1
|
Dugdale HF, Levy Y, Jungbluth H, Oldfors A, Ochala J. Aberrant myonuclear domains and impaired myofiber contractility despite marked hypertrophy in MYMK-related, Carey-Fineman-Ziter Syndrome. Acta Neuropathol Commun 2024; 12:80. [PMID: 38790073 PMCID: PMC11127446 DOI: 10.1186/s40478-024-01783-2] [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: 02/09/2024] [Accepted: 04/10/2024] [Indexed: 05/26/2024] Open
Abstract
Carey Fineman Ziter Syndrome (CFZS) is a rare autosomal recessive disease caused by mutations in the MYMK locus which encodes the protein, myomaker. Myomaker is essential for fusion and concurrent myonuclei donation of muscle progenitors during growth and development. Strikingly, in humans, MYMK mutations appear to prompt myofiber hypertrophy but paradoxically, induce generalised muscle weakness. As the underlying cellular mechanisms remain unexplored, the present study aimed to gain insights by combining myofiber deep-phenotyping and proteomic profiling. Hence, we isolated individual muscle fibers from CFZS patients and performed mechanical, 3D morphological and proteomic analyses. Myofibers from CFZS patients were ~ 4x larger than controls and possessed ~ 2x more myonuclei than those from healthy subjects, leading to disproportionally larger myonuclear domain volumes. These greater myonuclear domain sizes were accompanied by smaller intrinsic cellular force generating-capacities in myofibers from CFZS patients than in control muscle cells. Our complementary proteomic analyses indicated remodelling in 233 proteins particularly those associated with cellular respiration. Overall, our findings suggest that myomaker is somewhat functional in CFZS patients, but the associated nuclear accretion may ultimately lead to non-functional hypertrophy and altered energy-related mechanisms in CFZS patients. All of these are likely contributors of the muscle weakness experienced by CFZS patients.
Collapse
Affiliation(s)
- Hannah F Dugdale
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
- Centre for Human and Applied Physiological Sciences, School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Yotam Levy
- Centre for Human and Applied Physiological Sciences, School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Heinz Jungbluth
- Randall Centre for Cell and Molecular Biophysics, Muscle Signalling Section, Faculty of Life Sciences and Medicine (FoLSM), King's College London, London, UK
- Department of Paediatric Neurology, Neuromuscular Service, Evelina Children's Hospital, Guy's and St Thomas' Hospital NHS Foundation Trust, London, UK
| | - Anders Oldfors
- Department of Laboratory Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Julien Ochala
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
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.
Collapse
Affiliation(s)
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85724, USA;
| |
Collapse
|
4
|
Myofibre Hyper-Contractility in Horses Expressing the Myosin Heavy Chain Myopathy Mutation, MYH1E321G. Cells 2021; 10:cells10123428. [PMID: 34943936 PMCID: PMC8699922 DOI: 10.3390/cells10123428] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 11/30/2021] [Accepted: 12/02/2021] [Indexed: 11/17/2022] Open
Abstract
Myosinopathies are defined as a group of muscle disorders characterized by mutations in genes encoding myosin heavy chains. Their exact molecular and cellular mechanisms remain unclear. In the present study, we have focused our attention on a MYH1-related E321G amino acid substitution within the head region of the type IIx skeletal myosin heavy chain, associated with clinical signs of atrophy, inflammation and/or profound rhabdomyolysis, known as equine myosin heavy chain myopathy. We performed Mant-ATP chase experiments together with force measurements on isolated IIx myofibres from control horses (MYH1E321G−/−) and Quarter Horses homozygous (MYH1E321G+/+) or heterozygous (MYH1E321G+/−) for the E321G mutation. The single residue replacement did not affect the relaxed conformations of myosin molecules. Nevertheless, it significantly increased its active behaviour as proven by the higher maximal force production and Ca2+ sensitivity for MYH1E321G+/+ in comparison with MYH1E321G+/− and MYH1E321G−/− horses. Altogether, these findings indicate that, in the presence of the E321G mutation, a molecular and cellular hyper-contractile phenotype occurs which could contribute to the development of the myosin heavy chain myopathy.
Collapse
|
5
|
Gruszczynska-Biegala J, Stefan A, Kasprzak AA, Dobryszycki P, Khaitlina S, Strzelecka-Gołaszewska H. Myopathy-Sensitive G-Actin Segment 227-235 Is Involved in Salt-Induced Stabilization of Contacts within the Actin Filament. Int J Mol Sci 2021; 22:ijms22052327. [PMID: 33652657 PMCID: PMC7956362 DOI: 10.3390/ijms22052327] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 02/16/2021] [Accepted: 02/21/2021] [Indexed: 01/09/2023] Open
Abstract
Formation of stable actin filaments, critically important for actin functions, is determined by the ionic strength of the solution. However, not much is known about the elements of the actin fold involved in ionic-strength-dependent filament stabilization. In this work, F-actin was destabilized by Cu2+ binding to Cys374, and the effects of solvent conditions on the dynamic properties of F-actin were correlated with the involvement of Segment 227-235 in filament stabilization. The results of our work show that the presence of Mg2+ at the high-affinity cation binding site of Cu-modified actin polymerized with MgCl2 strongly enhances the rate of filament subunit exchange and promotes the filament instability. In the presence of 0.1 M KCl, the filament subunit exchange was 2-3-fold lower than that in the MgCl2-polymerized F-actin. This effect correlates with the reduced accessibility of the D-loop and Segment 227-235 on opposite filament strands, consistent with an ionic-strength-dependent conformational change that modulates involvement of Segment 227-235 in stabilization of the intermonomer interface. KCl may restrict the mobility of the α-helix encompassing part of Segment 227-235 and/or be bound to Asp236 at the boundary of Segment 227-235. These results provide experimental evidence for the involvement of Segment 227-235 in salt-induced stabilization of contacts within the actin filament and suggest that they can be weakened by mutations characteristic of actin-associated myopathies.
