Desmosomal protein degradation as underlying causes of arrhythmogenic cardiomyopathy
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ABSTRACT: Arrhythmogenic cardiomyopathy (ACM) is an inherited progressive cardiomyopathy. The pathophysiological events are well understood, yet the underlying molecular mechanisms remain undefined. Here we use patient originated hiPSC-derived cardiomyocytes bearing a pathogenic PKP2 mutation (PKP2 c.2013delC/WT), a corresponding knock-in mouse model carrying the equivalent murine mutation (Pkp2 c.1755delA/WT), and human explanted ACM hearts, to identify disease driving mechanisms. Pkp2 c.1755delA/WT mice over time displayed signs of ACM as observed by cardiac dysfunction and pathological remodeling. At a molecular level these mice showed a reduction in desmosomal and adherens junction proteins as well as disarray of the intercalated discs in areas of active fibrotic remodeling. These findings were validated in the mutant hiPSC-derived cardiomyocytes as well as human explanted ACM hearts, indicating both the conservation and relevance of protein degradation in the pathogenesis of the disease. Led by proteomics data, we demonstrated that the ubiquitin-proteasome system was responsible for the observed desmosomal protein degradation. These findings show the importance of appropriate disease modeling and provide means for therapeutic intervention for the prevention of ACM disease progression.
Project description:Arrhythmogenic cardiomyopathy (ACM) is an inherited progressive cardiomyopathy. The pathophysiological events are well understood, yet the underlying molecular mechanisms remain undefined. Here, we created a novel research platform comprising of patient originated hiPSC-derived cardiomyocytes bearing a pathological PKP2 mutation (PKP2 c.2013delC/WT), a novel knock-in murine model carrying the equivalent mutation (Pkp2 c.1755delA/WT), and human explanted ACM hearts, to identify disease driving mechanisms. Pkp2 c.1755delA/WT mice displayed reduced desmosomal and adherens junctions protein levels and protein disarray of the intercalated discs in areas of active fibrotic remodeling. These findings were validated in hiPSC-derived cardiomyocytes and human explanted ACM hearts. Led by proteomics data, we demonstrated that the ubiquitin-proteasome system was responsible for the observed desmosomal protein degradation. The research platform presented here provides a strong scientific basis to identify bona fide pathological processes and will aid in the development of potential therapies for the prevention of ACM disease progression.
Project description:Arrhythmogenic cardiomyopathy (ACM) is an inherited progressive cardiomyopathy. The pathophysiological events are well understood, yet the underlying molecular mechanisms remain undefined. Here we use patient originated hiPSC-derived cardiomyocytes bearing a pathogenic PKP2 mutation (PKP2 c.2013delC/WT), a corresponding knock-in mouse model carrying the equivalent murine mutation (Pkp2 c.1755delA/WT), and human explanted ACM hearts, to identify disease driving mechanisms. Pkp2 c.1755delA/WT mice over time displayed signs of ACM as observed by cardiac dysfunction and pathological remodeling. At a molecular level these mice showed a reduction in desmosomal and adherens junction proteins as well as disarray of the intercalated discs in areas of active fibrotic remodeling. These findings were validated in the mutant hiPSC-derived cardiomyocytes as well as human explanted ACM hearts, indicating both the conservation and relevance of protein degradation in the pathogenesis of the disease. Led by proteomics data, we demonstrated that the ubiquitin-proteasome system was responsible for the observed desmosomal protein degradation. These findings show the importance of appropriate disease modeling and provide means for therapeutic intervention for the prevention of ACM disease progression.
Project description:Arrhythmogenic cardiomyopathy (ACM) is frequently attributed to desmosomal mutations, such as those in the desmoplakin (DSP) gene. Patients with DSP- cardiomyopathy are predisposed to myocardial degeneration and arrhythmias. Despite advancements, the underlying molecular mechanisms remain incompletely understood, thus limiting therapeutic options. Here, we employed spatial transcriptomics on an explanted heart from a patient with a pathogenic DSP variant. Our transcriptional analysis revealed endothelial PAS domain-containing protein 1 (EPAS1) as a potential regulator of mitochondrial homeostasis in stressed cardiomyocytes. Elevated EPAS1 levels were associated with mitochondrial dysfunction and hypoxic stress in both human-relevant in vitro ACM models and additional explanted hearts with genetic cardiomyopathy. Collectively, cardiomyocytes bearing pathogenic DSP variants exhibit mitochondrial dysfunction, increased apoptosis, and impaired contractility, which are linked to the increased EPAS1 levels. These findings implicate EPAS1 as a key regulator of myocardial degeneration in DSP-cardiomyopathy, which expand to other forms of ACM.
