The frequency of familial dilated cardiomyopathy in a series of patients with idiopathic dilated cardiomyopathy

Genetic analysis and family screening for dilated cardiomyopathy: a retrospective analysis of the stepwise pedigree approach

AIMS

This study aimed to assess the practicality of using a stepwise pedigree-based approach to differentiate between familial and sporadic Dilated Cardiomyopathy (DCM), while also considering timing of the genetic analysis. The analysis includes an examination of the extent to which complete family investigations were conducted in real-world scenarios as well as the length of the investigation.

METHODS

The stepwise pedigree approach involved conducting a comprehensive family history spanning 3 to 4 generations, reviewing medical records of relatives, and conducting clinical screening using echocardiography and electrocardiogram on first-degree relatives. Familial DCM was diagnosed when at least 2 family members were found to have DCM, and genetic analysis was considered as an option. This study involved a manual review of all DCM investigations conducted at the Centre of Cardiovascular Genetics at Umeå University Hospital, where the stepwise pedigree approach has been employed since 2007.

RESULTS

The investigation process had a mean duration of 643 days (95% CI 560.5-724.9). Of the investigations preformed, 94 (68%) were complete, 12 (9%) were ongoing, and 33 (24%) were prematurely terminated and thus incomplete. At the conclusion of the investigations, 55 cases (43%) were classified as familial DCM, 50 (39%) as sporadic DCM, and 22 (18%) remained unassessed due to incomplete pedigrees. Among the familial cases, genetic verification was achieved in 40%.

CONCLUSION

The stepwise pedigree approach is time consuming, and the investigations are often incomplete which may suggest that a more direct approach to genetic analysis, may be warranted.

Risk Assessment and Personalized Treatment Options in Inherited Dilated Cardiomyopathies: A Narrative Review

Considering the worldwide impact of heart failure, it is crucial to develop approaches that can help us comprehend its root cause and make accurate predictions about its outcome. This is essential for lowering the suffering and death rates connected with this widespread illness. Cardiomyopathies frequently result from genetic factors, and the study of heart failure genetics is advancing quickly. Dilated cardiomyopathy (DCM) is the most prevalent kind of cardiomyopathy, encompassing both genetic and nongenetic abnormalities. It is distinguished by the enlargement of the left ventricle or both ventricles, accompanied by reduced contractility. The discovery of the molecular origins and subsequent awareness of the molecular mechanism is broadening our knowledge of DCM development. Additionally, it emphasizes the complicated nature of DCM and the necessity to formulate several different strategies to address the diverse underlying factors contributing to this disease. Genetic variants that can be transmitted from one generation to another can be a significant contributor to causing family or sporadic hereditary DCM. Genetic variants also play a significant role in determining susceptibility for acquired triggers for DCM. The genetic causes of DCM can have a large range of phenotypic expressions. It is crucial to select patients who are most probable to gain advantages from genetic testing. The purpose of this research is to emphasize the significance of identifying genetic DCM, the relationships between genotype and phenotype, risk assessment, and personalized therapy for both those affected and their relatives. This approach is expected to gain importance once treatment is guided by genotype-specific advice and disease-modifying medications.

Pediatric dilated cardiomyopathy: a review of current clinical approaches and pathogenesis

Pediatric dilated cardiomyopathy (DCM) is a rare, yet life-threatening cardiovascular condition characterized by systolic dysfunction with biventricular dilatation and reduced myocardial contractility. Therapeutic options are limited with nearly 40% of children undergoing heart transplant or death within 2 years of diagnosis. Pediatric patients are currently diagnosed based on correlating the clinical picture with echocardiographic findings. Patient age, etiology of disease, and parameters of cardiac function significantly impact prognosis. Treatments for pediatric DCM aim to ameliorate symptoms, reduce progression of disease, and prevent life-threatening arrhythmias. Many therapeutic agents with known efficacy in adults lack the same evidence in children. Unlike adult DCM, the pathogenesis of pediatric DCM is not well understood as approximately two thirds of cases are classified as idiopathic disease. Children experience unique gene expression changes and molecular pathway activation in response to DCM. Studies have pointed to a significant genetic component in pediatric DCM, with variants in genes related to sarcomere and cytoskeleton structure implicated. In this regard, pediatric DCM can be considered pediatric manifestations of inherited cardiomyopathy syndromes. Yet exciting recent studies in infantile DCM suggest that this subset has a distinct etiology involving defective postnatal cardiac maturation, such as the failure of programmed centrosome breakdown in cardiomyocytes. Improved knowledge of pathogenesis is central to developing child-specific treatment approaches. This review aims to discuss the established biological pathogenesis of pediatric DCM, current clinical guidelines, and promising therapeutic avenues, highlighting differences from adult disease. The overarching goal is to unravel the complexities surrounding this condition to facilitate the advancement of novel therapeutic interventions and improve prognosis and overall quality of life for pediatric patients affected by DCM.

Utilities and Limitations of Cardiac Magnetic Resonance Imaging in Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is one of the most common types of non-ischemic cardiomyopathy. DCM is characterized by left ventricle (LV) dilatation and systolic dysfunction without coronary artery disease or abnormal loading conditions. DCM is not a single disease entity and has a complex historical background of revisions and updates to its definition because of its diverse etiology and clinical manifestations. In cases of LV dilatation and dysfunction, conditions with phenotypic overlap should be excluded before establishing a DCM diagnosis. The differential diagnoses of DCM include ischemic cardiomyopathy, valvular heart disease, burned-out hypertrophic cardiomyopathy, arrhythmogenic cardiomyopathy, and non-compaction. Cardiac magnetic resonance (CMR) imaging is helpful for evaluating DCM because it provides precise measurements of cardiac size, function, mass, and tissue characterization. Comprehensive analyses using various sequences, including cine imaging, late gadolinium enhancement imaging, and T1 and T2 mapping, may help establish differential diagnoses, etiological work-up, disease stratification, prognostic determination, and follow-up procedures in patients with DCM phenotypes. This article aimed to review the utilities and limitations of CMR in the diagnosis and assessment of DCM.

Phenotypic variability of filamin C-related cardiomyopathy: Insights from a novel Dutch founder variant

BACKGROUND

Dilated cardiomyopathy (DCM) can be caused by truncating variants in the filamin C gene (FLNC). A new pathogenic FLNC variant, c.6864_6867dup, p.(Val2290Argfs∗23), was recently identified in Dutch patients with DCM.

OBJECTIVES

The report aimed to evaluate the phenotype of FLNC variant carriers and to determine whether this variant is a founder variant.

METHODS

Clinical and genetic data were retrospectively collected from variant carriers. Cardiovascular magnetic resonance studies were reassessed. Haplotypes were reconstructed to determine a founder effect. The geographical distribution and age of the variant were determined.

