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Weston TGR, Rees M, Gautel M, Fraternali F. Walking with giants: The challenges of variant impact assessment in the giant sarcomeric protein titin. WIREs Mech Dis 2024; 16:e1638. [PMID: 38155593 DOI: 10.1002/wsbm.1638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 12/01/2023] [Accepted: 12/04/2023] [Indexed: 12/30/2023]
Abstract
Titin, the so-called "third filament" of the sarcomere, represents a difficult challenge for the determination of damaging genetic variants. A single titin molecule extends across half the length of a sarcomere in striated muscle, fulfilling a variety of vital structural and signaling roles, and has been linked to an equally varied range of myopathies, resulting in a significant burden on individuals and healthcare systems alike. While the consequences of truncating variants of titin are well-documented, the ramifications of the missense variants prevalent in the general population are less so. We here present a compendium of titin missense variants-those that result in a single amino-acid substitution in coding regions-reported to be pathogenic and discuss these in light of the nature of titin and the variant position within the sarcomere and their domain, the structural, pathological, and biophysical characteristics that define them, and the methods used for characterization. Finally, we discuss the current knowledge and integration of the multiple fields that have contributed to our understanding of titin-related pathology and offer suggestions as to how these concurrent methodologies may aid the further development in our understanding of titin and hopefully extend to other, less well-studied giant proteins. This article is categorized under: Cardiovascular Diseases > Genetics/Genomics/Epigenetics Congenital Diseases > Genetics/Genomics/Epigenetics Congenital Diseases > Molecular and Cellular Physiology.
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Affiliation(s)
- Timir G R Weston
- Randall Centre for Cell & Molecular Biophysics, King's College London, London, UK
| | - Martin Rees
- Randall Centre for Cell & Molecular Biophysics, King's College London, London, UK
| | - Mathias Gautel
- Randall Centre for Cell & Molecular Biophysics, King's College London, London, UK
| | - Franca Fraternali
- Institute of Structural and Molecular Biology, University College London, London, UK
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2
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Insulin and Insulin-Like Growth Factor 1 Signaling Preserves Sarcomere Integrity in the Adult Heart. Mol Cell Biol 2022; 42:e0016322. [PMID: 36125265 PMCID: PMC9583714 DOI: 10.1128/mcb.00163-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Insulin and insulin-like growth factor 1 (IGF1) signaling is transduced by insulin receptor substrate 1 (IRS1) and IRS2. To elucidate physiological and redundant roles of insulin and IGF1 signaling in adult hearts, we generated mice with inducible cardiomyocyte-specific deletion of insulin and IGF1 receptors or IRS1 and IRS2. Both models developed dilated cardiomyopathy, and most mice died by 8 weeks post-gene deletion. Heart failure was characterized by cardiomyocyte loss and disarray, increased proapoptotic signaling, and increased autophagy. Suppression of autophagy by activating mTOR signaling did not prevent heart failure. Transcriptional profiling revealed reduced serum response factor (SRF) transcriptional activity and decreased mRNA levels of genes encoding sarcomere and gap junction proteins as early as 3 days post-gene deletion, in concert with ultrastructural evidence of sarcomere disruption and intercalated discs within 1 week after gene deletion. These data confirm conserved roles for constitutive insulin and IGF1 signaling in suppressing autophagic and apoptotic signaling in the adult heart. The present study also identifies an unexpected role for insulin and IGF1 signaling in regulating an SRF-mediated transcriptional program, which maintains expression of genes encoding proteins that support sarcomere integrity in the adult heart, reduction of which results in rapid development of heart failure.
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van der Pijl RJ, Domenighetti AA, Sheikh F, Ehler E, Ottenheijm CAC, Lange S. The titin N2B and N2A regions: biomechanical and metabolic signaling hubs in cross-striated muscles. Biophys Rev 2021; 13:653-677. [PMID: 34745373 PMCID: PMC8553726 DOI: 10.1007/s12551-021-00836-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 08/23/2021] [Indexed: 02/07/2023] Open
Abstract
Muscle specific signaling has been shown to originate from myofilaments and their associated cellular structures, including the sarcomeres, costameres or the cardiac intercalated disc. Two signaling hubs that play important biomechanical roles for cardiac and/or skeletal muscle physiology are the N2B and N2A regions in the giant protein titin. Prominent proteins associated with these regions in titin are chaperones Hsp90 and αB-crystallin, members of the four-and-a-half LIM (FHL) and muscle ankyrin repeat protein (Ankrd) families, as well as thin filament-associated proteins, such as myopalladin. This review highlights biological roles and properties of the titin N2B and N2A regions in health and disease. Special emphasis is placed on functions of Ankrd and FHL proteins as mechanosensors that modulate muscle-specific signaling and muscle growth. This region of the sarcomere also emerged as a hotspot for the modulation of passive muscle mechanics through altered titin phosphorylation and splicing, as well as tethering mechanisms that link titin to the thin filament system.
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Affiliation(s)
| | - Andrea A. Domenighetti
- Shirley Ryan AbilityLab, Chicago, IL USA
- Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL USA
| | - Farah Sheikh
- Division of Cardiology, School of Medicine, UC San Diego, La Jolla, CA USA
| | - Elisabeth Ehler
- Randall Centre for Cell and Molecular Biophysics, School of Cardiovascular Medicine and Sciences, King’s College London, London, UK
| | - Coen A. C. Ottenheijm
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ USA
- Department of Physiology, Amsterdam University Medical Centers, Amsterdam, The Netherlands
| | - Stephan Lange
- Division of Cardiology, School of Medicine, UC San Diego, La Jolla, CA USA
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
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4
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Zuo J, Zhan D, Xia J, Li H. Single-Molecule Force Spectroscopy Studies of Missense Titin Mutations That Are Likely Causing Cardiomyopathy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:12128-12137. [PMID: 34618459 PMCID: PMC9150697 DOI: 10.1021/acs.langmuir.1c02006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 09/20/2021] [Indexed: 06/13/2023]
Abstract
The giant muscle protein titin plays important roles in heart function. Mutations in titin have emerged as a major cause of familial cardiomyopathy. Missense mutations have been identified in cardiomyopathy patients; however, it is challenging to distinguish disease-causing mutations from benign ones. Given the importance of titin mechanics in heart function, it is critically important to elucidate the mechano-phenotypes of cardiomyopathy-causing mutations found in the elastic I-band part of cardiac titin. Using single-molecule atomic force microscopy (AFM) and equilibrium chemical denaturation, we investigated the mechanical and thermodynamic effects of two missense mutations, R57C-I94 and S22P-I84, found in the elastic I-band part of cardiac titin that were predicted to be likely causing cardiomyopathy by bioinformatics analysis. Our AFM results showed that mutation R57C had a significant destabilization effect on the I94 module. R57C reduced the mechanical unfolding force of I94 by ∼30-40 pN, accelerated the unfolding kinetics, and decelerated the folding. These effects collectively increased the unfolding propensity of I94, likely resulting in altered titin elasticity. In comparison, S22P led to only modest destabilization of I84, with a decrease in unfolding force by ∼10 pN. It is unlikely that such a modest destabilization would lead to a change in titin elasticity. These results will serve as the first step toward elucidating mechano-phenotypes of cardiomyopathy-causing mutations in the elastic I-band.
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Hypertrophic Cardiomyopathy: Diverse Pathophysiology Revealed by Genetic Research, Toward Future Therapy. Keio J Med 2020; 69:77-87. [PMID: 32224552 DOI: 10.2302/kjm.2019-0012-oa] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is an intractable disease that causes heart failure mainly due to unexplained severe cardiac hypertrophy and diastolic dysfunction. HCM, which occurs in 0.2% of the general population, is the most common cause of sudden cardiac death in young people. HCM has been studied extensively using molecular genetic approaches. Genes encoding cardiac β-myosin heavy chain, cardiac myosin-binding protein C, and troponin complex, which were originally identified as causative genes, were subsequently reported to be frequently implicated in HCM. Indeed, HCM has been considered a disease of sarcomere gene mutations. However, fewer than half of patients with HCM have mutations in sarcomere genes. The others have been documented to have mutations in cardiac proteins in various other locations, including the Z disc, sarcoplasmic reticulum, plasma membrane, nucleus, and mitochondria. Next-generation sequencing makes it possible to detect mutations at high throughput, and it has become increasingly common to identify multiple cardiomyopathy-causing gene mutations in a single HCM patient. Elucidating how mutations in different genes contribute to the disease pathophysiology will be a challenge. In studies using animal models, sarcomere mutations generally tend to increase myocardial Ca2+ sensitivity, and some mutations increase the activity of myosin ATPase. Clinical trials of drugs to treat HCM are ongoing, and further new therapies based on pathophysiological analyses of the causative genes are eagerly anticipated.
