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Iwanski JB, Pappas CT, Mayfield RM, Farman GP, Ahrens-Nicklas R, Churko JM, Gregorio CC. Leiomodin 2 neonatal dilated cardiomyopathy mutation results in altered actin gene signatures and cardiomyocyte dysfunction. NPJ Regen Med 2024; 9:21. [PMID: 39285234 PMCID: PMC11405699 DOI: 10.1038/s41536-024-00366-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 08/23/2024] [Indexed: 09/19/2024] Open
Abstract
Neonatal dilated cardiomyopathy (DCM) is a poorly understood muscular disease of the heart. Several homozygous biallelic variants in LMOD2, the gene encoding the actin-binding protein Leiomodin 2, have been identified to result in severe DCM. Collectively, LMOD2-related cardiomyopathies present with cardiac dilation and decreased heart contractility, often resulting in neonatal death. Thus, it is evident that Lmod2 is essential to normal human cardiac muscle function. This study aimed to understand the underlying pathophysiology and signaling pathways related to the first reported LMOD2 variant (c.1193 G > A, p.Trp398*). Using patient-specific human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and a mouse model harboring the homologous mutation to the patient, we discovered dysregulated actin-thin filament lengths, altered contractility and calcium handling properties, as well as alterations in the serum response factor (SRF)-dependent signaling pathway. These findings reveal that LMOD2 may be regulating SRF activity in an actin-dependent manner and provide a potential new strategy for the development of biologically active molecules to target LMOD2-related cardiomyopathies.
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Grants
- R01HL123078 U.S. Department of Health & Human Services | NIH | National Heart, Lung, and Blood Institute (NHLBI)
- R00 HL128906 NHLBI NIH HHS
- R01 HL164644 NHLBI NIH HHS
- R01 GM120137 NIGMS NIH HHS
- F30HL151139 U.S. Department of Health & Human Services | NIH | National Heart, Lung, and Blood Institute (NHLBI)
- T32HL007249 U.S. Department of Health & Human Services | NIH | National Heart, Lung, and Blood Institute (NHLBI)
- T32 HL007249 NHLBI NIH HHS
- R01 HL123078 NHLBI NIH HHS
- R01HL164644 U.S. Department of Health & Human Services | NIH | National Heart, Lung, and Blood Institute (NHLBI)
- F30 HL151139 NHLBI NIH HHS
- R01GM120137 U.S. Department of Health & Human Services | NIH | National Heart, Lung, and Blood Institute (NHLBI)
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Affiliation(s)
- Jessika B Iwanski
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85724, USA
| | - Christopher T Pappas
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85724, USA
| | - Rachel M Mayfield
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85724, USA
| | - Gerrie P Farman
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85724, USA
| | - Rebecca Ahrens-Nicklas
- Department of Pediatrics and Division of Human Genetics and Metabolism, The Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Jared M Churko
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85724, USA.
| | - Carol C Gregorio
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85724, USA.
- Department of Medicine and Cardiovascular Research Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
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2
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Burnham HV, Cizauskas HE, Barefield DY. Fine tuning contractility: atrial sarcomere function in health and disease. Am J Physiol Heart Circ Physiol 2024; 326:H568-H583. [PMID: 38156887 PMCID: PMC11221815 DOI: 10.1152/ajpheart.00252.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 12/20/2023] [Accepted: 12/21/2023] [Indexed: 01/03/2024]
Abstract
The molecular mechanisms of sarcomere proteins underlie the contractile function of the heart. Although our understanding of the sarcomere has grown tremendously, the focus has been on ventricular sarcomere isoforms due to the critical role of the ventricle in health and disease. However, atrial-specific or -enriched myofilament protein isoforms, as well as isoforms that become expressed in disease, provide insight into ways this complex molecular machine is fine-tuned. Here, we explore how atrial-enriched sarcomere protein composition modulates contractile function to fulfill the physiological requirements of atrial function. We review how atrial dysfunction negatively affects the ventricle and the many cardiovascular diseases that have atrial dysfunction as a comorbidity. We also cover the pathophysiology of mutations in atrial-enriched contractile proteins and how they can cause primary atrial myopathies. Finally, we explore what is known about contractile function in various forms of atrial fibrillation. The differences in atrial function in health and disease underscore the importance of better studying atrial contractility, especially as therapeutics currently in development to modulate cardiac contractility may have different effects on atrial sarcomere function.
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Affiliation(s)
- Hope V Burnham
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois, United States
| | - Hannah E Cizauskas
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois, United States
| | - David Y Barefield
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois, United States
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3
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Kuwabara Y, York AJ, Lin SC, Sargent MA, Grimes KM, Pirruccello JP, Molkentin JD. A human FLII gene variant alters sarcomeric actin thin filament length and predisposes to cardiomyopathy. Proc Natl Acad Sci U S A 2023; 120:e2213696120. [PMID: 37126682 PMCID: PMC10175844 DOI: 10.1073/pnas.2213696120] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 04/07/2023] [Indexed: 05/03/2023] Open
Abstract
To better understand the genetic basis of heart disease, we identified a variant in the Flightless-I homolog (FLII) gene that generates a R1243H missense change and predisposes to cardiac remodeling across multiple previous human genome-wide association studies (GWAS). Since this gene is of unknown function in the mammalian heart we generated gain- and loss-of-function genetically altered mice, as well as knock-in mice with the syntenic R1245H amino acid substitution, which showed that Flii protein binds the sarcomeric actin thin filament and influences its length. Deletion of Flii from the heart, or mice with the R1245H amino acid substitution, show cardiomyopathy due to shortening of the actin thin filaments. Mechanistically, Flii is a known actin binding protein that we show associates with tropomodulin-1 (TMOD1) to regulate sarcomere thin filament length. Indeed, overexpression of leiomodin-2 in the heart, which lengthens the actin-containing thin filaments, partially rescued disease due to heart-specific deletion of Flii. Collectively, the identified FLII human variant likely increases cardiomyopathy risk through an alteration in sarcomere structure and associated contractile dynamics, like other sarcomere gene-based familial cardiomyopathies.