RESULTS

Thirty-three individuals (of whom 23 [70%] were female) from 9 families were identified. Sudden cardiac death was the first presentation in a carrier at the age of 28 years. The median age at diagnosis was 41 years (range 19-67 years). The phenotype was heterogeneous. DCM with left ventricular dilation and reduced ejection fraction (<45%) was present in 11 (33%) individuals, 3 (9%) of whom underwent heart transplantation. Cardiovascular magnetic resonance showed late gadolinium enhancement in 13 (65%) of the assessed individuals, primarily in a ringlike distribution. Nonsustained ventricular arrhythmias were detected in 6 (18%), and 5 (15%) individuals received an implantable cardioverter-defibrillator. A shared haplotype spanning 2.1 Mb was found in all haplotyped individuals. The variant originated between 275 and 650 years ago.

CONCLUSION

The pathogenic FLNC variant c.6864_6867dup, p.(Val2290Argfs∗23) is a founder variant originating from the south of the Netherlands. Carriers are susceptible to developing heart failure and ventricular arrhythmias. The cardiac phenotype is characterized by ringlike late gadolinium enhancement, even in individuals without significantly reduced left ventricular function.

The Role of Genetics in the Management of Heart Failure Patients

Over the last decades, the relevance of genetics in cardiovascular diseases has expanded, especially in the context of cardiomyopathies. Its relevance extends to the management of patients diagnosed with heart failure (HF), given its capacity to provide invaluable insights into the etiology of cardiomyopathies and identify individuals at a heightened risk of poor outcomes. Notably, the identification of an etiological genetic variant necessitates a comprehensive evaluation of the family lineage of the affected patients. In the future, these genetic variants hold potential as therapeutic targets with the capability to modify gene expression. In this complex setting, collaboration among cardiologists, specifically those specializing in cardiomyopathies and HF, and geneticists becomes paramount to improving individual and family health outcomes, as well as therapeutic clinical results. This review is intended to offer geneticists and cardiologists an updated perspective on the value of genetic research in HF and its implications in clinical practice.

Novel MYBPC3 Mutations in Indian Population with Cardiomyopathies

Background

Mutations in Myosin Binding Protein C (MYBPC3) are one of the most frequent causes of cardiomyopathies in the world, but not much data are available in India.

Methods

We carried out targeted direct sequencing of MYBPC3 in 115 hypertrophic (HCM) and 127 dilated (DCM) cardiomyopathies against 197 ethnically matched healthy controls from India.

Results

We detected 34 single nucleotide variations in MYBPC3, of which 19 were novel. We found a splice site mutation [(IVS6+2T) T>G] and 16 missense mutations in Indian cardiomyopathies [5 in HCM; E258K, T262S, H287L, R408M, V483A: 4 in DCM; T146N, V321L, A392T, E393K and 7 in both HCM and DCM; L104M, V158M, S236G, R272C, T290A, G522E, A626V], but those were absent in 197 normal healthy controls. Interestingly, we found 7 out of 16 missense mutations (V158M, E258K, R272C, A392T, V483A, G522E, and A626V) in MYBPC3 were altering the evolutionarily conserved native amino acids, accounted for 8.7% and 6.3% in HCM and DCM, respectively. The bioinformatic tools predicted that those 7 missense mutations were pathogenic. Moreover, the co-segregation of those 7 mutations in families further confirmed their pathogenicity. Remarkably, we also identified compound mutations within the MYBPC3 gene of 6 cardiomyopathy patients (5%) with more severe disease phenotype; of which, 3 were HCM (2.6%) [(1. K244K + E258K + (IVS6+2T) T>G); (2. L104M + G522E + A626V); (3. P186P + G522E + A626V]; and 3 were DCM (2.4%) [(1. 5'UTR + A392T; 2. V158M+G522E; and 3.V158M + T262T + A626V].

Conclusion

The present comprehensive study on MYBPC3 has revealed both single and compound mutations in MYBPC3 and their association with disease in Indian Population with Cardiomyopathies. Our findings may perhaps help in initiating diagnostic strategies and eventually recognizing the targets for therapeutic interventions.

From the phenotype to precision medicine: an update on the cardiomyopathies diagnostic workflow

Cardiomyopathies are disease of the cardiac muscle largely due to genetic alterations of proteins with 'structural' or 'functional' roles within the cardiomyocyte, going from the regulation of contraction-relaxation, metabolic and energetic processes to ionic fluxes. Modifications occurring to these proteins are responsible, in the vast majority of cases, for the phenotypic manifestations of the disease, including hypertrophic, dilated, arrhythmogenic and restrictive cardiomyopathies. Secondary nonhereditary causes to be excluded include infections, toxicity from drugs or alcohol or medications, hormonal imbalance and so on. Obtaining a phenotypic definition and an etiological diagnosis is becoming increasingly relevant and feasible, thanks to the availability of new tailored treatments and the diagnostic advancements made particularly in the field of genetics. This is, for example, the case for transthyretin cardiac amyloidosis, Fabry disease or dilated cardiomyopathies due to laminopathies. For these diseases, specific medications have been developed, and a more tailored arrhythmic risk stratification guides the implantation of a defibrillator. In addition, new medications directly targeting the altered protein responsible for the phenotype are becoming available (including the myosin inhibitors mavacantem and aficamten, monoclonal antibodies against Ras-MAPK, genetic therapies for sarcoglycanopathies), thus making a precision medicine approach less unrealistic even in the field of cardiomyopathies. For these reasons, a contemporary approach to cardiomyopathies must consider diagnostic algorithms founded on the clinical suspicion of the disease and developed towards a more precise phenotypic definition and etiological diagnosis, based on a multidisciplinary methodology putting together specialists from different disciplines, facilities for advanced imaging testing and genetic and anatomopathological competencies.

Simple screening model based on electrocardiogram for patients with dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is one of the most common causes of heart failure. Therefore, screening and early diagnosis of potential DCM patients is beneficial. Electrocardiogram (ECG) can be an inexpensive and easily available screening tool. We aimed to construct a simple screening model for DCM based on electrocardiogram. In this retrospective observational study, we consecutively enrolled 117 DCM patients between July 1, 2016 and July 1, 2021 as the DCM group, while 117 patients hospitalized in the same period with normal echocardiography and ECG were selected as the non-DCM group. Patients were randomly assigned to the training and validation sets at 8:2. ECG parameters of left ventricular related leads were exacted. Logistic regression was performed to evaluate screening indicators of ECG parameters and a nomogram was conducted. The screening ability of the model was evaluated using receiver operating characteristic analysis. Furthermore, the nomogram was assessed using calibration curve and decision curve analysis. Screening indicators included in the nomogram were the amplitude of S wave in V1 and V3 leads, the amplitude of R wave in aVF and V6 leads, and PR interval. The nomogram performed satisfactory discrimination in the training (area under the receiver operating characteristic curve = 0.904) and validation (area under the receiver operating characteristic curve = 0.878) sets and good calibration (Hosmer-Lemeshow P = .066). Decision curve analysis demonstrated the model can generate a net benefit of 0.33 when the threshold probability was 0.543. The nomogram based on electrocardiogram is a simple and practical screening tool for potential DCM patients.

