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Wallgren-Pettersson C, Jokela M, Lehtokari VL, Tyynismaa H, Sainio MT, Ylikallio E, Tynninen O, Pelin K, Auranen M. Variants in tropomyosins TPM2 and TPM3 causing muscle hypertonia. Neuromuscul Disord 2024; 35:29-32. [PMID: 38219297 DOI: 10.1016/j.nmd.2023.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 11/28/2023] [Accepted: 12/11/2023] [Indexed: 01/16/2024]
Abstract
Patients with myopathies caused by pathogenic variants in tropomyosin genes TPM2 and TPM3 usually have muscle hypotonia and weakness, their muscle biopsies often showing fibre size disproportion and nemaline bodies. Here, we describe a series of patients with hypercontractile molecular phenotypes, high muscle tone, and mostly non-specific myopathic biopsy findings without nemaline bodies. Three of the patients had trismus, whilst in one patient, the distal joints of her fingers flexed on extension of the wrists. In one biopsy from a patient with a rare TPM3 pathogenic variant, cores and minicores were observed, an unusual finding in TPM3-caused myopathy. The variants alter conserved contact sites between tropomyosin and actin.
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Affiliation(s)
- Carina Wallgren-Pettersson
- The Folkhälsan Institute of Genetics, the Folkhälsan Research Center, Helsinki, Finland, and the Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland.
| | - Manu Jokela
- Division of Clinical Neurosciences, Turku University Hospital and University of Turku, Turku, Finland
| | - Vilma-Lotta Lehtokari
- The Folkhälsan Institute of Genetics, the Folkhälsan Research Center, Helsinki, Finland, and the Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| | - Henna Tyynismaa
- Stem Cells and Metabolism Research Programme, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Markus T Sainio
- Clinical Neurosciences, Neurology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Emil Ylikallio
- Clinical Neurosciences, Neurology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Olli Tynninen
- Olli Tynninen, Department of Pathology, Helsinki University Hospital and University of Helsinki, Helsinki, Finland
| | - Katarina Pelin
- The Folkhälsan Institute of Genetics, the Folkhälsan Research Center, Helsinki, Finland, and the Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland; Molecular and Integrative Biosciences Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Mari Auranen
- Clinical Neurosciences, Neurology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
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2
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Robaszkiewicz K, Wróbel J, Moraczewska J. Troponin and a Myopathy-Linked Mutation in TPM3 Inhibit Cofilin-2-Induced Thin Filament Depolymerization. Int J Mol Sci 2023; 24:16457. [PMID: 38003645 PMCID: PMC10671271 DOI: 10.3390/ijms242216457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 11/10/2023] [Accepted: 11/13/2023] [Indexed: 11/26/2023] Open
Abstract
Uniform actin filament length is required for synchronized contraction of skeletal muscle. In myopathies linked to mutations in tropomyosin (Tpm) genes, irregular thin filaments are a common feature, which may result from defects in length maintenance mechanisms. The current work investigated the effects of the myopathy-causing p.R91C variant in Tpm3.12, a tropomyosin isoform expressed in slow-twitch muscle fibers, on the regulation of actin severing and depolymerization by cofilin-2. The affinity of cofilin-2 for F-actin was not significantly changed by either Tpm3.12 or Tpm3.12-R91C, though it increased two-fold in the presence of troponin (without Ca2+). Saturation of the filament with cofilin-2 removed both Tpm variants from the filament, although Tpm3.12-R91C was more resistant. In the presence of troponin (±Ca2+), Tpm remained on the filament, even at high cofilin-2 concentrations. Both Tpm3.12 variants inhibited filament severing and depolymerization by cofilin-2. However, the inhibition was more efficient in the presence of Tpm3.12-R91C, indicating that the pathogenic variant impaired cofilin-2-dependent actin filament turnover. Troponin (±Ca2+) further inhibited but did not completely stop cofilin-2-dependent actin severing and depolymerization.
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Affiliation(s)
| | | | - Joanna Moraczewska
- Department of Biochemistry and Cell Biology, Faculty of Biological Sciences, Kazimierz Wielki University in Bydgoszcz, 85-671 Bydgoszcz, Poland; (K.R.); (J.W.)
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3
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Lambert MR, Gussoni E. Tropomyosin 3 (TPM3) function in skeletal muscle and in myopathy. Skelet Muscle 2023; 13:18. [PMID: 37936227 PMCID: PMC10629095 DOI: 10.1186/s13395-023-00327-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 10/10/2023] [Indexed: 11/09/2023] Open
Abstract
The tropomyosin genes (TPM1-4) contribute to the functional diversity of skeletal muscle fibers. Since its discovery in 1988, the TPM3 gene has been recognized as an indispensable regulator of muscle contraction in slow muscle fibers. Recent advances suggest that TPM3 isoforms hold more extensive functions during skeletal muscle development and in postnatal muscle. Additionally, mutations in the TPM3 gene have been associated with the features of congenital myopathies. The use of different in vitro and in vivo model systems has leveraged the discovery of several disease mechanisms associated with TPM3-related myopathy. Yet, the precise mechanisms by which TPM3 mutations lead to muscle dysfunction remain unclear. This review consolidates over three decades of research about the role of TPM3 in skeletal muscle. Overall, the progress made has led to a better understanding of the phenotypic spectrum in patients affected by mutations in this gene. The comprehensive body of work generated over these decades has also laid robust groundwork for capturing the multiple functions this protein plays in muscle fibers.
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Affiliation(s)
- Matthias R Lambert
- Division of Genetics and Genomics, Boston Children's Hospital, 300 Longwood Ave., Boston, MA, 02115, USA.
- Department of Pediatrics, Harvard Medical School, Boston, MA, 02115, USA.
| | - Emanuela Gussoni
- Division of Genetics and Genomics, Boston Children's Hospital, 300 Longwood Ave., Boston, MA, 02115, USA
- Department of Pediatrics, Harvard Medical School, Boston, MA, 02115, USA
- The Stem Cell Program, Boston Children's Hospital, Boston, MA, 02115, USA
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4
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Claassen WJ, Baelde RJ, Galli RA, de Winter JM, Ottenheijm CAC. Small molecule drugs to improve sarcomere function in those with acquired and inherited myopathies. Am J Physiol Cell Physiol 2023; 325:C60-C68. [PMID: 37212548 PMCID: PMC10281779 DOI: 10.1152/ajpcell.00047.2023] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 05/15/2023] [Accepted: 05/15/2023] [Indexed: 05/23/2023]
Abstract
Muscle weakness is a hallmark of inherited or acquired myopathies. It is a major cause of functional impairment and can advance to life-threatening respiratory insufficiency. During the past decade, several small-molecule drugs that improve the contractility of skeletal muscle fibers have been developed. In this review, we provide an overview of the available literature and the mechanisms of action of small-molecule drugs that modulate the contractility of sarcomeres, the smallest contractile units in striated muscle, by acting on myosin and troponin. We also discuss their use in the treatment of skeletal myopathies. The first of three classes of drugs discussed here increase contractility by decreasing the dissociation rate of calcium from troponin and thereby sensitizing the muscle to calcium. The second two classes of drugs directly act on myosin and stimulate or inhibit the kinetics of myosin-actin interactions, which may be useful in patients with muscle weakness or stiffness.NEW & NOTEWORTHY During the past decade, several small molecule drugs that improve the contractility of skeletal muscle fibers have been developed. In this review, we provide an overview of the available literature and the mechanisms of action of small molecule drugs that modulate the contractility of sarcomeres, the smallest contractile units in striated muscle, by acting on myosin and troponin.
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Affiliation(s)
- Wout J Claassen
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, De Boelelaan, Amsterdam, Netherlands
| | - Rianne J Baelde
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, De Boelelaan, Amsterdam, Netherlands
| | - Ricardo A Galli
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, De Boelelaan, Amsterdam, Netherlands
| | - Josine M de Winter
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, De Boelelaan, Amsterdam, Netherlands
| | - Coen A C Ottenheijm
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, De Boelelaan, Amsterdam, Netherlands
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5
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Karpicheva OE, Avrova SV, Bogdanov AL, Sirenko VV, Redwood CS, Borovikov YS. Molecular Mechanisms of Deregulation of Muscle Contractility Caused by the R168H Mutation in TPM3 and Its Attenuation by Therapeutic Agents. Int J Mol Sci 2023; 24:ijms24065829. [PMID: 36982903 PMCID: PMC10051413 DOI: 10.3390/ijms24065829] [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: 02/28/2023] [Revised: 03/13/2023] [Accepted: 03/13/2023] [Indexed: 03/30/2023] Open
Abstract
The substitution for Arg168His (R168H) in γ-tropomyosin (TPM3 gene, Tpm3.12 isoform) is associated with congenital muscle fiber type disproportion (CFTD) and muscle weakness. It is still unclear what molecular mechanisms underlie the muscle dysfunction seen in CFTD. The aim of this work was to study the effect of the R168H mutation in Tpm3.12 on the critical conformational changes that myosin, actin, troponin, and tropomyosin undergo during the ATPase cycle. We used polarized fluorescence microscopy and ghost muscle fibers containing regulated thin filaments and myosin heads (myosin subfragment-1) modified with the 1,5-IAEDANS fluorescent probe. Analysis of the data obtained revealed that a sequential interdependent conformational-functional rearrangement of tropomyosin, actin and myosin heads takes place when modeling the ATPase cycle in the presence of wild-type tropomyosin. A multistep shift of the tropomyosin strands from the outer to the inner domain of actin occurs during the transition from weak to strong binding of myosin to actin. Each tropomyosin position determines the corresponding balance between switched-on and switched-off actin monomers and between the strongly and weakly bound myosin heads. At low Ca2+, the R168H mutation was shown to switch some extra actin monomers on and increase the persistence length of tropomyosin, demonstrating the freezing of the R168HTpm strands close to the open position and disruption of the regulatory function of troponin. Instead of reducing the formation of strong bonds between myosin heads and F-actin, troponin activated it. However, at high Ca2+, troponin decreased the amount of strongly bound myosin heads instead of promoting their formation. Abnormally high sensitivity of thin filaments to Ca2+, inhibition of muscle fiber relaxation due to the appearance of the myosin heads strongly associated with F-actin, and distinct activation of the contractile system at submaximal concentrations of Ca2+ can lead to muscle inefficiency and weakness. Modulators of troponin (tirasemtiv and epigallocatechin-3-gallate) and myosin (omecamtiv mecarbil and 2,3-butanedione monoxime) have been shown to more or less attenuate the negative effects of the tropomyosin R168H mutant. Tirasemtiv and epigallocatechin-3-gallate may be used to prevent muscle dysfunction.
