1
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Gronseth JR, Nelson HN, Johnson TL, Mallon TA, Martell MR, Pfaffenbach KA, Duxbury BB, Henke JT, Treichel AJ, Hines JH. Synaptic vesicle release regulates pre-myelinating oligodendrocyte-axon interactions in a neuron subtype-specific manner. Front Cell Neurosci 2024; 18:1386352. [PMID: 38841202 PMCID: PMC11150666 DOI: 10.3389/fncel.2024.1386352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 05/02/2024] [Indexed: 06/07/2024] Open
Abstract
Oligodendrocyte-lineage cells are central nervous system (CNS) glia that perform multiple functions including the selective myelination of some but not all axons. During myelination, synaptic vesicle release from axons promotes sheath stabilization and growth on a subset of neuron subtypes. In comparison, it is unknown if pre-myelinating oligodendrocyte process extensions selectively interact with specific neural circuits or axon subtypes, and whether the formation and stabilization of these neuron-glia interactions involves synaptic vesicle release. In this study, we used fluorescent reporters in the larval zebrafish model to track pre-myelinating oligodendrocyte process extensions interacting with spinal axons utilizing in vivo imaging. Monitoring motile oligodendrocyte processes and their interactions with individually labeled axons revealed that synaptic vesicle release regulates the behavior of subsets of process extensions. Specifically, blocking synaptic vesicle release decreased the longevity of oligodendrocyte process extensions interacting with reticulospinal axons. Furthermore, blocking synaptic vesicle release increased the frequency that new interactions formed and retracted. In contrast, tracking the movements of all process extensions of singly-labeled oligodendrocytes revealed that synaptic vesicle release does not regulate overall process motility or exploratory behavior. Blocking synaptic vesicle release influenced the density of oligodendrocyte process extensions interacting with reticulospinal and serotonergic axons, but not commissural interneuron or dopaminergic axons. Taken together, these data indicate that alterations to synaptic vesicle release cause changes to oligodendrocyte-axon interactions that are neuron subtype specific.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Jacob H. Hines
- Biology Department, Winona State University, Winona, MN, United States
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2
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Osso LA, Hughes EG. Dynamics of mature myelin. Nat Neurosci 2024:10.1038/s41593-024-01642-2. [PMID: 38773349 DOI: 10.1038/s41593-024-01642-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 04/05/2024] [Indexed: 05/23/2024]
Abstract
Myelin, which is produced by oligodendrocytes, insulates axons to facilitate rapid and efficient action potential propagation in the central nervous system. Traditionally viewed as a stable structure, myelin is now known to undergo dynamic modulation throughout life. This Review examines these dynamics, focusing on two key aspects: (1) the turnover of myelin, involving not only the renewal of constituents but the continuous wholesale replacement of myelin membranes; and (2) the structural remodeling of pre-existing, mature myelin, a newly discovered form of neural plasticity that can be stimulated by external factors, including neuronal activity, behavioral experience and injury. We explore the mechanisms regulating these dynamics and speculate that myelin remodeling could be driven by an asymmetry in myelin turnover or reactivation of pathways involved in myelin formation. Finally, we outline how myelin remodeling could have profound impacts on neural function, serving as an integral component of behavioral adaptation.
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Affiliation(s)
- Lindsay A Osso
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Ethan G Hughes
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA.
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3
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Nabel AL, Teich L, Wohlfrom H, Alexandrova O, Heß M, Pecka M, Grothe B. Development of myelination and axon diameter for fast and precise action potential conductance. Glia 2024; 72:794-808. [PMID: 38174817 DOI: 10.1002/glia.24504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 12/19/2023] [Accepted: 12/22/2023] [Indexed: 01/05/2024]
Abstract
Axons of globular bushy cells in the cochlear nucleus convey hyper-accurate signals to the superior olivary complex, the initial site of binaural processing via comparably thick axons and the calyx of the Held synapse. Bushy cell fibers involved in hyper-accurate binaural processing of low-frequency sounds are known to have an unusual internode length-to-axon caliber ratio (L/d) correlating with higher conduction velocity and superior temporal precision of action potentials. How the L/d-ratio develops and what determines this unusual myelination pattern is unclear. Here we describe a gradual developmental transition from very simple to complex, mature nodes of Ranvier on globular bushy cell axons during a 2-week period starting at postnatal day P6/7. The molecular composition of nodes matured successively along the axons from somata to synaptic terminals with morphologically and molecularly mature nodes appearing almost exclusively after hearing onset. Internodal distances are initially coherent with the canonical L/d-ratio of ~100. Several days after hearing onset, however, an over-proportional increase in axon caliber occurs in cells signaling low-frequency sounds which alters their L/d ratio to ~60. Hence, oligodendrocytes initially myelinating axons according to their transient axon caliber but a subsequent differential axon thickening after hearing onset results in the unusual myelination pattern.
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Affiliation(s)
- Alisha L Nabel
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
- Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Laurin Teich
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
- Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
- Division of Neurobiology, Faculty of Biology, Munich Cluster for Systems Neurology (SyNergy), Martinsried, Germany
| | - Hilde Wohlfrom
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Olga Alexandrova
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Martin Heß
- Division of Systematic Zoology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Michael Pecka
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Benedikt Grothe
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
- Division of Neurobiology, Faculty of Biology, Munich Cluster for Systems Neurology (SyNergy), Martinsried, Germany
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4
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Bekku Y, Zotter B, You C, Piehler J, Leonard WJ, Salzer JL. Glia trigger endocytic clearance of axonal proteins to promote rodent myelination. Dev Cell 2024; 59:627-644.e10. [PMID: 38309265 PMCID: PMC11089820 DOI: 10.1016/j.devcel.2024.01.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 09/09/2023] [Accepted: 01/12/2024] [Indexed: 02/05/2024]
Abstract
Axons undergo striking changes in their content and distribution of cell adhesion molecules (CAMs) and ion channels during myelination that underlies the switch from continuous to saltatory conduction. These changes include the removal of a large cohort of uniformly distributed CAMs that mediate initial axon-Schwann cell interactions and their replacement by a subset of CAMs that mediate domain-specific interactions of myelinated fibers. Here, using rodent models, we examine the mechanisms and significance of this removal of axonal CAMs. We show that Schwann cells just prior to myelination locally activate clathrin-mediated endocytosis (CME) in axons, thereby driving clearance of a broad array of axonal CAMs. CAMs engineered to resist endocytosis are persistently expressed along the axon and delay both PNS and CNS myelination. Thus, glia non-autonomously activate CME in axons to downregulate axonal CAMs and presumptively axo-glial adhesion. This promotes the transition from ensheathment to myelination while simultaneously sculpting the formation of axonal domains.
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Affiliation(s)
- Yoko Bekku
- Neuroscience Institute, New York University Langone Medical Center, New York, NY 10016, USA.
| | - Brendan Zotter
- Neuroscience Institute, New York University Langone Medical Center, New York, NY 10016, USA
| | - Changjiang You
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics, Osnabrück University, Barbarastr. 11, 49076 Osnabrück, Germany
| | - Jacob Piehler
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics, Osnabrück University, Barbarastr. 11, 49076 Osnabrück, Germany
| | - Warren J Leonard
- Laboratory of Molecular Immunology and Immunology Center, National Heart, Lung, and Blood Institute, National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - James L Salzer
- Neuroscience Institute, New York University Langone Medical Center, New York, NY 10016, USA.
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5
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Chen J, Yu Y, Wang S, Shen Y, Tian Y, Rizzello L, Luo K, Tian X, Wang T, Xiong L. Nanoscale myelinogenesis image in developing brain via super-resolution nanoscopy by near-infrared emissive curcumin-BODIPY derivatives. J Nanobiotechnology 2024; 22:106. [PMID: 38468300 DOI: 10.1186/s12951-024-02377-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 02/28/2024] [Indexed: 03/13/2024] Open
Abstract
Understanding the intricate nanoscale architecture of neuronal myelin during central nervous system development is of utmost importance. However, current visualization methods heavily rely on electron microscopy or indirect fluorescent method, lacking direct and real-time imaging capabilities. Here, we introduce a breakthrough near-infrared emissive curcumin-BODIPY derivative (MyL-1) that enables direct visualization of myelin structure in brain tissues. The remarkable compatibility of MyL-1 with stimulated emission depletion nanoscopy allows for unprecedented super-resolution imaging of myelin ultrastructure. Through this innovative approach, we comprehensively characterize the nanoscale myelinogenesis in three dimensions over the course of brain development, spanning from infancy to adulthood in mouse models. Moreover, we investigate the correlation between myelin substances and Myelin Basic Protein (MBP), shedding light on the essential role of MBP in facilitating myelinogenesis during vertebral development. This novel material, MyL-1, opens up new avenues for studying and understanding the intricate process of myelinogenesis in a direct and non-invasive manner, paving the way for further advancements in the field of nanoscale neuroimaging.
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Affiliation(s)
- Junyang Chen
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical University, No. 149, Dalian Road, Huichuan District, Zunyi, 563000, Guizhou, China
- Functional and Molecular Imaging Key Laboratory of Sichuan Province, Huaxi MR Research Centre (HMRRC), Department of Radiology and National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, 610000, China
- Department of Chemistry, Key Laboratory of Functional Inorganic Material Chemistry of Anhui Province, Anhui University, Hefei, 230601, China
- Department of Chemistry, University College London, London, WC1H 0AJ, UK
- Laboratory of Aging Research and Cancer Drug Target, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, 610041, China
| | - Yifan Yu
- Functional and Molecular Imaging Key Laboratory of Sichuan Province, Huaxi MR Research Centre (HMRRC), Department of Radiology and National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, 610000, China
| | - Siyou Wang
- Department of Chemistry, Key Laboratory of Functional Inorganic Material Chemistry of Anhui Province, Anhui University, Hefei, 230601, China
| | - Yu Shen
- Department of Chemistry, Key Laboratory of Functional Inorganic Material Chemistry of Anhui Province, Anhui University, Hefei, 230601, China
| | - Yupeng Tian
- Department of Chemistry, Key Laboratory of Functional Inorganic Material Chemistry of Anhui Province, Anhui University, Hefei, 230601, China
| | - Loris Rizzello
- Department of Pharmaceutical Sciences, University of Milan, Via G. Balzaretti 9, 20133, Milan, Italy
- The National Institute of Molecular Genetics (INGM), Via Francesco Sforza 35, 20122, Milan, Italy
| | - Kui Luo
- Functional and Molecular Imaging Key Laboratory of Sichuan Province, Huaxi MR Research Centre (HMRRC), Department of Radiology and National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, 610000, China
| | - Xiaohe Tian
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical University, No. 149, Dalian Road, Huichuan District, Zunyi, 563000, Guizhou, China.
- Functional and Molecular Imaging Key Laboratory of Sichuan Province, Huaxi MR Research Centre (HMRRC), Department of Radiology and National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, 610000, China.
- Laboratory of Aging Research and Cancer Drug Target, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, 610041, China.
| | - Tinghua Wang
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical University, No. 149, Dalian Road, Huichuan District, Zunyi, 563000, Guizhou, China.
- Institute of Neurological Disease, Translational Neuroscience Center, West China Hospital, Sichuan University, Chengdu, 610041, China.
| | - Liulin Xiong
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical University, No. 149, Dalian Road, Huichuan District, Zunyi, 563000, Guizhou, China.
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6
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Li J, Miramontes TG, Czopka T, Monk KR. Synaptic input and Ca 2+ activity in zebrafish oligodendrocyte precursor cells contribute to myelin sheath formation. Nat Neurosci 2024; 27:219-231. [PMID: 38216650 DOI: 10.1038/s41593-023-01553-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 12/13/2023] [Indexed: 01/14/2024]
Abstract
In the nervous system, only one type of neuron-glial synapse is known to exist: that between neurons and oligodendrocyte precursor cells (OPCs), yet their composition, assembly, downstream signaling and in vivo functions remain largely unclear. Here, we address these questions using in vivo microscopy in zebrafish spinal cord and identify postsynaptic molecules PSD-95 and gephyrin in OPCs. The puncta containing these molecules in OPCs increase during early development and decrease upon OPC differentiation. These puncta are highly dynamic and frequently assemble at 'hotspots'. Gephyrin hotspots and synapse-associated Ca2+ activity in OPCs predict where a subset of myelin sheaths forms in differentiated oligodendrocytes. Further analyses reveal that spontaneous synaptic release is integral to OPC Ca2+ activity, while evoked synaptic release contributes only in early development. Finally, disruption of the synaptic genes dlg4a/dlg4b, gphnb and nlgn3b impairs OPC differentiation and myelination. Together, we propose that neuron-OPC synapses are dynamically assembled and can predetermine myelination patterns through Ca2+ signaling.
