1
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Herbst R, Huijbers MG, Oury J, Burden SJ. Building, Breaking, and Repairing Neuromuscular Synapses. Cold Spring Harb Perspect Biol 2024; 16:a041490. [PMID: 38697654 PMCID: PMC11065174 DOI: 10.1101/cshperspect.a041490] [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] [Indexed: 05/05/2024]
Abstract
A coordinated and complex interplay of signals between motor neurons, skeletal muscle cells, and Schwann cells controls the formation and maintenance of neuromuscular synapses. Deficits in the signaling pathway for building synapses, caused by mutations in critical genes or autoantibodies against key proteins, are responsible for several neuromuscular diseases, which cause muscle weakness and fatigue. Here, we describe the role that four key genes, Agrin, Lrp4, MuSK, and Dok7, play in this signaling pathway, how an understanding of their mechanisms of action has led to an understanding of several neuromuscular diseases, and how this knowledge has contributed to emerging therapies for treating neuromuscular diseases.
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Affiliation(s)
- Ruth Herbst
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, 1090 Vienna, Austria
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Centre LUMC, 2300 RC Leiden, the Netherlands
- Department of Neurology, Leiden University Medical Centre LUMC, 2333 ZA Leiden, the Netherlands
| | - Julien Oury
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, New York 10016, USA
| | - Steven J Burden
- Neurology Department, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA
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2
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Andrea ZA, Matteo FY, Alessandra B, Carlo PS. Molecular mechanisms and therapeutic strategies for neuromuscular diseases. Cell Mol Life Sci 2024; 81:198. [PMID: 38678519 PMCID: PMC11056344 DOI: 10.1007/s00018-024-05229-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Revised: 03/14/2024] [Accepted: 04/07/2024] [Indexed: 05/01/2024]
Abstract
Neuromuscular diseases encompass a heterogeneous array of disorders characterized by varying onset ages, clinical presentations, severity, and progression. While these conditions can stem from acquired or inherited causes, this review specifically focuses on disorders arising from genetic abnormalities, excluding metabolic conditions. The pathogenic defect may primarily affect the anterior horn cells, the axonal or myelin component of peripheral nerves, the neuromuscular junction, or skeletal and/or cardiac muscles. While inherited neuromuscular disorders have been historically deemed not treatable, the advent of gene-based and molecular therapies is reshaping the treatment landscape for this group of condition. With the caveat that many products still fail to translate the positive results obtained in pre-clinical models to humans, both the technological development (e.g., implementation of tissue-specific vectors) as well as advances on the knowledge of pathogenetic mechanisms form a collective foundation for potentially curative approaches to these debilitating conditions. This review delineates the current panorama of therapies targeting the most prevalent forms of inherited neuromuscular diseases, emphasizing approved treatments and those already undergoing human testing, offering insights into the state-of-the-art interventions.
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Affiliation(s)
- Zambon Alberto Andrea
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Institute for Experimental Neurology, Inspe, Milan, Italy
- Neurology Department, San Raffaele Scientific Institute, Milan, Italy
- Vita-Salute San Raffaele University, Milan, Italy
| | - Falzone Yuri Matteo
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Institute for Experimental Neurology, Inspe, Milan, Italy
- Neurology Department, San Raffaele Scientific Institute, Milan, Italy
| | - Bolino Alessandra
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Institute for Experimental Neurology, Inspe, Milan, Italy
- Vita-Salute San Raffaele University, Milan, Italy
| | - Previtali Stefano Carlo
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Institute for Experimental Neurology, Inspe, Milan, Italy.
- Neurology Department, San Raffaele Scientific Institute, Milan, Italy.
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3
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Cossins J, Kozma I, Canzonetta C, Hawkins A, Beeson D, Sepulveda P, Dong Y. Dose escalation pre-clinical trial of novel DOK7-AAV in mouse model of DOK7 congenital myasthenia. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.09.579626. [PMID: 38405691 PMCID: PMC10888934 DOI: 10.1101/2024.02.09.579626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Congenital myasthenic syndromes (CMS) are a group of inherited disorders characterised by defective neuromuscular transmission and fatigable muscle weakness. Mutations in DOK7 , a gene encoding a post-synaptic protein crucial in the formation and stabilisation of the neuromuscular junction (NMJ), rank among the leading three prevalent causes of CMS in diverse populations globally. The majority of DOK7 CMS patients experience varying degrees of disability despite receiving optimised treatment, necessitating the development of improved therapeutic approaches. Here we executed a dose escalation pre-clinical trial using a DOK7-CMS mouse model to assess the efficacy of Amp-101, an innovative AAV gene replacement therapy. Amp-101 is based on AAVrh74 and contains human DOK7 cDNA under the control of a muscle-restricted promoter. We show that at doses 6x10 13 vg/kg and 1x10 14 vg/kg, Amp-101 generated enlarged NMJs and rescued the very severe phenotype of the model. Treated mice became at least as strong as WT littermates and the diaphragm and tibialis anterior muscles displayed robust expression of DOK7. This data suggests that Amp-101 is a promising candidate to move forward to clinic trials.
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4
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Qaisar R. Targeting neuromuscular junction to treat neuromuscular disorders. Life Sci 2023; 333:122186. [PMID: 37858716 DOI: 10.1016/j.lfs.2023.122186] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Revised: 10/07/2023] [Accepted: 10/16/2023] [Indexed: 10/21/2023]
Abstract
The integrity and preservation of the neuromuscular junction (NMJ), the interface between the motor neuron and skeletal muscle, is critical for maintaining a healthy skeletal muscle. The structural and/or functional defects in the three cellular components of NMJ, namely the pre-synaptic terminal, synaptic cleft, and post-synaptic region, negatively affect skeletal muscle mass and/or strength. Therefore, NMJ repair appears to be an appropriate therapy for muscle disorders. Mouse models provide a detailed molecular characterization of various cellular components of NMJ with relevance to human diseases. This review discusses different molecular targets on the three cellular components of NMJ for treating muscle diseases. The potential effects of these therapies on NMJ morphology and motor performance, their therapeutic efficacy, and clinical relevance are discussed. Collectively, the available data supports targeting NMJ alone or as an adjunct therapy in treating muscle disorders. However, the potential impact of such interventions on human patients with muscle disorders requires further investigation.
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Affiliation(s)
- Rizwan Qaisar
- Basic Medical Sciences, College of Medicine, University of Sharjah, Sharjah, United Arab Emirates; Space Medicine Research Group, Sharjah Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates; Cardiovascular Research Group, Sharjah Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates.
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5
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Huang YT, Crick HR, Chaytow H, van der Hoorn D, Alhindi A, Jones RA, Hector RD, Cobb SR, Gillingwater TH. Long-term muscle-specific overexpression of DOK7 in mice using AAV9-tMCK-DOK7. MOLECULAR THERAPY. NUCLEIC ACIDS 2023; 33:617-628. [PMID: 37637210 PMCID: PMC10457688 DOI: 10.1016/j.omtn.2023.07.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 07/31/2023] [Indexed: 08/29/2023]
Abstract
Neuromuscular junction (NMJ) dysfunction underlies several diseases, including congenital myasthenic syndromes (CMSs) and motor neuron disease (MND). Molecular pathways governing NMJ stability are therefore of interest from both biological and therapeutic perspectives. Muscle-specific kinase (MuSK) is necessary for the formation and maintenance of post-synaptic elements of the NMJ, and downstream of tyrosine kinases 7 (DOK7) is crucial for activation of the MuSK pathway. Overexpression of DOK7 using AAV9 has been shown to ameliorate neuromuscular pathology in pre-clinical disease models of CMS and MND. However, long-term consequences of DOK7 expression have been sparsely investigated and targeted overexpression of DOK7 in skeletal muscle yet to be established. Here, we developed and characterized a novel AAV9-DOK7 facilitating forced expression of DOK7 under a skeletal muscle-specific promoter. AAV9-tMCK-DOK7 was systemically delivered to newborn mice that were monitored over 6 months. DOK7 overexpression was restricted to skeletal muscles. Body weight, blood biochemistry, and histopathological assessments were unaffected by AAV9-tMCK-DOK7 treatment. In contrast, forced expression of DOK7 resulted in enlargement of both the pre- and post-synaptic components of the NMJ, without causing denervation. We conclude that muscle-specific DOK7 overexpression can be achieved in a safe manner, with the capacity to target NMJs in vivo.
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Affiliation(s)
- Yu-Ting Huang
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh EH16 4SB, UK
| | - Hannah R. Crick
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh EH16 4SB, UK
| | - Helena Chaytow
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh EH16 4SB, UK
| | - Dinja van der Hoorn
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh EH16 4SB, UK
| | - Abrar Alhindi
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh EH16 4SB, UK
- Faculty of Medicine, Department of Anatomy, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Ross A. Jones
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh EH16 4SB, UK
| | | | | | - Thomas H. Gillingwater
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh EH16 4SB, UK
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6
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Spendiff S, Dong Y, Maggi L, Rodríguez Cruz PM, Beeson D, Lochmüller H. 260th ENMC International Workshop: Congenital myasthenic syndromes 11-13 March 2022, Hoofddorp, The Netherlands. Neuromuscul Disord 2023; 33:111-118. [PMID: 36609117 DOI: 10.1016/j.nmd.2022.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 12/02/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022]
Affiliation(s)
- Sally Spendiff
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada
| | - Yin Dong
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Lorenzo Maggi
- Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Pedro M Rodríguez Cruz
- Centro Nacional de Análisis Genómico (CNAG-CRG), Centre for Genomic Regulation, Barcelona, Spain; Department of Human Genetics, Université Cheikh Anta Diop, Dakar, Senegal; Department of Neuromuscular Diseases, UCL Institute of Neurology, London, UK
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Hanns Lochmüller
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada; Department of Medicine, Division of Neurology, The Ottawa Hospital, Ottawa, Canada; Brain and Mind Research Institute, University of Ottawa, Ottawa, Canada; Department of Neuropediatrics and Muscle Disorders, Medical Center - University of Freiburg, Faculty of Medicine, Freiburg, Germany; Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia, Spain.
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7
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Lim JL, Augustinus R, Plomp JJ, Roya-Kouchaki K, Vergoossen DLE, Fillié-Grijpma Y, Struijk J, Thomas R, Salvatori D, Steyaert C, Blanchetot C, Vanhauwaert R, Silence K, van der Maarel SM, Verschuuren JJ, Huijbers MG. Development and characterization of agonistic antibodies targeting the Ig-like 1 domain of MuSK. Sci Rep 2023; 13:7478. [PMID: 37156800 PMCID: PMC10167245 DOI: 10.1038/s41598-023-32641-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 03/30/2023] [Indexed: 05/10/2023] Open
Abstract
Muscle-specific kinase (MuSK) is crucial for acetylcholine receptor (AChR) clustering and thereby neuromuscular junction (NMJ) function. NMJ dysfunction is a hallmark of several neuromuscular diseases, including MuSK myasthenia gravis. Aiming to restore NMJ function, we generated several agonist monoclonal antibodies targeting the MuSK Ig-like 1 domain. These activated MuSK and induced AChR clustering in cultured myotubes. The most potent agonists partially rescued myasthenic effects of MuSK myasthenia gravis patient IgG autoantibodies in vitro. In an IgG4 passive transfer MuSK myasthenia model in NOD/SCID mice, MuSK agonists caused accelerated weight loss and no rescue of myasthenic features. The MuSK Ig-like 1 domain agonists unexpectedly caused sudden death in a large proportion of male C57BL/6 mice (but not female or NOD/SCID mice), likely caused by a urologic syndrome. In conclusion, these agonists rescued pathogenic effects in myasthenia models in vitro, but not in vivo. The sudden death in male mice of one of the tested mouse strains revealed an unexpected and unexplained role for MuSK outside skeletal muscle, thereby hampering further (pre-) clinical development of these clones. Future research should investigate whether other Ig-like 1 domain MuSK antibodies, binding different epitopes, do hold a safe therapeutic promise.
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Affiliation(s)
- Jamie L Lim
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Roy Augustinus
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Jaap J Plomp
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Kasra Roya-Kouchaki
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Dana L E Vergoossen
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Yvonne Fillié-Grijpma
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Josephine Struijk
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Rachel Thomas
- Department PDC-Pathologie, Leiden University Medical Center, Leiden, The Netherlands
| | - Daniela Salvatori
- Veterinary Faculty, Department Clinical Sciences, Universiteit Utrecht, Utrecht, The Netherlands
| | | | | | | | | | - Silvère M van der Maarel
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Jan J Verschuuren
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands.
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands.
