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de Lamotte JD, Polentes J, Roussange F, Lesueur L, Feurgard P, Perrier A, Nicoleau C, Martinat C. Optogenetically controlled human functional motor endplate for testing botulinum neurotoxins. Stem Cell Res Ther 2021; 12:599. [PMID: 34865655 PMCID: PMC8647380 DOI: 10.1186/s13287-021-02665-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 11/18/2021] [Indexed: 11/19/2022] Open
Abstract
Background The lack of physiologically relevant and predictive cell-based assays is one of the major obstacles for testing and developing botulinum neurotoxins (BoNTs) therapeutics. Human-induced pluripotent stem cells (hiPSCs)-derivatives now offer the opportunity to improve the relevance of cellular models and thus the translational value of preclinical data. Methods We investigated the potential of hiPSC-derived motor neurons (hMNs) optical stimulation combined with calcium imaging in cocultured muscle cells activity to investigate BoNT-sensitivity of an in vitro model of human muscle-nerve system. Results Functional muscle-nerve coculture system was developed using hMNs and human immortalized skeletal muscle cells. Our results demonstrated that hMNs can innervate myotubes and induce contractions and calcium transient in muscle cells, generating an in vitro human motor endplate showing dose-dependent sensitivity to BoNTs intoxication. The implementation of optogenetics combined with live calcium imaging allows to monitor the impact of BoNTs intoxication on synaptic transmission in human motor endplate model. Conclusions Altogether, our findings demonstrate the promise of optogenetically hiPSC-derived controlled muscle-nerve system for pharmaceutical BoNTs testing and development. Supplementary Information The online version contains supplementary material available at 10.1186/s13287-021-02665-3.
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Affiliation(s)
- Juliette Duchesne de Lamotte
- IPSEN Innovation, 5 avenue du Canada, 91940, Les Ulis, France.,Université Evry-Paris Saclay/INSERM UMR861, Institut Des Cellules Souches Pour Le Traitement Et L'étude Des Maladies Monogéniques (I-Stem), 2 rue Henri Auguste Desbruères, 91100, Corbeil-Essonne, France
| | - Jérôme Polentes
- Université Evry-Paris Saclay/INSERM UMR861, Institut Des Cellules Souches Pour Le Traitement Et L'étude Des Maladies Monogéniques (I-Stem), 2 rue Henri Auguste Desbruères, 91100, Corbeil-Essonne, France
| | - Florine Roussange
- Université Evry-Paris Saclay/INSERM UMR861, Institut Des Cellules Souches Pour Le Traitement Et L'étude Des Maladies Monogéniques (I-Stem), 2 rue Henri Auguste Desbruères, 91100, Corbeil-Essonne, France
| | - Léa Lesueur
- Université Evry-Paris Saclay/INSERM UMR861, Institut Des Cellules Souches Pour Le Traitement Et L'étude Des Maladies Monogéniques (I-Stem), 2 rue Henri Auguste Desbruères, 91100, Corbeil-Essonne, France
| | - Pauline Feurgard
- Université Evry-Paris Saclay/INSERM UMR861, Institut Des Cellules Souches Pour Le Traitement Et L'étude Des Maladies Monogéniques (I-Stem), 2 rue Henri Auguste Desbruères, 91100, Corbeil-Essonne, France
| | - Anselme Perrier
- Université Evry-Paris Saclay/INSERM UMR861, Institut Des Cellules Souches Pour Le Traitement Et L'étude Des Maladies Monogéniques (I-Stem), 2 rue Henri Auguste Desbruères, 91100, Corbeil-Essonne, France.,Laboratoire Des Maladies Neurodégénératives: Mécanismes, thérapies, imagerie, Université Paris Saclay/CEA/CNRS UMR9199, MIRCen, Bâtiment 61, CEA-Fontenay-Aux-Roses, 18 route du Panorama, 92265, Fontenay-aux-Roses, France
| | | | - Cécile Martinat
- Université Evry-Paris Saclay/INSERM UMR861, Institut Des Cellules Souches Pour Le Traitement Et L'étude Des Maladies Monogéniques (I-Stem), 2 rue Henri Auguste Desbruères, 91100, Corbeil-Essonne, France.
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Hörner SJ, Couturier N, Bruch R, Koch P, Hafner M, Rudolf R. hiPSC-Derived Schwann Cells Influence Myogenic Differentiation in Neuromuscular Cocultures. Cells 2021; 10:cells10123292. [PMID: 34943800 PMCID: PMC8699767 DOI: 10.3390/cells10123292] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 11/20/2021] [Accepted: 11/21/2021] [Indexed: 12/13/2022] Open
Abstract
Motoneurons, skeletal muscle fibers, and Schwann cells form synapses, termed neuromuscular junctions (NMJs). These control voluntary body movement and are affected in numerous neuromuscular diseases. Therefore, a variety of NMJ in vitro models have been explored to enable mechanistic and pharmacological studies. So far, selective integration of Schwann cells in these models has been hampered, due to technical limitations. Here we present robust protocols for derivation of Schwann cells from human induced pluripotent stem cells (hiPSC) and their coculture with hiPSC-derived motoneurons and C2C12 muscle cells. Upon differentiation with tuned BMP signaling, Schwann cells expressed marker proteins, S100b, Gap43, vimentin, and myelin protein zero. Furthermore, they displayed typical spindle-shaped morphologies with long processes, which often aligned with motoneuron axons. Inclusion of Schwann cells in coculture experiments with hiPSC-derived motoneurons and C2C12 myoblasts enhanced myotube growth and affected size and number of acetylcholine receptor plaques on myotubes. Altogether, these data argue for the availability of a consistent differentiation protocol for Schwann cells and their amenability for functional integration into neuromuscular in vitro models, fostering future studies of neuromuscular mechanisms and disease.
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Affiliation(s)
- Sarah Janice Hörner
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, 68163 Mannheim, Germany; (S.J.H.); (N.C.); (R.B.); (M.H.)
- Interdisciplinary Center for Neurosciences, Heidelberg University, 69120 Heidelberg, Germany
| | - Nathalie Couturier
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, 68163 Mannheim, Germany; (S.J.H.); (N.C.); (R.B.); (M.H.)
| | - Roman Bruch
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, 68163 Mannheim, Germany; (S.J.H.); (N.C.); (R.B.); (M.H.)
| | - Philipp Koch
- Central Institute of Mental Health, Medical Faculty Mannheim of Heidelberg University, 68159 Mannheim, Germany;
- Hector Institute for Translational Brain Research (HITBR gGmbH), 68159 Mannheim, Germany
- German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Mathias Hafner
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, 68163 Mannheim, Germany; (S.J.H.); (N.C.); (R.B.); (M.H.)