Genetic Association between Polymorphisms of Interleukin-32 and Dilated Cardiomyopathy in Chinese Han Population

Background

Dilated cardiomyopathy is a primary myocardial disease and one of the critical causes of heart failure. It is the most common indication for heart transplantation worldwide, and most idiopathic dilated cardiomyopathies are sporadic and multifactorial. Evidence has supported that several inflammatory cytokines and immune responses are involved in its pathological process. Interleukin-32 is a proinflammatory cytokine and is elevated during the worsening cardiac function. Herein, we evaluated the correlation between interleukin-32 gene polymorphisms (rs12934561 and rs28372698) and the susceptibility to dilated cardiomyopathy.

Methods

We enrolled 418 dilated cardiomyopathy patients and 437 healthy controls. The polymerase chain reaction-restriction fragment length polymorphism method was used for genotyping the two single-nucleotide polymorphisms (SNPs), and SPSS software was used for statistical analyses.

Results

The C allele and CC genotype frequencies of rs12934561 were remarkably elevated in dilated cardiomyopathy patients compared to controls (both P < 0.001). The A allele and AA genotype frequencies of rs28372698 significantly decreased in dilated cardiomyopathy patients (P = 0.004 and P = 0.02, respectively). Compared to TT/TC genotype carriers of rs12934561, CC homozygotes presented an increased risk of dilated cardiomyopathy when the left ventricular ejection fraction no more than 30% (P = 0.02).

Conclusions

The IL-32 gene polymorphisms might implicate in DCM risk in the Chinese Han population, and rs12934561 could be a potential forecasting factor for screening high-risk population for DCM.

Family Screening in Dilated Cardiomyopathy: Prevalence, Incidence, and Potential for Limiting Follow-Up

BACKGROUND

According to patterns of inheritance and incomplete penetrance, fewer than half of relatives to dilated cardiomyopathy probands will develop disease.

OBJECTIVES

The purpose of this study was to investigate the prevalence and incidence, and to identify predictors of developing familial dilated cardiomyopathy (FDC) in relatives participating in family screening.

METHODS

The study was a retrospective, longitudinal cohort study of families screened and followed from 2006 to 2020 at a regional assembly of clinics for inherited cardiomyopathies.

RESULTS

In total, 211 families (563 relatives, 50% women) were included. At baseline, 124 relatives (22%) were diagnosed with FDC. Genetic sequencing identified the etiology in 37% of screened families and classified 101 (18%) relatives as unaffected carriers (n = 43) or noncarriers (ie, not at risk of FDC [n = 58]). The combined clinical and genetic baseline yield was 30%. During follow-up (2,313 person-years, median 5.0 years), 45 developed FDC (incidence rate of 2.0% per person-year; 95% CI: 1.4%-2.8%), increasing the overall yield to 34%. The incidence rate of FDC was high in relatives with baseline abnormalities on electrocardiogram or echocardiography compared with relatives with normal findings (4.7% vs 0.4% per person-year; HR: 12.9; P < 0.001). In total, baseline screening identified 326 (58%) relatives to be at low risk of FDC.

CONCLUSIONS

Family screening identified a genetic predisposition to or overt FDC in 1 of 3 relatives at baseline. Genetic and clinical screening was normal in more than half of relatives, and these relatives had a low risk of developing FDC during follow-up. Thus, baseline screening identified a large proportion, in whom follow-up may safely be reduced, allowing focused follow-up of relatives at risk.

Genomic findings of hypertrophic and dilated cardiomyopathy characterized in a Thai clinical genetics service

Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) are the most common referrals in the Inherited Cardiovascular Condition (ICC) Genetics Service. Several issues must be discussed with patients and their families during the genetic consultation session, including the options for genetic testing and cardiovascular surveillance in family members. We developed an ICC registry and performed next-generation-based DNA sequencing for all patients affected by non-syndromic HCM and idiopathic DCM in our joint specialist genetics service. The target gene sequencing panel relied on the Human Phenotype Ontology with 237 genes for HCM (HP:0001639) and 142 genes for DCM (HP:0001644). All subjects were asked to contact their asymptomatic first-degree relatives for genetic counseling regarding their risks and to initiate cardiovascular surveillance and cascade genetic testing. The study was performed from January 1, 2014, to December 31, 2020, and a total of 62 subjects (31-HCM and 31-DCM) were enrolled. The molecular detection frequency was 48.39% (32.26% pathogenic/likely pathogenic, 16.13% variant of uncertain significance or VUS for HCM, and 25.81% (16.13% pathogenic/likely pathogenic, 9.68% VUS) for DCM. The most prevalent gene associated with HCM was MYBPC3. The others identified in this study included ACTN2, MYL2, MYH7, TNNI3, TPM1, and VCL. Among the DCM subjects, variants were detected in two cases with the TTN nonsense variants, while the others were missense and identified in MYH7, DRSP3, MYBPC3, and SCN5A. Following the echocardiogram surveillance and cascade genetic testing in the asymptomatic first-degree relatives, the detection rate of new cases was 8.82% and 6.25% in relatives of HCM and DCM subjects, respectively. Additionally, a new pre-symptomatic relative belonging to an HCM family was identified, although the genomic finding in the affected case was absent. Thus, ICC service is promising for the national healthcare system, aiming to prevent morbidity and mortality in asymptomatic family members.

A biallelic loss-of-function variant in MYZAP is associated with a recessive form of severe dilated cardiomyopathy

PURPOSE

Dilated cardiomyopathy (DCM) is a primary disorder of the cardiac muscle, characterised by dilatation of the left ventricle and contractile dysfunction. About 50% of DCM cases can be attributed to monogenic causes, whereas the aetiology in the remaining patients remains unexplained.

METHODS

We report a family with two brothers affected by severe DCM with onset in the adolescent period. Using exome sequencing, we identified a homozygous premature termination variant in the MYZAP gene in both affected sibs. MYZAP encodes for myocardial zonula adherens protein - a conserved cardiac protein in the intercalated disc structure of cardiomyocytes.

RESULTS

The effect of the variant was demonstrated by light and electron microscopy of the heart muscle and immunohistochemical and Western blot analysis of MYZAP protein in the heart tissue of the proband. Functional characterization using patient-derived induced pluripotent stem cell cardiomyocytes revealed significantly lower force and longer time to peak contraction and relaxation consistent with severe contractile dysfunction.

CONCLUSION

We provide independent support for the role of biallelic loss-of-function MYZAP variants in dilated cardiomyopathy. This report extends the spectrum of cardiac disease associated with dysfunction of cardiac intercalated disc junction and sheds light on the mechanisms leading to DCM.

Dilated cardiomyopathy in the era of precision medicine: latest concepts and developments

Dilated cardiomyopathy (DCM) is an umbrella term entailing a wide variety of genetic and non-genetic etiologies, leading to left ventricular systolic dysfunction and dilatation, not explained by abnormal loading conditions or coronary artery disease. The clinical presentation can vary from asymptomatic to heart failure symptoms or sudden cardiac death (SCD) even in previously asymptomatic individuals. In the last 2 decades, there has been striking progress in the understanding of the complex genetic basis of DCM, with the discovery of additional genes and genotype-phenotype correlation studies. Rigorous clinical work-up of DCM patients, meticulous family screening, and the implementation of advanced imaging techniques pave the way for a more efficient and earlier diagnosis as well as more precise indications for implantable cardioverter defibrillator implantation and prevention of SCD. In the era of precision medicine, genotype-directed therapies have started to emerge. In this review, we focus on updates of the genetic background of DCM, characteristic phenotypes caused by recently described pathogenic variants, specific indications for prevention of SCD in those individuals and genotype-directed treatments under development. Finally, the latest developments in distinguishing athletic heart syndrome from subclinical DCM are described.

