Genetic evaluation of dilated cardiomyopathy

[New pathogenic mutation in LMNA gene: Clinical case of familial cardiomyopathy]

We present a clinical case of familial LMNA-associated cardiomyopathy, confirmed by whole genome sequencing. The typical for lamin-associated cardiomyopathy indicates pathogenic nature of the mutation in the first exon of LMNA gene, previously considered a mutation of unknown clinical significance. The presented clinical case demonstrates a radical change in patient treatment strategies in the context of the widespread introduction of molecular genetic research methods into practice.

Frameshift variants in C10orf71 cause dilated cardiomyopathy in human, mouse, and organoid models

Research advances over the past 30 years have confirmed a critical role for genetics in the etiology of dilated cardiomyopathies (DCMs). However, full knowledge of the genetic architecture of DCM remains incomplete. We identified candidate DCM causal gene, C10orf71, in a large family with 8 patients with DCM by whole-exome sequencing. Four loss-of-function variants of C10orf71 were subsequently identified in an additional group of492 patients with sporadic DCM from 2 independent cohorts. C10orf71 was found to be an intrinsically disordered protein specifically expressed in cardiomyocytes. C10orf71-KO mice had abnormal heart morphogenesis during embryonic development and cardiac dysfunction as adults with altered expression and splicing of contractile cardiac genes. C10orf71-null cardiomyocytes exhibited impaired contractile function with unaffected sarcomere structure. Cardiomyocytes and heart organoids derived from human induced pluripotent stem cells with C10orf71 frameshift variants also had contractile defects with normal electrophysiological activity. A rescue study using a cardiac myosin activator, omecamtiv mecarbil, restored contractile function in C10orf71-KO mice. These data support C10orf71 as a causal gene for DCM by contributing to the contractile function of cardiomyocytes. Mutation-specific pathophysiology may suggest therapeutic targets and more individualized therapy.

Cardiomyopathies: An Overview

Background: Cardiomyopathies are a heterogeneous group of pathologies characterized by structural and functional alterations of the heart. Aims: The purpose of this narrative review is to focus on the most important cardiomyopathies and their epidemiology, diagnosis, and management. Methods: Clinical trials were identified by Pubmed until 30 March 2021. The search keywords were “cardiomyopathies, sudden cardiac arrest, dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), restrictive cardiomyopathy, arrhythmogenic cardiomyopathy (ARCV), takotsubo syndrome”. Results: Hypertrophic cardiomyopathy (HCM) is the most common primary cardiomyopathy, with a prevalence of 1:500 persons. Dilated cardiomyopathy (DCM) has a prevalence of 1:2500 and is the leading indication for heart transplantation. Restrictive cardiomyopathy (RCM) is the least common of the major cardiomyopathies, representing 2% to 5% of cases. Arrhythmogenic cardiomyopathy (ARCV) is a pathology characterized by the substitution of the myocardium by fibrofatty tissue. Takotsubo cardiomyopathy is defined as an abrupt onset of left ventricular dysfunction in response to severe emotional or physiologic stress. Conclusion: In particular, it has been reported that HCM is the most important cause of sudden death on the athletic field in the United States. It is needless to say how important it is to know which changes in the heart due to physical activity are normal, and when they are pathological.

Neurological complications of cardiomyopathies

There is a multifaceted relationship between the cardiomyopathies and a wide spectrum of neurological disorders. Severe acute neurological events, such as a status epilepticus and aneurysmal subarachnoid hemorrhage, may result in an acute cardiomyopathy the likes of Takotsubo cardiomyopathy. Conversely, the cardiomyopathies may result in a wide array of neurological disorders. Diagnosis of a cardiomyopathy may have already been established at the time of the index neurological event, or the neurological event may have prompted subsequent cardiac investigations, which ultimately lead to the diagnosis of a cardiomyopathy. The cardiomyopathies belong to one of the many phenotypes of complex genetic diseases or syndromes, which may also involve the central or peripheral nervous systems. A number of exogenous agents or risk factors such as diphtheria, alcohol, and several viruses may result in secondary cardiomyopathies accompanied by several neurological manifestations. A variety of neuromuscular disorders, such as myotonic dystrophy or amyloidosis, may demonstrate cardiac involvement during their clinical course. Furthermore, a number of genetic cardiomyopathies phenotypically incorporate during their clinical evolution, a gamut of neurological manifestations, usually neuromuscular in nature. Likewise, neurological complications may be the result of diagnostic procedures or medications for the cardiomyopathies and vice versa. Neurological manifestations of the cardiomyopathies are broad and include, among others, transient ischemic attacks, ischemic strokes, intracranial hemorrhages, syncope, muscle weakness and atrophy, myotonia, cramps, ataxia, seizures, intellectual developmental disorder, cognitive impairment, dementia, oculomotor palsies, deafness, retinal involvement, and headaches.

