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Ranta-Aho J, Felice KJ, Jonson PH, Sarparanta J, Yvorel C, Harzallah I, Touraine R, Pais L, Austin-Tse CA, Ganesh VS, O'Leary MC, Rehm HL, Hehir MK, Subramony S, Wu Q, Udd B, Savarese M. Protein-extending ACTN2 frameshift variants cause variable myopathy phenotypes by protein aggregation. Ann Clin Transl Neurol 2024. [PMID: 39095936 DOI: 10.1002/acn3.52154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2024] [Revised: 06/19/2024] [Accepted: 07/08/2024] [Indexed: 08/04/2024] Open
Abstract
OBJECTIVE The objective of the study is to characterize the pathomechanisms underlying actininopathies. Distal myopathies are a group of rare, inherited muscular disorders characterized by progressive loss of muscle fibers that begin in the distal parts of arms and legs. Recently, variants in a new disease gene, ACTN2, have been shown to cause distal myopathy. ACTN2, a gene previously only associated with cardiomyopathies, encodes alpha-actinin-2, a protein expressed in both cardiac and skeletal sarcomeres. The primary function of alpha-actinin-2 is to link actin and titin to the sarcomere Z-disk. New ACTN2 variants are continuously discovered; however, the clinical significance of many variants remains unknown. Thus, lack of clear genotype-phenotype correlations in ACTN2-related diseases, actininopathies, persists. METHODS Functional characterization in C2C12 cell model of several ACTN2 variants is conducted, including frameshift and missense variants associated with dominant and recessive actininopathies. We assess the genotype-phenotype correlations of actininopathies using clinical data from several patients carrying these variants. RESULTS The results show that the missense variants associated with a recessive form of actininopathy do not cause detectable alpha-actinin-2 aggregates in the cell model. Conversely, dominant frameshift variants causing a protein extension do form alpha-actinin-2 aggregates. INTERPRETATION The results suggest that alpha-actinin-2 aggregation is the disease mechanism underlying some dominant actininopathies, and thus, we recommend that protein-extending frameshift variants in ACTN2 should be classified as pathogenic. However, this mechanism is likely elicited by only a limited number of variants. Alternative functional characterization methods should be explored to further investigate other molecular mechanisms underlying actininopathies.
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Affiliation(s)
- Johanna Ranta-Aho
- Folkhälsan Research Center, Haartmaninkatu 8, 00290, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Haartmaninkatu 8, Helsinki, 00290, Finland
| | - Kevin J Felice
- Department of Neuromuscular Medicine, Hospital for Special Care, 2150 Corbin Avenue, New Britain, Connecticut, 06053, USA
| | - Per Harald Jonson
- Folkhälsan Research Center, Haartmaninkatu 8, 00290, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Haartmaninkatu 8, Helsinki, 00290, Finland
| | - Jaakko Sarparanta
- Folkhälsan Research Center, Haartmaninkatu 8, 00290, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Haartmaninkatu 8, Helsinki, 00290, Finland
| | - Cédric Yvorel
- Cardiology Department, Hôpital Nord, Hôpital Nord, CHU de Saint Etienne, Avenue Albert Raimond, Saint Priest-en-Jarez, 42270, France
| | - Ines Harzallah
- Genetic Department, Hôpital Nord, CHU de Saint Etienne, Avenue Albert Raimond, Saint Priest-en-Jarez, 42270, France
| | - Renaud Touraine
- Genetic Department, Hôpital Nord, CHU de Saint Etienne, Avenue Albert Raimond, Saint Priest-en-Jarez, 42270, France
| | - Lynn Pais
- Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, 105 Broadway, Cambridge, Massachusetts, 02142, USA
- Division of Genetics and Genomics, Boston Children's Hospital, Harvard Medical School, 2 Brookline Place, Boston, Massachusetts, 02445, USA
| | - Christina A Austin-Tse
- Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, 105 Broadway, Cambridge, Massachusetts, 02142, USA
