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Miyairi Y, Ohkawara B, Sato A, Sawada R, Ishii H, Tomita H, Inoue T, Nakashima H, Ito M, Masuda A, Hosono Y, Imagama S, Ohno K. A class of chemical compounds enhances clustering of muscle nicotinic acetylcholine receptor in cultured myogenic cells. Biochem Biophys Res Commun 2024; 731:150400. [PMID: 39024975 DOI: 10.1016/j.bbrc.2024.150400] [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: 05/07/2024] [Revised: 06/25/2024] [Accepted: 07/12/2024] [Indexed: 07/20/2024]
Abstract
Neuromuscular signal transmission is affected in various diseases including myasthenia gravis, congenital myasthenic syndromes, and sarcopenia. We used an ATF2-luciferase system to monitor the phosphorylation of MuSK in HEK293 cells introduced with MUSK and LRP4 cDNAs to find novel chemical compounds that enhanced agrin-mediated acetylcholine receptor (AChR) clustering. Four compounds with similar chemical structures carrying benzene rings and heterocyclic rings increased the luciferase activities 8- to 30-folds, and two of them showed continuously graded dose dependence. The effects were higher than that of disulfiram, a clinically available aldehyde dehydrogenase inhibitor, which we identified to be the most competent preapproved drug to enhance ATF2-luciferase activity in the same assay system. In C2C12 myotubes, all the compounds increased the area, intensity, length, and number of AChR clusters. Three of the four compounds increased the phosphorylation of MuSK, but not of Dok7, JNK. ERK, or p38. Monitoring cell toxicity using the neurite elongation of NSC34 neuronal cells as a surrogate marker showed that all the compounds had no effects on the neurite elongation up to 1 μM. Extensive docking simulation and binding structure prediction of the four compounds with all available human proteins using AutoDock Vina and DiffDock showed that the four compounds were unlikely to directly bind to MuSK or Dok7, and the exact target remained unknown. The identified compounds are expected to serve as a seed to develop a novel therapeutic agent to treat defective NMJ signal transmission.
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Affiliation(s)
- Yuichi Miyairi
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan; Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan.
| | - Bisei Ohkawara
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan.
| | - Ayato Sato
- Institute for Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan; Center for One Medicine Innovative Translational Research (COMIT), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.
| | - Ryusuke Sawada
- Department of Pharmacology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama, 700-8558, Japan.
| | - Hisao Ishii
- Department of Hand Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan.
| | - Hiroyuki Tomita
- Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan.
| | - Taro Inoue
- Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan.
| | - Hiroaki Nakashima
- Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan.
| | - Mikako Ito
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan.
| | - Akio Masuda
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan.
| | - Yasuyuki Hosono
- Department of Pharmacology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama, 700-8558, Japan.
| | - Shiro Imagama
- Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan.
| | - Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan; Graduate School of Nutritoinal Sciencess, Nagoya University of Arts and Sciences, 57 Takenoyama, Iwasaki, Nisshin, 470-0196, Japan.
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Harada R, Taniguchi-Ikeda M, Nagasaka M, Nishii T, Inui A, Yamamoto T, Morioka I, Kuroda R, Iijima K, Nozu K, Sakai Y, Toda T. Assessment of the upper limb muscles in patients with Fukuyama muscular dystrophy: Noninvasive assessment using visual ultrasound muscle analysis and shear wave elastography. Neuromuscul Disord 2022; 32:754-762. [DOI: 10.1016/j.nmd.2022.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 05/08/2022] [Accepted: 05/09/2022] [Indexed: 11/29/2022]
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Ganassi M, Zammit PS. Involvement of muscle satellite cell dysfunction in neuromuscular disorders: Expanding the portfolio of satellite cell-opathies. Eur J Transl Myol 2022; 32:10064. [PMID: 35302338 PMCID: PMC8992676 DOI: 10.4081/ejtm.2022.10064] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 02/11/2022] [Indexed: 12/03/2022] Open
Abstract
Neuromuscular disorders are a heterogeneous group of acquired or hereditary conditions that affect striated muscle function. The resulting decrease in muscle strength and motility irreversibly impacts quality of life. In addition to directly affecting skeletal muscle, pathogenesis can also arise from dysfunctional crosstalk between nerves and muscles, and may include cardiac impairment. Muscular weakness is often progressive and paralleled by continuous decline in the ability of skeletal muscle to functionally adapt and regenerate. Normally, the skeletal muscle resident stem cells, named satellite cells, ensure tissue homeostasis by providing myoblasts for growth, maintenance, repair and regeneration. We recently defined 'Satellite Cell-opathies' as those inherited neuromuscular conditions presenting satellite cell dysfunction in muscular dystrophies and myopathies (doi:10.1016/j.yexcr.2021.112906). Here, we expand the portfolio of Satellite Cell-opathies by evaluating the potential impairment of satellite cell function across all 16 categories of neuromuscular disorders, including those with mainly neurogenic and cardiac involvement. We explore the expression dynamics of myopathogenes, genes whose mutation leads to skeletal muscle pathogenesis, using transcriptomic analysis. This revealed that 45% of myopathogenes are differentially expressed during early satellite cell activation (0 - 5 hours). Of these 271 myopathogenes, 83 respond to Pax7, a master regulator of satellite cells. Our analysis suggests possible perturbation of satellite cell function in many neuromuscular disorders across all categories, including those where skeletal muscle pathology is not predominant. This characterisation further aids understanding of pathomechanisms and informs on development of prognostic and diagnostic tools, and ultimately, new therapeutics.
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Affiliation(s)
- Massimo Ganassi
- King's College London, Randall Centre for Cell and Molecular Biophysics, Guy's Campus, London.
| | - Peter S Zammit
- King's College London, Randall Centre for Cell and Molecular Biophysics, Guy's Campus, London.
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Kanagawa M. Dystroglycanopathy: From Elucidation of Molecular and Pathological Mechanisms to Development of Treatment Methods. Int J Mol Sci 2021; 22:ijms222313162. [PMID: 34884967 PMCID: PMC8658603 DOI: 10.3390/ijms222313162] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Revised: 12/02/2021] [Accepted: 12/03/2021] [Indexed: 01/13/2023] Open
Abstract
Dystroglycanopathy is a collective term referring to muscular dystrophies with abnormal glycosylation of dystroglycan. At least 18 causative genes of dystroglycanopathy have been identified, and its clinical symptoms are diverse, ranging from severe congenital to adult-onset limb-girdle types. Moreover, some cases are associated with symptoms involving the central nervous system. In the 2010s, the structure of sugar chains involved in the onset of dystroglycanopathy and the functions of its causative gene products began to be identified as if they were filling the missing pieces of a jigsaw puzzle. In parallel with these discoveries, various dystroglycanopathy model mice had been created, which led to the elucidation of its pathological mechanisms. Then, treatment strategies based on the molecular basis of glycosylation began to be proposed after the latter half of the 2010s. This review briefly explains the sugar chain structure of dystroglycan and the functions of the causative gene products of dystroglycanopathy, followed by introducing the pathological mechanisms involved as revealed from analyses of dystroglycanopathy model mice. Finally, potential therapeutic approaches based on the pathological mechanisms involved are discussed.