Distinct Myocardial Transcriptomic Profiles of Cardiomyopathies Stratified by the Mutant Genes

Cardiovascular diseases are the number one cause of morbidity and mortality worldwide, but the underlying molecular mechanisms remain not well understood. Cardiomyopathies are primary diseases of the heart muscle and contribute to high rates of heart failure and sudden cardiac deaths. Here, we distinguished four different genetic cardiomyopathies based on gene expression signatures. In this study, RNA-Sequencing was used to identify gene expression signatures in myocardial tissue of cardiomyopathy patients in comparison to non-failing human hearts. Therefore, expression differences between patients with specific affected genes, namely LMNA (lamin A/C), RBM20 (RNA binding motif protein 20), TTN (titin) and PKP2 (plakophilin 2) were investigated. We identified genotype-specific differences in regulated pathways, Gene Ontology (GO) terms as well as gene groups like secreted or regulatory proteins and potential candidate drug targets revealing specific molecular pathomechanisms for the four subtypes of genetic cardiomyopathies. Some regulated pathways are common between patients with mutations in RBM20 and TTN as the splice factor RBM20 targets amongst other genes TTN, leading to a similar response on pathway level, even though many differentially expressed genes (DEGs) still differ between both sample types. The myocardium of patients with mutations in LMNA is widely associated with upregulated genes/pathways involved in immune response, whereas mutations in PKP2 lead to a downregulation of genes of the extracellular matrix. Our results contribute to further understanding of the underlying molecular pathomechanisms aiming for novel and better treatment of genetic cardiomyopathies.

Chondroid and Osseous Metaplasia of the Central Fibrous Body in Adolescent Hearts with Mutations in TNNI3 and TNNT2 genes

The histological spectrum of the central fibrous body (CFB) of the heart, particularly in humans, is not fully characterized. Herein, we describe the presence of cartilage and bone within the CFB of 2 explanted heart specimens from patients with known mutation-driven cardiomyopathy involving the TNNI3 and TNNT2 genes, review the existing literature on the identified variants particularly TNNI3 (p.Asn185Thrfs*14) and TNNT2 (p.Arg141Trp), and provide insights into the plausible nature of such histopathological observation based on animal studies and the few reported cases in humans.

Drug Development and the Use of Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Disease Modeling and Drug Toxicity Screening

: Over the years, numerous groups have employed human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) as a superb human-compatible model for investigating the function and dysfunction of cardiomyocytes, drug screening and toxicity, disease modeling and for the development of novel drugs for heart diseases. In this review, we discuss the broad use of iPSC-CMs for drug development and disease modeling, in two related themes. In the first theme-drug development, adverse drug reactions, mechanisms of cardiotoxicity and the need for efficient drug screening protocols-we discuss the critical need to screen old and new drugs, the process of drug development, marketing and Adverse Drug reactions (ADRs), drug-induced cardiotoxicity, safety screening during drug development, drug development and patient-specific effect and different mechanisms of ADRs. In the second theme-using iPSC-CMs for disease modeling and developing novel drugs for heart diseases-we discuss the rationale for using iPSC-CMs and modeling acquired and inherited heart diseases with iPSC-CMs.

