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Gibson C, Jönsson H, Spelman TA. Mean-field theory approach to three-dimensional nematic phase transitions in microtubules. Phys Rev E 2023; 108:064414. [PMID: 38243538 DOI: 10.1103/physreve.108.064414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 11/16/2023] [Indexed: 01/21/2024]
Abstract
Microtubules are dynamic intracellular fibers that have been observed experimentally to undergo spontaneous self-alignment. We formulate a three-dimensional (3D) mean-field theory model to analyze the nematic phase transition of microtubules growing and interacting within a 3D space, then make a comparison with computational simulations. We identify a control parameter G_{eff} and predict a unique critical value G_{eff}=1.56 for which a phase transition can occur. Furthermore, we show both analytically and using simulations that this predicted critical value does not depend on the presence of zippering. The mean-field theory developed here provides an analytical estimate of microtubule patterning characteristics without running time-consuming simulations and is a step towards bridging scales from microtubule behavior to multicellular simulations.
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Affiliation(s)
- Cameron Gibson
- Sainsbury Laboratory, University of Cambridge, Cambridge, CB2 1LR, United Kingdom
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
- Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA
| | - Henrik Jönsson
- Sainsbury Laboratory, University of Cambridge, Cambridge, CB2 1LR, United Kingdom
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, United Kingdom
- Centre for Environmental and Climate Science, Lund University, SE-223 62 Lund, Sweden
| | - Tamsin A Spelman
- Sainsbury Laboratory, University of Cambridge, Cambridge, CB2 1LR, United Kingdom
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Nakamura A, Ikeda M, Kusayanagi S, Hayashi K. An alternative splice isoform of mouse CDK5RAP2 induced cytoplasmic microtubule nucleation. IBRO Neurosci Rep 2022; 13:264-273. [PMID: 36164503 PMCID: PMC9508486 DOI: 10.1016/j.ibneur.2022.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 09/11/2022] [Indexed: 10/29/2022] Open
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Centrosome regulation and function in mammalian cortical neurogenesis. Curr Opin Neurobiol 2021; 69:256-266. [PMID: 34303132 DOI: 10.1016/j.conb.2021.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Revised: 06/29/2021] [Accepted: 06/30/2021] [Indexed: 02/06/2023]
Abstract
As the primary microtubule-organizing center in animal cells, centrosomes regulate microtubule cytoskeleton to support various cellular behaviors. They also serve as the base for nucleating primary cilia, the hub of diverse signaling pathways. Cells typically possess one centrosome that contains two inequal centrioles and undergoes semi-conservative duplication during cell division, resulting in two centrosomes with an inherent asymmetry in age and properties. While the centrosome is ubiquitously present, mutations of centrosome proteins are strongly associated with human microcephaly characterized by a small cerebral cortex, underscoring the importance of an intact centrosome in supporting cortical neurogenesis. Here we review recent advances on centrosome regulation and function in mammalian cortical neural progenitors and discuss the implications for a better understanding of cortical neurogenesis and related disease mechanisms.
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Rai SK, Savastano A, Singh P, Mukhopadhyay S, Zweckstetter M. Liquid-liquid phase separation of tau: From molecular biophysics to physiology and disease. Protein Sci 2021; 30:1294-1314. [PMID: 33930220 PMCID: PMC8197432 DOI: 10.1002/pro.4093] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 04/24/2021] [Accepted: 04/27/2021] [Indexed: 12/14/2022]
Abstract
Biomolecular condensation via liquid-liquid phase separation (LLPS) of intrinsically disordered proteins/regions (IDPs/IDRs), with and without nucleic acids, has drawn widespread interest due to the rapidly unfolding role of phase-separated condensates in a diverse range of cellular functions and human diseases. Biomolecular condensates form via transient and multivalent intermolecular forces that sequester proteins and nucleic acids into liquid-like membrane-less compartments. However, aberrant phase transitions into gel-like or solid-like aggregates might play an important role in neurodegenerative and other diseases. Tau, a microtubule-associated neuronal IDP, is involved in microtubule stabilization, regulates axonal outgrowth and transport in neurons. A growing body of evidence indicates that tau can accomplish some of its cellular activities via LLPS. However, liquid-to-solid transition resulting in the abnormal aggregation of tau is associated with neurodegenerative diseases. The physical chemistry of tau is crucial for governing its propensity for biomolecular condensation which is governed by various intermolecular and intramolecular interactions leading to simple one-component and complex multi-component condensates. In this review, we aim at capturing the current scientific state in unveiling the intriguing molecular mechanism of phase separation of tau. We particularly focus on the amalgamation of existing and emerging biophysical tools that offer unique spatiotemporal resolutions on a wide range of length- and time-scales. We also discuss the link between quantitative biophysical measurements and novel biological insights into biomolecular condensation of tau. We believe that this account will provide a broad and multidisciplinary view of phase separation of tau and its association with physiology and disease.
