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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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Functional monovalency amplifies the pathogenicity of anti-MuSK IgG4 in myasthenia gravis. Proc Natl Acad Sci U S A 2021; 118:2020635118. [PMID: 33753489 PMCID: PMC8020787 DOI: 10.1073/pnas.2020635118] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
An expanding group of autoimmune diseases is now recognized to be hallmarked by pathogenic IgG4 autoantibodies. IgG4 has the unique ability to exchange Fab-arms, rendering it bispecific and functionally monovalent. Here we show that autoantibody functional monovalency significantly amplifies the pathogenicity of IgG4 autoantibodies using patient-derived monoclonal antibodies in an in vivo model of MuSK myasthenia gravis. Therefore, subclass switching to predominant IgG4 autoantibodies is a critical step in the development of MuSK myasthenia gravis. This new mechanism in autoimmunity is also potentially relevant to 29 other IgG4-mediated autoimmune diseases known to date, allergy and other disease settings where IgG4 antibodies contribute to pathology. Human immunoglobulin (Ig) G4 usually displays antiinflammatory activity, and observations of IgG4 autoantibodies causing severe autoimmune disorders are therefore poorly understood. In blood, IgG4 naturally engages in a stochastic process termed “Fab-arm exchange” in which unrelated IgG4s exchange half-molecules continuously. The resulting IgG4 antibodies are composed of two different binding sites, thereby acquiring monovalent binding and inability to cross-link for each antigen recognized. Here, we demonstrate that this process amplifies autoantibody pathogenicity in a classic IgG4-mediated autoimmune disease: muscle-specific kinase (MuSK) myasthenia gravis. In mice, monovalent anti-MuSK IgG4s caused rapid and severe myasthenic muscle weakness, whereas the same antibodies in their parental bivalent form were less potent or did not induce a phenotype. Mechanistically this could be explained by opposing effects on MuSK signaling. Isotype switching to IgG4 in an autoimmune response thereby may be a critical step in the development of disease. Our study establishes functional monovalency as a pathogenic mechanism in IgG4-mediated autoimmune disease and potentially other disorders.
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Ge D, Odierna GL, Phillips WD. Influence of cannabinoids upon nerve-evoked skeletal muscle contraction. Neurosci Lett 2020; 725:134900. [DOI: 10.1016/j.neulet.2020.134900] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 03/03/2020] [Accepted: 03/06/2020] [Indexed: 02/07/2023]
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Pęziński M, Daszczuk P, Pradhan BS, Lochmüller H, Prószyński TJ. An improved method for culturing myotubes on laminins for the robust clustering of postsynaptic machinery. Sci Rep 2020; 10:4524. [PMID: 32161296 PMCID: PMC7066178 DOI: 10.1038/s41598-020-61347-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 02/20/2020] [Indexed: 01/03/2023] Open
Abstract
Motor neurons form specialized synapses with skeletal muscle fibers, called neuromuscular junctions (NMJs). Cultured myotubes are used as a simplified in vitro system to study the postsynaptic specialization of muscles. The stimulation of myotubes with the glycoprotein agrin or laminin-111 induces the clustering of postsynaptic machinery that contains acetylcholine receptors (AChRs). When myotubes are grown on laminin-coated surfaces, AChR clusters undergo developmental remodeling to form topologically complex structures that resemble mature NMJs. Needing further exploration are the molecular processes that govern AChR cluster assembly and its developmental maturation. Here, we describe an improved protocol for culturing muscle cells to promote the formation of complex AChR clusters. We screened various laminin isoforms and showed that laminin-221 was the most potent for inducing AChR clusters, whereas laminin-121, laminin-211, and laminin-221 afforded the highest percentages of topologically complex assemblies. Human primary myotubes that were formed by myoblasts obtained from patient biopsies also assembled AChR clusters that underwent remodeling in vitro. Collectively, these results demonstrate an advancement of culturing myotubes that can facilitate high-throughput screening for potential therapeutic targets for neuromuscular disorders.
