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Galli RA, Borsboom TC, Gineste C, Brocca L, Rossi M, Hwee DT, Malik FI, Bottinelli R, Gondin J, Pellegrino MA, de Winter JM, Ottenheijm CA. Tirasemtiv enhances submaximal muscle tension in an Acta1:p.Asp286Gly mouse model of nemaline myopathy. J Gen Physiol 2024; 156:e202313471. [PMID: 38376469 PMCID: PMC10876480 DOI: 10.1085/jgp.202313471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 12/01/2023] [Accepted: 01/30/2024] [Indexed: 02/21/2024] Open
Abstract
Nemaline myopathies are the most common form of congenital myopathies. Variants in ACTA1 (NEM3) comprise 15-25% of all nemaline myopathy cases. Patients harboring variants in ACTA1 present with a heterogeneous disease course characterized by stable or progressive muscle weakness and, in severe cases, respiratory failure and death. To date, no specific treatments are available. Since NEM3 is an actin-based thin filament disease, we tested the ability of tirasemtiv, a fast skeletal muscle troponin activator, to improve skeletal muscle function in a mouse model of NEM3, harboring the patient-based p.Asp286Gly variant in Acta1. Acute and long-term tirasemtiv treatment significantly increased muscle contractile capacity at submaximal stimulation frequencies in both fast-twitch extensor digitorum longus and gastrocnemius muscle, and intermediate-twitch diaphragm muscle in vitro and in vivo. Additionally, long-term tirasemtiv treatment in NEM3 mice resulted in a decreased respiratory rate with preserved minute volume, suggesting more efficient respiration. Altogether, our data support the therapeutic potential of fast skeletal muscle troponin activators in alleviating skeletal muscle weakness in a mouse model of NEM3 caused by the Acta1:p.Asp286Gly variant.
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Affiliation(s)
- Ricardo A. Galli
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, Amsterdam, The Netherlands
- Amsterdam Movement Sciences, Musculoskeletal Health and Tissue Function and Regeneration, Amsterdam, The Netherlands
| | - Tamara C. Borsboom
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, Amsterdam, The Netherlands
| | | | - Lorenza Brocca
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Maira Rossi
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Darren T. Hwee
- Research and Early Development, Cytokinetics Inc., South San Francisco, CA, USA
| | - Fady I. Malik
- Research and Early Development, Cytokinetics Inc., South San Francisco, CA, USA
| | - Roberto Bottinelli
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
- IRCCS Mondino Foundation, Pavia, Italy
| | - Julien Gondin
- Aix-Marseille University, CNRS, CRMBM, Marseille, France
- Institut NeuroMyoGène, Unité Physiopathologie et Génétique du Neurone et du Muscle, Université Claude Bernard Lyon 1, CNRS UMR 5261, INSERM U1315, Université Lyon, Lyon, France
| | | | - Josine M. de Winter
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, Amsterdam, The Netherlands
- Amsterdam Movement Sciences, Musculoskeletal Health and Tissue Function and Regeneration, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure and Arrhythmias, Amsterdam, The Netherlands
| | - Coen A.C. Ottenheijm
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Pulmonary Hypertension and Atherosclerosis, Amsterdam, The Netherlands
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
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2
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Slick RA, Tinklenberg JA, Sutton J, Zhang L, Meng H, Beatka MJ, Vanden Avond M, Prom MJ, Ott E, Montanaro F, Heisner J, Toro R, Granzier H, Geurts AM, Stowe DF, Hill RB, Lawlor MW. Aberrations in Energetic Metabolism and Stress-Related Pathways Contribute to Pathophysiology in the Neb Conditional Knockout Mouse Model of Nemaline Myopathy. THE AMERICAN JOURNAL OF PATHOLOGY 2023; 193:1528-1547. [PMID: 37422147 PMCID: PMC10548278 DOI: 10.1016/j.ajpath.2023.06.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 05/08/2023] [Accepted: 06/08/2023] [Indexed: 07/10/2023]
Abstract
Nemaline myopathy (NM) is a genetically and clinically heterogeneous disease that is diagnosed on the basis of the presence of nemaline rods on skeletal muscle biopsy. Although NM has typically been classified by causative genes, disease severity or prognosis cannot be predicted. The common pathologic end point of nemaline rods (despite diverse genetic causes) and an unexplained range of muscle weakness suggest that shared secondary processes contribute to the pathogenesis of NM. We speculated that these processes could be identified through a proteome-wide interrogation using a mouse model of severe NM in combination with pathway validation and structural/functional analyses. A proteomic analysis was performed using skeletal muscle tissue from the Neb conditional knockout mouse model compared with its wild-type counterpart to identify pathophysiologically relevant biological processes that might impact disease severity or provide new treatment targets. A differential expression analysis and Ingenuity Pathway Core Analysis predicted perturbations in several cellular processes, including mitochondrial dysfunction and changes in energetic metabolism and stress-related pathways. Subsequent structural and functional studies demonstrated abnormal mitochondrial distribution, decreased mitochondrial respiratory function, an increase in mitochondrial transmembrane potential, and extremely low ATP content in Neb conditional knockout muscles relative to wild type. Overall, the findings of these studies support a role for severe mitochondrial dysfunction as a novel contributor to muscle weakness in NM.
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Affiliation(s)
- Rebecca A Slick
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Clinical and Translational Science Institute, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Jennifer A Tinklenberg
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Clinical and Translational Science Institute, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Jessica Sutton
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Liwen Zhang
- Mass Spectrometry and Proteomics Facility, Campus Chemical Instrument Center, The Ohio State University, Columbus, Ohio
| | - Hui Meng
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Margaret J Beatka
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Mark Vanden Avond
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Mariah J Prom
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Emily Ott
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Federica Montanaro
- Dubowitz Neuromuscular Centre, Molecular Neurosciences Section, Developmental Neuroscience Research and Teaching Department, UCL Great Ormond Street Institute of Child Health, London, United Kingdom the NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom; NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
| | - James Heisner
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Rafael Toro
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Henk Granzier
- College of Medicine, University of Arizona, Tucson, Arizona
| | - Aron M Geurts
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Mellowes Center for Genomic Sciences and Precision Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - David F Stowe
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Joint Department of Biomedical Engineering, Medical College of Wisconsin and Marquette University, Milwaukee, Wisconsin
| | - R Blake Hill
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Michael W Lawlor
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.
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3
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Culver A, Hamang M, Wang Y, Jiang H, Yanum J, White E, Gawrieh S, Vuppalanchi RK, Chalasani NP, Dai G, Yaden BC. GDF8 Contributes to Liver Fibrogenesis and Concomitant Skeletal Muscle Wasting. Biomedicines 2023; 11:1909. [PMID: 37509548 PMCID: PMC10377408 DOI: 10.3390/biomedicines11071909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 06/23/2023] [Accepted: 06/23/2023] [Indexed: 07/30/2023] Open
Abstract
Patients with end-stage liver disease exhibit progressive skeletal muscle atrophy, highlighting a negative crosstalk between the injured liver and muscle. Our study was to determine whether TGFβ ligands function as the mediators. Acute or chronic liver injury was induced by a single or repeated administration of carbon tetrachloride. Skeletal muscle injury and repair was induced by intramuscular injection of cardiotoxin. Activin type IIB receptor (ActRIIB) ligands and growth differentiation factor 8 (Gdf8) were neutralized with ActRIIB-Fc fusion protein and a Gdf8-specific antibody, respectively. We found that acute hepatic injury induced rapid and adverse responses in muscle, which was blunted by neutralizing ActRIIB ligands. Chronic liver injury caused muscle atrophy and repair defects, which were prevented or reversed by inactivating ActRIIB ligands. Furthermore, we found that pericentral hepatocytes produce excessive Gdf8 in injured mouse liver and cirrhotic human liver. Specific inactivation of Gdf8 prevented liver injury-induced muscle atrophy, similar to neutralization of ActRIIB ligands. Inhibition of Gdf8 also reversed muscle atrophy in a treatment paradigm following chronic liver injury. Direct injection of exogenous Gdf8 protein into muscle along with acute focal muscle injury recapitulated similar dysregulated muscle regeneration as that observed with liver injury. The results indicate that injured liver negatively communicate with the muscle largely via Gdf8. Unexpectedly, inactivation of Gdf8 simultaneously ameliorated liver fibrosis in mice following chronic liver injury. In vitro, Gdf8 induced human hepatic stellate (LX-2) cells to form a septa-like structure and stimulated expression of profibrotic factors. Our findings identified Gdf8 as a novel hepatomyokine contributing to injured liver-muscle negative crosstalk along with liver injury progression.
