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Zou X, Zhang Z, Lu H, Zhao W, Pan L, Chen Y. Functional effects of drugs and toxins interacting with Na V1.4. Front Pharmacol 2024; 15:1378315. [PMID: 38725668 PMCID: PMC11079311 DOI: 10.3389/fphar.2024.1378315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 04/08/2024] [Indexed: 05/12/2024] Open
Abstract
NaV1.4 is a voltage-gated sodium channel subtype that is predominantly expressed in skeletal muscle cells. It is essential for producing action potentials and stimulating muscle contraction, and mutations in NaV1.4 can cause various muscle disorders. The discovery of the cryo-EM structure of NaV1.4 in complex with β1 has opened new possibilities for designing drugs and toxins that target NaV1.4. In this review, we summarize the current understanding of channelopathies, the binding sites and functions of chemicals including medicine and toxins that interact with NaV1.4. These substances could be considered novel candidate compounds or tools to develop more potent and selective drugs targeting NaV1.4. Therefore, studying NaV1.4 pharmacology is both theoretically and practically meaningful.
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Affiliation(s)
- Xinyi Zou
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Zixuan Zhang
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Hui Lu
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Wei Zhao
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Lanying Pan
- Key Laboratory of Artificial Organs and Computational Medicine in Zhejiang Province, Shulan International Medical College, Zhejiang Shuren University, Hangzhou, China
| | - Yuan Chen
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou, China
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Matthews E, Palace J, Ramdas S, Sansone V, Tristani-Firouzi M, Vicart S, Willis T. Care Recommendations for the Investigation and Management of Children With Skeletal Muscle Channelopathies. Pediatr Neurol 2023; 145:102-111. [PMID: 37315339 DOI: 10.1016/j.pediatrneurol.2023.05.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/12/2023] [Accepted: 05/14/2023] [Indexed: 06/16/2023]
Abstract
The field of pediatric skeletal muscle channelopathies has seen major new advances in terms of a wider understanding of clinical presentations and new phenotypes. Skeletal muscle channelopathies cause significant disability and even death in some of the newly described phenotypes. Despite this, there are virtually no data on the epidemiology and longitudinal natural history of these conditions or randomized controlled trial evidence of efficacy or tolerability of any treatment in children, and thus best practice care recommendations do not exist. Clinical history, and to a lesser extent examination, is key to eliciting symptoms and signs that indicate a differential diagnosis of muscle channelopathy. Normal routine investigations should not deter one from the diagnosis. Specialist neurophysiologic investigations have an additional role, but their availability should not delay genetic testing. New phenotypes are increasingly likely to be identified by next-generation sequencing panels. Many treatments or interventions for symptomatic patients are available, with anecdotal data to support their benefit, but we lack trial data on efficacy, safety, or superiority. This lack of trial data in turn can lead to hesitancy in prescribing among doctors or in accepting medication by parents. Holistic management addressing work, education, activity, and additional symptoms of pain and fatigue provides significant benefit. Preventable morbidity and sometimes mortality occurs if the diagnosis and therefore treatment is delayed. Advances in genetic sequencing technology and greater access to testing may help to refine recently identified phenotypes, including histology, as more cases are described. Randomized controlled treatment trials are required to inform best practice care recommendations. A holistic approach to management is essential and should not be overlooked. Good quality data on prevalence, health burden, and optimal treatment are urgently needed.
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Affiliation(s)
- Emma Matthews
- Department of Neurology, Atkinson-Morley Neuromuscular Centre, St George's University Hospitals NHS Foundation Trust, and Molecular and Clinical Sciences Research Institute, St George's University of London, London, UK.
| | - Jacqueline Palace
- Clinical Neurology, John Radcliffe Hospital, Oxford University Foundation Trust, Oxford, UK; Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Sithara Ramdas
- Department of Paediatrics, MDUK Neuromuscular Centre, University of Oxford, Oxford, UK; Department of Paediatric Neurology, John Radcliffe Hospital, Oxford, UK
| | - Valeria Sansone
- Neurorehabilitation Unit, Neuromuscular Omnicentre Clinical Center, Niguarda Hospital, University of Milan, Milan, Italy
| | - Martin Tristani-Firouzi
- Nora Eccles Harrison Cardiovascular Research and Training Institute and the Division of Paediatric Cardiology, University of Utah, Salt Lake City, Utah
| | - Savine Vicart
- Reference Centre for Neuromuscular Disorders, APHP, Institute of Myology, Pitié-Salpêtrière Hospital, Paris, France
| | - Tracey Willis
- Robert Jones and Agnes Hunt Orthopaedic Hospital, NHS Foundation Trust, Oswestry, England
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Vicino A, Brugnoni R, Maggi L. Diagnostics in skeletal muscle channelopathies. Expert Rev Mol Diagn 2023; 23:1175-1193. [PMID: 38009256 DOI: 10.1080/14737159.2023.2288258] [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: 08/23/2023] [Accepted: 11/22/2023] [Indexed: 11/28/2023]
Abstract
INTRODUCTION Skeletal muscle channelopathies (SMCs) are a heterogenous group of disorders, caused by mutations in skeletal ion channels leading to abnormal muscle excitability, resulting in either delayed muscle relaxation (myotonia) which characterizes non-dystrophic myotonias (NDMs), or membrane transient inactivation, causing episodic weakness, typical of periodic paralyses (PPs). AREAS COVERED SMCs include myotonia congenita, paramyotonia congenita, and sodium-channel myotonia among NDMs, and hyper-normokalemic, hypokalemic, or late-onset periodic paralyses among PPs. When suspecting an SMC, a structured diagnostic approach is required. Detailed personal and family history and clinical examination are essential, while neurophysiological tests should confirm myotonia and rule out alternative diagnosis. Moreover, specific electrodiagnostic studies are important to further define the phenotype of de novo cases and drive molecular analyses together with clinical data. Definite diagnosis is achieved through genetic testing, either with Sanger sequencing or multigene next-generation sequencing panel. In still unsolved patients, more advanced techniques, as exome-variant sequencing or whole-genome sequencing, may be considered in expert centers. EXPERT OPINION The diagnostic approach to SMC is still mainly based on clinical data; moreover, definite diagnosis is sometimes complicated by the difficulty to establish a proper genotype-phenotype correlation. Lastly, further studies are needed to allow the genetic characterization of unsolved patients.
