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García-Hernández S, de la Higuera Romero L, Ochoa JP, McKenna WJ. Emerging Themes in Genetics of Hypertrophic Cardiomyopathy: Current Status and Clinical Application. Can J Cardiol 2024; 40:742-753. [PMID: 38244984 DOI: 10.1016/j.cjca.2024.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 01/07/2024] [Accepted: 01/08/2024] [Indexed: 01/22/2024] Open
Abstract
Hypertrophic cardiomyopathy (HCM), defined clinically by the presence of unexplained left ventricular hypertrophy (LVH), with wall thickness ≥ 1.5 cm, is a phenotype in search of a diagnosis, which is most often a genetically determined, cardiac exclusive, or systemic disorder. Familial evaluation and genetic testing are required for definitive diagnosis. The role of genetic findings in predicting development of disease, outcomes, and increasingly to guide management is evolving with access to larger data sets. The specific mutation and sex of the patient are important determinants that ultimately are likely to guide management. The genetic/familial evaluation is influenced by the accuracy of the clinical diagnosis and the extent/expertise of the genetic laboratory. Genetic testing in a patient with unexplained LVH without systemic manifestations will yield a definite/likely pathogenetic mutation in a sarcomere (30%-50%), regulatory/functional (10%-15%) or metabolic/syndromic (< 5%) gene associated with Mendelian inheritance. The importance of oligo- and polygenic determinants, usually in the absence of Mendelian inheritance, is under investigation with important implications, particularly related to familial evaluation and definition of risk of disease development in relatives of probands. The results of genetic testing are increasingly important in management strategies related to the use of the implantable cardioverter defibrillator for prevention of sudden death, use of myosin inhibitors for refractory symptoms in patients with and without outflow tract obstruction, and-on the immediate horizon-gene therapy. This review will focus on genetic and outcome data in sarcomeric HCM, and minor causative genes with robust evidence of their association will also be considered.
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Affiliation(s)
| | | | - Juan Pablo Ochoa
- Instituto de Investigación Biomédica de A Coruña (INIBIC), Universidade da Coruña, A Coruña, Spain; Centro Nacional de Investigaciones Cardiovasculades (CNIC), Madrid, Spain; Health in Code S.L., A Coruña, Spain
| | - William J McKenna
- Instituto de Investigación Biomédica de A Coruña (INIBIC), Universidade da Coruña, A Coruña, Spain; Institute of Cardiovascular Science, University College London, London, United Kingdom; Health in Code S.L., A Coruña, Spain.
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2
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Kumar P, Paramasivam G, Devasia T, Prabhu M, Rai MK, Prakashini K, Mallya S, Reghunathan D, Megha A, Nayak K, Moka R. A Novel TPM1 Mutation Causes Familial Hypertrophic Cardiomyopathy in an Indian Family: Genetic and Clinical Correlation. Indian J Clin Biochem 2024; 39:142-145. [PMID: 38223010 PMCID: PMC10784234 DOI: 10.1007/s12291-022-01036-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 02/21/2022] [Indexed: 11/26/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is a common inherited cardiac disorder characterised by unexplained left ventricular hypertrophy in the absence of abnormal loading conditions. The global prevalence of HCM is estimated to be 1 in 250 in the general population. It is caused due to mutations in genes coding for sarcomeric proteins. α-tropomyosin (TPM1) is an important protein in the sarcomeric thin filament which regulates sarcomere contraction. Mutations in TPM1 are known to cause hypertrophic cardiomyopathy, dilated cardiomyopathy and left ventricular non-compaction. Mutations in TPM1 causing hypertrophic cardiomyopathy are < 1%. However, some high-risk mutations causing sudden cardiac death are also known in this gene. We present a case of a novel heterozygous TPM1 mutation, NM_001018005.2:c.203A>G, p.Gln68Arg; co-segregating in an Indian family with hypertrophic cardiomyopathy. Our report expands the mutational spectrum of HCM due to TPM1 and provides the correlated cardiac phenotype.
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Affiliation(s)
- Prabodh Kumar
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education (MAHE), Planetarium Complex, Madhav Nagar, Manipal, 576104 Karnataka India
| | - Ganesh Paramasivam
- Department of Cardiology, Kasturba Medical College, Manipal Academy of Higher Education (MAHE), Manipal, 576104 Karnataka India
| | - Tom Devasia
- Department of Cardiology, Kasturba Medical College, Manipal Academy of Higher Education (MAHE), Manipal, 576104 Karnataka India
| | - Mukund Prabhu
- Department of Cardiology, Kasturba Medical College, Manipal Academy of Higher Education (MAHE), Manipal, 576104 Karnataka India
| | - Maneesh K. Rai
- Department of Cardiology, Kasturba Medical College, Manipal Academy of Higher Education (MAHE), Mangalore, 575001 Karnataka India
| | - K. Prakashini
- Department of Radiodiagnosis and Imaging, Kasturba Medical College, Manipal Academy of Higher Education (MAHE), Manipal, 576104 Karnataka India
| | - Sandeep Mallya
- Department of Bioinformatics, Manipal School of Life Sciences, Manipal Academy of Higher Education (MAHE), Manipal, 576104 Karnataka India
| | - Dinesh Reghunathan
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education (MAHE), Planetarium Complex, Madhav Nagar, Manipal, 576104 Karnataka India
| | - A. Megha
- Department of Cardiovascular Technology, Manipal College of Health Profession, Manipal Academy of Higher Education (Manipal), Manipal, 576104 Karnataka India
| | - Krishnananda Nayak
- Department of Cardiovascular Technology, Manipal College of Health Profession, Manipal Academy of Higher Education (Manipal), Manipal, 576104 Karnataka India
| | - Rajasekhar Moka
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education (MAHE), Planetarium Complex, Madhav Nagar, Manipal, 576104 Karnataka India
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Hayesmoore JB, Bhuiyan ZA, Coviello DA, du Sart D, Edwards M, Iascone M, Morris-Rosendahl DJ, Sheils K, van Slegtenhorst M, Thomson KL. EMQN: Recommendations for genetic testing in inherited cardiomyopathies and arrhythmias. Eur J Hum Genet 2023; 31:1003-1009. [PMID: 37443332 PMCID: PMC10474043 DOI: 10.1038/s41431-023-01421-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 06/21/2023] [Accepted: 06/22/2023] [Indexed: 07/15/2023] Open
Abstract
Inherited cardiomyopathies and arrhythmias (ICAs) are a prevalent and clinically heterogeneous group of genetic disorders that are associated with increased risk of sudden cardiac death and heart failure. Making a genetic diagnosis can inform the management of patients and their at-risk relatives and, as such, molecular genetic testing is now considered an integral component of the clinical care pathway. However, ICAs are characterised by high genetic and allelic heterogeneity, incomplete / age-related penetrance, and variable expressivity. Therefore, despite our improved understanding of the genetic basis of these conditions, and significant technological advances over the past two decades, identifying and recognising the causative genotype remains challenging. As clinical genetic testing for ICAs becomes more widely available, it is increasingly important for clinical laboratories to consolidate existing knowledge and experience to inform and improve future practice. These recommendations have been compiled to help clinical laboratories navigate the challenges of ICAs and thereby facilitate best practice and consistency in genetic test provision for this group of disorders. General recommendations on internal and external quality control, referral, analysis, result interpretation, and reporting are described. Also included are appendices that provide specific information pertinent to genetic testing for hypertrophic, dilated, and arrhythmogenic right ventricular cardiomyopathies, long QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia.
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Affiliation(s)
- Jesse B Hayesmoore
- Oxford Regional Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Zahurul A Bhuiyan
- Division of Genetic Medicine, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland
| | | | - Desirée du Sart
- Biological Sciences and Genomics, Monash University, Melbourne, VIC, Australia
| | - Matthew Edwards
- Clinical Genetics and Genomics Laboratory, Royal Brompton and Harefield Hospitals, Guy's and St. Thomas' NHS Foundation Trust, London, UK
| | - Maria Iascone
- Laboratorio di Genetica Medica, ASST Papa Giovanni XXIII, Bergamo, Italy
| | - Deborah J Morris-Rosendahl
- Clinical Genetics and Genomics Laboratory, Royal Brompton and Harefield Hospitals, Guy's and St. Thomas' NHS Foundation Trust, London, UK
| | | | | | - Kate L Thomson
- Oxford Regional Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, UK.
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4
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Wen W, Mead AJ, Thongjuea S. MARVEL: an integrated alternative splicing analysis platform for single-cell RNA sequencing data. Nucleic Acids Res 2023; 51:e29. [PMID: 36631981 PMCID: PMC10018366 DOI: 10.1093/nar/gkac1260] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 12/13/2022] [Accepted: 01/11/2023] [Indexed: 01/13/2023] Open
Abstract
Alternative splicing is an important source of heterogeneity underlying gene expression between individual cells but remains an understudied area due to the paucity of computational tools to analyze splicing dynamics at single-cell resolution. Here, we present MARVEL, a comprehensive R package for single-cell splicing analysis applicable to RNA sequencing generated from the plate- and droplet-based methods. We performed extensive benchmarking of MARVEL against available tools and demonstrated its utility by analyzing multiple publicly available datasets in diverse cell types, including in disease. MARVEL enables systematic and integrated splicing and gene expression analysis of single cells to characterize the splicing landscape and reveal biological insights.