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Muñoz-García MI, Guerrero-Molina MP, de Fuenmayor-Fernández de la Hoz CP, Bermejo-Guerrero L, Arteche-López A, Hernández-Laín A, Martín MA, Domínguez-González C. Delayed Diagnosis of Congenital Myasthenic Syndromes Erroneously Interpreted as Mitochondrial Myopathies. J Clin Med 2023; 12:jcm12093308. [PMID: 37176748 PMCID: PMC10179722 DOI: 10.3390/jcm12093308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Revised: 04/02/2023] [Accepted: 05/04/2023] [Indexed: 05/15/2023] Open
Abstract
BACKGROUND Congenital myasthenic syndromes (CMSs) and primary mitochondrial myopathies (PMMs) can present with ptosis, external ophthalmoplegia, and limb weakness. METHODS Our method involved the description of three cases of CMS that were initially characterized as probable PMM. RESULTS All patients were male and presented with ptosis and/or external ophthalmoplegia at birth, with proximal muscle weakness and fatigue on physical exertion. After normal repetitive nerve stimulation (RNS) studies performed on facial muscles, a muscle biopsy (at a median age of 9) was performed to rule out congenital myopathies. In all three cases, the biopsy findings (COX-negative fibers or respiratory chain defects) pointed to PMM. They were referred to our neuromuscular unit in adulthood to establish a genetic diagnosis. However, at this time, fatigability was evident in the physical exams and RNS in the spinal accessory nerve showed a decremental response in all cases. Targeted genetic studies revealed pathogenic variants in the MUSK, DOK7, and RAPSN genes. The median diagnostic delay was 29 years. Treatment resulted in functional improvement in all cases. CONCLUSIONS Early identification of CMS is essential as medical treatment can provide clear benefits. Its diagnosis can be challenging due to phenotypic overlap with other debilitating disorders. Thus, a high index of suspicion is necessary to guide the diagnostic strategy.
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Affiliation(s)
- Mariana I Muñoz-García
- Neuromuscular Unit, Neurology Department, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain
| | | | | | - Laura Bermejo-Guerrero
- Neuromuscular Unit, Neurology Department, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain
| | - Ana Arteche-López
- Genetics Department, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain
| | | | - Miguel A Martín
- Genetics Department, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain
- Spanish Network for Biomedical Research in Rare Diseases (CIBERER), 28041 Madrid, Spain
- Mitochondrial and Neuromuscular Diseases Research Group, 12 de Octubre, Hospital Research Institute (imas12), 28041 Madrid, Spain
| | - Cristina Domínguez-González
- Neuromuscular Unit, Neurology Department, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain
- Spanish Network for Biomedical Research in Rare Diseases (CIBERER), 28041 Madrid, Spain
- Mitochondrial and Neuromuscular Diseases Research Group, 12 de Octubre, Hospital Research Institute (imas12), 28041 Madrid, Spain
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Tu WY, Xu W, Zhang J, Qi S, Bai L, Shen C, Zhang K. C9orf72 poly-GA proteins impair neuromuscular transmission. Zool Res 2023; 44:331-340. [PMID: 36799225 PMCID: PMC10083233 DOI: 10.24272/j.issn.2095-8137.2022.356] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 02/15/2023] [Indexed: 02/18/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating motoneuron disease, in which lower motoneurons lose control of skeletal muscles. Degeneration of neuromuscular junctions (NMJs) occurs at the initial stage of ALS. Dipeptide repeat proteins (DPRs) from G4C2 repeat-associated non-ATG (RAN) translation are known to cause C9orf72-associated ALS (C9-ALS). However, DPR inclusion burdens are weakly correlated with neurodegenerative areas in C9-ALS patients, indicating that DPRs may exert cell non-autonomous effects, in addition to the known intracellular pathological mechanisms. Here, we report that poly-GA, the most abundant form of DPR in C9-ALS, is released from cells. Local administration of poly-GA proteins in peripheral synaptic regions causes muscle weakness and impaired neuromuscular transmission in vivo. The NMJ structure cannot be maintained, as evidenced by the fragmentation of postsynaptic acetylcholine receptor (AChR) clusters and distortion of presynaptic nerve terminals. Mechanistic study demonstrated that extracellular poly-GA sequesters soluble Agrin ligands and inhibits Agrin-MuSK signaling. Our findings provide a novel cell non-autonomous mechanism by which poly-GA impairs NMJs in C9-ALS. Thus, targeting NMJs could be an early therapeutic intervention for C9-ALS.
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Affiliation(s)
- Wen-Yo Tu
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, Department of Neurobiology, First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310020, China
| | - Wentao Xu
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, Department of Neurobiology, First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310020, China
| | - Jianmin Zhang
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, Department of Neurobiology, First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310020, China
| | - Shuyuan Qi
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, Department of Neurobiology, First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310020, China
| | - Lei Bai
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, Department of Neurobiology, First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310020, China
| | - Chengyong Shen
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, Department of Neurobiology, First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310020, China
- MOE Frontier Science, Center for Brain Research and Brain-Machine Integration, Zhejiang University, Hangzhou, Zhejiang 310058, China. E-mail:
| | - Kejing Zhang
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, Department of Neurobiology, First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310020, China. E-mail:
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10
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McMacken G, Whittaker RG, Wake R, Lochmuller H, Horvath R. Neuromuscular junction involvement in inherited motor neuropathies: genetic heterogeneity and effect of oral salbutamol treatment. J Neurol 2023; 270:3112-3119. [PMID: 36869887 DOI: 10.1007/s00415-023-11643-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 02/01/2023] [Accepted: 02/22/2023] [Indexed: 03/05/2023]
Abstract
OBJECTIVES Inherited defects of the neuromuscular junction (NMJ) comprise an increasingly diverse range of diseases. Several recently identified genes highlight the overlap between peripheral neuropathies and congenital myasthenic syndromes (CMS). The beta-2 adrenergic receptor agonist salbutamol has been shown to provide symptomatic benefit in CMS, while improving structural defects at the NMJ. Based on these findings, we identified cases of motor neuropathy with NMJ dysfunction and assessed the effect of salbutamol on motor function. METHODS Cases of motor neuropathy with significant NMJ dysfunction, were identified using repetitive nerve stimulation and single fibre electromyography. Oral salbutamol was administered for 12 months. Repeat neurophysiological and clinical assessments were undertaken at baseline, 6 months and 12 months. RESULTS Significant defects of neuromuscular transmission were identified in 15 patients harbouring a range of genetic defects, including mutations in GARS1, DNM2, SYT2 and DYNC1H. No clear benefit on motor function was seen following the administration of 12 months of oral salbutamol; however, there was a significant improvement in patient reported fatigue. In addition, no clear effect on neurophysiological parameters was seen in patients treated with salbutamol. Side-effects due to off-target beta-adrenergic effects were significant in the patient cohort. CONCLUSION These results highlight the involvement of the NMJ in several subtypes of motor neuropathies, including subtypes of neuropathy due to deficits in mitochondrial fusion-fission, synaptic vesicle transport, calcium channels and tRNA synthetases. Whether the NMJ dysfunction is simply due to muscle reinnervation or a pathology unrelated to denervation is unknown. The involvement of the NMJ may represent a novel therapeutic target in these conditions. However, treatment regimens will need to be more targeted for patients with primary inherited defects of neuromuscular transmission.
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Affiliation(s)
- Grace McMacken
- Department of Neurology, Royal Victoria Hospital, Belfast Health and Social Care Trust, Belfast, UK
| | - Roger G Whittaker
- Translational and Clinical Research Institute, Newcastle University, Newcastle Upon Tyne, UK
| | - Ruth Wake
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, UK
| | - Hanns Lochmuller
- Division of Neurology, Department of Medicine, Children's Hospital of Eastern Ontario Research Institute, The Ottawa Hospital and Brain and Mind Research Institute, University of Ottawa, Ottawa, Canada
| | - Rita Horvath
- Department of Clinical Neurosciences, John Van Geest Centre for Brain Repair, University of Cambridge School of Clinical Medicine, Level 3 A Block, Box 165, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK.
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11
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Mori S, Suzuki S, Konishi T, Kawaguchi N, Kishi M, Kuwabara S, Ishizuchi K, Zhou H, Shibasaki F, Tsumoto H, Omura T, Miura Y, Mori S, Higashihara M, Murayama S, Shigemoto K. Proteolytic ectodomain shedding of muscle-specific tyrosine kinase in myasthenia gravis. Exp Neurol 2023; 361:114300. [PMID: 36525997 DOI: 10.1016/j.expneurol.2022.114300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 11/07/2022] [Accepted: 12/10/2022] [Indexed: 12/15/2022]
Abstract
Autoantibodies to muscle-specific tyrosine kinase (MuSK) proteins at the neuromuscular junction (NMJ) cause refractory generalized myasthenia gravis (MG) with dyspnea more frequently than other MG subtypes. However, the mechanisms via which MuSK, a membrane protein locally expressed on the NMJ of skeletal muscle, is supplied to the immune system as an autoantigen remains unknown. Here, we identified MuSK in both mouse and human serum, with the amount of MuSK dramatically increasing in mice with motor nerve denervation and in MG model mice. Peptide analysis by liquid chromatography-tandem-mass spectrometry (LC-MS/MS) confirmed the presence of MuSK in both human and mouse serum. Furthermore, some patients with MG have significantly higher amounts of MuSK in serum than healthy controls. Our results indicated that the secretion of MuSK proteins from muscles into the bloodstream was induced by ectodomain shedding triggered by neuromuscular junction failure. The results may explain why MuSK-MG is refractory to treatments and causes rapid muscle atrophy in some patients due to the denervation associated with Ab-induced disruption of neuromuscular transmission at the NMJ. Such discoveries pave the way for new MG treatments, and MuSK may be used as a biomarker for other neuromuscular diseases in preclinical studies, clinical diagnostics, therapeutics, and drug discovery.
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Affiliation(s)
- Shuuichi Mori
- Research Team for Geriatric Medicine, Tokyo Metropolitan Institute of Gerontology (TMIG), Tokyo, Japan
| | - Shigeaki Suzuki
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | | | - Naoki Kawaguchi
- Dowa Institute of Clinical Neuroscience, Neurology Clinic Chiba, Chiba, Japan
| | - Masahiko Kishi
- Department of Internal Medicine, Toho University Sakura Medical Center, Chiba, Japan
| | - Satoshi Kuwabara
- Department of Neurology, Chiba University School of Medicine, Chiba, Japan
| | - Kei Ishizuchi
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | - Heying Zhou
- Research Team for Geriatric Medicine, Tokyo Metropolitan Institute of Gerontology (TMIG), Tokyo, Japan
| | - Futoshi Shibasaki
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Hiroki Tsumoto
- Research Team for Mechanism of Aging, TMIG, Tokyo, Japan
| | - Takuya Omura
- Research Team for Geriatric Medicine, Tokyo Metropolitan Institute of Gerontology (TMIG), Tokyo, Japan
| | - Yuri Miura
- Research Team for Mechanism of Aging, TMIG, Tokyo, Japan
| | - Seijiro Mori
- Research Team for Geriatric Medicine, Tokyo Metropolitan Institute of Gerontology (TMIG), Tokyo, Japan
| | - Mana Higashihara
- Department of Neurology, Tokyo Metropolitan Geriatric Hospital, Tokyo (TMGHIG), Japan
| | | | - Kazuhiro Shigemoto
- Research Team for Geriatric Medicine, Tokyo Metropolitan Institute of Gerontology (TMIG), Tokyo, Japan.
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12
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DOK7 Promotes NMJ Regeneration After Nerve Injury. Mol Neurobiol 2023; 60:1453-1464. [PMID: 36464749 DOI: 10.1007/s12035-022-03143-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 11/17/2022] [Indexed: 12/11/2022]
Abstract
Motor function recovery from injury requires the regeneration of not only muscle fibers, but also the neuromuscular junction-the synapse between motor nerve terminals and muscle fibers. However, unlike muscle regeneration which has been extensively studied, little is known about the molecular mechanisms of NMJ regeneration. Recognizing the critical role of agrin-LRP4-MuSK signaling in NMJ formation and maintenance, we investigated whether increasing MuSK activity promotes NMJ regeneration. To this end, we evaluated the effect of DOK7, a protein that stimulates MuSK, on NMJ regeneration. Reinnervation, AChR cluster density, and endplate area were improved, and fragmentation was reduced in the AAV9-DOK7-GFP-injected muscles compared with muscles injected with AAV9-GFP. These results demonstrated expedited NMJ regeneration associated with increased DOK7 expression and support the hypothesis that increasing agrin signaling benefits motor function recovery after injury. Our findings propose a potentially new therapeutic strategy for functional recovery after muscle and nerve injury, i.e., promoting NMJ regeneration by increasing agrin signaling.
