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Stroik D, Gregorich ZR, Raza F, Ge Y, Guo W. Titin: roles in cardiac function and diseases. Front Physiol 2024; 15:1385821. [PMID: 38660537 PMCID: PMC11040099 DOI: 10.3389/fphys.2024.1385821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 03/25/2024] [Indexed: 04/26/2024] Open
Abstract
The giant protein titin is an essential component of muscle sarcomeres. A single titin molecule spans half a sarcomere and mediates diverse functions along its length by virtue of its unique domains. The A-band of titin functions as a molecular blueprint that defines the length of the thick filaments, the I-band constitutes a molecular spring that determines cell-based passive stiffness, and various domains, including the Z-disk, I-band, and M-line, serve as scaffolds for stretch-sensing signaling pathways that mediate mechanotransduction. This review aims to discuss recent insights into titin's functional roles and their relationship to cardiac function. The role of titin in heart diseases, such as dilated cardiomyopathy and heart failure with preserved ejection fraction, as well as its potential as a therapeutic target, is also discussed.
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Affiliation(s)
- Dawson Stroik
- Cellular and Molecular Pathology Program, Department of Pathology and Laboratory Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
- Department of Animal and Dairy Sciences, College of Agriculture and Life Science, University of Wisconsin-Madison, Madison, WI, United States
| | - Zachery R. Gregorich
- Department of Animal and Dairy Sciences, College of Agriculture and Life Science, University of Wisconsin-Madison, Madison, WI, United States
| | - Farhan Raza
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Ying Ge
- Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Wei Guo
- Cellular and Molecular Pathology Program, Department of Pathology and Laboratory Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
- Department of Animal and Dairy Sciences, College of Agriculture and Life Science, University of Wisconsin-Madison, Madison, WI, United States
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2
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Verma SK, Kuyumcu-Martinez MN. RNA binding proteins in cardiovascular development and disease. Curr Top Dev Biol 2024; 156:51-119. [PMID: 38556427 DOI: 10.1016/bs.ctdb.2024.01.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/02/2024]
Abstract
Congenital heart disease (CHD) is the most common birth defect affecting>1.35 million newborn babies worldwide. CHD can lead to prenatal, neonatal, postnatal lethality or life-long cardiac complications. RNA binding protein (RBP) mutations or variants are emerging as contributors to CHDs. RBPs are wizards of gene regulation and are major contributors to mRNA and protein landscape. However, not much is known about RBPs in the developing heart and their contributions to CHD. In this chapter, we will discuss our current knowledge about specific RBPs implicated in CHDs. We are in an exciting era to study RBPs using the currently available and highly successful RNA-based therapies and methodologies. Understanding how RBPs shape the developing heart will unveil their contributions to CHD. Identifying their target RNAs in the embryonic heart will ultimately lead to RNA-based treatments for congenital heart disease.
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Affiliation(s)
- Sunil K Verma
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine Charlottesville, VA, United States.
| | - Muge N Kuyumcu-Martinez
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine Charlottesville, VA, United States; Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, United States; University of Virginia Cancer Center, Charlottesville, VA, United States.
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3
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Qi T, Zhang J, Zhang K, Zhang W, Song Y, Lian K, Kan C, Han F, Hou N, Sun X. Unraveling the role of the FHL family in cardiac diseases: Mechanisms, implications, and future directions. Biochem Biophys Res Commun 2024; 694:149468. [PMID: 38183876 DOI: 10.1016/j.bbrc.2024.149468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 12/23/2023] [Accepted: 01/02/2024] [Indexed: 01/08/2024]
Abstract
Heart diseases are a major cause of morbidity and mortality worldwide. Understanding the molecular mechanisms underlying these diseases is essential for the development of effective diagnostic and therapeutic strategies. The FHL family consists of five members: FHL1, FHL2, FHL3, FHL4, and FHL5/Act. These members exhibit different expression patterns in various tissues including the heart. FHL family proteins are implicated in cardiac remodeling, regulation of metabolic enzymes, and cardiac biomechanical stress perception. A large number of studies have explored the link between FHL family proteins and cardiac disease, skeletal muscle disease, and ovarian metabolism, but a comprehensive and in-depth understanding of the specific molecular mechanisms targeting FHL on cardiac disease is lacking. The aim of this review is to explore the structure and function of FHL family members, to comprehensively elucidate the mechanisms by which they regulate the heart, and to explore in depth the changes in FHL family members observed in different cardiac disorders, as well as the effects of mutations in FHL proteins on heart health.
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Affiliation(s)
- Tongbing Qi
- Department of Endocrinology and Metabolism, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China; Clinical Research Center, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China
| | - Jingwen Zhang
- Department of Endocrinology and Metabolism, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China; Clinical Research Center, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China
| | - Kexin Zhang
- Department of Endocrinology and Metabolism, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China; Clinical Research Center, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China
| | - Wenqiang Zhang
- Department of Endocrinology and Metabolism, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China; Clinical Research Center, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China; Department of Pathology, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China
| | - Yixin Song
- Department of Endocrinology and Metabolism, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China; Clinical Research Center, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China
| | - Kexin Lian
- Department of Nephrology, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China
| | - Chengxia Kan
- Department of Endocrinology and Metabolism, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China; Clinical Research Center, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China
| | - Fang Han
- Department of Endocrinology and Metabolism, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China; Clinical Research Center, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China; Department of Pathology, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China
| | - Ningning Hou
- Department of Endocrinology and Metabolism, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China.
| | - Xiaodong Sun
- Department of Endocrinology and Metabolism, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China; Clinical Research Center, Affiliated Hospital of Weifang Medical University, Weifang, 261031, China.
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Gotthardt M, Badillo-Lisakowski V, Parikh VN, Ashley E, Furtado M, Carmo-Fonseca M, Schudy S, Meder B, Grosch M, Steinmetz L, Crocini C, Leinwand L. Cardiac splicing as a diagnostic and therapeutic target. Nat Rev Cardiol 2023; 20:517-530. [PMID: 36653465 DOI: 10.1038/s41569-022-00828-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/09/2022] [Indexed: 01/19/2023]
Abstract
Despite advances in therapeutics for heart failure and arrhythmias, a substantial proportion of patients with cardiomyopathy do not respond to interventions, indicating a need to identify novel modifiable myocardial pathobiology. Human genetic variation associated with severe forms of cardiomyopathy and arrhythmias has highlighted the crucial role of alternative splicing in myocardial health and disease, given that it determines which mature RNA transcripts drive the mechanical, structural, signalling and metabolic properties of the heart. In this Review, we discuss how the analysis of cardiac isoform expression has been facilitated by technical advances in multiomics and long-read and single-cell sequencing technologies. The resulting insights into the regulation of alternative splicing - including the identification of cardiac splice regulators as therapeutic targets and the development of a translational pipeline to evaluate splice modulators in human engineered heart tissue, animal models and clinical trials - provide a basis for improved diagnosis and therapy. Finally, we consider how the medical and scientific communities can benefit from facilitated acquisition and interpretation of splicing data towards improved clinical decision-making and patient care.
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Affiliation(s)
- Michael Gotthardt
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany.
- DZHK (German Center for Cardiovascular Research Partner Site Berlin), Berlin, Germany.
- Department of Cardiology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
| | - Victor Badillo-Lisakowski
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- DZHK (German Center for Cardiovascular Research Partner Site Berlin), Berlin, Germany
| | - Victoria Nicole Parikh
- Stanford Center for Inherited Cardiovascular Disease, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Euan Ashley
- Stanford Center for Inherited Cardiovascular Disease, Stanford University School of Medicine, Palo Alto, CA, USA
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA, USA
- Department of Genetics, School of Medicine, Stanford University, Stanford, CA, USA
| | - Marta Furtado
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Maria Carmo-Fonseca
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Sarah Schudy
- Institute for Cardiomyopathies, Department of Medicine III, University of Heidelberg, Heidelberg, Germany
| | - Benjamin Meder
- Institute for Cardiomyopathies, Department of Medicine III, University of Heidelberg, Heidelberg, Germany
- DZHK (German Center for Cardiovascular Research Partner Site Heidelberg-Mannheim), Heidelberg, Germany
| | - Markus Grosch
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - Lars Steinmetz
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA, USA
- Department of Genetics, School of Medicine, Stanford University, Stanford, CA, USA
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - Claudia Crocini
- Department of Molecular, Cellular, and Developmental Biology and BioFrontiers Institute, University of Colorado, Boulder, CO, USA
| | - Leslie Leinwand
- Department of Molecular, Cellular, and Developmental Biology and BioFrontiers Institute, University of Colorado, Boulder, CO, USA
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Banga S, Cardoso R, Castellani C, Srivastava S, Watkins J, Lima J. Cardiac MRI as an Imaging Tool in Titin Variant-Related Dilated Cardiomyopathy. CARDIOVASCULAR REVASCULARIZATION MEDICINE 2023; 52:86-93. [PMID: 36934006 DOI: 10.1016/j.carrev.2023.03.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 02/05/2023] [Accepted: 03/01/2023] [Indexed: 03/08/2023]
Abstract
Dilated Cardiomyopathy is a common myocardial disease characterized by dilation and loss of function of one or both ventricles. A variety of etiologies have been implicated including genetic variation. Advancement in genetic sequencing, and diagnostic imaging allows for detection of genetic mutations in sarcomere protein titin (TTN) and high resolution assessment of cardiac function. This review article discusses the role of cardiac MRI in diagnosing dilated cardiomyopathy in patients with TTN variant related cardiomyopathy.