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Affiliation(s)
- Jiaxing Li
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA.
| | | | - Tim Czopka
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Kelly R Monk
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA.
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7
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Iyer M, Kantarci H, Cooper MH, Ambiel N, Novak SW, Andrade LR, Lam M, Jones G, Münch AE, Yu X, Khakh BS, Manor U, Zuchero JB. Oligodendrocyte calcium signaling promotes actin-dependent myelin sheath extension. Nat Commun 2024; 15:265. [PMID: 38177161 PMCID: PMC10767123 DOI: 10.1038/s41467-023-44238-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 12/05/2023] [Indexed: 01/06/2024] Open
Abstract
Myelin is essential for rapid nerve signaling and is increasingly found to play important roles in learning and in diverse diseases of the CNS. Morphological parameters of myelin such as sheath length are thought to precisely tune conduction velocity, but the mechanisms controlling sheath morphology are poorly understood. Local calcium signaling has been observed in nascent myelin sheaths and can be modulated by neuronal activity. However, the role of calcium signaling in sheath formation remains incompletely understood. Here, we use genetic tools to attenuate oligodendrocyte calcium signaling during myelination in the developing mouse CNS. Surprisingly, genetic calcium attenuation does not grossly affect the number of myelinated axons or myelin thickness. Instead, calcium attenuation causes myelination defects resulting in shorter, dysmorphic sheaths. Mechanistically, calcium attenuation reduces actin filaments in oligodendrocytes, and an intact actin cytoskeleton is necessary and sufficient to achieve accurate myelin morphology. Together, our work reveals a cellular mechanism required for accurate CNS myelin formation and may provide mechanistic insight into how oligodendrocytes respond to neuronal activity to sculpt and refine myelin sheaths.
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Affiliation(s)
- Manasi Iyer
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Husniye Kantarci
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Madeline H Cooper
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Nicholas Ambiel
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Sammy Weiser Novak
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Leonardo R Andrade
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Mable Lam
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Graham Jones
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Alexandra E Münch
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Xinzhu Yu
- Department of Molecular and Integrative Physiology, Beckman Institute, University of Illinois at Urbana-, Champaign, IL, USA
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Baljit S Khakh
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Uri Manor
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, CA, USA
- Department of Cell and Developmental Biology, University of California, San Diego, San Diego, CA, USA
| | - J Bradley Zuchero
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA.
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8
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Novitskiy N, Chan PHY, Chan M, Lai CM, Leung TY, Leung TF, Bornstein MH, Lam HS, Wong PCM. Deficits in neural encoding of speech in preterm infants. Dev Cogn Neurosci 2023; 61:101259. [PMID: 37257249 DOI: 10.1016/j.dcn.2023.101259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 05/19/2023] [Accepted: 05/25/2023] [Indexed: 06/02/2023] Open
Abstract
Preterm children show developmental cognitive and language deficits that can be subtle and sometimes undetectable until later in life. Studies of brain development in children who are born preterm have largely focused on vascular and gross anatomical characteristics rather than pathophysiological processes that may contribute to these developmental deficits. Neural encoding of speech as reflected in EEG recordings is predictive of future language development and could provide insights into those pathophysiological processes. We recorded EEG from 45 preterm (≤ 34 weeks of gestation) and 45 term (≥ 38 weeks) Chinese-learning infants 0-12 months of (corrected) age during natural sleep. Each child listened to three speech stimuli that differed in lexically meaningful pitch (2 native and 1 non-native speech categories). EEG measures associated with synchronization and gross power of the frequency following response (FFR) were examined. ANCOVAs revealed no main effect of stimulus nativeness but main effects of age, consistent with earlier studies. A main effect of prematurity also emerged, with synchronization measures showing stronger group differences than power. By detailing differences in FFR measures related to synchronization and power, this study brings us closer to identifying the pathophysiological pathway to often subtle language problems experienced by preterm children.
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Affiliation(s)
- Nikolay Novitskiy
- Brain and Mind Institute, The Chinese University of Hong Kong, Hong Kong, China
| | - Peggy H Y Chan
- Brain and Mind Institute, The Chinese University of Hong Kong, Hong Kong, China; Department of Paediatrics, The Chinese University of Hong Kong, Hong Kong, China
| | - Mavis Chan
- Brain and Mind Institute, The Chinese University of Hong Kong, Hong Kong, China
| | - Chin Man Lai
- Brain and Mind Institute, The Chinese University of Hong Kong, Hong Kong, China
| | - Tak Yeung Leung
- Department of Obsterics and Gynaecology, The Chinese University of Hong Kong, Hong Kong, China
| | - Ting Fan Leung
- Department of Paediatrics, The Chinese University of Hong Kong, Hong Kong, China
| | - Marc H Bornstein
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, USA; UNICEF, USA; Institute for Fiscal Studies, UK
| | - Hugh S Lam
- Department of Paediatrics, The Chinese University of Hong Kong, Hong Kong, China.
| | - Patrick C M Wong
- Brain and Mind Institute, The Chinese University of Hong Kong, Hong Kong, China.
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9
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Iyer M, Kantarci H, Ambiel N, Novak SW, Andrade LR, Lam M, Münch AE, Yu X, Khakh BS, Manor U, Zuchero JB. Oligodendrocyte calcium signaling sculpts myelin sheath morphology. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.11.536299. [PMID: 37090556 PMCID: PMC10120717 DOI: 10.1101/2023.04.11.536299] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
Myelin is essential for rapid nerve signaling and is increasingly found to play important roles in learning and in diverse diseases of the CNS. Morphological parameters of myelin such as sheath length and thickness are regulated by neuronal activity and can precisely tune conduction velocity, but the mechanisms controlling sheath morphology are poorly understood. Local calcium signaling has been observed in nascent myelin sheaths and can be modulated by neuronal activity. However, the role of calcium signaling in sheath formation and remodeling is unknown. Here, we used genetic tools to attenuate oligodendrocyte calcium signaling during active myelination in the developing mouse CNS. Surprisingly, we found that genetic calcium attenuation did not grossly affect the number of myelinated axons or myelin thickness. Instead, calcium attenuation caused striking myelination defects resulting in shorter, dysmorphic sheaths. Mechanistically, calcium attenuation reduced actin filaments in oligodendrocytes, and an intact actin cytoskeleton was necessary and sufficient to achieve accurate myelin morphology. Together, our work reveals a novel cellular mechanism required for accurate CNS myelin formation and provides mechanistic insight into how oligodendrocytes may respond to neuronal activity to sculpt myelin sheaths throughout the nervous system.
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10
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Chapman TW, Olveda GE, Bame X, Pereira E, Hill RA. Oligodendrocyte death initiates synchronous remyelination to restore cortical myelin patterns in mice. Nat Neurosci 2023; 26:555-569. [PMID: 36928635 PMCID: PMC10208560 DOI: 10.1038/s41593-023-01271-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 02/09/2023] [Indexed: 03/18/2023]
Abstract
Myelin degeneration occurs in neurodegenerative diseases and aging. In these conditions, resident oligodendrocyte progenitor cells (OPCs) differentiate into oligodendrocytes that carry out myelin repair. To investigate the cellular dynamics underlying these events, we developed a noninflammatory demyelination model that combines intravital two-photon imaging with a single-cell ablation technique called two-photon apoptotic targeted ablation (2Phatal). Oligodendrocyte 2Phatal in both sexes results in a myelin degeneration cascade that triggers rapid forms of synchronous remyelination on defined axons. This remyelination is driven by oligodendrocytes differentiated from a subset of morphologically distinct, highly branched OPCs. Moreover, remyelination efficiency depends on the initial myelin patterns, as well as the age of the organism. In summary, using 2Phatal, we show a form of rapid synchronous remyelination, mediated by a distinct subset of OPCs, capable of restoring the original myelin patterning in adulthood but not aging.
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Affiliation(s)
- Timothy W Chapman
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - Genaro E Olveda
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - Xhoela Bame
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - Elizabeth Pereira
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - Robert A Hill
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA.
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11
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Seidenthal M, Jánosi B, Rosenkranz N, Schuh N, Elvers N, Willoughby M, Zhao X, Gottschalk A. pOpsicle: An all-optical reporter system for synaptic vesicle recycling combining pH-sensitive fluorescent proteins with optogenetic manipulation of neuronal activity. Front Cell Neurosci 2023; 17:1120651. [PMID: 37066081 PMCID: PMC10102542 DOI: 10.3389/fncel.2023.1120651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Accepted: 03/15/2023] [Indexed: 04/03/2023] Open
Abstract
pH-sensitive fluorescent proteins are widely used to study synaptic vesicle (SV) fusion and recycling. When targeted to the lumen of SVs, fluorescence of these proteins is quenched by the acidic pH. Following SV fusion, they are exposed to extracellular neutral pH, resulting in a fluorescence increase. SV fusion, recycling and acidification can thus be tracked by tagging integral SV proteins with pH-sensitive proteins. Neurotransmission is generally activated by electrical stimulation, which is not feasible in small, intact animals. Previous in vivo approaches depended on distinct (sensory) stimuli, thus limiting the addressable neuron types. To overcome these limitations, we established an all-optical approach to stimulate and visualize SV fusion and recycling. We combined distinct pH-sensitive fluorescent proteins (inserted into the SV protein synaptogyrin) and light-gated channelrhodopsins (ChRs) for optical stimulation, overcoming optical crosstalk and thus enabling an all-optical approach. We generated two different variants of the pH-sensitive optogenetic reporter of vesicle recycling (pOpsicle) and tested them in cholinergic neurons of intact Caenorhabditis elegans nematodes. First, we combined the red fluorescent protein pHuji with the blue-light gated ChR2(H134R), and second, the green fluorescent pHluorin combined with the novel red-shifted ChR ChrimsonSA. In both cases, fluorescence increases were observed after optical stimulation. Increase and subsequent decline of fluorescence was affected by mutations of proteins involved in SV fusion and endocytosis. These results establish pOpsicle as a non-invasive, all-optical approach to investigate different steps of the SV cycle.
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Affiliation(s)
- Marius Seidenthal
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany
- Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Barbara Jánosi
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany
- Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Nils Rosenkranz
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany
- Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Noah Schuh
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany
- Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Nora Elvers
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany
- Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Miles Willoughby
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany
- Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Xinda Zhao
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany
- Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Alexander Gottschalk
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany
- Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
- *Correspondence: Alexander Gottschalk,
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12
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Oprea L, Desjardins N, Jiang X, Sareen K, Zheng JQ, Khadra A. Characterizing spontaneous Ca 2+ local transients in OPCs using computational modeling. Biophys J 2022; 121:4419-4432. [PMID: 36352783 PMCID: PMC9748374 DOI: 10.1016/j.bpj.2022.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Revised: 10/03/2022] [Accepted: 11/03/2022] [Indexed: 11/09/2022] Open
Abstract
Spontaneous Ca2+ local transients (SCaLTs) in isolated oligodendrocyte precursor cells are largely regulated by the following fluxes: store-operated Ca2+ entry (SOCE), Na+/Ca2+ exchange, Ca2+ pumping through Ca2+-ATPases, and Ca2+-induced Ca2+-release through ryanodine receptors and inositol-trisphosphate receptors. However, the relative contributions of these fluxes in mediating fast spiking and the slow baseline oscillations seen in SCaLTs remain incompletely understood. Here, we developed a stochastic spatiotemporal computational model to simulate SCaLTs in a homogeneous medium with ionic flow between the extracellular, cytoplasmic, and endoplasmic-reticulum compartments. By simulating the model and plotting both the histograms of SCaLTs obtained experimentally and from the model as well as the standard deviation of inter-SCaLT intervals against inter-SCaLT interval averages of multiple model and experimental realizations, we revealed the following: (1) SCaLTs exhibit very similar characteristics between the two data sets, (2) they are mostly random, (3) they encode information in their frequency, and (4) their slow baseline oscillations could be due to the stochastic slow clustering of inositol-trisphosphate receptors (modeled as an Ornstein-Uhlenbeck noise process). Bifurcation analysis of a deterministic temporal version of the model showed that the contribution of fluxes to SCaLTs depends on the parameter regime and that the combination of excitability, stochasticity, and mixed-mode oscillations are responsible for irregular spiking and doublets in SCaLTs. Additionally, our results demonstrated that blocking each flux reduces SCaLTs' frequency and that the reverse (forward) mode of Na+/Ca2+ exchange decreases (increases) SCaLTs. Taken together, these results provide a quantitative framework for SCaLT formation in oligodendrocyte precursor cells.