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Affiliation(s)
- Wei Xiong Wen
- MRC Molecular Haematology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
- MRC WIMM Centre for Computational Biology, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
| | - Adam J Mead
- Correspondence may also be addressed to Adam J. Mead.
| | - Supat Thongjuea
- To whom correspondence should be addressed. Tel: +49 015201091154;
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Keyt LK, Duran JM, Bui QM, Chen C, Miyamoto MI, Silva Enciso J, Tardiff JC, Adler ED. Thin filament cardiomyopathies: A review of genetics, disease mechanisms, and emerging therapeutics. Front Cardiovasc Med 2022; 9:972301. [PMID: 36158814 PMCID: PMC9489950 DOI: 10.3389/fcvm.2022.972301] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Accepted: 07/28/2022] [Indexed: 11/17/2022] Open
Abstract
All muscle contraction occurs due to the cyclical interaction between sarcomeric thin and thick filament proteins within the myocyte. The thin filament consists of the proteins actin, tropomyosin, Troponin C, Troponin I, and Troponin T. Mutations in these proteins can result in various forms of cardiomyopathy, including hypertrophic, restrictive, and dilated phenotypes and account for as many as 30% of all cases of inherited cardiomyopathy. There is significant evidence that thin filament mutations contribute to dysregulation of Ca2+ within the sarcomere and may have a distinct pathomechanism of disease from cardiomyopathy associated with thick filament mutations. A number of distinct clinical findings appear to be correlated with thin-filament mutations: greater degrees of restrictive cardiomyopathy and relatively less left ventricular (LV) hypertrophy and LV outflow tract obstruction than that seen with thick filament mutations, increased morbidity associated with heart failure, increased arrhythmia burden and potentially higher mortality. Most therapies that improve outcomes in heart failure blunt the neurohormonal pathways involved in cardiac remodeling, while most therapies for hypertrophic cardiomyopathy involve use of negative inotropes to reduce LV hypertrophy or septal reduction therapies to reduce LV outflow tract obstruction. None of these therapies directly address the underlying sarcomeric dysfunction associated with thin-filament mutations. With mounting evidence that thin filament cardiomyopathies occur through a distinct mechanism, there is need for therapies targeting the unique, underlying mechanisms tailored for each patient depending on a given mutation.
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Affiliation(s)
- Lucas K. Keyt
- Department of Internal Medicine, University of California, San Diego, San Diego, CA, United States
| | - Jason M. Duran
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | - Quan M. Bui
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | - Chao Chen
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | | | - Jorge Silva Enciso
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
| | - Jil C. Tardiff
- Department of Medicine and Biomedical Engineering, University of Arizona, Tucson, AZ, United States
| | - Eric D. Adler
- Department of Cardiology, University of California, San Diego, San Diego, CA, United States
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Lamounier Junior A, Guitián González A, Rodríguez Vilela A, Repáraz Andrade A, Rubio Alcaide Á, Berta Sousa A, Benito López C, Alonso García D, Fernández Ferro G, Cruz I, Cárdenas Reyes IJ, Salazar-Mendiguchía García J, Larrañaga-Moreira JM, Ochoa JP, Palomino-Doza J, de la Higuera Romero L, Nicolás Cicerchia M, Restrepo Córdoba MA, Peña-Peña ML, Noël Brögger M, Loureiro M, Mogollón Jiménez MV, Bilbao Quesada R, Franco Gutiérrez R, García Hernández S, Ripoll-Vera T, Fernández X, Azevedo O, García Pavía P, Lopes LR, Ortiz M, Brito D, Barriales-Villa R, Monserrat Iglesias L. Correlación genotipo-fenotipo en miocardiopatía hipertrófica: un estudio multicéntrico en Portugal y España sobre la variante p.Arg21Leu de TPM1. Rev Esp Cardiol 2022. [DOI: 10.1016/j.recesp.2020.12.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Hassoun R, Budde H, Mügge A, Hamdani N. Cardiomyocyte Dysfunction in Inherited Cardiomyopathies. Int J Mol Sci 2021; 22:11154. [PMID: 34681814 PMCID: PMC8541428 DOI: 10.3390/ijms222011154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/08/2021] [Accepted: 10/13/2021] [Indexed: 01/10/2023] Open
Abstract
Inherited cardiomyopathies form a heterogenous group of disorders that affect the structure and function of the heart. Defects in the genes encoding sarcomeric proteins are associated with various perturbations that induce contractile dysfunction and promote disease development. In this review we aimed to outline the functional consequences of the major inherited cardiomyopathies in terms of myocardial contraction and kinetics, and to highlight the structural and functional alterations in some sarcomeric variants that have been demonstrated to be involved in the pathogenesis of the inherited cardiomyopathies. A particular focus was made on mutation-induced alterations in cardiomyocyte mechanics. Since no disease-specific treatments for familial cardiomyopathies exist, several novel agents have been developed to modulate sarcomere contractility. Understanding the molecular basis of the disease opens new avenues for the development of new therapies. Furthermore, the earlier the awareness of the genetic defect, the better the clinical prognostication would be for patients and the better the prevention of development of the disease.
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Affiliation(s)
- Roua Hassoun
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Heidi Budde
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Andreas Mügge
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
| | - Nazha Hamdani
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, 44801 Bochum, Germany
- Department of Cardiology, St. Josef-Hospital and Bergmannsheil, Ruhr University Bochum, 44801 Bochum, Germany
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Pradeep R, Akram A, Proute MC, Kothur NR, Georgiou P, Serhiyenia T, Shi W, Kerolos ME, Mostafa JA. Understanding the Genetic and Molecular Basis of Familial Hypertrophic Cardiomyopathy and the Current Trends in Gene Therapy for Its Management. Cureus 2021; 13:e17548. [PMID: 34646605 PMCID: PMC8481153 DOI: 10.7759/cureus.17548] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 08/28/2021] [Indexed: 01/16/2023] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is a genetically acquired disease of cardiac myocytes. Studies show that 70% of this disease is a result of different mutations in various sarcomere genes. This review aims to discuss several genetic mutations, epigenetic factors, and signal transduction pathways leading to the development of HCM. In addition, this article elaborates on recent advances in gene therapies and their implications for managing this condition. We start by discussing the founding mutations in HCM and their effect on power stroke generation. The less explored field of epigenetics including methylation, acetylation, and the role of different micro RNAs in the development of cardiac muscle hypertrophy has been highlighted in this article. The signal transduction pathways that lead to gene transcription, which in turn lead to increased protein synthesis of cardiac muscle fibers are elaborated. Finally, the microscopic events leading to the pathophysiologic macro events of cardiac failure, and the current experimental trials of gene therapy models, and the clustered regularly interspaced short palindromic repeats (CRISPR) type 2 system proteins, are discussed. We have concluded our discussion by emphasizing the need for more studies on epigenomics and experimental designs for gene therapy in HCM patients. This review focuses on the process of HCM from initial mutation to the development of phenotypic expression and various points of intervention in cardiac myocardial hypertrophy development.
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Affiliation(s)
- Roshini Pradeep
- Internal Medicine, California Institute of Behavioral Neurosciences & Psychology, Fairfield, USA
| | - Aqsa Akram
- Internal Medicine, California Institute of Behavioral Neurosciences & Psychology, Fairfield, USA
| | - Matthew C Proute
- Family Medicine, California Institute of Behavioral Neurosciences & Psychology, Fairfield, USA
| | - Nageshwar R Kothur
- Internal Medicine, California Institute of Behavioral Neurosciences & Psychology, Fairfield, USA
| | - Petros Georgiou
- Internal Medicine, California Institute of Behavioral Neurosciences & Psychology, Fairfield, USA
| | - Tatsiana Serhiyenia
- Internal Medicine, California Institute of Behavioral Neurosciences & Psychology, Fairfield, USA
| | - Wangpan Shi
- Pathology, California Institute of Behavioral Neurosciences & Psychology, Fairfield, USA
| | - Mina E Kerolos
- Medicine, California Institute of Behavioral Neurosciences & Psychology, Fairfield, USA
| | - Jihan A Mostafa
- Psychiatry/Cognitive Behavioural Psychotherapy, California Institute of Behavioral Neurosciences & Psychology, Fairfield, USA
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Cao J, Routh AL, Kuyumcu-Martinez MN. Nanopore sequencing reveals full-length Tropomyosin 1 isoforms and their regulation by RNA-binding proteins during rat heart development. J Cell Mol Med 2021; 25:8352-8362. [PMID: 34302435 PMCID: PMC8419188 DOI: 10.1111/jcmm.16795] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 07/01/2021] [Accepted: 07/06/2021] [Indexed: 12/11/2022] Open
Abstract
Alternative splicing (AS) contributes to the diversity of the proteome by producing multiple isoforms from a single gene. Although short‐read RNA‐sequencing methods have been the gold standard for determining AS patterns of genes, they have a difficulty in defining full‐length mRNA isoforms assembled using different exon combinations. Tropomyosin 1 (TPM1) is an actin‐binding protein required for cytoskeletal functions in non‐muscle cells and for contraction in muscle cells. Tpm1 undergoes AS regulation to generate muscle versus non‐muscle TPM1 protein isoforms with distinct physiological functions. It is unclear which full‐length Tpm1 isoforms are produced via AS and how they are regulated during heart development. To address these, we utilized nanopore long‐read cDNA sequencing without gene‐specific PCR amplification. In rat hearts, we identified full‐length Tpm1 isoforms composed of distinct exons with specific exon linkages. We showed that Tpm1 undergoes AS transitions during embryonic heart development such that muscle‐specific exons are connected generating predominantly muscle‐specific Tpm1 isoforms in adult hearts. We found that the RNA‐binding protein RBFOX2 controls AS of rat Tpm1 exon 6a, which is important for cooperative actin binding. Furthermore, RBFOX2 regulates Tpm1 AS of exon 6a antagonistically to the RNA‐binding protein PTBP1. In sum, we defined full‐length Tpm1 isoforms with different exon combinations that are tightly regulated during cardiac development and provided insights into the regulation of Tpm1 AS by RNA‐binding proteins. Our results demonstrate that nanopore sequencing is an excellent tool to determine full‐length AS variants of muscle‐enriched genes.