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Affiliation(s)
- Alexander Culver
- Department of Biology, School of Science, Center for Developmental and Regenerative Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Matthew Hamang
- Department of Biology, School of Science, Center for Developmental and Regenerative Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Yan Wang
- Department of Biology, School of Science, Center for Developmental and Regenerative Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Huaizhou Jiang
- Department of Biology, School of Science, Center for Developmental and Regenerative Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Jennifer Yanum
- Department of Biology, School of Science, Center for Developmental and Regenerative Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Emily White
- Department of Biological Sciences, College of Science, Purdue University, West Lafayette, IN 46202, USA
| | - Samer Gawrieh
- Division of Gastroenterology and Hepatology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA
| | - Raj K Vuppalanchi
- Division of Gastroenterology and Hepatology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA
| | - Naga P Chalasani
- Division of Gastroenterology and Hepatology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA
| | - Guoli Dai
- Department of Biology, School of Science, Center for Developmental and Regenerative Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Benjamin C Yaden
- Department of Biology, School of Science, Center for Developmental and Regenerative Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
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4
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Mob4-dependent STRIPAK involves the chaperonin TRiC to coordinate myofibril and microtubule network growth. PLoS Genet 2022; 18:e1010287. [PMID: 35737712 PMCID: PMC9258817 DOI: 10.1371/journal.pgen.1010287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 07/06/2022] [Accepted: 06/08/2022] [Indexed: 11/19/2022] Open
Abstract
Myofibrils of the skeletal muscle are comprised of sarcomeres that generate force by contraction when myosin-rich thick filaments slide past actin-based thin filaments. Surprisingly little is known about the molecular processes that guide sarcomere assembly in vivo, despite deficits within this process being a major cause of human disease. To overcome this knowledge gap, we undertook a forward genetic screen coupled with reverse genetics to identify genes required for vertebrate sarcomere assembly. In this screen, we identified a zebrafish mutant with a nonsense mutation in mob4. In Drosophila, mob4 has been reported to play a role in spindle focusing as well as neurite branching and in planarians mob4 was implemented in body size regulation. In contrast, zebrafish mob4geh mutants are characterised by an impaired actin biogenesis resulting in sarcomere defects. Whereas loss of mob4 leads to a reduction in the amount of myofibril, transgenic expression of mob4 triggers an increase. Further genetic analysis revealed the interaction of Mob4 with the actin-folding chaperonin TRiC, suggesting that Mob4 impacts on TRiC to control actin biogenesis and thus myofibril growth. Additionally, mob4geh features a defective microtubule network, which is in-line with tubulin being the second main folding substrate of TRiC. We also detected similar characteristics for strn3-deficient mutants, which confirmed Mob4 as a core component of STRIPAK and surprisingly implicates a role of the STRIPAK complex in sarcomerogenesis.
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5
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McNamara EL, Taylor RL, Clayton JS, Goullee H, Dilworth KL, Pinós T, Brull A, Alexander IE, Lisowski L, Ravenscroft G, Laing NG, Nowak KJ. Systemic AAV8-mediated delivery of a functional copy of muscle glycogen phosphorylase (Pygm) ameliorates disease in a murine model of McArdle disease. Hum Mol Genet 2020; 29:20-30. [PMID: 31511858 DOI: 10.1093/hmg/ddz214] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 08/01/2019] [Accepted: 09/02/2019] [Indexed: 12/12/2022] Open
Abstract
McArdle disease is a disorder of carbohydrate metabolism that causes painful skeletal muscle cramps and skeletal muscle damage leading to transient myoglobinuria and increased risk of kidney failure. McArdle disease is caused by recessive mutations in the muscle glycogen phosphorylase (PYGM) gene leading to absence of PYGM enzyme in skeletal muscle and preventing access to energy from muscle glycogen stores. There is currently no cure for McArdle disease. Using a preclinical animal model, we aimed to identify a clinically translatable and relevant therapy for McArdle disease. We evaluated the safety and efficacy of recombinant adeno-associated virus serotype 8 (rAAV8) to treat a murine model of McArdle disease via delivery of a functional copy of the disease-causing gene, Pygm. Intraperitoneal injection of rAAV8-Pygm at post-natal day 1-3 resulted in Pygm expression at 8 weeks of age, accompanied by improved skeletal muscle architecture, reduced accumulation of glycogen and restoration of voluntary running wheel activity to wild-type levels. We did not observe any adverse reaction to the treatment at 8 weeks post-injection. Thus, we have investigated a highly promising gene therapy for McArdle disease with a clear path to the ovine large animal model endemic to Western Australia and subsequently to patients.
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Affiliation(s)
- Elyshia L McNamara
- Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia.,Centre for Medical Research, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia
| | - Rhonda L Taylor
- Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia.,Centre for Medical Research, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia
| | - Joshua S Clayton
- Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia.,Centre for Medical Research, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia
| | - Hayley Goullee
- Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia.,Centre for Medical Research, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia
| | - Kimberley L Dilworth
- Faculty of Medicine and Health, Vector and Genome Engineering Facility, Children's Medical Research Institute, The University of Sydney, Westmead, NSW 2145, Australia
| | - Tomàs Pinós
- Neuromuscular and Mitochondrial Disorders Laboratory, Vall d'Hebron Institut de Recerca, Universitat Autonoma de Barcelona, Barcelona 08035, Spain.,Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid 28029, Spain
| | - Astrid Brull
- Sorbonne Université, INSERM UMRS_974, Center of Research in Myology, Paris 75013, France
| | - Ian E Alexander
- Gene Therapy Research Unit, Faculty of Medicine and Health, Children's Medical Research Institute, The University of Sydney and Sydney Children's Hospitals Network, Westmead, NSW 2145, Australia.,Discipline of Child and Adolescent Health, Faculty of Medicine and Health, Sydney Medical School, The University of Sydney, Westmead, NSW 2145, Australia
| | - Leszek Lisowski
- Faculty of Medicine and Health, Vector and Genome Engineering Facility, Children's Medical Research Institute, The University of Sydney, Westmead, NSW 2145, Australia.,Translational Vectorology Group, Faculty of Medicine and Health, Children's Medical Research Institute, The University of Sydney, Sydney, NSW 2006, Australia.,Military Institute of Hygiene and Epidemiology, The Biological Threats Identification and Countermeasure Centre, Puławy 24-100, Poland
| | - Gianina Ravenscroft
- Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia.,Centre for Medical Research, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia
| | - Nigel G Laing
- Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia.,Centre for Medical Research, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia
| | - Kristen J Nowak
- Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia.,Faculty of Health and Medical Sciences, School of Biomedical Sciences, University of Western Australia, QEII Medical Centre, Nedlands, WA 6009, Australia.,Public and Aboriginal Health Division, Western Australian Department of Health, Office of Population Health Genomics, East Perth, WA 6004, Australia
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6
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Berger J, Berger S, Li M, Jacoby AS, Arner A, Bavi N, Stewart AG, Currie PD. In Vivo Function of the Chaperonin TRiC in α-Actin Folding during Sarcomere Assembly. Cell Rep 2019; 22:313-322. [PMID: 29320728 DOI: 10.1016/j.celrep.2017.12.069] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 09/11/2017] [Accepted: 12/19/2017] [Indexed: 12/14/2022] Open
Abstract
The TCP-1 ring complex (TRiC) is a multi-subunit group II chaperonin that assists nascent or misfolded proteins to attain their native conformation in an ATP-dependent manner. Functional studies in yeast have suggested that TRiC is an essential and generalized component of the protein-folding machinery of eukaryotic cells. However, TRiC's involvement in specific cellular processes within multicellular organisms is largely unknown because little validation of TRiC function exists in animals. Our in vivo analysis reveals a surprisingly specific role of TRiC in the biogenesis of skeletal muscle α-actin during sarcomere assembly in myofibers. TRiC acts at the sarcomere's Z-disk, where it is required for efficient assembly of actin thin filaments. Binding of ATP specifically by the TRiC subunit Cct5 is required for efficient actin folding in vivo. Furthermore, mutant α-actin isoforms that result in nemaline myopathy in patients obtain their pathogenic conformation via this function of TRiC.
