TY - JOUR A1 - Kolokotronis, Konstantinos A1 - Pluta, Natalie A1 - Klopocki, Eva A1 - Kunstmann, Erdmute A1 - Messroghli, Daniel A1 - Maack, Christoph A1 - Tejman-Yarden, Shai A1 - Arad, Michael A1 - Rost, Simone A1 - Gerull, Brenda T1 - New Insights on Genetic Diagnostics in Cardiomyopathy and Arrhythmia Patients Gained by Stepwise Exome Data Analysis JF - Journal of Clinical Medicine N2 - Inherited cardiomyopathies are characterized by clinical and genetic heterogeneity that challenge genetic diagnostics. In this study, we examined the diagnostic benefit of exome data compared to targeted gene panel analyses, and we propose new candidate genes. We performed exome sequencing in a cohort of 61 consecutive patients with a diagnosis of cardiomyopathy or primary arrhythmia, and we analyzed the data following a stepwise approach. Overall, in 64% of patients, a variant of interest (VOI) was detected. The detection rate in the main sub-cohort consisting of patients with dilated cardiomyopathy (DCM) was much higher than previously reported (25/36; 69%). The majority of VOIs were found in disease-specific panels, while a further analysis of an extended panel and exome data led to an additional diagnostic yield of 13% and 5%, respectively. Exome data analysis also detected variants in candidate genes whose functional profile suggested a probable pathogenetic role, the strongest candidate being a truncating variant in STK38. In conclusion, although the diagnostic yield of gene panels is acceptable for routine diagnostics, the genetic heterogeneity of cardiomyopathies and the presence of still-unknown causes favor exome sequencing, which enables the detection of interesting phenotype–genotype correlations, as well as the identification of novel candidate genes. KW - cardiomyopathy KW - cardiogenetics KW - whole exome sequencing KW - targeted gene panel KW - candidate genes Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-236094 VL - 9 IS - 7 ER - TY - JOUR A1 - Kühnisch, Jirko A1 - Herbst, Christopher A1 - Al‐Wakeel‐Marquard, Nadya A1 - Dartsch, Josephine A1 - Holtgrewe, Manuel A1 - Baban, Anwar A1 - Mearini, Giulia A1 - Hardt, Juliane A1 - Kolokotronis, Konstantinos A1 - Gerull, Brenda A1 - Carrier, Lucie A1 - Beule, Dieter A1 - Schubert, Stephan A1 - Messroghli, Daniel A1 - Degener, Franziska A1 - Berger, Felix A1 - Klaassen, Sabine T1 - Targeted panel sequencing in pediatric primary cardiomyopathy supports a critical role of TNNI3 JF - Clinical Genetics N2 - The underlying genetic mechanisms and early pathological events of children with primary cardiomyopathy (CMP) are insufficiently characterized. In this study, we aimed to characterize the mutational spectrum of primary CMP in a large cohort of patients ≤18 years referred to a tertiary center. Eighty unrelated index patients with pediatric primary CMP underwent genetic testing with a panel‐based next‐generation sequencing approach of 89 genes. At least one pathogenic or probably pathogenic variant was identified in 30/80 (38%) index patients. In all CMP subgroups, patients carried most frequently variants of interest in sarcomere genes suggesting them as a major contributor in pediatric primary CMP. In MYH7, MYBPC3, and TNNI3, we identified 18 pathogenic/probably pathogenic variants (MYH7 n = 7, MYBPC3 n = 6, TNNI3 n = 5, including one homozygous (TNNI3 c.24+2T>A) truncating variant. Protein and transcript level analysis on heart biopsies from individuals with homozygous mutation of TNNI3 revealed that the TNNI3 protein is absent and associated with upregulation of the fetal isoform TNNI1. The present study further supports the clinical importance of sarcomeric mutation—not only in adult—but also in pediatric primary CMP. TNNI3 is the third most important disease gene in this cohort and complete loss of TNNI3 leads to severe pediatric CMP. KW - cardiomyopathy KW - genetics KW - pediatrics KW - sarcomere KW - TNNI3 Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-213958 VL - 96 IS - 6 SP - 549 EP - 559 ER - TY - JOUR A1 - Gerull, Brenda A1 - Brodehl, Andreas T1 - Genetic Animal Models for Arrhythmogenic Cardiomyopathy JF - Frontiers in Physiology N2 - Arrhythmogenic cardiomyopathy has been clinically defined since the 1980s and causes right or biventricular cardiomyopathy associated with ventricular arrhythmia. Although it is a rare cardiac disease, it is responsible for a significant proportion of sudden cardiac deaths, especially in athletes. The majority of patients with arrhythmogenic cardiomyopathy carry one or more genetic variants in desmosomal genes. In the 1990s, several knockout mouse models of genes encoding for desmosomal proteins involved in cell–cell adhesion revealed for the first time embryonic lethality due to cardiac defects. Influenced by these initial discoveries in mice, arrhythmogenic cardiomyopathy received an increasing interest in human cardiovascular genetics, leading to the discovery of mutations initially in desmosomal genes and later on in more than 25 different genes. Of note, even in the clinic, routine genetic diagnostics are important for risk prediction of patients and their relatives with arrhythmogenic cardiomyopathy. Based on improvements in genetic animal engineering, different transgenic, knock-in, or cardiac-specific knockout animal models for desmosomal and nondesmosomal proteins have been generated, leading to important discoveries in this field. Here, we present an overview about the existing animal models of arrhythmogenic cardiomyopathy with a focus on the underlying pathomechanism and its importance for understanding of this disease. Prospectively, novel mechanistic insights gained from the whole animal, organ, tissue, cellular, and molecular levels will lead to the development of efficient personalized therapies for treatment of arrhythmogenic cardiomyopathy. KW - arrhythmogenic cardiomyopathy KW - desmosomes KW - animal models of human disease KW - sudden death KW - genetics KW - mouse KW - zebrafish Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-206903 SN - 1664-042X VL - 11 IS - 264 ER - TY - JOUR A1 - Seidlmayer, Lea K. A1 - Mages, Christine A1 - Berbner, Annette A1 - Eder-Negrin, Petra A1 - Arias-Loza, Paula Anahi A1 - Kaspar, Mathias A1 - Song, Moshi A1 - Dorn, Gerald W. A1 - Kohlhaas, Michael A1 - Frantz, Stefan A1 - Maack, Christoph A1 - Gerull, Brenda A1 - Dedkova, Elena N. T1 - Mitofusin 2 is essential for IP3-mediated SR/Mitochondria metabolic feedback in ventricular myocytes JF - Frontiers in Physiology N2 - Aim: Endothelin-1 (ET-1) and angiotensin II (Ang II) are multifunctional peptide hormones that regulate the function of the cardiovascular and renal systems. Both hormones increase the intracellular production of inositol-1,4,5-trisphosphate (IP\(_3\)) by activating their membrane-bound receptors. We have previously demonstrated that IP\(_3\)-mediated sarcoplasmic reticulum (SR) Ca\(^{2+}\) release results in mitochondrial Ca\(^{2+}\) uptake and activation of ATP production. In this study, we tested the hypothesis that intact SR/mitochondria microdomains are required for metabolic IP\(_3\)-mediated SR/mitochondrial feedback in ventricular myocytes. Methods: As a model for disrupted mitochondrial/SR microdomains, cardio-specific tamoxifen-inducible mitofusin 2 (Mfn2) knock out (KO) mice were used. Mitochondrial Ca\(^{2+}\) uptake, membrane potential, redox state, and ATP generation were monitored in freshly isolated ventricular myocytes from Mfn2 KO mice and their control wild-type (WT) littermates. Results: Stimulation of ET-1 receptors in healthy control myocytes increases mitochondrial Ca\(^{2+}\) uptake, maintains mitochondrial membrane potential and redox balance leading to the enhanced ATP generation. Mitochondrial Ca\(^{2+}\) uptake upon ET-1 stimulation was significantly higher in interfibrillar (IFM) and perinuclear (PNM) mitochondria