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Affiliation(s)
- Sandeep Banga
- Division of Cardiology, Michigan State University, Sparrow Hospital, Lansing, MI, USA.
| | | | - Carson Castellani
- Division of Internal Medicine, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Shaurya Srivastava
- Division of Internal Medicine, Michigan State University, Lansing, MI, USA
| | - Jennifer Watkins
- Division of Cardiology, Michigan State University, Sparrow Hospital, Lansing, MI, USA
| | - Joao Lima
- Division of Cardiology, Johns Hopkins University, Baltimore, MD, USA
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6
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Li J, Zhang X, Ren P, Wu Y, Wang Y, Zhou W, Wang Z, Chao P. Landscape of RNA-binding proteins in diagnostic utility, immune cell infiltration and PANoptosis features of heart failure. Front Genet 2022; 13:1004163. [PMID: 36313471 PMCID: PMC9614340 DOI: 10.3389/fgene.2022.1004163] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 09/27/2022] [Indexed: 11/13/2022] Open
Abstract
Objective: Heart failure remains a global public health problem linked to rising morbidity and mortality. RNA-binding proteins (RBPs) are crucial regulators in post-transcriptionally determining gene expression. Our study aimed to comprehensively elucidate the diagnostic utility and biological roles of RBPs in heart failure. Methods: Genomic data of human failing and nonfailing left ventricular myocardium specimens were retrieved from the GEO datasets. Heart failure-specific RBPs were screened with differential expression analyses, and RBP-based subtypes were clustered with consensus clustering approach. GSEA was implemented for comparing KEGG pathways across subtypes. RBP-based subtype-related genes were screened with WGCNA. Afterwards, characteristic genes were selected through integrating LASSO and SVM-RFE approaches. A nomogram based on characteristic genes was established and verified through calibration curve, decision curve and clinical impact curve analyses. The abundance of immune cell types was estimated with CIBERSORT approach. Results: Heart failure-specific RBPs were determined, which were remarkably linked to RNA metabolism process. Three RBP-based subtypes (namely C1, C2, C3) were established, characterized by distinct pathway activities and PANoptosis gene levels. C2 subtype presented the highest abundance of immune cells, followed by C1 and C3. Afterwards, ten characteristic genes were selected, which enabled to reliably diagnose heart failure risk. The characteristic gene-based nomogram enabled to accurately predict risk of heart failure, with the excellent clinical utility. Additionally, characteristic genes correlated to immune cell infiltration and PANoptosis genes. Conclusion: Our findings comprehensively described the roles of RBPs in heart failure. Further research is required for verifying the effectiveness of RBP-based subtypes and characteristic genes in heart failure.
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Affiliation(s)
- Jie Li
- Department of Cardiology, People’s Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China
| | - Xueqin Zhang
- Department of Nephrology, People’s Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China
| | - Peng Ren
- Department of Cardiology, People’s Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China
| | - Yu Wu
- Department of Medical Administration, People’s Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China
| | - Yaoguo Wang
- Department of Information Center, People’s Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China
| | - Wenzheng Zhou
- Department of Orthopaedics, People’s Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China
- *Correspondence: Wenzheng Zhou, ; Zhao Wang, ; Peng Chao,
| | - Zhao Wang
- Department of Cardiology, People’s Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China
- *Correspondence: Wenzheng Zhou, ; Zhao Wang, ; Peng Chao,
| | - Peng Chao
- Department of Cardiology, People’s Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China
- *Correspondence: Wenzheng Zhou, ; Zhao Wang, ; Peng Chao,
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7
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Li N, Hang W, Shu H, Zhou N. RBM20, a Therapeutic Target to Alleviate Myocardial Stiffness via Titin Isoforms Switching in HFpEF. Front Cardiovasc Med 2022; 9:928244. [PMID: 35783855 PMCID: PMC9243441 DOI: 10.3389/fcvm.2022.928244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 05/30/2022] [Indexed: 12/05/2022] Open
Abstract
Increased myocardial stiffness is critically involved in heart diseases with impaired cardiac compliance, especially heart failure with preserved ejection fraction (HFpEF). Myocardial stiffness mainly derives from cardiomyocyte- and extracellular matrix (ECM)-derived passive stiffness. Titin, a major component of sarcomeres, participates in myocardial passive stiffness and stress-sensitive signaling. The ratio of two titin isoforms, N2BA to N2B, was validated to influence diastolic dysfunction via several pathways. RNA binding motif protein 20 (RBM20) is a well-studied splicing factor of titin, functional deficiency of RBM20 in mice profile improved cardiac compliance and function, which indicated that RBM20 functions as a potential therapeutic target for mitigating myocardial stiffness by modulating titin isoforms. This minor review summarized how RBM20 and other splicing factors modify the titin isoforms ratio, therefore providing a promising target for improving the myocardial compliance of HFpEF.
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Radke MH, Badillo-Lisakowski V, Britto-Borges T, Kubli DA, Jüttner R, Parakkat P, Carballo JL, Hüttemeister J, Liss M, Hansen A, Dieterich C, Mullick AE, Gotthardt M. Therapeutic inhibition of RBM20 improves diastolic function in a murine heart failure model and human engineered heart tissue. Sci Transl Med 2021; 13:eabe8952. [PMID: 34851694 DOI: 10.1126/scitranslmed.abe8952] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Michael H Radke
- Department of Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany.,German Center for Cardiovascular Research (DZHK), partner site Berlin, 10785 Berlin, Germany
| | - Victor Badillo-Lisakowski
- Department of Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany.,German Center for Cardiovascular Research (DZHK), partner site Berlin, 10785 Berlin, Germany.,Humboldt-Universität zu Berlin, 10099 Berlin, Germany
| | - Thiago Britto-Borges
- Section of Bioinformatics and Systems Cardiology, Klaus Tschira Institute for Integrative Computational Cardiology and Department of Internal Medicine III, University Hospital Heidelberg, 69120 Heidelberg, Germany.,German Center for Cardiovascular Research (DZHK), partner site Heidelberg/Mannheim, 69120 Heidelberg, Germany
| | | | - René Jüttner
- Department of Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany
| | - Pragati Parakkat
- Department of Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany.,German Center for Cardiovascular Research (DZHK), partner site Berlin, 10785 Berlin, Germany.,Department of Cardiology, Charité Universitätsmedizin Berlin, 10115 Berlin, Germany
| | - Jacobo Lopez Carballo
- Department of Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany.,Department of Cardiology, Charité Universitätsmedizin Berlin, 10115 Berlin, Germany
| | - Judith Hüttemeister
- Department of Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany.,German Center for Cardiovascular Research (DZHK), partner site Berlin, 10785 Berlin, Germany
| | - Martin Liss
- Department of Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany.,German Center for Cardiovascular Research (DZHK), partner site Berlin, 10785 Berlin, Germany
| | - Arne Hansen
- Department of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,German Center for Cardiovascular Research (DZHK), partner site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | - Christoph Dieterich
- Section of Bioinformatics and Systems Cardiology, Klaus Tschira Institute for Integrative Computational Cardiology and Department of Internal Medicine III, University Hospital Heidelberg, 69120 Heidelberg, Germany.,German Center for Cardiovascular Research (DZHK), partner site Heidelberg/Mannheim, 69120 Heidelberg, Germany
| | | | - Michael Gotthardt
- Department of Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany.,German Center for Cardiovascular Research (DZHK), partner site Berlin, 10785 Berlin, Germany.,Department of Cardiology, Charité Universitätsmedizin Berlin, 10115 Berlin, Germany
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van der Pijl RJ, Domenighetti AA, Sheikh F, Ehler E, Ottenheijm CAC, Lange S. The titin N2B and N2A regions: biomechanical and metabolic signaling hubs in cross-striated muscles. Biophys Rev 2021; 13:653-677. [PMID: 34745373 PMCID: PMC8553726 DOI: 10.1007/s12551-021-00836-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 08/23/2021] [Indexed: 02/07/2023] Open
Abstract
Muscle specific signaling has been shown to originate from myofilaments and their associated cellular structures, including the sarcomeres, costameres or the cardiac intercalated disc. Two signaling hubs that play important biomechanical roles for cardiac and/or skeletal muscle physiology are the N2B and N2A regions in the giant protein titin. Prominent proteins associated with these regions in titin are chaperones Hsp90 and αB-crystallin, members of the four-and-a-half LIM (FHL) and muscle ankyrin repeat protein (Ankrd) families, as well as thin filament-associated proteins, such as myopalladin. This review highlights biological roles and properties of the titin N2B and N2A regions in health and disease. Special emphasis is placed on functions of Ankrd and FHL proteins as mechanosensors that modulate muscle-specific signaling and muscle growth. This region of the sarcomere also emerged as a hotspot for the modulation of passive muscle mechanics through altered titin phosphorylation and splicing, as well as tethering mechanisms that link titin to the thin filament system.