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Affiliation(s)
- Motoi Kanagawa
- Department of Cell Biology and Molecular Medicine, Graduate School of Medicine, Ehime University, 454 Shitsukawa, Toon 791-0295, Ehime, Japan
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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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Gonzalez-Perez P, Smith C, Sebetka WL, Gedlinske A, Perlman S, Mathews KD. Clinical and electrophysiological evaluation of myasthenic features in an alpha-dystroglycanopathy cohort (FKRP-predominant). Neuromuscul Disord 2020; 30:213-218. [PMID: 32115343 PMCID: PMC7778731 DOI: 10.1016/j.nmd.2020.01.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Revised: 01/16/2020] [Accepted: 01/21/2020] [Indexed: 01/29/2023]
Abstract
A postsynaptic dysfunction of the neuromuscular junction has been reported in patients with alpha-dystroglycanopathy associated with mutations in guanosine diphosphate (GDP)-mannose pyrophosphorylase B gene (GMPPB), some of whom benefit from symptomatic treatment. In this study, we determine the frequency of myasthenic and fatigue symptoms and neuromuscular junction transmission defects in a fukutin-related protein (FKRP)-predominant alpha-dystroglycanopathy cohort. Thirty-one patients with alpha-dystroglycanopathies due to mutations in FKRP (n = 25), GMPPB (n = 4), POMGNT1 (n = 1), and POMT2 (n = 1) completed a six-question modified questionnaire for myasthenic symptoms and the PROMIS Short Form v1.0-Fatigue 8a survey, and they underwent 3 Hz repetitive nerve stimulation of spinal accessory nerve-trapezius and radial nerve-anconeus pairs. Results showed that fatigue with activity was common; 63% of the cohort reported fatigue with chewing. A defective postsynaptic neuromuscular junction transmission was not identified in any of the patients carrying FKRP mutations but only in one mildly affected patient with GMPPB mutations (c.79 G>C, p.D27H and c.402+1G>A, splice site variant). We conclude that symptoms of fatigue with activity did not predict abnormal neuromuscular junction transmission on electrodiagnostic studies in this cohort and that, unlike GMPPB subgroup, a defective neuromuscular junction transmission does not appear to be present in patients with FKRP-associated muscular dystrophies.
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Affiliation(s)
- Paloma Gonzalez-Perez
- Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, United States.
| | - Cheryl Smith
- Department of Neurology, West Virginia University Hospitals, Morgantown, WV 26506, United States
| | - Wendy L Sebetka
- Department of Neurology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, United States
| | - Amber Gedlinske
- Department of Pediatrics, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, United States
| | - Seth Perlman
- Department of Neurology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, United States; Department of Pediatrics, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, United States
| | - Katherine D Mathews
- Department of Neurology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, United States; Department of Pediatrics, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, United States
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Nicolau S, Liewluck T, Shen XM, Selcen D, Engel AG, Milone M. A homozygous mutation in GMPPB leads to centronuclear myopathy with combined pre- and postsynaptic defects of neuromuscular transmission. Neuromuscul Disord 2019; 29:614-617. [PMID: 31378432 DOI: 10.1016/j.nmd.2019.07.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/14/2019] [Accepted: 07/02/2019] [Indexed: 11/26/2022]
Abstract
Mutations in GMPPB cause a wide spectrum of neuromuscular syndromes, including muscular dystrophies and congenital myasthenic syndrome. The mechanisms by which GMPPB mutations impair neuromuscular transmission however remain incompletely understood. We expand here upon a previous report of one such patient presenting with a myopathy-congenital myasthenic syndrome overlap phenotype. Fatigable proximal muscle weakness developed gradually between 13 and 25 years of age, with subsequent stabilization. Low-frequency repetitive nerve stimulation showed a decrement, while a muscle biopsy demonstrated the presence of a centronuclear myopathy. Genetic testing identified a homozygous c.458C > T (p.Thr153Ile) variant in GMPPB. In-vitro microelectrode recordings and ultrastructural studies showed impairment of both pre- and postsynaptic neuromuscular transmission, thus demonstrating the presence of not only postsynaptic, but also presynaptic pathology in GMPPB-related disorders.
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Affiliation(s)
- Stefan Nicolau
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States
| | - Teerin Liewluck
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States
| | - Xin-Ming Shen
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States
| | - Duygu Selcen
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States
| | - Andrew G Engel
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States
| | - Margherita Milone
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States.
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Nicole S, Azuma Y, Bauché S, Eymard B, Lochmüller H, Slater C. Congenital Myasthenic Syndromes or Inherited Disorders of Neuromuscular Transmission: Recent Discoveries and Open Questions. J Neuromuscul Dis 2019; 4:269-284. [PMID: 29125502 PMCID: PMC5701762 DOI: 10.3233/jnd-170257] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Congenital myasthenic syndromes (CMS) form a heterogeneous group of rare diseases characterized by fatigable muscle weakness. They are genetically-inherited and caused by defective synaptic transmission at the cholinergic neuromuscular junction (NMJ). The number of genes known to cause CMS when mutated is currently 30, and the relationship between fatigable muscle weakness and defective functions is quite well-understood for many of them. However, some of the most recent discoveries in individuals with CMS challenge our knowledge of the NMJ, where the basis of the pathology has mostly been investigated in animal models. Frontier forms between CMS and congenital myopathy, which have been genetically and clinically identified, underline the poorly understood interplay between the synaptic and extrasynaptic molecules in the neuromuscular system. In addition, precise electrophysiological and histopathological investigations of individuals with CMS suggest an important role of NMJ plasticity in the response to CMS pathogenesis. While efficient drug-based treatments are already available to improve neuromuscular transmission for most forms of CMS, others, as well as neurological and muscular comorbidities, remain resistant. Taken together, the available pathological data point to physiological issues which remain to be understood in order to achieve precision medicine with efficient therapeutics for all individuals suffering from CMS.
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Affiliation(s)
- Sophie Nicole
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, 75013 Paris, France
| | - Yoshiteru Azuma
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
| | - Stéphanie Bauché
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, 75013 Paris, France
| | - Bruno Eymard
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, 75013 Paris, France.,AP-HP, Hôpital Pitié-Salpétrière, 75013 Paris, France
| | - Hanns Lochmüller
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
| | - Clarke Slater
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
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Chen HH, Tsai LK, Liao KY, Wu TC, Huang YH, Huang YC, Chang SW, Wang PY, Tsao YP, Chen SL. Muscle-restricted nuclear receptor interaction protein knockout causes motor neuron degeneration through down-regulation of myogenin at the neuromuscular junction. J Cachexia Sarcopenia Muscle 2018; 9:771-785. [PMID: 29608040 PMCID: PMC6104115 DOI: 10.1002/jcsm.12299] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 02/05/2018] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND Nuclear receptor interaction protein (NRIP) is a calcium/calmodulin (CaM) binding protein. Nuclear receptor interaction protein interacts with CaM to activate calcineurin and CaMKII signalling. The conventional NRIP knockout mice (global knockout) showed muscular abnormality with reduction of muscle oxidative functions and motor function defects. METHODS To investigate the role of NRIP on neuromuscular system, we generated muscle-restricted NRIP knockout mice [conditional knockout (cKO)]. The muscle functions (including oxidative muscle markers and muscle strength) and lumbar motor neuron functions [motor neuron number, axon denervation, neuromuscular junction (NMJ)] were tested. The laser-captured microdissection at NMJ of skeletal muscles and adenovirus gene therapy for rescued effects were performed. RESULTS The cKO mice showed muscular abnormality with reduction of muscle oxidative functions and impaired motor performances as global knockout mice. To our surprise, cKO mice also displayed motor neuron degeneration with abnormal architecture of NMJ. Specifically, the cKO mice revealed reduced motor neuron number with small neuronal size in lumbar spinal cord as well as denervating change, small motor endplates, and decreased myonuclei number at NMJ in skeletal muscles. To explore the mechanisms, we screened various muscle-derived factors and found that myogenin is a potential candidate that myogenin expression was lower in skeletal muscles of cKO mice than wild-type mice. Because NRIP and myogenin were colocalized around acetylcholine receptors at NMJ, we extracted RNA from synaptic and extrasynaptic regions of muscles using laser capture microdissection and showed that myogenin expression was especially lower at synaptic region in cKO than wild-type mice. Notably, overexpression of myogenin using intramuscular adenovirus encoding myogenin treatment rescued abnormal NMJ architecture and preserved motor neuron death in cKO mice. CONCLUSIONS In summary, we demonstrated that deprivation of NRIP decreases myogenin expression at NMJ, possibly leading to abnormal NMJ formation, denervation of acetylcholine receptor, and subsequent loss of spinal motor neuron. Overexpression of myogenin in cKO mice can partially rescue abnormal NMJ architecture and motor neuron death. Therefore, muscular NRIP is a novel trophic factor supporting spinal motor neuron via stabilization of NMJ by myogenin expression.
