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ABSTRACT A new formulation is proposed for the electrical potential developed inside a horizontally-layered half-space for a direct current point-source at the surface. The recursion formula for the kernel coefficient in the potential integral is simpler than the generally used two-coefficient recursion. The numerical difficulties that may occur during the computation of the integrals and near the source axis are examined and solutions are proposed. The set of equations permits a stable and accurate computation of the tabular potential everywhere in the medium. [ABSTRACT FROM AUTHOR]

Mutations in ion channels involved in the generation and termination of action potentials constitute a family of molecular defects that underlie fatal cardiac arrhythmias in inherited long-QT syndrome. We report here that a loss-of-function (E1425G) mutation in ankyrin-B (also known as ankyrin 2), a member of a family of versatile membrane adapters, causes dominantly inherited type 4 long-QT cardiac arrhythmia in humans. Mice heterozygous for a null mutation in ankyrin-B are haploinsufficient and display arrhythmia similar to humans. Mutation of ankyrin-B results in disruption in the cellular organization of the sodium pump, the sodium/calcium exchanger, and inositol-1,4,5-trisphosphate receptors (all ankyrin-B-binding proteins), which reduces the targeting of these proteins to the transverse tubules as well as reducing overall protein level. Ankyrin-B mutation also leads to altered Ca2+ signalling in adult cardiomyocytes that results in extrasystoles, and provides a rationale for the arrhythmia. Thus, we identify a new mechanism for cardiac arrhythmia due to abnormal coordination of multiple functionally related ion channels and transporters. [ABSTRACT FROM AUTHOR]

Discusses the application of Bayesian inference to DC resistivity inversion for 1-D multilayer models. Exploration of the posterior distribution through Markov process; Focus on the main properties of the methods theoretical example; Illustration of methods capabilities from various context.

Reports on mutations in the gene encoding the homeobox transcription factor NKX2-5 that were found to cause nonsyndromic, human congenital heart disease. Three different NKX2-5 mutations that were identified; Indications of data that NKX2-5 is important for regulation of septation during cardiac morphogenesis and for maturation and maintenance of atrioventricular node function throughout life.

Defines progressive cardiac conduction defect (PCCD) or Lenegre of Lev disease, as one of the most common cardiac disturbances. Identification of the SCN5A as the first gene whose mutation causes an isolated cardiac conduction defect; Use of a genetic approach in a French family in which Lenegre-Lev disease was diagnosed; Increase in the conduction defect of patients in severity with age.

Aims Degenerative mitral valve dystrophy (MVD) leading to mitral valve prolapse is the most frequent form of MV disease, and there is currently no pharmacological treatment available. The limited understanding of the pathophysiological mechanisms leading to MVD limits our ability to identify therapeutic targets. This study aimed to reveal the main pathophysiological pathways involved in MVD via the multimodality imaging and transcriptomic analysis of the new and unique knock-in (KI) rat model for the FilaminA-P637Q (FlnA-P637Q) mutation associated-MVD. Methods and results Wild-type (WT) and KI rats were evaluated morphologically, functionally, and histologically between 3-week-old and 3-to-6-month-old based on Doppler echocardiography, 3D micro-computed tomography (microCT), and standard histology. RNA-sequencing and Assay for Transposase-Accessible Chromatin (ATAC-seq) were performed on 3-week-old WT and KI mitral valves and valvular cells, respectively, to highlight the main signalling pathways associated with MVD. Echocardiographic exploration confirmed MV elongation (2.0 ± 0.1 mm vs. 1.8 ± 0.1, P = 0.001), as well as MV thickening and prolapse in KI animals compared to WT at 3 weeks. 3D MV volume quantified by microCT was significantly increased in KI animals (+58% vs. WT, P = 0.02). Histological analyses revealed a myxomatous remodelling in KI MV characterized by proteoglycans accumulation. A persistent phenotype was observed in adult KI rats. Signalling pathways related to extracellular matrix homeostasis, response to molecular stress, epithelial cell migration, endothelial to mesenchymal transition, chemotaxis and immune cell migration, were identified based on RNA-seq analysis. ATAC-seq analysis points to the critical role of transforming growth factor-β and inflammation in the disease. Conclusion The KI FlnA-P637Q rat model mimics human myxomatous MVD, offering a unique opportunity to decipher pathophysiological mechanisms related to this disease. Extracellular matrix organization, epithelial cell migration, response to mechanical stress, and a central contribution of immune cells are highlighted as the main signalling pathways leading to myxomatous MVD. Our findings pave the road to decipher underlying molecular mechanisms and the specific role of distinct cell populations in this context. [ABSTRACT FROM AUTHOR]

Although a familial component of calcific aortic valve stenosis (CAVS) has been described, its heritability remains unknown. Hence, we aim to assess the heritability of CAVS and the prevalence of bicuspid aortic valve among CAVS families. Probands were recruited following aortic valve replacement (AVR) for severe CAVS on either tricuspid (TAV) or bicuspid aortic valve (BAV). After screening, relatives underwent a Doppler-echocardiography to assess the aortic valve morphology as well as the presence and severity of CAVS. Families were classified in two types according to proband's aortic valve phenotype: TAV or BAV families. Control families were recruited and screened for the presence of BAV. Among the 2371 relatives from 138 CAVS families (pedigree cohort), heritability of CAVS was significant (h2 = 0.47, p < 0.0001), in TAV (h2 = 0.49, p < 0.0001) and BAV families (h2 = 0.50, p < 0.0001). The prevalence of BAV in 790 relatives (phenotype cohort) was significantly increased in both TAV and BAV families compared to control families with a prevalence ratio of 2.6 ([95%CI:1.4–5.9]; p = 0.005) and 4.6 ([95%CI:2.4–13.4]; p < 0.0001), respectively. At least one relative had a BAV in 22.2% of tricuspid CAVS families. Our study confirms the heritability of CAVS in both TAV and BAV families, suggesting a genetic background of this frequent valvular disease. In addition, BAV enrichment in TAV families suggests an interplay between tricuspid CAVS and BAV. Overall results support the need to improve phenotyping (i.e. BAV, TAV, risk factors) in CAVS families in order to enhance the identification of rare and causal genetic variants of CAVS. Clinical Trials Identifier: NCT02890407. • Heritability of CAVS was significant, reinforcing the hypothesis of a genetic background • The enrichment of BAV phenotype in relatives of tricuspid CAVS was significant. • The results support the need to improve phenotyping in CAVS families to enhance the identification of genetic variants of CAVS. • The clinicians should be aware of the heritability of CAVS for questioning patients about familial history of CAVS. [ABSTRACT FROM AUTHOR]