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Affiliation(s)
- Sandeep K. Rai
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, and Department of Chemical SciencesIndian Institute of Science Education and Research (IISER)MohaliIndia
| | - Adriana Savastano
- Research group Translational Structural BiologyGerman Center for Neurodegenerative Diseases (DZNE)GöttingenGermany
| | - Priyanka Singh
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, and Department of Chemical SciencesIndian Institute of Science Education and Research (IISER)MohaliIndia
| | - Samrat Mukhopadhyay
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, and Department of Chemical SciencesIndian Institute of Science Education and Research (IISER)MohaliIndia
| | - Markus Zweckstetter
- Research group Translational Structural BiologyGerman Center for Neurodegenerative Diseases (DZNE)GöttingenGermany
- Department for NMR‐based Structural BiologyMax Planck Institute for Biophysical ChemistryGöttingenGermany
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Ide K, Muko M, Hayashi K. The Golgi apparatus is the main microtubule-organizing center in differentiating skeletal muscle cells. Histochem Cell Biol 2021; 156:273-281. [PMID: 34110464 DOI: 10.1007/s00418-021-01999-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/31/2021] [Indexed: 10/21/2022]
Abstract
Studies in differentiating skeletal muscle cells in vitro have revealed that the microtubule-organizing center shifts from the centrosome to the perinuclear sites. As the Golgi apparatus surrounds the nucleus in a myotube, it is unclear whether microtubules are nucleated at the nuclear envelope or at the surrounding Golgi apparatus. In this study, we investigated the positional relationship between the microtubule nucleating sites and the Golgi apparatus in C2C12 myotubes and in primary cultured mouse skeletal myotubes. We focused on gaps in the perinuclear Golgi apparatus where the nuclear envelope was not covered with the Golgi apparatus. In microtubule regrowth assay, microtubule regrowth after cold-nocodazole depolymerization of preexisting microtubules was not found at the gap of the perinuclear Golgi apparatus. Most of the microtubule regrowth was detected at the CDK5RAP2 (CDK5 regulatory subunit-associated protein 2)-rich spots on the perinuclear Golgi apparatus. Disruption of the perinuclear Golgi apparatus with brefeldin A treatment eliminated the perinuclear microtubule regrowth. The Golgi apparatus of undifferentiated myoblasts and those at the cytoplasm of myotubes were also the microtubule nucleating sites. From these observations, we concluded that most of the perinuclear microtubule nucleation occurs on the Golgi apparatus surrounding the nucleus.
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Affiliation(s)
- Koyo Ide
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo, Japan
| | - Mika Muko
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo, Japan
| | - Kensuke Hayashi
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo, Japan.
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Wilkes OR, Moore AW. Distinct Microtubule Organizing Center Mechanisms Combine to Generate Neuron Polarity and Arbor Complexity. Front Cell Neurosci 2020; 14:594199. [PMID: 33328893 PMCID: PMC7711044 DOI: 10.3389/fncel.2020.594199] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 11/02/2020] [Indexed: 01/15/2023] Open
Abstract
Dendrite and axon arbor wiring patterns determine the connectivity and computational characteristics of a neuron. The identities of these dendrite and axon arbors are created by differential polarization of their microtubule arrays, and their complexity and pattern are generated by the extension and organization of these arrays. We describe how several molecularly distinct microtubule organizing center (MTOC) mechanisms function during neuron differentiation to generate and arrange dendrite and axon microtubules. The temporal and spatial organization of these MTOCs generates, patterns, and diversifies arbor wiring.