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Affiliation(s)
| | - Andrea A. Domenighetti
- Shirley Ryan AbilityLab, Chicago, IL USA
- Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL USA
| | - Farah Sheikh
- Division of Cardiology, School of Medicine, UC San Diego, La Jolla, CA USA
| | - Elisabeth Ehler
- Randall Centre for Cell and Molecular Biophysics, School of Cardiovascular Medicine and Sciences, King’s College London, London, UK
| | - Coen A. C. Ottenheijm
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ USA
- Department of Physiology, Amsterdam University Medical Centers, Amsterdam, The Netherlands
| | - Stephan Lange
- Division of Cardiology, School of Medicine, UC San Diego, La Jolla, CA USA
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
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10
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Crocini C, Gotthardt M. Cardiac sarcomere mechanics in health and disease. Biophys Rev 2021; 13:637-652. [PMID: 34745372 PMCID: PMC8553709 DOI: 10.1007/s12551-021-00840-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 08/27/2021] [Indexed: 12/23/2022] Open
Abstract
The sarcomere is the fundamental structural and functional unit of striated muscle and is directly responsible for most of its mechanical properties. The sarcomere generates active or contractile forces and determines the passive or elastic properties of striated muscle. In the heart, mutations in sarcomeric proteins are responsible for the majority of genetically inherited cardiomyopathies. Here, we review the major determinants of cardiac sarcomere mechanics including the key structural components that contribute to active and passive tension. We dissect the molecular and structural basis of active force generation, including sarcomere composition, structure, activation, and relaxation. We then explore the giant sarcomere-resident protein titin, the major contributor to cardiac passive tension. We discuss sarcomere dynamics exemplified by the regulation of titin-based stiffness and the titin life cycle. Finally, we provide an overview of therapeutic strategies that target the sarcomere to improve cardiac contraction and filling.
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Affiliation(s)
- Claudia Crocini
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Neuromuscular and Cardiovascular Cell Biology, Berlin, Germany
- German Center for Cardiovascular Research (DZHK) Partner Site Berlin, Berlin, Germany
- BioFrontiers Institute & Department of Molecular and Cellular Development, University of Colorado Boulder, Boulder, USA
| | - Michael Gotthardt
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Neuromuscular and Cardiovascular Cell Biology, Berlin, Germany
- German Center for Cardiovascular Research (DZHK) Partner Site Berlin, Berlin, Germany
- Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
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11
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RBM20 is a candidate gene for hypertrophic cardiomyopathy. Can J Cardiol 2021; 37:1751-1759. [PMID: 34333030 DOI: 10.1016/j.cjca.2021.07.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 07/22/2021] [Accepted: 07/23/2021] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND The genetic basis of a considerable fraction of hypertrophic cardiomyopathy (HCM) cases remains unknown. Whether the gene encoding RNA Binding Motif Protein 20 (RBM20) is implicated in HCM and the correlation of clinical characteristics of RBM20 heterozygotes with HCM remain unresolved. We aimed to investigate the association between RBM20 variants and HCM. METHODS We compared rare variants in the RBM20 gene by exome sequencing in 793 HCM patients and 414 healthy controls. Based on a case-control approach, we used SKAT-O to explore whether RBM20 is associated with HCM. The genetic distribution of RBM20 rare variants was then compared between HCM heterozygotes and dilated cardiomyopathy (DCM) heterozygotes. Clinical features and prognosis of RBM20 heterozygotes were compared with non-heterozygotes. RESULTS Gene-based association analysis implicated RBM20 as a susceptibility gene for developing HCM. Patients with RBM20 variants displayed a higher prevalence of sudden cardiac arrest (SCA) (6.7% vs. 0.9%, p = 0.001), increased sudden cardiac death (SCD) risk factor counts and impaired left ventricle systolic function. Further survival analysis revealed that RBM20 heterozygotes had higher incidences of resuscitated cardiac arrest, recurrent non-sustained ventricular tachycardia and malignant arrhythmias. Mendelian randomization suggested that RBM20 expression in left ventricle was causally associated with HCM and DCM with opposite effects. CONCLUSIONS This study identified RBM20 as a potential causal gene of HCM. RBM20 variants are associated with increased risk for SCA in HCM.
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Abstract
PURPOSE OF REVIEW This review aims to give an update on recent findings related to the cardiac splicing factor RNA-binding motif protein 20 (RBM20) and RBM20 cardiomyopathy, a form of dilated cardiomyopathy caused by mutations in RBM20. RECENT FINDINGS While most research on RBM20 splicing targets has focused on titin (TTN), multiple studies over the last years have shown that other splicing targets of RBM20 including Ca2+/calmodulin-dependent kinase IIδ (CAMK2D) might be critically involved in the development of RBM20 cardiomyopathy. In this regard, loss of RBM20 causes an abnormal intracellular calcium handling, which may relate to the arrhythmogenic presentation of RBM20 cardiomyopathy. In addition, RBM20 presents clinically in a highly gender-specific manner, with male patients suffering from an earlier disease onset and a more severe disease progression. Further research on RBM20, and treatment of RBM20 cardiomyopathy, will need to consider both the multitude and relative contribution of the different splicing targets and related pathways, as well as gender differences.
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13
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Modifications of Titin Contribute to the Progression of Cardiomyopathy and Represent a Therapeutic Target for Treatment of Heart Failure. J Clin Med 2020; 9:jcm9092770. [PMID: 32859027 PMCID: PMC7564493 DOI: 10.3390/jcm9092770] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/22/2020] [Accepted: 08/24/2020] [Indexed: 12/20/2022] Open
Abstract
Titin is the largest human protein and an essential component of the cardiac sarcomere. With multiple immunoglobulin(Ig)-like domains that serve as molecular springs, titin contributes significantly to the passive tension, systolic function, and diastolic function of the heart. Mutations leading to early termination of titin are the most common genetic cause of dilated cardiomyopathy. Modifications of titin, which change protein length, and relative stiffness affect resting tension of the ventricle and are associated with acquired forms of heart failure. Transcriptional and post-translational changes that increase titin’s length and extensibility, making the sarcomere longer and softer, are associated with systolic dysfunction and left ventricular dilation. Modifications of titin that decrease its length and extensibility, making the sarcomere shorter and stiffer, are associated with diastolic dysfunction in animal models. There has been significant progress in understanding the mechanisms by which titin is modified. As molecular pathways that modify titin’s mechanical properties are elucidated, they represent therapeutic targets for treatment of both systolic and diastolic dysfunction. In this article, we review titin’s contribution to normal cardiac physiology, the pathophysiology of titin truncation variations leading to dilated cardiomyopathy, and transcriptional and post-translational modifications of titin. Emphasis is on how modification of titin can be utilized as a therapeutic target for treatment of heart failure.
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14
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Upadhyay SK, Mackereth CD. Structural basis of UCUU RNA motif recognition by splicing factor RBM20. Nucleic Acids Res 2020; 48:4538-4550. [PMID: 32187365 PMCID: PMC7192616 DOI: 10.1093/nar/gkaa168] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 02/28/2020] [Accepted: 03/07/2020] [Indexed: 12/16/2022] Open
Abstract
The vertebrate splicing factor RBM20 (RNA binding motif protein 20) regulates protein isoforms important for heart development and function, with mutations in the gene linked to cardiomyopathy. Previous studies have identified the four nucleotide RNA motif UCUU as a common element in pre-mRNA targeted by RBM20. Here, we have determined the structure of the RNA Recognition Motif (RRM) domain from mouse RBM20 bound to RNA containing a UCUU sequence. The atomic details show that the RRM domain spans a larger region than initially proposed in order to interact with the complete UCUU motif, with a well-folded C-terminal helix encoded by exon 8 critical for high affinity binding. This helix only forms upon binding RNA with the final uracil, and removing the helix reduces affinity as well as specificity. We therefore find that RBM20 uses a coupled folding-binding mechanism by the C-terminal helix to specifically recognize the UCUU RNA motif.
