published studies to infer underlying patterns of force generation and adhesion. Our results indicate that, during cytokinesis, there is a primary converge zone at the cleavage furrow that drives flow towards it; adhesions are symmetric across the cell, and as a result, cells are stationary. In mesenchymal, amoeboid, and neuronal migration, the site of the converge zone shifts, and differences in adhesion between the front and back of the cell drive crawling. During neuronal migration and axonal outgrowth, the primary convergence zone lies within the growth cone, which drives actin retrograde flow in the P-domain and bulk anterograde flow of the axonal shaft. They differ in that during neuronal migration, the cell body is weakly attached to the substrate and thus moves forward at the same velocity as the axon. In contrast, during axonal outgrowth, the cell body strongly adheres to the substrate and remains stationary, resulting in a decrease in flow velocity away from the growth cone. The simplicity with which cytokinesis, cell crawling, and axonal outgrowth can be modeled by varying coefficients in a simple model suggests a deep connection between them.
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Affiliation(s)
- Erin M. Craig
- Central Washington University, Department of Physics, 400 E. University Way, Ellensburg, WA 98926-7422, USA
| | - Francesca Oprea
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Sajid Alam
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Ania Grodsky
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Kyle E. Miller
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
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3
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Akhmanova A, Kapitein LC. Mechanisms of microtubule organization in differentiated animal cells. Nat Rev Mol Cell Biol 2022; 23:541-558. [PMID: 35383336 DOI: 10.1038/s41580-022-00473-y] [Citation(s) in RCA: 68] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/07/2022] [Indexed: 02/08/2023]
Abstract
Microtubules are polarized cytoskeletal filaments that serve as tracks for intracellular transport and form a scaffold that positions organelles and other cellular components and modulates cell shape and mechanics. In animal cells, the geometry, density and directionality of microtubule networks are major determinants of cellular architecture, polarity and proliferation. In dividing cells, microtubules form bipolar spindles that pull chromosomes apart, whereas in interphase cells, microtubules are organized in a cell type-specific fashion, which strongly correlates with cell physiology. In motile cells, such as fibroblasts and immune cells, microtubules are organized as radial asters, whereas in immotile epithelial and neuronal cells and in muscles, microtubules form parallel or antiparallel arrays and cortical meshworks. Here, we review recent work addressing how the formation of such microtubule networks is driven by the plethora of microtubule regulatory proteins. These include proteins that nucleate or anchor microtubule ends at different cellular structures and those that sever or move microtubules, as well as regulators of microtubule elongation, stability, bundling or modifications. The emerging picture, although still very incomplete, shows a remarkable diversity of cell-specific mechanisms that employ conserved building blocks to adjust microtubule organization in order to facilitate different cellular functions.
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Affiliation(s)
- Anna Akhmanova
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, the Netherlands.
| | - Lukas C Kapitein
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, the Netherlands.
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Rolls MM. Principles of microtubule polarity in linear cells. Dev Biol 2022; 483:112-117. [PMID: 35016908 PMCID: PMC10071391 DOI: 10.1016/j.ydbio.2022.01.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 01/06/2022] [Indexed: 01/30/2023]
Abstract
The microtubule cytoskeleton is critical for maintenance of long and long-lived neurons. The overlapping array of microtubules extends from the major site of synthesis in the cell body to the far reaches of axons and dendrites. New materials are transported from the cell body along these neuronal roads by motor proteins, and building blocks and information about the state of affairs in other parts of the cell are returned by motors moving in the opposite direction. As motor proteins walk only in one direction along microtubules, the combination of correct motor and correctly oriented microtubules is essential for moving cargoes in the right direction. In this review, we focus on how microtubule polarity is established and maintained in neurons. At first thought, it seems that figuring out how microtubules are organized in neurons should be simple. After all, microtubules are essentially sticks with a slow-growing minus end and faster-growing plus end, and arranging sticks within the constrained narrow tubes of axons and dendrites should be straightforward. It is therefore quite surprising how many mechanisms contribute to making sure they are arranged in the correct polarity. Some of these mechanisms operate to generate plus-end-out polarity of axons, and others control mixed or minus-end-out dendrites.
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Affiliation(s)
- Melissa M Rolls
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA
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5
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Del Castillo U, Norkett R, Lu W, Serpinskaya A, Gelfand VI. Ataxin-2 is essential for cytoskeletal dynamics and neurodevelopment in Drosophila. iScience 2022; 25:103536. [PMID: 34977501 PMCID: PMC8689088 DOI: 10.1016/j.isci.2021.103536] [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: 04/30/2021] [Revised: 08/19/2021] [Accepted: 11/25/2021] [Indexed: 12/03/2022] Open
Abstract
Ataxin-2 (Atx2) is a highly conserved RNA binding protein. Atx2 undergoes polyglutamine expansion leading to amyotrophic lateral sclerosis (ALS) or spinocerebellar ataxia type 2 (SCA2). However, the physiological functions of Atx2 in neurons remain unknown. Here, using the powerful genetics of Drosophila, we show that Atx2 is essential for normal neuronal cytoskeletal dynamics and organelle trafficking. Upon neuron-specific Atx2 loss, the microtubule and actin networks were abnormally stabilized and cargo transport was drastically inhibited. Depletion of Atx2 caused multiple morphological defects in the nervous system of third instar larvae. These include reduced brain size, impaired axon development, and decreased dendrite outgrowth. Defects in the nervous system caused loss of the ability to crawl and lethality at the pupal stage. Taken together, these data mark Atx2 as a major regulator of cytoskeletal dynamics and denote Atx2 as an essential gene in neurodevelopment, as well as a neurodegenerative factor. Atx2 is a major regulator of the cytoskeleton in neurons Atx2 is responsible for maintaining dynamic cytoskeletal networks Atx2 depletion in the Drosophila larval CNS severely impairs organelle transport Atx2 is necessary for correct neurite outgrowth and CNS development in Drosophila
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Affiliation(s)
- Urko Del Castillo
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Rosalind Norkett
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Wen Lu
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Anna Serpinskaya
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Vladimir I Gelfand
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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Mini-review: Microtubule sliding in neurons. Neurosci Lett 2021; 753:135867. [PMID: 33812935 DOI: 10.1016/j.neulet.2021.135867] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 03/22/2021] [Accepted: 03/23/2021] [Indexed: 12/28/2022]
Abstract
Microtubule sliding is an underappreciated mechanism that contributes to the establishment, organization, preservation, and plasticity of neuronal microtubule arrays. Powered by molecular motor proteins and regulated in part by static crosslinker proteins, microtubule sliding is the movement of microtubules relative to other microtubules or to non-microtubule structures such as the actin cytoskeleton. In addition to other important functions, microtubule sliding significantly contributes to the establishment and maintenance of microtubule polarity patterns in different regions of the neuron. The purpose of this article is to review the state of knowledge on microtubule sliding in the neuron, with emphasis on its mechanistic underpinnings as well as its functional significance.
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Meka DP, Scharrenberg R, Calderon de Anda F. Emerging roles of the centrosome in neuronal development. Cytoskeleton (Hoboken) 2020; 77:84-96. [DOI: 10.1002/cm.21593] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 12/16/2019] [Accepted: 01/04/2020] [Indexed: 12/24/2022]
Affiliation(s)
- Durga Praveen Meka
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH)University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Robin Scharrenberg
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH)University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Froylan Calderon de Anda
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH)University Medical Center Hamburg‐Eppendorf Hamburg Germany
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Norkett R, Del Castillo U, Lu W, Gelfand VI. Ser/Thr kinase Trc controls neurite outgrowth in Drosophila by modulating microtubule-microtubule sliding. eLife 2020; 9:52009. [PMID: 32022690 PMCID: PMC7021487 DOI: 10.7554/elife.52009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 02/05/2020] [Indexed: 12/28/2022] Open
Abstract
Correct neuronal development requires tailored neurite outgrowth. Neurite outgrowth is driven in part by microtubule-sliding - the transport of microtubules along each other. We have recently demonstrated that a 'mitotic' kinesin-6 (Pavarotti in Drosophila) effectively inhibits microtubule-sliding and neurite outgrowth. However, mechanisms regulating Pavarotti itself in interphase cells and specifically in neurite outgrowth are unknown. Here, we use a combination of live imaging and biochemical methods to show that the inhibition of microtubule-sliding by Pavarotti is controlled by phosphorylation. We identify the Ser/Thr NDR kinase Tricornered (Trc) as a Pavarotti-dependent regulator of microtubule sliding in neurons. Further, we show that Trc-mediated phosphorylation of Pavarotti promotes its interaction with 14-3-3 proteins. Loss of 14-3-3 prevents Pavarotti from associating with microtubules. Thus, we propose a pathway by which microtubule-sliding can be up- or downregulated in neurons to control neurite outgrowth, and establish parallels between microtubule-sliding in mitosis and post-mitotic neurons.
