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Radziwonik-Fraczyk W, Elert-Dobkowska E, Karpinski M, Pilch J, Ziora-Jakutowicz K, Kubalska J, Szczesniak D, Stepniak I, Zaremba J, Sulek A. Next generation sequencing panel as an effective approach to genetic testing in patients with a highly variable phenotype of neuromuscular disorders. Neurogenetics 2024:10.1007/s10048-024-00762-y. [PMID: 38758368 DOI: 10.1007/s10048-024-00762-y] [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: 03/19/2024] [Accepted: 05/09/2024] [Indexed: 05/18/2024]
Abstract
Neuromuscular disorders (NMDs) include a wide range of diseases affecting the peripheral nervous system. The genetic diagnoses are increasingly obtained with using the next generation sequencing (NGS). We applied the custom-design targeted NGS panel including 89 genes, together with genotyping and multiplex ligation-dependent probe amplification (MLPA) to identify a genetic spectrum of NMDs in 52 Polish patients. As a result, the genetic diagnosis was determined by NGS panel in 29 patients so its diagnostic utility is estimated at 55.8%. The most pathogenic variants were found in CLCN1, followed by CAPN3, SCN4A, and SGCA genes. Genotyping of myotonic dystrophy type 1 and 2 (DM1 and DM2) as a secondary approach has been performed. The co-occurrence of CAPN3 and CNBP mutations in one patient as well as DYSF and CNBP mutations in another suggests possibly more complex inheritance as well as expression of a phenotype. In 7 individuals with single nucleotide variant found in NGS testing, the MLPA of the CAPN3 gene was performed detecting the deletion encompassing exons 2-8 in the CAPN3 gene in one patient, confirming recessive limb-girdle muscular dystrophy type 1 (LGMDR1). Thirty patients obtained a genetic diagnosis (57.7%) after using NGS testing, genotyping and MLPA analysis. The study allowed for the identification of 27 known and 4 novel pathogenic/likely pathogenic variants and variants of uncertain significance (VUS) associated with NMDs.In conclusion, the diagnostic approach with diverse molecular techniques enables to broaden the mutational spectrum and maximizes the diagnostic yield. Furthermore, the co-occurrence of DM2 and LGMD has been detected in 2 individuals.
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Affiliation(s)
| | | | | | - Jacek Pilch
- Department of Pediatric Neurology, Medical University of Silesia, Katowice, Poland
| | | | - Jolanta Kubalska
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Dominika Szczesniak
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Iwona Stepniak
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Jacek Zaremba
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Anna Sulek
- Faculty of Medicine, Lazarski University, Warsaw, Poland.
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Frosio A, Micaglio E, Polsinelli I, Calamaio S, Melgari D, Prevostini R, Ghiroldi A, Binda A, Carrera P, Villa M, Mastrocinque F, Presi S, Salerno R, Boccellino A, Anastasia L, Ciconte G, Ricagno S, Pappone C, Rivolta I. Unravelling Novel SCN5A Mutations Linked to Brugada Syndrome: Functional, Structural, and Genetic Insights. Int J Mol Sci 2023; 24:15089. [PMID: 37894777 PMCID: PMC10606416 DOI: 10.3390/ijms242015089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 10/08/2023] [Accepted: 10/09/2023] [Indexed: 10/29/2023] Open
Abstract
Brugada Syndrome (BrS) is a rare inherited cardiac arrhythmia causing potentially fatal ventricular tachycardia or fibrillation, mainly occurring during rest or sleep in young individuals without heart structural issues. It increases the risk of sudden cardiac death, and its characteristic feature is an abnormal ST segment elevation on the ECG. While BrS has diverse genetic origins, a subset of cases can be conducted to mutations in the SCN5A gene, which encodes for the Nav1.5 sodium channel. Our study focused on three novel SCN5A mutations (p.A344S, p.N347K, and p.D349N) found in unrelated BrS families. Using patch clamp experiments, we found that these mutations disrupted sodium currents: p.A344S reduced current density, while p.N347K and p.D349N completely abolished it, leading to altered voltage dependence and inactivation kinetics when co-expressed with normal channels. We also explored the effects of mexiletine treatment, which can modulate ion channel function. Interestingly, the p.N347K and p.D349N mutations responded well to the treatment, rescuing the current density, while p.A344S showed a limited response. Structural analysis revealed these mutations were positioned in key regions of the channel, impacting its stability and function. This research deepens our understanding of BrS by uncovering the complex relationship between genetic mutations, ion channel behavior, and potential therapeutic interventions.
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Affiliation(s)
- Anthony Frosio
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
| | - Emanuele Micaglio
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
- Arrhythmia and Electrophysiology Department, IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (F.M.); (A.B.)
| | - Ivan Polsinelli
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
| | - Serena Calamaio
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
| | - Dario Melgari
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
| | - Rachele Prevostini
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
| | - Andrea Ghiroldi
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
- Laboratory of Stem Cells for Tissue Engineering, IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy
| | - Anna Binda
- School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore, 48, 20900 Monza, Italy;
| | - Paola Carrera
- Laboratory of Clinical Molecular Genetics and Cytogenetics, Unit of Genomics for Diagnosis of Human Diseases, IRCCS San Raffaele Scientific Institute, 20132 Milan, Italy; (P.C.); (S.P.)
| | - Marco Villa
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
| | - Flavio Mastrocinque
- Arrhythmia and Electrophysiology Department, IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (F.M.); (A.B.)
| | - Silvia Presi
- Laboratory of Clinical Molecular Genetics and Cytogenetics, Unit of Genomics for Diagnosis of Human Diseases, IRCCS San Raffaele Scientific Institute, 20132 Milan, Italy; (P.C.); (S.P.)
| | - Raffaele Salerno
- Faculty of Medicine and Surgery, Vita-Salute San Raffaele University, Via Olgettina, 58, 20132 Milan, Italy;
| | - Antonio Boccellino
- Arrhythmia and Electrophysiology Department, IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (F.M.); (A.B.)
| | - Luigi Anastasia
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
- Laboratory of Stem Cells for Tissue Engineering, IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy
- Faculty of Medicine and Surgery, Vita-Salute San Raffaele University, Via Olgettina, 58, 20132 Milan, Italy;
| | - Giuseppe Ciconte
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
- Arrhythmia and Electrophysiology Department, IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (F.M.); (A.B.)
- Faculty of Medicine and Surgery, Vita-Salute San Raffaele University, Via Olgettina, 58, 20132 Milan, Italy;
| | - Stefano Ricagno
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
- Department of Biosciences, Università degli Studi di Milano, Via Celoria, 26, 20133 Milan, Italy
| | - Carlo Pappone
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
- Arrhythmia and Electrophysiology Department, IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (F.M.); (A.B.)
- Faculty of Medicine and Surgery, Vita-Salute San Raffaele University, Via Olgettina, 58, 20132 Milan, Italy;
| | - Ilaria Rivolta
- Institute of Molecular and Translational Cardiology (IMTC), IRCCS Policlinico San Donato, 20097 San Donato Milanese, Italy; (A.F.); (E.M.); (I.P.); (S.C.); (D.M.); (R.P.); (A.G.); (M.V.); (L.A.); (G.C.); (S.R.); (C.P.)
