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Liao X, Wang Y, Lai X, Wang S. The role of Rapsyn in neuromuscular junction and congenital myasthenic syndrome. BIOMOLECULES & BIOMEDICINE 2023; 23:772-784. [PMID: 36815443 PMCID: PMC10494853 DOI: 10.17305/bb.2022.8641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 02/02/2023] [Accepted: 02/17/2023] [Indexed: 02/23/2023]
Abstract
Rapsyn, an intracellular scaffolding protein associated with the postsynaptic membranes in the neuromuscular junction (NMJ), is critical for nicotinic acetylcholine receptor clustering and maintenance. Therefore, Rapsyn is essential to the NMJ formation and maintenance, and Rapsyn mutant is one of the reasons causing the pathogenies of congenital myasthenic syndrome (CMS). In addition, there is little research on Rapsyn in the central nervous system (CNS). In this review, the role of Rapsyn in the NMJ formation and the mutation of Rapsyn leading to CMS will be reviewed separately and sequentially. Finally, the potential function of Rapsyn is prospected.
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Affiliation(s)
- Xufeng Liao
- Institute of Life Science and School of Life Sciences, Nanchang University, Nanchang, China
| | - Yingxing Wang
- Institute of Life Science and School of Life Sciences, Nanchang University, Nanchang, China
| | - Xinsheng Lai
- Institute of Life Science and School of Life Sciences, Nanchang University, Nanchang, China
- School of Basic Medical Sciences, Nanchang University, Nanchang, China
| | - Shunqi Wang
- Institute of Life Science and School of Life Sciences, Nanchang University, Nanchang, China
- School of Basic Medical Sciences, Nanchang University, Nanchang, China
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2
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Mendpara V, Bethanabotla S, Yadav M, Kanisetti V, Singh G, Das A, Sahu S, Patel H. When Breathing Becomes a Challenge: A Case of Congenital Myasthenia Gravis in an Indian Neonate With a DOK-7 Gene Mutation. Cureus 2023; 15:e38842. [PMID: 37303354 PMCID: PMC10256249 DOI: 10.7759/cureus.38842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/10/2023] [Indexed: 06/13/2023] Open
Abstract
A rare neuromuscular condition known as congenital myasthenia gravis (CMG) affects some people from birth or very soon after. It results in fatigue and muscle weakness because of genetic abnormalities that interfere with the neuromuscular junction's ability to function, where the nerves and muscles connect. Even among those who have the same genetic mutation, the severity of CMG symptoms might differ considerably. The most typical signs of CMG include eyelid drooping, breathing issues, muscle weakness and weariness, and difficulties swallowing. Clinical examinations, neurophysiologic tests, and genetic analyses are frequently combined to make the diagnosis of CMG. Although there is no known treatment for CMG, many patients may control their symptoms and lead relatively normal lives with the right care. A newborn with CMG due to a DOK-7 gene mutation is described in this article, along with its very early onset. The DOK-7 mutation is a rare variant in the Indian population that causes CMG and usually manifests as 'limb girdle' weakness. However, due to muscle weakness, the neonate in this case developed severe respiratory distress and later died despite rigorous life-saving measures.
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Affiliation(s)
- Vaidehi Mendpara
- Medicine and Surgery, Pediatrics, Government Medical College Surat, Surat, IND
| | | | - Megha Yadav
- Medicine and Surgery, Maharani Laxmi Bai Medical College, Jhansi, IND
| | | | - Gurpreet Singh
- Medicine, Government Medical College and Hospital, Amritsar, IND
| | - Abhirami Das
- Internal Medicine, Rajiv Gandhi Medical College, Thane, IND
| | - Sweta Sahu
- Surgery, Jagadguru Jayadeva Murugarajendra (JJM) Medical College, Davanagere, IND
| | - Hitesh Patel
- Pediatrics and Child Health, Government Medical College and Hospital, Surat, IND
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3
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Gómez-García de la Banda M, Simental-Aldaba E, Fahmy N, Sternberg D, Blondy P, Quijano-Roy S, Malfatti E. Case Report: A Novel AChR Epsilon Variant Causing a Clinically Discordant Salbutamol Responsive Congenital Myasthenic Syndrome in Two Egyptian Siblings. Front Neurol 2022; 13:909715. [PMID: 35720108 PMCID: PMC9201482 DOI: 10.3389/fneur.2022.909715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 05/02/2022] [Indexed: 12/05/2022] Open
Abstract
Congenital myasthenic syndromes (CMS) are inherited disorders that lead to abnormal neuromuscular transmission. Post-synaptic mutations are the main cause of CMS, particularly mutations in CHRNE. We report a novel homozygous CHRNE pathogenic variant in two Egyptian siblings showing a CMS. Interestingly, they showed different degrees of extraocular and skeletal muscle involvement; both presented only a partial response to cholinesterase inhibitors, and rapidly and substantially ameliorated after the addition of oral β2 adrenergic agonists. Here, we enlarge the genetic spectrum of CHRNE-related congenital myasthenic syndromes and highlight the importance of a β2 adrenergic agonists treatment.