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Affiliation(s)
- Rosalind Norkett
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Urko Del Castillo
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Wen Lu
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Vladimir I Gelfand
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, United States
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Hahn I, Voelzmann A, Liew YT, Costa-Gomes B, Prokop A. The model of local axon homeostasis - explaining the role and regulation of microtubule bundles in axon maintenance and pathology. Neural Dev 2019; 14:11. [PMID: 31706327 PMCID: PMC6842214 DOI: 10.1186/s13064-019-0134-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 10/02/2019] [Indexed: 12/20/2022] Open
Abstract
Axons are the slender, cable-like, up to meter-long projections of neurons that electrically wire our brains and bodies. In spite of their challenging morphology, they usually need to be maintained for an organism's lifetime. This makes them key lesion sites in pathological processes of ageing, injury and neurodegeneration. The morphology and physiology of axons crucially depends on the parallel bundles of microtubules (MTs), running all along to serve as their structural backbones and highways for life-sustaining cargo transport and organelle dynamics. Understanding how these bundles are formed and then maintained will provide important explanations for axon biology and pathology. Currently, much is known about MTs and the proteins that bind and regulate them, but very little about how these factors functionally integrate to regulate axon biology. As an attempt to bridge between molecular mechanisms and their cellular relevance, we explain here the model of local axon homeostasis, based on our own experiments in Drosophila and published data primarily from vertebrates/mammals as well as C. elegans. The model proposes that (1) the physical forces imposed by motor protein-driven transport and dynamics in the confined axonal space, are a life-sustaining necessity, but pose a strong bias for MT bundles to become disorganised. (2) To counterbalance this risk, MT-binding and -regulating proteins of different classes work together to maintain and protect MT bundles as necessary transport highways. Loss of balance between these two fundamental processes can explain the development of axonopathies, in particular those linking to MT-regulating proteins, motors and transport defects. With this perspective in mind, we hope that more researchers incorporate MTs into their work, thus enhancing our chances of deciphering the complex regulatory networks that underpin axon biology and pathology.
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Affiliation(s)
- Ines Hahn
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, The University of Manchester, School of Biology, Manchester, UK
| | - André Voelzmann
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, The University of Manchester, School of Biology, Manchester, UK
| | - Yu-Ting Liew
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, The University of Manchester, School of Biology, Manchester, UK
| | - Beatriz Costa-Gomes
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, The University of Manchester, School of Biology, Manchester, UK
| | - Andreas Prokop
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, The University of Manchester, School of Biology, Manchester, UK.
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Del Castillo U, Norkett R, Gelfand VI. Unconventional Roles of Cytoskeletal Mitotic Machinery in Neurodevelopment. Trends Cell Biol 2019; 29:901-911. [PMID: 31597609 DOI: 10.1016/j.tcb.2019.08.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/22/2019] [Accepted: 08/23/2019] [Indexed: 12/20/2022]
Abstract
At first look, cell division and neurite formation seem to be two different, essential biological processes. However, both processes require extensive reorganization of the cytoskeleton, and especially microtubules. Remarkably, in recent years, independent work from several groups has shown that multiple cytoskeletal components previously considered specific for the mitotic machinery play important roles in neurite initiation and extension. In this review article, we describe how several cytoplasmic and mitotic microtubule motors, components of mitotic kinetochores, and cortical actin participate in reorganization of the microtubule network required to form and maintain axons and dendrites. The emerging similarities between these two biological processes will certainly generate new insights into the mechanisms generating the unique morphology of neurons.
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Affiliation(s)
- Urko Del Castillo
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA
| | - Rosalind Norkett
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA
| | - Vladimir I Gelfand
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA.
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Didier MEP, Macias-Romero C, Teulon C, Jourdain P, Roke S. Mapping of real-time morphological changes in the neuronal cytoskeleton with label-free wide-field second-harmonic imaging: a case study of nocodazole. NEUROPHOTONICS 2019; 6:045006. [PMID: 31720311 PMCID: PMC6835049 DOI: 10.1117/1.nph.6.4.045006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 09/23/2019] [Indexed: 06/10/2023]
Abstract
We demonstrate the use of wide-field high-throughput second-harmonic (SH) microscopy for investigating cytoskeletal morphological changes on the single-cell level. The method allows for real-time, in vitro, label-free measurements of cytoskeletal changes that can, under certain conditions, be quantified in terms of orientational distribution or in terms of changes in the number of microtubules. As SH generation is intrinsically sensitive to noncentrosymmetrically structured microtubules, but not to isotropic or centrosymmetric materials, we use it to probe the microtubule structure in the cytoskeleton when it undergoes dynamic changes induced by the application of nocodazole, a well-known microtubule-destabilizing drug that reversibly depolymerizes microtubules. In addition, the orientational directionality of microtubules in neurites and cell bodies is determined label-free using SH polarimetry measurements. Finally, we use spatiotemporal SH imaging to show label-free, real-time nocodazole-induced morphological changes in neurons of different age and in a single axon.
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Affiliation(s)
- Marie E. P. Didier
- Institute of Bioengineering, and Institute of Materials Science, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne, Laboratory for fundamental BioPhotonics, CH 1015 Lausanne, Switzerland
| | - Carlos Macias-Romero
- Institute of Bioengineering, and Institute of Materials Science, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne, Laboratory for fundamental BioPhotonics, CH 1015 Lausanne, Switzerland
| | - Claire Teulon
- Institute of Bioengineering, and Institute of Materials Science, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne, Laboratory for fundamental BioPhotonics, CH 1015 Lausanne, Switzerland
| | - Pascal Jourdain
- Brain Mind Institute, École Polytechnique Fédérale de Lausanne, Laboratory of Neuroenergetics and Cellular Dynamics, CH 1015, Lausanne, Switzerland
| | - Sylvie Roke
- Institute of Bioengineering, and Institute of Materials Science, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne, Laboratory for fundamental BioPhotonics, CH 1015 Lausanne, Switzerland
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12
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Yamada M, Hayashi K. Microtubule nucleation in the cytoplasm of developing cortical neurons and its regulation by brain‐derived neurotrophic factor. Cytoskeleton (Hoboken) 2019; 76:339-345. [DOI: 10.1002/cm.21550] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 06/25/2019] [Accepted: 06/27/2019] [Indexed: 01/06/2023]
Affiliation(s)
- Mimori Yamada
- Department of Materials and Life SciencesFaculty of Science and Technology, Sophia University Tokyo Japan
| | - Kensuke Hayashi
- Department of Materials and Life SciencesFaculty of Science and Technology, Sophia University Tokyo Japan
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13
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Macias-Romero C, Teulon C, Didier M, Roke S. Endogenous SHG and 2PEF coherence imaging of substructures in neurons in 3D. OPTICS EXPRESS 2019; 27:2235-2247. [PMID: 30732263 DOI: 10.1364/oe.27.002235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Neuronal morphology, long-distance transport and signalling critically depend on the organization of microtubules in the cytoskeleton. Second harmonic generation (SHG) imaging has been recognized as a potentially powerful tool for in situ label-free neuroimaging with specific sensitivity to microtubules. We study here the structural organization of microtubules in living neurons using a wide-field multiphoton microscope that performs 3D imaging using a structured illumination. This microscope allows label-free high throughput imaging of living mammalian neurons. We show that we can image structural correlations by taking advantage of the structured illumination and the coherence of the emitted light. The result allows us to study the microtubule organization throughout the development of the neuron and to differentiate between the regions of the cytoskeleton in the matured neuron.
