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Abstract
Striated respiratory muscles are necessary for lung ventilation and to maintain the patency of the upper airway. The basic structural and functional properties of respiratory muscles are similar to those of other striated muscles (both skeletal and cardiac). The sarcomere is the fundamental organizational unit of striated muscles and sarcomeric proteins underlie the passive and active mechanical properties of muscle fibers. In this respect, the functional categorization of different fiber types provides a conceptual framework to understand the physiological properties of respiratory muscles. Within the sarcomere, the interaction between the thick and thin filaments at the level of cross-bridges provides the elementary unit of force generation and contraction. Key to an understanding of the unique functional differences across muscle fiber types are differences in cross-bridge recruitment and cycling that relate to the expression of different myosin heavy chain isoforms in the thick filament. The active mechanical properties of muscle fibers are characterized by the relationship between myoplasmic Ca2+ and cross-bridge recruitment, force generation and sarcomere length (also cross-bridge recruitment), external load and shortening velocity (cross-bridge cycling rate), and cross-bridge cycling rate and ATP consumption. Passive mechanical properties are also important reflecting viscoelastic elements within sarcomeres as well as the extracellular matrix. Conditions that affect respiratory muscle performance may have a range of underlying pathophysiological causes, but their manifestations will depend on their impact on these basic elemental structures.
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Affiliation(s)
- Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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152
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Ochala J, Gokhin DS, Iwamoto H, Fowler VM. Pointed-end capping by tropomodulin modulates actomyosin crossbridge formation in skeletal muscle fibers. FASEB J 2013; 28:408-15. [PMID: 24072783 DOI: 10.1096/fj.13-239640] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In skeletal muscle, thick and thin filaments are arranged in a myofibrillar lattice. Tropomodulin 1 (Tmod1) is a pointed-end capping and tropomyosin-binding protein that controls thin-filament assembly, stability, and lengths. It remains unknown whether Tmods have other functional roles, such as regulating muscle contractility. To investigate this, we recorded and analyzed the mechanical properties and X-ray diffraction patterns of single membrane-permeabilized skeletal muscle fibers from mice lacking Tmod1. Results show that absence of Tmod1 and its replacement by Tmod3 and Tmod4 may impair initial tropomyosin movement over actin subunits during thin-filament activation, thus reducing both the fraction of actomyosin crossbridges in the strongly bound state (-29%) and fiber force-generating capacity (-31%). Therefore, Tmods are novel regulators of actomyosin crossbridge formation and muscle contractility, and future investigations and models of skeletal muscle force production must incorporate Tmods.
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Affiliation(s)
- Julien Ochala
- 1Centre of Human and Aerospace Physiological Sciences, School of Biomedical Sciences, King's College London, Rm. 3.3, Shepherd's House, Guy's Campus, London SE1 1UL, UK.
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153
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Scholten A, Preisinger C, Corradini E, Bourgonje VJ, Hennrich ML, van Veen TAB, Swaminathan PD, Joiner ML, Vos MA, Anderson ME, Heck AJR. Phosphoproteomics study based on in vivo inhibition reveals sites of calmodulin-dependent protein kinase II regulation in the heart. J Am Heart Assoc 2013; 2:e000318. [PMID: 23926118 PMCID: PMC3828808 DOI: 10.1161/jaha.113.000318] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BACKGROUND The multifunctional Ca(2+)- and calmodulin-dependent protein kinase II (CaMKII) is a crucial mediator of cardiac physiology and pathology. Increased expression and activation of CaMKII has been linked to elevated risk for arrhythmic events and is a hallmark of human heart failure. A useful approach to determining CaMKII's role therein is large-scale analysis of phosphorylation events by mass spectrometry. However, current large-scale phosphoproteomics approaches have proved inadequate for high-fidelity identification of kinase-specific roles. The purpose of this study was to develop a phosphoproteomics approach to specifically identify CaMKII's downstream effects in cardiac tissue. METHODS AND RESULTS To identify putative downstream CaMKII targets in cardiac tissue, animals with myocardial-delimited expression of the specific peptide inhibitor of CaMKII (AC3-I) or an inactive control (AC3-C) were compared using quantitative phosphoproteomics. The hearts were isolated after isoproterenol injection to induce CaMKII activation downstream of β-adrenergic receptor agonist stimulation. Enriched phosphopeptides from AC3-I and AC3-C mice were differentially quantified using stable isotope dimethyl labeling, strong cation exchange chromatography and high-resolution LC-MS/MS. Phosphorylation levels of several hundred sites could be profiled, including 39 phosphoproteins noticeably affected by AC3-I-mediated CaMKII inhibition. CONCLUSIONS Our data set included known CaMKII substrates, as well as several new candidate proteins involved in functions not previously implicated in CaMKII signaling.
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Affiliation(s)
- Arjen Scholten
- Biomolecular Mass Spectrometry & Proteomics, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands
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154
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Pokrzywa W, Hoppe T. Chaperoning myosin assembly in muscle formation and aging. WORM 2013; 2:e25644. [PMID: 24778937 PMCID: PMC3875649 DOI: 10.4161/worm.25644] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 07/05/2013] [Indexed: 01/06/2023]
Abstract
The activity and assembly of various myosin subtypes is coordinated by conserved UCS (UNC-45/CRO1/She4p) domain proteins. One founding member of the UCS family is the Caenorhabditis elegans UNC-45 protein important for the organization of striated muscle filaments. Our recent structural and biochemical results demonstrated that UNC-45 forms a protein chain with defined periodicity of myosin interaction domains. Intriguingly, the UNC-45 chain serves as docking platform for myosin molecules, which promotes ordered spacing and incorporation of myosin into contractile muscle sarcomeres. The physiological relevance of this observation was demonstrated in C. elegans by transgenic expression of UNC-45 chain formation mutants, which provokes defects in muscle structure and size. Collaborating with the molecular chaperones, Hsp70 and Hsp90, chain formation of UNC-45 links myosin folding with myofilament assembly. Here, we discuss our recent findings on the dynamic regulation of UNC-45 structure and stability in the context of muscle regeneration mechanisms that are affected in myopathic diseases and during aging.
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Affiliation(s)
- Wojciech Pokrzywa
- Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD); University of Cologne; Cologne, Germany
| | - Thorsten Hoppe
- Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD); University of Cologne; Cologne, Germany
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155
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Carberry S, Brinkmeier H, Zhang Y, Winkler CK, Ohlendieck K. Comparative proteomic profiling of soleus, extensor digitorum longus, flexor digitorum brevis and interosseus muscles from the mdx mouse model of Duchenne muscular dystrophy. Int J Mol Med 2013; 32:544-56. [PMID: 23828267 PMCID: PMC3782555 DOI: 10.3892/ijmm.2013.1429] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 06/05/2013] [Indexed: 12/23/2022] Open
Abstract
Duchenne muscular dystrophy is due to genetic abnormalities in the dystrophin gene and represents one of the most frequent genetic childhood diseases. In the X-linked muscular dystrophy (mdx) mouse model of dystrophinopathy, different subtypes of skeletal muscles are affected to a varying degree albeit the same single base substitution within exon 23 of the dystrophin gene. Thus, to determine potential muscle subtype-specific differences in secondary alterations due to a deficiency in dystrophin, in this study, we carried out a comparative histological and proteomic survey of mdx muscles. We intentionally included the skeletal muscles that are often used for studying the pathomechanism of muscular dystrophy. Histological examinations revealed a significantly higher degree of central nucleation in the soleus and extensor digitorum longus muscles compared with the flexor digitorum brevis and interosseus muscles. Muscular hypertrophy of 20–25% was likewise only observed in the soleus and extensor digitorum longus muscles from mdx mice, but not in the flexor digitorum brevis and interosseus muscles. For proteomic analysis, muscle protein extracts were separated by fluorescence two-dimensional (2D) gel electrophoresis. Proteins with a significant change in their expression were identified by mass spectrometry. Proteomic profiling established an altered abundance of 24, 17, 19 and 5 protein species in the dystrophin-deficient soleus, extensor digitorum longus, flexor digitorum brevis and interosseus muscle, respectively. The key proteomic findings were verified by immunoblot analysis. The identified proteins are involved in the contraction-relaxation cycle, metabolite transport, muscle metabolism and the cellular stress response. Thus, histological and proteomic profiling of muscle subtypes from mdx mice indicated that distinct skeletal muscles are differentially affected by the loss of the membrane cytoskeletal protein, dystrophin. Varying degrees of perturbed protein expression patterns in the muscle subtypes from mdx mice may be due to dissimilar downstream events, including differences in muscle structure or compensatory mechanisms that counteract pathophysiological processes. The interosseus muscle from mdx mice possibly represents a naturally protected phenotype.
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Affiliation(s)
- Steven Carberry
- Department of Biology, National University of Ireland, Maynooth, Co. Kildare, Ireland
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156
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Age-related changes and nutritional regulation of myosin heavy-chain composition in longissimus dorsi of commercial pigs. Animal 2013; 7:1486-92. [PMID: 23764195 DOI: 10.1017/s1751731113000992] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The objective of this study is to investigate the age-related changes of and the effects of dietary conjugated linoleic acid (CLA) on muscle-fibre types in commercial pigs. We divided 25 crossbred male pigs into five age groups (7, 30, 60, 100 and 180 days) and 30 finishing pigs into two dietary groups (one fed a CLA-enriched diet and the other fed a control diet for 30 days). We analysed the composition (%) of myosin heavy-chain (MyHC) mRNA according to the absolute copies of each MyHC (I, IIa, IIb and IIx) mRNA, and the activities of succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) in the longissimus muscle. From days 7 to 180, the MyHC I mRNA abundance and SDH and MDH activities presented a decreasing trend, the MyHC IIb mRNA abundance presented a steady trend and the MyHC IIa and IIx mRNA abundances presented an increasing trend. On day 30, MyHC I and IIb mRNA abundances were at their lowest (P < 0.05), and the MyHC IIa and IIx mRNA abundances were at their highest (P < 0.05). In the CLA group, the MyHC I mRNA abundance and the activities of SDH and MDH were improved in the longissimus muscle, whereas pressure loss, drip loss and average back fat depth significantly decreased (P < 0.01) and shear force significantly increased (P < 0.01). Loin eye area, feed conversion rate and meat colour showed some tendency to be improved. These results indicated that more oxidative fibres might convert to glycolytic fibres with increasing age or weight, and that the early developmental stage might be a key stage for this conversion. During the finishing stage, the proportion of oxidative fibres might be increased by dietary CLA supplementation, which may contribute to the water-holding capacity of meat. The results would provide an important basis for the application of muscle-fibre types in the improvement of pork quality.