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13
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Younger DS. Neurogenetic motor disorders. HANDBOOK OF CLINICAL NEUROLOGY 2023; 195:183-250. [PMID: 37562870 DOI: 10.1016/b978-0-323-98818-6.00003-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
Advances in the field of neurogenetics have practical applications in rapid diagnosis on blood and body fluids to extract DNA, obviating the need for invasive investigations. The ability to obtain a presymptomatic diagnosis through genetic screening and biomarkers can be a guide to life-saving disease-modifying therapy or enzyme replacement therapy to compensate for the deficient disease-causing enzyme. The benefits of a comprehensive neurogenetic evaluation extend to family members in whom identification of the causal gene defect ensures carrier detection and at-risk counseling for future generations. This chapter explores the many facets of the neurogenetic evaluation in adult and pediatric motor disorders as a primer for later chapters in this volume and a roadmap for the future applications of genetics in neurology.
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Affiliation(s)
- David S Younger
- Department of Clinical Medicine and Neuroscience, CUNY School of Medicine, New York, NY, United States; Department of Medicine, Section of Internal Medicine and Neurology, White Plains Hospital, White Plains, NY, United States.
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14
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Klann PJ, Wang X, Elfert A, Zhang W, Köhler C, Güttsches AK, Jacobsen F, Weyen U, Roos A, Ehrke-Schulz E, Ehrhardt A, Vorgerd M, Bayer W. Seroprevalence of Binding and Neutralizing Antibodies against 39 Human Adenovirus Types in Patients with Neuromuscular Disorders. Viruses 2022; 15:79. [PMID: 36680119 PMCID: PMC9866721 DOI: 10.3390/v15010079] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/22/2022] [Accepted: 12/24/2022] [Indexed: 12/29/2022] Open
Abstract
High pre-existing antibodies against viral vectors reduce their functionality and may lead to adverse complications. To circumvent this problem in future gene therapy approaches, we tested the seroprevalence of a large range of human adenovirus types in patients with neuromuscular disorders (NMDs) to find appropriate viral vector candidates for gene replacement therapy for NMDs. Binding and neutralizing antibodies against 39 human adenovirus types were tested in the sera of 133 patients with NMDs and 76 healthy controls aged 17-92 years. The influence of age, sex, and NMDs on antibody levels was analyzed. The seroprevalence of different adenoviruses in the cohort varied widely. The highest levels of binding antibodies were detected against HAdV-D27, -C1, -D24, -D70, -B14, -C6, -D13, -B34, and -E4, whereas the lowest reactivity was detected against HAdV-F41, -A31, -B11, -D75, -D8, -D65, -D26, -D80, and -D17. The highest neutralizing reactivity was observed against HAdV-B3, -C2, -E4, -C1, -G52, -C5, and -F41, whereas the lowest neutralizing reactivity was observed against HAdV-D74, -B34, -D73, -B37, -D48, -D13, -D75, -D8, -B35, and -B16. We detected no influence of sex and only minor differences between different age groups. Importantly, there were no significant differences between healthy controls and patients with NMDs. Our data show that patients with NMDs have very similar levels of binding and neutralizing antibodies against HAdV compared to healthy individuals, and we identified HAdV-A31, -B16, -B34, -B35, -D8, -D37, -D48, -D73, -D74, -D75, and -D80 as promising candidates for future vector development due to their low binding and neutralizing antibody prevalence.
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Affiliation(s)
- Patrick Julian Klann
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, 45122 Essen, Germany
- Heimer Institute for Muscle Research, Department of Neurology, University Hospital Bergmannsheil, Ruhr-University Bochum, 44789 Bochum, Germany
| | - Xiaoyan Wang
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, 45122 Essen, Germany
| | - Anna Elfert
- Heimer Institute for Muscle Research, Department of Neurology, University Hospital Bergmannsheil, Ruhr-University Bochum, 44789 Bochum, Germany
| | - Wenli Zhang
- Virology and Microbiology, Center for Medical Education and Research, Department of Human Medicine, Faculty of Health, Witten/Herdecke University, 58453 Witten, Germany
| | - Cornelia Köhler
- Clinics for Pediatrics and Adolescent Medicine, University Hospital Sankt Josef, Ruhr-University Bochum, 44791 Bochum, Germany
| | - Anne-Katrin Güttsches
- Heimer Institute for Muscle Research, Department of Neurology, University Hospital Bergmannsheil, Ruhr-University Bochum, 44789 Bochum, Germany
| | - Frank Jacobsen
- Heimer Institute for Muscle Research, Department of Neurology, University Hospital Bergmannsheil, Ruhr-University Bochum, 44789 Bochum, Germany
| | - Ute Weyen
- Heimer Institute for Muscle Research, Department of Neurology, University Hospital Bergmannsheil, Ruhr-University Bochum, 44789 Bochum, Germany
| | - Andreas Roos
- Heimer Institute for Muscle Research, Department of Neurology, University Hospital Bergmannsheil, Ruhr-University Bochum, 44789 Bochum, Germany
| | - Eric Ehrke-Schulz
- Virology and Microbiology, Center for Medical Education and Research, Department of Human Medicine, Faculty of Health, Witten/Herdecke University, 58453 Witten, Germany
| | - Anja Ehrhardt
- Virology and Microbiology, Center for Medical Education and Research, Department of Human Medicine, Faculty of Health, Witten/Herdecke University, 58453 Witten, Germany
| | - Matthias Vorgerd
- Heimer Institute for Muscle Research, Department of Neurology, University Hospital Bergmannsheil, Ruhr-University Bochum, 44789 Bochum, Germany
| | - Wibke Bayer
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, 45122 Essen, Germany
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15
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Cardiac troponin T and autoimmunity in skeletal muscle aging. GeroScience 2022; 44:2025-2045. [PMID: 35034279 PMCID: PMC9616986 DOI: 10.1007/s11357-022-00513-7] [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: 09/02/2021] [Accepted: 01/05/2022] [Indexed: 01/03/2023] Open
Abstract
Age-related muscle mass and strength decline (sarcopenia) impairs the performance of daily living activities and can lead to mobility disability/limitation in older adults. Biological pathways in muscle that lead to mobility problems have not been fully elucidated. Immunoglobulin G (IgG) infiltration in muscle is a known marker of increased fiber membrane permeability and damage vulnerability, but whether this translates to impaired function is unknown. Here, we report that IgG1 and IgG4 are abundantly present in the skeletal muscle (vastus lateralis) of ~ 50% (11 out of 23) of older adults (> 65 years) examined. Skeletal muscle IgG1 was inversely correlated with physical performance (400 m walk time: r = 0.74, p = 0.005; SPPB score: r = - 0.73, p = 0.006) and muscle strength (r = - 0.6, p = 0.05). In a murine model, IgG was found to be higher in both muscle and blood of older, versus younger, C57BL/6 mice. Older mice with a higher level of muscle IgG had lower motor activity. IgG in mouse muscle co-localized with cardiac troponin T (cTnT) and markers of complement activation and apoptosis/necroptosis. Skeletal muscle-inducible cTnT knockin mice also showed elevated IgG in muscle and an accelerated muscle degeneration and motor activity decline with age. Most importantly, anti-cTnT autoantibodies were detected in the blood of cTnT knockin mice, old mice, and older humans. Our findings suggest a novel cTnT-mediated autoimmune response may be an indicator of sarcopenia.
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16
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Verma S, Khurana S, Vats A, Sahu B, Ganguly NK, Chakraborti P, Gourie-Devi M, Taneja V. Neuromuscular Junction Dysfunction in Amyotrophic Lateral Sclerosis. Mol Neurobiol 2022; 59:1502-1527. [PMID: 34997540 DOI: 10.1007/s12035-021-02658-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 11/18/2021] [Indexed: 12/11/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder characterized by progressive degeneration of motor neurons leading to skeletal muscle denervation. Earlier studies have shown that motor neuron degeneration begins in motor cortex and descends to the neuromuscular junction (NMJ) in a dying forward fashion. However, accumulating evidences support that ALS is a distal axonopathy where early pathological changes occur at the NMJ, prior to onset of clinical symptoms and propagates towards the motor neuron cell body supporting "dying back" hypothesis. Despite several evidences, series of events triggering NMJ disassembly in ALS are still obscure. Neuromuscular junction is a specialized tripartite chemical synapse which involves a well-coordinated communication among the presynaptic motor neuron, postsynaptic skeletal muscle, and terminal Schwann cells. This review provides comprehensive insight into the role of NMJ in ALS pathogenesis. We have emphasized the molecular alterations in cellular components of NMJ leading to loss of effective neuromuscular transmission in ALS. Further, we provide a preview into research involved in exploring NMJ as potential target for designing effective therapies for ALS.
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Affiliation(s)
- Sagar Verma
- Department of Research, Sir Ganga Ram Hospital, Delhi, India.,Department of Biotechnology, Jamia Hamdard, Delhi, India
| | - Shiffali Khurana
- Department of Research, Sir Ganga Ram Hospital, Delhi, India.,Department of Biomedical Science, Bhaskaracharya College of Applied Sciences, University of Delhi, Delhi, India
| | - Abhishek Vats
- Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bandana Sahu
- Department of Research, Sir Ganga Ram Hospital, Delhi, India
| | | | | | | | - Vibha Taneja
- Department of Research, Sir Ganga Ram Hospital, Delhi, India.
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17
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Ramdas S, Beeson D. Congenital myasthenic syndromes: where do we go from here? Neuromuscul Disord 2021; 31:943-954. [PMID: 34736634 DOI: 10.1016/j.nmd.2021.07.400] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 07/22/2021] [Accepted: 07/27/2021] [Indexed: 11/27/2022]
Abstract
Congenital myasthenia syndromes are rare but often treatable conditions affecting neuromuscular transmission. They result from loss or impaired function of one of a number of proteins secondary to a genetic defect. An estimate of the prevalence in the UK gave 9.2 cases per million, however, this is likely an underestimate since the adoption of next generation sequencing for diagnosis away from specialist centres is enhancing the 'pick up' rate. Next generation sequencing has helped identify a series of novel genes that harbour mutations causative for congenital myasthenic syndrome that include not only genes that encode proteins specifically expressed at the neuromuscular junction but also those that are ubiquitously expressed. The list of genes harbouring disease-causing mutations for congenital myasthenic syndrome continues to expand and is now over 30, but with many of the newly identified genes it is increasingly being recognised that abnormal neuromuscular transmission is only one component of a multifaceted phenotype in which muscle, the central nervous system, and other organs may also be affected. Treatment can be tailored to the underlying molecular mechanism for impaired neuromuscular transmission but treating the more complex multifaceted disorders and will require development of new therapies.
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Affiliation(s)
- Sithara Ramdas
- MDUK Neuromuscular centre, Children's Hospital, John Radcliffe Hospital, Oxford, OX3 9DU, UK
| | - David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, The John Radcliffe, Oxford OX3 9DS, UK.
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18
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Sha R, Wang Z, You X, Liu Y, Xie Z, Feng Y. Whole-mount Staining of Mouse Diaphragm Neuromuscular Junctions. Bio Protoc 2021; 11:e4215. [PMID: 34859130 DOI: 10.21769/bioprotoc.4215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 07/08/2021] [Accepted: 07/16/2021] [Indexed: 11/02/2022] Open
Abstract
The neuromuscular junction (NMJ) is a specialized synapse that connects the terminal end of a motor neuron and a skeletal muscle fiber. Defects in NMJ cause abnormalities of neuromuscular transmission, leading to NMJ disorders. The mammalian diaphragm muscle is essential for respiration and has been widely used to study NMJ formation. Here, we provide a simple and straightforward protocol for preparing diaphragms from embryonic, neonatal, and adult mice and for subsequent NMJ staining.
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Affiliation(s)
- Rula Sha
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Zhenzhen Wang
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Xue You
- Collaborative Innovation Center for Birth Defect Research and Transformation of Shandong Province, Jining Medical University, Jining, China
| | - Yuguo Liu
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Zhiqin Xie
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Ying Feng
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China.,Collaborative Innovation Center for Birth Defect Research and Transformation of Shandong Province, Jining Medical University, Jining, China
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19
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Webster RG, Vanhaesebrouck AE, Maxwell SE, Cossins JA, Liu W, Ueta R, Yamanashi Y, Beeson DMW. Effect of salbutamol on neuromuscular junction function and structure in a mouse model of DOK7 congenital myasthenia. Hum Mol Genet 2021; 29:2325-2336. [PMID: 32543656 PMCID: PMC7424765 DOI: 10.1093/hmg/ddaa116] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 06/07/2020] [Accepted: 06/08/2020] [Indexed: 12/28/2022] Open
Abstract
Congenital myasthenic syndromes (CMS) are characterized by fatigable muscle weakness resulting from impaired neuromuscular transmission. β2-adrenergic agonists are an effective treatment for DOK7-CMS. DOK7 is a component within the AGRN-LRP4-MUSK-DOK7 signalling pathway that is key for the formation and maintenance of the synaptic structure of the neuromuscular junction (NMJ). The precise mechanism of action of β2-adrenergic agonists at the NMJ is not fully understood. In this study, we investigated whether β2-adrenergic agonists improve both neurotransmission and structural integrity of the NMJ in a mouse model of DOK7-CMS. Ex-vivo electrophysiological techniques and microscopy of the NMJ were used to study the effect of salbutamol, a β2-adrenergic agonist, on synaptic structure and function. DOK7-CMS model mice displayed a severe phenotype with reduced weight gain and perinatal lethality. Salbutamol treatment improved weight gain and survival in DOK7 myasthenic mice. Model animals had fewer active NMJs, detectable by endplate recordings, compared with age-matched wild-type littermates. Salbutamol treatment increased the number of detectable NMJs during endplate recording. Correspondingly, model mice had fewer acetylcholine receptor-stained NMJs detected by fluorescent labelling, but following salbutamol treatment an increased number were detectable. The data demonstrate that salbutamol can prolong survival and increase NMJ number in a severe model of DOK7-CMS.