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Affiliation(s)
- Hsin-Hsiung Chen
- Graduate Institute of Microbiology, College of Medicine, National Taiwan University, 7F, No. 1, Sec. 1, Jen-Ai Rd., Taipei, 100, Taiwan
| | - Li-Kai Tsai
- Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan
| | - Kuan-Yu Liao
- Graduate Institute of Microbiology, College of Medicine, National Taiwan University, 7F, No. 1, Sec. 1, Jen-Ai Rd., Taipei, 100, Taiwan
| | - Tung-Chien Wu
- Graduate Institute of Microbiology, College of Medicine, National Taiwan University, 7F, No. 1, Sec. 1, Jen-Ai Rd., Taipei, 100, Taiwan
| | - Yun-Hsin Huang
- Graduate Institute of Microbiology, College of Medicine, National Taiwan University, 7F, No. 1, Sec. 1, Jen-Ai Rd., Taipei, 100, Taiwan
| | - Yuan-Chun Huang
- Graduate Institute of Microbiology, College of Medicine, National Taiwan University, 7F, No. 1, Sec. 1, Jen-Ai Rd., Taipei, 100, Taiwan
| | - Szu-Wei Chang
- Graduate Institute of Microbiology, College of Medicine, National Taiwan University, 7F, No. 1, Sec. 1, Jen-Ai Rd., Taipei, 100, Taiwan
| | - Pei-Yu Wang
- Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Yeou-Ping Tsao
- Department of Ophthalmology, Mackay Memorial Hospital, Taipei, Taiwan
| | - Show-Li Chen
- Graduate Institute of Microbiology, College of Medicine, National Taiwan University, 7F, No. 1, Sec. 1, Jen-Ai Rd., Taipei, 100, Taiwan
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Liewluck T, Milone M. Untangling the complexity of limb-girdle muscular dystrophies. Muscle Nerve 2018; 58:167-177. [PMID: 29350766 DOI: 10.1002/mus.26077] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2018] [Indexed: 12/16/2022]
Abstract
The limb-girdle muscular dystrophies (LGMDs) are a group of genetically heterogeneous, autosomal inherited muscular dystrophies with a childhood to adult onset, manifesting with hip- and shoulder-girdle muscle weakness. When the term LGMD was first conceptualized in 1954, it was thought to be a single entity. Currently, there are 8 autosomal dominant (LGMD1A-1H) and 26 autosomal recessive (LGMD2A-2Z) variants according to the Online Mendelian Inheritance in Man database. In addition, there are other genetically identified muscular dystrophies with an LGMD phenotype not yet classified as LGMD. This highlights the entanglement of LGMDs, which represents an area in continuous expansion. Herein we aim to simplify the complexity of LGMDs by subgrouping them on the basis of the underlying defective protein and impaired function. Muscle Nerve 58: 167-177, 2018.
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Affiliation(s)
- Teerin Liewluck
- Department of Neurology, Mayo Clinic, 200 First Street SW Rochester, Minnesota, 55905, USA
| | - Margherita Milone
- Department of Neurology, Mayo Clinic, 200 First Street SW Rochester, Minnesota, 55905, USA
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Ohno K, Ohkawara B, Ito M. Agrin-LRP4-MuSK signaling as a therapeutic target for myasthenia gravis and other neuromuscular disorders. Expert Opin Ther Targets 2017; 21:949-958. [PMID: 28825343 DOI: 10.1080/14728222.2017.1369960] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
INTRODUCTION Signal transduction at the neuromuscular junction (NMJ) is compromised in a diverse array of diseases including myasthenia gravis, Lambert-Eaton myasthenic syndrome, Isaacs' syndrome, congenital myasthenic syndromes, Fukuyama-type congenital muscular dystrophy, amyotrophic lateral sclerosis, and sarcopenia. Except for sarcopenia, all are orphan diseases. In addition, the NMJ signal transduction is impaired by tetanus, botulinum, curare, α-bungarotoxin, conotoxins, organophosphate, sarin, VX, and soman to name a few. Areas covered: This review covers the agrin-LRP4-MuSK signaling pathway, which drives clustering of acetylcholine receptors (AChRs) and ensures efficient signal transduction at the NMJ. We also address diseases caused by autoantibodies against the NMJ molecules and by germline mutations in genes encoding the NMJ molecules. Expert opinion: Representative small compounds to treat the defective NMJ signal transduction are cholinesterase inhibitors, which exert their effects by increasing the amount of acetylcholine at the synaptic space. Another possible therapeutic strategy to enhance the NMJ signal transduction is to increase the number of AChRs, but no currently available drug has this functionality.
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Affiliation(s)
- Kinji Ohno
- a Division of Neurogenetics , Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Bisei Ohkawara
- a Division of Neurogenetics , Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Mikako Ito
- a Division of Neurogenetics , Nagoya University Graduate School of Medicine , Nagoya , Japan
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Ohno K. Is the serum creatine kinase level elevated in congenital myasthenic syndrome? J Neurol Neurosurg Psychiatry 2016; 87:801. [PMID: 27151963 DOI: 10.1136/jnnp-2016-313416] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2016] [Accepted: 03/30/2016] [Indexed: 11/04/2022]
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Abnormal Skeletal Muscle Regeneration plus Mild Alterations in Mature Fiber Type Specification in Fktn-Deficient Dystroglycanopathy Muscular Dystrophy Mice. PLoS One 2016; 11:e0147049. [PMID: 26751696 PMCID: PMC4708996 DOI: 10.1371/journal.pone.0147049] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 12/28/2015] [Indexed: 02/07/2023] Open
Abstract
Glycosylated α-dystroglycan provides an essential link between extracellular matrix proteins, like laminin, and the cellular cytoskeleton via the dystrophin-glycoprotein complex. In secondary dystroglycanopathy muscular dystrophy, glycosylation abnormalities disrupt a complex O-mannose glycan necessary for muscle structural integrity and signaling. Fktn-deficient dystroglycanopathy mice develop moderate to severe muscular dystrophy with skeletal muscle developmental and/or regeneration defects. To gain insight into the role of glycosylated α-dystroglycan in these processes, we performed muscle fiber typing in young (2, 4 and 8 week old) and regenerated muscle. In mice with Fktn disruption during skeletal muscle specification (Myf5/Fktn KO), newly regenerated fibers (embryonic myosin heavy chain positive) peaked at 4 weeks old, while total regenerated fibers (centrally nucleated) were highest at 8 weeks old in tibialis anterior (TA) and iliopsoas, indicating peak degeneration/regeneration activity around 4 weeks of age. In contrast, mature fiber type specification at 2, 4 and 8 weeks old was relatively unchanged. Fourteen days after necrotic toxin-induced injury, there was a divergence in muscle fiber types between Myf5/Fktn KO (skeletal-muscle specific) and whole animal knockout induced with tamoxifen post-development (Tam/Fktn KO) despite equivalent time after gene deletion. Notably, Tam/Fktn KO retained higher levels of embryonic myosin heavy chain expression after injury, suggesting a delay or abnormality in differentiation programs. In mature fiber type specification post-injury, there were significant interactions between genotype and toxin parameters for type 1, 2a, and 2x fibers, and a difference between Myf5/Fktn and Tam/Fktn study groups in type 2b fibers. These data suggest that functionally glycosylated α-dystroglycan has a unique role in muscle regeneration and may influence fiber type specification post-injury.
