Abstract 5317: Identification and Characterization of a Novel Susceptibility Gene, SCN3B, for Idiopathic Ventricular Fibrillation

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Carmen R Valdivia ◽  
Argelia Mereidos-Domingo ◽  
Thimothy J Algiers ◽  
Michael J Ackerman ◽  
Jonathan C Makielski
Keyword(s):  
Ventricular Fibrillation ◽  
Sodium Channel ◽  
Brugada Syndrome ◽  
Mutational Analysis ◽  
Sodium Current ◽  
Susceptibility Gene ◽  
Site Directed Mutagenesis ◽  
Macromolecular Complex ◽  
Patch Clamp Technique ◽  
Idiopathic Ventricular Fibrillation

Background: Mutations in the Na V 1.5 sodium channel macromolecular complex have been identified in some cases classified as idiopathic ventricular fibrillation (IVF). IVF and Brugada syndrome (BrS) are partially overlapping syndromes. Here, we report a mutation in SCN3B- encoded sodium channel β3 subunit as a novel pathogenic mechanism for IVF. Methods: Comprehensive open reading frame mutational analysis of SCN5A, GPD1L, and the beta subunit genes ( SCN1–4B ) was performed using PCR, DHPLC, and direct DNA sequencing of DNA extracted from a 20-year-old patient diagnosed with IVF. The SCN3B mutation was made by site directed mutagenesis and co-transfected with SCN5A into HEK-293 cells for functional chraracterization using the patch clamp technique. Results: A novel missense mutation, V54G-SCN3B, was identified in a 20-year-old male following collapse and external defibrillation from VF. After recovery, there was no detectable electrocardiographic abnormality. Imaging studies demonstrated a structurally normal heart, and the patient was diagnosed with IVF. The mutation was absent in 800 reference alleles and involved a highly conserved residue in the extracellular domain of the beta 3 subunit. No other mutations were identified in the 5 other genes. HEK cells expressing SCN5A and either WT-, or V54G-SCN3B were studied 24 hours after transfection. Cells expressing V54G-SCN3B showed significant decrease in sodium current density of 60±20 pA/pF compared to 203±35 pA/pF in WT-SCN3B (n=14–19). In addition V54G-SCN3B significantly shifted the activation curve +5 mV without affecting inactivation. Conclusions: This study provides the first molecular and cellular evidence implicating SCN3B in IVF. Given the marked loss-of-function to the sodium channel by V54G-SCN3B and the overlap between IVF and BrS, it will be interesting to determine whether mutations in SCN3B explain some cases of genotype negative Brugada syndrome.

P1597Two novel mutations in SCN5A gene cause enhanced inactivation and lead to Brugada syndrome

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
A Zaytseva ◽  
A V Karpushev ◽  
A V Karpushev ◽  
Y Fomicheva ◽  
Y Fomicheva ◽  
...  
Keyword(s):  
Steady State ◽  
Sodium Channel ◽  
Brugada Syndrome ◽  
Slow Inactivation ◽  
Fast Inactivation ◽  
Novel Mutations ◽  
Patch Clamp Technique ◽  
Inactivation Curve ◽  
Voltage Gated ◽  
Cardiac Sodium Channel

Abstract Background Mutations in gene SCN5A, encoding cardiac potential-dependent sodium channel Nav1.5, are associated with various arrhythmogenic disorders among which the Brugada syndrome (BrS) and the Long QT syndrome (LQT) are the best characterized. BrS1 is associated with sodium channel dysfunction, which can be reflected by decreased current, impaired activation and enhanced inactivation. We found two novel mutations in our patients with BrS and explored their effect on fast and slow inactivation of cardiac sodium channel. Purpose The aim of this study was to investigate the effect of BrS (Y739D, L1582P) mutations on different inactivation processes in in vitro model. Methods Y739D and L1582P substitutions were introduced in SCN5A cDNA using site-directed mutagenesis. Sodium currents were recorded at room temperature in transfected HEK293-T cells using patch-clamp technique with holding potential −100 mV. In order to access the fast steady-state inactivation curve we used double-pulse protocol with 10 ms prepulses. To analyze voltage-dependence of slow inactivation we used two-pulse protocol with 10s prepulse, 20ms test pulse and 25ms interpulse at −100mV to allow recovery from fast inactivation. Electrophysiological measurements are presented as mean ±SEM. Results Y739D mutation affects highly conserved tyrosine 739 among voltage-gated sodium and calcium channels in the segment IIS2. Mutation L1582P located in the loop IVS4-S5, and leucine in this position is not conserved among voltage-gated channels superfamily. We have shown that Y739D leads to significant changes in both fast and slow inactivation, whereas L1582P enhanced slow inactivation only. Steady-state fast inactivation for Y739D was shifted on 8.9 mV towards more negative potentials compare with that for WT, while L1582P did not enhanced fast inactivation (V1/2 WT: −62.8±1.7 mV; Y739D: −71.7±2.3 mV; L1582P: −58.7±1.4 mV). Slow inactivation was increased for both substitutions (INa (+20mV)/INa (−100mV) WT: 0.45±0.03; Y739D: 0,34±0.09: L1582P: 0.38±0.04). Steady-state fast inactivation Conclusions Both mutations, observed in patients with Brugada syndrome, influence on the slow inactivation process. Enhanced fast inactivation was shown only for Y739D mutant. The more dramatic alterations in sodium channel biophysical characteristics are likely linked with mutated residue conservativity. Acknowledgement/Funding RSF #17-15-01292

