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Fabian L, Karimi E, Farman GP, Gohlke J, Ottenheijm CAC, Granzier HL, Dowling JJ. Comprehensive phenotypic characterization of an allelic series of zebrafish models of NEB-related nemaline myopathy. Hum Mol Genet 2024; 33:1036-1054. [PMID: 38493359 PMCID: PMC11153343 DOI: 10.1093/hmg/ddae033] [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: 01/11/2024] [Accepted: 02/20/2024] [Indexed: 03/18/2024] Open
Abstract
Nemaline myopathy (NM) is a rare congenital neuromuscular disorder characterized by muscle weakness and hypotonia, slow gross motor development, and decreased respiratory function. Mutations in at least twelve genes, all of each encode proteins that are either components of the muscle thin filament or regulate its length and stability, have been associated with NM. Mutations in Nebulin (NEB), a giant filamentous protein localized in the sarcomere, account for more than 50% of NM cases. At present, there remains a lack of understanding of whether NEB genotype influences nebulin function and NM-patient phenotypes. In addition, there is a lack of therapeutically tractable models that can enable drug discovery and address the current unmet treatment needs of patients. To begin to address these gaps, here we have characterized five new zebrafish models of NEB-related NM. These mutants recapitulate most aspects of NEB-based NM, showing drastically reduced survival, defective muscle structure, reduced contraction force, shorter thin filaments, presence of electron-dense structures in myofibers, and thickening of the Z-disks. This study represents the first extensive investigation of an allelic series of nebulin mutants, and thus provides an initial examination in pre-clinical models of potential genotype-phenotype correlations in human NEB patients. It also represents the first utilization of a set of comprehensive outcome measures in zebrafish, including correlation between molecular analyses, structural and biophysical investigations, and phenotypic outcomes. Therefore, it provides a rich source of data for future studies exploring the NM pathomechanisms, and an ideal springboard for therapy identification and development for NEB-related NM.
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Affiliation(s)
- Lacramioara Fabian
- Genetics and Genome Biology Program, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada
| | - Esmat Karimi
- Department of Cellular and Molecular Medicine, University of Arizona, 1007 E. Lowell Street, Tucson, AZ 85724, United States
| | - Gerrie P Farman
- Department of Cellular and Molecular Medicine, University of Arizona, 1007 E. Lowell Street, Tucson, AZ 85724, United States
| | - Jochen Gohlke
- Department of Cellular and Molecular Medicine, University of Arizona, 1007 E. Lowell Street, Tucson, AZ 85724, United States
| | - Coen A C Ottenheijm
- Department of Physiology, Amsterdam University Medical Center (location VUMC), De Boelelaan 1108, Amsterdam 1081 HZ, The Netherlands
| | - Hendrikus L Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, 1007 E. Lowell Street, Tucson, AZ 85724, United States
| | - James J Dowling
- Genetics and Genome Biology Program, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada
- Division of Neurology, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada
- Departments of Paediatrics and Molecular Genetics, University of Toronto, 1 King’s College Circle, Toronto, ON M5S 1A8, Canada
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2
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Karimi E, Gohlke J, van der Borgh M, Lindqvist J, Hourani Z, Kolb J, Cossette S, Lawlor MW, Ottenheijm C, Granzier H. Characterization of NEB pathogenic variants in patients reveals novel nemaline myopathy disease mechanisms and omecamtiv mecarbil force effects. Acta Neuropathol 2024; 147:72. [PMID: 38634969 PMCID: PMC11026289 DOI: 10.1007/s00401-024-02726-w] [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: 12/22/2023] [Revised: 03/19/2024] [Accepted: 03/26/2024] [Indexed: 04/19/2024]
Abstract
Nebulin, a critical protein of the skeletal muscle thin filament, plays important roles in physiological processes such as regulating thin filament length (TFL), cross-bridge cycling, and myofibril alignment. Pathogenic variants in the nebulin gene (NEB) cause NEB-based nemaline myopathy (NEM2), a genetically heterogeneous disorder characterized by hypotonia and muscle weakness, currently lacking curative therapies. In this study, we examined a cohort of ten NEM2 patients, each with unique pathogenic variants, aiming to understand their impact on mRNA, protein, and functional levels. Results show that pathogenic truncation variants affect NEB mRNA stability and lead to nonsense-mediated decay of the mutated transcript. Moreover, a high incidence of cryptic splice site activation was found in patients with pathogenic splicing variants that are expected to disrupt the actin-binding sites of nebulin. Determination of protein levels revealed patients with either relatively normal or markedly reduced nebulin. We observed a positive relation between the reduction in nebulin and a reduction in TFL, or reduction in tension (both maximal and submaximal tension). Interestingly, our study revealed a pathogenic duplication variant in nebulin that resulted in a four-copy gain in the triplicate region of NEB and a much larger nebulin protein and longer TFL. Additionally, we investigated the effect of Omecamtiv mecarbil (OM), a small-molecule activator of cardiac myosin, on force production of type 1 muscle fibers of NEM2 patients. OM treatment substantially increased submaximal tension across all NEM2 patients ranging from 87 to 318%, with the largest effects in patients with the lowest level of nebulin. In summary, this study indicates that post-transcriptional or post-translational mechanisms regulate nebulin expression. Moreover, we propose that the pathomechanism of NEM2 involves not only shortened but also elongated thin filaments, along with the disruption of actin-binding sites resulting from pathogenic splicing variants. Significantly, our findings highlight the potential of OM treatment to improve skeletal muscle function in NEM2 patients, especially those with large reductions in nebulin levels.
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Affiliation(s)
- Esmat Karimi
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
| | - Jochen Gohlke
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
| | - Mila van der Borgh
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
| | - Johan Lindqvist
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
| | - Zaynab Hourani
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
| | - Stacy Cossette
- Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Michael W Lawlor
- Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA
- Diverge Translational Science Laboratory, Milwaukee, WI, USA
| | - Coen Ottenheijm
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
- Department of Physiology, Amsterdam UMC (Location VUMC), Amsterdam, Netherlands
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA.
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3
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Galli RA, Borsboom TC, Gineste C, Brocca L, Rossi M, Hwee DT, Malik FI, Bottinelli R, Gondin J, Pellegrino MA, de Winter JM, Ottenheijm CA. Tirasemtiv enhances submaximal muscle tension in an Acta1:p.Asp286Gly mouse model of nemaline myopathy. J Gen Physiol 2024; 156:e202313471. [PMID: 38376469 PMCID: PMC10876480 DOI: 10.1085/jgp.202313471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 12/01/2023] [Accepted: 01/30/2024] [Indexed: 02/21/2024] Open
Abstract
Nemaline myopathies are the most common form of congenital myopathies. Variants in ACTA1 (NEM3) comprise 15-25% of all nemaline myopathy cases. Patients harboring variants in ACTA1 present with a heterogeneous disease course characterized by stable or progressive muscle weakness and, in severe cases, respiratory failure and death. To date, no specific treatments are available. Since NEM3 is an actin-based thin filament disease, we tested the ability of tirasemtiv, a fast skeletal muscle troponin activator, to improve skeletal muscle function in a mouse model of NEM3, harboring the patient-based p.Asp286Gly variant in Acta1. Acute and long-term tirasemtiv treatment significantly increased muscle contractile capacity at submaximal stimulation frequencies in both fast-twitch extensor digitorum longus and gastrocnemius muscle, and intermediate-twitch diaphragm muscle in vitro and in vivo. Additionally, long-term tirasemtiv treatment in NEM3 mice resulted in a decreased respiratory rate with preserved minute volume, suggesting more efficient respiration. Altogether, our data support the therapeutic potential of fast skeletal muscle troponin activators in alleviating skeletal muscle weakness in a mouse model of NEM3 caused by the Acta1:p.Asp286Gly variant.
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Affiliation(s)
- Ricardo A. Galli
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, Amsterdam, The Netherlands
- Amsterdam Movement Sciences, Musculoskeletal Health and Tissue Function and Regeneration, Amsterdam, The Netherlands
| | - Tamara C. Borsboom
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, Amsterdam, The Netherlands
| | | | - Lorenza Brocca
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Maira Rossi
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Darren T. Hwee
- Research and Early Development, Cytokinetics Inc., South San Francisco, CA, USA
| | - Fady I. Malik
- Research and Early Development, Cytokinetics Inc., South San Francisco, CA, USA
| | - Roberto Bottinelli
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
- IRCCS Mondino Foundation, Pavia, Italy
| | - Julien Gondin
- Aix-Marseille University, CNRS, CRMBM, Marseille, France
- Institut NeuroMyoGène, Unité Physiopathologie et Génétique du Neurone et du Muscle, Université Claude Bernard Lyon 1, CNRS UMR 5261, INSERM U1315, Université Lyon, Lyon, France
| | | | - Josine M. de Winter
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, Amsterdam, The Netherlands
- Amsterdam Movement Sciences, Musculoskeletal Health and Tissue Function and Regeneration, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure and Arrhythmias, Amsterdam, The Netherlands
| | - Coen A.C. Ottenheijm
- Amsterdam UMC Location Vrije Universiteit Amsterdam, Physiology, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Pulmonary Hypertension and Atherosclerosis, Amsterdam, The Netherlands
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA
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Haidong L, Yin L, Ping C, Xianzhao Z, Qi Q, Xiaoli M, Zheng L, Wenhao C, Yaguang Z, Qianqian Q. Clinico-pathological and gene features of 15 nemaline myopathy patients from a single Chinese neuromuscular center. Acta Neurol Belg 2024; 124:91-99. [PMID: 37525074 PMCID: PMC10874337 DOI: 10.1007/s13760-023-02333-8] [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: 04/17/2023] [Accepted: 07/12/2023] [Indexed: 08/02/2023]
Abstract
BACKGROUND Nemaline myopathy, the most common of the congenital myopathies, is caused by various genetic mutations. In this study, we attempted to investigate the clinical features, muscle pathology and genetic features of 15 patients with nemaline myopathy. RESULTS Among the 15 patients, there were 9 (60.00%) males and 6 (40.00%) females, and 9 (60.00%) of them came from three families respectively. The age of seeing a doctor ranged from 9 to 52 years old, the age of onset was from 5 to 23 years old, and the duration of disease ranged from 3 to 35 years. Ten out of the 15 patients had high arched palate and elongated face. Only one patient had mild respiratory muscle involvement and none had dysphagia. Muscle biopsies were performed in 9 out of the 15 patients. Pathologically, muscle fibers of different sizes, atrophic muscle fibers and compensatory hypertrophic fibers could be found, and occasionally degenerated and necrotic muscle fibers were observed. Different degrees of nemaline bodies aggregation could be seen in all 9 patients. The distribution of type I and type II muscle fibers were significantly abnormal in patients with nemaline myopathy caused by NEB gene, however, it was basically normal in patients with nemaline myopathy caused by TPM3 gene and ACTA1 gene. Electron microscopic analysis of 6 patients showed that nemaline bodies aggregated between myofibrils were found in 5(83.33%) cases, and most of them were located near the Z band, but no intranuclear rods were found. The gene analysis of 15 NM patients showed that three NM-related genes were harbored, including 11 (73.33%) patients with NEB, 3 (20.00%) patients with TPM3, and 1 (6.67%) patient with ACTA1, respectively. A total of 12 mutation sites were identified and included 10 (83.33%) mutations in exon and 2(16.67%) mutations in intron. CONCLUSIONS The clinical phenotype of nemaline myopathy is highly heterogeneous. Muscle pathology shows that nemaline bodies aggregation is an important feature for the diagnosis of NM. NEB is the most frequent causative gene in this cohort. The splicing mutation, c.21522 + 3A > G may be the hotspot mutation of the NEB gene in Chinese NM patients.
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Affiliation(s)
- Lv Haidong
- Department of Neurology, Jiaozuo People's Hospital of Henan Province, Henan, 454002, Henan Province, People's Republic of China
| | - Liu Yin
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, 430060, Hubei Province, People's Republic of China
| | - Chen Ping
- Department of Neurology, Jiaozuo People's Hospital of Henan Province, Henan, 454002, Henan Province, People's Republic of China
| | - Zheng Xianzhao
- Department of Neurology, Jiaozuo People's Hospital of Henan Province, Henan, 454002, Henan Province, People's Republic of China
| | - Qian Qi
- Department of Neurology, Jiaozuo People's Hospital of Henan Province, Henan, 454002, Henan Province, People's Republic of China
| | - Ma Xiaoli
- Department of Neurology, Jiaozuo People's Hospital of Henan Province, Henan, 454002, Henan Province, People's Republic of China
| | - Lv Zheng
- Department of Neurology, Jiaozuo People's Hospital of Henan Province, Henan, 454002, Henan Province, People's Republic of China
| | - Cui Wenhao
- Department of Neurology, Jiaozuo People's Hospital of Henan Province, Henan, 454002, Henan Province, People's Republic of China
| | - Zhou Yaguang
- Department of Neurology, Jiaozuo People's Hospital of Henan Province, Henan, 454002, Henan Province, People's Republic of China
| | - Qu Qianqian
- Department of Neurology, Jiaozuo People's Hospital of Henan Province, Henan, 454002, Henan Province, People's Republic of China.