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Affiliation(s)
- Olga E Karpicheva
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg 194064, Russia
| | - Stanislava V Avrova
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg 194064, Russia
| | - Andrey L Bogdanov
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg 194064, Russia
| | - Vladimir V Sirenko
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg 194064, Russia
| | - Charles S Redwood
- Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Yurii S Borovikov
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., St. Petersburg 194064, Russia
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6
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Gineste C, Laporte J. Therapeutic approaches in different congenital myopathies. Curr Opin Pharmacol 2023; 68:102328. [PMID: 36512981 DOI: 10.1016/j.coph.2022.102328] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/17/2022] [Accepted: 11/12/2022] [Indexed: 12/14/2022]
Abstract
Congenital myopathies are rare and severe genetic diseases affecting the skeletal muscle function in children and adults. They present a variable spectrum of phenotypes and a genetic heterogeneity. Subgroups are defined according to the clinical and histopathological features and encompass core myopathy, centronuclear myopathy, nemaline myopathy and other rare congenital myopathies. No approved treatment exists to date for any congenital myopathies. To tackle this important unmet need, an increased number of proof-of-concept studies recently assessed the therapeutic potential of various strategies, either pharmacological or genetic-based, aiming at counteracting muscle weakness or/and cure the pathology. Here, we list the implicated genes and cellular pathways, and review the therapeutic approaches preclinically tested and the ongoing/completed clinical trials for the different types of congenital myopathies.
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Affiliation(s)
- Charlotte Gineste
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Inserm U1258, Cnrs UMR7104, Strasbourg University, Illkirch 67404, France
| | - Jocelyn Laporte
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Inserm U1258, Cnrs UMR7104, Strasbourg University, Illkirch 67404, France.
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7
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Ranu N, Laitila J, Dugdale HF, Mariano J, Kolb JS, Wallgren-Pettersson C, Witting N, Vissing J, Vilchez JJ, Fiorillo C, Zanoteli E, Auranen M, Jokela M, Tasca G, Claeys KG, Voermans NC, Palmio J, Huovinen S, Moggio M, Beck TN, Kontrogianni-Konstantopoulos A, Granzier H, Ochala J. NEB mutations disrupt the super-relaxed state of myosin and remodel the muscle metabolic proteome in nemaline myopathy. Acta Neuropathol Commun 2022; 10:185. [PMID: 36528760 PMCID: PMC9758823 DOI: 10.1186/s40478-022-01491-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 12/08/2022] [Indexed: 12/23/2022] Open
Abstract
Nemaline myopathy (NM) is one of the most common non-dystrophic genetic muscle disorders. NM is often associated with mutations in the NEB gene. Even though the exact NEB-NM pathophysiological mechanisms remain unclear, histological analyses of patients' muscle biopsies often reveal unexplained accumulation of glycogen and abnormally shaped mitochondria. Hence, the aim of the present study was to define the exact molecular and cellular cascade of events that would lead to potential changes in muscle energetics in NEB-NM. For that, we applied a wide range of biophysical and cell biology assays on skeletal muscle fibres from NM patients as well as untargeted proteomics analyses on isolated myofibres from a muscle-specific nebulin-deficient mouse model. Unexpectedly, we found that the myosin stabilizing conformational state, known as super-relaxed state, was significantly impaired, inducing an increase in the energy (ATP) consumption of resting muscle fibres from NEB-NM patients when compared with controls or with other forms of genetic/rare, acquired NM. This destabilization of the myosin super-relaxed state had dynamic consequences as we observed a remodeling of the metabolic proteome in muscle fibres from nebulin-deficient mice. Altogether, our findings explain some of the hitherto obscure hallmarks of NM, including the appearance of abnormal energy proteins and suggest potential beneficial effects of drugs targeting myosin activity/conformations for NEB-NM.
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Affiliation(s)
- Natasha Ranu
- grid.13097.3c0000 0001 2322 6764Centre of Human and Applied Physiological Sciences, School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, King’s College London, London, UK
| | - Jenni Laitila
- grid.5254.60000 0001 0674 042XDepartment of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark ,grid.7737.40000 0004 0410 2071The Folkhälsan Institute of Genetics and Department of Medical and Clinical Genetics, Medicum, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
| | - Hannah F. Dugdale
- grid.13097.3c0000 0001 2322 6764Centre of Human and Applied Physiological Sciences, School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, King’s College London, London, UK ,grid.6571.50000 0004 1936 8542School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Jennifer Mariano
- grid.411024.20000 0001 2175 4264Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, USA
| | - Justin S. Kolb
- grid.134563.60000 0001 2168 186XDepartment of Cellular and Molecular Medicine, University of Arizona, Tucson, USA
| | - Carina Wallgren-Pettersson
- grid.7737.40000 0004 0410 2071The Folkhälsan Institute of Genetics and Department of Medical and Clinical Genetics, Medicum, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
| | - Nanna Witting
- grid.5254.60000 0001 0674 042XCopenhagen Neuromuscular Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - John Vissing
- grid.5254.60000 0001 0674 042XCopenhagen Neuromuscular Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Juan Jesus Vilchez
- grid.84393.350000 0001 0360 9602Neuromuscular and Ataxias Research Group, Instituto de Investigación Sanitaria La Fe, Valencia, Spain ,grid.452372.50000 0004 1791 1185Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) Spain, Valencia, Spain
| | - Chiara Fiorillo
- grid.5606.50000 0001 2151 3065Neuromuscular Disorders Unit, IRCCS Istituto Giannina Gaslini, DINOGMI, University of Genoa, Genoa, Italy
| | - Edmar Zanoteli
- grid.11899.380000 0004 1937 0722Department of Neurology, Faculdade de Medicina (FMUSP), Universidade de São Paulo, São Paulo, Brazil
| | - Mari Auranen
- grid.7737.40000 0004 0410 2071Clinical Neurosciences, University of Helsinki and Helsinki University Hospital, NeurologyHelsinki, Finland
| | - Manu Jokela
- grid.1374.10000 0001 2097 1371Neurology, Clinical Medicine, University of Turku, Turku, Finland ,grid.410552.70000 0004 0628 215XNeurocenter, Turku University Hospital, Turku, Finland ,grid.502801.e0000 0001 2314 6254Neuromuscular Research Center, Department of Neurology, Tampere University and University Hospital, Tampere, Finland
| | - Giorgio Tasca
- grid.414603.4Unità Operativa Complessa di Neurologia, Fondazione Policlinico Universitario “A. Gemelli”, IRCCS, Rome, Italy ,grid.1006.70000 0001 0462 7212John Walton Muscular Dystrophy Research Centre, Newcastle University and Newcastle Hospitals NHS Foundation Trusts, Newcastle Upon Tyne, UK
| | - Kristl G. Claeys
- grid.410569.f0000 0004 0626 3338Department of Neurology, University Hospitals Leuven, Leuven, Belgium ,grid.5596.f0000 0001 0668 7884Laboratory for Muscle Diseases and Neuropathies, Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Nicol C. Voermans
- grid.10417.330000 0004 0444 9382Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Johanna Palmio
- grid.502801.e0000 0001 2314 6254Neuromuscular Research Center, Department of Neurology, Tampere University and University Hospital, Tampere, Finland
| | - Sanna Huovinen
- grid.412330.70000 0004 0628 2985Department of Pathology, Fimlab Laboratories, Tampere University Hospital, Tampere, Finland
| | - Maurizio Moggio
- grid.414818.00000 0004 1757 8749Neuromuscular and Rare Diseases Unit, Department of Neuroscience, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Thomas Nyegaard Beck
- grid.5254.60000 0001 0674 042XDepartment of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Henk Granzier
- grid.134563.60000 0001 2168 186XDepartment of Cellular and Molecular Medicine, University of Arizona, Tucson, USA
| | - Julien Ochala
- grid.5254.60000 0001 0674 042XDepartment of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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8
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Karpicheva OE. Hallmark Features of the Tropomyosin
Regulatory Function in Several Variants of Congenital Myopathy. J EVOL BIOCHEM PHYS+ 2021. [DOI: 10.1134/s0022093021030133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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9
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Griffet J, Dieterich K, Bourg V, Bourgeois E. Amyoplasia and distal arthrogryposis. Orthop Traumatol Surg Res 2021; 107:102781. [PMID: 33321243 DOI: 10.1016/j.otsr.2020.102781] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 04/15/2020] [Accepted: 04/21/2020] [Indexed: 02/03/2023]
Abstract
Arthrogryposis multiplex congenita (AMC) consists of congenital joint contractures that affect at least two joints. There are two types: in the first, arthrogryposis is an additional sign in the context of various pathologies (neuromuscular diseases); in the second, it is the main and constant symptom. In the first type, the progression of the causal underlying disease must be considered. In the second type, there are two specific forms: Amyoplasia corresponds to a significant congenital absence of muscles (epigenetic disease or vascular origin) while distal arthrogryposis has a genetic component and is transmissible. The orthopedic surgeon's purpose, which is usually to enhance movement, is not appropriate for an arthrogryposis patient. One must keep in mind that without muscle, movement is impossible. The goal differs between the upper and lower limbs: for the upper limb, it is to allow grasping, and, if possible, to bring the hand to the mouth; for the lower limb, it is to ensure ambulation with plantigrade support, and the knees extended, which is the only stable position possible with little to no muscles. The rehabilitation, orthoses and/or surgical techniques are chosen to achieve this singular aim. While it may appear modest, it is crucial for patients. The goal is to achieve useful mobility, not maximum mobility. This multidisciplinary treatment, which evolves over time, must be explained to the family to get its adherence.