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Sakuma K, Aoi W, Yamaguchi A. The intriguing regulators of muscle mass in sarcopenia and muscular dystrophy. Front Aging Neurosci 2014; 6:230. [PMID: 25221510 PMCID: PMC4148637 DOI: 10.3389/fnagi.2014.00230] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 08/10/2014] [Indexed: 12/25/2022] Open
Abstract
Recent advances in our understanding of the biology of muscle have led to new interest in the pharmacological treatment of muscle wasting. Loss of muscle mass and increased intramuscular fibrosis occur in both sarcopenia and muscular dystrophy. Several regulators (mammalian target of rapamycin, serum response factor, atrogin-1, myostatin, etc.) seem to modulate protein synthesis and degradation or transcription of muscle-specific genes during both sarcopenia and muscular dystrophy. This review provides an overview of the adaptive changes in several regulators of muscle mass in both sarcopenia and muscular dystrophy.
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Affiliation(s)
- Kunihiro Sakuma
- Research Center for Physical Fitness, Sports and Health, Toyohashi University of Technology, Toyohashi, Japan
| | - Wataru Aoi
- Laboratory of Health Science, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
| | - Akihiko Yamaguchi
- Department of Physical Therapy, Health Sciences University of Hokkaido, Kanazawa, Japan
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Circulating Muscle-specific miRNAs in Duchenne Muscular Dystrophy Patients. MOLECULAR THERAPY. NUCLEIC ACIDS 2014; 3:e177. [PMID: 25050825 PMCID: PMC4121518 DOI: 10.1038/mtna.2014.29] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 05/27/2014] [Indexed: 02/08/2023]
Abstract
Noninvasive biomarkers with diagnostic value and prognostic applications have long been desired to replace muscle biopsy for Duchenne muscular dystrophy (DMD) patients. Growing evidence indicates that circulating microRNAs are biomarkers to assess pathophysiological status. Here, we show that the serum levels of six muscle-specific miRNAs (miR-1/206/133/499/208a/208b, also known as myomiRs) were all elevated in DMD patients (P < 0.01). The receiver operating characteristic curves of circulating miR-206, miR-499, miR-208b, and miR-133 levels reflected strong separation between Becker's muscular dystrophy (BMD) and DMD patients (P < 0.05). miR-206, miR-499, and miR-208b levels were positively correlated with both age and type IIc muscle fiber content in DMD patients (2–6 years), indicating that they might represent the stage of disease as well as the process of regeneration. miR-499 and miR-208b levels were correlated with slow and fast fiber content and might reflect the ratio of slow to fast fibers in DMD patient (>6 years). Fibroblast growth factor, transforming growth factor-β, and tumor necrosis factor-α could affect the secretion of myomiRs, suggesting that circulating myomiRs might reflect the effects of cytokines and growth factors on degenerating and regenerating muscles. Collectively, our data indicated that circulating myomiRs could serve as promising biomarkers for DMD diagnosis and disease progression.
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Rudolf R, Khan MM, Labeit S, Deschenes MR. Degeneration of neuromuscular junction in age and dystrophy. Front Aging Neurosci 2014; 6:99. [PMID: 24904412 PMCID: PMC4033055 DOI: 10.3389/fnagi.2014.00099] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 05/08/2014] [Indexed: 12/27/2022] Open
Abstract
Functional denervation is a hallmark of aging sarcopenia as well as of muscular dystrophy. It is thought to be a major factor reducing skeletal muscle mass, particularly in the case of sarcopenia. Neuromuscular junctions (NMJs) serve as the interface between the nervous and skeletal muscular systems, and thus they may receive pathophysiological input of both pre- and post-synaptic origin. Consequently, NMJs are good indicators of motor health on a systemic level. Indeed, upon sarcopenia and dystrophy, NMJs morphologically deteriorate and exhibit altered characteristics of primary signaling molecules, such as nicotinic acetylcholine receptor and agrin. Since a remarkable reversibility of these changes can be observed by exercise, there is significant interest in understanding the molecular mechanisms underlying synaptic deterioration upon aging and dystrophy and how synapses are reset by the aforementioned treatments. Here, we review the literature that describes the phenomena observed at the NMJ in sarcopenic and dystrophic muscle as well as to how these alterations can be reversed and to what extent. In a second part, the current information about molecular machineries underlying these processes is reported.
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Affiliation(s)
- Rüdiger Rudolf
- Institute of Molecular and Cell Biology, University of Applied Sciences Mannheim , Mannheim , Germany ; Institute of Medical Technology, University of Heidelberg and University of Applied Sciences Mannheim , Mannheim , Germany ; Institute of Toxicology and Genetics, Karlsruhe Institute of Technology , Eggenstein-Leopoldshafen , Germany
| | - Muzamil Majid Khan
- Institute of Molecular and Cell Biology, University of Applied Sciences Mannheim , Mannheim , Germany ; Institute of Toxicology and Genetics, Karlsruhe Institute of Technology , Eggenstein-Leopoldshafen , Germany
| | - Siegfried Labeit
- Institute of Integrative Pathophysiology, University Medical Centre Mannheim , Mannheim , Germany
| | - Michael R Deschenes
- Department of Kinesiology and Health Sciences, The College of William and Mary , Williamsburg, VA , USA
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Robinson KG, Mendonca JL, Militar JL, Theroux MC, Dabney KW, Shah SA, Miller F, Akins RE. Disruption of basal lamina components in neuromotor synapses of children with spastic quadriplegic cerebral palsy. PLoS One 2013; 8:e70288. [PMID: 23976945 PMCID: PMC3745387 DOI: 10.1371/journal.pone.0070288] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 06/18/2013] [Indexed: 11/18/2022] Open
Abstract
Cerebral palsy (CP) is a static encephalopathy occurring when a lesion to the developing brain results in disordered movement and posture. Patients present with sometimes overlapping spastic, athetoid/dyskinetic, and ataxic symptoms. Spastic CP, which is characterized by stiff muscles, weakness, and poor motor control, accounts for ∼80% of cases. The detailed mechanisms leading to disordered movement in spastic CP are not completely understood, but clinical experience and recent studies suggest involvement of peripheral motor synapses. For example, it is recognized that CP patients have altered sensitivities to drugs that target neuromuscular junctions (NMJs), and protein localization studies suggest that NMJ microanatomy is disrupted in CP. Since CP originates during maturation, we hypothesized that NMJ disruption in spastic CP is associated with retention of an immature neuromotor phenotype later in life. Scoliosis patients with spastic CP or idiopathic disease were enrolled in a prospective, partially-blinded study to evaluate NMJ organization and neuromotor maturation. The localization of synaptic acetylcholine esterase (AChE) relative to postsynaptic acetylcholine receptor (AChR), synaptic laminin β2, and presynaptic vesicle protein 2 (SV2) appeared mismatched in the CP samples; whereas, no significant disruption was found between AChR and SV2. These data suggest that pre- and postsynaptic NMJ components in CP children were appropriately distributed even though AChE and laminin β2 within the synaptic basal lamina appeared disrupted. Follow up electron microscopy indicated that NMJs from CP patients appeared generally mature and similar to controls with some differences present, including deeper postsynaptic folds and reduced presynaptic mitochondria. Analysis of maturational markers, including myosin, syntrophin, myogenin, and AChR subunit expression, and telomere lengths, all indicated similar levels of motor maturation in the two groups. Thus, NMJ disruption in CP was found to principally involve components of the synaptic basal lamina and subtle ultra-structural modifications but appeared unrelated to neuromotor maturational status.