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157
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Clark KA, Kadrmas JL. Drosophila melanogaster muscle LIM protein and alpha-actinin function together to stabilize muscle cytoarchitecture: a potential role for Mlp84B in actin-crosslinking. Cytoskeleton (Hoboken) 2013; 70:304-16. [PMID: 23606669 PMCID: PMC3716849 DOI: 10.1002/cm.21106] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 03/04/2013] [Accepted: 03/06/2013] [Indexed: 02/06/2023]
Abstract
Stabilization of tissue architecture during development and growth is essential to maintain structural integrity. Because of its contractile nature, muscle is especially susceptible to physiological stresses, and has multiple mechanisms to maintain structural integrity. The Drosophila melanogaster Muscle LIM Protein (MLP), Mlp84B, participates in muscle maintenance, yet its precise mechanism of action is still controversial. Through a candidate approach, we identified α-actinin as a protein that functions with Mlp84B to ensure muscle integrity. α-actinin RNAi animals die primarily as pupae, and Mlp84B RNAi animals are adult viable. RNAi knockdown of Mlp84B and α-actinin together produces synergistic early larval lethality and destabilization of Z-line structures. We recapitulated these phenotypes using combinations of traditional loss-of-function alleles and single-gene RNAi. We observe that Mlp84B induces the formation of actin loops in muscle cell nuclei in the absence of nuclear α-actinin, suggesting Mlp84B has intrinsic actin cross-linking activity, which may complement α-actinin cross-linking activity at sites of actin filament anchorage. These results reveal a molecular mechanism for MLP stabilization of muscle and implicate reduced actin crosslinking as the primary destabilizing defect in MLP-associated cardiomyopathies. Our data support a model in which α-actinin and Mlp84B have important and overlapping functions at sites of actin filament anchorage to preserve muscle structure and function.
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Affiliation(s)
- Kathleen A. Clark
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112
- Department of Biology, University of Utah, Salt Lake City, UT 84112
- Department of Oncological Sciences, University of Utah, Salt Lake City, UT 84112
| | - Julie L. Kadrmas
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112
- Department of Oncological Sciences, University of Utah, Salt Lake City, UT 84112
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158
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Domsch K, Ezzeddine N, Nguyen HT. Abba is an essential TRIM/RBCC protein to maintain the integrity of sarcomeric cytoarchitecture. J Cell Sci 2013; 126:3314-23. [PMID: 23729735 DOI: 10.1242/jcs.122366] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Organized sarcomeric striations are an evolutionarily conserved hallmark of functional skeletal muscles. Here, we demonstrate that the Drosophila Abba protein, a member of the TRIM/RBCC superfamily, has a pivotal regulatory role in maintaining proper sarcomeric cytoarchitecture during development and muscle usage. abba mutant embryos initially form muscles, but F-actin and Myosin striations become progressively disrupted when the muscles undergo growth and endure increased contractile forces during larval development. Abnormal Myosin aggregates and myofiber atrophy are also notable in the abba mutants. The larval defects result in compromised muscle function, and hence important morphogenetic events do not occur properly during pupation, leading to lethality. Abba is localized at larval Z-discs, and genetic evidence indicates that abba interacts with α-actinin, kettin/D-titin and mlp84B, genes that encode important Z-disc proteins for stable myofibrillar organization and optimal muscle function. RNAi experiments and ultrastructural analysis reveal that Abba has an additional crucial role in sarcomere maintenance in adult muscles. Abba is required to ensure the integrity and function of Z-discs and M-lines. Rescue experiments further show that Abba function is dependent upon its B-box/coiled-coil domain, NHL repeats and RING finger domain. The importance of these presumed protein-protein interactions and ubiquitin ligase-associated domains supports our hypothesis that Abba is needed for specific protein complex formation and stabilization at Z-discs and M-lines.
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Affiliation(s)
- Katrin Domsch
- Department of Biology, Division of Developmental Biology, Friedrich-Alexander University of Erlangen-Nürnberg, Staudtstrasse 5, 91058 Erlangen, Germany
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159
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Baraibar MA, Gueugneau M, Duguez S, Butler-Browne G, Bechet D, Friguet B. Expression and modification proteomics during skeletal muscle ageing. Biogerontology 2013; 14:339-52. [PMID: 23624703 DOI: 10.1007/s10522-013-9426-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 04/17/2013] [Indexed: 12/17/2022]
Abstract
Skeletal muscle ageing is characterized by a progressive and dramatic loss of muscle mass and strength leading to decreased muscular function resulting in muscle weakness which is often referred to as sarcopenia. Following the standardisation of "omics" approaches to study the genome (genomics) and the transcriptome (transcriptomics), the study of the proteins encoded by the genome, referred to as proteomics, is a tremendous challenge. Unlike the genome, the proteome varies in response to many physiological or pathological factors. In addition, the proteome is orders of magnitude more complex than the transcriptome due to post-translational modifications, protein oxidation and limited protein degradation. Proteomic studies, including the analysis of protein abundance as well as post-translational modified proteins have been shown to provide valuable information to unravel the key molecular pathways implicated in complex biological processes, such as tissue and organ ageing. In this article, we will describe proteomic approaches for the analysis of protein abundance as well as the specific protein targets for oxidative damage upon oxidative stress and/or during skeletal muscle ageing.
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Affiliation(s)
- Martin A Baraibar
- Laboratoire de Biologie Cellulaire du Vieillissement, UR4, UPMC Paris 6 University, 4 place Jussieu, 75252, Paris Cedex 05, France
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160
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Randazzo D, Giacomello E, Lorenzini S, Rossi D, Pierantozzi E, Blaauw B, Reggiani C, Lange S, Peter AK, Chen J, Sorrentino V. Obscurin is required for ankyrinB-dependent dystrophin localization and sarcolemma integrity. ACTA ACUST UNITED AC 2013; 200:523-36. [PMID: 23420875 PMCID: PMC3575540 DOI: 10.1083/jcb.201205118] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Obscurin contributes to the organization of subsarcolemma microtubules, localization of dystrophin at costameres, and maintenance of sarcolemmal integrity in skeletal muscle fibers. Obscurin is a large myofibrillar protein that contains several interacting modules, one of which mediates binding to muscle-specific ankyrins. Interaction between obscurin and the muscle-specific ankyrin sAnk1.5 regulates the organization of the sarcoplasmic reticulum in striated muscles. Additional muscle-specific ankyrin isoforms, ankB and ankG, are localized at the subsarcolemma level, at which they contribute to the organization of dystrophin and β-dystroglycan at costameres. In this paper, we report that in mice deficient for obscurin, ankB was displaced from its localization at the M band, whereas localization of ankG at the Z disk was not affected. In obscurin KO mice, localization at costameres of dystrophin, but not of β-dystroglycan, was altered, and the subsarcolemma microtubule cytoskeleton was disrupted. In addition, these mutant mice displayed marked sarcolemmal fragility and reduced muscle exercise tolerance. Altogether, the results support a model in which obscurin, by targeting ankB at the M band, contributes to the organization of subsarcolemma microtubules, localization of dystrophin at costameres, and maintenance of sarcolemmal integrity.
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Affiliation(s)
- Davide Randazzo
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
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161
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Nedergaard A, Karsdal MA, Sun S, Henriksen K. Serological muscle loss biomarkers: an overview of current concepts and future possibilities. J Cachexia Sarcopenia Muscle 2013; 4:1-17. [PMID: 22996343 PMCID: PMC3581612 DOI: 10.1007/s13539-012-0086-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 08/21/2012] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The skeletal muscle mass is the largest organ in the healthy body, comprising 30-40 % of the body weight of an adult man. It confers protection from trauma, locomotion, ventilation, and it represents a "sink" in glucose metabolism and a reservoir of amino acids to other tissues such as the brain and blood cells. Naturally, loss of muscle has dire consequences for health as well as functionality. Muscle loss is a natural consequence of especially aging, inactivity, and their associated metabolic dysfunction, but it is strongly accelerated in critical illness such as organ failure, sepsis, or cancer. Whether this muscle loss is considered a primary or secondary condition, it is known that muscle loss is a symptom that predicts morbidity and mortality and one that is known to impact quality of life and independence. Therefore, monitoring of muscle mass is relevant in a number of pathologies as well as in clinical trials as measures of efficacy as well as safety. METHODS AND RESULTS Existing biomarkers of muscle mass or muscle loss have shown to be either too unreliable or too impractical in relation to the perceived clinical benefit to reach regular clinical research or use. We suggest serological neoepitope biomarkers as a possible technology to address some of these problems. Blood biomarkers of this kind have previously been shown to respond with high sensitivity and shorter time to minimum significant change than available biomarkers of muscle mass. We provide brief reviews of existing muscle mass or function biomarker technologies, muscle protein biology, and existing neoepitope biomarkers and proceed to present tentative recommendations on how to select and detect neoepitope biomarkers. CONCLUSION We suggest that serological peptide biomarkers whose tissue and pathology specificity are derived from post-translational modification of proteins in tissues of interest, presenting so-called neoepitopes, represents an exciting candidate technology to fill out an empty niche in biomarker technology.