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Affiliation(s)
- Marta Gómez-García de la Banda
- Pediatric Neurology and ICU Department, AP-HP Université Paris Saclay, Hôpital Raymond Poincaré, Garches, France
- Reference Center for Neuromuscular Diseases Centre “Nord- Est- Ile de France”, FILNEMUS, Creteil, France
- European Reference Center Network (Euro-NMD ERN), Paris, France
| | - Emmanuel Simental-Aldaba
- APHP, Centre de Référence de Pathologie Neuromusculaire Nord-Est-Ile-de-France, Henri Mondor University Hospital, Créteil, France
- Department of Neurorehabilitation, Instituto Nacional de Rehabilitación “LGII”, Mexico City, Mexico
| | - Nagia Fahmy
- Neuromuscular Unit, Faculty of Medicine, Ain Shams University, Cairo, Egypt
| | - Damien Sternberg
- European Reference Center Network (Euro-NMD ERN), Paris, France
- Service de Biochimie Métabolique, Centre de Génétique, Groupe Hospitalier Pitié-Salpêtrière, APHP Sorbonne Université, Paris, France
| | - Patricia Blondy
- European Reference Center Network (Euro-NMD ERN), Paris, France
| | - Susana Quijano-Roy
- Pediatric Neurology and ICU Department, AP-HP Université Paris Saclay, Hôpital Raymond Poincaré, Garches, France
- Reference Center for Neuromuscular Diseases Centre “Nord- Est- Ile de France”, FILNEMUS, Creteil, France
- European Reference Center Network (Euro-NMD ERN), Paris, France
- Centre de Recherche en Myologie, UMRS974, Paris, France
| | - Edoardo Malfatti
- Reference Center for Neuromuscular Diseases Centre “Nord- Est- Ile de France”, FILNEMUS, Creteil, France
- APHP, Centre de Référence de Pathologie Neuromusculaire Nord-Est-Ile-de-France, Henri Mondor University Hospital, Créteil, France
- Univ Paris Est Créteil, INSERM, IMRB, Créteil, France
- AP-HP, Hôpital Mondor, Service d'histologie, Créteil, France
- *Correspondence: Edoardo Malfatti
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4
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Alsallum MS, Alshareef A, Abuzinadah AR, Bamaga AK, Dallol A. A novel DOK7 mutation causing congenital myasthenic syndrome with limb-girdle weakness: case series of three family members. Heliyon 2021; 7:e06869. [PMID: 34027146 PMCID: PMC8120944 DOI: 10.1016/j.heliyon.2021.e06869] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 11/05/2020] [Accepted: 04/16/2021] [Indexed: 11/12/2022] Open
Abstract
Congenital myasthenia syndrome (CMS) is a group of heterogeneous diseases affecting the neuromuscular endplate. CMS has a considerably different phenotypic presentations, with the onset time ranging from early infancy to late adulthood. Here, we report a case of a CMS due to a new DOK7 mutation in a 28-year-old man and two of his sisters, who have a pure limb-girdle weakness. DOK7 CMS has a varying presentation. Typically, the onset occurs in childhood with ptosis, bulbar symptoms, difficulty walking, weakness, and gait abnormality. This case sheds light on a novel DOK7 gene mutation with a unique presentation of CMS and provides insight into its unique phenotypic presentation.
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Affiliation(s)
- Mohammed S Alsallum
- Neurology Resident, King Abdulaziz University Hospital, P.O. Box: 80200, 21589, Jeddah, Saudi Arabia
| | - Aysha Alshareef
- King Abdulaziz University, Faculty of Medicine, King Abdulaziz University Hospital, Internal Medicine Department, Neurology Division, P.O. Box: 80200, 21589, Jeddah, Saudi Arabia.,Neuromuscular Unit, King Fahad Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Ahmad R Abuzinadah
- King Abdulaziz University, Faculty of Medicine, King Abdulaziz University Hospital, Internal Medicine Department, Neurology Division, P.O. Box: 80200, 21589, Jeddah, Saudi Arabia.,Neuromuscular Unit, King Fahad Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Ahmed K Bamaga
- Neuromuscular Unit, King Fahad Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia.,King Abdulaziz University, Faculty of Medicine, King Abdulaziz University Hospital, Pediatric Department, Neurology Division, P.O. Box: 80200, 21589, Jeddah, Saudi Arabia
| | - Ashraf Dallol
- Center of Excellence in Genomic Medicine Research and Faculty of Applied Medical Sciences, King Abdulaziz University, P.O. Box: 80200, 21589, Saudi Arabia
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5
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Novel compound heterozygous variants in the GFPT1 gene leading to rare limb-girdle congenital myasthenic syndrome with rimmed vacuoles. Neurol Sci 2021; 42:3485-3490. [PMID: 33438142 DOI: 10.1007/s10072-020-05021-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Accepted: 12/21/2020] [Indexed: 02/08/2023]
Abstract
BACKGROUND Congenital myasthenic syndrome (CMS) is a heterogeneous group of rare disorders with impaired neuromuscular transmission caused by genetic defects, which is characterized by fatigable muscle weakness. CASE PRESENTATION Herein, we report a case of limb-girdle CMS (LG-CMS) in a 15-year-old Chinese girl with limb weakness and mild ptosis. The patient presented with well-defined clinical manifestations, muscle imaging, and electrophysiological features associated with CMS. On muscle biopsy, in addition to tubular aggregates identified, an extremely unusual pathological change of rimmed vacuoles in muscle fibers was observed. Whole-exome sequencing disclosed two novel heterozygous variants (c.14 T>A and c.581 T>C) in the human glutamine-fructose-6-phosphate transaminase 1 (GFPT1) gene, leading to the substitutions of phenylalanine to tyrosine (p.F5Y) and serine (p.F194S), respectively. Both variants were predicted to be likely pathogenic by SIFT, Polyphen-2, and Mutation Taster. Treatments with pyridostigmine bromide and albuterol produced a dramatic improvement. CONCLUSIONS Collectively, molecular genetic analysis and muscle biopsy play crucial roles in the diagnosis of GFPT1-related LG-CMS with rimmed vacuoles (a rare phenotype of CMS) and have important implications for treatment decision.
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Congenital myasthenic syndromes in the Thai population: Clinical findings and novel mutations. Neuromuscul Disord 2020; 30:851-858. [PMID: 32978031 DOI: 10.1016/j.nmd.2020.08.362] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2019] [Revised: 08/26/2020] [Accepted: 08/27/2020] [Indexed: 11/23/2022]
Abstract
Congenital myasthenic syndromes (CMS) comprise a heterogeneous group of genetic disorders of the neuromuscular junction. Next generation sequencing has been increasingly used for molecular diagnosis in CMS patients. This study aimed to identify the disease-causing variants in Thai patients. We recruited patients with a diagnosis of CMS based on clinical and electrophysiologic findings, and whole exome sequencing was performed. Thirteen patients aged from 2 to 54 years (median: 8 years) from 12 families were enrolled. Variants were identified in 9 of 13 patients (69%). Five novel variants and two previously reported variant were found in the COLQ, RAPSN and CHRND gene. The previously reported c.393+1G>A splice site variant in the COLQ gene was found in a majority of patients. Five patients harbor the homozygous splice site c.393+1G>A variant, and two patients carry compound heterozygous c.393+1G>A, c.718-1G>T, and c.393+1G>A, c.865G>T (p.Gly289Ter) variants. The novel variants were also found in RAPSN (p.Cys251del, p.Arg282Cys) and CHRND (p.Met481del). Molecular diagnosis in CMS patients can guide treatment decisions and may be life changing, especially in patients with COLQ mutations.