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Affiliation(s)
- Joachim Berger
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia; Victoria Node, EMBL Australia, Clayton, VIC 3800, Australia.
| | - Silke Berger
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia; Victoria Node, EMBL Australia, Clayton, VIC 3800, Australia
| | - Mei Li
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia; Victoria Node, EMBL Australia, Clayton, VIC 3800, Australia; Department of Physiology and Pharmacology, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Arie S Jacoby
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia; Victoria Node, EMBL Australia, Clayton, VIC 3800, Australia
| | - Anders Arner
- Department of Physiology and Pharmacology, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Navid Bavi
- Department of Physiology, School of Medical Sciences, The University of New South Wales, Sydney, NSW, Australia
| | - Alastair G Stewart
- Molecular, Structural and Computational Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; Faculty of Medicine, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Peter D Currie
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia; Victoria Node, EMBL Australia, Clayton, VIC 3800, Australia.
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7
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Abstract
Nemaline myopathy (NM) is among the most common non-dystrophic congenital myopathies (incidence 1:50.000). Hallmark features of NM are skeletal muscle weakness and the presence of nemaline bodies in the muscle fiber. The clinical phenotype of NM patients is quite diverse, ranging from neonatal death to normal lifespan with almost normal motor function. As the respiratory muscles are involved as well, severely affected patients are ventilator-dependent. The mechanisms underlying muscle weakness in NM are currently poorly understood. Therefore, no therapeutic treatment is available yet. Eleven implicated genes have been identified: ten genes encode proteins that are either components of thin filament, or are thought to contribute to stability or turnover of thin filament proteins. The thin filament is a major constituent of the sarcomere, the smallest contractile unit in muscle. It is at this level of contraction – thin-thick filament interaction – where muscle weakness originates in NM patients. This review focusses on how sarcomeric gene mutations directly compromise sarcomere function in NM. Insight into the contribution of sarcomeric dysfunction to muscle weakness in NM, across the genes involved, will direct towards the development of targeted therapeutic strategies.
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Affiliation(s)
| | - Coen A.C. Ottenheijm
- Correspondence to: Coen Ottenheijm, PhD, Department of Physiology, VU University Medical Center, O|2 building, 12W-51, De Boelelaan 1118, 1081 HV Amsterdam, The Netherlands. Tel.: +31 20 4448123; Fax: +31 20 4448124; E-mail:
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8
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Sewry CA, Laitila JM, Wallgren-Pettersson C. Nemaline myopathies: a current view. J Muscle Res Cell Motil 2019; 40:111-126. [PMID: 31228046 PMCID: PMC6726674 DOI: 10.1007/s10974-019-09519-9] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 05/29/2019] [Indexed: 12/13/2022]
Abstract
Nemaline myopathies are a heterogenous group of congenital myopathies caused by de novo, dominantly or recessively inherited mutations in at least twelve genes. The genes encoding skeletal α-actin (ACTA1) and nebulin (NEB) are the commonest genetic cause. Most patients have congenital onset characterized by muscle weakness and hypotonia, but the spectrum of clinical phenotypes is broad, ranging from severe neonatal presentations to onset of a milder disorder in childhood. Most patients with adult onset have an autoimmune-related myopathy with a progressive course. The wide application of massively parallel sequencing methods is increasing the number of known causative genes and broadening the range of clinical phenotypes. Nemaline myopathies are identified by the presence of structures that are rod-like or ovoid in shape with electron microscopy, and with light microscopy stain red with the modified Gömöri trichrome technique. These rods or nemaline bodies are derived from Z lines (also known as Z discs or Z disks) and have a similar lattice structure and protein content. Their shape in patients with mutations in KLHL40 and LMOD3 is distinctive and can be useful for diagnosis. The number and distribution of nemaline bodies varies between fibres and different muscles but does not correlate with severity or prognosis. Additional pathological features such as caps, cores and fibre type disproportion are associated with the same genes as those known to cause the presence of rods. Animal models are advancing the understanding of the effects of various mutations in different genes and paving the way for the development of therapies, which at present only manage symptoms and are aimed at maintaining muscle strength, joint mobility, ambulation, respiration and independence in the activities of daily living.
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Affiliation(s)
- Caroline A Sewry
- Dubowitz Neuromuscular Centre, UCL Institute of Child Health and Great Ormond Street Hospital, 30 Guilford Street, London, WC1N 1EH, UK. .,Wolfson Centre of Inherited Neuromuscular Disorders, RJAH Orthopaedic Hospital, Oswestry, SY10 7AG, UK.
| | - Jenni M Laitila
- Folkhälsan Institute of Genetics, Folkhälsan Research Center, Helsinki, Finland.,Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| | - Carina Wallgren-Pettersson
- Folkhälsan Institute of Genetics, Folkhälsan Research Center, Helsinki, Finland.,Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland
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9
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Hayashi Y, Ono K, Ono S. Mutations in Caenorhabditis elegans actin, which are equivalent to human cardiomyopathy mutations, cause abnormal actin aggregation in nematode striated muscle. F1000Res 2019; 8:279. [PMID: 30984387 PMCID: PMC6446495 DOI: 10.12688/f1000research.18476.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/08/2019] [Indexed: 01/19/2023] Open
Abstract
Actin is a central component of muscle contractile apparatuses, and a number of actin mutations cause diseases in skeletal, cardiac, and smooth muscles. However, many pathogenic actin mutations have not been characterized at cell biological and physiological levels. In this study, we tested whether the nematode Caenorhabditis elegans could be used to characterize properties of actin mutants in muscle cells in vivo. Two representative actin mutations, E99K and P164A, which cause hypertrophic cardiomyopathy in humans, are introduced in a muscle-specific C. elegans actin ACT-4 as E100K and P165A, respectively. When green fluorescent protein-tagged wild-type ACT-4 (GFP-ACT-4), is transgenically expressed in muscle at low levels as compared with endogenous actin, it is incorporated into sarcomeres without disturbing normal structures. GFP-ACT-4 variants with E100K and P165A are incorporated into sarcomeres, but also accumulated in abnormal aggregates, which have not been reported for equivalent actin mutations in previous studies. Muscle contractility, as determined by worm motility, is not apparently affected by expression of ACT-4 mutants. Our results suggest that C. elegans muscle is a useful model system to characterize abnormalities caused by actin mutations.