Project description:Arrhythmogenic cardiomyopathy (ACM) is frequently attributed to desmosomal mutations, such as those in the desmoplakin (DSP) gene. Patients with DSP- cardiomyopathy are predisposed to myocardial degeneration and arrhythmias. Despite advancements, the underlying molecular mechanisms remain incompletely understood, thus limiting therapeutic options. Here, we employed spatial transcriptomics on an explanted heart from a patient with a pathogenic DSP variant. Our transcriptional analysis revealed endothelial PAS domain-containing protein 1 (EPAS1) as a potential regulator of mitochondrial homeostasis in stressed cardiomyocytes. Elevated EPAS1 levels were associated with mitochondrial dysfunction and hypoxic stress in both human-relevant in vitro ACM models and additional explanted hearts with genetic cardiomyopathy. Collectively, cardiomyocytes bearing pathogenic DSP variants exhibit mitochondrial dysfunction, increased apoptosis, and impaired contractility, which are linked to the increased EPAS1 levels. These findings implicate EPAS1 as a key regulator of myocardial degeneration in DSP-cardiomyopathy, which expand to other forms of ACM.
Project description:Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) are commonly used to model arrhythmogenic cardiomyopathy (ACM), a heritable cardiac disease characterized by severe ventricular arrhythmias, fibrofatty myocardial replacement and progressive ventricular dysfunction. Although ACM is inherited as an autosomal dominant disease, incomplete penetrance and variable expressivity are extremely common, resulting in different clinical manifestations. Here, we propose hiPSC-CMs as a powerful in vitro model to study incomplete penetrance in ACM. Six hiPSC lines were generated from blood samples of three ACM patients carrying a heterozygous deletion of exon 4 in the PKP2 gene, two asymptomatic (ASY) carriers of the same mutation and one healthy control (CTR), all belonging to the same family. Whole exome sequencing was performed in all family members and hiPSC-CMs were examined by ddPCR, western blot, Wes™ immunoassay system, patch clamp, immunofluorescence and RNASeq. Our results show molecular and functional differences between ACM and ASY hiPSC_x0002_CMs, including a higher amount of mutated PKP2 mRNA, a lower expression of the connexin-43 protein, a lower overall density of sodium current, a higher intracellular lipid accumulation and sarcomere disorganization in ACM compared to ASY hiPSC_x0002_CMs. Differentially expressed genes were also found, supporting a predisposition for a fatty phenotype in ACM hiPSC-CMs. These data indicate that hiPSC-CMs are a suitable model to study incomplete penetrance in ACM.
Project description:Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a familial cardiac disease associated with ventricular arrhythmias and an increased risk of sudden cardiac death. Currently, there are no approved treatments that address the underlying genetic cause of this disease, representing a significant unmet need. Mutations in Plakophilin-2 (PKP2), encoding a desmosomal protein, account for approximately 40% of ARVC cases and result in reduced gene expression. Methods: Our goal is to examine the feasibility and the efficacy of adeno-associated virus 9 (AAV9)-mediated restoration of PKP2 expression in a cardiac specific knock-out mouse model of Pkp2. Results: We show that a single dose of AAV9:PKP2 gene delivery prevents disease development before the onset of cardiomyopathy and attenuates disease progression after overt cardiomyopathy. Restoration of PKP2 expression leads to a significant extension of lifespan by restoring cellular structures of desmosomes and gap junctions, preventing or halting decline in left ventricular ejection fraction, preventing or reversing dilation of the right ventricle, ameliorating ventricular arrhythmia event frequency and severity, and preventing adverse fibrotic remodeling. RNA sequencing analyses show that restoration of PKP2 expression leads to highly coordinated and durable correction of PKP2-associated transcriptional networks beyond desmosomes, revealing a broad spectrum of biological perturbances behind ARVC disease etiology. Conclusions: We identify fundamental mechanisms of PKP2-associated ARVC beyond disruption of desmosome function. The observed PKP2 dose-function relationship indicates that cardiac-selective AAV9:PKP2 gene therapy may be a promising therapeutic approach to treat ARVC patients with PKP2 mutations.
