Objectives This study aimed to identify the genetic defect in a family with idiopathic ventricular fibrillation (IVF) manifesting in childhood and adolescence. Background Although sudden cardiac ...death in the young is rare, it frequently presents as the first clinical manifestation of an underlying inherited arrhythmia syndrome. Gene discovery for IVF is important as it enables the identification of individuals at risk, because except for arrhythmia, IVF does not manifest with identifiable clinical abnormalities. Methods Exome sequencing was carried out on 2 family members who were both successfully resuscitated from a cardiac arrest. Results We characterized a family presenting with a history of ventricular fibrillation (VF) and sudden death without electrocardiographic or echocardiographic abnormalities at rest. Two siblings died suddenly at the ages of 9 and 10 years, and another 2 were resuscitated from out-of-hospital cardiac arrest with documented VF at ages 10 and 16 years, respectively. Exome sequencing identified a missense mutation affecting a highly conserved residue (p.F90L) in the CALM1 gene encoding calmodulin. This mutation was also carried by 1 of the siblings who died suddenly, from whom DNA was available. The mutation was present in the mother and in another sibling, both asymptomatic but displaying a marginally prolonged QT interval during exercise. Conclusions We identified a mutation in CALM1 underlying IVF manifesting in childhood and adolescence. The causality of the mutation is supported by previous studies demonstrating that F90 mediates the direct interaction of CaM with target peptides. Our approach highlights the utility of exome sequencing in uncovering the genetic defect even in families with a small number of affected individuals.
Abstract Background Familial forms of primary sinus bradycardia have sometimes been attributed to mutations in HCN4 , SCN5A , and ANK2 . In these studies, no structural cardiac alterations were ...reported in mutation carriers. However, a cluster of reports in the literature describe patients presenting with sinus bradycardia in association with left ventricular noncompaction cardiomyopathy (LVNC), pointing to a shared genetic cause. Objectives This study sought to identify the genetic defect underlying the combined clinical presentation of bradycardia and LVNC, hypothesizing that these 2 clinical abnormalities have a common genetic cause. Methods Exome sequencing was carried out in 2 cousins from the index family that were affected by the combined bradycardia–LVNC phenotype; shared variants thus identified were subsequently overlaid with the chromosomal regions shared among 5 affected family members that were identified using single nucleotide polymorphism array analysis. Results The combined linkage analysis and exome sequencing in the index family identified 11 novel variants shared among the 2 affected cousins. One of these, p.Gly482Arg in HCN4, segregated with the combined bradycardia and LVNC phenotype in the entire family. Subsequent screening of HCN4 in 3 additional families with the same clinical combination of bradycardia and LVNC identified HCN4 mutations in each. In electrophysiological studies, all found HCN4 mutations showed a more negative voltage dependence of activation, consistent with the observed bradycardia. Conclusions Although mutations in HCN4 have been previously linked to bradycardia, our study provides the first evidence to our knowledge that mutations in this ion channel gene also may be associated with structural abnormalities of the myocardium.
Abstract Background Sudden arrhythmic death syndrome (SADS) describes a sudden death with negative autopsy and toxicological analysis. Cardiac genetic disease is a likely etiology. Objectives This ...study investigated the clinical utility and combined yield of post-mortem genetic testing (molecular autopsy) in cases of SADS and comprehensive clinical evaluation of surviving relatives. Methods We evaluated 302 expertly validated SADS cases with suitable DNA (median age: 24 years; 65% males) who underwent next-generation sequencing using an extended panel of 77 primary electrical disorder and cardiomyopathy genes. Pathogenic and likely pathogenic variants were classified using American College of Medical Genetics (ACMG) consensus guidelines. The yield of combined molecular autopsy and clinical evaluation in 82 surviving families was evaluated. A gene-level rare variant association analysis was conducted in SADS cases versus controls. Results A clinically actionable pathogenic or likely pathogenic variant was identified in 40 of 302 cases (13%). The main etiologies established were catecholaminergic polymorphic ventricular tachycardia and long QT syndrome (17 6% and 11 4%, respectively). Gene-based rare variants association analysis showed enrichment of rare predicted deleterious variants in RYR2 (p = 5 × 10-5 ). Combining molecular autopsy with clinical evaluation in surviving families increased diagnostic yield from 26% to 39%. Conclusions Molecular autopsy for electrical disorder and cardiomyopathy genes, using ACMG guidelines for variant classification, identified a modest but realistic yield in SADS. Our data highlighted the predominant role of catecholaminergic polymorphic ventricular tachycardia and long QT syndrome, especially the RYR2 gene, as well as the minimal yield from other genes. Furthermore, we showed the enhanced utility of combined clinical and genetic evaluation.