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Affiliation(s)
- Karyn G. Robinson
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Janet L. Mendonca
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Jaimee L. Militar
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Mary C. Theroux
- Department of Anesthesiology and Critical Care, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Kirk W. Dabney
- Department of Orthopedic Surgery, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Suken A. Shah
- Department of Orthopedic Surgery, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Freeman Miller
- Department of Orthopedic Surgery, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Robert E. Akins
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
- * E-mail:
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18
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Kanagawa M, Yu CC, Ito C, Fukada SI, Hozoji-Inada M, Chiyo T, Kuga A, Matsuo M, Sato K, Yamaguchi M, Ito T, Ohtsuka Y, Katanosaka Y, Miyagoe-Suzuki Y, Naruse K, Kobayashi K, Okada T, Takeda S, Toda T. Impaired viability of muscle precursor cells in muscular dystrophy with glycosylation defects and amelioration of its severe phenotype by limited gene expression. Hum Mol Genet 2013; 22:3003-15. [PMID: 23562821 DOI: 10.1093/hmg/ddt157] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
A group of muscular dystrophies, dystroglycanopathy is caused by abnormalities in post-translational modifications of dystroglycan (DG). To understand better the pathophysiological roles of DG modification and to establish effective clinical treatment for dystroglycanopathy, we here generated two distinct conditional knock-out (cKO) mice for fukutin, the first dystroglycanopathy gene identified for Fukuyama congenital muscular dystrophy. The first dystroglycanopathy model-myofiber-selective fukutin-cKO [muscle creatine kinase (MCK)-fukutin-cKO] mice-showed mild muscular dystrophy. Forced exercise experiments in presymptomatic MCK-fukutin-cKO mice revealed that myofiber membrane fragility triggered disease manifestation. The second dystroglycanopathy model-muscle precursor cell (MPC)-selective cKO (Myf5-fukutin-cKO) mice-exhibited more severe phenotypes of muscular dystrophy. Using an isolated MPC culture system, we demonstrated, for the first time, that defects in the fukutin-dependent modification of DG lead to impairment of MPC proliferation, differentiation and muscle regeneration. These results suggest that impaired MPC viability contributes to the pathology of dystroglycanopathy. Since our data suggested that frequent cycles of myofiber degeneration/regeneration accelerate substantial and/or functional loss of MPC, we expected that protection from disease-triggering myofiber degeneration provides therapeutic effects even in mouse models with MPC defects; therefore, we restored fukutin expression in myofibers. Adeno-associated virus (AAV)-mediated rescue of fukutin expression that was limited in myofibers successfully ameliorated the severe pathology even after disease progression. In addition, compared with other gene therapy studies, considerably low AAV titers were associated with therapeutic effects. Together, our findings indicated that fukutin-deficient dystroglycanopathy is a regeneration-defective disorder, and gene therapy is a feasible treatment for the wide range of dystroglycanopathy even after disease progression.
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Affiliation(s)
- Motoi Kanagawa
- Division of Neurology/Molecular Brain Science, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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19
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Beedle AM, Turner AJ, Saito Y, Lueck JD, Foltz SJ, Fortunato MJ, Nienaber PM, Campbell KP. Mouse fukutin deletion impairs dystroglycan processing and recapitulates muscular dystrophy. J Clin Invest 2012; 122:3330-42. [PMID: 22922256 DOI: 10.1172/jci63004] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 06/21/2012] [Indexed: 11/17/2022] Open
Abstract
Dystroglycan is a transmembrane glycoprotein that links the extracellular basement membrane to cytoplasmic dystrophin. Disruption of the extensive carbohydrate structure normally present on α-dystroglycan causes an array of congenital and limb girdle muscular dystrophies known as dystroglycanopathies. The essential role of dystroglycan in development has hampered elucidation of the mechanisms underlying dystroglycanopathies. Here, we developed a dystroglycanopathy mouse model using inducible or muscle-specific promoters to conditionally disrupt fukutin (Fktn), a gene required for dystroglycan processing. In conditional Fktn-KO mice, we observed a near absence of functionally glycosylated dystroglycan within 18 days of gene deletion. Twenty-week-old KO mice showed clear dystrophic histopathology and a defect in glycosylation near the dystroglycan O-mannose phosphate, whether onset of Fktn excision driven by muscle-specific promoters occurred at E8 or E17. However, the earlier gene deletion resulted in more severe phenotypes, with a faster onset of damage and weakness, reduced weight and viability, and regenerating fibers of smaller size. The dependence of phenotype severity on the developmental timing of muscle Fktn deletion supports a role for dystroglycan in muscle development or differentiation. Moreover, given that this conditional Fktn-KO mouse allows the generation of tissue- and timing-specific defects in dystroglycan glycosylation, avoids embryonic lethality, and produces a phenotype resembling patient pathology, it is a promising new model for the study of secondary dystroglycanopathy.
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Affiliation(s)
- Aaron M Beedle
- Howard Hughes Medical Institute, Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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20
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Abstract
MRF4 belongs to the basic helix-loop-helix class of transcription factors and this and other members of its family profoundly influence skeletal muscle development. Less is known about the role of these factors in aging. As MRF4 is preferentially expressed in subsynaptic nuclei, we postulated it might play a role in maintenance of the neuromuscular junction. To test this hypothesis, we examined the junctional regions of 19-20-month-old mice and found decreased levels of SV2B, a marker of synaptic vesicles, in MRF4-null mice relative to controls. There was a corresponding decrease in grip strength in MRF4-null mice. Taken together, these data suggest that the intrinsic muscle factor, MRF4 plays an important role in maintenance of neuromuscular junctions.
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21
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Stress and muscular dystrophy: a genetic screen for dystroglycan and dystrophin interactors in Drosophila identifies cellular stress response components. Dev Biol 2011; 352:228-42. [PMID: 21256839 DOI: 10.1016/j.ydbio.2011.01.013] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 01/11/2011] [Accepted: 01/12/2011] [Indexed: 11/24/2022]
Abstract
In Drosophila, like in humans, Dystrophin Glycoprotein Complex (DGC) deficiencies cause a life span shortening disease, associated with muscle dysfunction. We performed the first in vivo genetic interaction screen in ageing dystrophic muscles and identified genes that have not been shown before to have a role in the development of muscular dystrophy and interact with dystrophin and/or dystroglycan. Mutations in many of the found interacting genes cause age-dependent morphological and heat-induced physiological defects in muscles, suggesting their importance in the tissue. Majority of them is phylogenetically conserved and implicated in human disorders, mainly tumors and myopathies. Functionally they can be divided into three main categories: proteins involved in communication between muscle and neuron, and interestingly, in mechanical and cellular stress response pathways. Our data show that stress induces muscle degeneration and accelerates age-dependent muscular dystrophy. Dystrophic muscles are already compromised; and as a consequence they are less adaptive and more sensitive to energetic stress and to changes in the ambient temperature. However, only dystroglycan, but not dystrophin deficiency causes extreme myodegeneration induced by energetic stress suggesting that dystroglycan might be a component of the low-energy pathway and act as a transducer of energetic stress in normal and dystrophic muscles.