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Wang Y, Li D, Lu J, Chen L, Zhang S, Qi W, Li W, Xu H. Long noncoding RNA TTN-AS1 facilitates tumorigenesis and metastasis by maintaining TTN expression in skin cutaneous melanoma. Cell Death Dis 2020; 11:664. [PMID: 32820147 PMCID: PMC7441063 DOI: 10.1038/s41419-020-02895-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 08/01/2020] [Accepted: 08/03/2020] [Indexed: 01/23/2023]
Abstract
The antisense transcript, emanating from the opposite strand to a protein-coding or sense strand, has been reported to have critical roles in gene regulation. The perturbation of an antisense RNA can alter the expression of sense messenger RNAs. In this study, a long noncoding RNA TTN-AS1 (lncRNA-TTN-AS1), which is transcribed in the opposite direction of the human titin (TTN) gene, has been identified and explored in skin cutaneous melanoma (SKCM). We found that the expression of TTN and lncRNA-TTN-AS1 had a significantly positive correlation in SKCM cells. Functionally, ectopic expression of TTN and lncRNA-TTN-AS1 promoted SKCM tumorigenesis and metastasis both in vitro and in vivo. Moreover, knockdown of TTN partially abrogated lncRNA-TTN-AS1 induced SKCM tumorigenesis. Mechanistically, hypomethylation of transcription initiation site was responsible for lncRNA-TTN-AS1 high expression levels. LncRNA-TTN-AS1 facilitated SKCM progression by promoting TTN expression at both transcriptional and posttranscriptional levels. As detailed, lncRNA-TTN-AS1 had a significant effect on the increase of TTN promoter activity. Besides, lncRNA-TTN-AS1 also induced the accumulation of TTN in cytoplasm by increasing the stability of TTN mRNA. Clinically, we found that high TTN and lncRNA-TTN-AS1 expression were positively correlated with poor overall survival of SKCM patients, and may be considered as novel biomarkers and drug targets for SKCM patients.
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Affiliation(s)
- Ying Wang
- The Engineering Research Center of Synthetic Peptide Drug Discovery and Evaluation of Jiangsu Province, China Pharmaceutical University, Nanjing, 210009, China.,State Key Laboratory of Natural Medicines, Ministry of Education, China Pharmaceutical University, Nanjing, 210009, China
| | - Dongping Li
- The Engineering Research Center of Synthetic Peptide Drug Discovery and Evaluation of Jiangsu Province, China Pharmaceutical University, Nanjing, 210009, China.,State Key Laboratory of Natural Medicines, Ministry of Education, China Pharmaceutical University, Nanjing, 210009, China
| | - Jiqiang Lu
- The Engineering Research Center of Synthetic Peptide Drug Discovery and Evaluation of Jiangsu Province, China Pharmaceutical University, Nanjing, 210009, China.,State Key Laboratory of Natural Medicines, Ministry of Education, China Pharmaceutical University, Nanjing, 210009, China
| | - Lin Chen
- The Engineering Research Center of Synthetic Peptide Drug Discovery and Evaluation of Jiangsu Province, China Pharmaceutical University, Nanjing, 210009, China.,State Key Laboratory of Natural Medicines, Ministry of Education, China Pharmaceutical University, Nanjing, 210009, China
| | - Shengnan Zhang
- The Engineering Research Center of Synthetic Peptide Drug Discovery and Evaluation of Jiangsu Province, China Pharmaceutical University, Nanjing, 210009, China.,State Key Laboratory of Natural Medicines, Ministry of Education, China Pharmaceutical University, Nanjing, 210009, China
| | - Weiyan Qi
- The Engineering Research Center of Synthetic Peptide Drug Discovery and Evaluation of Jiangsu Province, China Pharmaceutical University, Nanjing, 210009, China.,State Key Laboratory of Natural Medicines, Ministry of Education, China Pharmaceutical University, Nanjing, 210009, China
| | - Weiguang Li
- The Engineering Research Center of Synthetic Peptide Drug Discovery and Evaluation of Jiangsu Province, China Pharmaceutical University, Nanjing, 210009, China.,State Key Laboratory of Natural Medicines, Ministry of Education, China Pharmaceutical University, Nanjing, 210009, China
| | - Hanmei Xu
- The Engineering Research Center of Synthetic Peptide Drug Discovery and Evaluation of Jiangsu Province, China Pharmaceutical University, Nanjing, 210009, China. .,State Key Laboratory of Natural Medicines, Ministry of Education, China Pharmaceutical University, Nanjing, 210009, China.
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Radke MH, Polack C, Methawasin M, Fink C, Granzier HL, Gotthardt M. Deleting Full Length Titin Versus the Titin M-Band Region Leads to Differential Mechanosignaling and Cardiac Phenotypes. Circulation 2020; 139:1813-1827. [PMID: 30700140 DOI: 10.1161/circulationaha.118.037588] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND Titin is a giant elastic protein that spans the half-sarcomere from Z-disk to M-band. It acts as a molecular spring and mechanosensor and has been linked to striated muscle disease. The pathways that govern titin-dependent cardiac growth and contribute to disease are diverse and difficult to dissect. METHODS To study titin deficiency versus dysfunction, the authors generated and compared striated muscle specific knockouts (KOs) with progressive postnatal loss of the complete titin protein by removing exon 2 (E2-KO) or an M-band truncation that eliminates proper sarcomeric integration, but retains all other functional domains (M-band exon 1/2 [M1/2]-KO). The authors evaluated cardiac function, cardiomyocyte mechanics, and the molecular basis of the phenotype. RESULTS Skeletal muscle atrophy with reduced strength, severe sarcomere disassembly, and lethality from 2 weeks of age were shared between the models. Cardiac phenotypes differed considerably: loss of titin leads to dilated cardiomyopathy with combined systolic and diastolic dysfunction-the absence of M-band titin to cardiac atrophy and preserved function. The elastic properties of M1/2-KO cardiomyocytes are maintained, while passive stiffness is reduced in the E2-KO. In both KOs, we find an increased stress response and increased expression of proteins linked to titin-based mechanotransduction (CryAB, ANKRD1, muscle LIM protein, FHLs, p42, Camk2d, p62, and Nbr1). Among them, FHL2 and the M-band signaling proteins p62 and Nbr1 are exclusively upregulated in the E2-KO, suggesting a role in the differential pathology of titin truncation versus deficiency of the full-length protein. The differential stress response is consistent with truncated titin contributing to the mechanical properties in M1/2-KOs, while low titin levels in E2-KOs lead to reduced titin-based stiffness and increased strain on the remaining titin molecules. CONCLUSIONS Progressive depletion of titin leads to sarcomere disassembly and atrophy in striated muscle. In the complete knockout, remaining titin molecules experience increased strain, resulting in mechanically induced trophic signaling and eventually dilated cardiomyopathy. The truncated titin in M1/2-KO helps maintain the passive properties and thus reduces mechanically induced signaling. Together, these findings contribute to the molecular understanding of why titin mutations differentially affect cardiac growth and have implications for genotype-phenotype relations that support a personalized medicine approach to the diverse titinopathies.
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Affiliation(s)
- Michael H Radke
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany (M.H.R., C.P., C.F., M.G.).,DZHK: German Centre for Cardiovascular Research, Partner Site, Berlin, Germany (M.H.R., M.G.)
| | - Christopher Polack
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany (M.H.R., C.P., C.F., M.G.)
| | - Mei Methawasin
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson (M.M., H.G.). The current affiliation for P.S. and T.S. is Department of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg University Mainz, Germany
| | - Claudia Fink
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany (M.H.R., C.P., C.F., M.G.)
| | - Henk L Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson (M.M., H.G.). The current affiliation for P.S. and T.S. is Department of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg University Mainz, Germany
| | - Michael Gotthardt
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany (M.H.R., C.P., C.F., M.G.).,DZHK: German Centre for Cardiovascular Research, Partner Site, Berlin, Germany (M.H.R., M.G.)
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8
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Kanduc D. The comparative biochemistry of viruses and humans: an evolutionary path towards autoimmunity. Biol Chem 2019; 400:629-638. [PMID: 30504522 DOI: 10.1515/hsz-2018-0271] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 11/07/2018] [Indexed: 11/15/2022]
Abstract
Analyses of the peptide sharing between five common human viruses (Borna disease virus, influenza A virus, measles virus, mumps virus and rubella virus) and the human proteome highlight a massive viral vs. human peptide overlap that is mathematically unexpected. Evolutionarily, the data underscore a strict relationship between viruses and the origin of eukaryotic cells. Indeed, according to the viral eukaryogenesis hypothesis and in light of the endosymbiotic theory, the first eukaryotic cell (our lineage) originated as a consortium consisting of an archaeal ancestor of the eukaryotic cytoplasm, a bacterial ancestor of the mitochondria and a viral ancestor of the nucleus. From a pathologic point of view, the peptide sequence similarity between viruses and humans may provide a molecular platform for autoimmune crossreactions during immune responses following viral infections/immunizations.
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Affiliation(s)
- Darja Kanduc
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, I-70124 Bari, Italy
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9
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Azad A, Poloni G, Sontayananon N, Jiang H, Gehmlich K. The giant titin: how to evaluate its role in cardiomyopathies. J Muscle Res Cell Motil 2019; 40:159-167. [PMID: 31147888 PMCID: PMC6726704 DOI: 10.1007/s10974-019-09518-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 05/28/2019] [Indexed: 01/02/2023]
Abstract
Titin, the largest protein known, has attracted a lot of interest in the cardiovascular field in recent years, since the discovery that truncating variants in titin are commonly found in patients with dilated cardiomyopathy. This review will discuss the contribution of variants in titin to inherited cardiac conditions (cardiomyopathies) and how model systems, such as animals and cellular systems, can help to provide insights into underlying disease mechanisms. It will also give an outlook onto exciting technological developments, such as in the field of CRISPR, which may facilitate future research on titin variants and their contributions to cardiomyopathies.
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Affiliation(s)
- Amar Azad
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, OX3 9DU, UK
- Swansea University Medical School, Swansea, SA2 8PP, UK
| | - Giulia Poloni
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, OX3 9DU, UK
| | - Naeramit Sontayananon
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, OX3 9DU, UK
| | - He Jiang
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, OX3 9DU, UK
| | - Katja Gehmlich
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, OX3 9DU, UK.
