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Carvalho A, Costa C, Pinto M, Taipa R, Gonçalves A, Oliveira ME, Ferreira S, Ribeiro JA. X-Linked Myotubular Myopathy: A Novel Mutation Expanding the Genotypic Spectrum of a Phenotypically Heterogeneous Myopathy. J Pediatr Genet 2023; 12:258-262. [PMID: 37575650 PMCID: PMC10421687 DOI: 10.1055/s-0041-1728745] [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: 12/13/2020] [Accepted: 03/09/2021] [Indexed: 10/21/2022]
Abstract
X-linked myotubular myopathy (XLMTM), a centronuclear congenital myopathy secondary to pathogenic variants in the MTM1 gene encoding myotubularin, is typically recognized for its classic and severe phenotype which includes neonatal hypotonia, severe muscle weakness, long-term ventilator dependence, markedly delayed gross motor milestones with inability to independently ambulate, and a high neonatal and childhood mortality. However, milder congenital forms of the condition and other phenotypes are recognized. We describe a 6-year-old boy with a mild XLMTM phenotype with independent gait and no respiratory insufficiency even in the neonatal period. The child has a hemizygous novel splice site variant in the MTM1 gene (c.232-25A > T) whose pathogenicity was confirmed by cDNA studies (exon 5 skipping) and muscle biopsy findings. We also compared the phenotype of our patient with the few reported cases that presented a mild XLMTM phenotype and no respiratory distress at birth, and discussed the potential mechanisms underlying this phenotype such as the presence of residual expression of the normal myotubularin transcript.
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Affiliation(s)
- Andreia Carvalho
- Neurology Department, Centro Hospitalar de Vila Nova de Gaia–Espinho, Portugal
| | - Carmen Costa
- Pediatric Neurology Department, Centro de Desenvolvimento da Criança, Hospital Pediátrico de Coimbra - Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
| | - Miguel Pinto
- Neuropathology Unit, Hospital de Santo António - Centro Hospitalar Universitário do Porto, Porto, Portugal
| | - Ricardo Taipa
- Neuropathology Unit, Hospital de Santo António - Centro Hospitalar Universitário do Porto, Porto, Portugal
- Unit for Multidisciplinary Research In Biomedicine, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Ana Gonçalves
- Unit for Multidisciplinary Research In Biomedicine, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
- Molecular Genetics Unit, Centro de Genética Médica Dr. Jacinto Magalhães, Centro Hospitalar Universitário do Porto, Porto, Portugal
| | - Márcia E. Oliveira
- Unit for Multidisciplinary Research In Biomedicine, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
- Molecular Genetics Unit, Centro de Genética Médica Dr. Jacinto Magalhães, Centro Hospitalar Universitário do Porto, Porto, Portugal
| | - Sofia Ferreira
- Pulmonology Department, Hospital Pediátrico de Coimbra - Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
| | - Joana Afonso Ribeiro
- Pediatric Neurology Department, Centro de Desenvolvimento da Criança, Hospital Pediátrico de Coimbra - Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
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Novel Splicing Mutation in MTM1 Leading to Two Abnormal Transcripts Causes Severe Myotubular Myopathy. Int J Mol Sci 2022; 23:ijms231810274. [PMID: 36142184 PMCID: PMC9499315 DOI: 10.3390/ijms231810274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 09/01/2022] [Accepted: 09/05/2022] [Indexed: 11/17/2022] Open
Abstract
X-linked myotubular myopathy (XLMTM) is a severe form of centronuclear myopathy, characterized by generalized weakness and respiratory insufficiency, associated with pathogenic variants in the MTM1 gene. NGS targeted sequencing on the DNA of a three-month-old child affected by XLMTM identified the novel hemizygous MTM1 c.1261-5T>G intronic variant, which interferes with the normal splicing process, generating two different abnormal transcripts simultaneously expressed in the patient’s muscular cells. The first aberrant transcript, induced by the activation of a cryptic splice site in intron 11, includes four intronic nucleotides upstream of exon 12, resulting in a shift in the transcript reading frame and introducing a new premature stop codon in the catalytic domain of the protein (p.Arg421SerfsTer7). The second aberrant MTM1 transcript, due to the lack of recognition of the 3′ acceptor splice site of intron 11 from the spliceosome complex, leads to the complete skipping of exon 12. We expanded the genotypic spectrum of XLMTM underlying the importance of intron−exons boundaries sequencing in male patients affected by XLMTM.
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Keegan NP, Wilton SD, Fletcher S. Analysis of Pathogenic Pseudoexons Reveals Novel Mechanisms Driving Cryptic Splicing. Front Genet 2022; 12:806946. [PMID: 35140743 PMCID: PMC8819188 DOI: 10.3389/fgene.2021.806946] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 12/09/2021] [Indexed: 12/16/2022] Open
Abstract
Understanding pre-mRNA splicing is crucial to accurately diagnosing and treating genetic diseases. However, mutations that alter splicing can exert highly diverse effects. Of all the known types of splicing mutations, perhaps the rarest and most difficult to predict are those that activate pseudoexons, sometimes also called cryptic exons. Unlike other splicing mutations that either destroy or redirect existing splice events, pseudoexon mutations appear to create entirely new exons within introns. Since exon definition in vertebrates requires coordinated arrangements of numerous RNA motifs, one might expect that pseudoexons would only arise when rearrangements of intronic DNA create novel exons by chance. Surprisingly, although such mutations do occur, a far more common cause of pseudoexons is deep-intronic single nucleotide variants, raising the question of why these latent exon-like tracts near the mutation sites have not already been purged from the genome by the evolutionary advantage of more efficient splicing. Possible answers may lie in deep intronic splicing processes such as recursive splicing or poison exon splicing. Because these processes utilize intronic motifs that benignly engage with the spliceosome, the regions involved may be more susceptible to exonization than other intronic regions would be. We speculated that a comprehensive study of reported pseudoexons might detect alignments with known deep intronic splice sites and could also permit the characterisation of novel pseudoexon categories. In this report, we present and analyse a catalogue of over 400 published pseudoexon splice events. In addition to confirming prior observations of the most common pseudoexon mutation types, the size of this catalogue also enabled us to suggest new categories for some of the rarer types of pseudoexon mutation. By comparing our catalogue against published datasets of non-canonical splice events, we also found that 15.7% of pseudoexons exhibit some splicing activity at one or both of their splice sites in non-mutant cells. Importantly, this included seven examples of experimentally confirmed recursive splice sites, confirming for the first time a long-suspected link between these two splicing phenomena. These findings have the potential to improve the fidelity of genetic diagnostics and reveal new targets for splice-modulating therapies.