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Ohkawara B, Shen X, Selcen D, Nazim M, Bril V, Tarnopolsky MA, Brady L, Fukami S, Amato AA, Yis U, Ohno K, Engel AG. Congenital myasthenic syndrome-associated agrin variants affect clustering of acetylcholine receptors in a domain-specific manner. JCI Insight 2020; 5:132023. [PMID: 32271162 DOI: 10.1172/jci.insight.132023] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 02/28/2020] [Indexed: 12/17/2022] Open
Abstract
Congenital myasthenic syndromes (CMS) are caused by mutations in molecules expressed at the neuromuscular junction. We report clinical, structural, ultrastructural, and electrophysiologic features of 4 CMS patients with 6 heteroallelic variants in AGRN, encoding agrin. One was a 7.9-kb deletion involving the N-terminal laminin-binding domain. Another, c.4744G>A - at the last nucleotide of exon 26 - caused skipping of exon 26. Four missense mutations (p.S1180L, p.R1509W, p.G1675S, and p.Y1877D) expressed in conditioned media decreased AChR clusters in C2C12 myotubes. The agrin-enhanced phosphorylation of MuSK was markedly attenuated by p.Y1877D in the LG3 domain and moderately attenuated by p.R1509W in the LG1 domain but not by the other 2 mutations. The p.S1180L mutation in the SEA domain facilitated degradation of secreted agrin. The p.G1675S mutation in the LG2 domain attenuated anchoring of agrin to the sarcolemma by compromising its binding to heparin. Anchoring of agrin with p.R1509W in the LG1 domain was similarly attenuated. Mutations of agrin affect AChR clustering by enhancing agrin degradation or by suppressing MuSK phosphorylation and/or by compromising anchoring of agrin to the sarcolemma of the neuromuscular junction.
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Affiliation(s)
- Bisei Ohkawara
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - XinMing Shen
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | - Duygu Selcen
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | - Mohammad Nazim
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Vera Bril
- Vera Bril, Department of Neurology, University of Toronto, Toronto, Canada
| | - Mark A Tarnopolsky
- Department of Pediatrics, McMaster University Medical Center, Hamilton, Ontario, Canada
| | - Lauren Brady
- Department of Pediatrics, McMaster University Medical Center, Hamilton, Ontario, Canada
| | - Sae Fukami
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Anthony A Amato
- Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Uluc Yis
- Division of Child Neurology, Department of Pediatrics, School of Medicine, Dokuz Eylul University, Izmir, Turkey
| | - Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Andrew G Engel
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
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8
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Luo HY, Zhao L, Mao CY, Yang ZH, Yang J, Wang YL, Niu HX, Liu YT, Shi CH, Xu YM. Novel compound heterozygous GFPT1 mutations in a family with limb-girdle myasthenia with tubular aggregates. Neuromuscul Disord 2019; 29:549-553. [PMID: 31255525 DOI: 10.1016/j.nmd.2019.05.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 05/06/2019] [Accepted: 05/22/2019] [Indexed: 02/07/2023]
Abstract
Limb-girdle myasthenia with tubular aggregates, a subtype of congenital myasthenic syndrome, is an extremely rare autosomal recessive genetic disease characterized by prominent limb-girdle weakness and good response to acetylcholinesterase inhibitor therapy. Herein, we reported two novel mutations of GFPT1 gene in a Chinese pedigree. Two siblings presented with fatigue, weakness of limb-girdle and decrement of the muscle action potential with repetitive nerve stimulation. Thus, myasthenia gravis was initially suspected, but anti-AChR antibodies were negative. Two novel missense mutations (p.Lys154Asn and p.Asn363Ser) in GFPT1 were identified through genetic testing conducted on 167 well-established genes associated with muscular diseases by targeted high throughput sequencing. Both mutations have not been recorded in the dsSNP database, Exome Aggregation Consortium database and 1000 Genomes Project database. The mutation sites were co-segregated with the phenotype and conserved between the different species. The mutations were not found in the 200 unrelated normal controls. Muscle biopsies revealed tubular aggregates, in accordance with previous reports with GFPT1 mutations. Subsequently, dramatic improvement in strength occurred following anti-cholinesterase therapy. Our study will be helpful for the diagnosis and treatment for Limb-girdle myasthenia with tubular aggregates.
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Affiliation(s)
- Hai-Yang Luo
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, 1 Jian-she East Road, Zhengzhou 450000, Henan, China; Institute of Clinical Medicine, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, Henan, China
| | - Lu Zhao
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, 1 Jian-she East Road, Zhengzhou 450000, Henan, China
| | - Cheng-Yuan Mao
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, 1 Jian-she East Road, Zhengzhou 450000, Henan, China
| | - Zhi-Hua Yang
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, 1 Jian-she East Road, Zhengzhou 450000, Henan, China
| | - Jing Yang
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, 1 Jian-she East Road, Zhengzhou 450000, Henan, China
| | - Yan-Lin Wang
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, 1 Jian-she East Road, Zhengzhou 450000, Henan, China
| | - Hui-Xia Niu
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, 1 Jian-she East Road, Zhengzhou 450000, Henan, China
| | - Yu-Tao Liu
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, 1 Jian-she East Road, Zhengzhou 450000, Henan, China
| | - Chang-He Shi
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, 1 Jian-she East Road, Zhengzhou 450000, Henan, China.
| | - Yu-Ming Xu
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, 1 Jian-she East Road, Zhengzhou 450000, Henan, China; Institute of Clinical Medicine, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, Henan, China.