- Institute of Medical Technology, Mannheim University of Applied Sciences and Heidelberg University, 68163 Mannheim, Germany
| | - Rüdiger Rudolf
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, 68163 Mannheim, Germany; (S.J.H.); (N.C.); (R.B.); (M.H.)
- Interdisciplinary Center for Neurosciences, Heidelberg University, 69120 Heidelberg, Germany
- Institute of Medical Technology, Mannheim University of Applied Sciences and Heidelberg University, 68163 Mannheim, Germany
- Correspondence:
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Fuertes-Alvarez S, Izeta A. Terminal Schwann Cell Aging: Implications for Age-Associated Neuromuscular Dysfunction. Aging Dis 2021; 12:494-514. [PMID: 33815879 PMCID: PMC7990373 DOI: 10.14336/ad.2020.0708] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 07/08/2020] [Indexed: 12/11/2022] Open
Abstract
Action potential is transmitted to muscle fibers through specialized synaptic interfaces called neuromuscular junctions (NMJs). These structures are capped by terminal Schwann cells (tSCs), which play essential roles during formation and maintenance of the NMJ. tSCs are implicated in the correct communication between nerves and muscles, and in reinnervation upon injury. During aging, loss of muscle mass and strength (sarcopenia and dynapenia) are due, at least in part, to the progressive loss of contacts between muscle fibers and nerves. Despite the important role of tSCs in NMJ function, very little is known on their implication in the NMJ-aging process and in age-associated denervation. This review summarizes the current knowledge about the implication of tSCs in the age-associated degeneration of NMJs. We also speculate on the possible mechanisms underlying the observed phenotypes.
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Affiliation(s)
- Sandra Fuertes-Alvarez
- 1Biodonostia, Tissue Engineering Group, Paseo Dr. Begiristain, s/n, San Sebastian 20014, Spain
| | - Ander Izeta
- 1Biodonostia, Tissue Engineering Group, Paseo Dr. Begiristain, s/n, San Sebastian 20014, Spain.,2Tecnun-University of Navarra, School of Engineering, Department of Biomedical Engineering and Science, Paseo Mikeletegi, 48, San Sebastian 20009, Spain
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Neuromuscular Junction as an Entity of Nerve-Muscle Communication. Cells 2019; 8:cells8080906. [PMID: 31426366 PMCID: PMC6721719 DOI: 10.3390/cells8080906] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 08/13/2019] [Accepted: 08/14/2019] [Indexed: 12/11/2022] Open
Abstract
One of the crucial systems severely affected in several neuromuscular diseases is the loss of effective connection between muscle and nerve, leading to a pathological non-communication between the two tissues. The neuromuscular junction (NMJ) represents the critical region at the level of which muscle and nerve communicate. Defects in signal transmission between terminal nerve endings and muscle membrane is a common feature of several physio-pathologic conditions including aging and Amyotrophic Lateral Sclerosis (ALS). Nevertheless, controversy exists on whether pathological events beginning at the NMJ precede or follow loss of motor units. In this review, the role of NMJ in the physio-pathologic interplay between muscle and nerve is discussed.
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Yue L, Talukder MAH, Gurjar A, Lee JI, Noble M, Dirksen RT, Chakkalakal J, Elfar JC. 4-Aminopyridine attenuates muscle atrophy after sciatic nerve crush injury in mice. Muscle Nerve 2019; 60:192-201. [PMID: 31093982 DOI: 10.1002/mus.26516] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 05/08/2019] [Accepted: 05/11/2019] [Indexed: 12/26/2022]
Abstract
INTRODUCTION We recently demonstrated the beneficial effects of 4-aminopyridine (4-AP), a potassium channel blocker, in enhancing remyelination and recovery of nerve conduction velocity and motor function after sciatic nerve crush injury in mice. Although muscle atrophy occurs very rapidly after nerve injury, the effect of 4-AP on muscle atrophy and intrinsic muscle contractile function is largely unknown. METHODS Mice were assigned to sciatic nerve crush injury and no-injury groups and were followed for 3, 7, and 14 days with/without 4-AP or saline treatment. Morphological, functional, and transcriptional properties of skeletal muscle were assessed. RESULTS In addition to improving in vivo function, 4-AP significantly reduced muscle atrophy with increased muscle fiber diameter and contractile force. Reduced muscle atrophy was associated with attenuated expression of atrophy-related genes and increased expression of proliferating stem cells. DISCUSSION These findings provide new insights into the potential therapeutic benefits of 4-AP against nerve injury-induced muscle atrophy and dysfunction. Muscle Nerve 60: 192-201, 2019.
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Affiliation(s)
- Li Yue
- Department of Orthopaedics, The Warren Alpert Medical School of Brown University/Rhode Island Hospital, Providence, Rhode Island, USA
| | - M A Hassan Talukder
- Department of Orthopaedics and Rehabilitation, Center for Orthopaedics and Translational Science, The Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, 500 University Drive, Mail Code H089, Hershey, Pennsylvania, 17033, USA
| | - Anagha Gurjar
- Department of Orthopaedics and Rehabilitation, Center for Orthopaedics and Translational Science, The Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, 500 University Drive, Mail Code H089, Hershey, Pennsylvania, 17033, USA
| | - Jung Il Lee
- Department of Orthopaedic Surgery, Hanyang University Guri Hospital, South Korea
| | - Mark Noble
- Department of Biomedical Genetics, The University of Rochester Medical Center Rochester, New York, USA
| | - Robert T Dirksen
- Department of Pharmacology & Physiology, The University of Rochester Medical Center Rochester, New York, USA
| | - Joe Chakkalakal
- Department of Pharmacology and Physiology and Biomedical Engineering, The University of Rochester Medical Center Rochester, New York, USA
| | - John C Elfar
- Department of Orthopaedics and Rehabilitation, Center for Orthopaedics and Translational Science, The Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, 500 University Drive, Mail Code H089, Hershey, Pennsylvania, 17033, USA
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Santosa KB, Keane AM, Jablonka-Shariff A, Vannucci B, Snyder-Warwick AK. Clinical relevance of terminal Schwann cells: An overlooked component of the neuromuscular junction. J Neurosci Res 2018; 96:1125-1135. [PMID: 29536564 PMCID: PMC6292684 DOI: 10.1002/jnr.24231] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 12/30/2017] [Accepted: 02/09/2018] [Indexed: 12/13/2022]
Abstract
The terminal Schwann cell (tSC), a type of nonmyelinating Schwann cell, is a significant yet relatively understudied component of the neuromuscular junction. In addition to reviewing the role tSCs play on formation, maintenance, and remodeling of the synapse, we review studies that implicate tSCs in neuromuscular diseases including spinal muscular atrophy, Miller-Fisher syndrome, and amyotrophic lateral sclerosis, among others. We also discuss the importance of these cells on degeneration and regeneration after nerve injury. Knowledge of tSC biology may improve our understanding of disease pathogenesis and help us identify new and innovative therapeutic strategies for the many patients who suffer from neuromuscular disorders and nerve injuries.
