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Sun S, Shen Y, Zhang X, Ding N, Xu Z, Zhang Q, Li L. The MuSK agonist antibody protects the neuromuscular junction and extends the lifespan in C9orf72-ALS mice. Mol Ther 2024; 32:2176-2189. [PMID: 38734896 DOI: 10.1016/j.ymthe.2024.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 04/06/2024] [Accepted: 05/09/2024] [Indexed: 05/13/2024] Open
Abstract
The disassembly of the neuromuscular junction (NMJ) is an early event in amyotrophic lateral sclerosis (ALS), ultimately leading to motor dysfunction and lethal respiratory paralysis. The hexanucleotide GGGGCC repeat expansion in the C9orf72 gene is the most common genetic mutation, and the dipeptide repeat (DPR) proteins have been shown to cause neurodegeneration. While no drugs can treat ALS patients efficiently, new treatment strategies are urgently needed. Here, we report that a MuSK agonist antibody alleviates poly-PR-induced NMJ deficits in C9orf72-ALS mice. The HB9-PRF/F mice, which express poly-PR proteins in motor neurons, exhibited impaired motor behavior and NMJ deficits. Mechanistically, poly-PR proteins interacted with Agrin to disrupt the interaction between Agrin and Lrp4, leading to attenuated activation of MuSK. Treatment with a MuSK agonist antibody rescued NMJ deficits, and extended the lifespan of C9orf72-ALS mice. Moreover, impaired NMJ transmission was observed in C9orf72-ALS patients. These findings identify the mechanism by which poly-PR proteins attenuate MuSK activation and NMJ transmission, highlighting the potential of promoting MuSK activation with an agonist antibody as a therapeutic strategy to protect NMJ function and prolong the lifespan of ALS patients.
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Affiliation(s)
- Shuangshuang Sun
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Yihui Shen
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Xu Zhang
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Ning Ding
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Zhe Xu
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Qijie Zhang
- Department of Neurology, Fujian Institute of Neurology, The First Affiliated Hospital, Fujian Medical University, Fuzhou 350005, China.
| | - Lei Li
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China.
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Tsalta-Mladenov M, Levkova M, Georgieva D, Andonova S. Congenital myasthenic syndrome due to a genetic mutation. J Am Assoc Nurse Pract 2023:01741002-990000000-00108. [PMID: 37141567 DOI: 10.1097/jxx.0000000000000878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 04/04/2023] [Indexed: 05/06/2023]
Abstract
ABSTRACT Congenital myasthenic syndrome (CMS) is a group of rare genetic disorders that mimics the symptoms of myasthenia gravis, but it is due to a genetic defect. We present a case of a male CMS patient, and the course of the disease through the years. The patient initially presented with generalized muscle weakness and difficulty swallowing. During the follow-up, he developed difficulty in chewing, bilateral external ophthalmoparesis with an almost full block of eye movements and bulbar syndrome. The case illustrates both the clinical heterogeneity and the progressive worsening of the symptoms of the disease over the years. The optimal treatment for CMS is based on the molecular defect and its localization in the neuromuscular junction. In our case, treatment with pyridostigmine resulted in good long-term control of symptoms. As a result of the patient's good compliance with treatment, he was not admitted to hospital because of respiratory distress. The lack of a unified protocol for the treatment of CMS highlights the need for a more personalized approach when dealing with patients with rare diseases.
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Affiliation(s)
- Mihael Tsalta-Mladenov
- Department of Neurology and Neuroscience, Medical University "Prof. Paraskev Stoyanov," Varna, Bulgaria
- Second Clinic of Neurology with ICU and Stroke Unit, University Multiprofile Hospital for Active Treatment "St. Marina," Varna, Bulgaria
| | - Mariya Levkova
- Department of Medical Genetics, Medical University "Prof. Paraskev Stoyanov," Varna, Bulgaria
- Laboratory of Medical Genetics, University Multiprofile Hospital for Active Treatment "St. Marina," Varna, Bulgaria
| | - Darina Georgieva
- Department of Neurology and Neuroscience, Medical University "Prof. Paraskev Stoyanov," Varna, Bulgaria
- Second Clinic of Neurology with ICU and Stroke Unit, University Multiprofile Hospital for Active Treatment "St. Marina," Varna, Bulgaria
| | - Silva Andonova
- Department of Neurology and Neuroscience, Medical University "Prof. Paraskev Stoyanov," Varna, Bulgaria
- Second Clinic of Neurology with ICU and Stroke Unit, University Multiprofile Hospital for Active Treatment "St. Marina," Varna, Bulgaria
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3
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Gu X, Hou Y, Chen Y, Ou R, Cao B, Wei Q, Zhang L, Song W, Zhao B, Wu Y, Li C, Shang H. Enrichment of rare variants in E3 ubiquitin ligase genes in Early onset Parkinson's disease. Neurobiol Aging 2021; 109:273-278. [PMID: 34544586 DOI: 10.1016/j.neurobiolaging.2021.08.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 06/15/2021] [Accepted: 08/18/2021] [Indexed: 02/08/2023]
Abstract
Altered ubiquitin signaling and disrupted protein quality control have been implicated in the pathogenesis of PD. The aim of the study was to systematically examine the overlaps between E3 ubiquitin ligase genes and early onset PD (EOPD). A total of 695 EOPD patients were analyzed aggregate burden for rare variants (MAF <0.001 and MAF <0.0001) in a total of 44 E3 ubiquitin ligase genes causing disorders involved in the nervous system. There was significant enrichment of the rare and rare damaging variants in the E3 ubiquitin ligase genes in EOPD patients. Detailly, in the gene-based level, the strongest associations were found in HERC1, IRF2BPL, KMT2D, RAPSN, RLIM, RNF168 and RNF216. Our findings highlighted the importance of UPS mechanism in the pathogenesis of PD from the genetic perspective. Moreover, our study also expanded the susceptible gene spectrum for PD.
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Affiliation(s)
- Xiaojing Gu
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Yanbing Hou
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Yongping Chen
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Ruwei Ou
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Bei Cao
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Qianqian Wei
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Lingyu Zhang
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Wei Song
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Bi Zhao
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Ying Wu
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Chunyu Li
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Huifang Shang
- Department of Neurology, Laboratory of Neurodegenerative Disorders, Rare disease Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
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Bhattacharjee I, Friedman N, Rodriguez RJ. Utility of Rapid Exome Sequencing in the Diagnosis of a Rare Congenital Myasthenic Syndromes in a Preterm Infant. JOURNAL OF PEDIATRIC NEUROLOGY 2021. [DOI: 10.1055/s-0040-1712177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
AbstractCongenital myasthenic syndromes (CMS) are rare and challenging diagnoses in preterm neonates. We presented in this case report a preterm infant with recurrent extubation failures. An exhaustive workup to rule out common etiologies of chronic ventilator dependence was negative including a neostigmine trial, acetylcholine receptor antibodies, and chromosomal microarray. Electromyography (EMG) showed features of a neuromuscular junction defect. After ruling out metabolic, inflammatory, and immune mediated causes, a rapid exome sequencing demonstrated CHRNB1 gene mutation diagnostic of autosomal dominant slow channel CMS. The patient was started on fluoxetine and nebulized salbutamol with a gradual improvement in her respiratory function over time with minimal ventilator support.
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Affiliation(s)
- Indrani Bhattacharjee
- Department of Neonatology, Cleveland Clinic Children's Hospital, Cleveland, Ohio, United States
| | - Neil Friedman
- Department of Neurology, Phoenix Children's Hospital, Phoenix, Arizona, United States
| | - Ricardio J. Rodriguez
- Department of Neonatology, Cleveland Clinic Children's Hospital, Cleveland, Ohio, United States
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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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6
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Abstract
Myasthenia gravis is an autoimmune disorder characterized by fluctuating weakness of extraocular and proximal limb muscles. It occurs in 1 in 5000 in the overall population and is 2 times more common in women than men. The onset in women is most common in the third decade, and risk of severe exacerbation occurs most frequently in the year after presentation. The disease does not have an impact on fertility and overlap with pregnancy is expected. This article provides a description of the disease process and its impact on the expecting mother, fetus, and newborn. Management options in pregnancy and lactation are discussed.