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Affiliation(s)
- Yuriko Hayashi
- Department of Pathology, Emory University, Atlanta, Georgia, 30322, USA
- Department of Cell Biology, Emory University, Atlanta, Georgia, 30322, USA
- Winship Cancer Institute, Emory University, Atlanta, Georgia, 30322, USA
| | - Kanako Ono
- Department of Pathology, Emory University, Atlanta, Georgia, 30322, USA
- Department of Cell Biology, Emory University, Atlanta, Georgia, 30322, USA
- Winship Cancer Institute, Emory University, Atlanta, Georgia, 30322, USA
| | - Shoichiro Ono
- Department of Pathology, Emory University, Atlanta, Georgia, 30322, USA
- Department of Cell Biology, Emory University, Atlanta, Georgia, 30322, USA
- Winship Cancer Institute, Emory University, Atlanta, Georgia, 30322, USA
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10
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Tinklenberg JA, Siebers EM, Beatka MJ, Meng H, Yang L, Zhang Z, Ross JA, Ochala J, Morris C, Owens JM, Laing NG, Nowak KJ, Lawlor MW. Myostatin inhibition using mRK35 produces skeletal muscle growth and tubular aggregate formation in wild type and TgACTA1D286G nemaline myopathy mice. Hum Mol Genet 2019; 27:638-648. [PMID: 29293963 DOI: 10.1093/hmg/ddx431] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 12/15/2017] [Indexed: 12/27/2022] Open
Abstract
Nemaline myopathy (NM) is a heterogeneous congenital skeletal muscle disease with cytoplasmic rod-like structures (nemaline bodies) in muscle tissue. While weakness in NM is related to contractile abnormalities, myofiber smallness is an additional abnormality in NM that may be treatable. We evaluated the effects of mRK35 (a myostatin inhibitor developed by Pfizer) treatment in the TgACTA1D286G mouse model of NM. mRK35 induced skeletal muscle growth that led to significant increases in animal bodyweight, forelimb grip strength and muscle fiber force, although it should be noted that animal weight and forelimb grip strength in untreated TgACTA1D286G mice was not different from controls. Treatment was also associated with an increase in the number of tubular aggregates found in skeletal muscle. These findings suggest that myostatin inhibition may be useful in promoting muscle growth and strength in Acta1-mutant muscle, while also further establishing the relationship between low levels of myostatin and tubular aggregate formation.
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Affiliation(s)
- Jennifer A Tinklenberg
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee 53226, WI, USA
| | - Emily M Siebers
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee 53226, WI, USA
| | - Margaret J Beatka
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee 53226, WI, USA
| | - Hui Meng
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee 53226, WI, USA
| | - Lin Yang
- Department of Biomedical Engineering, University of Florida, Gainesville 32607, FL, USA
| | - Zizhao Zhang
- Department of Biomedical Engineering, University of Florida, Gainesville 32607, FL, USA
| | - Jacob A Ross
- School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Julien Ochala
- School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | | | | | - Nigel G Laing
- Centre for Medical Research, The University of Western Australia, Perth, WA, Australia.,Harry Perkins Institute of Medical Research, Nedlands, WA, Australia
| | - Kristen J Nowak
- Harry Perkins Institute of Medical Research, Nedlands, WA, Australia.,Faculty of Health and Medical Sciences, School of Biomedical Sciences, The University of Western Australia, Perth, WA, Australia
| | - Michael W Lawlor
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee 53226, WI, USA
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11
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Fan J, Chan C, McNamara EL, Nowak KJ, Iwamoto H, Ochala J. Molecular Consequences of the Myopathy-Related D286G Mutation on Actin Function. Front Physiol 2018; 9:1756. [PMID: 30564146 PMCID: PMC6288369 DOI: 10.3389/fphys.2018.01756] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 11/20/2018] [Indexed: 01/06/2023] Open
Abstract
Myopathies are notably associated with mutations in genes encoding proteins known to be essential for the force production of skeletal muscle fibers, such as skeletal alpha-actin. The exact molecular mechanisms by which these specific defects induce myopathic phenotypes remain unclear. Hence, in the present study, to better understand actin dysfunction, we conducted a molecular dynamic simulation together with ex vivo experiments of the specific muscle disease-causing actin mutation, D286G located in the actin-actin interface. Our computational study showed that D286G impairs the flexural rigidity of actin filaments. However, upon activation, D286G did not have any direct consequences on actin filament extension. Hence, D286G may alter the structure of actin filaments but, when expressed together with normal actin molecules, it may only have minor effects on the ex vivo mechanics of actin filaments upon skeletal muscle fiber contraction.
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Affiliation(s)
- Jun Fan
- Department of Physics and Materials Science, The University of Hong Kong, Hong Kong, Hong Kong.,City University of Hong Kong Shenzhen Research Institute, Shenzhen, China
| | - Chun Chan
- Department of Physics and Materials Science, The University of Hong Kong, Hong Kong, Hong Kong
| | - Elyshia L McNamara
- Harry Perkins Institute of Medical Research, QEII Medical Centre, The University of Western Australia, Nedlands, WA, Australia
| | - Kristen J Nowak
- Harry Perkins Institute of Medical Research, QEII Medical Centre, The University of Western Australia, Nedlands, WA, Australia.,Department of Health, Office of Population Health Genomics, Public and Aboriginal Health Division, Government of Western Australia, East Perth, WA, Australia.,School of Biomedical Sciences, Faculty of Health and Medical Sciences, The University of Western Australia, Crawley, WA, Australia
| | - Hiroyuki Iwamoto
- SPring-8, Japan Synchrotron Radiation Research Institute, Sayo, Japan
| | - Julien Ochala
- School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, United Kingdom
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12
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Joureau B, de Winter JM, Conijn S, Bogaards SJP, Kovacevic I, Kalganov A, Persson M, Lindqvist J, Stienen GJM, Irving TC, Ma W, Yuen M, Clarke NF, Rassier DE, Malfatti E, Romero NB, Beggs AH, Ottenheijm CAC. Dysfunctional sarcomere contractility contributes to muscle weakness in ACTA1-related nemaline myopathy (NEM3). Ann Neurol 2018; 83:269-282. [PMID: 29328520 DOI: 10.1002/ana.25144] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 01/10/2018] [Accepted: 01/10/2018] [Indexed: 01/23/2023]
Abstract
OBJECTIVE Nemaline myopathy (NM) is one of the most common congenital nondystrophic myopathies and is characterized by muscle weakness, often from birth. Mutations in ACTA1 are a frequent cause of NM (ie, NEM3). ACTA1 encodes alpha-actin 1, the main constituent of the sarcomeric thin filament. The mechanisms by which mutations in ACTA1 contribute to muscle weakness in NEM3 are incompletely understood. We hypothesized that sarcomeric dysfunction contributes to muscle weakness in NEM3 patients. METHODS To test this hypothesis, we performed contractility measurements in individual muscle fibers and myofibrils obtained from muscle biopsies of 14 NEM3 patients with different ACTA1 mutations. To identify the structural basis for impaired contractility, low angle X-ray diffraction and stimulated emission-depletion microscopy were applied. RESULTS Our findings reveal that muscle fibers of NEM3 patients display a reduced maximal force-generating capacity, which is caused by dysfunctional sarcomere contractility in the majority of patients, as revealed by contractility measurements in myofibrils. Low angle X-ray diffraction and stimulated emission-depletion microscopy indicate that dysfunctional sarcomere contractility in NEM3 patients involves a lower number of myosin heads binding to actin during muscle activation. This lower number is not the result of reduced thin filament length. Interestingly, the calcium sensitivity of force is unaffected in some patients, but decreased in others. INTERPRETATION Dysfunctional sarcomere contractility is an important contributor to muscle weakness in the majority of NEM3 patients. This information is crucial for patient stratification in future clinical trials. Ann Neurol 2018;83:269-282.