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Affiliation(s)
- Yasuhide Kuwabara
- Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
| | - Allen J. York
- Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
| | - Suh-Chin Lin
- Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
| | - Michelle A. Sargent
- Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
| | - Kelly M. Grimes
- Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
| | - James P. Pirruccello
- Division of Cardiology, University of California San Francisco, San Francisco, CA94158
| | - Jeffery D. Molkentin
- Department of Pediatrics, Cincinnati Children’s Hospital and the University of Cincinnati, Cincinnati, OH45229
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4
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Yoneda K, Kanada R, Okada JI, Watanabe M, Sugiura S, Hisada T, Washio T. A thermodynamically consistent monte carlo cross-bridge model with a trapping mechanism reveals the role of stretch activation in heart pumping. Front Physiol 2022; 13:855303. [PMID: 36160842 PMCID: PMC9498833 DOI: 10.3389/fphys.2022.855303] [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: 01/15/2022] [Accepted: 07/18/2022] [Indexed: 11/24/2022] Open
Abstract
Changes in intracellular calcium concentrations regulate heart beats. However, the decline in the left ventricular pressure during early diastole is much sharper than that of the Ca2+ transient, resulting in a rapid supply of blood to the left ventricle during the diastole. At the tissue level, cardiac muscles have a distinct characteristic, known as stretch activation, similar to the function of insect flight muscles. Stretch activation, which is a delayed increase in force following a rapid muscle length increase, has been thought to be related to autonomous control in these muscles. In this numerical simulation study, we introduced a molecular mechanism of stretch activation and investigated the role of this mechanism in the pumping function of the heart, using the previously developed coupling multiple-step active stiffness integration scheme for a Monte Carlo (MC) cross-bridge model and a bi-ventricular finite element model. In the MC cross-bridge model, we introduced a mechanism for trapping the myosin molecule in its post-power stroke state. We then determined the rate constants of transitions for trapping and escaping in a thermodynamically consistent manner. Based on our numerical analysis, we draw the following conclusions regarding the stretch activation mechanism: (i) the delayed force becomes larger than the original isometric force because the population of trapped myosin molecules and their average force increase after stretching; (ii) the delayed force has a duration of more than a few seconds owing to a fairly small rate constant of escape from the trapped state. For the role of stretch activation in heart pumping, we draw the following conclusions: (iii) for the regions in which the contraction force decreases earlier than the neighboring region in the end-systole phase, the trapped myosin molecules prevent further lengthening of the myocytes, which then prevents further shortening of neighboring myocytes; (iv) as a result, the contraction forces are sustained longer, resulting in a larger blood ejection, and their degeneration is synchronized.
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Affiliation(s)
- Kazunori Yoneda
- Section Solutions Division, Healthcare Solutions Development Unit, Fujitsu Japan Limited, Shiodome City Center, Tokyo, Japan
| | - Ryo Kanada
- RIKEN Center for Computational Science HPC- and AI-driven Drug Development Platform Division, AI-driven Drug Discovery Collaborative Unit, Kobe, Japan
| | - Jun-ichi Okada
- UT-Heart Inc., Kashiwanoha Campus Satellite, Kashiwa, Japan
- Graduate School of Frontier Sciences, University of Tokyo, Kashiwanoha Campus Satellite, Kashiwa, Japan
| | - Masahiro Watanabe
- Section Solutions Division, Healthcare Solutions Development Unit, Fujitsu Japan Limited, Shiodome City Center, Tokyo, Japan
| | - Seiryo Sugiura
- UT-Heart Inc., Kashiwanoha Campus Satellite, Kashiwa, Japan
| | | | - Takumi Washio
- UT-Heart Inc., Kashiwanoha Campus Satellite, Kashiwa, Japan
- Graduate School of Frontier Sciences, University of Tokyo, Kashiwanoha Campus Satellite, Kashiwa, Japan
- *Correspondence: Takumi Washio,
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5
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Szikora S, Görög P, Mihály J. The Mechanisms of Thin Filament Assembly and Length Regulation in Muscles. Int J Mol Sci 2022; 23:5306. [PMID: 35628117 PMCID: PMC9140763 DOI: 10.3390/ijms23105306] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/05/2022] [Accepted: 05/06/2022] [Indexed: 02/01/2023] Open
Abstract
The actin containing tropomyosin and troponin decorated thin filaments form one of the crucial components of the contractile apparatus in muscles. The thin filaments are organized into densely packed lattices interdigitated with myosin-based thick filaments. The crossbridge interactions between these myofilaments drive muscle contraction, and the degree of myofilament overlap is a key factor of contractile force determination. As such, the optimal length of the thin filaments is critical for efficient activity, therefore, this parameter is precisely controlled according to the workload of a given muscle. Thin filament length is thought to be regulated by two major, but only partially understood mechanisms: it is set by (i) factors that mediate the assembly of filaments from monomers and catalyze their elongation, and (ii) by factors that specify their length and uniformity. Mutations affecting these factors can alter the length of thin filaments, and in human cases, many of them are linked to debilitating diseases such as nemaline myopathy and dilated cardiomyopathy.