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Affiliation(s)
- Lawrence Oprea
- Department of Physiology, McGill University, Montréal, Quebec, Canada
| | | | - Xiaoyu Jiang
- Department of Physiology, McGill University, Montréal, Quebec, Canada
| | - Kushagra Sareen
- Department of Physiology, McGill University, Montréal, Quebec, Canada
| | - James Q Zheng
- Department of Cell Biology, School of Medicine, Emory University, Atlanta, Georgia
| | - Anmar Khadra
- Department of Physiology, McGill University, Montréal, Quebec, Canada.
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13
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Lysko DE, Talbot WS. Unmyelinated sensory neurons use Neuregulin signals to promote myelination of interneurons in the CNS. Cell Rep 2022; 41:111669. [PMID: 36384112 PMCID: PMC9719401 DOI: 10.1016/j.celrep.2022.111669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 09/06/2022] [Accepted: 10/25/2022] [Indexed: 11/17/2022] Open
Abstract
The signaling mechanisms neurons use to modulate myelination of circuits in the central nervous system (CNS) are only partly understood. Through analysis of isoform-specific neuregulin1 (nrg1) mutants in zebrafish, we demonstrate that nrg1 type II is an important regulator of myelination of two classes of spinal cord interneurons. Surprisingly, nrg1 type II expression is prominent in unmyelinated Rohon-Beard sensory neurons, whereas myelination of neighboring interneurons is reduced in nrg1 type II mutants. Cell-type-specific loss-of-function studies indicate that nrg1 type II is required in Rohon-Beard neurons to signal to other neurons, not oligodendrocytes, to modulate spinal cord myelination. Together, our data support a model in which unmyelinated neurons express Nrg1 type II proteins to regulate myelination of neighboring neurons, a mode of action that may coordinate the functions of unmyelinated and myelinated neurons in the CNS.
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Affiliation(s)
- Daniel E Lysko
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA
| | - William S Talbot
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA.
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14
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Osanai Y, Yamazaki R, Shinohara Y, Ohno N. Heterogeneity and regulation of oligodendrocyte morphology. Front Cell Dev Biol 2022; 10:1030486. [PMID: 36393856 PMCID: PMC9644283 DOI: 10.3389/fcell.2022.1030486] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 10/10/2022] [Indexed: 09/24/2023] Open
Abstract
Oligodendrocytes form multiple myelin sheaths in the central nervous system (CNS), which increase nerve conduction velocity and are necessary for basic and higher brain functions such as sensory function, motor control, and learning. Structures of the myelin sheath such as myelin internodal length and myelin thickness regulate nerve conduction. Various parts of the central nervous system exhibit different myelin structures and oligodendrocyte morphologies. Recent studies supported that oligodendrocytes are a heterogenous population of cells and myelin sheaths formed by some oligodendrocytes can be biased to particular groups of axons, and myelin structures are dynamically modulated in certain classes of neurons by specific experiences. Structures of oligodendrocyte/myelin are also affected in pathological conditions such as demyelinating and neuropsychiatric disorders. This review summarizes our understanding of heterogeneity and regulation of oligodendrocyte morphology concerning central nervous system regions, neuronal classes, experiences, diseases, and how oligodendrocytes are optimized to execute central nervous system functions.
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Affiliation(s)
- Yasuyuki Osanai
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, Shimotsuke, Japan
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC, Australia
| | - Reiji Yamazaki
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, Shimotsuke, Japan
| | - Yoshiaki Shinohara
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, Shimotsuke, Japan
- Department of Anatomy and Cell Biology, Faculty of Medicine, University of Yamanashi, Chuo, Japan
| | - Nobuhiko Ohno
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, Shimotsuke, Japan
- Division of Ultrastructural Research, National Institute for Physiological Sciences, Okazaki, Japan
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15
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Wong HTC, Drerup CM. Using fluorescent indicators for in vivo quantification of spontaneous or evoked motor neuron presynaptic activity in transgenic zebrafish. STAR Protoc 2022; 3:101766. [PMID: 36240058 PMCID: PMC9568885 DOI: 10.1016/j.xpro.2022.101766] [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: 07/01/2022] [Revised: 08/22/2022] [Accepted: 09/20/2022] [Indexed: 11/07/2022] Open
Abstract
In this protocol, we describe steps that utilize the optical clarity of the zebrafish larvae and the stereotyped motor neuron axon structure in the trunk to measure spontaneous or evoked motor neuron axon activity. This activity is detected with transgenic fluorescent indicators introduced into the larvae by zygotic injection. Fluorescent indicator intensity changes in the small neuromuscular junctions are quantified to measure the presynaptic calcium activity and consequent synaptic vesicle release. For complete details on the use and execution of this protocol, please refer to Mandal et al. (2020).
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Affiliation(s)
- Hiu-tung Candy Wong
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA,Corresponding author
| | - Catherine M. Drerup
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA,Corresponding author
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16
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Bacmeister CM, Huang R, Osso LA, Thornton MA, Conant L, Chavez AR, Poleg-Polsky A, Hughes EG. Motor learning drives dynamic patterns of intermittent myelination on learning-activated axons. Nat Neurosci 2022; 25:1300-1313. [PMID: 36180791 PMCID: PMC9651929 DOI: 10.1038/s41593-022-01169-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 08/18/2022] [Indexed: 01/10/2023]
Abstract
Myelin plasticity occurs when newly formed and pre-existing oligodendrocytes remodel existing patterns of myelination. Myelin remodeling occurs in response to changes in neuronal activity and is required for learning and memory. However, the link between behavior-induced neuronal activity and circuit-specific changes in myelination remains unclear. Using longitudinal in vivo two-photon imaging and targeted labeling of learning-activated neurons in mice, we explore how the pattern of intermittent myelination is altered on individual cortical axons during learning of a dexterous reach task. We show that behavior-induced myelin plasticity is targeted to learning-activated axons and occurs in a staged response across cortical layers in the mouse primary motor cortex. During learning, myelin sheaths retract, which results in lengthening of nodes of Ranvier. Following motor learning, addition of newly formed myelin sheaths increases the number of continuous stretches of myelination. Computational modeling suggests that motor learning-induced myelin plasticity initially slows and subsequently increases axonal conduction speed. Finally, we show that both the magnitude and timing of nodal and myelin dynamics correlate with improvement of behavioral performance during motor learning. Thus, learning-induced and circuit-specific myelination changes may contribute to information encoding in neural circuits during motor learning.
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Affiliation(s)
- Clara M Bacmeister
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
- Neuroscience IDP Program, Stanford University School of Medicine, Stanford, CA, USA
| | - Rongchen Huang
- Department of Neurosurgery, University of Colorado School of Medicine, Aurora, CO, USA
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, CO, USA
| | - Lindsay A Osso
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Michael A Thornton
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Lauren Conant
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Anthony R Chavez
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Alon Poleg-Polsky
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, CO, USA
| | - Ethan G Hughes
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA.
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17
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Humanized zebrafish as a tractable tool for in vivo evaluation of pro-myelinating drugs. Cell Chem Biol 2022; 29:1541-1555.e7. [PMID: 36126653 DOI: 10.1016/j.chembiol.2022.08.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 05/25/2022] [Accepted: 08/24/2022] [Indexed: 12/14/2022]
Abstract
Therapies that promote neuroprotection and axonal survival by enhancing myelin regeneration are an unmet need to prevent disability progression in multiple sclerosis. Numerous potentially beneficial compounds have originated from phenotypic screenings but failed in clinical trials. It is apparent that current cell- and animal-based disease models are poor predictors of positive treatment options, arguing for novel experimental approaches. Here we explore the experimental power of humanized zebrafish to foster the identification of pro-remyelination compounds via specific inhibition of GPR17. Using biochemical and imaging techniques, we visualize the expression of zebrafish (zf)-gpr17 during the distinct stages of oligodendrocyte development, thereby demonstrating species-conserved expression between zebrafish and mammals. We also demonstrate species-conserved function of zf-Gpr17 using genetic loss-of-function and rescue techniques. Finally, using GPR17-humanized zebrafish, we provide proof of principle for in vivo analysis of compounds acting via targeted inhibition of human GPR17. We anticipate that GPR17-humanized zebrafish will markedly improve the search for effective pro-myelinating pharmacotherapies.
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18
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Abstract
Motor circuits develop in sequence from those governing fast movements to those governing slow. Here we examine whether upstream sensory circuits are organized by similar principles. Using serial-section electron microscopy in larval zebrafish, we generated a complete map of the gravity-sensing (utricular) system spanning from the inner ear to the brainstem. We find that both sensory tuning and developmental sequence are organizing principles of vestibular topography. Patterned rostrocaudal innervation from hair cells to afferents creates an anatomically inferred directional tuning map in the utricular ganglion, forming segregated pathways for rostral and caudal tilt. Furthermore, the mediolateral axis of the ganglion is linked to both developmental sequence and neuronal temporal dynamics. Early-born pathways carrying phasic information preferentially excite fast escape circuits, whereas later-born pathways carrying tonic signals excite slower postural and oculomotor circuits. These results demonstrate that vestibular circuits are organized by tuning direction and dynamics, aligning them with downstream motor circuits and behaviors. How sensory systems are organized during development remains unclear. Here, the authors used electron microscopy to examine the gravity-sensing system in zebrafish, finding that directional tuning and developmental age are organizing principles of the transformation from vestibular sensation to motor control.
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19
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Jia Y, Bagnall MW. Monosynaptic targets of utricular afferents in the larval zebrafish. Front Neurol 2022; 13:937054. [PMID: 35937055 PMCID: PMC9355653 DOI: 10.3389/fneur.2022.937054] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 06/30/2022] [Indexed: 12/27/2022] Open
Abstract
The larval zebrafish acquires a repertoire of vestibular-driven behaviors that aid survival early in development. These behaviors rely mostly on the utricular otolith, which senses inertial (tilt and translational) head movements. We previously characterized the known central brainstem targets of utricular afferents using serial-section electron microscopy of a larval zebrafish brain. Here we describe the rest of the central targets of utricular afferents, focusing on the neurons whose identities are less certain in our dataset. We find that central neurons with commissural projections have a wide range of predicted directional tuning, just as in other vertebrates. In addition, somata of central neurons with inferred responses to contralateral tilt are located more laterally than those with inferred responses to ipsilateral tilt. Many dorsally located central utricular neurons are unipolar, with an ipsilateral dendritic ramification and commissurally projecting axon emerging from a shared process. Ventrally located central utricular neurons tended to receive otolith afferent synaptic input at a shorter distance from the soma than in dorsally located neurons. Finally, we observe an unexpected synaptic target of utricular afferents: afferents from the medial (horizontal) semicircular canal. Collectively, these data provide a better picture of the gravity-sensing circuit. Furthermore, we suggest that vestibular circuits important for survival behaviors develop first, followed by the circuits that refine these behaviors.
