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Batheja A, Bayer-Vile J, Silverstein E, Couser N. Congenital Myasthenic Syndrome associated with acetylcholine receptor deficiency: case report and review of the literature. Ophthalmic Genet 2024:1-7. [PMID: 38832364 DOI: 10.1080/13816810.2024.2352391] [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: 12/21/2023] [Accepted: 05/02/2024] [Indexed: 06/05/2024]
Abstract
INTRODUCTION Congenital Myasthenic Syndromes are a diverse group of conditions with a broad array of genetic underpinnings and phenotypic presentations. Acetylcholine receptor deficiency is one form that usually involves pathogenic variants in the Cholinergic Receptor Nicotinic Epsilon Subunit (CHRNE) gene encoding the ɛ-subunit of the acetylcholine receptor. METHODS We report a case of a 4-year-old male with suspected Congenital Myasthenic Syndrome with Acetylcholine Receptor Deficiency who presented with ocular symptoms and generalized muscle weakness. We additionally summarize published findings regarding the genetic, phenotypic, and clinical considerations of Congenital Myasthenic Syndrome with Acetylcholine Receptor Deficiency. RESULTS Exome sequencing revealed biallelic variants in CHRNE gene with a pathogenic frameshift variant and a variant of uncertain significance. After suboptimal response to pyridostigmine and albuterol, the patient experienced benefit with 3,4-DAP. The most commonly reported clinical characteristics in the literature are ptosis, muscle fatigability or weakness, and ophthalmoplegia. CONCLUSION We present the case of a patient with biallelic variants in CHRNE gene including a variant of uncertain significance. Evaluation of variants of this gene, including the variant of uncertain significance identified in this case report, through further cases and studies may improve our understanding of Congenital Myasthenic Syndrome with Acetylcholine Receptor deficiency.
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Affiliation(s)
- Aashish Batheja
- School of Medicine, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - Julie Bayer-Vile
- Department of Pediatrics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - Evan Silverstein
- Department of Ophthalmology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - Natario Couser
- Department of Pediatrics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
- Department of Ophthalmology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
- Department of Human and Molecular Genetics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
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Polavarapu K, Sunitha B, Töpf A, Preethish-Kumar V, Thompson R, Vengalil S, Nashi S, Bardhan M, Sanka SB, Huddar A, Unnikrishnan G, Arunachal G, Girija MS, Porter A, Azuma Y, Lorenzoni PJ, Baskar D, Anjanappa RM, Keertipriya M, Padmanabh H, Harikrishna GV, Laurie S, Matalonga L, Horvath R, Nalini A, Lochmüller H. Clinical and genetic characterisation of a large Indian congenital myasthenic syndrome cohort. Brain 2024; 147:281-296. [PMID: 37721175 PMCID: PMC10766255 DOI: 10.1093/brain/awad315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 06/20/2023] [Accepted: 08/10/2023] [Indexed: 09/19/2023] Open
Abstract
Congenital myasthenic syndromes (CMS) are a rare group of inherited disorders caused by gene defects associated with the neuromuscular junction and potentially treatable with commonly available medications such as acetylcholinesterase inhibitors and β2 adrenergic receptor agonists. In this study, we identified and genetically characterized the largest cohort of CMS patients from India to date. Genetic testing of clinically suspected patients evaluated in a South Indian hospital during the period 2014-19 was carried out by standard diagnostic gene panel testing or using a two-step method that included hotspot screening followed by whole-exome sequencing. In total, 156 genetically diagnosed patients (141 families) were characterized and the mutational spectrum and genotype-phenotype correlation described. Overall, 87 males and 69 females were evaluated, with the age of onset ranging from congenital to fourth decade (mean 6.6 ± 9.8 years). The mean age at diagnosis was 19 ± 12.8 (1-56 years), with a mean diagnostic delay of 12.5 ± 9.9 (0-49 years). Disease-causing variants in 17 CMS-associated genes were identified in 132 families (93.6%), while in nine families (6.4%), variants in genes not associated with CMS were found. Overall, postsynaptic defects were most common (62.4%), followed by glycosylation defects (21.3%), synaptic basal lamina genes (4.3%) and presynaptic defects (2.8%). Other genes found to cause neuromuscular junction defects (DES, TEFM) in our cohort accounted for 2.8%. Among the individual CMS genes, the most commonly affected gene was CHRNE (39.4%), followed by DOK7 (14.4%), DPAGT1 (9.8%), GFPT1 (7.6%), MUSK (6.1%), GMPPB (5.3%) and COLQ (4.5%). We identified 22 recurrent variants in this study, out of which eight were found to be geographically specific to the Indian subcontinent. Apart from the known common CHRNE variants p.E443Kfs*64 (11.4%) and DOK7 p.A378Sfs*30 (9.3%), we identified seven novel recurrent variants specific to this cohort, including DPAGT1 p.T380I and DES c.1023+5G>A, for which founder haplotypes are suspected. This study highlights the geographic differences in the frequencies of various causative CMS genes and underlines the increasing significance of glycosylation genes (DPAGT1, GFPT1 and GMPPB) as a cause of neuromuscular junction defects. Myopathy and muscular dystrophy genes such as GMPPB and DES, presenting as gradually progressive limb girdle CMS, expand the phenotypic spectrum. The novel genes MACF1 and TEFM identified in this cohort add to the expanding list of genes with new mechanisms causing neuromuscular junction defects.
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Affiliation(s)
- Kiran Polavarapu
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, Canada
| | - Balaraju Sunitha
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
- Department of Clinical Neurosciences, University of Cambridge School of Clinical Medicine, Cambridge CB2 0SP, UK
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, UK
| | - Ana Töpf
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Veeramani Preethish-Kumar
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
- Department of Neurology, Neurofoundation, Salem, Tamil Nadu 636009, India
| | - Rachel Thompson
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, Canada
| | - Seena Vengalil
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
| | - Saraswati Nashi
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
| | - Mainak Bardhan
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
| | - Sai Bhargava Sanka
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
| | - Akshata Huddar
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
- Department of Neurology, St Johns Medical College Hospital, Bangalore 560034, India
| | - Gopikrishnan Unnikrishnan
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
- Department of Neurology, Amruta Institute of Medical Sciences, Kochi 682041, India
| | - Gautham Arunachal
- Department of Human Genetics, National Institute of Mental Health and Neurosciences, Bengaluru 560029, India
| | - Manu Santhappan Girija
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
| | - Anna Porter
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Yoshiteru Azuma
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Paulo José Lorenzoni
- Neuromuscular Disorders Division, Service of Neurology, Department of Internal Medicine, Hospital de Clínicas, Universidade Federal do Paraná, Rua General Carneiro, Curitiba - PR 80060-900, Brazil
| | - Dipti Baskar
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
| | - Ram Murthy Anjanappa
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
| | - Madassu Keertipriya
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
| | - Hansashree Padmanabh
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
| | | | - Steve Laurie
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia 08028, Spain
| | - Leslie Matalonga
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia 08028, Spain
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge School of Clinical Medicine, Cambridge CB2 0SP, UK
| | - Atchayaram Nalini
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
| | - Hanns Lochmüller
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, Canada
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia 08028, Spain
- Brain and Mind Research Institute, University of Ottawa, Ottawa, ON K1H 8M5, Canada
- Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, ON K1H 8M5, Canada
- Department of Neuropediatrics and Muscle Disorders, Medical Center–University of Freiburg, Faculty of Medicine, Freiburg 79110, Germany
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Ohno K, Ohkawara B, Shen XM, Selcen D, Engel AG. Clinical and Pathologic Features of Congenital Myasthenic Syndromes Caused by 35 Genes-A Comprehensive Review. Int J Mol Sci 2023; 24:ijms24043730. [PMID: 36835142 PMCID: PMC9961056 DOI: 10.3390/ijms24043730] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 02/09/2023] [Accepted: 02/09/2023] [Indexed: 02/16/2023] Open
Abstract
Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders characterized by impaired neuromuscular signal transmission due to germline pathogenic variants in genes expressed at the neuromuscular junction (NMJ). A total of 35 genes have been reported in CMS (AGRN, ALG14, ALG2, CHAT, CHD8, CHRNA1, CHRNB1, CHRND, CHRNE, CHRNG, COL13A1, COLQ, DOK7, DPAGT1, GFPT1, GMPPB, LAMA5, LAMB2, LRP4, MUSK, MYO9A, PLEC, PREPL, PURA, RAPSN, RPH3A, SCN4A, SLC18A3, SLC25A1, SLC5A7, SNAP25, SYT2, TOR1AIP1, UNC13A, VAMP1). The 35 genes can be classified into 14 groups according to the pathomechanical, clinical, and therapeutic features of CMS patients. Measurement of compound muscle action potentials elicited by repetitive nerve stimulation is required to diagnose CMS. Clinical and electrophysiological features are not sufficient to identify a defective molecule, and genetic studies are always required for accurate diagnosis. From a pharmacological point of view, cholinesterase inhibitors are effective in most groups of CMS, but are contraindicated in some groups of CMS. Similarly, ephedrine, salbutamol (albuterol), amifampridine are effective in most but not all groups of CMS. This review extensively covers pathomechanical and clinical features of CMS by citing 442 relevant articles.
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Affiliation(s)
- Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
- Correspondence: (K.O.); (A.G.E.)
| | - Bisei Ohkawara
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Xin-Ming Shen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
| | - Duygu Selcen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
| | - Andrew G. Engel
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
- Correspondence: (K.O.); (A.G.E.)
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Kramer JJ, Boon HTM, Leijten QH, Ter Laak H, Eshuis L, Kusters B, van Doorn JLM, Kamsteeg EJ, Eymard B, Doorduin J, Voermans NC. Dystrophic Myopathy of the Diaphragm with Recurrent Severe Respiratory Failure is Congenital Myasthenic Syndrome 11. J Neuromuscul Dis 2023; 10:271-277. [PMID: 36591657 PMCID: PMC10041432 DOI: 10.3233/jnd-221542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We here present the case of a patient with a congenital myasthenic syndrome (CMS) due to pathogenic variants in the RAPSN gene. During childhood he experienced recurrent episodes of respiratory failure during respiratory infections. This and other cases were reported as isolated dystrophy of the diaphragmatic musculature. In adulthood, whole exome sequencing revealed two heterozygous pathogenic variants in the RAPSN gene. This led to the revision of the diagnosis to rapsyn CMS11 (OMIM:616326, MONDO:0014588). EMG, muscle ultrasound and the revision of muscle biopsies taken in childhood support this diagnosis. After the revision of the diagnosis, treatment with pyridostigmine was started. This resulted in a reduction of fatigability and an improvement in functional abilities and quality of life.