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Affiliation(s)
- Marcin Pęziński
- Laboratory of Synaptogenesis, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Patrycja Daszczuk
- Laboratory of Synaptogenesis, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Bhola Shankar Pradhan
- Laboratory of Synaptogenesis, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.,Łukasiewicz Research Network - PORT Polish Center for Technology Development, Wrocław, Poland
| | - Hanns Lochmüller
- Department of Neuropediatrics and Muscle Disorders, Faculty of Medicine, Medical Centre, University of Freiburg, Freiburg, Germany.,Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada.,Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, Canada
| | - Tomasz J Prószyński
- Laboratory of Synaptogenesis, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland. .,Łukasiewicz Research Network - PORT Polish Center for Technology Development, Wrocław, Poland.
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Huda R. New Approaches to Targeting B Cells for Myasthenia Gravis Therapy. Front Immunol 2020; 11:240. [PMID: 32153573 PMCID: PMC7047318 DOI: 10.3389/fimmu.2020.00240] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 01/29/2020] [Indexed: 01/06/2023] Open
Abstract
Current therapies for myasthenia gravis (MG) are limited, and many investigations have recently focused on target-specific therapies. B cell-targeting monoclonal antibody (mAb) therapies for MG are increasingly attractive due to their specificity and efficacy. The targeted B cell biomarkers are mainly the cluster of differentiation (CD) proteins that mediate maturation, differentiation, or survival of pathogenic B cells. Additional B cell-directed therapies include non-specific peptide inhibitors that preferentially target specific B cell subsets. The primary goals of such therapies are to intercept autoantibodies and prevent the generation of an inflammatory response that contributes to the pathogenesis of MG. Treatment of patients with MG using B cell-directed mAbs, antibody fragments, or selective inhibitors have exhibited moderate to high efficacy in early studies, and some of these therapies appear to be highly promising for further drug development. Numerous other biologics targeting various B cell surface molecules have been approved for the treatment of other conditions or are either in clinical trials or preclinical development stages. These approaches remain to be tested in patients with MG or animal models of the disease. This review article provides an overview of B cell-targeted treatments for MG, including those already available and those still in preclinical and clinical development. We also discuss the potential benefits as well as the shortcomings of these approaches to development of new therapies for MG and future directions in the field.
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Affiliation(s)
- Ruksana Huda
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States
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Abstract
This article discusses antibodies associated with immune-mediated myasthenia gravis and the pathologic action of these antibodies at the neuromuscular junctions of skeletal muscle. To explain how these antibodies act, we consider the physiology of neuromuscular transmission with emphasis on 4 features: the structure of the neuromuscular junction; the roles of postsynaptic acetylcholine receptors and voltage-gated Na+ channels and in converting the chemical signal from the nerve terminal into a propagated action potential on the muscle fiber that triggers muscle contraction; the safety factor for neuromuscular transmission; and how the safety factor is reduced in different forms of autoimmune myasthenia gravis.
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Affiliation(s)
- Robert L Ruff
- Department of Neurology, Case Western University School of Medicine, The Metro Health System, 2500 Metro Health Drive, Cleveland, OH 44109, USA; Department of Neurosciences, Case Western Reserve University, Cleveland, OH, USA
| | - Robert P Lisak
- Department of Neurology, Wayne State University School of Medicine, 8D University Health Center, 4201 St Antoine, Detroit, MI 48201, USA; Department of Biochemistry, Microbiology and Immunology, Wayne State University, Detroit, MI, USA.