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22
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Nakamura N, Lyalin D, Panin VM. Protein O-mannosylation in animal development and physiology: from human disorders to Drosophila phenotypes. Semin Cell Dev Biol 2010; 21:622-30. [PMID: 20362685 DOI: 10.1016/j.semcdb.2010.03.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 03/10/2010] [Accepted: 03/25/2010] [Indexed: 12/13/2022]
Abstract
Protein O-mannosylation has a profound effect on the development and physiology of mammalian organisms. Mutations in genes affecting O-mannosyl glycan biosynthesis result in congenital muscular dystrophies. The main pathological mechanism triggered by O-mannosylation defects is a compromised interaction of cells with the extracellular matrix due to abnormal glycosylation of alpha-dystroglycan. Hypoglycosylation of alpha-dystroglycan impairs its ligand-binding activity and results in muscle degeneration and failure of neuronal migration. Recent experiments revealed the existence of compensatory mechanisms that could ameliorate defects of O-mannosylation. However, these mechanisms remain poorly understood. O-mannosylation and dystroglycan pathway genes show remarkable evolutionary conservation in a wide range of metazoans. Mutations and downregulation of these genes in zebrafish and Drosophila result in muscle defects and degeneration, also causing neurological phenotypes, which suggests that O-mannosylation has similar functions in mammals and lower animals. Thus, future studies in genetically tractable model organisms, such as zebrafish and Drosophila, should help to reveal molecular and genetic mechanisms of mammalian O-mannosylation and its role in the regulation of dystroglycan function.
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Affiliation(s)
- Naosuke Nakamura
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
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23
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Hewitt JE. Abnormal glycosylation of dystroglycan in human genetic disease. Biochim Biophys Acta Mol Basis Dis 2009; 1792:853-61. [DOI: 10.1016/j.bbadis.2009.06.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 06/05/2009] [Accepted: 06/10/2009] [Indexed: 10/20/2022]
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Herbst R, Iskratsch T, Unger E, Bittner RE. Aberrant development of neuromuscular junctions in glycosylation-defective Large(myd) mice. Neuromuscul Disord 2009; 19:366-78. [PMID: 19346129 DOI: 10.1016/j.nmd.2009.02.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Revised: 02/17/2009] [Accepted: 02/27/2009] [Indexed: 01/13/2023]
Abstract
Mice deficient in the glycosyltransferase Large are characterized by severe muscle and central nervous system abnormalities. In this study, we show that the formation and maintenance of neuromuscular junctions in Large(myd) mice are greatly compromised. Neuromuscular junctions are not confined to the muscle endplate zone but are widely spread and are frequently accompanied by exuberant nerve sprouting. Nerve terminals are highly fragmented and binding of alpha-bungarotoxin to postsynaptic acetylcholine receptors (AChRs) is greatly reduced. In vitro, Large(myd) myotubes are responsive to agrin but produce aberrant AChR clusters, which are larger in area and less densely packed with AChRs. In addition, AChR expression on the cell surface is diminished suggesting that AChR assembly or transport is defective. These results together with the finding that O-linked glycosylation at neuromuscular junctions of Large(myd) mice is compromised indicate that the action of Large is necessary for proper neuromuscular junction development.
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Affiliation(s)
- Ruth Herbst
- Center for Brain Research, Medical University of Vienna, Vienna, Austria.
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25
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Compton AG, Albrecht DE, Seto JT, Cooper ST, Ilkovski B, Jones KJ, Challis D, Mowat D, Ranscht B, Bahlo M, Froehner SC, North KN. Mutations in contactin-1, a neural adhesion and neuromuscular junction protein, cause a familial form of lethal congenital myopathy. Am J Hum Genet 2008; 83:714-24. [PMID: 19026398 DOI: 10.1016/j.ajhg.2008.10.022] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Revised: 10/16/2008] [Accepted: 10/29/2008] [Indexed: 01/06/2023] Open
Abstract
We have previously reported a group of patients with congenital onset weakness associated with a deficiency of members of the syntrophin-alpha-dystrobrevin subcomplex and have demonstrated that loss of syntrophin and dystrobrevin from the sarcolemma of skeletal muscle can also be associated with denervation. Here, we have further studied four individuals from a consanguineous Egyptian family with a lethal congenital myopathy inherited in an autosomal-recessive fashion and characterized by a secondary loss of beta2-syntrophin and alpha-dystrobrevin from the muscle sarcolemma, central nervous system involvement, and fetal akinesia. We performed homozygosity mapping and candidate gene analysis and identified a mutation that segregates with disease within CNTN1, the gene encoding for the neural immunoglobulin family adhesion molecule, contactin-1. Contactin-1 transcripts were markedly decreased on gene-expression arrays of muscle from affected family members compared to controls. We demonstrate that contactin-1 is expressed at the neuromuscular junction (NMJ) in mice and man in addition to the previously documented expression in the central and peripheral nervous system. In patients with secondary dystroglycanopathies, we show that contactin-1 is abnormally localized to the sarcolemma instead of exclusively at the NMJ. The cntn1 null mouse presents with ataxia, progressive muscle weakness, and postnatal lethality, similar to the affected members in this family. We propose that loss of contactin-1 from the NMJ impairs communication or adhesion between nerve and muscle resulting in the severe myopathic phenotype. This disorder is part of the continuum in the clinical spectrum of congenital myopathies and congenital myasthenic syndromes.
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Affiliation(s)
- Alison G Compton
- Institute for Neuromuscular Research, The Children's Hospital at Westmead, NSW, Australia
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26
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Kanagawa M, Nishimoto A, Chiyonobu T, Takeda S, Miyagoe-Suzuki Y, Wang F, Fujikake N, Taniguchi M, Lu Z, Tachikawa M, Nagai Y, Tashiro F, Miyazaki JI, Tajima Y, Takeda S, Endo T, Kobayashi K, Campbell KP, Toda T. Residual laminin-binding activity and enhanced dystroglycan glycosylation by LARGE in novel model mice to dystroglycanopathy. Hum Mol Genet 2008; 18:621-31. [PMID: 19017726 PMCID: PMC2638827 DOI: 10.1093/hmg/ddn387] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Hypoglycosylation and reduced laminin-binding activity of α-dystroglycan are common characteristics of dystroglycanopathy, which is a group of congenital and limb-girdle muscular dystrophies. Fukuyama-type congenital muscular dystrophy (FCMD), caused by a mutation in the fukutin gene, is a severe form of dystroglycanopathy. A retrotransposal insertion in fukutin is seen in almost all cases of FCMD. To better understand the molecular pathogenesis of dystroglycanopathies and to explore therapeutic strategies, we generated knock-in mice carrying the retrotransposal insertion in the mouse fukutin ortholog. Knock-in mice exhibited hypoglycosylated α-dystroglycan; however, no signs of muscular dystrophy were observed. More sensitive methods detected minor levels of intact α-dystroglycan, and solid-phase assays determined laminin binding levels to be ∼50% of normal. In contrast, intact α-dystroglycan is undetectable in the dystrophic Largemyd mouse, and laminin-binding activity is markedly reduced. These data indicate that a small amount of intact α-dystroglycan is sufficient to maintain muscle cell integrity in knock-in mice, suggesting that the treatment of dystroglycanopathies might not require the full recovery of glycosylation. To examine whether glycosylation defects can be restored in vivo, we performed mouse gene transfer experiments. Transfer of fukutin into knock-in mice restored glycosylation of α-dystroglycan. In addition, transfer of LARGE produced laminin-binding forms of α-dystroglycan in both knock-in mice and the POMGnT1 mutant mouse, which is another model of dystroglycanopathy. Overall, these data suggest that even partial restoration of α-dystroglycan glycosylation and laminin-binding activity by replacing or augmenting glycosylation-related genes might effectively deter dystroglycanopathy progression and thus provide therapeutic benefits.