Unfolding the genotype-to-phenotype black box of cardiovascular diseases through cross-scale modeling

Complex traits such as cardiovascular diseases (CVD) are the results of complicated processes jointly affected by genetic and environmental factors. Genome-wide association studies (GWAS) identified genetic variants associated with diseases but usually did not reveal the underlying mechanisms. There could be many intermediate steps at epigenetic, transcriptomic, and cellular scales inside the black box of genotype-phenotype associations. In this article, we present a machine-learning-based cross-scale framework GRPath to decipher putative causal paths (pcPaths) from genetic variants to disease phenotypes by integrating multiple omics data. Applying GRPath on CVD, we identified 646 and 549 pcPaths linking putative causal regions, variants, and gene expressions in specific cell types for two types of heart failure, respectively. The findings suggest new understandings of coronary heart disease. Our work promoted the modeling of tissue- and cell type-specific cross-scale regulation to uncover mechanisms behind disease-associated variants, and provided new findings on the molecular mechanisms of CVD.

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We defined one type of cross-scale genotype-to-phenotype regulation path

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We designed a framework GRPath to uncover putative regulation paths for diseases

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GRPath helped uncover molecular mechanisms for two major types of heart failure

Understanding the molecular basis of cardiomyopathy

Inherited cardiomyopathies are a major cause of mortality and morbidity worldwide and can be caused by mutations in a wide range of proteins located in different cellular compartments. The present review is based on Dr. Ju Chen's 2021 Robert M. Berne Distinguished Lectureship of the American Physiological Society Cardiovascular Section, in which he provided an overview of the current knowledge on the cardiomyopathy-associated proteins that have been studied in his laboratory. The review provides a general summary of the proteins in different compartments of cardiomyocytes associated with cardiomyopathies, with specific focus on the proteins that have been studied in Dr. Chen's laboratory.

Novel Mutations in β-MYH7 Gene in Indian Patients With Dilated Cardiomyopathy

Background

Methods

Results

Conclusions

Titin-Related Dilated Cardiomyopathy: The Clinical Trajectory and the Role of Circulating Biomarkers in the Clinical Assessment

Titin truncating variants (TTNtv) are known as the leading cause of inherited dilated cardiomyopathy (DCM). Nevertheless, it is unclear whether circulating cardiac biomarkers are helpful in detection and risk assessment. We sought to assess 1) early indicators of cardiotitinopathy including the serum biomarkers high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) in clinically stable patients, and 2) predictors of outcome among TTNtv carriers. Our single-center cohort consisted of 108 TTNtv carriers (including 70 DCM patients) from 43 families. Clinical, laboratory and follow-up data were analyzed. The earliest abnormality was left ventricular dysfunction, present in 8, 26 and 47% of patients in the second, third and fourth decade of life, respectively. It was followed by symptoms of heart failure, linked to NT-proBNP elevation and severe left ventricular systolic dysfunction, and later by arrhythmias. Hs-cTnT serum levels were increased in the late stage of the disease only. During the median follow-up of 5.2 years, both malignant ventricular arrhythmia (MVA) and end-stage heart failure (esHF) occurred in 12% of TTNtv carriers. In multivariable analysis, NT-proBNP level ≥650 pg/mL was the best predictor of both composite endpoints (MVA and esHF) and of MVA alone. In conclusion, echocardiographic abnormalities are the first detectable anomalies in the course of cardiotitinopathies. The assessment of circulating cardiac biomarkers is not useful in the detection of the disease onset but may be helpful in risk assessment.

The clinical utility of pediatric cardiomyopathy genetic testing: From diagnosis to a precision medicine-based approach to care

Background

Pediatric-onset cardiomyopathies are rare yet cause significant morbidity and mortality in affected children. Genetic testing has a major role in the clinical evaluation of pediatric-onset cardiomyopathies, and identification of a variant in an associated gene can be used to confirm the clinical diagnosis and exclude syndromic causes that may warrant different treatment strategies. Further, risk-predictive testing of first-degree relatives can assess who is at-risk of disease and requires continued clinical follow-up.

Aim of Review

In this review, we seek to describe the current role of genetic testing in the clinical diagnosis and management of patients and families with the five major cardiomyopathies. Further, we highlight the ongoing development of precision-based approaches to diagnosis, prognosis, and treatment.

Key Scientific Concepts of Review

Emerging application of genotype-phenotype correlations opens the door for genetics to guide a precision medicine-based approach to prognosis and potentially for therapies. Despite advances in our understanding of the genetic etiology of cardiomyopathy and increased accessibility of clinical genetic testing, not all pediatric cardiomyopathy patients have a clear genetic explanation for their disease. Expanded genomic studies are needed to understand the cause of disease in these patients, improve variant classification and genotype-driven prognostic predictions, and ultimately develop truly disease preventing treatment.

Effect of rs4646994 polymorphism of angiotensin converting enzyme on the risk of nonischemic cardiomyopathy

Background: Angiotensin-converting enzyme (ACE) gene polymorphisms have recently been shown to be associated with risk of developing left ventricular hypertrophy (LVH). However, the results were controversial. We aimed to conduct this meta-analysis to further confirm the association between ACE rs4646994 polymorphism and hypertrophic cardiomyopathy (HCM)/dilated cardiomyopathy (DCM).

Methods: PubMed, Embase, the Chinese National Knowledge Information, and Wanfang databases were searched for eligible studies. The Newcastle–Ottawa Scale (NOS) was used to evaluate the quality of included studies. Then we evaluated the association between ACE gene mutation and HCM/DCM by calculating odds ratios (ORs) and 95% confidence intervals (95% CIs). Subgroup analysis was further performed to explore situations in specialized subjects. Sensitivity analysis and publication bias was assessed to confirm the study reliability.

Results: There were 13 studies on DCM (2004 cases and 1376 controls) and 16 studies on HCM (2161 controls and 1192 patients). ACE rs4646994 polymorphism was significantly associated with DCM in all genetic models. However, in HCM, four genetic models (allele model, homozygous model, heterozygous model, and dominant model) showed significant association between ACE rs4646994 polymorphism and DCM. In subgroup analysis, we found that ACE rs4646994 polymorphism was significantly associated with DCM/HCM in Asian population. Finally, we also conducted a cumulative meta-analysis, which indicates that the results of our meta-analysis are highly reliable.

Conclusion: ACE rs4646994 polymorphism increases the risk of DCM/HCM in Asians, but not in Caucasians. More case–control studies are needed to strengthen our conclusions and to assess the gene–gene and gene–environment interactions between ACE rs4646994 polymorphism and DCM/HCM.