- Center for Genomic Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, Massachusetts, 02114, USA
| | - Vijay S Ganesh
- Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, 105 Broadway, Cambridge, Massachusetts, 02142, USA
- Department of Neurology, Brigham and Women's Hospital, 60 Fenwood Road, Boston, Massachusetts, 02115, USA
| | - Melanie C O'Leary
- Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, 105 Broadway, Cambridge, Massachusetts, 02142, USA
| | - Heidi L Rehm
- Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, 105 Broadway, Cambridge, Massachusetts, 02142, USA
- Center for Genomic Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, Massachusetts, 02114, USA
| | - Michael K Hehir
- Department of Neurology, Larner College of Medicine at the University of Vermont, 149 Beaumont Avenue, Burlington, Vermont, 05405, USA
| | - Sub Subramony
- Department of Neurology, University of Florida College of Medicine, 1505 SW Archer Road, Gainesville, Florida, 32610, USA
| | - Qian Wu
- Department of Pathology, University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, Connecticut, 06030, USA
| | - Bjarne Udd
- Folkhälsan Research Center, Haartmaninkatu 8, 00290, Helsinki, Finland
- Tampere Neuromuscular Center, Tampere University and Tampere University Hospital, Biokatu 8, Tampere, 33520, Finland
| | - Marco Savarese
- Folkhälsan Research Center, Haartmaninkatu 8, 00290, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Haartmaninkatu 8, Helsinki, 00290, Finland
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Ranta-Aho J, Felice KJ, Jonson PH, Sarparanta J, Palmio J, Tasca G, Sabatelli M, Yvorel C, Harzallah I, Touraine R, Pais L, Austin-Tse CA, Ganesh V, O'Leary MC, Rehm HL, Hehir MK, Subramony S, Wu Q, Udd B, Savarese M. Rare ACTN2 Frameshift Variants Resulting in Protein Extension Cause Distal Myopathy and Hypertrophic Cardiomyopathy through Protein Aggregation. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.01.17.23298671. [PMID: 38293186 PMCID: PMC10827258 DOI: 10.1101/2024.01.17.23298671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Distal myopathies are a group of rare, inherited muscular disorders characterized by progressive loss of muscle fibers that begins in the distal parts of arms and legs. Recently, variants in a new disease gene, ACTN2 , have been shown to cause distal myopathy. ACTN2 , a gene previously only associated with cardiomyopathies, encodes alpha-actinin-2, a protein expressed in both cardiac and skeletal sarcomeres. The primary function of alpha-actinin-2 is to link actin and titin to the sarcomere Z-disk. New ACTN2 variants are continuously discovered, however, the clinical significance of many variants remains unknown. Thus, lack of clear genotype-phenotype correlations in ACTN2 -related diseases, actininopathies, persists. Objective The objective of the study is to characterize the pathomechanisms underlying actininopathies. Methods Functional characterization in C2C12 cell models of several ACTN2 variants is conducted, including frameshift and missense variants associated with dominant actininopathies. We assess the genotype-phenotype correlations of actininopathies using clinical data from several patients carrying these variants. Results The results show that the missense variants associated with a recessive form of actininopathy do not cause detectable alpha-actinin-2 aggregates in the cell model. Conversely, dominant frameshift variants causing a protein extension do produce alpha-actinin-2 aggregates. Interpretation The results suggest that alpha-actinin-2 aggregation is the disease mechanism underlying some dominant actininopathies, and thus we recommend that protein-extending frameshift variants in ACTN2 should be classified as pathogenic. However, this mechanism is likely elicited by only a limited number of variants. Alternative functional characterization methods should be explored to further investigate other molecular mechanisms underlying actininopathies.
