Identification of sarcomeric variants in probands with a clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC)

Pathophysiology of dilated cardiomyopathy: from mechanisms to precision medicine

Dilated cardiomyopathy (DCM) is a complex disease with multiple causes and various pathogenic mechanisms. Despite improvements in the prognosis of patients with DCM in the past decade, this condition remains a leading cause of heart failure and premature death. Conventional treatment for DCM is based on the foundational therapies for heart failure with reduced ejection fraction. However, increasingly, attention is being directed towards individualized treatments and precision medicine. The ability to confirm genetic causality is gradually being complemented by an increased understanding of genotype-phenotype correlations. Non-genetic factors also influence the onset of DCM, and growing evidence links genetic background with concomitant non-genetic triggers or precipitating factors, increasing the extreme complexity of the pathophysiology of DCM. This Review covers the spectrum of pathophysiological mechanisms in DCM, from monogenic causes to the coexistence of genetic abnormalities and triggering environmental factors (the 'two-hit' hypothesis). The roles of common genetic variants in the general population and of gene modifiers in disease onset and progression are also discussed. Finally, areas for future research are highlighted, particularly novel therapies, such as small molecules, RNA and gene therapy, and measures for the prevention of arrhythmic death.

A Heterozygous Phospholamban Variant (p.R14del) Leads to Left Ventricular Involvement and Heart Failure Phenotypes in Arrhythmogenic Right Ventricular Cardiomyopathy

This study aimed to determine the prevalence and clinical features of Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) caused by pathogenic mutations in the Phospholamban (PLN) gene. The study included 170 patients who had a confirmed diagnosis of ARVC and underwent PLN genetic screening using next-generation sequencing. The findings of this study provide valuable insights into the association between PLN mutations and ARVC, which can aid in the development of more effective diagnostic and treatment strategies for ARVC patients. Out of the patients evaluated, six had a rare pathogenic mutation in PLN with the same p.R14del variant. Family screening revealed that heterozygous carriers of p.R14del exhibited a definite ARVC phenotype. In clinical studies, individuals with the p.R14del mutation experienced a similar rate of malignant arrhythmia events as those with classic desmosome mutations. After adjusting for covariates, individuals with PLN mutations had a two point one seven times greater likelihood of experiencing transplant-related risks compared to those who did not possess PLN mutations (95% CI 1.08-6.82, p = 0.035). The accumulation of left ventricular fat and fibers is a pathological marker for ARVC patients with p.R14del mutations. In a cohort of 170 Chinese ARVC patients, three point five percent of probands had the PLN pathogenic variant (p.R14del) and all were female. Our data shows that PLN-related ARVC patients are at high risk for ventricular arrhythmias and heart failure, which requires clinical differentiation from classic ARVC. Furthermore, carrying the p.R14del mutation can be an independent prognostic risk factor in ARVC patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43657-023-00126-w.

Application of next generation sequencing in cardiology: current and future precision medicine implications

Inherited cardiovascular diseases are highly heterogeneous conditions with multiple genetic loci involved. The application of advanced molecular tools, such as Next Generation Sequencing, has facilitated the genetic analysis of these disorders. Accurate analysis and variant identification are required to maximize the quality of the sequencing data. Therefore, the application of NGS for clinical purposes should be limited to laboratories with a high level of technological expertise and resources. In addition, appropriate gene selection and variant interpretation can result in the highest possible diagnostic yield. Implementation of genetics in cardiology is imperative for the accurate diagnosis, prognosis and management of several inherited disorders and could eventually lead to the realization of precision medicine in this field. However, genetic testing should also be accompanied by an appropriate genetic counseling procedure that clarifies the significance of the genetic analysis results for the proband and his family. In this regard, a multidisciplinary collaboration among physicians, geneticists, and bioinformaticians is imperative. In the present review, we address the current state of knowledge regarding genetic analysis strategies employed in the field of cardiogenetics. Variant interpretation and reporting guidelines are explored. Additionally, gene selection procedures are accessed, with a particular emphasis on information concerning gene-disease associations collected from international alliances such as the Gene Curation Coalition (GenCC). In this context, a novel approach to gene categorization is proposed. Moreover, a sub-analysis is conducted on the 1,502,769 variation records with submitted interpretations in the Clinical Variation (ClinVar) database, focusing on cardiology-related genes. Finally, the most recent information on genetic analysis's clinical utility is reviewed.