Artificial Intelligence-Enabled Electrocardiography to Screen Patients with Dilated Cardiomyopathy

Undiagnosed dilated cardiomyopathy (DC) can be asymptomatic or present as sudden cardiac death, therefore pre-emptively identifying and treating patients may be beneficial. Screening for DC with echocardiography is expensive and labor intensive and standard electrocardiography (ECG) is insensitive and non-specific. The performance and applicability of artificial intelligence-enabled electrocardiography (AI-ECG) for detection of DC is unknown. Diagnostic performance of an AI algorithm in determining reduced left ventricular ejection fraction (LVEF) was evaluated in a cohort that comprised of DC and normal LVEF control patients. DC patients and controls with 12-lead ECGs and a reference LVEF measured by echocardiography performed within 30 and 180 days of the ECG respectively were enrolled. The model was tested for its sensitivity, specificity, negative predictive (NPV) and positive predictive values (PPV) based on the prevalence of DC at 1% and 5%. The cohort consisted of 421 DC cases (60% males, 57±15 years, LVEF 28±11%) and 16,025 controls (49% males, age 69 ±16 years, LVEF 62±5%). For detection of LVEF≤45%, the area under the curve (AUC) was 0.955 with a sensitivity of 98.8% and specificity 44.8%. The NPV and PPV were 100% and 1.8% at a DC prevalence of 1% and 99.9% and 8.6% at a prevalence of 5%, respectively. In conclusion AI-ECG demonstrated high sensitivity and negative predictive value for detection of DC and could be used as a simple and cost-effective screening tool with implications for screening first degree relatives of DC patients.

Interpretation of Incidental Genetic Findings Localizing to Genes Associated With Cardiac Channelopathies and Cardiomyopathies

Recent advances in next-genetic sequencing technology have facilitated an expansion in the use of exome and genome sequencing in the research and clinical settings. While this has aided in the genetic diagnosis of individuals with atypical clinical presentations, there has been a marked increase in the number of incidentally identified variants of uncertain diagnostic significance in genes identified as clinically actionable by the American College of Medical Genetics guidelines. Approximately 20 of these genes are associated with cardiac diseases, which carry a significant risk of sudden cardiac death. While identification of at-risk individuals is paramount, increased discovery of incidental variants of uncertain diagnostic significance has placed a burden on the clinician tasked with determining the diagnostic significance of these findings. Herein, we describe the scope of this emerging problem using cardiovascular genetics to illustrate the challenges associated with variants of uncertain diagnostic significance interpretation. We review the evidence for diagnostic weight of these variants, discuss the role of clinical genetics providers in patient care, and put forward general recommendations about the interpretation of incidentally identified variants found with clinical genetic testing.

Genetics of dilated cardiomyopathy

PURPOSE OF REVIEW

Dilated cardiomyopathy (DCM), which include genetic and nongenetic forms, is the most common form of cardiomyopathy. DCM is characterized by left ventricular or biventricular dilation with impaired contraction. In the United States, DCM is a burden to healthcare that accounts for approximately 10,000 deaths and 46,000 hospitalizations annually. In this review, we will focus on the genetic forms of DCM and on recent advances in the understanding of cytoskeletal, sarcomeric, desmosomal, nuclear membrane, and RNA binding genes that contribute to the complexity and genetic heterogeneity of DCM.

RECENT FINDINGS

Although mutations in TTN remain the most common identifiable cause of genetic DCM, there is a growing appreciation for arrhythmogenic-prone DCM due to mutations in LMNA, desmosomal genes, and the recently described FLNC gene encoding the structural filamin C protein. Mutations in RBM20 highlight the relevance of RNA splicing regulation in the pathogenesis of DCM. Although expanded genetic testing has improved access to genetic diagnostic studies for many patients, the molecular mechanisms in the pathogenesis of the disease remained largely unknown.

SUMMARY

: The identification of the molecular causes and subsequent insight into the molecular mechanisms of DCM is expanding our understanding of DCM pathogenesis and highlights the complexity of DCM and the need to develop multifaceted strategies to treat the various causes of DCM.

Heterozygous desmin gene (DES) mutation contributes to familial dilated cardiomyopathy

Familial dilated cardiomyopathy (FDCM) is characterized by high genetic heterogeneity and an increased risk of heart failure or sudden cardiac death in adults. We report the case of a 62-year-old man with a 2-month history of shortness of breath during activity, without paroxysmal nocturnal dyspnea. The patient underwent a series of examinations including transthoracic echocardiography, coronary arteriography, transesophageal echocardiography, and myocardial perfusion imaging. After excluding secondary cardiac enlargement, he was diagnosed with dilated cardiomyopathy (DCM). His sister had also been diagnosed with DCM several years before. Genetic sequencing analysis revealed that the patient, his sister, and his son all had the same mutation in the desmin gene (DES) (chr2-220785662, c.1010C>T). Genetic testing confirmed a heterozygous DES mutation contributing to FDCM. In this case, the etiology of the patient’s whole-heart enlargement was determined as FDCM with DES gene mutation. This is the first report to describe DES c.1010C>T as a cause of FDCM.

Differences between familial and sporadic dilated cardiomyopathy: ESC EORP Cardiomyopathy & Myocarditis registry

AIMS

Dilated cardiomyopathy (DCM) is a complex disease where genetics interplay with extrinsic factors. This study aims to compare the phenotype, management, and outcome of familial DCM (FDCM) and non-familial (sporadic) DCM (SDCM) across Europe.

METHODS AND RESULTS

Patients with DCM that were enrolled in the prospective ESC EORP Cardiomyopathy & Myocarditis Registry were included. Baseline characteristics, genetic testing, genetic yield, and outcome were analysed comparing FDCM and SDCM; 1260 adult patients were studied (238 FDCM, 707 SDCM, and 315 not disclosed). Patients with FDCM were younger (P < 0.01), had less severe disease phenotype at presentation (P < 0.02), more favourable baseline cardiovascular risk profiles (P ≤ 0.007), and less medication use (P ≤ 0.042). Outcome at 1 year was similar and predicted by NYHA class (HR 0.45; 95% CI [0.25-0.81]) and LVEF per % decrease (HR 1.05; 95% CI [1.02-1.08]. Throughout Europe, patients with FDCM received more genetic testing (47% vs. 8%, P < 0.01) and had higher genetic yield (55% vs. 22%, P < 0.01).

CONCLUSIONS

We observed that FDCM and SDCM have significant differences at baseline but similar short-term prognosis. Whether modification of associated cardiovascular risk factors provide opportunities for treatment remains to be investigated. Our results also show a prevalent role of genetics in FDCM and a non-marginal yield in SDCM although genetic testing is largely neglected in SDCM. Limited genetic testing and heterogeneity in panels provides a scaffold for improvement of guideline adherence.