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162
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Kostrominova TY, Reiner DS, Haas RH, Ingermanson R, McDonough PM. Automated methods for the analysis of skeletal muscle fiber size and metabolic type. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 306:275-332. [PMID: 24016528 DOI: 10.1016/b978-0-12-407694-5.00007-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
It is of interest to quantify the size, shape, and metabolic subtype of skeletal muscle fibers in many areas of biomedical research. To do so, skeletal muscle samples are sectioned transversely to the length of the muscle and labeled for extracellular or membrane proteins to delineate the fiber boundaries and additionally for biomarkers related to function or metabolism. The samples are digitally photographed and the fibers "outlined" for quantification of fiber cross-sectional area (CSA) using pointing devices interfaced to a computer, which is tedious, prone to error, and can be nonobjective. Here, we review methods for characterizing skeletal muscle fibers and describe new automated techniques, which rapidly quantify CSA and biomarkers. We discuss the applications of these methods to the characterization of mitochondrial dysfunctions, which underlie a variety of human afflictions, and we present a novel approach, utilizing images from the online Human Protein Atlas to predict relationships between fiber-specific protein expression, function, and metabolism.
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163
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Abdul-Hussein S, van der Ven PFM, Tajsharghi H. Expression profiles of muscle disease-associated genes and their isoforms during differentiation of cultured human skeletal muscle cells. BMC Musculoskelet Disord 2012; 13:262. [PMID: 23273262 PMCID: PMC3549291 DOI: 10.1186/1471-2474-13-262] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 12/21/2012] [Indexed: 01/10/2023] Open
Abstract
Background The formation of contractile myofibrils requires the stepwise onset of expression of muscle specific proteins. It is likely that elucidation of the expression patterns of muscle-specific sarcomeric proteins is important to understand muscle disorders originating from defects in contractile sarcomeric proteins. Methods We investigated the expression profile of a panel of sarcomeric components with a focus on proteins associated with a group of congenital disorders. The analyses were performed in cultured human skeletal muscle cells during myoblast proliferation and myotube development. Results Our culture technique resulted in the development of striated myotubes and the expression of adult isoforms of the sarcomeric proteins, such as fast TnI, fast TnT, adult fast and slow MyHC isoforms and predominantly skeletal muscle rather than cardiac actin. Many proteins involved in muscle diseases, such as beta tropomyosin, slow TnI, slow MyBPC and cardiac TnI were readily detected in the initial stages of muscle cell differentiation, suggesting the possibility of an early role for these proteins as constituent of the developing contractile apparatus during myofibrillogenesis. This suggests that in disease conditions the mechanisms of pathogenesis for each of the mutated sarcomeric proteins might be reflected by altered expression patterns, and disturbed assembly of cytoskeletal, myofibrillar structures and muscle development. Conclusions In conclusion, we here confirm that cell cultures of human skeletal muscle are an appropriate tool to study developmental stages of myofibrillogenesis. The expression of several disease-associated proteins indicates that they might be a useful model system for studying the pathogenesis of muscle diseases caused by defects in specific sarcomeric constituents.
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Affiliation(s)
- Saba Abdul-Hussein
- Department of Pathology, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, SE, 413 45, Sweden
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164
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Smith LR, Meyer G, Lieber RL. Systems analysis of biological networks in skeletal muscle function. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2012. [PMID: 23188744 DOI: 10.1002/wsbm.1197] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Skeletal muscle function depends on the efficient coordination among subcellular systems. These systems are composed of proteins encoded by a subset of genes, all of which are tightly regulated. In the cases where regulation is altered because of disease or injury, dysfunction occurs. To enable objective analysis of muscle gene expression profiles, we have defined nine biological networks whose coordination is critical to muscle function. We begin by describing the expression of proteins necessary for optimal neuromuscular junction function that results in the muscle cell action potential. That action potential is transmitted to proteins involved in excitation-contraction coupling enabling Ca(2+) release. Ca(2+) then activates contractile proteins supporting actin and myosin cross-bridge cycling. Force generated by cross-bridges is transmitted via cytoskeletal proteins through the sarcolemma and out to critical proteins that support the muscle extracellular matrix. Muscle contraction is fueled through many proteins that regulate energy metabolism. Inflammation is a common response to injury that can result in alteration of many pathways within muscle. Muscle also has multiple pathways that regulate size through atrophy or hypertrophy. Finally, the isoforms associated with fast muscle fibers and their corresponding isoforms in slow muscle fibers are delineated. These nine networks represent important biological systems that affect skeletal muscle function. Combining high-throughput systems analysis with advanced networking software will allow researchers to use these networks to objectively study skeletal muscle systems.
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Affiliation(s)
- Lucas R Smith
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA
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165
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Orfanos Z, Sparrow JC. Myosin isoform switching during assembly of the Drosophila flight muscle thick filament lattice. J Cell Sci 2012. [PMID: 23178940 DOI: 10.1242/jcs.110361] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During muscle development myosin molecules form symmetrical thick filaments, which integrate with the thin filaments to produce the regular sarcomeric lattice. In Drosophila indirect flight muscles (IFMs) the details of this process can be studied using genetic approaches. The weeP26 transgenic line has a GFP-encoding exon inserted into the single Drosophila muscle myosin heavy chain gene, Mhc. The weeP26 IFM sarcomeres have a unique MHC-GFP-labelling pattern restricted to the sarcomere core, explained by non-translation of the GFP exon following alternative splicing. Characterisation of wild-type IFM MHC mRNA confirmed the presence of an alternately spliced isoform, expressed earlier than the major IFM-specific isoform. The two wild-type IFM-specific MHC isoforms differ by the presence of a C-terminal 'tailpiece' in the minor isoform. The sequential expression and assembly of these two MHCs into developing thick filaments suggest a role for the tailpiece in initiating A-band formation. The restriction of the MHC-GFP sarcomeric pattern in weeP26 is lifted when the IFM lack the IFM-specific myosin binding protein flightin, suggesting that it limits myosin dissociation from thick filaments. Studies of flightin binding to developing thick filaments reveal a progressive binding at the growing thick filament tips and in a retrograde direction to earlier assembled, proximal filament regions. We propose that this flightin binding restricts myosin molecule incorporation/dissociation during thick filament assembly and explains the location of the early MHC isoform pattern in the IFM A-band.
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166
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Thoss F, Dietrich F, Punkt K, Illenberger S, Rottner K, Himmel M, Ziegler WH. Metavinculin: New insights into functional properties of a muscle adhesion protein. Biochem Biophys Res Commun 2012; 430:7-13. [PMID: 23159629 DOI: 10.1016/j.bbrc.2012.11.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 11/04/2012] [Indexed: 11/16/2022]
Abstract
Metavinculin is a muscle-specific splice variant of the ubiquitously expressed cytoskeletal adaptor protein vinculin. Both proteins are thought to be co-expressed in all muscle types where they co-localize to microfilament-associated adhesion sites. It has been shown that a metavinculin-specific insertion of 68 amino acids alters the biochemical properties of the five-helix bundle in the tail domain. Here, we demonstrate that the metavinculin-specific helix H1' plays an important role for protein stability of the tail domain, since a point mutation in this helix, R975W, which is associated with the occurrence of dilated cardiomyopathy in man, further decreases thermal stability of the metavinculin tail domain. In striated muscle progenitor cells (myoblasts), both, metavinculin and the R975W mutant show significantly reduced, albeit distinctive residency and exchange rates in adhesion sites as compared to vinculin. In contrast to previous studies, we show that metavinculin is localized in a muscle fiber type-dependent fashion to the costameres of striated muscle, reflecting the individual metabolic and physiological status of a given muscle fiber. Metavinculin expression is highest in fast, glycolytic muscle fibers and virtually absent in M. diaphragmaticus, a skeletal muscle entirely lacking fast, glycolytic fibers. In summary, our data suggest that metavinculin enrichment in attachment sites of muscle cells leads to higher mechanical stability of adhesion complexes allowing for greater shear force resistance.
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Affiliation(s)
- Florian Thoss
- Interdisciplinary Center for Clinical Research (IZKF) Leipzig, Faculty of Medicine, University of Leipzig, D-04103 Leipzig, Germany
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167
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Liu H, Shao Y, Qin W, Runyan RB, Xu M, Ma Z, Borg TK, Markwald R, Gao BZ. Myosin filament assembly onto myofibrils in live neonatal cardiomyocytes observed by TPEF-SHG microscopy. Cardiovasc Res 2012; 97:262-70. [PMID: 23118131 DOI: 10.1093/cvr/cvs328] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
AIMS Understanding myofibrillogenesis is essential for elucidating heart muscle formation, development, and remodelling in response to physiological stimulation. Here, we report the dynamic assembly process of contractile myosin filaments onto myofibrils in a live cardiomyocyte culture during myofibrillogenesis. METHODS AND RESULTS Utilizing a custom-built, two-photon excitation fluorescence and second harmonic generation imaging system equipped with an on-stage incubator, we observed new sarcomere additions in rat neonatal cardiomyocytes during 10 h of on-stage incubation. The new sarcomere additions occurred at the side of existing myofibrils, where we observed mature myofibrils acting as templates, or at the interstice of several separated myofibrils. CONCLUSIONS During sarcomeric addition, myosin filaments are assembled onto the premyofibril laterally. This lateral addition, which proceeds stepwise along the axial direction, plays an important role in the accumulation of Z-bodies to form mature Z-disks and in the regulation of sarcomeric alignment during maturation.