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Affiliation(s)
- Alex Vicino
- Neurology IV Unit, Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
- Nerve-Muscle Unit, Neurology Service, Department of Clinical Neurosciences, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Raffaella Brugnoni
- Neurology IV Unit, Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Lorenzo Maggi
- Neurology IV Unit, Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
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Altamura C, Saltarella I, Campanale C, Laghetti P, Desaphy JF. Drug repurposing in skeletal muscle ion channelopathies. Curr Opin Pharmacol 2023; 68:102329. [PMID: 36512979 DOI: 10.1016/j.coph.2022.102329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/26/2022] [Accepted: 11/02/2022] [Indexed: 12/14/2022]
Abstract
Skeletal muscle ion channelopathies are rare genetic diseases mainly characterized by myotonia (muscle stiffness) or periodic paralysis (muscle weakness). Here, we reviewed the available therapeutic options in non-dystrophic myotonias (NDM) and periodic paralyses (PP), which consists essentially in drug repositioning to address stiffness or weakness attacks. Empirical use followed by successful randomized clinical trials eventually led to the orphan drug designation and marketing authorization granting of mexiletine for NDM and dichlorphenamide for PP. Yet, these treatments neither consider the genetic cause of the diseases nor address the individual variability in drug response. Thus, ongoing research aims at the identification of repurposed drugs alternative to mexiletine and dichlorphenamide to allow personalization of treatment. This review highlights how drug repurposing may represent an efficient strategy in rare diseases, allowing reduction of drug development time and costs in a context in which the return on investment may be particularly challenging.
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Affiliation(s)
- Concetta Altamura
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Ilaria Saltarella
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Carmen Campanale
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Paola Laghetti
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Jean-François Desaphy
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy.
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Altamura C, Conte D, Carratù MR, Desaphy JF. Target mutation-driven drug discovery. Curr Med Chem 2022; 29:5156-5158. [PMID: 35440295 DOI: 10.2174/1389450123666220418111200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 01/10/2022] [Accepted: 02/09/2022] [Indexed: 11/22/2022]
Affiliation(s)
- Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, I-70124 Italy
| | | | - Maria Rosaria Carratù
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, I-70124 Italy
| | - Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, I-70124 Italy
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Desaphy JF, Altamura C, Vicart S, Fontaine B. Targeted Therapies for Skeletal Muscle Ion Channelopathies: Systematic Review and Steps Towards Precision Medicine. J Neuromuscul Dis 2021; 8:357-381. [PMID: 33325393 PMCID: PMC8203248 DOI: 10.3233/jnd-200582] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Skeletal muscle ion channelopathies include non-dystrophic myotonias (NDM), periodic paralyses (PP), congenital myasthenic syndrome, and recently identified congenital myopathies. The treatment of these diseases is mainly symptomatic, aimed at reducing muscle excitability in NDM or modifying triggers of attacks in PP. OBJECTIVE This systematic review collected the evidences regarding effects of pharmacological treatment on muscle ion channelopathies, focusing on the possible link between treatments and genetic background. METHODS We searched databases for randomized clinical trials (RCT) and other human studies reporting pharmacological treatments. Preclinical studies were considered to gain further information regarding mutation-dependent drug effects. All steps were performed by two independent investigators, while two others critically reviewed the entire process. RESULTS For NMD, RCT showed therapeutic benefits of mexiletine and lamotrigine, while other human studies suggest some efficacy of various sodium channel blockers and of the carbonic anhydrase inhibitor (CAI) acetazolamide. Preclinical studies suggest that mutations may alter sensitivity of the channel to sodium channel blockers in vitro, which has been translated to humans in some cases. For hyperkalemic and hypokalemic PP, RCT showed efficacy of the CAI dichlorphenamide in preventing paralysis. However, hypokalemic PP patients carrying sodium channel mutations may have fewer benefits from CAI compared to those carrying calcium channel mutations. Few data are available for treatment of congenital myopathies. CONCLUSIONS These studies provided limited information about the response to treatments of individual mutations or groups of mutations. A major effort is needed to perform human studies for designing a mutation-driven precision medicine in muscle ion channelopathies.