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Affiliation(s)
- J J Kramer
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - H T M Boon
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | | | - Henk Ter Laak
- Department of Pathology, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - L Eshuis
- Department of Genetics, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - B Kusters
- Department of Pathology, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - J L M van Doorn
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - E J Kamsteeg
- Department of Genetics, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - B Eymard
- Institute de Myologie, Paris, France
| | - J Doorduin
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - N C Voermans
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
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Saito M, Ogasawara M, Inaba Y, Osawa Y, Nishioka M, Yamauchi S, Atsumi K, Takeuchi S, Imai K, Motobayashi M, Misawa Y, Iida A, Nishino I. Successful treatment of congenital myasthenic syndrome caused by a novel compound heterozygous variant in RAPSN. Brain Dev 2022; 44:50-55. [PMID: 34565654 DOI: 10.1016/j.braindev.2021.09.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 08/29/2021] [Accepted: 09/05/2021] [Indexed: 11/27/2022]
Abstract
BACKGROUND Congenital myasthenic syndrome (CMS) is a clinically and genetically heterogeneous neuromuscular disorder characterized by muscle weakness and caused by mutations in more than 35 different genes. This condition should not be overlooked as a subset of patients with CMS are treatable. However, the diagnosis of CMS is often difficult due to the broad variability in disease severity and course. CASE REPORT A five-year-old boy without remarkable family history was born with marked general muscle hypotonia and weakness, respiratory insufficiency, anomalies, and multiple joint contractures. Congenital myopathy was suspected based upon type 1 fiber predominance on muscle biopsy. However, he was diagnosed with CMS at age 4 years when his ptosis and ophthalmoplegia were found to be improved by edrophonium chloride and repetitive nerve stimulation showed attenuation of compound muscle action potentials. An exome sequencing identified a compound heterozygous missense variant of c.737C > T (p.A246V) and a novel intronic insertion c.1166 + 4_1166 + 5insAAGCCCACCAC in RAPSN. RT-PCR analysis which showed the skipping of exon 7 in a skeletal muscle sample confirmed that the intronic insertion was pathogenic. His myasthenic symptoms were remarkably improved by pyridostigmine. CONCLUSION The patient's diagnosis of CMS was confirmed by exome sequencing, and RT-PCR revealed that the skipping of exon 7 in RAPSN was caused by a novel intronic insertion. The genetic information uncovered in this case should therefore be added to the collection of tools for diagnosing and treating CMS.
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Affiliation(s)
- Maki Saito
- Division of Neuropediatrics, Nagano Children's Hospital, Azumino, Japan
| | - Masashi Ogasawara
- Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), Kodaira, Tokyo, Japan; Medical Genome Center, NCNP, Kodaira, Tokyo, Japan
| | - Yuji Inaba
- Division of Neuropediatrics, Nagano Children's Hospital, Azumino, Japan; Life Science Research Center, Nagano Children's Hospital, Azumino, Japan.
| | - Yoshihiro Osawa
- Department of Pediatrics, Iida Municipal Hospital, Iida, Japan
| | - Makoto Nishioka
- Division of Neuropediatrics, Nagano Children's Hospital, Azumino, Japan; Life Science Research Center, Nagano Children's Hospital, Azumino, Japan
| | - Shoko Yamauchi
- Division of Neuropediatrics, Nagano Children's Hospital, Azumino, Japan
| | - Kana Atsumi
- Division of Neuropediatrics, Nagano Children's Hospital, Azumino, Japan
| | - Shihoko Takeuchi
- Division of Neuropediatrics, Nagano Children's Hospital, Azumino, Japan
| | - Ken Imai
- Division of Neuropediatrics, Nagano Children's Hospital, Azumino, Japan
| | - Mitsuo Motobayashi
- Division of Neuropediatrics, Nagano Children's Hospital, Azumino, Japan; Life Science Research Center, Nagano Children's Hospital, Azumino, Japan
| | - Yuka Misawa
- Division of Rehabilitation, Nagano Children's Hospital, Azumino, Japan
| | | | - Ichizo Nishino
- Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), Kodaira, Tokyo, Japan; Medical Genome Center, NCNP, Kodaira, Tokyo, Japan
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6
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Beecroft SJ, Yau KS, Allcock RJN, Mina K, Gooding R, Faiz F, Atkinson VJ, Wise C, Sivadorai P, Trajanoski D, Kresoje N, Ong R, Duff RM, Cabrera-Serrano M, Nowak KJ, Pachter N, Ravenscroft G, Lamont PJ, Davis MR, Laing NG. Targeted gene panel use in 2249 neuromuscular patients: the Australasian referral center experience. Ann Clin Transl Neurol 2020; 7:353-362. [PMID: 32153140 PMCID: PMC7086001 DOI: 10.1002/acn3.51002] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/28/2020] [Accepted: 02/06/2020] [Indexed: 12/12/2022] Open
Abstract
Objective To develop, test, and iterate a comprehensive neuromuscular targeted gene panel in a national referral center. Methods We designed two iterations of a comprehensive targeted gene panel for neuromuscular disorders. Version 1 included 336 genes, which was increased to 464 genes in Version 2. Both panels used TargetSeqTM probe‐based hybridization for target enrichment followed by Ion Torrent sequencing. Targeted high‐coverage sequencing and analysis was performed on 2249 neurology patients from Australia and New Zealand (1054 Version 1, 1195 Version 2) from 2012 to 2015. No selection criteria were used other than referral from a suitable medical specialist (e.g., neurologist or clinical geneticist). Patients were classified into 15 clinical categories based on the clinical diagnosis from the referring clinician. Results Six hundred and sixty‐five patients received a genetic diagnosis (30%). Diagnosed patients were significantly younger that undiagnosed patients (26.4 and 32.5 years, respectively; P = 4.6326E‐9). The diagnostic success varied markedly between disease categories. Pathogenic variants in 10 genes explained 38% of the disease burden. Unexpected phenotypic expansions were discovered in multiple cases. Triage of unsolved cases for research exome testing led to the discovery of six new disease genes. Interpretation A comprehensive targeted diagnostic panel was an effective method for neuromuscular disease diagnosis within the context of an Australasian referral center. Use of smaller disease‐specific panels would have precluded diagnosis in many patients and increased cost. Analysis through a centralized laboratory facilitated detection of recurrent, but under‐recognized pathogenic variants.
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Affiliation(s)
- Sarah J Beecroft
- Centre for Medical Research, University of Western Australia, Harry Perkins Institute of Medical Research, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Kyle S Yau
- Centre for Medical Research, University of Western Australia, Harry Perkins Institute of Medical Research, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Richard J N Allcock
- School of Biomedical Sciences, University of Western Australia, Perth, Western Australia, Australia
| | - Kym Mina
- Department of Diagnostic Genomics, Department of Health, PathWest Laboratory Medicine, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Rebecca Gooding
- Department of Diagnostic Genomics, Department of Health, PathWest Laboratory Medicine, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Fathimath Faiz
- Department of Diagnostic Genomics, Department of Health, PathWest Laboratory Medicine, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Vanessa J Atkinson
- School of Biomedical Sciences, University of Western Australia, Perth, Western Australia, Australia.,Department of Diagnostic Genomics, Department of Health, PathWest Laboratory Medicine, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Cheryl Wise
- Department of Diagnostic Genomics, Department of Health, PathWest Laboratory Medicine, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Padma Sivadorai
- Department of Diagnostic Genomics, Department of Health, PathWest Laboratory Medicine, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Daniel Trajanoski
- Department of Diagnostic Genomics, Department of Health, PathWest Laboratory Medicine, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Nina Kresoje
- School of Biomedical Sciences, University of Western Australia, Perth, Western Australia, Australia
| | - Royston Ong
- Centre for Medical Research, University of Western Australia, Harry Perkins Institute of Medical Research, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Rachael M Duff
- Centre for Medical Research, University of Western Australia, Harry Perkins Institute of Medical Research, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Macarena Cabrera-Serrano
- Department of Neurology, Hospital Universitario Virgen del Rocio, Instituto de Biomedicina de Sevilla, CSIC, Universidad de Sevilla, Sevilla, Spain
| | - Kristen J Nowak
- Centre for Medical Research, University of Western Australia, Harry Perkins Institute of Medical Research, QEII Medical Centre, Nedlands, Western Australia, Australia.,Public and Aboriginal Health Division, Department of Health, Office of Population Health Genomics, Perth, Western Australia, Australia
| | - Nicholas Pachter
- Genetic Services of Western Australia, Department of Health, Government of Western Australia, Perth, Western Australia, Australia.,School of Paediatrics and Child Health, University of Western Australia, Perth, Western Australia, Australia
| | - Gianina Ravenscroft
- Centre for Medical Research, University of Western Australia, Harry Perkins Institute of Medical Research, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Phillipa J Lamont
- Neurogenetic Unit, Royal Perth Hospital, Perth, Western Australia, Australia
| | - Mark R Davis
- Department of Diagnostic Genomics, Department of Health, PathWest Laboratory Medicine, QEII Medical Centre, Nedlands, Western Australia, Australia
| | - Nigel G Laing
- Centre for Medical Research, University of Western Australia, Harry Perkins Institute of Medical Research, QEII Medical Centre, Nedlands, Western Australia, Australia.,Department of Diagnostic Genomics, Department of Health, PathWest Laboratory Medicine, QEII Medical Centre, Nedlands, Western Australia, Australia
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Xing G, Jing H, Zhang L, Cao Y, Li L, Zhao K, Dong Z, Chen W, Wang H, Cao R, Xiong WC, Mei L. A mechanism in agrin signaling revealed by a prevalent Rapsyn mutation in congenital myasthenic syndrome. eLife 2019; 8:e49180. [PMID: 31549961 PMCID: PMC6779466 DOI: 10.7554/elife.49180] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Accepted: 09/23/2019] [Indexed: 12/15/2022] Open
Abstract
Neuromuscular junction is a synapse between motoneurons and skeletal muscles, where acetylcholine receptors (AChRs) are concentrated to control muscle contraction. Studies of this synapse have contributed to our understanding of synapse assembly and pathological mechanisms of neuromuscular disorders. Nevertheless, underlying mechanisms of NMJ formation was not well understood. To this end, we took a novel approach - studying mutant genes implicated in congenital myasthenic syndrome (CMS). We showed that knock-in mice carrying N88K, a prevalent CMS mutation of Rapsyn (Rapsn), died soon after birth with profound NMJ deficits. Rapsn is an adapter protein that bridges AChRs to the cytoskeleton and possesses E3 ligase activity. In investigating how N88K impairs the NMJ, we uncovered a novel signaling pathway by which Agrin-LRP4-MuSK induces tyrosine phosphorylation of Rapsn, which is required for its self-association and E3 ligase activity. Our results also provide insight into pathological mechanisms of CMS.