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Affiliation(s)
- Szilárd Szikora
- Institute of Genetics, Biological Research Centre, H-6726 Szeged, Hungary;
| | - Péter Görög
- Institute of Genetics, Biological Research Centre, H-6726 Szeged, Hungary;
- Doctoral School of Multidisciplinary Medical Science, Faculty of Medicine, University of Szeged, H-6725 Szeged, Hungary
| | - József Mihály
- Institute of Genetics, Biological Research Centre, H-6726 Szeged, Hungary;
- Department of Genetics, University of Szeged, H-6726 Szeged, Hungary
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6
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Lookin O, Khokhlova A, Myachina T, Butova X, Cazorla O, de Tombe P. Contractile State Dependent Sarcomere Length Variability in Isolated Guinea-Pig Cardiomyocytes. Front Physiol 2022; 13:857471. [PMID: 35444559 PMCID: PMC9013801 DOI: 10.3389/fphys.2022.857471] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 03/11/2022] [Indexed: 11/13/2022] Open
Abstract
Cardiomyocytes contract keeping their sarcomere length (SL) close to optimal values for force generation. Transmural heterogeneity in SL across the ventricular wall coordinates the contractility of the whole-ventricle. SL heterogeneity (variability) exists not only at the tissue (macroscale) level, but also presents at the level of a single cardiomyocyte (microscale level). However, transmural differences in intracellular SL variability and its possible dependence on the state of contraction (e.g. end-diastole or end-systole) have not been previously reported. In the present study, we studied three aspects of sarcomere-to-sarcomere variability in intact cardiomyocytes isolated from the left ventricle of healthy guinea-pig: 1) transmural differences in SL distribution between subepi- (EPI) and subendocardial (ENDO) cardiomyocytes; 2) the dependence of intracellular variability in SL upon the state of contraction; 3) local differences in SL variability, comparing SL distributions between central and peripheral regions within the cardiomyocyte. To characterize the intracellular variability of SL, we used different normality tests for the assessment of SL distributions, as well as nonparametric coefficients to quantify the variability. We found that individual SL values in the end-systolic state of contraction followed a normal distribution to a lesser extent as compared to the end-diastolic state of contraction (∼1.3-fold and ∼1.6-fold in ENDO and EPI, respectively). The relative and absolute coefficients of sarcomere-to-sarcomere variability in end-systolic SL were significantly greater (∼1.3-fold) as compared to end-diastolic SL. This was independent of both the transmural region across the left ventricle and the intracellular region within the cardiomyocyte. We conclude that the intracellular variability in SL, which exists in normal intact guinea-pig cardiomyocytes, is affected by the contractile state of the myocyte. This phenomenon may play a role in inter-sarcomere communication in the beating heart.
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Affiliation(s)
- Oleg Lookin
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
- *Correspondence: Oleg Lookin,
| | - Anastasia Khokhlova
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
| | - Tatiana Myachina
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
| | - Xenia Butova
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
| | - Olivier Cazorla
- Laboratoire “Physiologie et Médecine Expérimentale du Coeur et des Muscles”, Phymedexp, INSERM—CNRS - Montpellier University, Montpellier, France
| | - Pieter de Tombe
- Laboratoire “Physiologie et Médecine Expérimentale du Coeur et des Muscles”, Phymedexp, INSERM—CNRS - Montpellier University, Montpellier, France
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, United States
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7
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The Oxidative Balance Orchestrates the Main Keystones of the Functional Activity of Cardiomyocytes. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2022; 2022:7714542. [PMID: 35047109 PMCID: PMC8763515 DOI: 10.1155/2022/7714542] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 11/03/2021] [Accepted: 12/15/2021] [Indexed: 12/11/2022]
Abstract
This review is aimed at providing an overview of the key hallmarks of cardiomyocytes in physiological and pathological conditions. The main feature of cardiac tissue is the force generation through contraction. This process requires a conspicuous energy demand and therefore an active metabolism. The cardiac tissue is rich of mitochondria, the powerhouses in cells. These organelles, producing ATP, are also the main sources of ROS whose altered handling can cause their accumulation and therefore triggers detrimental effects on mitochondria themselves and other cell components thus leading to apoptosis and cardiac diseases. This review highlights the metabolic aspects of cardiomyocytes and wanders through the main systems of these cells: (a) the unique structural organization (such as different protein complexes represented by contractile, regulatory, and structural proteins); (b) the homeostasis of intracellular Ca2+ that represents a crucial ion for cardiac functions and E-C coupling; and (c) the balance of Zn2+, an ion with a crucial impact on the cardiovascular system. Although each system seems to be independent and finely controlled, the contractile proteins, intracellular Ca2+ homeostasis, and intracellular Zn2+ signals are strongly linked to each other by the intracellular ROS management in a fascinating way to form a "functional tetrad" which ensures the proper functioning of the myocardium. Nevertheless, if ROS balance is not properly handled, one or more of these components could be altered resulting in deleterious effects leading to an unbalance of this "tetrad" and promoting cardiovascular diseases. In conclusion, this "functional tetrad" is proposed as a complex network that communicates continuously in the cardiomyocytes and can drive the switch from physiological to pathological conditions in the heart.
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Wang Z, Grange M, Pospich S, Wagner T, Kho AL, Gautel M, Raunser S. Structures from intact myofibrils reveal mechanism of thin filament regulation through nebulin. Science 2022; 375:eabn1934. [PMID: 35175800 DOI: 10.1126/science.abn1934] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In skeletal muscle, nebulin stabilizes and regulates the length of thin filaments, but the underlying mechanism remains nebulous. In this work, we used cryo-electron tomography and subtomogram averaging to reveal structures of native nebulin bound to thin filaments within intact sarcomeres. This in situ reconstruction provided high-resolution details of the interaction between nebulin and actin, demonstrating the stabilizing role of nebulin. Myosin bound to the thin filaments exhibited different conformations of the neck domain, highlighting its inherent structural variability in muscle. Unexpectedly, nebulin did not interact with myosin or tropomyosin, but it did interact with a troponin T linker through two potential binding motifs on nebulin, explaining its regulatory role. Our structures support the role of nebulin as a thin filament "molecular ruler" and provide a molecular basis for studying nemaline myopathies.
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Affiliation(s)
- Zhexin Wang
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Michael Grange
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Sabrina Pospich
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Thorsten Wagner
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Ay Lin Kho
- Randall Centre for Cell and Molecular Biophysics, School of Basic and Medical Biosciences, Kings College London BHF Centre of Research Excellence, Guy's Campus, London SE1 1UL, UK
| | - Mathias Gautel
- Randall Centre for Cell and Molecular Biophysics, School of Basic and Medical Biosciences, Kings College London BHF Centre of Research Excellence, Guy's Campus, London SE1 1UL, UK
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
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9
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Kawai M, Jin JP. Mechanisms of Frank-Starling law of the heart and stretch activation in striated muscles may have a common molecular origin. J Muscle Res Cell Motil 2021; 42:355-366. [PMID: 33575955 PMCID: PMC10905364 DOI: 10.1007/s10974-020-09595-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 12/24/2020] [Indexed: 01/24/2023]
Abstract
Vertebrate cardiac muscle generates progressively larger systolic force when the end diastolic chamber volume is increased, a property called the "Frank-Starling Law", or "length dependent activation (LDA)". In this mechanism a larger force develops when the sarcomere length (SL) increased, and the overlap between thick and thin filament decreases, indicating increased production of force per unit length of the overlap. To account for this phenomenon at the molecular level, we examined several hypotheses: as the muscle length is increased, (1) lattice spacing decreases, (2) Ca2+ sensitivity increases, (3) titin mediated rearrangement of myosin heads to facilitate actomyosin interaction, (4) increased SL activates cross-bridges (CBs) in the super relaxed state, (5) increased series stiffness at longer SL promotes larger elementary force/CB to account for LDA, and (6) stretch activation (SA) observed in insect muscles and LDA in vertebrate muscles may have similar mechanisms. SA is also known as delayed tension or oscillatory work, and universally observed among insect flight muscles, as well as in vertebrate skeletal and cardiac muscles. The sarcomere stiffness observed in relaxed muscles may significantly contributes to the mechanisms of LDA. In vertebrate striated muscles, the sarcomere stiffness is mainly caused by titin, a single filamentary protein spanning from Z-line to M-line and tightly associated with the myosin thick filament. In insect flight muscles, kettin connects Z-line and the thick filament to stabilize the sarcomere structure. In vertebrate cardiac muscles, titin plays a similar role, and may account for LDA and may constitute a molecular mechanism of Frank-Starling response.
