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Witting N, Andersen LK, Vissing J. Axial myopathy: an overlooked feature of muscle diseases. Brain 2015; 139:13-22. [DOI: 10.1093/brain/awv332] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 09/16/2015] [Indexed: 12/21/2022] Open
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van den Engel-Hoek L, de Groot IJM, de Swart BJM, Erasmus CE. Feeding and Swallowing Disorders in Pediatric Neuromuscular Diseases: An Overview. J Neuromuscul Dis 2015; 2:357-369. [PMID: 27858755 PMCID: PMC5240596 DOI: 10.3233/jnd-150122] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Feeding and swallowing problems in infants and children have a great impact on health and wellbeing. The aim of this study was to provide an overview of recognized feeding and swallowing problems in different groups of children with neuromuscular diseases, based on relevant literature and expert opinion, and to propose recommendations for the assessment and treatment of these problems. Almost all pediatric neuromuscular diseases are accompanied by feeding and swallowing problems during the different phases of deglutition, problems that give rise to a wide variety of signs and symptoms, which emphasizes the importance of a comprehensive feeding and swallowing assessment by a speech and language therapist.
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Affiliation(s)
- Lenie van den Engel-Hoek
- Donders Centre for Neuroscience, Department of Rehabilitation, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Imelda J M de Groot
- Donders Centre for Neuroscience, Department of Rehabilitation, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Bert J M de Swart
- Donders Centre for Neuroscience, Department of Rehabilitation, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Corrie E Erasmus
- Donders Centre for Neuroscience, Department of Neurology, Radboud University Medical Center, Nijmegen, The Netherlands
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Two families with MYH7 distal myopathy associated with cardiomyopathy and core formations. J Clin Neuromuscul Dis 2015; 16:164-9. [PMID: 25695922 DOI: 10.1097/cnd.0000000000000069] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
INTRODUCTION Laing distal myopathy is caused by MYH7 gene mutations. Multiple families have been reported with varying patterns of skeletal and cardiac involvement as well as histopathological findings. CASE SERIES We report 2 families with p.Glu1508del mutation with detailed electrophysiological and muscle pathology findings. RESULTS All patients displayed the classic phenotype with weakness starting in the anterior compartment of the legs with a "hanging great toe." It was followed by finger extensors involvement, relatively sparing the extensor indicis proprius, giving the appearance of a "pointing index" finger. All the affected individuals had a dilated cardiomyopathy and core formations on muscle biopsy. Unexpectedly, neurogenic changes were also observed in some individuals. Both families were initially misdiagnosed with either central core disease or hereditary neuropathy. CONCLUSIONS Recognizing the classic phenotype, screening for cardiac involvement that may be clinically silent, and determining the mode of inheritance help with selecting the appropriate genetic test.
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Luciano RDP, Puertas EB, Martins DE, Faloppa F, Del Curto D, Rodrigues LMR, Schmidt B, de Oliveira ASB, Wajchenberg M. Adolescent idiopathic scoliosis without limb weakness: a differential diagnosis of core myopathy? BMC Musculoskelet Disord 2015; 16:179. [PMID: 26242231 PMCID: PMC4524392 DOI: 10.1186/s12891-015-0629-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 07/13/2015] [Indexed: 11/10/2022] Open
Abstract
Background Core myopathies are a clinically and genetically heterogeneous group of congenital myopathies with the common defined histopathological feature of focally reduced oxidative activity on muscle biopsy. It has a low incidence, however, recent articles show broad clinical spectrum, suggesting that the real incidence should be considerably larger than previously described. Due to the important association between scoliosis and paravertebral muscle imbalance, numerous authors study, by biopsy of the spinal rotator muscles, potential changes that may elucidate the etiology of adolescent idiopathic scoliosis. Case presentation Two patients have been followed at Spine Group of Department of Orthopedics at Federal University of São Paulo, with an initial diagnosis of idiopathic scoliosis. Both patients had clinical and radiological findings compatible with it. The patients authorized, through the Term of Consent, intraoperative biopsy of muscle multifidus from the apex of the thoracic curve on concave and convex sides. After muscle biopsy was performed a histopathological analysis. As regard to the histopathological features: in both patients were identified, the presence of core structures in extensive areas with reduced oxidative activity running along the muscle fiber. Conclusions All patients with ‘idiopathic’ scoliosis deserve a careful neurological evaluation, even if they have minimal muscle symptoms in the extremities. The frequent occurrence of scoliosis in patients with CORE Myopathies, supports the thesis that the change in the paravertebral muscle fiber must be the underlying pathogenic factor in scoliosis and may help us understand the onset and progression of curves in patients previously diagnosed with idiopathic scoliosis.
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Affiliation(s)
- Rafael de Paiva Luciano
- Universidade Federal de Sao Paulo - Brazil - R. Borges Lagoa, 783, 5 andar, Vila Clementino, SP, Zip Code - 04038-031, Brazil.
| | - Eduardo Barros Puertas
- Universidade Federal de Sao Paulo - Brazil - R. Borges Lagoa, 783, 5 andar, Vila Clementino, SP, Zip Code - 04038-031, Brazil.
| | - Delio Eulalio Martins
- Universidade Federal de Sao Paulo - Brazil - R. Borges Lagoa, 783, 5 andar, Vila Clementino, SP, Zip Code - 04038-031, Brazil.
| | - Flavio Faloppa
- Universidade Federal de Sao Paulo - Brazil - R. Borges Lagoa, 783, 5 andar, Vila Clementino, SP, Zip Code - 04038-031, Brazil.
| | - David Del Curto
- Universidade Federal de Sao Paulo - Brazil - R. Borges Lagoa, 783, 5 andar, Vila Clementino, SP, Zip Code - 04038-031, Brazil.
| | - Luciano Miller Reis Rodrigues
- Universidade Federal de Sao Paulo - Brazil - R. Borges Lagoa, 783, 5 andar, Vila Clementino, SP, Zip Code - 04038-031, Brazil.
| | - Beny Schmidt
- Universidade Federal de Sao Paulo - Brazil - R. Borges Lagoa, 783, 5 andar, Vila Clementino, SP, Zip Code - 04038-031, Brazil.
| | - Acary Souza Bulle de Oliveira
- Universidade Federal de Sao Paulo - Brazil - R. Borges Lagoa, 783, 5 andar, Vila Clementino, SP, Zip Code - 04038-031, Brazil.
| | - Marcelo Wajchenberg
- Universidade Federal de Sao Paulo - Brazil - R. Borges Lagoa, 783, 5 andar, Vila Clementino, SP, Zip Code - 04038-031, Brazil.