Collapse
Affiliation(s)
- Joanna Gruszczynska-Biegala
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland; (J.G.-B.); (A.S.); (A.A.K.); (H.S.-G.)
- Molecular Biology Unit, Mossakowski Medical Research Institute Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Andrzej Stefan
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland; (J.G.-B.); (A.S.); (A.A.K.); (H.S.-G.)
| | - Andrzej A. Kasprzak
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland; (J.G.-B.); (A.S.); (A.A.K.); (H.S.-G.)
| | - Piotr Dobryszycki
- Faculty of Chemistry, Wrocław University of Technology, 50-370 Wroclaw, Poland;
| | - Sofia Khaitlina
- Laboratory of Cytology of Unicellular Organisms, Institute of Cytology, Russian Academy of Sciences, 194064 St. Petersburg, Russia
- Correspondence:
| | - Hanna Strzelecka-Gołaszewska
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland; (J.G.-B.); (A.S.); (A.A.K.); (H.S.-G.)
| |
Collapse
|
6
|
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.
Collapse
|
7
|
Sun YN, Huang JQ, Chen ZZ, Du M, Ren FZ, Luo J, Fang B. Amyotrophy Induced by a High-Fat Diet Is Closely Related to Inflammation and Protein Degradation Determined by Quantitative Phosphoproteomic Analysis in Skeletal Muscle of C57BL/6 J Mice. J Nutr 2020; 150:294-302. [PMID: 31618431 DOI: 10.1093/jn/nxz236] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Revised: 07/29/2019] [Accepted: 09/05/2019] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Ectopic fat accumulation in skeletal muscle results in dysfunction and atrophy, but the underlying molecular mechanisms remain unclear. OBJECTIVE The aim of this study was to investigate the effects of a high-fat diet (HFD) in modulating the structure and energy metabolism of skeletal muscle and the underlying mechanisms in mice. METHODS Four-week-old male C57BL/6 J mice (n = 30) were allowed 1 wk for acclimatization. After 6 mice with low body weight were removed from the study, the remaining 24 mice were fed with a normal-fat diet (NFD; 10% energy from fat, n = 12) or an HFD (60% energy from fat, n = 12) for 24 wk. At the end of the experiment, serum glucose and lipid concentrations were measured, and skeletal muscle was collected for atrophy analysis, inflammation measurements, and phosphoproteomic analysis. RESULTS Compared with the NFD, the HFD increased (P < 0.05) body weight (35.8%), serum glucose (64.5%), and lipid (27.3%) concentrations, along with elevated (P < 0.05) expressions of the atrophy-related proteins muscle ring finger 1 (MURF1; 27.6%) and muscle atrophy F-box (MAFBX; 44.5%) in skeletal muscle. Phosphoproteomic analysis illustrated 64 proteins with differential degrees of phosphorylation between the HFD and NFD groups. These proteins were mainly involved in modulating cytoskeleton [adenylyl cyclase-associated protein 2 (CAP2) and actin-α skeletal muscle (ACTA1)], inflammation [NF-κB-activating protein (NKAP) and serine/threonine-protein kinase RIO3 (RIOK3)], glucose metabolism [Cdc42-interacting protein 4 (TRIP10); protein kinase C, and casein kinase II substrate protein 3 (PACSIN3)], and protein degradation [heat shock protein 90 kDa (HSP90AA1)]. The HFD-induced inhibitions of the insulin signaling pathway and activations of inflammation in skeletal muscle were verified by Western blot analysis. CONCLUSIONS Quantitative phosphoproteomic analysis in C57BL/6 J mice fed an NFD or HFD for 24 wk revealed that the phosphorylation of inflammatory proteins and proteins associated with glucose metabolism at specific serine residues may play critical roles in the regulation of skeletal muscle atrophy induced by an HFD. This work provides information regarding underlying molecular mechanisms for inflammation-induced dysfunction and atrophy in skeletal muscle.
Collapse
Affiliation(s)
- Ya-Nan Sun
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Jia-Qiang Huang
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Zhong-Zhou Chen
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Min Du
- Department of Animal Sciences, Washington State University, Pullman, WA, USA
| | - Fa-Zheng Ren
- Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Government, China Agricultural University, Beijing, China.,Beijing Laboratory of Food Quality and Safety, Beijing University of Agriculture, Beijing, China
| | - Jie Luo
- Beijing Laboratory of Food Quality and Safety, Beijing University of Agriculture, Beijing, China.,College of Food Science and Technology, Hunan Agricultural University, Changsha, China
| | - Bing Fang
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Biological Sciences, China Agricultural University, Beijing, China
| |
Collapse
|
8
|
Ross JA, Levy Y, Ripolone M, Kolb JS, Turmaine M, Holt M, Lindqvist J, Claeys KG, Weis J, Monforte M, Tasca G, Moggio M, Figeac N, Zammit PS, Jungbluth H, Fiorillo C, Vissing J, Witting N, Granzier H, Zanoteli E, Hardeman EC, Wallgren-Pettersson C, Ochala J. Impairments in contractility and cytoskeletal organisation cause nuclear defects in nemaline myopathy. Acta Neuropathol 2019; 138:477-495. [PMID: 31218456 PMCID: PMC6689292 DOI: 10.1007/s00401-019-02034-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 05/28/2019] [Accepted: 06/05/2019] [Indexed: 02/07/2023]
Abstract
Nemaline myopathy (NM) is a skeletal muscle disorder caused by mutations in genes that are generally involved in muscle contraction, in particular those related to the structure and/or regulation of the thin filament. Many pathogenic aspects of this disease remain largely unclear. Here, we report novel pathological defects in skeletal muscle fibres of mouse models and patients with NM: irregular spacing and morphology of nuclei; disrupted nuclear envelope; altered chromatin arrangement; and disorganisation of the cortical cytoskeleton. Impairments in contractility are the primary cause of these nuclear defects. We also establish the role of microtubule organisation in determining nuclear morphology, a phenomenon which is likely to contribute to nuclear alterations in this disease. Our results overlap with findings in diseases caused directly by mutations in nuclear envelope or cytoskeletal proteins. Given the important role of nuclear shape and envelope in regulating gene expression, and the cytoskeleton in maintaining muscle fibre integrity, our findings are likely to explain some of the hallmarks of NM, including contractile filament disarray, altered mechanical properties and broad transcriptional alterations.