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Affiliation(s)
- Katherine B. Santosa
- Postdoctoral Research Fellow, Division of Plastic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO
| | - Alexandra M. Keane
- Medical Student, Washington University School of Medicine, St. Louis, MO
| | - Albina Jablonka-Shariff
- Research Scientist, Division of Plastic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO
| | - Bianca Vannucci
- Medical Student, Washington University School of Medicine, St. Louis, MO
| | - Alison K. Snyder-Warwick
- Assistant Professor, Division of Plastic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO
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Castro PATDS, Faccioni LC, Boer PA, Carvalho RF, Matheus SMM, Dal-Pai-Silva M. Neuromuscular junctions (NMJs): ultrastructural analysis and nicotinic acetylcholine receptor (nAChR) subunit mRNA expression in offspring subjected to protein restriction throughout pregnancy. Int J Exp Pathol 2017; 98:109-116. [PMID: 28543723 DOI: 10.1111/iep.12229] [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: 03/21/2016] [Accepted: 02/17/2017] [Indexed: 11/29/2022] Open
Abstract
Protein restriction during gestation can alter the skeletal muscle phenotype of offspring; however, little is known with regard to whether this also affects the neuromuscular junction (NMJ), as muscle phenotype maintenance depends upon NMJ functional integrity. This study aimed to evaluate the effects of a low protein (6%) intake by dams throughout gestation on male offspring NMJ morphology and nicotinic acetylcholine receptor (nAChR) α1, γ and ε subunit expression in the soleus (SOL) and extensor digitorum longus (EDL) muscles. Four groups of male Wistar offspring rats were studied. The offspring of dams fed low-protein (6% protein, LP) and normal protein (17% protein, NP) diets were evaluated at 30 and 120 days of age, and the SOL and EDL muscles were collected for analysis. Morphological studies using transmission electron microscopy revealed that only SOL NMJs were affected in 30-day-old offspring in the LP group compared with the NP group. SOL NMJs exhibited fewer synaptic folds, the postsynaptic membranes were smooth and myelin figures were also frequently observed in the terminal axons. With regard to the expression of mRNAs encoding nAChR subunits, only 30-day-old LP offspring EDL muscles exhibited reduced α, γ and ε subunit expression compared with the NP group. In conclusion, our results demonstrate that a low-protein diet (6%) imposed throughout pregnancy impairs the expression of mRNAs encoding the nAChR α, γ and ε subunits in EDL NMJs and promotes morphological changes in SOL NMJs of 30-day-old offspring, indicating specific differences among muscle types following long-term maternal protein restriction.
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Affiliation(s)
| | | | - Patrícia Aline Boer
- Department of Internal Medicine, State University of Campinas, Campinas, São Paulo, Brazil
| | | | | | - Maeli Dal-Pai-Silva
- Department of Morphology, UNESP Institute of Biosciences, Botucatu, São Paulo, Brazil
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Smith AS, Passey SL, Martin NR, Player DJ, Mudera V, Greensmith L, Lewis MP. Creating Interactions between Tissue-Engineered Skeletal Muscle and the Peripheral Nervous System. Cells Tissues Organs 2016; 202:143-158. [PMID: 27825148 PMCID: PMC5175300 DOI: 10.1159/000443634] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/22/2015] [Indexed: 12/22/2022] Open
Abstract
Effective models of mammalian tissues must allow and encourage physiologically (mimetic) correct interactions between co-cultured cell types in order to produce culture microenvironments as similar as possible to those that would normally occur in vivo. In the case of skeletal muscle, the development of such a culture model, integrating multiple relevant cell types within a biomimetic scaffold, would be of significant benefit for investigations into the development, functional performance, and pathophysiology of skeletal muscle tissue. Although some work has been published regarding the behaviour of in vitro muscle models co-cultured with organotypic slices of CNS tissue or with stem cell-derived neurospheres, little investigation has so far been made regarding the potential to maintain isolated motor neurons within a 3D biomimetic skeletal muscle culture platform. Here, we review the current state of the art for engineering neuromuscular contacts in vitro and provide original data detailing the development of a 3D collagen-based model for the co-culture of primary muscle cells and motor neurons. The devised culture system promotes increased myoblast differentiation, forming arrays of parallel, aligned myotubes on which areas of nerve-muscle contact can be detected by immunostaining for pre- and post-synaptic proteins. Quantitative RT-PCR results indicate that motor neuron presence has a positive effect on myotube maturation, suggesting neural incorporation influences muscle development and maturation in vitro. The importance of this work is discussed in relation to other published neuromuscular co-culture platforms along with possible future directions for the field.
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Affiliation(s)
- Alec S.T. Smith
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, UK
- Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, National Centre for Sport and Exercise Medicine (NCSEM) England, School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
- Department of Bioengineering, University of Washington, Seattle, Wash., USA
| | - Samantha L. Passey
- Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, National Centre for Sport and Exercise Medicine (NCSEM) England, School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
- Department of Pharmacology and Therapeutics, University of Melbourne, Melbourne, Vic., Australia
| | - Neil R.W. Martin
- Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, National Centre for Sport and Exercise Medicine (NCSEM) England, School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Darren J. Player
- Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, National Centre for Sport and Exercise Medicine (NCSEM) England, School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Vivek Mudera
- Division of Surgery and Interventional Science, UCL Institute of Orthopaedics and Musculoskeletal Science, London, UK
| | - Linda Greensmith
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, UK
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK
| | - Mark P. Lewis
- Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, National Centre for Sport and Exercise Medicine (NCSEM) England, School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
- *Prof. Mark P. Lewis, School of Sport, Exercise and Health Sciences, Loughborough University, Ashby Road, Loughborough LE11 3TU (UK), E-Mail
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Carrasco DI, Bahr BA, Seburn KL, Pinter MJ. Abnormal response of distal Schwann cells to denervation in a mouse model of motor neuron disease. Exp Neurol 2016; 278:116-26. [PMID: 26853136 PMCID: PMC4788963 DOI: 10.1016/j.expneurol.2016.02.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Revised: 01/27/2016] [Accepted: 02/02/2016] [Indexed: 01/22/2023]
Abstract
In several animal models of motor neuron disease, degeneration begins in the periphery. Clarifying the possible role of Schwann cells remains a priority. We recently showed that terminal Schwann cells (TSCs) exhibit abnormalities in postnatal mice that express mutations of the SOD1 enzyme found in inherited human motor neuron disease. TSC abnormalities appeared before disease-related denervation commenced and the extent of TSC abnormality at P30 correlated with the extent of subsequent denervation. Denervated neuromuscular junctions (NMJs) were also observed that lacked any labeling for TSCs. This suggested that SOD1 TSCs may respond differently than wildtype TSCs to denervation which remain at denervated NMJs for several months. In the present study, the response of SOD1 TSCs to experimental denervation was examined. At P30 and P60, SC-specific S100 labeling was quickly lost from SOD1 NMJs and from preterminal regions. Evidence indicates that this loss eventually becomes complete at most SOD1 NMJs before reinnervation occurs. The loss of labeling was not specific for S100 and did not depend on loss of activity. Although some post-denervation labeling loss occurred at wildtype NMJs, this loss was never complete. Soon after denervation, large cells appeared near SOD1 NMJ bands which colabeled for SC markers as well as for activated caspase-3 suggesting that distal SOD1 SCs may experience cell death following denervation. Denervated SOD1 NMJs viewed 7 days after denervation with the electron microscope confirmed the absence of TSCs overlying endplates. These observations demonstrate that SOD1 TSCs and distal SCs respond abnormally to denervation. This behavior can be expected to hinder reinnervation and raises further questions concerning the ability of SOD1 TSCs to support normal functioning of motor terminals.