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5
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Karimi E, van der Borgh M, Lindqvist J, Gohlke J, Hourani Z, Kolb J, Cossette S, Lawlor MW, Ottenheijm C, Granzier H. Characterization of NEB mutations in patients reveals novel nemaline myopathy disease mechanisms and omecamtiv mecarbil force effects. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.20.572678. [PMID: 38187705 PMCID: PMC10769406 DOI: 10.1101/2023.12.20.572678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Nebulin, a critical protein of the skeletal muscle thin filament, plays important roles in physiological processes such as regulating thin filament length (TFL), cross-bridge cycling, and myofibril alignment. Mutations in the nebulin gene ( NEB ) cause NEB-based nemaline myopathy (NEM2), a genetically heterogeneous disorder characterized by hypotonia and muscle weakness, currently lacking therapies targeting the underlying pathological mechanisms. In this study, we examined a cohort of ten NEM2 patients, each with unique mutations, aiming to understand their impact on mRNA, protein, and functional levels. Results show that truncation mutations affect NEB mRNA stability and lead to nonsense-mediated decay of the mutated transcript. Moreover, a high incidence of cryptic splice site activation was found in patients with splicing mutations which is expected to disrupt the actin-binding sites of nebulin. Determination of protein levels revealed patients with relatively normal nebulin levels and others with markedly reduced nebulin. We observed a positive relation between the reduction in nebulin and a reduction in TFL, and a positive relation between the reduction in nebulin level and the reduction in tension (both maximal and submaximal tension). Interestingly, our study revealed a duplication mutation in nebulin that resulted in a larger nebulin protein and longer TFL. Additionally, we investigated the effect of Omecamtiv mecarbil (OM), a small-molecule activator of cardiac myosin, on force production of type I muscle fibers of NEM2 patients. OM treatment substantially increased submaximal tension across all NEM2 patients ranging from 87-318%, with the largest effects in patients with the lowest level of nebulin. In summary, this study indicates that post-transcriptional or post-translational mechanisms regulate nebulin expression. Moreover, we propose that the pathomechanism of NEM2 involves not only shortened but also elongated thin filaments, along with the disruption of actin-binding sites resulting from splicing mutations. Significantly, our findings highlight the potential of OM treatment to improve skeletal muscle function in NEM2 patients, especially those with large reductions in nebulin levels.
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6
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Lindqvist J, Granzier H. Pharmacological Inhibition of Myostatin in a Mouse Model of Typical Nemaline Myopathy Increases Muscle Size and Force. Int J Mol Sci 2023; 24:15124. [PMID: 37894805 PMCID: PMC10606666 DOI: 10.3390/ijms242015124] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 09/27/2023] [Accepted: 10/03/2023] [Indexed: 10/29/2023] Open
Abstract
Nemaline myopathy is one of the most common non-dystrophic congenital myopathies. Individuals affected by this condition experience muscle weakness and muscle smallness, often requiring supportive measures like wheelchairs or respiratory support. A significant proportion of patients, approximately one-third, exhibit compound heterozygous nebulin mutations, which usually give rise to the typical form of the disease. Currently, there are no approved treatments available for nemaline myopathy. Our research explored the modulation of myostatin, a negative regulator of muscle mass, in combating the muscle smallness associated with the disease. To investigate the effect of myostatin inhibition, we employed a mouse model with compound heterozygous nebulin mutations that mimic the typical form of the disease. The mice were treated with mRK35, a myostatin antibody, through weekly intraperitoneal injections of 10 mg/kg mRK35, commencing at two weeks of age and continuing until the mice reached four months of age. The treatment resulted in an increase in body weight and an approximate 20% muscle weight gain across most skeletal muscles, without affecting the heart. The minimum Feret diameter of type IIA and IIB fibers exhibited an increase in compound heterozygous mice, while only type IIB fibers demonstrated an increase in wild-type mice. In vitro mechanical experiments conducted on intact extensor digitorum longus muscle revealed that mRK35 augmented the physiological cross-sectional area of muscle fibers and enhanced absolute tetanic force in both wild-type and compound heterozygous mice. Furthermore, mRK35 administration improved grip strength in treated mice. Collectively, these findings indicate that inhibiting myostatin can mitigate the muscle deficits in nebulin-based typical nemaline myopathy, potentially serving as a much-needed therapeutic option.
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Affiliation(s)
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85724, USA;
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7
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Slick RA, Tinklenberg JA, Sutton J, Zhang L, Meng H, Beatka MJ, Vanden Avond M, Prom MJ, Ott E, Montanaro F, Heisner J, Toro R, Granzier H, Geurts AM, Stowe DF, Hill RB, Lawlor MW. Aberrations in Energetic Metabolism and Stress-Related Pathways Contribute to Pathophysiology in the Neb Conditional Knockout Mouse Model of Nemaline Myopathy. THE AMERICAN JOURNAL OF PATHOLOGY 2023; 193:1528-1547. [PMID: 37422147 PMCID: PMC10548278 DOI: 10.1016/j.ajpath.2023.06.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 05/08/2023] [Accepted: 06/08/2023] [Indexed: 07/10/2023]
Abstract
Nemaline myopathy (NM) is a genetically and clinically heterogeneous disease that is diagnosed on the basis of the presence of nemaline rods on skeletal muscle biopsy. Although NM has typically been classified by causative genes, disease severity or prognosis cannot be predicted. The common pathologic end point of nemaline rods (despite diverse genetic causes) and an unexplained range of muscle weakness suggest that shared secondary processes contribute to the pathogenesis of NM. We speculated that these processes could be identified through a proteome-wide interrogation using a mouse model of severe NM in combination with pathway validation and structural/functional analyses. A proteomic analysis was performed using skeletal muscle tissue from the Neb conditional knockout mouse model compared with its wild-type counterpart to identify pathophysiologically relevant biological processes that might impact disease severity or provide new treatment targets. A differential expression analysis and Ingenuity Pathway Core Analysis predicted perturbations in several cellular processes, including mitochondrial dysfunction and changes in energetic metabolism and stress-related pathways. Subsequent structural and functional studies demonstrated abnormal mitochondrial distribution, decreased mitochondrial respiratory function, an increase in mitochondrial transmembrane potential, and extremely low ATP content in Neb conditional knockout muscles relative to wild type. Overall, the findings of these studies support a role for severe mitochondrial dysfunction as a novel contributor to muscle weakness in NM.
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Affiliation(s)
- Rebecca A Slick
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Clinical and Translational Science Institute, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Jennifer A Tinklenberg
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Clinical and Translational Science Institute, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Jessica Sutton
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Liwen Zhang
- Mass Spectrometry and Proteomics Facility, Campus Chemical Instrument Center, The Ohio State University, Columbus, Ohio
| | - Hui Meng
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Margaret J Beatka
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Mark Vanden Avond
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Mariah J Prom
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Emily Ott
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Federica Montanaro
- Dubowitz Neuromuscular Centre, Molecular Neurosciences Section, Developmental Neuroscience Research and Teaching Department, UCL Great Ormond Street Institute of Child Health, London, United Kingdom the NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom; NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
| | - James Heisner
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Rafael Toro
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Henk Granzier
- College of Medicine, University of Arizona, Tucson, Arizona
| | - Aron M Geurts
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Mellowes Center for Genomic Sciences and Precision Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - David F Stowe
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Joint Department of Biomedical Engineering, Medical College of Wisconsin and Marquette University, Milwaukee, Wisconsin
| | - R Blake Hill
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Michael W Lawlor
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.
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8
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Liu Y, Xu J, Lv Q, Liang Z, Li L, Pan Q. Case report: identification of one frameshift variant and two in cis non-canonical splice variants of NEB gene in prenatal arthrogryposis. Front Genet 2023; 14:1220170. [PMID: 37745844 PMCID: PMC10512086 DOI: 10.3389/fgene.2023.1220170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 08/14/2023] [Indexed: 09/26/2023] Open
Abstract
NEB mutation is associated with congenital nemaline myopathies. Here, we report a family with recurrent prenatal arthrogryposis. Trio whole exome sequencing (WES) disclosed three novel NEB (NM_001271208.2) variants including one paternal frameshift c.19049_19050delCA (p.Thr6350Argfs*14) and two double maternal variants in cis c. [24871G>T;24871-10C>G] (p. [Val8291Phe;?]). They are evaluated as "likely pathogenic (LP)", "variant of uncertain of significance (VUS)", and "VUS", respectively. After further prediction, the c.24871G>T, c.24871-10C>G, and c.[24871G>T;24871-10C>G] were respectively genetically engineered into the three plasmids. Compared with their wild-type counterparts, the three plasmids all produced truncated transcripts, and also a significant proportion of the full-length transcripts, which allowed us to reclassify NEB c.24871G>T and c.24871-10C>G variants as LP. As far as we know, this is the first case carrying NEB allele-specific function of partial loss. This result helped the couple make informed reproductive choices and opt for assisted reproduction for future pregnancies. This study also increased awareness to the phenotype of prenatal nemaline myopathy and expanded the variant spectrum of NEB.
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Affiliation(s)
- Yuefang Liu
- Genetic and Prenatal Diagnosis Center, Huai’an Maternity and Child Clinical College of Xuzhou Medical University, Huai’an, China
| | - Juan Xu
- Clinical Medical College, Yangzhou University, Yangzhou, China
| | - Qiaoyi Lv
- School of Medicine, Jiangsu University, Zhenjiang, China
| | - Zhe Liang
- Genetic and Prenatal Diagnosis Center, Huai’an Maternity and Child Clinical College of Xuzhou Medical University, Huai’an, China
| | - Lingling Li
- Family Planning Department, Huai’an Maternity and Child Clinical College of Xuzhou Medical University, Huai’an, China
| | - Qiong Pan
- Genetic and Prenatal Diagnosis Center, Huai’an Maternity and Child Clinical College of Xuzhou Medical University, Huai’an, China
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9
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Gartz M, Haberman M, Sutton J, Slick RA, Luttrell SM, Mack DL, Lawlor MW. ACTA1 H40Y mutant iPSC-derived skeletal myocytes display mitochondrial defects in an in vitro model of nemaline myopathy. Exp Cell Res 2023; 424:113507. [PMID: 36796746 PMCID: PMC9993434 DOI: 10.1016/j.yexcr.2023.113507] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 02/06/2023] [Accepted: 02/07/2023] [Indexed: 02/16/2023]
Abstract
Nemaline myopathies (NM) are a group of congenital myopathies that lead to muscle weakness and dysfunction. While 13 genes have been identified to cause NM, over 50% of these genetic defects are due to mutations in nebulin (NEB) and skeletal muscle actin (ACTA1), which are genes required for normal assembly and function of the thin filament. NM can be distinguished on muscle biopsies due to the presence of nemaline rods, which are thought to be aggregates of the dysfunctional protein. Mutations in ACTA1 have been associated with more severe clinical disease and muscle weakness. However, the cellular pathogenesis linking ACTA1 gene mutations to muscle weakness are unclear To evaluate cellular disease phenotypes, iPSC-derived skeletal myocytes (iSkM) harboring an ACTA1 H40Y point mutation were used to model NM in skeletal muscle. These were generated by Crispr-Cas9, and include one non-affected healthy control (C) and 2 NM iPSC clone lines, therefore representing isogenic controls. Fully differentiated iSkM were characterized to confirm myogenic status and subject to assays to evaluate nemaline rod formation, mitochondrial membrane potential, mitochondrial permeability transition pore (mPTP) formation, superoxide production, ATP/ADP/phosphate levels and lactate dehydrogenase release. C- and NM-iSkM demonstrated myogenic commitment as evidenced by mRNA expression of Pax3, Pax7, MyoD, Myf5 and Myogenin; and protein expression of Pax4, Pax7, MyoD and MF20. No nemaline rods were observed with immunofluorescent staining of NM-iSkM for ACTA1 or ACTN2, and these mRNA transcript and protein levels were comparable to C-iSkM. Mitochondrial function was altered in NM, as evidenced by decreased cellular ATP levels and altered mitochondrial membrane potential. Oxidative stress induction revealed the mitochondrial phenotype, as evidenced by collapsed mitochondrial membrane potential, early formation of the mPTP and increased superoxide production. Early mPTP formation was rescued with the addition of ATP to media. Together, these findings suggest that mitochondrial dysfunction and oxidative stress are disease phenotypes in the in vitro model of ACTA1 nemaline myopathy, and that modulation of ATP levels was sufficient to protect NM-iSkM mitochondria from stress-induced injury. Importantly, the nemaline rod phenotype was absent in our in vitro model of NM. We conclude that this in vitro model has the potential to recapitulate human NM disease phenotypes, and warrants further study.
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Affiliation(s)
- Melanie Gartz
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA; Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, USA.
| | - Margaret Haberman
- Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, USA; Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA; Diverge Translational Science Laboratory, Milwaukee, WI, USA
| | - Jessica Sutton
- Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, USA; Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA; Diverge Translational Science Laboratory, Milwaukee, WI, USA
| | - Rebecca A Slick
- Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, USA; Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Shawn M Luttrell
- Curi Bio Inc., 3000 Western Avenue, Seattle, WA, 98121, USA; Institute for Stem Cell and Regenerative Medicine, UW Medicine, Seattle, WA, USA
| | - David L Mack
- Department of Rehabilitation Medicine, University of Washington, Seattle, WA, USA; Institute for Stem Cell and Regenerative Medicine, UW Medicine, Seattle, WA, USA
| | - Michael W Lawlor
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA; Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, USA; Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA; Diverge Translational Science Laboratory, Milwaukee, WI, USA
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10
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Removal of MuRF1 Increases Muscle Mass in Nemaline Myopathy Models, but Does Not Provide Functional Benefits. Int J Mol Sci 2022; 23:ijms23158113. [PMID: 35897687 PMCID: PMC9331820 DOI: 10.3390/ijms23158113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 07/18/2022] [Accepted: 07/20/2022] [Indexed: 11/16/2022] Open
Abstract
Nemaline myopathy (NM) is characterized by skeletal muscle weakness and atrophy. No curative treatments exist for this debilitating disease. NM is caused by mutations in proteins involved in thin-filament function, turnover, and maintenance. Mutations in nebulin, encoded by NEB, are the most common cause. Skeletal muscle atrophy is tightly linked to upregulation of MuRF1, an E3 ligase, that targets proteins for proteasome degradation. Here, we report a large increase in MuRF1 protein levels in both patients with nebulin-based NM, also named NEM2, and in mouse models of the disease. We hypothesized that knocking out MuRF1 in animal models of NM with muscle atrophy would ameliorate the muscle deficits. To test this, we crossed MuRF1 KO mice with two NEM2 mouse models, one with the typical form and the other with the severe form. The crosses were viable, and muscles were studied in mice at 3 months of life. Ultrastructural examination of gastrocnemius muscle lacking MuRF1 and with severe NM revealed a small increase in vacuoles, but no significant change in the myofibrillar fractional area. MuRF1 deficiency led to increased weights of various muscle types in the NM models. However, this increase in muscle size was not associated with increased in vivo or in vitro force production. We conclude that knocking out MuRF1 in NEM2 mice increases muscle size, but does not improve muscle function.