Tissue Doppler echocardiography and outcome in arrhythmogenic right ventricular cardiomyopathy

AIMS

This study aimed at investigating whether tissue Doppler imaging (TDI) is associated with adverse events in arrhythmogenic right ventricular cardiomyopathy (ARVC).

METHODS AND RESULTS

Transthoracic echocardiography was performed in 72 patients with definite (n = 63) or borderline (n = 9) ARVC diagnosed according to the 2010 Task Force Criteria and included in the prospective Zurich ARVC registry. Myocardial peak systolic tissue velocity (S') was measured by TDI at lateral tricuspid (tricuspid S'), medial mitral (septal S'), and lateral mitral annulus (lateral S'). Association of echocardiographic parameters with outcome was assessed by univariable Cox regression. During a median follow-up of 4.9 ± 2.6 years, 6 (8.3%) patients died of cardiovascular cause or received heart transplantation and 21 (29.2%) patients developed sustained ventricular arrhythmia. Tricuspid, septal, and lateral S' were lower in patients who died (p = 0.001; p < 0.001; p = 0.008; respectively), while tricuspid and septal S' were lower in those with ventricular arrhythmia (p = 0.001; p = 0.008; respectively). There was a significant association of tricuspid, septal, and lateral S' with mortality (HR = 1.61, p = 0.011; HR = 2.15, p = 0.007; HR = 1.67, p = 0.017; respectively), while tricuspid and septal S' were associated with ventricular arrhythmia (HR = 1.20, p = 0.022; HR = 1.37, p = 0.004; respectively). Kaplan-Meier analyses demonstrated a higher freedom from mortality with tricuspid S' >8 cm/s (p = 0.001) and from ventricular arrhythmia with S' >10.5 cm/s (p = 0.021).

CONCLUSIONS

This study demonstrates that TDI provides information on the ARVC phenotype, is associated with adverse events in ARVC patients, and differentiates between patients with and without adverse events.

TMEM43 promotes pancreatic cancer progression by stabilizing PRPF3 and regulating RAP2B/ERK axis

BACKGROUND

Transmembrane protein 43 (TMEM43), a member of the transmembrane protein subfamily, plays a critical role in the initiation and development of cancers. However, little is known concerning the biological function and molecular mechanisms of TMEM43 in pancreatic cancer.

METHODS

In this study, TMEM43 expression levels were analyzed in pancreatic cancer samples compared with control samples. The relationship of TMEM43 expression and disease-free survival (DFS) and overall survival (OS) were assessed in pancreatic cancer patients. In vitro and in vivo assays were performed to explore the function and role of TMEM43 in pancreatic cancer. Coimmunoprecipitation (co-IP) followed by protein mass spectrometry was applied to analyze the molecular mechanisms of TMEM43 in pancreatic cancer.

RESULTS

We demonstrated that TMEM43 expression level is elevated in pancreatic cancer samples compared with control group, and is correlated with poor DFS and OS in pancreatic cancer patients. Knockdown of TMEM43 inhibited pancreatic cancer progression in vitro, decreased the percentage of S phase, and inhibited the tumorigenicity of pancreatic cancer in vivo. Moreover, we demonstrated that TMEM43 promoted pancreatic cancer progression by stabilizing PRPF3 and regulating the RAP2B/ERK axis.

CONCLUSIONS

The present study suggests that TMEM43 contributes to pancreatic cancer progression through the PRPF3/RAP2B/ERK axis, and might be a novel therapeutic target for pancreatic cancer.

Variants in MHY7 Gene Cause Arrhythmogenic Cardiomyopathy

BACKGROUND

Arrhythmogenic Cardiomyopathy (ACM) is a disease of the cardiac muscle, characterized by frequent ventricular arrhythmias and functional/ structural abnormalities, mainly of the right ventricle. To date, 20 different genes have been associated with ACM and the majority of them encode for desmosomal proteins. In this study, we describe the characterization of two novel variants in MHY7 gene, segregating in two ACM families. MYH7 encodes for myosin heavy chain β (MHC-β) isoform, involved in cardiac muscle contractility.