Background: Estimating relatedness is an important step for many genetic study designs. A variety of methods for estimating coefficients of pairwise relatedness from genotype data have been proposed. Both the kinship coefficient φ and the fraternity coefficient ψ for all pairs of individuals are of interest. However, when dealing with low-depth sequencing or imputation data, individual level genotypes cannot be confidently called. To ignore such uncertainty is known to result in biased estimates. Accordingly, methods have recently been developed to estimate kinship from uncertain genotypes. Results: We present new method-of-moment estimators of both the coefficients φ and ψ calculated directly from genotype likelihoods. We have simulated low-depth genetic data for a sample of individuals with extensive relatedness by using the complex pedigree of the known genetic isolates of Cilento in South Italy. Through this simulation, we explore the behaviour of our estimators, demonstrate their properties, and show advantages over alternative methods. A demonstration of our method is given for a sample of 150 French individuals with down-sampled sequencing data. Conclusions: We find that our method can provide accurate relatedness estimates whilst holding advantages over existing methods in terms of robustness, independence from external software, and required computation time. The method presented in this paper is referred to as LowKi (Low-depth Kinship) and has been made available in an R package (https://github.com/genostats/LowKi). [ABSTRACT FROM AUTHOR]

Abstract: Recent findings illustrate a critical role for ankyrin-B function in normal cardiovascular physiology. Specifically, decreased expression of ankyrin-B in mice or human mutations in the ankyrin-B gene (ANK2) results in potentially fatal cardiac arrhythmias. Despite the clear role of ankyrin-B in heart, the mechanisms underlying transcriptional regulation of ANK2 are unknown. In fact, to date there is no description of ANK2 genomic organization. The aims of this study were to provide a comprehensive description of the ANK2 gene and to evaluate the relative expression of alternative splicing events associated with ANK2 transcription in heart. Using reverse-transcriptase PCR on mRNA isolated from human hearts, we identify seven new exons associated with the ANK2 gene including an alternative first exon located ∼145 kb upstream of the previously-identified first exon. In addition, we identify over thirty alternative splicing events associated with ANK2 mRNA transcripts. Using real-time PCR and exon boundary-spanning primers to selectively amplify these splice variants, we demonstrate that these variants are expressed at varying levels in human heart. Finally, ankyrin-B immunoblot analysis demonstrates the expression of a heterogeneous population of ankyrin-B polypeptides in heart. ANK2 consists of 53 exons that span ∼560 kb on human chromosome 4. Additionally, our data demonstrates that ANK2 is subject to complex transcriptional regulation that likely results in differential ankyrin-B polypeptide function. [Copyright &y& Elsevier]

Background and aims: Mutations in KCNH2 cause long or short QT syndromes (LQTS or SQTS) predisposing to life‐threatening arrhythmias. Over 1000 hERG variants have been described by clinicians, but most remain to be characterised. The objective is to standardise and accelerate the phenotyping process to contribute to clinician diagnosis and patient counselling. In silico evaluation was also included to characterise the structural impact of the variants. Methods: We selected 11 variants from known LQTS patients and two variants for which diagnosis was problematic. Using the Gibson assembly strategy, we efficiently introduced mutations in hERG cDNA despite GC‐rich sequences. A pH‐sensitive fluorescent tag was fused to hERG for efficient evaluation of channel trafficking. An optimised 35‐s patch‐clamp protocol was developed to evaluate hERG channel activity in transfected cells. R software was used to speed up analyses. Results: In the present work, we observed a good correlation between cell surface expression, assessed by the pH‐sensitive tag, and current densities. Also, we showed that the new biophysical protocol allows a significant gain of time in recording ion channel properties and provides extensive information on WT and variant channel biophysical parameters, that can all be recapitulated in a single parameter defined herein as the repolarisation power. The impacts of the variants on channel structure were also reported where structural information was available. These three readouts (trafficking, repolarisation power and structural impact) define three pathogenicity indexes that may help clinical diagnosis. Conclusions: Fast‐track characterisation of KCNH2 genetic variants shows its relevance to discriminate mutants that affect hERG channel activity from variants with undetectable effects. It also helped the diagnosis of two new variants. This information is meant to fill a patient database, as a basis for personalised medicine. The next steps will be to further accelerate the process using an automated patch‐clamp system. [ABSTRACT FROM AUTHOR]

Global cellular electrophysiological phenotype was then evaluated with action potential (AP) recordings, but no AP basal parameters specifically segregated BrS hiPSC-CMs, and spontaneous beating frequencies did not differ between all cell lines (Figure S4). Brugada syndrome (BrS) is an inherited arrhythmic disease predisposing to sudden cardiac death (SCD), characterized by a typical electrocardiogram pattern that includes a J point elevation with a coved type ST segment.1 BrS is a complex genetic disease in which ~20% of patients carry rare variants in I SCN5A i gene, whereas the others remain genetically unresolved.2 Despite this genetic complexity, we hypothesize that a common cellular phenotypic trait is at the root of this specific BrS ECG pattern. Importantly, the expression of I SCN5A i , the main BrS culprit gene identified to date,4 remained unchanged, excluding I SCN5A i expression levels as a hallmark for BrS hiPSC-CM phenotype. Early afterdepolarizations (EADs) were observed in 39-70% of all six BrS ventricular-like hiPSC-CMs versus only in 4% and 4.7% of Ctrl and non-BrS hiPSC-CMs, respectively (Figure 3B, Figure S5). [Extracted from the article]

