151
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Jáchymová M, Muravská A, Paleček T, Kuchynka P, Řeháková H, Magage S, Král A, Zima T, Horký K, Linhart A. Genetic variation screening of TNNT2 gene in a cohort of patients with hypertrophic and dilated cardiomyopathy. Physiol Res 2012; 61:169-75. [PMID: 22292720 DOI: 10.33549/physiolres.932157] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Mutations in troponin T (TNNT2) gene represent the important part of currently identified disease-causing mutations in hypertrophic (HCM) and dilated (DCM) cardiomyopathy. The aim of this study was to analyze TNNT2 gene exons in patients with HCM and DCM diagnosis to improve diagnostic and genetic consultancy in affected families. All 15 exons and their flanking regions of the TNNT2 gene were analyzed by DNA sequence analysis in 174 patients with HCM and DCM diagnosis. We identified genetic variations in TNNT2 exon regions in 56 patients and genetic variations in TNNT2 intron regions in 164 patients. Two patients were found to carry unique mutations in the TNNT2 gene. Limited genetic screening analysis is not suitable for routine testing of disease-causing mutations in patients with HCM and DCM as only individual mutation-positive cases may be identified. Therefore, this approach cannot be recommended for daily clinical practice even though, due to financial constraints, it currently represents the only available strategy in a majority of cardio-centers.
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Affiliation(s)
- M Jáchymová
- Institute of Clinical Chemistry and Laboratory Diagnostics, Charles University, Prague, Czech Republic
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152
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Sinnecker D, Dirschinger RJ, Goedel A, Moretti A, Lipp P, Laugwitz KL. Induced pluripotent stem cells in cardiovascular research. Rev Physiol Biochem Pharmacol 2012; 163:1-26. [PMID: 22447279 DOI: 10.1007/112_2012_6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The discovery that somatic cells can be reprogrammed to induced pluripotent stem cells (iPSC) by overexpression of a combination of transcription factors bears the potential to spawn a wealth of new applications in both preclinical and clinical cardiovascular research. Disease modeling, which is accomplished by deriving iPSC lines from patients affected by heritable diseases and then studying the pathophysiology of the diseases in somatic cells differentiated from these patient-specific iPSC lines, is the so far most advanced of these applications. Long-QT syndrome and catecholaminergic polymorphic ventricular tachycardia are two heart rhythm disorders that have been already successfully modeled by several groups using this approach, which will likely serve to model other mono- or polygenetic cardiovascular disorders in the future. Test systems based on cells derived from iPSC might prove beneficial to screen for novel cardiovascular drugs or unwanted drug side effects and to individualize medical therapy. The application of iPSC for cell therapy of cardiovascular disorders, albeit promising, will only become feasible if the problem of biological safety of these cells will be mastered.
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Affiliation(s)
- Daniel Sinnecker
- Klinikum rechts der Isar - Technische Universität München, I. Medizinische Klinik - Kardiologie, Ismaninger Strasse 22, 81675, Munich, Germany.
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153
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Knöll R. Myosin binding protein C: implications for signal-transduction. J Muscle Res Cell Motil 2011; 33:31-42. [PMID: 22173300 PMCID: PMC3351598 DOI: 10.1007/s10974-011-9281-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Accepted: 11/28/2011] [Indexed: 12/29/2022]
Abstract
Myosin binding protein C (MYBPC) is a crucial component of the sarcomere and an important regulator of muscle function. While mutations in different myosin binding protein C (MYBPC) genes are well known causes of various human diseases, such as hypertrophic (HCM) and dilated (DCM) forms of cardiomyopathy as well as skeletal muscular disorders, the underlying molecular mechanisms remain not well understood. A variety of MYBPC3 (cardiac isoform) mutations have been studied in great detail and several corresponding genetically altered mouse models have been generated. Most MYBPC3 mutations may cause haploinsufficiency and with it they may cause a primary increase in calcium sensitivity which is potentially able to explain major features observed in HCM patients such as the hypercontractile phenotype and the well known secondary effects such as myofibrillar disarray, fibrosis, myocardial hypertrophy and remodelling including arrhythmogenesis. However the presence of poison peptides in some cases cannot be fully excluded and most probably other mechanisms are also at play. Here we shall discuss MYBPC interacting proteins and possible pathways linked to cardiomyopathy and heart failure.
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Affiliation(s)
- Ralph Knöll
- Imperial College, National Heart and Lung Institute, British Heart Foundation-Centre for Research Excellence, Myocardial Genetics, London, UK.
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154
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Abstract
Hypertrophic cardiomyopathy (HCM) is the most-common monogenically inherited form of heart disease, characterized by thickening of the left ventricular wall, contractile dysfunction, and potentially fatal arrhythmias. HCM is also the most-common cause of sudden cardiac death in individuals younger than 35 years of age. Much progress has been made in the elucidation of the genetic basis of HCM, resulting in the identification of more than 900 individual mutations in over 20 genes. Interestingly, most of these genes encode sarcomeric proteins, such as myosin-7 (also known as cardiac muscle β-myosin heavy chain; MYH7), cardiac myosin-binding protein C (MYBPC3), and cardiac muscle troponin T (TNNT2). However, the molecular events that ultimately lead to the clinical phenotype of HCM are still unclear. We discuss several potential pathways, which include altered calcium cycling and sarcomeric calcium sensitivity, increased fibrosis, disturbed biomechanical stress sensing, and impaired cardiac energy homeostasis. An improved understanding of the pathological mechanisms involved will result in greater specificity and success of therapies for patients with HCM.
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Affiliation(s)
- Norbert Frey
- Department of Cardiology and Angiology, University of Kiel, Schittenhelmstrasse 12, 24105 Kiel, Germany
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155
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Timmer SAJ, Germans T, Brouwer WP, Lubberink M, van der Velden J, Wilde AAM, Christiaans I, Lammertsma AA, Knaapen P, van Rossum AC. Carriers of the hypertrophic cardiomyopathy MYBPC3 mutation are characterized by reduced myocardial efficiency in the absence of hypertrophy and microvascular dysfunction. Eur J Heart Fail 2011; 13:1283-9. [PMID: 22021246 DOI: 10.1093/eurjhf/hfr135] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS Next to left ventricular (LV) hypertrophy, hypertrophic cardiomyopathy (HCM) is characterized by microvascular dysfunction and reduced myocardial external efficiency (MEE). Insights into the presence of these abnormalities as early markers of disease are of clinical importance in risk stratification, and development of therapeutic approaches. Therefore, the aim was to investigate myocardial perfusion and energetics in genotype-positive, phenotype-negative HCM subjects (carriers). METHODS AND RESULTS Fifteen carriers of an MYBPC3 mutation underwent [(15)O]water positron emission tomography (PET) to assess myocardial blood flow (MBF). [(11)C]acetate PET was performed to obtain myocardial oxygen consumption (MVO(2)). By use of cardiovascular magnetic resonance imaging, LV volumes and mass were defined to calculate MEE, i.e. the ratio between external work and MVO(2). Eleven healthy, genotype-negative, family relatives underwent similar scanning protocols to serve as a control group. Left ventricular mass was comparable between carriers and controls (93 ± 25 vs. 99 ± 21 g, P= 0.85), as was MBF at rest (1.19 ± 0.34 vs. 1.18 ± 0.32 mL min(-1) g(-1), P= 0.92), and during hyperaemia (3.87 ± 0.75 vs. 3.96 ± 0.86 mL min(-1) g(-1), P= 0.77). Myocardial oxygen consumption averaged 0.137 ± 0.057 mL min(-1) g(-1) in carriers and was not significantly different from controls (0.125 ± 0.043 mL min(-1) g(-1), P= 0.29). Cardiac work, however, was slightly reduced in carriers (7398 ± 1384 vs. 9139 ± 2484 mmHg mL in controls, P= 0.08). As a consequence, MEE was significantly decreased in carriers (27 ± 10 vs. 36 ± 8% in controls, P= 0.02). CONCLUSION Carriers display reduced myocardial work generation in relation to oxygen consumption, in the absence of hypertrophy and flow abnormalities. Hence, impaired myocardial energetics may constitute a primary component of HCM pathogenesis.