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Affiliation(s)
- Niall P. Keegan
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA, Australia
- Centre for Neuromuscular and Neurological Disorders, Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA, Australia
- *Correspondence: Niall P. Keegan,
| | - Steve D. Wilton
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA, Australia
- Centre for Neuromuscular and Neurological Disorders, Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA, Australia
| | - Sue Fletcher
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA, Australia
- Centre for Neuromuscular and Neurological Disorders, Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA, Australia
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Gómez-Oca R, Cowling BS, Laporte J. Common Pathogenic Mechanisms in Centronuclear and Myotubular Myopathies and Latest Treatment Advances. Int J Mol Sci 2021; 22:11377. [PMID: 34768808 PMCID: PMC8583656 DOI: 10.3390/ijms222111377] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Accepted: 10/18/2021] [Indexed: 01/18/2023] Open
Abstract
Centronuclear myopathies (CNM) are rare congenital disorders characterized by muscle weakness and structural defects including fiber hypotrophy and organelle mispositioning. The main CNM forms are caused by mutations in: the MTM1 gene encoding the phosphoinositide phosphatase myotubularin (myotubular myopathy), the DNM2 gene encoding the mechanoenzyme dynamin 2, the BIN1 gene encoding the membrane curvature sensing amphiphysin 2, and the RYR1 gene encoding the skeletal muscle calcium release channel/ryanodine receptor. MTM1, BIN1, and DNM2 proteins are involved in membrane remodeling and trafficking, while RyR1 directly regulates excitation-contraction coupling (ECC). Several CNM animal models have been generated or identified, which confirm shared pathological anomalies in T-tubule remodeling, ECC, organelle mispositioning, protein homeostasis, neuromuscular junction, and muscle regeneration. Dynamin 2 plays a crucial role in CNM physiopathology and has been validated as a common therapeutic target for three CNM forms. Indeed, the promising results in preclinical models set up the basis for ongoing clinical trials. Another two clinical trials to treat myotubular myopathy by MTM1 gene therapy or tamoxifen repurposing are also ongoing. Here, we review the contribution of the different CNM models to understanding physiopathology and therapy development with a focus on the commonly dysregulated pathways and current therapeutic targets.
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Affiliation(s)
- Raquel Gómez-Oca
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), 67400 Illkirch, France;
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, 67400 Illkirch, France
- Centre National de la Recherche Scientifique (CNRS), UMR7104, 67400 Illkirch, France
- Strasbourg University, 67081 Strasbourg, France
- Dynacure, 67400 Illkirch, France;
| | | | - Jocelyn Laporte
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), 67400 Illkirch, France;
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, 67400 Illkirch, France
- Centre National de la Recherche Scientifique (CNRS), UMR7104, 67400 Illkirch, France
- Strasbourg University, 67081 Strasbourg, France
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Reumers SFI, Braun F, Spillane JE, Böhm J, Pennings M, Schouten M, van der Kooi AJ, Foley AR, Bönnemann CG, Kamsteeg EJ, Erasmus CE, Schara-Schmidt U, Jungbluth H, Voermans NC. Spectrum of Clinical Features in X-Linked Myotubular Myopathy Carriers: An International Questionnaire Study. Neurology 2021; 97:e501-e512. [PMID: 34011573 DOI: 10.1212/wnl.0000000000012236] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 04/26/2021] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To characterize the spectrum of clinical features in a cohort of X-linked myotubular myopathy (XL-MTM) carriers, including prevalence, genetic features, clinical symptoms, and signs, as well as associated disease burden. METHODS We performed a cross-sectional online questionnaire study among XL-MTM carriers. Participants were recruited from patient associations, medical centers, and registries in the United Kingdom, Germany, and the Netherlands. We used a custom-made questionnaire, the Checklist Individual Strength (CIS), the Frenchay Activities Index (FAI), the Short Form 12 (SF-12) health survey, and the McGill Pain Questionnaire. Carriers were classified as manifesting or nonmanifesting on the basis of self-reported ambulation and muscle weakness. RESULTS The prevalence of manifesting carriers in this study population (n = 76) was 51%, subdivided into mild (independent ambulation, 39%), moderate (assisted ambulation, 9%), and severe (wheelchair dependent, 3%) phenotypes. In addition to muscle weakness, manifesting carriers frequently reported fatigue (70%) and exercise intolerance (49%). Manifesting carriers scored higher on the overall CIS (p = 0.001), the fatigue subscale (p < 0.001), and least severe pain subscale (p = 0.005) than nonmanifesting carriers. They scored lower on the FAI (p = 0.005) and the physical component of the SF-12 health survey (p < 0.001). CONCLUSIONS The prevalence of manifesting XL-MTM carriers may be higher than currently assumed, most having a mild phenotype and a wide variety of symptoms. Manifesting carriers are particularly affected by fatigue, limitations of daily activities, pain, and reduced quality of life. Our findings should increase awareness and provide useful information for health care providers and future clinical trials.
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Affiliation(s)
- Stacha F I Reumers
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Frederik Braun
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Jennifer E Spillane
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Johann Böhm
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Maartje Pennings
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Meyke Schouten
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Anneke J van der Kooi
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - A Reghan Foley
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Carsten G Bönnemann
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Erik-Jan Kamsteeg
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Corrie E Erasmus
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Ulrike Schara-Schmidt
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Heinz Jungbluth
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK
| | - Nicol C Voermans
- From the Department of Neurology (S.F.I.R., N.C.V.), Donders Institute for Brain, Cognition and Behaviour, Department of Human Genetics (M.P., E.-j.K.), and Department of Clinical Genetics (M.S.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatric Neurology and Neuromuscular Centre (F.B., U.S.-S.), University Hospital Essen, Germany; Department of Neurology (J.E.S.), St. Thomas Hospital, and Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, UK; Department of Neurobiology and Genetics (J.B.), Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Department of Neurology (A.J.v.d.K.), Amsterdam University Medical Center, Neuroscience Institute, the Netherlands; Neuromuscular and Neurogenetic Disorders of Childhood Section (A.R.F., C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Department of Pediatric Neurology (C.E.E.), Radboud University Medical Center Amalia Children's Hospital, Nijmegen, the Netherlands; and Muscle Signalling Section (H.J.), Randall Division for Cell and Molecular Biophysics, King's College, London, UK.