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11
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Yin X, Pu C, Wang Z, Li K, Wang H. Clinico-pathological features and mutational spectrum of 16 nemaline myopathy patients from a Chinese neuromuscular center. Acta Neurol Belg 2022; 122:631-639. [PMID: 33742414 PMCID: PMC9170660 DOI: 10.1007/s13760-020-01542-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 10/29/2020] [Indexed: 11/15/2022]
Abstract
Nemaline myopathy (NM) is a congenital myopathy of great heterogeneity, characterized by the presence of rods in the cytoplasm of muscle fibers. The samples of 16 nemaline myopathy patients diagnosed by characteristically pathological features went through whole exon sequencing. Clinico-pathological and genetic features of the cases were systematically analyzed. According to the classification of nemaline myopathy by ENMC, 8 cases are typical congenital subtype, 6 cases are childhood/juvenile onset subtype and 2 case are adult onset subtype. In histological findings, characteristic purple-colored rods are discovered under modified gömöri trichrome staining (MGT). Electron microscopy revealed the presence of high electron-dense nemaline bodies around the submucosa and the nucleus nine patients (9/16 56.3%) were detected pathogenic causative mutations, among whom mutations in the NEB gene were the most frequent (6 patients, 66.7%). KBTBD13 gene mutation was discovered in two patients and ACTA1 gene mutation was discovered in 1 patient. Nemaline myopathy is a congenital myopathy with highly clinico-pathological and genetic heterogeneity. NEB gene mutation is the most common mutation, in which splicing change c.21522 +3A > G is hotspot mutation in Chinese NM patients.
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12
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de Winter JM, Gineste C, Minardi E, Brocca L, Rossi M, Borsboom T, Beggs AH, Bernard M, Bendahan D, Hwee DT, Malik FI, Pellegrino MA, Bottinelli R, Gondin J, Ottenheijm CAC. Acute and chronic tirasemtiv treatment improves in vivo and in vitro muscle performance in actin-based nemaline myopathy mice. Hum Mol Genet 2021; 30:1305-1320. [PMID: 33909041 PMCID: PMC8255131 DOI: 10.1093/hmg/ddab112] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 03/09/2021] [Accepted: 04/07/2021] [Indexed: 12/13/2022] Open
Abstract
Nemaline myopathy, a disease of the actin-based thin filament, is one of the most frequent congenital myopathies. To date, no specific therapy is available to treat muscle weakness in nemaline myopathy. We tested the ability of tirasemtiv, a fast skeletal troponin activator that targets the thin filament, to augment muscle force—both in vivo and in vitro—in a nemaline myopathy mouse model with a mutation (H40Y) in Acta1. In Acta1H40Y mice, treatment with tirasemtiv increased the force response of muscles to submaximal stimulation frequencies. This resulted in a reduced energetic cost of force generation, which increases the force production during a fatigue protocol. The inotropic effects of tirasemtiv were present in locomotor muscles and, albeit to a lesser extent, in respiratory muscles, and they persisted during chronic treatment, an important finding as respiratory failure is the main cause of death in patients with congenital myopathy. Finally, translational studies on permeabilized muscle fibers isolated from a biopsy of a patient with the ACTA1H40Y mutation revealed that at physiological Ca2+ concentrations, tirasemtiv increased force generation to values that were close to those generated in muscle fibers of healthy subjects. These findings indicate the therapeutic potential of fast skeletal muscle troponin activators to improve muscle function in nemaline myopathy due to the ACTA1H40Y mutation, and future studies should assess their merit for other forms of nemaline myopathy and for other congenital myopathies.
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Affiliation(s)
| | | | | | - Lorenza Brocca
- Department of Molecular Medicine, University of Pavia, Pavia 27100, Italy
| | - Maira Rossi
- Department of Molecular Medicine, University of Pavia, Pavia 27100, Italy
| | - Tamara Borsboom
- Department of Physiology, Amsterdam UMC (location VUmc), Amsterdam 1081 HV, The Netherlands
| | - Alan H Beggs
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Monique Bernard
- Aix-Marseille Univ, CNRS, CRMBM, UMR 7339, 13005 Marseille, France
| | - David Bendahan
- Aix-Marseille Univ, CNRS, CRMBM, UMR 7339, 13005 Marseille, France
| | - Darren T Hwee
- Research and Early Development, Cytokinetics Inc., South San Francisco, CA 94080, USA
| | - Fady I Malik
- Research and Early Development, Cytokinetics Inc., South San Francisco, CA 94080, USA
| | - Maria Antonietta Pellegrino
- Department of Molecular Medicine, University of Pavia, Pavia 27100, Italy
- Interdipartimental Centre for Biology and Sport Medicine, University of Pavia, Pavia 27100, Italy
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13
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Fenwick AJ, Wood AM, Tanner BCW. The spatial distribution of thin filament activation influences force development and myosin activity in computational models of muscle contraction. Arch Biochem Biophys 2021; 703:108855. [PMID: 33781771 DOI: 10.1016/j.abb.2021.108855] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 03/03/2021] [Accepted: 03/18/2021] [Indexed: 01/22/2023]
Abstract
Striated muscle contraction is initiated by Ca2+ binding to, and activating, thin filament regulatory units (RU) within the sarcomere, which then allows myosin cross-bridges from the opposing thick filament to bind actin and generate force. The amount of overlap between the filaments dictates how many potential cross-bridges are capable of binding, and thus how force is generated by the sarcomere. Myopathies and atrophy can impair muscle function by limiting cross-bridge interactions between the filaments, which can occur when the length of the thin filament is reduced or when RU function is disrupted. To investigate how variations in thin filament length and RU density affect ensemble cross-bridge behavior and force production, we simulated muscle contraction using a spatially explicit computational model of the half-sarcomere. Thin filament RUs were disabled either uniformly from the pointed end of the filament (to model shorter thin filament length) or randomly throughout the length of the half-sarcomere. Both uniform and random RU 'knockout' schemes decreased overall force generation during maximal and submaximal activation. The random knockout scheme also led to decreased calcium sensitivity and cooperativity of the force-pCa relationship. We also found that the rate of force development slowed with the random RU knockout, compared to the uniform RU knockout or conditions of normal RU activation. These findings imply that the relationship between RU density and force production within the sarcomere involves more complex coordination than simply the raw number of RUs available for myosin cross-bridge binding, and that the spatial pattern in which activatable RU are distributed throughout the sarcomere influences the dynamics of force production.
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Affiliation(s)
- Axel J Fenwick
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, 99164, USA
| | - Alexander M Wood
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, 99164, USA
| | - Bertrand C W Tanner
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, 99164, USA.
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14
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Gohlke J, Tonino P, Lindqvist J, Smith JE, Granzier H. The number of Z-repeats and super-repeats in nebulin greatly varies across vertebrates and scales with animal size. J Gen Physiol 2020; 153:211611. [PMID: 33337482 PMCID: PMC7754682 DOI: 10.1085/jgp.202012783] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 11/20/2020] [Indexed: 12/18/2022] Open
Abstract
Nebulin is a skeletal muscle protein that associates with the sarcomeric thin filaments and has functions in regulating the length of the thin filament and the structure of the Z-disk. Here we investigated the nebulin gene in 53 species of birds, fish, amphibians, reptiles, and mammals. In all species, nebulin has a similar domain composition that mostly consists of ∼30-residue modules (or simple repeats), each containing an actin-binding site. All species have a large region where simple repeats are organized into seven-module super-repeats, each containing a tropomyosin binding site. The number of super-repeats shows high interspecies variation, ranging from 21 (zebrafish, hummingbird) to 31 (camel, chimpanzee), and, importantly, scales with body size. The higher number of super-repeats in large animals was shown to increase thin filament length, which is expected to increase the sarcomere length for optimal force production, increase the energy efficiency of isometric force production, and lower the shortening velocity of muscle. It has been known since the work of A.V. Hill in 1950 that as species increase in size, the shortening velocity of their muscle is reduced, and the present work shows that nebulin contributes to the mechanistic basis. Finally, we analyzed the differentially spliced simple repeats in nebulin's C terminus, whose inclusion correlates with the width of the Z-disk. The number of Z-repeats greatly varies (from 5 to 18) and correlates with the number of super-repeats. We propose that the resulting increase in the width of the Z-disk in large animals increases the number of contacts between nebulin and structural Z-disk proteins when the Z-disk is stressed for long durations.
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Affiliation(s)
- Jochen Gohlke
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Paola Tonino
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Johan Lindqvist
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - John E Smith
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
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15
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A childhood-onset nemaline myopathy caused by novel heterozygote variants in the nebulin gene with literature review. Acta Neurol Belg 2020; 120:1351-1360. [PMID: 31696431 DOI: 10.1007/s13760-019-01230-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Accepted: 10/17/2019] [Indexed: 10/25/2022]
Abstract
Nemaline myopathy, a rare congenital myopathy, is characterized by generalized muscle weakness, hypotonia, respiratory insufficiency, and the presence of rod structures on muscle biopsy, which is caused by mutations in at least 13 known genes. A patient showing gradually deteriorated proximal muscle weakness and rod-shaped structures found in muscle fibers was suspected of having nemaline myopathy, following by the next-generation sequencing. We report two novel compound heterozygous variants in nebulin gene in a family residing in China. One is an intron event caused by an underlying variant at the + 3 position of the donor site. Another is a novel nonsense variant, which may lead to the end of protein translation and have a significant impact on protein function. The pathogenicity of this novel compound heterozygous variant remains to be verified. Variants reported here could help to diagnose NM for clinicians.
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16
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Triggering typical nemaline myopathy with compound heterozygous nebulin mutations reveals myofilament structural changes as pathomechanism. Nat Commun 2020; 11:2699. [PMID: 32483185 PMCID: PMC7264197 DOI: 10.1038/s41467-020-16526-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 05/06/2020] [Indexed: 12/26/2022] Open
Abstract
Nebulin is a giant protein that winds around the actin filaments in the skeletal muscle sarcomere. Compound-heterozygous mutations in the nebulin gene (NEB) cause typical nemaline myopathy (NM), a muscle disorder characterized by muscle weakness with limited treatment options. We created a mouse model with a missense mutation p.Ser6366Ile and a deletion of NEB exon 55, the Compound-Het model that resembles typical NM. We show that Compound-Het mice are growth-retarded and have muscle weakness. Muscles have a reduced myofibrillar fractional-area and sarcomeres are disorganized, contain rod bodies, and have longer thin filaments. In contrast to nebulin-based severe NM where haplo-insufficiency is the disease driver, Compound-Het mice express normal amounts of nebulin. X-ray diffraction revealed that the actin filament is twisted with a larger radius, that tropomyosin and troponin behavior is altered, and that the myofilament spacing is increased. The unique disease mechanism of nebulin-based typical NM reveals novel therapeutic targets. Nebulin-based nemaline myopathy is a heterogenous disease with unclear pathological mechanisms. Here, the authors generate a mouse model that mimics the most common genetic cause of the disease and demonstrate that muscle weakness in this model is associated with twisted actin filaments and altered tropomyosin and troponin behaviour.
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17
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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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Li F, Kolb J, Crudele J, Tonino P, Hourani Z, Smith JE, Chamberlain JS, Granzier H. Expressing a Z-disk nebulin fragment in nebulin-deficient mouse muscle: effects on muscle structure and function. Skelet Muscle 2020; 10:2. [PMID: 31992366 PMCID: PMC6986074 DOI: 10.1186/s13395-019-0219-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 12/17/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Nebulin is a critical thin filament-binding protein that spans from the Z-disk of the skeletal muscle sarcomere to near the pointed end of the thin filament. Its massive size and actin-binding property allows it to provide the thin filaments with structural and regulatory support. When this protein is lost, nemaline myopathy occurs. Nemaline myopathy causes severe muscle weakness as well as structural defects on a sarcomeric level. There is no known cure for this disease. METHODS We studied whether sarcomeric structure and function can be improved by introducing nebulin's Z-disk region into a nebulin-deficient mouse model (Neb cKO) through adeno-associated viral (AAV) vector therapy. Following this treatment, the structural and functional characteristics of both vehicle-treated and AAV-treated Neb cKO and control muscles were studied. RESULTS Intramuscular injection of this AAV construct resulted in a successful expression of the Z-disk fragment within the target muscles. This expression was significantly higher in Neb cKO mice than control mice. Analysis of protein expression revealed that the nebulin fragment was localized exclusively to the Z-disks and that Neb cKO expressed the nebulin fragment at levels comparable to the level of full-length nebulin in control mice. Additionally, the Z-disk fragment displaced full-length nebulin in control mice, resulting in nemaline rod body formation and a worsening of muscle function. Neb cKO mice experienced a slight functional benefit from the AAV treatment, with a small increase in force and fatigue resistance. Disease progression was also slowed as indicated by improved muscle structure and myosin isoform expression. CONCLUSIONS This study reveals that nebulin fragments are well-received by nebulin-deficient mouse muscles and that limited functional benefits are achievable.