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20
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Green LA, Gallant RM, Brandt JP, Nichols EL, Smith CJ. A Subset of Oligodendrocyte Lineage Cells Interact With the Developing Dorsal Root Entry Zone During Its Genesis. Front Cell Neurosci 2022; 16:893629. [PMID: 35734217 PMCID: PMC9207214 DOI: 10.3389/fncel.2022.893629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 05/11/2022] [Indexed: 11/29/2022] Open
Abstract
Oligodendrocytes are the myelinating cell of the CNS and are critical for the functionality of the nervous system. In the packed CNS, we know distinct profiles of oligodendrocytes are present. Here, we used intravital imaging in zebrafish to identify a distinct oligodendrocyte lineage cell (OLC) that resides on the dorsal root ganglia sensory neurons in the spinal cord. Our profiling of OLC cellular dynamics revealed a distinct cell cluster that interacts with peripheral sensory neurons at the dorsal root entry zone (DREZ). With pharmacological, physical and genetic manipulations, we show that the entry of dorsal root ganglia pioneer axons across the DREZ is important to produce sensory located oligodendrocyte lineage cells. These oligodendrocyte lineage cells on peripherally derived sensory neurons display distinct processes that are stable and do not express mbpa. Upon their removal, sensory behavior related to the DRG neurons is abolished. Together, these data support the hypothesis that peripheral neurons at the DREZ can also impact oligodendrocyte development.
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Affiliation(s)
- Lauren A. Green
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
- Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, United States
| | - Robert M. Gallant
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
| | - Jacob P. Brandt
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
| | - Ev L. Nichols
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
| | - Cody J. Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
- Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, United States
- *Correspondence: Cody J. Smith,
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21
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Abstract
PURPOSE OF REVIEW The introduction some 30 years ago of β-interferon, followed by a panel of immunomodulators and immunosuppressants has led to a remarkable improvement in the management of multiple sclerosis (MS) patients. Despite these noticeable progresses, which lower the number of relapses and thereby ameliorate patients' quality of life, preventing long-term progression of disability is still an unmet need, highlighting the necessity to develop therapeutic strategies aimed at repairing demyelinated lesions and protecting axons from degeneration. The capacity of human brain to self-regenerate demyelinated lesion has opened a field of research aimed at fostering this endogenous potential. RECENT FINDINGS The pioneer electron microscopic evidence by Périer and Grégoire [Périer O, Grégoire A. Electron microscopic features of multiple sclerosis lesions. Brain 1965; 88:937-952] suggesting the capacity of human brain to self-regenerate demyelinated lesion has opened a field of research aimed at fostering this endogenous potential. Here we review some recently identified mechanisms involved in the remyelination process, focusing on the role of electrical activity and the involvement of innate immune cells. We then provide an update on current strategies promoting endogenous myelin repair. SUMMARY Identification of therapeutic targets for remyelination has opened an active therapeutic field in MS. Although still in early phase trials, with heterogenous efficacy, the door for myelin regeneration in MS is now opened.
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22
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Auer F, Schoppik D. The Larval Zebrafish Vestibular System Is a Promising Model to Understand the Role of Myelin in Neural Circuits. Front Neurosci 2022; 16:904765. [PMID: 35600621 PMCID: PMC9122096 DOI: 10.3389/fnins.2022.904765] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 04/11/2022] [Indexed: 12/27/2022] Open
Abstract
Myelin is classically known for its role in facilitating nerve conduction. However, recent work casts myelin as a key player in both proper neuronal circuit development and function. With this expanding role comes a demand for new approaches to characterize and perturb myelin in the context of tractable neural circuits as they mature. Here we argue that the simplicity, strong conservation, and clinical relevance of the vestibular system offer a way forward. Further, the tractability of the larval zebrafish affords a uniquely powerful means to test open hypotheses of myelin's role in normal development and disordered vestibular circuits. We end by identifying key open questions in myelin neurobiology that the zebrafish vestibular system is particularly well-suited to address.
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Affiliation(s)
| | - David Schoppik
- Departments of Otolaryngology, Neuroscience & Physiology, Neuroscience Institute, New York University Grossman School of Medicine, New York, NY, United States
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23
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Vagionitis S, Auer F, Xiao Y, Almeida RG, Lyons DA, Czopka T. Clusters of neuronal neurofascin prefigure the position of a subset of nodes of Ranvier along individual central nervous system axons in vivo. Cell Rep 2022; 38:110366. [PMID: 35172135 PMCID: PMC8864464 DOI: 10.1016/j.celrep.2022.110366] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 07/08/2021] [Accepted: 01/20/2022] [Indexed: 12/23/2022] Open
Abstract
The spacing of nodes of Ranvier crucially affects conduction properties along myelinated axons. It is assumed that node position is primarily driven by growing myelin sheaths. Here, we reveal an additional mechanism of node positioning that is driven by the axon. Through longitudinal live imaging of node formation dynamics in the zebrafish central nervous system, we show that stable clusters of the cell adhesion molecule neurofascin a can accumulate at specific sites along axons prior to myelination. While some of these clusters are pushed into future node position by extending myelin sheaths, others are not and thus prefigure the position of where a mature node forms. Animals that lack full-length neurofascin a show increased internodal distances and less regular nodal spacing along single axons. Together, our data reveal the existence of an axonal mechanism to position nodes of Ranvier that does not depend on regulation by myelin sheath growth. Stable clusters of neuronal neurofascin can form along axons prior to myelination Some clusters are pushed in place by developing myelin sheaths Other clusters restrict sheath growth and thus prefigure node position Animals lacking axonal neurofascin have longer and less regular internodal spacing
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Affiliation(s)
- Stavros Vagionitis
- Institute of Neuronal Cell Biology, Technical University of Munich, 80802 Munich, Germany
| | - Franziska Auer
- Institute of Neuronal Cell Biology, Technical University of Munich, 80802 Munich, Germany
| | - Yan Xiao
- Institute of Neuronal Cell Biology, Technical University of Munich, 80802 Munich, Germany
| | - Rafael G Almeida
- Centre for Discovery Brain Sciences, University of Edinburgh, EH16 4SB Edinburgh, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, EH16 4SB Edinburgh, UK
| | - Tim Czopka
- Institute of Neuronal Cell Biology, Technical University of Munich, 80802 Munich, Germany; Munich Cluster of Systems Neurology (SyNergy), 81377 Munich, Germany; Centre for Clinical Brain Sciences, University of Edinburgh, Chancellor's Building, 49 Little France Crescent, EH16 4SB Edinburgh, UK.
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24
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Carvalho E, Morais M, Ferreira H, Silva M, Guimarães S, Pêgo A. A paradigm shift: Bioengineering meets mechanobiology towards overcoming remyelination failure. Biomaterials 2022; 283:121427. [DOI: 10.1016/j.biomaterials.2022.121427] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 01/31/2022] [Accepted: 02/17/2022] [Indexed: 12/14/2022]
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25
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Thomason EJ, Suárez-Pozos E, Afshari FS, Rosenberg PA, Dupree JL, Fuss B. Deletion of the Sodium-Dependent Glutamate Transporter GLT-1 in Maturing Oligodendrocytes Attenuates Myelination of Callosal Axons During a Postnatal Phase of Central Nervous System Development. Front Cell Neurosci 2022; 16:905299. [PMID: 35722615 PMCID: PMC9203689 DOI: 10.3389/fncel.2022.905299] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Accepted: 05/16/2022] [Indexed: 11/13/2022] Open
Abstract
The sodium-dependent glutamate transporter GLT-1 (EAAT2, SLC1A2) has been well-described as an important regulator of extracellular glutamate homeostasis in the central nervous system (CNS), a function that is performed mainly through its presence on astrocytes. There is, however, increasing evidence for the expression of GLT-1 in CNS cells other than astrocytes and in functional roles that are mediated by mechanisms downstream of glutamate uptake. In this context, GLT-1 expression has been reported for both neurons and oligodendrocytes (OLGs), and neuronal presynaptic presence of GLT-1 has been implicated in the regulation of glutamate uptake, gene expression, and mitochondrial function. Much less is currently known about the functional roles of GLT-1 expressed by OLGs. The data presented here provide first evidence that GLT-1 expressed by maturing OLGs contributes to the modulation of developmental myelination in the CNS. More specifically, using inducible and conditional knockout mice in which GLT-1 was deleted in maturing OLGs during a peak period of myelination (between 2 and 4 weeks of age) revealed hypomyelinated characteristics in the corpus callosum of preferentially male mice. These characteristics included reduced percentages of smaller diameter myelinated axons and reduced myelin thickness. Interestingly, this myelination phenotype was not found to be associated with major changes in myelin gene expression. Taken together, the data presented here demonstrate that GLT-1 expressed by maturing OLGs is involved in the modulation of the morphological aspects associated with CNS myelination in at least the corpus callosum and during a developmental window that appears of particular vulnerability in males compared to females.
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Affiliation(s)
- Elizabeth J Thomason
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA, United States
| | - Edna Suárez-Pozos
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA, United States
| | - Fatemah S Afshari
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA, United States
| | - Paul A Rosenberg
- Department of Neurology and the F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, United States
| | - Jeffrey L Dupree
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA, United States
| | - Babette Fuss
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA, United States
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26
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Neely SA, Lyons DA. Insights Into Central Nervous System Glial Cell Formation and Function From Zebrafish. Front Cell Dev Biol 2021; 9:754606. [PMID: 34912801 PMCID: PMC8666443 DOI: 10.3389/fcell.2021.754606] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 10/05/2021] [Indexed: 12/23/2022] Open
Abstract
The term glia describes a heterogenous collection of distinct cell types that make up a large proportion of our nervous system. Although once considered the glue of the nervous system, the study of glial cells has evolved significantly in recent years, with a large body of literature now highlighting their complex and diverse roles in development and throughout life. This progress is due, in part, to advances in animal models in which the molecular and cellular mechanisms of glial cell development and function as well as neuron-glial cell interactions can be directly studied in vivo in real time, in intact neural circuits. In this review we highlight the instrumental role that zebrafish have played as a vertebrate model system for the study of glial cells, and discuss how the experimental advantages of the zebrafish lend themselves to investigate glial cell interactions and diversity. We focus in particular on recent studies that have provided insight into the formation and function of the major glial cell types in the central nervous system in zebrafish.
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Affiliation(s)
- Sarah A. Neely
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - David A. Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
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27
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Motavaf M, Piao X. Oligodendrocyte Development and Implication in Perinatal White Matter Injury. Front Cell Neurosci 2021; 15:764486. [PMID: 34803612 PMCID: PMC8599582 DOI: 10.3389/fncel.2021.764486] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 10/11/2021] [Indexed: 12/12/2022] Open
Abstract
Perinatal white matter injury (WMI) is the most common brain injury in premature infants and can lead to life-long neurological deficits such as cerebral palsy. Preterm birth is typically accompanied by inflammation and hypoxic-ischemic events. Such perinatal insults negatively impact maturation of oligodendrocytes (OLs) and cause myelination failure. At present, no treatment options are clinically available to prevent or cure WMI. Given that arrested OL maturation plays a central role in the etiology of perinatal WMI, an increased interest has emerged regarding the functional restoration of these cells as potential therapeutic strategy. Cell transplantation and promoting endogenous oligodendrocyte function are two potential options to address this major unmet need. In this review, we highlight the underlying pathophysiology of WMI with a specific focus on OL biology and their implication for the development of new therapeutic targets.
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Affiliation(s)
- Mahsa Motavaf
- Functional Neurosurgery Research Center, Shohada Tajrish Comprehensive Neurosurgical Center of Excellence, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Xianhua Piao
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA, United States.,Newborn Brain Research Institute, University of California, San Francisco, San Francisco, CA, United States.,Weill Institute for Neuroscience, University of California, San Francisco, San Francisco, CA, United States.,Division of Neonatology, Department of Pediatrics, University of California, San Francisco, San Francisco, CA, United States
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28
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Heflin JK, Sun W. Novel Toolboxes for the Investigation of Activity-Dependent Myelination in the Central Nervous System. Front Cell Neurosci 2021; 15:769809. [PMID: 34795563 PMCID: PMC8592894 DOI: 10.3389/fncel.2021.769809] [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: 09/02/2021] [Accepted: 10/06/2021] [Indexed: 11/13/2022] Open
Abstract
Myelination is essential for signal processing within neural networks. Emerging data suggest that neuronal activity positively instructs myelin development and myelin adaptation during adulthood. However, the underlying mechanisms controlling activity-dependent myelination have not been fully elucidated. Myelination is a multi-step process that involves the proliferation and differentiation of oligodendrocyte precursor cells followed by the initial contact and ensheathment of axons by mature oligodendrocytes. Conventional end-point studies rarely capture the dynamic interaction between neurons and oligodendrocyte lineage cells spanning such a long temporal window. Given that such interactions and downstream signaling cascades are likely to occur within fine cellular processes of oligodendrocytes and their precursor cells, overcoming spatial resolution limitations represents another technical hurdle in the field. In this mini-review, we discuss how advanced genetic, cutting-edge imaging, and electrophysiological approaches enable us to investigate neuron-oligodendrocyte lineage cell interaction and myelination with both temporal and spatial precision.