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6
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Lawal TA, Todd JJ, Witherspoon JW, Bönnemann CG, Dowling JJ, Hamilton SL, Meilleur KG, Dirksen RT. Ryanodine receptor 1-related disorders: an historical perspective and proposal for a unified nomenclature. Skelet Muscle 2020; 10:32. [PMID: 33190635 PMCID: PMC7667763 DOI: 10.1186/s13395-020-00243-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 08/18/2020] [Indexed: 12/14/2022] Open
Abstract
The RYR1 gene, which encodes the sarcoplasmic reticulum calcium release channel or type 1 ryanodine receptor (RyR1) of skeletal muscle, was sequenced in 1988 and RYR1 variations that impair calcium homeostasis and increase susceptibility to malignant hyperthermia were first identified in 1991. Since then, RYR1-related myopathies (RYR1-RM) have been described as rare, histopathologically and clinically heterogeneous, and slowly progressive neuromuscular disorders. RYR1 variants can lead to dysfunctional RyR1-mediated calcium release, malignant hyperthermia susceptibility, elevated oxidative stress, deleterious post-translational modifications, and decreased RyR1 expression. RYR1-RM-affected individuals can present with delayed motor milestones, contractures, scoliosis, ophthalmoplegia, and respiratory insufficiency. Historically, RYR1-RM-affected individuals were diagnosed based on morphologic features observed in muscle biopsies including central cores, cores and rods, central nuclei, fiber type disproportion, and multi-minicores. However, these histopathologic features are not always specific to RYR1-RM and often change over time. As additional phenotypes were associated with RYR1 variations (including King-Denborough syndrome, exercise-induced rhabdomyolysis, lethal multiple pterygium syndrome, adult-onset distal myopathy, atypical periodic paralysis with or without myalgia, mild calf-predominant myopathy, and dusty core disease) the overlap among diagnostic categories is ever increasing. With the continuing emergence of new clinical subtypes along the RYR1 disease spectrum and reports of adult-onset phenotypes, nuanced nomenclatures have been reported (RYR1- [related, related congenital, congenital] myopathies). In this narrative review, we provide historical highlights of RYR1 research, accounts of the main diagnostic disease subtypes and propose RYR1-related disorders (RYR1-RD) as a unified nomenclature to describe this complex and evolving disease spectrum.
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Affiliation(s)
- Tokunbor A Lawal
- Tissue Injury Branch, National Institute of Nursing Research, National Institutes of Health, Bethesda, MD, USA.
| | - Joshua J Todd
- Tissue Injury Branch, National Institute of Nursing Research, National Institutes of Health, Bethesda, MD, USA
| | - Jessica W Witherspoon
- Tissue Injury Branch, National Institute of Nursing Research, National Institutes of Health, Bethesda, MD, USA
| | - Carsten G Bönnemann
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - James J Dowling
- Departments of Paediatrics and Molecular Genetics, Hospital for Sick Children and University of Toronto, Toronto, Canada
| | - Susan L Hamilton
- Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Katherine G Meilleur
- Tissue Injury Branch, National Institute of Nursing Research, National Institutes of Health, Bethesda, MD, USA
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY, USA
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7
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Fitzgerald J, Feist C, Dietz P, Moore S, Basel D. A Deep Intronic Variant Activates a Pseudoexon in the MTM1 Gene in a Family with X-Linked Myotubular Myopathy. Mol Syndromol 2020; 11:264-270. [PMID: 33505229 DOI: 10.1159/000510286] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 07/19/2020] [Indexed: 12/22/2022] Open
Abstract
We report a novel intronic variant in the MTM1 gene in 4 males in a family with severe X-linked myotubular myopathy. The A>G variant in deep intronic space activates a cryptic 5' donor splice site resulting in the inclusion of a 48-bp pseudoexon into the mature MTM1 mRNA. The variant is present in all affected males, absent in unaffected males, and heterozygous in the mother of the affected males. The included intronic sequence contains a premature stop codon, and experiments using a translational inhibitor indicate that the mutant mRNAs undergo nonsense-mediated decay. We conclude that affected males produce no, or low, levels of MTM1 mRNA likely leading to a significant reduction of myotubularin-1 protein resulting in the severe neonatal myopathy present in this family. The study highlights the need to consider noncoding variants in genomic screening in families with X-linked myotubular myopathy.
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Affiliation(s)
- Jamie Fitzgerald
- Department of Orthopedic Surgery, Bone and Joint Center, Henry Ford Hospital System, Detroit, Michigan, USA.,Department of Orthopedics and Rehabilitation, Oregon Health and Science University, Portland, Oregon, USA.,Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, Oregon, USA
| | - Cori Feist
- Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, Oregon, USA
| | - Paula Dietz
- Department of Orthopedic Surgery, Bone and Joint Center, Henry Ford Hospital System, Detroit, Michigan, USA
| | - Stephen Moore
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, Oregon, USA.,Knight Diagnostic Laboratories, Oregon Health and Science University, Portland, Oregon, USA
| | - Donald Basel
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, Oregon, USA.,Department of Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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8
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Pathogenic deep intronic MTM1 variant activates a pseudo-exon encoding a nonsense codon resulting in severe X-linked myotubular myopathy. Eur J Hum Genet 2020; 29:61-66. [PMID: 32862205 DOI: 10.1038/s41431-020-00715-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 06/30/2020] [Accepted: 08/21/2020] [Indexed: 12/25/2022] Open
Abstract
X-linked myotubular myopathy (XLMTM) is a severe congenital myopathy characterised by generalised weakness and respiratory insufficiency. XLMTM is associated with pathogenic variants in MTM1; a gene encoding the lipid phosphatase myotubularin. Whole genome sequencing (WGS) of an exome-negative male proband with severe hypotonia, respiratory insufficiency and centralised nuclei on muscle biopsy identified a deep intronic MTM1 variant NG_008199.1(NM_000252.2):c.1468-577A>G, which strengthened a cryptic 5' splice site (A>G substitution at the +5 position). Muscle RNA sequencing was non-diagnostic due to low read depth. Reverse transcription PCR (RT-PCR) of muscle RNA confirmed the c.1468-577A>G variant activates inclusion of a pseudo-exon encoding a premature stop codon into all detected MTM1 transcripts. Western blot analysis establishes deficiency of myotubularin protein, consistent with the severe XLMTM phenotype. We expand the genotypic spectrum of XLMTM and highlight benefits of screening non-coding regions of MTM1 in male probands with phenotypically concordant XLMTM who remain undiagnosed following exome sequencing.