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Affiliation(s)
- Frank Li
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA
| | - Julie Crudele
- Department of Neurology, University of Washington, Seattle, WA, 98109-8055, USA
| | - Paola Tonino
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA
| | - Zaynab Hourani
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA
| | - John E Smith
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA
| | | | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA.
- Medical Research Building, RM 325, 1656 E Mabel St, Tucson, AZ, 85721, USA.
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Abstract
Nebulin, encoded by NEB, is a giant skeletal muscle protein of about 6669 amino acids which forms an integral part of the sarcomeric thin filament. In recent years, the nebula around this protein has been largely lifted resulting in the discovery that nebulin is critical for a number of tasks in skeletal muscle. In this review, we firstly discussed nebulin’s role as a structural component of the thin filament and the Z-disk, regulating the length and the mechanical properties of the thin filament as well as providing stability to myofibrils by interacting with structural proteins within the Z-disk. Secondly, we reviewed nebulin’s involvement in the regulation of muscle contraction, cross-bridge cycling kinetics, Ca2+-homeostasis and excitation contraction (EC) coupling. While its role in Ca2+-homeostasis and EC coupling is still poorly understood, a large number of studies have helped to improve our knowledge on how nebulin affects skeletal muscle contractile mechanics. These studies suggest that nebulin affects the number of force generating actin-myosin cross-bridges and may also affect the force that each cross-bridge produces. It may exert this effect by interacting directly with actin and myosin and/or indirectly by potentially changing the localisation and function of the regulatory complex (troponin and tropomyosin). Besides unravelling the biology of nebulin, these studies are particularly helpful in understanding the patho-mechanism of myopathies caused by NEB mutations, providing knowledge which constitutes the critical first step towards the development of therapeutic interventions. Currently, effective treatments are not available, although a number of therapeutic strategies are being investigated.
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20
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Gineste C, Ogier AC, Varlet I, Hourani Z, Bernard M, Granzier H, Bendahan D, Gondin J. In vivo characterization of skeletal muscle function in nebulin-deficient mice. Muscle Nerve 2020; 61:416-424. [PMID: 31893464 DOI: 10.1002/mus.26798] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 12/16/2019] [Accepted: 12/21/2019] [Indexed: 01/04/2023]
Abstract
INTRODUCTION The conditional nebulin knockout mouse is a new model mimicking nemaline myopathy, a rare disease characterized by muscle weakness and rods within muscle fibers. We investigated the impact of nebulin (NEB) deficiency on muscle function in vivo. METHODS Conditional nebulin knockout mice and control littermates were studied at 10 to 12 months. Muscle function (force and fatigue) and anatomy (muscles volume and fat content) were measured in vivo. Myosin heavy chain (MHC) composition and nebulin (NEB) protein expression were assessed by protein electrophoresis. RESULTS Conditional nebulin knockout mice displayed a lower NEB level (-90%) leading to a 40% and 45% reduction in specific maximal force production and muscles volume, respectively. Nebulin deficiency was also associated with higher resistance to fatigue and increased MHC I content. DISCUSSION Adult nebulin-deficient mice displayed severe muscle atrophy and weakness in vivo related to a low NEB content but an improved fatigue resistance due to a slower contractile phenotype.
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Affiliation(s)
| | - Augustin C Ogier
- Aix Marseille Univ, Université de Toulon, CNRS, LIS, Marseille, France
| | | | - Zaynab Hourani
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
| | | | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
| | | | - Julien Gondin
- Aix-Marseille Univ, CNRS, CRMBM, Marseille, France.,Institut NeuroMyoGène, UMR CNRS 5310 - INSERM U1217, Université Claude Bernard, Lyon, France
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Lassche S, Voermans NC, van der Pijl R, van den Berg M, Heerschap A, van Hees H, Kusters B, van der Maarel SM, Ottenheijm CAC, van Engelen BGM. Preserved single muscle fiber specific force in facioscapulohumeral muscular dystrophy. Neurology 2020; 94:e1157-e1170. [PMID: 31964688 DOI: 10.1212/wnl.0000000000008977] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Accepted: 09/20/2019] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To investigate single muscle fiber contractile performance in muscle biopsies from patients with facioscapulohumeral muscular dystrophy (FSHD), one of the most common hereditary muscle disorders. METHODS We collected 50 muscle biopsies (26 vastus lateralis, 24 tibialis anterior) from 14 patients with genetically confirmed FSHD and 12 healthy controls. Single muscle fibers (n = 547) were isolated for contractile measurements. Titin content and titin phosphorylation were examined in vastus lateralis muscle biopsies. RESULTS Single muscle fiber specific force was intact at saturating and physiologic calcium concentrations in all FSHD biopsies, with (FSHDFAT) and without (FSHDNORMAL) fatty infiltration, compared to healthy controls. Myofilament calcium sensitivity of force is increased in single muscle fibers obtained from FSHD muscle biopsies with increased fatty infiltration, but not in FSHD muscle biopsies without fatty infiltration (pCa50: 5.77-5.80 in healthy controls, 5.74-5.83 in FSHDNORMAL, and 5.86-5.90 in FSHDFAT single muscle fibers). Cross-bridge cycling kinetics at saturating calcium concentrations and myofilament cooperativity did not differ from healthy controls. Development of single muscle fiber passive tension was changed in all FSHD vastus lateralis and in FSHDFAT tibialis anterior, resulting in increased fiber stiffness. Titin content was increased in FSHD vastus lateralis biopsies; however, titin phosphorylation did not differ from healthy controls. CONCLUSION Muscle weakness in patients with FSHD is not caused by reduced specific force of individual muscle fibers, even in severely affected tissue with marked fatty infiltration of muscle tissue.
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Affiliation(s)
- Saskia Lassche
- From the Department of Neurology, Donders Institute for Brain, Cognition and Behaviour (S.L., N.C.V., B.G.M.v.E.), Department of Radiology (A.H.), and Department of Pulmonary Diseases (H.V.H.), Radboud University Medical Center, Nijmegen; Department of Physiology (S.L., R.v.d.P., M.v.d.B., C.A.C.O.) and Department of Pathology, Institute for Cardiovascular Research (B.K.), Amsterdam University Medical Center, the Netherlands; Department of Cellular and Molecular Medicine (R.v.d.P., C.A.C.O.), University of Arizona, Tucson; and Department of Human Genetics (S.M.v.d.M.), Leiden University Medical Centre, the Netherlands.
| | - Nicol C Voermans
- From the Department of Neurology, Donders Institute for Brain, Cognition and Behaviour (S.L., N.C.V., B.G.M.v.E.), Department of Radiology (A.H.), and Department of Pulmonary Diseases (H.V.H.), Radboud University Medical Center, Nijmegen; Department of Physiology (S.L., R.v.d.P., M.v.d.B., C.A.C.O.) and Department of Pathology, Institute for Cardiovascular Research (B.K.), Amsterdam University Medical Center, the Netherlands; Department of Cellular and Molecular Medicine (R.v.d.P., C.A.C.O.), University of Arizona, Tucson; and Department of Human Genetics (S.M.v.d.M.), Leiden University Medical Centre, the Netherlands
| | - Robbert van der Pijl
- From the Department of Neurology, Donders Institute for Brain, Cognition and Behaviour (S.L., N.C.V., B.G.M.v.E.), Department of Radiology (A.H.), and Department of Pulmonary Diseases (H.V.H.), Radboud University Medical Center, Nijmegen; Department of Physiology (S.L., R.v.d.P., M.v.d.B., C.A.C.O.) and Department of Pathology, Institute for Cardiovascular Research (B.K.), Amsterdam University Medical Center, the Netherlands; Department of Cellular and Molecular Medicine (R.v.d.P., C.A.C.O.), University of Arizona, Tucson; and Department of Human Genetics (S.M.v.d.M.), Leiden University Medical Centre, the Netherlands
| | - Marloes van den Berg
- From the Department of Neurology, Donders Institute for Brain, Cognition and Behaviour (S.L., N.C.V., B.G.M.v.E.), Department of Radiology (A.H.), and Department of Pulmonary Diseases (H.V.H.), Radboud University Medical Center, Nijmegen; Department of Physiology (S.L., R.v.d.P., M.v.d.B., C.A.C.O.) and Department of Pathology, Institute for Cardiovascular Research (B.K.), Amsterdam University Medical Center, the Netherlands; Department of Cellular and Molecular Medicine (R.v.d.P., C.A.C.O.), University of Arizona, Tucson; and Department of Human Genetics (S.M.v.d.M.), Leiden University Medical Centre, the Netherlands
| | - Arend Heerschap
- From the Department of Neurology, Donders Institute for Brain, Cognition and Behaviour (S.L., N.C.V., B.G.M.v.E.), Department of Radiology (A.H.), and Department of Pulmonary Diseases (H.V.H.), Radboud University Medical Center, Nijmegen; Department of Physiology (S.L., R.v.d.P., M.v.d.B., C.A.C.O.) and Department of Pathology, Institute for Cardiovascular Research (B.K.), Amsterdam University Medical Center, the Netherlands; Department of Cellular and Molecular Medicine (R.v.d.P., C.A.C.O.), University of Arizona, Tucson; and Department of Human Genetics (S.M.v.d.M.), Leiden University Medical Centre, the Netherlands
| | - Hieronymus van Hees
- From the Department of Neurology, Donders Institute for Brain, Cognition and Behaviour (S.L., N.C.V., B.G.M.v.E.), Department of Radiology (A.H.), and Department of Pulmonary Diseases (H.V.H.), Radboud University Medical Center, Nijmegen; Department of Physiology (S.L., R.v.d.P., M.v.d.B., C.A.C.O.) and Department of Pathology, Institute for Cardiovascular Research (B.K.), Amsterdam University Medical Center, the Netherlands; Department of Cellular and Molecular Medicine (R.v.d.P., C.A.C.O.), University of Arizona, Tucson; and Department of Human Genetics (S.M.v.d.M.), Leiden University Medical Centre, the Netherlands
| | - Benno Kusters
- From the Department of Neurology, Donders Institute for Brain, Cognition and Behaviour (S.L., N.C.V., B.G.M.v.E.), Department of Radiology (A.H.), and Department of Pulmonary Diseases (H.V.H.), Radboud University Medical Center, Nijmegen; Department of Physiology (S.L., R.v.d.P., M.v.d.B., C.A.C.O.) and Department of Pathology, Institute for Cardiovascular Research (B.K.), Amsterdam University Medical Center, the Netherlands; Department of Cellular and Molecular Medicine (R.v.d.P., C.A.C.O.), University of Arizona, Tucson; and Department of Human Genetics (S.M.v.d.M.), Leiden University Medical Centre, the Netherlands
| | - Silvère M van der Maarel
- From the Department of Neurology, Donders Institute for Brain, Cognition and Behaviour (S.L., N.C.V., B.G.M.v.E.), Department of Radiology (A.H.), and Department of Pulmonary Diseases (H.V.H.), Radboud University Medical Center, Nijmegen; Department of Physiology (S.L., R.v.d.P., M.v.d.B., C.A.C.O.) and Department of Pathology, Institute for Cardiovascular Research (B.K.), Amsterdam University Medical Center, the Netherlands; Department of Cellular and Molecular Medicine (R.v.d.P., C.A.C.O.), University of Arizona, Tucson; and Department of Human Genetics (S.M.v.d.M.), Leiden University Medical Centre, the Netherlands
| | - Coen A C Ottenheijm
- From the Department of Neurology, Donders Institute for Brain, Cognition and Behaviour (S.L., N.C.V., B.G.M.v.E.), Department of Radiology (A.H.), and Department of Pulmonary Diseases (H.V.H.), Radboud University Medical Center, Nijmegen; Department of Physiology (S.L., R.v.d.P., M.v.d.B., C.A.C.O.) and Department of Pathology, Institute for Cardiovascular Research (B.K.), Amsterdam University Medical Center, the Netherlands; Department of Cellular and Molecular Medicine (R.v.d.P., C.A.C.O.), University of Arizona, Tucson; and Department of Human Genetics (S.M.v.d.M.), Leiden University Medical Centre, the Netherlands
| | - Baziel G M van Engelen
- From the Department of Neurology, Donders Institute for Brain, Cognition and Behaviour (S.L., N.C.V., B.G.M.v.E.), Department of Radiology (A.H.), and Department of Pulmonary Diseases (H.V.H.), Radboud University Medical Center, Nijmegen; Department of Physiology (S.L., R.v.d.P., M.v.d.B., C.A.C.O.) and Department of Pathology, Institute for Cardiovascular Research (B.K.), Amsterdam University Medical Center, the Netherlands; Department of Cellular and Molecular Medicine (R.v.d.P., C.A.C.O.), University of Arizona, Tucson; and Department of Human Genetics (S.M.v.d.M.), Leiden University Medical Centre, the Netherlands
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22
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Prill K, Dawson JF. Assembly and Maintenance of Sarcomere Thin Filaments and Associated Diseases. Int J Mol Sci 2020; 21:E542. [PMID: 31952119 PMCID: PMC7013991 DOI: 10.3390/ijms21020542] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 01/06/2020] [Accepted: 01/12/2020] [Indexed: 12/22/2022] Open
Abstract
Sarcomere assembly and maintenance are essential physiological processes required for cardiac and skeletal muscle function and organism mobility. Over decades of research, components of the sarcomere and factors involved in the formation and maintenance of this contractile unit have been identified. Although we have a general understanding of sarcomere assembly and maintenance, much less is known about the development of the thin filaments and associated factors within the sarcomere. In the last decade, advancements in medical intervention and genome sequencing have uncovered patients with novel mutations in sarcomere thin filaments. Pairing this sequencing with reverse genetics and the ability to generate patient avatars in model organisms has begun to deepen our understanding of sarcomere thin filament development. In this review, we provide a summary of recent findings regarding sarcomere assembly, maintenance, and disease with respect to thin filaments, building on the previous knowledge in the field. We highlight debated and unknown areas within these processes to clearly define open research questions.