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Affiliation(s)
- Barbara Joureau
- Department of Physiology, VU University Medical Center Amsterdam, Amsterdam, the Netherlands
| | | | - Stefan Conijn
- Department of Physiology, VU University Medical Center Amsterdam, Amsterdam, the Netherlands
| | - Sylvia J P Bogaards
- Department of Physiology, VU University Medical Center Amsterdam, Amsterdam, the Netherlands
| | - Igor Kovacevic
- Department of Physiology, VU University Medical Center Amsterdam, Amsterdam, the Netherlands
| | - Albert Kalganov
- Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada
| | - Malin Persson
- Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada.,Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
| | - Johan Lindqvist
- Department of Molecular and Cellular Biology and Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ
| | - Ger J M Stienen
- Department of Physiology, VU University Medical Center Amsterdam, Amsterdam, the Netherlands
| | - Thomas C Irving
- Biophysics Collaborative Access Team, Center for Synchrotron Radiation Research and Instrumentation, and Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
| | - Weikang Ma
- Biophysics Collaborative Access Team, Center for Synchrotron Radiation Research and Instrumentation, and Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
| | - Michaela Yuen
- Department of Physiology, VU University Medical Center Amsterdam, Amsterdam, the Netherlands.,Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, Westmead, New South Wales, Australia.,Discipline of Pediatrics and Child Health, University of Sydney, Sydney, New South Wales, Australia
| | - Nigel F Clarke
- Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, Westmead, New South Wales, Australia.,Discipline of Pediatrics and Child Health, University of Sydney, Sydney, New South Wales, Australia
| | - Dilson E Rassier
- Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada
| | - Edoardo Malfatti
- Pierre and Marie Curie University/University of Paris VI, Sorbonne Universities, National Institute of Health and Medical Research UMRS974, National Center for Scientific Research FRE3617, Center for Research in Myology, Pitié-Salpêtrière Hospital Group, Paris, France
| | - Norma B Romero
- Pierre and Marie Curie University/University of Paris VI, Sorbonne Universities, National Institute of Health and Medical Research UMRS974, National Center for Scientific Research FRE3617, Center for Research in Myology, Pitié-Salpêtrière Hospital Group, Paris, France
| | - Alan H Beggs
- Division of Genetics and Genomics, Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Coen A C Ottenheijm
- Department of Physiology, VU University Medical Center Amsterdam, Amsterdam, the Netherlands.,Department of Molecular and Cellular Biology and Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ
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13
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Congenital myopathies: disorders of excitation-contraction coupling and muscle contraction. Nat Rev Neurol 2018; 14:151-167. [PMID: 29391587 DOI: 10.1038/nrneurol.2017.191] [Citation(s) in RCA: 177] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The congenital myopathies are a group of early-onset, non-dystrophic neuromuscular conditions with characteristic muscle biopsy findings, variable severity and a stable or slowly progressive course. Pronounced weakness in axial and proximal muscle groups is a common feature, and involvement of extraocular, cardiorespiratory and/or distal muscles can implicate specific genetic defects. Central core disease (CCD), multi-minicore disease (MmD), centronuclear myopathy (CNM) and nemaline myopathy were among the first congenital myopathies to be reported, and they still represent the main diagnostic categories. However, these entities seem to belong to a much wider phenotypic spectrum. To date, congenital myopathies have been attributed to mutations in over 20 genes, which encode proteins implicated in skeletal muscle Ca2+ homeostasis, excitation-contraction coupling, thin-thick filament assembly and interactions, and other mechanisms. RYR1 mutations are the most frequent genetic cause, and CCD and MmD are the most common subgroups. Next-generation sequencing has vastly improved mutation detection and has enabled the identification of novel genetic backgrounds. At present, management of congenital myopathies is largely supportive, although new therapeutic approaches are reaching the clinical trial stage.
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14
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Jungbluth H, Ochala J, Treves S, Gautel M. Current and future therapeutic approaches to the congenital myopathies. Semin Cell Dev Biol 2016; 64:191-200. [PMID: 27515125 DOI: 10.1016/j.semcdb.2016.08.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 08/04/2016] [Accepted: 08/08/2016] [Indexed: 12/14/2022]
Abstract
The congenital myopathies - including Central Core Disease (CCD), Multi-minicore Disease (MmD), Centronuclear Myopathy (CNM), Nemaline Myopathy (NM) and Congenital Fibre Type Disproportion (CFTD) - are a genetically heterogeneous group of early-onset neuromuscular conditions characterized by distinct histopathological features, and associated with a substantial individual and societal disease burden. Appropriate supportive management has substantially improved patient morbidity and mortality but there is currently no cure. Recent years have seen an exponential increase in the genetic and molecular understanding of these conditions, leading to the identification of underlying defects in proteins involved in calcium homeostasis and excitation-contraction coupling, thick/thin filament assembly and function, redox regulation, membrane trafficking and/or autophagic pathways. Based on these findings, specific therapies are currently being developed, or are already approaching the clinical trial stage. Despite undeniable progress, therapy development faces considerable challenges, considering the rarity and diversity of specific conditions, and the size and complexity of some of the genes and proteins involved. The present review will summarize the key genetic, histopathological and clinical features of specific congenital myopathies, and outline therapies already available or currently being developed in the context of known pathogenic mechanisms. The relevance of newly discovered molecular mechanisms and novel gene editing strategies for future therapy development will be discussed.
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Affiliation(s)
- Heinz Jungbluth
- Department of Paediatric Neurology, Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section Biophysics and Cardiovascular Division, King's College BHF Centre of Research Excellence, United Kingdom; Department of Basic and Clinical Neuroscience, IoPPN, King's College, London, United Kingdom.
| | - Julien Ochala
- Centre of Human and Aerospace Physiological Sciences, King's College London, United Kingdom
| | - Susan Treves
- Departments of Biomedicine and Anaesthesia, Basel University Hospital, 4031 Basel, Switzerland
| | - Mathias Gautel
- Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section Biophysics and Cardiovascular Division, King's College BHF Centre of Research Excellence, United Kingdom
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15
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Egorova IF, Penyaeva EV, Bockeria LA. [Altered Z-disks of myofibrils in the cardiomyocytes from patients with Ebstein's anomaly]. Arkh Patol 2016; 77:3-8. [PMID: 26841643 DOI: 10.17116/patol20157763-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
UNLABELLED The aim of the study was to examine the peculiarities of the changes in Z-bands of myofibrils in the cardiomyocytes from patients with Ebstein's anomaly. MATERIAL AND METHODS Electron microscopy assay of intraoperative biopsies of the right heart chambers in 41 patients aged from 9 months to 57 years was performed. RESULTS Some patients exhibited Z-disk alterations of two types in individual cardiomyocytes, namely: local symmetrical bead-like expansions of Z-disks or longitudinal deposits of Z-material of different lengths along the myofibrils. Z-disk alterations were more common in atrial cardiomyocytes than in the ventricle. The presence of Z-disk alterations in the cardiomyocytes correlated with a number of clinical parameters. In particular, the occurrence of longitudinal deposits of Z-material in atrial cardiomyocytes directly correlated with the manifestation of the Wolff-Parkinson-White syndrome in the patients. CONCLUSIONS Above characteristic ultrastructural changes in Z-bands of myofibrils in the cardiomyocytes from patients with Ebstein's anomaly have a certain similarity to Z-band diseases in skeletal muscle at sarcomeric protein gene mutations described in the literature, which suggests the mutations in the genes of proteins included in Z-bands of myofibrils in the cardiomyocytes from patients with Ebstein's anomaly.