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9
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Tasfaout H, Cowling BS, Laporte J. Centronuclear myopathies under attack: A plethora of therapeutic targets. J Neuromuscul Dis 2019; 5:387-406. [PMID: 30103348 PMCID: PMC6218136 DOI: 10.3233/jnd-180309] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Centronuclear myopathies are a group of congenital myopathies characterized by severe muscle weakness, genetic heterogeneity, and defects in the structural organization of muscle fibers. Their names are derived from the central position of nuclei on biopsies, while they are at the fiber periphery under normal conditions. No specific therapy exists yet for these debilitating diseases. Mutations in the myotubularin phosphoinositides phosphatase, the GTPase dynamin 2, or amphiphysin 2 have been identified to cause respectively X-linked centronuclear myopathies (also called myotubular myopathy) or autosomal dominant and recessive forms. Mutations in additional genes, as RYR1, TTN, SPEG or CACNA1S, were linked to phenotypes that can overlap with centronuclear myopathies. Numerous animal models of centronuclear myopathies have been studied over the last 15 years, ranging from invertebrate to large mammalian models. Their characterization led to a partial understanding of the pathomechanisms of these diseases and allowed the recent validation of therapeutic proof-of-concepts. Here, we review the different therapeutic strategies that have been tested so far for centronuclear myopathies, some of which may be translated to patients.
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Affiliation(s)
- Hichem Tasfaout
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, Illkirch, France
- Centre National de la Recherche Scientifique (CNRS), UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
| | - Belinda S. Cowling
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, Illkirch, France
- Centre National de la Recherche Scientifique (CNRS), UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
| | - Jocelyn Laporte
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, Illkirch, France
- Centre National de la Recherche Scientifique (CNRS), UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
- Correspondence to: Jocelyn Laporte, Tel.: 33 0 388653412; E-mail:
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10
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Single Intramuscular Injection of AAV-shRNA Reduces DNM2 and Prevents Myotubular Myopathy in Mice. Mol Ther 2018; 26:1082-1092. [PMID: 29506908 DOI: 10.1016/j.ymthe.2018.02.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 02/02/2018] [Accepted: 02/09/2018] [Indexed: 12/28/2022] Open
Abstract
Myotubular myopathy, or X-linked centronuclear myopathy, is a severe muscle disorder representing a significant burden for patients and their families. It is clinically characterized by neonatal and severe muscle weakness and atrophy. Mutations in the myotubularin (MTM1) gene cause myotubular myopathy, and no specific curative treatment is available. We previously found that dynamin 2 (DNM2) is upregulated in both Mtm1 knockout and patient muscle samples, whereas its reduction through antisense oligonucleotides rescues the clinical and histopathological features of this myopathy in mice. Here, we propose a novel approach targeting Dnm2 mRNA. We screened and validated in vitro and in vivo several short hairpin RNA (shRNA) sequences that efficiently target Dnm2 mRNA. A single intramuscular injection of AAV-shDnm2 resulted in long-term reduction of DNM2 protein level and restored muscle force, mass, histology, and myofiber ultrastructure and prevented molecular defects linked to the disease. Our results demonstrate a robust DNM2 knockdown and provide an alternative strategy based on reduction of DNM2 to treat myotubular myopathy.
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11
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Affected female carriers of MTM1 mutations display a wide spectrum of clinical and pathological involvement: delineating diagnostic clues. Acta Neuropathol 2017; 134:889-904. [PMID: 28685322 DOI: 10.1007/s00401-017-1748-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 06/24/2017] [Accepted: 07/02/2017] [Indexed: 01/14/2023]
Abstract
X-linked myotubular myopathy (XLMTM), a severe congenital myopathy, is caused by mutations in the MTM1 gene located on the X chromosome. A majority of affected males die in the early postnatal period, whereas female carriers are believed to be usually asymptomatic. Nevertheless, several affected females have been reported. To assess the phenotypic and pathological spectra of carrier females and to delineate diagnostic clues, we characterized 17 new unrelated affected females and performed a detailed comparison with previously reported cases at the clinical, muscle imaging, histological, ultrastructural and molecular levels. Taken together, the analysis of this large cohort of 43 cases highlights a wide spectrum of clinical severity ranging from severe neonatal and generalized weakness, similar to XLMTM male, to milder adult forms. Several females show a decline in respiratory function. Asymmetric weakness is a noteworthy frequent specific feature potentially correlated to an increased prevalence of highly skewed X inactivation. Asymmetry of growth was also noted. Other diagnostic clues include facial weakness, ptosis and ophthalmoplegia, skeletal and joint abnormalities, and histopathological signs that are hallmarks of centronuclear myopathy such as centralized nuclei and necklace fibers. The histopathological findings also demonstrate a general disorganization of muscle structure in addition to these specific hallmarks. Thus, MTM1 mutations in carrier females define a specific myopathy, which may be independent of the presence of an XLMTM male in the family. As several of the reported affected females carry large heterozygous MTM1 deletions not detectable by Sanger sequencing, and as milder phenotypes present as adult-onset limb-girdle myopathy, the prevalence of this myopathy is likely to be greatly underestimated. This report should aid diagnosis and thus the clinical management and genetic counseling of MTM1 carrier females. Furthermore, the clinical and pathological history of this cohort may be useful for therapeutic projects in males with XLMTM, as it illustrates the spectrum of possible evolution of the disease in patients surviving long term.