- School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore, 48, 20900 Monza, Italy;
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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: 0] [Impact Index Per Article: 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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Gonzalez-Perez P, D'Ambrosio ES, Picher-Martel V, Chuang K, David WS, Amato AA. Parent-of-Origin Effect on the Age at Symptom Onset in Myotonic Dystrophy Type 2. Neurol Genet 2023; 9:e200073. [PMID: 37123986 PMCID: PMC10136683 DOI: 10.1212/nxg.0000000000200073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 03/02/2023] [Indexed: 05/02/2023]
Abstract
Background and Objectives The existence of clinical anticipation, congenital form, and parent-of-origin effect in myotonic dystrophy type 2 (DM2) remains uncertain. Here, we aimed at investigating whether there is a parent-of-origin effect on the age at the first DM2-related clinical manifestation. Methods We identified patients with genetically confirmed DM2 with known parental inheritance from (1) the electronic medical records of our institutions and (2) a systematic review of the literature following the PRISMA 2020 guidelines and recorded their age at and type of first disease-related symptom. We also interrogated the Myotonic Dystrophy Foundation Family Registry (MDFFR) for patients with DM2 who completed a survey including questions about parental inheritance and age at the first medical problem which they related to their DM2 diagnosis. Results A total of 26 patients with DM2 from 18 families were identified at our institutions as having maternal (n = 14) or paternal (n = 12) inheritance of the disease, whereas our systematic review of the literature rendered a total of 61 patients with DM2 from 41 families reported by 24 eligible articles as having maternal (n = 40) or paternal (n = 21) inheritance of the disease. Both cohorts were combined for downstream analyses. Up to 61% and 58% of patients had muscle-related symptoms as the first disease manifestation in maternally and paternally inherited DM2 subgroups, respectively. Four patients developed hypotonia at birth and/or delayed motor milestones early in life, and 7 had nonmuscular presentations (2 had cardiac events within the second decade of life and 5 had cataracts), all of them with maternal inheritance. A maternal inheritance was associated with an earlier (within the first 3 decades of life) age at symptom onset relative to a paternal inheritance in this combined cohort, and this association was independent of the patient's sex (OR [95% CI] = 4.245 [1.429-13.820], p = 0.0117). However, this association was not observed in the MDFFR DM2 cohort (n = 127), possibly because age at onset was self-reported, and the information about the type of first symptom or medical problem that patients related to DM2 was lacking. Discussion A maternal inheritance may increase the risk of an early DM2 onset and of cataracts and cardiovascular events as first DM2 manifestations.
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Affiliation(s)
- Paloma Gonzalez-Perez
- Department of Neurology (P.G.-P., V.P.-M., K.C., W.S.D.), Massachusetts General Hospital, Harvard Medical School, Boston, MA; Department of Neurology (E.S.D.A.), Nationwide Children's Hospital, Columbus, OH; and Department of Neurology (V.P.-M., A.A.A.), Brigham Women's Hospital, Harvard Medical School, Boston, MA
| | - Eleonora S D'Ambrosio
- Department of Neurology (P.G.-P., V.P.-M., K.C., W.S.D.), Massachusetts General Hospital, Harvard Medical School, Boston, MA; Department of Neurology (E.S.D.A.), Nationwide Children's Hospital, Columbus, OH; and Department of Neurology (V.P.-M., A.A.A.), Brigham Women's Hospital, Harvard Medical School, Boston, MA
| | - Vincent Picher-Martel
- Department of Neurology (P.G.-P., V.P.-M., K.C., W.S.D.), Massachusetts General Hospital, Harvard Medical School, Boston, MA; Department of Neurology (E.S.D.A.), Nationwide Children's Hospital, Columbus, OH; and Department of Neurology (V.P.-M., A.A.A.), Brigham Women's Hospital, Harvard Medical School, Boston, MA
| | - Kathy Chuang
- Department of Neurology (P.G.-P., V.P.-M., K.C., W.S.D.), Massachusetts General Hospital, Harvard Medical School, Boston, MA; Department of Neurology (E.S.D.A.), Nationwide Children's Hospital, Columbus, OH; and Department of Neurology (V.P.-M., A.A.A.), Brigham Women's Hospital, Harvard Medical School, Boston, MA
| | - William S David
- Department of Neurology (P.G.-P., V.P.-M., K.C., W.S.D.), Massachusetts General Hospital, Harvard Medical School, Boston, MA; Department of Neurology (E.S.D.A.), Nationwide Children's Hospital, Columbus, OH; and Department of Neurology (V.P.-M., A.A.A.), Brigham Women's Hospital, Harvard Medical School, Boston, MA
| | - Anthony A Amato
- Department of Neurology (P.G.-P., V.P.-M., K.C., W.S.D.), Massachusetts General Hospital, Harvard Medical School, Boston, MA; Department of Neurology (E.S.D.A.), Nationwide Children's Hospital, Columbus, OH; and Department of Neurology (V.P.-M., A.A.A.), Brigham Women's Hospital, Harvard Medical School, Boston, MA
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Vivekanandam V, Jayaseelan D, Hanna MG. Muscle channelopathies. HANDBOOK OF CLINICAL NEUROLOGY 2023; 195:521-532. [PMID: 37562884 DOI: 10.1016/b978-0-323-98818-6.00006-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
Muscle channelopathies encompass a wide range of mainly episodic conditions that are characterized by muscle stiffness and weakness. The myotonic conditions, characterized predominantly by stiffness, include myotonia congenita, paramyotonia congenita, and sodium channel myotonia. The periodic paralysis conditions include hypokalemic periodic paralysis, hyperkalemic periodic paralysis, and Andersen-Tawil syndrome. Clinical history is key, and diagnosis is confirmed by next-generation genetic sequencing of a panel of known genes but can also be supplemented by neurophysiology studies and MRI. As genetic testing expands, so have the spectrum of phenotypes seen including pediatric presentations and congenital myopathies. Management of these conditions requires a multidisciplinary approach with extra support needed when patients require anesthetics or when pregnant. Patients with Andersen-Tawil syndrome will also need cardiac input. Diagnosis is important as symptomatic treatment is available for all of these conditions but need to be tailored to the gene and variant of the patient.
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Affiliation(s)
- Vinojini Vivekanandam
- Centre for Neuromuscular Disorders, Queen Square UCL Institute of Neurology, London, United Kingdom
| | | | - Michael G Hanna
- Centre for Neuromuscular Disorders, Queen Square UCL Institute of Neurology, London, United Kingdom.
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Abstract
PURPOSE OF REVIEW Myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2) are genetic disorders affecting skeletal and smooth muscle, heart, brain, eyes, and other organs. The multisystem involvement and disease variability of myotonic dystrophy have presented challenges for clinical care and research. This article focuses on the diagnosis and management of the disease. In addition, recent advances in characterizing the diverse clinical manifestations and variability of the disease are discussed. RECENT FINDINGS Studies of the multisystem involvement of myotonic dystrophy, including the most lethal cardiac and respiratory manifestations and their molecular underpinnings, expand our understanding of the myotonic dystrophy phenotype. Advances have been made in understanding the molecular mechanisms of both types of myotonic dystrophy, providing opportunities for developing targeted therapeutics, some of which have entered clinical trials in DM1. SUMMARY Continued efforts focus on advancing our molecular and clinical understanding of DM1 and DM2. Accurately measuring and monitoring the diverse and variable clinical manifestations of myotonic dystrophy in clinic and in research is important to provide adequate care, prevent complications, and find treatments that improve symptoms and life quality.
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Trivedi JR. Muscle Channelopathies. Continuum (Minneap Minn) 2022; 28:1778-1799. [PMID: 36537980 DOI: 10.1212/con.0000000000001183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
PURPOSE OF REVIEW This article describes the clinical features, diagnosis, pathophysiology, and management of nondystrophic myotonia and periodic paralysis. RECENT FINDINGS An increasing awareness exists about the genotype-phenotype overlap in skeletal muscle channelopathies, and thus genetic testing is needed to make a definitive diagnosis. Electrodiagnostic testing in channelopathies is highly specialized with significant overlap in various mutation subtypes. Randomized clinical trials have now been conducted in these disorders with expanded treatment options for patients with muscle channelopathies. SUMMARY Skeletal muscle channelopathies are rare heterogeneous conditions characterized by lifelong symptoms that require a comprehensive management plan that includes pharmacologic and nonpharmacologic interventions. The significant variability in biophysical features of various mutations, coupled with the difficulties of performing clinical trials in rare diseases, makes it challenging to design and implement treatment trials for muscle channelopathies.