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7
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Cognitive dysfunction in mice with passively induced MuSK antibody seropositive myasthenia gravis. J Neurol Sci 2019; 399:15-21. [DOI: 10.1016/j.jns.2019.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 01/23/2019] [Accepted: 02/01/2019] [Indexed: 11/19/2022]
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miR-1933-3p is upregulated in skeletal muscles of MuSK+ EAMG mice and affects Impa1 and Mrpl27. Neurosci Res 2019; 151:46-52. [PMID: 30763589 DOI: 10.1016/j.neures.2019.02.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 02/03/2019] [Accepted: 02/06/2019] [Indexed: 12/15/2022]
Abstract
MuSK antibody seropositive (MuSK+) Myasthenia Gravis (MG) typically affects skeletal muscles of the bulbar area, including the omohyoid muscle, causing focal fatigue, weakness and atrophy. The profile of circulating extracellular microRNA (miRNA) is changed in MuSK + MG, but the intracellular miRNA profile in skeletal muscles of MuSK + MG and MuSK + experimental autoimmune MG (EAMG) remains unknown. This study elucidated the intracellular miRNA profile in the omohyoid muscle of mice with MuSK + EAMG. The levels of eleven mouse miRNAs were elevated and two mouse miRNAs were reduced in muscles of MuSK + EAMG mice. Transient expression of miR-1933-3p and miR-1930-5p in mouse muscle (C2C12) cells revealed several downregulated genes, out of which five had predicted binding sites for miR-1933-3p. The mRNA expression of mitochondrial ribosomal protein L27 (Mrpl27) and Inositol monophosphatase I (Impa1) was reduced in miR-1933-3p transfected C2C12 cells compared to control cells (p = 0.032 versus p = 0.020). Further, transient expression of miR-1933-3p reduced Impa1 protein accumulation in C2C12 cells. These findings provide novel insights of dysregulated miRNAs and their intracellular pathways in muscle tissue afflicted with MuSK + EAMG, providing a possible link to mitochondrial dysfunction and muscle atrophy observed in MuSK + MG.
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Morren J, Li Y. Myasthenia gravis with muscle-specific tyrosine kinase antibodies: A narrative review. Muscle Nerve 2018; 58:344-358. [DOI: 10.1002/mus.26107] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 02/09/2018] [Accepted: 02/18/2018] [Indexed: 12/14/2022]
Affiliation(s)
- John Morren
- Neuromuscular Center, Neurological Institute, Cleveland Clinic, 9500 Euclid Avenue, Desk S90; Cleveland Ohio 44195 USA
| | - Yuebing Li
- Neuromuscular Center, Neurological Institute, Cleveland Clinic, 9500 Euclid Avenue, Desk S90; Cleveland Ohio 44195 USA
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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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11
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Kichkin E, Visvanathan A, Lovicu FJ, Shu DY, Das SJ, Reddel SW, McCann EP, Zhang KY, Williams KL, Blair IP, Phillips WD. Postnatal Development of Spasticity Following Transgene Insertion in the Mouse βIV Spectrin Gene (SPTBN4). J Neuromuscul Dis 2017; 4:159-164. [PMID: 28582869 DOI: 10.3233/jnd-160197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The L25 mouse line was generated by random genomic insertion of a lens-specific transgene. Inbreeding of L25 hemizygotes revealed an unanticipated spastic phenotype in the hind limbs. OBJECTIVE The goals were to characterize the motor phenotype in the L25 mice and to map the transgene insert site within the mouse genome. METHODS Six pairs of L25+/- mice were repeatedly mated. Beginning at weaning, all progeny were inspected for body weight and motor signs twice weekly until they displayed predefined ethical criteria for termination. The transgene insert site was determined by whole genome sequencing. Western blotting was used to compare the expression levels of beta-IV spectrin protein in the brain. RESULTS Matings of hemizygous L25+/- × L25+/- mice yielded 20% (29/148) affected weanlings, identified by an abnormal retraction of the hind limbs when lifted by the tail, and a fine tremor. Affected mice were less mobile and grew more slowly than wild-type littermates. All affected mice required termination due to >15% loss of body weight (50% survival age 92 days). At the endpoint, mice showed varying degrees of spastic paresis or spastic paralysis localised to the hind limbs. Motor endplates remained fully innervated. Genome sequencing confirmed that the transgene was inserted in the locus of βIV spectrin of L25 mice. Western blotting indicated that this random insertion had greatly reduced the expression of βIV spectrin protein in the affected L25 mice. CONCLUSIONS The results confirm the importance of βIV spectrin for maintaining central motor pathway control of the hind limbs, and provide a developmental time course for the phenotype.