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Affiliation(s)
- Jack Kent Heflin
- Department of Neuroscience, Wexner Medical Center, The Ohio State University, Columbus, OH, United States
| | - Wenjing Sun
- Department of Neuroscience, Wexner Medical Center, The Ohio State University, Columbus, OH, United States
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29
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Experience-dependent myelination following stress is mediated by the neuropeptide dynorphin. Neuron 2021; 109:3619-3632.e5. [PMID: 34536353 DOI: 10.1016/j.neuron.2021.08.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 07/14/2021] [Accepted: 08/13/2021] [Indexed: 11/22/2022]
Abstract
Emerging evidence implicates experience-dependent myelination in learning and memory. However, the specific signals underlying this process remain unresolved. We demonstrate that the neuropeptide dynorphin, which is released from neurons upon high levels of activity, promotes experience-dependent myelination. Following forced swim stress, an experience that induces striatal dynorphin release, we observe increased striatal oligodendrocyte precursor cell (OPC) differentiation and myelination, which is abolished by deleting dynorphin or blocking its endogenous receptor, kappa opioid receptor (KOR). We find that dynorphin also promotes developmental OPC differentiation and myelination and demonstrate that this effect requires KOR expression specifically in OPCs. We characterize dynorphin-expressing neurons and use genetic sparse labeling to trace their axonal projections. Surprisingly, we find that they are unmyelinated normally and following forced swim stress. We propose a new model whereby experience-dependent and developmental myelination is mediated by unmyelinated, neuropeptide-expressing neurons that promote OPC differentiation for the myelination of neighboring axons.
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30
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Bonetto G, Belin D, Káradóttir RT. Myelin: A gatekeeper of activity-dependent circuit plasticity? Science 2021; 374:eaba6905. [PMID: 34618550 DOI: 10.1126/science.aba6905] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Giulia Bonetto
- Wellcome-Medical Research Council Cambridge Stem Cell Institute and Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - David Belin
- Department of Psychology, University of Cambridge, Cambridge, UK
| | - Ragnhildur Thóra Káradóttir
- Wellcome-Medical Research Council Cambridge Stem Cell Institute and Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.,Department of Physiology, Biomedical Centre, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
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31
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Madden ME, Suminaite D, Ortiz E, Early JJ, Koudelka S, Livesey MR, Bianco IH, Granato M, Lyons DA. CNS Hypomyelination Disrupts Axonal Conduction and Behavior in Larval Zebrafish. J Neurosci 2021; 41:9099-9111. [PMID: 34544838 PMCID: PMC8570833 DOI: 10.1523/jneurosci.0842-21.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 08/11/2021] [Accepted: 08/16/2021] [Indexed: 11/21/2022] Open
Abstract
Myelination is essential for central nervous system (CNS) formation, health and function. As a model organism, larval zebrafish have been extensively employed to investigate the molecular and cellular basis of CNS myelination, because of their genetic tractability and suitability for non-invasive live cell imaging. However, it has not been assessed to what extent CNS myelination affects neural circuit function in zebrafish larvae, prohibiting the integration of molecular and cellular analyses of myelination with concomitant network maturation. To test whether larval zebrafish might serve as a suitable platform with which to study the effects of CNS myelination and its dysregulation on circuit function, we generated zebrafish myelin regulatory factor (myrf) mutants with CNS-specific hypomyelination and investigated how this affected their axonal conduction properties and behavior. We found that myrf mutant larvae exhibited increased latency to perform startle responses following defined acoustic stimuli. Furthermore, we found that hypomyelinated animals often selected an impaired response to acoustic stimuli, exhibiting a bias toward reorientation behavior instead of the stimulus-appropriate startle response. To begin to study how myelination affected the underlying circuitry, we established electrophysiological protocols to assess various conduction properties along single axons. We found that the hypomyelinated myrf mutants exhibited reduced action potential conduction velocity and an impaired ability to sustain high-frequency action potential firing. This study indicates that larval zebrafish can be used to bridge molecular and cellular investigation of CNS myelination with multiscale assessment of neural circuit function.SIGNIFICANCE STATEMENT Myelination of CNS axons is essential for their health and function, and it is now clear that myelination is a dynamic life-long process subject to modulation by neuronal activity. However, it remains unclear precisely how changes to myelination affects animal behavior and underlying action potential conduction along axons in intact neural circuits. In recent years, zebrafish have been employed to study cellular and molecular mechanisms of myelination, because of their relatively simple, optically transparent, experimentally tractable vertebrate nervous system. Here we find that changes to myelination alter the behavior of young zebrafish and action potential conduction along individual axons, providing a platform to integrate molecular, cellular, and circuit level analyses of myelination using this model.
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Affiliation(s)
- M E Madden
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
| | - D Suminaite
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
| | - E Ortiz
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - J J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
| | - S Koudelka
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
| | - M R Livesey
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, Sheffield S10 2HQ, United Kingdom
| | - I H Bianco
- Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - M Granato
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - D A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
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32
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Periods of synchronized myelin changes shape brain function and plasticity. Nat Neurosci 2021; 24:1508-1521. [PMID: 34711959 DOI: 10.1038/s41593-021-00917-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 07/30/2021] [Indexed: 12/11/2022]
Abstract
Myelin, a lipid membrane that wraps axons, enabling fast neurotransmission and metabolic support to axons, is conventionally thought of as a static structure that is set early in development. However, recent evidence indicates that in the central nervous system (CNS), myelination is a protracted and plastic process, ongoing throughout adulthood. Importantly, myelin is emerging as a potential modulator of neuronal networks, and evidence from human studies has highlighted myelin as a major player in shaping human behavior and learning. Here we review how myelin changes throughout life and with learning. We discuss potential mechanisms of myelination at different life stages, explore whether myelin plasticity provides the regenerative potential of the CNS white matter, and question whether changes in myelin may underlie neurological disorders.
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33
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The Akt-mTOR Pathway Drives Myelin Sheath Growth by Regulating Cap-Dependent Translation. J Neurosci 2021; 41:8532-8544. [PMID: 34475201 DOI: 10.1523/jneurosci.0783-21.2021] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 08/24/2021] [Accepted: 08/27/2021] [Indexed: 11/21/2022] Open
Abstract
In the vertebrate CNS, oligodendrocytes produce myelin, a specialized membrane, to insulate and support axons. Individual oligodendrocytes wrap multiple axons with myelin sheaths of variable lengths and thicknesses. Myelin grows at the distal ends of oligodendrocyte processes, and multiple lines of work have provided evidence that mRNAs and RNA binding proteins localize to myelin, together supporting a model where local translation controls myelin sheath growth. What signal transduction mechanisms could control this? One strong candidate is the Akt-mTOR pathway, a major cellular signaling hub that coordinates transcription, translation, metabolism, and cytoskeletal organization. Here, using zebrafish as a model system, we found that Akt-mTOR signaling promotes myelin sheath growth and stability during development. Through cell-specific manipulations to oligodendrocytes, we show that the Akt-mTOR pathway drives cap-dependent translation to promote myelination and that restoration of cap-dependent translation is sufficient to rescue myelin deficits in mTOR loss-of-function animals. Moreover, an mTOR-dependent translational regulator was phosphorylated and colocalized with mRNA encoding a canonically myelin-translated protein in vivo, and bioinformatic investigation revealed numerous putative translational targets in the myelin transcriptome. Together, these data raise the possibility that Akt-mTOR signaling in nascent myelin sheaths promotes sheath growth via translation of myelin-resident mRNAs during development.SIGNIFICANCE STATEMENT In the brain and spinal cord, oligodendrocytes extend processes that tightly wrap axons with myelin, a protein- and lipid-rich membrane that increases electrical impulses and provides trophic support. Myelin membrane grows dramatically following initial axon wrapping in a process that demands protein and lipid synthesis. How protein and lipid synthesis is coordinated with the need for myelin to be generated in certain locations remains unknown. Our study reveals that the Akt-mTOR signaling pathway promotes myelin sheath growth by regulating protein translation. Because we found translational regulators of the Akt-mTOR pathway in myelin, our data raise the possibility that Akt-mTOR activity regulates translation in myelin sheaths to deliver myelin on demand to the places it is needed.
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34
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Turan F, Yilmaz Ö, Schünemann L, Lindenberg TT, Kalanithy JC, Harder A, Ahmadi S, Duman T, MacDonald RB, Winter D, Liu C, Odermatt B. Effect of modulating glutamate signaling on myelinating oligodendrocytes and their development-A study in the zebrafish model. J Neurosci Res 2021; 99:2774-2792. [PMID: 34520578 DOI: 10.1002/jnr.24940] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 07/12/2021] [Accepted: 07/21/2021] [Indexed: 01/02/2023]
Abstract
Myelination is crucial for the development and maintenance of axonal integrity, especially fast axonal action potential conduction. There is increasing evidence that glutamate signaling and release through neuronal activity modulates the myelination process. In this study, we examine the effect of manipulating glutamate signaling on myelination of oligodendrocyte (OL) lineage cells and their development in zebrafish (zf). We use the "intensity-based glutamate-sensing fluorescent reporter" (iGluSnFR) in the zf model (both sexes) to address the hypothesis that glutamate is implicated in regulation of myelinating OLs. Our results show that glial iGluSnFR expression significantly reduces OL lineage cell number and the expression of myelin markers in larvae (zfl) and adult brains. The specific glutamate receptor agonist, L-AP4, rescues this iGluSnFR effect by significantly increasing the expression of the myelin-related genes, plp1b and mbpa, and enhances myelination in L-AP4-injected zfl compared to controls. Furthermore, we demonstrate that degrading glutamate using Glutamat-Pyruvate Transaminase (GPT) or the blockade of glutamate reuptake by L-trans-pyrrolidine-2,4-dicarboxylate (PDC) significantly decreases myelin-related genes and drastically declines myelination in brain ventricle-injected zfl. Moreover, we found that myelin-specific ClaudinK (CldnK) and 36K protein expression is significantly decreased in iGluSnFR-expressing zfl and adult brains compared to controls. Taken together, this study confirms that glutamate signaling is directly required for the preservation of myelinating OLs and for the myelination process itself. These findings further suggest that glutamate signaling may provide novel targets to therapeutically boost remyelination in several demyelinating diseases of the CNS.