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Affiliation(s)
- Masataka Kawai
- Department of Anatomy and Cell Biology, University of Iowa College of Medicine, 1-324 BSB, 51 Newton Rd, Iowa City, IA, 52242, USA.
| | - Jian-Ping Jin
- Departmewnt of Physiology, Wayne State University School of Medicine, Detroit, MI, 48201, USA
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10
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Alpha and beta myosin isoforms and human atrial and ventricular contraction. Cell Mol Life Sci 2021; 78:7309-7337. [PMID: 34704115 PMCID: PMC8629898 DOI: 10.1007/s00018-021-03971-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 10/03/2021] [Accepted: 10/08/2021] [Indexed: 01/15/2023]
Abstract
Human atrial and ventricular contractions have distinct mechanical characteristics including speed of contraction, volume of blood delivered and the range of pressure generated. Notably, the ventricle expresses predominantly β-cardiac myosin while the atrium expresses mostly the α-isoform. In recent years exploration of the properties of pure α- & β-myosin isoforms have been possible in solution, in isolated myocytes and myofibrils. This allows us to consider the extent to which the atrial vs ventricular mechanical characteristics are defined by the myosin isoform expressed, and how the isoform properties are matched to their physiological roles. To do this we Outline the essential feature of atrial and ventricular contraction; Explore the molecular structural and functional characteristics of the two myosin isoforms; Describe the contractile behaviour of myocytes and myofibrils expressing a single myosin isoform; Finally we outline the outstanding problems in defining the differences between the atria and ventricles. This allowed us consider what features of contraction can and cannot be ascribed to the myosin isoforms present in the atria and ventricles.
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11
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Kiss B, Gohlke J, Tonino P, Hourani Z, Kolb J, Strom J, Alekhina O, Smith JE, Ottenheijm C, Gregorio C, Granzier H. Nebulin and Lmod2 are critical for specifying thin-filament length in skeletal muscle. SCIENCE ADVANCES 2020; 6:6/46/eabc1992. [PMID: 33177085 PMCID: PMC7673738 DOI: 10.1126/sciadv.abc1992] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 09/23/2020] [Indexed: 06/07/2023]
Abstract
Regulating the thin-filament length in muscle is crucial for controlling the number of myosin motors that generate power. The giant protein nebulin forms a long slender filament that associates along the length of the thin filament in skeletal muscle with functions that remain largely obscure. Here nebulin's role in thin-filament length regulation was investigated by targeting entire super-repeats in the Neb gene; nebulin was either shortened or lengthened by 115 nm. Its effect on thin-filament length was studied using high-resolution structural and functional techniques. Results revealed that thin-filament length is strictly regulated by the length of nebulin in fast muscles. Nebulin's control is less tight in slow muscle types where a distal nebulin-free thin-filament segment exists, the length of which was found to be regulated by leiomodin-2 (Lmod2). We propose that strict length control by nebulin promotes high-speed shortening and that dual-regulation by nebulin/Lmod2 enhances contraction efficiency.
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Affiliation(s)
- Balázs Kiss
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Jochen Gohlke
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Paola Tonino
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Zaynab Hourani
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Joshua Strom
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Olga Alekhina
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - John E Smith
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Coen Ottenheijm
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Carol Gregorio
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA.
- Allan and Alfie Endowed Chair for Heart Disease in Women Research, Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85721, USA
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12
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Abstract
Nebulin, encoded by NEB, is a giant skeletal muscle protein of about 6669 amino acids which forms an integral part of the sarcomeric thin filament. In recent years, the nebula around this protein has been largely lifted resulting in the discovery that nebulin is critical for a number of tasks in skeletal muscle. In this review, we firstly discussed nebulin’s role as a structural component of the thin filament and the Z-disk, regulating the length and the mechanical properties of the thin filament as well as providing stability to myofibrils by interacting with structural proteins within the Z-disk. Secondly, we reviewed nebulin’s involvement in the regulation of muscle contraction, cross-bridge cycling kinetics, Ca2+-homeostasis and excitation contraction (EC) coupling. While its role in Ca2+-homeostasis and EC coupling is still poorly understood, a large number of studies have helped to improve our knowledge on how nebulin affects skeletal muscle contractile mechanics. These studies suggest that nebulin affects the number of force generating actin-myosin cross-bridges and may also affect the force that each cross-bridge produces. It may exert this effect by interacting directly with actin and myosin and/or indirectly by potentially changing the localisation and function of the regulatory complex (troponin and tropomyosin). Besides unravelling the biology of nebulin, these studies are particularly helpful in understanding the patho-mechanism of myopathies caused by NEB mutations, providing knowledge which constitutes the critical first step towards the development of therapeutic interventions. Currently, effective treatments are not available, although a number of therapeutic strategies are being investigated.