Novel heterozygous truncating titin variants affecting the A-band are associated with cardiomyopathy and myopathy/muscular dystrophy

BACKGROUND

Variants in TTN are frequently identified in the genetic evaluation of skeletal myopathy or cardiomyopathy. However, due to the high frequency of TTN variants in the general population, incomplete penetrance, and limited understanding of the spectrum of disease, interpretation of TTN variants is often difficult for laboratories and clinicians. Currently, cardiomyopathy is associated with heterozygous A-band TTN variants, whereas skeletal myopathy is largely associated with homozygous or compound heterozygous TTN variants. Recent reports show pathogenic variants in TTN may result in a broader phenotypic spectrum than previously recognized.

METHODS

Here we report the results of a multisite study that characterized the phenotypes of probands with variants in TTN. We investigated TTN genotype-phenotype correlations in probands with skeletal myopathy and/or cardiomyopathy. Probands with TTN truncating variants (TTNtv) or pathogenic missense variants were ascertained from two academic medical centers. Variants were identified via clinical genetic testing and reviewed according to the American College of Medical Genetics criteria. Clinical and family history data were documented via retrospective chart review. Family studies were performed for probands with atypical phenotypes.

RESULTS

Forty-nine probands were identified with TTNtv or pathogenic missense variants. Probands were classified by clinical presentation: cardiac (n = 30), skeletal muscle (n = 12), or both (cardioskeletal, n = 7). Within the cardioskeletal group, 5/7 probands had heterozygous TTNtv predicted to affect the distal (3') end of the A-band. All cardioskeletal probands had onset of proximal-predominant muscle weakness before diagnosis of cardiovascular disease, five pedigrees support dominant transmission.

CONCLUSION

Although heterozygous TTNtv in the A-band is known to cause dilated cardiomyopathy, we present evidence that these variants may in some cases cause a novel, dominant skeletal myopathy with a limb-girdle pattern of weakness. These findings emphasize the importance of multidisciplinary care for patients with A-band TTNtv who may be at risk for multisystem disease.

Advances in the role and mechanism of BAG3 in dilated cardiomyopathy

The B cell lymphoma 2-associated anthanogene (BAG3) is an anti-apoptotic co-chaperone protein. Previous reports suggest that mutations in BAG3 are associated with dilated cardiomyopathy. This review aims to summarize the current understanding of the relationship between BAG3 mutations and dilated cardiomyopathy, primarily focusing on the role and protective mechanism of BAG3 in cardiomyocytes from individuals with dilated cardiomyopathy. The results of published studies show that BAG3 is critically important for reducing cardiomyocyte apoptosis, maintaining protein homeostasis, regulating mitochondrial stability, modulating myocardial contraction, and reducing cardiac arrhythmia, which suggests an indispensable protective mechanism of BAG3 in dilated cardiomyopathy. The significant role of BAG3 in protecting cardiomyocytes provides a new direction for the diagnosis and treatment of dilated cardiomyopathy. However, further research is required to explore the molecular mechanisms that regulate BAG3 expression, to identify a novel therapy for patients with dilated cardiomyopathy.

Biallelic Variants in ASNA1, Encoding a Cytosolic Targeting Factor of Tail-Anchored Proteins, Cause Rapidly Progressive Pediatric Cardiomyopathy

Supplemental Digital Content is available in the text.

Pediatric cardiomyopathies are a clinically and genetically heterogeneous group of heart muscle disorders associated with high morbidity and mortality. Although knowledge of the genetic basis of pediatric cardiomyopathy has improved considerably, the underlying cause remains elusive in a substantial proportion of cases.

Risk Stratification of Genetic, Dilated Cardiomyopathies Associated With Neuromuscular Disorders: Role of Cardiac Imaging