Next-generation sequencing technologies made it possible to assay the effect of rare variants on complex diseases. As an extension of the “common disease-common variant” paradigm, rare variant studies are necessary to get a more complete insight into the genetic architecture of human traits. Association studies of these rare variations show new challenges in terms of statistical analysis. Due to their low frequency, rare variants must be tested by groups. This approach is then hindered by the fact that an unknown proportion of the variants could be neutral. The risk level of a rare variation may be determined by its impact but also by its position in the protein sequence. More generally, the molecular mechanisms underlying the disease architecture may involve specific protein domains or inter-genic regulatory regions. While a large variety of methods are optimizing functionality weights for each single marker, few evaluate variant position differences between cases and controls. Here, we propose a test called DoEstRare, which aims to simultaneously detect clusters of disease risk variants and global allele frequency differences in genomic regions. This test estimates, for cases and controls, variant position densities in the genetic region by a kernel method, weighted by a function of allele frequencies. We compared DoEstRare with previously published strategies through simulation studies as well as re-analysis of real datasets. Based on simulation under various scenarios, DoEstRare was the sole to consistently show highest performance, in terms of type I error and power both when variants were clustered or not. DoEstRare was also applied to Brugada syndrome and early-onset Alzheimer’s disease data and provided complementary results to other existing tests. DoEstRare, by integrating variant position information, gives new opportunities to explain disease susceptibility. DoEstRare is implemented in a user-friendly R package. [ABSTRACT FROM AUTHOR]

The GC-rich Binding Factor 2/Leucine Rich Repeat in the Flightless 1 Interaction Protein 1 gene ( GCF2/LRRFIP1 ) is predicted to be alternatively spliced in five different isoforms. Although important peptide sequence differences are expected to result from this alternative splicing, to date, only the gene transcription regulator properties of LRRFIP1-Iso5 were unveiled. Based on molecular, cellular and biochemical data, we show here that the five isoforms define two molecular entities with different expression profiles in human tissues, subcellular localizations, oligomerization properties and transcription enhancer properties of the canonical Wnt pathway. We demonstrated that LRRFIP1-Iso3, -4 and -5, which share over 80% sequence identity, are primarily located in the cell cytoplasm and form homo and hetero-multimers between each other. In contrast, LRRFIP1-Iso1 and -2 are primarily located in the cell nucleus in part thanks to their shared C-terminal domain. Furthermore, we showed that LRRFIP1-Iso1 is preferentially expressed in the myocardium and skeletal muscle. Using the in vitro Topflash reporter assay we revealed that among LRRFIP1 isoforms, LRRFIP1-Iso1 is the strongest enhancer of the β-catenin Wnt canonical transcription pathway thanks to a specific N-terminal domain harboring two critical tryptophan residues (W76, 82). In addition, we showed that the Wnt enhancer properties of LRRFIP1-Iso1 depend on its homo-dimerisation which is governed by its specific coiled coil domain. Together our study identified LRRFIP1-Iso1 as a critical regulator of the Wnt canonical pathway with a potential role in myocyte differentiation and myogenesis. [ABSTRACT FROM AUTHOR]

Background: Long QT syndrome (LQTS) is an inherited arrhythmic disorder characterized by prolongation of the QT interval, a risk of syncope, and sudden death. There are already a number of causal genes in LQTS, but not all LQTS patients have an identified mutation, which suggests LQTS unknown genes. Methods: A cohort of 178 LQTS patients, with no mutations in the 3 major LQTS genes (KCNQ1, KCNH2, and SCN5A), was screened for mutations in the transient potential melastatin 4 gene (TRPM4). Results: Four TRPM4 variants (2.2% of the cohort) were found to change highly conserved amino-acids and were either very rare or absent from control populations. Therefore, these four TRPM4 variants were predicted to be disease causing. Furthermore, no mutations were found in the DNA of these TRPM4 variant carriers in any of the 13 major long QT syndrome genes. Two of these variants were further studied by electrophysiology (p.Val441Met and p.Arg499Pro). Both variants showed a classical TRPM4 outward rectifying current, but the current was reduced by 61 and 90% respectively, compared to wild type TRPM4 current. Conclusions: This study supports the view that TRPM4 could account for a small percentage of LQTS patients. TRPM4 contribution to the QT interval might be multifactorial by modulating whole cell current but also, as shown in Trpm4-/-mice, by modulating cardiomyocyte proliferation. TRPM4 enlarges the subgroup of LQT genes (KCNJ2 in Andersen syndrome and CACNA1C in Timothy syndrome) known to increase the QT interval through a more complex pleiotropic effect than merely action potential alteration. [ABSTRACT FROM AUTHOR]

Background and aims Familial hypobetalipoproteinemia (FHBL) is a co-dominant disorder characterized by decreased plasma levels of LDL-cholesterol and apolipoprotein B (ApoB). Currently, genetic diagnosis in FHBL relies largely on Sanger sequencing to identify APOB and PCSK9 gene mutations and on western blotting to detect truncated ApoB species. Methods Here, we applied targeted enrichment and next-generation sequencing (NGS) on a panel of three FHBL genes and two abetalipoproteinemia genes ( APOB, PCSK9, ANGPTL3, MTTP and SAR1B ). Results In this study, we identified five likely pathogenic heterozygous rare variants. These include four novel nonsense mutations in APOB (p.Gln845*, p.Gln2571*, p.Cys2933* and p.Ser3718*) and a rare variant in PCSK9 (Minor Allele Frequency <0.1%). The affected family members tested were shown to be carriers, suggesting co-segregation with low LDL-C. Conclusions Our study further demonstrates that NGS is a reliable and practical approach for the molecular screening of FHBL-causative genes that may provide a mean for deciphering the genetic basis in FHBL. [ABSTRACT FROM AUTHOR]