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12
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Mansour R, Severin S, Xuereb JM, Gratacap MP, Laporte J, Buj-Bello A, Tronchère H, Payrastre B. Expression of myotubularins in blood platelets: Characterization and potential diagnostic of X-linked myotubular myopathy. Biochem Biophys Res Commun 2016; 476:167-73. [DOI: 10.1016/j.bbrc.2016.04.127] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 04/24/2016] [Indexed: 10/21/2022]
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13
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North KN, Wang CH, Clarke N, Jungbluth H, Vainzof M, Dowling JJ, Amburgey K, Quijano-Roy S, Beggs AH, Sewry C, Laing NG, Bönnemann CG. Approach to the diagnosis of congenital myopathies. Neuromuscul Disord 2014; 24:97-116. [PMID: 24456932 PMCID: PMC5257342 DOI: 10.1016/j.nmd.2013.11.003] [Citation(s) in RCA: 176] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 11/06/2013] [Accepted: 11/08/2013] [Indexed: 10/26/2022]
Abstract
Over the past decade there have been major advances in defining the genetic basis of the majority of congenital myopathy subtypes. However the relationship between each congenital myopathy, defined on histological grounds, and the genetic cause is complex. Many of the congenital myopathies are due to mutations in more than one gene, and mutations in the same gene can cause different muscle pathologies. The International Standard of Care Committee for Congenital Myopathies performed a literature review and consulted a group of experts in the field to develop a summary of (1) the key features common to all forms of congenital myopathy and (2) the specific features that help to discriminate between the different genetic subtypes. The consensus statement was refined by two rounds of on-line survey, and a three-day workshop. This consensus statement provides guidelines to the physician assessing the infant or child with hypotonia and weakness. We summarise the clinical features that are most suggestive of a congenital myopathy, the major differential diagnoses and the features on clinical examination, investigations, muscle pathology and muscle imaging that are suggestive of a specific genetic diagnosis to assist in prioritisation of genetic testing of known genes. As next generation sequencing becomes increasingly used as a diagnostic tool in clinical practise, these guidelines will assist in determining which sequence variations are likely to be pathogenic.
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Affiliation(s)
- Kathryn N North
- Murdoch Childrens Research Institute, Royal Children's Hospital, Flemington Road, Parkville, Melbourne, Victoria 3052, Australia; Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, University of Sydney, Sydney, Australia.
| | - Ching H Wang
- Driscoll Children's Hospital, Corpus Christi, TX, United States
| | - Nigel Clarke
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, University of Sydney, Sydney, Australia
| | - Heinz Jungbluth
- Evelina Children's Hospital, Department of Paediatric Neurology, London, United Kingdom; Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section, King's College, London, United Kingdom; Clinical Neuroscience Division, IoP, London, United Kingdom
| | - Mariz Vainzof
- Human Genome Research Center, University of Sao Paulo, Sao Paulo, Brazil
| | - James J Dowling
- Division of Neurology, Department of Paediatrics, Hospital for Sick Children, Toronto, ON, Canada
| | - Kimberly Amburgey
- Division of Neurology, Department of Paediatrics, Hospital for Sick Children, Toronto, ON, Canada
| | - Susana Quijano-Roy
- Department of Pediatrics, Garches Neuromuscular Reference Center (GNMH), APHP Raymond Poincare University Hospital (UVSQ), Garches, France
| | - Alan H Beggs
- Children's Hospital Boston, Boston, MA, United States
| | - Caroline Sewry
- Dubowitz Neuromuscular Centre, London, United Kingdom; Wolfson Centre of Inherited Neuromuscular Diseases, RJAH Orthopaedic Hospital, Oswestry, United Kingdom
| | - Nigel G Laing
- Centre for Medical Research, University of Western Australia and Harry Perkins Institute of Medical Research, QQ Building, QEII Medical Centre, Nedlands, Western Australia 6009, Australia
| | - Carsten G Bönnemann
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, Bethesda, MD, United States
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14
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Shichiji M, Biancalana V, Fardeau M, Hogrel JY, Osawa M, Laporte J, Romero NB. Extensive morphological and immunohistochemical characterization in myotubular myopathy. Brain Behav 2013; 3:476-86. [PMID: 24381816 PMCID: PMC3869686 DOI: 10.1002/brb3.147] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 05/02/2013] [Accepted: 05/06/2013] [Indexed: 11/30/2022] Open
Abstract
The X-linked myotubular myopathy (XLMTM) also called X-linked centronuclear myopathy is a rare congenital myopathy due to mutations in the MTM 1 gene encoding myotubularin. The disease gives rise to a severe muscle weakness in males at birth. The main muscle morphological characteristics (significant number of small muscle fibers with centralized nuclei and type 1 fiber predominance) are usually documented, but the sequence of formation and maintenance of this particular morphological pattern has not been extensively characterized in humans. In this study, we perform a reevaluation of morphological changes in skeletal muscle biopsies in severe XLMTM. We correlate the pathologic features observed in the muscle biopsies of 15 newborns with MTM 1-mutations according to the "adjusted-age" at the time of muscle biopsy, focusing on sequential analysis in the early period of the life (from 34 weeks of gestation to 3 months of age). We found a similar morphological pattern throughout the period analyzed; the proportion of myofibers with central nuclei was high in all muscle biopsies, independently of the muscle type, the age of the newborns at time of biopsy and the specific MTM 1 mutation. We did not observe a period free of morphological abnormalities in human skeletal muscle as observed in myotubularin-deficient mouse models. In addition, this study demonstrated some features of delayed maturation of the muscle fibers without any increase in the number of satellite cells, associated with a marked disorganization of the muscle T-tubules and cytoskeletal network in the skeletal muscle fibers.