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Suetterlin K, Matthews E, Sud R, McCall S, Fialho D, Burge J, Jayaseelan D, Haworth A, Sweeney MG, Kullmann DM, Schorge S, Hanna MG, Männikkö R. Translating genetic and functional data into clinical practice: a series of 223 families with myotonia. Brain 2022; 145:607-620. [PMID: 34529042 PMCID: PMC9014745 DOI: 10.1093/brain/awab344] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 07/13/2021] [Accepted: 08/05/2021] [Indexed: 11/14/2022] Open
Abstract
High-throughput DNA sequencing is increasingly employed to diagnose single gene neurological and neuromuscular disorders. Large volumes of data present new challenges in data interpretation and its useful translation into clinical and genetic counselling for families. Even when a plausible gene is identified with confidence, interpretation of the clinical significance and inheritance pattern of variants can be challenging. We report our approach to evaluating variants in the skeletal muscle chloride channel ClC-1 identified in 223 probands with myotonia congenita as an example of these challenges. Sequencing of CLCN1, the gene that encodes CLC-1, is central to the diagnosis of myotonia congenita. However, interpreting the pathogenicity and inheritance pattern of novel variants is notoriously difficult as both dominant and recessive mutations are reported throughout the channel sequence, ClC-1 structure-function is poorly understood and significant intra- and interfamilial variability in phenotype is reported. Heterologous expression systems to study functional consequences of CIC-1 variants are widely reported to aid the assessment of pathogenicity and inheritance pattern. However, heterogeneity of reported analyses does not allow for the systematic correlation of available functional and genetic data. We report the systematic evaluation of 95 CIC-1 variants in 223 probands, the largest reported patient cohort, in which we apply standardized functional analyses and correlate this with clinical assessment and inheritance pattern. Such correlation is important to determine whether functional data improves the accuracy of variant interpretation and likely mode of inheritance. Our data provide an evidence-based approach that functional characterization of ClC-1 variants improves clinical interpretation of their pathogenicity and inheritance pattern, and serve as reference for 34 previously unreported and 28 previously uncharacterized CLCN1 variants. In addition, we identify novel pathogenic mechanisms and find that variants that alter voltage dependence of activation cluster in the first half of the transmembrane domains and variants that yield no currents cluster in the second half of the transmembrane domain. None of the variants in the intracellular domains were associated with dominant functional features or dominant inheritance pattern of myotonia congenita. Our data help provide an initial estimate of the anticipated inheritance pattern based on the location of a novel variant and shows that systematic functional characterization can significantly refine the assessment of risk of an associated inheritance pattern and consequently the clinical and genetic counselling.
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Affiliation(s)
- Karen Suetterlin
- MRC International Centre for Genomic Medicine in Neuromuscular Diseases, Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, London, UK
- AGE Research Group, NIHR Newcastle Biomedical Research Centre, Newcastle-upon-Tyne Hospitals NHS Foundation Trust and Newcastle University, Newcastle-upon-Tyne, UK
| | - Emma Matthews
- MRC International Centre for Genomic Medicine in Neuromuscular Diseases, Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, London, UK
- Atkinson Morley Neuromuscular Centre, Department of Neurology, St Georges University Hospitals NHS Foundation Trust, London, UK
| | - Richa Sud
- Neurogenetics Unit, UCL Queen Square Institute of Neurology, London, UK
| | - Samuel McCall
- Neurogenetics Unit, UCL Queen Square Institute of Neurology, London, UK
| | - Doreen Fialho
- MRC International Centre for Genomic Medicine in Neuromuscular Diseases, Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, London, UK
- Department of Clinical Neurophysiology, King’s College Hospital, London, UK
| | - James Burge
- MRC International Centre for Genomic Medicine in Neuromuscular Diseases, Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, London, UK
- Department of Clinical Neurophysiology, King’s College Hospital, London, UK
| | - Dipa Jayaseelan
- MRC International Centre for Genomic Medicine in Neuromuscular Diseases, Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, London, UK
| | - Andrea Haworth
- Neurogenetics Unit, UCL Queen Square Institute of Neurology, London, UK
| | - Mary G Sweeney
- Neurogenetics Unit, UCL Queen Square Institute of Neurology, London, UK
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK
| | - Stephanie Schorge
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK
- Department of Pharmacology, UCL School of Pharmacy, London, UK
| | - Michael G Hanna
- MRC International Centre for Genomic Medicine in Neuromuscular Diseases, Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, London, UK
| | - Roope Männikkö
- MRC International Centre for Genomic Medicine in Neuromuscular Diseases, Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology, London, UK
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10
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Myotonic Dystrophies: A Genetic Overview. Genes (Basel) 2022; 13:genes13020367. [PMID: 35205411 PMCID: PMC8872148 DOI: 10.3390/genes13020367] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 02/09/2022] [Accepted: 02/16/2022] [Indexed: 02/01/2023] Open
Abstract
Myotonic dystrophies (DM) are the most common muscular dystrophies in adults, which can affect other non-skeletal muscle organs such as the heart, brain and gastrointestinal system. There are two genetically distinct types of myotonic dystrophy: myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2), both dominantly inherited with significant overlap in clinical manifestations. DM1 results from CTG repeat expansions in the 3′-untranslated region (3′UTR) of the DMPK (dystrophia myotonica protein kinase) gene on chromosome 19, while DM2 is caused by CCTG repeat expansions in intron 1 of the CNBP (cellular nucleic acid-binding protein) gene on chromosome 3. Recent advances in genetics and molecular biology, especially in the field of RNA biology, have allowed better understanding of the potential pathomechanisms involved in DM. In this review article, core clinical features and genetics of DM are presented followed by a discussion on the current postulated pathomechanisms and therapeutic approaches used in DM, including the ones currently in human clinical trial phase.
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11
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Montagnese F. Current Treatment Options for Patients with Myotonic Dystrophy Type 2. Curr Treat Options Neurol 2021. [DOI: 10.1007/s11940-021-00686-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Abstract
Purpose of the review
Myotonic dystrophy types 1 and 2 are frequent forms of muscular dystrophies in adulthood. Their clinical differences need to be taken into account for the most appropriate treatment of patients. The aim of this article is to provide an overview on the current and upcoming therapeutic options for patients with myotonic dystrophy type 2 (DM2).
Recent findings
At the moment, no disease-modifying therapies are available for DM2; next-generation therapies may however be available in the near future. In the meanwhile, the symptomatic management of patients has greatly improved, thank to the production of consensus-based standards of care and the growing evidence of efficacy of anti-myotonic drugs, promising employment of cannabinoids for symptom’s relief, regular monitoring, and early detection of treatable extra-muscular manifestations.
Summary
The treatment of DM2 is currently symptomatic and relies on the coordinated intervention of a multidisciplinary team. It remains to be determined whether upcoming causal therapies for myotonic dystrophy type 1 will be applicable also in DM2.
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12
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Botta A, Visconti VV, Fontana L, Bisceglia P, Bengala M, Massa R, Bagni I, Cardani R, Sangiuolo F, Meola G, Antonini G, Petrucci A, Pegoraro E, D'Apice MR, Novelli G. A 14-Year Italian Experience in DM2 Genetic Testing: Frequency and Distribution of Normal and Premutated CNBP Alleles. Front Genet 2021; 12:668094. [PMID: 34234810 PMCID: PMC8255792 DOI: 10.3389/fgene.2021.668094] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 05/05/2021] [Indexed: 11/16/2022] Open
Abstract
Myotonic dystrophy type 2 (DM2) is a multisystemic disorder caused by a (CCTG)n in intron 1 of the CNBP gene. The CCTG repeat tract is part of a complex (TG)v(TCTG)w(CCTG)x(NCTG)y(CCTG)z motif generally interrupted in CNBP healthy range alleles. Here we report our 14-year experience of DM2 postnatal genetic testing in a total of 570 individuals. The DM2 locus has been analyzed by a combination of SR-PCR, TP-PCR, LR-PCR, and Sanger sequencing of CNBP alleles. DM2 molecular diagnosis has been confirmed in 187/570 samples analyzed (32.8%) and is mainly associated with the presence of myotonia in patients. This set of CNBP alleles showed unimodal distribution with 25 different alleles ranging from 108 to 168 bp, in accordance with previous studies on European populations. The most frequent CNBP alleles consisted of 138, 134, 140, and 136 bps with an overall locus heterozygosity of 90%. Sequencing of 103 unexpanded CNBP alleles in DM2-positive patients revealed that (CCTG)5(NCTG)3(CCTG)7 and (CCTG)6(NCTG)3(CCTG)7 are the most common interruption motifs. We also characterized five CNBP premutated alleles with (CCTG)n repetitions from n = 36 to n = 53. However, the molecular and clinical consequences in our cohort of samples are not unequivocal. Data that emerged from this study are representative of the Italian population and are useful tools for National and European centers offering DM2 genetic testing and counseling.