Easily Missed: A Case Series of New Heart Failure in Young Adults

Background. While uncommon, heart failure (HF) can present in young adults from a variety of causes. Identifying HF in a young patient presents many challenges, the foremost of which is recognition of the signs and symptoms of HF. Case Summary. We present four cases of new diagnosis of HF (due to familial cardiomyopathy, tachycardia-induced cardiomyopathy, spontaneous coronary artery dissection, and peripartum cardiomyopathy) to highlight the range of etiologies and presentations requiring recognition in this patient population. Discussion. A high index of suspicion is needed to diagnose HF in young adults, who may not present with classic signs and symptoms. Young adults represent a unique patient population that differs from the older patients with HF. Young adults with newly diagnosed HF should be promptly referred to a center offering full diagnostic capabilities and advanced cardiac therapies.

Epidemiology of the inherited cardiomyopathies

In the absence of contemporary, population-based epidemiological studies, estimates of the incidence and prevalence of the inherited cardiomyopathies have been derived from screening studies, most often of young adult populations, to assess cardiovascular risk or to detect the presence of disease in athletes or military recruits. The global estimates for hypertrophic cardiomyopathy (1/500 individuals), dilated cardiomyopathy (1/250) and arrhythmogenic right ventricular cardiomyopathy (1/5,000) are probably conservative given that only individuals who fulfil diagnostic criteria would have been included. This caveat is highly relevant because a substantial minority or even a majority of individuals who carry disease-causing genetic variants and are at risk of disease complications have incomplete and/or late-onset disease expression. The genetic literature on cardiomyopathy, which is often focused on the identification of genetic variants, has been biased in favour of pedigrees with higher penetrance. In clinical practice, an abnormal electrocardiogram with normal or non-diagnostic imaging results is a common finding for the sarcomere variants that cause hypertrophic cardiomyopathy, the titin and sarcomere variants that cause dilated cardiomyopathy and the desmosomal variants that cause either arrhythmogenic right ventricular cardiomyopathy or dilated cardiomyopathy. Therefore, defining the genetic epidemiology is also challenging given the overlapping phenotypes, incomplete and age-related expression, and highly variable penetrance even within individual families carrying the same genetic variant.

Prognosis and Clinical Characteristics of Dilated Cardiomyopathy With Family History via Pedigree Analysis

BACKGROUND

The clinical characteristics and prognostic outcomes of dilated cardiomyopathy (DCM) with a familial history (FHx) via pedigree analysis are unclear.

METHODS AND RESULTS

We conducted a prospective observational study of 514 consecutive Japanese patients with DCM. FHx was defined as the presence of DCM in ≥1 family member within 2-degrees relative based on pedigree analysis. The primary endpoint was a composite of major cardiac events (sudden cardiac death and pump failure death). The prevalence of FHx was 7.4% (n=38). During a median follow-up of 3.6 years, 77 (15%) patients experienced a major cardiac event. Multivariable Cox regression analysis identified FHx as independently associated with major cardiac events (hazard ratio [HR] 4.32; 95% confidence interval [CI], 2.04-9.19; P<0.001) compared with conventional risk factors such as age, QRS duration, and left ventricular volume. In the propensity score-matched cohort (n=38 each), the FHx group had a significantly higher incidence of major cardiac events (HR, 4.48; 95% CI, 1.25-16.13; P=0.022). In addition, the FHx group had a higher prevalence of a diffuse late gadolinium enhancement (LGE) pattern than the no-FHx group (32% vs. 17%, P=0.022).

CONCLUSIONS

DCM patients with FHx had a worse prognosis, which was associated with a higher prevalence of a diffuse LGE pattern, than patients without FHx.

Genetic Factors Involved in Cardiomyopathies and in Cancer

Cancer therapy-induced cardiomyopathy (CCM) manifests as left ventricular (LV) dysfunction and heart failure (HF). It is associated withparticular pharmacological agents and it is typically dose dependent, but significant individual variability has been observed. History of prior cardiac disease, abuse of toxics, cardiac overload conditions, age, and genetic predisposing factors modulate the degree of the cardiac reserve and the response to the injury. Genetic/familial cardiomyopathies (CMY) are increasingly recognized in general populations with an estimated prevalence of 1:250. Association between cardiac and oncologic diseases regarding genetics involves not only the toxicity process, but pathogenicity. Genetic variants in germinal cells that cause CMY (LMNA, RAS/MAPK) can increase susceptibility for certain types of cancer. The study of mutations found in cancer cells (somatic) has revealed the implication of genes commonly associated with the development of CMY. In particular, desmosomal mutations have been related to increased undifferentiation and invasiveness of cancer. In this article, the authors review the knowledge on the relevance of environmental and genetic background in CCM and give insights into the shared genetic role in the pathogenicity of the cancer process and development of CMY.

Pigs with δ-sarcoglycan deficiency exhibit traits of genetic cardiomyopathy

Genetic cardiomyopathy is a group of intractable cardiovascular disorders involving heterogeneous genetic contribution. This heterogeneity has hindered the development of life-saving therapies for this serious disease. Genetic mutations in dystrophin and its associated glycoproteins cause cardiomuscular dysfunction. Large animal models incorporating these genetic defects are crucial for developing effective medical treatments, such as tissue regeneration and gene therapy. In the present study, we knocked out the δ-sarcoglycan (δ-SG) gene (SGCD) in domestic pig by using a combination of efficient de novo gene editing and somatic cell nuclear transfer. Loss of δ-SG expression in the SGCD knockout pigs caused a concomitant reduction in the levels of α-, β-, and γ-SG in the cardiac and skeletal sarcolemma, resulting in systolic dysfunction, myocardial tissue degeneration, and sudden death. These animals exhibited symptoms resembling human genetic cardiomyopathy and are thus promising for use in preclinical studies of next-generation therapies.

Genetics of dilated cardiomyopathy: practical implications for heart failure management

Given the global burden of heart failure, strategies to understand the underlying cause or to provide prognostic information are critical to reducing the morbidity and mortality associated with this highly prevalent disease. Cardiomyopathies often have a genetic cause, and the field of heart failure genetics is progressing rapidly. Through a deliberate investigation, evaluation for a familial component of cardiomyopathy can lead to increased identification of pathogenic genetic variants. Much research has also been focused on identifying markers of risk in patients with cardiomyopathy with the use of genetic testing. Advances in our understanding of genetic variants have been slightly offset by an increased recognition of the heterogeneity of disease expression. Greater breadth of genetic testing can increase the likelihood of identifying a variant of uncertain significance, which is resolved only rarely by cellular functional validation and segregation analysis. To increase the use of genetics in heart failure clinics, increased availability of genetic counsellors and other providers with experience in genetics is necessary. Ultimately, through ongoing research and increased clinical experience in cardiomyopathy genetics, an improved understanding of the disease processes will facilitate better clinical decision-making about the therapies offered, exemplifying the implementation of precision medicine.

Multigenic Disease and Bilineal Inheritance in Dilated Cardiomyopathy Is Illustrated in Nonsegregating LMNA Pedigrees

BACKGROUND

We have previously described 19 pedigrees with apparent lamin (LMNA)-related dilated cardiomyopathy (DCM) manifesting in affected family members across multiple generations. In 6 of 19 families, at least 1 individual with idiopathic DCM did not carry the family's LMNA variant. We hypothesized that additional genetic cause may underlie DCM in these families.