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Affiliation(s)
- I F Egorova
- A.N. Bakulev Scientific Center of Cardiovascular Surgery, Moscow
| | - E V Penyaeva
- A.N. Bakulev Scientific Center of Cardiovascular Surgery, Moscow
| | - L A Bockeria
- A.N. Bakulev Scientific Center of Cardiovascular Surgery, Moscow
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16
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Abstract
Actin is the central building block of the actin cytoskeleton, a highly regulated filamentous network enabling dynamic processes of cells and simultaneously providing structure. Mammals have six actin isoforms that are very conserved and thus share common functions. Tissue-specific expression in part underlies their differential roles, but actin isoforms also coexist in various cell types and tissues, suggesting specific functions and preferential interaction partners. Gene deletion models, antibody-based staining patterns, gene silencing effects, and the occurrence of isoform-specific mutations in certain diseases have provided clues for specificity on the subcellular level and its consequences on the organism level. Yet, the differential actin isoform functions are still far from understood in detail. Biochemical studies on the different isoforms in pure form are just emerging, and investigations in cells have to deal with a complex and regulated system, including compensatory actin isoform expression.
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Affiliation(s)
- Christophe Ampe
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, A. Baertsoenkaai 3, 9000, Ghent, Belgium.
| | - Marleen Van Troys
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, A. Baertsoenkaai 3, 9000, Ghent, Belgium
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17
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Sztal TE, Zhao M, Williams C, Oorschot V, Parslow AC, Giousoh A, Yuen M, Hall TE, Costin A, Ramm G, Bird PI, Busch-Nentwich EM, Stemple DL, Currie PD, Cooper ST, Laing NG, Nowak KJ, Bryson-Richardson RJ. Zebrafish models for nemaline myopathy reveal a spectrum of nemaline bodies contributing to reduced muscle function. Acta Neuropathol 2015; 130:389-406. [PMID: 25931053 PMCID: PMC4541704 DOI: 10.1007/s00401-015-1430-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 04/20/2015] [Accepted: 04/21/2015] [Indexed: 12/22/2022]
Abstract
Nemaline myopathy is characterized by muscle weakness and the presence of rod-like (nemaline) bodies. The genetic etiology of nemaline myopathy is becoming increasingly understood with mutations in ten genes now known to cause the disease. Despite this, the mechanism by which skeletal muscle weakness occurs remains elusive, with previous studies showing no correlation between the frequency of nemaline bodies and disease severity. To investigate the formation of nemaline bodies and their role in pathogenesis, we generated overexpression and loss-of-function zebrafish models for skeletal muscle α-actin (ACTA1) and nebulin (NEB). We identify three distinct types of nemaline bodies and visualize their formation in vivo, demonstrating these nemaline bodies not only exhibit different subcellular origins, but also have distinct pathological consequences within the skeletal muscle. One subtype is highly dynamic and upon breakdown leads to the accumulation of cytoplasmic actin contributing to muscle weakness. Examination of a Neb-deficient model suggests this mechanism may be common in nemaline myopathy. Another subtype results from a reduction of actin and forms a more stable cytoplasmic body. In contrast, the final type originates at the Z-disk and is associated with myofibrillar disorganization. Analysis of zebrafish and muscle biopsies from ACTA1 nemaline myopathy patients demonstrates that nemaline bodies also possess a different protein signature. In addition, we show that the ACTA1D286G mutation causes impaired actin incorporation and localization in the sarcomere. Together these data provide a novel examination of nemaline body origins and dynamics in vivo and identifies pathological changes that correlate with muscle weakness.
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Affiliation(s)
- Tamar E. Sztal
- />School of Biological Sciences, Monash University, Melbourne, VIC Australia
| | - Mo Zhao
- />School of Biological Sciences, Monash University, Melbourne, VIC Australia
| | - Caitlin Williams
- />School of Biological Sciences, Monash University, Melbourne, VIC Australia
| | - Viola Oorschot
- />Monash Micro-Imaging, Monash University, Melbourne, VIC Australia
| | - Adam C. Parslow
- />School of Biological Sciences, Monash University, Melbourne, VIC Australia
| | - Aminah Giousoh
- />Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC Australia
| | - Michaela Yuen
- />Institute for Neuroscience and Muscle Research, The Children’s Hospital at Westmead, Sydney, NSW Australia
| | - Thomas E. Hall
- />Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD Australia
| | - Adam Costin
- />Monash Micro-Imaging, Monash University, Melbourne, VIC Australia
| | - Georg Ramm
- />Monash Micro-Imaging, Monash University, Melbourne, VIC Australia
- />Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC Australia
| | - Phillip I. Bird
- />Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC Australia
| | | | - Derek L. Stemple
- />Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire UK
| | - Peter D. Currie
- />Australian Regenerative Medicine Institute, Monash University, Melbourne, VIC Australia
| | - Sandra T. Cooper
- />Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, Sydney, Australia
| | - Nigel G. Laing
- />Harry Perkins Institute of Medical Research and the Centre for Medical Research, University of Western Australia, Perth, WA Australia
| | - Kristen J. Nowak
- />Harry Perkins Institute of Medical Research and the Centre for Medical Research, University of Western Australia, Perth, WA Australia
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18
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Tian L, Ding S, You Y, Li TR, Liu Y, Wu X, Sun L, Xu T. Leiomodin-3-deficient mice display nemaline myopathy with fast-myofiber atrophy. Dis Model Mech 2015; 8:635-41. [PMID: 26035871 PMCID: PMC4457035 DOI: 10.1242/dmm.019430] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 04/10/2015] [Indexed: 12/24/2022] Open
Abstract
Nemaline myopathy (NM) is one of the most common forms of congenital myopathy, and affects either fast myofibers, slow myofibers, or both. However, an animal model for congenital myopathy with fast-myofiber-specific atrophy is not available. Furthermore, mutations in the leiomodin-3 (LMOD3) gene have recently been identified in a group of individuals with NM. However, it is not clear how loss of LMOD3 leads to NM. Here, we report a mouse mutant in which the piggyBac (PB) transposon is inserted into the Lmod3 gene and disrupts its expression. Lmod3PB/PB mice show severe muscle weakness and postnatal growth retardation. Electron microscopy and immunofluorescence studies of the mutant skeletal muscles revealed the presence of nemaline bodies, a hallmark of NM, and disorganized sarcomeric structures. Interestingly, Lmod3 deficiency caused muscle atrophy specific to the fast fibers. Together, our results show that Lmod3 is required in the fast fibers for sarcomere integrity, and this study offers the first NM mouse model with muscle atrophy that is specific to fast fibers. This model could be a valuable resource for interrogating myopathy pathogenesis and developing therapeutics for NM as well as other pathophysiological conditions with preferential atrophy of fast fibers, including cancer cachexia and sarcopenia. Highlighted Article: A leiomodin-3 mouse mutant generated by insertion of the piggyBac transposon exhibits nemaline myopathy with fast-myofiber-specific atrophy.