Project description:Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a familial cardiac disease associated with ventricular arrhythmias and an increased risk of sudden cardiac death. Currently, there are no approved treatments that address the underlying genetic cause of this disease, representing a significant unmet need. Mutations in Plakophilin-2 (PKP2), encoding a desmosomal protein, account for approximately 40% of ARVC cases and result in reduced gene expression. Methods: Our goal is to examine the feasibility and the efficacy of adeno-associated virus 9 (AAV9)-mediated restoration of PKP2 expression in a cardiac specific knock-out mouse model of Pkp2. Results: We show that a single dose of AAV9:PKP2 gene delivery prevents disease development before the onset of cardiomyopathy and attenuates disease progression after overt cardiomyopathy. Restoration of PKP2 expression leads to a significant extension of lifespan by restoring cellular structures of desmosomes and gap junctions, preventing or halting decline in left ventricular ejection fraction, preventing or reversing dilation of the right ventricle, ameliorating ventricular arrhythmia event frequency and severity, and preventing adverse fibrotic remodeling. RNA sequencing analyses show that restoration of PKP2 expression leads to highly coordinated and durable correction of PKP2-associated transcriptional networks beyond desmosomes, revealing a broad spectrum of biological perturbances behind ARVC disease etiology. Conclusions: We identify fundamental mechanisms of PKP2-associated ARVC beyond disruption of desmosome function. The observed PKP2 dose-function relationship indicates that cardiac-selective AAV9:PKP2 gene therapy may be a promising therapeutic approach to treat ARVC patients with PKP2 mutations.
Project description:Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a familial cardiac disease associated with ventricular arrhythmias and an increased risk of sudden cardiac death. Currently, there are no approved treatments that address the underlying genetic cause of this disease, representing a significant unmet need. Mutations in Plakophilin-2 (PKP2), encoding a desmosomal protein, account for approximately 40% of ARVC cases and result in reduced gene expression. Methods: Our goal is to examine the feasibility and the efficacy of adeno-associated virus 9 (AAV9)-mediated restoration of PKP2 expression in a cardiac specific knock-out mouse model of Pkp2. Results: We show that a single dose of AAV9:PKP2 gene delivery prevents disease development before the onset of cardiomyopathy and attenuates disease progression after overt cardiomyopathy. Restoration of PKP2 expression leads to a significant extension of lifespan by restoring cellular structures of desmosomes and gap junctions, preventing or halting decline in left ventricular ejection fraction, preventing or reversing dilation of the right ventricle, ameliorating ventricular arrhythmia event frequency and severity, and preventing adverse fibrotic remodeling. RNA sequencing analyses show that restoration of PKP2 expression leads to highly coordinated and durable correction of PKP2-associated transcriptional networks beyond desmosomes, revealing a broad spectrum of biological perturbances behind ARVC disease etiology. Conclusions: We identify fundamental mechanisms of PKP2-associated ARVC beyond disruption of desmosome function. The observed PKP2 dose-function relationship indicates that cardiac-selective AAV9:PKP2 gene therapy may be a promising therapeutic approach to treat ARVC patients with PKP2 mutations.
Project description:Aims Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disorder that is characterized by progressive fibro-fatty replacement of the myocardium, arrhythmias, and sudden death. While myocardial degeneration and fibro-fatty replacement occurs in specific locations, the underlying molecular changes remain poorly characterized. Here we aim to delineate local changes in gene expression to help identify new genes or pathways that are relevant for specific remodelling processes occurring during ACM. Methods and Results Using Tomo-Seq, a genome-wide transcriptional profiling with high spatial resolution, we created a transmural epicardial to endocardial gene expression atlas of an explanted ACM heart to gain molecular insights into disease-driving processes. This enabled us to link gene expression profiles to the different regional remodelling responses and allowed us to identify genes that are potentially relevant for disease progression. In doing we revealed BTB (broad-complex, tramtrack, bric-à-brac) domain containing 11 (ZBTB11) to be specifically enriched at sites of active fibrofatty replacement of myocardium. Immunohistochemistry indicated ZBTB11 to be enriched in cardiomyocytes flanking fibrofatty areas, which could be confirmed in multiple cardiomyopathy patients. Forced overexpression of ZBTB11 in iPS-derived cardiomyocytes showed ZBTB11 to function as a potent inducer of cardiomyocyte atrophy. Conclusion By combining spatial transcriptomics with classical histological approaches we identified gene expression changes underlying local remodelling responses in ACM. In doing so we found ZBTB11 to function as a relevant driver of cardiomyocyte atrophy. These data show the power of Tomo-Seq to unveil new molecular mechanisms and indicate ZBTB11 as a potential new target for cardiomyopathy.
Project description:Transcriptomic analysis of DSG2-W2A mouse heart tissue. In DSG2-W2A mice, adhesion of the desmosomal molecule desmoglein-2 (DSG2) is abrogated via mutation of its’ major interaction mechanism (so-called "tryptophan swap" (Harrison, Brasch et al. 2016)). Adult DSG2-W2A mut/mut mice resemble the phenotype of Arrhythmogenic Cardiomyopathy (ACM or ARVC) with biventricular fibrosis, impaired systolic output function and arrhythmia. This phenotype was present in mutant mice analysed at the age of 9 weeks compared to 5-days old hearts, which showed no morphological alterations.