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Affiliation(s)
- Jun Cao
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Andrew L Routh
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, USA.,Sealy Centre for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas, USA
| | - Muge N Kuyumcu-Martinez
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, USA.,Institute for Translational Sciences, University of Texas Medical Branch, Galveston, Texas, USA.,Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, Texas, USA
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Genotype-phenotype correlations in hypertrophic cardiomyopathy: a multicenter study in Portugal and Spain of the TPM1 p.Arg21Leu variant. ACTA ACUST UNITED AC 2021; 75:242-250. [PMID: 33642254 DOI: 10.1016/j.rec.2021.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 12/18/2020] [Indexed: 11/23/2022]
Abstract
INTRODUCTION AND OBJECTIVES TPM1 is one of the main hypertrophic cardiomyopathy (HCM) genes. Clinical information on carriers is relatively scarce, limiting the interpretation of genetic findings in individual patients. Our aim was to establish genotype-phenotype correlations of the TPM1 p.Arg21Leu variant in a serie of pedigrees. METHODS TPM1 was evaluated by next-generation sequencing in 10 561 unrelated probands with inherited heart diseases. Familial genetic screening was performed by the Sanger method. We analyzed TPM1 p.Arg21Leu pedigrees for cosegregation, clinical characteristics, and outcomes. We also estimated the geographical distribution of the carrier families in Portugal and Spain. RESULTS The TPM1 p.Arg21Leu variant was identified in 25/4099 (0.61%) HCM-cases, and was absent in 6462 control individuals with other inherited cardiac phenotypes (P<.0001). In total, 83 carriers (31 probands) were identified. The combined LOD score for familial cosegregation was 3.95. The cumulative probability of diagnosis in carriers was 50% at the age of 50 years for males, and was 25% in female carriers. At the age of 70 years, 17% of males and 46% of female carriers were unaffected. Mean maximal left ventricular wall thickness was 21.4 ±7.65mm. Calculated HCM sudden death risk was low in 34 carriers (77.5%), intermediated in 8 (18%), and high in only 2 (4.5%). Survival free of cardiovascular death or heart transplant was 87.5% at 50 years. Six percent of carriers were homozygous and 18% had an additional variant. Family origin was concentrated in Galicia, Extremadura, and northern Portugal, suggesting a founder effect. CONCLUSIONS TPM1 p.Arg21Leu is a pathogenic HCM variant associated with late-onset/incomplete penetrance and a generally favorable prognosis.
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11
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Dorsch LM, Kuster DWD, Jongbloed JDH, Boven LG, van Spaendonck-Zwarts KY, Suurmeijer AJH, Vink A, du Marchie Sarvaas GJ, van den Berg MP, van der Velden J, Brundel BJJM, van der Zwaag PA. The effect of tropomyosin variants on cardiomyocyte function and structure that underlie different clinical cardiomyopathy phenotypes. Int J Cardiol 2020; 323:251-258. [PMID: 32882290 DOI: 10.1016/j.ijcard.2020.08.101] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 08/20/2020] [Accepted: 08/28/2020] [Indexed: 12/27/2022]
Abstract
Background - Variants within the alpha-tropomyosin gene (TPM1) cause dominantly inherited cardiomyopathies, including dilated (DCM), hypertrophic (HCM) and restrictive (RCM) cardiomyopathy. Here we investigated whether TPM1 variants observed in DCM and HCM patients affect cardiomyocyte physiology differently. Methods - We identified a large family with DCM carrying a recently identified TPM1 gene variant (T201M) and a child with RCM with compound heterozygote TPM1 variants (E62Q and M281T) whose family members carrying single variants show diastolic dysfunction and HCM. The effects of TPM1 variants (T201M, E62Q or M281T) and of a plasmid containing both the E62Q and M281T variants on single-cell Ca2+ transients (CaT) in HL-1 cardiomyocytes were studied. To define toxic threshold levels, we performed dose-dependent transfection of TPM1 variants. In addition, cardiomyocyte structure was studied in human cardiac biopsies with TPM1 variants. Results - Overexpression of TPM1 variants led to time-dependent progressive deterioration of CaT, with the smallest effect seen for E62Q and larger and similar effects seen for the T201M and M281T variants. Overexpression of E62Q/M281T did not exacerbate the effects seen with overexpression of a single TPM1 variant. T201M (DCM) replaced endogenous tropomyosin dose-dependently, while M281T (HCM) did not. Human cardiac biopsies with TPM1 variants revealed loss of sarcomeric structures. Conclusion - All TPM1 variants result in reduced cardiomyocyte CaT amplitudes and loss of sarcomeric structures. These effects may underlie pathophysiology of different cardiomyopathy phenotypes.
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Affiliation(s)
- Larissa M Dorsch
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands.
| | - Diederik W D Kuster
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
| | - Jan D H Jongbloed
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Ludolf G Boven
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Karin Y van Spaendonck-Zwarts
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands; Department of Clinical Genetics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
| | - Albert J H Suurmeijer
- Department of Pathology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Aryan Vink
- Department of Pathology, University Medical Center Utrecht, Utrecht, the Netherlands
| | | | - Maarten P van den Berg
- Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Jolanda van der Velden
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
| | - Bianca J J M Brundel
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
| | - Paul A van der Zwaag
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
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Farman GP, Rynkiewicz MJ, Orzechowski M, Lehman W, Moore JR. HCM and DCM cardiomyopathy-linked α-tropomyosin mutations influence off-state stability and crossbridge interaction on thin filaments. Arch Biochem Biophys 2018; 647:84-92. [PMID: 29626422 DOI: 10.1016/j.abb.2018.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 04/02/2018] [Accepted: 04/03/2018] [Indexed: 12/19/2022]
Abstract
Calcium regulation of cardiac muscle contraction is controlled by the thin-filament proteins troponin and tropomyosin bound to actin. In the absence of calcium, troponin-tropomyosin inhibits myosin-interactions on actin and induces muscle relaxation, whereas the addition of calcium relieves the inhibitory constraint to initiate contraction. Many mutations in thin filament proteins linked to cardiomyopathy appear to disrupt this regulatory switching. Here, we tested perturbations caused by mutant tropomyosins (E40K, DCM; and E62Q, HCM) on intra-filament interactions affecting acto-myosin interactions including those induced further by myosin association. Comparison of wild-type and mutant human α-tropomyosin (Tpm1.1) behavior was carried out using in vitro motility assays and molecular dynamics simulations. Our results show that E62Q tropomyosin destabilizes thin filament off-state function by increasing calcium-sensitivity, but without apparent affect on global tropomyosin structure by modifying coiled-coil rigidity. In contrast, the E40K mutant tropomyosin appears to stabilize the off-state, demonstrates increased tropomyosin flexibility, while also decreasing calcium-sensitivity. In addition, the E40K mutation reduces thin filament velocity at low myosin concentration while the E62Q mutant tropomyosin increases velocity. Corresponding molecular dynamics simulations indicate specific residue interactions that are likely to redefine underlying molecular regulatory mechanisms, which we propose explain the altered contractility evoked by the disease-causing mutations.
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Affiliation(s)
- Gerrie P Farman
- Department of Biological Sciences, University of Massachusetts-Lowell, One University Avenue, Lowell, MA 01854, USA; Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
| | - Michael J Rynkiewicz
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
| | - Marek Orzechowski
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
| | - William Lehman
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
| | - Jeffrey R Moore
- Department of Biological Sciences, University of Massachusetts-Lowell, One University Avenue, Lowell, MA 01854, USA.