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Yang K, Cheng H, Yuan F, Meng L, Yin R, Zhang Y, Wang S, Wang C, Lu Y, Xi J, Lu Q, Chen Y. CHRNE compound heterozygous mutations in congenital myasthenic syndrome: A case report. Medicine (Baltimore) 2018; 97:e0347. [PMID: 29702980 PMCID: PMC5944527 DOI: 10.1097/md.0000000000010347] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
RATIONALE Congenital myasthenic syndrome (CMSs) are a group of rare genetic disorders of the neurological junction, which can result in structural or functional weakness. Here, we characterized a case of CMS in order to clarify the diagnosis and expand the understanding of it. The molecular diagnosis had implications for choice of treatment and genetic counseling. PATIENT CONCERNS A 3-year-old male patient with CMS had ptosis and limb weakness for 2 months after birth. Clinical course and electrophysiological, imaging, and genetic findings were assessed. Protein structure/function was predicted. A novel mutation of c.295C>T (exon 4) and another known mutation of c.442T>A (exon 5) were found in CHRNE. Both mutations localized in conserved sequences. The c.442T>A (p.C148S) missense mutation in CHRNE was predicted to be damaging/deleterious. The iterative threading assembly refinement (I-TASSER) server generated vastly different 3-dimensional (3D) atomic models based on protein sequences from wide-type and novel nonsense mutation of c.295C>T (p.R99X) in CHRNE. DIAGNOSES The diagnosis of CMS with CHRNE mutations in Han Chinese was confirmed. INTERVENTIONS The patient was given prednisone (10 mg, once daily, taken orally) and pyridostigmine (15 mg, three times a day, taken orally). OUTCOMES The patient had a moderate response to prednisone and pyridostigmine. LESSONS We expanded the genotype and phenotype of CMS with CHRNE mutations in Han Chinese and provided new insights into the molecular mechanism of CMS and help to the diagnosis and treatment of CMS.
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Affiliation(s)
| | | | | | - Linyi Meng
- Department of Pharmacy, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
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Natera-de Benito D, Domínguez-Carral J, Muelas N, Nascimento A, Ortez C, Jaijo T, Arteaga R, Colomer J, Vilchez JJ. Phenotypic heterogeneity in two large Roma families with a congenital myasthenic syndrome due to CHRNE 1267delG mutation. A long-term follow-up. Neuromuscul Disord 2016; 26:789-795. [PMID: 27634344 DOI: 10.1016/j.nmd.2016.08.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 07/22/2016] [Accepted: 08/10/2016] [Indexed: 11/29/2022]
Abstract
Congenital myasthenic syndromes (CMS) are a heterogeneous group of genetic disorders. Mutations in CHRNE are one of the most common cause of them and the ɛ1267delG frameshifting mutation is described to be present on at least one allele of 60% of patients with CHRNE mutations. We present a comprehensive description of the heterogeneous clinical features of the CMS caused by the homozygous 1267delG mutation in the AChR Ɛ subunit in nine members of two large Gipsy kindreds. Our observations indicate that founder Roma mutation 1267delG leads to a phenotype further characterized by ophthalmoplegia, bilateral ptosis, and good response to pyridostigmine and 3,4-DAP; but also by facial weakness, bulbar symptoms, neck muscle weakness, and proximal limb weakness that sometimes entails the loss of ambulation. Interestingly, we found in our series a remarkable proportion of patients with a progressive or fluctuating course of the disease. This finding is in some contrast with previous idea that considered this form of CMS as benign, non progressive, and with a low impact on the capacity of ambulation.
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Affiliation(s)
- D Natera-de Benito
- Department of Pediatrics, Hospital Universitario de Fuenlabrada, Madrid, Spain.
| | - J Domínguez-Carral
- Department of Pediatrics, Hospital Universitario Marqués de Valdecilla, Santander, Spain
| | - N Muelas
- Department of Neurology, Hospital Universitari La Fe, Valencia, Spain
| | - A Nascimento
- Department of Neuromuscular Diseases, Hospital Sant Joan de Déu, Barcelona, Spain
| | - C Ortez
- Department of Neuromuscular Diseases, Hospital Sant Joan de Déu, Barcelona, Spain
| | - T Jaijo
- Department of Neurology, Hospital Universitari La Fe, Valencia, Spain
| | - R Arteaga
- Department of Pediatrics, Hospital Universitario Marqués de Valdecilla, Santander, Spain
| | - J Colomer
- Department of Neuromuscular Diseases, Hospital Sant Joan de Déu, Barcelona, Spain
| | - J J Vilchez
- Department of Neurology, Hospital Universitari La Fe, Valencia, Spain
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11
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Tan JS, Ambang T, Ahmad-Annuar A, Rajahram GS, Wong KT, Goh KJ. Congenital myasthenic syndrome due to novel CHAT
mutations in an ethnic kadazandusun family. Muscle Nerve 2016; 53:822-6. [DOI: 10.1002/mus.25037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/08/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Joo-San Tan
- Division of Neurology, Department of Medicine, Faculty of Medicine; University of Malaya; Kuala Lumpur Malaysia
| | - Tomica Ambang
- Division of Neurology, Department of Medicine, Faculty of Medicine; University of Malaya; Kuala Lumpur Malaysia
| | - Azlina Ahmad-Annuar
- Department of Biomedical Science, Faculty of Medicine; University of Malaya; Kuala Lumpur Malaysia
| | - Giri Shan Rajahram
- Department of Medicine; Hospital Queen Elizabeth; Kota Kinabalu Sabah Malaysia
| | - Kum Thong Wong
- Department of Pathology, Faculty of Medicine; University of Malaya; Kuala Lumpur Malaysia
| | - Khean Jin Goh
- Division of Neurology, Department of Medicine, Faculty of Medicine; University of Malaya; Kuala Lumpur Malaysia
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12
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Finlayson S, Morrow JM, Rodriguez Cruz PM, Sinclair CDJ, Fischmann A, Thornton JS, Knight S, Norbury R, White M, Al-Hajjar M, Carboni N, Jayawant S, Robb SA, Yousry TA, Beeson D, Palace J. Muscle magnetic resonance imaging in congenital myasthenic syndromes. Muscle Nerve 2016; 54:211-9. [PMID: 26789134 PMCID: PMC4982021 DOI: 10.1002/mus.25035] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 12/27/2015] [Accepted: 01/06/2016] [Indexed: 11/26/2022]
Abstract
Introduction In this study we investigated muscle magnetic resonance imaging in congenital myasthenic syndromes (CMS). Methods Twenty‐six patients with 9 CMS subtypes and 10 controls were imaged. T1‐weighted (T1w) and short‐tau inversion recovery (STIR) 3‐Tesla MRI images obtained at thigh and calf levels were scored for severity. Results Overall mean the T1w score was increased in GFPT1 and DPAGT1 CMS. T1w scans of the AChR‐deficiency, COLQ, and CHAT subjects were indistinguishable from controls. STIR images from CMS patients did not differ significantly from those of controls. Mean T1w score correlated with age in the CMS cohort. Conclusions MRI appearances ranged from normal to marked abnormality. T1w images seem to be especially abnormal in some CMS caused by mutations of proteins involved in the glycosylation pathway. A non‐selective pattern of fat infiltration or a normal‐appearing scan in the setting of significant clinical weakness should suggest CMS as a potential diagnosis. Muscle MRI could play a role in differentiating CMS subtypes. Muscle Nerve54: 211–219, 2016