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Affiliation(s)
| | - Ben A Bahr
- Biotechnology Research and Training Center, University of North Carolina at Pembroke, Pembroke, NC, USA
| | | | - Martin J Pinter
- Department of Physiology, Emory University, Atlanta, GA, USA.
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Carrasco DI, Seburn KL, Pinter MJ. Altered terminal Schwann cell morphology precedes denervation in SOD1 mice. Exp Neurol 2015; 275 Pt 1:172-81. [PMID: 26416261 DOI: 10.1016/j.expneurol.2015.09.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 09/02/2015] [Accepted: 09/23/2015] [Indexed: 01/15/2023]
Abstract
In mice that express SOD1 mutations found in human motor neuron disease, degeneration begins in the periphery for reasons that remain unknown. At the neuromuscular junction (NMJ), terminal Schwann cells (TSCs) have an intimate relationship with motor terminals and are believed to help maintain the integrity of the motor terminal. Recent evidence indicates that TSCs in some SOD1 mice exhibit abnormal functional properties, but other aspects of possible TSC involvement remain unknown. In this study, an analysis of TSC morphology and number was performed in relation to NMJ innervation status in mice which express the G93A SOD1 mutation. At P30, all NMJs of the fast medial gastrocnemius (MG) muscle were fully innervated by a single motor axon but 50% of NMJs lacked TSC cell bodies and were instead covered by the processes of Schwann cells with cell bodies located on the preterminal axons. NMJs in P30 slow soleus muscles were also fully innervated by single motor axons and only 5% of NMJs lacked a TSC cell body. At P60, about 25% of MG NMJs were denervated and lacked labeling for TSCs while about 60% of innervated NMJs lacked TSC cell bodies. In contrast, 96% of P60 soleus NMJs were innervated while 9% of innervated NMJs lacked TSC cell bodies. The pattern of TSC abnormalities found at P30 thus correlates with the pattern of denervation found at P60. Evidence from mice that express the G85R SOD1 mutation indicate that TSC abnormalities are not unique for mice that express G93A SOD1 mutations. These results add to an emerging understanding that TSCs may play a role in motor terminal degeneration and denervation in animal models of motor neuron disease.
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Affiliation(s)
| | | | - Martin J Pinter
- Department of Physiology, Emory University, Atlanta, GA, USA.
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11
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Cui Q, Xie P. Correlation Between Daam2 Expression Changes and Demyelination in Guillain-Barre Syndrome. Cell Mol Neurobiol 2015; 36:683-8. [PMID: 26293489 DOI: 10.1007/s10571-015-0248-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 07/28/2015] [Indexed: 10/23/2022]
Abstract
Wnt signaling has been implicated in developmental and regenerative myelination of the CNS and PNS. The present translational investigation was undertaken to assess whether a soluble factor like Wnt may be responsible for the critically important skeletal muscle neuromuscular junction-Schwann cell communication. Specifically, three key aspects were examined: (a) whether the expression of Daam2, disheveled-associated activator of morphogenesis, a key Wnt signaling downstream effector, and PIP5K is changed in the demyelinating conditions and under different stages of progress of clinical recovery of patients with Guillain-Barre syndrome; (b) whether critical protein interactions of Daam2 with disheveled and Arf6 are changed; and (c) whether expression of c-Jun/Krox, a key negative regulator of remyelination, is changed. Daam2 was elevated in acute presentation in GB syndrome. Reduction occurred with clinical improvement of the patients. With progressive clinical improvement, c-Jun/Krox expression significantly reduced with time. Wnt signaling likely causes immediate early gene activation and transcriptional shutdown of factors critical for formation and maintenance of myelination. Whether the findings of the present study are specific to pathophysiology of demyelination in acute infectious polyradiculopathy and multiple sclerosis or a generalized aspect of demyelinating diseases merits to be examined in future studies.
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Affiliation(s)
- Quanquan Cui
- Department of Neurology, Hospital of Chongqing Armed Police Force, Chongqing, 404000, China
| | - Peng Xie
- Chongqing University of Medical Science, No.1 Yixueyuan Road, Yuzhong District, Chongqing, 400016, China.
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Darabid H, Perez-Gonzalez AP, Robitaille R. Neuromuscular synaptogenesis: coordinating partners with multiple functions. Nat Rev Neurosci 2014; 15:630-1. [DOI: 10.1038/nrn3821] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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13
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Corty MM, Freeman MR. Cell biology in neuroscience: Architects in neural circuit design: glia control neuron numbers and connectivity. ACTA ACUST UNITED AC 2014; 203:395-405. [PMID: 24217617 PMCID: PMC3824021 DOI: 10.1083/jcb.201306099] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Glia serve many important functions in the mature nervous system. In addition, these diverse cells have emerged as essential participants in nearly all aspects of neural development. Improved techniques to study neurons in the absence of glia, and to visualize and manipulate glia in vivo, have greatly expanded our knowledge of glial biology and neuron-glia interactions during development. Exciting studies in the last decade have begun to identify the cellular and molecular mechanisms by which glia exert control over neuronal circuit formation. Recent findings illustrate the importance of glial cells in shaping the nervous system by controlling the number and connectivity of neurons.