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Zheng W, Hitchcock-DeGregori SE, Barua B. Investigating the effects of tropomyosin mutations on its flexibility and interactions with filamentous actin using molecular dynamics simulation. J Muscle Res Cell Motil 2016; 37:131-147. [DOI: 10.1007/s10974-016-9447-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Accepted: 06/24/2016] [Indexed: 12/15/2022]
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14
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Gupte TM, Haque F, Gangadharan B, Sunitha MS, Mukherjee S, Anandhan S, Rani DS, Mukundan N, Jambekar A, Thangaraj K, Sowdhamini R, Sommese RF, Nag S, Spudich JA, Mercer JA. Mechanistic heterogeneity in contractile properties of α-tropomyosin (TPM1) mutants associated with inherited cardiomyopathies. J Biol Chem 2014; 290:7003-15. [PMID: 25548289 DOI: 10.1074/jbc.m114.596676] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The most frequent known causes of primary cardiomyopathies are mutations in the genes encoding sarcomeric proteins. Among those are 30 single-residue mutations in TPM1, the gene encoding α-tropomyosin. We examined seven mutant tropomyosins, E62Q, D84N, I172T, L185R, S215L, D230N, and M281T, that were chosen based on their clinical severity and locations along the molecule. The goal of our study was to determine how the biochemical characteristics of each of these mutant proteins are altered, which in turn could provide a structural rationale for treatment of the cardiomyopathies they produce. Measurements of Ca(2+) sensitivity of human β-cardiac myosin ATPase activity are consistent with the hypothesis that hypertrophic cardiomyopathies are hypersensitive to Ca(2+) activation, and dilated cardiomyopathies are hyposensitive. We also report correlations between ATPase activity at maximum Ca(2+) concentrations and conformational changes in TnC measured using a fluorescent probe, which provide evidence that different substitutions perturb the structure of the regulatory complex in different ways. Moreover, we observed changes in protein stability and protein-protein interactions in these mutants. Our results suggest multiple mechanistic pathways to hypertrophic and dilated cardiomyopathies. Finally, we examined a computationally designed mutant, E181K, that is hypersensitive, confirming predictions derived from in silico structural analysis.
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Affiliation(s)
- Tejas M Gupte
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Farah Haque
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Binnu Gangadharan
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the Manipal University, Madhav Nagar, Manipal 576104, India
| | - Margaret S Sunitha
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Souhrid Mukherjee
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Swetha Anandhan
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Deepa Selvi Rani
- the Council for Scientific and Industrial Research-Centre for Cellular and Molecular Biology, Hyderabad 500007, India
| | - Namita Mukundan
- the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Amruta Jambekar
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Kumarasamy Thangaraj
- the Council for Scientific and Industrial Research-Centre for Cellular and Molecular Biology, Hyderabad 500007, India
| | - Ramanathan Sowdhamini
- the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Ruth F Sommese
- the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - Suman Nag
- the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - James A Spudich
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - John A Mercer
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the McLaughlin Research Institute, Great Falls, Montana 59405
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15
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Chang AN, Greenfield NJ, Singh A, Potter JD, Pinto JR. Structural and protein interaction effects of hypertrophic and dilated cardiomyopathic mutations in alpha-tropomyosin. Front Physiol 2014; 5:460. [PMID: 25520664 PMCID: PMC4251307 DOI: 10.3389/fphys.2014.00460] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Accepted: 11/10/2014] [Indexed: 12/16/2022] Open
Abstract
The potential alterations to structure and associations with thin filament proteins caused by the dilated cardiomyopathy (DCM) associated tropomyosin (Tm) mutants E40K and E54K, and the hypertrophic cardiomyopathy (HCM) associated Tm mutants E62Q and L185R, were investigated. In order to ascertain what the cause of the known functional effects may be, structural and protein-protein interaction studies were conducted utilizing actomyosin ATPase activity measurements and spectroscopy. In actomyosin ATPase measurements, both HCM mutants and the DCM mutant E54K caused increases in Ca2+-induced maximal ATPase activities, while E40K caused a decrease. Investigation of Tm's ability to inhibit actomyosin ATPase in the absence of troponin showed that HCM-associated mutant Tms did not inhibit as well as wildtype, whereas the DCM associated mutant E40K inhibited better. E54K did not inhibit the actomyosin ATPase activity at any concentration of Tm tested. Thermal denaturation studies by circular dichroism and molecular modeling of the mutations in Tm showed that in general, the DCM mutants caused localized destabilization of the Tm dimers, while the HCM mutants resulted in increased stability. These findings demonstrate that the structural alterations in Tm observed here may affect the regulatory function of Tm on actin, thereby directly altering the ATPase rates of myosin.
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Affiliation(s)
- Audrey N Chang
- Department of Molecular and Cellular Pharmacology, Leonard Miller School of Medicine, University of Miami Miami, FL, USA
| | - Norma J Greenfield
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University New Jersey, NJ, USA
| | - Abhishek Singh
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University New Jersey, NJ, USA ; Department of Cardiology, UCSF Medical Center, University of California, San Francisco San Francisco, CA, USA
| | - James D Potter
- Department of Molecular and Cellular Pharmacology, Leonard Miller School of Medicine, University of Miami Miami, FL, USA
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine Tallahassee, FL, USA
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16
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Redwood C, Robinson P. Alpha-tropomyosin mutations in inherited cardiomyopathies. J Muscle Res Cell Motil 2013; 34:285-94. [DOI: 10.1007/s10974-013-9358-5] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 08/23/2013] [Indexed: 10/26/2022]
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17
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A study of tropomyosin's role in cardiac function and disease using thin-filament reconstituted myocardium. J Muscle Res Cell Motil 2013; 34:295-310. [PMID: 23700264 DOI: 10.1007/s10974-013-9343-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 05/07/2013] [Indexed: 10/26/2022]
Abstract
Tropomyosin (Tm) is the key regulatory component of the thin-filament and plays a central role in the cardiac muscle's cooperative activation mechanism. Many mutations of cardiac Tm are related to hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and left ventricular noncompaction (LVNC). Using the thin-filament extraction/reconstitution technique, we are able to incorporate various Tm mutants and protein isoforms into a muscle fiber environment to study their roles in Ca(2+) regulation, cross-bridge kinetics, and force generation. The thin-filament reconstitution technique poses several advantages compared to other in vitro and in vivo methods: (1) Tm mutants and isoforms are placed into the real muscle fiber environment to exhibit their effect on a level much higher than simple protein complexes; (2) only the primary and immediate effects of Tm mutants are studied in the thin-filament reconstituted myocardium; (3) lethal mutants of Tm can be studied without causing a problem; and (4) inexpensive. In transgenic models, various secondary effects (myocyte disarray, ECM fibrosis, altered protein phosphorylation levels, etc.) also affect the performance of the myocardium, making it very difficult to isolate the primary effect of the mutation. Our studies on Tm have demonstrated that: (1) Tm positively enhances the hydrophobic interaction between actin and myosin in the "closed state", which in turn enhances the isometric tension; (2) Tm's seven periodical repeats carry distinct functions, with the 3rd period being essential for the tension enhancement; (3) Tm mutants lead to HCM by impairing the relaxation on one hand, and lead to DCM by over inhibition of the AM interaction on the other hand. Ca(2+) sensitivity is affected by inorganic phosphate, ionic strength, and phosphorylation of constituent proteins; hence it may not be the primary cause of the pathogenesis. Here, we review our current knowledge regarding Tm's effect on the actomyosin interaction and the early molecular pathogenesis of Tm mutation related to HCM, DCM, and LVNC.
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18
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Brouwer WP, Germans T, Head MC, van der Velden J, Heymans MW, Christiaans I, Houweling AC, Wilde AA, van Rossum AC. Multiple myocardial crypts on modified long-axis view are a specific finding in pre-hypertrophic HCM mutation carriers. Eur Heart J Cardiovasc Imaging 2012; 13:292-7. [DOI: 10.1093/ehjci/jes005] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Germans T, Wilde AAM, van Echteld CJA, Kamp O, Pinto YM, van Rossum AC. Structural abnormalities of the left ventricle in hypertrophic cardiomyopathy mutation carriers detectable before the development of hypertrophy. Neth Heart J 2011; 15:161-3. [PMID: 18604279 DOI: 10.1007/bf03085974] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Affiliation(s)
- T Germans
- Department of Cardiology, VU University Medical Centre, Amsterdam, and Interuniversity Cardiology Institute of the Netherlands, Utrecht, the Netherlands
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20
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Chang B, Nishizawa T, Furutani M, Fujiki A, Tani M, Kawaguchi M, Ibuki K, Hirono K, Taneichi H, Uese K, Onuma Y, Bowles NE, Ichida F, Inoue H, Matsuoka R, Miyawaki T. Identification of a novel TPM1 mutation in a family with left ventricular noncompaction and sudden death. Mol Genet Metab 2011; 102:200-6. [PMID: 20965760 DOI: 10.1016/j.ymgme.2010.09.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 09/23/2010] [Indexed: 01/12/2023]
Abstract
Left ventricular noncompaction (LVNC) is a cardiomyopathy morphologically characterized by 2-layered myocardium, numerous prominent trabeculations, and deep intertrabecular recesses communicating with the left ventricular cavity. The purpose of this study was to investigate patients with LVNC for possible disease causing mutations. We screened 4 genes (TAZ, LDB3, DTNA and TPM1) in 51 patients with LVNC for mutations by polymerase chain reaction and direct DNA sequencing. A novel missense substitution in exon 1 of TPM1 (c.109A>G: p.Lys37Glu) was identified in three affected members of a family with isolated LVNC. The substitution brings about a change in amino acid charge at a highly conserved residue and could result in aberrant mRNA splicing. This variant was not identified in 200 normal control samples. Pathologic analysis of a right ventricular myocardial specimen from the proband's maternal aunt revealed endocardial and subendocardial fibrosis with prominent elastin deposition, as well as the presence of adipose tissue between muscle layers, pathologic changes that are distinct from those seen in patients with HCM or DCM. Screening of the proband and her mother for variants in other sarcomeric protein-encoding candidate genes, MYH7, MYBPC3, TNNT2, TNNI3, ACTC, MYL2, and MYL3, did not identify any other non-synonymous variants or variants in splice donor-acceptor sequences that were potentially disease causing. We conclude TPM1 is a potential candidate disease-causing gene for isolated LVNC, especially in patients experiencing sudden death.