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Affiliation(s)
- Annalisa Botta
- Medical Genetics Section, Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy
| | - Virginia Veronica Visconti
- Medical Genetics Section, Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy
| | - Luana Fontana
- Medical Genetics Section, Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy
| | - Paola Bisceglia
- Laboratory of Medical Genetics, Tor Vergata Hospital, Rome, Italy.,Research Laboratory, Complex Structure of Geriatrics, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | - Mario Bengala
- Laboratory of Medical Genetics, Tor Vergata Hospital, Rome, Italy
| | - Roberto Massa
- Neuromuscular Disease Unit, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Ilaria Bagni
- Laboratory of Medical Genetics, Tor Vergata Hospital, Rome, Italy
| | - Rosanna Cardani
- BioCor Biobank, UOC SMEL-1 of Clinical Pathology, IRCCS-Policlinico San Donato, Milan, Italy
| | - Federica Sangiuolo
- Medical Genetics Section, Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy.,Laboratory of Medical Genetics, Tor Vergata Hospital, Rome, Italy
| | - Giovanni Meola
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.,Department of Neurorehabilitation Sciences, Casa di Cura del Policlinico, Milan, Italy
| | - Giovanni Antonini
- Neuromuscular and Rare Disease Center, Department of Neuroscience, Mental Health and Sensory Organs (NESMOS), Sant'Andrea Hospital, Sapienza University of Rome, Rome, Italy
| | - Antonio Petrucci
- Center for Neuromuscular and Neurological Rare Diseases, S. Camillo Forlanini Hospital, Rome, Italy
| | - Elena Pegoraro
- Department of Neuroscience, University of Padua, Padua, Italy
| | | | - Giuseppe Novelli
- Medical Genetics Section, Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy.,Laboratory of Medical Genetics, Tor Vergata Hospital, Rome, Italy
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13
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Novel SCN5A p.Val1667Asp Missense Variant Segregation and Characterization in a Family with Severe Brugada Syndrome and Multiple Sudden Deaths. Int J Mol Sci 2021; 22:ijms22094700. [PMID: 33946750 PMCID: PMC8125150 DOI: 10.3390/ijms22094700] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 04/23/2021] [Accepted: 04/23/2021] [Indexed: 02/07/2023] Open
Abstract
Genetic testing in Brugada syndrome (BrS) is still not considered to be useful for clinical management of patients in the majority of cases, due to the current lack of understanding about the effect of specific variants. Additionally, family history of sudden death is generally not considered useful for arrhythmic risk stratification. We sought to demonstrate the usefulness of genetic testing and family history in diagnosis and risk stratification. The family history was collected for a proband who presented with a personal history of aborted cardiac arrest and in whom a novel variant in the SCN5A gene was found. Living family members underwent ajmaline testing, electrophysiological study, and genetic testing to determine genotype-phenotype segregation, if any. Patch-clamp experiments on transfected human embryonic kidney 293 cells enabled the functional characterization of the SCN5A novel variant in vitro. In this study, we provide crucial human data on the novel heterozygous variant NM_198056.2:c.5000T>A (p.Val1667Asp) in the SCN5A gene, and demonstrate its segregation with a severe form of BrS and multiple sudden deaths. Functional data revealed a loss of function of the protein affected by the variant. These results provide the first disease association with this variant and demonstrate the usefulness of genetic testing for diagnosis and risk stratification in certain patients. This study also demonstrates the usefulness of collecting the family history, which can assist in understanding the severity of the disease in certain situations and confirm the importance of the functional studies to distinguish between pathogenic mutations and harmless genetic variants.
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14
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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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15
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Meola G. Myotonic dystrophy type 2: the 2020 update. ACTA MYOLOGICA : MYOPATHIES AND CARDIOMYOPATHIES : OFFICIAL JOURNAL OF THE MEDITERRANEAN SOCIETY OF MYOLOGY 2020; 39:222-234. [PMID: 33458578 PMCID: PMC7783423 DOI: 10.36185/2532-1900-026] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 11/09/2020] [Indexed: 12/26/2022]
Abstract
The myotonic dystrophies are the commonest cause of adult-onset muscular dystrophy. Phenotypes of DM1 and DM2 are similar, but there are some important differences, including the presence or absence of congenital form, muscles primarily affected (distal vs proximal), involved muscle fiber types (type 1 vs type 2 fibers), and some associated multisystemic phenotypes. There is currently no cure for the myotonic dystrophies but effective management significantly reduces the morbidity and mortality of patients. For the enormous understanding of the molecular pathogenesis of myotonic dystrophy type 1 and myotonic dystrophy type 2, these diseases are now called "spliceopathies" and are mediated by a primary disorder of RNA rather than proteins. Despite clinical and genetic similarities, myotonic dystrophy type 1 and type 2 are distinct disorders requiring different diagnostic and management strategies. Gene therapy for myotonic dystrophy type 1 and myotonic dystrophy type 2 appears to be very close and the near future is an exciting time for clinicians and patients.
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Affiliation(s)
- Giovanni Meola
- Department of Biomedical Sciences for Health, University of Milan, Italy.,Department of Neurorehabilitation Sciences, Casa di Cura del Policlinico, Milan, Italy
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16
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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: 45] [Impact Index Per Article: 11.3] [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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17
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Juang JMJ, Binda A, Lee SJ, Hwang JJ, Chen WJ, Liu YB, Lin LY, Yu CC, Ho LT, Huang HC, Chen CYJ, Lu TP, Lai LC, Yeh SFS, Lai LP, Chuang EY, Rivolta I, Antzelevitch C. GSTM3 variant is a novel genetic modifier in Brugada syndrome, a disease with risk of sudden cardiac death. EBioMedicine 2020; 57:102843. [PMID: 32645615 PMCID: PMC7341360 DOI: 10.1016/j.ebiom.2020.102843] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/28/2020] [Accepted: 06/03/2020] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Brugada syndrome (BrS) is a rare inherited disease causing sudden cardiac death (SCD). Copy number variants (CNVs) can contribute to disease susceptibility, but their role in Brugada syndrome (BrS) is unknown. We aimed to identify a CNV associated with BrS and elucidated its clinical implications. METHODS We enrolled 335 unrelated BrS patients from 2000 to 2018 in the Taiwanese population. Microarray and exome sequencing were used for discovery phase whereas Sanger sequencing was used for the validation phase. HEK cells and zebrafish were used to characterize the function of the CNV variant. FINDINGS A copy number deletion of GSTM3 (chr1:109737011-109737301, hg38) containing the eighth exon and the transcription stop codon was observed in 23.9% of BrS patients versus 0.8% of 15,829 controls in Taiwan Biobank (P < 0.001), and 0% in gnomAD. Co-segregation analysis showed that the co-segregation rate was 20%. Patch clamp experiments showed that in an oxidative stress environment, GSTM3 down-regulation leads to a significant decrease of cardiac sodium channel current amplitude. Ventricular arrhythmia incidence was significantly greater in gstm3 knockout zebrafish at baseline and after flecainide, but was reduced after quinidine, consistent with clinical observations. BrS patients carrying the GSTM3 deletion had higher rates of sudden cardiac arrest and syncope compared to those without (OR: 3.18 (1.77-5.74), P<0.001; OR: 1.76 (1.02-3.05), P = 0.04, respectively). INTERPRETATION This GSTM3 deletion is frequently observed in BrS patients and is associated with reduced INa, pointing to this as a novel potential genetic modifier/risk predictor for the development of the electrocardiographic and arrhythmic manifestations of BrS. FUNDING This work was supported by the Ministry of Science and Technology (107-2314-B-002-261-MY3 to J.M.J. Juang), and by grants HL47678, HL138103 and HL152201 from the National Institutes of Health to CA.