The etiology of dilated cardiomyopathy (DCM) can be grouped as either genetic or nongenetic. More than 50 pathogenic genes have been described, with sarcomeric and lamin A/C mutations being the most common. Mutation carriers for genetic DCM are often asymptomatic until cardiac disease manifests with heart failure, arrhythmias, or sudden cardiac death. Preventive strategies are promising but can only be applied and tested adequately if genetic DCM can be diagnosed at an early stage. Early diagnosis of mutation carriers that may develop overt DCM requires advanced imaging techniques that can detect subtle structural and functional abnormalities. Advanced echocardiographic techniques such as tissue Doppler imaging and speckle tracking strain analysis permit early detection of functional abnormalities, whereas cardiovascular magnetic resonance techniques provide information on tissue characterization and myocardial energetics that may be altered at an early stage. Furthermore, nuclear imaging techniques provide information on cellular function (metabolism, perfusion). Once the diagnosis of overt DCM has been established, various imaging parameters such as echocardiography-based myocardial mechanics and cardiovascular magnetic resonance-based tissue characterization have shown incremental benefit to left ventricular ejection fraction in risk stratification. Further research is required to understand how imaging techniques may help to choose management strategies that could delay progression when instituted early in the course of the disease. The present article reviews the role of imaging in the risk stratification of genetic DCM in general, with specific emphasis on DCM associated with neuromuscular disorders.

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.

A common polymorphism in the SCN5A gene is associated with dilated cardiomyopathy

Aims

SCN5A is a disease-causing gene associated with familial dilated cardiomyopathy (FDC). We examined the possible association between a common polymorphism in the SCN5A gene (c.1673A>G-p.H558R; rs1805124) and the risk of dilated cardiomyopathy (DCM) occurrence.

Methods

We genotyped 185 DCM cases (familial DCM, idiopathic DCM and postischemic DCM) and 251 controls for the p.H558R polymorphism in the SCN5A gene, to test the association of the molecular epidemiology of the individuals with the presence/absence of various types of DCM.

Results

Our results showed that the rs1805124 polymorphism was significantly associated with DCM, and the association was more significant in patients with FDC; furthermore, in these individuals, the less frequent GG genotype was associated with a 7.39-fold increased risk of disease [95% confidence interval (95% CI) = 2.88–18.96; P < 0.0001] compared with the AA genotype. Moreover, logistic regression analysis showed that GG carriers had a higher risk of DCM than AA + AG carriers (odds ratio = 5.45, 95% CI = 2.23–13.35; P < 0.001). No association was observed between the rs1805124 and DCM risk in postischemic DCM patients.

Conclusion

Our study demonstrates an association between familial DCM and the rs1805124 polymorphism in the SCN5A gene, which may unravel additional genetic predisposition to the development of a multifactorial disease as DCM.

Contemporary genetic testing in inherited cardiac disease: tools, ethical issues, and clinical applications

Inherited cardiac diseases comprise a wide and heterogeneous spectrum of diseases of the heart, including the cardiomyopathies and the arrhythmic diseases in structurally normal hearts, that is, channelopathies. With a combined estimated prevalence of 3% in the general population, these conditions represent a relevant epidemiological entity worldwide, and are a major cause of cardiac morbidity and mortality in the young. The extraordinary progress achieved in molecular genetics over the last three decades has unveiled the complex molecular basis of many familial cardiac conditions, paving the way for routine use of gene testing in clinical practice. In current practice, genetic testing can be used in a clinically affected patient to confirm diagnosis, or to formulate a differential diagnosis among overlapping phenotypes or between hereditary and acquired (nongenetic) forms of disease. Although genotype–phenotype correlations are generally unpredictable, a precise molecular diagnosis can help predict prognosis in specific patient subsets and may guide management. In clinically unaffected relatives, genetic cascade testing is recommended, after the initial identification of a pathogenic variation, with the aim of identifying asymptomatic relatives who might be at risk of disease-related complications, including unexpected sudden cardiac death. Future implications include the identification of novel therapeutic targets and development of tailored treatments including gene therapy. This document reflects the multidisciplinary, ‘real-world’ experience required when implementing genetic testing in cardiomyopathies and arrhythmic syndromes, along the recommendations of various guidelines.