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Affiliation(s)
- Megan M Corty
- Department of Neurobiology, University of Massachusetts Medical School, Howard Hughes Medical Institute, Worcester, MA 01605
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Schaakxs D, Kalbermatten DF, Raffoul W, Wiberg M, Kingham PJ. Regenerative cell injection in denervated muscle reduces atrophy and enhances recovery following nerve repair. Muscle Nerve 2013; 47:691-701. [DOI: 10.1002/mus.23662] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2012] [Indexed: 12/17/2022]
Affiliation(s)
| | - Daniel F. Kalbermatten
- Department of Plastic; Reconstructive and Aesthetic Surgery; University Hospital of Basel; Basel; Switzerland
| | - Wassim Raffoul
- Division of Plastic; Reconstructive and Aesthetic Surgery; CHUV; University Hospital of Lausanne; Lausanne; Switzerland
| | | | - Paul J. Kingham
- Department of Integrative Medical Biology; Section for Anatomy; Umeå University; Umeå SE-901 87; Sweden
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15
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Thomson SR, Wishart TM, Patani R, Chandran S, Gillingwater TH. Using induced pluripotent stem cells (iPSC) to model human neuromuscular connectivity: promise or reality? J Anat 2012; 220:122-30. [PMID: 22133357 PMCID: PMC3275767 DOI: 10.1111/j.1469-7580.2011.01459.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Motor neuron diseases (MND) such as amyotrophic lateral sclerosis and spinal muscular atrophy are devastating, progressive and ultimately fatal diseases for which there are no effective treatments. Recent evidence from systematic studies of animal models and human patients suggests that the neuromuscular junction (NMJ) is an important early target in MND, demonstrating functional and structural abnormalities in advance of pathological changes occurring in the motor neuron cell body. The ability to study pathological changes occurring at the NMJ in humans is therefore likely to be important for furthering our understanding of disease pathogenesis, and also for designing and testing new therapeutics. However, there are many practical and technical reasons why it is not possible to visualise or record from NMJs in pre- and early-symptomatic MND patients in vivo. Other approaches are therefore required. The development of stem cell technologies has opened up the possibility of creating human NMJs in vitro, using pluripotent cells generated from healthy individuals and patients with MND. This review covers historical attempts to develop mature and functional NMJs in vitro, using co-cultures of muscle and nerve from animals, and discusses how recent developments in the generation and specification of human induced pluripotent stem cells provides an opportunity to build on these previous successes to recapitulate human neuromuscular connectivity in vitro.
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Affiliation(s)
- Sophie R Thomson
- Euan MacDonald Centre for Motor Neurone Disease Research, University of EdinburghEdinburgh, UK,Centre for Integrative Physiology, University of EdinburghEdinburgh, UK
| | - Thomas M Wishart
- Euan MacDonald Centre for Motor Neurone Disease Research, University of EdinburghEdinburgh, UK,Division of Neurobiology, The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of EdinburghEdinburgh, UK
| | - Rickie Patani
- Anne Mclaren Laboratory for Regenerative Medicine, University of CambridgeCambridge, UK,Cambridge Centre for Brain Repair, Department of Clinical Neurosciences, University of CambridgeCambridge, UK
| | - Siddharthan Chandran
- Euan MacDonald Centre for Motor Neurone Disease Research, University of EdinburghEdinburgh, UK
| | - Thomas H Gillingwater
- Euan MacDonald Centre for Motor Neurone Disease Research, University of EdinburghEdinburgh, UK,Centre for Integrative Physiology, University of EdinburghEdinburgh, UK
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16
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Tseng CN, Zhang L, Wu SL, Wang WF, Wang ZZ, Cascio M. Asparagine of z8 insert is critical for the affinity, conformation, and acetylcholine receptor-clustering activity of neural agrin. J Biol Chem 2010; 285:27641-51. [PMID: 20566625 DOI: 10.1074/jbc.m110.130625] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Agrin isoforms with different bioactivities are synthesized by the nerve and the muscle. Neural agrin containing an 8-amino acid insert (z8) introduced by alternative splicing is the active form that induces synaptic differentiation at the neuromuscular junction. In addition to alternative splicing, extracellular calcium is also required for the activity of neural agrin. To understand better how the activity of agrin is regulated by alternative splicing, we have applied alanine substitution mutagenesis to the z8 insert and the calcium binding site in the minimally functional AgG3z8 fragment. Single alanine substitutions in the 4th through the 7th amino acid of the z8 splice insert significantly reduced the function of agrin, in terms of acetylcholine receptor clustering activity and the affinity for binding to the muscle surface. Mutation of the asparagine at the 4th position drastically reduces bioactivity such that it is equivalent to that of muscle form AgG3z0. These reduced activity mutants also show reduced magnitudes of the calcium-induced CD spectrum change from that observed in AgG3z8 fragments, indicating that cross-talk between calcium and the z8 insert is critical for the normal activity of agrin. However, removal of Ca(2+) binding via mutation of both aspartic acids in the calcium binding site did not totally eliminate the activity of AgG3z8. These results suggest a model wherein the z8 insert is a Ca(2+)-responsive allosteric element that is essential in forming an active conformation in neuronal agrin.
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Affiliation(s)
- Chao-Neng Tseng
- Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung City 807, Taiwan
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17
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Motor axonal sprouting and neuromuscular junction loss in an animal model of Charcot-Marie-Tooth disease. J Neuropathol Exp Neurol 2010; 69:281-93. [PMID: 20142762 DOI: 10.1097/nen.0b013e3181d1e60f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Muscle weakness in Charcot-Marie-Tooth Type 1A disease (CMT1A) caused by mutations in peripheral myelin protein 22 (PMP22) has been attributed to an axonopathy that results in denervation and muscle atrophy. The underlying pathophysiological mechanisms involved are not understood. We investigated motor performance, neuromuscular junctions (NMJs), physiological parameters, and muscle morphometry of PMP22 transgenic mice. Neuromuscular junctions were progressively lost in hindlimb muscles of PMP22 transgenic mice, but their motor performance did not completely deteriorate during the observation period. There was considerable variability, including in laterality, in deficits among the animals. Cross-sectional areas and mean fiber size measurements indicated variable myofiber atrophy in hindlimb muscles. There was substantial concomitant axonal sprouting, and loss of neuromuscular junctions was inversely correlated with the accumulated length of axonal branches. Synaptic transmission studied in isolated nerve/muscle preparations indicated variable partial muscle denervation. Acetylcholine sensitivity was higher in the mutant muscles, and maximum tetanic force evoked by direct or indirect stimulation, specific force, and wet weights were markedly reduced in some mutant muscles. In summary, there is partial muscle denervation, and axons may retain some regenerative capacity but fail to reinnervate muscles in PMP22 transgenic mice.