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Affiliation(s)
- Janet Waters
- Women's Neurology, University of Pittsburgh Medical Center, 3471 Fifth Avenue Suite 810, Pittsburgh, PA 15213, USA.
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7
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Abstract
OBJECTIVES To investigate the mutational spectrum and genotype-phenotype correlation in Indian patients with congenital myasthenic syndrome (CMS), using next-generation sequencing of 5 genes. METHODS CHRNE, COLQ, DOK7, RAPSN, and GFPT1 were sequenced in 25 affected patients. RESULTS We found clinically significant variants in 18 patients, of which variants in CHRNE were the most common, and 9 were novel. A common pathogenic COLQ variant was also detected in 4 patients with isolated limb-girdle congenital myasthenia. CONCLUSIONS Targeted screening of 5 genes is an effective alternate test for CMS, and an affordable one even in a developing country such as India. In addition, we recommend that patients with isolated limb-girdle congenital myasthenia be screened initially for the common COLQ pathogenic variant. This study throws the first light on the genetic landscape of CMSs in India.
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8
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Congenital Myasthenic Syndromes. Neuromuscul Disord 2018. [DOI: 10.1007/978-981-10-5361-0_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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9
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French DM, Bridges EP, Hoskins MC, Andrews CM, Nelson CH. Myasthenic Crisis In Pregnancy. Clin Pract Cases Emerg Med 2017; 1:291-294. [PMID: 29849328 PMCID: PMC5965196 DOI: 10.5811/cpcem.2017.5.33404] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 04/30/2017] [Accepted: 05/11/2017] [Indexed: 12/28/2022] Open
Abstract
This case reviews the management of a 27-year-old pregnant female in myasthenic crisis. She presented to the emergency department in respiratory distress refractory to standard therapy, necessitating airway and ventilatory support and treatment with plasmapheresis. Myasthenic crisis in the setting of pregnancy is rare and presents unique management challenges for emergency physicians.
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Affiliation(s)
- David M French
- Medical University of South Carolina, Emergency Medicine, Charleston, South Carolina
| | - E Page Bridges
- Greenville Health System, Emergency Medicine, Greenville, South Carolina
| | - Matthew C Hoskins
- Medical University of South Carolina, Emergency Medicine, Charleston, South Carolina
| | - Charles M Andrews
- Medical University of South Carolina, Emergency Medicine, Charleston, South Carolina.,Medical University of South Carolina, Neurocritical Care, Charleston, South Carolina
| | - Cecil H Nelson
- Medical University of South Carolina, Department of Obstetrics and Gynecology, Charleston, South Carolina
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10
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Fatigue in Rapsyn-Deficient Zebrafish Reflects Defective Transmitter Release. J Neurosci 2017; 36:10870-10882. [PMID: 27798141 DOI: 10.1523/jneurosci.0505-16.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 09/03/2016] [Indexed: 12/29/2022] Open
Abstract
Rapsyn-deficient myasthenic syndrome is characterized by a weakness in voluntary muscle contraction, a direct consequence of greatly reduced synaptic responses that result from poorly clustered acetylcholine receptors. As with other myasthenic syndromes, the general muscle weakness is also accompanied by use-dependent fatigue. Here, we used paired motor neuron target muscle patch-clamp recordings from a rapsyn-deficient mutant line of zebrafish to explore for the first time the mechanisms causal to fatigue. We find that synaptic responses in mutant fish can follow faithfully low-frequency stimuli despite the reduced amplitude. This is in part helped by a compensatory increase in the number of presynaptic release sites in the mutant fish. In response to high-frequency stimulation, both wild-type and mutant neuromuscular junctions depress to steady-state response levels, but the latter shows exaggerated depression. Analysis of the steady-state transmission revealed that vesicle reloading and release at individual release sites is significantly slower in mutant fish during high-frequency activities. Therefore, reductions in postsynaptic receptor density and compromised presynaptic release collectively serve to reduce synaptic strength to levels that fall below the threshold for muscle action potential generation, thus accounting for use-dependent fatigue. Our findings raise the possibility that defects in motor neuron function may also be at play in other myasthenic syndromes that have been mapped to mutations in muscle-specific proteins. SIGNIFICANCE STATEMENT Use-dependent fatigue accompanies many neuromuscular myasthenic syndromes, including muscle rapsyn deficiency. Here, using a rapsyn-deficient line of zebrafish, we performed paired motor neuron target muscle patch-clamp recordings to investigate the mechanisms causal to this phenomenon. Our findings indicate that the reduced postsynaptic receptor density resulting from defective rapsyn contributes to weakness, but is not solely responsible for use-dependent fatigue. Instead, we find unexpected involvement of altered transmitter release from the motor neuron. Specifically, slowed reloading of vesicle release sites leads to augmented synaptic depression during repeated action potentials. Even at moderate stimulus frequencies, the depression levels for evoked synaptic responses fall below the threshold for the generation of muscle action potentials. The associated contraction failures are manifest as use-dependent fatigue.
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11
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Affiliation(s)
- Yuko Shimizu
- Department of Neurology; Tokyo Women's Medical University School of Medicine; Tokyo Japan
| | - Kazuo Kitagawa
- Department of Neurology; Tokyo Women's Medical University School of Medicine; Tokyo Japan
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12
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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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Sigoillot SM, Bourgeois F, Karmouch J, Molgó J, Dobbertin A, Chevalier C, Houlgatte R, Léger J, Legay C. Neuromuscular junction immaturity and muscle atrophy are hallmarks of the ColQ-deficient mouse, a model of congenital myasthenic syndrome with acetylcholinesterase deficiency. FASEB J 2016; 30:2382-99. [PMID: 26993635 DOI: 10.1096/fj.201500162] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 02/26/2016] [Indexed: 12/13/2022]
Abstract
The collagen ColQ anchors acetylcholinesterase (AChE) in the synaptic cleft of the neuromuscular junction (NMJ). It also binds MuSK and perlecan/dystroglycan, 2 signaling platforms of the postsynaptic domain. Mutations in ColQ cause a congenital myasthenic syndrome (CMS) with AChE deficiency. Because the absence of AChE does not fully explain the complexity of the syndrome and there is no curative treatment for the disease, we explored additional potential targets of ColQ by conducting a large genetic screening of ColQ-deficient mice, a model for CMS with AChE deficiency, and analyzed their NMJ and muscle phenotypes. We demonstrated that ColQ controls the development and the maturation of the postsynaptic domain by regulating synaptic gene expression. Notably, ColQ deficiency leads to an up-regulation of the 5 subunits of the nicotinic acetylcholine receptor (AChR), leading to mixed mature and immature AChRs at the NMJ of adult mice. ColQ also regulates the expression of extracellular matrix (ECM) components. However, whereas the ECM mRNAs were down-regulated in vitro, compensation seemed to occur in vivo to maintain normal levels of these mRNAs. Finally, ColQ deficiency leads to a general atrophic phenotype and hypoplasia that affect fast muscles. This study points to new specific hallmarks for this CMS.-Sigoillot, S. M., Bourgeois, F., Karmouch, J., Molgó, J., Dobbertin, A., Chevalier, C., Houlgatte, R., Léger, J., Legay, C. Neuromuscular junction immaturity and muscle atrophy are hallmarks of the ColQ-deficient mouse, a model of congenital myasthenic syndrome with acetylcholinesterase deficiency.