The difficulties arising from association analysis with rare variants underline the importance of suitable reference population cohorts, which integrate detailed spatial information. We analyzed a sample of 1684 individuals from Western France, who were genotyped at genome-wide level, from two cohorts D.E.S.I.R and CavsGen. We found that fine-scale population structure occurs at the scale of Western France, with distinct admixture proportions for individuals originating from the Brittany Region and the Vendée Department. Genetic differentiation increases with distance at a high rate in these two parts of Northwestern France and linkage disequilibrium is higher in Brittany suggesting a lower effective population size. When looking for genomic regions informative about Breton origin, we found two prominent associated regions that include the lactase region and the HLA complex. For both the lactase and the HLA regions, there is a low differentiation between Bretons and Irish, and this is also found at the genome-wide level. At a more refined scale, and within the Pays de la Loire Region, we also found evidence of fine-scale population structure, although principal component analysis showed that individuals from different departments cannot be confidently discriminated. Because of the evidence for fine-scale genetic structure in Western France, we anticipate that rare and geographically localized variants will be identified in future full-sequence analyses. [ABSTRACT FROM AUTHOR]

Aims Intravenous drug challenge is frequently performed to unmask Brugada syndrome (BrS). However, its true sensitivity has never been assessed. We used the obligate BrS transmitters in families affected by BrS to evaluate the true accuracy of drug challenge. Methods All consecutive patients from 2000 to 2014 who underwent drug challenge during familial screening for BrS were included in the study. Obligate BrS transmitters were defined as the presence of a descendant and non-descendant first-degree relative affected by BrS. Two physicians blinded to the clinical and genetic status reviewed the data. Results Among 705 drug challenges performed in 149 families, 50 were performed in obligate transmitters from 42 different families. SCN5A mutations were identified in 20 families. Two obligate transmitters were not carrier of the familial mutation. Based on obligate transmitters, sensitivity was 100% for Ajmaline vs 77% for Flecainide ( P = 0.002). Based on the presence of the familial SCN5A mutation in all family relatives, sensitivity and specificity of sodium channel blocker challenge were respectively 78% (95/122) and 46% (68/148). During a median follow-up of 91 (26–136) months, 2 ventricular fibrillations occurred in obligate transmitters. Conclusion We demonstrated that Ajmaline challenge presents an excellent sensitivity that may rule out the diagnosis of BrS when negative. Conversely, a negative Flecainide challenge may not prevent from Brs inheritance and risk of SCD. This may lead to suggest systematic use of Ajmaline during drug challenge. [ABSTRACT FROM AUTHOR]

Brugada syndrome (BrS) is characterized by ST-segment elevation in the right precordial leads and is associated with increased risk of sudden cardiac death. We have recently reported families with BrS and SCN5A mutations where some affected members do not carry the familial mutation. We evaluated the involvement of additional genetic determinants for BrS in an affected family. We identified three distinct gene variants within a family presenting BrS (5 individuals), cardiac conduction defects (CCD, 3 individuals) and shortened QT interval (4 individuals). The first mutation is nonsense, p.Q1695*, lying within the SCN5A gene, which encodes for NaV1.5, the α-subunit of the cardiac Na+ channel. The second mutation is missense, p.N300D, and alters the CACNA1C gene, which encodes the α-subunit CaV1.2 of the L-type cardiac Ca2+ channel. The SCN5A mutation strictly segregates with CCD. Four out of the 5 BrS patients carry the CACNA1C variant, and three of them present shortened QT interval. One of the BrS patients carries none of these mutations but a rare variant located in the ABCC9 gene as well as his asymptomatic mother. Patch-clamp studies identified a loss-of-function of the mutated CaV1.2 channel. Western-blot experiments showed a global expression defect while increased mobility of CaV1.2 channels on cell surface was revealed by FRAP experiments. Finally, computer simulations of the two mutations recapitulated patient phenotypes. We report a rare CACNA1C mutation as causing BrS and/or shortened QT interval in a family also carrying a SCN5A stop mutation, but which does not segregate with BrS. This study underlies the complexity of BrS inheritance and its pre-symptomatic genetic screening interpretation. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to identify families affected by early repolarization syndrome (ERS) and to determine the mode of transmission of the disease. Background: Early repolarization (ER) has recently been linked to idiopathic ventricular fibrillation. Familial inheritance of the disease has been suggested but not demonstrated. Methods: We screened relatives of 4 families affected by ERS. ER was defined as a distinct J-wave in at least 2 consecutive leads and a 1-mm amplitude above baseline. The Valsalva maneuver was performed in affected and unaffected family members to decrease heart rate and thus increase or reveal an ER pattern. Results: Twenty-two sudden cardiac deaths occurred in the 4 families including 10 before 35 years of age. In the 4 families, the prevalence of ER was 56%, 34%, 61%, and 33% of, respectively, 30, 82, 29, and 30 screened relatives. In these families, transmission of an ER pattern is compatible with an autosomal dominant mode of inheritance. All probands were screened for genes identified in ERS, and no mutation was found. The Valsalva maneuver was performed in 80 relatives, resulting in increased J-wave amplitude for 17 of 20 affected patients and revealing an ER pattern in 17 relatives in whom 5 are obligate transmitters of an ER pattern. Conclusions: ERS can be inherited through autosomal dominant transmission and should be considered a real inherited arrhythmia syndrome. Familial investigation can be facilitated by using the Valsalva maneuver to reveal the electrocardiographic pattern in family members. The prognosis value of this test remains to be assessed. [Copyright &y& Elsevier]

Brugada syndrome (BrS) is a condition defined by ST-segment alteration in right precordial leads and a risk of sudden death. Because BrS is often associated with right bundle branch block and the TRPM4 gene is involved in conduction blocks, we screened TRPM4 for anomalies in BrS cases. The DNA of 248 BrS cases with no SCN5A mutations were screened for TRPM4 mutations. Among this cohort, 20 patients had 11 TRPM4 mutations. Two mutations were previously associated with cardiac conduction blocks and 9 were new mutations (5 absent from ~14'000 control alleles and 4 statistically more prevalent in this BrS cohort than in control alleles). In addition to Brugada, three patients had a bifascicular block and 2 had a complete right bundle branch block. Functional and biochemical studies of 4 selected mutants revealed that these mutations resulted in either a decreased expression (p.Pro779Arg and p.Lys914X) or an increased expression (p.Thr873Ile and p.Leu1075Pro) of TRPM4 channel. TRPM4 mutations account for about 6% of BrS. Consequences of these mutations are diverse on channel electrophysiological and cellular expression. Because of its effect on the resting membrane potential, reduction or increase of TRPM4 channel function may both reduce the availability of sodium channel and thus lead to BrS. [ABSTRACT FROM AUTHOR]