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Affiliation(s)
- Guanglin Xing
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Hongyang Jing
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Lei Zhang
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Yu Cao
- Department of Neuroscience and Regenerative MedicineAugusta UniversityAugustaUnited States
| | - Lei Li
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Kai Zhao
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
- Department of Neuroscience and Regenerative MedicineAugusta UniversityAugustaUnited States
| | - Zhaoqi Dong
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Wenbing Chen
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Hongsheng Wang
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Rangjuan Cao
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Wen-Cheng Xiong
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
- Louis Stokes Cleveland Veterans Affairs Medical CenterClevelandUnited States
| | - Lin Mei
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
- Louis Stokes Cleveland Veterans Affairs Medical CenterClevelandUnited States
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8
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Rivner MH, Pasnoor M, Dimachkie MM, Barohn RJ, Mei L. Muscle-Specific Tyrosine Kinase and Myasthenia Gravis Owing to Other Antibodies. Neurol Clin 2019; 36:293-310. [PMID: 29655451 DOI: 10.1016/j.ncl.2018.01.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Around 20% of patients with myasthenia gravis are acetylcholine receptor antibody negative; muscle-specific tyrosine kinase antibodies (MuSK) were identified as the cause of myasthenia gravis in 30% to 40% of these cases. Anti MuSK myasthenia gravis is associated with specific clinical phenotypes. One is a bulbar form with fewer ocular symptoms. Others show an isolated head drop or symptoms indistinguishable from acetylcholine receptor-positive myasthenia gravis. These patients usually respond well to immunosuppressive therapy, but not as well to cholinesterase inhibitors. Other antibodies associated with myasthenia gravis, including low-density lipoprotein receptor-related protein 4, are discussed.
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Affiliation(s)
- Michael H Rivner
- EMG Lab, Augusta University, 1120 15th Street, BP-4390, Augusta, GA 30912, USA.
| | - Mamatha Pasnoor
- Department of Neurology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Mazen M Dimachkie
- Department of Neurology, University of Kansas Medical Center, 3599 Rainbow Boulevard, Mail Stop 2012, Kansas City, KS 66103, USA
| | - Richard J Barohn
- Department of Neurology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Mail Stop 4017, Kansas City, KS 66160, USA
| | - Lin Mei
- Department of Neuroscience and Regenerative Medicine, Augusta University, 1120 15th Street, CA-2014, Augusta, GA 30912, USA
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9
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Espinoza IO, Reynoso C, Chávez G, Engel AG. Congenital myasthenic syndrome due to rapsyn deficiency: A case report with a new mutation and compound heterozygosity. Medwave 2019; 19:e7645. [PMID: 31226102 DOI: 10.5867/medwave.2019.05.7645] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 05/19/2019] [Indexed: 11/27/2022] Open
Abstract
Introduction The congenital myasthenic syndromes are a heterogeneous group of genetic disorders characterized by an abnormal synaptic transmission in the neuromuscular plate. Report We present a two-year-old patient, male, with hypotonia, palpebral ptosis, and proximal symmetric weakness with a neonatal onset that motivated several and prolonged hospitalizations for pneumonia and respiratory failure. From two years of age, the parents noticed that the facial and general weakness worsened in the afternoons and with repeated or prolonged physical activity. The physical examination showed palpebral ptosis, predominantly proximal weakness, and fatigability with sustained muscular effort. The electromyography showed a 27% decrement in the Compound Muscular Action Potential and the case-parents genetic study showed compound heterozygosity with the transmission of two different mutations in the rapsyn gene from both parents. The patient received pyridostigmine with great improvement, achieving optimal performance in school, sports, and daily life activities. Conclusions Weakness and fatigability with neonatal onset, mainly affecting the muscles with brain stem innervation and the decrement greater than 10 percent in the Compound Muscular Action Potential in the electromyographic studies, should make us suspect in a congenital myasthenic syndrome. We review the literature and key clinical points to establish a timely diagnosis and effective treatment in some of these syndromes.
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Affiliation(s)
- Ivan O Espinoza
- Unidad de Neurología Pediátrica, Departamento de Clínicas Médicas, Universidad Peruana Cayetano Heredia, Lima, Perú. Address: Servicio de Especialidades Pediátricas del Hospital Cayetano Heredia, Avenida Honorio Delgado 262, San Martín de Porres, Lima, Perú, CP: 15102.
| | - Carolina Reynoso
- Unidad de Neurología Pediátrica, Departamento de Clínicas Médicas, Universidad Peruana Cayetano Heredia, Lima, Perú
| | - Giulliana Chávez
- Servicio de Especialidades Pediátricas, Departamento de Pediatría, Hospital Cayetano Heredia, Lima, Perú
| | - Andrew G Engel
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, Minnesota, USA
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10
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Cardiac autonomic function evaluation in pediatric and adult patients with congenital myasthenic syndromes. Neuromuscul Disord 2019; 29:290-295. [PMID: 30898524 DOI: 10.1016/j.nmd.2019.02.004] [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: 09/30/2018] [Revised: 12/27/2018] [Accepted: 02/12/2019] [Indexed: 11/21/2022]
Abstract
Cardiac autonomic dysfunction has been examined in myasthenia gravis but not in congenital myasthenic syndromes (CMS). We aimed to evaluate cardiac autonomic functions in genetically defined CMS. Patients diagnosed with and under treatment for CMS were reviewed for 24-hour cardiac rhythm monitoring. Heart rate variability (HRV) measures were defined as: SDNN, mean of the standard deviations for all R-R intervals; SDNNi, standard deviation of all R-R intervals in successive five-minute epochs; RMSSD, square root of the mean of squared differences between successive R-R intervals. Ten patients with mutations in the epsilon subunit of the acetylcholine receptor (AChRε) and five patients with mutations in the collagen-like tail of asymmetric acetylcholinesterase (ColQ) were included. Median age at evaluation was 17 (2.5-46) years. In the AChRε group, RMSSD values; and in the ColQ group, SDNN, SDNNi and RMSSD values were significantly lower than those of healthy subjects. This first extensive report examining HRV in CMS showed alterations in patients with ColQ mutations and, to a lesser extent, in the group with AChRε mutations. This might indicate an increased risk of cardiac arrhythmias. We suggest cardiological follow-up in CMS, and consideration of any potential cardiovascular effects of therapeutic agents used in management.
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11
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Estephan EDP, Zambon AA, Marchiori PE, da Silva AMS, Caldas VM, Moreno CAM, Reed UC, Horvath R, Töpf A, Lochmüller H, Zanoteli E. Clinical variability of early-onset congenital myasthenic syndrome due to biallelic RAPSN mutations in Brazil. Neuromuscul Disord 2018; 28:961-964. [DOI: 10.1016/j.nmd.2018.08.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 08/22/2018] [Indexed: 10/28/2022]
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12
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Kumar A, Asghar S, Kavanagh R, Wicklund MP. Unique presentation of rapidly fluctuating symptoms in a child with congenital myasthenic syndrome due to RAPSN mutation. Muscle Nerve 2018; 58:E23-E24. [PMID: 30028532 DOI: 10.1002/mus.26200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 06/09/2018] [Accepted: 06/12/2018] [Indexed: 10/28/2022]
Affiliation(s)
- Ashutosh Kumar
- Division of Pediatric Neurology, Penn State Milton S. Hershey Medical Center, 500 University Drive, Hershey, Pennsylvania, 17033, USA
| | - Sheila Asghar
- Division of Pediatric Neurology, Penn State Milton S. Hershey Medical Center, 500 University Drive, Hershey, Pennsylvania, 17033, USA
| | - Robert Kavanagh
- Division of Pediatric Critical Care, Penn State Milton S. Hershey Medical Center, Hershey, Pennsylvania, USA
| | - Matthew P Wicklund
- Department of Neurology, University of Colorado School of Medicine, Aurora, Colorado, USA
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13
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14
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Estephan EDP, Sobreira CFDR, Dos Santos ACJ, Tomaselli PJ, Marques W, Ortega RPM, Costa MCM, da Silva AMS, Mendonça RH, Caldas VM, Zambon AA, Abath Neto O, Marchiori PE, Heise CO, Reed UC, Azuma Y, Töpf A, Lochmüller H, Zanoteli E. A common CHRNE mutation in Brazilian patients with congenital myasthenic syndrome. J Neurol 2018; 265:708-713. [PMID: 29383513 DOI: 10.1007/s00415-018-8736-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 12/16/2017] [Accepted: 01/04/2018] [Indexed: 11/29/2022]
Abstract
The most common causes of congenital myasthenic syndromes (CMS) are CHRNE mutations, and some pathogenic allelic variants in this gene are especially frequent in certain ethnic groups. In the southern region of Brazil, a study found the c.130dupG CHRNE mutation in up to 33% of families with CMS. Here, we aimed to verify the frequency of this mutation among individuals with CMS in a larger cohort of CMS patients from different areas of Brazil and to characterize clinical features of these patients. Eighty-four patients with CMS, from 72 families, were clinically evaluated and submitted to direct sequencing of the exon 2 of CHRNE. The c.130dupG mutation was found in 32 patients (23 families), with 26 patients (19 families, 26.3%) in homozygosis, confirming its high prevalence in different regions of Brazil. Among the homozygous patients, the following characteristics were frequent: onset of symptoms before 2 years of age (92.3%), little functional restriction (92.3%), fluctuating symptoms (100%), ocular muscle impairment (96.1%), ptosis (100%), limb weakness (88.4%), response to pyridostigmine (100%), facial involvement (77%), and bulbar symptoms (70.8%). The pretest probability of finding at least one allele harbouring the c.130dupG mutation was 38.1%. Selecting only patients with impaired eye movement together with limb weakness and improvement with pyridostigmine, the probability increases to 72.2%. This clinical pre-selection of patients is likely a useful tool for regions where CHRNE mutations have a founder effect. In conclusion, the CHRNE mutation c.130dupG leads to fairly benign natural course of the disease with relative homogeneity.