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Affiliation(s)
- Sarah Finlayson
- Nuffield Department of Clinical Neurosciences, University of Oxford and Oxford Radcliffe Hospitals NHS Trust, Oxford, UK
| | - Jasper M Morrow
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK
| | - Pedro M Rodriguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford and Oxford Radcliffe Hospitals NHS Trust, Oxford, UK
| | | | - Arne Fischmann
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK
| | - John S Thornton
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK
| | - Steve Knight
- University of Oxford Centre for Clinical Magnetic Resonance Research, John Radcliffe Hospital, Oxford, UK
| | - Ray Norbury
- University of Oxford Centre for Clinical Magnetic Resonance Research, John Radcliffe Hospital, Oxford, UK
| | - Mel White
- Department of Paediatrics, University of Oxford and Children's Hospital, Oxford, UK
| | - Michal Al-Hajjar
- Nuffield Department of Clinical Neurosciences, University of Oxford and Oxford Radcliffe Hospitals NHS Trust, Oxford, UK
| | - Nicola Carboni
- Neurology Department, Hospital San Francesco of Nuoro, Sardinia, Italy
| | - Sandeep Jayawant
- Department of Paediatrics, University of Oxford and Children's Hospital, Oxford, UK
| | - Stephanie A Robb
- Dubowitz Neuromuscular Centre, Institute of Child Health and Great Ormond Street Hospital, London, UK
| | - Tarek A Yousry
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK
| | - David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Jacqueline Palace
- Nuffield Department of Clinical Neurosciences, University of Oxford and Oxford Radcliffe Hospitals NHS Trust, Oxford, UK
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Rodríguez Cruz PM, Palace J, Ramjattan H, Jayawant S, Robb SA, Beeson D. Salbutamol and ephedrine in the treatment of severe AChR deficiency syndromes. Neurology 2015; 85:1043-7. [PMID: 26296515 DOI: 10.1212/wnl.0000000000001952] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To evaluate the response to salbutamol and ephedrine in the treatment of congenital myasthenic syndromes due to CHRNE mutations causing severe acetylcholine receptor (AChR)deficiency. METHODS A cohort study of 6 patients with severe AChR deficiency, symptomatic despite optimal therapy with anticholinesterase and 3,4-diaminopyridine, were analyzed for their response to the addition of salbutamol or ephedrine to their medication. Baseline quantitative myasthenia gravis (QMG) (severity) scores were worse than 15 of 39. Patients were assessed in clinic with QMG and mobility scores. Pretreatment and 6- to 8-month follow-up scores were evaluated. RESULTS All 6 patients tolerated treatment well and reported no side effects. There was a strong positive response to treatment over the 6- to 8-month assessment period with significant improvement in QMG (p = 0.027) and mobility scores. The analysis of subcomponents of the QMG score revealed marked improvement in upper (p = 0.028) and lower (p = 0.028) limb raise times. All patients reported enhanced activities of daily living at 6 to 8 months. CONCLUSIONS Oral salbutamol and ephedrine appear to be effective treatments in severe cases ofAChR deficiency on pyridostigmine. They are well tolerated and improvement in strength can be dramatic. Classification of evidence: This study provides Class IV evidence that salbutamol or ephedrine improves muscle strength in patients with congenital myasthenia from severe AChR deficiency.
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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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15
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Dusl M, Senderek J, Muller JS, Vogel JG, Pertl A, Stucka R, Lochmuller H, David R, Abicht A. A 3'-UTR mutation creates a microRNA target site in the GFPT1 gene of patients with congenital myasthenic syndrome. Hum Mol Genet 2015; 24:3418-26. [DOI: 10.1093/hmg/ddv090] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Accepted: 03/08/2015] [Indexed: 01/07/2023] Open
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16
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Vrinten C, van der Zwaag AM, Weinreich SS, Scholten RJPM, Verschuuren JJGM. Ephedrine for myasthenia gravis, neonatal myasthenia and the congenital myasthenic syndromes. Cochrane Database Syst Rev 2014; 2014:CD010028. [PMID: 25515947 PMCID: PMC7387729 DOI: 10.1002/14651858.cd010028.pub2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Myasthenia is a condition in which neuromuscular transmission is affected by antibodies against neuromuscular junction components (autoimmune myasthenia gravis, MG; and neonatal myasthenia gravis, NMG) or by defects in genes for neuromuscular junction proteins (congenital myasthenic syndromes, CMSs). Clinically, some individuals seem to benefit from treatment with ephedrine, but its effects and adverse effects have not been systematically evaluated. OBJECTIVES To assess the effects and adverse effects of ephedrine in people with autoimmune MG, transient neonatal MG, and the congenital myasthenic syndromes. SEARCH METHODS On 17 November 2014, we searched the Cochrane Neuromuscular Disease Group Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. We also searched reference lists of articles, conference proceedings of relevant conferences, and prospective trial registers. In addition, we contacted manufacturers and researchers in the field. SELECTION CRITERIA We considered randomised controlled trials (RCTs) and quasi-RCTs comparing ephedrine as a single or add-on treatment with any other active treatment, placebo, or no treatment in adults or children with autoimmune MG, NMG, or CMSs. DATA COLLECTION AND ANALYSIS Two review authors independently assessed study design and quality, and extracted data. We contacted study authors for additional information. We collected information on adverse effects from included articles, and contacted authors. MAIN RESULTS We found no RCTs or quasi-RCTs, and therefore could not establish the effect of ephedrine on MG, NMG and CMSs. We describe the results of 53 non-randomised studies narratively in the Discussion section, including observations of endurance, muscle strength and quality of life. Effects may differ depending on the type of myasthenia. Thirty-seven studies were in participants with CMS, five in participants with MG, and in 11 the precise form of myasthenia was unknown. We found no studies for NMG. Reported adverse effects included tachycardia, sleep disturbances, nervousness, and withdrawal symptoms. AUTHORS' CONCLUSIONS There was no evidence available from RCTs or quasi-RCTs, but some observations from non-randomised studies are available. There is a need for more evidence from suitable forms of prospective RCTs, such as series of n-of-one RCTs, that use appropriate and validated outcome measures.