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Rosenberg H, Pollock N, Schiemann A, Bulger T, Stowell K. Malignant hyperthermia: a review. Orphanet J Rare Dis 2015; 10:93. [PMID: 26238698 PMCID: PMC4524368 DOI: 10.1186/s13023-015-0310-1] [Citation(s) in RCA: 286] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Accepted: 07/22/2015] [Indexed: 02/06/2023] Open
Abstract
Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle that presents as a hypermetabolic response to potent volatile anesthetic gases such as halothane, sevoflurane, desflurane, isoflurane and the depolarizing muscle relaxant succinylcholine, and rarely, in humans, to stressors such as vigorous exercise and heat. The incidence of MH reactions ranges from 1:10,000 to 1: 250,000 anesthetics. However, the prevalence of the genetic abnormalities may be as great as one in 400 individuals. MH affects humans, certain pig breeds, dogs and horses. The classic signs of MH include hyperthermia, tachycardia, tachypnea, increased carbon dioxide production, increased oxygen consumption, acidosis, hyperkalaemia, muscle rigidity, and rhabdomyolysis, all related to a hypermetabolic response. The syndrome is likely to be fatal if untreated. An increase in end-tidal carbon dioxide despite increased minute ventilation provides an early diagnostic clue. In humans the syndrome is inherited in an autosomal dominant pattern, while in pigs it is autosomal recessive. Uncontrolled rise of myoplasmic calcium, which activates biochemical processes related to muscle activation leads to the pathophysiologic changes. In most cases, the syndrome is caused by a defect in the ryanodine receptor. Over 400 variants have been identified in the RYR1 gene located on chromosome 19q13.1, and at least 34 are causal for MH. Less than 1 % of variants have been found in CACNA1S but not all of these are causal. Diagnostic testing involves the in vitro contracture response of biopsied muscle to halothane, caffeine, and in some centres ryanodine and 4-chloro-m-cresol. Elucidation of the genetic changes has led to the introduction of DNA testing for susceptibility to MH. Dantrolene sodium is a specific antagonist and should be available wherever general anesthesia is administered. Increased understanding of the clinical manifestation and pathophysiology of the syndrome, has lead to the mortality decreasing from 80 % thirty years ago to <5 % in 2006.
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Affiliation(s)
- Henry Rosenberg
- Department of Medical Education and Clinical Research, Saint Barnabas Medical Center, Livingston, NJ, 07039, USA.
| | - Neil Pollock
- Department of Anesthesia and Intensive Care, Palmerston North Hospital, Palmerston North, New Zealand.
| | - Anja Schiemann
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
| | - Terasa Bulger
- Department of Anesthesia and Intensive Care, Palmerston North Hospital, Palmerston North, New Zealand.
| | - Kathryn Stowell
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
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Rokach O, Sekulic-Jablanovic M, Voermans N, Wilmshurst J, Pillay K, Heytens L, Zhou H, Muntoni F, Gautel M, Nevo Y, Mitrani-Rosenbaum S, Attali R, Finotti A, Gambari R, Mosca B, Jungbluth H, Zorzato F, Treves S. Epigenetic changes as a common trigger of muscle weakness in congenital myopathies. Hum Mol Genet 2015; 24:4636-47. [DOI: 10.1093/hmg/ddv195] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 05/22/2015] [Indexed: 12/13/2022] Open
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Centronuclear myopathies: genotype-phenotype correlation and frequency of defined genetic forms in an Italian cohort. J Neurol 2015; 262:1728-40. [PMID: 25957634 DOI: 10.1007/s00415-015-7757-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 04/17/2015] [Accepted: 04/20/2015] [Indexed: 10/23/2022]
Abstract
Centronuclear myopathies (CNMs) are a group of clinically and genetically heterogeneous muscle disorders. To date, mutation in 7 different genes has been reported to cause CNMs but 30 % of cases still remain genetically undefined. Genetic investigations are often expensive and time consuming. Clinical and morphological clues are needed to facilitate genetic tests and to choose the best approach for genetic screening. We aimed to describe genotype-phenotype correlation in an Italian cohort of patients affected by CNMs, to define the relative frequencies of its defined genetic forms and to draw a diagnostic algorithm to address genetic investigations. We recruited patients with CNMs from all the Italian tertiary neuromuscular centers following clinical and histological criteria. All selected patients were screened for the four 'canonical' genes related to CNMs: MTM1, DNM2, RYR1 and BIN1. Pathogenetic mutations were found in 38 of the 54 screened patients (70 %), mostly in patients with congenital onset (25 of 30 patients, 83 %): 15 in MTM1, 6 in DNM2, 3 in RYR1 and one in TTN. Among the 13 patients with a childhood-adolescence onset, mutations were found in 6 patients (46 %), all in DNM2. In the group of the 11 patients with adult onset, mutations were identified in 7 patients (63 %), again in DNM2, confirming that variants in this gene are relatively more common in late-onset phenotypes. The present study provides the relative molecular frequency of centronuclear myopathy and of its genetically defined forms in Italy and also proposes a diagnostic algorithm to be used in clinical practice to address genetic investigations.
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58
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Scalco RS, Gardiner AR, Pitceathly RD, Zanoteli E, Becker J, Holton JL, Houlden H, Jungbluth H, Quinlivan R. Rhabdomyolysis: a genetic perspective. Orphanet J Rare Dis 2015; 10:51. [PMID: 25929793 PMCID: PMC4522153 DOI: 10.1186/s13023-015-0264-3] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Accepted: 04/09/2015] [Indexed: 01/19/2023] Open
Abstract
Rhabdomyolysis (RM) is a clinical emergency characterized by fulminant skeletal muscle damage and release of intracellular muscle components into the blood stream leading to myoglobinuria and, in severe cases, acute renal failure. Apart from trauma, a wide range of causes have been reported including drug abuse and infections. Underlying genetic disorders are also a cause of RM and can often pose a diagnostic challenge, considering their marked heterogeneity and comparative rarity. In this paper we review the range of rare genetic defects known to be associated with RM. Each gene has been reviewed for the following: clinical phenotype, typical triggers for RM and recommended diagnostic approach. The purpose of this review is to highlight the most important features associated with specific genetic defects in order to aid the diagnosis of patients presenting with hereditary causes of recurrent RM.