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Affiliation(s)
| | - John F. Dawson
- Centre for Cardiovascular Investigations, Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada;
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23
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Tinklenberg JA, Siebers EM, Beatka MJ, Fickau BA, Ayres S, Meng H, Yang L, Simpson P, Granzier HL, Lawlor MW. Myostatin Inhibition Using ActRIIB-mFc Does Not Produce Weight Gain or Strength in the Nebulin Conditional KO Mouse. J Neuropathol Exp Neurol 2019; 78:130-139. [PMID: 30597051 DOI: 10.1093/jnen/nly120] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Mutations in at least 12 genes are responsible for a group of congenital skeletal muscle diseases known as nemaline myopathies (NMs). NMs are associated with a range of clinical symptoms and pathological changes often including the presence of cytoplasmic rod-like structures (nemaline bodies) and myofiber hypotrophy. Our recent work has identified a variable degree of behavioral benefit when treating 2 NM mouse models due to mutations in Acta1 with myostatin inhibition. This study is focused on the effects of delivering ActRIIB-mFc (Acceleron; a myostatin inhibitor) to the nebulin conditional knockout KO (Neb cKO) mouse model of NM. Treatment of Neb cKO mice with ActRIIB-mFc did not produce increases in weight gain, strength, myofiber size, or hypertrophic pathway signaling. Overall, our studies demonstrate a lack of response in Neb cKO mice to myostatin inhibition, which differs from the response observed when treating other NM models.
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Affiliation(s)
- Jennifer A Tinklenberg
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine.,Neuroscience Research Center Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Emily M Siebers
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine.,Neuroscience Research Center Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Margaret J Beatka
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine.,Neuroscience Research Center Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Brittany A Fickau
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine.,Neuroscience Research Center Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Samuel Ayres
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine.,Neuroscience Research Center Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Hui Meng
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine
| | - Lin Yang
- Department of Biomedical Engineering, University of Florida, Gainesville, Florida
| | - Pippa Simpson
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine
| | - Henk L Granzier
- Division of Quantitative Health Sciences, Department of Pediatrics Medical College of Wisconsin, Milwaukee, Wisconsin (PS); and College of Medicine, University of Arizona, Tucson, Arizona
| | - Michael W Lawlor
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine.,Neuroscience Research Center Medical College of Wisconsin, Milwaukee, Wisconsin
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24
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Lindqvist J, Lee EJ, Karimi E, Kolb J, Granzier H. Omecamtiv mecarbil lowers the contractile deficit in a mouse model of nebulin-based nemaline myopathy. PLoS One 2019; 14:e0224467. [PMID: 31721788 PMCID: PMC6853306 DOI: 10.1371/journal.pone.0224467] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Accepted: 10/14/2019] [Indexed: 01/10/2023] Open
Abstract
Nemaline myopathy (NEM) is a congenital neuromuscular disorder primarily caused by nebulin gene (NEB) mutations. NEM is characterized by muscle weakness for which currently no treatments exist. In NEM patients a predominance of type I fibers has been found. Thus, therapeutic options targeting type I fibers could be highly beneficial for NEM patients. Because type I muscle fibers express the same myosin isoform as cardiac muscle (Myh7), the effect of omecamtiv mecarbil (OM), a small molecule activator of Myh7, was studied in a nebulin-based NEM mouse model (Neb cKO). Skinned single fibers were activated by exogenous calcium and force was measured at a wide range of calcium concentrations. Maximal specific force of type I fibers was much less in fibers from Neb cKO animals and calcium sensitivity of permeabilized single fibers was reduced (pCa50 6.12 ±0.08 (cKO) vs 6.36 ±0.08 (CON)). OM increased the calcium sensitivity of type I single muscle fibers. The greatest effect occurred in type I fibers from Neb cKO muscle where OM restored the calcium sensitivity to that of the control type I fibers. Forces at submaximal activation levels (pCa 6.0–6.5) were significantly increased in Neb cKO fibers (~50%) but remained below that of control fibers. OM also increased isometric force and power during isotonic shortening of intact whole soleus muscle of Neb cKO mice, with the largest effects at physiological stimulation frequencies. We conclude that OM has the potential to improve the quality of life of NEM patients by increasing the force of type I fibers at submaximal activation levels.
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Affiliation(s)
- Johan Lindqvist
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, United States of America
| | - Eun-Jeong Lee
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, United States of America
| | - Esmat Karimi
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, United States of America
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, United States of America
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, United States of America
- * E-mail:
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25
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Lee EJ, Kolb J, Hwee DT, Malik FI, Granzier HL. Functional Characterization of the Intact Diaphragm in a Nebulin-Based Nemaline Myopathy (NM) Model-Effects of the Fast Skeletal Muscle Troponin Activator tirasemtiv. Int J Mol Sci 2019; 20:E5008. [PMID: 31658633 PMCID: PMC6829460 DOI: 10.3390/ijms20205008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 10/05/2019] [Accepted: 10/06/2019] [Indexed: 02/08/2023] Open
Abstract
Respiratory failure due to diaphragm dysfunction is considered a main cause of death in nemaline myopathy (NM) and we studied both isometric force and isotonic shortening of diaphragm muscle in a mouse model of nebulin-based NM (Neb cKO). A large contractile deficit was found in nebulin-deficient intact muscle that is frequency dependent, with the largest deficits at low-intermediate stimulation frequencies (e.g., a deficit of 72% at a stimulation frequency of 20 Hz). The effect of the fast skeletal muscle troponin activator (FSTA) tirasemtiv on force was examined. Tirasemtiv had a negligible effect at maximal stimulation frequencies, but greatly reduced the force deficit of the diaphragm at sub-maximal stimulation levels with an effect that was largest in Neb cKO diaphragm. As a result, the force deficit of Neb cKO diaphragm fell (from 72% to 29% at 20 Hz). Similar effects were found in in vivo experiments on the nerve-stimulated gastrocnemius muscle complex. Load-clamp experiments on diaphragm muscle showed that tirasemtiv increased the shortening velocity, and reduced the deficit in mechanical power by 33%. Thus, tirasemtiv significantly improves muscle function in a mouse model of nebulin-based nemaline myopathy.
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Affiliation(s)
- Eun-Jeong Lee
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA.
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA.
| | - Darren T Hwee
- Research and Early Development, Cytokinetics, Inc., South San Francisco, CA 94080, USA.
| | - Fady I Malik
- Research and Early Development, Cytokinetics, Inc., South San Francisco, CA 94080, USA.
| | - Henk L Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA.
- Medical Research Building, RM 325, 1656 E Mabel St, Tucson, AZ 85721, USA.
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26
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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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27
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Patil D, Patil A, Khadke N, Borhade A. Highly selective and sensitive colorimetric probe for Al3+ and Fe3+ metal ions based on 2-aminoquinolin-3-yl phenyl hydrazone Schiff base. Inorganica Chim Acta 2019. [DOI: 10.1016/j.ica.2019.04.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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28
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Mijailovich SM, Stojanovic B, Nedic D, Svicevic M, Geeves MA, Irving TC, Granzier HL. Nebulin and titin modulate cross-bridge cycling and length-dependent calcium sensitivity. J Gen Physiol 2019; 151:680-704. [PMID: 30948421 PMCID: PMC6504291 DOI: 10.1085/jgp.201812165] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 01/15/2019] [Accepted: 03/03/2019] [Indexed: 12/13/2022] Open
Abstract
Various mutations in the structural proteins nebulin and titin that are present in human disease are known to affect the contractility of striated muscle. Loss of nebulin is associated with reduced actin filament length and impairment of myosin binding to actin, whereas titin is thought to regulate muscle passive elasticity and is likely involved in length-dependent activation. Here, we sought to assess the modulation of muscle function by these sarcomeric proteins by using the computational platform muscle simulation code (MUSICO) to quantitatively separate the effects of structural changes, kinetics of cross-bridge cycling, and calcium sensitivity of the thin filaments. The simulations show that variation in thin filament length cannot by itself account for experimental observations of the contractility in nebulin-deficient muscle, but instead must be accompanied by a decreased myosin binding rate. Additionally, to match the observed calcium sensitivity, the rate of TnI detachment from actin needed to be increased. Simulations for cardiac muscle provided quantitative estimates of the effects of different titin-based passive elasticities on muscle force and activation in response to changes in sarcomere length and interfilament lattice spacing. Predicted force-pCa relations showed a decrease in both active tension and sensitivity to calcium with a decrease in passive tension and sarcomere length. We conclude that this behavior is caused by partial redistribution of the muscle load between active muscle force and titin-dependent passive force, and also by redistribution of stretch along the thin filament, which together modulate the release of TnI from actin. These data help advance understanding of how nebulin and titin mutations affect muscle function.
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Affiliation(s)
- Srboljub M Mijailovich
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA .,Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
| | - Boban Stojanovic
- University of Kragujevac, Faculty of Science, Kragujevac, Serbia
| | - Djordje Nedic
- University of Kragujevac, Faculty of Science, Kragujevac, Serbia
| | - Marina Svicevic
- University of Kragujevac, Faculty of Science, Kragujevac, Serbia
| | - Michael A Geeves
- Department of Biosciences, University of Kent, Canterbury, Kent, UK
| | - Thomas C Irving
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
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29
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Lassche S, Rietveld A, Heerschap A, van Hees HW, Hopman MT, Voermans NC, Saris CG, van Engelen BG, Ottenheijm CA. Muscle fiber dysfunction contributes to weakness in inclusion body myositis. Neuromuscul Disord 2019; 29:468-476. [PMID: 31101463 DOI: 10.1016/j.nmd.2019.03.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 01/29/2019] [Accepted: 03/01/2019] [Indexed: 01/12/2023]
Abstract
Atrophy and fatty infiltration are important causes of muscle weakness in inclusion body myositis (IBM). Muscle weakness can also be caused by reduced specific force; i.e. the amount of force generated per unit of residual muscle tissue. This study investigates in vivo specific force of the quadriceps and ex vivo specific force of single muscle fibers in patients with IBM. We included 8 participants with IBM and 12 healthy controls, who all underwent quantitative muscle testing, quantitative MRI of the quadriceps and paired muscle biopsies of the quadriceps and tibialis anterior. Single muscle fibers were isolated to measure muscle fiber specific force and contractile properties. Both in vivo quadriceps specific force and ex vivo muscle fiber specific force were reduced. Muscle fiber dysfunction was accompanied by reduced active stiffness, which reflects a decrease in the number of attached actin-myosin cross-bridges during activation. Myosin concentration was reduced in IBM fibers. Because reduced specific force contributes to muscle weakness in patients with IBM, therapeutic strategies that augment muscle fiber strength may provide benefit to patients with IBM.
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Affiliation(s)
- Saskia Lassche
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands; Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, O/2 Building 11W53, 1081 HZ Amsterdam, The Netherlands.
| | - Anke Rietveld
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Arend Heerschap
- Department of Radiology, Radboud University Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Hieronymus W van Hees
- Department of Pulmonary Diseases, Radboud University Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Maria Te Hopman
- Department of Physiology, Radboud University Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Nicol C Voermans
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Christiaan Gj Saris
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Baziel Gm van Engelen
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Coen Ac Ottenheijm
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, O/2 Building 11W53, 1081 HZ Amsterdam, The Netherlands
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30
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A missense variant in the titin gene in Doberman pinscher dogs with familial dilated cardiomyopathy and sudden cardiac death. Hum Genet 2019; 138:515-524. [DOI: 10.1007/s00439-019-01973-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Accepted: 01/04/2019] [Indexed: 12/30/2022]
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31
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Tinklenberg JA, Siebers EM, Beatka MJ, Meng H, Yang L, Zhang Z, Ross JA, Ochala J, Morris C, Owens JM, Laing NG, Nowak KJ, Lawlor MW. Myostatin inhibition using mRK35 produces skeletal muscle growth and tubular aggregate formation in wild type and TgACTA1D286G nemaline myopathy mice. Hum Mol Genet 2019; 27:638-648. [PMID: 29293963 DOI: 10.1093/hmg/ddx431] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 12/15/2017] [Indexed: 12/27/2022] Open
Abstract
Nemaline myopathy (NM) is a heterogeneous congenital skeletal muscle disease with cytoplasmic rod-like structures (nemaline bodies) in muscle tissue. While weakness in NM is related to contractile abnormalities, myofiber smallness is an additional abnormality in NM that may be treatable. We evaluated the effects of mRK35 (a myostatin inhibitor developed by Pfizer) treatment in the TgACTA1D286G mouse model of NM. mRK35 induced skeletal muscle growth that led to significant increases in animal bodyweight, forelimb grip strength and muscle fiber force, although it should be noted that animal weight and forelimb grip strength in untreated TgACTA1D286G mice was not different from controls. Treatment was also associated with an increase in the number of tubular aggregates found in skeletal muscle. These findings suggest that myostatin inhibition may be useful in promoting muscle growth and strength in Acta1-mutant muscle, while also further establishing the relationship between low levels of myostatin and tubular aggregate formation.