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18
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The synaptic remodeling between regenerated perforant pathway and granule cells in slice culture. Cell Mol Neurobiol 2009; 30:309-16. [PMID: 19757022 DOI: 10.1007/s10571-009-9454-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Accepted: 08/28/2009] [Indexed: 10/20/2022]
Abstract
In order to understand the synaptic remodeling in the course of axonal regeneration, the synaptic remodeling of the perforant path in hippocampus was investigated in the present study with entorhino-hippocampal coculture, DiI DiOlistic assay and transmission electron microscopy. The results showed that the regeneration of the perforant pathway occurred in entorhino-hippocampal slice coculture, and putative synaptic contacts formed between the regenerated fibers and dendritic spines of granule cells. Ultrastructural analysis confirmed the formation of new synaptic contacts. In conclusion, the synaptic formation implicated in the neuroregeneration could integrate into the network in CNS.
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19
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Schmidt ER, Pasterkamp RJ, van den Berg LH. Axon guidance proteins: Novel therapeutic targets for ALS? Prog Neurobiol 2009; 88:286-301. [DOI: 10.1016/j.pneurobio.2009.05.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2008] [Revised: 04/06/2009] [Accepted: 05/27/2009] [Indexed: 12/12/2022]
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20
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Fagerlund M, Eriksson L. Current concepts in neuromuscular transmission. Br J Anaesth 2009; 103:108-14. [DOI: 10.1093/bja/aep150] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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21
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Rumsey JW, Das M, Stancescu M, Bott M, Fernandez-Valle C, Hickman JJ. Node of Ranvier formation on motoneurons in vitro. Biomaterials 2009; 30:3567-72. [PMID: 19361859 DOI: 10.1016/j.biomaterials.2009.03.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Accepted: 03/15/2009] [Indexed: 10/20/2022]
Abstract
One of the most significant interactions between Schwann cells and neurons is myelin sheath formation. Myelination is a vertebrate adaptation that enables rapid conduction of action potentials without a commensurate increase in axon diameter. In vitro neuronal systems provide a unique modality to study both factors influencing myelination and diseases associated with myelination. Currently, no in vitro system for motoneuron myelination by Schwann cells has been demonstrated. This work details the myelination of motoneuron axons by Schwann cells, with complete Node of Ranvier formation, in a defined in vitro culture system. This defined system utilizes a novel serum-free medium in combination with the non-biological substrate, N-1[3 (trimethoxysilyl) propyl] diethylenetriamine (DETA). The myelinated segments and nodal proteins were visualized and quantified using confocal microscopy. This defined system provides a highly controlled, reproducible model for studying Schwann cell interactions with motoneurons as well as the myelination process and its effect on neuronal plasticity. Furthermore, an in vitro system that would allow studies of motoneuron myelination would be beneficial for understanding peripheral demyelinating neuropathies such as diabetes induced peripheral neuropathy and could lead to a better understanding of CNS demyelinating diseases like multiple sclerosis, as well as neuromuscular junction maturation and maintenance.
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Affiliation(s)
- John W Rumsey
- Nanoscience Technology Center, University of Central Florida, Orlando, FL 32826, USA
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22
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Jayawardane P, Senanayake N, Dawson A. Electrophysiological correlates of intermediate syndrome following acute organophosphate poisoning. Clin Toxicol (Phila) 2009; 47:193-205. [DOI: 10.1080/15563650902832608] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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23
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Schwann cells promote synaptogenesis at the neuromuscular junction via transforming growth factor-beta1. J Neurosci 2008; 28:9599-609. [PMID: 18815246 DOI: 10.1523/jneurosci.2589-08.2008] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Recent studies suggest that glial cells actively participate in the formation, function, maintenance, and repair of the chemical synapse. However, the molecular mechanisms of glia-synapse interactions are largely unknown. We have shown previously that Schwann cell-conditioned medium (SC-CM) promotes synaptogenesis in Xenopus nerve-muscle cocultures. The present study aimed to identify the synaptogenic molecules in SC-CM. Combining biochemical approaches and in vitro bioassays, we found that SC-CM contains transforming growth factor (TGF)-beta1, which is expressed in Schwann cells both in vivo and in vitro. Similar to SC-CM, TGF-beta1 doubled the size of acetylcholine receptor (AChR) clusters at nerve-muscle contacts and significantly increased the percentage of nerve-muscle contacts that show AChR clusters to approximately 60%, compared with approximately 20% seen in control cultures. The synaptogenic effects of SC-CM were abolished if SC-CM was immunodepleted of TGF-beta1 or if the latency-associated protein or a TGF-beta1 receptor kinase inhibitor was added to block the bioactivity of TGF-beta1. Similar to frog SC-CM, mammalian SC-CM also showed synaptogenic effects, which were prevented by immunodepletion of TGF-beta1. TGF-beta1 upregulated agrin expression in spinal neurons, which could explain the increase in AChR clusters in cultures treated with SC-CM. These results suggest that Schwann cells express TGF-beta1, which is both sufficient and necessary for mediating the synapse-promoting effects of Schwann cells at the developing neuromuscular junction. Schwann cell-derived TGF-beta1 thus joins other astrocyte-derived synaptogenic factors in further strengthening the emerging concept that glial cells contribute to synaptogenesis in both the PNS and the CNS.
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24
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Feng Z, Ko CP. The Role of Glial Cells in the Formation and Maintenance of the Neuromuscular Junction. Ann N Y Acad Sci 2008; 1132:19-28. [DOI: 10.1196/annals.1405.016] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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25
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Wright MC, Cho WJ, Son YJ. Distinct patterns of motor nerve terminal sprouting induced by ciliary neurotrophic factor vs. botulinum toxin. J Comp Neurol 2007; 504:1-16. [PMID: 17614103 DOI: 10.1002/cne.21439] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Both diffusible and surface-bound molecules are thought to induce sprouting of motor nerve terminals in response to paralysis. Here we report that the sprouting induced by ciliary neurotrophic factor (CNTF) is qualitatively different from the sprouting induced by botulinum toxin (BoTX). We show first that subcutaneous application of CNTF to levator auris longus muscles of adult mice evokes sprouting from nearly all nerve terminals. Surprisingly, however, most terminal sprouts remain within the boundaries of the endplate region and rarely grow extrasynaptically even if CNTF is administered chronically. In contrast, terminal sprouts induced by BoTX extend vigorously along the extrasynaptic muscle surface. The different patterns of sprout elongation are attributable in part to different patterns of initiation: whereas CNTF-induced sprouts emerge randomly from the surface of terminal branches, BoTX-induced sprouts emerge exclusively along the perimeter of terminal branches in direct apposition to muscle fiber membranes. Combined treatment with CNTF and BoTX produces exceptionally robust extraterminal sprouting with little if any intrasynaptic growth of terminal sprouts. We interpret these results as showing that paralysis induces sprouting primarily by muscle-associated, surface-bound molecules rather than by diffusible factors. Our findings may be useful in defining the physiological role of the numerous candidate sprouting-inducers and in promoting compensatory sprouting after nerve injury for therapeutic benefit.