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Rodriguez Garcia M, Schmeckpeper J, Landim-Vieira M, Coscarella IL, Fang X, Ma W, Spran PA, Yuan S, Qi L, Kahmini AR, Shoemaker MB, Atkinson JB, Kekenes-Huskey PM, Irving TC, Chase PB, Knollmann BC, Pinto JR. Disruption of Z-Disc Function Promotes Mechanical Dysfunction in Human Myocardium: Evidence for a Dual Myofilament Modulatory Role by Alpha-Actinin 2. Int J Mol Sci 2023; 24:14572. [PMID: 37834023 PMCID: PMC10572656 DOI: 10.3390/ijms241914572] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Revised: 09/19/2023] [Accepted: 09/20/2023] [Indexed: 10/15/2023] Open
Abstract
The ACTN2 gene encodes α-actinin 2, located in the Z-disc of the sarcomeres in striated muscle. In this study, we sought to investigate the effects of an ACTN2 missense variant of unknown significance (p.A868T) on cardiac muscle structure and function. Left ventricular free wall samples were obtained at the time of cardiac transplantation from a heart failure patient with the ACTN2 A868T heterozygous variant. This variant is in the EF 3-4 domain known to interact with titin and α-actinin. At the ultrastructural level, ACTN2 A868T cardiac samples presented small structural changes in cardiomyocytes when compared to healthy donor samples. However, contractile mechanics of permeabilized ACTN2 A868T variant cardiac tissue displayed higher myofilament Ca2+ sensitivity of isometric force, reduced sinusoidal stiffness, and faster rates of tension redevelopment at all Ca2+ levels. Small-angle X-ray diffraction indicated increased separation between thick and thin filaments, possibly contributing to changes in muscle kinetics. Molecular dynamics simulations indicated that while the mutation does not significantly impact the structure of α-actinin on its own, it likely alters the conformation associated with titin binding. Our results can be explained by two Z-disc mediated communication pathways: one pathway that involves α-actinin's interaction with actin, affecting thin filament regulation, and the other pathway that involves α-actinin's interaction with titin, affecting thick filament activation. This work establishes the role of α-actinin 2 in modulating cross-bridge kinetics and force development in the human myocardium as well as how it can be involved in the development of cardiac disease.
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Affiliation(s)
| | - Jeffrey Schmeckpeper
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | | | | | - Xuan Fang
- Department of Cell & Molecular Physiology, Loyola University, Chicago, IL 60660, USA
| | - Weikang Ma
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Payton A. Spran
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Shengyao Yuan
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Lin Qi
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Aida Rahimi Kahmini
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL 32306, USA;
| | - M. Benjamin Shoemaker
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - James B. Atkinson
- Department of Pathology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | | | - Thomas C. Irving
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Prescott Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Björn C. Knollmann
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jose Renato Pinto
- Biomedical Sciences, Florida State University, Tallahassee, FL 32306, USA
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Chumakova OS, Baulina NM. Advanced searching for hypertrophic cardiomyopathy heritability in real practice tomorrow. Front Cardiovasc Med 2023; 10:1236539. [PMID: 37583586 PMCID: PMC10425241 DOI: 10.3389/fcvm.2023.1236539] [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: 06/07/2023] [Accepted: 07/17/2023] [Indexed: 08/17/2023] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease associated with morbidity and mortality at any age. As studies in recent decades have shown, the genetic architecture of HCM is quite complex both in the entire population and in each patient. In the rapidly advancing era of gene therapy, we have to provide a detailed molecular diagnosis to our patients to give them the chance for better and more personalized treatment. In addition to emphasizing the importance of genetic testing in routine practice, this review aims to discuss the possibility to go a step further and create an expanded genetic panel that contains not only variants in core genes but also new candidate genes, including those located in deep intron regions, as well as structural variations. It also highlights the benefits of calculating polygenic risk scores based on a combination of rare and common genetic variants for each patient and of using non-genetic HCM markers, such as microRNAs that can enhance stratification of risk for HCM in unselected populations alongside rare genetic variants and clinical factors. While this review is focusing on HCM, the discussed issues are relevant to other cardiomyopathies.