METHODS

Affected family members underwent exome sequencing to identify additional genetic cause of DCM in the 6 families with nonsegregating LMNA variants.

RESULTS

In 5 of 6 pedigrees, we identified at least 1 additional rare variant in a known DCM gene that could plausibly contribute to disease in the LMNA variant-negative individuals. Bilineal inheritance was clear or presumed to be present in 3 of 5 families and was possible in the remaining 2. At least 1 individual with a LMNA variant also carried a variant in an additional identified DCM gene in each family. Using a multivariate linear mixed model for quantitative traits, we demonstrated that the presence of these additional variants was associated with a more severe phenotype after adjusting for sex, age, and the presence/absence of the family's nonsegregating LMNA variant.

CONCLUSIONS

Our data support DCM as a genetically heterogeneous disease with, at times, multigene causation. Although the frequency of DCM resulting from multigenic cause is uncertain, our data suggest it may be higher than previously anticipated.

Dilated Cardiomyopathy Due to BLC2-Associated Athanogene 3 (BAG3) Mutations

BACKGROUND

The BAG3 (BLC2-associated athanogene 3) gene codes for an antiapoptotic protein located on the sarcomere Z-disc. Mutations in BAG3 are associated with dilated cardiomyopathy (DCM), but only a small number of cases have been reported to date, and the natural history of BAG3 cardiomyopathy is poorly understood.

OBJECTIVES

This study sought to describe the phenotype and prognosis of BAG3 mutations in a large multicenter DCM cohort.

METHODS

The study cohort comprised 129 individuals with a BAG3 mutation (62% males, 35.1 ± 15.0 years of age) followed at 18 European centers. Localization of BAG3 in cardiac tissue was analyzed in patients with truncating BAG3 mutations using immunohistochemistry.

RESULTS

At first evaluation, 57.4% of patients had DCM. After a median follow-up of 38 months (interquartile range: 7 to 95 months), 68.4% of patients had DCM and 26.1% who were initially phenotype-negative developed DCM. Disease penetrance in individuals >40 years of age was 80% at last evaluation, and there was a trend towards an earlier onset of DCM in men (age 34.6 ± 13.2 years vs. 40.7 ± 12.2 years; p = 0.053). The incidence of adverse cardiac events (death, left ventricular assist device, heart transplantation, and sustained ventricular arrhythmia) was 5.1% per year among individuals with DCM. Male sex, decreased left ventricular ejection fraction. and increased left ventricular end-diastolic diameter were associated with adverse cardiac events. Myocardial tissue from patients with a BAG3 mutation showed myofibril disarray and a relocation of BAG3 protein in the sarcomeric Z-disc.

CONCLUSIONS

DCM caused by mutations in BAG3 is characterized by high penetrance in carriers >40 years of age and a high risk of progressive heart failure. Male sex, decreased left ventricular ejection fraction, and enlarged left ventricular end-diastolic diameter are associated with adverse outcomes in patients with BAG3 mutations.

Homozygous damaging SOD2 variant causes lethal neonatal dilated cardiomyopathy

BACKGROUND

Idiopathic dilated cardiomyopathy (DCM) is recognised to be a heritable disorder, yet clinical genetic testing does not produce a diagnosis in >50% of paediatric patients. Identifying a genetic cause is crucial because this knowledge can affect management options, cardiac surveillance in relatives and reproductive decision-making. In this study, we sought to identify the underlying genetic defect in a patient born to consanguineous parents with rapidly progressive DCM that led to death in early infancy.

METHODS AND RESULTS

Exome sequencing revealed a potentially pathogenic, homozygous missense variant, c.542G>T, p.(Gly181Val), in SOD2. This gene encodes superoxide dismutase 2 (SOD2) or manganese-superoxide dismutase, a mitochondrial matrix protein that scavenges oxygen radicals produced by oxidation-reduction and electron transport reactions occurring in mitochondria via conversion of superoxide anion (O₂ ^-·) into H₂O₂. Measurement of hydroethidine oxidation showed a significant increase in O₂ ^-· levels in the patient's skin fibroblasts, as compared with controls, and this was paralleled by reduced catalytic activity of SOD2 in patient fibroblasts and muscle. Lentiviral complementation experiments demonstrated that mitochondrial SOD2 activity could be completely restored on transduction with wild type SOD2.

CONCLUSION

Our results provide evidence that defective SOD2 may lead to toxic increases in the levels of damaging oxygen radicals in the neonatal heart, which can result in rapidly developing heart failure and death. We propose SOD2 as a novel nuclear-encoded mitochondrial protein involved in severe human neonatal cardiomyopathy, thus expanding the wide range of genetic factors involved in paediatric cardiomyopathies.

Updates on the Genetic Paradigm in Heart Failure

PURPOSE OF REVIEW

The rapidly evolving field of cardiovascular genetics has already improved the care of patients with heart failure and families. The purpose of the current review is to describe the most and provide the most pertinent updates in the field of heart failure genetics.

RECENT FINDINGS

Recent advanced in heart failure genetics have begun to not only increase the yield of testing through improving technology and use of whole exome or whole genome screening, but also enabled the improving technology and increasing use of whole exome or whole genome screening, but also enabled an enhanced understanding of the implications of results of genetic testing. For instance, new data have described differential responses to heart failure therapies based on genetic testing. Additionally, variant analysis by locus in genetic cardiomyopathies has facilitated a much-improved prognostic understanding of phenotype. Recent years have seen advancements in the understanding of the genetics of rare disorders, including pediatric-onset cardiomyopathies, previously under-investigated; restrictive cardiomyopathies; and non-compaction cardiomyopathy. The last few years have heralded not only a broader understanding of the scope of the genetics of heart failure, but have also provided notable leaps in mechanistic and prognostic understanding, which will serve as the foundation for clinical investigation and future genetic variant assessment.

Whole-Exome Sequencing Reveals Novel Genetic Variation for Dilated Cardiomyopathy in Pediatric Chinese Patients

Dilated cardiomyopathy (DCM) is characterized by left or bilateral ventricular dilation and systolic dysfunction without rational conditions, which can lead to progressive heart failure and sudden cardiac death. Most of the pathogenic genes have been reported in adult population by locus mapping in familial cases and animal model studies. However, it still remains challenging to decipher the role of genetics in the etiology of pediatric DCM. We applied whole-exome sequencing (WES) for 30 sporadic pediatric DCM subjects and 100 non-DCM local controls. We identified the pathogenic mutations using bioinformatics tools based on genomic strategies synergistically and confirmed mutations by Sanger sequencing. We identified compound heterozygous nonsense mutations in DSP (c.3799C > T, p.R1267X; c.4444G > T, p.E1482X). In sporadic cases, the two heterozygous mutations in XIRP2 were identified. Then we performed an exome-wide association study with 30 case and 100 control subjects. Interestingly, we could not identify TTN truncating variants in all cases. Collectively, we observed a significant risk signal between carriers of TTN deleterious missense variants and DCM risk (odds ratio 4.0, 95% confidence interval 1.1-22.2, p = 3.12 × 10^-2). Our observations expanded the spectrum of mutations and were valuable in the pre- and postnatal screening and genetic diagnosis for DCM.