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Affiliation(s)
- Jacques Griffet
- Service d'orthopédie infantile, hôpital Couple-Enfant, CHU de Grenoble-Alpes, Grenoble-Alpes, France; Centre de référence de l'arthrogrypose, hôpital Couple-Enfant, CHU de Grenoble-Alpes, Grenoble-Alpes, France; Université Grenoble-Alpes, Université Joseph-Fournier, Grenoble, France.
| | - Klaus Dieterich
- Service de génétique, hôpital Couple-Enfant, CHU de Grenoble-Alpes, Grenoble-Alpes, France; Centre de référence de l'arthrogrypose, hôpital Couple-Enfant, CHU de Grenoble-Alpes, Grenoble-Alpes, France; Université Grenoble-Alpes, Université Joseph-Fournier, Grenoble, France
| | - Véronique Bourg
- Service de médecine physique et réadaptation pédiatrique, hôpital Couple-Enfant, CHU de Grenoble-Alpes, Grenoble-Alpes, France; Centre de référence de l'arthrogrypose, hôpital Couple-Enfant, CHU de Grenoble-Alpes, Grenoble-Alpes, France
| | - Emeline Bourgeois
- Service d'orthopédie infantile, hôpital Couple-Enfant, CHU de Grenoble-Alpes, Grenoble-Alpes, France; Centre de référence de l'arthrogrypose, hôpital Couple-Enfant, CHU de Grenoble-Alpes, Grenoble-Alpes, France
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10
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Contractile properties are impaired in congenital myopathies. Neuromuscul Disord 2020; 30:649-655. [PMID: 32675003 DOI: 10.1016/j.nmd.2020.06.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 06/11/2020] [Accepted: 06/16/2020] [Indexed: 11/23/2022]
Abstract
The ratio between muscle strength and muscle cross-sectional area is called the specific force. Fatty replacement of muscles is seen in many myopathies, affecting the specific force, without necessarily affecting the ability of the remaining muscle fibers to contract. This ability is called the contractility and is the ratio between muscle strength and the lean muscle cross-sectional area, i.e. the contractile cross-sectional area. We hypothesized that contractility is disrupted in patients with congenital myopathy, because of defects in contractile proteins of the sarcomere. Peak torque across ankle and knee joints was measured by isokinetic dynamometry in 16 patients with congenital myopathy and 13 healthy controls. Five patients only participated partially in the dynamometer measurements due to severe muscle weakness. Dixon MRI technique was used to quantify muscle fat fractions and calculate cross-sectional area. Patients with congenital myopathy had lower cross-sectional area in all muscle groups (P<0.01), higher fat fraction (P<0.01) and less strength (P<0.005) in all studied muscle groups. Their fat content was more than doubled and peak torque lower than half that in healthy controls. Muscle contractility was reduced (P<0.01) in three of four patient muscle groups. In conclusion, muscle contractility was reduced in patients with congenital myopathy, across different diagnoses, and was independent of the level of muscle fat fraction, suggesting that intrinsic defects of the myocyte are responsible for reduced contractility.
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11
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Laitila JM, McNamara EL, Wingate CD, Goullee H, Ross JA, Taylor RL, van der Pijl R, Griffiths LM, Harries R, Ravenscroft G, Clayton JS, Sewry C, Lawlor MW, Ottenheijm CAC, Bakker AJ, Ochala J, Laing NG, Wallgren-Pettersson C, Pelin K, Nowak KJ. Nebulin nemaline myopathy recapitulated in a compound heterozygous mouse model with both a missense and a nonsense mutation in Neb. Acta Neuropathol Commun 2020; 8:18. [PMID: 32066503 PMCID: PMC7027239 DOI: 10.1186/s40478-020-0893-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 02/05/2020] [Indexed: 12/31/2022] Open
Abstract
Nemaline myopathy (NM) caused by mutations in the gene encoding nebulin (NEB) accounts for at least 50% of all NM cases worldwide, representing a significant disease burden. Most NEB-NM patients have autosomal recessive disease due to a compound heterozygous genotype. Of the few murine models developed for NEB-NM, most are Neb knockout models rather than harbouring Neb mutations. Additionally, some models have a very severe phenotype that limits their application for evaluating disease progression and potential therapies. No existing murine models possess compound heterozygous Neb mutations that reflect the genotype and resulting phenotype present in most patients. We aimed to develop a murine model that more closely matched the underlying genetics of NEB-NM, which could assist elucidation of the pathogenetic mechanisms underlying the disease. Here, we have characterised a mouse strain with compound heterozygous Neb mutations; one missense (p.Tyr2303His), affecting a conserved actin-binding site and one nonsense mutation (p.Tyr935*), introducing a premature stop codon early in the protein. Our studies reveal that this compound heterozygous model, NebY2303H, Y935X, has striking skeletal muscle pathology including nemaline bodies. In vitro whole muscle and single myofibre physiology studies also demonstrate functional perturbations. However, no reduction in lifespan was noted. Therefore, NebY2303H,Y935X mice recapitulate human NEB-NM and are a much needed addition to the NEB-NM mouse model collection. The moderate phenotype also makes this an appropriate model for studying NEB-NM pathogenesis, and could potentially be suitable for testing therapeutic applications.
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12
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Aboelkassem Y, McCabe KJ, Huber GA, Regnier M, McCammon JA, McCulloch AD. A Stochastic Multiscale Model of Cardiac Thin Filament Activation Using Brownian-Langevin Dynamics. Biophys J 2019; 117:2255-2272. [PMID: 31547973 PMCID: PMC6990154 DOI: 10.1016/j.bpj.2019.08.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 07/31/2019] [Accepted: 08/02/2019] [Indexed: 11/16/2022] Open
Abstract
We use Brownian-Langevin dynamics principles to derive a coarse-graining multiscale myofilament model that can describe the thin-filament activation process during contraction. The model links atomistic molecular simulations of protein-protein interactions in the thin-filament regulatory unit to sarcomere-level activation dynamics. We first calculate the molecular interaction energy between tropomyosin and actin surface using Brownian dynamics simulations. This energy profile is then generalized to account for the observed tropomyosin transitions between its regulatory stable states. The generalized energy landscape then served as a basis for developing a filament-scale model using Langevin dynamics. This integrated analysis, spanning molecular to thin-filament scales, is capable of tracking the events of the tropomyosin conformational changes as it moves over the actin surface. The tropomyosin coil with flexible overlap regions between adjacent tropomyosins is represented in the model as a system of coupled stochastic ordinary differential equations. The proposed multiscale approach provides a more detailed molecular connection between tropomyosin dynamics, the trompomyosin-actin interaction-energy landscape, and the generated force by the sarcomere.
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Affiliation(s)
- Yasser Aboelkassem
- Department of Bioengineering, University of California San Diego, La Jolla, California.
| | - Kimberly J McCabe
- Department of Bioengineering, University of California San Diego, La Jolla, California
| | - Gary A Huber
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
| | - Michael Regnier
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - J Andrew McCammon
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
| | - Andrew D McCulloch
- Department of Bioengineering, University of California San Diego, La Jolla, California
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13
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Ross JA, Levy Y, Ripolone M, Kolb JS, Turmaine M, Holt M, Lindqvist J, Claeys KG, Weis J, Monforte M, Tasca G, Moggio M, Figeac N, Zammit PS, Jungbluth H, Fiorillo C, Vissing J, Witting N, Granzier H, Zanoteli E, Hardeman EC, Wallgren-Pettersson C, Ochala J. Impairments in contractility and cytoskeletal organisation cause nuclear defects in nemaline myopathy. Acta Neuropathol 2019; 138:477-495. [PMID: 31218456 PMCID: PMC6689292 DOI: 10.1007/s00401-019-02034-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 05/28/2019] [Accepted: 06/05/2019] [Indexed: 02/07/2023]
Abstract
Nemaline myopathy (NM) is a skeletal muscle disorder caused by mutations in genes that are generally involved in muscle contraction, in particular those related to the structure and/or regulation of the thin filament. Many pathogenic aspects of this disease remain largely unclear. Here, we report novel pathological defects in skeletal muscle fibres of mouse models and patients with NM: irregular spacing and morphology of nuclei; disrupted nuclear envelope; altered chromatin arrangement; and disorganisation of the cortical cytoskeleton. Impairments in contractility are the primary cause of these nuclear defects. We also establish the role of microtubule organisation in determining nuclear morphology, a phenomenon which is likely to contribute to nuclear alterations in this disease. Our results overlap with findings in diseases caused directly by mutations in nuclear envelope or cytoskeletal proteins. Given the important role of nuclear shape and envelope in regulating gene expression, and the cytoskeleton in maintaining muscle fibre integrity, our findings are likely to explain some of the hallmarks of NM, including contractile filament disarray, altered mechanical properties and broad transcriptional alterations.
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14
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Thin filament dysfunctions caused by mutations in tropomyosin Tpm3.12 and Tpm1.1. J Muscle Res Cell Motil 2019; 41:39-53. [PMID: 31270709 PMCID: PMC7109180 DOI: 10.1007/s10974-019-09532-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 06/26/2019] [Indexed: 12/14/2022]
Abstract
Tropomyosin is the major regulator of the thin filament. In striated muscle its function is to bind troponin complex and control the access of myosin heads to actin in a Ca2+-dependent manner. It also participates in the maintenance of thin filament length by regulation of tropomodulin and leiomodin, the pointed end-binding proteins. Because the size of the overlap between actin and myosin filaments affects the number of myosin heads which interact with actin, the filament length is one of the determinants of force development. Numerous point mutations in genes encoding tropomyosin lead to single amino acid substitutions along the entire length of the coiled coil that are associated with various types of cardiomyopathy and skeletal muscle disease. Specific regions of tropomyosin interact with different binding partners; therefore, the mutations affect diverse tropomyosin functions. In this review, results of studies on mutations in the genes TPM1 and TPM3, encoding Tpm1.1 and Tpm3.12, are described. The paper is particularly focused on mutation-dependent alterations in the mechanisms of actin-myosin interactions and dynamics of the thin filament at the pointed end.