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Affiliation(s)
- Minobu Shichiji
- Unité de Morphologie Neuromusculaire, Institut de Myologie GHU La Pitié-Salpêtrière, Paris, France ; Department of Pediatrics, Tokyo Woman's Medical University Tokyo, Japan
| | - Valérie Biancalana
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CNRS, UMR7104, INSERM, U964, Collège de France, Université de Strasbourg Illkirch, France ; Laboratoire Diagnostic Génétique, Faculté de Médecine - CHRU Strasbourg, France
| | - Michel Fardeau
- Unité de Morphologie Neuromusculaire, Institut de Myologie GHU La Pitié-Salpêtrière, Paris, France ; Groupe Hospitalier-Universitaire La Pitié-Salpêtrière, AP-HP, Centre de référence des maladies neuromusculaires Paris-Est, Paris, France
| | - Jean-Yves Hogrel
- UPMC-Paris6 UR76, INSERM UMR974, CNRS UMR 7215, Institut de Myologie GHU La Pitié-Salpêtrière, Paris, France
| | - Makiko Osawa
- Department of Pediatrics, Tokyo Woman's Medical University Tokyo, Japan
| | - Jocelyn Laporte
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CNRS, UMR7104, INSERM, U964, Collège de France, Université de Strasbourg Illkirch, France
| | - Norma Beatriz Romero
- Unité de Morphologie Neuromusculaire, Institut de Myologie GHU La Pitié-Salpêtrière, Paris, France ; Groupe Hospitalier-Universitaire La Pitié-Salpêtrière, AP-HP, Centre de référence des maladies neuromusculaires Paris-Est, Paris, France ; UPMC-Paris6 UR76, INSERM UMR974, CNRS UMR 7215, Institut de Myologie GHU La Pitié-Salpêtrière, Paris, France
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15
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Gupta VA, Hnia K, Smith LL, Gundry SR, McIntire JE, Shimazu J, Bass JR, Talbot EA, Amoasii L, Goldman NE, Laporte J, Beggs AH. Loss of catalytically inactive lipid phosphatase myotubularin-related protein 12 impairs myotubularin stability and promotes centronuclear myopathy in zebrafish. PLoS Genet 2013; 9:e1003583. [PMID: 23818870 PMCID: PMC3688503 DOI: 10.1371/journal.pgen.1003583] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 05/07/2013] [Indexed: 01/08/2023] Open
Abstract
X-linked myotubular myopathy (XLMTM) is a congenital disorder caused by mutations of the myotubularin gene, MTM1. Myotubularin belongs to a large family of conserved lipid phosphatases that include both catalytically active and inactive myotubularin-related proteins (i.e., "MTMRs"). Biochemically, catalytically inactive MTMRs have been shown to form heteroligomers with active members within the myotubularin family through protein-protein interactions. However, the pathophysiological significance of catalytically inactive MTMRs remains unknown in muscle. By in vitro as well as in vivo studies, we have identified that catalytically inactive myotubularin-related protein 12 (MTMR12) binds to myotubularin in skeletal muscle. Knockdown of the mtmr12 gene in zebrafish resulted in skeletal muscle defects and impaired motor function. Analysis of mtmr12 morphant fish showed pathological changes with central nucleation, disorganized Triads, myofiber hypotrophy and whorled membrane structures similar to those seen in X-linked myotubular myopathy. Biochemical studies showed that deficiency of MTMR12 results in reduced levels of myotubularin protein in zebrafish and mammalian C2C12 cells. Loss of myotubularin also resulted in reduction of MTMR12 protein in C2C12 cells, mice and humans. Moreover, XLMTM mutations within the myotubularin interaction domain disrupted binding to MTMR12 in cell culture. Analysis of human XLMTM patient myotubes showed that mutations that disrupt the interaction between myotubularin and MTMR12 proteins result in reduction of both myotubularin and MTMR12. These studies strongly support the concept that interactions between myotubularin and MTMR12 are required for the stability of their functional protein complex in normal skeletal muscles. This work highlights an important physiological function of catalytically inactive phosphatases in the pathophysiology of myotubular myopathy and suggests a novel therapeutic approach through identification of drugs that could stabilize the myotubularin-MTMR12 complex and hence ameliorate this disorder.
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Affiliation(s)
- Vandana A. Gupta
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Karim Hnia
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Inserm U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - Laura L. Smith
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Stacey R. Gundry
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jessica E. McIntire
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Junko Shimazu
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jessica R. Bass
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Ethan A. Talbot
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Leonela Amoasii
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Inserm U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - Nathaniel E. Goldman
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jocelyn Laporte
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Inserm U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - Alan H. Beggs
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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16
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Al-Qusairi L, Prokic I, Amoasii L, Kretz C, Messaddeq N, Mandel JL, Laporte J. Lack of myotubularin (MTM1) leads to muscle hypotrophy through unbalanced regulation of the autophagy and ubiquitin-proteasome pathways. FASEB J 2013; 27:3384-94. [PMID: 23695157 DOI: 10.1096/fj.12-220947] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mutations in the phosphoinositide phosphatase myotubularin (MTM1) results in X-linked myotubular/centronuclear myopathy (XLMTM), characterized by a severe decrease in muscle mass and strength in patients and murine models. However, the molecular mechanism involved in the muscle hypotrophy is unclear. Here we show that the IGF1R/Akt pathway is affected in Mtm1-deficient murine muscles, characterized by an increase in IGF1 receptor and Akt levels in both the presymptomatic and symptomatic phases. Moreover, up-regulation of atrogenes was observed in the presymptomatic phase of the myopathy, supporting overactivation of the ubiquitin-proteasome pathway. In parallel, the autophagy machinery was affected as indicated by the increase in the number of autophagosomes and of autophagy markers, such as LC3 and P62. However, phosphorylation of FOXO3a and mTOR were abnormal at late but not at early stages of the disease, suggesting that myotubularin acts both upstream in the IGF1R/Akt pathway and downstream on the balance between the autophagy and ubiquitin-proteasome pathways in vivo. Adeno-associated virus-mediated delivery of Mtm1 into Mtm1-null muscles rescued muscle mass and normalized the expression levels of IGF1 receptor, the ubiquitin-proteasome pathway, and autophagy markers. These data support the hypothesis that the unbalanced regulation of the ubiquitin proteasome pathway and the autophagy machinery is a primary cause of the XLMTM pathogenesis.
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Affiliation(s)
- Lama Al-Qusairi
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
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17
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Impacts of massively parallel sequencing for genetic diagnosis of neuromuscular disorders. Acta Neuropathol 2013; 125:173-85. [PMID: 23224362 DOI: 10.1007/s00401-012-1072-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 11/27/2012] [Accepted: 11/28/2012] [Indexed: 12/11/2022]
Abstract
Neuromuscular disorders (NMD) such as neuropathy or myopathy are rare and often severe inherited disorders, affecting muscle and/or nerves with neonatal, childhood or adulthood onset, with considerable burden for the patients, their families and public health systems. Genetic and clinical heterogeneity, unspecific clinical features, unidentified genes and the implication of large and/or several genes requiring complementary methods are the main drawbacks in routine molecular diagnosis, leading to increased turnaround time and delay in the molecular validation of the diagnosis. The application of massively parallel sequencing, also called next generation sequencing, as a routine diagnostic strategy could lead to a rapid screening and fast identification of mutations in rare genetic disorders like NMD. This review aims to summarize and to discuss recent advances in the genetic diagnosis of neuromuscular disorders, and more generally monogenic diseases, fostered by massively parallel sequencing. We remind the challenges and benefit of obtaining an accurate genetic diagnosis, introduce the massively parallel sequencing technology and its novel applications in diagnosis of patients, prenatal diagnosis and carrier detection, and discuss the limitations and necessary improvements. Massively parallel sequencing synergizes with clinical and pathological investigations into an integrated diagnosis approach. Clinicians and pathologists are crucial in patient selection and interpretation of data, and persons trained in data management and analysis need to be integrated to the diagnosis pipeline. Massively parallel sequencing for mutation identification is expected to greatly improve diagnosis, genetic counseling and patient management.