Aims We hypothesized that the structure and function of the mature valves is largely dependent upon how these tissues are built during development, and defects in how the valves are built can lead to the pathological progression of a disease phenotype. Thus, we sought to uncover potential developmental origins and mechanistic underpinnings causal to myxomatous mitral valve disease. We focus on how filamin-A, a cytoskeletal binding protein with strong links to human myxomatous valve disease, can function as a regulatory interface to control proper mitral valve development. Methods and results Filamin-A-deficient mice exhibit abnormally enlarged mitral valves during foetal life, which progresses to a myxomatous phenotype by 2 months of age. Through expression studies, in silico modelling, 3D morphometry, biochemical studies, and 3D matrix assays, we demonstrate that the inception of the valve disease occurs during foetal life and can be attributed, in part, to a deficiency of interstitial cells to efficiently organize the extracellular matrix (ECM). This ECM organization during foetal valve gestation is due, in part, to molecular interactions between filamin-A, serotonin, and the cross-linking enzyme, transglutaminase-2 (TG2). Pharmacological and genetic perturbations that inhibit serotonin-TG2-filamin-A interactions lead to impaired ECM remodelling and engender progression to a myxomatous valve phenotype. Conclusions These findings illustrate a molecular mechanism by which valve interstitial cells, through a serotonin, TG, and filamin-A pathway, regulate matrix organization during foetal valve development. Additionally, these data indicate that disrupting key regulatory interactions during valve development can set the stage for the generation of postnatal myxomatous valve disease. [ABSTRACT FROM AUTHOR]

Background-The origin of congenital or childhood nonimmune isolated atrioventricular (AV) block remains unknown. We hypothesized that this conduction abnormality in the young may be a heritable disease. Methods and Results-A multicenter retrospective study (13 French referral centers, from 1980-2009) included 141 children with AV block diagnosed in utero, at birth, or before 15 years of age without structural heart abnormalities and without maternal antibodies. Parents and matched control subjects were investigated for family history and for ECG screening. In parents, a family history of sudden death or progressive cardiac conduction defect was found in 1.4% and 11.1%, respectively. Screening ECGs from 130 parents (mean age 42.0±6.8 years, 57 couples) were compared with those of 130 matched healthy control subjects. All parents were asymptomatic and in sinus rhythm, except for 1 with undetected complete AV block. Conduction abnormalities were more frequent in parents than in control subjects, found in 50.8% versus 4.6%, respectively (P<0.001). A long PR interval was found in 18.5% of the parents but never in control subjects (PcO.OOOl). Complete or incomplete right bundle-branch block was observed in 39.2% of the parents and 1.5% of the control subjects (PC0.0001). Complete or incomplete left bundle-branch block was found in 15.4% of the parents and 3.1% of the control subjects (P<0.0006). Estimated heritability for isolated conduction disturbances was 91% (95% confidence interval, 80%-100%). SCN5A mutation screening identified 2 mutations in 2 patients among 97 children. Conclusions-ECG screening in parents of children affected by idiopathic AV block revealed a high prevalence of conduction abnormalities. These results support the hypothesis of an inheritable trait in congenital and childhood nonimmune isolated AV block. [ABSTRACT FROM AUTHOR]

Introduction Progressive cardiac conduction defect (PCCD) is a frequent disease attributed to degeneration and fibrosis of the His bundle. Over the past years, gene defects have been identified demonstrating that PCCD could be a genetic disease. The aim of this study was to show a familial aggregation for PCCD using a genetic epidemiological approach to improve in fine genetic knowledge of the transmission of the disease. Methods and results Using the French social security number, the authors have been able to determine the city of birth of the 6667 patients implanted with a pacemaker (PM) for PCCD between 1995 and 2005 in the western part of France. The authors then mapped the frequency of PM implantations for PCCD. A large heterogeneity of the frequency of the disease has been observed, with a frequency of 0.21% in the major city (Nantes) ranging up to 2.28% in specific parishes. Familial studies performed in the parishes with the highest frequency of the disease allowed the authors to identify five large families with PCCD. Clinical investigations demonstrated phenotype heterogeneity between families. Three patterns have been differentiated. Conclusions This study demonstrates a disparate geographical repartition of the frequency of PM implantation in the area of the authors at least in part related to a hereditary factor. The identification of five large families affected by PCCD using epidemiological approach underlines the existence of a major genetic background in PCCD. [ABSTRACT FROM AUTHOR]