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15
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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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16
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Moraczewska J, Robaszkiewicz K, Śliwinska M, Czajkowska M, Ly T, Kostyukova A, Wen H, Zheng W. Congenital myopathy-related mutations in tropomyosin disrupt regulatory function through altered actin affinity and tropomodulin binding. FEBS J 2019; 286:1877-1893. [PMID: 30768849 PMCID: PMC7202179 DOI: 10.1111/febs.14787] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 12/28/2018] [Accepted: 02/13/2019] [Indexed: 11/28/2022]
Abstract
Tropomyosin (Tpm) binds along actin filaments and regulates myosin binding to control muscle contraction. Tropomodulin binds to the pointed end of a filament and regulates actin dynamics, which maintains the length of a thin filament. To define the structural determinants of these Tpm functions, we examined the effects of two congenital myopathy mutations, A4V and R91C, in the Tpm gene, TPM3, which encodes the Tpm3.12 isoform, specific for slow-twitch muscle fibers. Mutation A4V is located in the tropomodulin-binding, N-terminal region of Tpm3.12. R91C is located in the actin-binding period 3 and directly interacts with actin. The A4V and R91C mutations resulted in a 2.5-fold reduced affinity of Tpm3.12 homodimers for F-actin in the absence and presence of troponin, and a two-fold decrease in actomyosin ATPase activation in the presence of Ca2+ . Actomyosin ATPase inhibition in the absence of Ca2+ was not affected. The Ca2+ sensitivity of ATPase activity was decreased by R91C, but not by A4V. In vitro, R91C altered the ability of tropomodulin 1 (Tmod1) to inhibit actin polymerization at the pointed end of the filaments, which correlated with the reduced affinity of Tpm3.12-R91C for Tmod1. Molecular dynamics simulations of Tpm3.12 in complex with F-actin suggested that both mutations reduce the affinity of Tpm3.12 for F-actin binding by perturbing the van der Waals energy, which may be attributable to two different molecular mechanisms-a reduced flexibility of Tpm3.12-R91C and an increased flexibility of Tpm3.12-A4V.
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Affiliation(s)
- Joanna Moraczewska
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
| | - Katarzyna Robaszkiewicz
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
| | - Małgorzata Śliwinska
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
| | - Marta Czajkowska
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
| | - Thu Ly
- Voiland School of Chemical Engineering and Bioengineering, University of Washington, Pullman, WA, USA
| | - Alla Kostyukova
- Voiland School of Chemical Engineering and Bioengineering, University of Washington, Pullman, WA, USA
| | - Han Wen
- Department of Physics, University at Buffalo, SUNY, NY, USA
| | - Wenjun Zheng
- Department of Physics, University at Buffalo, SUNY, NY, USA
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17
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Levy Y, Ross JA, Niglas M, Snetkov VA, Lynham S, Liao CY, Puckelwartz MJ, Hsu YM, McNally EM, Alsheimer M, Harridge SD, Young SG, Fong LG, Español Y, Lopez-Otin C, Kennedy BK, Lowe DA, Ochala J. Prelamin A causes aberrant myonuclear arrangement and results in muscle fiber weakness. JCI Insight 2018; 3:120920. [PMID: 30282816 PMCID: PMC6237469 DOI: 10.1172/jci.insight.120920] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 08/23/2018] [Indexed: 01/06/2023] Open
Abstract
Physiological and premature aging are frequently associated with an accumulation of prelamin A, a precursor of lamin A, in the nuclear envelope of various cell types. Here, we aimed to underpin the hitherto unknown mechanisms by which prelamin A alters myonuclear organization and muscle fiber function. By experimentally studying membrane-permeabilized myofibers from various transgenic mouse lines, our results indicate that, in the presence of prelamin A, the abundance of nuclei and myosin content is markedly reduced within muscle fibers. This leads to a concept by which the remaining myonuclei are very distant from each other and are pushed to function beyond their maximum cytoplasmic capacity, ultimately inducing muscle fiber weakness.
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Affiliation(s)
- Yotam Levy
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| | - Jacob A Ross
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| | - Marili Niglas
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| | - Vladimir A Snetkov
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| | - Steven Lynham
- Proteomics Facility, Centre of Excellence for Mass Spectrometry, King's College London, London, United Kingdom
| | - Chen-Yu Liao
- Buck Institute for Research on Aging, Novato, California, USA
| | - Megan J Puckelwartz
- Center for Genetic Medicine, Northwestern University, Chicago, Illinois, USA
| | - Yueh-Mei Hsu
- Buck Institute for Research on Aging, Novato, California, USA
| | - Elizabeth M McNally
- Center for Genetic Medicine, Northwestern University, Chicago, Illinois, USA
| | - Manfred Alsheimer
- Department of Cell and Developmental Biology, University of Würzburg, Würzburg, Germany
| | - Stephen Dr Harridge
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| | - Stephen G Young
- Department of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Loren G Fong
- Department of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Yaiza Español
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Instituto Universitario de Oncología (IUOPA), Universidad de Oviedo, Oviedo, Spain
| | - Carlos Lopez-Otin
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Instituto Universitario de Oncología (IUOPA), Universidad de Oviedo, Oviedo, Spain.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Spain
| | - Brian K Kennedy
- Buck Institute for Research on Aging, Novato, California, USA.,Departments of Biochemistry and Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Centre for Healthy Ageing, National University Health System, Singapore.,Singapore Institute for Clinical Sciences, Singapore
| | - Dawn A Lowe
- Divisions of Rehabilitation Science and Physical Therapy, Department of Rehabilitation Medicine, School of Medicine, University of Minnesota, Minneapolis, Minnesota, USA
| | - Julien Ochala
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
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18
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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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19
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Sui Z, Gokhin DS, Nowak RB, Guo X, An X, Fowler VM. Stabilization of F-actin by tropomyosin isoforms regulates the morphology and mechanical behavior of red blood cells. Mol Biol Cell 2017; 28:2531-2542. [PMID: 28720661 PMCID: PMC5597325 DOI: 10.1091/mbc.e16-10-0699] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 07/14/2017] [Accepted: 07/14/2017] [Indexed: 01/17/2023] Open
Abstract
The absence of Tpm3.1 in red blood cells (RBCs) induces a compensatory increase in Tpm1.9 and abnormally stable F-actin in the membrane skeleton, with reduced association of Band 3 and glycophorin A, leading to a compensated hemolytic anemia with abnormal RBC shapes and mechanical properties. The short F-actins in the red blood cell (RBC) membrane skeleton are coated along their lengths by an equimolar combination of two tropomyosin isoforms, Tpm1.9 and Tpm3.1. We hypothesized that tropomyosin’s ability to stabilize F-actin regulates RBC morphology and mechanical properties. To test this, we examined mice with a targeted deletion in alternatively spliced exon 9d of Tpm3 (Tpm3/9d–/–), which leads to absence of Tpm3.1 in RBCs along with a compensatory increase in Tpm1.9 of sufficient magnitude to maintain normal total tropomyosin content. The isoform switch from Tpm1.9/Tpm3.1 to exclusively Tpm1.9 does not affect membrane skeleton composition but causes RBC F-actins to become hyperstable, based on decreased vulnerability to latrunculin-A–induced depolymerization. Unexpectedly, this isoform switch also leads to decreased association of Band 3 and glycophorin A with the membrane skeleton, suggesting that tropomyosin isoforms regulate the strength of F-actin-to-membrane linkages. Tpm3/9d–/– mice display a mild compensated anemia, in which RBCs have spherocytic morphology with increased osmotic fragility, reduced membrane deformability, and increased membrane stability. We conclude that RBC tropomyosin isoforms directly influence RBC physiology by regulating 1) the stability of the short F-actins in the membrane skeleton and 2) the strength of linkages between the membrane skeleton and transmembrane glycoproteins.
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Affiliation(s)
- Zhenhua Sui
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037
| | - David S Gokhin
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037
| | - Roberta B Nowak
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037
| | - Xinhua Guo
- Laboratory of Membrane Biology, New York Blood Center, New York, NY 10065
| | - Xiuli An
- Laboratory of Membrane Biology, New York Blood Center, New York, NY 10065.,School of Life Science, Zhengzhou University, Henan, Zhengzhou 450001, China
| | - Velia M Fowler
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037
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20
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Ochala J, Sun YB. Novel myosin-based therapies for congenital cardiac and skeletal myopathies. J Med Genet 2016; 53:651-4. [PMID: 27412953 PMCID: PMC5099184 DOI: 10.1136/jmedgenet-2016-103881] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 06/15/2016] [Indexed: 12/13/2022]
Abstract
The dysfunction in a number of inherited cardiac and skeletal myopathies is primarily due to an altered ability of myofilaments to generate force and motion. Despite this crucial knowledge, there are, currently, no effective therapeutic interventions for these diseases. In this short review, we discuss recent findings giving strong evidence that genetically or pharmacologically modulating one of the myofilament proteins, myosin, could alleviate the muscle pathology. This should constitute a research and clinical priority.