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Affiliation(s)
- Oliver R Wilkes
- Laboratory for Neurodiversity, RIKEN Center for Brain Science, Wako-shi, Japan.,Department of Cellular and Molecular Biology, Institute for Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Adrian W Moore
- Laboratory for Neurodiversity, RIKEN Center for Brain Science, Wako-shi, Japan
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Mukherjee A, Brooks PS, Bernard F, Guichet A, Conduit PT. Microtubules originate asymmetrically at the somatic golgi and are guided via Kinesin2 to maintain polarity within neurons. eLife 2020; 9:e58943. [PMID: 32657758 PMCID: PMC7394546 DOI: 10.7554/elife.58943] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 07/12/2020] [Indexed: 12/12/2022] Open
Abstract
Neurons contain polarised microtubule arrays essential for neuronal function. How microtubule nucleation and polarity are regulated within neurons remains unclear. We show that γ-tubulin localises asymmetrically to the somatic Golgi within Drosophila neurons. Microtubules originate from the Golgi with an initial growth preference towards the axon. Their growing plus ends also turn towards and into the axon, adding to the plus-end-out microtubule pool. Any plus ends that reach a dendrite, however, do not readily enter, maintaining minus-end-out polarity. Both turning towards the axon and exclusion from dendrites depend on Kinesin-2, a plus-end-associated motor that guides growing plus ends along adjacent microtubules. We propose that Kinesin-2 engages with a polarised microtubule network within the soma to guide growing microtubules towards the axon; while at dendrite entry sites engagement with microtubules of opposite polarity generates a backward stalling force that prevents entry into dendrites and thus maintains minus-end-out polarity within proximal dendrites.
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Affiliation(s)
- Amrita Mukherjee
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Paul S Brooks
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Fred Bernard
- Université de Paris, CNRS, Institut Jacques MonodParisFrance
| | - Antoine Guichet
- Université de Paris, CNRS, Institut Jacques MonodParisFrance
| | - Paul T Conduit
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Université de Paris, CNRS, Institut Jacques MonodParisFrance
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Lüders J. Nucleating microtubules in neurons: Challenges and solutions. Dev Neurobiol 2020; 81:273-283. [PMID: 32324945 DOI: 10.1002/dneu.22751] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 01/08/2020] [Accepted: 04/20/2020] [Indexed: 11/08/2022]
Abstract
The highly polarized morphology of neurons is crucial for their function and involves formation of two distinct types of cellular extensions, the axonal and dendritic compartments. An important effector required for the morphogenesis and maintenance and thus the identity of axons and dendrites is the microtubule cytoskeleton. Microtubules in axons and dendrites are arranged with distinct polarities, to allow motor-dependent, compartment-specific sorting of cargo. Despite the importance of the microtubule cytoskeleton in neurons, the molecular mechanisms that generate the intricate compartment-specific microtubule configurations remain largely obscure. Work in other cell types has identified microtubule nucleation, the de novo formation of microtubules, and its spatio-temporal regulation as essential for the proper organization of the microtubule cytoskeleton. Whereas regulation of microtubule nucleation usually involves microtubule organizing centers such as the centrosome, neurons seem to rely largely on decentralized nucleation mechanisms. In this review, I will discuss recent advances in deciphering nucleation mechanisms in neurons, how they contribute to the arrangement of microtubules with specific polarities, and how this affects neuron morphogenesis. While this work has shed some light on these important processes, we are far from a comprehensive understanding. Thus, to provide a coherent model, my discussion will include both well-established mechanisms and mechanisms with more limited supporting data. Finally, I will also highlight important outstanding questions for future investigation.
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Affiliation(s)
- Jens Lüders
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
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Freal A, Hoogenraad CC. Neuronal Cytoskeleton: Presynaptic Boutons as Hotspots for Activity-Dependent Microtubule Nucleation. Curr Biol 2019; 29:R1307-R1309. [PMID: 31846677 DOI: 10.1016/j.cub.2019.11.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Local microtubule remodeling plays a crucial role in controlling the transport of neuronal cargo. A new study reveals that excitatory en passant boutons in the axon are hotspots for activity-induced microtubule nucleation and provide tracks for interbouton vesicle trafficking.
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Affiliation(s)
- Amélie Freal
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands; Department of Axonal Signaling, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Meibergdreef 47, 1105 BA Amsterdam, The Netherlands
| | - Casper C Hoogenraad
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands; Department of Neuroscience, Genentech, Inc., South San Francisco, CA 94080, USA.
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