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14
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NEK7 regulates dendrite morphogenesis in neurons via Eg5-dependent microtubule stabilization. Nat Commun 2018; 9:2330. [PMID: 29899413 PMCID: PMC5997995 DOI: 10.1038/s41467-018-04706-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 05/15/2018] [Indexed: 01/22/2023] Open
Abstract
Organization of microtubules into ordered arrays is best understood in mitotic systems, but remains poorly characterized in postmitotic cells such as neurons. By analyzing the cycling cell microtubule cytoskeleton proteome through expression profiling and targeted RNAi screening for candidates with roles in neurons, we have identified the mitotic kinase NEK7. We show that NEK7 regulates dendrite morphogenesis in vitro and in vivo. NEK7 kinase activity is required for dendrite growth and branching, as well as spine formation and morphology. NEK7 regulates these processes in part through phosphorylation of the kinesin Eg5/KIF11, promoting its accumulation on microtubules in distal dendrites. Here, Eg5 limits retrograde microtubule polymerization, which is inhibitory to dendrite growth and branching. Eg5 exerts this effect through microtubule stabilization, independent of its motor activity. This work establishes NEK7 as a general regulator of the microtubule cytoskeleton, controlling essential processes in both mitotic cells and postmitotic neurons. NEK7 is a kinase known for its role in mitotic spindle assembly, driving centrosome separation in prophase through regulation of the kinesin Eg5. Here, the authors show that NEK7 and Eg5 also control dendrite morphogenesis in postmitotic neurons.
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15
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Rao AN, Patil A, Black MM, Craig EM, Myers KA, Yeung HT, Baas PW. Cytoplasmic Dynein Transports Axonal Microtubules in a Polarity-Sorting Manner. Cell Rep 2018; 19:2210-2219. [PMID: 28614709 DOI: 10.1016/j.celrep.2017.05.064] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 04/20/2017] [Accepted: 05/18/2017] [Indexed: 01/20/2023] Open
Abstract
Axonal microtubules are predominantly organized into a plus-end-out pattern. Here, we tested both experimentally and with computational modeling whether a motor-based polarity-sorting mechanism can explain this microtubule pattern. The posited mechanism centers on cytoplasmic dynein transporting plus-end-out and minus-end-out microtubules into and out of the axon, respectively. When cytoplasmic dynein was acutely inhibited, the bi-directional transport of microtubules in the axon was disrupted in both directions, after which minus-end-out microtubules accumulated in the axon over time. Computational modeling revealed that dynein-mediated transport of microtubules can establish and preserve a predominantly plus-end-out microtubule pattern as per the details of the experimental findings, but only if a kinesin motor and a static cross-linker protein are also at play. Consistent with the predictions of the model, partial depletion of TRIM46, a protein that cross-links axonal microtubules in a manner that influences their polarity orientation, leads to an increase in microtubule transport.
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Affiliation(s)
- Anand N Rao
- Department of Neurobiology and Anatomy, Drexel University, Philadelphia, PA 19129, USA
| | - Ankita Patil
- Department of Neurobiology and Anatomy, Drexel University, Philadelphia, PA 19129, USA
| | - Mark M Black
- Department of Anatomy and Cell Biology, Temple University, Philadelphia, PA 19140, USA
| | - Erin M Craig
- Department of Physics, Central Washington University, Ellensburg, WA 98926, USA
| | - Kenneth A Myers
- Department Biological Sciences, University of the Sciences, Philadelphia, PA 19104, USA
| | - Howard T Yeung
- Department of Physics, Central Washington University, Ellensburg, WA 98926, USA
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University, Philadelphia, PA 19129, USA.
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17
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Golgi trafficking defects in postnatal microcephaly: The evidence for “Golgipathies”. Prog Neurobiol 2017; 153:46-63. [DOI: 10.1016/j.pneurobio.2017.03.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 02/22/2017] [Accepted: 03/29/2017] [Indexed: 12/17/2022]
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18
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Myers KA, He Y, Hasaka TP, Baas PW. Microtubule Transport in the Axon: Re-thinking a Potential Role for the Actin Cytoskeleton. Neuroscientist 2016; 12:107-18. [PMID: 16514008 DOI: 10.1177/1073858405283428] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Microtubules are transported down the axon as short pieces by molecular motor proteins. One popular idea is that these microtubules are transported by forces generated against the actin cytoskeleton. The motor for such transport is thought to be cytoplasmic dynein. Here, the authors review this model and discuss recent studies that sought to test it. These studies suggest that the model is valid but incomplete. Microtubule transport is bidirectional and can utilize either actin filaments or longer microtubules as a substrate in the anterograde direction but only longer microtubules in the retrograde direction. Cytoplasmic dynein is one participating motor but not the only one. The authors speculate that the category of anterograde microtubule transport that involves actin filaments may have specialized functions. The relevant forces that transport short microtubules may also be crucial for the manner by which the longer immobile microtubules interact with actin filaments during events such as axonal retraction and growth cone turning.
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Affiliation(s)
- Kenneth A Myers
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA
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Kahn OI, Baas PW. Microtubules and Growth Cones: Motors Drive the Turn. Trends Neurosci 2016; 39:433-440. [PMID: 27233682 DOI: 10.1016/j.tins.2016.04.009] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 04/19/2016] [Accepted: 04/21/2016] [Indexed: 01/09/2023]
Abstract
Navigation of the growth cone at the tip of the developing axon is crucial for the proper wiring of the nervous system. Mechanisms of actin-dependent growth cone steering, via signaling cascades, are well documented. Microtubules are also important in growth cone guidance, because their polarized invasion into the peripheral domain on one side of the growth cone is essential for it to turn in that direction. Classically, microtubules have been considered secondary players, invading the peripheral domain only where the actin cytoskeleton permits them to go. Presented here is evidence for an underappreciated mechanism by which signaling cascades can potentially affect growth cone turning, namely through regulatable forces imposed on the microtubules by molecular motor proteins.
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Affiliation(s)
- Olga I Kahn
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
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Rao AN, Falnikar A, O'Toole ET, Morphew MK, Hoenger A, Davidson MW, Yuan X, Baas PW. Sliding of centrosome-unattached microtubules defines key features of neuronal phenotype. J Cell Biol 2016; 213:329-41. [PMID: 27138250 PMCID: PMC4862329 DOI: 10.1083/jcb.201506140] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 03/28/2016] [Indexed: 12/25/2022] Open
Abstract
Contemporary models for neuronal migration are grounded in the view that virtually all functionally relevant microtubules (MTs) in migrating neurons are attached to the centrosome, which occupies a position between the nucleus and a short leading process. It is assumed that MTs do not undergo independent movements but rather transduce forces that enable movements of the centrosome and nucleus. The present results demonstrate that although this is mostly true, a small fraction of the MTs are centrosome-unattached, and this permits limited sliding of MTs. When this sliding is pharmacologically inhibited, the leading process becomes shorter, migration of the neuron deviates from its normal path, and the MTs within the leading process become buckled. Partial depletion of ninein, a protein that attaches MTs to the centrosome, leads to greater numbers of centrosome-unattached MTs as well as greater sliding of MTs. Concomitantly, the soma becomes less mobile and the leading process acquires an elongated morphology akin to an axon.