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Affiliation(s)
- Motoi Kanagawa
- Division of Clinical Genetics, Department of Medical Genetics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
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27
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Martin PT, Shelton GD, Dickinson PJ, Sturges BK, Xu R, LeCouteur RA, Guo LT, Grahn RA, Lo HP, North KN, Malik R, Engvall E, Lyons LA. Muscular dystrophy associated with alpha-dystroglycan deficiency in Sphynx and Devon Rex cats. Neuromuscul Disord 2008; 18:942-52. [PMID: 18990577 DOI: 10.1016/j.nmd.2008.08.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 07/27/2008] [Accepted: 08/16/2008] [Indexed: 11/28/2022]
Abstract
Recent studies have identified a number of forms of muscular dystrophy, termed dystroglycanopathies, which are associated with loss of natively glycosylated alpha-dystroglycan. Here we identify a new animal model for this class of disorders in Sphynx and Devon Rex cats. Affected cats displayed a slowly progressive myopathy with clinical and histologic hallmarks of muscular dystrophy including skeletal muscle weakness with no involvement of peripheral nerves or CNS. Skeletal muscles had myopathic features and reduced expression of alpha-dystroglycan, while beta-dystroglycan, sarcoglycans, and dystrophin were expressed at normal levels. In the Sphynx cat, analysis of laminin and lectin binding capacity demonstrated no loss in overall glycosylation or ligand binding for the alpha-dystroglycan protein, only a loss of protein expression. A reduction in laminin-alpha2 expression in the basal lamina surrounding skeletal myofibers was also observed. Sequence analysis of translated regions of the feline dystroglycan gene (DAG1) in affected cats did not identify a causative mutation, and levels of DAG1 mRNA determined by real-time QRT-PCR did not differ significantly from normal controls. Reduction in the levels of glycosylated alpha-dystroglycan by immunoblot was also identified in an affected Devon Rex cat. These data suggest that muscular dystrophy in Sphynx and Devon Rex cats results from a deficiency in alpha-dystroglycan protein expression, and as such may represent a new type of dystroglycanopathy where expression, but not glycosylation, is affected.
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Affiliation(s)
- Paul T Martin
- Center for Gene Therapy, The Research Institute at Nationwide Children's Hospital, Department of Pediatrics, Ohio State University, College of Medicine, Columbus, OH 43205, USA
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Bogdanik L, Framery B, Frölich A, Franco B, Mornet D, Bockaert J, Sigrist SJ, Grau Y, Parmentier ML. Muscle dystroglycan organizes the postsynapse and regulates presynaptic neurotransmitter release at the Drosophila neuromuscular junction. PLoS One 2008; 3:e2084. [PMID: 18446215 PMCID: PMC2323113 DOI: 10.1371/journal.pone.0002084] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Accepted: 03/17/2008] [Indexed: 12/21/2022] Open
Abstract
Background The Dystrophin-glycoprotein complex (DGC) comprises dystrophin, dystroglycan, sarcoglycan, dystrobrevin and syntrophin subunits. In muscle fibers, it is thought to provide an essential mechanical link between the intracellular cytoskeleton and the extracellular matrix and to protect the sarcolemma during muscle contraction. Mutations affecting the DGC cause muscular dystrophies. Most members of the DGC are also concentrated at the neuromuscular junction (NMJ), where their deficiency is often associated with NMJ structural defects. Hence, synaptic dysfunction may also intervene in the pathology of dystrophic muscles. Dystroglycan is a central component of the DGC because it establishes a link between the extracellular matrix and Dystrophin. In this study, we focused on the synaptic role of Dystroglycan (Dg) in Drosophila. Methodology/Principal Findings We show that Dg was concentrated postsynaptically at the glutamatergic NMJ, where, like in vertebrates, it controls the concentration of synaptic Laminin and Dystrophin homologues. We also found that synaptic Dg controlled the amount of postsynaptic 4.1 protein Coracle and alpha-Spectrin, as well as the relative subunit composition of glutamate receptors. In addition, both Dystrophin and Coracle were required for normal Dg concentration at the synapse. In electrophysiological recordings, loss of postsynaptic Dg did not affect postsynaptic response, but, surprisingly, led to a decrease in glutamate release from the presynaptic site. Conclusion/Significance Altogether, our study illustrates a conservation of DGC composition and interactions between Drosophila and vertebrates at the synapse, highlights new proteins associated with this complex and suggests an unsuspected trans-synaptic function of Dg.
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Affiliation(s)
- Laurent Bogdanik
- CNRS, UMR 5203, Institut de Génomique fonctionnelle, Montpellier, France
- INSERM, U661, Montpellier, France
- Université Montpellier,1,2, Montpellier, France
| | - Bérénice Framery
- CNRS, UMR 5203, Institut de Génomique fonctionnelle, Montpellier, France
- INSERM, U661, Montpellier, France
- Université Montpellier,1,2, Montpellier, France
| | - Andreas Frölich
- European Neuroscience Institute Göttingen, Göttingen, Germany
| | - Bénédicte Franco
- CNRS, UMR 5203, Institut de Génomique fonctionnelle, Montpellier, France
- INSERM, U661, Montpellier, France
- Université Montpellier,1,2, Montpellier, France
| | - Dominique Mornet
- INSERM, ERI 25, Muscle and Pathologies, Université de Montpellier1, EA 4202, 34295 Montpellier, France
| | - Joël Bockaert
- CNRS, UMR 5203, Institut de Génomique fonctionnelle, Montpellier, France
- INSERM, U661, Montpellier, France
- Université Montpellier,1,2, Montpellier, France
| | - Stephan J. Sigrist
- European Neuroscience Institute Göttingen, Göttingen, Germany
- Institut für Klinische Neurobiologie, Rudolf-Virchow Zentrum, Universität Würzburg, Würzburg, Germany
| | - Yves Grau
- CNRS, UMR 5203, Institut de Génomique fonctionnelle, Montpellier, France
- INSERM, U661, Montpellier, France
- Université Montpellier,1,2, Montpellier, France
| | - Marie-Laure Parmentier
- CNRS, UMR 5203, Institut de Génomique fonctionnelle, Montpellier, France
- INSERM, U661, Montpellier, France
- Université Montpellier,1,2, Montpellier, France
- * E-mail:
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29
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Percival JM, Froehner SC. Golgi complex organization in skeletal muscle: a role for Golgi-mediated glycosylation in muscular dystrophies? Traffic 2007; 8:184-94. [PMID: 17319799 DOI: 10.1111/j.1600-0854.2006.00523.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The Golgi complex (GC) is the central organelle of the classical secretory pathway, and it receives, modifies and packages proteins and lipids en route to their intracellular or extracellular destinations. Recent studies of congenital muscular dystrophies in skeletal muscle suggest an exciting new role for an old and well-established function of the GC: glycosylation. Glycosylation is the exquisitely regulated enzymatic addition of nucleotide sugars to proteins and lipids mediated by glycosyltransferases (GTs). Mutations in putative Golgi-resident GTs, fukutin, fukutin-related protein and large1 cause these progressive muscle-wasting diseases. The appropriate localization of GTs to specific subcompartments of the Golgi is critical for the correct assembly line-like addition of glycan groups to proteins and lipids as they pass through the GC. Consequently, these studies of congenital muscular dystrophies have focused attention on the organization and function of the GC in skeletal muscle. In contrast to other cells and tissues, the GC in skeletal muscle has received relatively little attention; however, in recent years, several studies have shown that GC distribution in muscle is highly dynamic or plastic and adopts different distributions in muscle cells undergoing myogenesis, denervation, regeneration and maturation. Here, we review the current understanding of the dynamic regulation of GC organization in skeletal muscle and focus on the targeting of fukutin, fukutin-related protein and large1 to the GC in muscle cells.