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Affiliation(s)
- Funda Turan
- Medical Faculty, Institute of Neuroanatomy, University of Bonn, Bonn, Germany.,Faculty of Science, Biology Department, Ankara University, Ankara, Turkey
| | - Öznur Yilmaz
- Medical Faculty, Institute of Anatomy and Cell-Biology, University of Bonn, Bonn, Germany
| | - Lena Schünemann
- Medical Faculty, Institute of Anatomy and Cell-Biology, University of Bonn, Bonn, Germany
| | - Tobias T Lindenberg
- Medical Faculty, Institute of Neuroanatomy, University of Bonn, Bonn, Germany
| | - Jeshurun C Kalanithy
- Medical Faculty, Institute of Anatomy and Cell-Biology, University of Bonn, Bonn, Germany
| | - Alexander Harder
- Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn, Germany
| | - Shiva Ahmadi
- Medical Faculty, Institute for Biochemistry and Molecular Biology (IBMB), University of Bonn, Bonn, Germany
| | - Türker Duman
- Faculty of Science, Biology Department, Ankara University, Ankara, Turkey
| | - Ryan B MacDonald
- Institute of Ophthalmology, University College London, London, UK
| | - Dominic Winter
- Medical Faculty, Institute for Biochemistry and Molecular Biology (IBMB), University of Bonn, Bonn, Germany
| | - Changsheng Liu
- Medical Faculty, Institute of Anatomy and Cell-Biology, University of Bonn, Bonn, Germany
| | - Benjamin Odermatt
- Medical Faculty, Institute of Neuroanatomy, University of Bonn, Bonn, Germany.,Medical Faculty, Institute of Anatomy and Cell-Biology, University of Bonn, Bonn, Germany
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35
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Almeida RG, Williamson JM, Madden ME, Early JJ, Voas MG, Talbot WS, Bianco IH, Lyons DA. Myelination induces axonal hotspots of synaptic vesicle fusion that promote sheath growth. Curr Biol 2021; 31:3743-3754.e5. [PMID: 34270947 PMCID: PMC8445327 DOI: 10.1016/j.cub.2021.06.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 05/17/2021] [Accepted: 06/11/2021] [Indexed: 02/08/2023]
Abstract
Myelination of axons by oligodendrocytes enables fast saltatory conduction. Oligodendrocytes are responsive to neuronal activity, which has been shown to induce changes to myelin sheaths, potentially to optimize conduction and neural circuit function. However, the cellular bases of activity-regulated myelination in vivo are unclear, partly due to the difficulty of analyzing individual myelinated axons over time. Activity-regulated myelination occurs in specific neuronal subtypes and can be mediated by synaptic vesicle fusion, but several questions remain: it is unclear whether vesicular fusion occurs stochastically along axons or in discrete hotspots during myelination and whether vesicular fusion regulates myelin targeting, formation, and/or growth. It is also unclear why some neurons, but not others, exhibit activity-regulated myelination. Here, we imaged synaptic vesicle fusion in individual neurons in living zebrafish and documented robust vesicular fusion along axons during myelination. Surprisingly, we found that axonal vesicular fusion increased upon and required myelination. We found that axonal vesicular fusion was enriched in hotspots, namely the heminodal non-myelinated domains into which sheaths grew. Blocking vesicular fusion reduced the stable formation and growth of myelin sheaths, and chemogenetically stimulating neuronal activity promoted sheath growth. Finally, we observed high levels of axonal vesicular fusion only in neuronal subtypes that exhibit activity-regulated myelination. Our results identify a novel "feedforward" mechanism whereby the process of myelination promotes the neuronal activity-regulated signal, vesicular fusion that, in turn, consolidates sheath growth along specific axons selected for myelination.
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Affiliation(s)
- Rafael G Almeida
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.
| | - Jill M Williamson
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Megan E Madden
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Matthew G Voas
- Department of Developmental Biology, Stanford University, Stanford, CA, USA; National Cancer Institute, Frederick, MD, USA
| | - William S Talbot
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Isaac H Bianco
- Department of Neuroscience, Physiology and Pharmacology, UCL, London, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.
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36
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Irfan M, Evonuk KS, DeSilva TM. Microglia phagocytose oligodendrocyte progenitor cells and synapses during early postnatal development: implications for white versus gray matter maturation. FEBS J 2021; 289:2110-2127. [PMID: 34496137 DOI: 10.1111/febs.16190] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 06/21/2021] [Accepted: 09/07/2021] [Indexed: 12/22/2022]
Abstract
Emerging roles for microglia in modifying normal brain development continue to provide new perspectives on the functions of this resident immune cell in the brain. While the molecular underpinnings driving microglia's position in regulating developmental programs remain largely an unchartered territory, innate immune signaling lies at the forefront. At least three innate immune receptors expressed on microglia-fractalkine, complement, and triggering receptor expressed on microglia (TREM2)-modulate developmental synaptic pruning to refine brain circuitry. Our laboratory recently published that microglia with a unique amoeboid morphology invade the corpus callosum and engulf oligodendrocyte progenitor cells (OPCs) during early postnatal development before myelination in a fractalkine receptor (CX3CR1)-dependent manner to modulate ensheathment of axons. Amoeboid microglia are observed in the corpus callosum but not cerebral cortex, and lose their amoeboid shape at the commencement of myelination assuming a resting phenotype. Furthermore, OPCs contacted or engulfed by microglia do not express markers of cell death suggesting a novel homeostatic mechanism facilitating an appropriate OPC:axon ratio for proper myelin ensheathment. The unique morphology of microglia and the restricted window for phagocytic engulfment of OPCs suggest a critical period for OPC engulfment important for action potential propagation during development when activity-dependent mechanisms regulate synaptic pruning. In this review, we summarize the role of activity-dependent mechanisms in sculpting brain circuitry, how myelin ensheathment influences action potential propagation, the spatial and temporal relationship of microglia-dependent elimination of OPCs and synapses, and implications for the synergistic role of microglial phagocytosis in shaping the architecture for neuronal function.
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Affiliation(s)
- Muhammad Irfan
- Department of Neurosciences, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Kirsten S Evonuk
- Department of Neurosciences, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Tara M DeSilva
- Department of Neurosciences, Cleveland Clinic Foundation, Cleveland, OH, USA
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37
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Franklin RJM, Frisén J, Lyons DA. Revisiting remyelination: Towards a consensus on the regeneration of CNS myelin. Semin Cell Dev Biol 2021; 116:3-9. [PMID: 33082115 DOI: 10.1016/j.semcdb.2020.09.009] [Citation(s) in RCA: 77] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 09/18/2020] [Accepted: 09/22/2020] [Indexed: 12/16/2022]
Abstract
The biology of CNS remyelination has attracted considerable interest in recent years because of its translational potential to yield regenerative therapies for the treatment of chronic and progressive demyelinating diseases such as multiple sclerosis (MS). Critical to devising myelin regenerative therapies is a detailed understanding of how remyelination occurs. The accepted dogma, based on animal studies, has been that the myelin sheaths of remyelination are made by oligodendrocytes newly generated from adult oligodendrocyte progenitor cells in a classical regenerative process of progenitor migration, proliferation and differentiation. However, recent human and a growing number of animal studies have revealed a second mode of remyelination in which mature oligodendrocytes surviving within an area of demyelination are able to regenerate new myelin sheaths. This discovery, while opening up new opportunities for therapeutic remyelination, has also raised the question of whether there are fundamental differences in myelin regeneration between humans and some of the species in which experimental remyelination studies are conducted. Here we review how this second mode of remyelination can be integrated into a wider and revised framework for understanding remyelination in which apparent species differences can be reconciled but that also raises important questions for future research.
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Affiliation(s)
- Robin J M Franklin
- Wellcome-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom.
| | - Jonas Frisén
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden.
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom.
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38
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Monje M, Káradóttir RT. The bright and the dark side of myelin plasticity: Neuron-glial interactions in health and disease. Semin Cell Dev Biol 2021; 116:10-15. [PMID: 33293232 PMCID: PMC8178421 DOI: 10.1016/j.semcdb.2020.11.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/24/2020] [Accepted: 11/26/2020] [Indexed: 12/16/2022]
Abstract
Neuron-glial interactions shape neural circuit establishment, refinement and function. One of the key neuron-glial interactions takes place between axons and oligodendroglial precursor cells. Interactions between neurons and oligodendrocyte precursor cells (OPCs) promote OPC proliferation, generation of new oligodendrocytes and myelination, shaping myelin development and ongoing adaptive myelin plasticity in the brain. Communication between neurons and OPCs can be broadly divided into paracrine and synaptic mechanisms. Following the Nobel mini-symposium "The Dark Side of the Brain" in late 2019 at the Karolinska Institutet, this mini-review will focus on the bright and dark sides of neuron-glial interactions and discuss paracrine and synaptic interactions between neurons and OPCs and their malignant counterparts.
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Affiliation(s)
- Michelle Monje
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA.
| | - Ragnhildur Thóra Káradóttir
- Wellcome - Medical Research Council Cambridge Stem Cell Institute & Department of Veterinary Medicine, University of Cambridge, Cambridge, UK; Department of Physiology, BioMedical Center, Faculty of Medicine, University of Iceland, Reykjavik, Iceland.
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39
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Piller M, Werkman IL, Brown RI, Latimer AJ, Kucenas S. Glutamate Signaling via the AMPAR Subunit GluR4 Regulates Oligodendrocyte Progenitor Cell Migration in the Developing Spinal Cord. J Neurosci 2021; 41:5353-5371. [PMID: 33975920 PMCID: PMC8221590 DOI: 10.1523/jneurosci.2562-20.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 04/28/2021] [Accepted: 05/03/2021] [Indexed: 11/21/2022] Open
Abstract
Oligodendrocyte progenitor cells (OPCs) are specified from discrete precursor populations during gliogenesis and migrate extensively from their origins, ultimately distributing throughout the brain and spinal cord during early development. Subsequently, a subset of OPCs differentiates into mature oligodendrocytes, which myelinate axons. This process is necessary for efficient neuronal signaling and organism survival. Previous studies have identified several factors that influence OPC development, including excitatory glutamatergic synapses that form between neurons and OPCs during myelination. However, little is known about how glutamate signaling affects OPC migration before myelination. In this study, we use in vivo, time-lapse imaging in zebrafish in conjunction with genetic and pharmacological perturbation to investigate OPC migration and myelination when the GluR4A ionotropic glutamate receptor subunit is disrupted. In our studies, we observed that gria4a mutant embryos and larvae displayed abnormal OPC migration and altered dorsoventral distribution in the spinal cord. Genetic mosaic analysis confirmed that these effects were cell-autonomous, and we identified that voltage-gated calcium channels were downstream of glutamate receptor signaling in OPCs and could rescue the migration and myelination defects we observed when glutamate signaling was perturbed. These results offer new insights into the complex system of neuron-OPC interactions and reveal a cell-autonomous role for glutamatergic signaling in OPCs during neural development.SIGNIFICANCE STATEMENT The migration of oligodendrocyte progenitor cells (OPCs) is an essential process during development that leads to uniform oligodendrocyte distribution and sufficient myelination for central nervous system function. Here, we demonstrate that the AMPA receptor (AMPAR) subunit GluR4A is an important driver of OPC migration and myelination in vivo and that activated voltage-gated calcium channels are downstream of glutamate receptor signaling in mediating this migration.
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Affiliation(s)
- Melanie Piller
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
| | - Inge L Werkman
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
| | - Robin Isadora Brown
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
| | - Andrew J Latimer
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
| | - Sarah Kucenas
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
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40
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Hughes AN. Glial Cells Promote Myelin Formation and Elimination. Front Cell Dev Biol 2021; 9:661486. [PMID: 34046407 PMCID: PMC8144722 DOI: 10.3389/fcell.2021.661486] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 04/07/2021] [Indexed: 12/13/2022] Open
Abstract
Building a functional nervous system requires the coordinated actions of many glial cells. In the vertebrate central nervous system (CNS), oligodendrocytes myelinate neuronal axons to increase conduction velocity and provide trophic support. Myelination can be modified by local signaling at the axon-myelin interface, potentially adapting sheaths to support the metabolic needs and physiology of individual neurons. However, neurons and oligodendrocytes are not wholly responsible for crafting the myelination patterns seen in vivo. Other cell types of the CNS, including microglia and astrocytes, modify myelination. In this review, I cover the contributions of non-neuronal, non-oligodendroglial cells to the formation, maintenance, and pruning of myelin sheaths. I address ways that these cell types interact with the oligodendrocyte lineage throughout development to modify myelination. Additionally, I discuss mechanisms by which these cells may indirectly tune myelination by regulating neuronal activity. Understanding how glial-glial interactions regulate myelination is essential for understanding how the brain functions as a whole and for developing strategies to repair myelin in disease.