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Affiliation(s)
- Lei Tian
- State Key Laboratory of Genetic Engineering and National Center for International Research of Development and Disease, Fudan-Yale Center for Biomedical Research, Innovation Center for International Cooperation of Genetics and Development, Institute of Developmental Biology and Molecular Medicine, School of Life Sciences, Fudan University, Shanghai 200433, China Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Sheng Ding
- State Key Laboratory of Genetic Engineering and National Center for International Research of Development and Disease, Fudan-Yale Center for Biomedical Research, Innovation Center for International Cooperation of Genetics and Development, Institute of Developmental Biology and Molecular Medicine, School of Life Sciences, Fudan University, Shanghai 200433, China Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Yun You
- Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Tong-ruei Li
- State Key Laboratory of Genetic Engineering and National Center for International Research of Development and Disease, Fudan-Yale Center for Biomedical Research, Innovation Center for International Cooperation of Genetics and Development, Institute of Developmental Biology and Molecular Medicine, School of Life Sciences, Fudan University, Shanghai 200433, China Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Yan Liu
- State Key Laboratory of Genetic Engineering and National Center for International Research of Development and Disease, Fudan-Yale Center for Biomedical Research, Innovation Center for International Cooperation of Genetics and Development, Institute of Developmental Biology and Molecular Medicine, School of Life Sciences, Fudan University, Shanghai 200433, China Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Xiaohui Wu
- State Key Laboratory of Genetic Engineering and National Center for International Research of Development and Disease, Fudan-Yale Center for Biomedical Research, Innovation Center for International Cooperation of Genetics and Development, Institute of Developmental Biology and Molecular Medicine, School of Life Sciences, Fudan University, Shanghai 200433, China
| | - Ling Sun
- State Key Laboratory of Genetic Engineering and National Center for International Research of Development and Disease, Fudan-Yale Center for Biomedical Research, Innovation Center for International Cooperation of Genetics and Development, Institute of Developmental Biology and Molecular Medicine, School of Life Sciences, Fudan University, Shanghai 200433, China
| | - Tian Xu
- State Key Laboratory of Genetic Engineering and National Center for International Research of Development and Disease, Fudan-Yale Center for Biomedical Research, Innovation Center for International Cooperation of Genetics and Development, Institute of Developmental Biology and Molecular Medicine, School of Life Sciences, Fudan University, Shanghai 200433, China Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, New Haven, CT 06536, USA
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19
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Wada K, Matsushima Y, Tada T, Hasegawa S, Obara Y, Yoshizawa Y, Takahashi G, Hiai H, Shimanuki M, Suzuki S, Saitou J, Yamamoto N, Ichikawa M, Watanabe K, Kikkawa Y. Expression of truncated PITX3 in the developing lens leads to microphthalmia and aphakia in mice. PLoS One 2014; 9:e111432. [PMID: 25347445 PMCID: PMC4210183 DOI: 10.1371/journal.pone.0111432] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 09/28/2014] [Indexed: 11/18/2022] Open
Abstract
Microphthalmia is a severe ocular disorder, and this condition is typically caused by mutations in transcription factors that are involved in eye development. Mice carrying mutations in these transcription factors would be useful tools for defining the mechanisms underlying developmental eye disorders. We discovered a new spontaneous recessive microphthalmos mouse mutant in the Japanese wild-derived inbred strain KOR1/Stm. The homozygous mutant mice were histologically characterized as microphthalmic by the absence of crystallin in the lens, a condition referred to as aphakia. By positional cloning, we identified the nonsense mutation c.444C>A outside the genomic region that encodes the homeodomain of the paired-like homeodomain transcription factor 3 gene (Pitx3) as the mutation responsible for the microphthalmia and aphakia. We examined Pitx3 mRNA expression of mutant mice during embryonic stages using RT-PCR and found that the expression levels are higher than in wild-type mice. Pitx3 over-expression in the lens during developmental stages was also confirmed at the protein level in the microphthalmos mutants via immunohistochemical analyses. Although lens fiber differentiation was not observed in the mutants, strong PITX3 protein signals were observed in the lens vesicles of the mutant lens. Thus, we speculated that abnormal PITX3, which lacks the C-terminus (including the OAR domain) as a result of the nonsense mutation, is expressed in mutant lenses. We showed that the expression of the downstream genes Foxe3, Prox1, and Mip was altered because of the Pitx3 mutation, with large reductions in the lens vesicles in the mutants. Similar profiles were observed by immunohistochemical analysis of these proteins. The expression profiles of crystallins were also altered in the mutants. Therefore, we speculated that the microphthalmos/aphakia in this mutant is caused by the expression of truncated PITX3, resulting in the abnormal expression of downstream targets and lens fiber proteins.
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Affiliation(s)
- Kenta Wada
- Department of Bioproduction, Tokyo University of Agriculture, Abashiri, Japan
- Mammalian Genetics Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Yoshibumi Matsushima
- Mammalian Genetics Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
- Research Institute for Clinical Oncology, Saitama Cancer Center, Saitama, Japan
| | - Tomoki Tada
- Department of Bioproduction, Tokyo University of Agriculture, Abashiri, Japan
| | - Sayaka Hasegawa
- Department of Bioproduction, Tokyo University of Agriculture, Abashiri, Japan
| | - Yo Obara
- Mammalian Genetics Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Yasuhiro Yoshizawa
- Department of Bioproduction, Tokyo University of Agriculture, Abashiri, Japan
| | - Gou Takahashi
- Department of Bioproduction, Tokyo University of Agriculture, Abashiri, Japan
| | - Hiroshi Hiai
- Medical Innovation Center, Graduate School of Medicine Kyoto University, Kyoto, Japan
| | - Midori Shimanuki
- Basic Research Center, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Sari Suzuki
- Department of Bioproduction, Tokyo University of Agriculture, Abashiri, Japan
- Mammalian Genetics Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Junichi Saitou
- Mammalian Genetics Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Naoki Yamamoto
- Institute of Joint Research, Fujita Health University, Toyoake, Japan
| | - Masumi Ichikawa
- Basic Research Center, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Kei Watanabe
- Mammalian Genetics Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Yoshiaki Kikkawa
- Mammalian Genetics Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
- * E-mail:
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20
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Multimodal MRI and (31)P-MRS investigations of the ACTA1(Asp286Gly) mouse model of nemaline myopathy provide evidence of impaired in vivo muscle function, altered muscle structure and disturbed energy metabolism. PLoS One 2013; 8:e72294. [PMID: 23977274 PMCID: PMC3748127 DOI: 10.1371/journal.pone.0072294] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 07/15/2013] [Indexed: 02/03/2023] Open
Abstract
Nemaline myopathy (NM), the most common non-dystrophic congenital disease of skeletal muscle, can be caused by mutations in the skeletal muscle α-actin gene (ACTA1) (~25% of all NM cases and up to 50% of severe forms of NM). Muscle function of the recently generated transgenic mouse model carrying the human Asp286Gly mutation in the ACTA1 gene (Tg(ACTA1)(Asp286Gly)) has been mainly investigated in vitro. Therefore, we aimed at providing a comprehensive picture of the in vivo hindlimb muscle function of Tg(ACTA1)(Asp286Gly) mice by combining strictly noninvasive investigations. Skeletal muscle anatomy (hindlimb muscles, intramuscular fat volumes) and microstructure were studied using multimodal magnetic resonance imaging (Dixon, T2, Diffusion Tensor Imaging [DTI]). Energy metabolism was studied using 31-phosphorus Magnetic Resonance Spectroscopy ((31)P-MRS). Skeletal muscle contractile performance was investigated while applying a force-frequency protocol (1-150 Hz) and a fatigue protocol (6 min-1.7 Hz). Tg(ACTA1)(Asp286Gly) mice showed a mild muscle weakness as illustrated by the reduction of both absolute (30%) and specific (15%) maximal force production. Dixon MRI did not show discernable fatty infiltration in Tg(ACTA1)(Asp286Gly) mice indicating that this mouse model does not reproduce human MRI findings. Increased T2 values were observed in Tg(ACTA1)(Asp286Gly) mice and might reflect the occurrence of muscle degeneration/regeneration process. Interestingly, T2 values were linearly related to muscle weakness. DTI experiments indicated lower λ2 and λ3 values in Tg(ACTA1)(Asp286Gly) mice, which might be associated to muscle atrophy and/or the presence of histological anomalies. Finally (31)P-MRS investigations illustrated an increased anaerobic energy cost of contraction in Tg(ACTA1)(Asp286Gly) mice, which might be ascribed to contractile and non-contractile processes. Overall, we provide a unique set of information about the anatomic, metabolic and functional consequences of the Asp286Gly mutation that might be considered as relevant biomarkers for monitoring the severity and/or the progression of NM and for assessing the efficacy of potential therapeutic interventions.