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Affiliation(s)
| | - Cameron D Mackereth
- Univ. Bordeaux, Institut Européen de Chimie et Biologie, 2 rue Robert Escarpit, 33607 Pessac Cedex, France.,Inserm U1212, CNRS UMR5320, ARNA Laboratory, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France
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15
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van der Pijl RJ, Hudson B, Granzier-Nakajima T, Li F, Knottnerus AM, Smith J, Chung CS, Gotthardt M, Granzier HL, Ottenheijm CAC. Deleting Titin's C-Terminal PEVK Exons Increases Passive Stiffness, Alters Splicing, and Induces Cross-Sectional and Longitudinal Hypertrophy in Skeletal Muscle. Front Physiol 2020; 11:494. [PMID: 32547410 PMCID: PMC7274174 DOI: 10.3389/fphys.2020.00494] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 04/23/2020] [Indexed: 12/13/2022] Open
Abstract
The Proline, Glutamate, Valine and Lysine-rich (PEVK) region of titin constitutes an entropic spring that provides passive tension to striated muscle. To study the functional and structural repercussions of a small reduction in the size of the PEVK region, we investigated skeletal muscles of a mouse with the constitutively expressed C-terminal PEVK exons 219-225 deleted, the TtnΔ219-225 model (MGI: TtnTM 2.1Mgot ). Based on this deletion, passive tension in skeletal muscle was predicted to be increased by ∼17% (sarcomere length 3.0 μm). In contrast, measured passive tension (sarcomere length 3.0 μm) in both soleus and EDL muscles was increased 53 ± 11% and 62 ± 4%, respectively. This unexpected increase was due to changes in titin, not to alterations in the extracellular matrix, and is likely caused by co-expression of two titin isoforms in TtnΔ219-225 muscles: a larger isoform that represents the TtnΔ219-225 N2A titin and a smaller isoform, referred to as N2A2. N2A2 represents a splicing adaption with reduced expression of spring element exons, as determined by titin exon microarray analysis. Maximal tetanic tension was increased in TtnΔ219-225 soleus muscle (WT 240 ± 9; TtnΔ219-225 276 ± 17 mN/mm2), but was reduced in EDL muscle (WT 315 ± 9; TtnΔ219-225 280 ± 14 mN/mm2). The changes in active tension coincided with a switch toward slow fiber types and, unexpectedly, faster kinetics of tension generation and relaxation. Functional overload (FO; ablation) and hindlimb suspension (HS; unloading) experiments were also conducted. TtnΔ219-225 mice showed increases in both longitudinal hypertrophy (increased number of sarcomeres in series) and cross-sectional hypertrophy (increased number of sarcomeres in parallel) in response to FO and attenuated cross-sectional atrophy in response to HS. In summary, slow- and fast-twitch muscles in a mouse model devoid of titin's PEVK exons 219-225 have high passive tension, due in part to alterations elsewhere in splicing of titin's spring region, increased kinetics of tension generation and relaxation, and altered trophic responses to both functional overload and unloading. This implicates titin's C-terminal PEVK region in regulating passive and active muscle mechanics and muscle plasticity.
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Affiliation(s)
- Robbert J van der Pijl
- Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, United States.,Department of Physiology, Amsterdam UMC, Amsterdam, Netherlands
| | - Brian Hudson
- Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, United States
| | | | - Frank Li
- Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, United States
| | - Anne M Knottnerus
- Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, United States
| | - John Smith
- Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, United States
| | - Charles S Chung
- Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, United States.,Department of Physiology, Wayne State University, Detroit, MI, United States
| | - Michael Gotthardt
- Max-Delbruck-Center for Molecular Medicine, Berlin, Germany.,Cardiology, Virchow Klinikum, Charité University Medicine, Berlin, Germany
| | - Henk L Granzier
- Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, United States
| | - Coen A C Ottenheijm
- Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, United States.,Department of Physiology, Amsterdam UMC, Amsterdam, Netherlands
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16
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Fochi S, Lorenzi P, Galasso M, Stefani C, Trabetti E, Zipeto D, Romanelli MG. The Emerging Role of the RBM20 and PTBP1 Ribonucleoproteins in Heart Development and Cardiovascular Diseases. Genes (Basel) 2020; 11:genes11040402. [PMID: 32276354 PMCID: PMC7230170 DOI: 10.3390/genes11040402] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 04/04/2020] [Accepted: 04/06/2020] [Indexed: 12/17/2022] Open
Abstract
Alternative splicing is a regulatory mechanism essential for cell differentiation and tissue organization. More than 90% of human genes are regulated by alternative splicing events, which participate in cell fate determination. The general mechanisms of splicing events are well known, whereas only recently have deep-sequencing, high throughput analyses and animal models provided novel information on the network of functionally coordinated, tissue-specific, alternatively spliced exons. Heart development and cardiac tissue differentiation require thoroughly regulated splicing events. The ribonucleoprotein RBM20 is a key regulator of the alternative splicing events required for functional and structural heart properties, such as the expression of TTN isoforms. Recently, the polypyrimidine tract-binding protein PTBP1 has been demonstrated to participate with RBM20 in regulating splicing events. In this review, we summarize the updated knowledge relative to RBM20 and PTBP1 structure and molecular function; their role in alternative splicing mechanisms involved in the heart development and function; RBM20 mutations associated with idiopathic dilated cardiovascular disease (DCM); and the consequences of RBM20-altered expression or dysfunction. Furthermore, we discuss the possible application of targeting RBM20 in new approaches in heart therapies.
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17
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Gao C, Wang Y. mRNA Metabolism in Cardiac Development and Disease: Life After Transcription. Physiol Rev 2020; 100:673-694. [PMID: 31751167 PMCID: PMC7327233 DOI: 10.1152/physrev.00007.2019] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 09/06/2019] [Accepted: 10/30/2019] [Indexed: 02/06/2023] Open
Abstract
The central dogma of molecular biology illustrates the importance of mRNAs as critical mediators between genetic information encoded at the DNA level and proteomes/metabolomes that determine the diverse functional outcome at the cellular and organ levels. Although the total number of protein-producing (coding) genes in the mammalian genome is ~20,000, it is evident that the intricate processes of cardiac development and the highly regulated physiological regulation in the normal heart, as well as the complex manifestation of pathological remodeling in a diseased heart, would require a much higher degree of complexity at the transcriptome level and beyond. Indeed, in addition to an extensive regulatory scheme implemented at the level of transcription, the complexity of transcript processing following transcription is dramatically increased. RNA processing includes post-transcriptional modification, alternative splicing, editing and transportation, ribosomal loading, and degradation. While transcriptional control of cardiac genes has been a major focus of investigation in recent decades, a great deal of progress has recently been made in our understanding of how post-transcriptional regulation of mRNA contributes to transcriptome complexity. In this review, we highlight some of the key molecular processes and major players in RNA maturation and post-transcriptional regulation. In addition, we provide an update to the recent progress made in the discovery of RNA processing regulators implicated in cardiac development and disease. While post-transcriptional modulation is a complex and challenging problem to study, recent technological advancements are paving the way for a new era of exciting discoveries and potential clinical translation in the context of cardiac biology and heart disease.