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Affiliation(s)
- Megan C Wright
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 9129, USA
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26
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Cao G, Ko CP. Schwann cell-derived factors modulate synaptic activities at developing neuromuscular synapses. J Neurosci 2007; 27:6712-22. [PMID: 17581958 PMCID: PMC6672697 DOI: 10.1523/jneurosci.1329-07.2007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Glial cells are active participants in the function, formation, and maintenance of the chemical synapse. To investigate the molecular basis of neuron-glia interactions at the peripheral synapse, we examined whether and how Schwann cell-derived factors modulate synaptic function at developing neuromuscular junctions (NMJs). Schwann cell-conditioned medium (SC-CM) from Xenopus Schwann cell cultures was collected and applied to Xenopus nerve-muscle cocultures. We found that SC-CM increased the frequency of spontaneous synaptic currents (SSCs) within 3-15 min by an average of approximately 150-fold at developing neuromuscular synapses. The increase in SSC frequency by SC-CM is a presynaptic effect independent of neuronal excitability and requires the influx of Ca2+. In contrast to its potentiating effect on spontaneous transmitter release, SC-CM suppressed the evoked transmitter release. The SC-CM effect required the presence of motoneuron soma but not protein synthesis. Using molecular weight cutoff filters and dialysis membranes, we found that the molecular weight of functional factor(s) in SC-CM was within 500 and 5000 Da. The SC-CM effect was not attributable to currently known factors that modulate synaptic efficacy, including neurotrophins, glutamate, and ATP. SC-CM also enhanced spontaneous synaptic release at developing NMJs in Xenopus tadpoles in situ. Our results suggest that Schwann cells release small molecules that enhance spontaneous synaptic activities acutely and potently at developing neuromuscular synapses, and the glial cell-enhanced spontaneous neurotransmission may contribute to synaptogenesis.
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Affiliation(s)
- Guan Cao
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520
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27
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Wright MC, Son YJ. Ciliary neurotrophic factor is not required for terminal sprouting and compensatory reinnervation of neuromuscular synapses: re-evaluation of CNTF null mice. Exp Neurol 2007; 205:437-48. [PMID: 17445802 PMCID: PMC1931609 DOI: 10.1016/j.expneurol.2007.03.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2006] [Revised: 02/28/2007] [Accepted: 03/01/2007] [Indexed: 11/28/2022]
Abstract
Loss of synaptic activity or innervation induces sprouting of intact motor nerve terminals that adds or restores nerve-muscle connectivity. Ciliary neurotrophic factor (CNTF) and terminal Schwann cells (tSCs) have been implicated as molecular and cellular mediators of the compensatory process. We wondered if the previously reported lack of terminal sprouting in CNTF null mice was due to abnormal reactivity of tSCs. To this end, we examined nerve terminal and tSC responses in CNTF null mice using experimental systems that elicited extensive sprouting in wildtype mice. Contrary to the previous report, we found that motor nerve terminals in the null mice sprout extensively in response to major sprouting-stimuli such as exogenously applied CNTF per se, botulinum toxin-elicited paralysis, and partial denervation by L4 spinal root transection. In addition, the number, length and growth patterns of terminal sprouts, and the extent of reinnervation by terminal or nodal sprouts, were similar in wildtype and null mice. tSCs in the null mice were also reactive to the sprouting-stimuli, elaborating cellular processes that accompanied terminal sprouts or guided reinnervation of denervated muscle fibers. Lastly, CNTF was absent in quiescent tSCs in intact, wildtype muscles and little if any was detected in reactive tSCs in denervated muscles. Thus, CNTF is not required for induction of nerve terminal sprouting, for reactivation of tSCs, and for compensatory reinnervation after nerve injury. We interpret these results to support the notion that compensatory sprouting in adult muscles is induced primarily by contact-mediated mechanisms, rather than by diffusible factors.
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Affiliation(s)
- Megan C Wright
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 W. Queen Lane, Philadelphia, PA 19129, USA
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28
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Hayworth CR, Moody SE, Chodosh LA, Krieg P, Rimer M, Thompson WJ. Induction of neuregulin signaling in mouse schwann cells in vivo mimics responses to denervation. J Neurosci 2006; 26:6873-84. [PMID: 16793894 PMCID: PMC6673827 DOI: 10.1523/jneurosci.1086-06.2006] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Neuregulins play crucial roles in early development of Schwann cells (SCs), but their roles in the activities of SCs during denervation and reinnervation of muscle are less clear. In the present study, the Tet-On system has been used in transgenic mice to enable inducible expression of a mutant, constitutively active neuregulin receptor (ErbB2) in SCs. This induction simulates neuregulin signaling to these cells. Reporter transgenes were used to show a tightly regulated, SC-selective expression in muscle. Induction leads to a number of changes in SCs at neuromuscular junctions that mimic the response to muscle denervation/reinnervation. These include process extension, soma migration, and proliferation. SCs also come to express nestin, a protein characteristic of their reaction to muscle denervation. This activation of SCs results in the sprouting of nerve terminals, and these sprouts follow the extensions of the SCs. However, these sprouts and their associated SCs disappear after the removal of the inducer. Last, induction of the active receptor is sufficient to rescue SCs in neonatal muscle from denervation-induced apoptosis. These findings show that the responses of SCs in muscle to denervation can be explained by induction of an autocrine/paracrine neuregulin signaling cascade suggested by previous molecular studies.
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29
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De Winter F, Vo T, Stam FJ, Wisman LAB, Bär PR, Niclou SP, van Muiswinkel FL, Verhaagen J. The expression of the chemorepellent Semaphorin 3A is selectively induced in terminal Schwann cells of a subset of neuromuscular synapses that display limited anatomical plasticity and enhanced vulnerability in motor neuron disease. Mol Cell Neurosci 2006; 32:102-17. [PMID: 16677822 DOI: 10.1016/j.mcn.2006.03.002] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 03/09/2006] [Accepted: 03/13/2006] [Indexed: 01/28/2023] Open
Abstract
Neuromuscular synapses differ markedly in their plasticity. Motor nerve terminals innervating slow muscle fibers sprout vigorously following synaptic blockage, while those innervating fast-fatigable muscle fibers fail to exhibit any sprouting. Here, we show that the axon repellent Semaphorin 3A is differentially expressed in terminal Schwann cells (TSCs) on different populations of muscle fibers: postnatal, regenerative and paralysis induced remodeling of neuromuscular connections is accompanied by increased expression of Sema3A selectively in TSCs on fast-fatigable muscle fibers. To our knowledge, this is the first demonstration of a molecular difference between TSCs on neuromuscular junctions of different subtypes of muscle fibers. Interestingly, also in a mouse model for amyotrophic lateral sclerosis (ALS), Sema3A is expressed at NMJs of fast-fatigable muscle fibers. We propose that expression of Sema3A by TSCs not only suppresses nerve terminal plasticity at specific neuromuscular synapses, but may also contribute to their early and selective loss in the motor neuron disease ALS.