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Affiliation(s)
- Eva Kichkin
- Physiology and Bosch Institute, University of Sydney, Sydney, Australia
| | | | - Frank J Lovicu
- Anatomy and Histology and Bosch Institute, University of Sydney, Sydney, Australia
| | - Daisy Y Shu
- Anatomy and Histology and Bosch Institute, University of Sydney, Sydney, Australia
| | - Shannon J Das
- Anatomy and Histology and Bosch Institute, University of Sydney, Sydney, Australia
| | - Stephen W Reddel
- Department of Molecular Medicine, Concord Hospital, Sydney, Australia
| | - Emily P McCann
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, Australia
| | - Katharine Y Zhang
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, Australia
| | - Kelly L Williams
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, Australia
| | - Ian P Blair
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, Australia
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Abstract
Myasthenia gravis is an autoimmune disease of the neuromuscular junction (NMJ) caused by antibodies that attack components of the postsynaptic membrane, impair neuromuscular transmission, and lead to weakness and fatigue of skeletal muscle. This can be generalised or localised to certain muscle groups, and involvement of the bulbar and respiratory muscles can be life threatening. The pathogenesis of myasthenia gravis depends upon the target and isotype of the autoantibodies. Most cases are caused by immunoglobulin (Ig)G1 and IgG3 antibodies to the acetylcholine receptor (AChR). They produce complement-mediated damage and increase the rate of AChR turnover, both mechanisms causing loss of AChR from the postsynaptic membrane. The thymus gland is involved in many patients, and there are experimental and genetic approaches to understand the failure of immune tolerance to the AChR. In a proportion of those patients without AChR antibodies, antibodies to muscle-specific kinase (MuSK), or related proteins such as agrin and low-density lipoprotein receptor-related protein 4 (LRP4), are present. MuSK antibodies are predominantly IgG4 and cause disassembly of the neuromuscular junction by disrupting the physiological function of MuSK in synapse maintenance and adaptation. Here we discuss how knowledge of neuromuscular junction structure and function has fed into understanding the mechanisms of AChR and MuSK antibodies. Myasthenia gravis remains a paradigm for autoantibody-mediated conditions and these observations show how much there is still to learn about synaptic function and pathological mechanisms.
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Affiliation(s)
- William D Phillips
- Physiology and Bosch Institute, University of Sydney, Anderson Stuart Bldg (F13), Sydney, 2006, Australia
| | - Angela Vincent
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
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MuSK induced experimental autoimmune myasthenia gravis does not require IgG1 antibody to MuSK. J Neuroimmunol 2016; 295-296:84-92. [DOI: 10.1016/j.jneuroim.2016.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 03/22/2016] [Accepted: 04/04/2016] [Indexed: 11/18/2022]
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Mantegazza R, Cordiglieri C, Consonni A, Baggi F. Animal models of myasthenia gravis: utility and limitations. Int J Gen Med 2016; 9:53-64. [PMID: 27019601 PMCID: PMC4786081 DOI: 10.2147/ijgm.s88552] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Myasthenia gravis (MG) is a chronic autoimmune disease caused by the immune attack of the neuromuscular junction. Antibodies directed against the acetylcholine receptor (AChR) induce receptor degradation, complement cascade activation, and postsynaptic membrane destruction, resulting in functional reduction in AChR availability. Besides anti-AChR antibodies, other autoantibodies are known to play pathogenic roles in MG. The experimental autoimmune MG (EAMG) models have been of great help over the years in understanding the pathophysiological role of specific autoantibodies and T helper lymphocytes and in suggesting new therapies for prevention and modulation of the ongoing disease. EAMG can be induced in mice and rats of susceptible strains that show clinical symptoms mimicking the human disease. EAMG models are helpful for studying both the muscle and the immune compartments to evaluate new treatment perspectives. In this review, we concentrate on recent findings on EAMG models, focusing on their utility and limitations.