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Affiliation(s)
- Bo Chang
- Department of Pediatrics, University of Toyama, 2630 Sugitani, Toyama, Japan
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21
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Rüssel IK, Brouwer WP, Germans T, Knaapen P, Marcus TJ, van der Velden J, Götte MJW, van Rossum AC. Increased left ventricular torsion in hypertrophic cardiomyopathy mutation carriers with normal wall thickness. J Cardiovasc Magn Reson 2011; 13:3. [PMID: 21219655 PMCID: PMC3025877 DOI: 10.1186/1532-429x-13-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Accepted: 01/10/2011] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Increased left ventricular (LV) torsion has been observed in patients with manifest familial hypertrophic cardiomyopathy (HCM), and is thought to be caused by subendocardial dysfunction. We hypothesize that increased LV torsion is already present in healthy mutation carriers with normal wall thickness. METHODS Seventeen carriers with an LV wall thickness <10 mm, and seventeen age and gender matched controls had cardiovascular magnetic resonance (CMR) cine imaging and tissue tagging. LV volumes and mass were calculated from the cine images. LV torsion, torsion rate, endocardial circumferential strain and torsion-to-endocardial-circumferential-shortening (TECS) ratio, which reflects the transmural distribution in contractile function, were determined using tissue tagging. RESULTS LV volumes, mass and circumferential strain were comparable between groups, whereas LV ejection fraction, torsion and TECS-ratio were increased in carriers compared to controls (63 ± 3% vs. 60 ± 3%, p = 0.04, 10.1 ± 2.5° vs. 7.7 ± 1.2°, p = 0.001, and 0.52 ± 0.14°/% vs. 0.42 ± 0.10°/%, p = 0.02, respectively). CONCLUSIONS Carriers with normal wall thickness display increased LV torsion and TECS-ratio with respect to controls, which might be due to subendocardial myocardial dysfunction. As similar abnormalities are observed in patients with manifest HCM, the changes in healthy carriers may be target for clinical intervention to delay or prevent the onset of hypertrophy.
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MESH Headings
- Adult
- Cardiomyopathy, Hypertrophic, Familial/genetics
- Cardiomyopathy, Hypertrophic, Familial/pathology
- Cardiomyopathy, Hypertrophic, Familial/physiopathology
- Case-Control Studies
- Female
- Humans
- Image Interpretation, Computer-Assisted
- Magnetic Resonance Imaging, Cine
- Male
- Middle Aged
- Mutation
- Myocardial Contraction/genetics
- Netherlands
- Torsion Abnormality/genetics
- Torsion Abnormality/pathology
- Torsion Abnormality/physiopathology
- Ventricular Dysfunction, Left/genetics
- Ventricular Dysfunction, Left/pathology
- Ventricular Dysfunction, Left/physiopathology
- Ventricular Function, Left/genetics
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Affiliation(s)
- Iris K Rüssel
- Department of Clinical Physics, Hagaziekenhuis, The Hague, The Netherlands
| | - Wessel P Brouwer
- Department of Cardiology, VU University Medical Center, Amsterdam, The Netherlands
- Interuniversity Cardiology Institute of the Netherlands (ICIN), Utrecht, The Netherlands
| | - Tjeerd Germans
- Department of Cardiology, VU University Medical Center, Amsterdam, The Netherlands
- Interuniversity Cardiology Institute of the Netherlands (ICIN), Utrecht, The Netherlands
| | - Paul Knaapen
- Department of Cardiology, VU University Medical Center, Amsterdam, The Netherlands
| | - Tim J Marcus
- Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands
| | | | - Marco JW Götte
- Department of cardiology, Hagaziekenhuis, The Hague, The Netherlands
| | - Albert C van Rossum
- Department of Cardiology, VU University Medical Center, Amsterdam, The Netherlands
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Polymorphisms in the tropomyosin TPM1 short isoform promoter alter gene expression and are associated with increased risk of metabolic syndrome. Am J Hypertens 2010; 23:399-404. [PMID: 20075843 DOI: 10.1038/ajh.2009.278] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Inflammation contributes to the development of atherosclerotic lesions in the metabolic syndrome. Tropomyosin isoform expression is altered in this disease and has a role in inflammatory cell plasticity, motility, and insulin sensitivity. We determined the frequency of haplotype carriage of three single-nucleotide polymorphisms (SNPs) in the short isoform promoter of the TPM1 gene in 300 normal controls and 500 metabolic syndrome patients. The effect of each haplotype on tropomyosin gene expression was assessed. METHODS PCR-restriction fragment length polymorphism assays were developed for each polymorphism. Promoter activity was measured using luciferase assays in the insulin-sensitive human embryonic kidney (HEK) 293 and the monocyte THP-1 lines. RESULTS The SNPs -111(T/C), -426(T/C), and -491(A/G), relative to the TPM1 short isoform transcription start site, occurred in haplotypes ATT, GCT, GTT, and GTC, and were in strong linkage disequilibrium. ATT had a frequency of 66%. The presence of -491G, which conforms to a predicted binding site for transcription factor AML-1, caused a decrease in gene expression of 24% in the HEK 293 cells. In the THP-1 cells, haplotypes GTC and GTT gave 24% lower expression, whereas haplotype GCT gave expression at wild-type levels. The carriage of a -491G allele gave an odds ratio of 1.4 (95% CI 1.02-1.8) for the metabolic syndrome (P < 0.03). CONCLUSIONS A polymorphism in the TPM1 short isoform promoter region is predicted to alter transcription factor binding, alters gene expression and is associated with the metabolic syndrome. This could affect inflammatory cells and cytoskeleton-mediated insulin signaling.
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23
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Germans T, Rüssel IK, Götte MJW, Spreeuwenberg MD, Doevendans PA, Pinto YM, van der Geest RJ, van der Velden J, Wilde AAM, van Rossum AC. How do hypertrophic cardiomyopathy mutations affect myocardial function in carriers with normal wall thickness? Assessment with cardiovascular magnetic resonance. J Cardiovasc Magn Reson 2010; 12:13. [PMID: 20230637 PMCID: PMC2842263 DOI: 10.1186/1532-429x-12-13] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Accepted: 03/15/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Clinical data on myocardial function in HCM mutation carriers (carriers) is sparse but suggests that subtle functional abnormalities can be measured with tissue Doppler imaging before the development of overt hypertrophy. We aimed to confirm the presence of functional abnormalities using cardiovascular magnetic resonance (CMR), and to investigate if sensitive functional assessment could be employed to identify carriers. RESULTS 28 carriers and 28 controls were studied. Global left atrial (LA) and left ventricular (LV) dimensions, segmental peak systolic circumferential strain (SCS) and peak diastolic circumferential strain rate (DCSR), as well as the presence of late Gadolinium enhancement (LGE) were determined with CMR. Septal and lateral myocardial velocities were measured with echocardiographic tissue Doppler imaging. LV mass and volumes were comparable between groups. Maximal septal to lateral wall thickness ratio (SL ratio) was larger in carriers than in controls (1.3+/-0.2 versus 1.1+/-0.1, p<0.001). Also, LA volumes were larger in carriers compared to controls (p<0.05). Both peak SCS (p<0.05) and peak DCSR (p<0.01) were lower in carriers compared to controls, particularly in the basal lateral wall. Focal LGE was present in 2 carriers and not in controls. The combination of a SL ratio>1.2 and a peak DCSR<105%.s-1 was present in 45% of carriers and in none of the controls, yielding a positive predictive value of 100%. Two carriers and 18 controls had a SL ratio<1.2 and peak DCSR>105%.s-1, yielding a negative predictive value of 90%. With multivariate analysis, HCM mutation carriership was an independent determinant of reduced peak SCS and peak DCSR. CONCLUSIONS HCM mutation carriership is an independent determinant of reduced peak SCS and peak DCSR when LV wall thickness is within normal limits, and is associated with increased LA volumes and SL ratio. Using SL ratio and peak DCSR has a high accuracy to identify carriers. However, since carriers also display structural abnormalities and focal LGE, we advocate to also evaluate morphology and presence of LGE when screening for carriers.