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Affiliation(s)
- Jyh-Ming Jimmy Juang
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Anna Binda
- University of Milano Bicocca School of Medicine and Surgery, Via Cadore, 48, 20900 Monza (MB), Italy
| | - Shyh-Jye Lee
- Department of Life Science, National Taiwan University, Taipei, Taiwan
| | - Juey-Jen Hwang
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wen-Jone Chen
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Yen-Bin Liu
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Lian-Yu Lin
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Chih-Chieh Yu
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Li-Ting Ho
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Hui-Chun Huang
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Ching-Yu Julius Chen
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Tzu-Pin Lu
- Institute of Epidemiology and Preventive Medicine, National Taiwan University, Taipei, Taiwan; Department of Public Health, National Taiwan University, Taipei, Taiwan.
| | - Liang-Chuan Lai
- Graduate Institute of Physiology, National Taiwan University, Taipei, Taiwan
| | - Shih-Fan Sherri Yeh
- Department of Environmental and Occupational Medicine, National Taiwan University Hospital, Hsin-Chu branch and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Ling-Ping Lai
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Eric Y Chuang
- Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan
| | - Ilaria Rivolta
- University of Milano Bicocca School of Medicine and Surgery, Via Cadore, 48, 20900 Monza (MB), Italy
| | - Charles Antzelevitch
- Lankenau Institute for Medical Research and Lankenau Heart Institute, Wynnewood, PA and Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA, USA.
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18
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Vivekanandam V, Männikkö R, Matthews E, Hanna MG. Improving genetic diagnostics of skeletal muscle channelopathies. Expert Rev Mol Diagn 2020; 20:725-736. [PMID: 32657178 DOI: 10.1080/14737159.2020.1782195] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
INTRODUCTION Skeletal muscle channelopathies are rare inherited conditions that cause significant morbidity and impact on quality of life. Some subsets have a mortality risk. Improved genetic methodology and understanding of phenotypes have improved diagnostic accuracy and yield. AREAS COVERED We discuss diagnostic advances since the advent of next-generation sequencing and the role of whole exome and genome sequencing. Advances in genotype-phenotype-functional correlations have improved understanding of inheritance and phenotypes. We outline new phenotypes, particularly in the pediatric setting and consider co-existing mutations that may act as genetic modifiers. We also discuss four newly identified genes associated with skeletal muscle channelopathies. EXPERT OPINION Next-generation sequencing using gene panels has improved diagnostic rates, identified new mutations, and discovered patients with co-existing pathogenic mutations ('double trouble'). This field has previously focussed on single genes, but we are now beginning to understand interactions between co-existing mutations, genetic modifiers, and their role in pathomechanisms. New genetic observations in pediatric presentations of channelopathies broadens our understanding of the conditions. Genetic and mechanistic advances have increased the potential to develop treatments.
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Affiliation(s)
- Vinojini Vivekanandam
- Queen Square Centre for Neuromuscular Diseases and Department of Neuromuscular Diseases, Queen Square Institute of Neurology, UCL and National Hospital for Neurology and Neurosurgery , London, UK
| | - Roope Männikkö
- Queen Square Centre for Neuromuscular Diseases and Department of Neuromuscular Diseases, Queen Square Institute of Neurology, UCL and National Hospital for Neurology and Neurosurgery , London, UK
| | - Emma Matthews
- Queen Square Centre for Neuromuscular Diseases and Department of Neuromuscular Diseases, Queen Square Institute of Neurology, UCL and National Hospital for Neurology and Neurosurgery , London, UK
| | - Michael G Hanna
- Queen Square Centre for Neuromuscular Diseases and Department of Neuromuscular Diseases, Queen Square Institute of Neurology, UCL and National Hospital for Neurology and Neurosurgery , London, UK
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19
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Hata T, Nagasaka T, Koh K, Tsuchiya M, Ichinose Y, Nan H, Shindo K, Takiyama Y. Pathological findings in a patient with non-dystrophic myotonia with a mutation of the SCN4A gene; a case report. BMC Neurol 2019; 19:125. [PMID: 31189464 PMCID: PMC6560775 DOI: 10.1186/s12883-019-1360-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 06/06/2019] [Indexed: 12/12/2022] Open
Abstract
Background Non-dystrophic myotonias (NDMs) are skeletal muscle disorders involving myotonia distinct from myotonic dystrophy. It has been reported that the muscle pathology is usually normal or comprises mild myopathic changes in NDMs. We describe various pathological findings mimicking those of myotonic dystrophy (DM) in biopsied muscle specimens from a patient with NDMs with a long disease duration. Case presentation A 66-year-old Japanease man presented eye closure myotonia, percussion myotonia and grip myotonia together with the warm-up phenomenon and cold aggravation from early childhood. On genetic analysis, a heterozygous mutation of the SCN4A gene (c.2065 C > T, p.L689F), with no mutation of the CLCN1, DMPK, or ZNF9/CNBP gene, was detected. He was diagnosed as having NDMs. A biopsy of the biceps brachii muscle showed increasing fiber size variation, internal nuclei, chained nuclei, necrotic fibers, fiber splitting, endomysial fibrosis, pyknotic nuclear clumps and disorganized intermyofibrillar networks. Sarcoplasmic masses, tubular aggregates and ragged-red fibers were absent. Conclusion It is noteworthy that the present study revealed various pathological findings resembling those seen in DM, although the pathology is usually normal or mild in NDMs. The pathological similarities may be due to muscular modification with long-standing myotonia or excessive muscle contraction based on abnormal channel activity. Electronic supplementary material The online version of this article (10.1186/s12883-019-1360-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Takanori Hata
- Department of Neurology, Faculty of Medicine, University of Yamanashi, 1110, Shimokato, Chuou-city, Yamanashi, 409-3898, Japan
| | - Takamura Nagasaka
- Department of Neurology, Faculty of Medicine, University of Yamanashi, 1110, Shimokato, Chuou-city, Yamanashi, 409-3898, Japan.