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Affiliation(s)
- Renato Mantegazza
- Neurology IV Unit, Neuroimmunology and Neuromuscular Disorders, Foundation IRCCS Neurological Institute "Carlo Besta", Milan, Italy
| | - Chiara Cordiglieri
- Neurology IV Unit, Neuroimmunology and Neuromuscular Disorders, Foundation IRCCS Neurological Institute "Carlo Besta", Milan, Italy
| | - Alessandra Consonni
- Neurology IV Unit, Neuroimmunology and Neuromuscular Disorders, Foundation IRCCS Neurological Institute "Carlo Besta", Milan, Italy
| | - Fulvio Baggi
- Neurology IV Unit, Neuroimmunology and Neuromuscular Disorders, Foundation IRCCS Neurological Institute "Carlo Besta", Milan, Italy
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Bradl M, Lassmann H. Neurologic autoimmunity: mechanisms revealed by animal models. HANDBOOK OF CLINICAL NEUROLOGY 2016; 133:121-43. [PMID: 27112675 DOI: 10.1016/b978-0-444-63432-0.00008-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Over the last decade, neurologic autoimmunity has become a major consideration in the diagnosis and management of patients with many neurologic presentations. The nature of the associated antibodies and their targets has led to appreciation of the importance of the accessibility of the target antigen to antibodies, and a partial understanding of the different mechanisms that can follow antibody binding. This chapter will first describe the basic principles of autoimmune inflammation and tissue damage in the central and peripheral nervous system, and will then demonstrate what has been learnt about neurologic autoimmunity from circumstantial clinical evidence and from passive, active, and occasionally spontaneous or genetic animal models. It will cover neurologic autoimmune diseases ranging from disorders of neuromuscular transmission, peripheral and ganglionic neuropathy, to diseases of the central nervous system, where autoantibodies are either pathogenic and cause destruction or changes in function of their targets, where they are harmless bystanders of T-cell-mediated tissue damage, or are not involved at all. Finally, this chapter will summarize the relevance of current animal models for studying the different neurologic autoimmune diseases, and it will identify aspects where future animal models need to be improved to better reflect the disease reality experienced by affected patients, e.g., the chronicity or the relapsing/remitting nature of their disease.
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Affiliation(s)
- Monika Bradl
- Department of Neuroimmunology, Center for Brain Research, Medical University Vienna, Vienna, Austria.
| | - Hans Lassmann
- Department of Neuroimmunology, Center for Brain Research, Medical University Vienna, Vienna, Austria
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Ghazanfari N, Linsao ELTB, Trajanovska S, Morsch M, Gregorevic P, Liang SX, Reddel SW, Phillips WD. Forced expression of muscle specific kinase slows postsynaptic acetylcholine receptor loss in a mouse model of MuSK myasthenia gravis. Physiol Rep 2015; 3:3/12/e12658. [PMID: 26702075 PMCID: PMC4760443 DOI: 10.14814/phy2.12658] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2015] [Accepted: 11/20/2015] [Indexed: 12/12/2022] Open
Abstract
We investigated the influence of postsynaptic tyrosine kinase signaling in a mouse model of muscle‐specific kinase (MuSK) myasthenia gravis (MG). Mice administered repeated daily injections of IgG from MuSK MG patients developed impaired neuromuscular transmission due to progressive loss of acetylcholine receptor (AChR) from the postsynaptic membrane of the neuromuscular junction. In this model, anti‐MuSK‐positive IgG caused a reduction in motor endplate immunolabeling for phosphorylated Src‐Y418 and AChR β‐subunit‐Y390 before any detectable loss of MuSK or AChR from the endplate. Adeno‐associated viral vector (rAAV) encoding MuSK fused to enhanced green fluorescent protein (MuSK‐EGFP) was injected into the tibialis anterior muscle to increase MuSK synthesis. When mice were subsequently challenged with 11 daily injections of IgG from MuSK MG patients, endplates expressing MuSK‐EGFP retained more MuSK and AChR than endplates of contralateral muscles administered empty vector. Recordings of compound muscle action potentials from myasthenic mice revealed less impairment of neuromuscular transmission in muscles that had been injected with rAAV‐MuSK‐EGFP than contralateral muscles (empty rAAV controls). In contrast to the effects of MuSK‐EGFP, forced expression of rapsyn‐EGFP provided no such protection to endplate AChR when mice were subsequently challenged with MuSK MG IgG. In summary, the immediate in vivo effect of MuSK autoantibodies was to suppress MuSK‐dependent tyrosine phosphorylation of proteins in the postsynaptic membrane, while increased MuSK synthesis protected endplates against AChR loss. These results support the hypothesis that reduced MuSK kinase signaling initiates the progressive disassembly of the postsynaptic membrane scaffold in this mouse model of MuSK MG.