Background-Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting >2 million patients in the United States alone. Despite decades of research, surprisingly little is known regarding the molecular pathways underlying the pathogenesis of AF. ANK2+ encodes ankyrin-B, a multifunctional adapter molecule implicated in membrane targeting of ion channels, transporters, and signaling molecules in excitable cells. Methods and Results-In the present study, we report early-onset AF in patients harboring loss-of-function mutations in ANK2+. In mice, we show that ankyrin-B deficiency results in atrial electrophysiological dysfunction and increased susceptibility to AF. Moreover, ankyrin-B+/- atrial myocytes display shortened action potentials, consistent with human AF. Ankyrin-B is expressed in atrial myocytes, and we demonstrate its requirement for the membrane targeting and function of a subgroup of voltage-gated Ca2+ channels (Cav 1.3) responsible for low voltage-activated L-type Ca2+ current. Ankyrin-B is associated directly with Cav 1.3, and this interaction is regulated by a short, highly conserved motif specific to Ca2+ 1.3. Moreover, loss of ankyrin-B in atrial myocytes results in decreased Cav 1.3 expression, membrane localization, and function sufficient to produce shortened atrial action potentials and arrhythmias. Finally, we demonstrate reduced ankyrin-B expression in atrial samples of patients with documented AF, further supporting an association between ankyrin-B and AF. Conclusions-These findings support that reduced ankyrin-B expression or mutations in ANK2 are associated with AF. Additionally, our data demonstrate a novel pathway for ankyrin-Bdependent regulation of Cav 1.3 channel membrane targeting and regulation in atrial myocytes. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to investigate, in a set of 93 mutation-negative long QT syndrome (LQTS) probands, the frequency of copy number variants (CNVs) in LQTS genes. Background: LQTS is an inherited cardiac arrhythmia characterized by a prolonged heart rate–corrected QT (QTc) interval associated with sudden cardiac death. Recent studies suggested the involvement of duplications or deletions in the occurrence of LQTS. However, their frequency remains unknown in LQTS patients. Methods: Point mutations in KCNQ1, KCNH2, and SCN5A genes were excluded by denaturing high-performance liquid chromatography or direct sequencing. We applied Multiplex Ligation-dependent Probe Amplification (MLPA) to detect CNVs in exons of these 3 genes. Abnormal exon copy numbers were confirmed by quantitative multiplex PCR of short fluorescent fragment (QMPSF). Array-based comparative genomic hybridization (array CGH) analysis was performed using Agilent Human Genome 244K Microarrays to further map the genomic rearrangements. Results: We identified 3 different deletions in 3 unrelated families: 1 in KCNQ1 and 2 involving KCNH2. We showed in the largest family that the deletion involving KCNH2 is fully penetrant and segregates with the long QT phenotype in 7 affected members. Conclusions: Our study demonstrates that CNVs in KCNQ1 and KCNH2 explain around 3% of LQTS in patients with no point mutation in these genes. This percentage is likely higher than the frequency of point mutations in ANKB, KCNE1, KCNE2, KCNJ2, CACNA1C, CAV3, SCN4B, AKAP9, and SNTA1 together. Thus, we propose that CNV screening in KCNQ1 and KCNH2 may be performed routinely in LQTS patients. [ABSTRACT FROM AUTHOR]

Background: Loss-of-function mutations in SCN5A, the gene encoding Nav1.5 NaP+ channel, are associated with inherited cardiac conduction defects and Brugada syndrome, which both exhibit variable phenotypic penetrance of conduction defects. We investigated the mechanisms of this heterogeneity in a mouse model with heterozygous targeted disruption of Scn5a (Scn5a+/- mice) and compared our results to those obtained in patients with loss-of-function mutations in SCN5A. Methodology/Principal Findings: Based on ECG, 10-week-old Scn5a+/- mice were divided into 2 subgroups, one displaying severe ventricular conduction defects (QRS interval>18 ms) and one a mild phenotype (QRS≤18 ms; QRS in wild-type littermates: 10-18 ms). Phenotypic difference persisted with aging. At 10 weeks, the Na+ channel blocker ajmaline prolonged QRS interval similarly in both groups of Scn5a+/- mice. In contrast, in old mice (>53 weeks), ajmaline effect was larger in the severely affected subgroup. These data matched the clinical observations on patients with SCN5A loss-of-function mutations with either severe or mild conduction defects. Ventricular tachycardia developed in 5/10 old severely affected Scn5a+/- mice but not in mildly affected ones. Correspondingly, symptomatic SCN5A-mutated Brugada patients had more severe conduction defects than asymptomatic patients. Old severely affected Scn5a+/-mice but not mildly affected ones showed extensive cardiac fibrosis. Mildly affected Scn5a+/- mice had similar Nav1.5 mRNA but higher Nav1.5 protein expression, and moderately larger INa current than severely affected Scn5a+/- mice. As a consequence, action potential upstroke velocity was more decreased in severely affected Scn5a+/- mice than in mildly affected ones. Conclusions: Scn5a+/- mice show similar phenotypic heterogeneity as SCN5A-mutated patients. In Scn5a+/- mice, phenotype severity correlates with wild-type Nav1.5 protein expression. [ABSTRACT FROM AUTHOR]

Background: Early repolarization in the inferolateral leads has been recently recognized as a frequent syndrome associated with idiopathic ventricular fibrillation (VF). We report the case of a patient presenting dramatic changes in the ECG in association with recurrent VF in whom a novel genetic variant has been identified. Case Report: This young female (14 years) was resuscitated in 2001 following an episode of sudden death due to VF. All examinations including coronary angiogram with ergonovine injection, MRI, and flecainide or isoproterenol infusion were normal. The patient had multiple (>100) recurrences of VF unresponsive to beta-blockers, lidocaine/mexiletine, verapamil, and amiodarone. Recurrences of VF were associated with massive accentuation of the early repolarization pattern at times mimicking acute myocardial ischemia. Coronary angiography during an episode with 1.2 mV J/ST elevation was normal. Isoproterenol infusion acutely suppressed electrical storms, while quinidine eliminated all recurrences of VF and restored a normal ECG over a follow-up of 65 months. Genomic DNA sequencing of KATP channel genes showed missense variant in exon 3 (NC_000012) of the KCNJ8 gene, a subunit of the KATP channel, conferring predisposition to dramatic repolarization changes and ventricular vulnerability. [ABSTRACT FROM AUTHOR]

The identification of nearly a dozen ion channel genes involved in the genesis of human atrial and ventricular arrhythmias has been critical for the diagnosis and treatment of fatal cardiovascular diseases. In contrast, very little is known about the genetic and molecular mechanisms underlying human sinus node dysfunction (SND). Here, we report a genetic and molecular mechanism for human SND. We mapped two families with highly penetrant and severe SND to the human ANK2 (ankyrin-B/AnkB) locus. Mice heterozygous for AnkB phenocopy human SND displayed severe bradycardia and rate variability. AnkB is essential for normal membrane organization of sinoatrial node cell channels and trans- porters, and AnkB is required for physiological cardiac pacing. Finally, dysfunction in AnkB-based trafficking pathways causes abnormal sinoatrial node (SAN) electrical activity and SND. Together, our findings associate abnormal channel targeting with human SND and highlight the critical role of local membrane organization for sinoatrial node excitability. [ABSTRACT FROM AUTHOR]