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Affiliation(s)
- Fred De Winter
- Graduate School for Neurosciences Amsterdam, Netherlands Institute for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam, Netherlands
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30
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Monani UR. Spinal muscular atrophy: a deficiency in a ubiquitous protein; a motor neuron-specific disease. Neuron 2006; 48:885-96. [PMID: 16364894 DOI: 10.1016/j.neuron.2005.12.001] [Citation(s) in RCA: 233] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Spinal muscular atrophy (SMA) is a neurodegenerative disease in humans and the most common genetic cause of infant mortality. The disease results in motor neuron loss and skeletal muscle atrophy. Despite a range of disease phenotypes, SMA is caused by mutations in a single gene, the Survival of Motor Neuron 1 (SMN1) gene. Recent advances have shed light on functions of the protein product of this gene and the pathophysiology of the disease, yet, fundamental questions remain. This review attempts to highlight some of the recent advances made in the understanding of the disease and how loss of the ubiquitously expressed survival of motor neurons (SMN) protein results in the SMA phenotype. Answers to some of the questions raised may ultimately result in a viable treatment for SMA.
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Affiliation(s)
- Umrao R Monani
- Department of Neurology, Center for Motor Neuron Biology and Disease, Columbia University Medical Center, New York, New York 10032, USA.
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31
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Abstract
The neuromuscular junction (NMJ) is a complex structure that serves to efficiently communicate the electrical impulse from the motor neuron to the skeletal muscle to signal contraction. Over the last 200 years, technological advances in microscopy allowed visualization of the existence of a gap between the motor neuron and skeletal muscle that necessitated the existence of a messenger, which proved to be acetylcholine. Ultrastructural analysis identified vesicles in the presynaptic nerve terminal, which provided a beautiful structural correlate for the quantal nature of neuromuscular transmission, and the imaging of synaptic folds on the muscle surface demonstrated that specializations of the underlying protein scaffold were required. Molecular analysis in the last 20 years has confirmed the preferential expression of synaptic proteins, which is guided by a precise developmental program and maintained by signals from nerve. Although often overlooked, the Schwann cell that caps the NMJ and the basal lamina is proving to be critical in maintenance of the junction. Genetic and autoimmune disorders are known that compromise neuromuscular transmission and provide further insights into the complexities of NMJ function as well as the subtle differences that exist among NMJ that may underlie the differential susceptibility of muscle groups to neuromuscular transmission diseases. In this review we summarize the synaptic physiology, architecture, and variations in synaptic structure among muscle types. The important roles of specific signaling pathways involved in NMJ development and acetylcholine receptor (AChR) clustering are reviewed. Finally, genetic and autoimmune disorders and their effects on NMJ architecture and neuromuscular transmission are examined.
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Affiliation(s)
- Benjamin W Hughes
- Department of Neurology, Case Western University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA
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32
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Abstract
Glial cells are widely distributed throughout the nervous system, including at the chemical synapse. However, our knowledge of the role of glial cells at the synapse is rudimentary. Recent studies using a model synapse, the vertebrate neuromuscular junction (NMJ), have demonstrated that perisynaptic Schwann cells (PSCs), which are the glia juxtaposed to the nerve terminal at the NMJ, play active and essential roles in synaptic function, maintenance, and development. PSCs can respond to nerve activity by increasing intracellular calcium and are capable of modulating synaptic function in response to pharmacological manipulations. Studies using PSC ablation in vivo have shown that PSCs are essential for the long-term maintenance of synaptic structure and function at the adult NMJ. In vivo observations have also shown that PSCs guide presynaptic nerve terminal extension and dictate the pattern of innervation during synaptic regeneration and remodeling at adult NMJs. PSCs may also induce postsynaptic acetylcholine receptor aggregation. Furthermore, PSCs play an essential role in synaptic growth and maintenance during development of NMJs in vivo, and Schwann cell-derived factors can promote synaptogenesis and enhance synaptic transmission in tissue culture. These recent findings advance the emerging concept that glial cells help make bigger, stronger, and more stable synapses.
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Affiliation(s)
- Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA
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33
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Corfas G, Velardez MO, Ko CP, Ratner N, Peles E. Mechanisms and roles of axon-Schwann cell interactions. J Neurosci 2005; 24:9250-60. [PMID: 15496660 PMCID: PMC6730082 DOI: 10.1523/jneurosci.3649-04.2004] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Gabriel Corfas
- Division of Neuroscience, Children's Hospital, Boston, Massachusetts 02115, USA
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34
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Grady RM, Starr DA, Ackerman GL, Sanes JR, Han M. Syne proteins anchor muscle nuclei at the neuromuscular junction. Proc Natl Acad Sci U S A 2005; 102:4359-64. [PMID: 15749817 PMCID: PMC555524 DOI: 10.1073/pnas.0500711102] [Citation(s) in RCA: 168] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Vertebrate skeletal muscle fibers contain hundreds of nuclei, of which three to six are functionally specialized and stably anchored beneath the postsynaptic membrane at the neuromuscular junction (NMJ). The mechanisms that localize synaptic nuclei and the roles they play in neuromuscular development are unknown. Syne-1 is concentrated at the nuclear envelope of synaptic nuclei; its Caenorhabditis elegans orthologue ANC-1 functions to tether nuclei to the cytoskeleton. To test the involvement of Syne proteins in nuclear anchoring, we generated transgenic mice overexpressing the conserved C-terminal Klarsicht/ANC-1/Syne homology domain of Syne-1. The transgene acted in a dominant interfering fashion, displacing endogenous Syne-1 from the nuclear envelope. Muscle nuclei failed to aggregate at the NMJ in transgenic mice, demonstrating that localization and positioning of synaptic nuclei require Syne proteins. We then exploited this phenotype to show that synaptic nuclear aggregates are dispensable for maturation of the NMJ.
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Affiliation(s)
- R Mark Grady
- Department of Anatomy and Neurobiology, Washington University, St. Louis, MO 63110, USA
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35
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Abstract
The process by which excess axons are pruned during development has remained unclear. In this issue of Neuron, Bishop et al. use time-lapse imaging and serial electron microscopy of developing neuromuscular junctions to describe a novel cellular mechanism in which retracting axon branches shed fragments rich in normal synaptic organelles. These "axosomes" are engulfed by adjacent Schwann cells and may be assimilated into the glial cytoplasm. Shedding of axosomes and glial engulfment may represent a widespread mechanism of synapse elimination.
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Affiliation(s)
- Samir Koirala
- Division of Neuroscience, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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