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Affiliation(s)
- Nazanin Ghazanfari
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
| | - Erna L T B Linsao
- 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
| | - Paul Gregorevic
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Simon X Liang
- Department of Biochemistry and Molecular Biology, College of Basic Medical Sciences, Liaoning Medical University, Liaoning, 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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Collagen Q and anti-MuSK autoantibody competitively suppress agrin/LRP4/MuSK signaling. Sci Rep 2015; 5:13928. [PMID: 26355076 PMCID: PMC4564764 DOI: 10.1038/srep13928] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 08/11/2015] [Indexed: 11/25/2022] Open
Abstract
MuSK antibody-positive myasthenia gravis (MuSK-MG) accounts for 5 to 15% of autoimmune MG. MuSK and LRP4 are coreceptors for agrin in the signaling pathway that causes clustering of acetylcholine receptor (AChR). MuSK also anchors the acetylcholinesterase (AChE)/collagen Q (ColQ) complex to the synaptic basal lamina. We previously reported that anti-MuSK antibodies (MuSK-IgG) block binding of ColQ to MuSK and cause partial endplate AChE deficiency in mice. We here analyzed the physiological significance of binding of ColQ to MuSK and block of this binding by MuSK-IgG. In vitro plate-binding assay showed that MuSK-IgG blocked MuSK-LRP4 interaction in the presence of agrin. Passive transfer of MuSK-IgG to Colq-knockout mice attenuated AChR clustering, indicating that lack of ColQ is not the key event causing defective clustering of AChR in MuSK-MG. In three MuSK-MG patients, the MuSK antibodies recognized the first and fourth immunoglobulin-like domains (Ig1 and Ig4) of MuSK. In two other MuSK-MG patients, they recognized only the Ig4 domain. LRP4 and ColQ also bound to the Ig1 and Ig4 domains of MuSK. Unexpectedly, the AChE/ColQ complex blocked MuSK-LRP4 interaction and suppressed agrin/LRP4/MuSK signaling. Quantitative analysis showed that MuSK-IgG suppressed agrin/LRP4/MuSK signaling to a greater extent than ColQ.
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Rodriguez Cruz PM, Huda S, López-Ruiz P, Vincent A. Use of cell-based assays in myasthenia gravis and other antibody-mediated diseases. Exp Neurol 2015; 270:66-71. [PMID: 25783660 DOI: 10.1016/j.expneurol.2015.01.011] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 01/14/2015] [Indexed: 11/25/2022]
Abstract
The increasing demand on diagnostic assays that are sensitive and specific for pathogenic antibodies, and the interest in identifying new antigens, prompted the development of cell-based assays for the detection of autoantibodies in myasthenia gravis and other autoimmune disorders. Cell-based assays were initially used to show that clustering the AChR improved the positivity in myasthenia gravis, and similar assays have now been applied to detection of antibodies to neuromuscular junction candidate proteins such as LRP4 and agrin. In addition cell-based assays have been used in the routine detection of antibodies to proteins expressed on the surface of neurons (NMDAR, LGI1, CASPR2, AMPAR, GABA-A/B, GlyR, and DPPX) and glia (AQP4, MOG). Here, we summarize the findings in myasthenia and discuss the advantages, disadvantages and controversial issues of using cell-based assays in the detection of these antibodies, and their relevance to the testing of preclinical models of disease.
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Affiliation(s)
- P M Rodriguez Cruz
- Nuffield Department of Clinical Neurosciences and Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - S Huda
- Nuffield Department of Clinical Neurosciences and Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - P López-Ruiz
- Nuffield Department of Clinical Neurosciences and Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - A Vincent
- Nuffield Department of Clinical Neurosciences and Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK.
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