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Affiliation(s)
- Renata Siciliani Scalco
- MRC Centre for Neuromuscular Diseases and Department of Molecular Neuroscience, University College London (UCL) Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK. .,Department of Neurology, HSL, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, Rio Grande do Sul, Brazil. .,CAPES Foundation, Ministry of Education of Brazil, Brasilia, DF, Brazil.
| | - Alice R Gardiner
- MRC Centre for Neuromuscular Diseases and Department of Molecular Neuroscience, University College London (UCL) Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK.
| | - Robert Ds Pitceathly
- MRC Centre for Neuromuscular Diseases and Department of Molecular Neuroscience, University College London (UCL) Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK. .,Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London (KCL), London, UK.
| | - Edmar Zanoteli
- Department of Neurology, School of Medicine, Universidade de São Paulo (FMUSP), São Paulo, SP, Brazil.
| | - Jefferson Becker
- Department of Neurology, HSL, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, Rio Grande do Sul, Brazil.
| | - Janice L Holton
- MRC Centre for Neuromuscular Diseases and Department of Molecular Neuroscience, University College London (UCL) Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK.
| | - Henry Houlden
- MRC Centre for Neuromuscular Diseases and Department of Molecular Neuroscience, University College London (UCL) Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK.
| | - Heinz Jungbluth
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London (KCL), London, UK. .,Department of Paediatric Neurology, Evelina Children's Hospital, Guy's & St Thomas NHS Foundation Trust, London, UK. .,Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section, King's College London, London, UK.
| | - Ros Quinlivan
- MRC Centre for Neuromuscular Diseases and Department of Molecular Neuroscience, University College London (UCL) Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK. .,Dubowitz Neuromuscular Centre, Great Ormond Street Hospital, London, UK.
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59
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Donkervoort S, Bonnemann C, Loeys B, Jungbluth H, Voermans N. The neuromuscular differential diagnosis of joint hypermobility. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2015; 169C:23-42. [DOI: 10.1002/ajmg.c.31433] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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60
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Forrest KM, Foulds N, Millar JS, Sutherland PD, Pappachan VJ, Holden S, Mein R, Hopkins PM, Jungbluth H. RYR1-related malignant hyperthermia with marked cerebellar involvement – A paradigm of heat-induced CNS injury? Neuromuscul Disord 2015; 25:138-40. [DOI: 10.1016/j.nmd.2014.10.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 10/19/2014] [Accepted: 10/27/2014] [Indexed: 10/24/2022]
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61
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Hanson MG, Wilde JJ, Moreno RL, Minic AD, Niswander L. Potassium dependent rescue of a myopathy with core-like structures in mouse. eLife 2015; 4. [PMID: 25564733 PMCID: PMC4309926 DOI: 10.7554/elife.02923] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 01/07/2015] [Indexed: 01/24/2023] Open
Abstract
Myopathies decrease muscle functionality. Mutations in ryanodine receptor 1 (RyR1) are often associated with myopathies with microscopic core-like structures in the muscle fiber. In this study, we identify a mouse RyR1 model in which heterozygous animals display clinical and pathological hallmarks of myopathy with core-like structures. The RyR1 mutation decreases sensitivity to activated calcium release and myoplasmic calcium levels, subsequently affecting mitochondrial calcium and ATP production. Mutant muscle shows a persistent potassium leak and disrupted expression of regulators of potassium homeostasis. Inhibition of KATP channels or increasing interstitial potassium by diet or FDA-approved drugs can reverse the muscle weakness, fatigue-like physiology and pathology. We identify regulators of potassium homeostasis as biomarkers of disease that may reveal therapeutic targets in human patients with myopathy of central core disease (CCD). Altogether, our results suggest that amelioration of potassium leaks through potassium homeostasis mechanisms may minimize muscle damage of myopathies due to certain RyR1 mutations.
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Affiliation(s)
- M Gartz Hanson
- Department of Pediatrics, University of Colorado, Anschutz Medical Campus, Aurora, United States
| | - Jonathan J Wilde
- Department of Pediatrics, University of Colorado, Anschutz Medical Campus, Aurora, United States
| | - Rosa L Moreno
- Department of Physiology, University of Colorado, Anschutz Medical Campus, Aurora, United States
| | - Angela D Minic
- Department of Pediatrics, University of Colorado, Anschutz Medical Campus, Aurora, United States
| | - Lee Niswander
- Department of Pediatrics, University of Colorado, Anschutz Medical Campus, Aurora, United States
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62
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de Haro-Hernández B, Macouzet-Sánchez C, Rodríguez-Balderrama I, de la O-Cavazos M. Congenital fiber-type disproportion myopathy: A case study. MEDICINA UNIVERSITARIA 2015. [DOI: 10.1016/j.rmu.2014.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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63
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Ravenscroft G, Laing NG, Bönnemann CG. Pathophysiological concepts in the congenital myopathies: blurring the boundaries, sharpening the focus. ACTA ACUST UNITED AC 2014; 138:246-68. [PMID: 25552303 DOI: 10.1093/brain/awu368] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The congenital myopathies are a diverse group of genetic skeletal muscle diseases, which typically present at birth or in early infancy. There are multiple modes of inheritance and degrees of severity (ranging from foetal akinesia, through lethality in the newborn period to milder early and later onset cases). Classically, the congenital myopathies are defined by skeletal muscle dysfunction and a non-dystrophic muscle biopsy with the presence of one or more characteristic histological features. However, mutations in multiple different genes can cause the same pathology and mutations in the same gene can cause multiple different pathologies. This is becoming ever more apparent now that, with the increasing use of next generation sequencing, a genetic diagnosis is achieved for a greater number of patients. Thus, considerable genetic and pathological overlap is emerging, blurring the classically established boundaries. At the same time, some of the pathophysiological concepts underlying the congenital myopathies are moving into sharper focus. Here we explore whether our emerging understanding of disease pathogenesis and underlying pathophysiological mechanisms, rather than a strictly gene-centric approach, will provide grounds for a different and perhaps complementary grouping of the congenital myopathies, that at the same time could help instil the development of shared potential therapeutic approaches. Stemming from recent advances in the congenital myopathy field, five key pathophysiology themes have emerged: defects in (i) sarcolemmal and intracellular membrane remodelling and excitation-contraction coupling; (ii) mitochondrial distribution and function; (iii) myofibrillar force generation; (iv) atrophy; and (v) autophagy. Based on numerous emerging lines of evidence from recent studies in cell lines and patient tissues, mouse models and zebrafish highlighting these unifying pathophysiological themes, here we review the congenital myopathies in relation to these emerging pathophysiological concepts, highlighting both areas of overlap between established entities, as well as areas of distinction within single gene disorders.