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Affiliation(s)
- Jennifer A Tinklenberg
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee 53226, WI, USA
| | - Emily M Siebers
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee 53226, WI, USA
| | - Margaret J Beatka
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee 53226, WI, USA
| | - Hui Meng
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee 53226, WI, USA
| | - Lin Yang
- Department of Biomedical Engineering, University of Florida, Gainesville 32607, FL, USA
| | - Zizhao Zhang
- Department of Biomedical Engineering, University of Florida, Gainesville 32607, FL, USA
| | - Jacob A Ross
- School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Julien Ochala
- School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | | | | | - Nigel G Laing
- Centre for Medical Research, The University of Western Australia, Perth, WA, Australia.,Harry Perkins Institute of Medical Research, Nedlands, WA, Australia
| | - Kristen J Nowak
- Harry Perkins Institute of Medical Research, Nedlands, WA, Australia.,Faculty of Health and Medical Sciences, School of Biomedical Sciences, The University of Western Australia, Perth, WA, Australia
| | - Michael W Lawlor
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee 53226, WI, USA
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32
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Laitila J, Lehtonen J, Lehtokari VL, Sagath L, Wallgren-Pettersson C, Grönholm M, Pelin K. A nebulin super-repeat panel reveals stronger actin binding toward the ends of the super-repeat region. Muscle Nerve 2018; 59:116-121. [PMID: 30265400 DOI: 10.1002/mus.26350] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 08/27/2018] [Accepted: 09/23/2018] [Indexed: 12/28/2022]
Abstract
INTRODUCTION Nebulin is a giant actin-binding protein in the thin filament of the skeletal muscle sarcomere. Studies of nebulin interactions are limited by the size, complexity, and poor solubility of the protein. We divided the nebulin super-repeat region into a super-repeat panel, and studied nebulin/actin interactions. METHODS Actin binding was studied using a co-sedimentation assay with filamentous actin and 26 different nebulin super-repeats. RESULTS The panel revealed notable differences in actin binding between the super-repeats. Both ends of the super-repeat region bound actin significantly more strongly, whereas the central part of the protein bound actin weakly. Thus, the binding between nebulin and actin formed a location-dependent pattern of strong vs. weak binding. DISCUSSION The nebulin super-repeat panel allowed us to study the actin binding of each super-repeat individually. The panel will be a powerful tool in elucidating nebulin function in health and disease. Muscle Nerve 59:116-121, 2019.
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Affiliation(s)
- Jenni Laitila
- The Folkhälsan Institute of Genetics and Department of Medical and Clinical Genetics, Biomedicum Helsinki, University of Helsinki, P.O. Box 63, 00014, Helsinki, Finland
| | - Johanna Lehtonen
- The Folkhälsan Institute of Genetics and Department of Medical and Clinical Genetics, Biomedicum Helsinki, University of Helsinki, P.O. Box 63, 00014, Helsinki, Finland
| | - Vilma-Lotta Lehtokari
- The Folkhälsan Institute of Genetics and Department of Medical and Clinical Genetics, Biomedicum Helsinki, University of Helsinki, P.O. Box 63, 00014, Helsinki, Finland
| | - Lydia Sagath
- The Folkhälsan Institute of Genetics and Department of Medical and Clinical Genetics, Biomedicum Helsinki, University of Helsinki, P.O. Box 63, 00014, Helsinki, Finland
| | - Carina Wallgren-Pettersson
- The Folkhälsan Institute of Genetics and Department of Medical and Clinical Genetics, Biomedicum Helsinki, University of Helsinki, P.O. Box 63, 00014, Helsinki, Finland
| | - Mikaela Grönholm
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Programme, University of Helsinki, Helsinki, Finland
| | - Katarina Pelin
- The Folkhälsan Institute of Genetics and Department of Medical and Clinical Genetics, Biomedicum Helsinki, University of Helsinki, P.O. Box 63, 00014, Helsinki, Finland.,Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Programme, University of Helsinki, Helsinki, Finland
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Kawai M, Karam TS, Kolb J, Wang L, Granzier HL. Nebulin increases thin filament stiffness and force per cross-bridge in slow-twitch soleus muscle fibers. J Gen Physiol 2018; 150:1510-1522. [PMID: 30301869 PMCID: PMC6219688 DOI: 10.1085/jgp.201812104] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 09/19/2018] [Indexed: 01/15/2023] Open
Abstract
Nebulin stabilizes the thin filament and regulates force generation in skeletal muscle, but its precise role is not understood. Using conditional knockout mice, Kawai et al. demonstrate that nebulin functions to increase the force per cross-bridge in skinned slow-twitch soleus muscle fibers. Nebulin (Neb) is associated with the thin filament in skeletal muscle cells, but its functions are not well understood. For this goal, we study skinned slow-twitch soleus muscle fibers from wild-type (Neb+) and conditional Neb knockout (Neb−) mice. We characterize cross-bridge (CB) kinetics and the elementary steps of the CB cycle by sinusoidal analysis during full Ca2+ activation and observe that Neb increases active tension 1.9-fold, active stiffness 2.7-fold, and rigor stiffness 3.0-fold. The ratio of stiffness during activation and rigor states is 62% in Neb+ fibers and 68% in Neb− fibers. These are approximately proportionate to the number of strongly attached CBs during activation. Because the thin filament length is 15% shorter in Neb− fibers than in Neb+ fibers, the increase in force per CB in the presence of Neb is ∼1.5 fold. The equilibrium constant of the CB detachment step (K2), its rate (k2), and the rate of the reverse force generation step (k−4) are larger in Neb+ fibers than in Neb− fibers. The rates of the force generation step (k4) and the reversal detachment step (k−2) change in the opposite direction. These effects can be explained by Le Chatelier’s principle: Increased CB strain promotes less force-generating state(s) and/or detached state(s). Further, when CB distributions among the six states are calculated, there is no significant difference in the number of strongly attached CBs between fibers with and without Neb. These results demonstrate that Neb increases force per CB. We also confirm that force is generated by isomerization of actomyosin (AM) from the AM.ADP.Pi state (ADP, adenosine diphophate; Pi, phosphate) to the AM*ADP.Pi state, where the same force is maintained after Pi release to result in the AM*ADP state. We propose that Neb changes the actin (and myosin) conformation for better ionic and hydrophobic/stereospecific AM interaction, and that the effect of Neb is similar to that of tropomyosin.
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Affiliation(s)
- Masataka Kawai
- Departments of Anatomy and Cell Biology, and Internal Medicine, College of Medicine, University of Iowa, Iowa City, IA
| | - Tarek S Karam
- Departments of Anatomy and Cell Biology, and Internal Medicine, College of Medicine, University of Iowa, Iowa City, IA
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Li Wang
- Departments of Anatomy and Cell Biology, and Internal Medicine, College of Medicine, University of Iowa, Iowa City, IA.,School of Nursing, Soochow University, Suzhou, China
| | - Henk L Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
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Nebulin stiffens the thin filament and augments cross-bridge interaction in skeletal muscle. Proc Natl Acad Sci U S A 2018; 115:10369-10374. [PMID: 30249654 PMCID: PMC6187167 DOI: 10.1073/pnas.1804726115] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Nebulin is a giant sarcomeric protein that spans along the actin filament in skeletal muscle, from the Z-disk to near the thin filament pointed end. Mutations in nebulin cause muscle weakness in nemaline myopathy patients, suggesting that nebulin plays important roles in force generation, yet little is known about nebulin's influence on thin filament structure and function. Here, we used small-angle X-ray diffraction and compared intact muscle deficient in nebulin (using a conditional nebulin-knockout, Neb cKO) with control (Ctrl) muscle. When muscles were activated, the spacing of the actin subunit repeat (27 Å) increased in both genotypes; when converted to thin filament stiffness, the obtained value was 30 pN/nm in Ctrl muscle and 10 pN/nm in Neb cKO muscle; that is, the thin filament was approximately threefold stiffer when nebulin was present. In contrast, the thick filament stiffness was not different between the genotypes. A significantly shorter left-handed (59 Å) thin filament helical pitch was found in passive and contracting Neb cKO muscles, as well as impaired tropomyosin and troponin movement. Additionally, a reduced myosin mass transfer toward the thin filament in contracting Neb cKO muscle was found, suggesting reduced cross-bridge interaction. We conclude that nebulin is critically important for physiological force levels, as it greatly stiffens the skeletal muscle thin filament and contributes to thin filament activation and cross-bridge recruitment.
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Lindqvist J, van den Berg M, van der Pijl R, Hooijman PE, Beishuizen A, Elshof J, de Waard M, Girbes A, Spoelstra-de Man A, Shi ZH, van den Brom C, Bogaards S, Shen S, Strom J, Granzier H, Kole J, Musters RJP, Paul MA, Heunks LMA, Ottenheijm CAC. Positive End-Expiratory Pressure Ventilation Induces Longitudinal Atrophy in Diaphragm Fibers. Am J Respir Crit Care Med 2018; 198:472-485. [PMID: 29578749 PMCID: PMC6118031 DOI: 10.1164/rccm.201709-1917oc] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2017] [Accepted: 03/26/2018] [Indexed: 01/11/2023] Open
Abstract
RATIONALE Diaphragm weakness in critically ill patients prolongs ventilator dependency and duration of hospital stay and increases mortality and healthcare costs. The mechanisms underlying diaphragm weakness include cross-sectional fiber atrophy and contractile protein dysfunction, but whether additional mechanisms are at play is unknown. OBJECTIVES To test the hypothesis that mechanical ventilation with positive end-expiratory pressure (PEEP) induces longitudinal atrophy by displacing the diaphragm in the caudal direction and reducing the length of fibers. METHODS We studied structure and function of diaphragm fibers of mechanically ventilated critically ill patients and mechanically ventilated rats with normal and increased titin compliance. MEASUREMENTS AND MAIN RESULTS PEEP causes a caudal movement of the diaphragm, both in critically ill patients and in rats, and this caudal movement reduces fiber length. Diaphragm fibers of 18-hour mechanically ventilated rats (PEEP of 2.5 cm H2O) adapt to the reduced length by absorbing serially linked sarcomeres, the smallest contractile units in muscle (i.e., longitudinal atrophy). Increasing the compliance of titin molecules reduces longitudinal atrophy. CONCLUSIONS Mechanical ventilation with PEEP results in longitudinal atrophy of diaphragm fibers, a response that is modulated by the elasticity of the giant sarcomeric protein titin. We postulate that longitudinal atrophy, in concert with the aforementioned cross-sectional atrophy, hampers spontaneous breathing trials in critically ill patients: during these efforts, end-expiratory lung volume is reduced, and the shortened diaphragm fibers are stretched to excessive sarcomere lengths. At these lengths, muscle fibers generate less force, and diaphragm weakness ensues.
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Affiliation(s)
- Johan Lindqvist
- Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
| | | | - Robbert van der Pijl
- Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
- Department of Physiology
| | | | - Albertus Beishuizen
- Department of Intensive Care, Medisch Spectrum Twente, Enschede, the Netherlands; and
| | | | | | | | | | - Zhong-Hua Shi
- Department of Critical Care Medicine, Beijing Tiantan Hospital, Capital Medical University, Beijing, PR China
| | | | | | - Shengyi Shen
- Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
| | - Joshua Strom
- Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
| | - Henk Granzier
- Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
| | | | | | - Marinus A. Paul
- Department of Cardiothoracic Surgery, Vrije Universiteit Medical Center, Amsterdam, the Netherlands
| | | | - Coen A. C. Ottenheijm
- Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
- Department of Physiology
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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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37
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Abstract
During muscle development, nuclei travel from the centre of the myofibre to the periphery, a process defective in certain diseases. A new study reveals that this movement is due to centripetal forces imposed on nuclei by the crosslinking and contraction of myofibrils.
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38
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A chromone-derived Schiff-base as Al3+ “turn-on” fluorescent probe based on photoinduced electron-transfer (PET) and CN isomerization. Tetrahedron Lett 2016. [DOI: 10.1016/j.tetlet.2016.09.058] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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39
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Muscle weakness in respiratory and peripheral skeletal muscles in a mouse model for nebulin-based nemaline myopathy. Neuromuscul Disord 2016; 27:83-89. [PMID: 27890461 DOI: 10.1016/j.nmd.2016.10.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2016] [Revised: 09/21/2016] [Accepted: 10/11/2016] [Indexed: 12/28/2022]
Abstract
Nemaline myopathy is among the most common non-dystrophic congenital myopathies, and is characterized by the presence of nemaline rods in skeletal muscles fibers, general muscle weakness, and hypotonia. Although respiratory failure is the main cause of death in nemaline myopathy, only little is known regarding the contractile strength of the diaphragm, the main muscle of inspiration. To investigate diaphragm contractility, in the present study we took advantage of a mouse model for nebulin-based nemaline myopathy that we recently developed. In this mouse model, exon 55 of Neb is deleted (NebΔExon55), a mutation frequently found in patients. Diaphragm contractility was determined in permeabilized muscle fibers and was compared to the contractility of permeabilized fibers from three peripheral skeletal muscles: soleus, extensor digitorum longus, and gastrocnemius. The force generating capacity of diaphragm muscle fibers of NebΔExon55 mice was reduced to 25% of wildtype levels, indicating severe contractile weakness. The contractile weakness of diaphragm fibers was more pronounced than that observed in soleus muscle, but not more pronounced than that observed in extensor digitorum longus and gastrocnemius muscles. The reduced muscle contractility was at least partly caused by changes in cross-bridge cycling kinetics which reduced the number of bound cross-bridges. The severe diaphragm weakness likely contributes to the development of respiratory failure in NebΔExon55 mice and might explain their early, postnatal death.