| | - Kishin Koh
- Department of Neurology, Faculty of Medicine, University of Yamanashi, 1110, Shimokato, Chuou-city, Yamanashi, 409-3898, Japan
| | - Mai Tsuchiya
- Department of Neurology, Faculty of Medicine, University of Yamanashi, 1110, Shimokato, Chuou-city, Yamanashi, 409-3898, Japan
| | - Yuta Ichinose
- Department of Neurology, Faculty of Medicine, University of Yamanashi, 1110, Shimokato, Chuou-city, Yamanashi, 409-3898, Japan
| | - Haitian Nan
- Department of Neurology, Faculty of Medicine, University of Yamanashi, 1110, Shimokato, Chuou-city, Yamanashi, 409-3898, Japan
| | - Kazumasa Shindo
- Department of Neurology, Faculty of Medicine, University of Yamanashi, 1110, Shimokato, Chuou-city, Yamanashi, 409-3898, Japan
| | - Yoshihisa Takiyama
- Department of Neurology, Faculty of Medicine, University of Yamanashi, 1110, Shimokato, Chuou-city, Yamanashi, 409-3898, Japan
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20
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Abstract
Myotonic dystrophy is an autosomal dominant muscular dystrophy not only associated with muscle weakness, atrophy, and myotonia but also prominent multisystem involvement. There are 2 similar, but distinct, forms of myotonic dystrophy; type 1 is caused by a CTG repeat expansion in the DMPK gene, and type 2 is caused by a CCTG repeat expansion in the CNBP gene. Type 1 is associated with distal limb, neck flexor, and bulbar weakness and results in different phenotypic subtypes with variable onset from congenital to very late-onset as well as variable signs and symptoms. The classically described adult-onset form is the most common. In contrast, myotonic dystrophy type 2 is adult-onset or late-onset, has proximal predominant muscle weakness, and generally has less severe multisystem involvement. In both forms of myotonic dystrophy, the best characterized disease mechanism is a RNA toxic gain-of-function during which RNA repeats form nuclear foci resulting in sequestration of RNA-binding proteins and, therefore, dysregulated splicing of premessenger RNA. There are currently no disease-modifying therapies, but clinical surveillance, preventative measures, and supportive treatments are used to reduce the impact of muscular impairment and other systemic involvement including cataracts, cardiac conduction abnormalities, fatigue, central nervous system dysfunction, respiratory weakness, dysphagia, and endocrine dysfunction. Exciting preclinical progress has been made in identifying a number of potential strategies including genome editing, small molecule therapeutics, and antisense oligonucleotide-based therapies to target the pathogenesis of type 1 and type 2 myotonic dystrophies at the DNA, RNA, or downstream target level.
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Affiliation(s)
- Samantha LoRusso
- Department of Neurology, The Ohio State University, 395 West 12th Avenue, Columbus, OH, 43210, USA
| | - Benjamin Weiner
- The Ohio State University College of Medicine, The Ohio State University, 370 West 9th Avenue, Columbus, OH, 43210, USA
| | - W David Arnold
- Department of Neurology, The Ohio State University, 395 West 12th Avenue, Columbus, OH, 43210, USA.
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21
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Abstract
Skeletal muscle channelopathies are rare heterogeneous diseases with marked genotypic and phenotypic variability. These disorders cause lifetime disability and impact quality of life. Despite advances in understanding of the molecular pathology of these disorders, the diverse phenotypic manifestations remain a challenge in diagnosis, therapeutic, genetic counseling, and research planning. Electrodiagnostic testing is useful in directing the diagnosis, but has several limitations: patient discomfort, time consuming, and significant overlap of findings in muscle channelopathies. Although genetic testing is the gold standard in making a definitive diagnosis, a mutation might not be identified in many patients with a well-supported clinical diagnosis of periodic paralysis. In the recent past, there have been landmark clinical trials in non-dystrophic myotonia and periodic paralysis which are encouraging as they demonstrate the ability of robust clinical research consortia to conduct well-controlled trials of rare diseases.
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Affiliation(s)
- Lauren Phillips
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas, 75390, USA
| | - Jaya R Trivedi
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas, 75390, USA.
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22
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SCN4A as modifier gene in patients with myotonic dystrophy type 2. Sci Rep 2018; 8:11058. [PMID: 30038349 PMCID: PMC6056531 DOI: 10.1038/s41598-018-29302-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 07/02/2018] [Indexed: 01/05/2023] Open
Abstract
A patient with an early severe myotonia diagnosed for Myotonic Dystrophy type 2 (DM2) was found bearing the combined effects of DM2 mutation and Nav1.4 S906T substitution. To investigate the mechanism underlying his atypical phenotype,whole-cell patch-clamp in voltage- and current-clamp mode was performed in myoblasts and myotubes obtained from his muscle biopsy. Results characterizing the properties of the sodium current and of the action potentials have been compared to those obtained in muscle cells derived from his mother, also affected by DM2, but without the S906T polymorphism. A faster inactivation kinetics and a +5 mV shift in the availability curve were found in the sodium current recorded in patient’s myoblasts compared to his mother. 27% of his myotubes displayed spontaneous activity. Patient’s myotubes showing a stable resting membrane potential had a lower rheobase current respect to the mother’s while the overshoot and the maximum slope of the depolarizing phase of action potential were higher. These findings suggest that SCN4A polymorphisms may be responsible for a higher excitability of DM2 patients sarcolemma, supporting the severe myotonic phenotype observed. We suggest SCN4A as a modifier factor and that its screening should be performed in DM2 patients with uncommon clinical features.
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23
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Portaro S, Naro A, Bramanti A, Leo A, Manuli A, Balletta T, Trinchera A, Bramanti P, Calabrò RS. Beyond the muscular involvement in non-dystrophic myotonias: The emerging role of neuromodulation. Restor Neurol Neurosci 2018; 36:459-467. [PMID: 29889082 DOI: 10.3233/rnn-170796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The central nervous system involvement, in terms of a maladaptive sensory-motor plasticity, is well known in patients with dystrophic myotonias (DMs). To date, there are no data suggesting a central nervous system involvement in non-dystrophic myotonias (NDMs). OBJECTIVE To investigate sensory-motor plasticity in patients with Myotonia Congenita (MC) and Paramyotonia Congenita (PMC) with or without mexiletine. METHODS Twelve patients with a clinical, genetic, and electromyographic evidence of MC, fifteen with PMC, and 25 healthy controls (HC) were included in the study. TMS on both primary motor cortices (M1) and a rapid paired associative stimulation (rPAS) paradigm were carried out to assess M1 excitability and sensory-motor plasticity. RESULTS patients showed a higher cortical excitability and a deterioration of the topographic specificity of rPAS aftereffects, as compared to HCs. There was no correlation among neurophysiological and clinical-demographic characteristics. Noteworthy, the patients who were under mexiletine showed a minor impairment of the topographic specificity of rPAS aftereffects as compared to those who did not take the drug. CONCLUSION our findings could suggest the deterioration of cortical sensory-motor plasticity in patients with NDMs as a trait of the disease.
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Affiliation(s)
| | - Antonino Naro
- IRCSS Centro Neurolesi Bonino Pulejo, Messina, Italy
| | - Alessia Bramanti
- Institute of Applied Sciences and Intelligent Systems "Edoardo Caianello" (ISASI), National Research Council of Italy, Messina, Italy
| | - Antonino Leo
- IRCSS Centro Neurolesi Bonino Pulejo, Messina, Italy
| | | | - Tina Balletta
- IRCSS Centro Neurolesi Bonino Pulejo, Messina, Italy
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24
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Wenninger S, Montagnese F, Schoser B. Core Clinical Phenotypes in Myotonic Dystrophies. Front Neurol 2018; 9:303. [PMID: 29770119 PMCID: PMC5941986 DOI: 10.3389/fneur.2018.00303] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 04/18/2018] [Indexed: 12/22/2022] Open
Abstract
Myotonic dystrophy type 1 (DM1) and type 2 (DM2) represent the most frequent multisystemic muscular dystrophies in adulthood. They are progressive, autosomal dominant diseases caused by an abnormal expansion of an unstable nucleotide repeat located in the non-coding region of their respective genes DMPK for DM1 and CNBP in DM2. Clinically, these multisystemic disorders are characterized by a high variability of muscular and extramuscular symptoms, often causing a delay in diagnosis. For both subtypes, many symptoms overlap, but some differences allow their clinical distinction. This article highlights the clinical core features of myotonic dystrophies, thus facilitating their early recognition and diagnosis. Particular attention will be given to signs and symptoms of muscular involvement, to issues related to respiratory impairment, and to the multiorgan involvement. This article is part of a Special Issue entitled “Beyond Borders: Myotonic Dystrophies—A European Perception.”