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, B15 2TT, UK.
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Fichna JP, Maruszak A, Żekanowski C. Myofibrillar myopathy in the genomic context. J Appl Genet 2018; 59:431-439. [PMID: 30203143 DOI: 10.1007/s13353-018-0463-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 08/30/2018] [Indexed: 12/31/2022]
Abstract
Myofibrillar myopathy (MFM) is a group of inherited muscular disorders characterized by myofibril dissolution and abnormal accumulation of degradation products. The diagnosis of muscular disorders based on clinical presentation is difficult due to phenotypic heterogeneity and overlapping symptoms. In addition, precise diagnosis does not always explain the disease etiopathology or the highly variable clinical course even among patients diagnosed with the same type of myopathy. The advent of high-throughput next-generation sequencing (NGS) has provided a successful and cost-effective strategy for identification of novel causative genes in myopathies, including MFM. So far, pathogenic mutations associated with MFM phenotype, including atypical MFM-like cases, have been identified in 17 genes: DES, CRYAB, MYOT, ZASP, FLNC, BAG3, FHL1, TTN, DNAJB6, PLEC, LMNA, ACTA1, HSPB8, KY, PYROXD1, and SQSTM + TIA1 (digenic). Most of these genes are also associated with other forms of muscle diseases. In addition, in many MFM patients, numerous genomic variants in muscle-related genes have been identified. The various myopathies and muscular dystrophies seem to form a single disease continuum; therefore, gene identification in one disease impacts the genetic etiology of the others. In this review, we describe the heterogeneity of the MFM genetic background focusing on the role of rare variants, the importance of whole genome sequencing in the identification of novel disease-associated mutations, and the emerging concept of variant load as the basis of the phenotypic heterogeneity.
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Affiliation(s)
- Jakub Piotr Fichna
- Department of Neurodegenerative Disorders, Mossakowski Medical Research Centre, Polish Academy of Sciences, 5 Pawinskiego St., 02-106, Warsaw, Poland.
| | - Aleksandra Maruszak
- Department of Neurodegenerative Disorders, Mossakowski Medical Research Centre, Polish Academy of Sciences, 5 Pawinskiego St., 02-106, Warsaw, Poland
| | - Cezary Żekanowski
- Department of Neurodegenerative Disorders, Mossakowski Medical Research Centre, Polish Academy of Sciences, 5 Pawinskiego St., 02-106, Warsaw, Poland
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11
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Ye L, Su L, Wang C, Loo S, Tee G, Tan S, Khin SW, Ko S, Su B, Cook SA. Truncations of the titin Z-disc predispose to a heart failure with preserved ejection phenotype in the context of pressure overload. PLoS One 2018; 13:e0201498. [PMID: 30063764 PMCID: PMC6067738 DOI: 10.1371/journal.pone.0201498] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/15/2018] [Indexed: 01/02/2023] Open
Abstract
Titin (TTN) Truncating variants (TTNtv) in the A-band of TTN predispose the mouse heart to systolic dysfunction when subjected to pressure-loading. However, the effects of TTNtv of the Z-disc are largely unexplored. A rat model of pressure-loaded heart is developed by trans-aortic constriction (TAC). Rats with TTNtv of the Z-disc were randomly assigned to TAC (Z-TAC) or sham-surgery (Z-Sham) and wildtype (WT) littermates served as controls (WT-TAC or WT-Sham). Left ventricular (LV) function was assessed by echocardiography. Pressure volume (PV) loops, histology and molecular profiling were performed eight months after surgery. Pressure-load by TAC increased LV mass in all cases when compared with Sham animals. Notably, systolic function was preserved in TAC animals throughout the study period, which was confirmed by terminal PV loops. Diastolic function was impaired in Z-disc TTNtv rats at baseline as compared to WT and became impaired further after TAC (dp/dtmin, mmHg/s): Z-TAC = -3435±763, WT-TAC = -6497±1299 (p<0.01). Z-TAC animals had greater cardiac fibrosis, with elevated collagen content and decreased vascular density as compared to WT-TAC animals associated with enhanced apoptosis of myocyte and non-myocyte populations. In the context of pressure overload, Z-disc TTNtv is associated with cardiac fibrosis, diastolic dysfunction, and capillary rarefaction in the absence of overt systolic dysfunction.
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Affiliation(s)
- Lei Ye
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
- * E-mail:
| | - Liping Su
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
| | - Chenxu Wang
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
| | - Szejie Loo
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
| | - Guizhen Tee
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
| | - Shihua Tan
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
| | - Sandar Win Khin
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
| | - Shijie Ko
- Duke-National University of Singapore Medical School, Singapore, Singapore
| | - Boyang Su
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
| | - Stuart A. Cook
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
- Duke-National University of Singapore Medical School, Singapore, Singapore
- National Heart and Lung Institute, Imperial College, London, United Kingdom
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12
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Four and a half LIM domain protein signaling and cardiomyopathy. Biophys Rev 2018; 10:1073-1085. [PMID: 29926425 DOI: 10.1007/s12551-018-0434-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 06/06/2018] [Indexed: 01/10/2023] Open
Abstract
Four and a half LIM domain (FHL) protein family members, FHL1 and FHL2, are multifunctional proteins that are enriched in cardiac muscle. Although they both localize within the cardiomyocyte sarcomere (titin N2B), they have been shown to have important yet unique functions within the context of cardiac hypertrophy and disease. Studies in FHL1-deficient mice have primarily uncovered mitogen-activated protein kinase (MAPK) scaffolding functions for FHL1 as part of a novel biomechanical stretch sensor within the cardiomyocyte sarcomere, which acts as a positive regulator of pressure overload-mediated cardiac hypertrophy. New data have highlighted a novel role for the serine/threonine protein phosphatase (PP5) as a deactivator of the FHL1-based biomechanical stretch sensor, which has implications in not only cardiac hypertrophy but also heart failure. In contrast, studies in FHL2-deficient mice have primarily uncovered an opposing role for FHL2 as a negative regulator of adrenergic-mediated signaling and cardiac hypertrophy, further suggesting unique functions targeted by FHL proteins in the "stressed" cardiomyocyte. In this review, we provide current knowledge of the role of FHL1 and FHL2 in cardiac muscle as it relates to their actions in cardiac hypertrophy and cardiomyopathy. A specific focus will be to dissect the pathways and protein-protein interactions that underlie FHLs' signaling role in cardiac hypertrophy as well as provide a comprehensive list of FHL mutations linked to cardiac disease, using evidence gained from genetic mouse models and human genetic studies.
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13
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Ehsan M, Jiang H, L Thomson K, Gehmlich K. When signalling goes wrong: pathogenic variants in structural and signalling proteins causing cardiomyopathies. J Muscle Res Cell Motil 2017; 38:303-316. [PMID: 29119312 PMCID: PMC5742121 DOI: 10.1007/s10974-017-9487-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 10/28/2017] [Indexed: 12/20/2022]
Abstract
Cardiomyopathies are a diverse group of cardiac disorders with distinct phenotypes, depending on the proteins and pathways affected. A substantial proportion of cardiomyopathies are inherited and those will be the focus of this review article. With the wide application of high-throughput sequencing in the practice of clinical genetics, the roles of novel genes in cardiomyopathies are recognised. Here, we focus on a subgroup of cardiomyopathy genes [TTN, FHL1, CSRP3, FLNC and PLN, coding for Titin, Four and a Half LIM domain 1, Muscle LIM Protein, Filamin C and Phospholamban, respectively], which, despite their diverse biological functions, all have important signalling functions in the heart, suggesting that disturbances in signalling networks can contribute to cardiomyopathies.
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Affiliation(s)
- Mehroz Ehsan
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, UK
| | - He Jiang
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, UK
| | - Kate L Thomson
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, UK
| | - Katja Gehmlich
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, UK.
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14
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Trivedi DV, Adhikari AS, Sarkar SS, Ruppel KM, Spudich JA. Hypertrophic cardiomyopathy and the myosin mesa: viewing an old disease in a new light. Biophys Rev 2017; 10:27-48. [PMID: 28717924 PMCID: PMC5803174 DOI: 10.1007/s12551-017-0274-6] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 06/12/2017] [Indexed: 12/15/2022] Open
Abstract
The sarcomere is an exquisitely designed apparatus that is capable of generating force, which in the case of the heart results in the pumping of blood throughout the body. At the molecular level, an ATP-dependent interaction of myosin with actin drives the contraction and force generation of the sarcomere. Over the past six decades, work on muscle has yielded tremendous insights into the workings of the sarcomeric system. We now stand on the cusp where the acquired knowledge of how the sarcomere contracts and how that contraction is regulated can be extended to an understanding of the molecular mechanisms of sarcomeric diseases, such as hypertrophic cardiomyopathy (HCM). In this review we present a picture that combines current knowledge of the myosin mesa, the sequestered state of myosin heads on the thick filament, known as the interacting-heads motif (IHM), their possible interaction with myosin binding protein C (MyBP-C) and how these interactions can be abrogated leading to hyper-contractility, a key clinical manifestation of HCM. We discuss the structural and functional basis of the IHM state of the myosin heads and identify HCM-causing mutations that can directly impact the equilibrium between the 'on state' of the myosin heads (the open state) and the IHM 'off state'. We also hypothesize a role of MyBP-C in helping to maintain myosin heads in the IHM state on the thick filament, allowing release in a graded manner upon adrenergic stimulation. By viewing clinical hyper-contractility as the result of the destabilization of the IHM state, our aim is to view an old disease in a new light.