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40
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Winter JMD, Joureau B, Lee EJ, Kiss B, Yuen M, Gupta VA, Pappas CT, Gregorio CC, Stienen GJM, Edvardson S, Wallgren-Pettersson C, Lehtokari VL, Pelin K, Malfatti E, Romero NB, Engelen BGV, Voermans NC, Donkervoort S, Bönnemann CG, Clarke NF, Beggs AH, Granzier H, Ottenheijm CAC. Mutation-specific effects on thin filament length in thin filament myopathy. Ann Neurol 2016; 79:959-69. [PMID: 27074222 DOI: 10.1002/ana.24654] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 03/22/2016] [Accepted: 03/27/2016] [Indexed: 12/24/2022]
Abstract
OBJECTIVE Thin filament myopathies are among the most common nondystrophic congenital muscular disorders, and are caused by mutations in genes encoding proteins that are associated with the skeletal muscle thin filament. Mechanisms underlying muscle weakness are poorly understood, but might involve the length of the thin filament, an important determinant of force generation. METHODS We investigated the sarcomere length-dependence of force, a functional assay that provides insights into the contractile strength of muscle fibers as well as the length of the thin filaments, in muscle fibers from 51 patients with thin filament myopathy caused by mutations in NEB, ACTA1, TPM2, TPM3, TNNT1, KBTBD13, KLHL40, and KLHL41. RESULTS Lower force generation was observed in muscle fibers from patients of all genotypes. In a subset of patients who harbor mutations in NEB and ACTA1, the lower force was associated with downward shifted force-sarcomere length relations, indicative of shorter thin filaments. Confocal microscopy confirmed shorter thin filaments in muscle fibers of these patients. A conditional Neb knockout mouse model, which recapitulates thin filament myopathy, revealed a compensatory mechanism; the lower force generation that was associated with shorter thin filaments was compensated for by increasing the number of sarcomeres in series. This allowed muscle fibers to operate at a shorter sarcomere length and maintain optimal thin-thick filament overlap. INTERPRETATION These findings might provide a novel direction for the development of therapeutic strategies for thin filament myopathy patients with shortened thin filament lengths. Ann Neurol 2016;79:959-969.
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Affiliation(s)
- Josine M de Winter
- Department of Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Barbara Joureau
- Department of Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Eun-Jeong Lee
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Balázs Kiss
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Michaela Yuen
- Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, Westmead, New South Wales, Australia.,Discipline of Paediatrics and Child Health, University of Sydney, Sydney, New South Wales, Australia
| | - Vandana A Gupta
- Division of Genetics and Genomics, Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Christopher T Pappas
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Carol C Gregorio
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Ger J M Stienen
- Department of Physiology, VU University Medical Center, Amsterdam, the Netherlands.,Department of Physics and Astronomy, VU University, Amsterdam, the Netherlands
| | - Simon Edvardson
- Pediatric Neurology Unit, Hadassah University Hospital, Jerusalem, Israel
| | - Carina Wallgren-Pettersson
- Department of Medical and Clinical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland.,Folkhaelsan Institute of Genetics, Biomedicum Helsinki, Helsinki, Finland
| | - Vilma-Lotta Lehtokari
- Department of Medical and Clinical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland.,Folkhaelsan Institute of Genetics, Biomedicum Helsinki, Helsinki, Finland
| | - Katarina Pelin
- Folkhaelsan Institute of Genetics, Biomedicum Helsinki, Helsinki, Finland.,Division of Genetics, Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - Edoardo Malfatti
- Center for Research in Myology, Pitié-Salpêtrière Hospital Group, Paris, France
| | - Norma B Romero
- Center for Research in Myology, Pitié-Salpêtrière Hospital Group, Paris, France
| | - Baziel G van Engelen
- Department of Neurology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Nicol C Voermans
- Department of Neurology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Sandra Donkervoort
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institutes of Health, Bethesda, MD
| | - C G Bönnemann
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institutes of Health, Bethesda, MD
| | - Nigel F Clarke
- Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, Westmead, New South Wales, Australia.,Discipline of Paediatrics and Child Health, University of Sydney, Sydney, New South Wales, Australia
| | - Alan H Beggs
- Division of Genetics and Genomics, Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Coen A C Ottenheijm
- Department of Physiology, VU University Medical Center, Amsterdam, the Netherlands.,Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
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Treatment with ActRIIB-mFc Produces Myofiber Growth and Improves Lifespan in the Acta1 H40Y Murine Model of Nemaline Myopathy. THE AMERICAN JOURNAL OF PATHOLOGY 2016; 186:1568-81. [PMID: 27102768 DOI: 10.1016/j.ajpath.2016.02.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 02/04/2016] [Accepted: 02/11/2016] [Indexed: 11/22/2022]
Abstract
Nemaline myopathies (NMs) are a group of congenital muscle diseases caused by mutations in at least 10 genes and associated with a range of clinical symptoms. NM is defined on muscle biopsy by the presence of cytoplasmic rod-like structures (nemaline rods) composed of cytoskeletal material. Myofiber smallness is also found in many cases of NM and may represent a cause of weakness that can be counteracted by treatment. We have used i.p. injection of activin type IIB receptor (ActRIIB)-mFc (an inhibitor of myostatin signaling) to promote hypertrophy and increase strength in our prior murine work; we therefore tested whether ActRIIB-mFc could improve weakness in NM mice through myofiber hypertrophy. We report a study of ActRIIB-mFc treatment in the Acta1 H40Y mouse model of NM. Treatment of Acta1 H40Y mice produced significant increases in body mass, muscle mass, quadriceps myofiber size, and survival, but other measurements of strength (forelimb grip strength, ex vivo measurements of contractile function) did not improve. Our studies also identified that the complications of urethral obstruction are associated with mortality in male hemizygote Acta1 H40Y mice. The incidence of urethral obstruction and histologic evidence of chronic obstruction (inflammation) were significantly lower in Acta1 H40Y mice that had been treated with ActRIIB-mFc. ActRIIB-mFc treatment produces a mild benefit to the disease phenotype in Acta1 H40Y mice.
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Park YE, Shin JH, Kang B, Lee CH, Kim DS. NEB-related core-rod myopathy with distinct clinical and pathological features. Muscle Nerve 2016; 53:479-84. [PMID: 26562614 DOI: 10.1002/mus.24966] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2015] [Indexed: 12/14/2022]
Abstract
INTRODUCTION Mutations in the gene encoding nebulin (NEB) are known to cause several types of congenital myopathy including recessive nemaline myopathy and distal nebulin myopathy. Core-rod myopathy has recently been reported to be another type of NEB-related myopathy, and is pathologically characterized by the coexistence of cores and nemaline rods within muscle fibers. METHODS We describe 2 patients with core-rod myopathy who were analyzed genetically by whole exome sequencing and evaluated clinically and pathologically. Findings were compared with those of patients with the disease of other genetic causes. RESULTS Three NEB mutations were identified, 2 of which were novel. Mild clinical features, unusual patterns of muscle involvement, and atypical pathological findings were observed. CONCLUSIONS We propose that the clinical and pathological spectrum of core-rod myopathy should be widened. A significant amount of residual nebulin expression is believed to contribute to the much milder phenotype exhibited by the patients we describe here.
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Affiliation(s)
- Young-Eun Park
- Department of Neurology, Pusan National University Yangsan Hospital, Beomo-ri, Mulgeum-eup, Yangsan, 626-770, Gyeongnam, South Korea.,Biomedical Research Institute, Pusan National University Hospital, Busan, South Korea
| | - Jin-Hong Shin
- Department of Neurology, Pusan National University Yangsan Hospital, Beomo-ri, Mulgeum-eup, Yangsan, 626-770, Gyeongnam, South Korea.,Research Institute for Convergence of Biomedical Research and Technology, Pusan National University Yangsan Hospital, Gyeongnam, South Korea
| | - Boram Kang
- Research Institute for Convergence of Biomedical Research and Technology, Pusan National University Yangsan Hospital, Gyeongnam, South Korea
| | - Chang-Hoon Lee
- Biomedical Research Institute, Pusan National University Hospital, Busan, South Korea.,Department of Pathology, Pusan National University, Busan, South Korea
| | - Dae-Seong Kim
- Department of Neurology, Pusan National University Yangsan Hospital, Beomo-ri, Mulgeum-eup, Yangsan, 626-770, Gyeongnam, South Korea.,Research Institute for Convergence of Biomedical Research and Technology, Pusan National University Yangsan Hospital, Gyeongnam, South Korea
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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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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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45
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Li F, Buck D, De Winter J, Kolb J, Meng H, Birch C, Slater R, Escobar YN, Smith JE, Yang L, Konhilas J, Lawlor MW, Ottenheijm C, Granzier HL. Nebulin deficiency in adult muscle causes sarcomere defects and muscle-type-dependent changes in trophicity: novel insights in nemaline myopathy. Hum Mol Genet 2015; 24:5219-33. [PMID: 26123491 DOI: 10.1093/hmg/ddv243] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 06/22/2015] [Indexed: 01/07/2023] Open
Abstract
Nebulin is a giant filamentous protein that is coextensive with the actin filaments of the skeletal muscle sarcomere. Nebulin mutations are the main cause of nemaline myopathy (NEM), with typical adult patients having low expression of nebulin, yet the roles of nebulin in adult muscle remain poorly understood. To establish nebulin's functional roles in adult muscle, we studied a novel conditional nebulin KO (Neb cKO) mouse model in which nebulin deletion was driven by the muscle creatine kinase (MCK) promotor. Neb cKO mice are born with high nebulin levels in their skeletal muscles, but within weeks after birth nebulin expression rapidly falls to barely detectable levels Surprisingly, a large fraction of the mice survive to adulthood with low nebulin levels (<5% of control), contain nemaline rods and undergo fiber-type switching toward oxidative types. Nebulin deficiency causes a large deficit in specific force, and mechanistic studies provide evidence that a reduced fraction of force-generating cross-bridges and shortened thin filaments contribute to the force deficit. Muscles rich in glycolytic fibers upregulate proteolysis pathways (MuRF-1, Fbxo30/MUSA1, Gadd45a) and undergo hypotrophy with smaller cross-sectional areas (CSAs), worsening their force deficit. Muscles rich in oxidative fibers do not have smaller weights and can even have hypertrophy, offsetting their specific-force deficit. These studies reveal nebulin as critically important for force development and trophicity in adult muscle. The Neb cKO phenocopies important aspects of NEM (muscle weakness, oxidative fiber-type predominance, variable trophicity effects, nemaline rods) and will be highly useful to test therapeutic approaches to ameliorate muscle weakness.