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Affiliation(s)
- Stefan A J Timmer
- Department of Cardiology, VU University Medical Center, De Boelelaan 1117, Amsterdam, The Netherlands
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156
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Wu B, Wang L, Liu Q, Luo Q. Myocardial contractile and metabolic properties of familial hypertrophic cardiomyopathy caused by cardiac troponin I gene mutations: a simulation study. Exp Physiol 2011; 97:155-69. [PMID: 21967901 DOI: 10.1113/expphysiol.2011.059956] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Familial hypertrophic cardiomyopathy (FHC) is an inherited disease that is caused by sarcomeric protein gene mutations. The mechanism by which these mutant proteins cause disease is uncertain. Experimentally, cardiac troponin I (CTnI) gene mutations mainly alter myocardial performance via increases in the Ca(2+) sensitivity of cardiac contractility. In this study, we used an integrated simulation that links electrophysiology, contractile activity and energy metabolism of the myocardium to investigate alterations in myocardial contractile function and energy metabolism regulation as a result of increased Ca(2+) sensitivity in CTnI mutations. Simulation results reproduced the following typical features of FHC: (1) slower relaxation (diastolic dysfunction) caused by prolonged [Ca(2+)](i) and force transients; (2) higher energy consumption with the increase in Ca(2+) sensitivity; and (3) reduced fatty acid oxidation and enhanced glucose utilization in hypertrophied heart metabolism. Furthermore, the simulation indicated that in conditions of high energy consumption (that is, more than an 18.3% increase in total energy consumption), the myocardial energetic metabolic network switched from a net consumer to a net producer of lactate, resulting in a low coupling of glucose oxidation to glycolysis, which is a common feature of hypertrophied hearts. This study provides a novel systematic myocardial contractile and metabolic analysis to help elucidate the pathogenesis of FHC and suggests that the alterations in resting heart energy supply and demand could contribute to disease progression.
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Affiliation(s)
- Bo Wu
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
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157
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Myerson SG, Holloway CJ, Francis JM, Neubauer S. Cardiovascular magnetic resonance (CMR)--an update and review. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2011; 59:213-222. [PMID: 21920218 DOI: 10.1016/j.pnmrs.2010.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 12/11/2010] [Indexed: 05/31/2023]
Affiliation(s)
- Saul G Myerson
- University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, United Kingdom.
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158
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Drosatos K, Drosatos-Tampakaki Z, Khan R, Homma S, Schulze PC, Zannis VI, Goldberg IJ. Inhibition of c-Jun-N-terminal kinase increases cardiac peroxisome proliferator-activated receptor alpha expression and fatty acid oxidation and prevents lipopolysaccharide-induced heart dysfunction. J Biol Chem 2011; 286:36331-9. [PMID: 21873422 DOI: 10.1074/jbc.m111.272146] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Septic shock results from bacterial infection and is associated with multi-organ failure, high mortality, and cardiac dysfunction. Sepsis causes both myocardial inflammation and energy depletion. We hypothesized that reduced cardiac energy production is a primary cause of ventricular dysfunction in sepsis. The JNK pathway is activated in sepsis and has also been implicated in impaired fatty acid oxidation in several tissues. Therefore, we tested whether JNK activation inhibits cardiac fatty acid oxidation and whether blocking JNK would restore fatty acid oxidation during LPS treatment. LPS treatment of C57BL/6 mice and adenovirus-mediated activation of the JNK pathway in cardiomyocytes inhibited peroxisome proliferator-activated receptor α expression and fatty acid oxidation. Surprisingly, none of the adaptive responses that have been described in other types of heart failure, such as increased glucose utilization, reduced αMHC:βMHC ratio or induction of certain microRNAs, occurred in LPS-treated mice. Treatment of C57BL/6 mice with a general JNK inhibitor (SP600125) increased fatty acid oxidation in mice and a cardiomyocyte-derived cell line. JNK inhibition also prevented LPS-mediated reduction in fatty acid oxidation and cardiac dysfunction. Inflammation was not alleviated in LPS-treated mice that received the JNK inhibitor. We conclude that activation of JNK signaling reduces fatty acid oxidation and prevents the peroxisome proliferator-activated receptor α down-regulation that occurs with LPS.
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Affiliation(s)
- Konstantinos Drosatos
- Division of Preventive Medicine and Nutrition, Columbia University College of Physicians and Surgeons, New York, New York, USA
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159
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Ashrafian H, McKenna WJ, Watkins H. Disease pathways and novel therapeutic targets in hypertrophic cardiomyopathy. Circ Res 2011; 109:86-96. [PMID: 21700950 DOI: 10.1161/circresaha.111.242974] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
As described in earlier reviews in this series on the molecular basis of hypertrophic cardiomyopathy (HCM), HCM is one of the archetypal monogenic cardiovascular disorders to be understood at the molecular level. Twenty years after the discovery of the first HCM disease gene, genetic studies still confirm that HCM is principally a disease of the sarcomere. At the biophysical level, myofilament mutations generally enhance Ca(2+) sensitivity, maximal force production, and ATPase activity. These defects ultimately appear to converge on energy deficiency and altered Ca(2+) handling as major common paths leading to the anatomic (hypertrophy, myofiber disarray, and fibrosis) and functional features (pathological signaling and diastolic dysfunction) characteristic of HCM. In this review, we provide an account of the consequences of HCM mutations and describe how specifically targeting these molecular features has already yielded early promise for novel therapies for HCM. Although substantial efforts are still required to understand the molecular link between HCM mutations and their clinical consequences, HCM endures as an exemplar of how novel insights derived from molecular characterization of Mendelian disorders can inform the understanding of biological processes and translate into rational therapies.
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Affiliation(s)
- Houman Ashrafian
- Department of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom
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160
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Song W, Dyer E, Stuckey DJ, Copeland O, Leung MC, Bayliss C, Messer A, Wilkinson R, Tremoleda JL, Schneider MD, Harding SE, Redwood CS, Clarke K, Nowak K, Monserrat L, Wells D, Marston SB. Molecular mechanism of the E99K mutation in cardiac actin (ACTC Gene) that causes apical hypertrophy in man and mouse. J Biol Chem 2011; 286:27582-93. [PMID: 21622575 PMCID: PMC3149350 DOI: 10.1074/jbc.m111.252320] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 05/18/2011] [Indexed: 11/06/2022] Open
Abstract
We generated a transgenic mouse model expressing the apical hypertrophic cardiomyopathy-causing mutation ACTC E99K at 50% of total heart actin and compared it with actin from patients carrying the same mutation. The actin mutation caused a higher Ca(2+) sensitivity in reconstituted thin filaments measured by in vitro motility assay (2.3-fold for mice and 1.3-fold for humans) and in skinned papillary muscle. The mutation also abolished the change in Ca(2+) sensitivity normally linked to troponin I phosphorylation. MyBP-C and troponin I phosphorylation levels were the same as controls in transgenic mice and human carrier heart samples. ACTC E99K mice exhibited a high death rate between 28 and 45 days (48% females and 22% males). At 21 weeks, the hearts of the male survivors had enlarged atria, increased interstitial fibrosis, and sarcomere disarray. MRI showed hypertrophy, predominantly at the apex of the heart. End-diastolic volume and end-diastolic pressure were increased, and relaxation rates were reduced compared with nontransgenic littermates. End-systolic pressures and volumes were unaltered. ECG abnormalities were present, and the contractile response to β-adrenergic stimulation was much reduced. Older mice (29-week-old females and 38-week-old males) developed dilated cardiomyopathy with increased end-systolic volume and continuing increased end-diastolic pressure and slower contraction and relaxation rates. ECG showed atrial flutter and frequent atrial ectopic beats at rest in some ACTC E99K mice. We propose that the ACTC E99K mutation causes higher myofibrillar Ca(2+) sensitivity that is responsible for the sudden cardiac death, apical hypertrophy, and subsequent development of heart failure in humans and mice.