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Affiliation(s)
- Darshan V Trivedi
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Arjun S Adhikari
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Saswata S Sarkar
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Kathleen M Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA. .,Department of Pediatrics (Cardiology), Stanford University School of Medicine, Stanford, CA, 94305, USA.
| | - James A Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA.
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15
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Abstract
Cardiomyopathies represent a heterogeneous group of diseases that negatively affect heart function. Primary cardiomyopathies specifically target the myocardium, and may arise from genetic [hypertrophic cardiomyopathy (HCM), arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D), mitochondrial cardiomyopathy] or genetic and acquired [dilated cardiomyopathy (DCM), restrictive cardiomyopathy (RCM)] etiology. Modern genomics has identified mutations that are common in these populations, while in vitro and in vivo experimentation with these mutations have provided invaluable insight into the molecular mechanisms native to these diseases. For example, increased myosin heavy chain (MHC) binding and ATP utilization lead to the hypercontractile sarcomere in HCM, while abnormal protein–protein interaction and impaired Ca2+ flux underlie the relaxed sarcomere of DCM. Furthermore, expanded access to genetic testing has facilitated identification of potential risk factors that appear through inheritance and manifest sometimes only in the advanced stages of the disease. In this review, we discuss the genetic and molecular abnormalities unique to and shared between these primary cardiomyopathies and discuss some of the important advances made using more traditional basic science experimentation.
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16
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Genetic epidemiology of titin-truncating variants in the etiology of dilated cardiomyopathy. Biophys Rev 2017; 9:207-223. [PMID: 28510119 PMCID: PMC5498329 DOI: 10.1007/s12551-017-0265-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 04/10/2017] [Indexed: 02/07/2023] Open
Abstract
Heart failure (HF) is a complex clinical syndrome defined by the inability of the heart to pump enough blood to meet the body's metabolic demands. Major causes of HF are cardiomyopathies (diseases of the myocardium associated with mechanical and/or electrical dysfunction), among which the most common form is dilated cardiomyopathy (DCM). DCM is defined by ventricular chamber enlargement and systolic dysfunction with normal left ventricular wall thickness, which leads to progressive HF. Over 60 genes are linked to the etiology of DCM. Titin (TTN) is the largest known protein in biology, spanning half the cardiac sarcomere and, as such, is a basic structural and functional unit of striated muscles. It is essential for heart development as well as mechanical and regulatory functions of the sarcomere. Next-generation sequencing (NGS) in clinical DCM cohorts implicated truncating variants in titin (TTNtv) as major disease alleles, accounting for more than 25% of familial DCM cases, but these variants have also been identified in 2-3% of the general population, where these TTNtv blur diagnostic and clinical utility. Taking into account the published TTNtv and their association to DCM, it becomes clear that TTNtv harm the heart with position-dependent occurrence, being more harmful when present in the A-band TTN, presumably with dominant negative/gain-of-function mechanisms. However, these insights are challenged by the depiction of position-independent toxicity of TTNtv acting via haploinsufficient alleles, which are sufficient to induce cardiac pathology upon stress. In the current review, we provide an overview of TTN and discuss studies investigating various TTN mutations. We also present an overview of different mechanisms postulated or experimentally validated in the pathogenicity of TTNtv. DCM-causing genes are also discussed with respect to non-truncating mutations in the etiology of DCM. One way of understanding pathogenic variants is probably to understand the context in which they may or may not affect protein-protein interactions, changes in cell signaling, and substrate specificity. In this regard, we also provide a brief overview of TTN interactions in situ. Quantitative models in the risk assessment of TTNtv are also discussed. In summary, we highlight the importance of gene-environment interactions in the etiology of DCM and further mechanistic studies used to delineate the pathways which could be targeted in the management of DCM.
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17
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Abstract
Striated cardiac and skeletal muscles play very different roles in the body, but they are similar at the molecular level. In particular, contraction, regardless of the type of muscle, is a precise and complex process involving the integral protein myofilaments and their associated regulatory components. The smallest functional unit of muscle contraction is the sarcomere. Within the sarcomere can be found a sophisticated ensemble of proteins associated with the thick filaments (myosin, myosin binding protein-C, titin, and obscurin) and thin myofilaments (actin, troponin, tropomyosin, nebulin, and nebulette). These parallel thick and thin filaments slide across one another, pulling the two ends of the sarcomere together to regulate contraction. More specifically, the regulation of both timing and force of contraction is accomplished through an intricate network of intra- and interfilament interactions belonging to each myofilament. This review introduces the sarcomere proteins involved in striated muscle contraction and places greater emphasis on the more recently identified and less well-characterized myofilaments: cardiac myosin binding protein-C, titin, nebulin, and obscurin. © 2017 American Physiological Society. Compr Physiol 7:675-692, 2017.
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Affiliation(s)
- Brian Leei Lin
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois, USA
| | - Taejeong Song
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois, USA.,Department of Internal Medicine, Heart, Lung and Vascular Institute, Division of Cardiovascular Health and Sciences, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Sakthivel Sadayappan
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois, USA.,Department of Internal Medicine, Heart, Lung and Vascular Institute, Division of Cardiovascular Health and Sciences, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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18
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Bogomolovas J, Fleming JR, Anderson BR, Williams R, Lange S, Simon B, Khan MM, Rudolf R, Franke B, Bullard B, Rigden DJ, Granzier H, Labeit S, Mayans O. Exploration of pathomechanisms triggered by a single-nucleotide polymorphism in titin's I-band: the cardiomyopathy-linked mutation T2580I. Open Biol 2016; 6:160114. [PMID: 27683155 PMCID: PMC5043576 DOI: 10.1098/rsob.160114] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 09/01/2016] [Indexed: 02/06/2023] Open
Abstract
Missense single-nucleotide polymorphisms (mSNPs) in titin are emerging as a main causative factor of heart failure. However, distinguishing between benign and disease-causing mSNPs is a substantial challenge. Here, we research the question of whether a single mSNP in a generic domain of titin can affect heart function as a whole and, if so, how. For this, we studied the mSNP T2850I, seemingly linked to arrhythmogenic right ventricular cardiomyopathy (ARVC). We used structural biology, computational simulations and transgenic muscle in vivo methods to track the effect of the mutation from the molecular to the organismal level. The data show that the T2850I exchange is compatible with the domain three-dimensional fold, but that it strongly destabilizes it. Further, it induces a change in the conformational dynamics of the titin chain that alters its reactivity, causing the formation of aberrant interactions in the sarcomere. Echocardiography of knock-in mice indicated a mild diastolic dysfunction arising from increased myocardial stiffness. In conclusion, our data provide evidence that single mSNPs in titin's I-band can alter overall muscle behaviour. Our suggested mechanisms of disease are the development of non-native sarcomeric interactions and titin instability leading to a reduced I-band compliance. However, understanding the T2850I-induced ARVC pathology mechanistically remains a complex problem and will require a deeper understanding of the sarcomeric context of the titin region affected.
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Affiliation(s)
- Julius Bogomolovas
- Department of Integrative Pathophysiology, Medical Faculty Mannheim, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool, L69 7ZB, UK
| | - Jennifer R Fleming
- Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool, L69 7ZB, UK Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Brian R Anderson
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85724, USA
| | - Rhys Williams
- Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool, L69 7ZB, UK Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Stephan Lange
- School of Medicine, University of California San Diego, 9500 Gilman Drive, MC-0613C, La Jolla, CA 92093, USA
| | - Bernd Simon
- European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Muzamil M Khan
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, Paul-Wittsackstraße 110, 68163 Mannheim, Germany Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Rüdiger Rudolf
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, Paul-Wittsackstraße 110, 68163 Mannheim, Germany Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Barbara Franke
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Belinda Bullard
- Department of Biology, University of York, York YO10 5DD, UK
| | - Daniel J Rigden
- Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool, L69 7ZB, UK
| | - Henk Granzier
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85724, USA
| | - Siegfried Labeit
- Department of Integrative Pathophysiology, Medical Faculty Mannheim, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany
| | - Olga Mayans
- Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool, L69 7ZB, UK Department of Biology, University of Konstanz, 78457 Konstanz, Germany
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19
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Akinrinade O, Koskenvuo JW, Alastalo TP. Prevalence of Titin Truncating Variants in General Population. PLoS One 2015; 10:e0145284. [PMID: 26701604 PMCID: PMC4689403 DOI: 10.1371/journal.pone.0145284] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 12/02/2015] [Indexed: 11/29/2022] Open
Abstract
Background Truncating titin (TTN) mutations, especially in A-band region, represent the most common cause of dilated cardiomyopathy (DCM). Clinical interpretation of these variants can be challenging, as these variants are also present in reference populations. We carried out systematic analyses of TTN truncating variants (TTNtv) in publicly available reference populations, including, for the first time, data from Exome Aggregation Consortium (ExAC). The goal was to establish more accurate estimate of prevalence of different TTNtv to allow better clinical interpretation of these findings. Methods and Results Using data from 1000 Genomes Project, Exome Sequencing Project (ESP) and ExAC, we estimated the prevalence of TTNtv in the population. In the three population datasets, 52–54% of TTNtv were not affecting all TTN transcripts. The frequency of truncations affecting all transcripts in ExAC was 0.36% (0.32% - 0.41%, 95% CI) and 0.19% (0.16% - 0.23%, 95% CI) for those affecting the A-band. In the A-band region, the prevalences of frameshift, nonsense and essential splice site variants were 0.057%, 0.090%, and 0.047% respectively. Cga/Tga (arginine/nonsense–R/*) transitional change at CpG mutation hotspots was the most frequent type of TTN nonsense mutation accounting for 91.3% (21/23) of arginine residue nonsense mutation (R/*) at TTN A-band region. Non-essential splice-site variants had significantly lower proportion of private variants and higher proportion of low-frequency variants compared to essential splice-site variants (P = 0.01; P = 5.1 X 10−4, respectively). Conclusion A-band TTNtv are more rare in the general population than previously reported. Based on this analysis, one in 500 carries a truncation in TTN A-band suggesting the penetrance of these potentially harmful variants is still poorly understood, and some of these variants do not manifest as autosomal dominant DCM. This calls for caution when interpreting TTNtv in individuals and families with no history of DCM. Considering the size of TTN, expertise in DNA library preparation, high coverage NGS strategies, validated bioinformatics approach, accurate variant assessment strategy, and confirmatory sequencing are prerequisites for reliable evaluation of TTN in clinical settings, and ideally with the inclusion of mRNA and/or protein level assessment for a definite diagnosis.