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Affiliation(s)
- Frank Li
- Department of Cellular and Molecular Medicine
| | | | - Josine De Winter
- Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
| | - Justin Kolb
- Department of Cellular and Molecular Medicine
| | - Hui Meng
- Department of Pathology and Laboratory Medicine, Medical College of Wisconsin, Milwaukee, WI, USA and
| | - Camille Birch
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | | | | | | | - Lin Yang
- Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA
| | - John Konhilas
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - Michael W Lawlor
- Department of Pathology and Laboratory Medicine, Medical College of Wisconsin, Milwaukee, WI, USA and
| | - Coen Ottenheijm
- Department of Cellular and Molecular Medicine, Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
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46
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de Winter JM, Joureau B, Sequeira V, Clarke NF, van der Velden J, Stienen GJ, Granzier H, Beggs AH, Ottenheijm CA. Effect of levosimendan on the contractility of muscle fibers from nemaline myopathy patients with mutations in the nebulin gene. Skelet Muscle 2015; 5:12. [PMID: 25949787 PMCID: PMC4422316 DOI: 10.1186/s13395-015-0037-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 04/01/2015] [Indexed: 11/25/2022] Open
Abstract
Background Nemaline myopathy (NM), the most common non-dystrophic congenital myopathy, is characterized by generalized skeletal muscle weakness, often from birth. To date, no therapy exists that enhances the contractile strength of muscles of NM patients. Mutations in NEB, encoding the giant protein nebulin, are the most common cause of NM. The pathophysiology of muscle weakness in NM patients with NEB mutations (NEB-NM) includes a lower calcium-sensitivity of force generation. We propose that the lower calcium-sensitivity of force generation in NEB-NM offers a therapeutic target. Levosimendan is a calcium sensitizer that is approved for use in humans and has been developed to target cardiac muscle fibers. It exerts its effect through binding to slow skeletal/cardiac troponin C. As slow skeletal/cardiac troponin C is also the dominant troponin C isoform in slow-twitch skeletal muscle fibers, we hypothesized that levosimendan improves slow-twitch muscle fiber strength at submaximal levels of activation in patients with NEB-NM. Methods To test whether levosimendan affects force production, permeabilized slow-twitch muscle fibers isolated from biopsies of NEB-NM patients and controls were exposed to levosimendan and the force response was measured. Results No effect of levosimendan on muscle fiber force in NEB-NM and control skeletal muscle fibers was found, both at a submaximal calcium level using incremental levosimendan concentrations, and at incremental calcium concentrations in the presence of levosimendan. In contrast, levosimendan did significantly increase the calcium-sensitivity of force in human single cardiomyocytes. Protein analysis confirmed that the slow skeletal/cardiac troponin C isoform was present in the skeletal muscle fibers tested. Conclusions These findings indicate that levosimendan does not improve the contractility in human skeletal muscle fibers, and do not provide rationale for using levosimendan as a therapeutic to restore muscle weakness in NEB-NM patients. We stress the importance of searching for compounds that improve the calcium-sensitivity of force generation of slow-twitch muscle fibers. Such compounds provide an appealing approach to restore muscle force in patients with NEB-NM, and also in patients with other neuromuscular disorders. Electronic supplementary material The online version of this article (doi:10.1186/s13395-015-0037-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Josine M de Winter
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands
| | - Barbara Joureau
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands
| | - Vasco Sequeira
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands
| | - Nigel F Clarke
- INMR, The Children's Hospital at Westmead and Discipline of Paediatrics & Child Health, University of Sydney, Cnr Hawkesbury Road & Hainsworth Street, Sydney, Australia
| | - Jolanda van der Velden
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands
| | - Ger Jm Stienen
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands ; Department of Physics and Astronomy, Faculty of Science, VU University, De Boelelaan 1105, Amsterdam, The Netherlands
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, 1333 N. Martin Avenue, Tucson, USA
| | - Alan H Beggs
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, 25 Shattuck Street, Boston, USA
| | - Coen Ac Ottenheijm
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands ; Department of Cellular and Molecular Medicine, University of Arizona, 1333 N. Martin Avenue, Tucson, USA
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47
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Ravenscroft G, Laing NG, Bönnemann CG. Pathophysiological concepts in the congenital myopathies: blurring the boundaries, sharpening the focus. ACTA ACUST UNITED AC 2014; 138:246-68. [PMID: 25552303 DOI: 10.1093/brain/awu368] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The congenital myopathies are a diverse group of genetic skeletal muscle diseases, which typically present at birth or in early infancy. There are multiple modes of inheritance and degrees of severity (ranging from foetal akinesia, through lethality in the newborn period to milder early and later onset cases). Classically, the congenital myopathies are defined by skeletal muscle dysfunction and a non-dystrophic muscle biopsy with the presence of one or more characteristic histological features. However, mutations in multiple different genes can cause the same pathology and mutations in the same gene can cause multiple different pathologies. This is becoming ever more apparent now that, with the increasing use of next generation sequencing, a genetic diagnosis is achieved for a greater number of patients. Thus, considerable genetic and pathological overlap is emerging, blurring the classically established boundaries. At the same time, some of the pathophysiological concepts underlying the congenital myopathies are moving into sharper focus. Here we explore whether our emerging understanding of disease pathogenesis and underlying pathophysiological mechanisms, rather than a strictly gene-centric approach, will provide grounds for a different and perhaps complementary grouping of the congenital myopathies, that at the same time could help instil the development of shared potential therapeutic approaches. Stemming from recent advances in the congenital myopathy field, five key pathophysiology themes have emerged: defects in (i) sarcolemmal and intracellular membrane remodelling and excitation-contraction coupling; (ii) mitochondrial distribution and function; (iii) myofibrillar force generation; (iv) atrophy; and (v) autophagy. Based on numerous emerging lines of evidence from recent studies in cell lines and patient tissues, mouse models and zebrafish highlighting these unifying pathophysiological themes, here we review the congenital myopathies in relation to these emerging pathophysiological concepts, highlighting both areas of overlap between established entities, as well as areas of distinction within single gene disorders.
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Affiliation(s)
- Gianina Ravenscroft
- 1 Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia, Australia
| | - Nigel G Laing
- 1 Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia, Australia
| | - Carsten G Bönnemann
- 2 National Institute of Neurological Disorders and Stroke/NIH, Porter Neuroscience Research Centre, Bethesda, MD, USA
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48
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Marttila M, Hanif M, Lemola E, Nowak KJ, Laitila J, Grönholm M, Wallgren-Pettersson C, Pelin K. Nebulin interactions with actin and tropomyosin are altered by disease-causing mutations. Skelet Muscle 2014; 4:15. [PMID: 25110572 PMCID: PMC4126377 DOI: 10.1186/2044-5040-4-15] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 06/09/2014] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Nemaline myopathy (NM) is a rare genetic muscle disorder, but one of the most common among the congenital myopathies. NM is caused by mutations in at least nine genes: Nebulin (NEB), α-actin (ACTA1), α-tropomyosin (TPM3), β-tropomyosin (TPM2), troponin T (TNNT1), cofilin-2 (CFL2), Kelch repeat and BTB (POZ) domain-containing 13 (KBTBD13), and Kelch-like family members 40 and 41 (KLHL40 and KLHL41). Nebulin is a giant (600 to 900 kDa) filamentous protein constituting part of the skeletal muscle thin filament. Around 90% of the primary structure of nebulin is composed of approximately 35-residue α-helical domains, which form super repeats that bind actin with high affinity. Each super repeat has been proposed to harbor one tropomyosin-binding site. METHODS We produced four wild-type (WT) nebulin super repeats (S9, S14, S18, and S22), 283 to 347 amino acids long, and five corresponding repeats with a patient mutation included: three missense mutations (p.Glu2431Lys, p.Ser6366Ile, and p.Thr7382Pro) and two in-frame deletions (p.Arg2478_Asp2512del and p.Val3924_Asn3929del). We performed F-actin and tropomyosin-binding experiments for the nebulin super repeats, using co-sedimentation and GST (glutathione-S-transferase) pull-down assays. We also used the GST pull-down assay to test the affinity of WT nebulin super repeats for WT α- and β-tropomyosin, and for β-tropomyosin with six patient mutations: p.Lys7del, p.Glu41Lys, p.Lys49del, p.Glu117Lys, p.Glu139del and p.Gln147Pro. RESULTS WT nebulin was shown to interact with actin and tropomyosin. Both the nebulin super repeats containing the p.Glu2431Lys mutation and nebulin super repeats lacking exon 55 (p.Arg2478_Asp2512del) showed weak affinity for F-actin compared with WT fragments. Super repeats containing the p.Ser6366Ile mutation showed strong affinity for actin. When tested for tropomyosin affinity, super repeats containing the p.Glu2431Lys mutation showed stronger binding than WT proteins to tropomyosin, and the super repeat containing the p.Thr7382Pro mutation showed weaker binding than WT proteins to tropomyosin. Super repeats containing the deletion p.Val3924_Asn3929del showed similar affinity for actin and tropomyosin as that seen with WT super repeats. Of the tropomyosin mutations, only p.Glu41Lys showed weaker affinity for nebulin (super repeat 18). CONCLUSIONS We demonstrate for the first time the existence of direct tropomyosin-nebulin interactions in vitro, and show that nebulin interactions with actin and tropomyosin are altered by disease-causing mutations in nebulin and tropomyosin.
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Affiliation(s)
- Minttu Marttila
- The Folkhälsan Institute of Genetics, Biomedicum Helsinki, Helsinki, Finland.,Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland
| | - Mubashir Hanif
- The Folkhälsan Institute of Genetics, Biomedicum Helsinki, Helsinki, Finland.,Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland
| | - Elina Lemola
- The Folkhälsan Institute of Genetics, Biomedicum Helsinki, Helsinki, Finland.,Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland
| | - Kristen J Nowak
- Molecular Neurogenetics Laboratory, Centre for Medical Research, University of Western Australia, Nedlands, Australia
| | - Jenni Laitila
- The Folkhälsan Institute of Genetics, Biomedicum Helsinki, Helsinki, Finland.,Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland
| | - Mikaela Grönholm
- Department of Biosciences, Division of Biochemistry and Biotechnology, University of Helsinki, Helsinki, Finland
| | - Carina Wallgren-Pettersson
- The Folkhälsan Institute of Genetics, Biomedicum Helsinki, Helsinki, Finland.,Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland
| | - Katarina Pelin
- Department of Biosciences, Division of Genetics, University of Helsinki, Helsinki, Finland
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49
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Hooijman PE, Paul MA, Stienen GJM, Beishuizen A, Van Hees HWH, Singhal S, Bashir M, Budak MT, Morgen J, Barsotti RJ, Levine S, Ottenheijm CAC. Unaffected contractility of diaphragm muscle fibers in humans on mechanical ventilation. Am J Physiol Lung Cell Mol Physiol 2014; 307:L460-70. [PMID: 25038190 DOI: 10.1152/ajplung.00076.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Several studies have indicated that diaphragm dysfunction develops in patients on mechanical ventilation (MV). Here, we tested the hypothesis that the contractility of sarcomeres, i.e., the smallest contractile unit in muscle, is affected in humans on MV. To this end, we compared diaphragm muscle fibers of nine brain-dead organ donors (cases) that had been on MV for 26 ± 5 h with diaphragm muscle fibers from nine patients (controls) undergoing surgery for lung cancer that had been on MV for less than 2 h. In each diaphragm specimen we determined 1) muscle fiber cross-sectional area in cryosections by immunohistochemical methods and 2) the contractile performance of permeabilized single muscle fibers by means of maximum specific force, kinetics of cross-bridge cycling by rate of tension redevelopment, myosin heavy chain content and concentration, and calcium sensitivity of force of slow-twitch and fast-twitch muscle fibers. In case subjects, we noted no statistically significant decrease in outcomes compared with controls in slow-twitch or fast-twitch muscle fibers. These observations indicate that 26 h of MV of humans is not invariably associated with changes in the contractile performance of sarcomeres in the diaphragm.
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Affiliation(s)
| | | | - Ger J M Stienen
- Departments of Physiology, Faculty of Science, Department of Physics and Astronomy, Vrije Universiteit, Amsterdam, The Netherlands
| | - Albertus Beishuizen
- Intensive Care, Vrije Universiteit Medical Center, Amsterdam, The Netherlands
| | - Hieronymus W H Van Hees
- Department of Pulmonary Diseases, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Sunil Singhal
- Department of Surgery, University of Pennsylvania and Veterans Affairs Medical Center, Philadelphia, Pennsylvania
| | - Muhammad Bashir
- Department of Surgery, University of Pennsylvania and Veterans Affairs Medical Center, Philadelphia, Pennsylvania
| | - Murat T Budak
- Department of Surgery, University of Pennsylvania and Veterans Affairs Medical Center, Philadelphia, Pennsylvania
| | - Jacqueline Morgen
- Department of Surgery, University of Pennsylvania and Veterans Affairs Medical Center, Philadelphia, Pennsylvania
| | - Robert J Barsotti
- Department of Physiology, Philadelphia College of Osteopathic Medicine, Philadelphia, Pennsylvania
| | - Sanford Levine
- Department of Surgery, University of Pennsylvania and Veterans Affairs Medical Center, Philadelphia, Pennsylvania; Gift of Life Donor Program, Philadelphia, Pennsylvania; and
| | - Coen A C Ottenheijm
- Departments of Physiology, Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
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50
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Yin X, Pu CQ, Wang Q, Liu JX, Mao YL. Clinical and pathological features of patients with nemaline myopathy. Mol Med Rep 2014; 10:175-82. [PMID: 24788569 DOI: 10.3892/mmr.2014.2184] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 03/18/2014] [Indexed: 11/06/2022] Open
Abstract
Nemaline myopathy (NM) is a rare congenital myopathy of great heterogeneity, characterized by the presence of rods in the cytoplasm of muscle fibers. This study aimed to summarize and analyze retrospectively the clinicopathological features of 28 patients with NM. Among the 28 patients, 15 were classified as of the typical congenital type, manifested as lower- or four-limb weakness as the first symptom and slowly progressive course. Six patients were classified as of childhood onset type, with lower-limb weakness and progressive course. Seven patients were classified as of the adult onset type, with rapidly progressive course and obvious muscle atrophy. Patient's 1, 16 and 23 had rapid clinical progression. On follow up, the three patients showed respiratory failure. Limb weakness in all patients was proximal‑dominant. Hypotonia was observed in most patients. High arched feet were also observed as dysmorfic features. In all patients, the creatine kinase (CK) level was normal or mildly elevated, and electromyography revealed myogenic changes. Nemaline bodies were observed under a light microscope in more than half of the patients' muscle fibers, and especially in type I fibers. All patients showed fiber type I predominance and atrophy. Modified Gömöri trichrome staining showed characteristic purple‑colored rods. Muscle electron microscopy revealed the presence of high electron‑dense nemaline bodies around the nucleus, and of a disorganized myofibrillar apparatus, with broken myofilaments and irregular myofibrils and Z lines. The 28 patients with NM shared a number of clinical features, such as proximal limb weakness, reduced deep tendon reflex and dysmorfic features. Differences were also observed between the three types of patients, with regards to course progression, disease severity and respiratory failure. In conclusion, patients with NM showed great clinical heterogeneity. The diagnosis of NM was mainly based on the muscle biopsy.
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Affiliation(s)
- Xi Yin
- Department of Neurology, Chinese People's Liberation Army General Hospital, Beijing 100853, P.R. China
| | - Chuan Qiang Pu
- Department of Neurology, Chinese People's Liberation Army General Hospital, Beijing 100853, P.R. China
| | - Qian Wang
- Department of Neurology, Chinese People's Liberation Army General Hospital, Beijing 100853, P.R. China
| | - Jie Xiao Liu
- Department of Neurology, Chinese People's Liberation Army General Hospital, Beijing 100853, P.R. China
| | - Yan Ling Mao
- Department of Neurology, Chinese People's Liberation Army General Hospital, Beijing 100853, P.R. China
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