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Affiliation(s)
- Séverine M Sigoillot
- Centre de Neurophysique, Physiologie et Pathologie, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 8119, Université Paris Descartes, Sorbonne Paris Cité, Paris France
| | - Francine Bourgeois
- Centre de Neurophysique, Physiologie et Pathologie, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 8119, Université Paris Descartes, Sorbonne Paris Cité, Paris France
| | - Jennifer Karmouch
- Centre de Neurophysique, Physiologie et Pathologie, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 8119, Université Paris Descartes, Sorbonne Paris Cité, Paris France
| | - Jordi Molgó
- Commissariat à l'énergie Atomique et aux Energies Alternatives, Institut de Biologie et Technologies de Saclay, Service d'Ingénierie Moléculaire des Protéines, Gif sur Yvette, France; Institut des Neurosciences Paris-Saclay, UMR 9197, CNRS/Université Paris-Sud, Paris, France; and
| | - Alexandre Dobbertin
- Centre de Neurophysique, Physiologie et Pathologie, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 8119, Université Paris Descartes, Sorbonne Paris Cité, Paris France
| | - Catherine Chevalier
- Institut de Recherche Thérapeutique de l'Université de Nantes, Plateforme Génomique Intégrative, Nantes, France
| | - Rémi Houlgatte
- Institut de Recherche Thérapeutique de l'Université de Nantes, Plateforme Génomique Intégrative, Nantes, France
| | - Jean Léger
- Institut de Recherche Thérapeutique de l'Université de Nantes, Plateforme Génomique Intégrative, Nantes, France
| | - Claire Legay
- Centre de Neurophysique, Physiologie et Pathologie, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 8119, Université Paris Descartes, Sorbonne Paris Cité, Paris France;
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Ngo ST, Steyn FJ, McCombe PA. Gender differences in autoimmune disease. Front Neuroendocrinol 2014; 35:347-69. [PMID: 24793874 DOI: 10.1016/j.yfrne.2014.04.004] [Citation(s) in RCA: 583] [Impact Index Per Article: 58.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 04/20/2014] [Accepted: 04/22/2014] [Indexed: 12/21/2022]
Abstract
Autoimmune diseases are a range of diseases in which the immune response to self-antigens results in damage or dysfunction of tissues. Autoimmune diseases can be systemic or can affect specific organs or body systems. For most autoimmune diseases there is a clear sex difference in prevalence, whereby females are generally more frequently affected than males. In this review, we consider gender differences in systemic and organ-specific autoimmune diseases, and we summarize human data that outlines the prevalence of common autoimmune diseases specific to adult males and females in countries commonly surveyed. We discuss possible mechanisms for sex specific differences including gender differences in immune response and organ vulnerability, reproductive capacity including pregnancy, sex hormones, genetic predisposition, parental inheritance, and epigenetics. Evidence demonstrates that gender has a significant influence on the development of autoimmune disease. Thus, considerations of gender should be at the forefront of all studies that attempt to define mechanisms that underpin autoimmune disease.
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Affiliation(s)
- S T Ngo
- School of Biomedical Sciences, University of Queensland, St Lucia, Queensland, Australia; University of Queensland Centre for Clinical Research, University of Queensland, Herston, Queensland, Australia
| | - F J Steyn
- School of Biomedical Sciences, University of Queensland, St Lucia, Queensland, Australia
| | - P A McCombe
- University of Queensland Centre for Clinical Research, University of Queensland, Herston, Queensland, Australia; Department of Neurology, Royal Brisbane & Women's Hospital, Herston, Queensland, Australia.
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15
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Clinical and molecular analysis of a novel COLQ missense mutation causing congenital myasthenic syndrome in a Syrian family. Pediatr Neurol 2014; 51:165-9. [PMID: 24938146 DOI: 10.1016/j.pediatrneurol.2014.03.012] [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: 01/01/2014] [Revised: 03/12/2014] [Accepted: 03/15/2014] [Indexed: 02/08/2023]
Abstract
BACKGROUND Congenital myasthenic syndromes with end-plate acetylcholinesterase deficiency are rare autosomal recessive disorders characterized by onset of the disease in early childhood, general weakness exacerbated by exertion, ophthalmoplegia, and refractoriness to anticholinesterase drugs. To date, all reported cases have been attributed to mutations in 18 genes including the COLQ gene that encodes a specific collagen that anchors acetylcholinesterase at the basal lamina of the neuromuscular junction. We identified a Syrian family with two children of consanguineous parents from two branches affected with congenital myasthenic syndrome with end-plate acetylcholinesterase deficiency. METHOD The absence of acetylcholinesterase antibodies was demonstrated biochemically. Consequently, all the coding regions, exon-intron boundaries, and the 5' and 3' untranslated regions of the COLQ gene were amplified and sequenced using the Sanger sequencing method. RESULTS We observed that the severity of the phenotype in the two affected children differed. One child had mild symptoms that included difficulties in gait and feeding with mild respiratory insufficiency. Her sibling died in the first months of life because of severe respiratory failure. The second patient had severe symptoms from birth and has been mechanically ventilated. DNA sequencing revealed a novel homozygous single nucleotide substitution mutation (c.1010T>C) in the COLQ gene in both patients. This substitution leads to a missense amino acid substitution at position 337 of the protein (p.Ile337Thr). This mutation is likely to impair ColQ's trimeric organization and therefore its anchoring within the synaptic basal lamina. CONCLUSION We identified the molecular cause underlying congenital myasthenic syndrome in two patients. The marked phenotypic variation suggests that other factors including modifier genes may affect the severity of this disease.
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16
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Severe scoliosis in a patient with COLQ mutation and congenital myasthenic syndrome: a clue for diagnosis. Acta Neurol Belg 2013; 113:531-2. [PMID: 23371844 DOI: 10.1007/s13760-013-0179-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 01/10/2013] [Indexed: 10/27/2022]
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17
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Abstract
Myasthenia gravis is an autoimmune disease of the neuromuscular junction characterized by painless fluctuating skeletal muscle weakness. Disease exacerbations are more likely to occur in the first trimester or puerperium. A number of medications commonly used in obstetric practice can exacerbate the disease. The effect of pregnancy on myasthenia varies substantially from woman to woman and also from pregnancy to pregnancy in the same woman. Mainstay treatments involve acetylcholine esterase inhibitors, corticosteroids and other immunosuppressants, and adequate rest. Newborns may suffer in utero or neonatal consequences, usually transient, of transplacental antibody exposure.
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Maladies musculaires en réanimation. Quand les évoquer ? Comment orienter la recherche diagnostique ? MEDECINE INTENSIVE REANIMATION 2012. [DOI: 10.1007/s13546-012-0515-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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19
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Maselli RA, Fernandez JM, Arredondo J, Navarro C, Ngo M, Beeson D, Cagney Ó, Williams DC, Wollmann RL, Yarov-Yarovoy V, Ferns MJ. LG2 agrin mutation causing severe congenital myasthenic syndrome mimics functional characteristics of non-neural (z-) agrin. Hum Genet 2012; 131:1123-35. [PMID: 22205389 PMCID: PMC4795461 DOI: 10.1007/s00439-011-1132-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 12/11/2011] [Indexed: 10/14/2022]
Abstract
We describe a severe form of congenital myasthenic syndrome (CMS) caused by two heteroallelic mutations: a nonsense and a missense mutation in the gene encoding agrin (AGRN). The identified mutations, Q353X and V1727F, are located at the N-terminal and at the second laminin G-like (LG2) domain of agrin, respectively. A motor-point muscle biopsy demonstrated severe disruption of the architecture of the neuromuscular junction (NMJ), including: dispersion and fragmentation of endplate areas with normal expression of acetylcholinesterase; simplification of postsynaptic membranes; pronounced reduction of the axon terminal size; widening of the primary synaptic cleft; and, collection of membranous debris material in the primary synaptic cleft and in the subsynaptic cytoplasm. Expression studies in heterologous cells revealed that the Q353X mutation abolished expression of full-length agrin. Moreover, the V1727F mutation decreased agrin-induced clustering of the acetylcholine receptor (AChR) in cultured C2 muscle cells by >100-fold, and phosphorylation of the MuSK receptor and AChR beta subunit by ~tenfold. Surprisingly, the V1727F mutant also displayed increased binding to α-dystroglycan but decreased binding to a neural (z+) agrin-specific antibody. Our findings demonstrate that agrin mutations can associate with a severe form of CMS and cause profound distortion of the architecture and function of the NMJ. The impaired ability of V1727F agrin to activate MuSK and cluster AChRs, together with its increased affinity to α-dystroglycan, mimics non-neural (z-) agrin and are important determinants of the pathogenesis of the disease.