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Affiliation(s)
- Oyediran Akinrinade
- Children’s Hospital Helsinki, Institute of Clinical Medicine, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland
| | - Juha W. Koskenvuo
- Blueprint Genetics, Helsinki, Finland
- Department of Clinical Physiology and Nuclear Medicine, HUS Medical Imaging Center, Helsinki University Central Hospital and University of Helsinki, Finland
| | - Tero-Pekka Alastalo
- Children’s Hospital Helsinki, Institute of Clinical Medicine, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland
- Blueprint Genetics, Helsinki, Finland
- * E-mail:
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20
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Gerull B. The Rapidly Evolving Role of Titin in Cardiac Physiology and Cardiomyopathy. Can J Cardiol 2015; 31:1351-9. [DOI: 10.1016/j.cjca.2015.08.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 08/03/2015] [Accepted: 08/19/2015] [Indexed: 12/30/2022] Open
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21
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Kimura A. Molecular genetics and pathogenesis of cardiomyopathy. J Hum Genet 2015; 61:41-50. [PMID: 26178429 DOI: 10.1038/jhg.2015.83] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 06/15/2015] [Indexed: 12/19/2022]
Abstract
Cardiomyopathy is defined as a disease of functional impairment in the cardiac muscle and its etiology includes both extrinsic and intrinsic factors. Cardiomyopathy caused by the intrinsic factors is called as primary cardiomyopathy of which two major clinical phenotypes are hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Genetic approaches have revealed the disease genes for hereditary primary cardiomyopathy and functional studies have demonstrated that characteristic functional alterations induced by the disease-associated mutations are closely related to the clinical types, such that increased and decreased Ca(2+) sensitivities of muscle contraction are associated with HCM and DCM, respectively. In addition, recent studies have suggested that mutations in the Z-disc components found in HCM and DCM may result in increased and decreased stiffness of sarcomere, respectively. Moreover, functional analysis of mutations in the other components of cardiac muscle have suggested that the altered response to metabolic stresses is associated with cardiomyopathy, further indicating the heterogeneity in the etiology and pathogenesis of cardiomyopathy.
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Affiliation(s)
- Akinori Kimura
- Department of Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
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22
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The sarcomeric M-region: a molecular command center for diverse cellular processes. BIOMED RESEARCH INTERNATIONAL 2015; 2015:714197. [PMID: 25961035 PMCID: PMC4413555 DOI: 10.1155/2015/714197] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 02/08/2015] [Indexed: 02/07/2023]
Abstract
The sarcomeric M-region anchors thick filaments and withstands the mechanical stress of contractions by deformation, thus enabling distribution of physiological forces along the length of thick filaments. While the role of the M-region in supporting myofibrillar structure and contractility is well established, its role in mediating additional cellular processes has only recently started to emerge. As such, M-region is the hub of key protein players contributing to cytoskeletal remodeling, signal transduction, mechanosensing, metabolism, and proteasomal degradation. Mutations in genes encoding M-region related proteins lead to development of severe and lethal cardiac and skeletal myopathies affecting mankind. Herein, we describe the main cellular processes taking place at the M-region, other than thick filament assembly, and discuss human myopathies associated with mutant or truncated M-region proteins.
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23
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Abstract
The giant sarcomeric protein titin is a key determinant of myocardial passive stiffness and stress-sensitive signaling. Titin stiffness is modulated by isoform variation, phosphorylation by protein kinases, and, possibly, oxidative stress through disulfide bond formation. Titin has also emerged as an important human disease gene. Early studies in patients with dilated cardiomyopathy (DCM) revealed shifts toward more compliant isoforms, an adaptation that offsets increases in passive stiffness based on the extracellular matrix. Similar shifts are observed in heart failure with preserved ejection fraction. In contrast, hypophosphorylation of PKA/G sites contributes to a net increase in cardiomyocyte resting tension in heart failure with preserved ejection fraction. More recently, titin mutations have been recognized as the most common etiology of inherited DCM. In addition, some DCM-causing mutations affect RBM20, a titin splice factor. Titin mutations are a rare cause of hypertrophic cardiomyopathy and also underlie some cases of arrhythmogenic right ventricular dysplasia. Finally, mutations of genes encoding proteins that interact with and/or bind to titin are responsible for both DCM and hypertrophic cardiomyopathy. Targeting titin as a therapeutic strategy is in its infancy, but it could potentially involve manipulation of isoforms, posttranslational modifications, and upregulation of normal protein in patients with disease-causing mutations.
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24
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Chauveau C, Rowell J, Ferreiro A. A rising titan: TTN review and mutation update. Hum Mutat 2014; 35:1046-59. [PMID: 24980681 DOI: 10.1002/humu.22611] [Citation(s) in RCA: 173] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 06/20/2014] [Indexed: 01/10/2023]
Abstract
The 364 exon TTN gene encodes titin (TTN), the largest known protein, which plays key structural, developmental, mechanical, and regulatory roles in cardiac and skeletal muscles. Prior to next-generation sequencing (NGS), routine analysis of the whole TTN gene was impossible due to its giant size and complexity. Thus, only a few TTN mutations had been reported and the general incidence and spectrum of titinopathies was significantly underestimated. In the last months, due to the widespread use of NGS, TTN is emerging as a major gene in human-inherited disease. So far, 127 TTN disease-causing mutations have been reported in patients with at least 10 different conditions, including isolated cardiomyopathies, purely skeletal muscle phenotypes, or infantile diseases affecting both types of striated muscles. However, the identification of TTN variants in virtually every individual from control populations, as well as the multiplicity of TTN isoforms and reference sequences used, stress the difficulties in assessing the relevance, inheritance, and correlation with the phenotype of TTN sequence changes. In this review, we provide the first comprehensive update of the TTN mutations reported and discuss their distribution, molecular mechanisms, associated phenotypes, transmission pattern, and phenotype-genotype correlations, alongside with their implications for basic research and for human health.
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Affiliation(s)
- Claire Chauveau
- Inserm, U787 Myology Group, Institut de Myologie, Groupe Hospitalier Pitié-Salpêtrière, Paris, France; UPMC, UMR787, Paris, France
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25
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Alegre-Cebollada J, Kosuri P, Giganti D, Eckels E, Rivas-Pardo JA, Hamdani N, Warren CM, Solaro RJ, Linke WA, Fernández JM. S-glutathionylation of cryptic cysteines enhances titin elasticity by blocking protein folding. Cell 2014; 156:1235-1246. [PMID: 24630725 DOI: 10.1016/j.cell.2014.01.056] [Citation(s) in RCA: 147] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 10/17/2013] [Accepted: 01/24/2014] [Indexed: 12/16/2022]
Abstract
The giant elastic protein titin is a determinant factor in how much blood fills the left ventricle during diastole and thus in the etiology of heart disease. Titin has been identified as a target of S-glutathionylation, an end product of the nitric-oxide-signaling cascade that increases cardiac muscle elasticity. However, it is unknown how S-glutathionylation may regulate the elasticity of titin and cardiac tissue. Here, we show that mechanical unfolding of titin immunoglobulin (Ig) domains exposes buried cysteine residues, which then can be S-glutathionylated. S-glutathionylation of cryptic cysteines greatly decreases the mechanical stability of the parent Ig domain as well as its ability to fold. Both effects favor a more extensible state of titin. Furthermore, we demonstrate that S-glutathionylation of cryptic cysteines in titin mediates mechanochemical modulation of the elasticity of human cardiomyocytes. We propose that posttranslational modification of cryptic residues is a general mechanism to regulate tissue elasticity.
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Affiliation(s)
| | - Pallav Kosuri
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA; Graduate Program in Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - David Giganti
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Edward Eckels
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA; Columbia College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | | | - Nazha Hamdani
- Department of Cardiovascular Physiology, Ruhr University Bochum, 44780 Bochum, Germany
| | - Chad M Warren
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - R John Solaro
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Wolfgang A Linke
- Department of Cardiovascular Physiology, Ruhr University Bochum, 44780 Bochum, Germany
| | - Julio M Fernández
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
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26
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Abstract
The giant protein titin forms a unique filament network in cardiomyocytes, which engages in both mechanical and signaling functions of the heart. TTN, which encodes titin, is also a major human disease gene. In this review, we cover the roles of cardiac titin in normal and failing hearts, with a special emphasis on the contribution of titin to diastolic stiffness. We provide an update on disease-associated titin mutations in cardiac and skeletal muscles and summarize what is known about the impact of protein-protein interactions on titin properties and functions. We discuss the importance of titin-isoform shifts and titin phosphorylation, as well as titin modifications related to oxidative stress, in adjusting the diastolic stiffness of the healthy and the failing heart. Along the way we distinguish among titin alterations in systolic and in diastolic heart failure and ponder the evidence for titin stiffness as a potential target for pharmacological intervention in heart disease.