Abstract 15210: Do Idiopathic Ventricular Fibrillation and Brugada Syndrome Patients Have Favor Outcomes in the Targeted Temperature Management Era?

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Eisuke Kagawa ◽  
Masaya Kato ◽  
Noboru Oda ◽  
Eiji Kunita ◽  
Michiaki NAGAI ◽  
...  
Keyword(s):  
Cardiac Arrest ◽  
Survival Rate ◽  
Ventricular Fibrillation ◽  
Brugada Syndrome ◽  
Cardiac Dysfunction ◽  
Targeted Temperature Management ◽  
Temperature Management ◽  
Circulatory Support ◽  
Idiopathic Ventricular Fibrillation ◽  
Coronary Syndrome

Introduction: Idiopathic ventricular fibrillation (IVF) including Brugada syndrome (BS) is one of causes of cardiac arrest without prior overt cardiac dysfunction. Hypothesis: We assessed the hypothesis that patents of IVF had favor outcomes than those of non-IVF after cardiac arrest treated with targeted temperature management (TTM). Methods: Patients who were treated with TTM after cardiac arrest between 2000 and 2019 were enrolled in the study. Patients were divided into 2 groups according to whether the patients were diagnosed as IVF or not. The patients treated with TTM were routinely performed coronary angiography. Results: Among the study patients (N = 306), 35 (11%) patients were IVF and 7 were BS. The patients of the IVF group were significantly younger (median 53 y vs. 64 y) than those of the non-IVF group. The prevalence of initial rhythm was shockable (69% vs. 47%, P = 0.02) was significantly higher in the patients of the IVF group than those of the non-IVF group. Among the patients in the non-IVF group, 114 patients (42%) were diagnosed as acute coronary syndrome and 93 patients (35%) were treated with coronary revascularization. The prevalence of male sex (77% vs 74%, P = 0.70) and witnessed to arrest (80% vs. 81%, P = 0.87), and low-flow time (29 min vs. 38 min [20 - 43 min vs. 21 - 52 min, P = 0.15]) were similar between the 2 groups. The prevalence of performing extracorporeal resuscitation (9% s 43%, P < 0.001) were lower in the patients of the IVF group. The 8-y survival rate were shown in the figure. All of the BS patients were witnessed arrest and were discharged without severe neurological deficit. The IVF as the cause of arrest was independently associated with 8-y survival. Conclusions: The patients of IVF had favor outcomes than those of non-VF. One of causes may be the lower prevalence of requiring extracorporeal circulatory support due to less cardiac dysfunction. The patients of BS had the tendency toward higher survival rate than those of non-BS IVF patients.

Abstract 15925: Localization of Nav1.5 at the Intercellular Junctions Resolved by Diffraction-Unlimited Microscopy in Three Dimensions and by Correlative Light-Electron Microscopy

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Alejandra Leo-Macias ◽  
Esperanza Agullo-Pascual ◽  
Eli Rothenberg ◽  
Mario Delmar
Keyword(s):  
Electron Microscopy ◽  
Sodium Channel ◽  
Ventricular Myocytes ◽  
Sodium Current ◽  
Intercellular Junctions ◽  
Three Dimensions ◽  
Macromolecular Complex ◽  
Adult Heart ◽  
Mechanical Coupling ◽  
Cardiac Sodium Channel