Association Between AXIN1 Gene Polymorphisms and Dilated Cardiomyopathy in a Chinese Han Population

Dilated cardiomyopathy (DCM) is a common type of cardiomyopathy. The pathogenesis of DCM remains unclear and involves varied genes. AXIN1 is a crucial gene in regulating various functions in cells, it encodes protein Axin1, which regulates the assembly and disassembly of β-catenin destruction complex. In addition, Wnt/β-catenin signaling pathway plays an important role in cardiogenesis. We aimed to detect whether AXIN1 polymorphisms contribute to the susceptibility and prognosis of DCM in a Chinese Han population. A total of 340 DCM patients and 430 controls were enrolled, and patients who had complete contact information were followed up for a median period of 49 months. Polymerase chain reaction-restriction fragment length polymorphism was carried out to genotype the two AXIN1 tag single nucleotide polymorphisms (SNPs) (rs12921862 and rs1805105). All data were analyzed using the statistical software package, SPSS 21.0. The frequencies of allele A in rs12921862 and allele C in rs1805015 were increased in DCM patients compared with healthy controls (p < 0.001). Genotypic frequencies of rs12921862 and rs1805105 were associated with the susceptibility of DCM in codominant, dominant, and overdominant models (p < 0.01). AA/AC and AC genotypes of rs12921862 in the dominant and the overdominant genetic models also presented a correlation with poor prognosis of DCM in both univariate (p < 0.01) and multivariate analyses (p < 0.01) after adjusting for age, gender, left ventricular (LV) end-diastolic diameter, and LV ejection fraction. Our results suggest that AXIN1 polymorphisms are associated with the susceptibility and prognosis of DCM in a Chinese Han population.

"Primary" dilated hearts

Dilated cardiomyopathy is part of the spectrum of heart failure which is a syndrome with certain morphological and functional characteristics. Although significant progress in the management of those patients has been achieved, seems that risk stratification and future treatments will be related to the specific pathological substrate.

PP2A negatively regulates the hypertrophic response by dephosphorylating HDAC2 S394 in the heart

Cardiac hypertrophy occurs in response to increased hemodynamic demand and can progress to heart failure. Identifying the key regulators of this process is clinically important. Though it is thought that the phosphorylation of histone deacetylase (HDAC) 2 plays a crucial role in the development of pathological cardiac hypertrophy, the detailed mechanism by which this occurs remains unclear. Here, we performed immunoprecipitation and peptide pull-down assays to characterize the functional complex of HDAC2. Protein phosphatase (PP) 2 A was confirmed as a binding partner of HDAC2. PPP2CA, the catalytic subunit of PP2A, bound to HDAC2 and prevented its phosphorylation. Transient overexpression of PPP2CA specifically regulated both the phosphorylation of HDAC2 S394 and hypertrophy-associated HDAC2 activation. HDAC2 S394 phosphorylation was increased in a dose-dependent manner by PP2A inhibitors. Hypertrophic stresses, such as phenylephrine in vitro or pressure overload in vivo, caused PPP2CA to dissociate from HDAC2. Forced expression of PPP2CA negatively regulated the hypertrophic response, but PP2A inhibitors provoked hypertrophy. Adenoviral delivery of a phosphomimic HDAC2 mutant, adenovirus HDAC2 S394E, successfully blocked the anti-hypertrophic effect of adenovirus-PPP2CA, implicating HDAC2 S394 phosphorylation as a critical event for the anti-hypertrophic response. PPP2CA transgenic mice were protected against isoproterenol-induced cardiac hypertrophy and subsequent cardiac fibrosis, whereas simultaneous expression of HDAC2 S394E in the heart did induce hypertrophy. Taken together, our results suggest that PP2A is a critical regulator of HDAC2 activity and pathological cardiac hypertrophy and is a promising target for future therapeutic interventions.

Toward Genetics-Driven Early Intervention in Dilated Cardiomyopathy: Design and Implementation of the DCM Precision Medicine Study

BACKGROUND

The cause of idiopathic dilated cardiomyopathy (DCM) is unknown by definition, but its familial subtype is considered to have a genetic component. We hypothesize that most idiopathic DCM, whether familial or nonfamilial, has a genetic basis, in which case a genetics-driven approach to identifying at-risk family members for clinical screening and early intervention could reduce morbidity and mortality.

METHODS

On the basis of this hypothesis, we have launched the National Heart, Lung, and Blood Institute- and National Human Genome Research Institute-funded DCM Precision Medicine Study, which aims to enroll 1300 individuals (600 non-Hispanic African ancestry, 600 non-Hispanic European ancestry, and 100 Hispanic) who meet rigorous clinical criteria for idiopathic DCM along with 2600 of their relatives. Enrolled relatives will undergo clinical cardiovascular screening to identify asymptomatic disease, and all individuals with idiopathic DCM will undergo exome sequencing to identify relevant variants in genes previously implicated in DCM. Results will be returned by genetic counselors 12 to 14 months after enrollment. The data obtained will be used to describe the prevalence of familial DCM among idiopathic DCM cases and the genetic architecture of idiopathic DCM in multiple ethnicity-ancestry groups. We will also conduct a randomized controlled trial to test the effectiveness of Family Heart Talk, an intervention to aid family communication, for improving uptake of preventive screening and surveillance in at-risk first-degree relatives.

CONCLUSIONS

We anticipate that this study will demonstrate that idiopathic DCM has a genetic basis and guide best practices for a genetics-driven approach to early intervention in at-risk relatives.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT03037632.

Exploring the Crosstalk Between LMNA and Splicing Machinery Gene Mutations in Dilated Cardiomyopathy

Mutations in the LMNA gene, which encodes for the nuclear lamina proteins lamins A and C, are responsible for a diverse group of diseases known as laminopathies. One type of laminopathy is Dilated Cardiomyopathy (DCM), a heart muscle disease characterized by dilation of the left ventricle and impaired systolic function, often leading to heart failure and sudden cardiac death. LMNA is the second most commonly mutated gene in DCM. In addition to LMNA, mutations in more than 60 genes have been associated with DCM. The DCM-associated genes encode a variety of proteins including transcription factors, cytoskeletal, Ca2+-regulating, ion-channel, desmosomal, sarcomeric, and nuclear-membrane proteins. Another important category among DCM-causing genes emerged upon the identification of DCM-causing mutations in RNA binding motif protein 20 (RBM20), an alternative splicing factor that is chiefly expressed in the heart. In addition to RBM20, several essential splicing factors were validated, by employing mouse knock out models, to be embryonically lethal due to aberrant cardiogenesis. Furthermore, heart-specific deletion of some of these splicing factors was found to result in aberrant splicing of their targets and DCM development. In addition to splicing alterations, advances in next generation sequencing highlighted the association between splice-site mutations in several genes and DCM. This review summarizes LMNA mutations and splicing alterations in DCM and discusses how the interaction between LMNA and splicing regulators could possibly explain DCM disease mechanisms.