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Affiliation(s)
- Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Savine Vicart
- Sorbonne Université, INSERM, Assistance Publique Hôpitaux de Paris, Centre de Recherche en Myologie-UMR 974, Reference center in neuro-muscular channelopathies, Institute of Myology, Hôpital Universitaire Pitié-Salpêtrière, Paris, France
| | - Bertrand Fontaine
- Sorbonne Université, INSERM, Assistance Publique Hôpitaux de Paris, Centre de Recherche en Myologie-UMR 974, Reference center in neuro-muscular channelopathies, Institute of Myology, Hôpital Universitaire Pitié-Salpêtrière, Paris, France
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Stunnenberg BC, LoRusso S, Arnold WD, Barohn RJ, Cannon SC, Fontaine B, Griggs RC, Hanna MG, Matthews E, Meola G, Sansone VA, Trivedi JR, van Engelen BG, Vicart S, Statland JM. Guidelines on clinical presentation and management of nondystrophic myotonias. Muscle Nerve 2020; 62:430-444. [PMID: 32270509 PMCID: PMC8117169 DOI: 10.1002/mus.26887] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 04/01/2020] [Accepted: 04/04/2020] [Indexed: 12/26/2022]
Abstract
The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1 gene. Clinically, they are characterized by myotonia, defined as delayed muscle relaxation after voluntary contraction, which leads to symptoms of muscle stiffness, pain, fatigue, and weakness. Diagnosis is based on history and examination findings, the presence of electrical myotonia on electromyography, and genetic confirmation. In the absence of genetic confirmation, the diagnosis is supported by detailed electrophysiological testing, exclusion of other related disorders, and analysis of a variant of uncertain significance if present. Symptomatic treatment with a sodium channel blocker, such as mexiletine, is usually the first step in management, as well as educating patients about potential anesthetic complications.
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Affiliation(s)
- Bas C. Stunnenberg
- Department of Neurology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Samantha LoRusso
- Department of Neurology, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - W. David Arnold
- Department of Neurology, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Richard J. Barohn
- Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas
| | - Stephen C. Cannon
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Bertrand Fontaine
- Assistance Publique-Hôpitaix de Paris, Sorbonne Université, INSERM, Service of Neuro-Myology and UMR 974, Institute of Myology, University Hospital Pitié-Salpêtrière, Paris, France
| | - Robert C. Griggs
- Department of Neurology, University of Rochester, Rochester, New York
| | - Michael G. Hanna
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular diseases, UCL Queen Square Institute of Neurology, United Kingdom
| | - Emma Matthews
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular diseases, UCL Queen Square Institute of Neurology, United Kingdom
| | - Giovanni Meola
- Department of Neurorehabilitation Sciences, Casa Cura Policlinico, Milan, Italy
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Valeria A. Sansone
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
- Neurorehabilitation Unit, University of Milan, NEuroMuscular Omnicentre (NEMO), Fondazione Serena Onlus, Milan, Italy
| | - Jaya R. Trivedi
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, Texas
| | | | - Savine Vicart
- Assistance Publique-Hôpitaix de Paris, Sorbonne Université, INSERM, Service of Neuro-Myology and UMR 974, Institute of Myology, University Hospital Pitié-Salpêtrière, Paris, France
| | - Jeffrey M. Statland
- Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas
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Abstract
PURPOSE OF REVIEW This article aims to review the current and upcoming treatment options of primary muscle channelopathies including the non-dystrophic myotonias and periodic paralyses. RECENT FINDINGS The efficacy of mexiletine in the treatment of myotonia is now supported by two randomised placebo-controlled trials, one of which utilised a novel aggregated n-of-1 design. This has resulted in licencing of the drug via orphan drug status. There is also good evidence that mexiletine is well tolerated and safe in this patient group without the need for intensive monitoring. A range of alternative antimyotonic treatment options include lamotrigine, carbamazepine and ranolazine exist with variable evidence base. In vitro studies have shown insight into reasons for treatment failure of some medications with certain genotypes opening the era of mutation-specific therapy such as use of flecainide. In the periodic paralyses, the ability of MRI to distinguish between reversible oedema and irreversible fatty replacement makes it an increasingly useful tool to guide and assess pharmacological treatment. Unfortunately, the striking efficacy of bumetanide in hypokalaemic periodic paralysis animal models was not replicated in a recent pilot study in humans. SUMMARY The treatment of skeletal muscle channelopathies combines dietary and lifestyle advice together with pharmacological interventions. The rarity of these conditions remains a barrier for clinical studies but the example of the aggregated n-of-1 trial of mexiletine shows that innovative trial design can overcome these hurdles. Further research is required to test efficacy of drugs shown to have promising characteristics in preclinical experiments such as safinamide, riluzule and magnesium for myotonia or bumetanide for hypokalaemic periodic paralysis.
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Affiliation(s)
- Nantaporn Jitpimolmard
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
- Rehabilitation Medicine Department, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Emma Matthews
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
- Atkinson-Morley Neuromuscular Centre, St George’s University Hospitals Foundation Trust, London, UK
| | - Doreen Fialho
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
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Avila-Smirnow D, Vargas Leal CP, Beytía Reyes MDLA, Cortés Zepeda R, Escobar RG, Kleinsteuber Saa K, Lagos Lucero M, Avaria Benapres MDLA, Padilla Pérez O, Casar Leturia JC, Mellado Sagredo C, Sternberg D. Non-dystrophic myotonia Chilean cohort with predominance of the SCN4A Gly1306Glu variant. Neuromuscul Disord 2020; 30:554-561. [DOI: 10.1016/j.nmd.2020.04.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 04/03/2020] [Accepted: 04/23/2020] [Indexed: 01/31/2023]
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Changes of Resurgent Na + Currents in the Na v1.4 Channel Resulting from an SCN4A Mutation Contributing to Sodium Channel Myotonia. Int J Mol Sci 2020; 21:ijms21072593. [PMID: 32276507 PMCID: PMC7177622 DOI: 10.3390/ijms21072593] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 03/30/2020] [Accepted: 04/06/2020] [Indexed: 12/19/2022] Open
Abstract
Myotonia congenita (MC) is a rare disorder characterized by stiffness and weakness of the limb and trunk muscles. Mutations in the SCN4A gene encoding the alpha-subunit of the voltage-gated sodium channel Nav1.4 have been reported to be responsible for sodium channel myotonia (SCM). The Nav1.4 channel is expressed in skeletal muscles, and its related channelopathies affect skeletal muscle excitability, which can manifest as SCM, paramyotonia and periodic paralysis. In this study, the missense mutation p.V445M was identified in two individual families with MC. To determine the functional consequences of having a mutated Nav1.4 channel, whole-cell patch-clamp recording of transfected Chinese hamster ovary cells was performed. Evaluation of the transient Na+ current found that a hyperpolarizing shift occurs at both the activation and inactivation curves with an increase of the window currents in the mutant channels. The Nav1.4 channel's co-expression with the Navβ4 peptide can generate resurgent Na+ currents at repolarization following a depolarization. The magnitude of the resurgent currents is higher in the mutant than in the wild-type (WT) channel. Although the decay kinetics are comparable between the mutant and WT channels, the time to the peak of resurgent Na+ currents in the mutant channel is significantly protracted compared with that in the WT channel. These findings suggest that the p.V445M mutation in the Nav1.4 channel results in an increase of both sustained and resurgent Na+ currents, which may contribute to hyperexcitability with repetitive firing and is likely to facilitate recurrent myotonia in SCM patients.
