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Isbister JC, Nowak N, Butters A, Yeates L, Gray B, Sy RW, Ingles J, Bagnall RD, Semsarian C. "Concealed cardiomyopathy" as a cause of previously unexplained sudden cardiac arrest. Int J Cardiol 2020; 324:96-101. [PMID: 32931854 DOI: 10.1016/j.ijcard.2020.09.031] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Accepted: 09/09/2020] [Indexed: 11/17/2022]
Abstract
BACKGROUND Genetic heart disease is a common cause of sudden cardiac arrest (SCA) in the young and those without an ischaemic precipitant. Identifying a cause of SCA in these patients allows for targeted care and family screening. Current guidelines recommend limited, phenotype-guided genetic testing in SCA survivors where a specific genetic condition is suspected and genetic testing is not recommended in clinically-idiopathic SCA survivors. OBJECTIVE To investigate the diagnostic utility of broad, multi-phenotype genetic testing in clinically-idiopathic SCA survivors. METHODS Clinically-idiopathic SCA survivors underwent analysis of genes known to be associated with either cardiomyopathy or primary arrhythmia syndromes, following referral to a specialised genetic heart disease clinic in Sydney, Australia between 1997 and 2019. Comprehensive review of clinical records, investigations and re-appraisal of genetic data according to current variant classification criteria was performed. RESULTS In total, 22% (n = 8/36) of clinically-idiopathic SCA survivors (mean age 36.9 ± 16.9 years, 61% male) had a disease-causing variant identified on broad genetic testing. Of these, 7 (88%) variants resided in cardiomyopathy-associated genes (ACTN2, DES, DSP, MYBPC3, MYH7, PKP2) despite structurally normal hearts or sub-diagnostic structural changes at the time of arrest, so-called "concealed cardiomyopathy". Only one SCA survivor had a variant identified in a channelopathy associated gene (SCN5A). CONCLUSION Extended molecular analysis with multi-phenotype genetic testing can identify a "concealed cardiomyopathy", and increase the diagnosis rate for clinically-idiopathic SCA survivors.
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Affiliation(s)
- Julia C Isbister
- Agnes Ginges Centre for Molecular Cardiology Centenary Institute, The University of Sydney, Sydney, Australia; Faculty of Medicine and Heath, The University of Sydney, Sydney, Australia; Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia
| | - Natalie Nowak
- Agnes Ginges Centre for Molecular Cardiology Centenary Institute, The University of Sydney, Sydney, Australia
| | - Alexandra Butters
- Agnes Ginges Centre for Molecular Cardiology Centenary Institute, The University of Sydney, Sydney, Australia; Faculty of Medicine and Heath, The University of Sydney, Sydney, Australia
| | - Laura Yeates
- Agnes Ginges Centre for Molecular Cardiology Centenary Institute, The University of Sydney, Sydney, Australia; Faculty of Medicine and Heath, The University of Sydney, Sydney, Australia; Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia
| | - Belinda Gray
- Faculty of Medicine and Heath, The University of Sydney, Sydney, Australia; Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia
| | - Raymond W Sy
- Faculty of Medicine and Heath, The University of Sydney, Sydney, Australia; Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia
| | - Jodie Ingles
- Agnes Ginges Centre for Molecular Cardiology Centenary Institute, The University of Sydney, Sydney, Australia; Faculty of Medicine and Heath, The University of Sydney, Sydney, Australia; Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia
| | - Richard D Bagnall
- Faculty of Medicine and Heath, The University of Sydney, Sydney, Australia; Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia
| | - Christopher Semsarian
- Agnes Ginges Centre for Molecular Cardiology Centenary Institute, The University of Sydney, Sydney, Australia; Faculty of Medicine and Heath, The University of Sydney, Sydney, Australia; Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia.
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Gupte TM, Haque F, Gangadharan B, Sunitha MS, Mukherjee S, Anandhan S, Rani DS, Mukundan N, Jambekar A, Thangaraj K, Sowdhamini R, Sommese RF, Nag S, Spudich JA, Mercer JA. Mechanistic heterogeneity in contractile properties of α-tropomyosin (TPM1) mutants associated with inherited cardiomyopathies. J Biol Chem 2014; 290:7003-15. [PMID: 25548289 DOI: 10.1074/jbc.m114.596676] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The most frequent known causes of primary cardiomyopathies are mutations in the genes encoding sarcomeric proteins. Among those are 30 single-residue mutations in TPM1, the gene encoding α-tropomyosin. We examined seven mutant tropomyosins, E62Q, D84N, I172T, L185R, S215L, D230N, and M281T, that were chosen based on their clinical severity and locations along the molecule. The goal of our study was to determine how the biochemical characteristics of each of these mutant proteins are altered, which in turn could provide a structural rationale for treatment of the cardiomyopathies they produce. Measurements of Ca(2+) sensitivity of human β-cardiac myosin ATPase activity are consistent with the hypothesis that hypertrophic cardiomyopathies are hypersensitive to Ca(2+) activation, and dilated cardiomyopathies are hyposensitive. We also report correlations between ATPase activity at maximum Ca(2+) concentrations and conformational changes in TnC measured using a fluorescent probe, which provide evidence that different substitutions perturb the structure of the regulatory complex in different ways. Moreover, we observed changes in protein stability and protein-protein interactions in these mutants. Our results suggest multiple mechanistic pathways to hypertrophic and dilated cardiomyopathies. Finally, we examined a computationally designed mutant, E181K, that is hypersensitive, confirming predictions derived from in silico structural analysis.