Collapse
|
9
|
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.
Collapse
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:
| |
Collapse
|
10
|
Sewry CA, Laitila JM, Wallgren-Pettersson C. Nemaline myopathies: a current view. J Muscle Res Cell Motil 2019; 40:111-126. [PMID: 31228046 PMCID: PMC6726674 DOI: 10.1007/s10974-019-09519-9] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 05/29/2019] [Indexed: 12/13/2022]
Abstract
Nemaline myopathies are a heterogenous group of congenital myopathies caused by de novo, dominantly or recessively inherited mutations in at least twelve genes. The genes encoding skeletal α-actin (ACTA1) and nebulin (NEB) are the commonest genetic cause. Most patients have congenital onset characterized by muscle weakness and hypotonia, but the spectrum of clinical phenotypes is broad, ranging from severe neonatal presentations to onset of a milder disorder in childhood. Most patients with adult onset have an autoimmune-related myopathy with a progressive course. The wide application of massively parallel sequencing methods is increasing the number of known causative genes and broadening the range of clinical phenotypes. Nemaline myopathies are identified by the presence of structures that are rod-like or ovoid in shape with electron microscopy, and with light microscopy stain red with the modified Gömöri trichrome technique. These rods or nemaline bodies are derived from Z lines (also known as Z discs or Z disks) and have a similar lattice structure and protein content. Their shape in patients with mutations in KLHL40 and LMOD3 is distinctive and can be useful for diagnosis. The number and distribution of nemaline bodies varies between fibres and different muscles but does not correlate with severity or prognosis. Additional pathological features such as caps, cores and fibre type disproportion are associated with the same genes as those known to cause the presence of rods. Animal models are advancing the understanding of the effects of various mutations in different genes and paving the way for the development of therapies, which at present only manage symptoms and are aimed at maintaining muscle strength, joint mobility, ambulation, respiration and independence in the activities of daily living.
Collapse
Affiliation(s)
- Caroline A Sewry
- Dubowitz Neuromuscular Centre, UCL Institute of Child Health and Great Ormond Street Hospital, 30 Guilford Street, London, WC1N 1EH, UK. .,Wolfson Centre of Inherited Neuromuscular Disorders, RJAH Orthopaedic Hospital, Oswestry, SY10 7AG, UK.
| | - Jenni M Laitila
- Folkhälsan Institute of Genetics, Folkhälsan Research Center, Helsinki, Finland.,Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| | - Carina Wallgren-Pettersson
- Folkhälsan Institute of Genetics, Folkhälsan Research Center, Helsinki, Finland.,Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| |
Collapse
|
11
|
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.
Collapse
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
| |
Collapse
|
12
|
Fan J, Chan C, McNamara EL, Nowak KJ, Iwamoto H, Ochala J. Molecular Consequences of the Myopathy-Related D286G Mutation on Actin Function. Front Physiol 2018; 9:1756. [PMID: 30564146 PMCID: PMC6288369 DOI: 10.3389/fphys.2018.01756] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 11/20/2018] [Indexed: 01/06/2023] Open
Abstract
Myopathies are notably associated with mutations in genes encoding proteins known to be essential for the force production of skeletal muscle fibers, such as skeletal alpha-actin. The exact molecular mechanisms by which these specific defects induce myopathic phenotypes remain unclear. Hence, in the present study, to better understand actin dysfunction, we conducted a molecular dynamic simulation together with ex vivo experiments of the specific muscle disease-causing actin mutation, D286G located in the actin-actin interface. Our computational study showed that D286G impairs the flexural rigidity of actin filaments. However, upon activation, D286G did not have any direct consequences on actin filament extension. Hence, D286G may alter the structure of actin filaments but, when expressed together with normal actin molecules, it may only have minor effects on the ex vivo mechanics of actin filaments upon skeletal muscle fiber contraction.
Collapse
Affiliation(s)
- Jun Fan
- Department of Physics and Materials Science, The University of Hong Kong, Hong Kong, Hong Kong.,City University of Hong Kong Shenzhen Research Institute, Shenzhen, China
| | - Chun Chan
- Department of Physics and Materials Science, The University of Hong Kong, Hong Kong, Hong Kong
| | - Elyshia L McNamara
- Harry Perkins Institute of Medical Research, QEII Medical Centre, The University of Western Australia, Nedlands, WA, Australia
| | - Kristen J Nowak
- Harry Perkins Institute of Medical Research, QEII Medical Centre, The University of Western Australia, Nedlands, WA, Australia.,Department of Health, Office of Population Health Genomics, Public and Aboriginal Health Division, Government of Western Australia, East Perth, WA, Australia.,School of Biomedical Sciences, Faculty of Health and Medical Sciences, The University of Western Australia, Crawley, WA, Australia
| | - Hiroyuki Iwamoto
- SPring-8, Japan Synchrotron Radiation Research Institute, Sayo, Japan
| | - Julien Ochala
- School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, United Kingdom
| |
Collapse
|
13
|
Levy Y, Ross JA, Niglas M, Snetkov VA, Lynham S, Liao CY, Puckelwartz MJ, Hsu YM, McNally EM, Alsheimer M, Harridge SD, Young SG, Fong LG, Español Y, Lopez-Otin C, Kennedy BK, Lowe DA, Ochala J. Prelamin A causes aberrant myonuclear arrangement and results in muscle fiber weakness. JCI Insight 2018; 3:120920. [PMID: 30282816 PMCID: PMC6237469 DOI: 10.1172/jci.insight.120920] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 08/23/2018] [Indexed: 01/06/2023] Open
Abstract
Physiological and premature aging are frequently associated with an accumulation of prelamin A, a precursor of lamin A, in the nuclear envelope of various cell types. Here, we aimed to underpin the hitherto unknown mechanisms by which prelamin A alters myonuclear organization and muscle fiber function. By experimentally studying membrane-permeabilized myofibers from various transgenic mouse lines, our results indicate that, in the presence of prelamin A, the abundance of nuclei and myosin content is markedly reduced within muscle fibers. This leads to a concept by which the remaining myonuclei are very distant from each other and are pushed to function beyond their maximum cytoplasmic capacity, ultimately inducing muscle fiber weakness.