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Affiliation(s)
- Wolfgang A Linke
- From the Department of Cardiovascular Physiology, Ruhr University Bochum, Bochum, Germany
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28
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Abstract
PURPOSE OF REVIEW Hypertrophic cardiomyopathy (HCM), the most common inherited cardiac disorder, exhibits remarkable genetic and clinical heterogeneity. This manuscript reviews recent discoveries of disease-causing genes and their clinical consequences, and provides an overview of research that aims to elucidate how HCM ensues from a single-nucleotide mutation. RECENT FINDINGS The spectrum of genes that are mutated in HCM has expanded. In combination with newly developed sequencing technologies, there are now robust strategies for gene-based diagnosis in HCM. Understanding the molecular pathophysiology of HCM has emerged from the study of genetically engineered animal models of disease, and new data indicate important roles for altered intracellular Ca²⁺ regulation and oxidative stress. Pharmacologic strategies to normalize these processes show promise in attenuating HCM in experimental models. SUMMARY The current repertoire of HCM genes allows effective gene-based diagnosis, information that enables accurate assessment of disease risk in family members, and provides some insight into clinical course. From mechanistic insights gleaned from fundamental investigations of experimental HCM models, novel therapeutic targets that may provide new benefits for HCM patients have surfaced.
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29
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Novel mutations in the sarcomeric protein myopalladin in patients with dilated cardiomyopathy. Eur J Hum Genet 2012; 21:294-300. [PMID: 22892539 DOI: 10.1038/ejhg.2012.173] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Recently, missense mutations in titin-associated proteins have been linked to the pathogenesis of dilated cardiomyopathy (DCM). The objective of this study was to search for novel disease-associated mutations in the two human titin-binding proteins myopalladin and its amino-terminal-interacting partner cardiac ankyrin-repeat protein (CARP). In a cohort of 255 cases with familial and sporadic DCM, we analyzed the coding regions and all corresponding intron flanks located in the MYPN and CARP-encoding ANKRD1 gene. Two heterozygous missense mutations were detected in the MYPN gene (p.R955W and p.P961L), but neither of these mutations was found in 300 healthy controls. Both mutations were located in the α-actinin-binding region of myopalladin. Endomyocardial biopsies from the p.R955W carrier showed normal subcellular localization of myopalladin and α-actinin in cardiac myocytes, while their regular sarcomeric staining pattern was significantly disrupted in the p.P961L carrier, indicating that disturbed myofibrillogenesis and altered sarcomere assembly are the cause of the disease. In the ANKRD1 gene, we identified synonymous base exchanges (c.108T>C and c.-79C>T, respectively), but no non-synonymous mutations. In summary, we have identified novel missense mutations in the third immunoglobulin-like domain of myopalladin, which have either no or profound effects on the molecular composition of the sarcomere. According to our epidemiological data, the prevalence of ANKRD1 mutations seems to be lower than that of its binding partner myopalladin, indicating the clinical significance of myopalladin for the functional integrity of the sarcomeric apparatus and the protection against DCM.
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Raskin A, Lange S, Banares K, Lyon RC, Zieseniss A, Lee LK, Yamazaki KG, Granzier HL, Gregorio CC, McCulloch AD, Omens JH, Sheikh F. A novel mechanism involving four-and-a-half LIM domain protein-1 and extracellular signal-regulated kinase-2 regulates titin phosphorylation and mechanics. J Biol Chem 2012; 287:29273-84. [PMID: 22778266 DOI: 10.1074/jbc.m112.372839] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Understanding mechanisms underlying titin regulation in cardiac muscle function is of critical importance given recent compelling evidence that highlight titin mutations as major determinants of human cardiomyopathy. We previously identified a cardiac biomechanical stress-regulated complex at the cardiac-specific N2B region of titin that includes four-and-a-half LIM domain protein-1 (Fhl1) and components of the mitogen-activated protein signaling cascade, which impacted muscle compliance in Fhl1 knock-out cardiac muscle. However, direct regulation of these molecular components in mediating titin N2B function remained unresolved. Here we identify Fhl1 as a novel negative regulator of titin N2B levels and phosphorylation-mediated mechanics. We specifically identify titin N2B as a novel substrate of extracellular signal regulated-kinase-2 (Erk2) and demonstrate that Fhl1 directly interferes with Erk2-mediated titin-N2B phosphorylation. We highlight the critical region in titin-N2B that interacts with Fhl1 and residues that are dependent on Erk2-mediated phosphorylation in situ. We also propose a potential mechanism for a known titin-N2B cardiomyopathy-causing mutation that involves this regulatory complex. These studies shed light on a novel mechanism regulating titin-N2B mechano-signaling as well as suggest that dysfunction of these pathways could be important in cardiac disease states affecting muscle compliance.
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Affiliation(s)
- Anna Raskin
- Department of Medicine, University of California-San Diego, La Jolla, CA 92093, USA
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The mutations associated with dilated cardiomyopathy. Biochem Res Int 2012; 2012:639250. [PMID: 22830024 PMCID: PMC3399391 DOI: 10.1155/2012/639250] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Revised: 04/25/2012] [Accepted: 05/17/2012] [Indexed: 01/18/2023] Open
Abstract
Cardiomyopathy is an important cause of heart failure and a major indication for heart transplantation in children and adults. This paper describes the state of the genetic knowledge of dilated cardiomyopathy (DCM). The identification of the causing mutation is important since presymptomatic interventions of DCM have proven value in preventing morbidity and mortality. Additionally, as in general in genetic studies, the identification of the mutated genes has a direct clinical impact for the families and population involved. Identifying causative mutations immediately amplifies the possibilities for disease prevention through carrier screening and prenatal testing. This often lifts a burden of social isolation from affected families, since healthy family members can be assured of having healthy children. Identification of the mutated genes holds the potential to lead to the understanding of disease etiology, pathophysiology, and therefore potential therapy. This paper presents the genetic variations, or disease-causing mutations, contributing to the pathogenesis of hereditary DCM, and tries to relate these to the functions of the mutated genes.
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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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Pasipoularides A. LV twisting and untwisting in HCM: ejection begets filling. Diastolic functional aspects of HCM. Am Heart J 2011; 162:798-810. [PMID: 22093194 DOI: 10.1016/j.ahj.2011.08.019] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Accepted: 08/21/2011] [Indexed: 12/31/2022]
Abstract
Conventional and emerging concepts on mechanisms by which hypertrophic cardiomyopathy (HCM) engenders diastolic dysfunction are surveyed. A shift from familiar left ventricular (LV) diastolic function approaches to large-scale (twist-untwist) and small-scale (titin unfolding-refolding, etc.) wall rebound models, incorporating interaction and dynamic distortions and rearrangements of myofiber sheets and ultrastructural constituents, is suggested. Such an emerging new paradigm of diastolic dynamics, emphasizing the relationship of myofiber sheet and ultraconstituent distortion to LV mechanics and end-systolic shape, might clarify intricate patterns of early diastolic rebound and suction, needed for LV filling in many of the polymorphic phenotypes of HCM.
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Taylor M, Graw S, Sinagra G, Barnes C, Slavov D, Brun F, Pinamonti B, Salcedo EE, Sauer W, Pyxaras S, Anderson B, Simon B, Bogomolovas J, Labeit S, Granzier H, Mestroni L. Genetic variation in titin in arrhythmogenic right ventricular cardiomyopathy-overlap syndromes. Circulation 2011; 124:876-85. [PMID: 21810661 PMCID: PMC3167235 DOI: 10.1161/circulationaha.110.005405] [Citation(s) in RCA: 210] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Accepted: 06/14/2011] [Indexed: 12/16/2022]
Abstract
BACKGROUND Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited genetic myocardial disease characterized by fibrofatty replacement of the myocardium and a predisposition to cardiac arrhythmias and sudden death. We evaluated the cardiomyopathy gene titin (TTN) as a candidate ARVC gene because of its proximity to an ARVC locus at position 2q32 and the connection of the titin protein to the transitional junction at intercalated disks. METHODS AND RESULTS All 312 titin exons known to be expressed in human cardiac titin and the complete 3' untranslated region were sequenced in 38 ARVC families. Eight unique TTN variants were detected in 7 families, including a prominent Thr2896Ile mutation that showed complete segregation with the ARVC phenotype in 1 large family. The Thr2896IIe mutation maps within a highly conserved immunoglobulin-like fold (Ig10 domain) located in the spring region of titin. Native gel electrophoresis, nuclear magnetic resonance, intrinsic fluorescence, and proteolysis assays of wild-type and mutant Ig10 domains revealed that the Thr2896IIe exchange reduces the structural stability and increases the propensity for degradation of the Ig10 domain. The phenotype of TTN variant carriers was characterized by a history of sudden death (5 of 7 families), progressive myocardial dysfunction causing death or heart transplantation (8 of 14 cases), frequent conduction disease (11 of 14), and incomplete penetrance (86%). CONCLUSIONS Our data provide evidence that titin mutations can cause ARVC, a finding that further expands the origin of the disease beyond desmosomal proteins. Structural impairment of the titin spring is a likely cause of ARVC and constitutes a novel mechanism underlying myocardial remodeling and sudden cardiac death.