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Affiliation(s)
- Julien Ochala
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, UK
| | - Yin-Biao Sun
- Randall Division of Cell and Molecular Biophysics, British Heart Foundation Centre of Research Excellence, King's College London, London, UK
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21
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Marston SB. Why Is there a Limit to the Changes in Myofilament Ca 2+-Sensitivity Associated with Myopathy Causing Mutations? Front Physiol 2016; 7:415. [PMID: 27725803 PMCID: PMC5035734 DOI: 10.3389/fphys.2016.00415] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 09/05/2016] [Indexed: 12/15/2022] Open
Abstract
Mutations in striated muscle contractile proteins have been found to be the cause of a number of inherited muscle diseases; in most cases the mechanism proposed for causing the disease is derangement of the thin filament-based Ca2+-regulatory system of the muscle. When considering the results of experiments reported over the last 15 years, one feature has been frequently noted, but rarely discussed: the magnitude of changes in myofilament Ca2+-sensitivity due to myopathy-causing mutations in skeletal or heart muscle seems to be always in the range 1.5-3x EC50. Such consistency suggests it may be related to a fundamental property of muscle regulation; in this article we will investigate whether this observation is true and consider why this should be so. A literature search found 71 independent measurements of HCM mutation-induced change of EC50 ranging from 1.15 to 3.8-fold with a mean of 1.87 ± 0.07 (sem). We also found 11 independent measurements of increased Ca2+-sensitivity due to mutations in skeletal muscle proteins ranging from 1.19 to 2.7-fold with a mean of 2.00 ± 0.16. Investigation of dilated cardiomyopathy-related mutations found 42 independent determinations with a range of EC50 wt/mutant from 0.3 to 2.3. In addition we found 14 measurements of Ca2+-sensitivity changes due skeletal muscle myopathy mutations ranging from 0.39 to 0.63. Thus, our extensive literature search, although not necessarily complete, found that, indeed, the changes in myofilament Ca2+-sensitivity due to disease-causing mutations have a bimodal distribution and that the overall changes in Ca2+-sensitivity are quite small and do not extend beyond a three-fold increase or decrease in Ca2+-sensitivity. We discuss two mechanism that are not necessarily mutually exclusive. Firstly, it could be that the limit is set by the capabilities of the excitation-contraction machinery that supplies activating Ca2+ and that striated muscle cannot work in a way compatible with life outside these limits; or it may be due to a fundamental property of the troponin system and the permitted conformational transitions compatible with efficient regulation.
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Affiliation(s)
- Steven B Marston
- National Heart & Lung Institute, Imperial College London London, UK
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22
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Gokhin DS, Fowler VM. Software-based measurement of thin filament lengths: an open-source GUI for Distributed Deconvolution analysis of fluorescence images. J Microsc 2016; 265:11-20. [PMID: 27644080 DOI: 10.1111/jmi.12456] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/09/2016] [Accepted: 07/19/2016] [Indexed: 12/25/2022]
Abstract
The periodically arranged thin filaments within the striated myofibrils of skeletal and cardiac muscle have precisely regulated lengths, which can change in response to developmental adaptations, pathophysiological states, and genetic perturbations. We have developed a user-friendly, open-source ImageJ plugin that provides a graphical user interface (GUI) for super-resolution measurement of thin filament lengths by applying Distributed Deconvolution (DDecon) analysis to periodic line scans collected from fluorescence images. In the workflow presented here, we demonstrate thin filament length measurement using a phalloidin-stained cryosection of mouse skeletal muscle. The DDecon plugin is also capable of measuring distances of any periodically localized fluorescent signal from the Z- or M-line, as well as distances between successive Z- or M-lines, providing a broadly applicable tool for quantitative analysis of muscle cytoarchitecture. These functionalities can also be used to analyse periodic fluorescence signals in nonmuscle cells.
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Affiliation(s)
- David S Gokhin
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California, U.S.A
| | - Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California, U.S.A
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23
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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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Gokhin DS, Ochala J, Domenighetti AA, Fowler VM. Tropomodulin 1 directly controls thin filament length in both wild-type and tropomodulin 4-deficient skeletal muscle. Development 2015; 142:4351-62. [PMID: 26586224 DOI: 10.1242/dev.129171] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 11/05/2015] [Indexed: 01/10/2023]
Abstract
The sarcomeric tropomodulin (Tmod) isoforms Tmod1 and Tmod4 cap thin filament pointed ends and functionally interact with the leiomodin (Lmod) isoforms Lmod2 and Lmod3 to control myofibril organization, thin filament lengths, and actomyosin crossbridge formation in skeletal muscle fibers. Here, we show that Tmod4 is more abundant than Tmod1 at both the transcript and protein level in a variety of muscle types, but the relative abundances of sarcomeric Tmods are muscle specific. We then generate Tmod4(-/-) mice, which exhibit normal thin filament lengths, myofibril organization, and skeletal muscle contractile function owing to compensatory upregulation of Tmod1, together with an Lmod isoform switch wherein Lmod3 is downregulated and Lmod2 is upregulated. However, RNAi depletion of Tmod1 from either wild-type or Tmod4(-/-) muscle fibers leads to thin filament elongation by ∼15%. Thus, Tmod1 per se, rather than total sarcomeric Tmod levels, controls thin filament lengths in mouse skeletal muscle, whereas Tmod4 appears to be dispensable for thin filament length regulation. These findings identify Tmod1 as the key direct regulator of thin filament length in skeletal muscle, in both adult muscle homeostasis and in developmentally compensated contexts.
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Affiliation(s)
- David S Gokhin
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Julien Ochala
- Centre of Human and Aerospace Physiological Sciences, King's College London, London SE1 1UL, UK
| | - Andrea A Domenighetti
- Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA Rehabilitation Institute of Chicago, Chicago, IL 60611, USA
| | - Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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25
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Donkervoort S, Papadaki M, de Winter JM, Neu MB, Kirschner J, Bolduc V, Yang ML, Gibbons MA, Hu Y, Dastgir J, Leach ME, Rutkowski A, Foley AR, Krüger M, Wartchow EP, McNamara E, Ong R, Nowak KJ, Laing NG, Clarke NF, Ottenheijm C, Marston SB, Bönnemann CG. TPM3 deletions cause a hypercontractile congenital muscle stiffness phenotype. Ann Neurol 2015; 78:982-994. [PMID: 26418456 DOI: 10.1002/ana.24535] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 09/02/2015] [Accepted: 09/05/2015] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Mutations in TPM3, encoding Tpm3.12, cause a clinically and histopathologically diverse group of myopathies characterized by muscle weakness. We report two patients with novel de novo Tpm3.12 single glutamic acid deletions at positions ΔE218 and ΔE224, resulting in a significant hypercontractile phenotype with congenital muscle stiffness, rather than weakness, and respiratory failure in one patient. METHODS The effect of the Tpm3.12 deletions on the contractile properties in dissected patient myofibers was measured. We used quantitative in vitro motility assay to measure Ca(2+) sensitivity of thin filaments reconstituted with recombinant Tpm3.12 ΔE218 and ΔE224. RESULTS Contractility studies on permeabilized myofibers demonstrated reduced maximal active tension from both patients with increased Ca(2+) sensitivity and altered cross-bridge cycling kinetics in ΔE224 fibers. In vitro motility studies showed a two-fold increase in Ca(2+) sensitivity of the fraction of filaments motile and the filament sliding velocity concentrations for both mutations. INTERPRETATION These data indicate that Tpm3.12 deletions ΔE218 and ΔE224 result in increased Ca(2+) sensitivity of the troponin-tropomyosin complex, resulting in abnormally active interaction of the actin and myosin complex. Both mutations are located in the charged motifs of the actin-binding residues of tropomyosin 3, thus disrupting the electrostatic interactions that facilitate accurate tropomyosin binding with actin necessary to prevent the on-state. The mutations destabilize the off-state and result in excessively sensitized excitation-contraction coupling of the contractile apparatus. This work expands the phenotypic spectrum of TPM3-related disease and provides insights into the pathophysiological mechanisms of the actin-tropomyosin complex.
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Affiliation(s)
- S Donkervoort
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - M Papadaki
- National Heart and Lung Institute, Imperial College London, London, UK
| | - J M de Winter
- Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
| | - M B Neu
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - J Kirschner
- Department of Neuropediatrics and Muscle Disorders, University Medical Center Freiburg, Freiburg, Germany
| | - V Bolduc
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - M L Yang
- University of Colorado School of Medicine, Department of Pediatrics and Neurology, Section of Child Neurology, Aurora, CO, USA
| | - M A Gibbons
- University of Colorado Denver School of Medicine, Aurora, CO, USA
| | - Y Hu
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - J Dastgir
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - M E Leach
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA.,Children's National Health System, Washington DC, USA
| | - A Rutkowski
- Kaiser SCPMG, Cure CMD, P.O. Box 701, Olathe, KS 66051, USA
| | - A R Foley
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - M Krüger
- Department of General Pediatrics, Adolescent Medicine and Neonatology, University Medical Center Freiburg, Freiburg, Germany
| | - E P Wartchow
- Department of Pathology, Children's Hospital Colorado, Aurora, Colorado, USA
| | - E McNamara
- Neuromuscular Diseases Laboratory, Centre for Medical Research, Faculty of Medicine, Dentistry and Health Sciences, The University of Western Australia Crawley, WA, Australia
| | - R Ong
- Neuromuscular Diseases Laboratory, Centre for Medical Research, Faculty of Medicine, Dentistry and Health Sciences, The University of Western Australia Crawley, WA, Australia
| | - K J Nowak
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - N G Laing
- Centre for Medical Research, University of Western Australia, Harry Perkins Institute of Medical Research, QEII Medical Centre, Perth, Western Australia, Australia
| | - N F Clarke
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, University of Sydney, Sydney, Australia
| | - Cac Ottenheijm
- Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
| | - S B Marston
- National Heart and Lung Institute, Imperial College London, London, UK
| | - C G Bönnemann
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
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26
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Affiliation(s)
- J Compston
- Bone Medicine, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK.
| | - K C H Fearon
- Department of Clinical and Surgical Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK.