Whole exome sequencing identified 1 base pair novel deletion in BCL2-associated athanogene 3 (BAG3) gene associated with severe dilated cardiomyopathy (DCM) requiring heart transplant in multiple family members

Dilated cardiomyopathy (DCM) is characterized by dilation and impaired contraction of the left ventricle or both ventricles. Among hereditary DCM, the genetic causes are heterogeneous, and include mutations encoding cytoskeletal, nucleoskeletal, mitochondrial, and calcium-handling proteins. We report three severely affected males, in a four-generation pedigree, with DCM phenotype who underwent cardiac transplant. Cardiomegaly with marked biventricular dilation and fibrosis were noticeable histopathological findings. The affected males had tested negative on a 46-gene pancardiomyopathy panel. Whole Exome Sequencing (WES) was performed to reveal mutation in the gene responsible in generation of DCM phenotypes. The 1-bp (Chr10:121435979delC; c.913delC) novel heterozygous deletion in exon 4 of BAG3, was identified in three affected males, resulted in frame-shift and a premature termination codon (p.Met306-Stop) producing a truncated BAG3 protein lacking functionally important PXXP and BAG domains. WES data were further utilized to map 10 SNP markers around the discovered mutation to generate shared disease haplotype in all affected individuals encompassing 11 Mb on 10q25.3-26.2 harboring BAG3. Finally genotypes were inferred for the unavailable/deceased individuals in the pedigrees. Here we propose that Chr10:121435979delC in BAG3 is a causal mutation in these subjects. Our and earlier studies indicate that BAG3 mutations are associated with DCM phenotypes. BAG3 should be added to cardiomyopathy gene panels for screening of DCM patients, and patients previously considered gene elusive should undergo sequencing of the BAG3 gene. © 2017 Wiley Periodicals, Inc.

Dilated cardiomyopathy

Dilated cardiomyopathy is defined by the presence of left ventricular dilatation and contractile dysfunction. Genetic mutations involving genes that encode cytoskeletal, sarcomere, and nuclear envelope proteins, among others, account for up to 35% of cases. Acquired causes include myocarditis and exposure to alcohol, drugs and toxins, and metabolic and endocrine disturbances. The most common presenting symptoms relate to congestive heart failure, but can also include circulatory collapse, arrhythmias, and thromboembolic events. Secondary neurohormonal changes contribute to reverse remodelling and ongoing myocyte damage. The prognosis is worst for individuals with the lowest ejection fractions or severe diastolic dysfunction. Treatment of chronic heart failure comprises medications that improve survival and reduce hospital admission-namely, angiotensin converting enzyme inhibitors and β blockers. Other interventions include enrolment in a multidisciplinary heart failure service, and device therapy for arrhythmia management and sudden death prevention. Patients who are refractory to medical therapy might benefit from mechanical circulatory support and heart transplantation. Treatment of preclinical disease and the potential role of stem-cell therapy are being investigated.

Differences in Presentation and Outcomes Between Children With Familial Dilated Cardiomyopathy and Children With Idiopathic Dilated Cardiomyopathy: A Report From the Pediatric Cardiomyopathy Registry Study Group

BACKGROUND

Research comparing the survival of children with familial dilated cardiomyopathy (FDCM) to that of children with idiopathic dilated cardiomyopathy (IDCM) has produced conflicting results.

METHODS AND RESULTS

We analyzed data from children with FDCM or IDCM using the National Heart, Lung, and Blood Institute-funded Pediatric Cardiomyopathy Registry. Compared to children with IDCM (n=647), children with FDCM (n=223) were older (mean 6.2 versus 4.5 years, P<0.001), less often had heart failure (64% versus 78%, P<0.001), had less-depressed mean left ventricular fractional shortening z scores (-7.85±3.98 versus -9.06±3.89, P<0.001) and lower end-diastolic dimension z scores (4.12±2.61 versus 4.91±2.57, P<0.001) at diagnosis. The cumulative incidence of death was lower for patients with FDCM compared with IDCM (P=0.04; hazard ratio 0.64, P=0.06), but no difference in risk of transplant or the combined death or transplant outcome. There was no difference in the proportion of children with echocardiographic normalization at 3 years of follow-up (FDCM, 30% versus IDCM, 26%; P=0.33). Multivariable analysis showed no difference in outcomes between FDCM and IDCM but for both groups older age, congestive heart failure, and increased left ventricular end-systolic dimension zscore at diagnosis were independently associated with an increased risk of death or heart transplantation (all Ps<0.001).