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13
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Lindqvist J, Lee EJ, Karimi E, Kolb J, Granzier H. Omecamtiv mecarbil lowers the contractile deficit in a mouse model of nebulin-based nemaline myopathy. PLoS One 2019; 14:e0224467. [PMID: 31721788 PMCID: PMC6853306 DOI: 10.1371/journal.pone.0224467] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Accepted: 10/14/2019] [Indexed: 01/10/2023] Open
Abstract
Nemaline myopathy (NEM) is a congenital neuromuscular disorder primarily caused by nebulin gene (NEB) mutations. NEM is characterized by muscle weakness for which currently no treatments exist. In NEM patients a predominance of type I fibers has been found. Thus, therapeutic options targeting type I fibers could be highly beneficial for NEM patients. Because type I muscle fibers express the same myosin isoform as cardiac muscle (Myh7), the effect of omecamtiv mecarbil (OM), a small molecule activator of Myh7, was studied in a nebulin-based NEM mouse model (Neb cKO). Skinned single fibers were activated by exogenous calcium and force was measured at a wide range of calcium concentrations. Maximal specific force of type I fibers was much less in fibers from Neb cKO animals and calcium sensitivity of permeabilized single fibers was reduced (pCa50 6.12 ±0.08 (cKO) vs 6.36 ±0.08 (CON)). OM increased the calcium sensitivity of type I single muscle fibers. The greatest effect occurred in type I fibers from Neb cKO muscle where OM restored the calcium sensitivity to that of the control type I fibers. Forces at submaximal activation levels (pCa 6.0–6.5) were significantly increased in Neb cKO fibers (~50%) but remained below that of control fibers. OM also increased isometric force and power during isotonic shortening of intact whole soleus muscle of Neb cKO mice, with the largest effects at physiological stimulation frequencies. We conclude that OM has the potential to improve the quality of life of NEM patients by increasing the force of type I fibers at submaximal activation levels.
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Affiliation(s)
- Johan Lindqvist
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, United States of America
| | - Eun-Jeong Lee
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, United States of America
| | - Esmat Karimi
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, United States of America
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, United States of America
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, United States of America
- * E-mail:
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14
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Zaunbrecher RJ, Abel AN, Beussman K, Leonard A, von Frieling-Salewsky M, Fields PA, Pabon L, Reinecke H, Yang X, Macadangdang J, Kim DH, Linke WA, Sniadecki NJ, Regnier M, Murry CE. Cronos Titin Is Expressed in Human Cardiomyocytes and Necessary for Normal Sarcomere Function. Circulation 2019; 140:1647-1660. [PMID: 31587567 PMCID: PMC6911360 DOI: 10.1161/circulationaha.119.039521] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 08/27/2019] [Indexed: 01/15/2023]
Abstract
BACKGROUND The giant sarcomere protein titin is important in both heart health and disease. Mutations in the gene encoding for titin (TTN) are the leading known cause of familial dilated cardiomyopathy. The uneven distribution of these mutations within TTN motivated us to seek a more complete understanding of this gene and the isoforms it encodes in cardiomyocyte (CM) sarcomere formation and function. METHODS To investigate the function of titin in human CMs, we used CRISPR/Cas9 to generate homozygous truncations in the Z disk (TTN-Z-/-) and A-band (TTN-A-/-) regions of the TTN gene in human induced pluripotent stem cells. The resulting CMs were characterized with immunostaining, engineered heart tissue mechanical measurements, and single-cell force and calcium measurements. RESULTS After differentiation, we were surprised to find that despite the more upstream mutation, TTN-Z-/--CMs had sarcomeres and visibly contracted, whereas TTN-A-/--CMs did not. We hypothesized that sarcomere formation was caused by the expression of a recently discovered isoform of titin, Cronos, which initiates downstream of the truncation in TTN-Z-/--CMs. Using a custom Cronos antibody, we demonstrate that this isoform is expressed and integrated into myofibrils in human CMs. TTN-Z-/--CMs exclusively express Cronos titin, but these cells produce lower contractile force and have perturbed myofibril bundling compared with controls expressing both full-length and Cronos titin. Cronos titin is highly expressed in human fetal cardiac tissue, and when knocked out in human induced pluripotent stem cell derived CMs, these cells exhibit reduced contractile force and myofibrillar disarray despite the presence of full-length titin. CONCLUSIONS We demonstrate that Cronos titin is expressed in developing human CMs and is able to support partial sarcomere formation in the absence of full-length titin. Furthermore, Cronos titin is necessary for proper sarcomere function in human induced pluripotent stem cell derived CMs. Additional investigation is necessary to understand the molecular mechanisms of this novel isoform and how it contributes to human cardiac disease.
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Affiliation(s)
- Rebecca J. Zaunbrecher
- Department of Bioengineering, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Ashley N. Abel
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Kevin Beussman
- Department of Mechanical Engineering, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Andrea Leonard
- Department of Mechanical Engineering, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | | | - Paul A. Fields
- Department of Pathology, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Lil Pabon
- Department of Pathology, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Hans Reinecke
- Department of Pathology, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Xiulan Yang
- Department of Pathology, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Jesse Macadangdang
- Department of Bioengineering, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Deok-Ho Kim
- Department of Bioengineering, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Wolfgang A. Linke
- Institute of Physiology II, University of Muenster, Robert-Koch-Str. 27b, D-48149 Muenster, Germany
- Deutsches Zentrum für Herz-Kreislaufforschung, Partner Site Goettingen, Germany
| | - Nathan J. Sniadecki
- Department of Mechanical Engineering, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Michael Regnier
- Department of Bioengineering, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
| | - Charles E. Murry
- Department of Bioengineering, University of Washington, Seattle, WA
- Department of Pathology, University of Washington, Seattle, WA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA
- Department of Medicine/Cardiology, University of Washington, Seattle, WA
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15
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Effect of myofibril passive elastic properties on the mechanical communication between motor proteins on adjacent sarcomeres. Sci Rep 2019; 9:9355. [PMID: 31249348 PMCID: PMC6597731 DOI: 10.1038/s41598-019-45772-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 06/10/2019] [Indexed: 11/08/2022] Open
Abstract
Rapid sarcomere lengthening waves propagate along a single muscle myofibril during spontaneous oscillatory contraction (SPOC). In asynchronous insect flight muscles, SPOC is thought to be almost completely synchronized over the entire myofibril. This phenomenon does not require Ca2+ regulation of the dynamics of the motor proteins, and cannot be explained simply by the longitudinal mechanical equilibrium among sarcomeres in the myofibril. In the present study, we rationalize these phenomena by considering the lateral mechanical equilibrium, in which two tensions originating from the inverse relationship between sarcomere length and lattice spacing, along with the lattice alignment, play important roles in the mechanical communication between motor proteins on adjacent filaments via the Z-disc. The proposed model is capable of explaining various SPOC phenomena based on the stochastic power-stroke mechanism of motor proteins, which responds to temporal changes in longitudinal mechanical load.