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Affiliation(s)
- Charlotte Vrinten
- VU University Medical CenterCommunity Genetics Section, Clinical GeneticsBS7, D450PO Box 7057AmsterdamNetherlands1007 MB
| | - Angeli M van der Zwaag
- VU University Medical CenterCommunity Genetics Section, Clinical GeneticsBS7, D450PO Box 7057AmsterdamNetherlands1007 MB
| | - Stephanie S Weinreich
- VU University Medical CenterCommunity Genetics Section, Clinical GeneticsBS7, D450PO Box 7057AmsterdamNetherlands1007 MB
| | - Rob JPM Scholten
- Julius Center for Health Sciences and Primary Care / University Medical Center UtrechtDutch Cochrane CentreRoom Str. 6.126P.O. Box 85500UtrechtNetherlands3508 GA
| | - Jan JGM Verschuuren
- Leiden University Medical CenterDepartment of NeurologyPO Box 9600LeidenNetherlands2300 RC
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Das AS, Agamanolis DP, Cohen BH. Use of next-generation sequencing as a diagnostic tool for congenital myasthenic syndrome. Pediatr Neurol 2014; 51:717-20. [PMID: 25194721 DOI: 10.1016/j.pediatrneurol.2014.07.032] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 07/29/2014] [Accepted: 07/31/2014] [Indexed: 11/30/2022]
Abstract
BACKGROUND The clinical presentation of congenital myasthenic syndromes is similar to many other neuromuscular disorders of infancy, and with 12 known discrete genetic forms of congenital myasthenic syndromes, both the diagnosis and treatment decisions present clinical challenges. PATIENT DESCRIPTION We report a 20-month-old boy with rapsyn deficiency. At birth, he presented with a weak cry, hypotonia, joint contractures, and facial deformity. Because of respiratory difficulty associated with muscle fatigue, he spent a total of 71 days in the neonatal intensive care unit and 47 days in the pediatric intensive care unit. Imaging study results were normal, along with a battery of metabolic tests and electrodiagnostic studies. A limited genetic evaluation for reversible cytochrome c oxidase deficiency was negative, as was the oligonucleotide microarray. A muscle biopsy demonstrated myofiber atrophy in a pattern consistent with early denervation. Based on nonspecific and nondiagnostic results, whole-exome (next generation) sequencing was performed. This study identified two confirmed pathogenic mutations in the RAPSN gene that are associated with congenital myasthenic syndrome (OMIM 608931). The patient was treated with pyridostigmine at 16 months of age, which resulted in a dramatic improvement in muscle tone and strength and a steady resolution of joint contractures. Four months after treatment was initiated, he was beginning to bear weight and was able to sit unsupported and vocalize full words. CONCLUSIONS This patient serves to highlight next-generation sequencing as an important diagnostic tool that can result in life-saving treatment.
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Affiliation(s)
- Alvin S Das
- Northeast Ohio Medical University, Rootstown, Ohio
| | - Dimitri P Agamanolis
- Department of Pathology and Laboratory Medicine, Akron Children's Hospital, Akron, Ohio; Department of Pathology, Northeast Ohio Medical University, Rootstown, Ohio
| | - Bruce H Cohen
- Division of Neurology, NeuroDevelopmental Science Center, Akron Children's Hospital, Akron, Ohio; Department of Pediatrics, Northeast Ohio Medical University, Rootstown, Ohio.
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Webster R, Liu WW, Chaouch A, Lochmüller H, Beeson D. Fast-channel congenital myasthenic syndrome with a novel acetylcholine receptor mutation at the α-ε subunit interface. Neuromuscul Disord 2013; 24:143-7. [PMID: 24295813 DOI: 10.1016/j.nmd.2013.10.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 10/22/2013] [Accepted: 10/25/2013] [Indexed: 01/24/2023]
Abstract
Congenital myasthenic syndromes (CMS) result from the failure to achieve muscle depolarisation due to disorders in the structure and/or function of the neuromuscular synapse. Mutations of the nicotinic acetylcholine receptor (nAChR) form a major subset of CMS. We describe a patient who presented with recurrent apnoeic crises in the neonatal period requiring ventilator support. Electromyography revealed compound muscle action potential decrement upon repetitive stimulation. Sequencing of nAChR subunit genes revealed two missense mutations. One previously reported null mutation p.εTyr15His, and a second novel missense mutation, p.εThr38Lys, that is well expressed in mammalian cell culture and thus likely to exert its effect via alteration of ion channel kinetics. Functional analysis revealed abbreviated ion channel bursts characteristic of a fast channel CMS. The mutation p.εThr38Lys occurs at the interface between the α and ε subunits of the nAChR pentamer and leads to instability of the open channel. The effects of this mutation on channel function were investigated in relation to other fast channel mutants at an analogous subunit interface within the nAChR pentamer. Fast channel syndromes are frequently characterised by severe myasthenic weakness with apnoeic crises; knowledge of the underlying mutation and its functional consequences can be vital for appropriate therapy and patient management.
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Affiliation(s)
- Richard Webster
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Headley Way, Oxford, UK
| | - Wei-Wei Liu
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Headley Way, Oxford, UK
| | - Amina Chaouch
- Institute of Genetic Medicine, International Centre for Life, Newcastle upon Tyne, UK
| | - Hanns Lochmüller
- Institute of Genetic Medicine, International Centre for Life, Newcastle upon Tyne, UK
| | - David Beeson
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Headley Way, Oxford, UK.