CONCLUSIONS

There was no survival difference between FDCM and IDCM after adjustment for other factors. Older age, congestive heart failure, and greater left ventricular dilation at diagnosis were independently associated with increased risk of the combined end point of death or transplantation.

CLINICAL TRIAL REGISTRATION

URL: https://clinicaltrials.gov. Unique identifier: NCT00005391.

Familial Dilated Cardiomyopathy Caused by a Novel Frameshift in the BAG3 Gene

BACKGROUND

Dilated cardiomyopathy, a major cause of chronic heart failure and cardiac transplantation, is characterized by left ventricular or biventricular heart dilatation. In nearly 50% of cases the pathology is inherited, and more than 60 genes have been reported as disease-causing. However, in 30% of familial cases the mutation remains unidentified even after comprehensive genetic analysis. This study clinically and genetically assessed a large Spanish family affected by dilated cardiomyopathy to search for novel variations.

METHODS AND RESULTS

Our study included a total of 100 family members. Clinical assessment was performed in alive, and genetic analysis was also performed in alive and 1 deceased relative. Genetic screening included resequencing of 55 genes associated with sudden cardiac death, and Sanger sequencing of main disease-associated genes. Genetic analysis identified a frame-shift variation in BAG3 (p.H243Tfr*64) in 32 patients. Genotype-phenotype correlation identified substantial heterogeneity in disease expression. Of 32 genetic carriers (one deceased), 21 relatives were clinically affected, and 10 were asymptomatic. Seventeen of the symptomatic genetic carriers exhibited proto-diastolic septal knock by echocardiographic assessment.

CONCLUSIONS

We report p.H243Tfr*64_BAG3 as a novel pathogenic variation responsible for familial dilated cardiomyopathy. This variation correlates with a more severe phenotype of the disease, mainly in younger individuals. Genetic analysis in families, even asymptomatic individuals, enables early identification of individuals at risk and allows implementation of preventive measures.

An uncommon clinical presentation of relapsing dilated cardiomyopathy with identification of sequence variations in MYNPC3, KCNH2 and mitochondrial tRNA cysteine

We describe a young girl with dilated cardiomyopathy, long QT syndrome, and possible energy deficiency. Two major sequence changes were identified by whole exome sequencing (WES) and mitochondrial DNA analysis that were interpreted as potentially causative. Changes were identified in the KCNH2 gene and mitochondrial tRNA for cysteine. A variation was also seen in MYPBC3. Since the launch of WES as a clinically available technology in 2010, there has been concern regarding the identification of variants unrelated to the patient's phenotype. However, in cases where targeted sequencing fails to explain the clinical presentation, the underlying etiology could be more complex than anticipated. In this situation, the extensive reach of this tool helped explain both her phenotype and family history.

Proposal for a revised definition of dilated cardiomyopathy, hypokinetic non-dilated cardiomyopathy, and its implications for clinical practice: a position statement of the ESC working group on myocardial and pericardial diseases

In this paper the Working Group on Myocardial and Pericardial Disease proposes a revised definition of dilated cardiomyopathy (DCM) in an attempt to bridge the gap between our recent understanding of the disease spectrum and its clinical presentation in relatives, which is key for early diagnosis and the institution of potential preventative measures. We also provide practical hints to identify subsets of the DCM syndrome where aetiology directed management has great clinical relevance.

Patent Highlight

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

Molecular Signature of Nitroso-Redox Balance in Idiopathic Dilated Cardiomyopathies

BACKGROUND

Idiopathic dilated cardiomyopathy is one of the most common types of cardiomyopathy. It has been proposed that an increase in oxidative stress in heart failure leads to a decrease in nitric oxide signaling, leading to impaired nitroso-redox signaling. To test this hypothesis, we investigated the occurrence of protein S-nitrosylation (SNO) and oxidation in biopsies from explanted dilated cardiomyopathy and nonfailing donor male and female human hearts.