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Affiliation(s)
- Eduardo de Paula Estephan
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), Av. Enéas de Carvalho Aguiar, 255, 5o andar, sala 5084, Cerqueira César, São Paulo, 05403-900, Brazil
| | | | | | - Pedro José Tomaselli
- Department of Neurosciences, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Wilson Marques
- Department of Neurosciences, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | | | | | - André Macedo Serafim da Silva
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), Av. Enéas de Carvalho Aguiar, 255, 5o andar, sala 5084, Cerqueira César, São Paulo, 05403-900, Brazil
| | - Rodrigo Holanda Mendonça
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), Av. Enéas de Carvalho Aguiar, 255, 5o andar, sala 5084, Cerqueira César, São Paulo, 05403-900, Brazil
| | - Vitor Marques Caldas
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), Av. Enéas de Carvalho Aguiar, 255, 5o andar, sala 5084, Cerqueira César, São Paulo, 05403-900, Brazil
| | - Antonio Alberto Zambon
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), Av. Enéas de Carvalho Aguiar, 255, 5o andar, sala 5084, Cerqueira César, São Paulo, 05403-900, Brazil
| | - Osório Abath Neto
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), Av. Enéas de Carvalho Aguiar, 255, 5o andar, sala 5084, Cerqueira César, São Paulo, 05403-900, Brazil
| | - Paulo Eurípedes Marchiori
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), Av. Enéas de Carvalho Aguiar, 255, 5o andar, sala 5084, Cerqueira César, São Paulo, 05403-900, Brazil
| | - Carlos Otto Heise
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), Av. Enéas de Carvalho Aguiar, 255, 5o andar, sala 5084, Cerqueira César, São Paulo, 05403-900, Brazil
| | - Umbertina Conti Reed
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), Av. Enéas de Carvalho Aguiar, 255, 5o andar, sala 5084, Cerqueira César, São Paulo, 05403-900, Brazil
| | - Yoshiteru Azuma
- Institute of Genetic Medicine, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
| | - Ana Töpf
- Institute of Genetic Medicine, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
| | - Hanns Lochmüller
- Institute of Genetic Medicine, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
| | - Edmar Zanoteli
- Departamento de Neurologia, Faculdade de Medicina da Universidade de São Paulo (FMUSP), Av. Enéas de Carvalho Aguiar, 255, 5o andar, sala 5084, Cerqueira César, São Paulo, 05403-900, Brazil.
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15
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Engel AG. Genetic basis and phenotypic features of congenital myasthenic syndromes. HANDBOOK OF CLINICAL NEUROLOGY 2018; 148:565-589. [PMID: 29478601 DOI: 10.1016/b978-0-444-64076-5.00037-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
Abstract
The congenital myasthenic syndromes (CMS) are heterogeneous disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. The disease proteins reside in the nerve terminal, the synaptic basal lamina, or in the postsynaptic region, or at multiple sites at the neuromuscular junction as well as in other tissues. Targeted mutation analysis by Sanger or exome sequencing has been facilitated by characteristic phenotypic features of some CMS. No fewer than 20 disease genes have been recognized to date. In one-half of the currently identified probands, the disease stems from mutations in genes encoding subunits of the muscle form of the acetylcholine receptor (CHRNA1, CHRNB, CHRNAD1, and CHRNE). In 10-14% of the probands the disease is caused by mutations in RAPSN, DOK 7, or COLQ, and in 5% by mutations in CHAT. Other less frequently identified disease genes include LAMB2, AGRN, LRP4, MUSK, GFPT1, DPAGT1, ALG2, and ALG 14 as well as SCN4A, PREPL, PLEC1, DNM2, and MTM1. Identification of the genetic basis of each CMS is important not only for genetic counseling and disease prevention but also for therapy, because therapeutic agents that benefit one type of CMS can be harmful in another.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN, United States.
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16
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Lam CW, Wong KS, Leung HW, Law CY. Limb girdle myasthenia with digenic RAPSN and a novel disease gene AK9 mutations. Eur J Hum Genet 2016; 25:192-199. [PMID: 27966543 DOI: 10.1038/ejhg.2016.162] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 10/04/2016] [Accepted: 10/18/2016] [Indexed: 12/19/2022] Open
Abstract
Though dysfunction of neuromuscular junction (NMJ) is associated with congenital myasthenic syndrome (CMS), the proteins involved in neuromuscular transmission have not been completely identified. In this study, we aimed to identify a novel CMS gene in a consanguineous family with limb-girdle type CMS. Homozygosity mapping of the novel CMS gene was performed using high-density single-nucleotide polymorphism microarrays. The variants in CMS gene were identified by whole-exome sequencing (WES) and Sanger sequencing. A 20 MB-region of homozygosity (ROH) was mapped on chromosome 6q15-21. This was the only ROH that present in all clinically affected siblings and absent in all clinically unaffected siblings. WES showed a novel variant of AK9 gene located in this ROH. This variant was a start-gain mutation and introduced a cryptic 5'-UTR signal in intron 5 of the AK9 gene. The normal splicing signal would be interfered by the cryptic translation signal leading to defective splicing. Another 25 MB-ROH was found on chromosome 11p13-q12 in all siblings. WES showed a homozygous RAPSN pathogenic variant in this ROH. Since RAPSN-associated limb-girdle type CMS was only manifested in AK9 homozygous variant carriers, the disease phenotype was of digenic inheritance, and was determined by the novel disease modifier AK9 which provides NTPs for N-glycosylation. This is the first time that this specific genotype-phenotype correlation is reported. Importantly, the AK9-associated nucleotide deficiency may replete by dietary supplements. Since AK9 is a disease modifier, enhancing N-glycosylation by increasing dietary nucleotides may be a new therapeutic option for CMS patients.
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Affiliation(s)
- Ching-Wan Lam
- Department of Pathology, The University of Hong Kong, Hong Kong, China
| | - Ka-Sing Wong
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China
| | - Ho-Wan Leung
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China
| | - Chun-Yiu Law
- Department of Pathology, The University of Hong Kong, Hong Kong, China
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17
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Aharoni S, Sadeh M, Shapira Y, Edvardson S, Daana M, Dor-Wollman T, Mimouni-Bloch A, Halevy A, Cohen R, Sagie L, Argov Z, Rabie M, Spiegel R, Chervinsky I, Orenstein N, Engel AG, Nevo Y. Congenital myasthenic syndrome in Israel: Genetic and clinical characterization. Neuromuscul Disord 2016; 27:136-140. [PMID: 28024842 DOI: 10.1016/j.nmd.2016.11.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 11/20/2016] [Accepted: 11/21/2016] [Indexed: 10/20/2022]
Abstract
The objective of the study was to evaluate the epidemiology of patients with congenital myasthenic syndrome (CMS) in Israel. Targeted mutation analysis was performed based on the clinical symptoms and electrophysiological findings for known CMS. Additional specific tests were performed in patients of Iranian and/or Iraqi Jewish origin. All medical records were reviewed and clinical data, genetic mutations and outcomes were recorded. Forty-five patients with genetic mutations in known CMS genes from 35 families were identified. Mutations in RAPSN were identified in 13 kinships in Israel. The most common mutation was c.-38A>G detected in 8 patients of Iranian and/or Iraqi Jewish origin. Four different recessive mutations in COLQ were identified in 11 kinships, 10 of which were of Muslim-Arab descent. Mutations in CHRNE were identified in 7 kinships. Less commonly detected mutations were in CHRND, CHAT, GFPT1 and DOK7. In conclusion, mutations in RAPSN and COLQ are the most common causes of CMS in our cohort. Specific mutations in COLQ, RAPSN, and CHRNE occur in specific ethnic populations and should be taken into account when the diagnosis of a CMS is suspected.