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MESH Headings
- Acetylcholinesterase/metabolism
- Adult
- Agrin/chemistry
- Agrin/genetics
- Agrin/metabolism
- Base Sequence
- Cell Line
- Codon, Nonsense
- Dystroglycans/metabolism
- Female
- HEK293 Cells
- Humans
- Male
- Models, Molecular
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/pathology
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Mutation, Missense
- Myasthenic Syndromes, Congenital/genetics
- Myasthenic Syndromes, Congenital/metabolism
- Neuromuscular Junction/metabolism
- Neuromuscular Junction/pathology
- Pedigree
- Receptors, Cholinergic/genetics
- Receptors, Cholinergic/metabolism
- Sequence Analysis, DNA
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Affiliation(s)
- Ricardo A. Maselli
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - Jose M. Fernandez
- Service of Clinical Neurophysiology. University Hospital of Vigo, Vigo (Pontevedra), Spain
| | - Juan Arredondo
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - Carmen Navarro
- Department of Pathology, University Hospital of Vigo and CIBERER (Centro de Investigacion Biomedica en Red en Enfermedades Raras), Vigo (Pontevedra), Spain
| | - Maian Ngo
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Órla Cagney
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - D. Colette Williams
- Veterinary Medical Teaching Hospital, University of California Davis, Davis, California, 95616, USA
| | - Robert L. Wollmann
- Department of Pathology, University of Chicago, Chicago, Illinois, 60637, USA
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California Davis, Davis, California 95616, USA
| | - Michael J Ferns
- Department of Physiology and Membrane Biology, University of California Davis, Davis, California 95616, USA
- Department of Anesthesiology, University of California Davis, Davis, California 95616, USA
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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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21
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Chaouch A, Beeson D, Hantaï D, Lochmüller H. 186th ENMC International Workshop: Congenital myasthenic syndromes 24–26 June 2011, Naarden, The Netherlands. Neuromuscul Disord 2012; 22:566-76. [DOI: 10.1016/j.nmd.2011.12.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Accepted: 12/13/2011] [Indexed: 12/24/2022]
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22
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Leshinsky-Silver E, Shapira D, Yosovitz K, Ginsberg M, Lerman-Sagie T, Lev D. A novel mutation in the TPR6 domain of the RAPSN gene associated with congenital myasthenic syndrome. J Neurol Sci 2012; 316:112-5. [PMID: 22326364 DOI: 10.1016/j.jns.2012.01.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 12/20/2011] [Accepted: 01/13/2012] [Indexed: 10/14/2022]
Abstract
Congenital myasthenic syndromes (CMS) are rare genetic disorders characterized by impaired neuromuscular transmission. They are caused by mutations in synaptic, presynaptic and post synaptic proteins. Rapsyn is a postsynaptic peripheral membrane protein that anchors the nicotinic acetylcholine receptor to the motor endplate. CMS patients of Iraqi and Persian Jewish origin, carry a common founder mutation in the E box of the RAPSN promoter region (-38A-G) that causes impaired transcriptional activities of the promoter region. We describe a Persian Jewish family with two siblings affected with typical CMS, harboring the common heterozygous (-38A-G) E-box mutation associated with a previously unreported heterozygous p.224 insT causing an insertion of Threonine in the TPR6 domain. To the best of our knowledge, this is the first mutation in the TPR6 domain and might give supportive evidence to the role of this domain in rapsyn self association and consequently co-clustering with AchR in the post synaptic membrane.
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23
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Han JY, Kim JB. Familial hyperkalemic periodic paralysis caused by a de novo mutation in the sodium channel gene SCN4A. KOREAN JOURNAL OF PEDIATRICS 2012; 54:470-2. [PMID: 22253644 PMCID: PMC3254893 DOI: 10.3345/kjp.2011.54.11.470] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 06/07/2011] [Accepted: 07/06/2011] [Indexed: 11/27/2022]
Abstract
Familial hyperkalemic periodic paralysis (HYPP) is an autosomaldominant channelopathy characterized by transient and recurrent episodes of paralysis with concomitant hyperkalemia. Mutations in the skeletal muscle voltage-gated sodium channel gene SCN4A have been reported to be responsible for this disease. Here, we report the case of a 16-year-old girl with HYPP whose mutational analysis revealed a heterozygous c.2111C>T substitution in the SCN4A gene leading to a Thr704Met mutation in the protein sequence. The parents were clinically unaffected and did not have a mutation in the SCN4A gene. A de novo SCN4A mutation for familial HYPP has not previously been reported. The patient did not respond to acetazolamide, but showed a marked improvement in paralytic symptoms upon treatment with hydrochlorothiazide. The findings in this case indicate that a de novo mutation needs to be considered when an isolated family member is found to have a HYPP phenotype.
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Affiliation(s)
- Ji-Yeon Han
- Department of Pediatrics, Konyang University College of Medicine, Daejeon, Korea
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24
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Chaouch A, Müller JS, Guergueltcheva V, Dusl M, Schara U, Rakocević-Stojanović V, Lindberg C, Scola RH, Werneck LC, Colomer J, Nascimento A, Vilchez JJ, Muelas N, Argov Z, Abicht A, Lochmüller H. A retrospective clinical study of the treatment of slow-channel congenital myasthenic syndrome. J Neurol 2011; 259:474-81. [PMID: 21822932 DOI: 10.1007/s00415-011-6204-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 07/19/2011] [Accepted: 07/24/2011] [Indexed: 10/17/2022]
Abstract
Slow-channel congenital myasthenic syndrome (CMS) is a rare subtype of CMS caused by dominant "gain of function" mutations in the acetylcholine receptor. Clinically, the cervical and forearm extensor muscles seem to be preferentially weaker; and conventional treatment with anticholinesterases fails to improve symptoms. In contrast, open channel blockers such as fluoxetine and quinidine have been shown to be of benefit. The objectives of our study were to provide further insight into the clinical features of slow-channel CMS and evaluate response to recommended therapy. We carried out a retrospective clinical follow up study of 15 slow-channel CMS patients referred to the Munich CMS Centre. Detailed clinical data were collected by clinicians involved in the care of each patient, with a particular focus on response and tolerability to recommended therapy. Patients varied widely as regard onset of symptoms, severity of disease and mutations involved. Patients received up to four different medications and some had none. Our results strengthen previous reported findings in terms of clinical phenotype variability and the poor response to pyridostigmine. Although treatment with fluoxetine was beneficial in most patients, a number of our patients suffered significant adverse effects that hindered optimum dose titration or led to treatment cessation. Slow-channel CMS is rare and exhibits distinct clinical and genetic characteristics. Our study suggests that fluoxetine, despite being effective in most patients, can be associated with significant side effects, thus reducing treatment effectiveness in clinical practice.