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Affiliation(s)
- Richard G Webster
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| | - An E Vanhaesebrouck
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| | - Susan E Maxwell
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| | - Judith A Cossins
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| | - Weiwei Liu
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| | - Ryo Ueta
- Division of Genetics, Department of Cancer Biology, Institute of Medical Science, The University of Tokyo, Tokyo 135-8550, Japan
| | - Yuji Yamanashi
- Division of Genetics, Department of Cancer Biology, Institute of Medical Science, The University of Tokyo, Tokyo 135-8550, Japan
| | - David M W Beeson
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
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20
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The Neuromuscular Junction: Roles in Aging and Neuromuscular Disease. Int J Mol Sci 2021; 22:ijms22158058. [PMID: 34360831 PMCID: PMC8347593 DOI: 10.3390/ijms22158058] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 07/20/2021] [Accepted: 07/22/2021] [Indexed: 02/07/2023] Open
Abstract
The neuromuscular junction (NMJ) is a specialized synapse that bridges the motor neuron and the skeletal muscle fiber and is crucial for conversion of electrical impulses originating in the motor neuron to action potentials in the muscle fiber. The consideration of contributing factors to skeletal muscle injury, muscular dystrophy and sarcopenia cannot be restricted only to processes intrinsic to the muscle, as data show that these conditions incur denervation-like findings, such as fragmented NMJ morphology and corresponding functional changes in neuromuscular transmission. Primary defects in the NMJ also influence functional loss in motor neuron disease, congenital myasthenic syndromes and myasthenia gravis, resulting in skeletal muscle weakness and heightened fatigue. Such findings underscore the role that the NMJ plays in neuromuscular performance. Regardless of cause or effect, functional denervation is now an accepted consequence of sarcopenia and muscle disease. In this short review, we provide an overview of the pathologic etiology, symptoms, and therapeutic strategies related to the NMJ. In particular, we examine the role of the NMJ as a disease modifier and a potential therapeutic target in neuromuscular injury and disease.
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21
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Vergoossen DLE, Keo A, Mahfouz A, Huijbers MG. Timing and localization of myasthenia gravis-related gene expression. Eur J Neurosci 2021; 54:5574-5585. [PMID: 34228850 PMCID: PMC8457065 DOI: 10.1111/ejn.15382] [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: 03/26/2021] [Revised: 06/01/2021] [Accepted: 07/01/2021] [Indexed: 11/29/2022]
Abstract
Myasthenia gravis (MG) is an acquired autoimmune disorder caused by autoantibodies binding acetylcholine receptors (AChR), muscle‐specific kinase (MuSK), agrin or low‐density lipoprotein receptor‐related protein 4 (Lrp4). These autoantibodies inhibit neuromuscular transmission by blocking the function of these proteins and thereby cause fluctuating skeletal muscle weakness. Several reports suggest that these autoantibodies might also affect the central nervous system (CNS) in MG patients. A comprehensive overview of the timing and localization of the expression of MG‐related antigens in other organs is currently lacking. To investigate the spatio‐temporal expression of MG‐related genes outside skeletal muscle, we used in silico tools to assess public expression databases. Acetylcholine esterase, nicotinic AChR α1 subunit, agrin, collagen Q, downstream of kinase‐7, Lrp4, MuSK and rapsyn were included as MG‐related genes because of their well‐known involvement in either congenital or autoimmune MG. We investigated expression of MG‐related genes in (1) all human tissues using GTEx data, (2) specific brain regions, (3) neurodevelopmental stages, and (4) cell types using datasets from the Allen Institute for Brain Sciences. MG‐related genes show heterogenous spatio‐temporal expression patterns in the human body as well as in the CNS. For each of these genes, several (new) tissues, brain areas and cortical cell types with (relatively) high expression were identified suggesting a potential role for these genes outside skeletal muscle. The possible presence of MG‐related antigens outside skeletal muscle suggests that autoimmune MG, congenital MG or treatments targeting the same proteins may affect MG‐related protein function in other organs.
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Affiliation(s)
- Dana L E Vergoossen
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Arlin Keo
- Leiden Computational Biology Center, Leiden University Medical Center, Leiden, The Netherlands.,Delft Bioinformatics Lab, Delft University of Technology, Delft, The Netherlands
| | - Ahmed Mahfouz
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.,Leiden Computational Biology Center, Leiden University Medical Center, Leiden, The Netherlands.,Delft Bioinformatics Lab, Delft University of Technology, Delft, The Netherlands
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.,Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
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22
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Sugita S, Tamura K, Yano M, Minegishi Y, Ota N. The Impact of Milk Fat Globule Membrane with Exercise on Age-Related Degeneration of Neuromuscular Junctions. Nutrients 2021; 13:nu13072310. [PMID: 34371820 PMCID: PMC8308682 DOI: 10.3390/nu13072310] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 06/28/2021] [Accepted: 06/30/2021] [Indexed: 12/19/2022] Open
Abstract
Morphological changes in neuromuscular junctions (NMJs), which are synapses formed between α-motor neurons and skeletal muscle fibers, are considered to be important in age-related motor dysfunction. We have previously shown that the intake of dietary milk fat globule membrane (MFGM) combined with exercise attenuates age-related NMJ alterations in the early phase of aging. However, it is unclear whether the effect of MFGM with exercise on age-related NMJ alterations persists into old age, and whether intervention from old age is still effective when age-related changes in NMJs have already occurred. In this study, 6- or 18-month-old mice were treated with a 1% MFGM diet and daily running wheel exercise until 23 or 24 months of age, respectively. MFGM treatment with exercise was effective in suppressing the progression of age-related NMJ alterations in old age, and even after age-related changes in NMJs had already occurred. Moreover, the effect of MFGM intake with exercise was not restricted to NMJs but extended to the structure and function of peripheral nerves. This study demonstrates that MFGM intake with exercise may be a novel approach for improving motor function in the elderly by suppressing age-related NMJ alterations.
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23
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Oury J, Zhang W, Leloup N, Koide A, Corrado AD, Ketavarapu G, Hattori T, Koide S, Burden SJ. Mechanism of disease and therapeutic rescue of Dok7 congenital myasthenia. Nature 2021; 595:404-408. [PMID: 34163073 PMCID: PMC8277574 DOI: 10.1038/s41586-021-03672-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 05/25/2021] [Indexed: 11/09/2022]
Abstract
Congenital myasthenia (CM) is a devastating neuromuscular disease, and mutations in DOK7, an adaptor protein that is crucial for forming and maintaining neuromuscular synapses, are a major cause of CM1,2. The most common disease-causing mutation (DOK71124_1127 dup) truncates DOK7 and leads to the loss of two tyrosine residues that are phosphorylated and recruit CRK proteins, which are important for anchoring acetylcholine receptors at synapses. Here we describe a mouse model of this common form of CM (Dok7CM mice) and a mouse with point mutations in the two tyrosine residues (Dok72YF). We show that Dok7CM mice had severe deficits in neuromuscular synapse formation that caused neonatal lethality. Unexpectedly, these deficits were due to a severe deficiency in phosphorylation and activation of muscle-specific kinase (MUSK) rather than a deficiency in DOK7 tyrosine phosphorylation. We developed agonist antibodies against MUSK and show that these antibodies restored neuromuscular synapse formation and prevented neonatal lethality and late-onset disease in Dok7CM mice. These findings identify an unexpected cause for disease and a potential therapy for both DOK7 CM and other forms of CM caused by mutations in AGRIN, LRP4 or MUSK, and illustrate the potential of targeted therapy to rescue congenital lethality.
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Affiliation(s)
- Julien Oury
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU Grossman School of Medicine, New York, NY, USA
| | - Wei Zhang
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU Grossman School of Medicine, New York, NY, USA
| | - Nadia Leloup
- Perlmutter Cancer Center, NYU Langone Health, New York, NY, USA
| | - Akiko Koide
- Perlmutter Cancer Center, NYU Langone Health, New York, NY, USA.,Department of Medicine, NYU Grossman School of Medicine, New York, NY, USA
| | | | | | - Takamitsu Hattori
- Perlmutter Cancer Center, NYU Langone Health, New York, NY, USA.,Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY, USA
| | - Shohei Koide
- Perlmutter Cancer Center, NYU Langone Health, New York, NY, USA. .,Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY, USA.
| | - Steven J Burden
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU Grossman School of Medicine, New York, NY, USA.
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24
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Ban J, Beqaj B, Phillips WD. Vector-mediated expression of muscle specific kinase restores specific force to muscles in the mdx mouse model of Duchenne muscular dystrophy. Exp Physiol 2021; 106:1794-1805. [PMID: 34114278 DOI: 10.1113/ep089439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 06/08/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? The (dystrophin-deficient) muscles of mdx mice generate less contractile force per cross-sectional area (specific force) than those of healthy wild-type mice: what is the influence of muscle specific kinase (MuSK) upon the properties of the tibialis anterior (TA) muscle in mdx mice? What is the main finding and its importance? Injection of adeno-associated viral vector encoding MuSK into the TA muscle of young mdx mice increased the specific force of the muscle, suggesting the MuSK signalling system has the potential to restore healthy growth to dystrophin-deficient muscles. ABSTRACT In the mdx mouse model of Duchenne muscular dystrophy, muscle fibres are fragile and prone to injury and degeneration. Compared to wild-type mice, muscles of mdx mice also develop less specific force (contractile force/cross-sectional area). We recently reported that injecting adeno-associated viral vector encoding muscle specific kinase (AAV-MuSK) into muscles of mdx mice increased utrophin expression and made the muscles more resistant to acute stretch-induced injury. Here we injected AAV-MuSK unilaterally into the tibialis anterior muscle of mdx mice at a younger age (4 weeks), and recorded contraction force from the muscles in situ at 12 weeks of age. Compared to contralateral empty-vector control muscles, muscles injected with AAV-MuSK produced 28% greater specific force (P = 0.0005). They did not undergo the compensatory hypertrophy that normally occurs in muscles of mdx mice. Injection of AAV encoding rapsyn (a downstream effector of MuSK signalling) caused no such improvement in muscle strength. Muscles injected with AAV-MuSK displayed a 10% reduction in the number of fibres with centralized nuclei (P = 0.0015). Our results in mdx mice suggest that elevating the expression of MuSK can reduce the incidence of muscle fibre regeneration and improve the strength of dystrophin-deficient muscles.
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Affiliation(s)
- Joanne Ban
- Physiology and Bosch Institute, University of Sydney, Sydney, NSW, Australia
| | - Besa Beqaj
- Physiology and Bosch Institute, University of Sydney, Sydney, NSW, Australia
| | - William D Phillips
- Physiology and Bosch Institute, University of Sydney, Sydney, NSW, Australia
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25
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Hui T, Jing H, Lai X. Neuromuscular junction-specific genes screening by deep RNA-seq analysis. Cell Biosci 2021; 11:81. [PMID: 33933147 PMCID: PMC8088568 DOI: 10.1186/s13578-021-00590-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 04/17/2021] [Indexed: 01/17/2023] Open
Abstract
Background Neuromuscular junctions (NMJs) are chemical synapses formed between motor neurons and skeletal muscle fibers and are essential for controlling muscle contraction. NMJ dysfunction causes motor disorders, muscle wasting, and even breathing difficulties. Increasing evidence suggests that many NMJ disorders are closely related to alterations in specific gene products that are highly concentrated in the synaptic region of the muscle. However, many of these proteins are still undiscovered. Thus, screening for NMJ-specific proteins is essential for studying NMJ and the pathogenesis of NMJ diseases. Results In this study, synaptic regions (SRs) and nonsynaptic regions (NSRs) of diaphragm samples from newborn (P0) and adult (3-month-old) mice were used for RNA-seq. A total of 92 and 182 genes were identified as differentially expressed between the SR and NSR in newborn and adult mice, respectively. Meanwhile, a total of 1563 genes were identified as differentially expressed between the newborn SR and adult SR. Gene Ontology (GO) enrichment analyses, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and gene set enrichment analysis (GSEA) of the DEGs were performed. Protein–protein interaction (PPI) networks were constructed using STRING and Cytoscape. Further analysis identified some novel proteins and pathways that may be important for NMJ development, maintenance and maturation. Specifically, Sv2b, Ptgir, Gabrb3, P2rx3, Dlgap1 and Rims1 may play roles in NMJ development. Hcn1 may localize to the muscle membrane to regulate NMJ maintenance. Trim63, Fbxo32 and several Asb family proteins may regulate muscle developmental-related processes. Conclusion Here, we present a complete dataset describing the spatiotemporal transcriptome changes in synaptic genes and important synaptic pathways. The neuronal projection-related pathway, ion channel activity and neuroactive ligand-receptor interaction pathway are important for NMJ development. The myelination and voltage-gated ion channel activity pathway may be important for NMJ maintenance. These data will facilitate the understanding of the molecular mechanisms underlying the development and maintenance of NMJ and the pathogenesis of NMJ disorders.