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Affiliation(s)
- Weihua Song
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
| | - Emma Dyer
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
| | - Daniel J. Stuckey
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
| | - O'Neal Copeland
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
| | - Man-Ching Leung
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
| | - Christopher Bayliss
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
| | - Andrew Messer
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
| | - Ross Wilkinson
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
| | - Jordi Lopez Tremoleda
- the Medical Research Council Clinical Sciences Centre, Imperial College London, London W12 0NN, United Kingdom
| | - Michael D. Schneider
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
| | - Sian E. Harding
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
| | - Charles S. Redwood
- the Department of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, United Kingdom
| | - Kieran Clarke
- the Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Kristen Nowak
- the Center for Medical Research, University of Western Australia, Nedlands, Western Australia 6009, Australia
| | - Lorenzo Monserrat
- the Cardiology Department, Complejo Hospitalario Universitario Juan Canalejo, A Coruña 15006, Spain
| | - Dominic Wells
- the Centre for Neuroscience, Imperial College London, London W12 0NN, United Kingdom, and
| | - Steven B. Marston
- From the National Heart and Lung Institute, Imperial College London, London SW32 6LY, United Kingdom
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161
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Ventura-Clapier R, Garnier A, Veksler V, Joubert F. Bioenergetics of the failing heart. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1360-72. [DOI: 10.1016/j.bbamcr.2010.09.006] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 08/24/2010] [Accepted: 09/14/2010] [Indexed: 10/19/2022]
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162
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Aletras AH, Tilak GS, Hsu LY, Arai AE. Heterogeneity of intramural function in hypertrophic cardiomyopathy: mechanistic insights from MRI late gadolinium enhancement and high-resolution displacement encoding with stimulated echoes strain maps. Circ Cardiovasc Imaging 2011; 4:425-34. [PMID: 21576279 PMCID: PMC3460377 DOI: 10.1161/circimaging.110.958751] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Accepted: 05/09/2011] [Indexed: 02/06/2023]
Abstract
BACKGROUND In hypertrophic cardiomyopathy (HCM), myocardial abnormalities are commonly heterogeneous. Two patterns of late gadolinium enhancement (LGE) have been reported: a bright "confluent" and an intermediate intensity abnormality termed "diffuse," each representing different degrees of myocardial scarring. We used MRI to study the relation between intramural cardiac function and the extent of fibrosis in HCM. The aim of this study was to determine whether excess collagen or myocardial scarring, as determined by LGE MRI, are the primary mechanisms leading to heterogeneous regional contractile function in patients with HCM. METHODS AND RESULTS Intramural left ventricular strain, transmural left ventricular function, and regions of myocardial fibrosis/scarring were imaged in 22 patients with HCM, using displacement encoding with stimulated echoes (DENSE), cine MRI, and LGE. DENSE systolic strain maps were qualitatively and quantitatively compared with LGE images. Intramural systolic strain by DENSE was significantly depressed within areas of confluent and diffuse LGE but also in the core of the most hypertrophic nonenhanced segment (all P < 0.001 versus nonhypertrophied segments). DENSE demonstrated an unexpected inner rim of largely preserved contractile function and a noncontracting outer wall within hypertrophic segments in 91% of patients. CONCLUSIONS LGE predicted some but not all of the heterogeneity of intramural contractile abnormalities. This indicates that myocardial scarring or excess interstitial collagen deposition does not fully explain the observed contractile heterogeneity in HCM. Thus, myofibril disarray or other nonfibrotic processes affect systolic function in a large number of patients with HCM.
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Affiliation(s)
- Anthony H. Aletras
- Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, U.S.A
- Department of Computer Science and Biomedical Informatics University of Central Greece, Lamia, Greece
| | - Gauri S. Tilak
- Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, U.S.A
| | - Li-Yueh Hsu
- Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, U.S.A
| | - Andrew E. Arai
- Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, U.S.A
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163
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Davis RP, van den Berg CW, Casini S, Braam SR, Mummery CL. Pluripotent stem cell models of cardiac disease and their implication for drug discovery and development. Trends Mol Med 2011; 17:475-84. [PMID: 21703926 DOI: 10.1016/j.molmed.2011.05.001] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 05/02/2011] [Accepted: 05/05/2011] [Indexed: 12/13/2022]
Abstract
Recent advances in pluripotent stem cell biology now make it possible to generate human cardiomyocytes in vitro from both healthy individuals and from patients with cardiac abnormalities. This offers unprecedented opportunities to study cardiac disease development 'in a dish' and establish novel platforms for drug discovery, either to prevent disease progression or to reverse it. In this review paper, we discuss some of the genetic diseases that affect the heart and illustrate how these new paradigms could assist our understanding of cardiac pathogenesis and aid in drug discovery. In particular, we highlight the limitations of other commonly used model systems in predicting the consequences of drug exposure on the human heart.
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Affiliation(s)
- Richard P Davis
- Department of Anatomy and Embryology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands.
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164
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Abstract
In the 20 years since the discovery of the first mutation linked to familial hypertrophic cardiomyopathy (HCM), an astonishing number of mutations affecting numerous sarcomeric proteins have been described. Among the most prevalent of these are mutations that affect thick filament binding proteins, including the myosin essential and regulatory light chains and cardiac myosin binding protein (cMyBP)-C. However, despite the frequency with which myosin binding proteins, especially cMyBP-C, have been linked to inherited cardiomyopathies, the functional consequences of mutations in these proteins and the mechanisms by which they cause disease are still only partly understood. The purpose of this review is to summarize the known disease-causing mutations that affect the major thick filament binding proteins and to relate these mutations to protein function. Conclusions emphasize the impact that discovery of HCM-causing mutations has had on fueling insights into the basic biology of thick filament proteins and reinforce the idea that myosin binding proteins are dynamic regulators of the activation state of the thick filament that contribute to the speed and force of myosin-driven muscle contraction. Additional work is still needed to determine the mechanisms by which individual mutations induce hypertrophic phenotypes.
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Affiliation(s)
- Samantha P Harris
- Department of Neurobiology, Physiology, and Behavior College of Biological Sciences, University of California, One Shields Ave, Davis, CA 95616, USA.
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165
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Brouwer WP, van Dijk SJ, Stienen GJM, van Rossum AC, van der Velden J, Germans T. The development of familial hypertrophic cardiomyopathy: from mutation to bedside. Eur J Clin Invest 2011; 41:568-78. [PMID: 21158848 DOI: 10.1111/j.1365-2362.2010.02439.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is a familial disorder characterized by left ventricular hypertrophy in the absence of other cardiac or systemic disease likely to cause this hypertrophy. HCM is considered a disease of the sarcomere as most causal mutations are identified in genes encoding sarcomeric proteins, although several other disorders have also been linked to the HCM phenotype. The clinical course of HCM is characterized by a large inter- and intrafamilial variability, ranging from severe symptomatic HCM to asymptomatic individuals. The general picture emerges that the underlying pathophysiology of HCM is complex and still scarcely clarified. Recent findings indicated that both functional and morphological (macroscopic and microscopic) changes of the HCM muscle are present before the occurrence of HCM phenotype. This review aims to provide an overview of the myocardial alterations that occur during the gradual process of wall thickening in HCM on a myofilament level, as well as the structural and functional abnormalities that can be observed in genetically affected individuals prior to the development of HCM with state of the art imaging techniques, such as tissue Doppler echocardiography and cardiovascular magnetic resonance imaging. Additionally, present and future therapeutic options will be briefly discussed.
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Affiliation(s)
- Wessel P Brouwer
- Department of Cardiology, VU University Medical Center, Amsterdam, The Netherlands.
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166
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Affiliation(s)
- Hugh Watkins
- Department of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom.
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167
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Orenes-Piñero E, Hernández-Romero D, Jover E, Valdés M, Lip GYH, Marín F. Impact of polymorphisms in the renin–angiotensin–aldosterone system on hypertrophic cardiomyopathy. J Renin Angiotensin Aldosterone Syst 2011; 12:521-30. [DOI: 10.1177/1470320311405247] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is a clinically heterogeneous autosomal dominant heart disease characterised by left ventricular hypertrophy in the absence of another cardiac or systemic disease that is capable of producing significant wall thickening. Microscopically it is characterised by cardiomyocyte hypertrophy, myofibrillar disarray and fibrosis. The phenotypic expression of HCM is multifactorial, with the majority of cases occurring secondary to mutations in genes encoding the sarcomere proteins. In conjunction with the genetic heterogeneity of HCM, phenotypic expression also exhibits a high level of variability even within families with the same aetiological mutation, and may be influenced by additional genetic factors. Polymorphisms of the renin–angiotensin–aldosterone system (RAAS) represent an attractive hypothesis as potential disease modifiers, as these genetic variants alter the ‘activation status’ of the RAAS, which leads to more left ventricular hypertrophy through different pathways. The main objective of this review is to provide an overview of the role of different polymorphisms identified in the RAAS, in patients with HCM.