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Desaphy JF, Farinato A, Altamura C, De Bellis M, Imbrici P, Tarantino N, Caccia C, Melloni E, Padoani G, Vailati S, Keywood C, Carratù MR, De Luca A, Conte D, Pierno S. Safinamide's potential in treating nondystrophic myotonias: Inhibition of skeletal muscle voltage-gated sodium channels and skeletal muscle hyperexcitability in vitro and in vivo. Exp Neurol 2020; 328:113287. [PMID: 32205118 DOI: 10.1016/j.expneurol.2020.113287] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 03/14/2020] [Accepted: 03/19/2020] [Indexed: 12/26/2022]
Abstract
The antiarrhythmic sodium-channel blocker mexiletine is used to treat patients with myotonia. However, around 30% of patients do not benefit from mexiletine due to poor tolerability or suboptimal response. Safinamide is an add-on therapy to levodopa for Parkinson's disease. In addition to MAOB inhibition, safinamide inhibits neuronal sodium channels, conferring anticonvulsant activity in models of epilepsy. Here, we investigated the effects of safinamide on skeletal muscle hNav1.4 sodium channels and in models of myotonia, in-vitro and in-vivo. Using patch-clamp, we showed that safinamide reversibly inhibited sodium currents in HEK293T cells transfected with hNav1.4. At the holding potential (hp) of -120 mV, the half-maximum inhibitory concentrations (IC50) were 160 and 33 μM at stimulation frequencies of 0.1 and 10 Hz, respectively. The calculated affinity constants of safinamide were dependent on channel state: 420 μM for closed channels and 9 μM for fast-inactivated channels. The p.F1586C mutation in hNav1.4 greatly impaired safinamide inhibition, suggesting that the drug binds to the local anesthetic receptor site in the channel pore. In a condition mimicking myotonia, i.e. hp. of -90 mV and 50-Hz stimulation, safinamide inhibited INa with an IC50 of 6 μM, being two-fold more potent than mexiletine. Using the two-intracellular microelectrodes current-clamp method, action potential firing was recorded in vitro in rat skeletal muscle fibers in presence of the chloride channel blocker, 9-anthracene carboxylic acid (9-AC), to increase excitability. Safinamide counteracted muscle fiber hyperexcitability with an IC50 of 13 μM. In vivo, oral safinamide was tested in the rat model of myotonia. In this model, intraperitoneal injection of 9-AC greatly increased the time of righting reflex (TRR) due to development of muscle stiffness. Safinamide counteracted 9-AC induced TRR increase with an ED50 of 1.2 mg/kg, which is 7 times lower than that previously determined for mexiletine. In conclusion, safinamide is a potent voltage and frequency dependent blocker of skeletal muscle sodium channels. Accordingly, the drug was able to counteract abnormal muscle hyperexcitability induced by 9-AC, both in vitro and in vivo. Thus, this study suggests that safinamide may have potential in treating myotonia and warrants further preclinical and human studies to fully evaluate this possibility.
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Affiliation(s)
- Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy.
| | - Alessandro Farinato
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Michela De Bellis
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Paola Imbrici
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Nancy Tarantino
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Carla Caccia
- Open R&D Department, Zambon S.p.A., Bresso, MI, Italy
| | - Elsa Melloni
- Open R&D Department, Zambon S.p.A., Bresso, MI, Italy
| | | | | | | | - Maria Rosaria Carratù
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Annamaria De Luca
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Diana Conte
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Sabata Pierno
- Department of Pharmacy & Drug Sciences, University of Bari Aldo Moro, Bari, Italy
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Horie R, Kubota T, Koh J, Tanaka R, Nakamura Y, Sasaki R, Ito H, Takahashi MP. EF hand-like motif mutations of Nav1.4 C-terminus cause myotonic syndrome by impairing fast inactivation. Muscle Nerve 2020; 61:808-814. [PMID: 32129495 DOI: 10.1002/mus.26849] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Revised: 01/27/2020] [Accepted: 03/01/2020] [Indexed: 12/22/2022]
Abstract
INTRODUCTION Mutations of the voltage-gated sodium channel gene (SCN4A), which encodes Nav1.4, cause nondystrophic myotonia that occasionally is associated with severe apnea and laryngospasm. There are case reports of nondystrophic myotonia due to mutations in the C-terminal tail (CTerm) of Nav1.4, but the functional analysis is scarce. METHODS We present two families with nondystrophic myotonia harboring a novel heterozygous mutation (E1702del) and a known heterozygous mutation (E1702K). RESULTS The proband with E1702K exhibited repeated rhabdomyolysis, and the daughter showed laryngospasm and cyanosis. Functional analysis of the two mutations as well as another known heterozygous mutation (T1700_E1703del), all located on EF hand-like motif in CTerm, was conducted with whole-cell recording of heterologously expressed channel. All mutations displayed impaired fast inactivation. DISCUSSION The CTerm of Nav1.4 is vital for regulating fast inactivation. The study highlights the importance of accumulating pathological mutations of Nav1.4 and their functional analysis data.