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Affiliation(s)
- Tejas M Gupte
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Farah Haque
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Binnu Gangadharan
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the Manipal University, Madhav Nagar, Manipal 576104, India
| | - Margaret S Sunitha
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Souhrid Mukherjee
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Swetha Anandhan
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Deepa Selvi Rani
- the Council for Scientific and Industrial Research-Centre for Cellular and Molecular Biology, Hyderabad 500007, India
| | - Namita Mukundan
- the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Amruta Jambekar
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Kumarasamy Thangaraj
- the Council for Scientific and Industrial Research-Centre for Cellular and Molecular Biology, Hyderabad 500007, India
| | - Ramanathan Sowdhamini
- the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Ruth F Sommese
- the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - Suman Nag
- the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - James A Spudich
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and
| | - John A Mercer
- From the Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India, the McLaughlin Research Institute, Great Falls, Montana 59405
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Chang AN, Greenfield NJ, Singh A, Potter JD, Pinto JR. Structural and protein interaction effects of hypertrophic and dilated cardiomyopathic mutations in alpha-tropomyosin. Front Physiol 2014; 5:460. [PMID: 25520664 PMCID: PMC4251307 DOI: 10.3389/fphys.2014.00460] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Accepted: 11/10/2014] [Indexed: 12/16/2022] Open
Abstract
The potential alterations to structure and associations with thin filament proteins caused by the dilated cardiomyopathy (DCM) associated tropomyosin (Tm) mutants E40K and E54K, and the hypertrophic cardiomyopathy (HCM) associated Tm mutants E62Q and L185R, were investigated. In order to ascertain what the cause of the known functional effects may be, structural and protein-protein interaction studies were conducted utilizing actomyosin ATPase activity measurements and spectroscopy. In actomyosin ATPase measurements, both HCM mutants and the DCM mutant E54K caused increases in Ca2+-induced maximal ATPase activities, while E40K caused a decrease. Investigation of Tm's ability to inhibit actomyosin ATPase in the absence of troponin showed that HCM-associated mutant Tms did not inhibit as well as wildtype, whereas the DCM associated mutant E40K inhibited better. E54K did not inhibit the actomyosin ATPase activity at any concentration of Tm tested. Thermal denaturation studies by circular dichroism and molecular modeling of the mutations in Tm showed that in general, the DCM mutants caused localized destabilization of the Tm dimers, while the HCM mutants resulted in increased stability. These findings demonstrate that the structural alterations in Tm observed here may affect the regulatory function of Tm on actin, thereby directly altering the ATPase rates of myosin.
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Affiliation(s)
- Audrey N Chang
- Department of Molecular and Cellular Pharmacology, Leonard Miller School of Medicine, University of Miami Miami, FL, USA
| | - Norma J Greenfield
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University New Jersey, NJ, USA
| | - Abhishek Singh
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University New Jersey, NJ, USA ; Department of Cardiology, UCSF Medical Center, University of California, San Francisco San Francisco, CA, USA
| | - James D Potter
- Department of Molecular and Cellular Pharmacology, Leonard Miller School of Medicine, University of Miami Miami, FL, USA
| | - Jose R Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine Tallahassee, FL, USA
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Abstract
The heritable cardiomyopathies are relatively common conditions that can lead to heart failure and sudden cardiac death. Family history collection, genetic testing and genetic counseling are recommended for these patients and families in multiple practice guidelines and consensus statements. Research discoveries and rapidly dropping costs of DNA sequencing technologies have resulted in the availability of multiple cardiomyopathy genetic testing panels. Genetic testing not only helps in determining the underlying etiology of idiopathic and familial cardiomyopathies, but is also a powerful tool in the determination of which relatives are at-risk and which are not. Both pre- and post-test genetic counseling is an imperative component of genetic testing, as there are many benefits and limitations of genetic testing that need discussed with each patient undergoing this process.
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Affiliation(s)
- Amy Curry Sturm
- Division of Human Genetics, Internal Medicine, Wexner Medical Center at The Ohio State University, 2001 Polaris Parkway, Columbus, OH 43240, USA.
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