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Affiliation(s)
- Anand N Rao
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Aditi Falnikar
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Eileen T O'Toole
- Boulder Laboratory for 3D Electron Microscopy of Cells, University of Colorado, Boulder, CO 80309
| | - Mary K Morphew
- Boulder Laboratory for 3D Electron Microscopy of Cells, University of Colorado, Boulder, CO 80309
| | - Andreas Hoenger
- Boulder Laboratory for 3D Electron Microscopy of Cells, University of Colorado, Boulder, CO 80309
| | - Michael W Davidson
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 Department of Biological Science, Florida State University, Tallahassee, FL 32310
| | - Xiaobing Yuan
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
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del Castillo U, Winding M, Lu W, Gelfand VI. Interplay between kinesin-1 and cortical dynein during axonal outgrowth and microtubule organization in Drosophila neurons. eLife 2015; 4:e10140. [PMID: 26615019 PMCID: PMC4739764 DOI: 10.7554/elife.10140] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 11/27/2015] [Indexed: 12/21/2022] Open
Abstract
In this study, we investigated how microtubule motors organize microtubules in Drosophila neurons. We showed that, during the initial stages of axon outgrowth, microtubules display mixed polarity and minus-end-out microtubules push the tip of the axon, consistent with kinesin-1 driving outgrowth by sliding antiparallel microtubules. At later stages, the microtubule orientation in the axon switches from mixed to uniform polarity with plus-end-out. Dynein knockdown prevents this rearrangement and results in microtubules of mixed orientation in axons and accumulation of microtubule minus-ends at axon tips. Microtubule reorganization requires recruitment of dynein to the actin cortex, as actin depolymerization phenocopies dynein depletion, and direct recruitment of dynein to the membrane bypasses the actin requirement. Our results show that cortical dynein slides ‘minus-end-out’ microtubules from the axon, generating uniform microtubule arrays. We speculate that differences in microtubule orientation between axons and dendrites could be dictated by differential activity of cortical dynein. DOI:http://dx.doi.org/10.7554/eLife.10140.001 Motor proteins can move along filaments called microtubules to transport proteins and other materials to different parts of the cell. Microtubules are “polar” filaments, meaning that they have two distinct ends that have different chemical properties. Motor proteins can only move along these filaments in one direction, for example, the kinesin motor proteins generally move toward the so-called “plus-end”, while dynein motors move in the opposite direction. A typical nerve cell (or neuron) is composed of a cell body, a long projection called an axon and many small branch-like structures called dendrites. Within the axon, the microtubules are arranged so that their plus-ends point outwards, but the microtubules in dendrites are arranged differently so that many minus-ends point outwards instead. This polarity is important for the neuron in deciding which proteins should be transported to axons, and which should go to the dendrites. However, it is not clear how these different microtubule arrangements are established. Here, del Castillo et al. used microscopy to study microtubules in the axons of fruit fly neurons. The experiments show that in the very early stages of neuron development, the axons contained microtubules of mixed polarity. However, by the later stages, the microtubules had become uniform with all the plus-ends directed outwards. Further experiments show that dynein is responsible for this organization as it pushes the minus-end-out microtubules out of the axons. Dynein uses a scaffold made of a protein called actin to attach to the inner surface of the cell and move the minus-end microtubules to the cell body of the neuron. Thus, del Castillo et al.’s findings reveal that these dynein motors are responsible for the polarity of microtubules in mature axons. The next challenge is to understand how dynein is attached to the actin scaffold and why it rearranges microtubules in axons, but not in dendrites. DOI:http://dx.doi.org/10.7554/eLife.10140.002
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Affiliation(s)
- Urko del Castillo
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Michael Winding
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Wen Lu
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, United States
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Abstract
Neurons begin their life as simple spheres, but can ultimately assume an elaborate morphology with numerous, highly arborized dendrites, and long axons. This is achieved via an astounding developmental progression which is dependent upon regulated assembly and dynamics of the cellular cytoskeleton. As neurites emerge out of the soma, neurons break their spherical symmetry and begin to acquire the morphological features that define their structure and function. Neurons regulate their cytoskeleton to achieve changes in cell shape, velocity, and direction as they migrate, extend neurites, and polarize. Of particular importance, the organization and dynamics of actin and microtubules directs the migration and morphogenesis of neurons. This review focuses on the regulation of intrinsic properties of the actin and microtubule cytoskeletons and how specific cytoskeletal structures and dynamics are associated with the earliest phase of neuronal morphogenesis—neuritogenesis.
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Del Castillo U, Lu W, Winding M, Lakonishok M, Gelfand VI. Pavarotti/MKLP1 regulates microtubule sliding and neurite outgrowth in Drosophila neurons. Curr Biol 2014; 25:200-205. [PMID: 25557664 DOI: 10.1016/j.cub.2014.11.008] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 10/03/2014] [Accepted: 11/04/2014] [Indexed: 11/16/2022]
Abstract
Recently, we demonstrated that kinesin-1 can slide microtubules against each other, providing the mechanical force required for initial neurite extension in Drosophila neurons. This sliding is only observed in young neurons actively forming neurites and is dramatically downregulated in older neurons. The downregulation is not caused by the global shutdown of kinesin-1, as the ability of kinesin-1 to transport membrane organelles is not diminished in mature neurons, suggesting that microtubule sliding is regulated by a dedicated mechanism. Here, we have identified the "mitotic" kinesin-6 Pavarotti (Pav-KLP) as an inhibitor of kinesin-1-driven microtubule sliding. Depletion of Pav-KLP in neurons strongly stimulated the sliding of long microtubules and neurite outgrowth, while its ectopic overexpression in the cytoplasm blocked both of these processes. Furthermore, postmitotic depletion of Pav-KLP in Drosophila neurons in vivo reduced embryonic and larval viability, with only a few animals surviving to the third instar larval stage. A detailed examination of motor neurons in the surviving larvae revealed the overextension of axons and mistargeting of neuromuscular junctions, resulting in uncoordinated locomotion. Taken together, our results identify a new role for Pav-KLP as a negative regulator of kinesin-1-driven neurite formation. These data suggest an important parallel between long microtubule-microtubule sliding in anaphase B and sliding of interphase microtubules during neurite formation.
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Affiliation(s)
- Urko Del Castillo
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 E Chicago Avenue, Chicago, IL 60611, USA; IKERBASQUE, Basque Foundation for Science, Bilbao 48011, Spain
| | - Wen Lu
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 E Chicago Avenue, Chicago, IL 60611, USA
| | - Michael Winding
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 E Chicago Avenue, Chicago, IL 60611, USA
| | - Margot Lakonishok
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 E Chicago Avenue, Chicago, IL 60611, USA
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 E Chicago Avenue, Chicago, IL 60611, USA.
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Baas PW, Ahmad FJ. Beyond taxol: microtubule-based treatment of disease and injury of the nervous system. ACTA ACUST UNITED AC 2013; 136:2937-51. [PMID: 23811322 DOI: 10.1093/brain/awt153] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Contemporary research has revealed a great deal of information on the behaviours of microtubules that underlie critical events in the lives of neurons. Microtubules in the neuron undergo dynamic assembly and disassembly, bundling and splaying, severing, and rapid transport as well as integration with other cytoskeletal elements such as actin filaments. These various behaviours are regulated by signalling pathways that affect microtubule-related proteins such as molecular motor proteins and microtubule severing enzymes, as well as a variety of proteins that promote the assembly, stabilization and bundling of microtubules. In recent years, translational neuroscientists have earmarked microtubules as a promising target for therapy of injury and disease of the nervous system. Proof-of-principle has come mainly from studies using taxol and related drugs to pharmacologically stabilize microtubules in animal models of nerve injury and disease. However, concerns persist that the negative consequences of abnormal microtubule stabilization may outweigh the positive effects. Other potential approaches include microtubule-active drugs with somewhat different properties, but also expanding the therapeutic toolkit to include intervention at the level of microtubule regulatory proteins.
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Affiliation(s)
- Peter W Baas
- 1 Drexel University College of Medicine, Philadelphia, PA, USA
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Reiner O. LIS1 and DCX: Implications for Brain Development and Human Disease in Relation to Microtubules. SCIENTIFICA 2013; 2013:393975. [PMID: 24278775 PMCID: PMC3820303 DOI: 10.1155/2013/393975] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 02/07/2013] [Indexed: 05/29/2023]
Abstract
Proper lamination of the cerebral cortex requires the orchestrated motility of neurons from their place of birth to their final destination. Improper neuronal migration may result in a wide range of diseases, including brain malformations, such as lissencephaly, mental retardation, schizophrenia, and autism. Ours and other studies have implicated that microtubules and microtubule-associated proteins play an important role in the regulation of neuronal polarization and neuronal migration. Here, we will review normal processes of brain development and neuronal migration, describe neuronal migration diseases, and will focus on the microtubule-associated functions of LIS1 and DCX, which participate in the regulation of neuronal migration and are involved in the human developmental brain disease, lissencephaly.