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16
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Mijailovich SM, Stojanovic B, Nedic D, Svicevic M, Geeves MA, Irving TC, Granzier HL. Nebulin and titin modulate cross-bridge cycling and length-dependent calcium sensitivity. J Gen Physiol 2019; 151:680-704. [PMID: 30948421 PMCID: PMC6504291 DOI: 10.1085/jgp.201812165] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 01/15/2019] [Accepted: 03/03/2019] [Indexed: 12/13/2022] Open
Abstract
Various mutations in the structural proteins nebulin and titin that are present in human disease are known to affect the contractility of striated muscle. Loss of nebulin is associated with reduced actin filament length and impairment of myosin binding to actin, whereas titin is thought to regulate muscle passive elasticity and is likely involved in length-dependent activation. Here, we sought to assess the modulation of muscle function by these sarcomeric proteins by using the computational platform muscle simulation code (MUSICO) to quantitatively separate the effects of structural changes, kinetics of cross-bridge cycling, and calcium sensitivity of the thin filaments. The simulations show that variation in thin filament length cannot by itself account for experimental observations of the contractility in nebulin-deficient muscle, but instead must be accompanied by a decreased myosin binding rate. Additionally, to match the observed calcium sensitivity, the rate of TnI detachment from actin needed to be increased. Simulations for cardiac muscle provided quantitative estimates of the effects of different titin-based passive elasticities on muscle force and activation in response to changes in sarcomere length and interfilament lattice spacing. Predicted force-pCa relations showed a decrease in both active tension and sensitivity to calcium with a decrease in passive tension and sarcomere length. We conclude that this behavior is caused by partial redistribution of the muscle load between active muscle force and titin-dependent passive force, and also by redistribution of stretch along the thin filament, which together modulate the release of TnI from actin. These data help advance understanding of how nebulin and titin mutations affect muscle function.
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Affiliation(s)
- Srboljub M Mijailovich
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA .,Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
| | - Boban Stojanovic
- University of Kragujevac, Faculty of Science, Kragujevac, Serbia
| | - Djordje Nedic
- University of Kragujevac, Faculty of Science, Kragujevac, Serbia
| | - Marina Svicevic
- University of Kragujevac, Faculty of Science, Kragujevac, Serbia
| | - Michael A Geeves
- Department of Biosciences, University of Kent, Canterbury, Kent, UK
| | - Thomas C Irving
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
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17
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Li KL, Methawasin M, Tanner BCW, Granzier HL, Solaro RJ, Dong WJ. Sarcomere length-dependent effects on Ca 2+-troponin regulation in myocardium expressing compliant titin. J Gen Physiol 2018; 151:30-41. [PMID: 30523116 PMCID: PMC6314383 DOI: 10.1085/jgp.201812218] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 11/01/2018] [Indexed: 11/20/2022] Open
Abstract
Increases in sarcomere length cause enhanced force generation in cardiomyocytes by an unknown mechanism. Li et al. reveal that titin-based passive tension contributes to length-dependent activation of myofilaments and that tightly bound myosin–actin cross-bridges are associated with this effect. Cardiac performance is tightly regulated at the cardiomyocyte level by sarcomere length, such that increases in sarcomere length lead to sharply enhanced force generation at the same Ca2+ concentration. Length-dependent activation of myofilaments involves dynamic and complex interactions between a multitude of thick- and thin-filament components. Among these components, troponin, myosin, and the giant protein titin are likely to be key players, but the mechanism by which these proteins are functionally linked has been elusive. Here, we investigate this link in the mouse myocardium using in situ FRET techniques. Our objective was to monitor how length-dependent Ca2+-induced conformational changes in the N domain of cardiac troponin C (cTnC) are modulated by myosin–actin cross-bridge (XB) interactions and increased titin compliance. We reconstitute FRET donor- and acceptor-modified cTnC(13C/51C)AEDANS-DDPM into chemically skinned myocardial fibers from wild-type and RBM20-deletion mice. The Ca2+-induced conformational changes in cTnC are quantified and characterized using time-resolved FRET measurements as XB state and sarcomere length are varied. The RBM20-deficient mouse expresses a more compliant N2BA titin isoform, leading to reduced passive tension in the myocardium. This provides a molecular tool to investigate how altered titin-based passive tension affects Ca2+-troponin regulation in response to mechanical stretch. In wild-type myocardium, we observe a direct association of sarcomere length–dependent enhancement of troponin regulation with both Ca2+ activation and strongly bound XB states. In comparison, measurements from titin RBM20-deficient animals show blunted sarcomere length–dependent effects. These results suggest that titin-based passive tension contributes to sarcomere length–dependent Ca2+-troponin regulation. We also conclude that strong XB binding plays an important role in linking the modulatory effect of titin compliance to Ca2+-troponin regulation of the myocardium.
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Affiliation(s)
- King-Lun Li
- Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA
| | - Mei Methawasin
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Bertrand C W Tanner
- Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
| | - Henk L Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - R John Solaro
- The Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Wen-Ji Dong
- Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA .,Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
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18
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Pappas CT, Farman GP, Mayfield RM, Konhilas JP, Gregorio CC. Cardiac-specific knockout of Lmod2 results in a severe reduction in myofilament force production and rapid cardiac failure. J Mol Cell Cardiol 2018; 122:88-97. [PMID: 30102883 DOI: 10.1016/j.yjmcc.2018.08.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 07/30/2018] [Accepted: 08/10/2018] [Indexed: 11/29/2022]
Abstract
Leiomodin-2 (Lmod2) is a striated muscle-specific actin binding protein that is implicated in assembly of thin filaments. The necessity of Lmod2 in the adult mouse and role it plays in the mechanics of contraction are unknown. To answer these questions, we generated cardiac-specific conditional Lmod2 knockout mice (cKO). These mice die within a week of induction of the knockout with severe left ventricular systolic dysfunction and little change in cardiac morphology. Cardiac trabeculae isolated from cKO mice have a significant decrease in maximum force production and a blunting of myofilament length-dependent activation. Thin filaments are non-uniform and substantially reduced in length in cKO hearts, affecting the functional overlap of the thick and thin filaments. Remarkably, we also found that Lmod2 levels are directly linked to thin filament length and cardiac function in vivo, with a low amount (<20%) of Lmod2 necessary to maintain cardiac function. Thus, Lmod2 plays an essential role in maintaining proper cardiac thin filament length in adult mice, which in turn is necessary for proper generation of contractile force. Dysregulation of thin filament length in the absence of Lmod2 contributes to heart failure.