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18
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Abstract
Congenital myopathies are a heterogeneous group of inherited muscle disorders, characterized by the predominance of particular histopathological features on muscle biopsy, such as cores (central core disease) or rods (nemaline myopathy). Clinically, early onset of the disease, stable or slowly progressive muscle weakness, hypotonia and delayed motor development are common in most forms. As a result, the diagnosis of a subtype of congenital myopathy is largely based on the presence of specific structural abnormalities in the skeletal muscle detected by enzyme-histochemistry and electron microscopy studies. During the last decades there have been significant advances in the identification of the genetic basis of most congenital myopathies. However, there is significant genetic heterogeneity within the main groups of congenital myopathies, and mutations in one particular gene may also cause diverse clinical and morphological phenotypes. Thus, the nosography and nosology in this field is still evolving.
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Affiliation(s)
- Norma Beatriz Romero
- Morphology Neuromuscular Unit of the Myology Institute, GHU Pitié-Salpêtrière, Paris, France.
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19
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Amburgey K, Lawlor MW, Del Gaudio D, Cheng YW, Fitzpatrick C, Minor A, Li X, Aughton D, Das S, Beggs AH, Dowling JJ. Large duplication in MTM1 associated with myotubular myopathy. Neuromuscul Disord 2012; 23:214-8. [PMID: 23273872 DOI: 10.1016/j.nmd.2012.11.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 10/23/2012] [Accepted: 11/23/2012] [Indexed: 11/26/2022]
Abstract
Myotubular myopathy is a subtype of centronuclear myopathy with X-linked inheritance and distinctive clinical and pathologic features. Most boys with myotubular myopathy have MTM1 mutations. In remaining individuals, it is not clear if disease is due to an undetected alteration in MTM1 or mutation of another gene. We describe a boy with myotubular myopathy but without mutation in MTM1 by conventional sequencing. Array-CGH analysis of MTM1 uncovered a large MTM1 duplication. This finding suggests that at least some unresolved cases of myotubular myopathy are due to duplications in MTM1, and that array-CGH should be considered when MTM1 sequencing is unrevealing.
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Affiliation(s)
- K Amburgey
- Department of Pediatrics, University of Michigan, Ann Arbor, MI, USA
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20
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Amoasii L, Bertazzi DL, Tronchère H, Hnia K, Chicanne G, Rinaldi B, Cowling BS, Ferry A, Klaholz B, Payrastre B, Laporte J, Friant S. Phosphatase-dead myotubularin ameliorates X-linked centronuclear myopathy phenotypes in mice. PLoS Genet 2012; 8:e1002965. [PMID: 23071445 PMCID: PMC3469422 DOI: 10.1371/journal.pgen.1002965] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 08/08/2012] [Indexed: 12/27/2022] Open
Abstract
Myotubularin MTM1 is a phosphoinositide (PPIn) 3-phosphatase mutated in X-linked centronuclear myopathy (XLCNM; myotubular myopathy). We investigated the involvement of MTM1 enzymatic activity on XLCNM phenotypes. Exogenous expression of human MTM1 in yeast resulted in vacuolar enlargement, as a consequence of its phosphatase activity. Expression of mutants from patients with different clinical progression and determination of PtdIns3P and PtdIns5P cellular levels confirmed the link between vacuolar morphology and MTM1 phosphatase activity, and showed that some disease mutants retain phosphatase activity. Viral gene transfer of phosphatase-dead myotubularin mutants (MTM1(C375S) and MTM1(S376N)) significantly improved most histological signs of XLCNM displayed by a Mtm1-null mouse, at similar levels as wild-type MTM1. Moreover, the MTM1(C375S) mutant improved muscle performance and restored the localization of nuclei, triad alignment, and the desmin intermediate filament network, while it did not normalize PtdIns3P levels, supporting phosphatase-independent roles of MTM1 in maintaining normal muscle performance and organelle positioning in skeletal muscle. Among the different XLCNM signs investigated, we identified only triad shape and fiber size distribution as being partially dependent on MTM1 phosphatase activity. In conclusion, this work uncovers MTM1 roles in the structural organization of muscle fibers that are independent of its enzymatic activity. This underlines that removal of enzymes should be used with care to conclude on the physiological importance of their activity.
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MESH Headings
- Animals
- Desmin/metabolism
- Disease Models, Animal
- Enzyme Activation/genetics
- Gene Expression
- Humans
- Male
- Mice
- Mice, Knockout
- Muscle Strength/genetics
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/ultrastructure
- Mutation
- Myopathies, Structural, Congenital/genetics
- Myopathies, Structural, Congenital/metabolism
- Phenotype
- Phosphatidylinositol Phosphates/metabolism
- Phosphoric Monoester Hydrolases/metabolism
- Protein Tyrosine Phosphatases, Non-Receptor/genetics
- Protein Tyrosine Phosphatases, Non-Receptor/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
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Affiliation(s)
- Leonela Amoasii
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
| | - Dimitri L. Bertazzi
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
| | | | - Karim Hnia
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
| | - Gaëtan Chicanne
- INSERM, U1048 and Université Toulouse 3, I2MC, Toulouse, France
| | - Bruno Rinaldi
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
| | - Belinda S. Cowling
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
| | - Arnaud Ferry
- UMRS974, Université Pierre et Marie Curie, Paris, France
| | - Bruno Klaholz
- Department of Integrated Structural Biology, IGBMC, INSERM U964, CNRS UMR7104, Université de Strasbourg, Illkirch, France
| | - Bernard Payrastre
- INSERM, U1048 and Université Toulouse 3, I2MC, Toulouse, France
- CHU de Toulouse, Laboratoire d'Hématologie, Toulouse, France
- * E-mail: (SF); (JL); (BP)
| | - Jocelyn Laporte
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
- * E-mail: (SF); (JL); (BP)
| | - Sylvie Friant
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
- * E-mail: (SF); (JL); (BP)
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21
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Biancalana V, Beggs AH, Das S, Jungbluth H, Kress W, Nishino I, North K, Romero NB, Laporte J. Clinical utility gene card for: Centronuclear and myotubular myopathies. Eur J Hum Genet 2012; 20:ejhg201291. [PMID: 22617344 DOI: 10.1038/ejhg.2012.91] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Valérie Biancalana
- Laboratoire de Diagnostic Génétique, Faculté de Médecine-CHRU, 1 place de l'Hôpital, Strasbourg, France.