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19
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Klein A, Pitt MC, McHugh JC, Niks EH, Sewry CA, Phadke R, Feng L, Manzur AY, Tirupathi S, DeVile C, Jayawant S, Finlayson S, Palace J, Muntoni F, Beeson D, Robb SA. DOK7 congenital myasthenic syndrome in childhood: Early diagnostic clues in 23 children. Neuromuscul Disord 2013; 23:883-91. [DOI: 10.1016/j.nmd.2013.06.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 05/24/2013] [Accepted: 06/05/2013] [Indexed: 10/26/2022]
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20
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Gallenmüller C, Müller-Felber W, Dusl M, Stucka R, Guergueltcheva V, Blaschek A, von der Hagen M, Huebner A, Müller JS, Lochmüller H, Abicht A. Salbutamol-responsive limb-girdle congenital myasthenic syndrome due to a novel missense mutation and heteroallelic deletion in MUSK. Neuromuscul Disord 2013; 24:31-5. [PMID: 24183479 PMCID: PMC4018985 DOI: 10.1016/j.nmd.2013.08.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 07/20/2013] [Accepted: 08/01/2013] [Indexed: 12/24/2022]
Abstract
Congenital myasthenic syndromes (CMS) are clinically and genetically heterogeneous disorders characterized by a neuromuscular transmission defect. In recent years, causative mutations have been identified in atleast 15 genes encoding proteins of the neuromuscular junction. Mutations in MUSK are known as a very rare genetic cause of CMS and have been described in only three families, world-wide. Consequently, the knowledge about efficient drug therapy is very limited. We identified a novel missense mutation (p.Asp38Glu) heteroallelic to a genomic deletion affecting exons 2–3 of MUSK as cause of a limb-girdle CMS in two brothers of Turkish origin. Clinical symptoms included fatigable limb weakness from early childhood on. Upon diagnosis of a MUSK-related CMS at the age of 16 and 13 years, respectively, treatment with salbutamol was initiated leading to an impressive improvement of clinical symptoms, while treatment with esterase inhibitors did not show any benefit. Our findings highlight the importance of a molecular diagnosis in CMS and demonstrate considerable similarities between patients with MUSK and DOK7-related CMS in terms of clinical phenotype and treatment options.
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Affiliation(s)
| | | | - Marina Dusl
- Friedrich-Baur-Institut, Ludwig Maximilians University, Munich, Germany
| | - Rolf Stucka
- Friedrich-Baur-Institut, Ludwig Maximilians University, Munich, Germany
| | - Velina Guergueltcheva
- Friedrich-Baur-Institut, Ludwig Maximilians University, Munich, Germany; Clinic of Neurology, University Hospital Alexandrovska, Sofia, Bulgaria
| | - Astrid Blaschek
- Haunersche Kinderklinik, Ludwig Maximilians University, Munich, Germany
| | | | - Angela Huebner
- Children's Hospital, Technical University Dresden, Germany
| | - Juliane S Müller
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Hanns Lochmüller
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Angela Abicht
- Friedrich-Baur-Institut, Ludwig Maximilians University, Munich, Germany; Medical Genetics Center, Munich, Germany.
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21
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Verschuuren JJ, Huijbers MG, Plomp JJ, Niks EH, Molenaar PC, Martinez-Martinez P, Gomez AM, De Baets MH, Losen M. Pathophysiology of myasthenia gravis with antibodies to the acetylcholine receptor, muscle-specific kinase and low-density lipoprotein receptor-related protein 4. Autoimmun Rev 2013; 12:918-23. [DOI: 10.1016/j.autrev.2013.03.001] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2013] [Indexed: 01/13/2023]
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22
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Webster RG, Cossins J, Lashley D, Maxwell S, Liu WW, Wickens JR, Martinez-Martinez P, de Baets M, Beeson D. A mouse model of the slow channel myasthenic syndrome: Neuromuscular physiology and effects of ephedrine treatment. Exp Neurol 2013; 248:286-98. [PMID: 23797154 DOI: 10.1016/j.expneurol.2013.06.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 05/10/2013] [Accepted: 06/14/2013] [Indexed: 02/04/2023]
Abstract
In the slow channel congenital myasthenic syndrome mutations in genes encoding the muscle acetylcholine receptor give rise to prolonged ion channel activations. The resulting cation overload in the postsynaptic region leads to damage of synaptic structures, impaired neuromuscular transmission and fatigable muscle weakness. Previously we identified and characterised in detail the properties of the slow channel syndrome mutation εL221F. Here, using this mutation, we generate a transgenic mouse model for the slow channel syndrome that expresses mutant human ε-subunits harbouring an EGFP tag within the M3-M4 cytoplasmic region, driven by a ~1500 bp region of the CHRNB promoter. Fluorescent mutant acetylcholine receptors are assembled, cluster at the motor endplates and give rise to a disease model that mirrors the human condition. Mice demonstrate mild fatigable muscle weakness, prolonged endplate and miniature endplate potentials, and variable degeneration of the postsynaptic membrane. We use our model to investigate ephedrine as a potential treatment. Mice were assessed before and after six weeks on oral ephedrine (serum ephedrine concentration 89 ± 3 ng/ml) using an inverted screen test and in vivo electromyography. Treated mice demonstrated modest benefit for screen hang time, and in measures of compound muscle action potentials and mean jitter that did not reach statistical significance. Ephedrine and salbutamol show clear benefit when used in the treatment of DOK7 or COLQ congenital myasthenic syndromes. Our results highlight only a modest potential benefit of these β2-adrenergic receptor agonists for the treatment of the slow channel syndrome.
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Affiliation(s)
- R G Webster
- Neurosciences Group, Nuffield Dept. of Clinical Neurosciences, University of Oxford, Oxford, UK
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23
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Nakata T, Ito M, Azuma Y, Otsuka K, Noguchi Y, Komaki H, Okumura A, Shiraishi K, Masuda A, Natsume J, Kojima S, Ohno K. Mutations in the C-terminal domain of ColQ in endplate acetylcholinesterase deficiency compromise ColQ-MuSK interaction. Hum Mutat 2013; 34:997-1004. [PMID: 23553736 DOI: 10.1002/humu.22325] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2013] [Accepted: 03/19/2013] [Indexed: 11/11/2022]
Abstract
Acetylcholinesterase (AChE) at the neuromuscular junction (NMJ) is mostly composed of an asymmetric form in which three tetramers of catalytic AChE subunits are linked to a triple helical collagen Q (ColQ). Mutations in COLQ cause endplate AChE deficiency. We report three patients with endplate AChE deficiency with five recessive COLQ mutations. Sedimentation profiles showed that p.Val322Asp and p.Arg227X, but not p.Cys444Tyr, p.Asp447His, or p.Arg452Cys, inhibit formation of triple helical ColQ. In vitro overlay of mutant ColQ-tailed AChE on muscle sections of Colq(-/-) mice revealed that p.Cys444Tyr, p.Asp447His, and p.Arg452Cys in the C-terminal domain (CTD) abrogate anchoring ColQ-tailed AChE to the NMJ. In vitro plate-binding assay similarly demonstrated that the three mutants inhibit binding of ColQ-tailed AChE to MuSK. We also confirmed the pathogenicity of p.Asp447His by treating Colq(-/-) mice with adeno-associated virus serotype 8 carrying mutant COLQ-p.Asp447His. The treated mice showed no improvement in motor functions and no anchoring of ColQ-tailed AChE at the NMJ. Electroporation of mutant COLQ harboring p.Cys444Tyr, p.Asp447His, and p.Arg452Cys into anterior tibial muscles of Colq(-/-) mice similarly failed to anchor ColQ-tailed AChE at the NMJ. We proved that the missense mutations in ColQ-CTD cause endplate AChE deficiency by compromising ColQ-MuSK interaction at the NMJ.