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Affiliation(s)
- Honghai Liu
- Department of Bioengineering and COMSET, Clemson University, Clemson, SC 29634, USA
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168
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Criswell TL, Corona BT, Wang Z, Zhou Y, Niu G, Xu Y, Christ GJ, Soker S. The role of endothelial cells in myofiber differentiation and the vascularization and innervation of bioengineered muscle tissue in vivo. Biomaterials 2012; 34:140-9. [PMID: 23059002 DOI: 10.1016/j.biomaterials.2012.09.045] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Accepted: 09/20/2012] [Indexed: 12/25/2022]
Abstract
Musculoskeletal disorders are a major cause of disability and effective treatments are currently lacking. Tissue engineering affords the possibility of new therapies utilizing cells and biomaterials for the recovery of muscle volume and function. A major consideration in skeletal muscle engineering is the integration of a functional vasculature within the regenerating tissue. In this study we employed fluorescent cell labels to track the location and differentiation of co-cultured cells in vivo and in vitro. We first utilized a co-culture of fluorescently labeled endothelial cells (ECs) and muscle progenitor cells (MPCs) to investigate the ability of ECs to enhance muscle tissue formation and vascularization in an in vivo model of bioengineered muscle. Scaffolds that had been seeded with both MPCs and ECs showed significantly greater vascularization, tissue formation and enhanced innervation as compared to scaffolds seeded with MPCs alone. Subsequently, we performed in vitro experiments using a 3-cell type system (ECs, MPCs, and pericytes (PCs)) to demonstrate the utility of fluorescent cell labeling for monitoring cell growth and differentiation. The growth and differentiation of individual cell types was determined using live cell fluorescent microscopy demonstrating the utility of fluorescent labels to monitor tissue organization in real time.
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Affiliation(s)
- Tracy L Criswell
- Wake Forest Institute for Regenerative Medicine, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA
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169
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Müller M, Mazur AJ, Behrmann E, Diensthuber RP, Radke MB, Qu Z, Littwitz C, Raunser S, Schoenenberger CA, Manstein DJ, Mannherz HG. Functional characterization of the human α-cardiac actin mutations Y166C and M305L involved in hypertrophic cardiomyopathy. Cell Mol Life Sci 2012; 69:3457-79. [PMID: 22643837 PMCID: PMC11115188 DOI: 10.1007/s00018-012-1030-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 04/22/2012] [Accepted: 05/07/2012] [Indexed: 11/25/2022]
Abstract
Inherited cardiomyopathies are caused by point mutations in sarcomeric gene products, including α-cardiac muscle actin (ACTC1). We examined the biochemical and cell biological properties of the α-cardiac actin mutations Y166C and M305L identified in hypertrophic cardiomyopathy (HCM). Untagged wild-type (WT) cardiac actin, and the Y166C and M305L mutants were expressed by the baculovirus/Sf9-cell system and affinity purified by immobilized gelsolin G4-6. Their correct folding was verified by a number of assays. The mutant actins also displayed a disturbed intrinsic ATPase activity and an altered polymerization behavior in the presence of tropomyosin, gelsolin, and Arp2/3 complex. Both mutants stimulated the cardiac β-myosin ATPase to only 50 % of WT cardiac F-actin. Copolymers of WT and increasing amounts of the mutant actins led to a reduced stimulation of the myosin ATPase. Transfection of established cell lines revealed incorporation of EGFP- and hemagglutinin (HA)-tagged WT and both mutant actins into cytoplasmic stress fibers. Adenoviral vectors of HA-tagged WT and Y166C actin were successfully used to infect adult and neonatal rat cardiomyocytes (NRCs). The expressed HA-tagged actins were incorporated into the minus-ends of NRC thin filaments, demonstrating the ability to form hybrid thin filaments with endogenous actin. In NRCs, the Y166C mutant led after 72 h to a shortening of the sarcomere length when compared to NRCs infected with WT actin. Thus our data demonstrate that a mutant actin can be integrated into cardiomyocyte thin filaments and by its reduced mode of myosin interaction might be the basis for the initiation of HCM.
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Affiliation(s)
- Mirco Müller
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Antonina Joanna Mazur
- Department of Anatomy and Molecular Embryology, Ruhr-University, Universitätsstrasse 150, 44780 Bochum, Germany
- Present Address: Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, 51-148 Wroclaw, Poland
| | - Elmar Behrmann
- Department of Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, 44227 Dortmund, Germany
| | - Ralph P. Diensthuber
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Michael B. Radke
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Zheng Qu
- Department of Anatomy and Molecular Embryology, Ruhr-University, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Christoph Littwitz
- Department of Physiology, Stritch School of Medicine, Loyola University Chicago, Chicago, USA
| | - Stefan Raunser
- Department of Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, 44227 Dortmund, Germany
| | - Cora-Ann Schoenenberger
- Maurice E. Müller Institute for Structural Biology, Biozentrum, University of Basel, 4046 Basel, Switzerland
| | - Dietmar J. Manstein
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Hans Georg Mannherz
- Department of Anatomy and Molecular Embryology, Ruhr-University, Universitätsstrasse 150, 44780 Bochum, Germany
- Department of Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, 44227 Dortmund, Germany
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170
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Hernández-Ochoa EO, Robison P, Contreras M, Shen T, Zhao Z, Schneider MF. Elevated extracellular glucose and uncontrolled type 1 diabetes enhance NFAT5 signaling and disrupt the transverse tubular network in mouse skeletal muscle. Exp Biol Med (Maywood) 2012; 237:1068-83. [PMID: 22966145 DOI: 10.1258/ebm.2012.012052] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The transcription factor nuclear factor of activated T-cells 5 (NFAT5) is a key protector from hypertonic stress in the kidney, but its role in skeletal muscle is unexamined. Here, we evaluate the effects of glucose hypertonicity and hyperglycemia on endogenous NFAT5 activity, transverse tubular system morphology and Ca(2+) signaling in adult murine skeletal muscle fibers. We found that exposure to elevated glucose (25-50 mmol/L) increased NFAT5 expression and nuclear translocation, and NFAT-driven transcriptional activity. These effects were insensitive to the inhibition of calcineurin A, but sensitive to both p38α mitogen-activated protein kinases and phosphoinositide 3-kinase-related kinase inhibition. Fibers exposed to elevated glucose exhibited disrupted transverse tubular morphology, characterized by swollen transverse tubules and an increase in longitudinal connections between adjacent transverse tubules. Ca(2+) transients elicited by a single, brief electric field stimuli were increased in amplitude in fibers challenged by elevated glucose. Muscle fibers from type 1 diabetic mice exhibited increased NFAT5 expression and transverse tubule disruptions, but no differences in electrically evoked Ca(2+) transients. Our results suggest the hypothesis that these changes in skeletal muscle could play a role in the pathophysiology of acute and severe hyperglycemic episodes commonly observed in uncontrolled diabetes.
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Affiliation(s)
- Erick O Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, University of Maryland, School of Medicine, Baltimore, MD 21201, USA.
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171
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Papanicolaou KN, Kikuchi R, Ngoh GA, Coughlan KA, Dominguez I, Stanley WC, Walsh K. Mitofusins 1 and 2 are essential for postnatal metabolic remodeling in heart. Circ Res 2012; 111:1012-26. [PMID: 22904094 DOI: 10.1161/circresaha.112.274142] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
RATIONALE At birth, there is a switch from placental to pulmonary circulation and the heart commences its aerobic metabolism. In cardiac myocytes, this transition is marked by increased mitochondrial biogenesis and remodeling of the intracellular architecture. The mechanisms governing the formation of new mitochondria and their expansion within myocytes remain largely unknown. Mitofusins (Mfn-1 and Mfn-2) are known regulators of mitochondrial networks, but their role during perinatal maturation of the heart has yet to be examined. OBJECTIVE The objective of this study was to determine the significance of mitofusins during early postnatal cardiac development. METHODS AND RESULTS We genetically inactivated Mfn-1 and Mfn-2 in midgestational and postnatal cardiac myocytes using a loxP/Myh6-cre approach. At birth, cardiac morphology and function of double-knockout (DKO) mice are normal. At that time, DKO mitochondria increase in numbers, appear to be spherical and heterogeneous in size, but exhibit normal electron density. By postnatal day 7, the mitochondrial numbers in DKO myocytes remain abnormally expanded and many lose matrix components and membrane organization. At this time point, DKO mice have developed cardiomyopathy. This leads to a rapid decline in survival and all DKO mice die before 16 days of age. Gene expression analysis of DKO hearts shows that mitochondria biogenesis genes are downregulated, the mitochondrial DNA is reduced, and mitochondrially encoded transcripts and proteins are also reduced. Furthermore, mitochondrial turnover pathways are dysregulated. CONCLUSIONS Our findings establish that Mfn-1 and Mfn-2 are essential in mediating mitochondrial remodeling during postnatal cardiac development, a time of dramatic transitions in the bioenergetics and growth of the heart.
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172
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Steinmetz PRH, Kraus JEM, Larroux C, Hammel JU, Amon-Hassenzahl A, Houliston E, Wörheide G, Nickel M, Degnan BM, Technau U. Independent evolution of striated muscles in cnidarians and bilaterians. Nature 2012; 487:231-4. [PMID: 22763458 PMCID: PMC3398149 DOI: 10.1038/nature11180] [Citation(s) in RCA: 165] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Accepted: 05/03/2012] [Indexed: 12/22/2022]
Abstract
Striated muscles are present in bilaterian animals (for example, vertebrates, insects and annelids) and some non-bilaterian eumetazoans (that is, cnidarians and ctenophores). The considerable ultrastructural similarity of striated muscles between these animal groups is thought to reflect a common evolutionary origin. Here we show that a muscle protein core set, including a type II myosin heavy chain (MyHC) motor protein characteristic of striated muscles in vertebrates, was already present in unicellular organisms before the origin of multicellular animals. Furthermore, 'striated muscle' and 'non-muscle' myhc orthologues are expressed differentially in two sponges, compatible with a functional diversification before the origin of true muscles and the subsequent use of striated muscle MyHC in fast-contracting smooth and striated muscle. Cnidarians and ctenophores possess striated muscle myhc orthologues but lack crucial components of bilaterian striated muscles, such as genes that code for titin and the troponin complex, suggesting the convergent evolution of striated muscles. Consistently, jellyfish orthologues of a shared set of bilaterian Z-disc proteins are not associated with striated muscles, but are instead expressed elsewhere or ubiquitously. The independent evolution of eumetazoan striated muscles through the addition of new proteins to a pre-existing, ancestral contractile apparatus may serve as a model for the evolution of complex animal cell types.