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Affiliation(s)
- Sharon Aharoni
- Institute of Child Neurology, Schneider Children's Medical Center of Israel, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
| | - Menachem Sadeh
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Department of Neurology, Wolfson Medical Center, Holon, Israel
| | - Yehuda Shapira
- Neuropediatric Unit, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Simon Edvardson
- Neuropediatric Unit, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Muhannad Daana
- Neuropediatric Unit, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Talia Dor-Wollman
- Neuropediatric Unit, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Aviva Mimouni-Bloch
- Pediatric Neurology and Developmental Unit, Loewenstein Rehabilitation Hospital, Raanana, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ayelet Halevy
- Institute of Child Neurology, Schneider Children's Medical Center of Israel, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Rony Cohen
- Institute of Child Neurology, Schneider Children's Medical Center of Israel, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Liora Sagie
- Pediatric Neurology Unit, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
| | - Zohar Argov
- Department of Neurology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Malcolm Rabie
- Institute of Child Neurology, Schneider Children's Medical Center of Israel, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ronen Spiegel
- Genetic Institute, Emek Medical Center, Afula, Israel
| | | | - Naama Orenstein
- Genetics Unit, Schneider Children's Medical Center of Israel, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Andrew G Engel
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN, USA
| | - Yoram Nevo
- Institute of Child Neurology, Schneider Children's Medical Center of Israel, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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18
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Visser AC, Laughlin RS, Litchy WJ, Benarroch EE, Milone M. Rapsyn congenital myasthenic syndrome worsened by fluoxetine. Muscle Nerve 2016; 55:131-135. [DOI: 10.1002/mus.25244] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/02/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Amy C. Visser
- Department of NeurologyMayo Clinic200 First Street SWRochester Minnesota55905 USA
| | - Ruple S. Laughlin
- Department of NeurologyMayo Clinic200 First Street SWRochester Minnesota55905 USA
| | - William J. Litchy
- Department of NeurologyMayo Clinic200 First Street SWRochester Minnesota55905 USA
| | - Eduardo E. Benarroch
- Department of NeurologyMayo Clinic200 First Street SWRochester Minnesota55905 USA
| | - Margherita Milone
- Department of NeurologyMayo Clinic200 First Street SWRochester Minnesota55905 USA
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19
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Garg N, Yiannikas C, Hardy TA, Belaya K, Cheung J, Beeson D, Reddel SW. Late presentations of congenital myasthenic syndromes: How many do we miss? Muscle Nerve 2016; 54:721-7. [DOI: 10.1002/mus.25085] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/16/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Nidhi Garg
- Neuroimmunology Clinic; Concord Hospital and University of Sydney; NSW Australia
| | - Con Yiannikas
- Departments of Neurology and Molecular Medicine; University of Sydney, Concord Hospital; Sydney New South Wales 2139 Australia
| | - Todd A. Hardy
- Neuroimmunology Clinic; Concord Hospital and University of Sydney; NSW Australia
| | - Katsiaryna Belaya
- The Weatherall Institute of Molecular Medicine; University of Oxford, John Radcliffe Hospital; Oxford UK
| | - Jonathan Cheung
- The Weatherall Institute of Molecular Medicine; University of Oxford, John Radcliffe Hospital; Oxford UK
| | - David Beeson
- The Weatherall Institute of Molecular Medicine; University of Oxford, John Radcliffe Hospital; Oxford UK
| | - Stephen W. Reddel
- Neuroimmunology Clinic; Concord Hospital and University of Sydney; NSW Australia
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20
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Natera-de Benito D, Bestué M, Vilchez JJ, Evangelista T, Töpf A, García-Ribes A, Trujillo-Tiebas MJ, García-Hoyos M, Ortez C, Camacho A, Jiménez E, Dusl M, Abicht A, Lochmüller H, Colomer J, Nascimento A. Long-term follow-up in patients with congenital myasthenic syndrome due to RAPSN mutations. Neuromuscul Disord 2015; 26:153-9. [PMID: 26782015 DOI: 10.1016/j.nmd.2015.10.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 10/27/2015] [Accepted: 10/29/2015] [Indexed: 11/19/2022]
Abstract
Rapsyn (RAPSN) mutations are a common cause of postsynaptic congenital myasthenic syndromes. We present a comprehensive description of the clinical and molecular findings of ten patients with CMS due to mutations in RAPSN, mostly with a long-term follow-up. Two patients were homozygous and eight were heterozygous for the common p.Asn88Lys mutation. In three of the heterozygous patients we have identified three novel mutations (c.869T > C; p.Leu290Pro, c.1185delG; p.Thr396Profs*12, and c.358delC; p.Gln120Serfs*8). In our cohort, the RAPSN mutations lead to a relatively homogeneous phenotype, characterized by fluctuating ptosis, occasional bulbar symptoms, neck muscle weakness, and mild proximal muscle weakness with exacerbations precipitated by minor infections. Interestingly, episodic exacerbations continue to occur during adulthood. These were characterized by proximal limb girdle weakness and ptosis, and not so much by respiratory insufficiency after age 6. All patients presented during neonatal period and responded to cholinergic agonists. In most of the affected patients, additional use of 3,4-diaminopyridine resulted in significant clinical benefit. The disease course is stable except for intermittent worsening.
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Affiliation(s)
- D Natera-de Benito
- Department of Pediatrics, Hospital Universitario de Fuenlabrada, Madrid, Spain.
| | - M Bestué
- Department of Neurology, Hospital General San Jorge, Huesca, Spain
| | - J J Vilchez
- Department of Neurology, Hospital Universitari La Fe, Valencia, Spain
| | - T Evangelista
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - A Töpf
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - A García-Ribes
- Department of Pediatrics, Hospital Universitario Cruces, Bilbao, Spain
| | - M J Trujillo-Tiebas
- Department of Genetics, Hospital Universitario Fundación Jiménez Díaz, Madrid, Spain
| | - M García-Hoyos
- Department of Genetics, Instituto de Medicina Genómica, Valencia, Spain
| | - C Ortez
- Department of Neuromuscular Diseases, Hospital Sant Joan de Déu, Barcelona, Spain
| | - A Camacho
- Department of Pediatric Neurology, Hospital Universitario 12 de Octubre, Madrid, Spain
| | - E Jiménez
- Department of Pediatrics, Hospital Universitario Rey Juan Carlos, Madrid, Spain
| | - M Dusl
- Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Munich 80336,Germany
| | - A Abicht
- Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Munich 80336,Germany; Medical Genetics Center, Munich, Germany
| | - H Lochmüller
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - J Colomer
- Department of Neuromuscular Diseases, Hospital Sant Joan de Déu, Barcelona, Spain
| | - A Nascimento
- Department of Neuromuscular Diseases, Hospital Sant Joan de Déu, Barcelona, Spain
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21
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Engel AG, Shen XM, Selcen D, Sine SM. Congenital myasthenic syndromes: pathogenesis, diagnosis, and treatment. Lancet Neurol 2015; 14:420-34. [PMID: 25792100 PMCID: PMC4520251 DOI: 10.1016/s1474-4422(14)70201-7] [Citation(s) in RCA: 329] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The congenital myasthenic syndromes (CMS) are a diverse group of genetic disorders caused by abnormal signal transmission at the motor endplate, a special synaptic contact between motor axons and each skeletal muscle fibre. Most CMS stem from molecular defects in the muscle nicotinic acetylcholine receptor, but they can also be caused by mutations in presynaptic proteins, mutations in proteins associated with the synaptic basal lamina, defects in endplate development and maintenance, or defects in protein glycosylation. The specific diagnosis of some CMS can sometimes be reached by phenotypic clues pointing to the mutated gene. In the absence of such clues, exome sequencing is a useful technique for finding the disease gene. Greater understanding of the mechanisms of CMS have been obtained from structural and electrophysiological studies of the endplate, and from biochemical studies. Present therapies for the CMS include cholinergic agonists, long-lived open-channel blockers of the acetylcholine receptor ion channel, and adrenergic agonists. Although most CMS are treatable, caution should be exercised as some drugs that are beneficial in one syndrome can be detrimental in another.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, Rochester, MN, USA.
| | - Xin-Ming Shen
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - Duygu Selcen
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - Steven M Sine
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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Eymard B, Stojkovic T, Sternberg D, Richard P, Nicole S, Fournier E, Béhin A, Laforêt P, Servais L, Romero N, Fardeau M, Hantaï D. [Congenital myasthenic syndromes: difficulties in the diagnosis, course and prognosis, and therapy--The French National Congenital Myasthenic Syndrome Network experience]. Rev Neurol (Paris) 2013; 169 Suppl 1:S45-55. [PMID: 23452772 DOI: 10.1016/s0035-3787(13)70060-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders caused by genetic defects affecting neuromuscular transmission and leading to muscle weakness accentuated by exertion. Three different aspects have been investigated by members of the national French CMS Network: the difficulties in making a proper diagnosis; the course and long-term prognosis; and the response to therapy, especially for CMS that do not respond to cholinesterase inhibitors. CMS diagnosis is late in most cases because of confusion with other entities such as: congenital myopathies, due to the frequent presentation in patients of myopathies such as permanent muscle weakness, atrophy and scoliosis, and the abnormalities of internal structure, diameter and distribution of fibers (type I predominance, type II atrophy) seen on biopsy; seronegative autoimmune myasthenia gravis, when CMS is of late onset; and metabolic myopathy, with the presence of lipidosis in muscle. The long-term prognosis of CMS was studied in a series of 79 patients recruited with the following gene mutations: CHRNA; CHRNE; DOK7; COLQ; RAPSN; AGRN; and MUSK. Disease-course patterns (progressive worsening, exacerbation, stability, improvement) could be variable throughout life in a given patient. DOK7 patients had the most severe disease course with progressive worsening: of the eight wheelchair-bound and ventilated patients, six had mutations of this gene. Pregnancy was a frequent cause of exacerbation. Anticholinesterase agents are the first-line therapy for CMS patients, except for cases of slow-channel CMS, COLQ and DOK7. In our experience, 3,4-DAP was a useful complement for several patients harboring CMS with AChR loss or RAPSN gene mutations. Ephedrine was given to 18 patients (eight DOK7, five COLQ, four AGRN and one RAPSN). Tolerability was good. Therapeutic responses were encouraging even in the most severely affected patients, particularly with DOK7 and COLQ. Salbutamol was a good alternative in one patient who was allergic to ephedrine.
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Affiliation(s)
- B Eymard
- Centre de référence des affections neuromusculaires Paris-Est, service de Neurologie 2, Institut de Myologie, Hôpital de la Pitié-Salpêtrière, 47 bd de l'Hôpital, 75013 Paris, France.