Collapse
Affiliation(s)
- Yotam Levy
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| | - Jacob A Ross
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| | - Marili Niglas
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| | - Vladimir A Snetkov
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| | - Steven Lynham
- Proteomics Facility, Centre of Excellence for Mass Spectrometry, King's College London, London, United Kingdom
| | - Chen-Yu Liao
- Buck Institute for Research on Aging, Novato, California, USA
| | - Megan J Puckelwartz
- Center for Genetic Medicine, Northwestern University, Chicago, Illinois, USA
| | - Yueh-Mei Hsu
- Buck Institute for Research on Aging, Novato, California, USA
| | - Elizabeth M McNally
- Center for Genetic Medicine, Northwestern University, Chicago, Illinois, USA
| | - Manfred Alsheimer
- Department of Cell and Developmental Biology, University of Würzburg, Würzburg, Germany
| | - Stephen Dr Harridge
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| | - Stephen G Young
- Department of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Loren G Fong
- Department of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Yaiza Español
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Instituto Universitario de Oncología (IUOPA), Universidad de Oviedo, Oviedo, Spain
| | - Carlos Lopez-Otin
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Instituto Universitario de Oncología (IUOPA), Universidad de Oviedo, Oviedo, Spain.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Spain
| | - Brian K Kennedy
- Buck Institute for Research on Aging, Novato, California, USA.,Departments of Biochemistry and Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Centre for Healthy Ageing, National University Health System, Singapore.,Singapore Institute for Clinical Sciences, Singapore
| | - Dawn A Lowe
- Divisions of Rehabilitation Science and Physical Therapy, Department of Rehabilitation Medicine, School of Medicine, University of Minnesota, Minneapolis, Minnesota, USA
| | - Julien Ochala
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, and
| |
Collapse
|
14
|
Ross JA, Levy Y, Svensson K, Philp A, Schenk S, Ochala J. SIRT1 regulates nuclear number and domain size in skeletal muscle fibers. J Cell Physiol 2018; 233:7157-7163. [PMID: 29574748 PMCID: PMC5993587 DOI: 10.1002/jcp.26542] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 02/12/2018] [Indexed: 12/16/2022]
Abstract
Skeletal muscle fibers are giant multinucleated cells wherein individual nuclei govern the protein synthesis in a finite volume of cytoplasm; this is termed the myonuclear domain (MND). The factors that control MND size remain to be defined. In the present study, we studied the contribution of the NAD+‐dependent deacetylase, sirtuin 1 (SIRT1), to the regulation of nuclear number and MND size. For this, we isolated myofibers from mice with tissue‐specific inactivation (mKO) or inducible overexpression (imOX) of SIRT1 and analyzed the 3D organisation of myonuclei. In imOX mice, the number of nuclei was increased whilst the average MND size was decreased as compared to littermate controls. Our findings were the opposite in mKO mice. Muscle stem cell (satellite cell) numbers were reduced in mKO muscles, a possible explanation for the lower density of myonuclei in these mice; however, no change was observed in imOX mice, suggesting that other factors might also be involved, such as the functional regulation of stem cells/muscle precursors. Interestingly, however, the changes in the MND volume did not impact the force‐generating capacity of muscle fibers. Taken together, our results demonstrate that SIRT1 is a key regulator of MND sizes, although the underlying molecular mechanisms and the cause‐effect relationship between MND and muscle function remain to be fully defined.
Collapse
Affiliation(s)
- Jacob A Ross
- School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Yotam Levy
- School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Kristoffer Svensson
- Department of Orthopaedic Surgery, University of California San Diego, La Jolla, California.,Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California
| | - Andrew Philp
- School of Sport and Exercise Sciences, University of Birmingham, Birmingham, UK
| | - Simon Schenk
- Department of Orthopaedic Surgery, University of California San Diego, La Jolla, California.,Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California
| | - Julien Ochala
- School of Basic and Medical Biosciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| |
Collapse
|
15
|
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.
Collapse
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
| |
Collapse
|
16
|
Jungbluth H, Ochala J, Treves S, Gautel M. Current and future therapeutic approaches to the congenital myopathies. Semin Cell Dev Biol 2016; 64:191-200. [PMID: 27515125 DOI: 10.1016/j.semcdb.2016.08.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 08/04/2016] [Accepted: 08/08/2016] [Indexed: 12/14/2022]
Abstract
The congenital myopathies - including Central Core Disease (CCD), Multi-minicore Disease (MmD), Centronuclear Myopathy (CNM), Nemaline Myopathy (NM) and Congenital Fibre Type Disproportion (CFTD) - are a genetically heterogeneous group of early-onset neuromuscular conditions characterized by distinct histopathological features, and associated with a substantial individual and societal disease burden. Appropriate supportive management has substantially improved patient morbidity and mortality but there is currently no cure. Recent years have seen an exponential increase in the genetic and molecular understanding of these conditions, leading to the identification of underlying defects in proteins involved in calcium homeostasis and excitation-contraction coupling, thick/thin filament assembly and function, redox regulation, membrane trafficking and/or autophagic pathways. Based on these findings, specific therapies are currently being developed, or are already approaching the clinical trial stage. Despite undeniable progress, therapy development faces considerable challenges, considering the rarity and diversity of specific conditions, and the size and complexity of some of the genes and proteins involved. The present review will summarize the key genetic, histopathological and clinical features of specific congenital myopathies, and outline therapies already available or currently being developed in the context of known pathogenic mechanisms. The relevance of newly discovered molecular mechanisms and novel gene editing strategies for future therapy development will be discussed.