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27
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Yuen M, Cooper ST, Marston SB, Nowak KJ, McNamara E, Mokbel N, Ilkovski B, Ravenscroft G, Rendu J, de Winter JM, Klinge L, Beggs AH, North KN, Ottenheijm CAC, Clarke NF. Muscle weakness in TPM3-myopathy is due to reduced Ca2+-sensitivity and impaired acto-myosin cross-bridge cycling in slow fibres. Hum Mol Genet 2015; 24:6278-92. [PMID: 26307083 DOI: 10.1093/hmg/ddv334] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 08/10/2015] [Indexed: 11/13/2022] Open
Abstract
Dominant mutations in TPM3, encoding α-tropomyosinslow, cause a congenital myopathy characterized by generalized muscle weakness. Here, we used a multidisciplinary approach to investigate the mechanism of muscle dysfunction in 12 TPM3-myopathy patients. We confirm that slow myofibre hypotrophy is a diagnostic hallmark of TPM3-myopathy, and is commonly accompanied by skewing of fibre-type ratios (either slow or fast fibre predominance). Patient muscle contained normal ratios of the three tropomyosin isoforms and normal fibre-type expression of myosins and troponins. Using 2D-PAGE, we demonstrate that mutant α-tropomyosinslow was expressed, suggesting muscle dysfunction is due to a dominant-negative effect of mutant protein on muscle contraction. Molecular modelling suggested mutant α-tropomyosinslow likely impacts actin-tropomyosin interactions and, indeed, co-sedimentation assays showed reduced binding of mutant α-tropomyosinslow (R168C) to filamentous actin. Single fibre contractility studies of patient myofibres revealed marked slow myofibre specific abnormalities. At saturating [Ca(2+)] (pCa 4.5), patient slow fibres produced only 63% of the contractile force produced in control slow fibres and had reduced acto-myosin cross-bridge cycling kinetics. Importantly, due to reduced Ca(2+)-sensitivity, at sub-saturating [Ca(2+)] (pCa 6, levels typically released during in vivo contraction) patient slow fibres produced only 26% of the force generated by control slow fibres. Thus, weakness in TPM3-myopathy patients can be directly attributed to reduced slow fibre force at physiological [Ca(2+)], and impaired acto-myosin cross-bridge cycling kinetics. Fast myofibres are spared; however, they appear to be unable to compensate for slow fibre dysfunction. Abnormal Ca(2+)-sensitivity in TPM3-myopathy patients suggests Ca(2+)-sensitizing drugs may represent a useful treatment for this condition.
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Affiliation(s)
- Michaela Yuen
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Westmead, Australia, Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia,
| | - Sandra T Cooper
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Westmead, Australia, Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia
| | - Steve B Marston
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Kristen J Nowak
- Harry Perkins Institute of Medical Research and the Centre for Medical Research, University of Western Australia, Nedlands, Australia
| | - Elyshia McNamara
- Harry Perkins Institute of Medical Research and the Centre for Medical Research, University of Western Australia, Nedlands, Australia
| | - Nancy Mokbel
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Westmead, Australia, Faculty of Health Sciences, St. George Health Complex, The University of Balamand, Beirut, Lebanon
| | - Biljana Ilkovski
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Westmead, Australia
| | - Gianina Ravenscroft
- Harry Perkins Institute of Medical Research and the Centre for Medical Research, University of Western Australia, Nedlands, Australia
| | - John Rendu
- Département de Biochimie Toxicologie et Pharmacologie, Département de Biochimie Génétique et Moléculaire, Centre Hospitalier Universitaire de Grenoble, Grenoble, France
| | - Josine M de Winter
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Lars Klinge
- Department of Pediatrics and Adolescent Medicine, Division of Pediatric Neurology, Faculty of Medicine, Georg August University, Göttingen, Germany
| | - Alan H Beggs
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Kathryn N North
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Westmead, Australia, Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia, Murdoch Children's Research Institute, the Royal Children's Hospital, Parkville, Australia and Department of Paediatrics, University of Melbourne, Melbourne, Australia
| | - Coen A C Ottenheijm
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Nigel F Clarke
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Westmead, Australia, Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia
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28
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Poorly understood aspects of striated muscle contraction. BIOMED RESEARCH INTERNATIONAL 2015; 2015:245154. [PMID: 25961006 PMCID: PMC4415482 DOI: 10.1155/2015/245154] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 10/28/2014] [Indexed: 11/23/2022]
Abstract
Muscle contraction results from cyclic interactions between the contractile proteins myosin and actin, driven by the turnover of adenosine triphosphate (ATP). Despite intense studies, several molecular events in the contraction process are poorly understood, including the relationship between force-generation and phosphate-release in the ATP-turnover. Different aspects of the force-generating transition are reflected in the changes in tension development by muscle cells, myofibrils and single molecules upon changes in temperature, altered phosphate concentration, or length perturbations. It has been notoriously difficult to explain all these events within a given theoretical framework and to unequivocally correlate observed events with the atomic structures of the myosin motor. Other incompletely understood issues include the role of the two heads of myosin II and structural changes in the actin filaments as well as the importance of the three-dimensional order. We here review these issues in relation to controversies regarding basic physiological properties of striated muscle. We also briefly consider actomyosin mutation effects in cardiac and skeletal muscle function and the possibility to treat these defects by drugs.
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29
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Robaszkiewicz K, Ostrowska Z, Cyranka-Czaja A, Moraczewska J. Impaired tropomyosin-troponin interactions reduce activation of the actin thin filament. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:381-90. [PMID: 25603119 DOI: 10.1016/j.bbapap.2015.01.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 01/09/2015] [Accepted: 01/13/2015] [Indexed: 01/23/2023]
Abstract
Tropomyosin and troponin are bound to the actin filament to control the contraction of striated muscle in the Ca-dependent manner. The interactions between both regulatory proteins important for the regulation process are not fully understood. To gain more insight into the mechanisms of the thin filament regulation by skeletal α-tropomyosin and troponin, we analyzed effects of seven myopathy-related substitutions: Leu99Met, Ala155Thr, Arg167Gly, Arg167Cys, Arg167His, Lys168Glu, and Arg244Gly. All substitutions reduced Ca-dependent activation of the actomyosin ATPase. The effects of mutations in Arg167 and Lys168 were the most severe. The amino acid substitutions did not significantly affect troponin binding to the whole filament, but reduced 1.2-2.8 fold the affinity of troponin to tropomyosin alone. The excimer fluorescence of N-(1-pyrene)iodoacetamide, a probe attached to the central Cys190, demonstrated that substitutions located near the troponin core domain-binding region strongly affected conformational changes accompanying the tropomyosin-troponin interactions. The thermal stability of all tropomyosin mutants was lower than the stability of the wild type tropomyosin, with TM reduced by 5.3-8.5°C. Together the analyses demonstrated that the myopathy-causing mutations affected tropomyosin structure and led to changes in interactions between tropomyosin and troponin, which impaired the transition of the thin filament from the inactive off to the active on state.
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Affiliation(s)
- Katarzyna Robaszkiewicz
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University in Bydgoszcz, Chodkiewicz 30, Str., 85-064 Bydgoszcz, Poland
| | - Zofia Ostrowska
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University in Bydgoszcz, Chodkiewicz 30, Str., 85-064 Bydgoszcz, Poland
| | | | - Joanna Moraczewska
- Department of Biochemistry and Cell Biology, Faculty of Natural Sciences, Kazimierz Wielki University in Bydgoszcz, Chodkiewicz 30, Str., 85-064 Bydgoszcz, Poland.
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30
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Gupte TM, Haque F, Gangadharan B, Sunitha MS, Mukherjee S, Anandhan S, Rani DS, Mukundan N, Jambekar A, Thangaraj K, Sowdhamini R, Sommese RF, Nag S, Spudich JA, Mercer JA. Mechanistic heterogeneity in contractile properties of α-tropomyosin (TPM1) mutants associated with inherited cardiomyopathies. J Biol Chem 2014; 290:7003-15. [PMID: 25548289 DOI: 10.1074/jbc.m114.596676] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The most frequent known causes of primary cardiomyopathies are mutations in the genes encoding sarcomeric proteins. Among those are 30 single-residue mutations in TPM1, the gene encoding α-tropomyosin. We examined seven mutant tropomyosins, E62Q, D84N, I172T, L185R, S215L, D230N, and M281T, that were chosen based on their clinical severity and locations along the molecule. The goal of our study was to determine how the biochemical characteristics of each of these mutant proteins are altered, which in turn could provide a structural rationale for treatment of the cardiomyopathies they produce. Measurements of Ca(2+) sensitivity of human β-cardiac myosin ATPase activity are consistent with the hypothesis that hypertrophic cardiomyopathies are hypersensitive to Ca(2+) activation, and dilated cardiomyopathies are hyposensitive. We also report correlations between ATPase activity at maximum Ca(2+) concentrations and conformational changes in TnC measured using a fluorescent probe, which provide evidence that different substitutions perturb the structure of the regulatory complex in different ways. Moreover, we observed changes in protein stability and protein-protein interactions in these mutants. Our results suggest multiple mechanistic pathways to hypertrophic and dilated cardiomyopathies. Finally, we examined a computationally designed mutant, E181K, that is hypersensitive, confirming predictions derived from in silico structural analysis.