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Affiliation(s)
- Chen Gao
- Departments of Anesthesiology, Medicine, and Physiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
| | - Yibin Wang
- Departments of Anesthesiology, Medicine, and Physiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
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18
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Radke MH, Polack C, Methawasin M, Fink C, Granzier HL, Gotthardt M. Deleting Full Length Titin Versus the Titin M-Band Region Leads to Differential Mechanosignaling and Cardiac Phenotypes. Circulation 2020; 139:1813-1827. [PMID: 30700140 DOI: 10.1161/circulationaha.118.037588] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND Titin is a giant elastic protein that spans the half-sarcomere from Z-disk to M-band. It acts as a molecular spring and mechanosensor and has been linked to striated muscle disease. The pathways that govern titin-dependent cardiac growth and contribute to disease are diverse and difficult to dissect. METHODS To study titin deficiency versus dysfunction, the authors generated and compared striated muscle specific knockouts (KOs) with progressive postnatal loss of the complete titin protein by removing exon 2 (E2-KO) or an M-band truncation that eliminates proper sarcomeric integration, but retains all other functional domains (M-band exon 1/2 [M1/2]-KO). The authors evaluated cardiac function, cardiomyocyte mechanics, and the molecular basis of the phenotype. RESULTS Skeletal muscle atrophy with reduced strength, severe sarcomere disassembly, and lethality from 2 weeks of age were shared between the models. Cardiac phenotypes differed considerably: loss of titin leads to dilated cardiomyopathy with combined systolic and diastolic dysfunction-the absence of M-band titin to cardiac atrophy and preserved function. The elastic properties of M1/2-KO cardiomyocytes are maintained, while passive stiffness is reduced in the E2-KO. In both KOs, we find an increased stress response and increased expression of proteins linked to titin-based mechanotransduction (CryAB, ANKRD1, muscle LIM protein, FHLs, p42, Camk2d, p62, and Nbr1). Among them, FHL2 and the M-band signaling proteins p62 and Nbr1 are exclusively upregulated in the E2-KO, suggesting a role in the differential pathology of titin truncation versus deficiency of the full-length protein. The differential stress response is consistent with truncated titin contributing to the mechanical properties in M1/2-KOs, while low titin levels in E2-KOs lead to reduced titin-based stiffness and increased strain on the remaining titin molecules. CONCLUSIONS Progressive depletion of titin leads to sarcomere disassembly and atrophy in striated muscle. In the complete knockout, remaining titin molecules experience increased strain, resulting in mechanically induced trophic signaling and eventually dilated cardiomyopathy. The truncated titin in M1/2-KO helps maintain the passive properties and thus reduces mechanically induced signaling. Together, these findings contribute to the molecular understanding of why titin mutations differentially affect cardiac growth and have implications for genotype-phenotype relations that support a personalized medicine approach to the diverse titinopathies.
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Affiliation(s)
- Michael H Radke
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany (M.H.R., C.P., C.F., M.G.).,DZHK: German Centre for Cardiovascular Research, Partner Site, Berlin, Germany (M.H.R., M.G.)
| | - Christopher Polack
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany (M.H.R., C.P., C.F., M.G.)
| | - Mei Methawasin
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson (M.M., H.G.). The current affiliation for P.S. and T.S. is Department of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg University Mainz, Germany
| | - Claudia Fink
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany (M.H.R., C.P., C.F., M.G.)
| | - Henk L Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson (M.M., H.G.). The current affiliation for P.S. and T.S. is Department of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg University Mainz, Germany
| | - Michael Gotthardt
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany (M.H.R., C.P., C.F., M.G.).,DZHK: German Centre for Cardiovascular Research, Partner Site, Berlin, Germany (M.H.R., M.G.)
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19
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Resolving titin's lifecycle and the spatial organization of protein turnover in mouse cardiomyocytes. Proc Natl Acad Sci U S A 2019; 116:25126-25136. [PMID: 31757849 DOI: 10.1073/pnas.1904385116] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cardiac protein homeostasis, sarcomere assembly, and integration of titin as the sarcomeric backbone are tightly regulated to facilitate adaptation and repair. Very little is known on how the >3-MDa titin protein is synthesized, moved, inserted into sarcomeres, detached, and degraded. Here, we generated a bifluorescently labeled knockin mouse to simultaneously visualize both ends of the molecule and follow titin's life cycle in vivo. We find titin mRNA, protein synthesis and degradation compartmentalized toward the Z-disk in adult, but not embryonic cardiomyocytes. Originating at the Z-disk, titin contributes to a soluble protein pool (>15% of total titin) before it is integrated into the sarcomere lattice. Titin integration, disintegration, and reintegration are stochastic and do not proceed sequentially from Z-disk to M-band, as suggested previously. Exchange between soluble and integrated titin depends on titin protein composition and differs between individual cardiomyocytes. Thus, titin dynamics facilitate embryonic vs. adult sarcomere remodeling with implications for cardiac development and disease.
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20
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Najafi A, van de Locht M, Schuldt M, Schönleitner P, van Willigenburg M, Bollen I, Goebel M, Ottenheijm CAC, van der Velden J, Helmes M, Kuster DWD. End-diastolic force pre-activates cardiomyocytes and determines contractile force: role of titin and calcium. J Physiol 2019; 597:4521-4531. [PMID: 31314138 PMCID: PMC6852589 DOI: 10.1113/jp277985] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 07/10/2019] [Indexed: 12/22/2022] Open
Abstract
Titin functions as a molecular spring, and cardiomyocytes are able, through splicing, to control the length of titin. We hypothesized that together with diastolic [Ca2+], titin‐based stretch pre‐activates cardiomyocytes during diastole and is a major determinant of force production in the subsequent contraction. Through this mechanism titin would play an important role in active force development and length‐dependent activation. Mutations in the splicing factor RNA binding motif protein 20 (RBM20) result in expression of large, highly compliant titin isoforms. We measured single cardiomyocyte work loops that mimic the cardiac cycle in wild‐type (WT) and heterozygous (HET) RBM20‐deficient rats. In addition, we studied the role of diastolic [Ca2+] in membrane‐permeabilized WT and HET cardiomyocytes. Intact cardiomyocytes isolated from HET left ventricles were unable to produce normal levels of work (55% of WT) at low pacing frequencies, but this difference disappeared at high pacing frequencies. Length‐dependent activation (force–sarcomere length relationship) was blunted in HET cardiomyocytes, but the force–end‐diastolic force relationship was not different between HET and WT cardiomyocytes. To delineate the effects of diastolic [Ca2+] and titin pre‐activation on force generation, measurements were performed in detergent‐permeabilized cardiomyocytes. Cardiac twitches were simulated by transiently exposing permeabilized cardiomyocytes to 2 µm Ca2+. Increasing diastolic [Ca2+] from 1 to 80 nm increased force development twofold in WT. Higher diastolic [Ca2+] was needed in HET. These findings are consistent with our hypothesis that pre‐activation increases active force development. Highly compliant titin allows cells to function at higher diastolic [Ca2+].
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Affiliation(s)
- Aref Najafi
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands.,Netherlands Heart Institute, PO box 19258, 3501 DG, Utrecht, the Netherlands
| | - Martijn van de Locht
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
| | - Maike Schuldt
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
| | | | | | - Ilse Bollen
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
| | - Max Goebel
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
| | - Coen A C Ottenheijm
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
| | - Jolanda van der Velden
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands.,Netherlands Heart Institute, PO box 19258, 3501 DG, Utrecht, the Netherlands
| | - Michiel Helmes
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands.,Ionoptix, de Boelelaan 1108, 1081 HV, Amsterdam, the Netherlands.,CytoCypher, de Boelelaan 1108, 1081 HV, Amsterdam, the Netherlands
| | - Diederik W D Kuster
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
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21
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Kellermayer D, Smith JE, Granzier H. Titin mutations and muscle disease. Pflugers Arch 2019; 471:673-682. [PMID: 30919088 DOI: 10.1007/s00424-019-02272-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 03/11/2019] [Indexed: 12/12/2022]
Abstract
The introduction of next-generation sequencing technology has revealed that mutations in the gene that encodes titin (TTN) are linked to multiple skeletal and cardiac myopathies. The most prominent of these myopathies is dilated cardiomyopathy (DCM). Over 60 genes are linked to the etiology of DCM, but by far, the leading cause of DCM is mutations in TTN with truncating variants in TTN (TTNtvs) associated with familial DCM in ∼ 20% of the cases. Titin is a large (3-4 MDa) and abundant protein that forms the third myofilament type of striated muscle where it spans half the sarcomere, from the Z-disk to the M-line. The underlying mechanisms by which titin mutations induce disease are poorly understood and targeted therapies are not available. Here, we review what is known about TTN mutations in muscle disease, with a major focus on DCM. We highlight that exon skipping might provide a possible therapeutic avenue to address diseases that arise from TTNtvs.
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Affiliation(s)
- Dalma Kellermayer
- Department of Cellular and Molecular Medicine, University of Arizona, MRB 325. 1656 E Mabel Street, Tucson, AZ, 85724-5217, USA.,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85721, USA
| | - John E Smith
- Department of Cellular and Molecular Medicine, University of Arizona, MRB 325. 1656 E Mabel Street, Tucson, AZ, 85724-5217, USA.,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85721, USA
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, MRB 325. 1656 E Mabel Street, Tucson, AZ, 85724-5217, USA. .,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85721, USA.