METHODS AND RESULTS

Redox-based resin-assisted capture for oxidation and SNO proteomic analysis was used to measure protein oxidation and SNO, respectively. In addition, 2-dimensional difference gel electrophoresis using maleimide sulfhydryl-reactive fluors was used to identify the SNO proteins. Protein oxidation increased in dilated cardiomyopathy biopsies in comparison with those from healthy donors. Interestingly, we did not find a consistent decrease in SNO in failing hearts; we found that some proteins showed an increase in SNO and others showed a decrease, and there were sex-specific differences in the response. We found 10 proteins with a significant decrease in SNO and 4 proteins with an increase in SNO in failing female hearts. Comparing nonfailing and failing male hearts, we found 9 proteins with a significant decrease and 12 proteins with a significant increase. We also found an increase in S-glutathionylation of endothelial nitric oxide synthase in failing female versus male hearts, suggesting an increase in uncoupled nitric oxide synthase in female hearts.

CONCLUSION

These findings highlight the importance of nitroso-redox signaling in both physiological and pathological conditions, suggesting a potential target to treat heart failure.

Genetics of Human and Canine Dilated Cardiomyopathy

Cardiovascular disease is a leading cause of death in both humans and dogs. Dilated cardiomyopathy (DCM) accounts for a large number of these cases, reported to be the third most common form of cardiac disease in humans and the second most common in dogs. In human studies of DCM there are more than 50 genetic loci associated with the disease. Despite canine DCM having similar disease progression to human DCM studies into the genetic basis of canine DCM lag far behind those of human DCM. In this review the aetiology, epidemiology, and clinical characteristics of canine DCM are examined, along with highlighting possible different subtypes of canine DCM and their potential relevance to human DCM. Finally the current position of genetic research into canine and human DCM, including the genetic loci, is identified and the reasons many studies may have failed to find a genetic association with canine DCM are reviewed.

Novel linkage of LMNA Single Nucleotide Polymorphism with Dilated Cardiomyopathy in an Indian case study

BACKGROUND

Dilated Cardiomyopathy (DCM) is one of the most commonly encountered heart diseases reported globally. It is characterized by enlarged ventricles with impaired systolic and diastolic functions. Mutations in LMNA gene are one of the causative factors to precipitate the disease. However, association of SNPs of LMNA with DCM in particular has not been well documented.

METHOD

Here we present a limited and restricted case study of patients from south eastern part of India afflicted with idiopathic DCM and conduction defects. By using next generation sequencing we have sequenced the exons of LMNA gene from genomic DNA isolated from patients.

RESULT

We have identified the linkage of 8 different LMNA SNPs with idiopathic DCM viz. rs121117552, rs538089, rs505058, rs4641, rs646840, rs534807, rs80356803 and rs7339. These SNPs are scattered throughout the gene with prevalence for the region encoding the central rod domain of lamin A/C.

CONCLUSION

Most of these SNPs in LMNA were previously reported to be involved in various disorders other than DCM. We conclude that, variation in LMNA is one of the major underlying genetic causes for the pathogenesis of DCM, as observed in few Indian populations.

Future translational applications from the contemporary genomics era: a scientific statement from the American Heart Association

The field of genetics and genomics has advanced considerably with the achievement of recent milestones encompassing the identification of many loci for cardiovascular disease and variable drug responses. Despite this achievement, a gap exists in the understanding and advancement to meaningful translation that directly affects disease prevention and clinical care. The purpose of this scientific statement is to address the gap between genetic discoveries and their practical application to cardiovascular clinical care. In brief, this scientific statement assesses the current timeline for effective translation of basic discoveries to clinical advances, highlighting past successes. Current discoveries in the area of genetics and genomics are covered next, followed by future expectations, tools, and competencies for achieving the goal of improving clinical care.