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Affiliation(s)
- Tejas M Gupte
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Farah Haque
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Binnu Gangadharan
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the Manipal University, Madhav Nagar, Manipal 576104, India
| | - Margaret S Sunitha
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Souhrid Mukherjee
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Swetha Anandhan
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Deepa Selvi Rani
- the Council for Scientific and Industrial Research-Centre for Cellular and Molecular Biology, Hyderabad 500007, India
| | - Namita Mukundan
- the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Amruta Jambekar
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Kumarasamy Thangaraj
- the Council for Scientific and Industrial Research-Centre for Cellular and Molecular Biology, Hyderabad 500007, India
| | - Ramanathan Sowdhamini
- the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Ruth F Sommese
- the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - Suman Nag
- the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - James A Spudich
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - John A Mercer
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the McLaughlin Research Institute, Great Falls, Montana 59405
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31
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Alterations at the cross-bridge level are associated with a paradoxical gain of muscle function in vivo in a mouse model of nemaline myopathy. PLoS One 2014; 9:e109066. [PMID: 25268244 PMCID: PMC4182639 DOI: 10.1371/journal.pone.0109066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 09/09/2014] [Indexed: 11/29/2022] Open
Abstract
Nemaline myopathy is the most common disease entity among non-dystrophic skeletal muscle congenital diseases. The first disease causing mutation (Met9Arg) was identified in the gene encoding α-tropomyosinslow gene (TPM3). Considering the conflicting findings of the previous studies on the transgenic (Tg) mice carrying the TPM3Met9Arg mutation, we investigated carefully the effect of the Met9Arg mutation in 8–9 month-old Tg(TPM3)Met9Arg mice on muscle function using a multiscale methodological approach including skinned muscle fibers analysis and invivo investigations by magnetic resonance imaging and 31-phosphorus magnetic resonance spectroscopy. While invitro maximal force production was reduced in Tg(TPM3)Met9Arg mice as compared to controls, invivo measurements revealed an improved mechanical performance in the transgenic mice as compared to the former. The reduced invitro muscle force might be related to alterations occuring at the cross-bridges level with muscle-specific underlying mechanisms. In vivo muscle improvement was not associated with any changes in either muscle volume or energy metabolism. Our findings indicate that TPM3(Met9Arg) mutation leads to a mild muscle weakness invitro related to an alteration at the cross-bridges level and a paradoxical gain of muscle function invivo. These results clearly point out that invitro alterations are muscle-dependent and do not necessarily translate into similar changes invivo.
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32
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Gokhin DS, Dubuc EA, Lian KQ, Peters LL, Fowler VM. Alterations in thin filament length during postnatal skeletal muscle development and aging in mice. Front Physiol 2014; 5:375. [PMID: 25324783 PMCID: PMC4178374 DOI: 10.3389/fphys.2014.00375] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 09/10/2014] [Indexed: 11/13/2022] Open
Abstract
The lengths of the sarcomeric thin filaments vary in a skeletal muscle-specific manner and help specify the physiological properties of skeletal muscle. Since the extent of overlap between the thin and thick filaments determines the amount of contractile force that a sarcomere can actively produce, thin filament lengths are accurate predictors of muscle-specific sarcomere length-tension relationships and sarcomere operating length ranges. However, the striking uniformity of thin filament lengths within sarcomeres, specified during myofibril assembly, has led to the widely held assumption that thin filament lengths remain constant throughout an organism's lifespan. Here, we rigorously tested this assumption by using computational super-resolution image analysis of confocal fluorescence images to explore the effects of postnatal development and aging on thin filament length in mice. We found that thin filaments shorten in postnatal tibialis anterior (TA) and gastrocnemius muscles between postnatal days 7 and 21, consistent with the developmental program of myosin heavy chain (MHC) gene expression in this interval. By contrast, thin filament lengths in TA and extensor digitorum longus (EDL) muscles remained constant between 2 mo and 2 yr of age, while thin filament lengths in soleus muscle became shorter, suggestive of a slow-muscle-specific mechanism of thin filament destabilization associated with aging. Collectively, these data are the first to show that thin filament lengths change as part of normal skeletal muscle development and aging, motivating future investigations into the cellular and molecular mechanisms underlying thin filament adaptation across the lifespan.
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Affiliation(s)
- David S Gokhin
- Department of Cell and Molecular Biology, The Scripps Research Institute La Jolla, CA, USA
| | - Emily A Dubuc
- Department of Cell and Molecular Biology, The Scripps Research Institute La Jolla, CA, USA
| | - Kendra Q Lian
- Department of Cell and Molecular Biology, The Scripps Research Institute La Jolla, CA, USA
| | | | - Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute La Jolla, CA, USA
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33
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Energy landscapes reveal the myopathic effects of tropomyosin mutations. Arch Biochem Biophys 2014; 564:89-99. [PMID: 25241052 DOI: 10.1016/j.abb.2014.09.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 09/03/2014] [Accepted: 09/09/2014] [Indexed: 11/24/2022]
Abstract
Striated muscle contraction is regulated by an interaction network connecting the effects of troponin, Ca(2+), and myosin-heads to the azimuthal positioning of tropomyosin along thin filaments. Many missense mutations, located at the actin-tropomyosin interface, however, reset the regulatory switching mechanism either by weakening or strengthening residue-specific interactions, leading to hyper- or hypo-contractile pathologies. Here, we compute energy landscapes for the actin-tropomyosin interface and quantify contributions of single amino acid residues to actin-tropomyosin binding. The method is a useful tool to assess effects of actin and tropomyosin mutations, potentially relating initial stages of myopathy to alterations in thin filament stability and regulation. Landscapes for mutant filaments linked to hyper-contractility provide a simple picture that describes a decrease in actin-tropomyosin interaction energy. Destabilizing the blocked (relaxed)-state parallels previously noted enhanced Ca(2+)-sensitivity conferred by these mutants. Energy landscapes also identify post-translational modifications that can rescue regulatory imbalances. For example, cardiomyopathy-associated E62Q tropomyosin mutation weakens actin-tropomyosin interaction, but phosphorylation of neighboring S61 rescues the binding-deficit, results confirmed experimentally by in vitro motility assays. Unlike results on hyper-contractility-related mutants, landscapes for tropomyosin mutants tied to hypo-contractility do not present a straightforward picture. These mutations may affect other components of the regulatory network, e.g., troponin-tropomyosin signaling.
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34
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Månsson A. Hypothesis and theory: mechanical instabilities and non-uniformities in hereditary sarcomere myopathies. Front Physiol 2014; 5:350. [PMID: 25309450 PMCID: PMC4163974 DOI: 10.3389/fphys.2014.00350] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 08/26/2014] [Indexed: 12/23/2022] Open
Abstract
Familial hypertrophic cardiomyopathy (HCM), due to point mutations in genes for sarcomere proteins such as myosin, occurs in 1/500 people and is the most common cause of sudden death in young individuals. Similar mutations in skeletal muscle, e.g., in the MYH7 gene for slow myosin found in both the cardiac ventricle and slow skeletal muscle, may also cause severe disease but the severity and the morphological changes are often different. In HCM, the modified protein function leads, over years to decades, to secondary remodeling with substantial morphological changes, such as hypertrophy, myofibrillar disarray, and extensive fibrosis associated with severe functional deterioration. Despite intense studies, it is unclear how the moderate mutation-induced changes in protein function cause the long-term effects. In hypertrophy of the heart due to pressure overload (e.g., hypertension), mechanical stress in the myocyte is believed to be major initiating stimulus for activation of relevant cell signaling cascades. Here it is considered how expression of mutated proteins, such as myosin or regulatory proteins, could have similar consequences through one or both of the following mechanisms: (1) contractile instabilities within each sarcomere (with more than one stable velocity for a given load), (2) different tension generating capacities of cells in series. These mechanisms would have the potential to cause increased tension and/or stretch of certain cells during parts of the cardiac cycle. Modeling studies are used to illustrate these ideas and experimental tests are proposed. The applicability of similar ideas to skeletal muscle is also postulated, and differences between heart and skeletal muscle are discussed.
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Affiliation(s)
- Alf Månsson
- Department of Chemistry and Biomedical Sciences, Linnaeus University Kalmar, Sweden
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Marttila M, Lehtokari VL, Marston S, Nyman TA, Barnerias C, Beggs AH, Bertini E, Ceyhan-Birsoy O, Cintas P, Gerard M, Gilbert-Dussardier B, Hogue JS, Longman C, Eymard B, Frydman M, Kang PB, Klinge L, Kolski H, Lochmüller H, Magy L, Manel V, Mayer M, Mercuri E, North KN, Peudenier-Robert S, Pihko H, Probst FJ, Reisin R, Stewart W, Taratuto AL, de Visser M, Wilichowski E, Winer J, Nowak K, Laing NG, Winder TL, Monnier N, Clarke NF, Pelin K, Grönholm M, Wallgren-Pettersson C. Mutation update and genotype-phenotype correlations of novel and previously described mutations in TPM2 and TPM3 causing congenital myopathies. Hum Mutat 2014; 35:779-90. [PMID: 24692096 DOI: 10.1002/humu.22554] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 03/17/2014] [Indexed: 01/14/2023]
Abstract
Mutations affecting skeletal muscle isoforms of the tropomyosin genes may cause nemaline myopathy, cap myopathy, core-rod myopathy, congenital fiber-type disproportion, distal arthrogryposes, and Escobar syndrome. We correlate the clinical picture of these diseases with novel (19) and previously reported (31) mutations of the TPM2 and TPM3 genes. Included are altogether 93 families: 53 with TPM2 mutations and 40 with TPM3 mutations. Thirty distinct pathogenic variants of TPM2 and 20 of TPM3 have been published or listed in the Leiden Open Variant Database (http://www.dmd.nl/). Most are heterozygous changes associated with autosomal-dominant disease. Patients with TPM2 mutations tended to present with milder symptoms than those with TPM3 mutations, DA being present only in the TPM2 group. Previous studies have shown that five of the mutations in TPM2 and one in TPM3 cause increased Ca(2+) sensitivity resulting in a hypercontractile molecular phenotype. Patients with hypercontractile phenotype more often had contractures of the limb joints (18/19) and jaw (6/19) than those with nonhypercontractile ones (2/22 and 1/22), whereas patients with the non-hypercontractile molecular phenotype more often (19/22) had axial contractures than the hypercontractile group (7/19). Our in silico predictions show that most mutations affect tropomyosin-actin association or tropomyosin head-to-tail binding.