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Affiliation(s)
- Stephan Wenninger
- Friedrich-Baur-Institute, Klinikum der Universität München, Munich, Germany
| | | | - Benedikt Schoser
- Friedrich-Baur-Institute, Klinikum der Universität München, Munich, Germany
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25
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Thomas JD, Oliveira R, Sznajder ŁJ, Swanson MS. Myotonic Dystrophy and Developmental Regulation of RNA Processing. Compr Physiol 2018; 8:509-553. [PMID: 29687899 DOI: 10.1002/cphy.c170002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Myotonic dystrophy (DM) is a multisystemic disorder caused by microsatellite expansion mutations in two unrelated genes leading to similar, yet distinct, diseases. DM disease presentation is highly variable and distinguished by differences in age-of-onset and symptom severity. In the most severe form, DM presents with congenital onset and profound developmental defects. At the molecular level, DM pathogenesis is characterized by a toxic RNA gain-of-function mechanism that involves the transcription of noncoding microsatellite expansions. These mutant RNAs disrupt key cellular pathways, including RNA processing, localization, and translation. In DM, these toxic RNA effects are predominantly mediated through the modulation of the muscleblind-like and CUGBP and ETR-3-like factor families of RNA binding proteins (RBPs). Dysfunction of these RBPs results in widespread RNA processing defects culminating in the expression of developmentally inappropriate protein isoforms in adult tissues. The tissue that is the focus of this review, skeletal muscle, is particularly sensitive to mutant RNA-responsive perturbations, as patients display a variety of developmental, structural, and functional defects in muscle. Here, we provide a comprehensive overview of DM1 and DM2 clinical presentation and pathology as well as the underlying cellular and molecular defects associated with DM disease onset and progression. Additionally, fundamental aspects of skeletal muscle development altered in DM are highlighted together with ongoing and potential therapeutic avenues to treat this muscular dystrophy. © 2018 American Physiological Society. Compr Physiol 8:509-553, 2018.
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Affiliation(s)
- James D Thomas
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, Florida, USA
| | - Ruan Oliveira
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, Florida, USA
| | - Łukasz J Sznajder
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, Florida, USA
| | - Maurice S Swanson
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, Florida, USA
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26
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Santoro M, Fontana L, Maiorca F, Centofanti F, Massa R, Silvestri G, Novelli G, Botta A. Expanded [CCTG]n repetitions are not associated with abnormal methylation at the CNBP locus in myotonic dystrophy type 2 (DM2) patients. Biochim Biophys Acta Mol Basis Dis 2018; 1864:917-924. [DOI: 10.1016/j.bbadis.2017.12.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 12/21/2017] [Accepted: 12/28/2017] [Indexed: 01/10/2023]
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27
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Limpitikul W, Ong CS, Tomaselli GF. Neuromuscular Disease: Cardiac Manifestations and Sudden Death Risk. Card Electrophysiol Clin 2017; 9:731-747. [PMID: 29173414 DOI: 10.1016/j.ccep.2017.07.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Cardiovascular complications of neuromuscular diseases disproportionately affect the cardiac conduction system. Cardiomyopathy and cardiac arrhythmias produce significant morbidity and mortality. Patients with neuromuscular diseases should be carefully and frequently evaluated for the presence of bradycardia, heart block, and tachyarrhythmias. Preemptive treatment with permanent pacemakers or implanted defibrillators is appropriate in patients with conduction system disease or who are at risk for ventricular arrhythmias.
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Affiliation(s)
- Worawan Limpitikul
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Chin Siang Ong
- Department of Medicine, Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Gordon F Tomaselli
- Department of Medicine, Division of Cardiology, Johns Hopkins University School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA.
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28
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Montagnese F, Mondello S, Wenninger S, Kress W, Schoser B. Assessing the influence of age and gender on the phenotype of myotonic dystrophy type 2. J Neurol 2017; 264:2472-2480. [PMID: 29086017 DOI: 10.1007/s00415-017-8653-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Revised: 10/16/2017] [Accepted: 10/20/2017] [Indexed: 12/20/2022]
Abstract
This study aims to provide a detailed clinical characterization of a large cohort of myotonic dystrophy type 2 (DM2) patients investigating the influence of age and gender as modifying factors of DM2 phenotype. A retrospective study was conducted on 307 patients with genetically confirmed DM2. The following data were analyzed: (1) demographics, (2) clinical features (first symptom, muscular complaints, and multisystemic involvement), (3) diagnostics (serological tests, electromyography, and muscle biopsy). In this cohort (186 females, 121 males), a proximal weakness was the leading symptom at onset (55.4%), followed by myalgia (35.5%) and myotonia (25.4%). Proximal weakness was more common in women than men (64.9 vs. 43.8%, p = 0.0006), whereas being male was associated with higher odds for developing myalgia [OR 2.94 (95% CI 1.53-5.67)]. Patients with muscle weakness at onset were older than those with myalgia and myotonia (p < 0.0001), while each additional disease year was associated with 10% decrease in the odds of developing myotonia [OR 0.9 (95% CI 0.87-0.93)] and 6% decrease of myalgia [OR 0.94 (95% CI 0.91-0.97)]. Cataract and thyroid diseases occurred more frequently in women (p = 0.002 and p = 0.002, respectively). Early onset of DM2 is an independent risk factor for the occurrence of multisystemic involvement [OR 0.94 (95% CI 0.90-0.98)]. In this updated clinical description of DM2 emerges a profound gender and age influence on the phenotype, emphasizing that female gender and ageing may be associated with a higher disease burden. These age- and gender-specific differences should be considered in diagnostics, management, and future clinical studies of DM2.
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Affiliation(s)
- Federica Montagnese
- Friedrich-Baur-Institute, Department of Neurology, University Clinics Ludwig-Maximilians-University of Munich, Ziemssenstr. 1a, 80336, Munich, Germany
| | - Stefania Mondello
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Stephan Wenninger
- Friedrich-Baur-Institute, Department of Neurology, University Clinics Ludwig-Maximilians-University of Munich, Ziemssenstr. 1a, 80336, Munich, Germany
| | | | - Benedikt Schoser
- Friedrich-Baur-Institute, Department of Neurology, University Clinics Ludwig-Maximilians-University of Munich, Ziemssenstr. 1a, 80336, Munich, Germany.
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29
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Maggi L, Ravaglia S, Farinato A, Brugnoni R, Altamura C, Imbrici P, Camerino DC, Padovani A, Mantegazza R, Bernasconi P, Desaphy JF, Filosto M. Coexistence of CLCN1 and SCN4A mutations in one family suffering from myotonia. Neurogenetics 2017; 18:219-225. [PMID: 28993909 DOI: 10.1007/s10048-017-0525-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 10/01/2017] [Indexed: 01/28/2023]
Abstract
Non-dystrophic myotonias are characterized by clinical overlap making it challenging to establish genotype-phenotype correlations. We report clinical and electrophysiological findings in a girl and her father concomitantly harbouring single heterozygous mutations in SCN4A and CLCN1 genes. Functional characterization of N1297S hNav1.4 mutant was performed by patch clamp. The patients displayed a mild phenotype, mostly resembling a sodium channel myotonia. The CLCN1 c.501C>G (p.F167L) mutation has been already described in recessive pedigrees, whereas the SCN4A c.3890A>G (p.N1297S) variation is novel. Patch clamp experiments showed impairment of fast and slow inactivation of the mutated Nav1.4 sodium channel. The present findings suggest that analysis of both SCN4A and CLCN1 genes should be considered in myotonic patients with atypical clinical and neurophysiological features.