Collapse
Affiliation(s)
- Heinz Jungbluth
- Department of Paediatric Neurology, Neuromuscular Service, Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section Biophysics and Cardiovascular Division, King's College BHF Centre of Research Excellence, United Kingdom; Department of Basic and Clinical Neuroscience, IoPPN, King's College, London, United Kingdom.
| | - Julien Ochala
- Centre of Human and Aerospace Physiological Sciences, King's College London, United Kingdom
| | - Susan Treves
- Departments of Biomedicine and Anaesthesia, Basel University Hospital, 4031 Basel, Switzerland
| | - Mathias Gautel
- Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section Biophysics and Cardiovascular Division, King's College BHF Centre of Research Excellence, United Kingdom
| |
Collapse
|
17
|
Lindqvist J, Levy Y, Pati-Alam A, Hardeman EC, Gregorevic P, Ochala J. Modulating myosin restores muscle function in a mouse model of nemaline myopathy. Ann Neurol 2016; 79:717-725. [PMID: 26891371 PMCID: PMC4950341 DOI: 10.1002/ana.24619] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 02/16/2016] [Accepted: 02/16/2016] [Indexed: 12/18/2022]
Abstract
OBJECTIVE Nemaline myopathy, one of the most common congenital myopathies, is associated with mutations in various genes including ACTA1. This disease is also characterized by various forms/degrees of muscle weakness, with most cases being severe and resulting in death in infancy. Recent findings have provided valuable insight into the underlying pathophysiological mechanisms. Mutations in ACTA1 directly disrupt binding interactions between actin and myosin, and consequently the intrinsic force-generating capacity of muscle fibers. ACTA1 mutations are also associated with variations in myofiber size, the mechanisms of which have been unclear. In the present study, we sought to test the hypotheses that the compromised functional and morphological attributes of skeletal muscles bearing ACTA1 mutations (1) would be directly due to the inefficient actomyosin complex and (2) could be restored by manipulating myosin expression. METHODS We used a knockin mouse model expressing the ACTA1 His40Tyr actin mutation found in human patients. We then performed in vivo intramuscular injections of recombinant adeno-associated viral vectors harboring a myosin transgene known to facilitate muscle contraction. RESULTS We observed that in the presence of the transgene, the intrinsic force-generating capacity was restored and myofiber size was normal. INTERPRETATION This demonstrates a direct link between disrupted attachment of myosin molecules to actin monomers and muscle fiber atrophy. These data also suggest that further therapeutic interventions should primarily target myosin dysfunction to alleviate the pathology of ACTA1-related nemaline myopathy. Ann Neurol 2016;79:717-725.
Collapse
Affiliation(s)
- Johan Lindqvist
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Yotam Levy
- Centre of Human and Aerospace Physiological Sciences, Faculty of Life Sciences & Medicine, King's College London, London, United Kingdom
| | - Alisha Pati-Alam
- Centre of Human and Aerospace Physiological Sciences, Faculty of Life Sciences & Medicine, King's College London, London, United Kingdom
| | - Edna C Hardeman
- Neuromuscular and Regenerative Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Paul Gregorevic
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia
- Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia
- Department of Neurology, University of Washington School of Medicine, Seattle, WA
| | - Julien Ochala
- Centre of Human and Aerospace Physiological Sciences, Faculty of Life Sciences & Medicine, King's College London, London, United Kingdom
| |
Collapse
|
18
|
Ochala J, Ravenscroft G, McNamara E, Nowak KJ, Iwamoto H. X-ray recordings reveal how a human disease-linked skeletal muscle α-actin mutation leads to contractile dysfunction. J Struct Biol 2015; 192:331-335. [PMID: 26407659 DOI: 10.1016/j.jsb.2015.09.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2015] [Revised: 08/13/2015] [Accepted: 09/22/2015] [Indexed: 10/23/2022]
Abstract
In humans, mutant skeletal muscle α-actin proteins are associated with contractile dysfunction, skeletal muscle weakness and a wide range of primarily skeletal muscle diseases. Despite this knowledge, the exact molecular mechanisms triggering the contractile dysfunction remain unknown. Here, we aimed to unravel these. Hence, we used a transgenic mouse model expressing a well-described D286G mutant skeletal muscle α-actin protein and recapitulating the human condition of contractile deregulation and severe skeletal muscle weakness. We then recorded and analyzed the small-angle X-ray diffraction patterns of isolated membrane-permeabilized myofibers. Results showed that upon addition of Ca(2+), the intensity changes of the second (1/19 nm(-1)) and sixth (1/5.9 nm(-1)) actin layer lines and of the first myosin meridional reflection (1/14.3 nm(-1)) were disrupted when the thin-thick filament overlap was optimal (sarcomere length of 2.5-2.6 μm). However these reflections were normal when the thin and thick filaments were not interacting (sarcomere length>3.6 μm). These findings demonstrate, for the first time, that the replacement of just one amino acid in the skeletal muscle α-actin protein partly prevents actin conformational changes during activation, disrupting the strong binding of myosin molecules. This leads to a limited myosin-related tropomyosin movement over the thin filaments, further affecting the amount of cross-bridges, explaining the contractile dysfunction.