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Affiliation(s)
- Amina Chaouch
- Institute of Genetic Medicine, Newcastle University, NE1 3BZ, Newcastle upon Tyne, UK
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25
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Witoonpanich R, Pulkes T, Dejthevaporn C, Yodnopklao P, Witoonpanich P, Wetchaphanphesat S, Brengman JM, Engel AG. Phenotypic heterogeneity in a large Thai slow-channel congenital myasthenic syndrome kinship. Neuromuscul Disord 2011; 21:214-8. [PMID: 21316238 PMCID: PMC3327811 DOI: 10.1016/j.nmd.2010.12.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 10/20/2010] [Accepted: 12/13/2010] [Indexed: 11/28/2022]
Abstract
The slow-channel congenital myasthenic syndrome (SCCMS) is an autosomal dominant neuromuscular disorder caused by mutations in different subunits of the acetylcholine receptor (AChR). We here report our clinical findings in three generations of a large Thai kinship suffering from SCCMS and trace the disease to the p.Gly153Ser mutation in the AChR α subunit. The same mutation had previously been reported only in Caucasian but not in Asian patients. The clinical features include ptosis, ophthalmoparesis, and weakness of the cervical and finger extensor muscles as well as marked phenotypic heterogeneity.
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Affiliation(s)
- Rawiphan Witoonpanich
- Division of Neurology, Department of Medicine, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
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26
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Aguiar ADAX, Carvalho AF, Costa CMDC, Fernandes JMA, D'Almeida JAC, Furtado LETDA, Cunha FMBD. Myasthenia gravis in Ceará, Brazil: clinical and epidemiological aspects. ARQUIVOS DE NEURO-PSIQUIATRIA 2010; 68:843-8. [DOI: 10.1590/s0004-282x2010000600003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Accepted: 06/08/2010] [Indexed: 11/22/2022]
Abstract
A retrospective chart review was performed on patients diagnosed as having myasthenia gravis in Ceará State, Brazil and who were followed from October 1981 to June 2009. Clinical and epidemiologic aspects were evaluated. In this work, 122 patients were studied, of whom 85 (69.7%) were females and 37 (30.3%) were males. The disease duration ranged from five months to 50 years (8.9±8.1 years). Age at the first symptoms varied from 0 to 74 years (31.9±14.4 years). The first main symptoms and signs were ptosis, diplopia and limb weakness. Generalized myasthenia was the most common clinical presentation, but 5.1% (n=6) persisted as ocular myasthenia. Thymectomy was performed in 42.6% (n=52) of myasthenic patients. A thymoma was present in 10 patients. Serum acetylcholine receptor (AChR) antibodies were present in 80% (n=20) of specimens tested. The data presented are similar to those of studies performed in other countries.
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27
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Schara U, Christen HJ, Durmus H, Hietala M, Krabetz K, Rodolico C, Schreiber G, Topaloglu H, Talim B, Voss W, Pihko H, Abicht A, Müller JS, Lochmüller H. Long-term follow-up in patients with congenital myasthenic syndrome due to CHAT mutations. Eur J Paediatr Neurol 2010; 14:326-33. [PMID: 19900826 DOI: 10.1016/j.ejpn.2009.09.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Revised: 09/19/2009] [Accepted: 09/28/2009] [Indexed: 10/20/2022]
Abstract
BACKGROUND Congenital myasthenic syndromes (CMSs) are a group of clinically and genetically heterogeneous inherited disorders of the neuromuscular junction. Mutations in the acetylcholine transferase (CHAT) gene cause a pre-synaptic CMS, typically associated with episodic apnoea and worsening of myasthenic symptoms during crises caused by infections, fever or stress. Between crises symptoms may be mild and variable. Acetylcholinesterase - inhibitor therapy is reported to improve clinical symptoms and reduce crises. PATIENTS AND METHODS We present data on the long-term follow-up of 11 patients with a congenital myasthenic syndrome due to nine different CHAT mutations; ten of the patients have not been previously reported. RESULTS AND CONCLUSIONS Manifestation varied from the neonatal period to the age of two years, follow-up time from nine months to 12 years. This cohort of CHAT patients studied here enabled us to describe two distinct phenotypes: The neonatal-onset group suffers from apnoeic crises, respirator dependency and bulbar weakness. Apnoea should be carefully distinguished from seizures; a CMS should be taken into account early to start appropriate therapy. Infantile-onset patients show mild permanent weakness, but experience apnoeic crises and worsening which resolve with Acetylcholinesterase - inhibitor treatment. However, after several years of treatment proximal muscle strength may decrease and lead to wheelchair dependency despite the continuation of Acetylcholinesterase - inhibitor therapy.
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Affiliation(s)
- Ulrike Schara
- Dept. of Paediatric Neurology, University of Essen, Hufelandstr. 55, D-45122 Essen, Germany.
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28
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Maselli RA, Arredondo J, Cagney O, Ng JJ, Anderson JA, Williams C, Gerke BJ, Soliven B, Wollmann RL. Mutations in MUSK causing congenital myasthenic syndrome impair MuSK-Dok-7 interaction. Hum Mol Genet 2010; 19:2370-9. [PMID: 20371544 PMCID: PMC2876883 DOI: 10.1093/hmg/ddq110] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We describe a severe congenital myasthenic syndrome (CMS) caused by two missense mutations in the gene encoding the muscle specific receptor tyrosine kinase (MUSK). The identified MUSK mutations M605I and A727V are both located in the kinase domain of MuSK. Intracellular microelectrode recordings and microscopy studies of the neuromuscular junction conducted in an anconeus muscle biopsy revealed decreased miniature endplate potential amplitudes, reduced endplate size and simplification of secondary synaptic folds, which were consistent with postsynaptic deficit. The study also showed a striking reduction of the endplate potential quantal content, consistent with additional presynaptic failure. Expression studies in MuSK deficient myotubes revealed that A727V, which is located within the catalytic loop of the enzyme, caused severe impairment of agrin-dependent MuSK phosphorylation, aggregation of acetylcholine receptors (AChRs) and interaction of MuSK with Dok-7, an essential intracellular binding protein of MuSK. In contrast, M605I, resulted in only moderate impairment of agrin-dependent MuSK phosphorylation, aggregation of AChRs and interaction of MuSK with Dok-7. There was no impairment of interaction of mutants with either the low-density lipoprotein receptor-related protein, Lrp4 (a co-receptor of agrin) or with the mammalian homolog of the Drosophila tumorous imaginal discs (Tid1). Our findings demonstrate that missense mutations in MUSK can result in a severe form of CMS and indicate that the inability of MuSK mutants to interact with Dok-7, but not with Lrp4 or Tid1, is a major determinant of the pathogenesis of the CMS caused by MUSK mutations.
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Affiliation(s)
- Ricardo A Maselli
- Department of Neurology, School of Veterinary Medicine, University of California Davis, Davis, CA 95618, USA.
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29
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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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Abstract
CollagenQ (ColQ) plays an important structural role at vertebrate neuromuscular junctions (NMJs) by anchoring and accumulating acetylcholinesterase (AChE) in the extracellular matrix (ECM). Moreover, ColQ interacts with perlecan/dystroglycan and the muscle-specific receptor tyrosine kinase (MuSK), key molecules in the NMJ formation. MuSK promotes acetylcholine receptor (AChR) clustering in a process mediated by rapsyn, a cytoplasmic protein that stimulates AChR packing in clusters and regulates synaptic gene transcription. Here, we investigated a regulatory role for ColQ by comparing the clustering and expression of synaptic proteins in wild type and ColQ-deficient muscle cells in culture and at NMJ. We show first that AChR clusters are smaller and more densely packed in the absence of ColQ both in vitro and in vivo. Second, we find that like AChRs and rapsyn, MuSK mRNA levels are increased in cultured cells but not in muscles lacking ColQ. However, membrane-bound MuSK is decreased both in vitro and in vivo suggesting that ColQ controls MuSK sorting or stabilization in the muscle membrane. In line with this, our data show that activation of the MuSK signaling pathway is altered in the absence of ColQ leading to (1) perturbation of AChR clustering and/or beta-AChR subunit phosphorylation and (2) modifications of AChR mRNA level due to the lack of ColQ-MuSK interaction. Together, our results demonstrate that ColQ, in addition to its structural role, has important regulatory functions at the synapse by controlling AChR clustering and synaptic gene expression through its interaction with MuSK.