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Affiliation(s)
- Orly Reiner
- Department of Molecular Genetics, The Weizmann Institute of Science, 76100 Rehovot, Israel
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Yan J, Chao DL, Toba S, Koyasako K, Yasunaga T, Hirotsune S, Shen K. Kinesin-1 regulates dendrite microtubule polarity in Caenorhabditis elegans. eLife 2013; 2:e00133. [PMID: 23482306 PMCID: PMC3591006 DOI: 10.7554/elife.00133] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 01/28/2013] [Indexed: 11/13/2022] Open
Abstract
In neurons, microtubules (MTs) span the length of both axons and dendrites, and the molecular motors use these intracellular ‘highways' to transport diverse cargo to the appropriate subcellular locations. Whereas axonal MTs are organized such that the plus-end is oriented out from the cell body, dendrites exhibit a mixed MTs polarity containing both minus-end-out and plus-end-out MTs. The molecular mechanisms underlying this differential organization, as well as its functional significance, are unknown. Here, we show that kinesin-1 is critical in establishing the characteristic minus-end-out MT organization of the dendrite in vivo. In unc-116 (kinesin-1/kinesin heavy chain) mutants, the dendritic MTs adopt an axonal-like plus-end-out organization. Kinesin-1 protein is able to cross-link anti-paralleled MTs in vitro. We propose that kinesin-1 regulates the dendrite MT polarity through directly gliding the plus-end-out MTs out of the dendrite using both the motor domain and the C-terminal MT-binding domain. DOI:http://dx.doi.org/10.7554/eLife.00133.001 Neurons, or nerve cells, are excitable cells that transmit information using electrical and chemical signals. Nerve cells are generally composed of a cell body, multiple dendrites, and a single axon. The dendrites are responsible for receiving inputs and for transferring these signals to the cell body, whereas the axon carries signals away from the cell body and relays them to other cells. Like all cells, nerve cells have a cytoskeleton made up of microtubules, which help to determine cellular shape and which act as ‘highways' for intracellular transport. Microtubules are long hollow fibers composed of alternating α- and β-tubulin proteins: each microtubule has a ‘plus'-end, where the β subunits are exposed, and a ‘minus'-end, where the α subunits are exposed. Nerve cells are highly polarized: within the axon, the microtubules are uniformly oriented with their plus-ends pointing outward, whereas in dendrites, there are many microtubules with their minus-ends pointing outward. This arrangement is conserved across the animal kingdom, but the mechanisms that establish it are largely unknown. Yan et al. use the model organism Caenorhabditis elegans (the nematode worm) to conduct a detailed in vivo analysis of dendritic microtubule organization. They find that a motor protein called kinesin-1 is critical for generating the characteristic minus-end-out pattern in dendrites: when the gene that codes for this protein is knocked out, the dendrites in microtubules undergo a dramatic polarity shift and adopt the plus-end-out organization that is typical of axons. The mutant dendrites also show other axon-like features: for example, they lack many of the proteins that are usually found in dendrites. Based on these and other data, Yan et al. propose that kinesin-1 determines microtubule polarity in dendrites by moving plus-end-out microtubules out of dendrites. These first attempts to explain, at the molecular level, how dendritic microtubule polarity is achieved in vivo could lead to new insights into the structure and function of the neuronal cytoskeleton. DOI:http://dx.doi.org/10.7554/eLife.00133.002
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Affiliation(s)
- Jing Yan
- Department of Biology , Howard Hughes Medical Institute, Stanford University , Stanford , United States
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27
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Abstract
Microtubules are nearly uniformly oriented in the axons of vertebrate neurons but are non-uniformly oriented in their dendrites. Studies to date suggest a scenario for establishing these microtubule patterns whereby microtubules are transported into the axon and nascent dendrites with plus-ends-leading, and then additional microtubules of the opposite orientation are transported into the developing dendrites. Here, we used contemporary tools to confirm that depletion of kinesin-6 (also called CHO1/MKLP1 or kif23) from rat sympathetic neurons causes a reduction in the appearance of minus-end-distal microtubules in developing dendrites, which in turn causes them to assume an axon-like morphology. Interestingly, we observed a similar phenomenon when we depleted kinesin-12 (also called kif15 or HKLP2). Both motors are best known for their participation in mitosis in other cell types, and both are enriched in the cell body and dendrites of neurons. Unlike kinesin-12, which is present throughout the neuron, kinesin-6 is barely detectable in the axon. Accordingly, depletion of kinesin-6, unlike depletion of kinesin-12, has no effect on axonal branching or navigation. Interestingly, depletion of either motor results in faster growing axons with greater numbers of mobile microtubules. Based on these observations, we posit a model whereby these two motors generate forces that attenuate the transport of microtubules with plus-ends-leading from the cell body into the axon. Some of these microtubules are not only prevented from moving into the axon but are driven with minus-ends-leading into developing dendrites. In this manner, these so-called "mitotic" motors coregulate the microtubule patterns of axons and dendrites.
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Abstract
Development, polarization, structural integrity, and plasticity of neuronal cells critically depend on the microtubule network and its dynamic properties. SLAIN1 and SLAIN2 are microtubule plus-end tracking proteins that have been recently identified as regulators of microtubule dynamics. SLAINs are targeted to microtubule tips through an interaction with the core components of microtubule plus-end tracking protein network, End Binding family members. SLAINs promote persistent microtubule growth by recruiting the microtubule polymerase ch-TOG to microtubule plus-ends. Here, we show that SLAIN1/2 and ch-TOG-proteins are highly enriched in brain and are expressed throughout mouse brain development. Disruption of the SLAIN-ch-TOG complex in cultured primary rat hippocampal neurons by RNA interference-mediated knockdown and a dominant-negative approach perturbs microtubule growth by increasing catastrophe frequency and inhibits axon extension during neuronal development. Our study shows that proper control of microtubule dynamics is important for axon elongation in developing neurons.
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Shea TB, Lee S. The discontinuous nature of neurofilament transport accommodates both establishment and repair of the axonal neurofilament array. Cytoskeleton (Hoboken) 2012; 70:67-73. [PMID: 23124969 DOI: 10.1002/cm.21087] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 10/08/2012] [Accepted: 10/11/2012] [Indexed: 12/19/2022]
Abstract
Neurofilaments (NFs) provide structural support to axons. Timely and regional deposition of NFs is essential during axonogenesis, since progressive stabilization of proximal axons is essential to support continued pathfinding of distal axonal regions. NFs undergo short bursts of microtubule-mediated axonal transport interspersed by prolonged pauses. We demonstrate herein that it is this unique "on-off" method of axonal transport, coupled with the ability of NFs to form cation-dependent, phosphomediated lateral associations that allow neurons to mediate the orderly transition from exploratory process to stabilized axon following synaptogenesis. We further demonstrate how this transport method provides for NF maintenance following maturation and encompasses the potential for regeneration.
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Affiliation(s)
- Thomas B Shea
- Department of Biological Sciences, Center for Cellular Neurobiology and Neurodegeneration Research, University of Massachusetts, Lowell, One University Avenue, Lowell, MA 01854, USA.
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Abstract
In order for growth cones to turn, microtubules from the central domain must preferentially invade the peripheral domain in the direction of the turn. Recent studies suggest that kinesin-5 (also called Eg5 or kif11) suppresses the invasion of microtubules into the peripheral domain on the side of the growth cone opposite the direction of turning. In theory, kinesin-5 could elicit these effects by acting on the microtubules within the peripheral domain itself, by acting on microtubules in the central domain, or in the transition zone between these two domains. In rat neurons expressing kinesin-5, we documented the presence of kinesin-5 in both domains of the growth cone and especially enriched in the transition zone. We then focally inactivated kinesin-5 in various regions of the growth cone, using micro-chromophore-assisted laser inactivation. We found that a greater invasion of microtubules into the peripheral domain occurred when kinesin-5 was inactivated specifically in the transition zone. However, there was no effect on microtubule invasion into the peripheral domain when kinesin-5 was inactivated in the peripheral domain itself or in the central domain. In other experiments, frog growth cones were observed to turn toward a gradient of a drug that inhibits kinesin-5, confirming that asymmetric inactivation of kinesin-5 can cause the growth cone to turn. Finally, expression of a phospho-mutant of kinesin-5 resulted in greater microtubule invasion throughout the peripheral domain and an inhibition of growth cone turning, implicating phosphorylation as a means by which kinesin-5 is regulated in the growth cone.