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Affiliation(s)
- Patrick R H Steinmetz
- Department for Molecular Evolution and Development, Centre for Organismal Systems Biology, University of Vienna, A-1090 Vienna, Austria
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173
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Kan-O M, Takeya R, Abe T, Kitajima N, Nishida M, Tominaga R, Kurose H, Sumimoto H. Mammalian formin Fhod3 plays an essential role in cardiogenesis by organizing myofibrillogenesis. Biol Open 2012; 1:889-96. [PMID: 23213483 PMCID: PMC3507241 DOI: 10.1242/bio.20121370] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 06/18/2012] [Indexed: 11/20/2022] Open
Abstract
Heart development requires organized integration of actin filaments into the sarcomere, the contractile unit of myofibrils, although it remains largely unknown how actin filaments are assembled during myofibrillogenesis. Here we show that Fhod3, a member of the formin family of proteins that play pivotal roles in actin filament assembly, is essential for myofibrillogenesis at an early stage of heart development. Fhod3−/− mice appear normal up to embryonic day (E) 8.5, when the developing heart, composed of premyofibrils, initiates spontaneous contraction. However, these premyofibrils fail to mature and myocardial development does not continue, leading to embryonic lethality by E11.5. Transgenic expression of wild-type Fhod3 in the heart restores myofibril maturation and cardiomyogenesis, which allow Fhod3−/− embryos to develop further. Moreover, cardiomyopathic changes with immature myofibrils are caused in mice overexpressing a mutant Fhod3, defective in binding to actin. These findings indicate that actin dynamics, regulated by Fhod3, participate in sarcomere organization during myofibrillogenesis and thus play a crucial role in heart development.
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Affiliation(s)
- Meikun Kan-O
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences , 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 , Japan
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174
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Yang J, Xu X. α-Actinin2 is required for the lateral alignment of Z discs and ventricular chamber enlargement during zebrafish cardiogenesis. FASEB J 2012; 26:4230-42. [PMID: 22767232 DOI: 10.1096/fj.12-207969] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
α-Actinin2 (Actn2) is a predominant protein in the sarcomere Z disc whose mutation can lead to cardiomyopathy. However, the function of Actn2 in Z-disc assembly and cardiomyopathy in vertebrates remains elusive. We leveraged genetic tools in zebrafish embryos to elucidate the function of Actn2. We identified a single Actn2 homologue expressed in the zebrafish heart and conducted loss-of-function studies by antisense morpholino technology. Although zebrafish Actn2 assembles early into the Z disc, depletion of actn2 did not affect the early steps of sarcomere assembly. Instead, Actn2 is required for Z bodies to register laterally, forming well-aligned Z discs. Presumably as a consequence to this structural defect in the sarcomere, the depletion of Actn2 resulted in reduced cardiac function, primarily characterized as a reduced end-diastolic diameter. The depletion of actn2 also significantly reduced the ventricle chamber size, due to both reduced cardiomyocyte (CM) size and CM number. Interestingly, reduced CM size can be rescued by the cessation of heart contractions. The genetic studies of zebrafish uncovered a function for actn2 in lateral registration of Z body. In actn2 morphant fish, the Z-disc defect sequentially affects cardiac function, which leads to morphological changes in the ventricle through a mechanical force-dependent mechanism.
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Affiliation(s)
- Jingchun Yang
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905, USA
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175
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Balse E, Steele DF, Abriel H, Coulombe A, Fedida D, Hatem SN. Dynamic of Ion Channel Expression at the Plasma Membrane of Cardiomyocytes. Physiol Rev 2012; 92:1317-58. [DOI: 10.1152/physrev.00041.2011] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cardiac myocytes are characterized by distinct structural and functional entities involved in the generation and transmission of the action potential and the excitation-contraction coupling process. Key to their function is the specific organization of ion channels and transporters to and within distinct membrane domains, which supports the anisotropic propagation of the depolarization wave. This review addresses the current knowledge on the molecular actors regulating the distinct trafficking and targeting mechanisms of ion channels in the highly polarized cardiac myocyte. In addition to ubiquitous mechanisms shared by other excitable cells, cardiac myocytes show unique specialization, illustrated by the molecular organization of myocyte-myocyte contacts, e.g., the intercalated disc and the gap junction. Many factors contribute to the specialization of the cardiac sarcolemma and the functional expression of cardiac ion channels, including various anchoring proteins, motors, small GTPases, membrane lipids, and cholesterol. The discovery of genetic defects in some of these actors, leading to complex cardiac disorders, emphasizes the importance of trafficking and targeting of ion channels to cardiac function. A major challenge in the field is to understand how these and other actors work together in intact myocytes to fine-tune ion channel expression and control cardiac excitability.
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Affiliation(s)
- Elise Balse
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - David F. Steele
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Hugues Abriel
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Alain Coulombe
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - David Fedida
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Stéphane N. Hatem
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
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176
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Friedrich BM, Fischer-Friedrich E, Gov NS, Safran SA. Sarcomeric pattern formation by actin cluster coalescence. PLoS Comput Biol 2012; 8:e1002544. [PMID: 22685394 PMCID: PMC3369942 DOI: 10.1371/journal.pcbi.1002544] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 03/26/2012] [Indexed: 01/10/2023] Open
Abstract
Contractile function of striated muscle cells depends crucially on the almost crystalline order of actin and myosin filaments in myofibrils, but the physical mechanisms that lead to myofibril assembly remains ill-defined. Passive diffusive sorting of actin filaments into sarcomeric order is kinetically impossible, suggesting a pivotal role of active processes in sarcomeric pattern formation. Using a one-dimensional computational model of an initially unstriated actin bundle, we show that actin filament treadmilling in the presence of processive plus-end crosslinking provides a simple and robust mechanism for the polarity sorting of actin filaments as well as for the correct localization of myosin filaments. We propose that the coalescence of crosslinked actin clusters could be key for sarcomeric pattern formation. In our simulations, sarcomere spacing is set by filament length prompting tight length control already at early stages of pattern formation. The proposed mechanism could be generic and apply both to premyofibrils and nascent myofibrils in developing muscle cells as well as possibly to striated stress-fibers in non-muscle cells. Muscle contraction driving voluntary movements and the beating of the heart relies on the contraction of highly regular bundles of actin and myosin filaments, which share a periodic, sarcomeric pattern. We know little about the mechanisms by which these ‘biological crystals’ are assembled and it is a general question how order on a scale of 100 micrometers can emerge from the interactions of micrometer-sized building blocks, such as actin and myosin filaments. In our paper, we consider a computational model for a bundle of actin filaments and discuss physical mechanisms by which periodic order emerges spontaneously. Mutual crosslinking of actin filaments results in the formation and coalescence of growing actin clusters. Active elongation and shrinkage dynamics of actin filaments generates polymerization forces and causes local actin flow that can act like a conveyor belt to sort myosin filaments in place.
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Affiliation(s)
- Benjamin M Friedrich
- Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel.
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177
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2D and 3D-organized cardiac cells shows differences in cellular morphology, adhesion junctions, presence of myofibrils and protein expression. PLoS One 2012; 7:e38147. [PMID: 22662278 PMCID: PMC3360656 DOI: 10.1371/journal.pone.0038147] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2011] [Accepted: 04/30/2012] [Indexed: 12/03/2022] Open
Abstract
Cardiac cells are organized in vivo in a complex tridimensional structural organization that is crucial for heart function. While in vitro studies can reveal details about cardiac cell biology, usually cells are grown on simplified two-dimensional (2D) environments. To address these differences, we established a cardiac cell culture composed of both 2D and three-dimensional (3D)-organized cells. Our results shows significant differences between the two culture contexts in relation to the overall morphology of the cells, contraction ability, proliferation rate, presence of intercellular adhesion structures, organization of myofibrils, mitochondria morphology, endoplasmic reticulum contents, cytoskeletal filaments and extracellular matrix distribution, and expression of markers of cardiac differentiation. Cardiac cells grown in 2D-context displayed a flattened and well spread shape, were mostly isolated and their cytoplasm was filled with a large network of microfilaments and microtubules. In contrast, 3D-cells were smaller in size, were always in close contact with each other with several cellular junctions, and displayed a less conspicuous cytoskeletal network. 3D-cells had more mitochondria and myofibrils and these cells contract spontaneously more often than 2D-cells. On the other hand, endoplasmic reticulum membranes were present in higher amounts in 2D-cells when compared to 3D-cells. The expression of desmin, cadherin and alpha-actinin was higher in 3D-aggregates compared to 2D-spread cells. These findings indicate that the tridimensional environment in which the cardiac cells are grown influence several aspects of cardiac differentiation, including cell adhesion, cell shape, myofibril assembly, mitochondria contents and protein expression. We suggest that the use of this cardiac culture model, with 2D and 3D-context cells, could be useful for studies on the effects of different drugs, or growth factors, giving valuable information on the biological response of cells grown in different spatial organizations.
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178
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Nomura K, Ono K, Ono S. CAS-1, a C. elegans cyclase-associated protein, is required for sarcomeric actin assembly in striated muscle. J Cell Sci 2012; 125:4077-89. [PMID: 22623720 DOI: 10.1242/jcs.104950] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Assembly of contractile apparatuses in striated muscle requires precisely regulated reorganization of the actin cytoskeletal proteins into sarcomeric organization. Regulation of actin filament dynamics is one of the essential processes of myofibril assembly, but the mechanism of actin regulation in striated muscle is not clearly understood. Actin depolymerizing factor (ADF)/cofilin is a key enhancer of actin filament dynamics in striated muscle in both vertebrates and nematodes. Here, we report that CAS-1, a cyclase-associated protein in Caenorhabditis elegans, promotes ADF/cofilin-dependent actin filament turnover in vitro and is required for sarcomeric actin organization in striated muscle. CAS-1 is predominantly expressed in striated muscle from embryos to adults. In vitro, CAS-1 binds to actin monomers and enhances exchange of actin-bound ATP/ADP even in the presence of UNC-60B, a muscle-specific ADF/cofilin that inhibits the nucleotide exchange. As a result, CAS-1 and UNC-60B cooperatively enhance actin filament turnover. The two proteins also cooperate to shorten actin filaments. A cas-1 mutation is homozygous lethal with defects in sarcomeric actin organization. cas-1-mutant embryos and worms have aggregates of actin in muscle cells, and UNC-60B is mislocalized to the aggregates. These results provide genetic and biochemical evidence that cyclase-associated protein is a critical regulator of sarcomeric actin organization in striated muscle.