METHOD AND RESULTS

In family A, the autopsy revealed ACM with biventricular involvement in both the proband and his father. In family B, the proband had been diagnosed as affected by ACM and implanted with implantable cardioverter defibrillator (ICD), due to ECG evidence of monomorphic ventricular tachycardia after syncope. After clinical evaluation, a molecular diagnosis was performed using a NGS custom panel. The two novel variants identified predicted damaging, located in a highly conserved domain: c. 2630T>C is not described while c.2609G>A has a frequency of 0.00000398. In silico analyses evaluated the docking characteristics between proteins using the Haddock2.2 webserver.

CONCLUSIONS

Our results reveal two variants in sarcomeric genes to be the molecular cause of ACM, further increasing the genetic heterogeneity of the disease; in fact, sarcomeric variants are usually associated with HCM phenotype. Studies on the role of sarcomere genes in the pathogenesis of ACM are surely recommended in those ACM patients negative for desmosomal mutation screening.

International Evidence Based Reappraisal of Genes Associated With Arrhythmogenic Right Ventricular Cardiomyopathy Using the Clinical Genome Resource Framework

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited disease characterized by ventricular arrhythmias and progressive ventricular dysfunction. Genetic testing is recommended, and a pathogenic variant in an ARVC-associated gene is a major criterion for diagnosis according to the 2010 Task Force Criteria. As incorrect attribution of a gene to ARVC can contribute to misdiagnosis, we assembled an international multidisciplinary ARVC Clinical Genome Resource Gene Curation Expert Panel to reappraise all reported ARVC genes.

METHODS

Following a comprehensive literature search, six 2-member teams conducted blinded independent curation of reported ARVC genes using the semiquantitative Clinical Genome Resource framework.

RESULTS

Of 26 reported ARVC genes, only 6 (PKP2, DSP, DSG2, DSC2, JUP, and TMEM43) had strong evidence and were classified as definitive for ARVC causation. There was moderate evidence for 2 genes, DES and PLN. The remaining 18 genes had limited or no evidence. RYR2 was refuted as an ARVC gene since clinical data and model systems exhibited a catecholaminergic polymorphic ventricular tachycardia phenotype. In ClinVar, only 5 pathogenic/likely pathogenic variants (1.1%) in limited evidence genes had been reported in ARVC cases in contrast to 450 desmosome gene variants (97.4%).

CONCLUSIONS

Using the Clinical Genome Resource approach to gene-disease curation, only 8 genes (PKP2, DSP, DSG2, DSC2, JUP, TMEM43, PLN, and DES) had definitive or moderate evidence for ARVC, and these genes accounted for nearly all pathogenic/likely pathogenic ARVC variants in ClinVar. Therefore, only pathogenic/likely pathogenic variants in these 8 genes should yield a major criterion for ARVC diagnosis. Pathogenic/likely pathogenic variants identified in other genes in a patient should prompt further phenotyping as variants in many of these genes are associated with other cardiovascular conditions.

2019 HRS expert consensus statement on evaluation, risk stratification, and management of arrhythmogenic cardiomyopathy: Executive summary

Arrhythmogenic cardiomyopathy (ACM) is an arrhythmogenic disorder of the myocardium not secondary to ischemic, hypertensive, or valvular heart disease. ACM incorporates a broad spectrum of genetic, systemic, infectious, and inflammatory disorders. This designation includes, but is not limited to, arrhythmogenic right/left ventricular cardiomyopathy, cardiac amyloidosis, sarcoidosis, Chagas disease, and left ventricular noncompaction. The ACM phenotype overlaps with other cardiomyopathies, particularly dilated cardiomyopathy with arrhythmia presentation that may be associated with ventricular dilatation and/or impaired systolic function. This expert consensus statement provides the clinician with guidance on evaluation and management of ACM and includes clinically relevant information on genetics and disease mechanisms. PICO questions were utilized to evaluate contemporary evidence and provide clinical guidance related to exercise in arrhythmogenic right ventricular cardiomyopathy. Recommendations were developed and approved by an expert writing group, after a systematic literature search with evidence tables, and discussion of their own clinical experience, to present the current knowledge in the field. Each recommendation is presented using the Class of Recommendation and Level of Evidence system formulated by the American College of Cardiology and the American Heart Association and is accompanied by references and explanatory text to provide essential context. The ongoing recognition of the genetic basis of ACM provides the opportunity to examine the diverse triggers and potential common pathway for the development of disease and arrhythmia.

The Role of MicroRNAs in Arrhythmogenic Cardiomyopathy: Biomarkers or Innocent Bystanders of Disease Progression?