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Pavone P, Polizzi A, Longo MR, Romano K, Vecchio M, Praticò AD, Falsaperla R. Congenital myasthenic syndromes: Clinical and molecular report on 7 Sicilian patients. J Pediatr Neurosci 2013; 8:19-21. [PMID: 23772238 PMCID: PMC3680889 DOI: 10.4103/1817-1745.111416] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Background: Congenital myasthenic syndromes (CMS) are a heterogeneous group of diseases involving neuromuscular transmission. The classification of these syndromes is based on the localization of the defect (pre-synaptic, post-synaptic, and neuromuscular junction) and on the molecular analysis. Aim: To report on a series of 7 patients affected by post-synaptic CMS. Patients and Methods: We examined sex, familiarity, age of onset, clinical symptoms, and response to tensilon test, patellar and pupillary reflexes, presence of cranial nerve involvement, Gowers′ sign, presence of ptosis, grade of muscular weakness, and response to the treatment and gene deletions. Results: Ptosis, muscular hypotonia, and light variability in muscular weakness were the main clinical signs. Cholinergic receptor, nicotinic, epsilon (CHRNE) gene mutations were mainly reported. Conclusions: The study points out that the clinical and molecular pattern reported in our patients do not differentiate from the data reported in the literature. Treatment with pyridostigmine and modulation of the therapy allows a good quality of life.
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Affiliation(s)
- Piero Pavone
- Department of Pediatric and Pediatric Neurology, Azienda Ospedaliera Universitaria OVE-Policlinico, University of Catania, Catania, Italy
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Pavone P, Praticò AD, Pavone V, Falsaperla R. Congenital familial myasthenic syndromes: disease and course in an affected dizygotic twin pair. BMJ Case Rep 2013; 2013:bcr-2012-007651. [PMID: 23365176 DOI: 10.1136/bcr-2012-007651] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The present report describes clinical variability in an affected dizygotic twin pair. Twin 1 showed classical features of the congenital myasthenic syndromes (CMS), that is, ptosis, dysphonia, asthenia and hypotonia. In twin 2, these clinical signs were less pronounced, but subtle resulting in severe lumbar hyperlordosis. Molecular analysis, performed for both twins, revealed the presence of three polymorphisms in the heterozygous form in RAPSN gene. The present report highlights the clinical variability of the CMS.
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Affiliation(s)
- Piero Pavone
- Unit of Pediatrics and Pediatric Emergency, University Hospital OVE-Policlinico, Catania, Italy.
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Abstract
Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders caused by genetic defects affecting neuromuscular transmission and leading to muscle weakness accentuated by exertion. The characterization of CMS comprises two complementary steps: establishing the diagnosis and identifying the pathophysiological type of CMS. The combination of clinical, electrophysiological, and morphological studies allows the physician to refer a given CMS to mutation(s) in one of the 18 causative genes discovered to date and, in turn, to classify the CMS according to the location of the mutated proteins at the neuromuscular junction into presynaptic compartment, synaptic basal lamina, and postsynaptic compartment CMS. This complete characterization is essential for counseling and therapy of the patient, depending on the molecular background of the respective CMS. Despite comprehensive characterization, the phenotypic expression of one given gene involved is variable, and the etiology of many CMS remains to be discovered.
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Affiliation(s)
- Bruno Eymard
- Reference Center for Neuromuscular Diseases, Institute of Myology, Pitié-Salpêtrière Hospital, Paris, France
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Abicht A, Dusl M, Gallenmüller C, Guergueltcheva V, Schara U, Della Marina A, Wibbeler E, Almaras S, Mihaylova V, von der Hagen M, Huebner A, Chaouch A, Müller JS, Lochmüller H. Congenital myasthenic syndromes: Achievements and limitations of phenotype-guided gene-after-gene sequencing in diagnostic practice: A study of 680 patients. Hum Mutat 2012; 33:1474-84. [DOI: 10.1002/humu.22130] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 04/30/2012] [Indexed: 11/09/2022]
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Khan A, Hussain N, Gosalakkal JA. Bulbar dysfunction: An early presentation of congenital myasthenic syndrome in three infants. J Pediatr Neurosci 2012; 6:124-6. [PMID: 22408661 PMCID: PMC3296406 DOI: 10.4103/1817-1745.92832] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Congenital myasthenic syndromes are a group of rare genetic disorders affecting neuromuscular transmission. A high index of suspicion is required as clinical manifestations can be variable and nonspecific. Clinical phenotype includes arthrogryposis, respiratory crises, facial deformities, and weakness. With the availability of molecular genetics, this group of conditions can now be more clearly delineated and targeted treatment can be initiated. We describe three children who presented with bulbar difficulties and had Cholinergic receptor, nicotinic, and epsilon or receptor associated protein of the synapse mutations.
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Affiliation(s)
- Arif Khan
- Department of Paediatric Neurology, Leicester Royal Infirmary, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom
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Abstract
Congenital myasthenic syndromes (CMS) represent a heterogeneous group of disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. Clinical, electrophysiologic, and morphologic studies have paved the way for detecting CMS-related mutations in proteins residing in the nerve terminal, the synaptic basal lamina, or in the postsynaptic region of the motor endplate. The disease proteins identified to date include the acetylcholine receptor, acetylcholinesterase, choline acetyltransferase, rapsyn, and Na(v)1.4, muscle-specific kinase, agrin, β2-laminin, downstream of tyrosine kinase 7, and glutamine-fructose-6-phosphate transaminase 1. Analysis of electrophysiologic and biochemical properties of mutant proteins expressed in heterologous systems have contributed crucially to defining the molecular consequences of the observed mutations and have resulted in improved therapy of most CMS.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
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Engel AG. Current status of the congenital myasthenic syndromes. Neuromuscul Disord 2012; 22:99-111. [PMID: 22104196 PMCID: PMC3269564 DOI: 10.1016/j.nmd.2011.10.009] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2011] [Revised: 10/11/2011] [Accepted: 10/13/2011] [Indexed: 01/04/2023]
Abstract
Congenital myasthenic syndromes (CMS) are heterogeneous disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. Clinical, electrophysiologic, and morphologic studies have paved the way for detecting CMS-related mutations in proteins residing in the nerve terminal, the synaptic basal lamina, and in the postsynaptic region of the motor endplate. The disease proteins identified to date include choline acetyltransferase (ChAT), the endplate species of acetylcholinesterase (AChE), β2-laminin, the acetylcholine receptor (AChR), rapsyn, plectin, Na(v)1.4, the muscle specific protein kinase (MuSK), agrin, downstream of tyrosine kinase 7 (Dok-7), and glutamine-fructose-6-phosphate transaminase 1 (GFPT1). Myasthenic syndromes associated with centronuclear myopathies were recently recognized. Analysis of properties of expressed mutant proteins contributed to finding improved therapy for most CMS. Despite these advances, the molecular basis of some phenotypically characterized CMS remains elusive. Moreover, other types of CMS and disease genes likely exist and await discovery.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, United States.
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Diagnosis of congenital myasthenic syndrome with mutation of the RAPSN gene after general anaesthesia. Eur J Anaesthesiol 2012; 28:748-9. [PMID: 21372719 DOI: 10.1097/eja.0b013e3283453f4b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Guergueltcheva V, Müller JS, Dusl M, Senderek J, Oldfors A, Lindbergh C, Maxwell S, Colomer J, Mallebrera CJ, Nascimento A, Vilchez JJ, Muelas N, Kirschner J, Nafissi S, Kariminejad A, Nilipour Y, Bozorgmehr B, Najmabadi H, Rodolico C, Sieb JP, Schlotter B, Schoser B, Herrmann R, Voit T, Steinlein OK, Najafi A, Urtizberea A, Soler DM, Muntoni F, Hanna MG, Chaouch A, Straub V, Bushby K, Palace J, Beeson D, Abicht A, Lochmüller H. Congenital myasthenic syndrome with tubular aggregates caused by GFPT1 mutations. J Neurol 2011; 259:838-50. [DOI: 10.1007/s00415-011-6262-z] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 09/13/2011] [Accepted: 09/15/2011] [Indexed: 02/04/2023]
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[Neuromuscular signal transmission in adulthood. Current facets of acquired and hereditary disorders]. DER NERVENARZT 2011; 82:707-11. [PMID: 21584790 DOI: 10.1007/s00115-010-2969-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The availability of early diagnosis and modern effective therapies has reduced mortality and disability linked to late-onset acquired or hereditary neuromuscular transmission disorders. Nevertheless, identification of the pathogenesis of these diseases remains a challenge. In addition to non-specific and fluctuating presenting symptoms current diagnostic work-up strategies include electrophysiology, antibody measurements and less frequently molecular genetics. For differential diagnostic purposes there is an increasing demand for improving awareness concerning late-onset congenital myasthenic syndromes (CMS) which are rare but nevertheless symptomatically treatable diseases. Especially in seronegative myasthenic syndromes, molecular genetic analyses of CMS genes should be integrated into the differential diagnostic work-up. Therefore, some facets of neuromuscular synaptogenesis in the context of seronegative acquired myasthenic syndromes and recently uncovered congenital myasthenic syndromes are reviewed.
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Alseth EH, Maniaol AH, Elsais A, Nakkestad HL, Tallaksen C, Gilhus NE, Skeie GO. Investigation for RAPSN and DOK-7 mutations in a cohort of seronegative myasthenia gravis patients. Muscle Nerve 2011; 43:574-7. [DOI: 10.1002/mus.21919] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/14/2011] [Indexed: 11/12/2022]
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Verschuuren JJGM, Palace J, Erik Gilhus N. Clinical aspects of myasthenia explained. Autoimmunity 2010; 43:344-52. [DOI: 10.3109/08916931003602130] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Brugnoni R, Maggi L, Canioni E, Moroni I, Pantaleoni C, D’Arrigo S, Riva D, Cornelio F, Bernasconi P, Mantegazza R. Identification of previously unreported mutations in CHRNA1, CHRNE and RAPSN genes in three unrelated Italian patients with congenital myasthenic syndromes. J Neurol 2010; 257:1119-23. [DOI: 10.1007/s00415-010-5472-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Revised: 01/12/2010] [Accepted: 01/15/2010] [Indexed: 11/24/2022]
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Milone M, Shen XM, Selcen D, Ohno K, Brengman J, Iannaccone ST, Harper CM, Engel AG. Myasthenic syndrome due to defects in rapsyn: Clinical and molecular findings in 39 patients. Neurology 2009; 73:228-35. [PMID: 19620612 PMCID: PMC2715575 DOI: 10.1212/wnl.0b013e3181ae7cbc] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Pathogenic mutations in rapsyn result in endplate acetylcholine receptor (AChR) deficiency and are a common cause of postsynaptic congenital myasthenic syndromes. METHODS Clinical, electrophysiologic, pathologic, and molecular studies were done in 39 patients. RESULTS In all but one patient, the disease presented in the first 2 years of life. In 9 patients, the myasthenic symptoms included constant or episodic ophthalmoparesis, and 1 patient had a pure limb-girdle phenotype. More than one-half of the patients experienced intermittent exacerbations. Long-term follow-up was available in 25 patients after start of cholinergic therapy: 21 became stable or were improved and 2 of these became asymptomatic; 3 had a progressive course; and 1 died in infancy. In 7 patients who had endplate studies, the average counts of AChR per endplate and the synaptic response to ACh were less reduced than in patients harboring low AChR expressor mutations. Eight patients were homozygous and 23 heterozygous for the common p.N88K mutation. Six mutations, comprising 3 missense mutations, an in-frame deletion, a splice-site mutation, and a nonsense mutation, are novel. Homozygosity for p.N88K was associated with varying grades of severity. No genotype-phenotype correlations were observed except in 8 Near-Eastern patients homozygous for the promoter mutation (c.-38A>G), who had a mild course. CONCLUSIONS All but 1 patient presented early in life and most responded to cholinergic agonists. With early diagnosis and therapy, rapsyn deficiency has a benign course in most patients. There was no consistent phenotype-genotype correlation except for an E-box mutation associated with jaw deformities.