Collapse
Affiliation(s)
- Julien Ochala
- Centre of Human and Aerospace Physiological Sciences, School of Biomedical Sciences, King's College London, London, United Kingdom.
| | - Gianina Ravenscroft
- Harry Perkins Institute of Medical Research, The University of Western Australia, Nedlands, Australia
| | - Elyshia McNamara
- Harry Perkins Institute of Medical Research, The University of Western Australia, Nedlands, Australia
| | - Kristen J Nowak
- Harry Perkins Institute of Medical Research, The University of Western Australia, Nedlands, Australia
| | - Hiroyuki Iwamoto
- Japan Synchrotron Radiation Research Institute, SPring8, Hyogo, Japan
| |
Collapse
|
19
|
Sztal TE, Zhao M, Williams C, Oorschot V, Parslow AC, Giousoh A, Yuen M, Hall TE, Costin A, Ramm G, Bird PI, Busch-Nentwich EM, Stemple DL, Currie PD, Cooper ST, Laing NG, Nowak KJ, Bryson-Richardson RJ. Zebrafish models for nemaline myopathy reveal a spectrum of nemaline bodies contributing to reduced muscle function. Acta Neuropathol 2015; 130:389-406. [PMID: 25931053 PMCID: PMC4541704 DOI: 10.1007/s00401-015-1430-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 04/20/2015] [Accepted: 04/21/2015] [Indexed: 12/22/2022]
Abstract
Nemaline myopathy is characterized by muscle weakness and the presence of rod-like (nemaline) bodies. The genetic etiology of nemaline myopathy is becoming increasingly understood with mutations in ten genes now known to cause the disease. Despite this, the mechanism by which skeletal muscle weakness occurs remains elusive, with previous studies showing no correlation between the frequency of nemaline bodies and disease severity. To investigate the formation of nemaline bodies and their role in pathogenesis, we generated overexpression and loss-of-function zebrafish models for skeletal muscle α-actin (ACTA1) and nebulin (NEB). We identify three distinct types of nemaline bodies and visualize their formation in vivo, demonstrating these nemaline bodies not only exhibit different subcellular origins, but also have distinct pathological consequences within the skeletal muscle. One subtype is highly dynamic and upon breakdown leads to the accumulation of cytoplasmic actin contributing to muscle weakness. Examination of a Neb-deficient model suggests this mechanism may be common in nemaline myopathy. Another subtype results from a reduction of actin and forms a more stable cytoplasmic body. In contrast, the final type originates at the Z-disk and is associated with myofibrillar disorganization. Analysis of zebrafish and muscle biopsies from ACTA1 nemaline myopathy patients demonstrates that nemaline bodies also possess a different protein signature. In addition, we show that the ACTA1D286G mutation causes impaired actin incorporation and localization in the sarcomere. Together these data provide a novel examination of nemaline body origins and dynamics in vivo and identifies pathological changes that correlate with muscle weakness.
Collapse
Affiliation(s)
- Tamar E. Sztal
- />School of Biological Sciences, Monash University, Melbourne, VIC Australia
| | - Mo Zhao
- />School of Biological Sciences, Monash University, Melbourne, VIC Australia
| | - Caitlin Williams
- />School of Biological Sciences, Monash University, Melbourne, VIC Australia
| | - Viola Oorschot
- />Monash Micro-Imaging, Monash University, Melbourne, VIC Australia
| | - Adam C. Parslow
- />School of Biological Sciences, Monash University, Melbourne, VIC Australia
| | - Aminah Giousoh
- />Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC Australia
| | - Michaela Yuen
- />Institute for Neuroscience and Muscle Research, The Children’s Hospital at Westmead, Sydney, NSW Australia
| | - Thomas E. Hall
- />Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD Australia
| | - Adam Costin
- />Monash Micro-Imaging, Monash University, Melbourne, VIC Australia
| | - Georg Ramm
- />Monash Micro-Imaging, Monash University, Melbourne, VIC Australia
- />Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC Australia
| | - Phillip I. Bird
- />Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC Australia
| | | | - Derek L. Stemple
- />Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire UK
| | - Peter D. Currie
- />Australian Regenerative Medicine Institute, Monash University, Melbourne, VIC Australia
| | - Sandra T. Cooper
- />Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, Sydney, Australia
| | - Nigel G. Laing
- />Harry Perkins Institute of Medical Research and the Centre for Medical Research, University of Western Australia, Perth, WA Australia
| | - Kristen J. Nowak
- />Harry Perkins Institute of Medical Research and the Centre for Medical Research, University of Western Australia, Perth, WA Australia
| | | |
Collapse
|
20
|
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.
Collapse
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
| |
Collapse
|
21
|
Sexually dimorphic myofilament function in a mouse model of nemaline myopathy. Arch Biochem Biophys 2014; 564:37-42. [PMID: 25261348 DOI: 10.1016/j.abb.2014.09.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/07/2014] [Accepted: 09/16/2014] [Indexed: 10/24/2022]
Abstract
Nemaline myopathy, the most common congenital myopathy, is characterized by mutations in genes encoding myofilament proteins such as skeletal α-actin. These mutations are thought to ultimately lead to skeletal muscle weakness. Interestingly, some of the mutations appear to be more potent in males than in females. The underlying mechanisms remain obscure but may be related to sex-specific differences in the myofilament function of both limb and respiratory muscles. To verify this, in the present study, we used skeletal muscles (tibialis anterior and diaphragm) from a transgenic mouse model harbouring the His40Tyr amino acid substitution in skeletal α-actin. In this animal model, 60% of males die by 13weeks of age (the underlying causes of death are obscure but probably due to respiratory insufficiency) whereas females have a normal lifespan. By recording and analysing the mechanics of membrane-permeabilized myofibres, we only observed sex-related differences in the tibialis anterior muscles. Indeed, the concomitant deficits in maximal steady-state isometric force and stiffness of myofibres were less exacerbated in transgenic females than in males, potentially explaining the lower potency in limb muscles. However, the absence of sex-difference in the diaphragm muscles was rather unexpected and suggests that myofilament dysfunction does not solely underlie the sexually dimorphic phenotypes.