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Affiliation(s)
- Esteban Orenes-Piñero
- Department of Cardiology, Hospital Universitario Virgen de la Arrixaca, Murcia, Spain
| | | | - Eva Jover
- Department of Cardiology, Hospital Universitario Virgen de la Arrixaca, Murcia, Spain
| | - Mariano Valdés
- Department of Cardiology, Hospital Universitario Virgen de la Arrixaca, Murcia, Spain
| | - Gregory YH Lip
- Haemostasis, Thrombosis and Vascular Biology Unit, University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Birmingham, UK
| | - Francisco Marín
- Department of Cardiology, Hospital Universitario Virgen de la Arrixaca, Murcia, Spain
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168
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169
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How do mutations in contractile proteins cause the primary familial cardiomyopathies? J Cardiovasc Transl Res 2011; 4:245-55. [PMID: 21424860 DOI: 10.1007/s12265-011-9266-2] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 02/17/2011] [Indexed: 01/11/2023]
Abstract
In this article, the available evidence about the functional effects of the contractile protein mutations that cause hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) is assessed. The molecular mechanism of the contractile apparatus of cardiac muscle and its regulation by Ca(2+) and PKA phosphorylation have been extensively studied. Therefore, when a number of point mutations in the contractile protein genes were found to cause the well-defined phenotypes of HCM and DCM, it was expected that the diseases could be explained at the molecular level. However, the search for a distinctive molecular phenotype did not yield rapid results. Now that a substantial number of mutations that cause HCM or DCM have been investigated in physiologically relevant systems and with a range of experimental techniques, a pattern is emerging. In the case of HCM, the hypothesis that the major effect of mutations is to increase myofibrillar Ca(2+)-sensitivity seems to be well established, but the mechanisms by which an increase in myofibrillar Ca(2+)-sensitivity induces hypertrophy remain obscure. In contrast, DCM mutations are not correlated with a specific effect on Ca(2+)-sensitivity. It has recently been proposed that DCM mutations uncouple troponin I phosphorylation from Ca(2+)-sensitivity changes, albeit based on only a few mutations so far. A plausible link between uncoupling and DCM has been proposed via blunting of the response to α-adrenergic stimulation.
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170
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Locher MR, Razumova MV, Stelzer JE, Norman HS, Moss RL. Effects of low-level α-myosin heavy chain expression on contractile kinetics in porcine myocardium. Am J Physiol Heart Circ Physiol 2011; 300:H869-78. [PMID: 21217059 DOI: 10.1152/ajpheart.00452.2010] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Myosin heavy chain (MHC) isoforms are principal determinants of work capacity in mammalian ventricular myocardium. The ventricles of large mammals including humans normally express ∼10% α-MHC on a predominantly β-MHC background, while in failing human ventricles α-MHC is virtually eliminated, suggesting that low-level α-MHC expression in normal myocardium can accelerate the kinetics of contraction and augment systolic function. To test this hypothesis in a model similar to human myocardium we determined composite rate constants of cross-bridge attachment (f(app)) and detachment (g(app)) in porcine myocardium expressing either 100% α-MHC or 100% β-MHC in order to predict the MHC isoform-specific effect on twitch kinetics. Right atrial (∼100% α-MHC) and left ventricular (∼100% β-MHC) tissue was used to measure myosin ATPase activity, isometric force, and the rate constant of force redevelopment (k(tr)) in solutions of varying Ca(2+) concentration. The rate of ATP utilization and k(tr) were approximately ninefold higher in atrial compared with ventricular myocardium, while tension cost was approximately eightfold greater in atrial myocardium. From these values, we calculated f(app) to be ∼10-fold higher in α- compared with β-MHC, while g(app) was 8-fold higher in α-MHC. Mathematical modeling of an isometric twitch using these rate constants predicts that the expression of 10% α-MHC increases the maximal rate of rise of force (dF/dt(max)) by 92% compared with 0% α-MHC. These results suggest that low-level expression of α-MHC significantly accelerates myocardial twitch kinetics, thereby enhancing systolic function in large mammalian myocardium.
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Affiliation(s)
- Matthew R Locher
- 1Department of Physiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53711, USA.
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171
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Abozguia K, Elliott P, McKenna W, Phan TT, Nallur-Shivu G, Ahmed I, Maher AR, Kaur K, Taylor J, Henning A, Ashrafian H, Watkins H, Frenneaux M. Metabolic modulator perhexiline corrects energy deficiency and improves exercise capacity in symptomatic hypertrophic cardiomyopathy. Circulation 2010; 122:1562-9. [PMID: 20921440 DOI: 10.1161/circulationaha.109.934059] [Citation(s) in RCA: 212] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Hypertrophic cardiomyopathy patients exhibit myocardial energetic impairment, but a causative role for this energy deficiency in the pathophysiology of hypertrophic cardiomyopathy remains unproven. We hypothesized that the metabolic modulator perhexiline would ameliorate myocardial energy deficiency and thereby improve diastolic function and exercise capacity. METHODS AND RESULTS Forty-six consecutive patients with symptomatic exercise limitation (peak Vo(2) <75% of predicted) caused by nonobstructive hypertrophic cardiomyopathy (mean age, 55±0.26 years) were randomized to perhexiline 100 mg (n=24) or placebo (n=22). Myocardial ratio of phosphocreatine to adenosine triphosphate, an established marker of cardiac energetic status, as measured by (31)P magnetic resonance spectroscopy, left ventricular diastolic filling (heart rate normalized time to peak filling) at rest and during exercise using radionuclide ventriculography, peak Vo(2), symptoms, quality of life, and serum metabolites were assessed at baseline and study end (4.6±1.8 months). Perhexiline improved myocardial ratios of phosphocreatine to adenosine triphosphate (from 1.27±0.02 to 1.73±0.02 versus 1.29±0.01 to 1.23±0.01; P=0.003) and normalized the abnormal prolongation of heart rate normalized time to peak filling between rest and exercise (0.11±0.008 to -0.01±0.005 versus 0.15±0.007 to 0.11±0.008 second; P=0.03). These changes were accompanied by an improvement in primary end point (peak Vo(2)) (22.2±0.2 to 24.3±0.2 versus 23.6±0.3 to 22.3±0.2 mL · kg(-1) · min(-1); P=0.003) and New York Heart Association class (P<0.001) (all P values ANCOVA, perhexiline versus placebo). CONCLUSIONS In symptomatic hypertrophic cardiomyopathy, perhexiline, a modulator of substrate metabolism, ameliorates cardiac energetic impairment, corrects diastolic dysfunction, and increases exercise capacity. This study supports the hypothesis that energy deficiency contributes to the pathophysiology and provides a rationale for further consideration of metabolic therapies in hypertrophic cardiomyopathy.
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Affiliation(s)
- Khalid Abozguia
- School of Medicine and Dentistry, University of Aberdeen, Aberdeen, UK
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172
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Association between cardiac energy metabolism and gain of left ventricular mass in Fabry disease. Int J Cardiol 2010; 144:337-9. [DOI: 10.1016/j.ijcard.2009.03.045] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2009] [Accepted: 03/04/2009] [Indexed: 11/19/2022]
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173
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Spectrum and clinical significance of systolic function and myocardial fibrosis assessed by cardiovascular magnetic resonance in hypertrophic cardiomyopathy. Am J Cardiol 2010; 106:261-7. [PMID: 20599013 DOI: 10.1016/j.amjcard.2010.03.020] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 03/02/2010] [Accepted: 03/02/2010] [Indexed: 11/23/2022]
Abstract
In hypertrophic cardiomyopathy (HCM), the clinical significance attributable to the broad range of left ventricular (LV) systolic function, assessed as the ejection fraction (EF), is incompletely resolved. We evaluated the EF using cardiovascular magnetic resonance (CMR) imaging in a large cohort of patients with HCM with respect to the clinical status and evidence of left ventricular remodeling with late gadolinium enhancement (LGE). CMR imaging was performed in 310 consecutive patients, aged 42 +/- 17 years. The EF in patients with HCM was 71 +/- 10% (range 28% to 89%), exceeding that of 606 healthy controls without cardiovascular disease (66 +/- 5%, p <0.001). LGE reflecting LV remodeling showed an independent, inverse relation to the EF (B-0.69, 95% confidence interval -0.86 to -0.52; p <0.001) and was greatest in patients with an EF <50%, in whom it constituted a median value of 29% of the LV volume (interquartile range 16% to 40%). However, the substantial subgroup with low-normal EF values of 50% to 65% (n = 45; 15% of the whole cohort), who were mostly asymptomatic or mildly symptomatic (37 or 82% with New York Heart Association functional class I to II), showed substantial LGE (median 5% of LV volume, interquartile range 2% to 10%). This overlapped with the subgroup with systolic dysfunction and significantly exceeded that of patients with an EF of 66% to 75% and >75% (median 2% of the LV volume, interquartile range 1.5% to 4%; p <0.01). In conclusion, in a large cohort of patients with HCM, a subset of patients with low-normal EF values (50% to 65%) was identified by contrast-enhanced CMR imaging as having substantial degrees of LGE, suggesting a transition phase, potentially heralding advanced LV remodeling and systolic dysfunction, with implications for clinical surveillance and management.