The role of post-translational modifications in acute and chronic cardiovascular disease

Cardiovascular disease (CVD) in one of the leading causes of mortality and morbidity worldwide, accounting for both primary diseases of the heart and vasculature and arising as a co-morbidity with numerous pathologies, including type 2 diabetes mellitus (T2DM). There has been significant emphasis on the role of the genome in CVD, aiding in the definition of 'at-risk' patients. The extent of disease penetrance however, can be influenced by environmental factors that are not detectable by investigating the genome alone. By targeting the transcriptome in response to CVD, the interplay between genome and environment is more apparent, however this implies the level of protein expression without reference to proteolytic turnover, or potentially more importantly, without defining the role of PTMs in the development of disease. Here, we discuss the role of both brief and irreversible PTMs in the setting of myocardial ischemia/reperfusion injury. Key proteins involved in calcium regulation have been observed as differentially modified by phosphorylation/O-GlcNAcylation or phosphorylation/redox modifications, with the level of interplay dependent on the physiological or pathophysiological state. The ability to modify crucial sites to produce the desired functional output is modulated by the presence of other PTMs as exemplified in the T2DM heart, where hyperglycemia results in aberrant O-GlcNAcylation and advanced glycation end products. By using the signalling events predicted to be critical to post-conditioning, an intervention with great promise for the cardioprotection of the ischemia/reperfusion injured heart, as an example, we discuss the level of PTMs and their interplay. The inability of post-conditioning to protect the diabetic heart may be regulated by aberrant PTMs influencing those sites necessary for protection.

Decreased levels of BAG3 in a family with a rare variant and in idiopathic dilated cardiomyopathy

The most common cause of dilated cardiomyopathy and heart failure (HF) is ischemic heart disease; however, in a third of all patients the cause remains undefined and patients are diagnosed as having idiopathic dilated cardiomyopathy (IDC). Recent studies suggest that many patients with IDC have a family history of HF and rare genetic variants in over 35 genes have been shown to be causative of disease. We employed whole-exome sequencing to identify the causative variant in a large family with autosomal dominant transmission of dilated cardiomyopathy. Sequencing and subsequent informatics revealed a novel 10-nucleotide deletion in the BCL2-associated athanogene 3 (BAG3) gene (Ch10:del 121436332_12143641: del. 1266_1275 [NM 004281]) that segregated with all affected individuals. The deletion predicted a shift in the reading frame with the resultant deletion of 135 amino acids from the C-terminal end of the protein. Consistent with genetic variants in genes encoding other sarcomeric proteins there was a considerable amount of genetic heterogeneity in the affected family members. Interestingly, we also found that the levels of BAG3 protein were significantly reduced in the hearts from unrelated patients with end-stage HF undergoing cardiac transplantation when compared with non-failing controls. Diminished levels of BAG3 protein may be associated with both familial and non-familial forms of dilated cardiomyopathy.

Inherited cardiomyopathies

Cardiomyopathies (ie, diseases of the heart muscle) are major causes of morbidity and mortality. A significant percentage of patients with cardiomyopathies have genetic-based, inheritable disease and, over the past 2 decades the genetic causes of these disorders have been increasingly discovered. The genes causing these disorders when they are mutated appear to encode proteins that frame a "final common pathway" for that specific disorder, but the specifics of the phenotype, including age of onset, severity, and outcome is variable for reasons not yet understood. The "final common pathways" for the classified forms of cardiomyopathy include the sarcomere in the primarily diastolic dysfunction disorders hypertrophic cardiomyopathy and restrictive cardiomyopathy, the linkage of the sarcomere and sarcolemma in the systolic dysfunction disorder dilated cardiomyopathy, and the desmosome in arrhythmogenic cardiomyopathy. Left ventricular noncompaction cardiomyopathy (LVNC) is an overlap disorder and it appears that any of these "final common pathways" can be involved depending on the specific form of LVNC. The genetics and mechanisms responsible for these clinical phenotypes will be described.

Adult genetic risk screening

Recent advances in genetic analysis especially DNA sequencing technology open a new strategy for adult disease prevention by genetic screening. Physicians presently treat disease pathology with less emphasis on disease risk prevention/reduction. Genetic screening has reduced the incidence of untreatable childhood genetic diseases and improved the care of newborns. The opportunity exists to expand screening programs and reduce the incidence of adult onset diseases via genetic risk identification and disease intervention. This article outlines the approach, challenges, and benefits of such screening for adult genetic disease risks.