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Affiliation(s)
- Tiankun Hui
- School of Life Science, Nanchang University, Nanchang, Jiangxi, China.,Laboratory of Synaptic Development and Plasticity, Institute of Life Science, Nanchang University, Nanchang, Jiangxi, China
| | - Hongyang Jing
- School of Life Science, Nanchang University, Nanchang, Jiangxi, China.,Laboratory of Synaptic Development and Plasticity, Institute of Life Science, Nanchang University, Nanchang, Jiangxi, China
| | - Xinsheng Lai
- School of Life Science, Nanchang University, Nanchang, Jiangxi, China. .,Laboratory of Synaptic Development and Plasticity, Institute of Life Science, Nanchang University, Nanchang, Jiangxi, China.
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26
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Skeletal and Cardiac Muscle Disorders Caused by Mutations in Genes Encoding Intermediate Filament Proteins. Int J Mol Sci 2021; 22:ijms22084256. [PMID: 33923914 PMCID: PMC8073371 DOI: 10.3390/ijms22084256] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/12/2021] [Accepted: 04/15/2021] [Indexed: 02/08/2023] Open
Abstract
Intermediate filaments are major components of the cytoskeleton. Desmin and synemin, cytoplasmic intermediate filament proteins and A-type lamins, nuclear intermediate filament proteins, play key roles in skeletal and cardiac muscle. Desmin, encoded by the DES gene (OMIM *125660) and A-type lamins by the LMNA gene (OMIM *150330), have been involved in striated muscle disorders. Diseases include desmin-related myopathy and cardiomyopathy (desminopathy), which can be manifested with dilated, restrictive, hypertrophic, arrhythmogenic, or even left ventricular non-compaction cardiomyopathy, Emery–Dreifuss Muscular Dystrophy (EDMD2 and EDMD3, due to LMNA mutations), LMNA-related congenital Muscular Dystrophy (L-CMD) and LMNA-linked dilated cardiomyopathy with conduction system defects (CMD1A). Recently, mutations in synemin (SYNM gene, OMIM *606087) have been linked to cardiomyopathy. This review will summarize clinical and molecular aspects of desmin-, lamin- and synemin-related striated muscle disorders with focus on LMNA and DES-associated clinical entities and will suggest pathogenetic hypotheses based on the interplay of desmin and lamin A/C. In healthy muscle, such interplay is responsible for the involvement of this network in mechanosignaling, nuclear positioning and mitochondrial homeostasis, while in disease it is disturbed, leading to myocyte death and activation of inflammation and the associated secretome alterations.
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27
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Scaricamazza S, Salvatori I, Ferri A, Valle C. Skeletal Muscle in ALS: An Unappreciated Therapeutic Opportunity? Cells 2021; 10:cells10030525. [PMID: 33801336 PMCID: PMC8000428 DOI: 10.3390/cells10030525] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 02/23/2021] [Accepted: 02/24/2021] [Indexed: 12/11/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by the selective degeneration of upper and lower motor neurons and by the progressive weakness and paralysis of voluntary muscles. Despite intense research efforts and numerous clinical trials, it is still an incurable disease. ALS had long been considered a pure motor neuron disease; however, recent studies have shown that motor neuron protection is not sufficient to prevent the course of the disease since the dismantlement of neuromuscular junctions occurs before motor neuron degeneration. Skeletal muscle alterations have been described in the early stages of the disease, and they seem to be mainly involved in the “dying back” phenomenon of motor neurons and metabolic dysfunctions. In recent years, skeletal muscles have been considered crucial not only for the etiology of ALS but also for its treatment. Here, we review clinical and preclinical studies that targeted skeletal muscles and discuss the different approaches, including pharmacological interventions, supplements or diets, genetic modifications, and training programs.
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Affiliation(s)
- Silvia Scaricamazza
- Fondazione Santa Lucia IRCCS, c/o CERC, 00143 Rome, Italy
- Department of Biology, University of Rome Tor Vergata, 00133 Rome, Italy
| | - Illari Salvatori
- Fondazione Santa Lucia IRCCS, c/o CERC, 00143 Rome, Italy
- Department of Experimental Medicine, University of Rome "La Sapienza", 00161 Rome, Italy
| | - Alberto Ferri
- Fondazione Santa Lucia IRCCS, c/o CERC, 00143 Rome, Italy
- Institute of Translational Pharmacology, National Research Council, 00133 Rome, Italy
| | - Cristiana Valle
- Fondazione Santa Lucia IRCCS, c/o CERC, 00143 Rome, Italy
- Institute of Translational Pharmacology, National Research Council, 00133 Rome, Italy
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28
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Bao Z, Cui C, Chow SKH, Qin L, Wong RMY, Cheung WH. AChRs Degeneration at NMJ in Aging-Associated Sarcopenia-A Systematic Review. Front Aging Neurosci 2020; 12:597811. [PMID: 33362532 PMCID: PMC7759742 DOI: 10.3389/fnagi.2020.597811] [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: 08/22/2020] [Accepted: 11/19/2020] [Indexed: 12/16/2022] Open
Abstract
Sarcopenia is an aging process with a decline of skeletal muscle mass and function, which is a challenging public health problem with reduced quality of life in patients. The endplate, the post-synaptic part of the neuromuscular junction (NMJ), occupies 0.1% of the myofiber surface area only, but is composed of millions of acetylcholine receptors (AChRs) that are efficient in binding to acetylcholine (ACh) and triggering skeletal muscle contraction. This systematic review aims to examine aging-associated alterations of post-synaptic AChRs, including morphology, function and related gene expression. A systematic literature search was conducted in PubMed, Embase and Web of Science with relevant keywords by two independent reviewers. Original pre-clinical and clinical studies regarding AChRs changes during aging with available full text and written in English were included. Information was extracted from the included studies for further review. In total, 30 articles were included. Various parameters assessing AChRs alterations by radioassay, immunofluorescence, electrophysiology and mechanical test were reported. Endplate fragmentation and denervation were common in old skeletal muscles during aging. To ensure efficient NMJ transmission and force generation, type I or IIb muscle fibers tended to have increased ACh quanta releasing after electrical stimulations, while type IIa muscle fibers tended to have stronger binding between ACh and AChRs, but the overall function of AChRs was reduced during aging. Alterations of AChRs area depended on muscle type, species and the progress of muscle atrophy and type I muscles fibers tended to demonstrate enlarging AChRs areas. Myogenic regulator factors (MRFs) can regulate the expression of AChRs subunits, while decreased MRF4 may lead to expression changes of AChRs subunits during aging. Sarcoglycan-α can delay low-density lipoprotein receptor-related protein 4 (LRP4) degradation. This protein was increased in old muscles but still cannot suppress the degradation of LRP4. Investigating the role of these AChRs-related genes in the process of aging may provide a potential target to treat sarcopenia.
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Affiliation(s)
- Zhengyuan Bao
- Department of Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
| | - Can Cui
- Department of Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
| | - Simon Kwoon-Ho Chow
- Department of Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.,The CUHK-ACC Space Medicine Centre on Health Maintenance of Musculoskeletal System, The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, China
| | - Ling Qin
- Department of Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
| | - Ronald Man Yeung Wong
- Department of Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
| | - Wing-Hoi Cheung
- Department of Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.,The CUHK-ACC Space Medicine Centre on Health Maintenance of Musculoskeletal System, The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, China
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29
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Rodríguez Cruz PM, Cossins J, Beeson D, Vincent A. The Neuromuscular Junction in Health and Disease: Molecular Mechanisms Governing Synaptic Formation and Homeostasis. Front Mol Neurosci 2020; 13:610964. [PMID: 33343299 PMCID: PMC7744297 DOI: 10.3389/fnmol.2020.610964] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 10/30/2020] [Indexed: 12/28/2022] Open
Abstract
The neuromuscular junction (NMJ) is a highly specialized synapse between a motor neuron nerve terminal and its muscle fiber that are responsible for converting electrical impulses generated by the motor neuron into electrical activity in the muscle fibers. On arrival of the motor nerve action potential, calcium enters the presynaptic terminal, which leads to the release of the neurotransmitter acetylcholine (ACh). ACh crosses the synaptic gap and binds to ACh receptors (AChRs) tightly clustered on the surface of the muscle fiber; this leads to the endplate potential which initiates the muscle action potential that results in muscle contraction. This is a simplified version of the events in neuromuscular transmission that take place within milliseconds, and are dependent on a tiny but highly structured NMJ. Much of this review is devoted to describing in more detail the development, maturation, maintenance and regeneration of the NMJ, but first we describe briefly the most important molecules involved and the conditions that affect their numbers and function. Most important clinically worldwide, are myasthenia gravis (MG), the Lambert-Eaton myasthenic syndrome (LEMS) and congenital myasthenic syndromes (CMS), each of which causes specific molecular defects. In addition, we mention the neurotoxins from bacteria, snakes and many other species that interfere with neuromuscular transmission and cause potentially fatal diseases, but have also provided useful probes for investigating neuromuscular transmission. There are also changes in NMJ structure and function in motor neuron disease, spinal muscle atrophy and sarcopenia that are likely to be secondary but might provide treatment targets. The NMJ is one of the best studied and most disease-prone synapses in the nervous system and it is amenable to in vivo and ex vivo investigation and to systemic therapies that can help restore normal function.
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Affiliation(s)
- Pedro M Rodríguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
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30
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Ng SY, Ljubicic V. Recent insights into neuromuscular junction biology in Duchenne muscular dystrophy: Impacts, challenges, and opportunities. EBioMedicine 2020; 61:103032. [PMID: 33039707 PMCID: PMC7648118 DOI: 10.1016/j.ebiom.2020.103032] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/28/2020] [Accepted: 09/11/2020] [Indexed: 12/13/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is the most common and relentless form of muscular dystrophy. The pleiotropic effects of dystrophin deficiency include remarkable impacts on neuromuscular junction (NMJ) structure and function. Some of these alterations contribute to the severe muscle wasting and weakness that distinguish DMD, while others attempt to compensate for them. Experimental approaches that correct NMJ biology in pre-clinical models of DMD attenuate disease progression and improve functional outcomes, which suggests that targeting the NMJ may be an effective therapeutic strategy for DMD patients. The objectives of this review are to 1) survey the distinctions in NMJ structure, function, and gene expression in the dystrophic context as compared to the healthy condition, and 2) summarize the efforts, opportunities and challenges to correct NMJ biology in DMD. This information will expand our basic understanding of neuromuscular biology and may be useful for designing novel NMJ-targeted drug or behavioural strategies to mitigate the dystrophic pathology and other disorders of the neuromuscular system.
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Affiliation(s)
- Sean Y Ng
- Department of Kinesiology, McMaster University, Hamilton L8S 4L8, Ontario, Canada
| | - Vladimir Ljubicic
- Department of Kinesiology, McMaster University, Hamilton L8S 4L8, Ontario, Canada.