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Affiliation(s)
- Gianina Ravenscroft
- 1 Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia, Australia
| | - Nigel G Laing
- 1 Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia, Australia
| | - Carsten G Bönnemann
- 2 National Institute of Neurological Disorders and Stroke/NIH, Porter Neuroscience Research Centre, Bethesda, MD, USA
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Jungbluth H, Gautel M. Pathogenic mechanisms in centronuclear myopathies. Front Aging Neurosci 2014; 6:339. [PMID: 25566070 PMCID: PMC4271577 DOI: 10.3389/fnagi.2014.00339] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 12/02/2014] [Indexed: 12/30/2022] Open
Abstract
Centronuclear myopathies (CNMs) are a genetically heterogeneous group of inherited neuromuscular disorders characterized by clinical features of a congenital myopathy and abundant central nuclei as the most prominent histopathological feature. The most common forms of congenital myopathies with central nuclei have been attributed to X-linked recessive mutations in the MTM1 gene encoding myotubularin (“X-linked myotubular myopathy”), autosomal-dominant mutations in the DNM2 gene encoding dynamin-2 and the BIN1 gene encoding amphiphysin-2 (also named bridging integrator-1, BIN1, or SH3P9), and autosomal-recessive mutations in BIN1, the RYR1 gene encoding the skeletal muscle ryanodine receptor, and the TTN gene encoding titin. Models to study and rescue the affected cellular pathways are now available in yeast, C. elegans, drosophila, zebrafish, mouse, and dog. Defects in membrane trafficking have emerged as a key pathogenic mechanisms, with aberrant T-tubule formation, abnormalities of triadic assembly, and disturbance of the excitation–contraction machinery the main downstream effects studied to date. Abnormal autophagy has recently been recognized as another important collateral of defective membrane trafficking in different genetic forms of CNM, suggesting an intriguing link to primary disorders of defective autophagy with overlapping histopathological features. The following review will provide an overview of clinical, histopathological, and genetic aspects of the CNMs in the context of the key pathogenic mechanism, outline unresolved questions, and indicate promising future lines of enquiry.
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Affiliation(s)
- Heinz Jungbluth
- Neuromuscular Service, Department of Paediatric Neurology, Evelina Children's Hospital, St Thomas' Hospital , London , UK ; Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London , London , UK ; Randall Division of Cell and Molecular Biophysics and Cardiovascular Division, King's College London BHF Centre of Research Excellence , London , UK
| | - Mathias Gautel
- Randall Division of Cell and Molecular Biophysics and Cardiovascular Division, King's College London BHF Centre of Research Excellence , London , UK
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Abstract
The triad is a skeletal muscle substructure responsible for the regulation of excitation-contraction coupling. It is formed by the close apposition of the T-tubule and the terminal sarcoplasmic reticulum. A rapidly growing list of skeletal myopathies, here referred to as triadopathies, are caused by gene mutations in components of the triad. These disorders, at their root, are caused by defects in excitation contraction coupling and intracellular calcium homeostasis. Secondary abnormalities in triad structure and/or function are also reported in several muscle diseases, most notably certain muscular dystrophies. This review highlights the current understanding of both primary and secondary triadopathies, and identifies important concepts yet to be fully addressed in the field. The emphasis of the review is both on the pathogenesis of triadopathies and their potential treatment.
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Affiliation(s)
- James J Dowling
- Division of Neurology and Genetics and Genome Biology Program, Hospital for Sick Children, Toronto, ON, Canada,
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66
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Fernandez-Fuente M, Terracciano CM, Martin-Duque P, Brown SC, Vassaux G, Piercy RJ. Calcium homeostasis in myogenic differentiation factor 1 (MyoD)-transformed, virally-transduced, skin-derived equine myotubes. PLoS One 2014; 9:e105971. [PMID: 25148524 PMCID: PMC4141859 DOI: 10.1371/journal.pone.0105971] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 07/30/2014] [Indexed: 11/19/2022] Open
Abstract
Dysfunctional skeletal muscle calcium homeostasis plays a central role in the pathophysiology of several human and animal skeletal muscle disorders, in particular, genetic disorders associated with ryanodine receptor 1 (RYR1) mutations, such as malignant hyperthermia, central core disease, multiminicore disease and certain centronuclear myopathies. In addition, aberrant skeletal muscle calcium handling is believed to play a pivotal role in the highly prevalent disorder of Thoroughbred racehorses, known as Recurrent Exertional Rhabdomyolysis. Traditionally, such defects were studied in human and equine subjects by examining the contractile responses of biopsied muscle strips exposed to caffeine, a potent RYR1 agonist. However, this test is not widely available and, due to its invasive nature, is potentially less suitable for valuable animals in training or in the human paediatric setting. Furthermore, increasingly, RYR1 gene polymorphisms (of unknown pathogenicity and significance) are being identified through next generation sequencing projects. Consequently, we have investigated a less invasive test that can be used to study calcium homeostasis in cultured, skin-derived fibroblasts that are converted to the muscle lineage by viral transduction with a MyoD (myogenic differentiation 1) transgene. Similar models have been utilised to examine calcium homeostasis in human patient cells, however, to date, there has been no detailed assessment of the cells’ calcium homeostasis, and in particular, the responses to agonists and antagonists of RYR1. Here we describe experiments conducted to assess calcium handling of the cells and examine responses to treatment with dantrolene, a drug commonly used for prophylaxis of recurrent exertional rhabdomyolysis in horses and malignant hyperthermia in humans.