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Affiliation(s)
- Kazumi Nomura
- Department of Pathology and Department of Cell Biology, Emory University, Atlanta, GA 30322, USA
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Garcia de la Serrana D, Estévez A, Andree K, Johnston IA. Fast skeletal muscle transcriptome of the gilthead sea bream (Sparus aurata) determined by next generation sequencing. BMC Genomics 2012; 13:181. [PMID: 22577894 PMCID: PMC3418159 DOI: 10.1186/1471-2164-13-181] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 03/30/2012] [Indexed: 01/04/2023] Open
Abstract
Background The gilthead sea bream (Sparus aurata L.) occurs around the Mediterranean and along Eastern Atlantic coasts from Great Britain to Senegal. It is tolerant of a wide range of temperatures and salinities and is often found in brackish coastal lagoons and estuarine areas, particularly early in its life cycle. Gilthead sea bream are extensively cultivated in the Mediterranean with an annual production of 125,000 metric tonnes. Here we present a de novo assembly of the fast skeletal muscle transcriptome of gilthead sea bream using 454 reads and identify gene paralogues, splice variants and microsatellite repeats. An annotated transcriptome of the skeletal muscle will facilitate understanding of the genetic and molecular basis of traits linked to production in this economically important species. Results Around 2.7 million reads of mRNA sequence data were generated from the fast myotomal of adult fish (~2 kg) and juvenile fish (~0.09 kg) that had been either fed to satiation, fasted for 3-5d or transferred to low (11°C) or high (33°C) temperatures for 3-5d. Newbler v2.5 assembly resulted in 43,461 isotigs >100 bp. The number of sequences annotated by searching protein and gene ontology databases was 10,465. The average coverage of the annotated isotigs was x40 containing 5655 unique gene IDs and 785 full-length cDNAs coding for proteins containing 58–1536 amino acids. The v2.5 assembly was found to be of good quality based on validation using 200 full-length cDNAs from GenBank. Annotated isotigs from the reference transcriptome were attributable to 344 KEGG pathway maps. We identified 26 gene paralogues (20 of them teleost-specific) and 43 splice variants, of which 12 had functional domains missing that were likely to affect their biological function. Many key transcription factors, signaling molecules and structural proteins necessary for myogenesis and muscle growth have been identified. Physiological status affected the number of reads that mapped to isotigs, reflecting changes in gene expression between treatments. Conclusions We have produced a comprehensive fast skeletal muscle transcriptome for the gilthead sea bream, which will provide a resource for SNP discovery in genes with a large effect on production traits of commercial interest and for expression studies of growth and adaptation.
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Affiliation(s)
- Daniel Garcia de la Serrana
- Physiological and Evolutionary Genomics Laboratory, Scottish Oceans Institute, School of Biology, University of St Andrews, Fife, KY16 8LB, , Scotland, UK.
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180
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Expression and subcellular localization of mammalian formin Fhod3 in the embryonic and adult heart. PLoS One 2012; 7:e34765. [PMID: 22509354 PMCID: PMC3324543 DOI: 10.1371/journal.pone.0034765] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 03/05/2012] [Indexed: 11/28/2022] Open
Abstract
The formin family proteins play pivotal roles in actin filament assembly via the FH2 domain. The mammalian formin Fhod3 is highly expressed in the heart, and its mRNA in the adult heart contains exons 11, 12, and 25, which are absent from non-muscle Fhod3 isoforms. In cultured neonatal cardiomyocytes, Fhod3 localizes to the middle of the sarcomere and appears to function in its organization, although it is suggested that Fhod3 localizes differently in the adult heart. Here we show, using immunohistochemical analysis with three different antibodies, each recognizing distinct regions of Fhod3, that Fhod3 localizes as two closely spaced bands in middle of the sarcomere in both embryonic and adult hearts. The bands are adjacent to the M-line that crosslinks thick myosin filaments at the center of a sarcomere but distant from the Z-line that forms the boundary of the sarcomere, which localization is the same as that observed in cultured cardiomyocytes. Detailed immunohistochemical and immuno-electron microscopic analyses reveal that Fhod3 localizes not at the pointed ends of thin actin filaments but to a more peripheral zone, where thin filaments overlap with thick myosin filaments. We also demonstrate that the embryonic heart of mice specifically expresses the Fhod3 mRNA isoform harboring the three alternative exons, and that the characteristic localization of Fhod3 in the sarcomere does not require a region encoded by exon 25, in contrast to an essential role of exons 11 and 12. Furthermore, the exon 25-encoded region appears to be dispensable for actin-organizing activities both in vivo and in vitro, albeit it is inserted in the catalytic FH2 domain.
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181
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Xu Y, Qian H, Feng X, Xiong Y, Lei M, Ren Z, Zuo B, Xu D, Ma Y, Yuan H. Differential proteome and transcriptome analysis of porcine skeletal muscle during development. J Proteomics 2012; 75:2093-108. [DOI: 10.1016/j.jprot.2012.01.013] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2011] [Revised: 01/04/2012] [Accepted: 01/08/2012] [Indexed: 11/26/2022]
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182
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Salvi SS, Kumar RP, Ramachandra NB, Sparrow JC, Nongthomba U. Mutations in Drosophila myosin rod cause defects in myofibril assembly. J Mol Biol 2012; 419:22-40. [PMID: 22370558 DOI: 10.1016/j.jmb.2012.02.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 01/17/2012] [Accepted: 02/17/2012] [Indexed: 11/15/2022]
Abstract
The roles of myosin during muscle contraction are well studied, but how different domains of this protein are involved in myofibril assembly in vivo is far less understood. The indirect flight muscles (IFMs) of Drosophila melanogaster provide a good model for understanding muscle development and function in vivo. We show that two missense mutations in the rod region of the myosin heavy-chain gene, Mhc, give rise to IFM defects and abnormal myofibrils. These defects likely result from thick filament abnormalities that manifest during early sarcomere development or later by hypercontraction. The thick filament defects are accompanied by marked reduction in accumulation of flightin, a myosin binding protein, and its phosphorylated forms, which are required to stabilise thick filaments. We investigated with purified rod fragments whether the mutations affect the coiled-coil structure, rod aggregate size or rod stability. No significant changes in these parameters were detected, except for rod thermodynamic stability in one mutation. Molecular dynamics simulations suggest that these mutations may produce localised rod instabilities. We conclude that the aberrant myofibrils are a result of thick filament defects, but that these in vivo effects cannot be detected in vitro using the biophysical techniques employed. The in vivo investigation of these mutant phenotypes in IFM development and function provides a useful platform for studying myosin rod and thick filament formation generically, with application to the aetiology of human myosin rod myopathies.
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Affiliation(s)
- Sheetal S Salvi
- Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560 012, India
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183
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Bricceno KV, Fischbeck KH, Burnett BG. Neurogenic and myogenic contributions to hereditary motor neuron disease. NEURODEGENER DIS 2012; 9:199-209. [PMID: 22327341 DOI: 10.1159/000335311] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 11/23/2011] [Indexed: 12/21/2022] Open
Abstract
Spinal muscular atrophy and spinal and bulbar muscular atrophy are characterized by lower motor neuron loss and muscle atrophy. Although it is accepted that motor neuron loss is a primary event in disease pathogenesis, inherent defects in muscle may also contribute to the disease progression and severity. In this review, we discuss the relative contributions of primary pathological processes in the motor axons, neuromuscular junctions and muscle to disease manifestations. Characterizing these contributions helps us to better understand the disease mechanisms and to better target therapeutic intervention.
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Affiliation(s)
- Katherine V Bricceno
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
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184
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Etheridge T, Oczypok EA, Lehmann S, Fields BD, Shephard F, Jacobson LA, Szewczyk NJ. Calpains mediate integrin attachment complex maintenance of adult muscle in Caenorhabditis elegans. PLoS Genet 2012; 8:e1002471. [PMID: 22253611 PMCID: PMC3257289 DOI: 10.1371/journal.pgen.1002471] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 11/23/2011] [Indexed: 11/23/2022] Open
Abstract
Two components of integrin containing attachment complexes, UNC-97/PINCH and UNC-112/MIG-2/Kindlin-2, were recently identified as negative regulators of muscle protein degradation and as having decreased mRNA levels in response to spaceflight. Integrin complexes transmit force between the inside and outside of muscle cells and signal changes in muscle size in response to force and, perhaps, disuse. We therefore investigated the effects of acute decreases in expression of the genes encoding these multi-protein complexes. We find that in fully developed adult Caenorhabditis elegans muscle, RNAi against genes encoding core, and peripheral, members of these complexes induces protein degradation, myofibrillar and mitochondrial dystrophies, and a movement defect. Genetic disruption of Z-line– or M-line–specific complex members is sufficient to induce these defects. We confirmed that defects occur in temperature-sensitive mutants for two of the genes: unc-52, which encodes the extra-cellular ligand Perlecan, and unc-112, which encodes the intracellular component Kindlin-2. These results demonstrate that integrin containing attachment complexes, as a whole, are required for proper maintenance of adult muscle. These defects, and collapse of arrayed attachment complexes into ball like structures, are blocked when DIM-1 levels are reduced. Degradation is also blocked by RNAi or drugs targeting calpains, implying that disruption of integrin containing complexes results in calpain activation. In wild-type animals, either during development or in adults, RNAi against calpain genes results in integrin muscle attachment disruptions and consequent sub-cellular defects. These results demonstrate that calpains are required for proper assembly and maintenance of integrin attachment complexes. Taken together our data provide in vivo evidence that a calpain-based molecular repair mechanism exists for dealing with attachment complex disruption in adult muscle. Since C. elegans lacks satellite cells, this mechanism is intrinsic to the muscles and raises the question if such a mechanism also exists in higher metazoans. Muscle is a dynamic tissue that grows in response to use and nutrition and shrinks in response to lack of use, poor nutrition, or disease. Loss of muscle mass is an important public health problem, but we understand little of the genes that regulate muscle shrinkage. We have found that, in adult worm muscle, attachment to the basement membrane is continuously required to prevent catastrophic sub-cellular defects that result in impaired ability of muscle to function. We have also identified a group of proteases that are activated when the attachment fails to be properly maintained. Conversely, when these proteases are lacking in adult muscle, the muscles fail to maintain attachment to the basement membrane. Thus, we have discovered a group of proteases that appear to act to maintain attachment to the basement membrane and therefore to maintain muscle itself. Because these worms lack satellite cells, this maintenance system is intrinsic to muscle, thus raising the question whether a similar or identical system also works in humans.