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31
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Postganglionic sympathetic neurons, but not locus coeruleus optostimulation, activates neuromuscular transmission in the adult mouse in vivo. Mol Cell Neurosci 2020; 109:103563. [PMID: 33039519 DOI: 10.1016/j.mcn.2020.103563] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 09/13/2020] [Accepted: 09/30/2020] [Indexed: 01/28/2023] Open
Abstract
Recent work demonstrated that sympathetic neurons innervate the skeletal muscle near the neuromuscular junction (NMJ), and muscle sympathectomy and sympathomimetic agents strongly influence motoneuron synaptic vesicle release ex vivo. Moreover, reports attest that the pontine nucleus locus coeruleus (LC) projects to preganglionic sympathetic neurons and regulates human mobility and skeletal muscle physiology. Thus, we hypothesized that peripheral and central sympathetic neurons projecting directly or indirectly to the skeletal muscle regulate NMJ transmission. The aim of this study was to define the specific neuronal groups in the peripheral and central nervous systems that account for such regulation in adult mice in vivo by using optogenetics and NMJ transmission recordings in 3-5-month-old, male and female ChR2(H134R/EYFP)/TH-Cre mice. After detecting ChR2(H134R)/EYFP fluorescence in the paravertebral ganglia and LC neurons, we tested whether optostimulating the plantar nerve near the lumbricalis muscle or LC neurons effectively modulates motor nerve terminal synaptic vesicle release in living mice. Nerve optostimulation increased motor synaptic vesicle release in vitro and in vivo, while the presynaptic adrenoceptor blockers propranolol (β1/β2) and atenolol (β1) prevented this outcome. The effect is primarily presynaptic since miniature end-plate potential (MEPP) kinetics remained statistically unmodified after stimulation. In contrast, optostimulation of LC neurons did not regulate NMJ transmission. In summary, we conclude that postganglionic sympathetic neurons, but not LC neurons, increased NMJ transmission by acting on presynaptic β1-adrenergic receptors in vivo.
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32
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Brooks PJ, Ottinger EA, Portero D, Lomash RM, Alimardanov A, Terse P, Xu X, Chandler RJ, Geist Hauserman J, Esposito E, Bönnemann CG, Venditti CP, Austin CP, Pariser A, Lo DC. The Platform Vector Gene Therapies Project: Increasing the Efficiency of Adeno-Associated Virus Gene Therapy Clinical Trial Startup. Hum Gene Ther 2020; 31:1034-1042. [PMID: 32993373 PMCID: PMC7585601 DOI: 10.1089/hum.2020.259] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Philip J Brooks
- Office of Rare Disease Research, National Center for Advancing Translational Sciences (NCATS)
| | - Elizabeth A Ottinger
- Therapeutic Development Branch, National Center for Advancing Translational Sciences (NCATS)
| | - Deanna Portero
- Office of Rare Disease Research, National Center for Advancing Translational Sciences (NCATS)
| | - Richa Madan Lomash
- Therapeutic Development Branch, National Center for Advancing Translational Sciences (NCATS)
| | - Asaf Alimardanov
- Therapeutic Development Branch, National Center for Advancing Translational Sciences (NCATS)
| | - Pramod Terse
- Therapeutic Development Branch, National Center for Advancing Translational Sciences (NCATS)
| | - Xin Xu
- Therapeutic Development Branch, National Center for Advancing Translational Sciences (NCATS)
| | - Randy J Chandler
- Organic Acid Research Section, Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute (NHGRI)
| | - Janelle Geist Hauserman
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke (NINDS); National Institutes of Health, Bethesda, Maryland, USA
| | - Eric Esposito
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke (NINDS); National Institutes of Health, Bethesda, Maryland, USA
| | - Carsten G Bönnemann
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke (NINDS); National Institutes of Health, Bethesda, Maryland, USA
| | - Charles P Venditti
- Organic Acid Research Section, Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute (NHGRI)
| | - Christopher P Austin
- Office of the Director, National Center for Advancing Translational Sciences (NCATS)
| | - Anne Pariser
- Office of Rare Disease Research, National Center for Advancing Translational Sciences (NCATS)
| | - Donald C Lo
- Therapeutic Development Branch, National Center for Advancing Translational Sciences (NCATS)
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33
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DOK7 Gene Therapy Enhances Neuromuscular Junction Innervation and Motor Function in Aged Mice. iScience 2020; 23:101385. [PMID: 32758427 PMCID: PMC7452162 DOI: 10.1016/j.isci.2020.101385] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 06/21/2020] [Accepted: 07/16/2020] [Indexed: 12/14/2022] Open
Abstract
Muscle denervation at the neuromuscular junction (NMJ), the essential synapse between motor neuron and skeletal muscle, is associated with age-related motor impairment. Therefore, improving muscle innervation at aged NMJs may be an effective therapeutic strategy for treating the impairment. We previously demonstrated that the muscle protein Dok-7 plays an essential role in NMJ formation, and, indeed, its forced expression in muscle enlarges NMJs. Moreover, therapeutic administration of an adeno-associated virus vector encoding human Dok-7 (DOK7 gene therapy) suppressed muscle denervation and enhanced motor activity in a mouse model of amyotrophic lateral sclerosis (ALS). Here, we show that DOK7 gene therapy significantly enhances motor function and muscle strength together with NMJ innervation in aged mice. Furthermore, the treated mice showed greatly increased compound muscle action potential (CMAP) amplitudes compared with the controls, suggesting enhanced neuromuscular transmission. Thus, therapies aimed at enhancing NMJ innervation have potential for treating age-related motor impairment. DOK7 gene therapy enhances motor function and muscle strength in aged (≥2 years) mice DOK7 gene therapy enhances neuromuscular junction (NMJ) innervation in aged mice DOK7 gene therapy increases compound muscle action potential amplitudes in aged mice Enhancing NMJ innervation in the elderly may strengthen muscles and motor activities
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34
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AAV9-DOK7 gene therapy reduces disease severity in Smn 2B/- SMA model mice. Biochem Biophys Res Commun 2020; 530:107-114. [PMID: 32828271 DOI: 10.1016/j.bbrc.2020.07.031] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 07/07/2020] [Indexed: 11/23/2022]
Abstract
Spinal Muscular Atrophy (SMA) is an autosomal recessive neuromuscular disease caused by deletions or mutations in the survival motor neuron (SMN1) gene. An important hallmark of disease progression is the pathology of neuromuscular junctions (NMJs). Affected NMJs in the SMA context exhibit delayed maturation, impaired synaptic transmission, and loss of contact between motor neurons and skeletal muscle. Protection and maintenance of NMJs remains a focal point of therapeutic strategies to treat SMA, and the recent implication of the NMJ-organizer Agrin in SMA pathology suggests additional NMJ organizing molecules may contribute. DOK7 is an NMJ organizer that functions downstream of Agrin. The potential of DOK7 as a putative therapeutic target was demonstrated by adeno-associated virus (AAV)-mediated gene therapy delivery of DOK7 in Amyotrophic Lateral Sclerosis (ALS) and Emery Dreyefuss Muscular Dystrophy (EDMD). To assess the potential of DOK7 as a disease modifier of SMA, we administered AAV-DOK7 to an intermediate mouse model of SMA. AAV9-DOK7 treatment conferred improvements in NMJ architecture and reduced muscle fiber atrophy. Additionally, these improvements resulted in a subtle reduction in phenotypic severity, evidenced by improved grip strength and an extension in survival. These findings reveal DOK7 is a novel modifier of SMA.
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35
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Chen A, Bai L, Zhong K, Shu X, Wang A, Xiao Y, Zhang K, Shen C. APC2
CDH1
negatively regulates agrin signaling by promoting the ubiquitination and proteolytic degradation of DOK7. FASEB J 2020; 34:12009-12023. [PMID: 32687671 DOI: 10.1096/fj.202000485r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 06/24/2020] [Accepted: 06/25/2020] [Indexed: 01/28/2023]
Affiliation(s)
- Aizhong Chen
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Lei Bai
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Keke Zhong
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Xiaoqiu Shu
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Ailian Wang
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Yatao Xiao
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Kejing Zhang
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Chengyong Shen
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
- Department of Neurobiology Key Laboratory of Medical Neurobiology of Zhejiang Province School of Medicine Zhejiang University Zhejiang China
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36
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Yano M, Haramizu S, Ota N, Minegishi Y, Shimotoyodome A. Continuous Supplementation of Milk Fat Globule Membrane with Habitual Exercise from a Young Age Improves Motor Coordination and Skeletal Muscle Function in Aged Mice. J Nutr Sci Vitaminol (Tokyo) 2020; 65:405-413. [PMID: 31666477 DOI: 10.3177/jnsv.65.405] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Since the decline of physical performance gradually progresses with aging, continuous exercise with nutritional supplementation from a young age is a feasible and effective way to maintain a comfortable life until late old age. We examined the effects of continuous milk fat globule membrane (MFGM) supplementation combined with voluntary running exercise (VR) for prevention of aging-associated declines in physical performance in naturally aging mice. The MFGM with VR group showed a significantly attenuated age-related decline in motor coordination and suppression of the loss of muscle mass and strength. Compared with the control group, the MFGM with VR group showed significantly higher mRNA and protein expression for docking protein 7, which maintains neuromuscular junction (NMJ) integrity, in the quadriceps muscles. These results suggest that dietary MFGM and VR attenuate natural aging-related decline in motor coordination and muscle function by regulating NMJ integrity.
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Affiliation(s)
- Michiko Yano
- Biological Science Research, Health Science, Kao Corporation Tochigi Research Center
| | - Satoshi Haramizu
- Biological Science Research, Health Science, Kao Corporation Tochigi Research Center
| | - Noriyasu Ota
- Biological Science Research, Health Science, Kao Corporation Tochigi Research Center
| | - Yoshihiko Minegishi
- Biological Science Research, Health Science, Kao Corporation Tochigi Research Center
| | - Akira Shimotoyodome
- Biological Science Research, Health Science, Kao Corporation Tochigi Research Center
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Overexpression of Dok-7 in skeletal muscle enhances neuromuscular transmission with structural alterations of neuromuscular junctions: Implications in robustness of neuromuscular transmission. Biochem Biophys Res Commun 2019; 523:214-219. [PMID: 31848047 DOI: 10.1016/j.bbrc.2019.12.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 12/02/2019] [Indexed: 11/24/2022]
Abstract
Neuromuscular junctions (NMJs) are cholinergic synapses characterized by ultrastructural specializations, including the presynaptic active zones, the acetylcholine (ACh) release sites of the motor nerve terminal, and the postsynaptic junctional folds of muscle membrane, where ACh receptors (AChRs) cluster for efficient neuromuscular transmission. The formation and maintenance of NMJs are governed by the muscle-specific receptor tyrosine kinase MuSK. We had previously demonstrated that the muscle cytoplasmic protein Dok-7 is an essential activator of MuSK, and its activation and NMJ formation are enhanced in the Dok-7 transgenic (Tg) mice, in which Dok-7 is specifically overexpressed in skeletal muscle. Although Dok-7 Tg mice develop abnormally large NMJs but show normal motor function, the forced expression of Dok-7 in the muscle improves impaired motor activity in mouse models of neuromuscular disorders with NMJ defects. However, the effect of Dok-7 overexpression in skeletal muscle on ultrastructure and neuromuscular transmission of NMJs is yet to be studied. Here, we investigated the structural and electrophysiological properties of NMJs in the diaphragm muscle of 8-week-old Dok-7 Tg mice. The areas of the presynaptic motor nerve terminals and postsynaptic muscle membrane of NMJs were 2.7 and 4.3 times greater in Dok-7 Tg mice than in WT mice, respectively. Electrophysiological analyses revealed that neuromuscular transmission via NMJs in Dok-7 Tg mice was significantly enhanced but not proportionally with the increased size of the synaptic contact. Consistent with this, the densities of active zones and synaptic vesicles (ACh carriers) in the presynaptic motor nerve terminals were reduced. In addition, the density and size of postsynaptic junctional folds in the muscle membrane were also reduced. Moreover, terminal Schwann cells exhibited significantly greater penetration of their processes into the synaptic clefts, which connect the pre- and post-synaptic specializations. Together, our findings demonstrate that transgenic overexpression of Dok-7 in the skeletal muscle enhances neuromuscular transmission with significant enlargement and ultrastructural alterations of NMJs, the latter of which might prevent toxic overactivation of AChRs at the abnormally enlarged NMJs.
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Huijbers MG, Verschuuren JJGM. Treating muscle-specific kinase myasthenia gravis from the inside out. NEUROLOGY-NEUROIMMUNOLOGY & NEUROINFLAMMATION 2019; 7:7/1/e646. [PMID: 31831572 PMCID: PMC6935833 DOI: 10.1212/nxi.0000000000000646] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 10/30/2019] [Indexed: 11/21/2022]
Affiliation(s)
- Maartje G Huijbers
- From the Department of Neurology (M.G.H., J.J.G.M.V.) and Department of Human Genetics (M.G.H.), Leiden University Medical Center, The Netherlands
| | - Jan J G M Verschuuren
- From the Department of Neurology (M.G.H., J.J.G.M.V.) and Department of Human Genetics (M.G.H.), Leiden University Medical Center, The Netherlands.