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Affiliation(s)
- Christopher T Pappas
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA; Department of Physiology and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, USA.
| | - Gerrie P Farman
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA; Department of Physiology and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, USA
| | - Rachel M Mayfield
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA; Department of Physiology and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, USA
| | - John P Konhilas
- Department of Physiology and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, USA
| | - Carol C Gregorio
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA; Department of Physiology and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, USA
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19
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de Tombe PP, Tyberg JV. Frank's law of the heart: Found in translation. J Mol Cell Cardiol 2018; 121:33-35. [PMID: 29908919 DOI: 10.1016/j.yjmcc.2018.06.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Revised: 05/17/2018] [Accepted: 06/06/2018] [Indexed: 11/30/2022]
Affiliation(s)
- Pieter P de Tombe
- Magdi Yacoub Institute, Harefield, United Kingdom; University of Illinois at Chicago, Chicago, USA; Freiburg University, Freiburg, Germany; Imperial College London, London, UK.
| | - John V Tyberg
- Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Canada
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20
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Williams CD, Holt NC. Spatial Scale and Structural Heterogeneity in Skeletal Muscle Performance. Integr Comp Biol 2018; 58:163-173. [DOI: 10.1093/icb/icy057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- C D Williams
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA 98109, USA
| | - N C Holt
- Department of Biology, Northern Arizona University, S. San Francisco Street, Flagstaff, AZ 86011, USA
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21
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Cappelli K, Capomaccio S, Viglino A, Silvestrelli M, Beccati F, Moscati L, Chiaradia E. Circulating miRNAs as Putative Biomarkers of Exercise Adaptation in Endurance Horses. Front Physiol 2018; 9:429. [PMID: 29740341 PMCID: PMC5928201 DOI: 10.3389/fphys.2018.00429] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 04/06/2018] [Indexed: 12/13/2022] Open
Abstract
Endurance exercise induces metabolic adaptations and has recently been reported associated with the modulation of a particular class of small noncoding RNAs, microRNAs, that act as post-transcriptional regulators of gene expression. Released into body fluids, they termed circulating miRNAs, and they have been recognized as more effective and accurate biomarkers than classical serum markers. This study examined serum profile of miRNAs through massive parallel sequencing in response to prolonged endurance exercise in samples obtained from four competitive Arabian horses before and 2 h after the end of competition. MicroRNA identification, differential gene expression (DGE) analysis and a protein-protein interaction (PPI) network showing significantly enriched pathways of target gene clusters, were assessed and explored. Our results show modulation of more than 100 miRNAs probably arising from tissues involved in exercise responses and indicating the modulation of correlated processes as muscle remodeling, immune and inflammatory responses. Circulating miRNA high-throughput sequencing is a promising approach for sports medicine for the discovery of putative biomarkers for predicting risks related to prolonged activity and monitoring metabolic adaptations.
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Affiliation(s)
- Katia Cappelli
- Dipartimento di Medicina Veterinaria, Centro di Studio del Cavallo Sportivo, University of Perugia, Perugia, Italy
| | - Stefano Capomaccio
- Dipartimento di Medicina Veterinaria, Centro di Studio del Cavallo Sportivo, University of Perugia, Perugia, Italy
| | - Andrea Viglino
- Facoltà di Scienze Agrarie, Alimentari e Ambientali, Istituto di Zootecnica, Università Cattolica del Sacro Cuore, Piacenza, Italy
| | - Maurizio Silvestrelli
- Dipartimento di Medicina Veterinaria, Centro di Studio del Cavallo Sportivo, University of Perugia, Perugia, Italy
| | - Francesca Beccati
- Dipartimento di Medicina Veterinaria, Centro di Studio del Cavallo Sportivo, University of Perugia, Perugia, Italy
| | - Livia Moscati
- Istituto Zooprofilattico Sperimentale dell'Umbria e delle Marche, Perugia, Italy
| | - Elisabetta Chiaradia
- Dipartimento di Medicina Veterinaria, Centro di Studio del Cavallo Sportivo, University of Perugia, Perugia, Italy
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22
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Savarese M, Jonson PH, Huovinen S, Paulin L, Auvinen P, Udd B, Hackman P. The complexity of titin splicing pattern in human adult skeletal muscles. Skelet Muscle 2018; 8:11. [PMID: 29598826 PMCID: PMC5874998 DOI: 10.1186/s13395-018-0156-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 03/05/2018] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Mutations in the titin gene (TTN) cause a large spectrum of diseases affecting skeletal and/or cardiac muscle. TTN includes 363 coding exons, a repeated region with a high degree of complexity, isoform-specific elements, and metatranscript-only exons thought to be expressed only during fetal development. Although three main classes of isoforms have been described so far, alternative splicing events (ASEs) in different tissues or in different developmental and physiological states have been reported. METHODS To achieve a comprehensive view of titin ASEs in adult human skeletal muscles, we performed a RNA-Sequencing experiment on 42 human biopsies collected from 12 anatomically different skeletal muscles of 11 individuals without any skeletal-muscle disorders. RESULTS We confirmed that the skeletal muscle N2A isoforms are highly prevalent, but we found an elevated number of alternative splicing events, some at a very high level. These include previously unknown exon skipping events and alternative 5' and 3' splice sites. Our data suggests the partial inclusion in the TTN transcript of some metatranscript-only exons and the partial exclusion of canonical N2A exons. CONCLUSIONS This study provides an extensive picture of the complex TTN splicing pattern in human adult skeletal muscle, which is crucial for a proper clinical interpretation of TTN variants.