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Affiliation(s)
- Marta Fernandez-Fuente
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Sciences and Services, Royal Veterinary College, London, United Kingdom
| | - Cesare M. Terracciano
- Laboratory of Cell Electrophysiology, Imperial College London, Myocardial Function, National Heart and Lung Institute, Hammersmith Hospital, London, United Kingdom
| | - Pilar Martin-Duque
- Universidad Francisco de Vitoria, Facultad de Ciencias Biosanitarias: Pozuelo de Alarcón (Madrid), Madrid, Spain
| | - Susan C. Brown
- Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom
| | - Georges Vassaux
- Laboratoire TIRO, UMRE 4320, iBEB, DSV, Commissariat a’ l’Energie Atomique, Nice, France
| | - Richard J. Piercy
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Sciences and Services, Royal Veterinary College, London, United Kingdom
- * E-mail:
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Cuperman T, Fernandes SA, Lourenço NCV, Yamamoto LU, Silva HCA, Pavanello RCM, Yamamoto GL, Zatz M, Oliveira ASB, Vainzof M. Silent polymorphisms in the RYR1 gene do not modify the phenotype of the p.4898 I>T pathogenic mutation in central core disease: a case report. BMC Res Notes 2014; 7:487. [PMID: 25084811 PMCID: PMC4124474 DOI: 10.1186/1756-0500-7-487] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 07/25/2014] [Indexed: 12/21/2022] Open
Abstract
Background Central core disease is a congenital myopathy, characterized by presence of central core-like areas in muscle fibers. Patients have mild or moderate weakness, hypotonia and motor developmental delay. The disease is caused by mutations in the human ryanodine receptor gene (RYR1), which encodes a calcium-release channel. Since the RYR1 gene is huge, containing 106 exons, mutation screening has been limited to three ‘hot spots’, with particular attention to the C-terminal region. Recent next- generation sequencing methods are now identifying multiple numbers of variants in patients, in which interpretation and phenotype prevision is difficult. Case presentation In a Brazilian Caucasian family, clinical, histopathological and molecular analysis identified a new case of central core disease in a 48-year female. Sanger sequencing of the C-terminal region of the RYR1 gene identified two different missense mutations: c.14256 A > C polymorphism in exon 98 and c.14693 T > C in exon 102, which have already been described as pathogenic. Trans-position of the 2 mutations was confirmed because patient’s daughter, mother and sister carried only the exon 98’s mutation, a synonymous variant that was subsequently found in the frequency of 013–0,05 of alleles. Further next generation sequencing study of the whole RYR1 gene in the patient revealed the presence of additional 5 common silent polymorphisms in homozygosis and 8 polymorphisms in heterozygosis. Conclusions Considering that patient’s relatives showed no pathologic phenotype, and the phenotype presented by the patient is within the range observed in other central core disease patients with the same mutation, it was concluded that the c.14256 A > C polymorphism alone is not responsible for disease, and the associated additional silent polymorphisms are not acting as modifiers of the primary pathogenic mutation in the affected patient. The case described above illustrates the present reality where new methods for wide genome screening are becoming more accessible and able to identify a great variety of mutations and polymorphisms of unknown function in patients and their families.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Mariz Vainzof
- Laboratory of Muscle Proteins and Comparative Histopathology, Human Genome Research Center, Biosciences Institute, University of São Paulo, R, do Matão, 106 - Cidade Universitária, São Paulo, SP CEP 05508-900, Brazil.
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68
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Rocha J, Taipa R, Melo Pires M, Oliveira J, Santos R, Santos M. Ryanodine myopathies without central cores--clinical, histopathologic, and genetic description of three cases. Pediatr Neurol 2014; 51:275-8. [PMID: 24950660 DOI: 10.1016/j.pediatrneurol.2014.04.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 04/18/2014] [Accepted: 04/24/2014] [Indexed: 10/25/2022]
Abstract
BACKGROUND Mutations in ryanodine receptor 1 gene (RYR1) are frequent causes of myopathies. They classically present with central core disease; however, clinical variability and histopathologic overlap are being increasingly recognized. PATIENTS Patient 1 is a 15-year-old girl with mild proximal, four-limb weakness from age 5, presenting with a progressive scoliosis starting at age 10. Patient 2 is an 18-year-old girl with progressively worsening muscle hypotrophy and mild proximal, four-limb weakness. She developed a rapidly progressive scoliosis from age 11 and needed surgical treatment at age 14 years. Patient 3 is an 11-year-old boy with moderate proximal limb weakness and progressive neck flexor weakness, first noticed at age 2. Muscle biopsies revealed type 1 fiber predominance (Patients 1 and 2) or abnormal type 1 fiber uniformity (Patient 3). Different RYR1 variants were identified in all patients. In Patients 1 and 3, these changes were validated as being pathogenic. CONCLUSIONS These patients illustrate early-onset, progressive myopathies with predominant axial involvement. Histopathologic findings were abnormal but not specific for a diagnosis, particularly central core myopathy. Genetic testing helped broaden the range of phenotypes included in the RYR1-related myopathies. Our patients reinforce the need to recognize the broad histopathologic variability of RYR1-related myopathies and sometimes lack of pathognomonic findings that may reduce the diagnostic threshold of this disease. We suggest that the predominance of type 1 fibers and involvement of axial muscles may be an important element to consider the RYR1 gene as candidate.
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Affiliation(s)
- João Rocha
- Department of Neurology, Hospital de Braga, Braga, Portugal.
| | - Ricardo Taipa
- Neuropathology Unit, Centro Hospitalar do Porto, Porto, Portugal
| | | | - Jorge Oliveira
- Molecular Genetics Unit, Centro de Genética Médica Dr. Jacinto Magalhães, Centro Hospitalar do Porto, Porto, Portugal
| | - Rosário Santos
- Molecular Genetics Unit, Centro de Genética Médica Dr. Jacinto Magalhães, Centro Hospitalar do Porto, Porto, Portugal
| | - Manuela Santos
- Neuromuscular Diseases Unit, Department of Pediatric Neurology, Centro Hospitalar do Porto, Porto, Portugal
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Abstract
With advances in the genetics of muscle disease, the term, muscular dystrophy, has expanded to include mutations in an increasing large list of genes. This review discusses the genetics, pathophysiology, and potential treatments of the most common forms of muscular dystrophy: Duchenne muscular dystrophy, Becker muscular dystrophy, facioscapulohumeral muscular dystrophy, and myotonic dystrophy. Other forms of muscular dystrophy and other genetic muscle disorders are also discussed to provide an overview of this complex clinical problem.
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Affiliation(s)
- Perry B Shieh
- Department of Neurology, UCLA Medical Center, 300 Medical Plaza, Suite B-200, Los Angeles, CA 90095, USA.