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Affiliation(s)
- M Milone
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA.
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Martínez-Martínez P, Phernambucq M, Steinbusch L, Schaeffer L, Berrih-Aknin S, Duimel H, Frederik P, Molenaar P, De Baets MH, Losen M. Silencing rapsyn in vivo decreases acetylcholine receptors and augments sodium channels and secondary postsynaptic membrane folding. Neurobiol Dis 2009; 35:14-23. [PMID: 19344765 DOI: 10.1016/j.nbd.2009.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2008] [Revised: 02/23/2009] [Accepted: 03/18/2009] [Indexed: 10/21/2022] Open
Abstract
The receptor-associated protein of the synapse (rapsyn) is required for anchoring and stabilizing the nicotinic acetylcholine receptor (AChR) in the postsynaptic membrane of the neuromuscular junction (NMJ) during development. Here we studied the role of rapsyn in the maintenance of the adult NMJ by reducing rapsyn expression levels with short hairpin RNA (shRNA). Silencing rapsyn led to the average reduction of the protein levels of rapsyn (31% loss) and AChR (36% loss) at the NMJ within 2 weeks, corresponding to previously reported half life of these proteins. On the other hand, the sodium channel protein expression was augmented (66%) in rapsyn-silenced muscles. Unexpectedly, at the ultrastructural level a significant increase in the amount of secondary folds of the postsynaptic membrane in silenced muscles was observed. The neuromuscular transmission in rapsyn-silenced muscles was mildly impaired. The results suggest that the adult NMJ can rapidly produce postsynaptic folds to compensate for AChR and rapsyn loss.
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Affiliation(s)
- Pilar Martínez-Martínez
- Department of Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands, Maastricht, The Netherlands.
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Vogt J, Harrison BJ, Spearman H, Cossins J, Vermeer S, ten Cate LN, Morgan NV, Beeson D, Maher ER. Mutation analysis of CHRNA1, CHRNB1, CHRND, and RAPSN genes in multiple pterygium syndrome/fetal akinesia patients. Am J Hum Genet 2008; 82:222-7. [PMID: 18179903 DOI: 10.1016/j.ajhg.2007.09.016] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Revised: 09/06/2007] [Accepted: 09/12/2007] [Indexed: 01/12/2023] Open
Abstract
Multiple pterygium syndromes (MPS) comprise a group of multiple congenital anomaly disorders characterized by webbing (pterygia) of the neck, elbows, and/or knees and joint contractures (arthrogryposis). MPS are phenotypically and genetically heterogeneous but are traditionally divided into prenatally lethal and nonlethal (Escobar) types. Previously, we and others reported that recessive mutations in the embryonal acetylcholine receptor g subunit (CHRNG) can cause both lethal and nonlethal MPS, thus demonstrating that pterygia resulted from fetal akinesia. We hypothesized that mutations in acetylcholine receptor-related genes might also result in a MPS/fetal akinesia phenotype and so we analyzed 15 cases of lethal MPS/fetal akinesia without CHRNG mutations for mutations in the CHRNA1, CHRNB1, CHRND, and rapsyn (RAPSN) genes. No CHRNA1, CHRNB1, or CHRND mutations were detected, but a homozygous RAPSN frameshift mutation, c.1177-1178delAA, was identified in a family with three children affected with lethal fetal akinesia sequence. Previously, RAPSN mutations have been reported in congenital myasthenia. Functional studies were consistent with the hypothesis that whereas incomplete loss of rapsyn function may cause congenital myasthenia, more severe loss of function can result in a lethal fetal akinesia phenotype.
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Affiliation(s)
- Julie Vogt
- Department of Medical and Molecular Genetics and WellChild Paediatric Research Centre, Division of Reproductive and Child Health, University of Birmingham, Birmingham B15 2TT, UK
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Müller JS, Mihaylova V, Abicht A, Lochmüller H. Congenital myasthenic syndromes: spotlight on genetic defects of neuromuscular transmission. Expert Rev Mol Med 2007; 9:1-20. [PMID: 17686188 DOI: 10.1017/s1462399407000427] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The neuromuscular junction (NMJ) is a complex structure that efficiently communicates the electrical impulse from the motor neuron to the skeletal muscle to induce muscle contraction. Genetic and autoimmune disorders known to compromise neuromuscular transmission are providing further insights into the complexities of NMJ function. Congenital myasthenic syndromes (CMSs) are a genetically and phenotypically heterogeneous group of rare hereditary disorders affecting neuromuscular transmission. The understanding of the molecular basis of the different types of CMSs has evolved rapidly in recent years. Mutations were first identified in the subunits of the nicotinic acetylcholine receptor (AChR), but now mutations in ten different genes - encoding post-, pre- or synaptic proteins - are known to cause CMSs. Pathogenic mechanisms leading to an impaired neuromuscular transmission modify AChRs or endplate structure or lead to decreased acetylcholine synthesis and release. However, the genetic background of many CMS forms is still unresolved. A precise molecular classification of CMS type is of paramount importance for the diagnosis, counselling and therapy of a patient, as different drugs may be beneficial or deleterious depending on the molecular background of the particular CMS.
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Affiliation(s)
- Juliane S Müller
- Friedrich-Baur-Institute, Department of Neurology, Ludwig-Maximilians-University, Munich, Germany
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Richard P, Gaudon K, Fournier E, Jackson C, Bauché S, Haddad H, Koenig J, Echenne B, Hantaï D, Eymard B. A synonymous CHRNE mutation responsible for an aberrant splicing leading to congenital myasthenic syndrome. Neuromuscul Disord 2007; 17:409-14. [PMID: 17363247 DOI: 10.1016/j.nmd.2007.01.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2006] [Revised: 12/29/2006] [Accepted: 01/22/2007] [Indexed: 11/16/2022]
Abstract
Congenital myasthenic syndromes (CMSs) are rare hereditary disorders transmitted in a recessive or dominant pattern, and are caused by mutations in the genes encoding proteins of the neuromuscular junction. They are classified in three groups depending on the origin of the molecular defect. Postsynaptic defects are the most frequent and have been reported to be partly due to abnormalities of the acetylcholine receptor, and particularly to mutations in CHRNE, the gene encoding the acetylcholine receptor epsilon-subunit. In a Portuguese patient with a mild form of recessive CMS, CHRNE sequencing identified an unknown homozygous transition. This variation affects the third nucleotide of the glycine 285 condon, and leads to a synonymous variant. Analysis of transcripts demonstrated that this single change creates a new splice donor site located 4 nucleotides upstream of the normal site, leading to a deletion and generating a frameshift in exon 9 followed by a premature termination codon. This paper relates the identification of a synonymous mutation in CHRNE that creates a new splice donor site leading to an aberrant splicing of pre-mRNAs and so to their instability. This is the first synonymous mutation in CHRNE known to generate a cryptic splice site, and mRNA quantification strongly suggests that it is the disease-causing mutation.
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Affiliation(s)
- Pascale Richard
- AP-HP, Groupe Hospitalier Pitié-Salpêtrière, Unité Fonctionnelle de Cardiogénétique et Myogénétique, Service de Biochimie B, Paris, France.
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Rambold H, Sander T, Helmchen C, Heide W. Different types of intra-saccadic slowing in congenital (RAPSN-mutation) and acquired myasthenic syndromes. Eur J Neurol 2006; 13:e3-4. [PMID: 16987151 DOI: 10.1111/j.1468-1331.2006.01393.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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von der Hagen M, Schallner J, Kaindl AM, Koehler K, Mitzscherling P, Abicht A, Grieben U, Korinthenberg R, Kress W, von Moers A, Müller JS, Schara U, Vorgerd M, Walter MC, Müller-Reible C, Hübner C, Lochmüller H, Huebner A. Facing the genetic heterogeneity in neuromuscular disorders: Linkage analysis as an economic diagnostic approach towards the molecular diagnosis. Neuromuscul Disord 2006; 16:4-13. [PMID: 16378727 DOI: 10.1016/j.nmd.2005.10.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Revised: 09/20/2005] [Accepted: 10/05/2005] [Indexed: 02/08/2023]
Abstract
The identification of an ever increasing number of gene defects in patients with neuromuscular disorders has disclosed both marked phenotype and genotype variability and considerable disease overlap. In order to offer an economic strategy to characterise the molecular defect in patients with unclassified neuromuscular disorders, we designed DNA marker sets for linkage analysis of 62 distinct neuromuscular disorders gene loci, including all known muscular dystrophies, congenital myopathies, congenital myasthenic syndromes and myotonias. Genotyping of marker loci of 140 clinically well-characterised families with unclassified neuromuscular disorders reduced the number of candidates to one or two genes in 49 % of the families. Subsequent mutation analysis and genome-wide scans enabled the determination of the genetic defect in 31 % of the families including the identification of a new gene and a new mutation in an unexpected candidate gene. This highlights the effective application of this approach both for diagnostic strategies as well as for the identification of new loci and genes.