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Affiliation(s)
- Minttu Marttila
- The Folkhälsan Institute of Genetics and the Department of Medical Genetics, University of Helsinki, Haartman Institute, Biomedicum Helsinki, Finland
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36
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Marston S, Memo M, Messer A, Papadaki M, Nowak K, McNamara E, Ong R, El-Mezgueldi M, Li X, Lehman W. Mutations in repeating structural motifs of tropomyosin cause gain of function in skeletal muscle myopathy patients. Hum Mol Genet 2013; 22:4978-87. [PMID: 23886664 DOI: 10.1093/hmg/ddt345] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The congenital myopathies include a wide spectrum of clinically, histologically and genetically variable neuromuscular disorders many of which are caused by mutations in genes for sarcomeric proteins. Some congenital myopathy patients have a hypercontractile phenotype. Recent functional studies demonstrated that ACTA1 K326N and TPM2 ΔK7 mutations were associated with hypercontractility that could be explained by increased myofibrillar Ca(2+) sensitivity. A recent structure of the complex of actin and tropomyosin in the relaxed state showed that both these mutations are located in the actin-tropomyosin interface. Tropomyosin is an elongated molecule with a 7-fold repeated motif of around 40 amino acids corresponding to the 7 actin monomers it interacts with. Actin binds to tropomyosin electrostatically at two points, through Asp25 and through a cluster of amino acids that includes Lys326, mutated in the gain-of-function mutation. Asp25 interacts with tropomyosin K6, next to K7 that was mutated in the other gain-of-function mutation. We identified four tropomyosin motifs interacting with Asp25 (K6-K7, K48-K49, R90-R91 and R167-K168) and three E-E/D-K/R motifs interacting with Lys326 (E139, E181 and E218), and we predicted that the known skeletal myopathy mutations ΔK7, ΔK49, R91G, ΔE139, K168E and E181K would cause a gain of function. Tests by an in vitro motility assay confirmed that these mutations increased Ca(2+) sensitivity, while mutations not in these motifs (R167H, R244G) decreased Ca(2+) sensitivity. The work reported here explains the molecular mechanism for 6 out of 49 known disease-causing mutations in the TPM2 and TPM3 genes, derived from structural data of the actin-tropomyosin interface.
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Memo M, Marston S. Skeletal muscle myopathy mutations at the actin tropomyosin interface that cause gain- or loss-of-function. J Muscle Res Cell Motil 2013; 34:165-9. [PMID: 23719967 DOI: 10.1007/s10974-013-9344-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 05/09/2013] [Indexed: 12/31/2022]
Abstract
It is well known that the regulation of muscle contraction relies on the ability of tropomyosin to switch between different positions on the actin filament, but it is still not well understood which amino acids are directly involved in the different states of the interaction. Recently the structure of the actin-tropomyosin interface has been determined both in the absence and presence of myosin heads. Interestingly, a number of mutations in tropomyosin that are associated with skeletal muscle myopathy are located within this interface. We first give an overview of the functional effect of mutations on amino acids that are involved in the contact with actin asp25, which represent a pattern repeated seven times along tropomyosin. It is explained how some of these amino acids (R167 and R244) which are thought to be involved in a salt bridge contact with actin in the closed state can produce a loss-of-function when mutated, while other positively charged tropomyosin amino acids positioned on the downstream side of the contact (K7, K49, R91, K168) can produce a gain-of-function when mutated. We then consider mutations of amino acids involved in another salt bridge contact between the two proteins in the closed state, actin K326N (which binds on five different points of tropomyosin) and tropomyosin ∆E139 and E181K, and we report how all of these mutations produce a gain-of-function. These observations can be important to validate the proposed structures and to understand more deeply how mutations affect the function of these proteins and to enable prediction of their outcomes.
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38
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Ochala J, Iwamoto H. Myofilament lattice structure in presence of a skeletal myopathy-related tropomyosin mutation. J Muscle Res Cell Motil 2013; 34:171-5. [PMID: 23686574 DOI: 10.1007/s10974-013-9345-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 05/10/2013] [Indexed: 10/26/2022]
Abstract
Human tropomyosin mutations deregulate skeletal muscle contraction at the cellular level. One key feature is the slowing of the kinetics of force development. The aim of the present study was to characterize the potential underlying molecular mechanisms by recording and analyzing the X-ray diffraction patterns of human membrane-permeabilized muscle cells expressing a particular β-tropomyosin mutation (E41K). During resting conditions, the d1,0 lattice spacing, Δ1,0 and I1,1 to I1,0 ratio were not different from control values. These results suggest that, in presence of the E41K β-tropomyosin mutation, the myofilament lattice geometry is well maintained and therefore may not have any detrimental influence on the contraction mechanisms and thus, on the rate of force generation.
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Affiliation(s)
- Julien Ochala
- Centre of Human & Aerospace Physiological Sciences, King's College London, Room 3.3, Shepherd's House, Guy's Campus, London, SE1 1UL, UK,
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de Winter JM, Buck D, Hidalgo C, Jasper JR, Malik FI, Clarke NF, Stienen GJM, Lawlor MW, Beggs AH, Ottenheijm CAC, Granzier H. Troponin activator augments muscle force in nemaline myopathy patients with nebulin mutations. J Med Genet 2013; 50:383-92. [PMID: 23572184 PMCID: PMC3865762 DOI: 10.1136/jmedgenet-2012-101470] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Background Nemaline myopathy—the most common non-dystrophic congenital myopathy—is caused by mutations in thin filament genes, of which the nebulin gene is the most frequently affected one. The nebulin gene codes for the giant sarcomeric protein nebulin, which plays a crucial role in skeletal muscle contractile performance. Muscle weakness is a hallmark feature of nemaline myopathy patients with nebulin mutations, and is caused by changes in contractile protein function, including a lower calcium-sensitivity of force generation. To date no therapy exists to treat muscle weakness in nemaline myopathy. Here, we studied the ability of the novel fast skeletal muscle troponin activator, CK-2066260, to augment force generation at submaximal calcium levels in muscle cells from nemaline myopathy patients with nebulin mutations. Methods Contractile protein function was determined in permeabilised muscle cells isolated from frozen patient biopsies. The effect of 5 µM CK-2066260 on force production was assessed. Results Nebulin protein concentrations were severely reduced in muscle cells from these patients compared to controls, while myofibrillar ultrastructure was largely preserved. Both maximal active tension and the calcium-sensitivity of force generation were lower in patients compared to controls. Importantly, CK-2066260 greatly increased the calcium-sensitivity of force generation—without affecting the cooperativity of activation—in patients to levels that exceed those observed in untreated control muscle. Conclusions Fast skeletal troponin activation is a therapeutic mechanism to augment contractile protein function in nemaline myopathy patients with nebulin mutations and with other neuromuscular diseases.
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Affiliation(s)
- Josine Marieke de Winter
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
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Mokbel N, Ilkovski B, Kreissl M, Memo M, Jeffries CM, Marttila M, Lehtokari VL, Lemola E, Grönholm M, Yang N, Menard D, Marcorelles P, Echaniz-Laguna A, Reimann J, Vainzof M, Monnier N, Ravenscroft G, McNamara E, Nowak KJ, Laing NG, Wallgren-Pettersson C, Trewhella J, Marston S, Ottenheijm C, North KN, Clarke NF. K7del is a common TPM2 gene mutation associated with nemaline myopathy and raised myofibre calcium sensitivity. ACTA ACUST UNITED AC 2013; 136:494-507. [PMID: 23378224 DOI: 10.1093/brain/aws348] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Mutations in the TPM2 gene, which encodes β-tropomyosin, are an established cause of several congenital skeletal myopathies and distal arthrogryposis. We have identified a TPM2 mutation, p.K7del, in five unrelated families with nemaline myopathy and a consistent distinctive clinical phenotype. Patients develop large joint contractures during childhood, followed by slowly progressive skeletal muscle weakness during adulthood. The TPM2 p.K7del mutation results in the loss of a highly conserved lysine residue near the N-terminus of β-tropomyosin, which is predicted to disrupt head-to-tail polymerization of tropomyosin. Recombinant K7del-β-tropomyosin incorporates poorly into sarcomeres in C2C12 myotubes and has a reduced affinity for actin. Two-dimensional gel electrophoresis of patient muscle and primary patient cultured myotubes showed that mutant protein is expressed but incorporates poorly into sarcomeres and likely accumulates in nemaline rods. In vitro studies using recombinant K7del-β-tropomyosin and force measurements from single dissected patient myofibres showed increased myofilament calcium sensitivity. Together these data indicate that p.K7del is a common recurrent TPM2 mutation associated with mild nemaline myopathy. The p.K7del mutation likely disrupts head-to-tail polymerization of tropomyosin, which impairs incorporation into sarcomeres and also affects the equilibrium of the troponin/tropomyosin-dependent calcium switch of muscle. Joint contractures may stem from chronic muscle hypercontraction due to increased myofibrillar calcium sensitivity while declining strength in adulthood likely arises from other mechanisms, such as myofibre decompensation and fatty infiltration. These results suggest that patients may benefit from therapies that reduce skeletal muscle calcium sensitivity, and we highlight late muscle decompensation as an important cause of morbidity.
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Affiliation(s)
- Nancy Mokbel
- Institute for Neuroscience and Muscle Research, Children’s Hospital at Westmead, Sydney, NSW 2145, Australia
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Gokhin DS, Fowler VM. A two-segment model for thin filament architecture in skeletal muscle. Nat Rev Mol Cell Biol 2013; 14:113-9. [PMID: 23299957 DOI: 10.1038/nrm3510] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Correct specification of myofilament length is essential for efficient skeletal muscle contraction. The length of thin actin filaments can be explained by a novel 'two-segment' model, wherein the thin filaments consist of two concatenated segments, which are of either constant or variable length. This is in contrast to the classic 'nebulin ruler' model, which postulates that thin filaments are uniform structures, the lengths of which are dictated by nebulin. The two-segment model implicates position-specific microregulation of actin dynamics as a general principle underlying actin filament length and stability.
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Affiliation(s)
- David S Gokhin
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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