52 Genetic Loci Influencing Myocardial Mass van der Harst, Pim, MD, PhD; Verweij, Niek, PhD; Vogler, Georg, PhD ...
Journal of the American College of Cardiology,
09/2016, Letnik:
68, Številka:
13
Journal Article
Recenzirano
Odprti dostop
Abstract Background Myocardial mass is a key determinant of cardiac muscle function and hypertrophy. Myocardial depolarization leading to cardiac muscle contraction is reflected by the amplitude and ...duration of the QRS complex on the electrocardiogram (ECG). Abnormal QRS amplitude or duration reflect changes in myocardial mass and conduction, and are associated with increased risk of heart failure and death. Objectives This meta-analysis sought to gain insights into the genetic determinants of myocardial mass. Methods We carried out a genome-wide association meta-analysis of 4 QRS traits in up to 73,518 individuals of European ancestry, followed by extensive biological and functional assessment. Results We identified 52 genomic loci, of which 32 are novel, that are reliably associated with 1 or more QRS phenotypes at p < 1 × 10−8 . These loci are enriched in regions of open chromatin, histone modifications, and transcription factor binding, suggesting that they represent regions of the genome that are actively transcribed in the human heart. Pathway analyses provided evidence that these loci play a role in cardiac hypertrophy. We further highlighted 67 candidate genes at the identified loci that are preferentially expressed in cardiac tissue and associated with cardiac abnormalities in Drosophila melanogaster and Mus musculus . We validated the regulatory function of a novel variant in the SCN5A/SCN10A locus in vitro and in vivo. Conclusions Taken together, our findings provide new insights into genes and biological pathways controlling myocardial mass and may help identify novel therapeutic targets.
Patients carrying loss-of-function SCN5A mutations linked to Brugada syndrome (BrS) or progressive cardiac conduction disease (PCCD) are at risk of sudden cardiac death at a young age. The penetrance ...and expressivity of the disease are highly variable, and new tools for risk stratification are needed.
We aimed to establish whether the type of SCN5A mutation correlates with the clinical and electrocardiographic phenotype.
We studied BrS or PCCD probands and their relatives who carried a SCN5A mutation. Mutations were divided into 2 main groups: missense mutations (M) or mutations leading to premature truncation of the protein (T). The M group was subdivided according to available biophysical properties: M mutations with <or=90% (M(active)) or >90% (M(inactive)) peak I(Na) reduction were analyzed separately.
The study group was composed of 147 individuals with 32 different mutations. No differences in age and sex distribution were found between the groups. Subjects carrying a T mutation had significantly more syncopes than those with an M(active) mutation (19 of 75 versus 2 of 35, P = .03). Also, mutations associated with drastic peak I(Na) reduction (T and M(inactive) mutants) had a significantly longer PR interval, compared with M(active) mutations. All other electrocardiographic parameters were comparable. After drug provocation testing, both PR and QRS intervals were significantly longer in the T and M(inactive) groups than in the M(active) group.
In loss-of-function SCN5A channelopathies, patients carrying T and M(inactive) mutations develop a more severe phenotype than those with M(active) mutations. This is associated with more severe conduction disorders. This is the first time that genetic data are proposed for risk stratification in BrS.
Dilation of the ascending aorta was detected in 20 of 26 (77%) HCN4 mutation-positive patients in whom we could obtain images with diagnostic quality sufficient to assess the ascending aorta. Because ...our data suggested that dilation of the aorta in HCN4 mutation carriers displays an age-dependent penetrance, this was subsequently tested. Because aortic diameter is correlated with age in the general population (where the aortic diameter increases with 0.19 mm/year; p < 2e-16) (4) we used a multiple regression model to assess whether there was an additive effect of HCN4 mutation carriership on increase in aortic dilation with increasing age. ...we here report on multiple families harboring HCN4 mutations, who show significant dilation of the aorta ascendens, besides the recently established combined phenotype of bradycardia, NCCM, and mitral valve disease.