Arrhythmogenic cardiomyopathy (AC) is an inherited cardiac disease characterized by a progressive fibro-fatty replacement of the working myocardium and by life-threatening arrhythmias and risk of sudden cardiac death. Pathogenic variants are identified in nearly 50% of affected patients mostly in genes encoding for desmosomal proteins. AC incomplete penetrance and phenotypic variability advocate that other factors than genetics may modulate the disease, such as microRNAs (miRNAs). MiRNAs are small noncoding RNAs with a primary role in gene expression regulation and network of cellular processes. The implication of miRNAs in AC pathogenesis and their role as biomarkers for early disease detection or differential diagnosis has been the objective of multiple studies employing diverse designs and methodologies to detect miRNAs and measure their expression levels. Here we summarize experiments, evidence, and flaws of the different studies and hitherto knowledge of the implication of miRNAs in AC pathogenesis and diagnosis.

2019 HRS expert consensus statement on evaluation, risk stratification, and management of arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is an arrhythmogenic disorder of the myocardium not secondary to ischemic, hypertensive, or valvular heart disease. ACM incorporates a broad spectrum of genetic, systemic, infectious, and inflammatory disorders. This designation includes, but is not limited to, arrhythmogenic right/left ventricular cardiomyopathy, cardiac amyloidosis, sarcoidosis, Chagas disease, and left ventricular noncompaction. The ACM phenotype overlaps with other cardiomyopathies, particularly dilated cardiomyopathy with arrhythmia presentation that may be associated with ventricular dilatation and/or impaired systolic function. This expert consensus statement provides the clinician with guidance on evaluation and management of ACM and includes clinically relevant information on genetics and disease mechanisms. PICO questions were utilized to evaluate contemporary evidence and provide clinical guidance related to exercise in arrhythmogenic right ventricular cardiomyopathy. Recommendations were developed and approved by an expert writing group, after a systematic literature search with evidence tables, and discussion of their own clinical experience, to present the current knowledge in the field. Each recommendation is presented using the Class of Recommendation and Level of Evidence system formulated by the American College of Cardiology and the American Heart Association and is accompanied by references and explanatory text to provide essential context. The ongoing recognition of the genetic basis of ACM provides the opportunity to examine the diverse triggers and potential common pathway for the development of disease and arrhythmia.

Sarcomere variants in arrhythmogenic cardiomyopathy: Pathogenic factor or bystander?

BACKGROUND

Arrhythmogenic cardiomyopathy (ACM) is an inherited heart muscle disease, which is mainly caused by desmosomal mutations. Sarcomere variants were the primary genetic basis of hypertrophic cardiomyopathy (HCM) and were recently detected in arrhythmogenic cardiomyopathy (ACM). Our aim is to seek potential pathogenic variants of sarcomere genes in our ACM cohort and describe their characteristics.

METHODS

We performed targeted sequencing of 14 sarcomere genes in 84 patients with ACM and set strict criteria to identify potential pathogenic variants. Clinical screening was performed on all available family members of the patients carrying sarcomere variants and specific variants were tested in screened family members by Sanger sequencing.

RESULTS

We identified 6 sarcomere variants in 6 (7%) patients, which were all definite ACM. Sarcomere variants were detected in NEBL, MYH7, MYH6 and TNNI3, with low prevalence in controls and predicted pathogenic in silico. Among these patients, three had previous detected PKP2 variants. Patients with sarcomere variants all experienced major arrhythmic cardiac event (MACE) with the average age of the first documented MACE being 41.2 ± 11.0 years. Pedigrees analysis showed none of the sarcomere variants carriers among the family members were affected, indicating very low penetrance.

CONCLUSIONS

We detected some sarcomere variants in our ACM cohort. Although those patients with sarcomere variants had severe arrhythmic burden, family co-segregation analysis didn't strongly support a primary role in the pathogenesis of ACM.

Arrhythmogenic Right Ventricular Cardiomyopathy: Progress Toward Personalized Management

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart disease characterized by fibrofatty replacement of the ventricular myocardium, a high risk of ventricular arrhythmias, and progressive ventricular dysfunction. The clinical course is highly variable, and optimal approaches to management remain undefined. ARVC is associated with pathogenic variants in genes encoding the cardiac desmosome. Genetic testing facilitates identification of at-risk family members, but penetrance of ARVC in pathogenic variant carriers is difficult to predict. Participation in endurance exercise is a known key risk factor. However, there remains significant uncertainty about which family member will develop disease and how best to approach longitudinal screening. Our clinically focused review describes how new insights gained from natural history studies, improved understanding of pathogenic mechanisms, and appreciation of genetic and environmental modifiers have set the stage for developing personalized approaches to managing both ARVC patients and their at-risk family members.