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Affiliation(s)
- Alexandria N Hughes
- Section of Developmental Biology, Department of Pediatrics, University of Colorado, Aurora, Aurora, CO, United States
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41
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James OG, Selvaraj BT, Magnani D, Burr K, Connick P, Barton SK, Vasistha NA, Hampton DW, Story D, Smigiel R, Ploski R, Brophy PJ, Ffrench-Constant C, Lyons DA, Chandran S. iPSC-derived myelinoids to study myelin biology of humans. Dev Cell 2021; 56:1346-1358.e6. [PMID: 33945785 PMCID: PMC8098746 DOI: 10.1016/j.devcel.2021.04.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 01/20/2021] [Accepted: 04/06/2021] [Indexed: 01/03/2023]
Abstract
Myelination is essential for central nervous system (CNS) formation, health, and function. Emerging evidence of oligodendrocyte heterogeneity in health and disease and divergent CNS gene expression profiles between mice and humans supports the development of experimentally tractable human myelination systems. Here, we developed human iPSC-derived myelinating organoids ("myelinoids") and quantitative tools to study myelination from oligodendrogenesis through to compact myelin formation and myelinated axon organization. Using patient-derived cells, we modeled a monogenetic disease of myelinated axons (Nfasc155 deficiency), recapitulating impaired paranodal axo-glial junction formation. We also validated the use of myelinoids for pharmacological assessment of myelination-both at the level of individual oligodendrocytes and globally across whole myelinoids-and demonstrated reduced myelination in response to suppressed synaptic vesicle release. Our study provides a platform to investigate human myelin development, disease, and adaptive myelination.
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Affiliation(s)
- Owen G James
- UK Dementia Research Institute at the University of Edinburgh, Edinburgh EH16 4SB, UK; Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK; Euan MacDonald Centre for Motor Neurone Disease Research University of Edinburgh, Edinburgh EH16 4SB, UK; Anne Rowling Regenerative Neurology Clinic, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Bhuvaneish T Selvaraj
- UK Dementia Research Institute at the University of Edinburgh, Edinburgh EH16 4SB, UK; Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK; Euan MacDonald Centre for Motor Neurone Disease Research University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Dario Magnani
- UK Dementia Research Institute at the University of Edinburgh, Edinburgh EH16 4SB, UK; Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK; Euan MacDonald Centre for Motor Neurone Disease Research University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Karen Burr
- UK Dementia Research Institute at the University of Edinburgh, Edinburgh EH16 4SB, UK; Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK; Euan MacDonald Centre for Motor Neurone Disease Research University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Peter Connick
- UK Dementia Research Institute at the University of Edinburgh, Edinburgh EH16 4SB, UK; Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK; Anne Rowling Regenerative Neurology Clinic, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Samantha K Barton
- UK Dementia Research Institute at the University of Edinburgh, Edinburgh EH16 4SB, UK; Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK; Euan MacDonald Centre for Motor Neurone Disease Research University of Edinburgh, Edinburgh EH16 4SB, UK; Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Navneet A Vasistha
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK; Euan MacDonald Centre for Motor Neurone Disease Research University of Edinburgh, Edinburgh EH16 4SB, UK; Biotech Research and Innovation Centre, Copenhagen N 2200, Denmark
| | - David W Hampton
- UK Dementia Research Institute at the University of Edinburgh, Edinburgh EH16 4SB, UK; Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK; Euan MacDonald Centre for Motor Neurone Disease Research University of Edinburgh, Edinburgh EH16 4SB, UK
| | - David Story
- UK Dementia Research Institute at the University of Edinburgh, Edinburgh EH16 4SB, UK; Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK; Euan MacDonald Centre for Motor Neurone Disease Research University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Robert Smigiel
- Department of Pediatrics and Rare Disorders, Wroclaw Medical University, Wrocław 51-618, Poland
| | - Rafal Ploski
- Department of Medical Genetics, Medical University of Warsaw, Warsaw 02-106, Poland
| | - Peter J Brophy
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK
| | | | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Siddharthan Chandran
- UK Dementia Research Institute at the University of Edinburgh, Edinburgh EH16 4SB, UK; Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK; Euan MacDonald Centre for Motor Neurone Disease Research University of Edinburgh, Edinburgh EH16 4SB, UK; Anne Rowling Regenerative Neurology Clinic, University of Edinburgh, Edinburgh EH16 4SB, UK; Centre for Brain Development and Repair, inStem, Bangalore 560065, India.
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42
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Nishiyama A, Shimizu T, Sherafat A, Richardson WD. Life-long oligodendrocyte development and plasticity. Semin Cell Dev Biol 2021; 116:25-37. [PMID: 33741250 PMCID: PMC8292179 DOI: 10.1016/j.semcdb.2021.02.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 02/16/2021] [Accepted: 02/17/2021] [Indexed: 12/25/2022]
Abstract
Oligodendrocyte precursor cells (OPCs) originate in localized germinal zones in the embryonic neural tube, then migrate and proliferate to populate the entire central nervous system, both white and gray matter. They divide and generate myelinating oligodendrocytes (OLs) throughout postnatal and adult life. OPCs express NG2 and platelet-derived growth factor receptor alpha subunit (PDGFRα), two functionally important cell surface proteins, which are also widely used as markers for OPCs. The proliferation of OPCs, their terminal differentiation into OLs, survival of new OLs, and myelin synthesis are orchestrated by signals in the local microenvironment. We discuss advances in our mechanistic understanding of paracrine effects, including those mediated through PDGFRα and neuronal activity-dependent signals such as those mediated through AMPA receptors in OL survival and myelination. Finally, we review recent studies supporting the role of new OL production and “adaptive myelination” in specific behaviours and cognitive processes contributing to learning and long-term memory formation. Our article is not intended to be comprehensive but reflects the authors’ past and present interests.
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Affiliation(s)
- Akiko Nishiyama
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT 06269-3156, USA.
| | - Takahiro Shimizu
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Amin Sherafat
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT 06269-3156, USA
| | - William D Richardson
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK.
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43
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Pease-Raissi SE, Chan JR. Building a (w)rapport between neurons and oligodendroglia: Reciprocal interactions underlying adaptive myelination. Neuron 2021; 109:1258-1273. [PMID: 33621477 DOI: 10.1016/j.neuron.2021.02.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/12/2021] [Accepted: 01/29/2021] [Indexed: 12/27/2022]
Abstract
Myelin, multilayered lipid-rich membrane extensions formed by oligodendrocytes around neuronal axons, is essential for fast and efficient action potential propagation in the central nervous system. Initially thought to be a static and immutable process, myelination is now appreciated to be a dynamic process capable of responding to and modulating neuronal function throughout life. While the importance of this type of plasticity, called adaptive myelination, is now well accepted, we are only beginning to understand the underlying cellular and molecular mechanisms by which neurons communicate experience-driven circuit activation to oligodendroglia and precisely how changes in oligodendrocytes and their myelin refine neuronal function. Here, we review recent findings addressing this reciprocal relationship in which neurons alter oligodendroglial form and oligodendrocytes conversely modulate neuronal function.
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Affiliation(s)
- Sarah E Pease-Raissi
- Weill Institute for Neuroscience, Department of Neurology, University of California, San Francisco, San Francisco, CA 94158, USA.
| | - Jonah R Chan
- Weill Institute for Neuroscience, Department of Neurology, University of California, San Francisco, San Francisco, CA 94158, USA.
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44
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Tsata V, Kroehne V, Wehner D, Rost F, Lange C, Hoppe C, Kurth T, Reinhardt S, Petzold A, Dahl A, Loeffler M, Reimer MM, Brand M. Reactive oligodendrocyte progenitor cells (re-)myelinate the regenerating zebrafish spinal cord. Development 2020; 147:dev193946. [PMID: 33158923 DOI: 10.1242/dev.193946] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 10/28/2020] [Indexed: 12/11/2022]
Abstract
Spinal cord injury (SCI) results in loss of neurons, oligodendrocytes and myelin sheaths, all of which are not efficiently restored. The scarcity of oligodendrocytes in the lesion site impairs re-myelination of spared fibres, which leaves axons denuded, impedes signal transduction and contributes to permanent functional deficits. In contrast to mammals, zebrafish can functionally regenerate the spinal cord. Yet, little is known about oligodendroglial lineage biology and re-myelination capacity after SCI in a regeneration-permissive context. Here, we report that, in adult zebrafish, SCI results in axonal, oligodendrocyte and myelin sheath loss. We find that OPCs, the oligodendrocyte progenitor cells, survive the injury, enter a reactive state, proliferate and differentiate into oligodendrocytes. Concomitantly, the oligodendrocyte population is re-established to pre-injury levels within 2 weeks. Transcriptional profiling revealed that reactive OPCs upregulate the expression of several myelination-related genes. Interestingly, global reduction of axonal tracts and partial re-myelination, relative to pre-injury levels, persist at later stages of regeneration, yet are sufficient for functional recovery. Taken together, these findings imply that, in the zebrafish spinal cord, OPCs replace lost oligodendrocytes and, thus, re-establish myelination during regeneration.
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Affiliation(s)
- Vasiliki Tsata
- Center for Regenerative Therapies Dresden TU Dresden (CRTD) and Cluster of Excellence, Physics of Life (PoL), TU Dresden, Dresden 01307, Germany
| | - Volker Kroehne
- Center for Regenerative Therapies Dresden TU Dresden (CRTD) and Cluster of Excellence, Physics of Life (PoL), TU Dresden, Dresden 01307, Germany
| | - Daniel Wehner
- Center for Regenerative Therapies Dresden TU Dresden (CRTD) and Cluster of Excellence, Physics of Life (PoL), TU Dresden, Dresden 01307, Germany
- Max Planck Institute for the Science of Light, Erlangen 91058, Germany
- Max-Planck-Zentrum für Physik und Medizin, Erlangen 91058, Germany
| | - Fabian Rost
- Center for Regenerative Therapies Dresden TU Dresden (CRTD) and Cluster of Excellence, Physics of Life (PoL), TU Dresden, Dresden 01307, Germany
- Center for Information Services and High Performance Computing, TU Dresden, Dresden 01062, Germany
| | - Christian Lange
- Center for Regenerative Therapies Dresden TU Dresden (CRTD) and Cluster of Excellence, Physics of Life (PoL), TU Dresden, Dresden 01307, Germany
| | - Cornelia Hoppe
- Center for Regenerative Therapies Dresden TU Dresden (CRTD) and Cluster of Excellence, Physics of Life (PoL), TU Dresden, Dresden 01307, Germany
| | - Thomas Kurth
- Center for Molecular and Cellular Bioengineering (CMCB), TU Dresden, Technology Platform, Dresden 01307, Germany
| | - Susanne Reinhardt
- Dresden Genome Center c/o Center for Regenerative Therapies TU Dresden (CRTD), TU Dresden, Dresden 01307, Germany
| | - Andreas Petzold
- Dresden Genome Center c/o Center for Regenerative Therapies TU Dresden (CRTD), TU Dresden, Dresden 01307, Germany
| | - Andreas Dahl
- Dresden Genome Center c/o Center for Regenerative Therapies TU Dresden (CRTD), TU Dresden, Dresden 01307, Germany
| | - Markus Loeffler
- Center for Advancing Electronics Dresden (cfaed)/Dresden Center for Nanoanalysis (DCN), TU Dresden, Dresden 01062, Germany
| | - Michell M Reimer
- Center for Regenerative Therapies Dresden TU Dresden (CRTD) and Cluster of Excellence, Physics of Life (PoL), TU Dresden, Dresden 01307, Germany
| | - Michael Brand
- Center for Regenerative Therapies Dresden TU Dresden (CRTD) and Cluster of Excellence, Physics of Life (PoL), TU Dresden, Dresden 01307, Germany
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45
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Nelson HN, Treichel AJ, Eggum EN, Martell MR, Kaiser AJ, Trudel AG, Gronseth JR, Maas ST, Bergen S, Hines JH. Individual neuronal subtypes control initial myelin sheath growth and stabilization. Neural Dev 2020; 15:12. [PMID: 32988384 PMCID: PMC7523326 DOI: 10.1186/s13064-020-00149-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 09/17/2020] [Indexed: 01/21/2023] Open
Abstract
Background In the developing central nervous system, pre-myelinating oligodendrocytes sample candidate nerve axons by extending and retracting process extensions. Some contacts stabilize, leading to the initiation of axon wrapping, nascent myelin sheath formation, concentric wrapping and sheath elongation, and sheath stabilization or pruning by oligodendrocytes. Although axonal signals influence the overall process of myelination, the precise oligodendrocyte behaviors that require signaling from axons are not completely understood. In this study, we investigated whether oligodendrocyte behaviors during the early events of myelination are mediated by an oligodendrocyte-intrinsic myelination program or are over-ridden by axonal factors. Methods To address this, we utilized in vivo time-lapse imaging in embryonic and larval zebrafish spinal cord during the initial hours and days of axon wrapping and myelination. Transgenic reporter lines marked individual axon subtypes or oligodendrocyte membranes. Results In the larval zebrafish spinal cord, individual axon subtypes supported distinct nascent sheath growth rates and stabilization frequencies. Oligodendrocytes ensheathed individual axon subtypes at different rates during a two-day period after initial axon wrapping. When descending reticulospinal axons were ablated, local spinal axons supported a constant ensheathment rate despite the increased ratio of oligodendrocytes to target axons. Conclusion We conclude that properties of individual axon subtypes instruct oligodendrocyte behaviors during initial stages of myelination by differentially controlling nascent sheath growth and stabilization.