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Affiliation(s)
- Justin M Percival
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
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Saito F, Masaki T, Saito Y, Nakamura A, Takeda S, Shimizu T, Toda T, Matsumura K. Defective peripheral nerve myelination and neuromuscular junction formation in fukutin-deficient chimeric mice. J Neurochem 2007; 101:1712-22. [PMID: 17326765 DOI: 10.1111/j.1471-4159.2007.04462.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Dystroglycan is a central component of the dystrophin-glycoprotein complex that links the extracellular matrix with cytoskeleton. Recently, mutations of the genes encoding putative glycosyltransferases were identified in several forms of congenital muscular dystrophies accompanied by brain anomalies and eye abnormalities, and aberrant glycosylation of alpha-dystroglycan has been implicated in their pathogeneses. These diseases are now collectively called alpha-dystroglycanopathy. In this study, we demonstrate that peripheral nerve myelination is defective in the fukutin-deficient chimeric mice, a mouse model of Fukuyama-type congenital muscular dystrophy, which is the most common alpha-dystroglycanopathy in Japan. In the peripheral nerve of these mice, the density of myelinated nerve fibers was significantly decreased and clusters of abnormally large non-myelinated axons were ensheathed by a single Schwann cell, indicating a defect of the radial sorting mechanism. The sugar chain moiety and laminin-binding activity of alpha-dystroglycan were severely reduced, while the expression of beta1-integrin was not altered in the peripheral nerve of the chimeric mice. We also show that the clustering of acetylcholine receptor is defective and neuromuscular junctions are fragmented in appearance in these mice. Expression of agrin and laminin as well as the binding activity of alpha-dystroglycan to these ligands was severely reduced at the neuromuscular junction. These results demonstrate that fukutin plays crucial roles in the myelination of peripheral nerve and formation of neuromuscular junction. They also suggest that defective glycosylation of alpha-dystroglycan may play a role in the impairment of these processes in the deficiency of fukutin.
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Affiliation(s)
- Fumiaki Saito
- Department of Neurology and Neuroscience, Teikyo University, Tokyo, Japan
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31
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Keira Y, Noguchi S, Kurokawa R, Fujita M, Minami N, Hayashi YK, Kato T, Nishino I. Characterization of lobulated fibers in limb girdle muscular dystrophy type 2A by gene expression profiling. Neurosci Res 2007; 57:513-21. [PMID: 17258832 DOI: 10.1016/j.neures.2006.12.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Revised: 11/15/2006] [Accepted: 12/13/2006] [Indexed: 11/22/2022]
Abstract
Limb girdle muscular dystrophy type 2A (LGMD2A) is caused by mutations in CAPN3, which encodes an intracellular cysteine protease. To elucidate the fundamental molecular changes that may be responsible for the pathological features of LGMD2A, we employed cDNA microarray analysis. We divided LGMD2A muscles into two groups according to specific pathological features: an early-stage group characterized by the presence of active necrosis and a regeneration process and a later-stage group characterized by the presence of lobulated fibers. After comparing the gene expression profiles of the two groups of LGMD2A muscles with control muscles, we identified 29 genes whose mRNA expression profiles were specifically altered in muscles with lobulated fibers. Interestingly, this group included genes that encode actin filament binding and regulatory proteins, such as gelsolin, PDZ and LIM domain 3 (PDLIM3) and troponin I1. Western blot analysis confirmed the upregulation of these proteins. From these results, we propose that abnormal increased expression of actin filament binding proteins may contribute to the changes of the intra-myofiber structures, observed in lobulated fibers in LGMD2A.
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Affiliation(s)
- Yoko Keira
- Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8502, Japan
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32
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Saint-Amant L, Sprague SM, Hirata H, Li Q, Cui WW, Zhou W, Poudou O, Hume RI, Kuwada JY. The zebrafishennui behavioral mutation disrupts acetylcholine receptor localization and motor axon stability. Dev Neurobiol 2007; 68:45-61. [DOI: 10.1002/dneu.20569] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Xiong H, Kobayashi K, Tachikawa M, Manya H, Takeda S, Chiyonobu T, Fujikake N, Wang F, Nishimoto A, Morris GE, Nagai Y, Kanagawa M, Endo T, Toda T. Molecular interaction between fukutin and POMGnT1 in the glycosylation pathway of α-dystroglycan. Biochem Biophys Res Commun 2006; 350:935-41. [PMID: 17034757 DOI: 10.1016/j.bbrc.2006.09.129] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Accepted: 09/25/2006] [Indexed: 10/24/2022]
Abstract
The recent identification of mutations in genes encoding demonstrated or putative glycosyltransferases has revealed a novel mechanism for congenital muscular dystrophy. Hypoglycosylated alpha-dystroglycan (alpha-DG) is commonly seen in Fukuyama-type congenital muscular dystrophy (FCMD), muscle-eye-brain disease (MEB), Walker-Warburg syndrome (WWS), and Large(myd) mice. POMGnT1 and POMTs, the gene products responsible for MEB and WWS, respectively, synthesize unique O-mannose sugar chains on alpha-DG. The function of fukutin, the gene product responsible for FCMD, remains undetermined. Here we show that fukutin co-localizes with POMGnT1 in the Golgi apparatus. Direct interaction between fukutin and POMGnT1 was confirmed by co-immunoprecipitation and two-hybrid analyses. The transmembrane region of fukutin mediates its localization to the Golgi and participates in the interaction with POMGnT1. Y371C, a missense mutation found in FCMD, retains fukutin in the ER and also redirects POMGnT1 to the ER. Finally, we demonstrate reduced POMGnT1 enzymatic activity in transgenic knock-in mice carrying the retrotransposal insertion in the fukutin gene, the prevalent mutation in FCMD. From these findings, we propose that fukutin forms a complex with POMGnT1 and may modulate its enzymatic activity.
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Affiliation(s)
- Hui Xiong
- Division of Clinical Genetics, Department of Medical Genetics, Osaka University Graduate School of Medicine, 2-2-B9 Yamadaoka, Suita, Osaka 565-0871, Japan
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34
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Kanagawa M, Toda T. The genetic and molecular basis of muscular dystrophy: roles of cell-matrix linkage in the pathogenesis. J Hum Genet 2006; 51:915-926. [PMID: 16969582 DOI: 10.1007/s10038-006-0056-7] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Accepted: 08/18/2006] [Indexed: 10/24/2022]
Abstract
Muscular dystrophies are a heterogeneous group of genetic disorders. In addition to genetic information, a combination of various approaches such as the use of genetic animal models, muscle cell biology, and biochemistry has contributed to improving the understanding of the molecular basis of muscular dystrophy's etiology. Several lines of evidence confirm that the structural linkage between the muscle extracellular matrix and the cytoskeleton is crucial to prevent the progression of muscular dystrophy. The dystrophin-glycoprotein complex links the extracellular matrix to the cytoskeleton, and mutations in the component of this complex cause Duchenne-type or limb-girdle-type muscular dystrophy. Mutations in laminin or collagen VI, muscle matrix proteins, are known to cause a congenital type of muscular dystrophy. Moreover, it is not only the primary genetic defects in the structural or matrix proteins, but also the primary mutations of enzymes involved in the protein glycosylation pathway that are now recognized to disrupt the matrix-cell interaction in a certain group of muscular dystrophies. This group of diseases is caused by the secondary functional defects of dystroglycan, a transmembrane matrix receptor. This review considers recent advances in understanding the molecular pathogenesis of muscular dystrophies that can be caused by the disruption of the cell-matrix linkage.
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Affiliation(s)
- Motoi Kanagawa
- Division of Clinical Genetics, Department of Medical Genetics, Osaka University Graduate School of Medicine, 2-2-B9, Yamadaoka, Suita, 565-0871, Japan
| | - Tatsushi Toda
- Division of Clinical Genetics, Department of Medical Genetics, Osaka University Graduate School of Medicine, 2-2-B9, Yamadaoka, Suita, 565-0871, Japan.
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