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22
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van der Velden J, Stienen GJM. Cardiac Disorders and Pathophysiology of Sarcomeric Proteins. Physiol Rev 2019; 99:381-426. [PMID: 30379622 DOI: 10.1152/physrev.00040.2017] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The sarcomeric proteins represent the structural building blocks of heart muscle, which are essential for contraction and relaxation. During recent years, it has become evident that posttranslational modifications of sarcomeric proteins, in particular phosphorylation, tune cardiac pump function at rest and during exercise. This delicate, orchestrated interaction is also influenced by mutations, predominantly in sarcomeric proteins, which cause hypertrophic or dilated cardiomyopathy. In this review, we follow a bottom-up approach starting from a description of the basic components of cardiac muscle at the molecular level up to the various forms of cardiac disorders at the organ level. An overview is given of sarcomere changes in acquired and inherited forms of cardiac disease and the underlying disease mechanisms with particular reference to human tissue. A distinction will be made between the primary defect and maladaptive/adaptive secondary changes. Techniques used to unravel functional consequences of disease-induced protein changes are described, and an overview of current and future treatments targeted at sarcomeric proteins is given. The current evidence presented suggests that sarcomeres not only form the basis of cardiac muscle function but also represent a therapeutic target to combat cardiac disease.
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Affiliation(s)
- Jolanda van der Velden
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, Amsterdam , The Netherlands ; and Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Ger J M Stienen
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, Amsterdam , The Netherlands ; and Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
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23
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Slater RE, Strom JG, Methawasin M, Liss M, Gotthardt M, Sweitzer N, Granzier HL. Metformin improves diastolic function in an HFpEF-like mouse model by increasing titin compliance. J Gen Physiol 2018; 151:42-52. [PMID: 30567709 PMCID: PMC6314384 DOI: 10.1085/jgp.201812259] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 11/14/2018] [Indexed: 12/20/2022] Open
Abstract
Heart failure with preserved ejection fraction (HFpEF) is a syndrome characterized by increased diastolic stiffness, for which effective therapies are lacking. Slater et al. show that metformin lowers titin-based passive stiffness in an HFpEF mouse model and may therefore be of therapeutic benefit. Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome characterized by a preserved ejection fraction but increased diastolic stiffness and abnormalities of filling. Although the prevalence of HFpEF is high and continues to rise, no effective therapies exist; however, the diabetic drug metformin has been associated with improved diastolic function in diabetic patients. Here we determine the therapeutic potential of metformin for improving diastolic function in a mouse model with HFpEF-like symptoms. We combine transverse aortic constriction (TAC) surgery with deoxycorticosterone acetate (DOCA) supplementation to obtain a mouse model with increased diastolic stiffness and exercise intolerance. Echocardiography and pressure–volume analysis reveal that providing metformin to TAC/DOCA mice improves diastolic function in the left ventricular (LV) chamber. Muscle mechanics show that metformin lowers passive stiffness of the LV wall muscle. Concomitant with this improvement in diastolic function, metformin-treated TAC/DOCA mice also demonstrate preserved exercise capacity. No metformin effects are seen in sham operated mice. Extraction experiments on skinned ventricular muscle strips show that the metformin-induced reduction of passive stiffness in TAC/DOCA mice is due to an increase in titin compliance. Using phospho-site-specific antibodies, we assay the phosphorylation of titin’s PEVK and N2B spring elements. Metformin-treated mice have unaltered PEVK phosphorylation but increased phosphorylation of PKA sites in the N2B element, a change which has previously been shown to lower titin’s stiffness. Consistent with this result, experiments with a mouse model deficient in the N2B element reveal that the beneficial effect of metformin on LV chamber and muscle stiffness requires the presence of the N2B element. We conclude that metformin offers therapeutic benefit during HFpEF by lowering titin-based passive stiffness.
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Affiliation(s)
- Rebecca E Slater
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Joshua G Strom
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Mei Methawasin
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Martin Liss
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany.,German Center for Cardiovascular Research, Partner Site Berlin, Berlin, Germany
| | - Michael Gotthardt
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany.,German Center for Cardiovascular Research, Partner Site Berlin, Berlin, Germany
| | - Nancy Sweitzer
- Sarver Heart Center, College of Medicine, University of Arizona, Tucson, AZ
| | - Henk L Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ .,Sarver Heart Center, College of Medicine, University of Arizona, Tucson, AZ
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24
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Watanabe T, Kimura A, Kuroyanagi H. Alternative Splicing Regulator RBM20 and Cardiomyopathy. Front Mol Biosci 2018; 5:105. [PMID: 30547036 PMCID: PMC6279932 DOI: 10.3389/fmolb.2018.00105] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 11/09/2018] [Indexed: 12/17/2022] Open
Abstract
RBM20 is a vertebrate-specific RNA-binding protein with two zinc finger (ZnF) domains, one RNA-recognition motif (RRM)-type RNA-binding domain and an arginine/serine (RS)-rich region. RBM20 has initially been identified as one of dilated cardiomyopathy (DCM)-linked genes. RBM20 is a regulator of heart-specific alternative splicing and Rbm20ΔRRM mice lacking the RRM domain are defective in the splicing regulation. The Rbm20ΔRRM mice, however, do not exhibit a characteristic DCM-like phenotype such as dilatation of left ventricles or systolic dysfunction. Considering that most of the RBM20 mutations identified in familial DCM cases were heterozygous missense mutations in an arginine-serine-arginine-serine-proline (RSRSP) stretch whose phosphorylation is crucial for nuclear localization of RBM20, characterization of a knock-in animal model is awaited. One of the major targets for RBM20 is the TTN gene, which is comprised of the largest number of exons in mammals. Alternative splicing of the TTN gene is exceptionally complicated and RBM20 represses >160 of its consecutive exons, yet detailed mechanisms for such extraordinary regulation are to be elucidated. The TTN gene encodes the largest known protein titin, a multi-functional sarcomeric structural protein specific to striated muscles. As titin is the most important factor for passive tension of cardiomyocytes, extensive heart-specific and developmentally regulated alternative splicing of the TTN pre-mRNA by RBM20 plays a critical role in passive stiffness and diastolic function of the heart. In disease models with diastolic dysfunctions, the phenotypes were rescued by increasing titin compliance through manipulation of the Ttn pre-mRNA splicing, raising RBM20 as a potential therapeutic target.
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Affiliation(s)
- Takeshi Watanabe
- Laboratory of Gene Expression, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.,Department of Psychosomatic Dentistry, Graduate School of Medical and Dental Science, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Akinori Kimura
- Division of Pathology, Department of Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.,Laboratory for Integrated Research Projects on Intractable Diseases Advanced Technology Laboratories, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Hidehito Kuroyanagi
- Laboratory of Gene Expression, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.,Laboratory for Integrated Research Projects on Intractable Diseases Advanced Technology Laboratories, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.,Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, United States
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25
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van der Pijl R, Strom J, Conijn S, Lindqvist J, Labeit S, Granzier H, Ottenheijm C. Titin-based mechanosensing modulates muscle hypertrophy. J Cachexia Sarcopenia Muscle 2018; 9:947-961. [PMID: 29978560 PMCID: PMC6204599 DOI: 10.1002/jcsm.12319] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 04/30/2018] [Accepted: 05/22/2018] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Titin is an elastic sarcomeric filament that has been proposed to play a key role in mechanosensing and trophicity of muscle. However, evidence for this proposal is scarce due to the lack of appropriate experimental models to directly test the role of titin in mechanosensing. METHODS We used unilateral diaphragm denervation (UDD) in mice, an in vivo model in which the denervated hemidiaphragm is passively stretched by the contralateral, innervated hemidiaphragm and hypertrophy rapidly occurs. RESULTS In wildtype mice, the denervated hemidiaphragm mass increased 48 ± 3% after 6 days of UDD, due to the addition of both sarcomeres in series and in parallel. To test whether titin stiffness modulates the hypertrophy response, RBM20ΔRRM and TtnΔIAjxn mouse models were used, with decreased and increased titin stiffness, respectively. RBM20ΔRRM mice (reduced stiffness) showed a 20 ± 6% attenuated hypertrophy response, whereas the TtnΔIAjxn mice (increased stiffness) showed an 18 ± 8% exaggerated response after UDD. Thus, muscle hypertrophy scales with titin stiffness. Protein expression analysis revealed that titin-binding proteins implicated previously in muscle trophicity were induced during UDD, MARP1 & 2, FHL1, and MuRF1. CONCLUSIONS Titin functions as a mechanosensor that regulates muscle trophicity.
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Affiliation(s)
- Robbert van der Pijl
- Department of Cellular and Molecular MedicineUniversity of ArizonaTucsonAZUSA
- Dept of PhysiologyVU University Medical CenterAmsterdamThe Netherlands
| | - Joshua Strom
- Department of Cellular and Molecular MedicineUniversity of ArizonaTucsonAZUSA
| | - Stefan Conijn
- Dept of PhysiologyVU University Medical CenterAmsterdamThe Netherlands
| | - Johan Lindqvist
- Department of Cellular and Molecular MedicineUniversity of ArizonaTucsonAZUSA
| | - Siegfried Labeit
- Department of Integrative PathophysiologyMedical Faculty MannheimMannheimGermany
- Myomedix GmbHNeckargemuendGermany
| | - Henk Granzier
- Department of Cellular and Molecular MedicineUniversity of ArizonaTucsonAZUSA
| | - Coen Ottenheijm
- Department of Cellular and Molecular MedicineUniversity of ArizonaTucsonAZUSA
- Dept of PhysiologyVU University Medical CenterAmsterdamThe Netherlands
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26
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Affiliation(s)
- Mei Methawasin
- From the Cellular and Molecular Medicine Department and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson
| | - Henk Granzier
- From the Cellular and Molecular Medicine Department and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson.