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Affiliation(s)
- Olga S. Chumakova
- Laboratory of Functional Genomics of Cardiovascular Diseases, National Medical Research Centre of Cardiology Named After E.I. Chazov, Moscow, Russia
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Zhou L, Huang J, Li H, Duan H, Hua Y, Guo Y, Zhou K, Li Y. Impaired Cardiomyocyte Maturation Leading to DCM: A Case Report and Literature Review. MEDICINA (KAUNAS, LITHUANIA) 2023; 59:1158. [PMID: 37374362 DOI: 10.3390/medicina59061158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 05/23/2023] [Accepted: 06/12/2023] [Indexed: 06/29/2023]
Abstract
Background: The maturation of cardiomyocytes is a rapidly evolving area of research within the field of cardiovascular medicine. Understanding the molecular mechanisms underlying cardiomyocyte maturation is essential to advancing our knowledge of the underlying causes of cardiovascular disease. Impaired maturation can lead to the development of cardiomyopathy, particularly dilated cardiomyopathy (DCM). Recent studies have confirmed the involvement of the ACTN2 and RYR2 genes in the maturation process, facilitating the functional maturation of the sarcomere and calcium handling. Defective sarcomere and electrophysiological maturation have been linked to severe forms of cardiomyopathy. This report presents a rare case of DCM with myocardial non-compaction, probably resulting from allelic collapse of both the ACTN2 and RYR2 genes. Case Presentation: The proband in this case was a four-year-old male child who presented with a recurrent and aggressive reduction in activity tolerance, decreased ingestion volume, and profuse sweating. Electrocardiography revealed significant ST-T segment depression (II, III, aVF V3-V6 ST segment depression >0.05 mV with inverted T-waves). Echocardiography showed an enlarged left ventricle and marked myocardial non-compaction. Cardiac magnetic resonance imaging revealed increased left ventricular trabeculae, an enlarged left ventricle, and a reduced ejection fraction. Whole exome sequencing revealed a restricted genomic depletion in the 1q43 region (chr1:236,686,454-237,833,988/Hg38), encompassing the coding genes ACTN2, MTR, and RYR2. The identified variant resulted in heterozygous variations in these three genes, with the ACTN2 g.236,686,454-236,764,631_del and RYR2 g.237,402,134-237,833,988_del variants being the dominant contributors to the induction of cardiomyopathy. The patient was finally diagnosed with DCM and left ventricular myocardial non-compaction. Conclusions: This study reports a rare case of DCM with myocardial non-compaction caused by the allelic collapse of the ACTN2 and RYR2 genes. This case provides the first human validation of the critical role of cardiomyocyte maturation in maintaining cardiac function and stability and confirms the key findings of previous experimental research conducted by our group. This report emphasizes the connection between genes involved in regulating the maturation of cardiomyocytes and the development of cardiomyopathy.
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Affiliation(s)
- Letao Zhou
- Key Laboratory of Birth Defects and Related Diseases of Women and Children of MOE, Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu 610041, China
| | - Jinglan Huang
- Key Laboratory of Birth Defects and Related Diseases of Women and Children of MOE, Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu 610041, China
| | - Hong Li
- Key Laboratory of Birth Defects and Related Diseases of Women and Children of MOE, Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu 610041, China
- Department of Nursing, West China Second University Hospital, Sichuan University, Chengdu 610041, China
| | - Hongyu Duan
- Key Laboratory of Birth Defects and Related Diseases of Women and Children of MOE, Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu 610041, China
| | - Yimin Hua
- Key Laboratory of Birth Defects and Related Diseases of Women and Children of MOE, Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu 610041, China
| | - Yuxuan Guo
- Key Laboratory of Molecular Cardiovascular Science of Ministry of Education, Beijing Key Laboratory of Cardiovascular Receptors Research, Health Science Center, School of Basic Medical Sciences, The Institute of Cardiovascular Sciences, Peking University, Beijing 100191, China
| | - Kaiyu Zhou
- Key Laboratory of Birth Defects and Related Diseases of Women and Children of MOE, Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu 610041, China
| | - Yifei Li
- Key Laboratory of Birth Defects and Related Diseases of Women and Children of MOE, Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu 610041, China
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