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Affiliation(s)
- Riho Horie
- Department of Functional Diagnostic Science, Osaka University Graduate School of Medicine, Yamadaoka, Suita, Osaka, Japan
| | - Tomoya Kubota
- Department of Functional Diagnostic Science, Osaka University Graduate School of Medicine, Yamadaoka, Suita, Osaka, Japan
| | - Jinsoo Koh
- Department of Neurology, Wakayama Medical University, Kimiidera, Wakayama, Wakayama, Japan
| | - Rieko Tanaka
- Nanairo Kodomo Clinic, Fukiage, Wakayama, Wakayama, Japan
| | - Yuichiro Nakamura
- Department of Functional Diagnostic Science, Osaka University Graduate School of Medicine, Yamadaoka, Suita, Osaka, Japan
| | - Ryogen Sasaki
- Department of Neurology, Kuwana City Medical Center, Kotobukicho, Kuwana, Mie, Japan
| | - Hidefumi Ito
- Department of Neurology, Wakayama Medical University, Kimiidera, Wakayama, Wakayama, Japan
| | - Masanori P Takahashi
- Department of Functional Diagnostic Science, Osaka University Graduate School of Medicine, Yamadaoka, Suita, Osaka, Japan
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13
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Matthews E, Balestrini S, Sisodiya SM, Hanna MG. Muscle and brain sodium channelopathies: genetic causes, clinical phenotypes, and management approaches. THE LANCET CHILD & ADOLESCENT HEALTH 2020; 4:536-547. [PMID: 32142633 DOI: 10.1016/s2352-4642(19)30425-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 10/29/2019] [Accepted: 12/12/2019] [Indexed: 01/26/2023]
Abstract
Voltage-gated sodium channels are essential for excitability of skeletal muscle fibres and neurons. An increasing number of disabling or fatal paediatric neurological disorders linked to mutations of voltage-gated sodium channel genes are recognised. Muscle phenotypes include episodic paralysis, myotonia, neonatal hypotonia, respiratory compromise, laryngospasm or stridor, congenital myasthenia, and myopathy. Evidence suggests a possible link between sodium channel dysfunction and sudden infant death. Increasingly recognised phenotypes of brain sodium channelopathies include several epilepsy disorders and complex encephalopathies. Together, these early-onset muscle and brain phenotypes have a substantial morbidity and a considerable mortality. Important advances in understanding the pathophysiological mechanisms underlying these channelopathies have helped to identify effective targeted therapies. The availability of effective treatments underlines the importance of increasing clinical awareness and the need to achieve a precise genetic diagnosis. In this Review, we describe the expanded range of phenotypes of muscle and brain sodium channelopathies and the underlying knowledge regarding mechanisms of sodium channel dysfunction. We also outline a diagnostic approach and review the available treatment options.
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Affiliation(s)
- Emma Matthews
- Department of Neuromuscular Diseases, Medical Research Council Centre for Neuromuscular Diseases, University College London Queen Square Institute of Neurology, London, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK.
| | - Simona Balestrini
- Department of Clinical and Experimental Epilepsy, University College London Queen Square Institute of Neurology, London, UK; Chalfont Centre for Epilepsy, Buckinghamshire, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK
| | - Sanjay M Sisodiya
- Department of Clinical and Experimental Epilepsy, University College London Queen Square Institute of Neurology, London, UK; Chalfont Centre for Epilepsy, Buckinghamshire, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK
| | - Michael G Hanna
- Department of Neuromuscular Diseases, Medical Research Council Centre for Neuromuscular Diseases, University College London Queen Square Institute of Neurology, London, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK
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14
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Elia N, Nault T, McMillan HJ, Graham GE, Huang L, Cannon SC. Myotonic Myopathy With Secondary Joint and Skeletal Anomalies From the c.2386C>G, p.L769V Mutation in SCN4A. Front Neurol 2020; 11:77. [PMID: 32117035 PMCID: PMC7031655 DOI: 10.3389/fneur.2020.00077] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 01/22/2020] [Indexed: 11/22/2022] Open
Abstract
The phenotypic spectrum associated with the skeletal muscle voltage-gated sodium channel gene (SCN4A) has expanded with advancements in genetic testing. Autosomal dominant SCN4A mutations were first linked to hyperkalemic periodic paralysis, then subsequently included paramyotonia congenita, several variants of myotonia, and finally hypokalemic periodic paralysis. Biallelic recessive mutations were later identified in myasthenic myopathy and in infants showing a severe congenital myopathy with hypotonia. We report a patient with a pathogenic de novo SCN4A variant, c.2386C>G p.L769V at a highly conserved leucine. The phenotype was manifest at birth with arthrogryposis multiplex congenita, severe episodes of bronchospasm that responded immediately to carbamazepine therapy, and electromyographic evidence of widespread myotonia. Another de novo case of p.L769V has been reported with hip dysplasia, scoliosis, myopathy, and later paramyotonia. Expression studies of L796V mutant channels showed predominantly gain-of-function changes, that included defects of slow inactivation. Computer simulations of muscle excitability reveal a strong predisposition to myotonia with exceptionally prolonged bursts of discharges, when the L796V defects are included. We propose L769V is a pathogenic variant, that along with other cases in the literature, defines a new dominant SCN4A disorder of myotonic myopathy with secondary congenital joint and skeletal involvement.