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Affiliation(s)
- Tjeerd Germans
- Department of Cardiology, VU University Medical Center, Amsterdam, the Netherlands
- Interuniversity Cardiology Institute of the Netherlands, Utrecht, the Netherlands
| | - Iris K Rüssel
- Department of Cardiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Marco JW Götte
- Department of Cardiology, HagaZiekenhuis, the Hague, the Netherlands
| | - Marieke D Spreeuwenberg
- Department of Clinical Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, the Netherlands
| | - Pieter A Doevendans
- Interuniversity Cardiology Institute of the Netherlands, Utrecht, the Netherlands
- Department of Cardiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Yigal M Pinto
- Interuniversity Cardiology Institute of the Netherlands, Utrecht, the Netherlands
- Department of Cardiology, Academic Medical Center Amsterdam, Amsterdam, the Netherlands
| | - Rob J van der Geest
- Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
| | | | - Arthur AM Wilde
- Department of Cardiology, Academic Medical Center Amsterdam, Amsterdam, the Netherlands
| | - Albert C van Rossum
- Department of Cardiology, VU University Medical Center, Amsterdam, the Netherlands
- Interuniversity Cardiology Institute of the Netherlands, Utrecht, the Netherlands
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24
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Espectro mutacional de los genes sarcoméricos MYH7, MYBPC3, TNNT2, TNNI3 y TPM1 en pacientes con miocardiopatía hipertrófica. Rev Esp Cardiol 2009. [DOI: 10.1016/s0300-8932(09)70020-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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García-Castro M, Coto E, Reguero JR, Berrazueta JR, Álvarez V, Alonso B, Sainz R, Martín M, Morís C. Mutations in Sarcomeric Genes MYH7, MYBPC3, TNNT2, TNNI3, and TPM1 in Patients With Hypertrophic Cardiomyopathy. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/s1885-5857(09)71513-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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26
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Ochala J, Li M, Ohlsson M, Oldfors A, Larsson L. Defective regulation of contractile function in muscle fibres carrying an E41K beta-tropomyosin mutation. J Physiol 2008; 586:2993-3004. [PMID: 18420702 DOI: 10.1113/jphysiol.2008.153650] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
A novel E41K beta-tropomyosin (beta-Tm) mutation, associated with congenital myopathy and muscle weakness, was recently identified in a woman and her daughter. In both patients, muscle weakness was coupled with muscle fibre atrophy. It remains unknown, however, whether the E41K beta-Tm mutation directly affects regulation of muscle contraction, contributing to the muscle weakness. To address this question, we studied a broad range of contractile characteristics in skinned muscle fibres from the two patients and eight healthy controls. Results showed decreases (i) in speed of contraction at saturated Ca(2+) concentration (apparent rate constant of force redevelopment (k(tr)) and unloaded shortening speed (V(0))); and (ii) in contraction sensitivity to Ca(2+) concentration, in fibres from patients compared with controls, suggesting that the mutation has a negative effect on contractile function, contributing to the muscle weakness. To investigate whether these negative impacts are reversible, we exposed skinned muscle fibres to the Ca(2+) sensitizer EMD 57033. In fibres from patients, 30 mum of EMD 57033 (i) had no effect on speed of contraction (k(tr) and V(0)) at saturated Ca(2+) concentration but (ii) increased Ca(2+) sensitivity of contraction, suggesting a potential therapeutic approach in patients carrying the E41K beta-Tm mutation.
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Affiliation(s)
- Julien Ochala
- Department of Neuroscience, Clinical Neurophysiology, University Hospital, Entrance 85, 3rd floor, SE-751 85 Uppsala, Sweden.
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27
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The role of tropomyosin in heart disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 644:132-42. [PMID: 19209819 DOI: 10.1007/978-0-387-85766-4_11] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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28
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Bobkowski W, Sobieszczańska M, Turska-Kmieć A, Nowak A, Jagielski J, Gonerska M, Lebioda A, Siwińska A. Mutation of the MYH7 gene in a child with hypertrophic cardiomyopathy and Wolff-Parkinson-White syndrome. J Appl Genet 2007; 48:185-8. [PMID: 17495353 DOI: 10.1007/bf03194677] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Familial hypertrophic cardiomyopathy (HCM) displays autosomal dominant inheritance with incomplete penetration of defective genes. Data concerning the familial occurrence of ventricular preexcitation, i.e. Wolff-Parkinson-White (WPW) syndrome, also indicate autosomal dominant inheritance. In the literature, only a gene mutation on chromosome 7q3 has been described in familial HCM coexisting with WPW syndrome to date. The present paper describes the case of a 7-year-old boy with HCM and coexisting WPW syndrome. On his chromosome 14, molecular diagnostics revealed a C 9123 mutation (arginine changed into cysteine in position 453) in exon 14 in a copy of the gene for beta-myosin heavy chain (MYH7). It is the first known case of mutation of the MYH7 gene in a child with both HCM and WPW. Since no linkage between MYH7 mutation and HCM with WPW syndrome has been reported to date, we cannot conclude whether the observed mutation is a common cause for both diseases, or this patient presents an incidental co-occurrence of HCM (caused by MYH7 mutation) and WPW syndrome.
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Affiliation(s)
- Waldemar Bobkowski
- Department of Paediatric Cardiology, University of Medical Sciences, Szpitalna 27/33, 60-572 Poznań, and Department of Cardiology, Children's Memorial Health Institute, Warszawa, Poland.
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29
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Jagatheesan G, Rajan S, Petrashevskaya N, Schwartz A, Boivin G, Arteaga GM, Solaro RJ, Liggett SB, Wieczorek DF. Rescue of tropomyosin-induced familial hypertrophic cardiomyopathy mice by transgenesis. Am J Physiol Heart Circ Physiol 2007; 293:H949-58. [PMID: 17416600 DOI: 10.1152/ajpheart.01341.2006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Familial hypertrophic cardiomyopathy (FHC) is a disease caused by mutations in contractile proteins of the sarcomere. Our laboratory developed a mouse model of FHC with a mutation in the thin filament protein alpha-tropomyosin (TM) at amino acid 180 (Glu180Gly). The hearts of these mice exhibit dramatic systolic and diastolic dysfunction, and their myofilaments demonstrate increased calcium sensitivity. The mice also develop severe cardiac hypertrophy, with death ensuing by 6 mo. In an attempt to normalize calcium sensitivity in the cardiomyofilaments of the hypertrophic mice, we generated a chimeric alpha-/beta-TM protein that decreases calcium sensitivity in transgenic mouse cardiac myofilaments. By mating mice from these two models together, we tested the hypothesis that an attenuation of myofilament calcium sensitivity would modulate the severe physiological and pathological consequences of the FHC mutation. These double-transgenic mice "rescue" the hypertrophic phenotype by exhibiting a normal morphology with no pathological abnormalities. Physiological analyses of these rescued mice show improved cardiac function and normal myofilament calcium sensitivity. These results demonstrate that alterations in calcium response by modification of contractile proteins can prevent the pathological and physiological effects of this disease.
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MESH Headings
- Actin Cytoskeleton/drug effects
- Actin Cytoskeleton/metabolism
- Adrenergic beta-Agonists/pharmacology
- Animals
- Calcium/metabolism
- Cardiomyopathy, Hypertrophic, Familial/genetics
- Cardiomyopathy, Hypertrophic, Familial/metabolism
- Cardiomyopathy, Hypertrophic, Familial/pathology
- Cardiomyopathy, Hypertrophic, Familial/physiopathology
- Cardiomyopathy, Hypertrophic, Familial/therapy
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Gene Transfer Techniques
- Genetic Therapy/methods
- Genotype
- Heart Rate
- Isoproterenol/pharmacology
- Mice
- Mice, Transgenic
- Mutation
- Myocardial Contraction/drug effects
- Myocardium/metabolism
- Myocardium/pathology
- Phenotype
- RNA, Messenger/metabolism
- Recombinant Fusion Proteins/metabolism
- Sarcomeres/metabolism
- Severity of Illness Index
- Time Factors
- Tropomyosin/genetics
- Tropomyosin/metabolism
- Ventricular Pressure
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Affiliation(s)
- Ganapathy Jagatheesan
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0524, USA
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30
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Germans T, Wilde AAM, Dijkmans PA, Chai W, Kamp O, Pinto YM, van Rossum AC. Structural Abnormalities of the Inferoseptal Left Ventricular Wall Detected by Cardiac Magnetic Resonance Imaging in Carriers of Hypertrophic Cardiomyopathy Mutations. J Am Coll Cardiol 2006; 48:2518-23. [PMID: 17174192 DOI: 10.1016/j.jacc.2006.08.036] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2006] [Revised: 06/27/2006] [Accepted: 08/07/2006] [Indexed: 11/17/2022]
Abstract
OBJECTIVES The purpose of this study was to evaluate whether structural left ventricular (LV) abnormalities can be observed in hypertrophic cardiomyopathy (HCM) mutation carriers who have not yet developed echocardiographic signs of hypertrophy by using cardiac magnetic resonance imaging (CMR). BACKGROUND Hypertrophic cardiomyopathy is caused by mutations of genes encoding for sarcomeric proteins. Myocyte disarray and interstitial fibrosis precede the development of regional hypertrophy in HCM mutation carriers (carriers). No macroscopic LV structural abnormalities have been observed in carriers without LV hypertrophy. METHODS A CMR, echocardiogram, and electrocardiogram (ECG) were performed in 16 carriers. Delayed contrast enhancement imaging was used with CMR to detect fibrosis. In 16 age- and gender-matched control subjects, CMR and ECG were performed and an echocardiogram was made when structural abnormalities were detected with CMR. All carriers had an LV wall thickness <13 mm in the year before the study, measured by echocardiography. RESULTS In 13 carriers (81%), crypts were discerned with CMR in the basal and mid inferoseptal LV wall, not detected by routine echocardiography and not observed in healthy volunteers. In 4 of the crypt-positive carriers, both the echocardiogram and ECG were normal. Two HCM carriers revealed regional hypertrophy of the inferoseptum not detected by echocardiography, and in both carriers, focal fibrosis was present. CONCLUSIONS In carriers who have not yet developed frank hypertrophy, crypts can be detected with CMR in the inferoseptal LV wall, even when echocardiography and ECG are normal. The crypts might represent one of the early pathological alterations of myocardium in carriers that ultimately progress into manifest HCM.