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Affiliation(s)
- Matthew Taylor
- Adult Medical Genetics Program and Division of Cardiology, University of Colorado Denver, Aurora, USA.
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Kimura A. Contribution of genetic factors to the pathogenesis of dilated cardiomyopathy: the cause of dilated cardiomyopathy: genetic or acquired? (genetic-side). Circ J 2011; 75:1756-65; discussion 1765. [PMID: 21617319 DOI: 10.1253/circj.cj-11-0368] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dilated cardiomyopathy (DCM) is characterized by dilated ventricles and systolic dysfunction. Its etiology is not fully unraveled, but both extrinsic and intrinsic factors are considered to be involved. The intrinsic factors include genetic variations in the genes (ie, disease-causing mutations and disease-associated polymorphisms), which play key roles in controlling the susceptibility to the disease by affecting the performance, regulation, and/or maintenance of cardiac function. DCM can be classified into 2 types: hereditary and non-hereditary. The genetic variations, or disease-causing mutations, contributing to the pathogenesis of hereditary DCM can be found in various genes, especially those for sarcolemma elements, contractile elements, Z-disc elements, sarcoplasmic elements, and nuclear lamina elements of cardiomyocytes. On the other hand, disease-associated polymorphisms, which control the susceptibility to non-hereditary DCM, may be found in genes expressing not only in cardiomyocytes but also other non-cardiac cells involved in the immune system. Because functional alterations caused by these genetic variations can be classified into several categories, it is necessary to understand the pathogenesis and hence to develop diagnostic and therapeutic strategies for both hereditary and non-hereditary DCM from the viewpoint of genetic factors.
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Affiliation(s)
- Akinori Kimura
- Department of Molecular Pathogenesis, Medical Research Institute, and Laboratory of Genome Diversity, Graduate School of Biomedical Science, Tokyo Medical and Dental University
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Abstract
Mechanosensation (the ultimate conversion of a mechanical stimulus into a biochemical signal) as well as mechanotransduction (transmission of mechanically induced signals) belong to the most fundamental processes in biology. These effects, because of their dynamic nature, are particularly important for the cardiovascular system. Therefore, it is not surprising that defects in cardiac mechanosensation, are associated with various types of cardiomyopathy and heart failure. However, our current knowledge regarding the genetic basis of impaired mechanosensation in the cardiovascular system is beginning to shed light on this subject and is at the centre of this brief review.
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Kimura A. Molecular basis of hereditary cardiomyopathy: abnormalities in calcium sensitivity, stretch response, stress response and beyond. J Hum Genet 2010; 55:81-90. [PMID: 20075948 DOI: 10.1038/jhg.2009.138] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cardiomyopathy is caused by functional abnormality of cardiac muscle. The functional abnormality involved in its etiology includes both extrinsic and intrinsic factors, and cardiomyopathy caused by the intrinsic factors is called as idiopathic or primary cardiomyopathy. There are several clinical types of primary cardiomyopathy including hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Linkage studies and candidate gene approaches have explored the disease genes for hereditary primary cardiomyopathy. The most notable finding was that mutations in the same disease gene can be found in different clinical types of cardiomyopathy. Functional analyses of disease-related mutations have revealed that characteristic functional alterations are associated with the clinical types, such that increased and decreased Ca(2+) sensitivity due to sarcomere mutations are associated with HCM and DCM, respectively. In addition, our recent studies have suggested that mutations in the Z-disc components found in HCM and DCM may result in increased and decreased stiffness of sarcomere; that is, stiff sarcomere and loose sarcomere, respectively, and hence altered stretch response. More recently, mutations in the components of I region were found in hereditary cardiomyopathy and the functional analyses of the mutations suggested that the altered stress response was associated with cardiomyopathy, further complicating the etiology and pathogenesis. However, elucidation of genetic etiology and functional alterations caused by the mutations shed lights on the new therapeutic approaches to hereditary cardiomyopathy, such that treatment of DCM with a Ca(2+) sensitizer prevented the disease in a mouse model.
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Affiliation(s)
- Akinori Kimura
- Department of Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University, Japan.
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38
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Kontrogianni-Konstantopoulos A, Ackermann MA, Bowman AL, Yap SV, Bloch RJ. Muscle giants: molecular scaffolds in sarcomerogenesis. Physiol Rev 2009; 89:1217-67. [PMID: 19789381 PMCID: PMC3076733 DOI: 10.1152/physrev.00017.2009] [Citation(s) in RCA: 186] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Myofibrillogenesis in striated muscles is a highly complex process that depends on the coordinated assembly and integration of a large number of contractile, cytoskeletal, and signaling proteins into regular arrays, the sarcomeres. It is also associated with the stereotypical assembly of the sarcoplasmic reticulum and the transverse tubules around each sarcomere. Three giant, muscle-specific proteins, titin (3-4 MDa), nebulin (600-800 kDa), and obscurin (approximately 720-900 kDa), have been proposed to play important roles in the assembly and stabilization of sarcomeres. There is a large amount of data showing that each of these molecules interacts with several to many different protein ligands, regulating their activity and localizing them to particular sites within or surrounding sarcomeres. Consistent with this, mutations in each of these proteins have been linked to skeletal and cardiac myopathies or to muscular dystrophies. The evidence that any of them plays a role as a "molecular template," "molecular blueprint," or "molecular ruler" is less definitive, however. Here we review the structure and function of titin, nebulin, and obscurin, with the literature supporting a role for them as scaffolding molecules and the contradictory evidence regarding their roles as molecular guides in sarcomerogenesis.
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Gueneau L, Bertrand AT, Jais JP, Salih MA, Stojkovic T, Wehnert M, Hoeltzenbein M, Spuler S, Saitoh S, Verschueren A, Tranchant C, Beuvin M, Lacene E, Romero NB, Heath S, Zelenika D, Voit T, Eymard B, Ben Yaou R, Bonne G. Mutations of the FHL1 gene cause Emery-Dreifuss muscular dystrophy. Am J Hum Genet 2009; 85:338-53. [PMID: 19716112 DOI: 10.1016/j.ajhg.2009.07.015] [Citation(s) in RCA: 158] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Revised: 07/15/2009] [Accepted: 07/29/2009] [Indexed: 12/11/2022] Open
Abstract
Emery-Dreifuss muscular dystrophy (EDMD) is a rare disorder characterized by early joint contractures, muscular dystrophy, and cardiac involvement with conduction defects and arrhythmias. So far, only 35% of EDMD cases are genetically elucidated and associated with EMD or LMNA gene mutations, suggesting the existence of additional major genes. By whole-genome scan, we identified linkage to the Xq26.3 locus containing the FHL1 gene in three informative families belonging to our EMD- and LMNA-negative cohort. Analysis of the FHL1 gene identified seven mutations, in the distal exons of FHL1 in these families, three additional families, and one isolated case, which differently affect the three FHL1 protein isoforms: two missense mutations affecting highly conserved cysteines, one abolishing the termination codon, and four out-of-frame insertions or deletions. The predominant phenotype was characterized by myopathy with scapulo-peroneal and/or axial distribution, as well as joint contractures, and associated with a peculiar cardiac disease characterized by conduction defects, arrhythmias, and hypertrophic cardiomyopathy in all index cases of the seven families. Heterozygous female carriers were either asymptomatic or had cardiac disease and/or mild myopathy. Interestingly, four of the FHL1-mutated male relatives had isolated cardiac disease, and an overt hypertrophic cardiomyopathy was present in two. Expression and functional studies demonstrated that the FHL1 proteins were severely reduced in all tested patients and that this was associated with a severe delay in myotube formation in the two patients for whom myoblasts were available. In conclusion, FHL1 should be considered as a gene associated with the X-linked EDMD phenotype, as well as with hypertrophic cardiomyopathy.