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Affiliation(s)
- Nathaniel Elia
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
- Molecular, Cellular, and Integrative Physiology Program, UCLA, Los Angeles, CA, United States
| | - Trystan Nault
- Division of Neurology, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, ON, Canada
| | - Hugh J. McMillan
- Division of Neurology, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, ON, Canada
| | - Gail E. Graham
- Department of Genetics, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, ON, Canada
| | - Lijia Huang
- Department of Genetics, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, ON, Canada
| | - Stephen C. Cannon
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
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15
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Cea G, Andreu D, Fletcher E, Ramdas S, Sud R, Hanna MG, Matthews E. Sodium channel myotonia may be associated with high-risk brief resolved unexplained events. Wellcome Open Res 2020; 5:57. [PMID: 32509969 PMCID: PMC7241273 DOI: 10.12688/wellcomeopenres.15798.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/23/2020] [Indexed: 11/20/2022] Open
Abstract
Brief resolved unexplained events (BRUEs) have numerous and varied causes posing a challenge to investigation and management. A subset of infants with the neuromuscular disorder sodium channel myotonia, due to mutations in the SCN4A gene, experience apnoeic events due to laryngospasm (myotonia) of the upper airway muscles that may present as a BRUE. We sought to ascertain the frequency, severity and outcome of infants carrying the G1306E SCN4A mutation commonly associated with this presentation. We report 12 new cases of individuals with the G1306E mutation from three unrelated families and perform a literature review of all published cases. Infants with the G1306E mutation almost universally experience laryngospasm and apnoeic events. The severity varies significantly, spans both low and high-risk BRUE categories or can be more severe than criteria for a BRUE would allow. At least a third of cases require intensive care unit (ICU) care. Seizure disorder is a common erroneous diagnosis. Apnoeas are effectively reduced or abolished by appropriate treatment with anti-myotonic agents. Probands with the G1306E mutation who are family planning need to be counselled for the likelihood of post-natal complications. There is readily available and extremely effective treatment for the episodic laryngospasm and apnoea caused by this mutation. Proactively seeking clinical evidence of myotonia or muscle hypertrophy with consideration of CK and EMG in high risk BRUEs or more complex apnoeic events may reduce avoidable and prolonged ICU admissions, patient morbidity and potentially mortality.
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Affiliation(s)
- Gabriel Cea
- Departamento de Ciencias Neurológicas, Universidad de Chile, Santiago, Chile
- Servicio de Neurología, Hospital Salvador, Santiago, Chile
| | - Daniel Andreu
- Departamento de Ciencias Neurológicas, Universidad de Chile, Santiago, Chile
| | - Elaine Fletcher
- Department of Clinical Genetics, Centre for Genomic and Experimental Medicine, Western General Hospital, Edinburgh, EH5 2GL, UK
| | - Sithara Ramdas
- Department of Paediatric Neurology, John Radcliffe Hospital NHS Foundation Trust, Oxford, UK
| | - Richa Sud
- Neurogenetics Unit, UCL Queen Square Institute of Neurology, London, UK
| | - Michael G. Hanna
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Emma Matthews
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
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16
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Cea G, Andreu D, Fletcher E, Ramdas S, Sud R, Hanna MG, Matthews E. Sodium channel myotonia may be associated with high-risk brief resolved unexplained events. Wellcome Open Res 2020; 5:57. [PMID: 32509969 PMCID: PMC7241273 DOI: 10.12688/wellcomeopenres.15798.2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/01/2020] [Indexed: 12/02/2022] Open
Abstract
Brief resolved unexplained events (BRUEs) have numerous and varied causes posing a challenge to investigation and management. A subset of infants with the neuromuscular disorder sodium channel myotonia, due to mutations in the SCN4A gene, experience apnoeic events due to laryngospasm (myotonia) of the upper airway muscles that may present as a BRUE. We sought to ascertain the frequency, severity and outcome of infants carrying the G1306E SCN4A mutation commonly associated with this presentation. We report 14 new cases of individuals with the G1306E mutation from three unrelated families and perform a literature review of all published cases. Infants with the G1306E mutation almost universally experience laryngospasm and apnoeic events. The severity varies significantly, spans both low and high-risk BRUE categories or can be more severe than criteria for a BRUE would allow. At least a third of cases require intensive care unit (ICU) care. Seizure disorder is a common erroneous diagnosis. Apnoeas are effectively reduced or abolished by appropriate treatment with anti-myotonic agents. Probands with the G1306E mutation who are family planning need to be counselled for the likelihood of post-natal complications. There is readily available and extremely effective treatment for the episodic laryngospasm and apnoea caused by this mutation. Proactively seeking clinical evidence of myotonia or muscle hypertrophy with consideration of CK,EMG and genetic testing in high risk BRUEs or more complex apnoeic events may reduce avoidable and prolonged ICU admissions, patient morbidity and potentially mortality.