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Affiliation(s)
- Tjeerd Germans
- Department of Cardiology, VU University Medical Center, Amsterdam, The Netherlands.
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31
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Rajan S, Williams SS, Jagatheesan G, Ahmed RPH, Fuller-Bicer G, Schwartz A, Aronow BJ, Wieczorek DF. Microarray analysis of gene expression during early stages of mild and severe cardiac hypertrophy. Physiol Genomics 2006; 27:309-17. [PMID: 16882888 DOI: 10.1152/physiolgenomics.00072.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Familial hypertrophic cardiomyopathy (FHC) is a disease characterized by ventricular hypertrophy, fibrosis, and aberrant systolic and/or diastolic function. We previously developed two transgenic mouse models that carry FHC-associated mutations in α-tropomyosin (TM): FHC α-TM175 mice show patchy areas of mild ventricular disorganization and limited hypertrophy, whereas FHC α-TM180 mice exhibit severe hypertrophy and fibrosis and die within 6 mo. To obtain a better understanding of the molecular mechanisms associated with the early onset of cardiac hypertrophy, we conducted a detailed comparative analysis of gene expression in 2.5-mo-old control, FHC α-TM175, and α-TM180 ventricular tissue. Results show that 754 genes (from a total of 22,600) were differentially expressed between the nontransgenic (NTG) and the FHC hearts. There are 178 differentially regulated genes between NTG and the FHC α-TM175 hearts, 388 genes are differentially expressed between NTG and FHC α-TM180 hearts, and 266 genes are differentially expressed between FHC α-TM175 and FHC α-TM180 hearts. Genes that exhibit the largest increase in expression belong to the “secreted/extracellular matrix” category, and those with the most significant decrease in expression are associated with “metabolic enzymes.” Confirmation of the microarray analysis was conducted by quantitative real-time PCR on gene transcripts commonly associated with cardiac hypertrophy.
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Affiliation(s)
- Sudarsan Rajan
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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32
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Brown JH, Zhou Z, Reshetnikova L, Robinson H, Yammani RD, Tobacman LS, Cohen C. Structure of the mid-region of tropomyosin: bending and binding sites for actin. Proc Natl Acad Sci U S A 2005; 102:18878-83. [PMID: 16365313 PMCID: PMC1323185 DOI: 10.1073/pnas.0509269102] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Tropomyosin is a two-chain alpha-helical coiled coil whose periodic interactions with the F-actin helix are critical for thin filament stabilization and the regulation of muscle contraction. Here we deduce the mechanical and chemical basis of these interactions from the 2.3-A-resolution crystal structure of the middle three of tropomyosin's seven periods. Geometrically specific bends of the coiled coil, produced by clusters of core alanines, and variable bends about gaps in the core, produced by isolated alanines, occur along the molecule. The crystal packing is notable in signifying that the functionally important fifth period includes an especially favorable protein-binding site, comprising an unusual apolar patch on the surface together with surrounding charged residues. Based on these and other results, we have constructed a specific model of the thin filament, with the N-terminal halves of each period (i.e., the so-called "alpha zones") of tropomyosin axially aligned with subdomain 3 of each monomer in F-actin.
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Affiliation(s)
- Jerry H Brown
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454-9110, USA
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33
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Chang AN, Harada K, Ackerman MJ, Potter JD. Functional Consequences of Hypertrophic and Dilated Cardiomyopathy-causing Mutations in α-Tropomyosin. J Biol Chem 2005; 280:34343-9. [PMID: 16043485 DOI: 10.1074/jbc.m505014200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To study the functional consequences of various cardiomyopathic mutations in human cardiac alpha-tropomyosin (Tm), a method of depletion/reconstitution of native Tm and troponin (Tn) complex (Tm-Tn) in cardiac myofibril preparations has been developed. The endogenous Tm-Tn complex was selectively removed from myofibrils and replaced with recombinant wild-type or mutant proteins. Successful depletion and reconstitution steps were verified by SDS-gel electrophoresis and by the loss and regain of Ca2+-dependent regulation of ATPase activity. Five Tm mutations were chosen for this study: the hypertrophic cardiomyopathy (HCM) mutations E62Q, E180G, and L185R and the dilated cardiomyopathy (DCM) mutations E40K and E54K. Through the use of this new depletion/reconstitution method, the functional consequences of these mutations were determined utilizing myofibrillar ATPase measurements. The results of our studies showed that 1) depletion of >80% of Tm-Tn from myofibrils resulted in a complete loss of the Ca2+-regulated ATPase activity and a significant loss in the maximal ATPase activity, 2) reconstitution of exogenous wild-type Tm-Tn resulted in complete regain in the calcium regulation and in the maximal ATPase activity, and 3) all HCM-associated Tm mutations increased the Ca2+ sensitivity of ATPase activity and all had decreased abilities to inhibit ATPase activity. In contrast, the DCM-associated mutations both decreased the Ca2+ sensitivity of ATPase activity and had no effect on the inhibition of ATPase activity. These findings have demonstrated that the mutations which cause HCM and DCM disrupt discrete mechanisms, which may culminate in the distinct cardiomyopathic phenotypes.
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Affiliation(s)
- Audrey N Chang
- Department of Medicine, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
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34
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Abstract
PURPOSE OF REVIEW As the underlying genetic basis of hypertrophic cardiomyopathy is being characterized, there has been increasing recognition of the wide spectrum and variable evolution of this disease within the pediatric age range. This review outlines recent evidence relevant to the diagnosis, management, and prognosis of hypertrophic cardiomyopathy specific to children and adolescents. RECENT FINDINGS Studies of putative causal genes are leading to the discovery of factors affecting the variability of phenotypic expression and possible avenues for new therapies. Nonetheless, the use of genetic testing currently remains for research purposes only. Echocardiography is the primary means for evaluation, with an increasing focus on diastolic performance. Useful prognostic information can be obtained from the safe performance of cardiopulmonary stress testing. Sudden death can occur in children, although the risk factors are likely different than in adults. The role and mechanisms for possible ischemia remain controversial, and likely differ between individuals. Activity restrictions are recommended, with medical therapy reserved for those who are symptomatic. For those with important left ventricular outflow obstruction, surgical myectomy may be indicated, with little current role for alcohol septal ablation. Advances in implantable defibrillators now make this therapy feasible in younger children. SUMMARY There are important differences from adults in the approach to the diagnosis and management of hypertrophic cardiomyopathy in children and adolescents. Care regarding prognostication and therapy must be taken given the potential life-long implications.
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Affiliation(s)
- Anji T Yetman
- University of Colorado Health Sciences Center, The Children's Hospital, Denver, Colorado, USA
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35
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Hilario E, da Silva SLF, Ramos CHI, Bertolini MC. Effects of cardiomyopathic mutations on the biochemical and biophysical properties of the human alpha-tropomyosin. ACTA ACUST UNITED AC 2005; 271:4132-40. [PMID: 15479242 DOI: 10.1111/j.1432-1033.2004.04351.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mutations in the protein alpha-tropomyosin (Tm) can cause a disease known as familial hypertrophic cardiomyopathy. In order to understand how such mutations lead to protein dysfunction, three point mutations were introduced into cDNA encoding the human skeletal tropomyosin, and the recombinant Tms were produced at high levels in the yeast Pichia pastoris. Two mutations (A63V and K70T) were located in the N-terminal region of Tm and one (E180G) was located close to the calcium-dependent troponin T binding domain. The functional and structural properties of the mutant Tms were compared to those of the wild type protein. None of the mutations altered the head-to-tail polymerization, although slightly higher actin binding was observed in the mutant Tm K70T, as demonstrated in a cosedimentation assay. The mutations also did not change the cooperativity of the thin filament activation by increasing the concentrations of Ca2+. However, in the absence of troponin, all mutant Tms were less effective than the wild type in regulating the actomyosin subfragment 1 Mg2+ ATPase activity. Circular dichroism spectroscopy revealed no differences in the secondary structure of the Tms. However, the thermally induced unfolding, as monitored by circular dichroism or differential scanning calorimetry, demonstrated that the mutants were less stable than the wild type. These results indicate that the main effect of the mutations is related to the overall stability of Tm as a whole, and that the mutations have only minor effects on the cooperative interactions among proteins that constitute the thin filament.