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22
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Hedberg C, Lindberg C, Máthé G, Moslemi AR, Oldfors A. Myopathy in a woman and her daughter associated with a novel splice site MTM1 mutation. Neuromuscul Disord 2012; 22:244-51. [DOI: 10.1016/j.nmd.2011.10.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 09/20/2011] [Accepted: 10/13/2011] [Indexed: 01/26/2023]
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23
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Myotubular myopathy caused by multiple abnormal splicing variants in the MTM1 RNA in a patient with a mild phenotype. Eur J Hum Genet 2012; 20:701-4. [PMID: 22258523 DOI: 10.1038/ejhg.2011.256] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mutations impacting on the splicing of pre-mRNA are one important cause of genetically inherited diseases. However, detection of splice mutations, that are mainly due to intronic variations, and characterization of their effects are usually not performed as a first approach during genetic diagnosis. X-linked recessive myotubular myopathy is a severe congenital myopathy due to mutations in the MTM1 gene encoding myotubularin. Here, we screened a male patient showing an unusually mild phenotype without respiratory distress by western blot with specific myotubularin antibodies and detected a strong reduction of the protein level.The disease was subsequently linked to a hemizygous point mutation affecting the acceptor splice site of exon 8 of MTM1, proven by protein, transcript and genomic DNA analysis. Detailed analysis of the MTM1 mRNA by RT-PCR, sequencing and quantitative PCR revealed multiple abnormal transcripts with retention of a truncated exon 8, and neighboring exons 7 and 9 but exclusion of several other exons, suggesting a complex effect of this mutation on the splicing of non-adjacent exons. We conclude that the analysis of RNA by RT-PCR and sequencing is an important step to characterize the precise impact of detected splice variants. It is likely that complex splice aberrations due to a single mutation also account for unsolved cases in other diseases.
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24
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Trump N, Cullup T, Verheij JBGM, Manzur A, Muntoni F, Abbs S, Jungbluth H. X-linked myotubular myopathy due to a complex rearrangement involving a duplication of MTM1 exon 10. Neuromuscul Disord 2011; 22:384-8. [PMID: 22153990 DOI: 10.1016/j.nmd.2011.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 11/11/2011] [Accepted: 11/16/2011] [Indexed: 11/18/2022]
Abstract
X-linked myotubular myopathy is a predominantly severe congenital myopathy with central nuclei on muscle biopsy due to mutations in the MTM1 gene encoding myotubularin. We report a boy with typical features of X-linked myotubular myopathy. Sequencing of the MTM1 gene did not reveal any causative mutations. Subsequent MLPA analysis identified a duplication of MTM1 exon 10 both in the patient and his mother. Additional quantitative fluorescent PCR and long-range PCR revealed an additional large deletion (2536bp) within intron 10, 143bp downstream of exon 10, and confirmed the duplication of exon 10. Our findings suggest that complex rearrangements have to be considered in typically affected males with X-linked myotubular myopathy.
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Affiliation(s)
- N Trump
- DNA Laboratory, GSTS Pathology, Guy's Hospital, London, UK.
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25
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26
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Toussaint A, Cowling BS, Hnia K, Mohr M, Oldfors A, Schwab Y, Yis U, Maisonobe T, Stojkovic T, Wallgren-Pettersson C, Laugel V, Echaniz-Laguna A, Mandel JL, Nishino I, Laporte J. Defects in amphiphysin 2 (BIN1) and triads in several forms of centronuclear myopathies. Acta Neuropathol 2011; 121:253-66. [PMID: 20927630 DOI: 10.1007/s00401-010-0754-2] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 09/24/2010] [Accepted: 09/25/2010] [Indexed: 11/24/2022]
Abstract
Myotubular myopathy and centronuclear myopathies (CNM) are congenital myopathies characterized by generalized muscle weakness and mislocalization of muscle fiber nuclei. Genetically distinct forms exist, and mutations in BIN1 were recently identified in autosomal recessive cases (ARCNM). Amphiphysins have been implicated in membrane remodeling in brain and skeletal muscle. Our objective was to decipher the pathogenetic mechanisms underlying different forms of CNM, with a focus on ARCNM cases. In this study, we compare the histopathological features from patients with X-linked, autosomal recessive, and dominant forms, respectively, mutated in myotubularin (MTM1), amphiphysin 2 (BIN1), and dynamin 2 (DNM2). We further characterize the ultrastructural defects in ARCNM muscles. We demonstrate that the two BIN1 isoforms expressed in skeletal muscle possess the phosphoinositide-binding domain and are specifically targeted to the triads close to the DHPR-RYR1 complex. Cardiac isoforms do not contain this domain, suggesting that splicing of BIN1 regulates its specific function in skeletal muscle. Immunofluorescence analyses of muscles from patients with BIN1 mutations reveal aberrations of BIN1 localization and triad organization. These defects are also observed in X-linked and autosomal dominant forms of CNM and in Mtm1 knockout mice. In addition to previously reported implications of BIN1 in cancer as a tumor suppressor, these findings sustain an important role for BIN1 skeletal muscle isoforms in membrane remodeling and organization of the excitation-contraction machinery. We propose that aberrant BIN1 localization and defects in triad structure are part of a common pathogenetic mechanism shared between the three forms of centronuclear myopathies.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adolescent
- Adult
- Brain/pathology
- Brain/ultrastructure
- Child
- Dynamin II/genetics
- Female
- Humans
- Infant
- Male
- Microscopy, Electron, Transmission/methods
- Muscle, Skeletal/pathology
- Muscle, Skeletal/ultrastructure
- Mutation/genetics
- Myopathies, Structural, Congenital/classification
- Myopathies, Structural, Congenital/genetics
- Nuclear Proteins/genetics
- Protein Tyrosine Phosphatases, Non-Receptor/genetics
- Tumor Suppressor Proteins/genetics
- Young Adult
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Affiliation(s)
- Anne Toussaint
- Department of Neurobiology and Genetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France
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