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70
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Megaconial congenital muscular dystrophy due to loss-of-function mutations in choline kinase β. Curr Opin Neurol 2014; 26:536-43. [PMID: 23945283 DOI: 10.1097/wco.0b013e328364c82d] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
PURPOSE OF REVIEW Recessive mutations in CHKB cause a megaconial congenital muscular dystrophy whose most characteristic feature is mitochondrial enlargement at the periphery of muscle fibers and loss of mitochondria in the center of muscle fibers. This review will summarize clinicopathological features, genetic cause, and biochemical abnormalities of the disease, trying to decipher the mechanism of this complex disorder. RECENT FINDINGS Since our report of CHKB mutations found in 15 cases with megaconial congenital muscular dystrophy from Japanese, Turkish, and British populations, we have further identified two British and one French patients. One African-American patient has also been reported by another group. All patients have relatively homogenous phenotype although severity varies to some extent. The peculiar distribution pattern of enlarged mitochondria on muscle section seems to be due to a compensatory mechanism after the elimination of functionally defective mitochondria by mitophagy. SUMMARY CHKB encodes choline kinase β, an enzyme that catalyzes the first de-novo biosynthetic step of phosphatidylcholine, the most abundant phospholipid in the eukaryotic membrane. The identification of a new muscle disease caused by the defect in phospholipid metabolism will pave the way for a novel biological pathway that connects phospholipid metabolism, mitochondria biology, and muscular dystrophy.
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71
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Chauveau C, Bonnemann CG, Julien C, Kho AL, Marks H, Talim B, Maury P, Arne-Bes MC, Uro-Coste E, Alexandrovich A, Vihola A, Schafer S, Kaufmann B, Medne L, Hübner N, Foley AR, Santi M, Udd B, Topaloglu H, Moore SA, Gotthardt M, Samuels ME, Gautel M, Ferreiro A. Recessive TTN truncating mutations define novel forms of core myopathy with heart disease. Hum Mol Genet 2013; 23:980-91. [PMID: 24105469 DOI: 10.1093/hmg/ddt494] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Core myopathies (CM), the main non-dystrophic myopathies in childhood, remain genetically unexplained in many cases. Heart disease is not considered part of the typical CM spectrum. No congenital heart defect has been reported, and childhood-onset cardiomyopathy has been documented in only two CM families with homozygous mutations of the TTN gene. TTN encodes titin, a giant protein of striated muscles. Recently, heterozygous TTN truncating mutations have also been reported as a major cause of dominant dilated cardiomyopathy. However, relatively few TTN mutations and phenotypes are known, and titin pathophysiological role in cardiac and skeletal muscle conditions is incompletely understood. We analyzed a series of 23 families with congenital CM and primary heart disease using TTN M-line-targeted sequencing followed in selected patients by whole-exome sequencing and functional studies. We identified seven novel homozygous or compound heterozygous TTN mutations (five in the M-line, five truncating) in 17% patients. Heterozygous parents were healthy. Phenotype analysis identified four novel titinopathies, including cardiac septal defects, left ventricular non-compaction, Emery-Dreifuss muscular dystrophy or arthrogryposis. Additionally, in vitro studies documented the first-reported absence of a functional titin kinase domain in humans, leading to a severe antenatal phenotype. We establish that CM are associated with a large range of heart conditions of which TTN mutations are a major cause, thereby expanding the TTN mutational and phenotypic spectrum. Additionally, our results suggest titin kinase implication in cardiac morphogenesis and demonstrate that heterozygous TTN truncating mutations may not manifest unless associated with a second mutation, reassessing the paradigm of their dominant expression.
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Affiliation(s)
- Claire Chauveau
- Inserm, U787 Myology group, Institut de Myologie, Groupe Hospitalier Pitié-Salpêtrière, Paris, France
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72
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Brislin RP, Theroux MC. Core myopathies and malignant hyperthermia susceptibility: a review. Paediatr Anaesth 2013; 23:834-41. [PMID: 23617272 DOI: 10.1111/pan.12175] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/09/2013] [Indexed: 11/30/2022]
Abstract
The core myopathies are a subset of myopathies that present in infancy with hypotonia and muscle weakness. They were formerly considered a rare type of congenital myopathy but are now recognized as being more prevalent. Due to their genetic linkage to mutations in the ryanodine receptor gene (RYR1), core myopathies (in particular, central core disease) carry a high risk of malignant hyperthermia susceptibility. In this review article, we describe the phenotypical, genetic, and histopathological characteristics of core myopathies and further describe the currently understood nature of their risk of malignant hyperthermia. We also review the level of suspicion a clinician should exhibit with a child who has a possible core myopathy or other congenital myopathy presenting for an anesthetic prior to a definitive genetic analysis. For this review article, we performed literature searches using the key words anesthesiology, core myopathies, pediatric neurology, malignant hyperthermia, genetics, ryanodine receptor, and molecular biology. We also relied on literature accumulated by the two authors, who served as hotline consultants for the Malignant Hyperthermia Hotline of the Malignant Hyperthermia Association of the United States (MHAUS) for the past 12 years.
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Affiliation(s)
- Robert P Brislin
- Department of Anesthesiology and Critical Care Medicine, Nemours/Alfred I. duPont Hospital for Children, Wilmington, DE 19899, USA.
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73
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Katsetos CD, Koutzaki S, Melvin JJ. Mitochondrial dysfunction in neuromuscular disorders. Semin Pediatr Neurol 2013; 20:202-15. [PMID: 24331362 DOI: 10.1016/j.spen.2013.10.010] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
This review deciphers aspects of mitochondrial (mt) dysfunction among nosologically, pathologically, and genetically diverse diseases of the skeletal muscle, lower motor neuron, and peripheral nerve, which fall outside the traditional realm of mt cytopathies. Special emphasis is given to well-characterized mt abnormalities in collagen VI myopathies (Ullrich congenital muscular dystrophy and Bethlem myopathy), megaconial congenital muscular dystrophy, limb-girdle muscular dystrophy type 2 (calpainopathy), centronuclear myopathies, core myopathies, inflammatory myopathies, spinal muscular atrophy, Charcot-Marie-Tooth neuropathy type 2, and drug-induced peripheral neuropathies. Among inflammatory myopathies, mt abnormalities are more prominent in inclusion body myositis and a subset of polymyositis with mt pathology, both of which are refractory to corticosteroid treatment. Awareness is raised about instances of phenotypic mimicry between cases harboring primary mtDNA depletion, in the context of mtDNA depletion syndrome, and established neuromuscular disorders such as spinal muscular atrophy. A substantial body of experimental work, derived from animal models, attests to a major role of mitochondria (mt) in the early process of muscle degeneration. Common mechanisms of mt-related cell injury include dysregulation of the mt permeability transition pore opening and defective autophagy. The therapeutic use of mt permeability transition pore modifiers holds promise in various neuromuscular disorders, including muscular dystrophies.