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Affiliation(s)
- Eduardo Hilario
- Instituto de Química, UNESP, Departamento de Bioquímica e Tecnologia Química, Araraquara, São Paulo, Brazil
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36
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Wernicke D, Thiel C, Duja-Isac CM, Essin KV, Spindler M, Nunez DJR, Plehm R, Wessel N, Hammes A, Edwards RJ, Lippoldt A, Zacharias U, Strömer H, Neubauer S, Davies MJ, Morano I, Thierfelder L. α-Tropomyosin mutations Asp175Asn and Glu180Gly affect cardiac function in transgenic rats in different ways. Am J Physiol Regul Integr Comp Physiol 2004; 287:R685-95. [PMID: 15031138 DOI: 10.1152/ajpregu.00620.2003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To study the mechanisms by which missense mutations in α-tropomyosin cause familial hypertrophic cardiomyopathy, we generated transgenic rats overexpressing α-tropomyosin with one of two disease-causing mutations, Asp175Asn or Glu180Gly, and analyzed phenotypic changes at molecular, morphological, and physiological levels. The transgenic proteins were stably integrated into the sarcomere, as shown by immunohistochemistry using a human-specific anti-α-tropomyosin antibody, ARG1. In transgenic rats with either α-tropomyosin mutation, molecular markers of cardiac hypertrophy were induced. Ca2+sensitivity of cardiac skinned-fiber preparations from animals with mutation Asp175Asn, but not Glu180Gly, was decreased. Furthermore, elevated frequency and amplitude of spontaneous Ca2+waves were detected only in cardiomyocytes from animals with mutation Asp175Asn, suggesting an increase in intracellular Ca2+concentration compensating for the reduced Ca2+sensitivity of isometric force generation. Accordingly, in Langendorff-perfused heart preparations, myocardial contraction and relaxation were accelerated in animals with mutation Asp175Asn. The results allow us to propose a hypothesis of the pathogenetic changes caused by α-tropomyosin mutation Asp175Asn in familial hypertrophic cardiomyopathy on the basis of changes in Ca2+handling as a sensitive mechanism to compensate for alterations in sarcomeric structure.
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MESH Headings
- Animals
- Animals, Genetically Modified
- Asparagine
- Aspartic Acid
- Biomarkers/analysis
- Calcium/metabolism
- Calcium/pharmacology
- Cardiomyopathy, Hypertrophic, Familial/genetics
- Cardiomyopathy, Hypertrophic, Familial/metabolism
- Cardiomyopathy, Hypertrophic, Familial/physiopathology
- Gene Expression
- Glutamic Acid
- Glycine
- Heart/physiopathology
- Heart Ventricles
- Humans
- Immunohistochemistry
- In Vitro Techniques
- Muscle Fibers, Skeletal/drug effects
- Mutation, Missense
- Myocardial Contraction
- Myocytes, Cardiac/metabolism
- Rats
- Sarcomeres/metabolism
- Transgenes
- Tropomyosin/genetics
- Tropomyosin/metabolism
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Affiliation(s)
- Dirk Wernicke
- Max-Delbrück Center for Molecular Medicine, Robert-Roessle-Str. 10, Berlin 13092, Germany.
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37
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Coutu P, Bennett CN, Favre EG, Day SM, Metzger JM. Parvalbumin Corrects Slowed Relaxation in Adult Cardiac Myocytes Expressing Hypertrophic Cardiomyopathy-Linked α-Tropomyosin Mutations. Circ Res 2004; 94:1235-41. [PMID: 15059934 DOI: 10.1161/01.res.0000126923.46786.fd] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Hypertrophic cardiomyopathy mutations A63V and E180G in α-tropomyosin (α-Tm) have been shown to cause slow cardiac muscle relaxation. In this study, we used two complementary genetic strategies, gene transfer in isolated rat myocytes and transgenesis in mice, to ascertain whether parvalbumin (Parv), a myoplasmic calcium buffer, could correct the diastolic dysfunction caused by these mutations. Sarcomere shortening measurements in rat cardiac myocytes expressing the α-Tm A63V mutant revealed a slower time to 50% relengthening (T50R: 44.2±1.4 ms in A63V, 36.8±1.0 ms in controls; n=96 to 108;
P
<0.001) when compared with controls. Dual gene transfer of α-Tm A63V and Parv caused a marked decrease in T50R (29.8±1.0 ms). However, this increase in relaxation rate was accompanied with a decrease in shortening amplitude (114.6±4.4 nm in A63+Parv, 137.8±5.3 nm in controls). Using an asynchronous gene transfer strategy, Parv expression was reduced (from ≈0.12 to ≈0.016 mmol/L), slow relaxation redressed, and shortening amplitude maintained (T50R=33.9±1.6 ms, sarcomere shortening amplitude=132.2±7.0 nm in A63V+PVdelayed; n=56). Transgenic mice expressing the E180G α-Tm mutation and mice expressing Parv in the heart were crossed. In isolated adult myocytes, the α-Tm mutation alone (E180G
+
/PV
−
) had slower sarcomere relengthening kinetics than the controls (T90R: 199±7 ms in E180G
+
/PV
−
, 130±4 ms in E180G
−
/PV
−
; n=71 to 72), but when coexpressed with Parv, cellular relaxation was faster (T90R: 36±4 ms in E180G
+
/PV
+
). Collectively, these findings show that slow relaxation caused by α-Tm mutants can be corrected by modifying calcium handling with Parv.
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Affiliation(s)
- Pierre Coutu
- Department of Biomedical Engineering , University of Michigan, Ann Arbor, Mich 48109-0622, USA
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38
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Maytum R, Bathe F, Konrad M, Geeves MA. Tropomyosin exon 6b is troponin-specific and required for correct acto-myosin regulation. J Biol Chem 2004; 279:18203-9. [PMID: 14752114 DOI: 10.1074/jbc.m311636200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The specificity of tropomyosin (Tm) exon 6b for interaction with and functioning of troponin (Tn) has been studied using recombinant fibroblast Tm isoforms 5a and 5b. These isoforms differ internally by exons 6a/6b and possess non-muscle exons 1b/9d at the termini, hence they lack the primary TnT(1)-tropomyosin interaction, allowing study of exon 6 exchange in isolation from this. Using kinetic techniques to measure regulation of myosin S1 binding to actin and fluorescently labeled Tm to directly measure Tn binding, we show that binding of Tn to both isoforms is similar (0.1-0.5 microm) and both produce well regulated systems. Calcium has little effect on Tn binding to the actin.Tm complex and both exons produce a 3-fold reduction in the S1 binding rate to actin.Tm.Tn in its absence. This confirms previous results that show exon 6 has little influence on Tn affinity to actin.Tm or its ability to fully inhibit the acto-myosin interaction. Thin filaments reconstituted with Tn and Tm5a or skeletal Tm (containing exon 6b) show nearly identical calcium dependence of acto-myosin regulation. However, Tm5b produces a dramatic increase in calcium sensitivity, shifting the activation mid-point by almost an order of magnitude. This shows that exon 6 sequence and, hence, Tm structure in this region have a significant effect upon the calcium regulation of Tn. This finding supports evidence that familial hypertrophic cardiomyopathy mutations occurring adjacent to this region can effect calcium regulation.
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Affiliation(s)
- Robin Maytum
- University of Kent at Canterbury, Canterbury, Kent CT2 7NJ, United Kingdom.
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39
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Abstract
The clinical diagnostic hallmark of hypertrophic cardiomyopathy (HCM) is unexplained cardiac hypertrophy, commonly found on an echocardiogram and in unfortunate occasions, in an autopsy. The latter is most tragic as HCM, a relatively common disease (1 ) often presenting with sudden cardiac death (SCD) in apparently healthy young individuals (2 ,3 ). Indeed, HCM is considered the most common cause of SCD in young competitive athletes (2 ). The unexpected SCD of young athletic individuals in conjunction with the results of earlier studies from major referral centers, reporting an annual mortality rate of approximately 2% to 6% (3 –5 ), led to the impression that HCM is a relatively malignant disease. Population-based studies, however, suggested a more benign course with an annual mortality rate of approximately 1% (6 –9 ). In the largest series comprised of 744 patients, the annual mortality rate was 1.2% of which approximately half were sudden unexpected deaths (9 ).
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Affiliation(s)
- Ali J Marian
- Section of Cardiology, Department of Medicine, Baylor College of Medicine, One Baylor Plaza 519D, Houston, Texas 77030, USA.
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