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27
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Liss M, Radke MH, Eckhard J, Neuenschwander M, Dauksaite V, von Kries JP, Gotthardt M. Drug discovery with an RBM20 dependent titin splice reporter identifies cardenolides as lead structures to improve cardiac filling. PLoS One 2018; 13:e0198492. [PMID: 29889873 PMCID: PMC5995442 DOI: 10.1371/journal.pone.0198492] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 05/20/2018] [Indexed: 02/07/2023] Open
Abstract
Diastolic dysfunction is increasingly prevalent in our ageing society and an important contributor to heart failure. The giant protein titin could serve as a therapeutic target, as its elastic properties are a main determinant of cardiac filling in diastole. This study aimed to develop a high throughput pharmacological screen to identify small molecules that affect titin isoform expression through differential inclusion of exons encoding the elastic PEVK domains. We used a dual luciferase splice reporter assay that builds on the titin splice factor RBM20 to screen ~34,000 small molecules and identified several compounds that inhibit the exclusion of PEVK exons. These compounds belong to the class of cardenolides and affect RBM20 dependent titin exon exclusion but did not affect RBFOX1 mediated splicing of FMNL3. We provide evidence that cardenolides do not bind to the RNA interacting domain of RBM20, but reduce RBM20 protein levels and alter transcription of select splicing factors that interact with RBM20. Cardenolides affect titin isoform expression. Understanding their mode of action and harnessing the splice effects through chemical modifications that suppress the effects on ion homeostasis and more selectively affect cardiac splicing has the potential to improve cardiac filling and thus help patients with diastolic heart failure, for which currently no targeted therapy exists.
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Affiliation(s)
- Martin Liss
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Michael H. Radke
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Berlin, Berlin, Germany
| | - Jamina Eckhard
- Screening Unit, Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
| | | | - Vita Dauksaite
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | | | - Michael Gotthardt
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Berlin, Berlin, Germany
- * E-mail:
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28
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Lygirou V, Latosinska A, Makridakis M, Mullen W, Delles C, Schanstra JP, Zoidakis J, Pieske B, Mischak H, Vlahou A. Plasma proteomic analysis reveals altered protein abundances in cardiovascular disease. J Transl Med 2018; 16:104. [PMID: 29665821 PMCID: PMC5905170 DOI: 10.1186/s12967-018-1476-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 04/06/2018] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Cardiovascular disease (CVD) describes the pathological conditions of the heart and blood vessels. Despite the large number of studies on CVD and its etiology, its key modulators remain largely unknown. To this end, we performed a comprehensive proteomic analysis of blood plasma, with the scope to identify disease-associated changes after placing them in the context of existing knowledge, and generate a well characterized dataset for further use in CVD multi-omics integrative analysis. METHODS LC-MS/MS was employed to analyze plasma from 32 subjects (19 cases of various CVD phenotypes and 13 controls) in two steps: discovery (13 cases and 8 controls) and test (6 cases and 5 controls) set analysis. Following label-free quantification, the detected proteins were correlated to existing plasma proteomics datasets (plasma proteome database; PPD) and functionally annotated (Cytoscape, Ingenuity Pathway Analysis). Differential expression was defined based on identification confidence (≥ 2 peptides per protein), statistical significance (Mann-Whitney p value ≤ 0.05) and a minimum of twofold change. RESULTS Peptides detected in at least 50% of samples per group were considered, resulting in a total of 3796 identified proteins (838 proteins based on ≥ 2 peptides). Pathway annotation confirmed the functional relevance of the findings (representation of complement cascade, fibrin clot formation, platelet degranulation, etc.). Correlation of the relative abundance of the proteins identified in the discovery set with their reported concentrations in the PPD was significant, confirming the validity of the quantification method. The discovery set analysis revealed 100 differentially expressed proteins between cases and controls, 39 of which were verified (≥ twofold change) in the test set. These included proteins already studied in the context of CVD (such as apolipoprotein B, alpha-2-macroglobulin), as well as novel findings (such as low density lipoprotein receptor related protein 2 [LRP2], protein SZT2) for which a mechanism of action is suggested. CONCLUSIONS This proteomic study provides a comprehensive dataset to be used for integrative and functional studies in the field. The observed protein changes reflect known CVD-related processes (e.g. lipid uptake, inflammation) but also novel hypotheses for further investigation including a potential pleiotropic role of LPR2 but also links of SZT2 to CVD.
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Affiliation(s)
- Vasiliki Lygirou
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou Street, 115 27, Athens, Greece
| | | | - Manousos Makridakis
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou Street, 115 27, Athens, Greece
| | - William Mullen
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK
| | - Christian Delles
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK
| | - Joost P Schanstra
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1048, Institute of Cardiovascular and Metabolic Disease, Toulouse, France.,Université Toulouse III Paul-Sabatier, Toulouse, France
| | - Jerome Zoidakis
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou Street, 115 27, Athens, Greece
| | - Burkert Pieske
- Deutsches Herzzentrum Berlin, Augustenburger Pl. 1, 13353, Berlin, Germany
| | - Harald Mischak
- Mosaiques Diagnostics GmbH, Rotenburger Straße 20, 30659, Hannover, Germany
| | - Antonia Vlahou
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou Street, 115 27, Athens, Greece.
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29
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Chen Z, Song J, Chen L, Zhu C, Cai H, Sun M, Stern A, Mozdziak P, Ge Y, Means WJ, Guo W. Characterization of TTN Novex Splicing Variants across Species and the Role of RBM20 in Novex-Specific Exon Splicing. Genes (Basel) 2018; 9:genes9020086. [PMID: 29438341 PMCID: PMC5852582 DOI: 10.3390/genes9020086] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 01/30/2018] [Accepted: 01/30/2018] [Indexed: 11/22/2022] Open
Abstract
Titin (TTN) is a major disease-causing gene in cardiac muscle. Titin (TTN) contains 363 exons in human encoding various sizes of TTN protein due to alternative splicing regulated mainly by RNA binding motif 20 (RBM20). Three isoforms of TTN protein are produced by mutually exclusive exons 45 (Novex 1), 46 (Novex 2), and 48 (Novex 3). Alternatively splicing in Novex isoforms across species and whether Novex isoforms are associated with heart disease remains completely unknown. Cross-species exon comparison with the mVISTA online tool revealed that exon 45 is more highly conserved across all species than exons 46 and 48. Importantly, a conserved region between exons 47 and 48 across species was revealed for the first time. Reverse transcript polymerase chain reaction (RT-PCR) and DNA sequencing confirmed a new exon named as 48′ in Novex 3. In addition, with primer pairs for Novex 1, a new truncated form preserving introns 44 and 45 was discovered. We discovered that Novex 2 is not expressed in the pig, mouse, and rat with Novex 2 primer pairs. Unexpectedly, three truncated forms were identified. One TTN variant with intron 46 retention is mainly expressed in the human and frog heart, another variant with co-expression of exons 45 and 46 exists predominantly in chicken and frog heart, and a third with retention of introns 45 and 46 is mainly expressed in pig, mouse, rat, and chicken. Using Rbm20 knockout rat heart, we revealed that RBM20 is not a splicing regulator of Novex variants. Furthermore, the expression levels of Novex variants in human hearts with cardiomyopathies suggested that Novexes 2 and 3 could be associated with dilated cardiomyopathy (DCM) and/or arrhythmogenic right ventricular cardiomyopathy (ARVC). Taken together, our study reveals that splicing diversity of Novex exons across species and Novex variants might play a role in cardiomyopathy.
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Affiliation(s)
- Zhilong Chen
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China.
- Animal Science, University of Wyoming, Laramie, WY 82071, USA.
| | - Jiangping Song
- Department of Cardiac Surgery, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China.
| | - Liang Chen
- Department of Cardiac Surgery, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China.
| | - Chaoqun Zhu
- Animal Science, University of Wyoming, Laramie, WY 82071, USA.
| | - Hanfang Cai
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China.