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31
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Huzé C, Bauché S, Richard P, Chevessier F, Goillot E, Gaudon K, Ben Ammar A, Chaboud A, Grosjean I, Lecuyer HA, Bernard V, Rouche A, Alexandri N, Kuntzer T, Fardeau M, Fournier E, Brancaccio A, Rüegg MA, Koenig J, Eymard B, Schaeffer L, Hantaï D. Identification of an agrin mutation that causes congenital myasthenia and affects synapse function. Am J Hum Genet 2009; 85:155-67. [PMID: 19631309 DOI: 10.1016/j.ajhg.2009.06.015] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 06/16/2009] [Accepted: 06/23/2009] [Indexed: 11/16/2022] Open
Abstract
We report the case of a congenital myasthenic syndrome due to a mutation in AGRN, the gene encoding agrin, an extracellular matrix molecule released by the nerve and critical for formation of the neuromuscular junction. Gene analysis identified a homozygous missense mutation, c.5125G>C, leading to the p.Gly1709Arg variant. The muscle-biopsy specimen showed a major disorganization of the neuromuscular junction, including changes in the nerve-terminal cytoskeleton and fragmentation of the synaptic gutters. Experiments performed in nonmuscle cells or in cultured C2C12 myotubes and using recombinant mini-agrin for the mutated and the wild-type forms showed that the mutated form did not impair the activation of MuSK or change the total number of induced acetylcholine receptor aggregates. A solid-phase assay using the dystrophin glycoprotein complex showed that the mutation did not affect the binding of agrin to alpha-dystroglycan. Injection of wild-type or mutated agrin into rat soleus muscle induced the formation of nonsynaptic acetylcholine receptor clusters, but the mutant protein specifically destabilized the endogenous neuromuscular junctions. Importantly, the changes observed in rat muscle injected with mutant agrin recapitulated the pre- and post-synaptic modifications observed in the patient. These results indicate that the mutation does not interfere with the ability of agrin to induce postsynaptic structures but that it dramatically perturbs the maintenance of the neuromuscular junction.
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MESH Headings
- Adult
- Agrin/chemistry
- Agrin/genetics
- Agrin/metabolism
- Animals
- Biopsy
- Cell Line
- DNA Mutational Analysis
- Dystroglycans/metabolism
- Female
- Humans
- Male
- Models, Chemical
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/metabolism
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/surgery
- Muscle, Skeletal/ultrastructure
- Mutation, Missense
- Myasthenic Syndromes, Congenital/genetics
- Neuromuscular Junction/genetics
- Neuromuscular Junction/metabolism
- Neuromuscular Junction/physiology
- Neuromuscular Junction/ultrastructure
- Pedigree
- Protein Structure, Tertiary
- Rats
- Receptors, Cholinergic/genetics
- Receptors, Cholinergic/metabolism
- Receptors, Cholinergic/physiology
- Recombinant Proteins/chemistry
- Recombinant Proteins/metabolism
- Synapses/metabolism
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Affiliation(s)
- Caroline Huzé
- Equipe Différenciation Neuromusculaire, UMR 5239, Ecole Normale Supérieure Lyon, CNRS, Université Lyon 1, Lyon, France
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32
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Maselli RA, Ng JJ, Anderson JA, Cagney O, Arredondo J, Williams C, Wessel HB, Abdel-Hamid H, Wollmann RL. Mutations in LAMB2 causing a severe form of synaptic congenital myasthenic syndrome. J Med Genet 2009; 46:203-8. [PMID: 19251977 PMCID: PMC2643050 DOI: 10.1136/jmg.2008.063693] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Background: We describe a severe form of congenital myasthenic syndrome (CMS) associated with congenital nephrosis and ocular malformations caused by two truncating mutations in the gene encoding the laminin β2 subunit (LAMB2). Methods and results: Mutational analysis in the affected patient, who has a history of a serious untoward reaction to treatment with acetylcholinesterase inhibition, revealed two frame-shifting heteroallelic mutations, a maternally inherited 1478delG and a paternally inherited 4804delC. An anconeus muscle biopsy demonstrated a profound distortion of the architecture and function of the neuromuscular junction, which was strikingly similar to that seen in mice lacking laminin β2 subunit. The findings included: pronounced reduction of the axon terminal size with encasement of the nerve endings by Schwann cells, severe widening of the primary synaptic cleft and invasion of the synaptic space by the processes of Schwann cells, and moderate simplification of postsynaptic folds and intact expression of the endplate acetylcholinesterase. The endplate potential quantal content was notably reduced, while the frequencies and amplitudes of miniature endplate potentials were only moderately diminished and the decay phases of miniature endplate potentials were normal. Western blot analysis of muscle and kidney tissue and immunohistochemistry of kidney tissue showed no laminin β2 expression. Conclusion: This case, which represents a new type of synaptic CMS, exemplifies the wide variability of phenotypes associated with LAMB2 mutations and underscores the fundamental role that laminin β2 plays in the development of the human neuromuscular junction.
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Affiliation(s)
- R A Maselli
- Department of Neurology, University of California Davis, Davis, CA, 95618, USA.
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33
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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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Nam S, Min K, Hwang H, Lee HO, Lee JH, Yoon J, Lee H, Park S, Lee J. Control of rapsyn stability by the CUL-3-containing E3 ligase complex. J Biol Chem 2009; 284:8195-206. [PMID: 19158078 PMCID: PMC3282941 DOI: 10.1074/jbc.m808230200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Revised: 01/13/2009] [Indexed: 11/06/2022] Open
Abstract
Rapsyn is a postsynaptic protein required for clustering of nicotinic acetylcholine receptors (nAChRs) at the neuromuscular junction. Here we report the mechanism for posttranslational control of rapsyn protein stability. We confirmed that C18H9.7-encoded RPY-1 is a rapsyn homolog in Caenorhabditis elegans by showing that human rapsyn rescued rpy-1 mutant phenotypes in nematodes, as determined by levamisole assays and micropost array behavioral assays. We found that RPY-1 was degraded in the absence of functional UNC-29, a non-alpha subunit of the receptor, in an allele-specific manner, but not in the absence of other receptor subunits. The cytoplasmic loop of UNC-29 was found to be critical for RPY-1 stability. Through RNA interference screening, we found that UBC-1, UBC-12, NEDD-8, and RBX-1 were required for degradation of RPY-1. We identified cullin (CUL)-3 as a component of E3 ligase and KEL-8 as the substrate adaptor of RPY-1. Mammalian rapsyn was ubiquitinated by the CUL3/KLHL8-containing E3 ligase in vitro, and the knockdown of KLHL-8, a mammalian KEL-8 homolog, inhibited rapsyn ubiquitination in vivo, implying evolutionary conservation of the rapsyn stability control machinery. kel-8 suppression and rpy-1 overexpression in C. elegans produced a phenotype similar to that of a loss-of-function mutation of rpy-1, suggesting that control of rapsyn abundance is important for proper function of the receptor. Our results suggest a link between the control of rapsyn abundance and congenital myasthenic syndromes.