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Affiliation(s)
- M von der Hagen
- Department of Neuropaediatrics, Technical University, 01307 Dresden, Germany
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Beeson D, Hantaï D, Lochmüller H, Engel AG. 126th International Workshop: congenital myasthenic syndromes, 24-26 September 2004, Naarden, the Netherlands. Neuromuscul Disord 2005; 15:498-512. [PMID: 15951177 DOI: 10.1016/j.nmd.2005.05.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Indexed: 11/16/2022]
Affiliation(s)
- David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, The John Radcliff, Oxford, UK
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Abstract
PURPOSE OF REVIEW Congenital myasthenic syndromes are a heterogeneous group of diseases caused by genetic defects affecting neuromuscular transmission. In this article, a strategy that leads to the diagnosis of congenital myasthenic syndromes is presented, and recent advances in the clinical, genetic and molecular aspects of congenital myasthenic syndrome are outlined. RECENT FINDINGS Besides the identification of new mutations in genes already known to be implicated in congenital myasthenic syndromes (genes for the acetylcholine receptor subunits and the collagen tail of acetylcholinesterase), mutations in other genes have more recently been discovered and characterized (genes for choline acetyltransferase, rapsyn, and the muscle sodium channel SCN4A). Fluoxetine has recently been proposed as an alternative treatment for 'slow channel' congenital myasthenic syndrome. SUMMARY The characterization of congenital myasthenic syndromes comprises two complementary steps: establishing the diagnosis and identifying the pathophysiological type of congenital myasthenic syndrome. Characterization of the type of congenital myasthenic syndrome has allowed it to be classified as caused by presynaptic, synaptic and postsynaptic defects. A clinically and muscle histopathologically oriented genetic study has identified several genes in which mutations cause the disease. Despite comprehensive characterization, the phenotypic expression of one given gene involved is variable, and the aetiology of many congenital myasthenic syndromes remains to be discovered.
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Affiliation(s)
- Daniel Hantaï
- Inserm U582 and Unité Clinique de Pathologie Neuromusculaire, Institut de Myologie, Hôpital de la Salpêtrière, Paris, France.
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47
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Diagnose und Therapie der kongenitalen Myastheniesyndrome. Monatsschr Kinderheilkd 2005. [DOI: 10.1007/s00112-003-0874-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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48
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Müller JS, Abicht A, Christen HJ, Stucka R, Schara U, Mortier W, Huebner A, Lochmüller H. A newly identified chromosomal microdeletion of the rapsyn gene causes a congenital myasthenic syndrome. Neuromuscul Disord 2005; 14:744-9. [PMID: 15482960 DOI: 10.1016/j.nmd.2004.06.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2004] [Revised: 06/01/2004] [Accepted: 06/09/2004] [Indexed: 10/26/2022]
Abstract
The objective is mutation analysis of the RAPSN gene in a patient with sporadic congenital myasthenic syndrome (CMS). Mutations in various genes encoding proteins expressed at the neuromuscular junction may cause CMS. Most mutations affect the epsilon subunit gene of the acetylcholine receptor (AChR) leading to endplate AChR deficiency. Recently, mutations in the RAPSN gene have been identified in several CMS patients with AChR deficiency. In most patients, RAPSN N88K was identified, either homozygously or heteroallelic to a second missense mutation. A sporadic CMS patient from Germany was analyzed for RAPSN mutations by RFLP, long-range PCR and sequence analysis. Clinically, the patient presents with an early onset CMS, associated with arthrogryposis multiplex congenita, recurrent episodes of respiratory insufficiency provoked by infections, and a moderate general weakness, responsive to anticholinesterase treatment. The mutation RAPSN N88K was found heterozygously to a large deletion of about 4.5 kb disrupting the RAPSN gene. Interestingly, an Alu-mediated unequal homologous recombination may have caused the deletion. We hypothesize that numerous interspersed Alu elements may predispose the RAPSN locus for genetic rearrangements.
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Affiliation(s)
- Juliane S Müller
- Department of Neurology and Gene Center, Friedrich-Baur-Institute, Ludwig-Maximilians-University, Munich, Germany
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Rodova M, Kelly KF, VanSaun M, Daniel JM, Werle MJ. Regulation of the rapsyn promoter by kaiso and delta-catenin. Mol Cell Biol 2004; 24:7188-96. [PMID: 15282317 PMCID: PMC479716 DOI: 10.1128/mcb.24.16.7188-7196.2004] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rapsyn is a synapse-specific protein that is required for clustering acetylcholine receptors at the neuromuscular junction. Analysis of the rapsyn promoter revealed a consensus site for the transcription factor Kaiso within a region that is mutated in a subset of patients with congenital myasthenic syndrome. Kaiso is a POZ-zinc finger family transcription factor which recognizes the specific core consensus sequence CTGCNA (where N is any nucleotide). Previously, the only known binding partner for Kaiso was the cell adhesion cofactor, p120 catenin. Here we show that delta-catenin, a brain-specific member of the p120 catenin subfamily, forms a complex with Kaiso. Antibodies against Kaiso and delta-catenin recognize proteins in the nuclei of C2C12 myocytes and at the postsynaptic domain of the mouse neuromuscular junction. Endogenous Kaiso in C2C12 cells coprecipitates with the rapsyn promoter in vivo as shown by chromatin immunoprecipitation assay. Minimal promoter assays demonstrated that the rapsyn promoter can be activated by Kaiso and delta-catenin; this activation is apparently muscle specific. These results provide the first experimental evidence that rapsyn is a direct sequence-specific target of Kaiso and delta-catenin. We propose a new model of synapse-specific transcription that involves the interaction of Kaiso, delta-catenin, and myogenic transcription factors at the neuromuscular junction.
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MESH Headings
- Active Transport, Cell Nucleus/physiology
- Animals
- Antibiotics, Antineoplastic/pharmacology
- Armadillo Domain Proteins
- Base Sequence
- Catenins
- Cell Adhesion Molecules
- Cell Line
- Chickens
- Cytoskeletal Proteins/metabolism
- Fatty Acids, Unsaturated/pharmacology
- Gene Expression Regulation
- Genes, Reporter
- Humans
- Macromolecular Substances
- Mice
- Molecular Sequence Data
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Muscle Proteins/genetics
- Muscle Proteins/metabolism
- Muscle, Skeletal/chemistry
- Muscle, Skeletal/cytology
- Muscle, Skeletal/metabolism
- Myasthenic Syndromes, Congenital/genetics
- Myasthenic Syndromes, Congenital/metabolism
- Neuromuscular Junction/physiology
- Phosphoproteins
- Promoter Regions, Genetic
- Sequence Alignment
- Transcription Factors/metabolism
- Delta Catenin
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Affiliation(s)
- Marianna Rodova
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, 66160-7421, USA
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50
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Burke G, Cossins J, Maxwell S, Robb S, Nicolle M, Vincent A, Newsom-Davis J, Palace J, Beeson D. Distinct phenotypes of congenital acetylcholine receptor deficiency. Neuromuscul Disord 2004; 14:356-64. [PMID: 15145336 DOI: 10.1016/j.nmd.2004.03.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2004] [Revised: 03/23/2004] [Accepted: 03/23/2004] [Indexed: 10/26/2022]
Abstract
We contrast the phenotypes associated with hereditary acetylcholine receptor deficiency arising from mutations in either the acetylcholine receptor epsilon subunit or the endplate acetylcholine receptor clustering protein rapsyn. Mutational screening was performed by amplification of promoter and coding regions by PCR and direct DNA sequencing. We identified mutations in 37 acetylcholine receptor deficiency patients; 18 had acetylcholine receptor-epsilon mutations, 19 had rapsyn mutations. Mutated acetylcholine receptor-epsilon associated with bulbar symptoms, ptosis and ophthalmoplegia at birth, and generalized weakness. Mutated rapsyn caused either an early onset (rapsyn-EO) or late onset (rapsyn-LO) phenotype. Rapsyn-EO associated with arthrogryposis and life-threatening exacerbations during early childhood. Rapsyn-LO presented with limb weakness in adolescence or adulthood resembling seronegative myasthenia gravis. Awareness of distinct phenotypic features of acetylcholine receptor deficiency resulting from acetylcholine receptor-epsilon or rapsyn mutations should facilitate targeted genetic diagnosis, avoid inappropriate immunological therapy and, in some infants, prompt the rapid introduction of treatment that could be life saving.
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MESH Headings
- 4-Aminopyridine/analogs & derivatives
- 4-Aminopyridine/therapeutic use
- Adolescent
- Adult
- Aged
- Amifampridine
- Cell Line
- Child
- Child, Preschool
- Cholinesterase Inhibitors/therapeutic use
- DNA Mutational Analysis/methods
- Drug Therapy, Combination
- Electric Stimulation
- Electromyography/methods
- Electrophysiology/methods
- Embryo, Mammalian
- Ephedrine/therapeutic use
- Evoked Potentials, Motor/drug effects
- Evoked Potentials, Motor/radiation effects
- Female
- Fluorescent Antibody Technique/methods
- Humans
- Kidney
- Male
- Middle Aged
- Muscle Proteins/genetics
- Muscles
- Mutation/genetics
- Myasthenic Syndromes, Congenital/classification
- Myasthenic Syndromes, Congenital/drug therapy
- Myasthenic Syndromes, Congenital/genetics
- Myasthenic Syndromes, Congenital/physiopathology
- Phenotype
- Potassium Channel Blockers/therapeutic use
- Protein Subunits/deficiency
- Protein Subunits/genetics
- Pyridostigmine Bromide/therapeutic use
- RNA, Messenger/biosynthesis
- Receptors, Cholinergic/deficiency
- Receptors, Cholinergic/genetics
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Sequence Analysis, DNA/methods
- Severity of Illness Index
- Sympathomimetics/therapeutic use
- Transfection/methods
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Affiliation(s)
- G Burke
- Department of Clinical Neurology, Radcliffe Infirmary, Oxford, UK
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