Distinct molecular signature of phospholamban p.Arg14del arrhythmogenic cardiomyopathy

Phospholamban (PLN) p.Arg14del cardiomyopathy is characterized by a distinct arrhythmogenic biventricular phenotype that can be predominantly left ventricular, right ventricular, or both. Our aim was to further elucidate distinct features of this cardiomyopathy with respect to the distribution of desmosomal proteins observed by immunofluorescence (IF) in comparison to desmosomal arrhythmogenic cardiomyopathy and co-existent genetic variants. We studied eight explanted heart specimens from PLN p.Arg14del mutation carriers. Macro- and microscopic examination revealed biventricular presence of fibrofatty replacement and interstitial fibrosis. Five out of 8 (63%) patients met consensus criteria for both arrhythmogenic right ventricular cardiomyopathy (ARVC) and dilated cardiomyopathy (DCM). In four cases, targeted next-generation sequencing revealed one additional pathogenic variant and six variants of unknown significance. IF showed diminished junction plakoglobin signal intensity at the intercalated disks in 4 (67%) out of 6 cases fulfilling ARVC criteria but normal intensity in both cases fulfilling only DCM criteria. Notably, the four cases with diminished junction plakoglobin were also those where an additional gene variant was detected. IF for two proteins recently investigated in desmosomal arrhythmogenic cardiomyopathy (ACM), synapse-associated protein 97 and glycogen synthase kinase-3 beta, showed a distinct distributional pattern in comparison to desmosomal ACM. In 7 (88%) out of 8 cases we observed both a strong synapse-associated protein 97 signal at the sarcomeres and no glycogen synthase kinase-3 beta translocation to the intercalated discs. Phospholamban p.Arg14del cardiomyopathy is characterized by a distinct molecular signature compared to desmosomal ACM, specifically a different desmosomal protein distribution. This study substantiates the idea that additional genetic variants play a role in the phenotypical heterogeneity.

Arrhythmogenic cardiomyopathy: what blood can reveal?

Blood, serum and plasma represent accessible sources of data about physiological and pathologic status. In arrhythmogenic cardiomyopathy (ACM), circulating nucleated cells are routinely used for detection of germinal genetic mutations. In addition, different biomarkers have been proposed for diagnostic purposes and for monitoring disease progression, including inflammatory cytokines, markers of myocardial dysfunction and damage, and microRNAs. This review summarizes the current information that can be retrieved from the blood of ACM patients and considers the future prospects. Improvements in current knowledge of circulating factors may provide noninvasive means to simplify and improve the diagnosis, prognosis prediction, and management of ACM patients.

Identification of sarcomeric variants in probands with a clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC)

Aims

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy characterized by ventricular arrhythmias and sudden death. Currently 60% of patients meeting Task Force Criteria (TFC) have an identifiable mutation in one of the desmosomal genes. As much overlap is described between other cardiomyopathies and ARVC, we examined the prevalence of rare, possibly pathogenic sarcomere variants in the ARVC population.

Methods

One hundred and thirty‐seven (137) individuals meeting 2010 TFC for a diagnosis of ARVC, negative for pathogenic desmosomal variants, TMEM43, SCN5A, and PLN were screened for variants in the sarcomere genes (ACTC1, MYBPC3, MYH7, MYL2, MYL3, TNNC1, TNNI3, TNNT2, and TPM1) through either clinical or research genetic testing.

Results

Six probands (6/137, 4%) were found to carry rare variants in the sarcomere genes. These variants have low prevalence in controls, are predicted damaging by Polyphen‐2, and some of the variants are known pathogenic hypertrophic cardiomyopathy mutations. Sarcomere variant carriers had a phenotype that did not differ significantly from desmosomal mutation carriers. As most of these probands were the only affected individuals in their families, however, segregation data are noninformative.

Conclusion

These data show variants in the sarcomere can be identified in individuals with an ARVC phenotype. Although rare and predicted damaging, proven functional and segregational evidence that these variants can cause ARVC is lacking. Therefore, caution is warranted in interpreting these variants when identified on large next‐generation sequencing panels for cardiomyopathies.