compared to subsarcolemmal mitochondria (SSM) in WT myocytes. Mfn2 KO completely abolished mitochondrial Ca\(^{2+}\) uptake in IFM and PNM mitochondria but not in SSM. However, mitochondrial Ca2+ uptake induced by beta-adrenergic receptors activation with isoproterenol (ISO) was highest in SSM, intermediate in IFM, and smallest in PNM regions. Furthermore, Mfn2 KO did not affect ISO-induced mitochondrial Ca\(^{2+}\) uptake in SSM and IFM mitochondria; however, enhanced mitochondrial Ca\(^{2+}\) uptake in PNM. In contrast to ET-1, ISO induced a decrease in ATP levels in WT myocytes. Mfn2 KO abolished ATP generation upon ET-1 stimulation but increased ATP levels upon ISO application with highest levels observed in PNM regions. Conclusion: When the physical link between SR and mitochondria by Mfn2 was disrupted, the SR/mitochondrial metabolic feedback mechanism was impaired resulting in the inability of the IP\(_3\)-mediated SR Ca\(^{2+}\) release to induce ATP production in ventricular myocytes from Mfn2 KO mice. Furthermore, we revealed the difference in Mfn2-mediated SR-mitochondrial communication depending on mitochondrial location and type of communication (IP\(_3\)R-mRyR1 vs. ryanodine receptor type 2-mitochondrial calcium uniporter). KW - mitofusin 2 KW - IP3 KW - SR/mitochondria metabolic feedback KW - mitochondrial mRyR1 KW - ATP generation KW - endothelin-1 KW - Mfn2 KO mice Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-199141 SN - 1664-042X VL - 10 IS - 733 ER - TY - JOUR A1 - Brodehl, Andreas A1 - Belke, Darrell D. A1 - Garnett, Lauren A1 - Martens, Kristina A1 - Abdelfatah, Nelly A1 - Rodriguez, Marcela A1 - Diao, Catherine A1 - Chen, Yong-Xiang A1 - Gordon, Paul M. K. A1 - Nygren, Anders A1 - Gerull, Brenda T1 - Transgenic mice overexpressing desmocollin-2 (DSC2) develop cardiomyopathy associated with myocardial inflammation and fibrotic remodeling JF - PLoS ONE N2 - Background Arrhythmogenic cardiomyopathy is an inherited heart muscle disorder leading to ventricular arrhythmias and heart failure, mainly as a result of mutations in cardiac desmosomal genes. Desmosomes are cell-cell junctions mediating adhesion of cardiomyocytes; however, the molecular and cellular mechanisms underlying the disease remain widely unknown. Desmocollin-2 is a desmosomal cadherin serving as an anchor molecule required to reconstitute homeostatic intercellular adhesion with desmoglein-2. Cardiac specific lack of desmoglein-2 leads to severe cardiomyopathy, whereas overexpression does not. In contrast, the corresponding data for desmocollin-2 are incomplete, in particular from the view of protein overexpression. Therefore, we developed a mouse model overexpressing desmocollin-2 to determine its potential contribution to cardiomyopathy and intercellular adhesion pathology. Methods and results We generated transgenic mice overexpressing DSC2 in cardiac myocytes. Transgenic mice developed a severe cardiac dysfunction over 5 to 13 weeks as indicated by 2D-echocardiography measurements. Corresponding histology and immunohistochemistry demonstrated fibrosis, necrosis and calcification which were mainly localized in patches near the epi- and endocardium of both ventricles. Expressions of endogenous desmosomal proteins were markedly reduced in fibrotic areas but appear to be unchanged in non-fibrotic areas. Furthermore, gene expression data indicate an early up-regulation of inflammatory and fibrotic remodeling pathways between 2 to 3.5 weeks of age. Conclusion Cardiac specific overexpression of desmocollin-2 induces necrosis, acute inflammation and patchy cardiac fibrotic remodeling leading to fulminant biventricular cardiomyopathy. KW - heart KW - mouse models KW - gene expression KW - fibrosis KW - inflammation KW - gene expression KW - genetically modified animals KW - cardiomyopathies KW - hyperexpression techniques Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171084 VL - 12 IS - 3 ER -