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174
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Hoskins AC, Jacques A, Bardswell SC, McKenna WJ, Tsang V, dos Remedios CG, Ehler E, Adams K, Jalilzadeh S, Avkiran M, Watkins H, Redwood C, Marston SB, Kentish JC. Normal passive viscoelasticity but abnormal myofibrillar force generation in human hypertrophic cardiomyopathy. J Mol Cell Cardiol 2010; 49:737-45. [PMID: 20615414 PMCID: PMC2954357 DOI: 10.1016/j.yjmcc.2010.06.006] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 06/02/2010] [Accepted: 06/20/2010] [Indexed: 01/13/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy, increased ventricular stiffness and impaired diastolic filling. We investigated to what extent myocardial functional defects can be explained by alterations in the passive and active properties of human cardiac myofibrils. Skinned ventricular myocytes were prepared from patients with obstructive HCM (two patients with MYBPC3 mutations, one with a MYH7 mutation, and three with no mutation in either gene) and from four donors. Passive stiffness, viscous properties, and titin isoform expression were similar in HCM myocytes and donor myocytes. Maximal Ca2+-activated force was much lower in HCM myocytes (14 ± 1 kN/m2) than in donor myocytes (23 ± 3 kN/m2; P < 0.01), though cross-bridge kinetics (ktr) during maximal Ca2+ activation were 10% faster in HCM myocytes. Myofibrillar Ca2+ sensitivity in HCM myocytes (pCa50 = 6.40 ± 0.05) was higher than for donor myocytes (pCa50 = 6.09 ± 0.02; P < 0.001) and was associated with reduced phosphorylation of troponin-I (ser-23/24) and MyBP-C (ser-282) in HCM myocytes. These characteristics were common to all six HCM patients and may therefore represent a secondary consequence of the known and unknown underlying genetic variants. Some HCM patients did however exhibit an altered relationship between force and cross-bridge kinetics at submaximal Ca2+ concentrations, which may reflect the primary mutation. We conclude that the passive viscoelastic properties of the myocytes are unlikely to account for the increased stiffness of the HCM ventricle. However, the low maximum Ca2+-activated force and high Ca2+ sensitivity of the myofilaments are likely to contribute substantially to any systolic and diastolic dysfunction, respectively, in hearts of HCM patients.
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Affiliation(s)
- Anita C Hoskins
- Cardiovascular Division, King's College London British Heart Foundation Centre, London, UK
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175
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Ashrafian H, Docherty L, Leo V, Towlson C, Neilan M, Steeples V, Lygate CA, Hough T, Townsend S, Williams D, Wells S, Norris D, Glyn-Jones S, Land J, Barbaric I, Lalanne Z, Denny P, Szumska D, Bhattacharya S, Griffin JL, Hargreaves I, Fernandez-Fuentes N, Cheeseman M, Watkins H, Dear TN. A mutation in the mitochondrial fission gene Dnm1l leads to cardiomyopathy. PLoS Genet 2010; 6:e1001000. [PMID: 20585624 PMCID: PMC2891719 DOI: 10.1371/journal.pgen.1001000] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Accepted: 05/25/2010] [Indexed: 12/03/2022] Open
Abstract
Mutations in a number of genes have been linked to inherited dilated cardiomyopathy (DCM). However, such mutations account for only a small proportion of the clinical cases emphasising the need for alternative discovery approaches to uncovering novel pathogenic mutations in hitherto unidentified pathways. Accordingly, as part of a large-scale N-ethyl-N-nitrosourea mutagenesis screen, we identified a mouse mutant, Python, which develops DCM. We demonstrate that the Python phenotype is attributable to a dominant fully penetrant mutation in the dynamin-1-like (Dnm1l) gene, which has been shown to be critical for mitochondrial fission. The C452F mutation is in a highly conserved region of the M domain of Dnm1l that alters protein interactions in a yeast two-hybrid system, suggesting that the mutation might alter intramolecular interactions within the Dnm1l monomer. Heterozygous Python fibroblasts exhibit abnormal mitochondria and peroxisomes. Homozygosity for the mutation results in the death of embryos midway though gestation. Heterozygous Python hearts show reduced levels of mitochondria enzyme complexes and suffer from cardiac ATP depletion. The resulting energy deficiency may contribute to cardiomyopathy. This is the first demonstration that a defect in a gene involved in mitochondrial remodelling can result in cardiomyopathy, showing that the function of this gene is needed for the maintenance of normal cellular function in a relatively tissue-specific manner. This disease model attests to the importance of mitochondrial remodelling in the heart; similar defects might underlie human heart muscle disease.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Cardiomyopathy, Dilated/congenital
- Cardiomyopathy, Dilated/genetics
- Cardiomyopathy, Dilated/metabolism
- Cardiomyopathy, Dilated/pathology
- Dynamins
- Embryo, Mammalian/metabolism
- Embryo, Mammalian/pathology
- GTP Phosphohydrolases/chemistry
- GTP Phosphohydrolases/genetics
- GTP Phosphohydrolases/metabolism
- Genes, Mitochondrial
- Genetic Predisposition to Disease
- Male
- Mice
- Mice, Inbred BALB C
- Microscopy, Electron, Transmission
- Microtubule-Associated Proteins/chemistry
- Microtubule-Associated Proteins/genetics
- Microtubule-Associated Proteins/metabolism
- Models, Molecular
- Molecular Sequence Data
- Mutation
- Protein Structure, Quaternary
- Sequence Alignment
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Affiliation(s)
- Houman Ashrafian
- Department of Cardiovascular Medicine and Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Louise Docherty
- Mammalian Genetics of Disease Unit, School of Medicine, University of Sheffield, Sheffield, United Kingdom
| | - Vincenzo Leo
- Leeds Institute of Molecular Medicine, Wellcome Trust Brenner Building, St. James's University Hospital, Leeds, United Kingdom
| | - Christopher Towlson
- Mammalian Genetics of Disease Unit, School of Medicine, University of Sheffield, Sheffield, United Kingdom
| | - Monica Neilan
- Mammalian Genetics of Disease Unit, School of Medicine, University of Sheffield, Sheffield, United Kingdom
| | - Violetta Steeples
- Department of Cardiovascular Medicine and Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Craig A. Lygate
- Department of Cardiovascular Medicine and Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Tertius Hough
- Leeds Institute of Molecular Medicine, Wellcome Trust Brenner Building, St. James's University Hospital, Leeds, United Kingdom
| | - Stuart Townsend
- Leeds Institute of Molecular Medicine, Wellcome Trust Brenner Building, St. James's University Hospital, Leeds, United Kingdom
| | - Debbie Williams
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, United Kingdom
| | - Sara Wells
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, United Kingdom
| | - Dominic Norris
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, United Kingdom
| | - Sarah Glyn-Jones
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - John Land
- Neurometabolic Unit, National Hospital, London, United Kingdom
| | - Ivana Barbaric
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Zuzanne Lalanne
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, United Kingdom
| | - Paul Denny
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, United Kingdom
| | - Dorota Szumska
- Department of Cardiovascular Medicine and Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Shoumo Bhattacharya
- Department of Cardiovascular Medicine and Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Julian L. Griffin
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Iain Hargreaves
- Neurometabolic Unit, National Hospital, London, United Kingdom
| | - Narcis Fernandez-Fuentes
- Leeds Institute of Molecular Medicine, Wellcome Trust Brenner Building, St. James's University Hospital, Leeds, United Kingdom
| | - Michael Cheeseman
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, United Kingdom
| | - Hugh Watkins
- Department of Cardiovascular Medicine and Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - T. Neil Dear
- Mammalian Genetics of Disease Unit, School of Medicine, University of Sheffield, Sheffield, United Kingdom
- Leeds Institute of Molecular Medicine, Wellcome Trust Brenner Building, St. James's University Hospital, Leeds, United Kingdom
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, United Kingdom
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176
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Rajagopalan B, Francis JM, Cooke F, Korlipara LVP, Blamire AM, Schapira AHV, Madan J, Neubauer S, Cooper JM. Analysis of the factors influencing the cardiac phenotype in Friedreich's ataxia. Mov Disord 2010; 25:846-52. [PMID: 20461801 DOI: 10.1002/mds.22864] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Friedreich's ataxia (FRDA) has been associated with both cardiac hypertrophy and to a lesser degree dilated cardiomyopathy. We have conducted a cross sectional magnetic resonance imaging (MRI) study of 25 patients with clinically and genetically confirmed FRDA and 24 healthy controls to analyse how disease parameters influence cardiac features in FRDA. MR cine imaging in the long and short axis planes was performed alongside clinical assessments. LV mass was most pronounced in FRDA patients with a larger genetic mutation (GAA1 repeats >600), earlier age of onset (<16years) and a shorter disease duration (<15 years). LV mass decreased with longer disease duration (>15 years), and independent of GAA1 repeat size and age of onset, suggesting cardiac thinning occurred with prolonged disease. Heart function was lower in patients with larger GAA1 repeat number and longer disease duration. Consequently, cardiac hypertrophy was more marked in FRDA patients with a larger GAA1 repeat number and younger age of onset, while prolonged disease duration was associated with lower LV mass and decreased heart function. It is important not only to understand the biochemical basis for these cardiac changes but also allow for these changes when assessing the effect of treatment of FRDA patients.