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Affiliation(s)
- Seunghee Nam
- Research Center for
Cellulomics, Institute of Molecular Biology and Genetics, School of Biological
Sciences, Seoul National University, 151-742 Seoul, Korea, the
Division of Nano Sciences (BK21),
Ewha Womans University, 120-750 Seoul, Korea,
Protein Network Research Center,
Department of Biochemistry, Yonsei University, 134 Shinchon, 120-749 Seoul,
Korea
| | - Kyoengwoo Min
- Research Center for
Cellulomics, Institute of Molecular Biology and Genetics, School of Biological
Sciences, Seoul National University, 151-742 Seoul, Korea, the
Division of Nano Sciences (BK21),
Ewha Womans University, 120-750 Seoul, Korea,
Protein Network Research Center,
Department of Biochemistry, Yonsei University, 134 Shinchon, 120-749 Seoul,
Korea
| | - Hyejin Hwang
- Research Center for
Cellulomics, Institute of Molecular Biology and Genetics, School of Biological
Sciences, Seoul National University, 151-742 Seoul, Korea, the
Division of Nano Sciences (BK21),
Ewha Womans University, 120-750 Seoul, Korea,
Protein Network Research Center,
Department of Biochemistry, Yonsei University, 134 Shinchon, 120-749 Seoul,
Korea
| | - Hae-ock Lee
- Research Center for
Cellulomics, Institute of Molecular Biology and Genetics, School of Biological
Sciences, Seoul National University, 151-742 Seoul, Korea, the
Division of Nano Sciences (BK21),
Ewha Womans University, 120-750 Seoul, Korea,
Protein Network Research Center,
Department of Biochemistry, Yonsei University, 134 Shinchon, 120-749 Seoul,
Korea
| | - Jung Hwa Lee
- Research Center for
Cellulomics, Institute of Molecular Biology and Genetics, School of Biological
Sciences, Seoul National University, 151-742 Seoul, Korea, the
Division of Nano Sciences (BK21),
Ewha Womans University, 120-750 Seoul, Korea,
Protein Network Research Center,
Department of Biochemistry, Yonsei University, 134 Shinchon, 120-749 Seoul,
Korea
| | - Jongbok Yoon
- Research Center for
Cellulomics, Institute of Molecular Biology and Genetics, School of Biological
Sciences, Seoul National University, 151-742 Seoul, Korea, the
Division of Nano Sciences (BK21),
Ewha Womans University, 120-750 Seoul, Korea,
Protein Network Research Center,
Department of Biochemistry, Yonsei University, 134 Shinchon, 120-749 Seoul,
Korea
| | - Hyunsook Lee
- Research Center for
Cellulomics, Institute of Molecular Biology and Genetics, School of Biological
Sciences, Seoul National University, 151-742 Seoul, Korea, the
Division of Nano Sciences (BK21),
Ewha Womans University, 120-750 Seoul, Korea,
Protein Network Research Center,
Department of Biochemistry, Yonsei University, 134 Shinchon, 120-749 Seoul,
Korea
| | - Sungsu Park
- Research Center for
Cellulomics, Institute of Molecular Biology and Genetics, School of Biological
Sciences, Seoul National University, 151-742 Seoul, Korea, the
Division of Nano Sciences (BK21),
Ewha Womans University, 120-750 Seoul, Korea,
Protein Network Research Center,
Department of Biochemistry, Yonsei University, 134 Shinchon, 120-749 Seoul,
Korea
| | - Junho Lee
- Research Center for
Cellulomics, Institute of Molecular Biology and Genetics, School of Biological
Sciences, Seoul National University, 151-742 Seoul, Korea, the
Division of Nano Sciences (BK21),
Ewha Womans University, 120-750 Seoul, Korea,
Protein Network Research Center,
Department of Biochemistry, Yonsei University, 134 Shinchon, 120-749 Seoul,
Korea
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35
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Elenes S, Decker M, Cymes GD, Grosman C. Decremental response to high-frequency trains of acetylcholine pulses but unaltered fractional Ca2+ currents in a panel of "slow-channel syndrome" nicotinic receptor mutants. ACTA ACUST UNITED AC 2009; 133:151-69. [PMID: 19171769 PMCID: PMC2638206 DOI: 10.1085/jgp.200810089] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The slow-channel congenital myasthenic syndrome (SCCMS) is a disorder of the neuromuscular junction caused by gain-of-function mutations to the muscle nicotinic acetylcholine (ACh) receptor (AChR). Although it is clear that the slower deactivation time course of the ACh-elicited currents plays a central role in the etiology of this disease, it has been suggested that other abnormal properties of these mutant receptors may also be critical in this respect. We characterized the kinetics of a panel of five SCCMS AChRs (αS269I, βV266M, εL221F, εT264P, and εL269F) at the ensemble level in rapidly perfused outside-out patches. We found that, for all of these mutants, the peak-current amplitude decreases along trains of nearly saturating ACh pulses delivered at physiologically relevant frequencies in a manner that is consistent with enhanced entry into desensitization during the prolonged deactivation phase. This suggests that the increasingly reduced availability of activatable AChRs upon repetitive stimulation may well contribute to the fatigability and weakness of skeletal muscle that characterize this disease. Also, these results emphasize the importance of explicitly accounting for entry into desensitization as one of the pathways for burst termination, if meaningful mechanistic insight is to be inferred from the study of the effect of these naturally occurring mutations on channel function. Applying a novel single-channel–based approach to estimate the contribution of Ca2+ to the total cation currents, we also found that none of these mutants affects the Ca2+-conduction properties of the AChR to an extent that seems to be of physiological importance. Our estimate of the Ca2+-carried component of the total (inward) conductance of wild-type and SCCMS AChRs in the presence of 150 mM Na+, 1.8 mM Ca2+, and 1.7 mM Mg2+ on the extracellular side of cell-attached patches turned out be in the 5.0–9.4 pS range, representing a fractional Ca2+ current of ∼14%, on average. Remarkably, these values are nearly identical to those we estimated for the NR1-NR2A N-methyl-d-aspartate receptor (NMDAR), which has generally been considered to be the main neurotransmitter-gated pathway of Ca2+ entry into the cell. Our estimate of the rat NMDAR Ca2+ conductance (using the same single-channel approach as for the AChR but in the nominal absence of extracellular Mg2+) was 7.9 pS, corresponding to a fractional Ca2+ current of 13%.
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Affiliation(s)
- Sergio Elenes
- Department of Molecular and Integrative Physiology, Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, 61801, USA
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36
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Remaniements expérimentaux et pathologiques de la jonction neuromusculaire. Neurochirurgie 2009; 55 Suppl 1:S104-9. [DOI: 10.1016/j.neuchi.2008.05.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Accepted: 05/09/2008] [Indexed: 10/21/2022]
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Abstract
Congenital myasthenic syndromes (CMS) are classified in terms of the located defect: presynaptic, postsynaptic, and synaptic. They are inherited disorders caused by various genetic defects, all but the slow-channel CMS by recessive inheritance. To date, 10 different CMS are known and further CMS subtypes and their genetic cause may be disclosed by future investigations. Prognosis in CMS is variable and largely depends on the pathophysiological and genetic defect. Subtypes showing progression and life-threatening crises with apneas are generally less favorable than others. Therapeutic agents used in CMS depend on the underlying defect and include acetylcholinesterase inhibitor, 3,4-diaminopyridine, quinidine sulfate, fluoxetine, acetazolamide, and ephedrine. Although there are no double-blind, placebo-controlled clinical trials for CMS, several drugs have shown convincingly positive clinical effects. It is therefore necessary to start a rational therapy regime as early as possible. In most CMS, however, mild and severe clinical courses are reported, which makes assessment on an individual basis necessary. This review emphasizes therapeutic strategies in CMS.
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Affiliation(s)
- Ulrike Schara
- Department of Pediatric Neurology, University of Essen, Essen, Germany.