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Mestroni L. Phenotypic heterogeneity of sarcomeric gene mutations: a matter of gain and loss? J Am Coll Cardiol 2009; 54:343-5. [PMID: 19608032 PMCID: PMC2756576 DOI: 10.1016/j.jacc.2009.04.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Accepted: 04/02/2009] [Indexed: 01/21/2023]
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Greaser ML. Stressing the giant: a new approach to understanding dilated cardiomyopathy. J Mol Cell Cardiol 2009; 47:347-9. [PMID: 19555694 DOI: 10.1016/j.yjmcc.2009.06.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Accepted: 06/12/2009] [Indexed: 11/29/2022]
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Bovill E, Westaby S, Crisp A, Jacobs S, Shaw T. Reduction of four-and-a-half LIM-protein 2 expression occurs in human left ventricular failure and leads to altered localization and reduced activity of metabolic enzymes. J Thorac Cardiovasc Surg 2009; 137:853-61. [PMID: 19327508 DOI: 10.1016/j.jtcvs.2008.09.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Revised: 08/13/2008] [Accepted: 09/01/2008] [Indexed: 10/21/2022]
Abstract
OBJECTIVE We sought to identify changes in four-and-a-half LIM-protein 2 levels and location in human cardiomyocytes during the transition from compensated aortic stenosis to left ventricular failure. We also sought to characterize four-and-a-half LIM-protein 2 binding with the metabolic enzymes phosphofructokinase 2, adenylate kinase, and creatine kinase M isoform during this transition and their consequential subcellular localization in failing human ventricles. METHODS Left ventricular biopsy specimens from selected patients undergoing aortic valve replacement for aortic stenosis were allocated to one of 2 groups: (1) nondilated with preserved left ventricular function (nonfailing group, n = 16) and (2) grossly dilated with poor left ventricular function (failing group, n = 15). These were compared with a control group of unused donor hearts (n = 6). Protein levels and subcellular localization were determined by means of Western blotting and immunofluorescence. Four-and-a-half LIM-protein 2 binding to adenylate kinase, creatine kinase M isoform, or phosphofructokinase 2 was studied by means of coimmunoprecipitation. Phosphofructokinase 2, adenylate kinase, and creatine kinase M isoform activities were assayed in protein extractions. RESULTS Four-and-a-half LIM-protein 2 levels were preserved in nonfailing hypertrophied hearts but reduced by 53% in failing hearts. The pattern of four-and-a-half LIM-protein 2 staining was disrupted in failing hearts: four-and-a-half LIM-protein 2 was lost from the sarcomere but present in the perinuclear Golgi apparatus complex. Phosphofructokinase 2, adenylate kinase, and creatine kinase M isoform coimmunoprecipitated in vitro and colocalized with four-and-a-half LIM-protein 2 in both hypertrophied and failing hearts. Phosphofructokinase 2 and adenylate kinase activities were reduced to 77% and 58% of normal values in compensated aortic stenosis, with phosphofructokinase 2 activity decreased further to 56% of normal value in failing hearts, but creatine kinase activity remained unchanged. CONCLUSIONS Altered four-and-a-half LIM-protein 2 expression in heart failure is associated with disruption of the normal subcellular localization of phosphofructokinase 2, adenylate kinase, and creatine kinase M isoform and reduced activity of phosphofructokinase 2 and adenylate kinase, which might have important consequences for myocardial energy metabolism in heart failure.
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Affiliation(s)
- Esta Bovill
- Department of Medicine, University College London, London, United Kingdom.
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Sheikh F, Raskin A, Chu PH, Lange S, Domenighetti AA, Zheng M, Liang X, Zhang T, Yajima T, Gu Y, Dalton ND, Mahata SK, Dorn GW, Brown JH, Heller-Brown J, Peterson KL, Omens JH, McCulloch AD, Chen J. An FHL1-containing complex within the cardiomyocyte sarcomere mediates hypertrophic biomechanical stress responses in mice. J Clin Invest 2008; 118:3870-80. [PMID: 19033658 DOI: 10.1172/jci34472] [Citation(s) in RCA: 184] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Accepted: 09/24/2008] [Indexed: 11/17/2022] Open
Abstract
The response of cardiomyocytes to biomechanical stress can determine the pathophysiology of hypertrophic cardiac disease, and targeting the pathways regulating these responses is a therapeutic goal. However, little is known about how biomechanical stress is sensed by the cardiomyocyte sarcomere to transduce intracellular hypertrophic signals or how the dysfunction of these pathways may lead to disease. Here, we found that four-and-a-half LIM domains 1 (FHL1) is part of a complex within the cardiomyocyte sarcomere that senses the biomechanical stress-induced responses important for cardiac hypertrophy. Mice lacking Fhl1 displayed a blunted hypertrophic response and a beneficial functional response to pressure overload induced by transverse aortic constriction. A link to the Galphaq (Gq) signaling pathway was also observed, as Fhl1 deficiency prevented the cardiomyopathy observed in Gq transgenic mice. Mechanistic studies demonstrated that FHL1 plays an important role in the mechanism of pathological hypertrophy by sensing biomechanical stress responses via the N2B stretch sensor domain of titin and initiating changes in the titin- and MAPK-mediated responses important for sarcomere extensibility and intracellular signaling. These studies shed light on the physiological regulation of the sarcomere in response to hypertrophic stress.
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Affiliation(s)
- Farah Sheikh
- Department of Medicine, UCSD, La Jolla, California 92093, USA
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Abstract
Cardiomyopathy is defined as a cardiac disease caused by functional abnormality of cardiac muscle, and the etiology of the functional abnormality includes both extrinsic and intrinsic factors. Cardiomyopathy caused by the intrinsic factors is defined as idiopathic or primary cardiomyopathy, and there are several clinical phenotypes, including hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). The major intrinsic factor is gene mutations, and linkage studies, as well as candidate gene approaches, have deciphered multiple disease genes for hereditary primary cardiomyopathy. Of note is that mutations in the same disease gene can be found in different clinical phenotypes of cardiomyopathy. Functional analyses of disease-related mutations have revealed that characteristic functional alterations are associated with the clinical phenotypes, such that increased and decreased Ca(2+) sensitivity because of sarcomere mutations are associated with HCM and DCM, respectively. In addition, recent data have suggested that mutations in the Z-disc components found in HCM and DCM may result in increased and decreased stiffness of the sarcomere (ie, stiff sarcomere and loose sarcomere, respectively). More recently, mutations in the components of the I region can be found in hereditary cardiomyopathy, further complicating the etiology of primary cardiomyopathy.
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Affiliation(s)
- Akinori Kimura
- Department of Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.
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46
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Abstract
Hypertrophic cardiomyopathy (HCM) is a disease characterized by primary hypertrophy of the left (and sometimes right) ventricle. The clinical manifestations of the disease are dyspnea, angina, and a continuum encompassing lightheadedness, presyncope, syncope, and sudden death. Although HCM is often caused by an identifiable mutation in a gene coding for a sarcomeric protein and inherited in an autosomal-dominant pattern, many patients do not have any relatives in whom the disease is manifest. The prevalence of HCM is estimated to be 0.2%, with nearly 600,000 Americans affected. This limited exposure of clinicians to HCM understandably accounts for the uncertainty that prevails regarding this disease and its management.
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47
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Abstract
Over the last two decades, a large number of mutations have been identified in sarcomeric proteins as a cause of hypertrophic, dilated or restrictive cardiomyopathy. Functional analyses of mutant proteins in vitro have revealed several important functional changes in sarcomeric proteins that might be primarily involved in the pathogenesis of each cardiomyopathy. Creation of transgenic or knock-in animals expressing mutant proteins in their hearts confirmed that these mutations in genes for sarcomeric proteins induced distinct types of cardiomyopathies and provided useful animal models to explore the molecular pathogenic mechanisms and potential therapeutics of cardiomyopathy in vivo. In this review, I discuss the functional consequences of mutations in different sarcomeric proteins found in hypertrophic, dilated, and restrictive cardiomyopathies in conjunction with their effects on cardiac structure and function in vivo and their possible molecular and cellular mechanisms, which underlie the pathogenesis of these inherited cardiomyopathies.
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Affiliation(s)
- Sachio Morimoto
- Laboratory of Clinical Pharmacology, Kyushu University Graduate School of Medicine, Fukuoka, Japan.
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48
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Frank D, Kuhn C, Katus HA, Frey N. Role of the sarcomeric Z-disc in the pathogenesis of cardiomyopathy. Future Cardiol 2007; 3:611-22. [DOI: 10.2217/14796678.3.6.611] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The Z-disc has traditionally been viewed as a structure required to maintain sarcomeric function and integrity. More recently, the sarcomeric Z-disc has also emerged as a nodal point in cardiomyocyte signaling and mechanotransduction. This notion is not only supported by several transgenic animal models, but also by the identification of mutations in various Z-disc proteins, resulting in dilated or hypertrophic cardiomyopathy in patients. This review will thus focus on the role of the sarcomeric Z-disc and its associated proteins in the pathogenesis of cardiomyopathy.
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Affiliation(s)
- Derk Frank
- University of Heidelberg, Department of Internal Medicine III, Germany
| | - Christian Kuhn
- University of Heidelberg, Department of Internal Medicine III, Germany
| | - Hugo A Katus
- University of Heidelberg, Department of Internal Medicine III, Germany
| | - Norbert Frey
- Im Neuenheimer Feld 350, D-69120 Heidelberg, Germany
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Alcalai R, Seidman JG, Seidman CE. Genetic basis of hypertrophic cardiomyopathy: from bench to the clinics. J Cardiovasc Electrophysiol 2007; 19:104-10. [PMID: 17916152 DOI: 10.1111/j.1540-8167.2007.00965.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is a common inherited cardiac disorder that characterized by marked thickening of the left ventricular wall that occurs in the absence of increased external load. HCM is the most common cause of sudden cardiac death under 35 years and in addition causes heart failure. HCM is usually inherited as an autosomal dominant mutation in genes that encode protein constituents of the sarcomere. To date, more than 450 different mutations have been identified within 13 myofilament-related genes. This review focuses current research involved in the discovery of other causative genes, investigation of the mechanisms by which sarcomere genes mutations produce hypertrophy and arrhythmia, and identification of modifying factors that influence clinical expression in HCM patients. The clinical implications of molecular advances in HCM are discussed.
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Affiliation(s)
- Ronny Alcalai
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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50
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Beletskaya LV, Kupriyanova AG, Zaidenov VA, Kormer AY, Golts AM, Chestukhin VV, Kazakov EN, Shumakov VI. Altered cytoskeletal protein localization in cardiomyocytes of idiopathic cardiomyopathy patients. J Heart Lung Transplant 2007; 26:868-70. [PMID: 17692796 DOI: 10.1016/j.healun.2007.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Revised: 05/17/2007] [Accepted: 05/28/2007] [Indexed: 11/26/2022] Open
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