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Affiliation(s)
- Bheeshma Rajagopalan
- Nuffield Department of Medicine, Department of Biochemistry, University of Oxford, Oxford, UK
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177
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Huke S, Knollmann BC. Increased myofilament Ca2+-sensitivity and arrhythmia susceptibility. J Mol Cell Cardiol 2010; 48:824-33. [PMID: 20097204 PMCID: PMC2854218 DOI: 10.1016/j.yjmcc.2010.01.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 01/12/2010] [Accepted: 01/12/2010] [Indexed: 10/19/2022]
Abstract
Increased myofilament Ca(2+) sensitivity is a common attribute of many inherited and acquired cardiomyopathies that are associated with cardiac arrhythmias. Accumulating evidence supports the concept that increased myofilament Ca(2+) sensitivity is an independent risk factor for arrhythmias. This review describes and discusses potential underlying molecular and cellular mechanisms how myofilament Ca(2+) sensitivity affects cardiac excitation and leads to the generation of arrhythmias. Emphasized are downstream effects of increased myofilament Ca(2+) sensitivity: altered Ca(2+) buffering/handling, impaired energy metabolism and increased mechanical stretch, and how they may contribute to arrhythmogenesis.
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Affiliation(s)
- Sabine Huke
- Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN 37232-0575, USA
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178
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Cardiac challenges in patients with Fabry disease. Int J Cardiol 2010; 141:3-10. [DOI: 10.1016/j.ijcard.2009.08.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Revised: 06/15/2009] [Accepted: 08/11/2009] [Indexed: 11/24/2022]
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179
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Abstract
Mutation of the mitochondrial protein tafazzin causes dilated cardiomyopathy in Barth syndrome. We employed an adenovirus as a vector to transfer tafazzin small hairpin RNA (shRNA) into neonatal ventricular myocytes (NVMs) to investigate the effects of tafazzin knockdown. The tafazzin shRNA adenovirus consistently knocked down tafazzin mRNA and lowered cardiolipin while significantly decreasing the production of ATP by the mitochondria. The phosphorylation of AMP-activated protein kinase and mitochondrial density were both increased in tafazzin knockdown NVMs compared with scrambled shRNA controls. When we tested whether tafazzin knockdown causes hypertrophy in vitro, we found that the surface area of NVMs infected with tafazzin shRNA adenovirus was significantly increased, as were the protein synthesis and expression of the hypertrophic marker gene, brain natriuretic peptide. Taken together, our data support the concept that a decreased tafazzin expression causes cardiomyocyte hypertrophy in vitro.
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Affiliation(s)
- Quan He
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, 2799 W. Grand Blvd., Detroit, MI 48202-2689, USA.
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180
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Willott RH, Gomes AV, Chang AN, Parvatiyar MS, Pinto JR, Potter JD. Mutations in Troponin that cause HCM, DCM AND RCM: what can we learn about thin filament function? J Mol Cell Cardiol 2009; 48:882-92. [PMID: 19914256 DOI: 10.1016/j.yjmcc.2009.10.031] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 10/19/2009] [Accepted: 10/30/2009] [Indexed: 12/25/2022]
Abstract
Troponin (Tn) is a critical regulator of muscle contraction in cardiac muscle. Mutations in Tn subunits are associated with hypertrophic, dilated and restrictive cardiomyopathies. Improved diagnosis of cardiomyopathies as well as intensive investigation of new mouse cardiomyopathy models has significantly enhanced this field of research. Recent investigations have showed that the physiological effects of Tn mutations associated with hypertrophic, dilated and restrictive cardiomyopathies are different. Impaired relaxation is a universal finding of most transgenic models of HCM, predicted directly from the significant changes in Ca(2+) sensitivity of force production. Mutations associated with HCM and RCM show increased Ca(2+) sensitivity of force production while mutations associated with DCM demonstrate decreased Ca(2+) sensitivity of force production. This review spotlights recent advances in our understanding on the role of Tn mutations on ATPase activity, maximal force development and heart function as well as the correlation between the locations of these Tn mutations within the thin filament and myofilament function.
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Affiliation(s)
- Ruth H Willott
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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181
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Mechanical and Energetic Consequences of HCM-Causing Mutations. J Cardiovasc Transl Res 2009; 2:441-51. [DOI: 10.1007/s12265-009-9131-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Accepted: 09/15/2009] [Indexed: 10/20/2022]
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182
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Lam L, Tsoutsman T, Arthur J, Semsarian C. Differential protein expression profiling of myocardial tissue in a mouse model of hypertrophic cardiomyopathy. J Mol Cell Cardiol 2009; 48:1014-22. [PMID: 19715700 DOI: 10.1016/j.yjmcc.2009.08.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 08/13/2009] [Accepted: 08/13/2009] [Indexed: 11/30/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is a genetic disorder caused by mutations in genes encoding sarcomere proteins. The mechanisms involved in the development of cardiac hypertrophy and heart failure remain poorly understood. Global proteomic profiling was used to study the cardiac proteome of mice predisposed to developing HCM. Hearts from three groups of mice (n=3 hearts per group) were studied: non-transgenic (NTG) and cardiac-specific transgenic models over-expressing either the normal (TnI(WT)) or a mutant cardiac troponin I gene (Gly203Ser; TnI(G203S)). Two-dimensional gel electrophoresis (2-DE) coupled with tandem mass spectrometry was used to identify proteins. Image analysis was performed using Progenesis SameSpots. A total of 34 proteins with at least a twofold change in the TnI(G203S) mouse model were identified. Alterations were detected in components involved in energy production, Ca(2+) handling, and cardiomyocyte structure. Expression level changes in cytoskeletal and contractile proteins were well represented in the study, including the intermediate filament protein desmin, which was further investigated in two additional physiological and pathological settings, i.e., exercise treatment, and severe heart failure in a novel double-mutant TnI-203/MHC-403 model of HCM. This study highlights the potential role of tissue proteomic profiling for mapping proteins, which may be critical in cardiac dysfunction and progression to heart failure in HCM.
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Affiliation(s)
- Lien Lam
- Agnes Ginges Centre for Molecular Cardiology, Centenary Institute, Sydney, Australia
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183
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Phosphofructo-1-kinase deficiency leads to a severe cardiac and hematological disorder in addition to skeletal muscle glycogenosis. PLoS Genet 2009; 5:e1000615. [PMID: 19696889 PMCID: PMC2721631 DOI: 10.1371/journal.pgen.1000615] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Accepted: 07/24/2009] [Indexed: 01/26/2023] Open
Abstract
Mutations in the gene for muscle phosphofructo-1-kinase (PFKM), a key regulatory enzyme of glycolysis, cause Type VII glycogen storage disease (GSDVII). Clinical manifestations of the disease span from the severe infantile form, leading to death during childhood, to the classical form, which presents mainly with exercise intolerance. PFKM deficiency is considered as a skeletal muscle glycogenosis, but the relative contribution of altered glucose metabolism in other tissues to the pathogenesis of the disease is not fully understood. To elucidate this issue, we have generated mice deficient for PFKM (Pfkm−/−). Here, we show that Pfkm−/− mice had high lethality around weaning and reduced lifespan, because of the metabolic alterations. In skeletal muscle, including respiratory muscles, the lack of PFK activity blocked glycolysis and resulted in considerable glycogen storage and low ATP content. Although erythrocytes of Pfkm−/− mice preserved 50% of PFK activity, they showed strong reduction of 2,3-biphosphoglycerate concentrations and hemolysis, which was associated with compensatory reticulocytosis and splenomegaly. As a consequence of these haematological alterations, and of reduced PFK activity in the heart, Pfkm−/− mice developed cardiac hypertrophy with age. Taken together, these alterations resulted in muscle hypoxia and hypervascularization, impaired oxidative metabolism, fiber necrosis, and exercise intolerance. These results indicate that, in GSDVII, marked alterations in muscle bioenergetics and erythrocyte metabolism interact to produce a complex systemic disorder. Therefore, GSDVII is not simply a muscle glycogenosis, and Pfkm−/− mice constitute a unique model of GSDVII which may be useful for the design and assessment of new therapies. Type VII glycogen storage disease (GSDVII), or Tarui disease, is a rare genetic disorder characterized by glycogen accumulation in skeletal muscle. The molecular cause is loss of activity of the muscle isoform of phosphofructokinase (PFK), which phosphorylates fructose-6-phosphate to fructose-1,6-bisphosphate, commiting glucose to glycolysis. Entry of fructose-6-phosphate into glycolysis is thus blocked, increasing glycogen synthesis and accumulation. Clinical manifestations of the disease are heterogeneous, ranging from exercise intolerance to early childhood death. To further understand the human pathology, we generated mice lacking muscle PFK. As in human patients, these mice showed severe exercise intolerance, hemolysis, and most died young. Lack of glycolysis in skeletal muscle also causes alterations in bioenergetics and compensatory changes in key metabolic genes. Additionally, although erythrocytes retained 50% of normal PFK activity, their overall functionality was impaired, aggravating the muscle dysfunction. Moreover, marked metabolic alterations in the heart lead to chronic hypertrophy, suggesting that cardiac pathology in GSDVII may be underestimated or misdiagnosed. This study indicates that this disease is more complex than a muscle glycogenosis and that symptoms other than those classically described should be taken into consideration. Finally, this animal model will enable us to develop new therapeutic approaches and better diagnostic tools.