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38
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Terblanche N, Maxwell C, Keunen J, Carvalho JCA. Obstetric and Anesthetic Management of Severe Congenital Myasthenia Syndrome. Anesth Analg 2008; 107:1313-5. [DOI: 10.1213/ane.0b013e3181823d11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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39
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López Laso E, Pérez Navero J, Rumbao Aguirre J, Mateos González M, Méndez García M, Cárdenas Aranzana M, Ibarra de la Rosa I. Botulismo del lactante. An Pediatr (Barc) 2008; 68:499-502. [DOI: 10.1157/13120050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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40
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Pitt M. Neurophysiological strategies for the diagnosis of disorders of the neuromuscular junction in children. Dev Med Child Neurol 2008; 50:328-33. [PMID: 18312422 DOI: 10.1111/j.1469-8749.2008.02038.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The disorders of the neuromuscular junction seen in children, the congenital myasthenic syndromes and autoimmune myasthenia gravis, are very rare. Their clinical symptoms and signs may be variable, most notably in the neonate and infant. They should enter the differential diagnosis of many different clinical presentations, such as 'floppy infant' or attacks of episodic apnoea. Many molecular genetic abnormalities have been discovered in congenital myasthenic syndromes, but screening for these is impracticable without confirmation of a disorder of the neuromuscular junction. In this review, the different neurophysiological tests that can be used are discussed, with their merits and contraindications in children. After consideration of the acceptability of the different techniques, it has been found that stimulation single-fibre electromyography (stimSFEMG) of orbicularis oculi seems to be the best choice in children. In most instances it can be performed on the conscious child and it has a good specificity and high sensitivity. A protocol for using stimSFEMG is described.
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Affiliation(s)
- Matthew Pitt
- Department of Clinical Neurophysiology, Great Ormond Street Hospital for Children, London, UK.
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41
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Kalamida D, Poulas K, Avramopoulou V, Fostieri E, Lagoumintzis G, Lazaridis K, Sideri A, Zouridakis M, Tzartos SJ. Muscle and neuronal nicotinic acetylcholine receptors. FEBS J 2007; 274:3799-845. [PMID: 17651090 DOI: 10.1111/j.1742-4658.2007.05935.x] [Citation(s) in RCA: 216] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are integral membrane proteins and prototypic members of the ligand-gated ion-channel superfamily, which has precursors in the prokaryotic world. They are formed by the assembly of five transmembrane subunits, selected from a pool of 17 homologous polypeptides (alpha1-10, beta1-4, gamma, delta, and epsilon). There are many nAChR subtypes, each consisting of a specific combination of subunits, which mediate diverse physiological functions. They are widely expressed in the central nervous system, while, in the periphery, they mediate synaptic transmission at the neuromuscular junction and ganglia. nAChRs are also found in non-neuronal/nonmuscle cells (keratinocytes, epithelia, macrophages, etc.). Extensive research has determined the specific function of several nAChR subtypes. nAChRs are now important therapeutic targets for various diseases, including myasthenia gravis, Alzheimer's and Parkinson's diseases, and schizophrenia, as well as for the cessation of smoking. However, knowledge is still incomplete, largely because of a lack of high-resolution X-ray structures for these molecules. Nevertheless, electron microscopy studies on 2D crystals of nAChR from fish electric organs and the determination of the high-resolution X-ray structure of the acetylcholine binding protein (AChBP) from snails, a homolog of the extracellular domain of the nAChR, have been major steps forward and the data obtained have important implications for the design of subtype-specific drugs. Here, we review some of the latest advances in our understanding of nAChRs and their involvement in physiology and pathology.
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Affiliation(s)
- Dimitra Kalamida
- Department of Pharmacy, University of Patras, Rio Patras, Greece
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42
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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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43
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Ifergane G, Al-Sayed I, Birk O, Harel T, Wirguin I. Co-morbidity of Emery-Dreifuss muscular dystrophy and a congenital myasthenic syndrome possibly affecting the phenotype in a large Bedouin kindred. Eur J Neurol 2007; 14:305-8. [PMID: 17355552 DOI: 10.1111/j.1468-1331.2006.01657.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Emery-Dreifuss muscular dystrophy (EDMD) is an X-linked humero-peroneal muscular dystrophy associated with contractures and cardiomyopathy. In a 90 member family, we found 11 affected male individuals, three of whom displayed areflexia and neurogenic electromyographic changes. Muscle biopsy performed in one case demonstrated type grouping suggestive of a neurogenic disorder. These three individuals and another family member, who suffers from mild, static limb weakness but is clinically and genetically unaffected by EDMD showed an abnormal incremental response of over 100% to tetanic stimulation. In contrast, one affected family member showed myopathic features on needle electromyography and no definite pathology in repetitive stimulation studies. The diagnosis of EDMD was established by demonstrating a 1712_1713insTGGGC mutation in the emerin gene. This family apparently expresses co-morbidity of EDMD with an exceptionally mild form of pre-synaptic congenital myasthenic syndrome resembling the Lambert-Eaton myasthenic syndrome (LEMS). The superimposed pre-synaptic disorder may have contributed to the development of the neurogenic features demonstrated in these patients.
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MESH Headings
- Adolescent
- Adult
- Arabs/genetics
- Child
- Child, Preschool
- Comorbidity
- DNA Mutational Analysis
- Disease Progression
- Female
- Genetic Diseases, X-Linked/ethnology
- Genetic Diseases, X-Linked/genetics
- Genetic Diseases, X-Linked/physiopathology
- Genetic Linkage/genetics
- Genetic Predisposition to Disease/genetics
- Genetic Testing
- Genotype
- Humans
- Male
- Membrane Proteins/genetics
- Middle Aged
- Muscle, Skeletal/innervation
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Muscular Dystrophy, Emery-Dreifuss/ethnology
- Muscular Dystrophy, Emery-Dreifuss/genetics
- Muscular Dystrophy, Emery-Dreifuss/physiopathology
- Myasthenic Syndromes, Congenital/ethnology
- Myasthenic Syndromes, Congenital/genetics
- Myasthenic Syndromes, Congenital/physiopathology
- Nuclear Proteins/genetics
- Pedigree
- Phenotype
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Affiliation(s)
- G Ifergane
- Department of Neurology, Soroka Medical Center, Beer-Sheva, Israel
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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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45
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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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46
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Chevessier F, Faraut B, Ravel-Chapuis A, Richard P, Gaudon K, Bauché S, Prioleau C, Herbst R, Goillot E, Ioos C, Azulay JP, Attarian S, Leroy JP, Fournier E, Legay C, Schaeffer L, Koenig J, Fardeau M, Eymard B, Pouget J, Hantaï D. MUSK, a new target for mutations causing congenital myasthenic syndrome. Hum Mol Genet 2004; 13:3229-40. [PMID: 15496425 DOI: 10.1093/hmg/ddh333] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
We report the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding the muscle-specific receptor tyrosine kinase (MuSK). Gene analysis identified two heteroallelic mutations, a frameshift mutation (c.220insC) and a missense mutation (V790M). The muscle biopsy showed dramatic pre- and postsynaptic structural abnormalities of the neuromuscular junction and severe decrease in acetylcholine receptor (AChR) epsilon-subunit and MuSK expression. In vitro and in vivo expression experiments were performed using mutant MuSK reproducing the human mutations. The frameshift mutation led to the absence of MuSK expression. The missense mutation did not affect MuSK catalytic kinase activity but diminished expression and stability of MuSK leading to decreased agrin-dependent AChR aggregation, a critical step in the formation of the neuromuscular junction. In electroporated mouse muscle, overexpression of the missense mutation induced, within a week, a phenotype similar to the patient muscle biopsy: a severe decrease in synaptic AChR and an aberrant axonal outgrowth. These results strongly suggest that the missense mutation, in the presence of a null mutation on the other allele, is responsible for the dramatic synaptic changes observed in the patient.
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Affiliation(s)
- Frédéric Chevessier
- INSERM U582 & IFR Cur, Muscle, Vaisseaux, Institut de Myologie, Hôpital de la Salpêtrière and Université Pierre et Marie Curie, Paris, France
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