Collapse
|
22
|
Abstract
PURPOSE OF REVIEW This article reviews recent advances in the understanding of nemaline myopathy, with a focus on the genetic basis of the disorder, histology, and pathogenesis. RECENT FINDINGS Pathogenic mutations have been identified in eight genes and there is evidence of further genetic heterogeneity in nemaline myopathy. Clinical presentation, histological features on skeletal muscle biopsy, and pattern of changes on muscle MRI may guide prioritization of molecular genetic testing. It is anticipated that use of new technologies such as whole exome sequencing and comparative genomic hybridization will increase the number of genes associated with nemaline myopathy and the proportion of patients in whom the genetic basis of the disorder is identified. Single fiber studies and animal models continue to add to understanding of the pathogenesis of this disorder. Current management focuses on supportive treatment; however, encouraging advances are emerging for the future. SUMMARY Recent advances in understanding of nemaline myopathy have important implications for clinical practice and for genetic diagnosis of patients with nemaline myopathy.
Collapse
|
23
|
Multimodal MRI and (31)P-MRS investigations of the ACTA1(Asp286Gly) mouse model of nemaline myopathy provide evidence of impaired in vivo muscle function, altered muscle structure and disturbed energy metabolism. PLoS One 2013; 8:e72294. [PMID: 23977274 PMCID: PMC3748127 DOI: 10.1371/journal.pone.0072294] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 07/15/2013] [Indexed: 02/03/2023] Open
Abstract
Nemaline myopathy (NM), the most common non-dystrophic congenital disease of skeletal muscle, can be caused by mutations in the skeletal muscle α-actin gene (ACTA1) (~25% of all NM cases and up to 50% of severe forms of NM). Muscle function of the recently generated transgenic mouse model carrying the human Asp286Gly mutation in the ACTA1 gene (Tg(ACTA1)(Asp286Gly)) has been mainly investigated in vitro. Therefore, we aimed at providing a comprehensive picture of the in vivo hindlimb muscle function of Tg(ACTA1)(Asp286Gly) mice by combining strictly noninvasive investigations. Skeletal muscle anatomy (hindlimb muscles, intramuscular fat volumes) and microstructure were studied using multimodal magnetic resonance imaging (Dixon, T2, Diffusion Tensor Imaging [DTI]). Energy metabolism was studied using 31-phosphorus Magnetic Resonance Spectroscopy ((31)P-MRS). Skeletal muscle contractile performance was investigated while applying a force-frequency protocol (1-150 Hz) and a fatigue protocol (6 min-1.7 Hz). Tg(ACTA1)(Asp286Gly) mice showed a mild muscle weakness as illustrated by the reduction of both absolute (30%) and specific (15%) maximal force production. Dixon MRI did not show discernable fatty infiltration in Tg(ACTA1)(Asp286Gly) mice indicating that this mouse model does not reproduce human MRI findings. Increased T2 values were observed in Tg(ACTA1)(Asp286Gly) mice and might reflect the occurrence of muscle degeneration/regeneration process. Interestingly, T2 values were linearly related to muscle weakness. DTI experiments indicated lower λ2 and λ3 values in Tg(ACTA1)(Asp286Gly) mice, which might be associated to muscle atrophy and/or the presence of histological anomalies. Finally (31)P-MRS investigations illustrated an increased anaerobic energy cost of contraction in Tg(ACTA1)(Asp286Gly) mice, which might be ascribed to contractile and non-contractile processes. Overall, we provide a unique set of information about the anatomic, metabolic and functional consequences of the Asp286Gly mutation that might be considered as relevant biomarkers for monitoring the severity and/or the progression of NM and for assessing the efficacy of potential therapeutic interventions.
Collapse
|
24
|
Distinct underlying mechanisms of limb and respiratory muscle fiber weaknesses in nemaline myopathy. J Neuropathol Exp Neurol 2013; 72:472-81. [PMID: 23656990 DOI: 10.1097/nen.0b013e318293b1cc] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Nemaline myopathy is the most common congenital myopathy and is caused by mutations in various genes such as ACTA1 (encoding skeletal α-actin). It is associated with limb and respiratory muscle weakness. Despite increasing clinical and scientific interest, the molecular and cellular events leading to such weakness remain unknown, which prevents the development of specific therapeutic interventions. To unravel the potential mechanisms involved, we dissected lower limb and diaphragm muscles from a knock-in mouse model of severe nemaline myopathy expressing the ACTA1 His40Tyr actin mutation found in human patients. We then studied a broad range of structural and functional characteristics assessing single-myofiber contraction, protein expression, and electron microscopy. One of the major findings in the diaphragm was the presence of numerous noncontractile areas (including disrupted sarcomeric structures and nemaline bodies). This greatly reduced the number of functional sarcomeres, decreased the force generation capacity at the muscle fiber level, and likely would contribute to respiratory weakness. In limb muscle, by contrast, there were fewer noncontractile areas and they did not seem to have a major role in the pathogenesis of weakness. These divergent muscle-specific results provide new important insights into the pathophysiology of severe nemaline myopathy and crucial information for future development of therapeutic strategies.
Collapse
|
25
|
Colpan M, Moroz NA, Kostyukova AS. Tropomodulins and tropomyosins: working as a team. J Muscle Res Cell Motil 2013; 34:247-60. [PMID: 23828180 DOI: 10.1007/s10974-013-9349-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 05/24/2013] [Indexed: 11/25/2022]
Abstract
Actin filaments are major components of the cytoskeleton in eukaryotic cells and are involved in vital cellular functions such as cell motility and muscle contraction. Tmod and TM are crucial constituents of the actin filament network, making their presence indispensable in living cells. Tropomyosin (TM) is an alpha-helical, coiled coil protein that covers the grooves of actin filaments and stabilizes them. Actin filament length is optimized by tropomodulin (Tmod), which caps the slow growing (pointed end) of thin filaments to inhibit polymerization or depolymerization. Tmod consists of two structurally distinct regions: the N-terminal and the C-terminal domains. The N-terminal domain contains two TM-binding sites and one TM-dependent actin-binding site, whereas the C-terminal domain contains a TM-independent actin-binding site. Tmod binds to two TM molecules and at least one actin molecule during capping. The interaction of Tmod with TM is a key regulatory factor for actin filament organization. The binding efficacy of Tmod to TM is isoform-dependent. The affinities of Tmod/TM binding influence the proper localization and capping efficiency of Tmod at the pointed end of actin filaments in cells. Here we describe how a small difference in the sequence of the TM-binding sites of Tmod may result in dramatic change in localization of Tmod in muscle cells or morphology of non-muscle cells. We also suggest most promising directions to study and elucidate the role of Tmod-TM interaction in formation and maintenance of sarcomeric and cytoskeletal structure.