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184
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Reflections of Inflections in Hypertrophic Cardiomyopathy. J Am Coll Cardiol 2009; 54:212-9. [DOI: 10.1016/j.jacc.2009.03.052] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Accepted: 03/18/2009] [Indexed: 11/18/2022]
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185
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Affiliation(s)
- Michael Bamshad
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle Children's Hospital, 1959 Northeast Pacific Street, HSC RR349, M/S Box 356320, Seattle, WA 98195. E-mail address:
| | - Ann E. Van Heest
- Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Avenue, Suite R200, Minneapolis, MN 55454
| | - David Pleasure
- Departments of Neurology and Pediatrics, UC Davis School of Medicine, c/o Shriners Hospital, 2425 Stockton Boulevard, Sacramento, CA 95817
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186
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McKenna WJ, Sen-Chowdhry S. From Teare to the present day: a fifty year odyssey in hypertrophic cardiomyopathy, a paradigm for the logic of the discovery process. Rev Esp Cardiol 2009; 61:1239-44. [PMID: 19080961 DOI: 10.1016/s1885-5857(09)60050-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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187
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The cardiac troponin C mutation Leu29Gln found in a patient with hypertrophic cardiomyopathy does not alter contractile parameters in skinned murine myocardium. Basic Res Cardiol 2009; 104:751-60. [PMID: 19506933 PMCID: PMC2758205 DOI: 10.1007/s00395-009-0038-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Revised: 04/22/2009] [Accepted: 05/13/2009] [Indexed: 11/12/2022]
Abstract
The present study investigates the effects of the first mutation of troponin C (hcTnCL29Q) found in a patient with hypertrophic cardiomyopathy (HCM) on force–pCa relations and the interplay with phosphorylation of sarcomeric PKA substrates. In triton-skinned murine cardiac fibers, the endogenous mcTnC was extracted and the fibers were subsequently reconstituted with recombinant wild-type and mutant hcTnC. Force–pCa relations of preparations containing hcTnCL29Q or hcTnCWT were similar. Incubation of fibers reconstituted with the recombinant proteins with phosphatase to dephosphorylate sarcomeric PKA substrates induced an increase in Ca2+ sensitivity, slightly more pronounced (0.04 pCa units) in hcTnCL29Q-containing fibers. Incubation of the dephosphorylated fibers with PKA induced significant rightward shifts of force–pCa relations of similar magnitude with both, hcTnCL29Q and hcTnCWT. No significant effects of hcTnCL29Q on the velocity of unloaded shortening were observed. In conclusion, no major differences in contractile parameters of preparations containing hcTnCL29Q compared to hcTnCWT were observed. Therefore, it appears unlikely that hcTnCL29Q induces the development of HCM by affecting the regulation of Ca2+-activated force and interference with PKA-mediated modulation of the Ca2+ sensitivity of contraction.
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188
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Unno K, Isobe S, Izawa H, Cheng XW, Kobayashi M, Hirashiki A, Yamada T, Harada K, Ohshima S, Noda A, Nagata K, Kato K, Yokota M, Murohara T. Relation of functional and morphological changes in mitochondria to myocardial contractile and relaxation reserves in asymptomatic to mildly symptomatic patients with hypertrophic cardiomyopathy. Eur Heart J 2009; 30:1853-62. [DOI: 10.1093/eurheartj/ehp184] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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189
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Decreased contractility due to energy deprivation in a transgenic rat model of hypertrophic cardiomyopathy. J Mol Med (Berl) 2009; 87:411-22. [PMID: 19189074 DOI: 10.1007/s00109-008-0436-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Revised: 11/18/2008] [Accepted: 12/10/2008] [Indexed: 12/13/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is associated with cardiac hypertrophy, diastolic dysfunction, and sudden death. Recently, it has been suggested that inefficient energy utilization could be a common molecular pathway of HCM-related mutations. We have previously generated transgenic Sprague-Dawley rats overexpressing a truncated cardiac troponin T (DEL-TNT) molecule, displaying typical features of HCM such as diastolic dysfunction and an increased susceptibility to ventricular arrhythmias. We now studied these rats using 31P magnetic resonance spectroscopy (MRS). MRS demonstrated that cardiac energy metabolism was markedly impaired, as indicated by a decreased phosphocreatine to ATP ratio (-31%, p < 0.05). In addition, we assessed contractility of isolated cardiomyocytes. While DEL-TNT and control cardiomyocytes showed no difference under baseline conditions, DEL-TNT cardiomyocytes selectively exhibited a decrease in fractional shortening by 28% after 1 h in glucose-deprived medium (p < 0.05). Moreover, significant decreases in contraction velocity and relaxation velocity were observed. To identify the underlying molecular pathways, we performed transcriptional profiling using real-time PCR. DEL-TNT hearts exhibited induction of several genes critical for cardiac energy supply, including CD36, CPT-1/-2, and PGC-1alpha. Finally, DEL-TNT rats and controls were studied by radiotelemetry after being stressed by isoproterenol, revealing a significantly increased frequency of arrhythmias in transgenic animals. In summary, we demonstrate profound energetic alterations in DEL-TNT hearts, supporting the notion that inefficient cellular ATP utilization contributes to the pathogenesis of HCM.
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190
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Cambronero F, Marín F, Roldán V, Hernández-Romero D, Valdés M, Lip GYH. Biomarkers of pathophysiology in hypertrophic cardiomyopathy: implications for clinical management and prognosis. Eur Heart J 2009; 30:139-51. [PMID: 19136482 DOI: 10.1093/eurheartj/ehn538] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The study of biomarkers and their signalling pathways has allowed the development of new therapeutic strategies in a range of disorders. The aim of the present systematic review is to provide an overview of different biomarkers in patients with hypertrophic cardiomyopathy that could give some insight into the pathophysiologic mechanism(s) underlying the typical clinical and histological manifestations of the disease. Several pathophysiological models are presented and discussed, including studies that have investigated these biomarkers for diagnostic and prognostic reasons, in relation to disease progression and/or mortality.
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Affiliation(s)
- Francisco Cambronero
- Department of Cardiology, Hospital Universitario Virgen de la Arrixaca, Murcia, Spain
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191
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Hudsmith LE, Neubauer S. Magnetic Resonance Spectroscopy in Myocardial Disease. JACC Cardiovasc Imaging 2009; 2:87-96. [DOI: 10.1016/j.jcmg.2008.08.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Accepted: 08/06/2008] [Indexed: 10/21/2022]
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192
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Mckenna WJ, Sen-Chowdhry S. De Teare a nuestros días: una odisea de cincuenta años en la miocardiopatía hipertrófica, un paradigma en la lógica del proceso de descubrimiento. Rev Esp Cardiol 2008. [DOI: 10.1016/s0300-8932(08)75730-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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193
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Fiset C, Giles WR. Cardiac troponin T mutations promote life-threatening arrhythmias. J Clin Invest 2008; 118:3845-7. [PMID: 19033655 DOI: 10.1172/jci37787] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Mutations in contractile proteins in heart muscle can cause anatomical changes that result in cardiac arrhythmias and sudden cardiac death. However, a conundrum has existed because mutations in one such contractile protein, a so-called Ca2+ sensor troponin T (TnT), can promote ventricular rhythm disturbances even in the absence of hypertrophy or fibrosis. Thus, these mutations must enhance abnormal electrophysiological events via alternative means. In this issue of the JCI, Baudenbacher et al. report a novel mechanism to explain this puzzle (see the related article beginning on page 3893). They show that a selected TnT mutation in the adult mouse heart can markedly increase the sensitivity of cardiac muscle myofilaments to Ca2+ and enhance the susceptibility to arrhythmia, even in the absence of anatomical deformities. As these same mutations can cause some forms of arrhythmias in humans, these findings are of both basic and translational significance.