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Affiliation(s)
- Gabriel Cea
- Departamento de Ciencias Neurológicas, Universidad de Chile, Santiago, Chile
- Servicio de Neurología, Hospital Salvador, Santiago, Chile
| | - Daniel Andreu
- Departamento de Ciencias Neurológicas, Universidad de Chile, Santiago, Chile
| | - Elaine Fletcher
- Department of Clinical Genetics, Centre for Genomic and Experimental Medicine, Western General Hospital, Edinburgh, EH5 2GL, UK
| | - Sithara Ramdas
- Department of Paediatric Neurology, John Radcliffe Hospital NHS Foundation Trust, Oxford, UK
| | - Richa Sud
- Neurogenetics Unit, UCL Queen Square Institute of Neurology, London, UK
| | - Michael G. Hanna
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Emma Matthews
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
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Türkdoğan D, Matthews E, Usluer S, Gündoğdu A, Uluç K, Mannikko R, Hanna MG, Sisodiya SM, Çağlayan HS. Possible role of SCN4A skeletal muscle mutation in apnea during seizure. Epilepsia Open 2019; 4:498-503. [PMID: 31440732 PMCID: PMC6698682 DOI: 10.1002/epi4.12347] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 05/20/2019] [Accepted: 06/08/2019] [Indexed: 01/05/2023] Open
Abstract
SCN4A gene mutations cause a number of neuromuscular phenotypes including myotonia. A subset of infants with myotonia-causing mutations experience severe life-threatening episodic laryngospasm with apnea. We have recently identified similar SCN4A mutations in association with sudden infant death syndrome. Laryngospasm has also been proposed as a contributory mechanism to some cases of sudden unexpected death in epilepsy (SUDEP). We report an infant with EEG-confirmed seizures and recurrent apneas. Whole-exome sequencing identified a known pathogenic mutation in the SCN4A gene that has been reported in several unrelated families with myotonic disorder. We propose that the SCN4A mutation contributed to the apneas in our case, irrespective of the underlying cause of the epilepsy. We suggest this supports the notion that laryngospasm may contribute to some cases of SUDEP, and implicates a possible shared mechanism between a proportion of sudden infant deaths and sudden unexpected deaths in epilepsy.
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Affiliation(s)
- Dilşad Türkdoğan
- Medical Faculty, Department of Child NeurologyMarmara UniversityIstanbulTurkey
| | - Emma Matthews
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of NeurologyUCL and National Hospital for Neurology and NeurosurgeryLondonUK
| | - Sunay Usluer
- Formerly Affiliated with Department of Molecular Biology and GeneticsBoğaziçi UniversityIstanbulTurkey
| | - Aslı Gündoğdu
- Department of Molecular Biology and GeneticsBoğaziçi UniversityIstanbulTurkey
| | - Kayıhan Uluç
- Medical Faculty, Department of Clinical Neurophysiology and NeurologyMarmara UniversityIstanbulTurkey
| | - Roope Mannikko
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of NeurologyUCL and National Hospital for Neurology and NeurosurgeryLondonUK
| | - Michael G. Hanna
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of NeurologyUCL and National Hospital for Neurology and NeurosurgeryLondonUK
| | - Sanjay M. Sisodiya
- Department of Clinical and Experimental EpilepsyUCL Queen Square Institute of NeurologyLondonUK
- Chalfont Centre for EpilepsyBucksUK
| | - Hande S. Çağlayan
- Department of Molecular Biology and GeneticsBoğaziçi UniversityIstanbulTurkey
- İzmir Biomedicine and Genome CenterİzmirTurkey
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18
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Pharmacogenetics of myotonic hNav1.4 sodium channel variants situated near the fast inactivation gate. Pharmacol Res 2019; 141:224-235. [DOI: 10.1016/j.phrs.2019.01.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 01/02/2019] [Accepted: 01/02/2019] [Indexed: 12/13/2022]
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19
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Vita G, Vita GL, Musumeci O, Rodolico C, Messina S. Genetic neuromuscular disorders: living the era of a therapeutic revolution. Part 2: diseases of motor neuron and skeletal muscle. Neurol Sci 2019; 40:671-681. [PMID: 30805745 DOI: 10.1007/s10072-019-03764-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 02/13/2019] [Indexed: 12/22/2022]
Abstract
This is the second part of a two-part document intended to discuss recent therapeutic progresses in genetic neuromuscular disorders. The present review is for diseases of motor neuron and skeletal muscle, some of which reached recently the most innovative therapeutic approaches. Nusinersen, an SMN2 mRNA splicing modifier, was approved as first-ever therapy of spinal muscular atrophy (SMA) by FDA in 2016 and by EMA in 2017. The orally administered small-molecule risdiplam, which increases SMN protein levels similarly but also in peripheral organs, is tested in ongoing phase 2 and 3 trials. After positive results with phase 1 treatment with AAV9-SMN, the first gene therapy for SMA, a phase 3 clinical trial is ongoing. Ataluren is the first approved drug for Duchenne muscular dystrophy (DMD) patients with premature stop codon mutations and its indication has been recently extended since the age of 2 years. Exon skipping technology was and is currently tested in many phase 3 trials, and eteplirsen received a conditional approval by FDA for patients amenable to exon 51 skipping, but not by EMA. Many other compounds with different mechanisms of action are now tested in DMD by phase 2 and 3 trials, including phase 1 gene therapy. Other innovative approaches are under investigation, i.e., gene therapy in X-linked myotubular myopathy and Pompe disease, and antisense oligonucleotides in myotonic dystrophy type 1. Positive evidences are discussed about lamotrigine and ranolazine in non-dystrophic myotonias, chaperons in Pompe disease, and nucleosides in mitochondrial DNA depletion induced by thymidine kinase 2 deficiency.