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Affiliation(s)
- Tomohiko Nakata
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Pappalardo A, Pitto L, Fiorillo C, Alice Donati M, Bruno C, Santorelli FM. Neuromuscular disorders in zebrafish: state of the art and future perspectives. Neuromolecular Med 2013; 15:405-19. [PMID: 23584918 DOI: 10.1007/s12017-013-8228-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2012] [Accepted: 03/30/2013] [Indexed: 12/22/2022]
Abstract
Neuromuscular disorders are a broad group of inherited conditions affecting the structure and function of the motor system with polymorphic clinical presentation and disease severity. Although individually rare, collectively neuromuscular diseases have an incidence of 1 in 3,000 and represent a significant cause of disability of the motor system. The past decade has witnessed the identification of a large number of human genes causing muscular disorders, yet the underlying pathogenetic mechanisms remain largely unclear, limiting the developing of targeted therapeutic strategies. To overcome this barrier, model systems that replicate the different steps of human disorders are increasingly being developed. Among these, the zebrafish (Danio rerio) has emerged as an excellent organism for studying genetic disorders of the central and peripheral motor systems. In this review, we will encounter most of the available zebrafish models for childhood neuromuscular disorders, providing a brief overview of results and the techniques, mainly transgenesis and chemical biology, used for genetic manipulation. The amount of data collected in the past few years will lead zebrafish to became a common functional tool for assessing rapidly drug efficacy and off-target effects in neuromuscular diseases and, furthermore, to shed light on new etiologies emerging from large-scale massive sequencing studies.
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Affiliation(s)
- Andrea Pappalardo
- Molecular Medicine, and Neuromuscular Lab, IRCCS Stella Maris, Via dei Giacinti 2, 56128 Pisa, Italy
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25
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Cossins J, Liu WW, Belaya K, Maxwell S, Oldridge M, Lester T, Robb S, Beeson D. The spectrum of mutations that underlie the neuromuscular junction synaptopathy in DOK7 congenital myasthenic syndrome. Hum Mol Genet 2012; 21:3765-75. [PMID: 22661499 DOI: 10.1093/hmg/dds198] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Congenital myasthenic syndromes (CMS) are a group of inherited diseases that affect synaptic transmission at the neuromuscular junction and result in fatiguable muscle weakness. A subgroup of CMS patients have a recessively inherited limb-girdle pattern of weakness caused by mutations in DOK7. DOK7 encodes DOK7, an adaptor protein that is expressed in the skeletal muscle and heart and that is essential for the development and maintenance of the neuromuscular junction. We have screened the DOK7 gene for mutations by polymerase chain reaction amplification and bi-directional sequencing of exonic and promoter regions and performed acetylcholine receptor (AChR) clustering assays and used exon trapping to determine the pathogenicity of detected variants. Approximately 18% of genetically diagnosed CMSs in the UK have mutations in DOK7, with mutations in this gene identified in more than 60 kinships to date. Thirty-four different pathogenic mutations were identified as well as 27 variants likely to be non-pathogenic. An exon 7 frameshift duplication c.1124_1127dupTGCC is commonly found in at least one allele. We analyse the effect of the common frameshift c.1124_1127dupTGCC and show that 10/11 suspected missense mutations have a deleterious effect on AChR clustering. We identify for the first time homozygous or compound heterozygous mutations that are localized 5' to exon 7. In addition, three silent variants in the N-terminal half of DOK7 are predicted to alter the splicing of the DOK7 RNA transcript. The DOK7 gene is highly polymorphic, and within these many variants, we define a spectrum of mutations that can underlie DOK7 CMS that will inform in managing this disorder.
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Affiliation(s)
- Judith Cossins
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK
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Lorenzoni PJ, Scola RH, Kay CSK, Werneck LC. Congenital myasthenic syndrome: a brief review. Pediatr Neurol 2012; 46:141-8. [PMID: 22353287 DOI: 10.1016/j.pediatrneurol.2011.12.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2011] [Accepted: 12/22/2011] [Indexed: 01/04/2023]
Abstract
Congenital myasthenic syndromes comprise heterogeneous genetic diseases characterized by compromised neuromuscular transmission. Congenital myasthenic syndromes are classified as presynaptic, synaptic, or postsynaptic, depending on the primary defect's location within the neuromuscular junction. Presynaptic forms are the rarest, affecting an estimated 7-8% of patients; synaptic forms account for approximately 14-15% of patients; and the remaining 75-80% are attributable to postsynaptic defects. Clinical manifestations vary by congenital myasthenic syndrome subtype. Electrophysiologic, morphologic, and molecular descriptions of various forms of congenital myasthenic syndromes have led to an enhanced understanding of clinical manifestations and disease pathophysiology. Although congenital myasthenic syndromes are indicated by clinical manifestations, family history, electrophysiologic studies, and responses to acetylcholinesterase inhibitors, overlap in some presentations occurs. Therefore, genetic testing may be necessary to identify specific mutations in CHAT, COLQ, LAMB2, CHRNA, CHRNB, CHRND, CHRNE, CHRNG, RAPSN, DOK7, MUSK, AGRN, SCN4A, GFPT1, or PLEC1 genes. The identification of congenital myasthenic syndromes subtypes will prove important in the treatment of these patients. Different drugs may be beneficial, or should be avoided because they are ineffective or worsen some forms of congenital myasthenic syndromes. We explore the classification, clinical manifestations, electrophysiologic features, genetics, and treatment responses of each congenital myasthenic syndrome subtype.
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Affiliation(s)
- Paulo José Lorenzoni
- Neuromuscular Disorders Unit, Division of Neurology, Department of Internal Medicine, Hospital de Clínicas da Universidade Federal do Paraná, Curitiba, PR, Brazil
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