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Sharp DJ, O'Rourke B, Zhang D. Microtubules cut loose at the cell cortex. Fly (Austin) 2012; 6:12-5. [PMID: 22388006 DOI: 10.4161/fly.18306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The ability of the microtubule cytoskeleton to rapidly and locally reorganize itself in response to intra- and extracellular signals is essential to its wide range of functions. A site of tightly regulated microtubule dynamics--and the major interface between the microtubule cytoskeleton and the extracellular environment--is the cell cortex, where the selective stabilization and destabilization of microtubule plus-ends is required for normal cell division, morphogenesis and migration. In a recent study, we found that the cortex of Drosophila S2 and D17 cells is coated with the microtubule severing enzyme and plus-end depolymerase, Kat-60, which actively suppresses microtubule growth and stability along the cell edge. We have proposed that cortical Kat-60 functions by uncapping plus-ends, thereby activating another microtubule depolymerase, KLP10A, preloaded onto the end. The localized destruction of microtubule plus-ends at a specific cortical could feed into larger regulatory pathways, such as those in control of the actin cytoskeleton, to influence cell polarization and motility.
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Affiliation(s)
- David J Sharp
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY, USA
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Baas PW, Mozgova OI. A novel role for retrograde transport of microtubules in the axon. Cytoskeleton (Hoboken) 2012; 69:416-25. [PMID: 22328357 DOI: 10.1002/cm.21013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 01/26/2012] [Accepted: 01/27/2012] [Indexed: 01/14/2023]
Abstract
Short microtubules move within the axon in both directions. In the past, it had been assumed that all of the short moving microtubules are oriented with their plus-ends distal to the cell body, regardless of their direction of movement. The anterogradely moving microtubules were posited to play critical roles in the establishment, expansion, and maintenance of the axonal microtubule array. There was no known function for the retrogradely moving microtubules. In considering the mechanism of their transport, we had assumed that all of the short microtubules have a plus-end-distal polarity orientation, as is characteristic of the long microtubules that dominate the axon. Here we discuss an alternative hypothesis, namely that the short microtubules moving retrogradely have the opposite polarity orientation of those moving anterogradely. Those that move anterogradely have their plus-ends distal to the cell body while those that move retrogradely have their minus ends distal to the cell body. In this view, retrograde transport is a means for clearing the axon of incorrectly oriented microtubules. This new model, if correct, has profound implications for the manner by which healthy axons preserve their characteristic pattern of microtubule polarity orientation. We speculate that pathological flaws in this mechanism may be a critical factor in the degeneration of axons during disease and injury, as well as in neuropathy caused by microtubule-active drugs.
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Affiliation(s)
- Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, Pennsylvania 19129, USA.
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Manneville JB, Etienne-Manneville S. Positioning centrosomes and spindle poles: looking at the periphery to find the centre. Biol Cell 2012; 98:557-65. [PMID: 16907664 DOI: 10.1042/bc20060017] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Centrosome positioning is tightly controlled throughout the cell cycle and probably shares common regulatory mechanisms with spindle-pole positioning. In this article, we detail the possible mechanisms controlling centrosome and spindle positioning in various organisms both in interphase and mitotic cells, and discuss recent findings showing how microtubule plus-end-associated proteins interact with the cell cortex. We suggest that microtubule plus-end complexes simultaneously regulate microtubule dynamics and microtubule anchoring at the cell periphery to allow proper centrosome and spindle-pole positioning.
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Nguyen MM, Stone MC, Rolls MM. Microtubules are organized independently of the centrosome in Drosophila neurons. Neural Dev 2011; 6:38. [PMID: 22145670 PMCID: PMC3271965 DOI: 10.1186/1749-8104-6-38] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Accepted: 12/06/2011] [Indexed: 01/26/2023] Open
Abstract
Background The best-studied arrangement of microtubules is that organized by the centrosome, a cloud of microtubule nucleating and anchoring proteins is clustered around centrioles. However, noncentrosomal microtubule arrays are common in many differentiated cells, including neurons. Although microtubules are not anchored at neuronal centrosomes, it remains unclear whether the centrosome plays a role in organizing neuronal microtubules. We use Drosophila as a model system to determine whether centrosomal microtubule nucleation is important in mature neurons. Results In developing and mature neurons, centrioles were not surrounded by the core nucleation protein γ-tubulin. This suggests that the centrioles do not organize functional centrosomes in Drosophila neurons in vivo. Consistent with this idea, centriole position was not correlated with a specific region of the cell body in neurons, and growing microtubules did not cluster around the centriole, even after axon severing when the number of growing plus ends is dramatically increased. To determine whether the centrosome was required for microtubule organization in mature neurons, we used two approaches. First, we used DSas-4 centriole duplication mutants. In these mutants, centrioles were present in many larval sensory neurons, but they were not fully functional. Despite reduced centriole function, microtubule orientation was normal in axons and dendrites. Second, we used laser ablation to eliminate the centriole, and again found that microtubule polarity in axons and dendrites was normal, even 3 days after treatment. Conclusion We conclude that the centrosome is not a major site of microtubule nucleation in Drosophila neurons, and is not required for maintenance of neuronal microtubule organization in these cells.
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Affiliation(s)
- Michelle M Nguyen
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
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Neukirchen D, Bradke F. Neuronal polarization and the cytoskeleton. Semin Cell Dev Biol 2011; 22:825-33. [DOI: 10.1016/j.semcdb.2011.08.007] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 07/29/2011] [Accepted: 08/16/2011] [Indexed: 12/26/2022]
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Abstract
A hallmark of neurons is their ability to polarize with dendrite and axon specification to allow the proper flow of information through the nervous system. Over the past decade, extensive research has been performed in an attempt to understand the molecular and cellular machinery mediating this neuronal polarization process. It has become evident that many of the critical regulators involved in establishing neuronal polarity are evolutionarily conserved proteins that had previously been implicated in controlling the polarization of other cell types. At the forefront of this research are the partition defective (Par) proteins. In this review,we will provide a commentary on the progress of work regarding the central importance of Parproteins in the establishment of neuronal polarity.
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Affiliation(s)
- Ryan Insolera
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
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Schuster M, Kilaru S, Fink G, Collemare J, Roger Y, Steinberg G. Kinesin-3 and dynein cooperate in long-range retrograde endosome motility along a nonuniform microtubule array. Mol Biol Cell 2011; 22:3645-57. [PMID: 21832152 PMCID: PMC3183019 DOI: 10.1091/mbc.e11-03-0217] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The polarity of microtubules (MTs) determines the motors for intracellular motility, with kinesins moving to plus ends and dynein to minus ends. In elongated cells of Ustilago maydis, dynein is thought to move early endosomes (EEs) toward the septum (retrograde), whereas kinesin-3 transports them to the growing cell tip (anterograde). Occasionally, EEs run up to 90 μm in one direction. The underlying MT array consists of unipolar MTs at both cell ends and antipolar bundles in the middle region of the cell. Cytoplasmic MT-organizing centers, labeled with a γ-tubulin ring complex protein, are distributed along the antipolar MTs but are absent from the unipolar regions. Dynein colocalizes with EEs for 10-20 μm after they have left the cell tip. Inactivation of temperature-sensitive dynein abolishes EE motility within the unipolar MT array, whereas long-range motility is not impaired. In contrast, kinesin-3 is continuously present, and its inactivation stops long-range EE motility. This indicates that both motors participate in EE motility, with dynein transporting the organelles through the unipolar MT array near the cell ends, and kinesin-3 taking over at the beginning of the medial antipolar MT array. The cooperation of both motors mediates EE movements over the length of the entire cell.
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Affiliation(s)
- Martin Schuster
- Department of Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom
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Differential regulation of dendritic and axonal development by the novel Krüppel-like factor Dar1. J Neurosci 2011; 31:3309-19. [PMID: 21368042 DOI: 10.1523/jneurosci.6307-10.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Dendrites and axons are two major neuronal compartments with differences that are critical for neuronal functions. To learn about the differential regulation of dendritic and axonal development, we conducted a genetic screen in Drosophila and isolated the dendritic arbor reduction 1 (dar1) mutants, which display defects in dendritic but not axonal growth. The dar1 gene encodes a novel transcription regulator in the Krüppel-like factor family. Neurons lacking dar1 function have severely reduced growth of microtubule- but not F-actin-based dendritic branches. In contrast, overexpression of Dar1 dramatically increased the growth of microtubule-based dendritic branches. Our results suggest that Dar1 promotes dendrite growth in part by suppressing the expression of the microtubule-severing protein Spastin. Our study thus uncovers a novel transcriptional program for microtubule regulation that preferentially controls dendrite growth.