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Trajanovska S, Ban J, Huang J, Gregorevic P, Morsch M, Allen DG, Phillips WD. Muscle specific kinase protects dystrophic mdx mouse muscles from eccentric contraction-induced loss of force-producing capacity. J Physiol 2019; 597:4831-4850. [PMID: 31340406 DOI: 10.1113/jp277839] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 07/17/2019] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS Adeno-associated viral vector was used to elevate the expression of muscle specific kinase (MuSK) and rapsyn (a cytoplasmic MuSK effector protein) in the tibialis anterior muscle of wild-type and dystrophic (mdx) mice. In mdx mice, enhanced expression of either MuSK or rapsyn ameliorated the acute loss of muscle force associated with strain injury. Increases in sarcolemmal immunolabelling for utrophin and β-dystroglycan suggest a mechanism for the protective effect of MuSK in mdx muscles. MuSK also caused subtle changes to the structure and function of the neuromuscular junction, suggesting novel roles for MuSK in muscle physiology and pathophysiology. ABSTRACT Muscle specific kinase (MuSK) has a well-defined role in stabilizing the developing mammalian neuromuscular junction, but MuSK might also be protective in some neuromuscular diseases. In the dystrophin-deficient mdx mouse model of Duchenne muscular dystrophy, limb muscles are especially fragile. We injected the tibialis anterior muscle of 8-week-old mdx and wild-type (C57BL10) mice with adeno-associated viral vectors encoding either MuSK or rapsyn (a cytoplasmic MuSK effector protein) fused to green fluorescent protein (MuSK-GFP and rapsyn-GFP, respectively). Contralateral muscles injected with empty vector served as controls. One month later mice were anaesthetized with isoflurane and isometric force-producing capacity was recorded from the distal tendon. MuSK-GFP caused an unexpected decay in nerve-evoked tetanic force, both in wild-type and mdx muscles, without affecting contraction elicited by direct electrical stimulation of the muscle. Muscle fragility was probed by challenging muscles with a strain injury protocol consisting of a series of four strain-producing eccentric contractions in vivo. When applied to muscles of mdx mice, eccentric contraction produced an acute 27% reduction in directly evoked muscle force output, affirming the susceptibility of mdx muscles to strain injury. mdx muscles overexpressing MuSK-GFP or rapsyn-GFP exhibited significantly milder force deficits after the eccentric contraction challenge (15% and 14%, respectively). The protective effect of MuSK-GFP in muscles of mdx mice was associated with increased immunolabelling for utrophin and β-dystroglycan in the sarcolemma. Elevating the expression of MuSK or rapsyn revealed several distinct synaptic and extrasynaptic effects, suggesting novel roles for MuSK signalling in muscle physiology and pathophysiology.
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Affiliation(s)
- S Trajanovska
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
| | - J Ban
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
| | - J Huang
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
| | - P Gregorevic
- Department of Physiology, The University of Melbourne, Melbourne, Victoria, Australia.,Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia.,Department of Neurology, University of Washington School of Medicine, Seattle, WA, USA
| | - M Morsch
- Department of Biomedical Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - D G Allen
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
| | - W D Phillips
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
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40
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McMacken G, Cox D, Roos A, Müller J, Whittaker R, Lochmüller H. The beta-adrenergic agonist salbutamol modulates neuromuscular junction formation in zebrafish models of human myasthenic syndromes. Hum Mol Genet 2019; 27:1556-1564. [PMID: 29462491 PMCID: PMC5905648 DOI: 10.1093/hmg/ddy062] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Accepted: 02/14/2018] [Indexed: 11/15/2022] Open
Abstract
Inherited defects of the neuromuscular junction (NMJ) comprise an increasingly diverse range of disorders, termed congenital myasthenic syndromes (CMS). Therapies acting on the sympathetic nervous system, including the selective β2 adrenergic agonist salbutamol and the α and β adrenergic agonist ephedrine, have become standard treatment for several types of CMS. However, the mechanism of the therapeutic effect of sympathomimetics in these disorders is not understood. Here, we examined the effect of salbutamol on NMJ development using zebrafish with deficiency of the key postsynaptic proteins Dok-7 and MuSK. Treatment with salbutamol reduced motility defects in zebrafish embryos and larvae. In addition, salbutamol lead to morphological improvement of postsynaptic acetycholine receptor (AChR) clustering and size of synaptic contacts in Dok-7-deficient zebrafish. In MuSK-deficient zebrafish, salbutamol treatment reduced motor axon pathfinding defects and partially restored the formation of aneural prepatterned AChRs. In addition, the effects of salbutamol treatment were prevented by pre-treatment with a selective β2 antagonist. Treatment with the cyclic adenosine monophosphate (cAMP) activator forskolin, replicated the effects of salbutamol treatment. These results suggest that sympathomimetics exert a direct effect on neuromuscular synaptogenesis and do so via β2 adrenoceptors and via a cAMP-dependent pathway.
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Affiliation(s)
- Grace McMacken
- Institute of Genetic Medicine, The John Walton Muscular Dystrophy Research Centre, Newcastle University, International Centre for Life, Newcastle Upon Tyne NE1 3BZ, UK
| | - Dan Cox
- Institute of Genetic Medicine, The John Walton Muscular Dystrophy Research Centre, Newcastle University, International Centre for Life, Newcastle Upon Tyne NE1 3BZ, UK
| | - Andreas Roos
- Institute of Genetic Medicine, The John Walton Muscular Dystrophy Research Centre, Newcastle University, International Centre for Life, Newcastle Upon Tyne NE1 3BZ, UK.,Tissue Omics Project Group, Biomedical Research Department, Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., 44227 Dortmund, Germany
| | - Juliane Müller
- Institute of Genetic Medicine, Wellcome Trust Centre for Mitochondrial Research, Newcastle University, International Centre for Life, Newcastle Upon Tyne NE1 3BZ, UK
| | - Roger Whittaker
- Institute of Neuroscience, Newcastle University, Newcastle Upon Tyne NE1 7RU, UK
| | - Hanns Lochmüller
- Institute of Genetic Medicine, The John Walton Muscular Dystrophy Research Centre, Newcastle University, International Centre for Life, Newcastle Upon Tyne NE1 3BZ, UK
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41
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Animal Models of the Neuromuscular Junction, Vitally Informative for Understanding Function and the Molecular Mechanisms of Congenital Myasthenic Syndromes. Int J Mol Sci 2018; 19:ijms19051326. [PMID: 29710836 PMCID: PMC5983836 DOI: 10.3390/ijms19051326] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 04/24/2018] [Accepted: 04/25/2018] [Indexed: 01/16/2023] Open
Abstract
The neuromuscular junction is the point of contact between motor nerve and skeletal muscle, its vital role in muscle function is reliant on the precise location and function of many proteins. Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders of neuromuscular transmission with 30 or more implicated proteins. The use of animal models has been instrumental in determining the specific role of many CMS-related proteins. The mouse neuromuscular junction (NMJ) has been extensively studied in animal models of CMS due to its amenability for detailed electrophysiological and histological investigations and relative similarity to human NMJ. As well as their use to determine the precise molecular mechanisms of CMS variants, where an animal model accurately reflects the human phenotype they become useful tools for study of therapeutic interventions. Many of the animal models that have been important in deconvolving the complexities of neuromuscular transmission and revealing the molecular mechanisms of disease are highlighted.
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42
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Dowling JJ, D. Gonorazky H, Cohn RD, Campbell C. Treating pediatric neuromuscular disorders: The future is now. Am J Med Genet A 2018; 176:804-841. [PMID: 28889642 PMCID: PMC5900978 DOI: 10.1002/ajmg.a.38418] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 07/31/2017] [Indexed: 12/12/2022]
Abstract
Pediatric neuromuscular diseases encompass all disorders with onset in childhood and where the primary area of pathology is in the peripheral nervous system. These conditions are largely genetic in etiology, and only those with a genetic underpinning will be presented in this review. This includes disorders of the anterior horn cell (e.g., spinal muscular atrophy), peripheral nerve (e.g., Charcot-Marie-Tooth disease), the neuromuscular junction (e.g., congenital myasthenic syndrome), and the muscle (myopathies and muscular dystrophies). Historically, pediatric neuromuscular disorders have uniformly been considered to be without treatment possibilities and to have dire prognoses. This perception has gradually changed, starting in part with the discovery and widespread application of corticosteroids for Duchenne muscular dystrophy. At present, several exciting therapeutic avenues are under investigation for a range of conditions, offering the potential for significant improvements in patient morbidities and mortality and, in some cases, curative intervention. In this review, we will present the current state of treatment for the most common pediatric neuromuscular conditions, and detail the treatment strategies with the greatest potential for helping with these devastating diseases.
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Affiliation(s)
- James J. Dowling
- Division of NeurologyHospital for Sick ChildrenTorontoOntarioCanada
- Program for Genetics and Genome BiologyHospital for Sick ChildrenTorontoOntarioCanada
- Departments of Paediatrics and Molecular GeneticsUniversity of TorontoTorontoOntarioCanada
| | | | - Ronald D. Cohn
- Program for Genetics and Genome BiologyHospital for Sick ChildrenTorontoOntarioCanada
- Departments of Paediatrics and Molecular GeneticsUniversity of TorontoTorontoOntarioCanada
| | - Craig Campbell
- Department of PediatricsClinical Neurological SciencesEpidemiologyWestern UniversityLondonOntarioCanada
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43
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Miyoshi S, Tezuka T, Arimura S, Tomono T, Okada T, Yamanashi Y. DOK7 gene therapy enhances motor activity and life span in ALS model mice. EMBO Mol Med 2018; 9:880-889. [PMID: 28490573 PMCID: PMC5494517 DOI: 10.15252/emmm.201607298] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive, multifactorial motor neurodegenerative disease with severe muscle atrophy. The glutamate release inhibitor riluzole is the only medication approved by the FDA, and prolongs patient life span by a few months, testifying to a strong need for new treatment strategies. In ALS, motor neuron degeneration first becomes evident at the motor nerve terminals in neuromuscular junctions (NMJs), the cholinergic synapse between motor neuron and skeletal muscle; degeneration then progresses proximally, implicating the NMJ as a therapeutic target. We previously demonstrated that activation of muscle‐specific kinase MuSK by the cytoplasmic protein Dok‐7 is essential for NMJ formation, and forced expression of Dok‐7 in muscle activates MuSK and enlarges NMJs. Here, we show that therapeutic administration of an adeno‐associated virus vector encoding the human DOK7 gene suppressed motor nerve terminal degeneration at NMJs together with muscle atrophy in the SOD1‐G93A ALS mouse model. Ultimately, we show that DOK7 gene therapy enhanced motor activity and life span in ALS model mice.
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Affiliation(s)
- Sadanori Miyoshi
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Tohru Tezuka
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Sumimasa Arimura
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Taro Tomono
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan.,Graduate School of Comprehensive Human Sciences, Majors in Medical Sciences University of Tsukuba, Ibaraki, Japan
| | - Takashi Okada
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan
| | - Yuji Yamanashi
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
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44
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Cantor S, Zhang W, Delestrée N, Remédio L, Mentis GZ, Burden SJ. Preserving neuromuscular synapses in ALS by stimulating MuSK with a therapeutic agonist antibody. eLife 2018; 7:34375. [PMID: 29460776 PMCID: PMC5837562 DOI: 10.7554/elife.34375] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 02/02/2018] [Indexed: 12/22/2022] Open
Abstract
In amyotrophic lateral sclerosis (ALS) and animal models of ALS, including SOD1-G93A mice, disassembly of the neuromuscular synapse precedes motor neuron loss and is sufficient to cause a decline in motor function that culminates in lethal respiratory paralysis. We treated SOD1-G93A mice with an agonist antibody to MuSK, a receptor tyrosine kinase essential for maintaining neuromuscular synapses, to determine whether increasing muscle retrograde signaling would slow nerve terminal detachment from muscle. The agonist antibody, delivered after disease onset, slowed muscle denervation, promoting motor neuron survival, improving motor system output, and extending the lifespan of SOD1-G93A mice. These findings suggest a novel therapeutic strategy for ALS, using an antibody format with clinical precedence, which targets a pathway essential for maintaining attachment of nerve terminals to muscle. Amyotrophic lateral sclerosis – often shortened to ALS – is a disease that starts with difficulties moving and progresses to paralysis of many muscles, including those used for breathing. The disease is usually lethal, with patients rarely surviving more than a few years after diagnosis. There is no cure or effective treatment for the disease. It begins with the breakdown of the connections, or synapses, between the muscles and the nerve cells that connect with them. After this, the nerve cell itself breaks down. Many therapeutic approaches have focused on attempts to prevent the nerve cells from dying, but few target the initial degeneration of the synapse. Cantor et al. asked if intervening when the synapse has already begun to break down could slow the progression of the disease in mice with ALS. Their approach involved using an antibody to bind to a receptor protein called MuSK, which plays an important role in maintaining the synapse between muscle and nerve cell. The antibody boosted the receptor’s activity, helping to preserve synapses, including those that connect nerve cells to the diaphragm muscle. The experiments showed that the antibody treatment led to fewer synapses breaking down, and kept more of the nerve cells alive. Healthier connections between the nervous system and the diaphragm improved the function of this muscle. As a result, the mice given the antibody treatment had a slightly extended lifespan, compared with those given no treatment. The findings suggest a possible new way to develop treatments for ALS, which could be used in combination with other therapies, such as those aimed at improving the health of the nerve cells. Together, this could improve quality of life for the majority of patients with ALS. Similar strategies could be used to develop treatments to preserve synapses in other neurodegenerative diseases, such as Alzheimer’s, Parkinson’s and Huntington’s disease, as well as some kinds of dementia. Preserving synapses early on, before the significant loss of nerve cells, could help to slow the progression of these diseases, improve the patients' quality of life and extend their lifespans too.