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Affiliation(s)
- Timothy Etheridge
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
| | - Elizabeth A. Oczypok
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Susann Lehmann
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
| | - Brandon D. Fields
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Freya Shephard
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
| | - Lewis A. Jacobson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Nathaniel J. Szewczyk
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
- * E-mail:
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185
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Mayans O, Labeit S. MuRFs: specialized members of the TRIM/RBCC family with roles in the regulation of the trophic state of muscle and its metabolism. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 770:119-29. [PMID: 23631004 DOI: 10.1007/978-1-4614-5398-7_9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
MuRFs, brief for muscle specific RING finger proteins, correspond to a subfamily of the TRIM/RBCC protein family. Here, we review recent progress on the structural biology of MuRF1, the MuRF family member being most clearly associated with muscle diseases. The emerging understanding of the structural biology of MuRFs and their interaction with their numerous myocellular proteins, at least in part representing ubiquitination targets for MuRFs, is likely to provide future rationales to modulate their activity, thus affecting their roles in muscle disease progression.
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Affiliation(s)
- Olga Mayans
- School of Biological Sciences, University of Liverpool, Liverpool, UK.
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186
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Takagaki Y, Yamagishi H, Matsuoka R. Factors Involved in Signal Transduction During Vertebrate Myogenesis. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 296:187-272. [DOI: 10.1016/b978-0-12-394307-1.00004-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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187
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Cutroneo G, Lentini S, Favaloro A, Anastasi G, Di Mauro D. Costameric proteins: from benchside to future translational cardiovascular research. Ann Cardiol Angeiol (Paris) 2011; 61:55-60. [PMID: 22264821 DOI: 10.1016/j.ancard.2011.12.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 12/04/2011] [Indexed: 11/16/2022]
Abstract
Costameres encircle the myocyte perpendicular to its long axis, and comprise two protein complexes: the dystrophin-glycoprotein complex (DGC) and the vinculin-talin-integrin system. They participate in signaling functions and protect muscle cells from damage induced by workload. The behaviour of those proteins has been a focus of study starting from skeletal and smooth muscle cells to cardiomyocytes, and still represents a topical subject for cardiovascular translational research. This review summarizes the past and present novel approaches of our and other groups of work on this subject of research.
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Affiliation(s)
- Giuseppina Cutroneo
- Department of Biomorphology and Biotechnologies, School of Medicine, University of Messina, Messina, Italy
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188
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Kojic S, Radojkovic D, Faulkner G. Muscle ankyrin repeat proteins: their role in striated muscle function in health and disease. Crit Rev Clin Lab Sci 2011; 48:269-94. [DOI: 10.3109/10408363.2011.643857] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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189
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Guillemin N, Bonnet M, Jurie C, Picard B. Functional analysis of beef tenderness. J Proteomics 2011; 75:352-65. [DOI: 10.1016/j.jprot.2011.07.026] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 07/06/2011] [Accepted: 07/26/2011] [Indexed: 11/30/2022]
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190
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The sarcomeric Z-disc and Z-discopathies. J Biomed Biotechnol 2011; 2011:569628. [PMID: 22028589 PMCID: PMC3199094 DOI: 10.1155/2011/569628] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 08/12/2011] [Indexed: 02/06/2023] Open
Abstract
The sarcomeric Z-disc defines the lateral borders of the sarcomere and has primarily been seen as a structure important for mechanical stability. This view has changed dramatically within the last one or two decades. A multitude of novel Z-disc proteins and their interacting partners have been identified, which has led to the identification of additional functions and which have now been assigned to this structure. This includes its importance for intracellular signalling, for mechanosensation and mechanotransduction in particular, an emerging importance for protein turnover and autophagy, as well as its molecular links to the t-tubular system and the sarcoplasmic reticulum. Moreover, the discovery of mutations in a wide variety of Z-disc proteins, which lead to perturbations of several of the above-mentioned systems, gives rise to a diverse group of diseases which can be termed Z-discopathies. This paper provides a brief overview of these novel aspects as well as points to future research directions.
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191
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Tropomodulin capping of actin filaments in striated muscle development and physiology. J Biomed Biotechnol 2011; 2011:103069. [PMID: 22013379 PMCID: PMC3196151 DOI: 10.1155/2011/103069] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 08/18/2011] [Indexed: 11/17/2022] Open
Abstract
Efficient striated muscle contraction requires precise assembly and regulation of diverse actin filament systems, most notably the sarcomeric thin filaments of the contractile apparatus. By capping the pointed ends of actin filaments, tropomodulins (Tmods) regulate actin filament assembly, lengths, and stability. Here, we explore the current understanding of the expression patterns, localizations, and functions of Tmods in both cardiac and skeletal muscle. We first describe the mechanisms by which Tmods regulate myofibril assembly and thin filament lengths, as well as the roles of closely related Tmod family variants, the leiomodins (Lmods), in these processes. We also discuss emerging functions for Tmods in the sarcoplasmic reticulum. This paper provides abundant evidence that Tmods are key structural regulators of striated muscle cytoarchitecture and physiology.
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192
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Myosin binding protein-C: a regulator of actomyosin interaction in striated muscle. J Biomed Biotechnol 2011; 2011:636403. [PMID: 22028592 PMCID: PMC3196898 DOI: 10.1155/2011/636403] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Accepted: 07/25/2011] [Indexed: 01/13/2023] Open
Abstract
Myosin-Binding protein-C (MyBP-C) is a family of accessory proteins of striated muscles that contributes to the assembly and stabilization of thick filaments, and regulates the formation of actomyosin cross-bridges, via direct interactions with both thick myosin and thin actin filaments. Three distinct MyBP-C isoforms have been characterized; cardiac, slow skeletal, and fast skeletal. Numerous mutations in the gene for cardiac MyBP-C (cMyBP-C) have been associated with familial hypertrophic cardiomyopathy (FHC) and have led to increased interest in the regulation and roles of the cardiac isoform. This review will summarize our current knowledge on MyBP-C and its role in modulating contractility, focusing on its interactions with both myosin and actin filaments in cardiac and skeletal muscles.
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193
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CHIODIN MARTA, ACHATZ JOHANNESG, WANNINGER ANDREAS, MARTINEZ PEDRO. Molecular architecture of muscles in an acoel and its evolutionary implications. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2011; 316:427-39. [PMID: 21538843 PMCID: PMC3501712 DOI: 10.1002/jez.b.21416] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Revised: 03/12/2011] [Accepted: 04/01/2011] [Indexed: 12/14/2022]
Abstract
We have characterized the homologs of an actin, a troponin I, and a tropomyosin gene in the acoel Symsagittifera roscoffensis. These genes are expressed in muscles and most likely coexpressed in at least a subset of them. In addition, and for the first time for Acoela, we have produced a species-specific muscular marker, an antibody against the tropomyosin protein. We have followed tropomyosin gene and protein expression during postembryonic development and during the posterior regeneration of amputated adults, showing that preexisting muscle fibers contribute to the wound closure. The three genes characterized in this study interact in the striated muscles of vertebrates and invertebrates, where troponin I and tropomyosin are key regulators of the contraction of the sarcomere. S. roscoffensis and all other acoels so far described have only smooth muscles, but the molecular architecture of these is the same as that of striated fibers of other bilaterians. Given the proposed basal position of acoels within the Bilateria, we suggest that sarcomeric muscles arose from a smooth muscle type, which had the molecular repertoire of striated musculature already in place. We discuss this model in a broad comparative perspective.
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Affiliation(s)
- MARTA CHIODIN
- Departament de Genètica, Universitat de Barcelona, Barcelona, Spain
| | | | - ANDREAS WANNINGER
- Department of Evolutionary Biology, Section of Morphology, University of Vienna, Vienna, Austria
| | - PEDRO MARTINEZ
- Departament de Genètica, Universitat de Barcelona, Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, Barcelona, Spain
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194
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Ewen EP, Snyder CM, Wilson M, Desjardins D, Naya FJ. The Mef2A transcription factor coordinately regulates a costamere gene program in cardiac muscle. J Biol Chem 2011; 286:29644-53. [PMID: 21724844 DOI: 10.1074/jbc.m111.268094] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The Mef2 family of transcription factors regulates muscle differentiation, but the specific gene programs controlled by each member remain unknown. Characterization of Mef2A knock-out mice has revealed severe myofibrillar defects in cardiac muscle indicating a requirement for Mef2A in cytoarchitectural integrity. Through comprehensive expression analysis of Mef2A-deficient hearts, we identified a cohort of dysregulated genes whose products localize to the peripheral Z-disc/costamere region. Many of these genes are essential for costamere integrity and function. Here we demonstrate that these genes are directly regulated by Mef2A, establishing a mechanism by which Mef2A controls the costamere. In an independent model system, acute knockdown of Mef2A in primary neonatal cardiomyocytes resulted in profound malformations of myofibrils and focal adhesions accompanied by adhesion-dependent programmed cell death. These findings indicate a role for Mef2A in cardiomyocyte survival through regulation of costamere integrity. Finally, bioinformatics analysis identified over-represented transcription factor-binding sites in this network of costamere promoters that may provide insight into the mechanism by which costamere genes are regulated by Mef2A. The global control of costamere gene expression adds another dimension by which this essential macromolecular complex may be regulated in health and disease.