Collapse
Affiliation(s)
- Mert Colpan
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, 118 Dana Hall, Spokane St., Pullman, WA, 99164, USA
| | | | | |
Collapse
|
26
|
Karpicheva OE, Robinson P, Piers A, Borovikov YS, Redwood CS. The nemaline myopathy-causing E117K mutation in β-tropomyosin reduces thin filament activation. Arch Biochem Biophys 2013; 536:25-30. [PMID: 23689010 DOI: 10.1016/j.abb.2013.05.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 04/30/2013] [Accepted: 05/02/2013] [Indexed: 01/05/2023]
Abstract
The effect of the nemaline myopathy-causing E117K mutation in β-tropomyosin (TM) on the structure and function of this regulatory protein was studied. The E117K mutant was found to have indistinguishable actin affinity compared with wild-type (WT) and similar secondary structure as measured by circular dichroism. However the E117K mutation significantly lowered maximum activation of actomyosin ATPase. To explain the molecular mechanism of impaired ATPase activation, WT and E117K TMs were covalently labeled at Cys-36 with 5-iodoacetimido-fluorescein and incorporated into ghost muscle fibers. The changes in the position and flexibility of tropomyosin strands on the thin filaments were observed at simulation of weak and strong binding states of actomyosin at high or low Ca(2+) by polarized fluorescence techniques. The E117K mutation was found to shift the tropomyosin strands towards the closed position and restrict the tropomyosin displacement during the transformation of actomyosin from weak to strong binding state thus leading to a reduction in thin filament activation.
Collapse
Affiliation(s)
- Olga E Karpicheva
- Laboratory of Mechanisms of Cell Motility, Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia
| | | | | | | | | |
Collapse
|
27
|
Gineste C, Le Fur Y, Vilmen C, Le Troter A, Pecchi E, Cozzone PJ, Hardeman EC, Bendahan D, Gondin J. Combined MRI and ³¹P-MRS investigations of the ACTA1(H40Y) mouse model of nemaline myopathy show impaired muscle function and altered energy metabolism. PLoS One 2013; 8:e61517. [PMID: 23613869 PMCID: PMC3629063 DOI: 10.1371/journal.pone.0061517] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 03/11/2013] [Indexed: 11/19/2022] Open
Abstract
Nemaline myopathy (NM) is the most common disease entity among non-dystrophic skeletal muscle congenital diseases. Mutations in the skeletal muscle α-actin gene (ACTA1) account for ∼25% of all NM cases and are the most frequent cause of severe forms of NM. So far, the mechanisms underlying muscle weakness in NM patients remain unclear. Additionally, recent Magnetic Resonance Imaging (MRI) studies reported a progressive fatty infiltration of skeletal muscle with a specific muscle involvement in patients with ACTA1 mutations. We investigated strictly noninvasively the gastrocnemius muscle function of a mouse model carrying a mutation in the ACTA1 gene (H40Y). Skeletal muscle anatomy (hindlimb muscles and fat volumes) and energy metabolism were studied using MRI and 31Phosphorus magnetic resonance spectroscopy. Skeletal muscle contractile performance was investigated while applying a force-frequency protocol (from 1–150 Hz) and a fatigue protocol (80 stimuli at 40 Hz). H40Y mice showed a reduction of both absolute (−40%) and specific (−25%) maximal force production as compared to controls. Interestingly, muscle weakness was associated with an improved resistance to fatigue (+40%) and an increased energy cost. On the contrary, the force frequency relationship was not modified in H40Y mice and the extent of fatty infiltration was minor and not different from the WT group. We concluded that the H40Y mouse model does not reproduce human MRI findings but shows a severe muscle weakness which might be related to an alteration of intrinsic muscular properties. The increased energy cost in H40Y mice might be related to either an impaired mitochondrial function or an alteration at the cross-bridges level. Overall, we provided a unique set of anatomic, metabolic and functional biomarkers that might be relevant for monitoring the progression of NM disease but also for assessing the efficacy of potential therapeutic interventions at a preclinical level.
Collapse
Affiliation(s)
- Charlotte Gineste
- Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Centre de Résonance Magnétique Biologique et Médicale (CRMBM) Unité Mixte de Recherche (UMR), Marseille, France
| | - Yann Le Fur
- Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Centre de Résonance Magnétique Biologique et Médicale (CRMBM) Unité Mixte de Recherche (UMR), Marseille, France
| | - Christophe Vilmen
- Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Centre de Résonance Magnétique Biologique et Médicale (CRMBM) Unité Mixte de Recherche (UMR), Marseille, France
| | - Arnaud Le Troter
- Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Centre de Résonance Magnétique Biologique et Médicale (CRMBM) Unité Mixte de Recherche (UMR), Marseille, France
| | - Emilie Pecchi
- Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Centre de Résonance Magnétique Biologique et Médicale (CRMBM) Unité Mixte de Recherche (UMR), Marseille, France
| | - Patrick J. Cozzone
- Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Centre de Résonance Magnétique Biologique et Médicale (CRMBM) Unité Mixte de Recherche (UMR), Marseille, France
| | - Edna C. Hardeman
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - David Bendahan
- Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Centre de Résonance Magnétique Biologique et Médicale (CRMBM) Unité Mixte de Recherche (UMR), Marseille, France
| | - Julien Gondin
- Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Centre de Résonance Magnétique Biologique et Médicale (CRMBM) Unité Mixte de Recherche (UMR), Marseille, France
- * E-mail:
| |
Collapse
|