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Affiliation(s)
- Marco Savarese
- Folkhälsan Research Center, University of Helsinki, Helsinki, Finland. .,Folkhälsan Institute of Genetics, Department of Medical Genetics, University of Helsinki, Biomedicum, Haartmaninkatu 8, Pb 63, 00014, Helsinki, Finland.
| | - Per Harald Jonson
- Folkhälsan Research Center, University of Helsinki, Helsinki, Finland
| | - Sanna Huovinen
- Department of Pathology, Fimlab Laboratories, Tampere University Hospital, Tampere, Finland
| | - Lars Paulin
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Petri Auvinen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Bjarne Udd
- Folkhälsan Research Center, University of Helsinki, Helsinki, Finland.,Department of Pathology, Fimlab Laboratories, Tampere University Hospital, Tampere, Finland.,Vaasa Central Hospital, Vaasa, Finland
| | - Peter Hackman
- Folkhälsan Research Center, University of Helsinki, Helsinki, Finland
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23
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Abstract
Cardiac and skeletal striated muscles are intricately designed machines responsible for muscle contraction. Coordination of the basic contractile unit, the sarcomere, and the complex cytoskeletal networks are critical for contractile activity. The sarcomere is comprised of precisely organized individual filament systems that include thin (actin), thick (myosin), titin, and nebulin. Connecting the sarcomere to other organelles (e.g., mitochondria and nucleus) and serving as the scaffold to maintain cellular integrity are the intermediate filaments. The costamere, on the other hand, tethers the sarcomere to the cell membrane. Unique structures like the intercalated disc in cardiac muscle and the myotendinous junction in skeletal muscle help synchronize and transmit force. Intense investigation has been done on many of the proteins that make up these cytoskeletal assemblies. Yet the details of their function and how they interconnect have just started to be elucidated. A vast number of human myopathies are contributed to mutations in muscle proteins; thus understanding their basic function provides a mechanistic understanding of muscle disorders. In this review, we highlight the components of striated muscle with respect to their interactions, signaling pathways, functions, and connections to disease. © 2017 American Physiological Society. Compr Physiol 7:891-944, 2017.
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Affiliation(s)
- Christine A Henderson
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Christopher G Gomez
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Stefanie M Novak
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Lei Mi-Mi
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Carol C Gregorio
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
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24
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Smart N, Riegler J, Turtle CW, Lygate CA, McAndrew DJ, Gehmlich K, Dubé KN, Price AN, Muthurangu V, Taylor AM, Lythgoe MF, Redwood C, Riley PR. Aberrant developmental titin splicing and dysregulated sarcomere length in Thymosin β4 knockout mice. J Mol Cell Cardiol 2017; 102:94-107. [PMID: 27914791 PMCID: PMC5319848 DOI: 10.1016/j.yjmcc.2016.10.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 10/20/2016] [Accepted: 10/22/2016] [Indexed: 02/07/2023]
Abstract
Sarcomere assembly is a highly orchestrated and dynamic process which adapts, during perinatal development, to accommodate growth of the heart. Sarcomeric components, including titin, undergo an isoform transition to adjust ventricular filling. Many sarcomeric genes have been implicated in congenital cardiomyopathies, such that understanding developmental sarcomere transitions will inform the aetiology and treatment. We sought to determine whether Thymosin β4 (Tβ4), a peptide that regulates the availability of actin monomers for polymerization in non-muscle cells, plays a role in sarcomere assembly during cardiac morphogenesis and influences adult cardiac function. In Tβ4 null mice, immunofluorescence-based sarcomere analyses revealed shortened thin filament, sarcomere and titin spring length in cardiomyocytes, associated with precocious up-regulation of the short titin isoforms during the postnatal splicing transition. By magnetic resonance imaging, this manifested as diminished stroke volume and limited contractile reserve in adult mice. Extrapolating to an in vitro cardiomyocyte model, the altered postnatal splicing was corrected with addition of synthetic Tβ4, whereby normal sarcomere length was restored. Our data suggest that Tβ4 is required for setting correct sarcomere length and for appropriate splicing of titin, not only in the heart but also in skeletal muscle. Distinguishing between thin filament extension and titin splicing as the primary defect is challenging, as these events are intimately linked. The regulation of titin splicing is a previously unrecognised role of Tβ4 and gives preliminary insight into a mechanism by which titin isoforms may be manipulated to correct cardiac dysfunction.
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Affiliation(s)
- Nicola Smart
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
| | - Johannes Riegler
- Centre for Advanced Biomedical Imaging, Department of Medicine, University College London (UCL), London, UK
| | - Cameron W Turtle
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Craig A Lygate
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Debra J McAndrew
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Katja Gehmlich
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | | | - Anthony N Price
- Centre for Advanced Biomedical Imaging, Department of Medicine, University College London (UCL), London, UK
| | - Vivek Muthurangu
- Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, London, UK
| | - Andrew M Taylor
- Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, London, UK
| | - Mark F Lythgoe
- Centre for Advanced Biomedical Imaging, Department of Medicine, University College London (UCL), London, UK
| | - Charles Redwood
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Paul R Riley
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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25
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Gokhin DS, Fowler VM. Software-based measurement of thin filament lengths: an open-source GUI for Distributed Deconvolution analysis of fluorescence images. J Microsc 2016; 265:11-20. [PMID: 27644080 DOI: 10.1111/jmi.12456] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/09/2016] [Accepted: 07/19/2016] [Indexed: 12/25/2022]
Abstract
The periodically arranged thin filaments within the striated myofibrils of skeletal and cardiac muscle have precisely regulated lengths, which can change in response to developmental adaptations, pathophysiological states, and genetic perturbations. We have developed a user-friendly, open-source ImageJ plugin that provides a graphical user interface (GUI) for super-resolution measurement of thin filament lengths by applying Distributed Deconvolution (DDecon) analysis to periodic line scans collected from fluorescence images. In the workflow presented here, we demonstrate thin filament length measurement using a phalloidin-stained cryosection of mouse skeletal muscle. The DDecon plugin is also capable of measuring distances of any periodically localized fluorescent signal from the Z- or M-line, as well as distances between successive Z- or M-lines, providing a broadly applicable tool for quantitative analysis of muscle cytoarchitecture. These functionalities can also be used to analyse periodic fluorescence signals in nonmuscle cells.
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Affiliation(s)
- David S Gokhin
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California, U.S.A
| | - Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California, U.S.A
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