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Affiliation(s)
- Sarah Cantor
- Molecular Neurobiology Program, Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU Medical School, New York, United States
| | - Wei Zhang
- Molecular Neurobiology Program, Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU Medical School, New York, United States
| | - Nicolas Delestrée
- Center for Motor Neuron Biology and Disease and Departments of Pathology and Cell Biology and Neurology, Columbia University, New York, United States
| | - Leonor Remédio
- Molecular Neurobiology Program, Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU Medical School, New York, United States
| | - George Z Mentis
- Center for Motor Neuron Biology and Disease and Departments of Pathology and Cell Biology and Neurology, Columbia University, New York, United States
| | - Steven J Burden
- Molecular Neurobiology Program, Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU Medical School, New York, United States
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45
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Affiliation(s)
- Lei Li
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Wen-Cheng Xiong
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
- Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
| | - Lin Mei
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
- Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
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46
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Fundamental Molecules and Mechanisms for Forming and Maintaining Neuromuscular Synapses. Int J Mol Sci 2018; 19:ijms19020490. [PMID: 29415504 PMCID: PMC5855712 DOI: 10.3390/ijms19020490] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 01/24/2018] [Accepted: 01/29/2018] [Indexed: 02/08/2023] Open
Abstract
The neuromuscular synapse is a relatively large synapse with hundreds of active zones in presynaptic motor nerve terminals and more than ten million acetylcholine receptors (AChRs) in the postsynaptic membrane. The enrichment of proteins in presynaptic and postsynaptic membranes ensures a rapid, robust, and reliable synaptic transmission. Over fifty years ago, classic studies of the neuromuscular synapse led to a comprehensive understanding of how a synapse looks and works, but these landmark studies did not reveal the molecular mechanisms responsible for building and maintaining a synapse. During the past two-dozen years, the critical molecular players, responsible for assembling the specialized postsynaptic membrane and regulating nerve terminal differentiation, have begun to be identified and their mechanism of action better understood. Here, we describe and discuss five of these key molecular players, paying heed to their discovery as well as describing their currently understood mechanisms of action. In addition, we discuss the important gaps that remain to better understand how these proteins act to control synaptic differentiation and maintenance.
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47
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O'Connor E, Töpf A, Zahedi RP, Spendiff S, Cox D, Roos A, Lochmüller H. Clinical and research strategies for limb-girdle congenital myasthenic syndromes. Ann N Y Acad Sci 2018; 1412:102-112. [PMID: 29315608 DOI: 10.1111/nyas.13520] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/05/2017] [Accepted: 09/12/2017] [Indexed: 12/21/2022]
Abstract
Congenital myasthenic syndromes (CMS) are a group of rare disorders that cause fatigable muscle weakness due to defective signal transmission at the neuromuscular junction, a specialized synapse between peripheral motor neurons and their target muscle fibers. There are now over 30 causative genes that have been reported for CMS. Of these, there are 10 that are associated with a limb-girdle pattern of muscle weakness and are thus classed as LG-CMS. Next-generation sequencing and advanced methods of data sharing are likely to uncover further genes that are associated with similar clinical phenotypes, contributing to better diagnosis and effective treatment of LG-CMS patients. This review highlights clinical and pathological hallmarks of LG-CMS in relation to the underlying genetic defects and pathways. Tailored animal and cell models are essential to elucidate the exact function and pathomechanisms at the neuromuscular synapse that underlie LG-CMS. The integration of genomics and proteomics data derived from these models and patients reveals new and often unexpected insights that are relevant beyond the rare genetic disorder of LG-CMS and may extend to the functioning of mammalian synapses in health and disease more generally.
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Affiliation(s)
- Emily O'Connor
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Ana Töpf
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - René P Zahedi
- Leibniz-Institut für Analytische Wissenschaften, ISAS e.V., Dortmund, Germany
| | - Sally Spendiff
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Daniel Cox
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Andreas Roos
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK.,Leibniz-Institut für Analytische Wissenschaften, ISAS e.V., Dortmund, Germany
| | - Hanns Lochmüller
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
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48
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Ghazanfari N, Trajanovska S, Morsch M, Liang SX, Reddel SW, Phillips WD. The mouse passive-transfer model of MuSK myasthenia gravis: disrupted MuSK signaling causes synapse failure. Ann N Y Acad Sci 2017; 1412:54-61. [DOI: 10.1111/nyas.13513] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 09/05/2017] [Accepted: 09/09/2017] [Indexed: 12/21/2022]
Affiliation(s)
- Nazanin Ghazanfari
- Physiology and Bosch Institute; University of Sydney; Sydney New South Wales Australia
| | - Sofie Trajanovska
- Physiology and Bosch Institute; University of Sydney; Sydney New South Wales Australia
| | - Marco Morsch
- Physiology and Bosch Institute; University of Sydney; Sydney New South Wales Australia
- Department of Biomedical Sciences; Macquarie University; Sydney New South Wales Australia
| | - Simon X. Liang
- Department of Biochemistry and Molecular Biology, College of Basic Medical Sciences; Liaoning Medical University; Jinzhou China
| | - Stephen W. Reddel
- Department of Molecular Medicine; Concord Hospital; Sydney New South Wales Australia
| | - William D. Phillips
- Physiology and Bosch Institute; University of Sydney; Sydney New South Wales Australia
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49
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Xu Z, Feng X, Dong J, Wang ZM, Lee J, Furdui C, Files DC, Beavers KM, Kritchevsky S, Milligan C, Jin JP, Delbono O, Zhang T. Cardiac troponin T and fast skeletal muscle denervation in ageing. J Cachexia Sarcopenia Muscle 2017; 8:808-823. [PMID: 28419739 PMCID: PMC5659053 DOI: 10.1002/jcsm.12204] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 02/13/2017] [Accepted: 03/01/2017] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Ageing skeletal muscle undergoes chronic denervation, and the neuromuscular junction (NMJ), the key structure that connects motor neuron nerves with muscle cells, shows increased defects with ageing. Previous studies in various species have shown that with ageing, type II fast-twitch skeletal muscle fibres show more atrophy and NMJ deterioration than type I slow-twitch fibres. However, how this process is regulated is largely unknown. A better understanding of the mechanisms regulating skeletal muscle fibre-type specific denervation at the NMJ could be critical to identifying novel treatments for sarcopenia. Cardiac troponin T (cTnT), the heart muscle-specific isoform of TnT, is a key component of the mechanisms of muscle contraction. It is expressed in skeletal muscle during early development, after acute sciatic nerve denervation, in various neuromuscular diseases and possibly in ageing muscle. Yet the subcellular localization and function of cTnT in skeletal muscle is largely unknown. METHODS Studies were carried out on isolated skeletal muscles from mice, vervet monkeys, and humans. Immunoblotting, immunoprecipitation, and mass spectrometry were used to analyse protein expression, real-time reverse transcription polymerase chain reaction was used to measure gene expression, immunofluorescence staining was performed for subcellular distribution assay of proteins, and electromyographic recording was used to analyse neurotransmission at the NMJ. RESULTS Levels of cTnT expression in skeletal muscle increased with ageing in mice. In addition, cTnT was highly enriched at the NMJ region-but mainly in the fast-twitch, not the slow-twitch, muscle of old mice. We further found that the protein kinase A (PKA) RIα subunit was largely removed from, while PKA RIIα and RIIβ are enriched at, the NMJ-again, preferentially in fast-twitch but not slow-twitch muscle in old mice. Knocking down cTnT in fast skeletal muscle of old mice: (i) increased PKA RIα and reduced PKA RIIα at the NMJ; (ii) decreased the levels of gene expression of muscle denervation markers; and (iii) enhanced neurotransmission efficiency at NMJ. CONCLUSIONS Cardiac troponin T at the NMJ region contributes to NMJ functional decline with ageing mainly in the fast-twitch skeletal muscle through interfering with PKA signalling. This knowledge could inform useful targets for prevention and therapy of age-related decline in muscle function.
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Affiliation(s)
- Zherong Xu
- Department of Internal Medicine, Section on Gerontology and Geriatic Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA.,Department of Geriatrics, First Affiliated Hospital, Zhejiang University, School of Medicine, Hangzhou, China
| | - Xin Feng
- Department of Otolaryngology, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Juan Dong
- Department of Internal Medicine, Section on Gerontology and Geriatic Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Zhong-Min Wang
- Department of Internal Medicine, Section on Gerontology and Geriatic Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Jingyun Lee
- Department of Internal Medicine, Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Cristina Furdui
- Department of Internal Medicine, Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Daniel Clark Files
- Internal Medicine-Pulmonary, Critical Care, Allergy and Immunology, Gerontology and Geriatric Medicine and the Critical Illness Injury and Recovery Research Center, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Kristen M Beavers
- Department of Health and Exercise Science, Wake Forest University, Winston-Salem, NC, USA
| | - Stephen Kritchevsky
- Department of Internal Medicine, Section on Gerontology and Geriatic Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA.,Sticht Center for Healthy Aging and Alzheimer's Prevention, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Carolanne Milligan
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Jian-Ping Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Osvaldo Delbono
- Department of Internal Medicine, Section on Gerontology and Geriatic Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA.,Sticht Center for Healthy Aging and Alzheimer's Prevention, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Tan Zhang
- Department of Internal Medicine, Section on Gerontology and Geriatic Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA.,Sticht Center for Healthy Aging and Alzheimer's Prevention, Wake Forest School of Medicine, Winston-Salem, NC, USA
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Yano M, Minegishi Y, Sugita S, Ota N. Milk fat globule membrane supplementation with voluntary running exercise attenuates age-related motor dysfunction by suppressing neuromuscular junction abnormalities in mice. Exp Gerontol 2017; 97:29-37. [PMID: 28729214 DOI: 10.1016/j.exger.2017.07.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 07/05/2017] [Accepted: 07/17/2017] [Indexed: 11/28/2022]
Abstract
Age-related loss of skeletal muscle mass and function attenuates physical performance, and maintaining fine muscle innervation is known to play an important role in its prevention. We had previously shown that consumption of milk fat globule membrane (MFGM) with habitual exercise improves the muscle mass and motor function in humans and mice. Improvement of neuromuscular junction (NMJ) was suggested as one of the mechanisms underlying these effects. In this study, we evaluated the effect of MFGM intake combined with voluntary running (MFGM-VR) on morphological changes of NMJ and motor function in aging mice. Seven months following the intervention, the MFGM-VR group showed a significantly improved motor coordination in the rotarod test and muscle force in the grip strength test compared with the control group at 13 and 14months of age, respectively. In 14-month old control mice, the extensor digitorum longus muscle showed increased abnormal NMJs, such as fragmentation and denervation, compared with 6-month old young mice. However, such age-related deteriorations of NMJs were significantly suppressed in the MFGM-VR group. Increase in the expression of NMJ formation-related genes, such as agrin and LDL Receptor Related Protein 4 (LRP4), might contribute to this beneficial effect. Rotarod performance and grip strength showed significant negative correlation with the status of denervation and fragmentation of NMJs. These results suggest that MFGM intake with voluntary running exercise effectively suppresses age-related morphological deterioration of NMJ, thus contributing to improvement of motor function.
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Affiliation(s)
- Michiko Yano
- Biological Science Research, Kao Corporation, 2606 Akabane, Ichikai-machi, Haga-gun, Tochigi 321-3497, Japan
| | - Yoshihiko Minegishi
- Biological Science Research, Kao Corporation, 2606 Akabane, Ichikai-machi, Haga-gun, Tochigi 321-3497, Japan
| | - Satoshi Sugita
- Biological Science Research, Kao Corporation, 2606 Akabane, Ichikai-machi, Haga-gun, Tochigi 321-3497, Japan
| | - Noriyasu Ota
- Biological Science Research, Kao Corporation, 2606 Akabane, Ichikai-machi, Haga-gun, Tochigi 321-3497, Japan.
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