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Affiliation(s)
- Christos D Katsetos
- Department of Pediatrics, Drexel University College of Medicine, St. Christopher's Hospital for Children, Philadelphia, PA; Department of Pathology and Laboratory Medicine, Drexel University College of Medicine, Philadelphia, PA; Department of Neurology, Drexel University College of Medicine, Philadelphia, PA.
| | - Sirma Koutzaki
- Department of Pathology and Laboratory Medicine, Drexel University College of Medicine, Philadelphia, PA
| | - Joseph J Melvin
- Department of Pediatrics, Drexel University College of Medicine, St. Christopher's Hospital for Children, Philadelphia, PA; Department of Neurology, Drexel University College of Medicine, Philadelphia, PA
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Jungbluth H, Wallgren-Pettersson C, Laporte JF. 198th ENMC International Workshop: 7th Workshop on Centronuclear (Myotubular) myopathies, 31st May - 2nd June 2013, Naarden, The Netherlands. Neuromuscul Disord 2013; 23:1033-43. [PMID: 24070817 DOI: 10.1016/j.nmd.2013.08.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 08/19/2013] [Indexed: 12/23/2022]
Affiliation(s)
- Heinz Jungbluth
- Department of Paediatric Neurology - Neuromuscular Service, Evelina Children's Hospital, St Thomas' Hospital, London, UK; Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section, London, UK; Clinical Neuroscience Division, King's College, London, UK
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75
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Myopathic changes in malignant hyperthermia-susceptible patients. Can J Anaesth 2013; 60:955-9. [DOI: 10.1007/s12630-013-0011-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 07/03/2013] [Indexed: 10/26/2022] Open
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Abstract
Congenital myopathies are severe muscle disorders affecting adults as well as children in all populations. The diagnosis of congenital myopathies is constrained by strong clinical and genetic heterogeneity. Moreover, the majority of patients present with unspecific histological features, precluding purposive molecular diagnosis and demonstrating the need for an alternative and more efficient diagnostic approach. We used exome sequencing complemented by histological and ultrastructural analysis of muscle biopsies to identify the causative mutations in eight patients with clinically different skeletal muscle pathologies, ranging from a fatal neonatal myopathy to a mild and slowly progressive myopathy with adult onset. We identified RYR1 (ryanodine receptor) mutations in six patients and NEB (nebulin) mutations in two patients. We found novel missense and nonsense mutations, unraveled small insertions/deletions and confirmed their impact on splicing and mRNA/protein stability. Histological and ultrastructural findings of the muscle biopsies of the patients validated the exome sequencing results. We provide the evidence that an integrated strategy combining exome sequencing with clinical and histopathological investigations overcomes the limitations of the individual approaches to allow a fast and efficient diagnosis, accelerating the patient's access to a better healthcare and disease management. This is of particular interest for the diagnosis of congenital myopathies, which involve very large genes like RYR1 and NEB as well as genetic and phenotypic heterogeneity.
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77
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Brandom BW, Bina S, Wong CA, Wallace T, Visoiu M, Isackson PJ, Vladutiu GD, Sambuughin N, Muldoon SM. Ryanodine receptor type 1 gene variants in the malignant hyperthermia-susceptible population of the United States. Anesth Analg 2013; 116:1078-1086. [PMID: 23558838 PMCID: PMC3633164 DOI: 10.1213/ane.0b013e31828a71ff] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Mutations in the ryanodine receptor type 1 gene (RYR1) that encodes the skeletal muscle-specific intracellular calcium (Ca(2+)) release channel are a cause of malignant hyperthermia (MH). In this study, we examined RYR1 mutations in a large number of North American MH-susceptible (MHS) subjects without prior genetic diagnosis. METHODS RYR1 was examined in 120 unrelated MHS subjects from the United States in a tiered manner. The α-1 subunit of the dihydropyridine receptor gene (CACNA1S) was screened for 4 variants in subjects in whom no abnormality was found in ≥ 100 exons of RYR1. RESULTS Ten known causative MH mutations were found in 26 subjects. Variants of uncertain significance in RYR1 were found in 36 subjects, 16 of which are novel. Novel variants in both RYR1 and CACNA1S were found in the 1 subject who died of MH. Two RYR1 variants were found in 4 subjects. Variants of uncertain significance were found outside and inside the hotspots of RYR1. Maximal contractures in the caffeine-halothane contracture test were greater in those who had a known MH mutation or variant of uncertain significance in RYR1 than in those who did not. CONCLUSIONS The identification of novel RYR1 variants and previously observed RYR1 variants of uncertain significance in independent MHS families is necessary for demonstrating the significance of these variants for MH susceptibility and supports the need for functional studies of these variants. Continued reporting of the clinical phenotypes of MH is necessary for interpretation of genetic findings, especially because the pathogenicity of most of these genetic variants associated with MHS remains to be elucidated.
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Affiliation(s)
- Barbara W Brandom
- From the Department of Anesthesiology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania; Department of Anesthesiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland; Department of Anesthesiology, Northwestern University, Chicago, Illinois; Children's Hospital, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania; and Departments of Pediatrics, Neurology, Pathology and Anatomical Sciences, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York
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78
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Bharucha-Goebel DX, Santi M, Medne L, Zukosky K, Zukosky K, Dastgir J, Shieh PB, Winder T, Tennekoon G, Finkel RS, Dowling JJ, Monnier N, Bönnemann CG. Severe congenital RYR1-associated myopathy: the expanding clinicopathologic and genetic spectrum. Neurology 2013; 80:1584-9. [PMID: 23553484 DOI: 10.1212/wnl.0b013e3182900380] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To report a series of 11 patients on the severe end of the spectrum of ryanodine receptor 1 (RYR1) gene-related myopathy, in order to expand the clinical, histologic, and genetic heterogeneity associated with this group of patients. METHODS Eleven patients evaluated in the neonatal period with severe neonatal-onset RYR1-associated myopathy confirmed by genetic testing were ascertained. Clinical features, molecular testing results, muscle imaging, and muscle histology are reviewed. RESULTS Clinical features associated with the severe neonatal presentation of RYR1-associated myopathy included decreased fetal movement, hypotonia, poor feeding, respiratory involvement, arthrogryposis, and ophthalmoplegia in 3 patients, and femur fractures or hip dislocation at birth. Four patients had dominant RYR1 mutations, and 7 had recessive RYR1 mutations. One patient had a cleft palate, and another a congenital rigid spine phenotype-findings not previously described in the literature in patients with early-onset RYR1 mutations. Six patients who underwent muscle ultrasound showed relative sparing of the rectus femoris muscle. Histologically, all patients with dominant mutations had classic central cores on muscle biopsy. Patients with recessive mutations showed great histologic heterogeneity, including fibrosis, variation in fiber size, skewed fiber typing, very small fibers, and nuclear internalization with or without ill-defined cores. CONCLUSIONS This series confirms and expands the clinical and histologic variability associated with severe congenital RYR1-associated myopathy. Both dominant and recessive mutations of the RYR1 gene can result in a severe neonatal-onset phenotype, but more clinical and histologic heterogeneity has been seen in those with recessive RYR1 gene mutations. Central cores are not obligatory histologic features in recessive RYR1 mutations. Sparing of the rectus femoris muscle on imaging should prompt evaluation for RYR1-associated myopathy in the appropriate clinical context.