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Affiliation(s)
- Céline Fiset
- Research Center, Montreal Heart Institute, Faculty of Pharmacy, University de Montréal, Montreal, Quebec, Canada
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194
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Missihoun C, Zisa D, Shabbir A, Lin H, Lee T. Myocardial oxidative stress, osteogenic phenotype, and energy metabolism are differentially involved in the initiation and early progression of delta-sarcoglycan-null cardiomyopathy. Mol Cell Biochem 2008; 321:45-52. [PMID: 18726675 DOI: 10.1007/s11010-008-9908-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Accepted: 08/19/2008] [Indexed: 12/11/2022]
Abstract
Dilated cardiomyopathy (DCM) is a common cause of heart failure, and identification of early pathogenic events occurring prior to the onset of cardiac dysfunction is of mechanistic, diagnostic, and therapeutic importance. The work characterized early biochemical pathogenesis in TO2 strain hamsters lacking delta-sarcoglycan. Although the TO2 hamster heart exhibits normal function at 1 month of age (presymptomatic stage), elevated levels of myeloperoxidase, monocyte chemotactic protein-1, malondialdehyde, osteopontin, and alkaline phosphatase were evident, indicating the presence of inflammation, oxidative stress, and osteogenic phenotype. These changes were localized primarily to the myocardium. Derangement in energy metabolism was identified at the symptomatic stage (4 month), and is marked by attenuated activity and expression of pyruvate dehydrogenase E1 subunit, which catalyzes the rate-limiting step in aerobic glucose metabolism. Thus, this study illustrates differential involvement of oxidative stress, osteogenic phenotype, and glucose metabolism in the initiation and early progression of delta-sarcoglycan-null DCM.
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Affiliation(s)
- Comlan Missihoun
- Department of Biochemistry and Center for Research in Cardiovascular Medicine, University at Buffalo, Buffalo, NY 14214, USA
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195
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Detection of myocardial disorders by magnetic resonance spectroscopy. ACTA ACUST UNITED AC 2008; 5 Suppl 2:S49-56. [DOI: 10.1038/ncpcardio1158] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2007] [Accepted: 12/14/2007] [Indexed: 11/08/2022]
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196
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Belus A, Piroddi N, Scellini B, Tesi C, D'Amati G, Girolami F, Yacoub M, Cecchi F, Olivotto I, Poggesi C. The familial hypertrophic cardiomyopathy-associated myosin mutation R403Q accelerates tension generation and relaxation of human cardiac myofibrils. J Physiol 2008; 586:3639-44. [PMID: 18565996 DOI: 10.1113/jphysiol.2008.155952] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The R403Q mutation in beta-myosin heavy chain was the first mutation to be identified as responsible for familial hypertrophic cardiomyopathy (FHC). In spite of extensive work on the functional sequelae of this mutation, the mechanism by which the mutant protein causes the disease has not been definitely identified. Here we directly compare contraction and relaxation mechanics of single myofibrils from left ventricular samples of one patient carrying the R403Q mutation to those from a healthy control heart. Tension generation and relaxation following sudden increase and decrease in [Ca(2+)] were much faster in the R403Q myofibrils with relaxation rates being the most affected parameters. The results show that the R403Q mutation leads to an apparent gain of protein function but a greater energetic cost of tension generation. Increased energy cost of tension generation may be central to the FHC disease process, help explain some unresolved clinical observations, and carry significant therapeutic implications.
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Affiliation(s)
- Alexandra Belus
- Department of Physiology, University of Florence, Florence, Italy
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197
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Sinagra G, Di Lenarda A, Moretti M, Mestroni L, Pinamonti B, Perkan A, Salvi A, Pyxaras S, Bussani R, Silvestri F, Camerini F. The challenge of cardiomyopathies in 2007. J Cardiovasc Med (Hagerstown) 2008; 9:545-54. [DOI: 10.2459/jcm.0b013e3282f2c9f9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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198
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Geier C, Gehmlich K, Ehler E, Hassfeld S, Perrot A, Hayess K, Cardim N, Wenzel K, Erdmann B, Krackhardt F, Posch MG, Bublak A, Nägele H, Scheffold T, Dietz R, Chien KR, Spuler S, Fürst DO, Nürnberg P, Özcelik C. Beyond the sarcomere: CSRP3 mutations cause hypertrophic cardiomyopathy. Hum Mol Genet 2008; 17:2753-65. [DOI: 10.1093/hmg/ddn160] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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199
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Govada L, Carpenter L, da Fonseca PCA, Helliwell JR, Rizkallah P, Flashman E, Chayen NE, Redwood C, Squire JM. Crystal structure of the C1 domain of cardiac myosin binding protein-C: implications for hypertrophic cardiomyopathy. J Mol Biol 2008; 378:387-97. [PMID: 18374358 DOI: 10.1016/j.jmb.2008.02.044] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 02/17/2008] [Accepted: 02/19/2008] [Indexed: 11/24/2022]
Abstract
C-protein is a major component of skeletal and cardiac muscle thick filaments. Mutations in the gene encoding cardiac C-protein [cardiac myosin binding protein-C (cMyBP-C)] are one of the principal causes of hypertrophic cardiomyopathy. cMyBP-C is a string of globular domains including eight immunoglobulin-like and three fibronectin-like domains termed C0-C10. It binds to myosin and titin, and probably to actin, and may have both a structural and a regulatory role in muscle function. To help to understand the pathology of the known mutations, we have solved the structure of the immunoglobulin-like C1 domain of MyBP-C by X-ray crystallography to a resolution of 1.55 A. Mutations associated with hypertrophic cardiomyopathy are clustered at one end towards the C-terminus, close to the important C1C2 linker, where they alter the structural integrity of this region and its interactions.
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Affiliation(s)
- Lata Govada
- Biomolecular Medicine Department, SORA Division, Imperial College London, London SW7 2AZ, UK
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200
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Liang B, Chung F, Qu Y, Pavlov D, Gillis TE, Tikunova SB, Davis JP, Tibbits GF. Familial hypertrophic cardiomyopathy-related cardiac troponin C mutation L29Q affects Ca2+ binding and myofilament contractility. Physiol Genomics 2008; 33:257-66. [PMID: 18285522 DOI: 10.1152/physiolgenomics.00154.2007] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cardiac troponin C (cTnC) mutation, L29Q, has been found in a patient with familial hypertrophic cardiomyopathy. We previously showed that L29, together with neighboring residues, Asp2, Val28, and Gly30, plays an important role in determining the Ca(2+) affinity of site II, the regulatory site of mammalian cardiac troponin C (McTnC). Here we report on the Ca(2+) binding characteristics of L29Q McTnC and D2N/V28I/L29Q/G30D McTnC (NIQD) utilizing the Phe(27) --> Trp (F27W) substitution, allowing one to monitor Ca(2+) binding and release. We also studied the effect of these mutants on Ca(2+) activation of force generation in single mouse cardiac myocytes using cTnC replacement, together with sarcomere length (SL) dependence. The Ca(2+)-binding affinity of site II of L29Q McTnC(F27W) and NIQD McTnC(F27W) was approximately 1.3- and approximately 1.9-fold higher, respectively, than that of McTnC(F27W). The Ca(2+) disassociation rate from site II of L29Q McTnC(F27W) and NIQD McTnC(F27W) was not significantly different than that of control (McTnC(F27W)). However, the rate of Ca(2+) binding to site II was higher in L29Q McTnC(F27W) and NIQD McTnC(F27W) relative to control (approximately 1.5-fold and approximately 2.0-fold respectively). The Ca(2+) sensitivity of force generation was significantly higher in myocytes reconstituted with L29Q McTnC (approximately 1.4-fold) and NIQD McTnC (approximately 2-fold) compared with those reconstituted with McTnC. Interestingly, the change in Ca(2+) sensitivity of force generation in response to an SL change (1.9, 2.1, and 2.3 mum) was significantly reduced in myocytes containing L29Q McTnC or NIQD McTnC. These results demonstrate that the L29Q mutation enhances the Ca(2+)-binding characteristics of cTnC and that when incorporated into cardiac myocytes, this mutant alters myocyte contractility.
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Affiliation(s)
- Bo Liang
- Cardiac Membrane Research Laboratory, Kinesiology, Simon Fraser University, Burnaby, Canada
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