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Affiliation(s)
- Giuseppe Vita
- Unit of Neurology and Neuromuscular Diseases, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy. .,Nemo Sud Clinical Centre for Neuromuscular Disorders, Messina, Italy.
| | - Gian Luca Vita
- Nemo Sud Clinical Centre for Neuromuscular Disorders, Messina, Italy
| | - Olimpia Musumeci
- Unit of Neurology and Neuromuscular Diseases, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Carmelo Rodolico
- Unit of Neurology and Neuromuscular Diseases, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Sonia Messina
- Unit of Neurology and Neuromuscular Diseases, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy.,Nemo Sud Clinical Centre for Neuromuscular Disorders, Messina, Italy
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20
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Cavalli M, Fossati B, Vitale R, Brigonzi E, Ricigliano VAG, Saraceno L, Cardani R, Pappone C, Meola G. Flecainide-Induced Brugada Syndrome in a Patient With Skeletal Muscle Sodium Channelopathy: A Case Report With Critical Therapeutical Implications and Review of the Literature. Front Neurol 2018; 9:385. [PMID: 29899727 PMCID: PMC5988887 DOI: 10.3389/fneur.2018.00385] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 05/11/2018] [Indexed: 12/31/2022] Open
Abstract
Skeletal muscle sodium channelopathies are a group of neuromuscular disorders associated with mutations in the SCN4A gene. Because principal sodium channel isoforms expressed in the skeletal muscles and the heart are distinct one from the other, this condition usually spares cardiac functioning. Nonetheless, evidence on a possible link between skeletal muscle and cardiac sodium channelopathies has emerged in recent years. To date, eight patients bearing pathogenetic mutations in the SCN4A gene and manifesting cardiac electrophysiological alterations have been reported in literature. Among these patients, three presented a phenotype compatible with Brugada syndrome. We report the case of a 29-year-old patient affected by non-dystrophic myotonia associated with a p.G1306E mutation in the SCN4A gene, who presented symptoms of syncope and palpitation after the introduction of flecainide as an anti-myotonic agent. ECG and ajmaline challenge were consistent with the diagnosis of Brugada syndrome, leading to the implantation of a cardioverter defibrillator. No mutation in causative genes for Brugada syndrome was detected. Mexiletine treatment reduced myotonia without any cardiac adverse events. This case report highlights the clinical relevance of the recognition of cardiac electrophysiological alterations in skeletal muscle sodium channelopathies. The discovery of a possible pathogenetic linkage between skeletal muscle and cardiac sodium channelopathies may have significant implications in patients' management, also in light of the fact that class 1C anti-arrhythmics are potential triggers for life-threatening arrhythmias in patients with Brugada syndrome.
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Affiliation(s)
- Michele Cavalli
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Barbara Fossati
- Department of Neurology, IRCCS Policlinico San Donato, Milan, Italy
| | - Raffaele Vitale
- Clinical Arrhythmology and Electrophysiology Department, IRCCS Policlinico San Donato, Milan, Italy
| | - Elisa Brigonzi
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Vito A G Ricigliano
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Lorenzo Saraceno
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Rosanna Cardani
- Laboratory of Muscle Histopathology and Molecular Biology, IRCCS Policlinico San Donato, Milan, Italy
| | - Carlo Pappone
- Clinical Arrhythmology and Electrophysiology Department, IRCCS Policlinico San Donato, Milan, Italy
| | - Giovanni Meola
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.,Department of Neurology, IRCCS Policlinico San Donato, Milan, Italy
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21
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Matthews E, Silwal A, Sud R, Hanna MG, Manzur AY, Muntoni F, Munot P. Skeletal Muscle Channelopathies: Rare Disorders with Common Pediatric Symptoms. J Pediatr 2017; 188:181-185.e6. [PMID: 28662944 DOI: 10.1016/j.jpeds.2017.05.081] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 03/31/2017] [Accepted: 05/31/2017] [Indexed: 10/19/2022]
Abstract
OBJECTIVE To ascertain the presenting symptoms of children with skeletal muscle channelopathies to promote early diagnosis and treatment. STUDY DESIGN Retrospective case review of 38 children with a skeletal muscle channelopathy attending the specialist pediatric neuromuscular service at Great Ormond Street Hospital over a 15-year period. RESULTS Gait disorder and leg cramps are a frequent presentation of myotonic disorders (19 of 29). Strabismus or extraocular myotonia (9 of 19) and respiratory and/or bulbar symptoms (11 of 19) are common among those with sodium channelopathy. Neonatal hypotonia was observed in periodic paralysis. Scoliosis and/or contractures were demonstrated in 6 of 38 children. School attendance or ability to engage fully in all activities was often limited (25 of 38). CONCLUSIONS Children with skeletal muscle channelopathies frequently display symptoms that are uncommon in adult disease. Any child presenting with abnormal gait, leg cramps, or strabismus, especially if intermittent, should prompt examination for myotonia. Those with sodium channel disease should be monitored for respiratory or bulbar complications. Neonatal hypotonia can herald periodic paralysis. Early diagnosis is essential for children to reach their full educational potential.
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Affiliation(s)
- Emma Matthews
- Medical Research Council Center for Neuromuscular Diseases, University College London and National Hospital for Neurology and Neurosurgery, London, UK.
| | - Arpana Silwal
- Dubowitz Neuromuscular Center and MRC Center for Neuromuscular Diseases, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Richa Sud
- Neurogenetics Unit, Institute of Neurology, London, UK
| | - Michael G Hanna
- Medical Research Council Center for Neuromuscular Diseases, University College London and National Hospital for Neurology and Neurosurgery, London, UK
| | - Adnan Y Manzur
- Dubowitz Neuromuscular Center and MRC Center for Neuromuscular Diseases, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Francesco Muntoni
- Dubowitz Neuromuscular Center and MRC Center for Neuromuscular Diseases, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Pinki Munot
- Dubowitz Neuromuscular Center and MRC Center for Neuromuscular Diseases, UCL Great Ormond Street Institute of Child Health, London, UK
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