- Animal Science, University of Wyoming, Laramie, WY 82071, USA.
| | - Mingming Sun
- Animal Science, University of Wyoming, Laramie, WY 82071, USA.
| | - Allysa Stern
- Prestage Department of Poultry Science, North Carolina State University, Raleigh, NC 27695, USA.
| | - Paul Mozdziak
- Prestage Department of Poultry Science, North Carolina State University, Raleigh, NC 27695, USA.
| | - Ying Ge
- Department of Cell and Regenerative Biology, Department of Chemistry, Human Proteomics Program, University of Wisconsin, Madison, WI 53705, USA.
| | - Warrie J Means
- Animal Science, University of Wyoming, Laramie, WY 82071, USA.
| | - Wei Guo
- Animal Science, University of Wyoming, Laramie, WY 82071, USA.
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30
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Guo W, Sun M. RBM20, a potential target for treatment of cardiomyopathy via titin isoform switching. Biophys Rev 2018; 10:15-25. [PMID: 28577155 PMCID: PMC5803173 DOI: 10.1007/s12551-017-0267-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 05/16/2017] [Indexed: 12/18/2022] Open
Abstract
Cardiomyopathy, also known as heart muscle disease, is an unfavorable condition leading to alterations in myocardial contraction and/or impaired ability of ventricular filling. The onset and development of cardiomyopathy have not currently been well defined. Titin is a giant multifunctional sarcomeric filament protein that provides passive stiffness to cardiomyocytes and has been implicated to play an important role in the origin and development of cardiomyopathy and heart failure. Titin-based passive stiffness can be mainly adjusted by isoform switching and post-translational modifications in the spring regions. Recently, genetic mutations of TTN have been identified that can also contribute to variable passive stiffness, though the detailed mechanisms remain unclear. In this review, we will discuss titin isoform switching as it relates to alternative splicing during development stages and differences between species and muscle types. We provide an update on the regulatory mechanisms of TTN splicing controlled by RBM20 and cover the roles of TTN splicing in adjusting the diastolic stiffness and systolic compliance of the healthy and the failing heart. Finally, this review attempts to provide future directions for RBM20 as a potential target for pharmacological intervention in cardiomyopathy and heart failure.
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Affiliation(s)
- Wei Guo
- Animal Science, University of Wyoming, Laramie, WY, 82071, USA.
- Center for Cardiovascular Research and Integrative Medicine, University of Wyoming, Laramie, WY, 82071, USA.
| | - Mingming Sun
- Animal Science, University of Wyoming, Laramie, WY, 82071, USA
- Center for Cardiovascular Research and Integrative Medicine, University of Wyoming, Laramie, WY, 82071, USA
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31
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Muscle-Specific Mis-Splicing and Heart Disease Exemplified by RBM20. Genes (Basel) 2018; 9:genes9010018. [PMID: 29304022 PMCID: PMC5793171 DOI: 10.3390/genes9010018] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 12/23/2017] [Accepted: 12/27/2017] [Indexed: 11/17/2022] Open
Abstract
Alternative splicing is an essential post-transcriptional process to generate multiple functional RNAs or proteins from a single transcript. Progress in RNA biology has led to a better understanding of muscle-specific RNA splicing in heart disease. The recent discovery of the muscle-specific splicing factor RNA-binding motif 20 (RBM20) not only provided great insights into the general alternative splicing mechanism but also demonstrated molecular mechanism of how this splicing factor is associated with dilated cardiomyopathy. Here, we review our current knowledge of muscle-specific splicing factors and heart disease, with an emphasis on RBM20 and its targets, RBM20-dependent alternative splicing mechanism, RBM20 disease origin in induced Pluripotent Stem Cells (iPSCs), and RBM20 mutations in dilated cardiomyopathy. In the end, we will discuss the multifunctional role of RBM20 and manipulation of RBM20 as a potential therapeutic target for heart disease.
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32
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Tonino P, Kiss B, Strom J, Methawasin M, Smith JE, Kolb J, Labeit S, Granzier H. The giant protein titin regulates the length of the striated muscle thick filament. Nat Commun 2017; 8:1041. [PMID: 29051486 PMCID: PMC5648799 DOI: 10.1038/s41467-017-01144-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 08/22/2017] [Indexed: 01/13/2023] Open
Abstract
The contractile machinery of heart and skeletal muscles has as an essential component the thick filament, comprised of the molecular motor myosin. The thick filament is of a precisely controlled length, defining thereby the force level that muscles generate and how this force varies with muscle length. It has been speculated that the mechanism by which thick filament length is controlled involves the giant protein titin, but no conclusive support for this hypothesis exists. Here we show that in a mouse model in which we deleted two of titin’s C-zone super-repeats, thick filament length is reduced in cardiac and skeletal muscles. In addition, functional studies reveal reduced force generation and a dilated cardiomyopathy (DCM) phenotype. Thus, regulation of thick filament length depends on titin and is critical for maintaining muscle health. Thick filaments in skeletal muscle and heart are composed of myosin. The authors show that the length of thick filaments is defined by titin, and that alterations in titin length affect force generation and lead to dilated cardiomyopathy in mice.
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Affiliation(s)
- Paola Tonino
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, 85721, USA.,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona, 85721, USA
| | - Balazs Kiss
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, 85721, USA.,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona, 85721, USA
| | - Josh Strom
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, 85721, USA.,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona, 85721, USA
| | - Mei Methawasin
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, 85721, USA.,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona, 85721, USA
| | - John E Smith
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, 85721, USA.,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona, 85721, USA
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, 85721, USA.,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona, 85721, USA
| | - Siegfried Labeit
- Department of Integrative Pathophysiology, Medical Faculty Mannheim, Mannheim, 68167, Germany.,DZHK, Mannheim-Heidelberg, 68167, Germany
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, 85721, USA. .,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona, 85721, USA.
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33
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Alternative Splicing in Genetic Diseases: Improved Diagnosis and Novel Treatment Options. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2017; 335:85-141. [PMID: 29305015 DOI: 10.1016/bs.ircmb.2017.07.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Alternative splicing is an important mechanism to regulate gene expression and to expand the repertoire of gene products in order to accommodate an increase in complexity of multicellular organisms. It needs to be precisely regulated, which is achieved via RNA structure, splicing factors, transcriptional regulation, and chromatin. Changes in any of these factors can lead to disease. These may include the core spliceosome, splicing enhancer/repressor sequences and their interacting proteins, the speed of transcription by RNA polymerase II, and histone modifications. While the basic principle of splicing is well understood, it is still very difficult to predict splicing outcome, due to the multiple levels of regulation. Current molecular diagnostics mainly uses Sanger sequencing of exons, or next-generation sequencing of gene panels or the whole exome. Functional analysis of potential splicing variants is scarce, and intronic variants are often not considered. This likely results in underestimation of the percentage of splicing variants. Understanding how sequence variants may affect splicing is not only crucial for confirmation of diagnosis and for genetic counseling, but also for the development of novel treatment options. These include small molecules, transsplicing, antisense oligonucleotides, and gene therapy. Here we review the current state of molecular mechanisms of splicing regulation and how deregulation can lead to human disease, diagnostics to detect splicing variants, and novel treatment options based on splicing correction.
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34
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Abstract
The giant multi-functional striated muscle protein titin is the third most abundant muscle protein after myosin and actin. Titin plays a pivotal role in myocardial passive stiffness, structural integrity and stress-initiated signaling pathways. The complete sequence of the human titin gene contains three isoform-specific mutually exclusive exons [termed novel exons (novex)] coding for the I-band sequence, named novex-1 (exon 45), novex-2 (exon 46) and novex-3 (exon 48). Transcripts containing either the novex-1 or novex-2 exons code for the novex-1 and novex-2 titin isoforms. The novex-3 transcript contains a stop codon and polyA tail signal, resulting in an unusually small (∼700 kDa) isoform, referred to as novex-3 titin. This 'tiny titin' isoform extends from the Z-disc (N-terminus) to novex-3 (C-terminus) and is expressed in all striated muscles. Biochemical analysis of novex-3 titin in cardiomyocytes shows that obscurin, a vertebrate muscle protein, binds to novex-3 titin. The novex-3/obscurin complex localizes to the Z-disc region and may regulate calcium, and SH3- and GTPase-associated myofibrillar signaling pathways. Therefore, novex-3 titin could be involved in stress-initiated sarcomeric restructuring.
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35
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Methawasin M, Granzier H. Response by Methawasin and Granzier to Letter Regarding Article, "Experimentally Increasing the Compliance of Titin Through RNA Binding Motif-20 (RBM20) Inhibition Improves Diastolic Function in a Mouse Model of Heart Failure With Preserved Ejection Fraction". Circulation 2017; 135:e681-e682. [PMID: 28289010 DOI: 10.1161/circulationaha.117.026955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Mei Methawasin
- From Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson
| | - Henk Granzier
- From Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson
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