Sodium current amplitude, kinetics and regulation depend on the properties of the pore-forming protein (mostly NaV1.5 in adult heart) and on the specific molecular partners with which the channel protein associates. The composition of the voltage-gated sodium channel macromolecular complex is location-specific; yet, the exact position of NaV1.5 in the subcellular landscape of the intercalated disc (ID), remains unclear. We implemented diffraction unlimited microscopy (direct stochastic optical reconstruction microscopy, or “dSTORM”) to localize the pore-forming subunit of the cardiac sodium channel NaV1.5 with a resolution of 20nm on the XY plane. In isolated adult ventricular myocytes, NaV1.5 was found in distinct semi-circular clusters. When the entire population of clusters within a 500 nm window from the ID was considered (more than 350 individual clusters analyzed), 75% of them localized to N-cadherin rich sites. NaV1.5-distal clusters were found at an average 313±15 nm from the cell end. Introducing an astigmatic lens in the light path allowed us to solve cluster location in three dimensions, at resolutions of 20 nm in XY and 40 nm in the z plane. Three-dimensional images confirmed the preferential localization at or near N-cadherin plaques, and further suggested that NaV1.5 arrives to the membrane via N-cadherin-anchored paths, most likely microtubules. In additional experiments, we developed a novel approach to correlate the image of NaV1.5 clusters by dSTORM with the cellular ultrastructure as resolved by electron microscopy on the same sample. This “correlative light-electron microscopy” method confirmed the preference of NaV1.5 clusters at sites of mechanical coupling. Overall, we provide the first ultrastructural description of NaV1.5 at the cardiac ID and its relation with the major electron-dense domains of the adult heart. Our data support a model by which microtubule-mediated delivery of NaV1.5 anchors at N-cadherin-rich sites, likely “mixed junctions” also containing desmosomal molecules (such as plakophilin-2; see Cerrone et al; Circulation 129:1092-1103, 2014) and connexin43. These findings have major implications to the understanding of sodium current disruption in diseases affecting the integrity of the ID.

Sodium channel kinetic changes that produce Brugada syndrome or progressive cardiac conduction system disease

2007 ◽  
Vol 292 (1) ◽  
pp. H399-H407 ◽  
Author(s):  
Zhu-Shan Zhang ◽  
Joseph Tranquillo ◽  
Valentina Neplioueva ◽  
Nenad Bursac ◽  
Augustus O. Grant
Keyword(s):  
Action Potential ◽  
Sodium Channel ◽  
Brugada Syndrome ◽  
Sodium Current ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Cardiac Conduction System ◽  
Wild Type ◽  
System Disease ◽  
Conduction System Disease

Some mutations of the sodium channel gene NaV1.5 are multifunctional, causing combinations of LQTS, Brugada syndrome and progressive cardiac conduction system disease (PCCD). The combination of Brugada syndrome and PCCD is uncommon, although they both result from a reduction in the sodium current. We hypothesize that slow conduction is sufficient to cause S-T segment elevation and undertook a combined experimental and theoretical study to determine whether conduction slowing alone can produce the Brugada phenotype. Deletion of lysine 1479 in one of two positively charged clusters in the III/IV inter-domain linker causes both syndromes. We have examined the functional effects of this mutation using heterologous expression of the wild-type and mutant sodium channel in HEK-293-EBNA cells. We show that ΔK1479 shifts the potential of half-activation, V1/2m, to more positive potentials ( V1/2m = −36.8 ± 0.8 and −24.5 ± 1.3 mV for the wild-type and ΔK1479 mutant respectively, n = 11, 10). The depolarizing shift increases the extent of depolarization required for activation. The potential of half-inactivation, V1/2h, is also shifted to more positive potentials ( V1/2h = −85 ± 1.1 and −79.4 ± 1.2 mV for wild-type and ΔK1479 mutant respectively), increasing the fraction of channels available for activation. These shifts are quantitatively the same as a mutation that produces PCCD only, G514C. We incorporated experimentally derived parameters into a model of the cardiac action potential and its propagation in a one dimensional cable (simulating endo-, mid-myocardial and epicardial regions). The simulations show that action potential and ECG changes consistent with Brugada syndrome may result from conduction slowing alone; marked repolarization heterogeneity is not required. The findings also suggest how Brugada syndrome and PCCD which both result from loss of sodium channel function are sometimes present alone and at other times in combination.

scholarly journals Novel SCN5A mutation associated with idiopathic ventricular fibrillation due to subclinical Brugada syndrome

2011 ◽  
Vol 2 (1) ◽  
pp. 1
Author(s):  
Juan Jiménez-Jáimez ◽  
Miguel Álvarez-López ◽  
Luis Tercedor-Sánchez ◽  
Pablo Santiago ◽  
Maria Algarra ◽  
...  
Keyword(s):  
Ventricular Fibrillation ◽  
Brugada Syndrome ◽  
Idiopathic Ventricular Fibrillation ◽  
Scn5a Mutation

A novel SCN5A mutation associated with idiopathic ventricular fibrillation without typical ECG findings of Brugada syndrome

FEBS Letters ◽  
2000 ◽  
Vol 479 (1-2) ◽  
pp. 29-34 ◽  
Author(s):  
Jun Akai ◽  
Naomasa Makita ◽  
Harumizu Sakurada ◽  
Nobumasa Shirai ◽  
Kazuo Ueda ◽  
...  
Keyword(s):  
Ventricular Fibrillation ◽  
Brugada Syndrome ◽  
Idiopathic Ventricular Fibrillation ◽  
Scn5a Mutation
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