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79
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Joyce NC, Oskarsson B, Jin LW. Muscle biopsy evaluation in neuromuscular disorders. Phys Med Rehabil Clin N Am 2013; 23:609-31. [PMID: 22938878 DOI: 10.1016/j.pmr.2012.06.006] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
This article reviews the indications for a muscle biopsy, and then gives a step-by-step description of the processes of muscle selection through to interpreting the biopsy report. The article aims to aid the clinician in preparing for a muscle biopsy procedure to avoid common pitfalls and obtain optimal results from this minimally invasive procedure. The basic anatomic structure of normal muscle is reviewed to provide a foundation for understanding common patterns of pathologic change observed in muscle disease and common and disease-specific histopathologic findings are presented, focusing on a select group of neuromuscular diseases.
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Affiliation(s)
- Nanette C Joyce
- Department of Physical Medicine and Rehabilitation, University of California Davis School of Medicine, 4860 Y Street, Suite 3850, Sacramento, CA 95817, USA.
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TREAT-NMD workshop: pattern recognition in genetic muscle diseases using muscle MRI: 25-26 February 2011, Rome, Italy. Neuromuscul Disord 2013; 22 Suppl 2:S42-53. [PMID: 22980768 DOI: 10.1016/j.nmd.2012.08.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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81
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Amoasii L, Hnia K, Chicanne G, Brech A, Cowling BS, Müller MM, Schwab Y, Koebel P, Ferry A, Payrastre B, Laporte J. Myotubularin and PtdIns3P remodel the sarcoplasmic reticulum in muscle in vivo. J Cell Sci 2013; 126:1806-19. [PMID: 23444364 DOI: 10.1242/jcs.118505] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The sarcoplasmic reticulum (SR) is a specialized form of endoplasmic reticulum (ER) in skeletal muscle and is essential for calcium homeostasis. The mechanisms involved in SR remodeling and maintenance of SR subdomains are elusive. In this study, we identified myotubularin (MTM1), a phosphoinositide phosphatase mutated in X-linked centronuclear myopathy (XLCNM, or myotubular myopathy), as a key regulator of phosphatidylinositol 3-monophosphate (PtdIns3P) levels at the SR. MTM1 is predominantly located at the SR cisternae of the muscle triads, and Mtm1-deficient mouse muscles and myoblasts from XLCNM patients exhibit abnormal SR/ER networks. In vivo modulation of MTM1 enzymatic activity in skeletal muscle using ectopic expression of wild-type or a dead-phosphatase MTM1 protein leads to differential SR remodeling. Active MTM1 is associated with flat membrane stacks, whereas dead-phosphatase MTM1 mutant promotes highly curved cubic membranes originating from the SR and enriched in PtdIns3P. Overexpression of a tandem FYVE domain with high affinity for PtdIns3P alters the shape of the SR cisternae at the triad. Our findings, supported by the parallel analysis of the Mtm1-null mouse and an in vivo study, reveal a direct function of MTM1 enzymatic activity in SR remodeling and a key role for PtdIns3P in promoting SR membrane curvature in skeletal muscle. We propose that alteration in SR remodeling is a primary cause of X-linked centronuclear myopathy. The tight regulation of PtdIns3P on specific membrane subdomains may be a general mechanism to control membrane curvature.
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Affiliation(s)
- Leonela Amoasii
- Department of Translational Medicine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, 67404 Illkirch, France
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A novel late-onset axial myopathy associated with mutations in the skeletal muscle ryanodine receptor (RYR1) gene. J Neurol 2013; 260:1504-10. [DOI: 10.1007/s00415-012-6817-7] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 12/17/2012] [Accepted: 12/19/2012] [Indexed: 11/27/2022]
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Yasuda T, Delbono O, Wang ZM, Messi ML, Girard T, Urwyler A, Treves S, Zorzato F. JP-45/JSRP1 variants affect skeletal muscle excitation-contraction coupling by decreasing the sensitivity of the dihydropyridine receptor. Hum Mutat 2012; 34:184-90. [PMID: 22927026 DOI: 10.1002/humu.22209] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 08/14/2012] [Indexed: 11/12/2022]
Abstract
JP-45 (also JP45; encoded by JSRP1) is an integral protein constituent of the skeletal muscle sarcoplasmic reticulum junctional face membrane interacting with Ca(v) 1.1 (the α.1 subunit of the voltage-sensing dihydropyridine receptor, DHPR) and the luminal calcium-binding protein calsequestrin. Two JSRP1 variants have been found in the human population: c.323C>T (p.P108L) in exon 5 and c.449G>C (p.G150A) in exon 6, but nothing is known concerning the incidence of these polymorphisms in the general population or in patients with neuromuscular diseases nor the impact of the polymorphisms on excitation-contraction (EC) coupling. In the present report, we investigated the frequencies of these two JSRP1 polymorphisms in the Swiss malignant hyperthermia population and studied the functional impact of the variants on EC coupling. Our results show that the polymorphisms are equally distributed among malignant hyperthermia negative, malignant hyperthermia equivocal, and malignant hyperthermia susceptible individuals. Interestingly, however, the presence of either one of these JP-45 variants decreased the sensitivity of the DHPR to activation. The presence of a JSRP1 variant may explain the variable phenotype seen in patients with malignant hyperthermia carrying the same mutation and, more importantly, may counteract the hypersensitivity of EC coupling caused by mutations in the RYR1 gene.
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Affiliation(s)
- Toshimichi Yasuda
- Department of Anesthesiology and Critical Care, Hiroshima University, Manami-ku, Hiroshima, Japan
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