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Angelov DN. Factors Limiting Motor Recovery After Facial Nerve Injury. PHYSICAL REHABILITATION OF PARALYSED FACIAL MUSCLES: FUNCTIONAL AND MORPHOLOGICAL CORRELATES 2011. [DOI: 10.1007/978-3-642-18120-7_1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Directed microtubule growth, +TIPs, and kinesin-2 are required for uniform microtubule polarity in dendrites. Curr Biol 2010; 20:2169-77. [PMID: 21145742 DOI: 10.1016/j.cub.2010.11.050] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 10/06/2010] [Accepted: 11/18/2010] [Indexed: 01/12/2023]
Abstract
BACKGROUND in many differentiated cells, microtubules are organized into polarized noncentrosomal arrays, yet few mechanisms that control these arrays have been identified. For example, mechanisms that maintain microtubule polarity in the face of constant remodeling by dynamic instability are not known. Drosophila neurons contain uniform-polarity minus-end-out microtubules in dendrites, which are often highly branched. Because undirected microtubule growth through dendrite branch points jeopardizes uniform microtubule polarity, we have used this system to understand how cells can maintain dynamic arrays of polarized microtubules. RESULTS we find that growing microtubules navigate dendrite branch points by turning the same way, toward the cell body, 98% of the time and that growing microtubules track along stable microtubules toward their plus ends. Using RNAi and genetic approaches, we show that kinesin-2, and the +TIPS EB1 and APC, are required for uniform dendrite microtubule polarity. Moreover, the protein-protein interactions and localization of Apc2-GFP and Apc-RFP to branch points suggests that these proteins work together at dendrite branches. The functional importance of this polarity mechanism is demonstrated by the failure of neurons with reduced kinesin-2 to regenerate an axon from a dendrite. CONCLUSIONS we conclude that microtubule growth is directed at dendrite branch points and that kinesin-2, APC, and EB1 are likely to play a role in this process. We propose that kinesin-2 is recruited to growing microtubules by +TIPS and that the motor protein steers growing microtubules at branch points. This represents a newly discovered mechanism for maintaining polarized arrays of microtubules.
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Kinesin-12, a mitotic microtubule-associated motor protein, impacts axonal growth, navigation, and branching. J Neurosci 2010; 30:14896-906. [PMID: 21048148 DOI: 10.1523/jneurosci.3739-10.2010] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Kinesin-12 (also called Kif15) is a mitotic motor protein that continues to be expressed in developing neurons. Depletion of kinesin-12 causes axons to grow faster, more than doubles the frequency of microtubule transport in both directions in the axon, prevents growth cones from turning properly, and enhances the invasion of microtubules into filopodia. These results are remarkably similar to those obtained in previous studies in which neurons were depleted of kinesin-5 (also called Eg5 or Kif11), another mitotic motor protein that continues to be expressed in developing neurons. However, there are also notable differences in the phenotypes obtained with depleting each of these motors. Depleting kinesin-12 decreases axonal branching and growth cone size, whereas inhibiting kinesin-5 increases these parameters. In addition, depleting kinesin-12 diminishes the appearance of growth-cone-like waves along the length of the axon, an effect not observed with depletion of kinesin-5. Finally, depletion of kinesin-12 abolishes the "waggling" behavior of microtubules that occurs as they assemble along actin bundles within filopodia, whereas inhibition of kinesin-5 does not. Interestingly, and perhaps relevant to these differences in phenotype, in biochemical studies, kinesin-12 coimmunoprecipitates with actin but kinesin-5 does not. Collectively, these findings support a scenario whereby kinesin-12 shares functions with kinesin-5 related to microtubule-microtubule interactions, but kinesin-12 has other functions not shared by kinesin-5 that are related to the ability of kinesin-12 to interact with actin.
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Kapitein LC, Hoogenraad CC. Which way to go? Cytoskeletal organization and polarized transport in neurons. Mol Cell Neurosci 2010; 46:9-20. [PMID: 20817096 DOI: 10.1016/j.mcn.2010.08.015] [Citation(s) in RCA: 173] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Accepted: 08/25/2010] [Indexed: 01/01/2023] Open
Abstract
To establish and maintain their polarized morphology, neurons employ active transport driven by cytoskeletal motor proteins to sort cargo between axons and dendrites. These motors can move in a specific direction over either microtubules (kinesins, dynein) or actin filaments (myosins). The basic traffic rules governing polarized transport on the neuronal cytoskeleton have long remained unclear, but recent work has revealed several fundamental sorting principles based on differences in the cytoskeletal organization in axons versus dendrites. We will highlight the basic characteristics of the neuronal cytoskeleton and review existing evidence for microtubule and actin based traffic rules in polarized neuronal transport. We will propose a model in which polarized sorting of cargo is established by recruiting or activating the proper subset of motor proteins, which are subsequently guided to specific directions by the polarized organization of the neuronal cytoskeleton.
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Affiliation(s)
- Lukas C Kapitein
- Department of Neuroscience, Erasmus Medical Center, Dr. Molewaterplein 50, 3015 GE, Rotterdam, The Netherlands
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Scales TME, Lin S, Kraus M, Goold RG, Gordon-Weeks PR. Nonprimed and DYRK1A-primed GSK3 beta-phosphorylation sites on MAP1B regulate microtubule dynamics in growing axons. J Cell Sci 2009; 122:2424-35. [PMID: 19549690 PMCID: PMC2704879 DOI: 10.1242/jcs.040162] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/21/2009] [Indexed: 12/26/2022] Open
Abstract
MAP1B is a developmentally regulated microtubule-associated phosphoprotein that regulates microtubule dynamics in growing axons and growth cones. We used mass spectrometry to map 28 phosphorylation sites on MAP1B, and selected for further study a putative primed GSK3 beta site and compared it with two nonprimed GSK3 beta sites that we had previously characterised. We raised a panel of phosphospecific antibodies to these sites on MAP1B and used it to assess the distribution of phosphorylated MAP1B in the developing nervous system. This showed that the nonprimed sites are restricted to growing axons, whereas the primed sites are also expressed in the neuronal cell body. To identify kinases phosphorylating MAP1B, we added kinase inhibitors to cultured embryonic cortical neurons and monitored MAP1B phosphorylation with our panel of phosphospecific antibodies. These experiments identified dual-specificity tyrosine-phosphorylation-regulated kinase (DYRK1A) as the kinase that primes sites of GSK3 beta phosphorylation in MAP1B, and we confirmed this by knocking down DYRK1A in cultured embryonic cortical neurons by using shRNA. DYRK1A knockdown compromised neuritogenesis and was associated with alterations in microtubule stability. These experiments demonstrate that MAP1B has DYRK1A-primed and nonprimed GSK3 beta sites that are involved in the regulation of microtubule stability in growing axons.
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Affiliation(s)
- Timothy M E Scales
- The MRC Centre for Developmental Neurobiology, New Hunt's House, Guy's Campus, King's College London, London SE1 1UL, UK
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Shea TB, Lee S, Kushkuley J, Dubey M, Chan WKH. Neurofilament dynamics: a tug of war by microtubule motors. FUTURE NEUROLOGY 2009. [DOI: 10.2217/fnl.09.4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Structural support for axons, which can consist of volumes thousands of times larger than the neuronal perikaryon, is provided in part by neurofilaments (NFs), the major fibrous constituent of the axonal cytoskeleton. Most NFs undergo anterograde transport (towards the synapse or growth cone), while a few undergo retrograde transport (back towards the perikaryon). Some NFs exhibit an extended residence time along axons, which allows NFs to provide structural support to the axon yet minimizes NF turnover, which would otherwise impart a prohibitive metabolic burden upon the neuron. Herein, we explore known and hypothesized roles for microtubule motors in transport and distribution of NFs along axons. We present evidence that those NFs that display extended residence along axons are critically dependent upon surrounding microtubules, and that simultaneous interaction with multiple microtubule motors provides the architectural force regulating their distribution.