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21
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Distinct underlying mechanisms of limb and respiratory muscle fiber weaknesses in nemaline myopathy. J Neuropathol Exp Neurol 2013; 72:472-81. [PMID: 23656990 DOI: 10.1097/nen.0b013e318293b1cc] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Nemaline myopathy is the most common congenital myopathy and is caused by mutations in various genes such as ACTA1 (encoding skeletal α-actin). It is associated with limb and respiratory muscle weakness. Despite increasing clinical and scientific interest, the molecular and cellular events leading to such weakness remain unknown, which prevents the development of specific therapeutic interventions. To unravel the potential mechanisms involved, we dissected lower limb and diaphragm muscles from a knock-in mouse model of severe nemaline myopathy expressing the ACTA1 His40Tyr actin mutation found in human patients. We then studied a broad range of structural and functional characteristics assessing single-myofiber contraction, protein expression, and electron microscopy. One of the major findings in the diaphragm was the presence of numerous noncontractile areas (including disrupted sarcomeric structures and nemaline bodies). This greatly reduced the number of functional sarcomeres, decreased the force generation capacity at the muscle fiber level, and likely would contribute to respiratory weakness. In limb muscle, by contrast, there were fewer noncontractile areas and they did not seem to have a major role in the pathogenesis of weakness. These divergent muscle-specific results provide new important insights into the pathophysiology of severe nemaline myopathy and crucial information for future development of therapeutic strategies.
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22
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Gineste C, De Winter JM, Kohl C, Witt CC, Giannesini B, Brohm K, Le Fur Y, Gretz N, Vilmen C, Pecchi E, Jubeau M, Cozzone PJ, Stienen GJM, Granzier H, Labeit S, Ottenheijm CAC, Bendahan D, Gondin J. In vivo and in vitro investigations of heterozygous nebulin knock-out mice disclose a mild skeletal muscle phenotype. Neuromuscul Disord 2013; 23:357-69. [PMID: 23375831 DOI: 10.1016/j.nmd.2012.12.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 12/07/2012] [Accepted: 12/29/2012] [Indexed: 01/30/2023]
Abstract
Nemaline myopathy is the most common congenital skeletal muscle disease, and mutations in the nebulin gene account for 50% of all cases. Recent studies suggest that the disease severity might be related to the nebulin expression levels. Considering that mutations in the nebulin gene are typically recessive, one would expect that a single functional nebulin allele would maintain nebulin protein expression which would result in preserved skeletal muscle function. We investigated skeletal muscle function of heterozygous nebulin knock-out (i.e., nebulin(+/-)) mice using a multidisciplinary approach including protein and gene expression analysis and combined in vivo and in vitro force measurements. Skeletal muscle anatomy and energy metabolism were studied strictly non-invasively using magnetic resonance imaging and 31P-magnetic resonance spectroscopy. Maximal force production was reduced by around 16% in isolated muscle of nebulin(+/-) mice while in vivo force generating capacity was preserved. Muscle weakness was associated with a shift toward a slower proteomic phenotype, but was not related to nebulin protein deficiency or to an impaired energy metabolism. Further studies would be warranted in order to determine the mechanisms leading to a mild skeletal muscle phenotype resulting from the expression of a single nebulin allele.
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Affiliation(s)
- C Gineste
- Aix-Marseille Université, CRMBM, 13005 Marseille, France
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Sevdali M, Kumar V, Peckham M, Sparrow J. Human congenital myopathy actin mutants cause myopathy and alter Z-disc structure in Drosophila flight muscle. Neuromuscul Disord 2013; 23:243-55. [PMID: 23294764 DOI: 10.1016/j.nmd.2012.11.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 10/23/2012] [Accepted: 11/29/2012] [Indexed: 01/05/2023]
Abstract
Over 190 mutations in the human skeletal muscle α-actin gene, ACTA1 cause congenital actin myopathies. We transgenically expressed six different mutant actins, G15R, I136M, D154N, V163L, V163M and D292V in Drosophila indirect flight muscles and investigated their effects in flies that express one wild type and one mutant actin copy. All the flies were flightless, and the IFMs showed incomplete Z-discs, disorganised actin filaments and 'zebra bodies'. No differences in levels of sarcomeric protein expression were observed, but tropomodulin staining was somewhat disrupted in D164N, V163L, G15R and V163M heterozygotes. A single copy of D292V mutant actin rescued the hypercontractile phenotypes caused by TnI and TnT mutants, suggesting that the D292V mutation interferes with thin filament regulation. Our results show that expression of actin mutations homologous to those in humans in the indirect flight muscles of Drosophila disrupt sarcomere organisation, with somewhat similar phenotypes to those observed in humans. Using Drosophila to study actin mutations may help aid our understanding of congential myopathies caused by actin mutations.
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Affiliation(s)
- Maria Sevdali
- Department of Biology (Area 10), University of York, York YO10 5DD, UK
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Skeletal muscle α-actin diseases (actinopathies): pathology and mechanisms. Acta Neuropathol 2013; 125:19-32. [PMID: 22825594 DOI: 10.1007/s00401-012-1019-z] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 07/12/2012] [Indexed: 01/18/2023]
Abstract
Mutations in the skeletal muscle α-actin gene (ACTA1) cause a range of congenital myopathies characterised by muscle weakness and specific skeletal muscle structural lesions. Actin accumulations, nemaline and intranuclear bodies, fibre-type disproportion, cores, caps, dystrophic features and zebra bodies have all been seen in biopsies from patients with ACTA1 disease, with patients frequently presenting with multiple pathologies. Therefore increasingly it is considered that these entities may represent a continuum of structural abnormalities arising due to ACTA1 mutations. Recently an ACTA1 mutation has also been associated with a hypertonic clinical presentation with nemaline bodies. Whilst multiple genes are known to cause many of the pathologies associated with ACTA1 mutations, to date actin aggregates, intranuclear rods and zebra bodies have solely been attributed to ACTA1 mutations. Approximately 200 different ACTA1 mutations have been identified, with 90 % resulting in dominant disease and 10 % resulting in recessive disease. Despite extensive research into normal actin function and the functional consequences of ACTA1 mutations in cell culture, animal models and patient tissue, the mechanisms underlying muscle weakness and the formation of structural lesions remains largely unknown. Whilst precise mechanisms are being grappled with, headway is being made in terms of developing therapeutics for ACTA1 disease, with gene therapy (specifically reducing the proportion of mutant skeletal muscle α-actin protein) and pharmacological agents showing promising results in animal models and patient muscle. The use of small molecules to sensitise the contractile apparatus to Ca(2+) is a promising therapeutic for patients with various neuromuscular disorders, including ACTA1 disease.
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Ochala J, Ravenscroft G, Laing NG, Nowak KJ. Nemaline myopathy-related skeletal muscle α-actin (ACTA1) mutation, Asp286Gly, prevents proper strong myosin binding and triggers muscle weakness. PLoS One 2012; 7:e45923. [PMID: 23029319 PMCID: PMC3447773 DOI: 10.1371/journal.pone.0045923] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 08/23/2012] [Indexed: 12/12/2022] Open
Abstract
Many mutations in the skeletal muscle α-actin gene (ACTA1) lead to muscle weakness and nemaline myopathy. Despite increasing clinical and scientific interest, the molecular and cellular pathogenesis of weakness remains unclear. Therefore, in the present study, we aimed at unraveling these mechanisms using muscles from a transgenic mouse model of nemaline myopathy expressing the ACTA1 Asp286Gly mutation. We recorded and analyzed the mechanics of membrane-permeabilized single muscle fibers. We also performed molecular energy state computations in the presence or absence of Asp286Gly. Results demonstrated that during contraction, the Asp286Gly acts as a “poison-protein” and according to the computational analysis it modifies the actin-actin interface. This phenomenon is likely to prevent proper myosin cross-bridge binding, limiting the fraction of actomyosin interactions in the strong binding state. At the cell level, this decreases the force-generating capacity, and, overall, induces muscle weakness. To counterbalance such negative events, future potential therapeutic strategies may focus on the inappropriate actin-actin interface or myosin binding.
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Affiliation(s)
- Julien Ochala
- Department of Neuroscience, Clinical Neurophysiology, Uppsala University, Sweden.
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