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Affiliation(s)
- Elizabeth P Ewen
- Department of Biology, Boston University, Boston, Massachusetts 02215, USA
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195
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Gokhin DS, Fowler VM. The sarcoplasmic reticulum: Actin and tropomodulin hit the links. BIOARCHITECTURE 2011; 1:175-179. [PMID: 22069510 DOI: 10.4161/bioa.1.4.17533] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 07/22/2011] [Accepted: 07/26/2011] [Indexed: 12/29/2022]
Abstract
Skeletal muscle exhibits strikingly regular intracellular sorting of actin and tropomodulin (Tmod) isoforms, which are essential for efficient muscle contraction. A recent study from our laboratory demonstrates that the skeletal muscle sarcoplasmic reticulum (SR) is associated with cytoplasmic γ-actin (γ(cyto)-actin) filaments, which are predominantly capped by Tmod3. When Tmod3 is experimentally induced to vacate its SR compartment, the cytoskeletal organization of SR-associated γ(cyto)-actin is perturbed, leading to SR swelling, depressed SR Ca(2+) release and myofibril misalignment. Based on these findings, Tmod3-capped γ(cyto)-actin filaments mechanically stabilize SR structure and regulate SR function via a novel lateral linkage. Furthermore, by placing these findings in the context of studies in nonmuscle cells, we conclude that Tmodcapped actin filaments are emerging as critical regulators of membrane stability and physiology in a broad assortment of cell types.
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Affiliation(s)
- David S Gokhin
- Department of Cell Biology; The Scripps Research Institute; La Jolla, CA USA
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196
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Whitman SA, Cover C, Yu L, Nelson DL, Zarnescu DC, Gregorio CC. Desmoplakin and talin2 are novel mRNA targets of fragile X-related protein-1 in cardiac muscle. Circ Res 2011; 109:262-71. [PMID: 21659647 DOI: 10.1161/circresaha.111.244244] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
RATIONALE The proper function of cardiac muscle requires the precise assembly and interactions of numerous cytoskeletal and regulatory proteins into specialized structures that orchestrate contraction and force transmission. Evidence suggests that posttranscriptional regulation is critical for muscle function, but the mechanisms involved remain understudied. OBJECTIVE To investigate the molecular mechanisms and targets of the muscle-specific fragile X mental retardation, autosomal homolog 1 (FXR1), an RNA binding protein whose loss leads to perinatal lethality in mice and cardiomyopathy in zebrafish. METHODS AND RESULTS Using RNA immunoprecipitation approaches we found that desmoplakin and talin2 mRNAs associate with FXR1 in a complex. In vitro assays indicate that FXR1 binds these mRNA targets directly and represses their translation. Fxr1 KO hearts exhibit an up-regulation of desmoplakin and talin2 proteins, which is accompanied by severe disruption of desmosome as well as costamere architecture and composition in the heart, as determined by electron microscopy and deconvolution immunofluorescence analysis. CONCLUSIONS Our findings reveal the first direct mRNA targets of FXR1 in striated muscle and support translational repression as a novel mechanism for regulating heart muscle development and function, in particular the assembly of specialized cytoskeletal structures.
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Affiliation(s)
- Samantha A Whitman
- Department of Cellular and Molecular Medicine, University of Arizona, 1656 East Mabel, Tucson, AZ 85724, USA
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197
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Schraders M, Haas SA, Weegerink NJD, Oostrik J, Hu H, Hoefsloot LH, Kannan S, Huygen PLM, Pennings RJE, Admiraal RJC, Kalscheuer VM, Kunst HPM, Kremer H. Next-generation sequencing identifies mutations of SMPX, which encodes the small muscle protein, X-linked, as a cause of progressive hearing impairment. Am J Hum Genet 2011; 88:628-34. [PMID: 21549342 DOI: 10.1016/j.ajhg.2011.04.012] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Revised: 04/07/2011] [Accepted: 04/18/2011] [Indexed: 01/12/2023] Open
Abstract
In a Dutch family with an X-linked postlingual progressive hearing impairment, a critical linkage interval was determined to span a region of 12.9 Mb flanked by the markers DXS7108 and DXS7110. This interval overlaps with the previously described DFNX4 locus and contains 75 annotated genes. Subsequent next-generation sequencing (NGS) detected one variant within the linkage interval, a nonsense mutation in SMPX. SMPX encodes the small muscle protein, X-linked (SMPX). Further screening was performed on 26 index patients from small families for which X-linked inheritance of nonsyndromic hearing impairment (NSHI) was not excluded. We detected a frameshift mutation in SMPX in one of the patients. Segregation analysis of both mutations in the families in whom they were found revealed that the mutations cosegregated with hearing impairment. Although we show that SMPX is expressed in many different organs, including the human inner ear, no obvious symptoms other than hearing impairment were observed in the patients. SMPX had previously been demonstrated to be specifically expressed in striated muscle and, therefore, seemed an unlikely candidate gene for hearing impairment. We hypothesize that SMPX functions in inner ear development and/or maintenance in the IGF-1 pathway, the integrin pathway through Rac1, or both.
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Affiliation(s)
- Margit Schraders
- Department of Otorhinolaryngology, Head and Neck Surgery, Nijmegen, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Abstract
Costameres are sub-membranous, Z-line associated structures found in striated muscle. They have been shown to have important roles in transmission of force from the sarcomere to the sarcolemma and extracellular matrix, maintaining mechanical integrity of the sarcolemma, and orchestrating mechanically related signaling. The costamere is akin to the more well-known focal adhesion complex present in most cells. The Z-line is a critical structural anchor for the sarcomere, but it is also a hot-spot for muscle cell signaling. Therefore functionally, the costamere represents a two-way signaling highway tethered between the Z-line and the extracellular matrix, relaying mechanical stress signals from outside the cell to intracellular signaling networks. In this role it can modulate myofibril growth and contraction. The major force generated by sarcomeres is transduced in the lateral direction from the sarcomere to the extracellular matrix through the costamere. Two major protein complexes have been described at the costamere: the dystrophin-glycoprotein complex and the integrin-vinculin-talin complex. The importance of these two protein complexes in striated muscle function has between demonstrated both in human disease and mouse models. Members of the dystrophin glycoprotein complex and integrins have both been reported to interact directly with filamin-C, thus linking costameric complexes with those present at the Z-line. Moreover, studies from our labs and others have shown that the Z-line proteins belonging to the PDZ-LIM domain protein family, enigma homolog (ENH) and cypher, may directly or indirectly be involved in this linkage. The following review will focus on the protein components of this linkage, their function in force transmission, and how the dysfunction or loss of proteins within these complexes contributes to muscular disease.
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Schoffstall B, LaBarbera VA, Brunet NM, Gavino BJ, Herring L, Heshmati S, Kraft BH, Inchausti V, Meyer NL, Moonoo D, Takeda AK, Chase PB. Interaction between troponin and myosin enhances contractile activity of myosin in cardiac muscle. DNA Cell Biol 2011; 30:653-9. [PMID: 21438758 DOI: 10.1089/dna.2010.1163] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Ca(2+) signaling in striated muscle cells is critically dependent upon thin filament proteins tropomyosin (Tm) and troponin (Tn) to regulate mechanical output. Using in vitro measurements of contractility, we demonstrate that even in the absence of actin and Tm, human cardiac Tn (cTn) enhances heavy meromyosin MgATPase activity by up to 2.5-fold in solution. In addition, cTn without Tm significantly increases, or superactivates sliding speed of filamentous actin (F-actin) in skeletal motility assays by at least 12%, depending upon [cTn]. cTn alone enhances skeletal heavy meromyosin's MgATPase in a concentration-dependent manner and with sub-micromolar affinity. cTn-mediated increases in myosin ATPase may be the cause of superactivation of maximum Ca(2+)-activated regulated thin filament sliding speed in motility assays relative to unregulated skeletal F-actin. To specifically relate this classical superactivation to cardiac muscle, we demonstrate the same response using motility assays where only cardiac proteins were used, where regulated cardiac thin filament sliding speeds with cardiac myosin are >50% faster than unregulated cardiac F-actin. We additionally demonstrate that the COOH-terminal mobile domain of cTnI is not required for this interaction or functional enhancement of myosin activity. Our results provide strong evidence that the interaction between cTn and myosin is responsible for enhancement of cross-bridge kinetics when myosin binds in the vicinity of Tn on thin filaments. These data imply a novel and functionally significant molecular interaction that may provide new insights into Ca(2+) activation in cardiac muscle cells.
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Transcriptional analysis of the titin cap gene. Mol Genet Genomics 2011; 285:261-72. [PMID: 21305318 DOI: 10.1007/s00438-011-0603-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Accepted: 01/23/2011] [Indexed: 10/18/2022]
Abstract
Mutations in titin cap (Tcap), also known as telethonin, cause limb-girdle muscular dystrophy type 2G (LGMD2G). Tcap is one of the titin interacting Z-disc proteins involved in the regulation and development of normal sarcomeric structure. Given the essential role of Tcap in establishing and maintaining normal skeletal muscle architecture, we were interested in determining the regulatory elements required for expression of this gene in myoblasts. We have defined a highly conserved 421 bp promoter proximal promoter fragment that contains two E boxes and multiple putative Mef2 binding sequences. This promoter can be activated by MyoD and myogenin in NIH3T3 fibroblast cells, and maintains the differentiated cell-specific expression pattern of the endogenous Tcap in C2C12 cells. We find that while both E boxes are required for full activation by MyoD or myogenin in NIH3T3 cells, the promoter proximal E box has a greater contribution to activation of this promoter in C2C12 cells and to activation by MyoD in NIH3T3 cells. Together, the data suggest an important role for MyoD in activating Tcap expression through the promoter proximal E box. We also show that myogenin is required for normal expression in vivo and physically binds to the Tcap promoter during embryogenesis.
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