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Affiliation(s)
| | | | - Erin N Eggum
- Biology Department, Winona State University, Winona, MN, USA
| | | | - Amanda J Kaiser
- Biology Department, Winona State University, Winona, MN, USA
| | - Allie G Trudel
- Biology Department, Winona State University, Winona, MN, USA
| | | | - Samantha T Maas
- Biology Department, Winona State University, Winona, MN, USA
| | - Silas Bergen
- Biology Department, Winona State University, Winona, MN, USA
| | - Jacob H Hines
- Biology Department, Winona State University, Winona, MN, USA.
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Hughes AN, Appel B. Microglia phagocytose myelin sheaths to modify developmental myelination. Nat Neurosci 2020; 23:1055-1066. [PMID: 32632287 PMCID: PMC7483351 DOI: 10.1038/s41593-020-0654-2] [Citation(s) in RCA: 172] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Accepted: 05/13/2020] [Indexed: 12/15/2022]
Abstract
During development, oligodendrocytes contact and wrap neuronal axons with myelin. Similarly to neurons and synapses, excess myelin sheaths are produced and selectively eliminated, but how elimination occurs is unknown. Microglia, the resident immune cells of the central nervous system, engulf surplus neurons and synapses. To determine whether microglia also prune myelin sheaths, we used zebrafish to visualize and manipulate interactions between microglia, oligodendrocytes, and neurons during development. We found that microglia closely associate with oligodendrocytes and specifically phagocytose myelin sheaths. By using a combination of optical, genetic, chemogenetic, and behavioral approaches, we reveal that neuronal activity bidirectionally balances microglial association with neuronal cell bodies and myelin phagocytosis in the optic tectum. Furthermore, multiple strategies to deplete microglia resulted in oligodendrocytes maintaining excessive and ectopic myelin. Our work reveals a neuronal activity-regulated role for microglia in modifying developmental myelin targeting by oligodendrocytes.
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Affiliation(s)
| | - Bruce Appel
- Department of Pediatrics, Section of Developmental Biology, University of Colorado, Aurora, CO, USA.
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47
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Lubetzki C, Zalc B, Williams A, Stadelmann C, Stankoff B. Remyelination in multiple sclerosis: from basic science to clinical translation. Lancet Neurol 2020; 19:678-688. [PMID: 32702337 DOI: 10.1016/s1474-4422(20)30140-x] [Citation(s) in RCA: 174] [Impact Index Per Article: 43.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 04/03/2020] [Accepted: 04/09/2020] [Indexed: 01/19/2023]
Abstract
The treatment of multiple sclerosis has been transformed by the successful development of immunotherapies that efficiently reduce disease activity and related clinical relapses during the relapsing-remitting phase of the disease. However, the prevention of disability progression, which is due to axonal and neuronal damage and loss, has yet to be achieved and is therapeutically challenging, particularly during the progressive phase of the disease. One strategy to counteract neurodegeneration is to promote neuroprotection by enhancing myelin regeneration, hence restoring nerve conduction and metabolic support to the axon. Animal studies have provided targets for interventions to improve brain and spinal cord remyelination, paving the way for the translation of this research to humans. From these initial and promising forays, further problems have emerged, including questions on how best to design these clinical trials and appropriately measure the outcomes. Solving these problems will need additional work before efficacious pro-remyelination therapies will be ready for people with multiple sclerosis, but there is a real sense of hope that researchers are getting closer to a successful therapy.
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Affiliation(s)
- Catherine Lubetzki
- Sorbonne University, Institut National de la Santé et de la Recherche Médicale (INSERM), Centre National de la Recherche Scientifique (CNRS), Institut du Cerveau (ICM), Groupe Hospitalier APHP-Sorbonne University, Paris, France; Neurology Department Pitié-Salpêtrière, Groupe Hospitalier APHP-Sorbonne University, Paris, France.
| | - Bernard Zalc
- Sorbonne University, Institut National de la Santé et de la Recherche Médicale (INSERM), Centre National de la Recherche Scientifique (CNRS), Institut du Cerveau (ICM), Groupe Hospitalier APHP-Sorbonne University, Paris, France
| | - Anna Williams
- Centre for Regenerative Medicine, University of Edinburgh, Edinburgh, UK
| | - Christine Stadelmann
- Institute of Neuropathology, University Medical Center Göttingen, Göttingen, Germany
| | - Bruno Stankoff
- Sorbonne University, Institut National de la Santé et de la Recherche Médicale (INSERM), Centre National de la Recherche Scientifique (CNRS), Institut du Cerveau (ICM), Groupe Hospitalier APHP-Sorbonne University, Paris, France; Neurology Department Saint-Antoine, Groupe Hospitalier APHP-Sorbonne University, Paris, France
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48
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Haessig G, Milde MB, Aceituno PV, Oubari O, Knight JC, van Schaik A, Benosman RB, Indiveri G. Event-Based Computation for Touch Localization Based on Precise Spike Timing. Front Neurosci 2020; 14:420. [PMID: 32528239 PMCID: PMC7248403 DOI: 10.3389/fnins.2020.00420] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Accepted: 04/07/2020] [Indexed: 11/13/2022] Open
Abstract
Precise spike timing and temporal coding are used extensively within the nervous system of insects and in the sensory periphery of higher order animals. However, conventional Artificial Neural Networks (ANNs) and machine learning algorithms cannot take advantage of this coding strategy, due to their rate-based representation of signals. Even in the case of artificial Spiking Neural Networks (SNNs), identifying applications where temporal coding outperforms the rate coding strategies of ANNs is still an open challenge. Neuromorphic sensory-processing systems provide an ideal context for exploring the potential advantages of temporal coding, as they are able to efficiently extract the information required to cluster or classify spatio-temporal activity patterns from relative spike timing. Here we propose a neuromorphic model inspired by the sand scorpion to explore the benefits of temporal coding, and validate it in an event-based sensory-processing task. The task consists in localizing a target using only the relative spike timing of eight spatially-separated vibration sensors. We propose two different approaches in which the SNNs learns to cluster spatio-temporal patterns in an unsupervised manner and we demonstrate how the task can be solved both analytically and through numerical simulation of multiple SNN models. We argue that the models presented are optimal for spatio-temporal pattern classification using precise spike timing in a task that could be used as a standard benchmark for evaluating event-based sensory processing models based on temporal coding.
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Affiliation(s)
- Germain Haessig
- Institute of Neuroinformatics, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Moritz B Milde
- International Centre for Neuromorphic Systems, MARCS Institute, Western Sydney University, Penrith, NSW, Australia
| | - Pau Vilimelis Aceituno
- Max Planck Institute for Mathematics in the Sciences, Leipzig, Germany.,Max Planck School of Cognition, Leipzig, Germany
| | - Omar Oubari
- Institut de la Vision, Sorbonne Université, Paris, France
| | - James C Knight
- Centre for Computational Neuroscience and Robotics, School of Engineering and Informatics, University of Sussex, Brighton, United Kingdom
| | - André van Schaik
- International Centre for Neuromorphic Systems, MARCS Institute, Western Sydney University, Penrith, NSW, Australia
| | - Ryad B Benosman
- Institut de la Vision, Sorbonne Université, Paris, France.,University of Pittsburgh, Pittsburgh, PA, United States.,Carnegie Mellon University, Pittsburgh, PA, United States
| | - Giacomo Indiveri
- Institute of Neuroinformatics, University of Zurich and ETH Zurich, Zurich, Switzerland
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49
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Bonetto G, Kamen Y, Evans KA, Káradóttir RT. Unraveling Myelin Plasticity. Front Cell Neurosci 2020; 14:156. [PMID: 32595455 PMCID: PMC7301701 DOI: 10.3389/fncel.2020.00156] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 05/11/2020] [Indexed: 12/24/2022] Open
Abstract
Plasticity in the central nervous system (CNS) allows for responses to changing environmental signals. While the majority of studies on brain plasticity focus on neuronal synapses, myelin plasticity has now begun to emerge as a potential modulator of neuronal networks. Oligodendrocytes (OLs) produce myelin, which provides fast signal transmission, allows for synchronization of neuronal inputs, and helps to maintain neuronal function. Thus, myelination is also thought to be involved in learning. OLs differentiate from oligodendrocyte precursor cells (OPCs), which are distributed throughout the adult brain, and myelination continues into late adulthood. This process is orchestrated by numerous cellular and molecular signals, such as axonal diameter, growth factors, extracellular signaling molecules, and neuronal activity. However, the relative importance of, and cooperation between, these signaling pathways is currently unknown. In this review, we focus on the current knowledge about myelin plasticity in the CNS. We discuss new insights into the link between this type of plasticity, learning and behavior, as well as mechanistic aspects of myelin formation that may underlie myelin plasticity, highlighting OPC diversity in the CNS.
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Affiliation(s)
- Giulia Bonetto
- Wellcome - Medical Research Council Cambridge Stem Cell Institute and Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Yasmine Kamen
- Wellcome - Medical Research Council Cambridge Stem Cell Institute and Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Kimberley Anne Evans
- Wellcome - Medical Research Council Cambridge Stem Cell Institute and Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Ragnhildur Thóra Káradóttir
- Wellcome - Medical Research Council Cambridge Stem Cell Institute and Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.,Department of Physiology, Biomedical Centre, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
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50
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Craig GA, Yoo S, Du TY, Xiao J. Plasticity in oligodendrocyte lineage progression: An OPC puzzle on our nerves. Eur J Neurosci 2020; 54:5747-5761. [PMID: 32478920 DOI: 10.1111/ejn.14845] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 05/20/2020] [Accepted: 05/21/2020] [Indexed: 11/28/2022]
Abstract
Myelin deposition in the central nervous system has been shown to be responsive to experience, with sensory enrichment increasing myelination and sensory or social deprivation decreasing myelination. This process is referred to as "adaptive myelination" or "myelin plasticity" and signifies an essential component of new learning. However, whether these experience-driven adaptations are driven by (a) underlying changes in the generation of myelinating cells, (b) altered interactions between myelin sheath and axon, or (c) a combination of the above remains unclear. It has been suggested that myelination largely follows an "innate" and automatic programme, allowing for a predictable pattern of central nervous system myelin deposition over time. Adaptive myelination is thought to account for more nuanced alterations that do not dramatically shift this pattern, but ultimately drive functional responses. This makes the study of myelin plasticity particularly difficult, as it necessitates being able to clearly and specifically draw boundaries between the innate and adaptive programme. Thus, the field requires a holistic understanding of the remit of innate myelin development, prior to investigation of adaptive myelination. This review will collate literature regarding different aspects of oligodendrocyte and myelin development (namely, oligodendrocyte proliferation, differentiation, death and myelin sheath formation) in an innate context, before discussing how these parameters are proposed to change under adaptive conditions. It is the hope that this review will highlight the need for a comprehensive and integrated approach towards studying both innate and adaptive forms of myelination.
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Affiliation(s)
- Georgina A Craig
- Department of Anatomy and Neuroscience, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Vic., Australia
| | - SangWon Yoo
- Department of Anatomy and Neuroscience, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Vic., Australia
| | - Tian Y Du
- Department of Anatomy and Neuroscience, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Vic., Australia
| | - Junhua Xiao
- Department of Anatomy and Neuroscience, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Vic., Australia
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