Brugada syndrome is a genetic disease associated with sudden cardiac death that is characterized by ventricular fibrillation and right precordial ST segment elevation on ECG. Loss-of-function mutations in SCN5A, which encodes the predominant cardiac sodium channel alpha subunit NaV1.5, can cause Brugada syndrome and cardiac conduction disease. However, SCN5A mutations are not detected in the majority of patients with these syndromes, suggesting that other genes can cause or modify presentation of these disorders. Here, we investigated SCN1B, which encodes the function-modifying sodium channel beta1 subunit, in 282 probands with Brugada syndrome and in 44 patients with conduction disease, none of whom had SCN5A mutations. We identified 3 mutations segregating with arrhythmia in 3 kindreds. Two of these mutations were located in a newly described alternately processed transcript, beta1B. Both the canonical and alternately processed transcripts were expressed in the human heart and were expressed to a greater degree in Purkinje fibers than in heart muscle, consistent with the clinical presentation of conduction disease. Sodium current was lower when NaV1.5 was coexpressed with mutant beta1 or beta1B subunits than when it was coexpressed with WT subunits. These findings implicate SCN1B as a disease gene for human arrhythmia susceptibility. [ABSTRACT FROM AUTHOR]

Introduction: Loss-of-function mutations in the SCN5A gene encoding the cardiac sodium channel are responsible for Brugada syndrome (BS) and also for progressive cardiac conduction disease (inherited Lenègre disease). In an attempt to clarify the frontier between these two entities, we have characterized cardiac conduction defect and its evolution with aging in a cohort of 78 patients carrying a SCN5A mutation linked to Brugada syndrome. Methods and Results: Families were included in the study if a SCN5A mutation was identified in a BS proband and if at least two family members were mutation carriers. Sixteen families met the study criteria, representing 78 carriers. Resting ECG showed a spontaneous BS ECG pattern in 28 of 78 (36%) gene carriers. Intraventricular conduction anomalies were identified in 59 of 78 gene carriers including complete (17) or incomplete (24) right bundle branch block, right bundle branch block plus hemiblock (6), left bundle branch block (1), hemiblock (1), and parietal block (10). PR and QRS duration were longer in the gene carrier cohort in comparison with their relatives carrying no mutation. Finally, in the gene carrier cohort conduction defect progressively aggravated with aging leading in five occasions to pacemaker implantations. Conclusion: The present study shows that the most common phenotype of gene carriers of a BS-type SCN5A mutation is progressive cardiac conduction defects similar to the Lenègre disease phenotype. In consequence, we propose that carriers of a SCN5A mutation need a clinical and ECG follow-up because of the risk associated with severe conduction defects. [ABSTRACT FROM AUTHOR]

Mutations in the SCN5A gene can cause Brugada syndrome, a genetically inherited form of idiopathic ventricular fibrillation. We describe the case of a 3-year-old child with a structurally normal heart presenting with monomorphic ventricular tachycardia. Her electrocardiogram suggested a Brugada syndrome and the diagnosis was confirmed by the identification of a Brugada syndrome in her mother and in two other family members. Genetic study led to the identification of a c.2516T→C SCN5A mutation. The child was treated with quinidine therapy without recurrence of arrhythmic events for a time period of 16 months. [ABSTRACT FROM AUTHOR]

Although mutations in cardiac sodium and potassium channel genes are associated with congenital long QT syndrome (LQTS), a "modifier" role of the sympathetic nervous system was proposed to explain the distinct severity of the disease. We evaluated cardiac sympathetic innervation using [[sup 11]C]hydroxyephedrine ([[sup 11]C]HED) and positron emission tomography (PET) in genotyped LQTS patients. H[sub 2][sup 15]O and [[sup 11]C]HED PET studies were performed in 11 patients (5 symptomatic) and 8 controls. Perfusion and [[sup 11]C]HED images were depicted as 36-sector polar maps. Sectorial values of perfusion (H[sub 2]O[sub %]), absolute (HED[sub Ret]) and relative retention (HED[sub %Ret]) of [[sup 11]C]HED, and the ratio of HED[sub %Ret] to H[sub 2]O% (HED[sub %Ret]H[sub 2]O[sub %]) were calculated. Normal databases were obtained from controls. Sectorial values below 2SD database values were defined as "outside sectors." Controls and patients showed similar sectorial perfusion. Sectorial HEDger did not differ between groups, but means of HED[sub %Ret] were lower in three sectors for patients (P < 0.05). Three sectors from 3 controls had HED[sub %Ret] below 2SD, whereas 36 sectors in 9 patients were outside sectors (P < 0.01). In patients, average HED[sub %Ret/H[sub 2]O[sub %] was lower in 9 sectors (P < 0.05 vs. controls); 2 outside sectors were found in controls, but 43 outside sectors were found in patients (P < 0.01), 77% of them in the 5 symptomatic patients. Heterogeneous [[sup 11]C]HED retention was localized in the septal, anterior, and lateral walls. Most LQTS patients showed a localized and decreased pattern of [[sup 11]C]HED retention. The larger number of heterogeneous sectors in symptomatic patients suggests that sympathetic function could play an amplifier role for severity of the disease. [ABSTRACT FROM AUTHOR]

: ObjectivesThe goal of this study was to investigate the genotype-to-phenotype relationship between SCN5A gene mutation and progressive cardiac conduction defect in order to gain insights into the pathophysiologic mechanisms of the disease.: BackgroundProgressive cardiac conduction defect is a frequent disease commonly attributed to degeneration and fibrosis of the His bundle and its branches. In a French family, we have identified a splicing mutation in the SCN5A gene leading to hereditary progressive cardiac conduction defect.: MethodsWe have extended the size of the pedigree and phenotyped and genotyped all family members, and also investigated in vitro the functional consequences of the mutation.: ResultsAmong 65 potentially affected members, 25 individuals were carriers of the IVS.22+2 T→C SCN5A mutation. In relation to aging, gene carriers exhibit various types of conduction defects. P-wave, PR, and QRS duration increased progressively with age in gene carriers and in noncarriers. Whatever the age, conduction parameters were longer in gene carriers. The widening in the QRS complex with aging was more pronounced in gene carriers older than 40 years. Functional studies show that the IVS.22+2 T→C SCN5A mutation lead to exon 22 skipping and to a complete loss of function of the affected allele, but to a normal trafficking of the mutated gene product.: ConclusionsOur findings demonstrate that hereditary Lene&grave;gre disease is caused by a haploinsufficiency mechanism, which in combination with aging leads to progressive alteration in conduction velocity. [Copyright &y& Elsevier]