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Affiliation(s)
- Thomas B Shea
- Center for Cellular Neurobiology & Neurodegeneration Research, Departments of Biological Sciences & Biochemistry, University of Massachusetts–Lowell, One University Avenue, Lowell, MA 01854, USA
| | - Sangmook Lee
- Center for Cellular Neurobiology & Neurodegeneration Research, Departments of Biological Sciences & Biochemistry, University of Massachusetts–Lowell, One University Avenue, Lowell, MA 01854, USA
| | - Jacob Kushkuley
- Center for Cellular Neurobiology & Neurodegeneration Research, Departments of Biological Sciences & Biochemistry, University of Massachusetts–Lowell, One University Avenue, Lowell, MA 01854, USA
| | - Maya Dubey
- Center for Cellular Neurobiology & Neurodegeneration Research, Departments of Biological Sciences & Biochemistry, University of Massachusetts–Lowell, One University Avenue, Lowell, MA 01854, USA
| | - Walter K-H Chan
- Center for Cellular Neurobiology & Neurodegeneration Research, Departments of Biological Sciences & Biochemistry, University of Massachusetts–Lowell, One University Avenue, Lowell, MA 01854, USA
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Park SJ, Lee BH, Kim DJ. Identification of proteins that interact with podocin using the yeast 2-hybrid system. Yonsei Med J 2009; 50:273-9. [PMID: 19430563 PMCID: PMC2678704 DOI: 10.3349/ymj.2009.50.2.273] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 08/28/2008] [Accepted: 08/28/2008] [Indexed: 11/27/2022] Open
Abstract
PURPOSE As a membrane protein at the insertion site of the slit diaphragm (SD) complex in podocyte foot processes, podocin has been reported to act as a scaffolding protein required to maintain or regulate the structural integrity of the SD. In order to identify proteins that associate or interact with podocin, we screened a mouse kidney complementary DNA (cDNA) library using a yeast 2-hybrid system. MATERIALS AND METHODS 1) The full-length cDNA of podocin from the mouse kidney was amplified by Polymerase Chain Reaction (PCR), 2) The PCR product was cloned into a pGBKT7 vector, pGBKT7-podocin, 3) After the pGBKT7-podocin was transformed into AH109, the AH109/pGBKT7-podocin product was obtained, 4) The mouse kidney cDNA library was transformed into the AH109/pGBKT7-podocin and screened by selection steps, 5) Next, twelve clones were cultured and isolated, 6) The yeast-purified plasmids were transformed into Escherichia coli (E. coli) by heat shock, and 7) To identify the activation domain (AD)/library inserts, we digested them with Him III, and the fragments were then sequenced. RESULTS 12 positive clones that interacted with podocin were obtained by screening a mouse kidney cDNA library using pGBKT7-podocin. Among them, only 4 clones were found to function at the podocyte where podocin is present. CONCLUSION Additional studies are needed to clarify the role and interaction with podocin and candidates.
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Affiliation(s)
- Soo Jin Park
- Clinical Research Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Byung Ha Lee
- Clinical Research Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Dae Joong Kim
- Division of Nephrology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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Abstract
Axons are occupied by dense arrays of cytoskeletal elements called microtubules, which are critical for generating and maintaining the architecture of the axon, and for acting as railways for the transport of organelles in both directions within the axon. Microtubules are organized and regulated by molecules that affect their assembly and disassembly, their stabilization, their association with other cytoskeletal elements, and their alignment and bundling with one another. Recent studies have accentuated the role of molecular motor proteins and microtubule-severing proteins in the establishment and maintenance of the axonal microtubule array. The growing body of knowledge on the proteins and mechanisms that regulate axonal microtubules has fostered a better understanding of how many debilitating diseases cause axons to degenerate. The purpose of this chapter is to provide an update on current knowledge of axonal microtubules and the proteins that regulate them, and to reflect on cutting-edge findings linking these proteins and mechanisms to diseases that afflict the human population.
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Venoux M, Delmouly K, Milhavet O, Vidal-Eychenié S, Giorgi D, Rouquier S. Gene organization, evolution and expression of the microtubule-associated protein ASAP (MAP9). BMC Genomics 2008; 9:406. [PMID: 18782428 PMCID: PMC2551623 DOI: 10.1186/1471-2164-9-406] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 09/09/2008] [Indexed: 11/10/2022] Open
Abstract
Background ASAP is a newly characterized microtubule-associated protein (MAP) essential for proper cell-cycling. We have previously shown that expression deregulation of human ASAP results in profound defects in mitotic spindle formation and mitotic progression leading to aneuploidy, cytokinesis defects and/or cell death. In the present work we analyze the structure and evolution of the ASAP gene, as well as the domain composition of the encoded protein. Mouse and Xenopus cDNAs were cloned, the tissue expression characterized and the overexpression profile analyzed. Results Bona fide ASAP orthologs are found in vertebrates with more distantly related potential orthologs in invertebrates. This single-copy gene is conserved in mammals where it maps to syntenic chromosomal regions, but is also clearly identified in bird, fish and frog. The human gene is strongly expressed in brain and testis as a 2.6 Kb transcript encoding a ~110 KDa protein. The protein contains MAP, MIT-like and THY domains in the C-terminal part indicative of microtubule interaction, while the N-terminal part is more divergent. ASAP is composed of ~42% alpha helical structures, and two main coiled-coil regions have been identified. Different sequence features may suggest a role in DNA damage response. As with human ASAP, the mouse and Xenopus proteins localize to the microtubule network in interphase and to the mitotic spindle during mitosis. Overexpression of the mouse protein induces mitotic defects similar to those observed in human. In situ hybridization in testis localized ASAP to the germ cells, whereas in culture neurons ASAP localized to the cell body and growing neurites. Conclusion The conservation of ASAP indicated in our results reflects an essential function in vertebrates. We have cloned the ASAP orthologs in mouse and Xenopus, two valuable models to study the function of ASAP. Tissue expression of ASAP revealed a high expression in brain and testis, two tissues rich in microtubules. ASAP associates to the mitotic spindle and cytoplasmic microtubules, and represents a key factor of mitosis with possible involvement in other cell cycle processes. It may have a role in spermatogenesis and also represents a potential new target for antitumoral drugs. Possible involvement in neuron dynamics also highlights ASAP as a candidate target in neurodegenerative diseases.
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Affiliation(s)
- Magali Venoux
- Groupe Microtubules et Cycle Cellulaire, Institut de Génétique Humaine, CNRS UPR 1142, rue de cardonille, 34396 Montpellier cédex 5, France.
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Sbai O, Ferhat L, Bernard A, Gueye Y, Ould-Yahoui A, Thiolloy S, Charrat E, Charton G, Tremblay E, Risso JJ, Chauvin JP, Arsanto JP, Rivera S, Khrestchatisky M. Vesicular trafficking and secretion of matrix metalloproteinases-2, -9 and tissue inhibitor of metalloproteinases-1 in neuronal cells. Mol Cell Neurosci 2008; 39:549-68. [PMID: 18817873 DOI: 10.1016/j.mcn.2008.08.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 07/08/2008] [Accepted: 08/09/2008] [Indexed: 11/17/2022] Open
Abstract
Matrix metalloproteinases (MMPs) are endopeptidases that cleave matrix, soluble and membrane-bound proteins and are regulated by their endogenous inhibitors the tissue inhibitors of MMPs (TIMPs). Nothing is known about MMP/TIMP trafficking and secretion in neuronal cells. We focussed our attention on the gelatinases MMP-2 and MMP-9, and their inhibitor TIMP-1. MMPs and TIMP-1 fused to GFP were expressed in N2a neuroblastoma and primary neuronal cells to study trafficking and secretion using real time video-microscopy, imaging, electron microscopy and biochemical approaches. We show that MMPs and TIMP-1 are secreted in 160-200 nm vesicles in a Golgi-dependent pathway. These vesicles distribute along microtubules and microfilaments, co-localise differentially with the molecular motors kinesin and myosin Va and undergo both anterograde and retrograde trafficking. MMP-9 retrograde transport involves the dynein/dynactin molecular motor. In hippocampal neurons, MMP-2 and MMP-9 vesicles are preferentially distributed in the somato-dendritic compartment and are found in dendritic spines. Non-transfected hippocampal neurons also demonstrate vesicular secretion of MMP-2 in both its pro- and active forms and gelatinolytic activity localised within dendritic spines. Our results show differential trafficking of MMP and TIMP-1-containing vesicles in neuronal cells and suggest that these vesicles could play a role in neuronal and synaptic plasticity.
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Affiliation(s)
- Oualid Sbai
- Neurobiologie des Interactions Cellulaires et Neurophysiopathologie (NICN), UMR 6184 CNRS-Université de la Méditerranée, Faculté de Médecine, IFR Jean Roche, Bd Pierre Dramard, 13916 Marseille Cedex 20, France
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