The Brugada sign has been associated with mutations in SCN5A and with right ventricular structural abnormalities. Their role in the Brugada sign and the associated ventricular arrhythmias is unknown.
...The purpose of this study was to delineate the role of structural abnormalities and sodium channel dysfunction in the Brugada sign.
Activation and repolarization characteristics of the explanted heart of a patient with a loss-of-function mutation in SCN5A (G752R) and dilated cardiomyopathy were determined after induction of right-sided ST-segment elevation by ajmaline. In addition, right ventricular structural discontinuities and sodium channel dysfunction were simulated in a computer model encompassing the heart and thorax.
In the explanted heart, disappearance of local activation in unipolar electrograms at the basal right ventricular epicardium was followed by monophasic ST-segment elevation. The local origin of this phenomenon was confirmed by coaxial electrograms. Neither early repolarization nor late activation correlated with ST-segment elevation. At sites of local ST-segment elevation, the subepicardium was interspersed with adipose tissue and contained more fibrous tissue than either the left ventricle or control hearts. In computer simulations entailing right ventricular structural discontinuities, reduction of sodium channel conductance or size of the gaps between introduced barriers resulted in subepicardial excitation failure or delayed activation by current-to-load mismatch and in the Brugada sign on the ECG.
Right ventricular excitation failure and activation delay by current-to-load mismatch in the subepicardium can cause the Brugada sign. Therefore, current-to-load mismatch may underlie the ventricular arrhythmias in patients with the Brugada sign.
Objectives The aim of this study was to investigate the modulatory effect of the coxsackie and adenovirus receptor (CAR) on ventricular conduction and arrhythmia vulnerability in the setting of ...myocardial ischemia. Background A heritable component in the risk of ventricular fibrillation during myocardial infarction has been well established. A recent genome-wide association study of ventricular fibrillation during acute myocardial infarction led to the identification of a locus on chromosome 21q21 (rs2824292) in the vicinity of the CXADR gene. CXADR encodes the CAR, a cell adhesion molecule predominantly located at the intercalated disks of the cardiomyocyte. Methods The correlation between CAR transcript levels and rs2824292 genotype was investigated in human left ventricular samples. Electrophysiological studies and molecular analyses were performed using CAR haploinsufficient (CAR+/− ) mice. Results In human left ventricular samples, the risk allele at the chr21q21 genome-wide association study locus was associated with lower CXADR messenger ribonucleic acid levels, suggesting that decreased cardiac levels of CAR predispose to ischemia-induced ventricular fibrillation. Hearts from CAR+/− mice displayed slowing of ventricular conduction in addition to an earlier onset of ventricular arrhythmias during the early phase of acute myocardial ischemia after ligation of the left anterior descending artery. Expression and distribution of connexin 43 were unaffected, but CAR+/− hearts displayed increased arrhythmia susceptibility on pharmacological electrical uncoupling. Patch-clamp analysis of isolated CAR+/− myocytes showed reduced sodium current magnitude specifically at the intercalated disk. Moreover, CAR coprecipitated with NaV 1.5 in vitro, suggesting that CAR affects sodium channel function through a physical interaction with NaV 1.5. Conclusions CAR is a novel modifier of ventricular conduction and arrhythmia vulnerability in the setting of myocardial ischemia. Genetic determinants of arrhythmia susceptibility (such as CAR) may constitute future targets for risk stratification of potentially lethal ventricular arrhythmias in patients with coronary artery disease.
Abstract We present a family from a founder population referred to cardiogenetic evaluation for atrioventricular block in three siblings. Genetic testing including whole-exome sequencing did not ...identify a disease-causing mutation. After reconsidering the differential diagnosis, a non-genetic cause was identified. This case highlights the importance of a thorough clinical evaluation even when a genetic etiology is seemingly obvious.
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