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Affiliation(s)
- Lorenzo Maggi
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133, Milan, Italy.
| | | | - Alessandro Farinato
- Department of Pharmacy and Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Raffaella Brugnoni
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133, Milan, Italy
| | - Concetta Altamura
- Department of Pharmacy and Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Paola Imbrici
- Department of Pharmacy and Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Diana Conte Camerino
- Department of Pharmacy and Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Alessandro Padovani
- Center for Neuromuscular Diseases and Neuropathies, Unit of Neurology ASST "Spedali Civili", University of Brescia, Brescia, Italy
| | - Renato Mantegazza
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133, Milan, Italy
| | - Pia Bernasconi
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133, Milan, Italy
| | - Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, University of Bari Aldo Moro, Bari, Italy
| | - Massimiliano Filosto
- Center for Neuromuscular Diseases and Neuropathies, Unit of Neurology ASST "Spedali Civili", University of Brescia, Brescia, Italy
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30
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Biomolecular diagnosis of myotonic dystrophy type 2: a challenging approach. J Neurol 2017; 264:1705-1714. [PMID: 28550479 DOI: 10.1007/s00415-017-8504-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 05/02/2017] [Indexed: 01/23/2023]
Abstract
Myotonic dystrophy type 1 (DM1) and type 2 (DM2) are the most common adult form of muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia, and multiorgan involvement. The onset and symptoms of the myotonic dystrophies are diverse, complicating their diagnoses and limiting a comprehensive approach to their clinical care. Diagnostic delay in DM2 is due not only to the heterogeneous phenotype and the aspecific onset but also to the unfamiliarity with the disorder by most clinicians. Moreover, the DM2 diagnostic odyssey is complicated by the difficulties to develop an accurate, robust, and cost-effective method for a routine molecular assay. The aim of this review is to underline by challenging approach the diagnostic limits and pitfalls that could results in failure to recognize the presence of DM2 disease. Understanding and preventing delays in DM2 diagnosis may facilitate family planning, improve symptom management in the short term, and facilitate more specific treatment in the long term.
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31
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Meola G, Cardani R. Myotonic dystrophy type 2 and modifier genes: an update on clinical and pathomolecular aspects. Neurol Sci 2017; 38:535-546. [PMID: 28078562 DOI: 10.1007/s10072-016-2805-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 12/22/2016] [Indexed: 12/20/2022]
Abstract
Myotonic dystrophy (DM) is the most common adult muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia, and multiorgan involvement. To date, two distinct forms caused by similar mutations in two different genes have been identified: myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2). Aberrant transcription and mRNA processing of multiple genes due to RNA-mediated toxic gain-of function has been suggested to cause the complex phenotype in DM1 and DM2. However, despite clinical and genetic similarities, DM1 and DM2 may be considered as distinct disorders. This review is an update on the latest findings specific to DM2, including explanations for the differences in clinical manifestations and pathophysiology between the two forms of myotonic dystrophies.
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Affiliation(s)
- Giovanni Meola
- Department of Biomedical Sciences for Health, University of Milan, IRCCS Policlinico San Donato, Piazza E. Malan, 1, San Donato Mil., 20097, Milan, Italy. .,Department of Neurology, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy.
| | - Rosanna Cardani
- Laboratory of Muscle Histopathology and Molecular Biology, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
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32
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Chardon JW, Jasmin BJ, Kothary R, Parks RJ. Report on the 3rd Ottawa International Conference on Neuromuscular Biology, Disease and Therapy - September 24-26, 2015, Ottawa, Canada. J Neuromuscul Dis 2016; 3:431-442. [PMID: 27854234 PMCID: PMC5123627 DOI: 10.3233/jnd-169001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Jodi Warman Chardon
- Department of Medicine, The Ottawa Hospital and University of Ottawa.,Centre for Neuromuscular Disease, University of Ottawa.,Department of Pediatrics (Genetics), Children's Hospital of Eastern Ontario.,Neurosciences and Clinical Epidemiology Programs, Ottawa Hospital Research Institute
| | - Bernard J Jasmin
- Centre for Neuromuscular Disease, University of Ottawa.,Department of Cellular and Molecular Medicine, University of Ottawa
| | - Rashmi Kothary
- Regenerative Medicine Program, Ottawa Hospital Research Institute.,Department of Medicine, The Ottawa Hospital and University of Ottawa.,Centre for Neuromuscular Disease, University of Ottawa.,Department of Cellular and Molecular Medicine, University of Ottawa
| | - Robin J Parks
- Regenerative Medicine Program, Ottawa Hospital Research Institute.,Department of Medicine, The Ottawa Hospital and University of Ottawa.,Department of Biochemistry, Microbiology and Immunology, University of Ottawa.,Centre for Neuromuscular Disease, University of Ottawa
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33
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Desaphy JF, Carbonara R, D'Amico A, Modoni A, Roussel J, Imbrici P, Pagliarani S, Lucchiari S, Lo Monaco M, Conte Camerino D. Translational approach to address therapy in myotonia permanens due to a new SCN4A mutation. Neurology 2016; 86:2100-8. [PMID: 27164696 PMCID: PMC4891212 DOI: 10.1212/wnl.0000000000002721] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 02/19/2016] [Indexed: 01/26/2023] Open
Abstract
Objective: We performed a clinical, functional, and pharmacologic characterization of the novel p.P1158L Nav1.4 mutation identified in a young girl presenting a severe myotonic phenotype. Methods: Wild-type hNav1.4 channel and P1158L mutant were expressed in tsA201 cells for functional and pharmacologic studies using patch-clamp. Results: The patient shows pronounced myotonia, slowness of movements, and generalized muscle hypertrophy. Because of general discomfort with mexiletine, she was given flecainide with satisfactory response. In vitro, mutant channels show a slower current decay and a rightward shift of the voltage dependence of fast inactivation. The voltage dependence of activation and slow inactivation were not altered. Mutant channels were less sensitive to mexiletine, whereas sensitivity to flecainide was not altered. The reduced inhibition of mutant channels by mexiletine was also observed using clinically relevant drug concentrations in a myotonic-like condition. Conclusions: Clinical phenotype and functional alterations of P1158L support the diagnosis of myotonia permanens. Impairment of fast inactivation is consistent with the possible role of the channel domain III S4-S5 loop in the inactivation gate docking site. The reduced sensitivity of P1158L to mexiletine may have contributed to the unsatisfactory response of the patient. The success of flecainide therapy underscores the usefulness of in vitro functional studies to help in the choice of the best drug for each individual.
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Affiliation(s)
- Jean-François Desaphy
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy.
| | - Roberta Carbonara
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Adele D'Amico
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Anna Modoni
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Julien Roussel
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Paola Imbrici
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Serena Pagliarani
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Sabrina Lucchiari
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Mauro Lo Monaco
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Diana Conte Camerino
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
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Czesnik D, Howells J, Negro F, Wagenknecht M, Hanner S, Farina D, Burke D, Paulus W. Increased HCN channel driven inward rectification in benign cramp fasciculation syndrome. Brain 2015; 138:3168-79. [DOI: 10.1093/brain/awv254] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 07/08/2015] [Indexed: 12/13/2022] Open
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Meola G, Cardani R. Myotonic Dystrophy Type 2: An Update on Clinical Aspects, Genetic and Pathomolecular Mechanism. J Neuromuscul Dis 2015; 2:S59-S71. [PMID: 27858759 PMCID: PMC5240594 DOI: 10.3233/jnd-150088] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Myotonic dystrophy (DM) is the most common adult muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia and multiorgan involvement. To date two distinct forms caused by similar mutations have been identified. Myotonic dystrophy type 1 (DM1, Steinert's disease) is caused by a (CTG)n expansion in DMPK, while myotonic dystrophy type 2 (DM2) is caused by a (CCTG)n expansion in CNBP. Despite clinical and genetic similarities, DM1 and DM2 are distinct disorders. The pathogenesis of DM is explained by a common RNA gain-of-function mechanism in which the CUG and CCUG repeats alter cellular function, including alternative splicing of various genes. However additional pathogenic mechanism like changes in gene expression, modifier genes, protein translation and micro-RNA metabolism may also contribute to disease pathology and to clarify the phenotypic differences between these two types of myotonic dystrophies.This review is an update on the latest findings specific to DM2, including explanations for the differences in clinical manifestations and pathophysiology between the two forms of myotonic dystrophies.
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Affiliation(s)
- Giovanni Meola
- Department of Biomedical Sciences for Health, IRCCS Policlinico San Donato, University of Milan, San Donato Milanese, Milan, Italy
- Laboratory of Muscle Histopathology and Molecular Biology, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
| | - Rosanna Cardani
- Laboratory of Muscle Histopathology and Molecular Biology, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
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