SCN5A Mutation and ST Segment Elevation in Inferior Leads. Mutations in the SCN5A gene can lead to the Brugada syndrome, a genetically inherited form of idiopathic ventricular fibrillation that has a characteristic ECG phenotype usually restricted to precordial leads V[sub 1]–V[sub 3]. We identified a novel G752R SCN5A missense mutation leading to various degrees of the Brugada ECG phenotype in members of a French family. In the proband, the G752R mutation produced ST segment elevation and prominent J wave in leads II, III, and aVF. In four other relatives, ST segment elevation in the right precordial but not in the inferior leads was observed either spontaneously or under flecainide challenge. Recombinant G752R mutant exhibited a markedly reduced Na[sup +] current amplitude and a voltage shift in both activation and inactivation curves. The mutant was found in all affected but not in nonaffected family members. One additional gene-carrier had an almost normal ECG (silent gene-carrier). We provide genetic demonstration that Brugada ECG anomalies related to a unique SCN5A mutation can be observed either in the inferior or the right precordial leads. (J Cardiovasc Electrophysiol, Vol. 14, pp. 200-203, February 2003). [ABSTRACT FROM AUTHOR]

: ObjectivesWe have tested whether a genotype-phenotype relationship exists in Brugada syndrome (BS) by trying to distinguish BS patients with (carriers) and those without (non-carriers) a mutation in the gene encoding the cardiac sodium channel (SCN5A) using clinical parameters.: BackgroundBrugada syndrome is an inherited cardiac disease characterized by a varying degree of ST-segment elevation in the right precordial leads and (non)specific conduction disorders. In a minority of patients, SCN5A mutations can be found. Genetic heterogeneity has been demonstrated, but other causally related genes await identification. If a genotype-phenotype relationship exists, this might facilitate screening.: MethodsIn a multi-center study, we have collected data on demographics, clinical history, family history, electrocardiogram (ECG) parameters, His to ventricle interval (HV), and ECG parameters after pharmacologic challenge with INa blocking drugs for BS patients with (n = 23), or those without (n = 54), an identified SCN5A mutation.: ResultsNo differences were found in demographics, clinical history, or family history. Carriers had a significantly longer PQ interval on the baseline ECG and a significantly longer HV time. A PQ interval of ≥210 ms and an HV interval ≥60 ms seem to be predictive for the presence of an SCN5A mutation. After INa blocking drugs, carriers had significantly longer PQ and QRS intervals and more increase in QRS duration.: ConclusionsWe observed significantly longer conduction intervals on baseline ECG in patients with established SCN5A mutations (PQ and HV interval and, upon class I drugs, more QRS increase). These results concur with the observed loss of function of mutated BS-related sodium channels. Brugada syndrome patients with, and those without, an SCN5A mutation can be differentiated by phenotypical differences. [Copyright &y& Elsevier]

A family was identified, of whom which 11 members were carriers of the G14876A ryanodine 2 receptor mutation. All but 1 were symptomatic at the time of the study. Exercise testing showed bidirectional or polymorphic arrhythmias in 4 patients, whereas in 5 patients, it showed monomorphic or rare minor polymorphic ventricular arrhythmias. Two young patients died suddenly at rest while asleep. This study demonstrates that arrhythmias occurring during exercise stress testing in patients affected by catecholaminergic polymorphic ventricular tachycardia (CPVT) could be minor even in very symptomatic patients. The diagnosis of CPVT must be considered in these patients with a familial history of typical CPVT. [Copyright &y& Elsevier]

Background: Filamin-A (FLNA) mutations have been associated with the development of mitral valve prolapse and a unique mitral valve features described as a paradoxical restrictive leaflets motion in diastole has been recently described using a comprehensive echocardiographic screening. Polyvalvular diseases have also been reported in these patients, especially affecting the aortic valve. Objectifs: The objective of this study was to perform a comprehensive echocardiographic analysis of the aortic valve (AV) and the proximal aortic root of patients with FLNA mutations, and assess the impact of the aortic disease on outcomes. Methods: We included in this analysis 256 subjects (42±22 years, 136 men, 76 mutated: FLNA+) with confirmed genetic status, from 5 FLNA families. Comprehensive echocardiographic characterization of the aortic valve and the proximal aortic root, including the measurement of the aortic annulus, sinuses of Valsalva, sinotubular junction and ascending aorta, was performed in FLNA+ patients vs control relatives. Results: Overall, 47 subjects (18%) presented an aortic valve alteration: 40 (53%) of FLNA+ compared to 7 (4%) FLNA- subjects (p<0.001). Among the 76 FLNA+ patients, 7 (9%) had a bicuspid aortic valve phenotype as opposed to 2 (1%) in control relatives (p=0.02). The underlying disease affecting the aortic valve was AV sclerosis, stenosis and AV regurgitation with either prolapse or restricted cusps motion. A restrictive opening of the AV was also reported in some patients. Aortic valve mean gradient was slightly increased in FLNA+ compared with FLNA- subjects (5.7±5.1 vs 4.2±1.8 mmHg, P= 0.02). In adults, left ventricular outflow tract diameter (12.5±1.4 vs 12.0±1.0 mm/m2; p=0.02), sinuses of Valsalva (17.8±2.5 vs 16.2±1.9 mm/m2; p<0.001) and sinotubular junction (15.0±2.0 vs 13.7±1.6 mm/m2; p<0.001) were larger in FLNA+ subjects as compared to control relatives. 8 FLNA+ subjects (11%; 6 males) underwent aortic valve-related surgery versus 0 in controls (p<0.001). Survival was also impaired in FLNA+ male subjects (70 year old: 72% vs 64%, p=0.03). Conclusion: The FLNA -mutated patients presented aortic valve disease more frequently, including a higher prevalence of bicuspid valve, stenosis, and regurgitation owing to either cusp prolapsed or restrictive motion. This unique features described in this population was associated with worse clinical outcomes, especially in FLNA+ males. Management and decision making should be done according to the features of these patients with polyvalvular diseases [ABSTRACT FROM AUTHOR]