Dataset Information

Molecular genetic and functional association of Brugada and early repolarization syndromes with S422L missense mutation in KCNJ8.

ABSTRACT: Adenosine triphosphate (ATP)-sensitive potassium cardiac channels consist of inward-rectifying channel subunits Kir6.1 or Kir6.2 (encoded by KCNJ8 or KCNJ11) and the sulfonylurea receptor subunits SUR2A (encoded by ABCC9).To examine the association of mutations in KCNJ8 with Brugada syndrome (BrS) and early repolarization syndrome (ERS) and to elucidate the mechanism underlying the gain of function of ATP-sensitive potassium channel current.Direct sequencing of KCNJ8 and other candidate genes was performed on 204 BrS and ERS probands and family members. Whole-cell and inside-out patch-clamp methods were used to study mutated channels expressed in TSA201 cells.The same missense mutation, p.Ser422Leu (c.1265C>T) in KCNJ8, was identified in 3 BrS and 1 ERS probands but was absent in 430 alleles from ethnically matched healthy controls. Additional genetic variants included CACNB2b-D601E. Whole-cell patch-clamp studies showed a 2-fold gain of function of glibenclamide-sensitive ATP-sensitive potassium channel current when KCNJ8-S422L was coexpressed with SUR2A-wild type. Inside-out patch-clamp evaluation yielded a significantly greater half maximal inhibitory concentration for ATP in the mutant channels (785.5 ± 2 vs 38.4 ± 3 ?M; n = 5; P <.01), pointing to incomplete closing of the ATP-sensitive potassium channels under normoxic conditions. Patients with a CACNB2b-D601E polymorphism displayed longer QT/corrected QT intervals, likely owing to their effect to induce an increase in L-type calcium channel current (I(Ca-L)).Our results support the hypothesis that KCNJ8 is a susceptibility gene for BrS and ERS and point to S422L as a possible hotspot mutation. Our findings suggest that the S422L-induced gain of function in ATP-sensitive potassium channel current is due to reduced sensitivity to intracellular ATP.

SUBMITTER: Barajas-Martinez H

PROVIDER: S-EPMC3288170 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature

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Molecular genetic and functional association of Brugada and early repolarization syndromes with S422L missense mutation in KCNJ8.

Barajas-Martínez Hector H Hu Dan D Ferrer Tania T Onetti Carlos G CG Wu Yuesheng Y Burashnikov Elena E Boyle Madalene M Surman Tyler T Urrutia Janire J Veltmann Christian C Schimpf Rainer R Borggrefe Martin M Wolpert Christian C Ibrahim Bassiema B BB Sánchez-Chapula José Antonio JA Winters Stephen S Haïssaguerre Michel M Antzelevitch Charles C Antzelevitch Charles C

Heart rhythm 20111103 4

<h4>Background</h4>Adenosine triphosphate (ATP)-sensitive potassium cardiac channels consist of inward-rectifying channel subunits Kir6.1 or Kir6.2 (encoded by KCNJ8 or KCNJ11) and the sulfonylurea receptor subunits SUR2A (encoded by ABCC9).<h4>Objective</h4>To examine the association of mutations in KCNJ8 with Brugada syndrome (BrS) and early repolarization syndrome (ERS) and to elucidate the mechanism underlying the gain of function of ATP-sensitive potassium channel current.<h4>Methods</h4>Di ...[more]

PMID: 22056721

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Project description:Background: Early repolarization syndrome (ERS) is an inherited sudden cardiac death (SCD) syndrome. The present study investigates the role of genetic variants in cardiac calcium-channel genes in the pathogenesis of ERS and probes the underlying mechanisms. Methods: Polymerase chain reaction-based next-generation sequencing was carried out using a targeted gene approach. Unrelated ERS probands carrying calcium-channel variants were evaluated clinically and compared with matched healthy controls. Wild-type (WT) and mutant CACNA1C genes were coexpressed with CACNB2b and CACNA2D1 in HEK293 cells and studied using whole-cell patch-clamp techniques and confocal fluorescence microscope. Results: Among 104 ERS probands, 16 carried pathogenic variants in calcium-channel genes (32.2 ± 14.6 years old, 87.5% male). The symptoms at diagnosis included syncope (56.3%), ventricular tachycardia/fibrillation (62.5%), and SCD (56.3%). Three cases (18.8%) had a family history of SCD or syncope. Eight patients (50.0%) had a single calcium gene rare variant. The other half carried rare variants in other ERS-susceptible genes. Compared with controls, the heart rate was slower (72.7 ± 8.9 vs. 65.6 ± 16.1 beats/min, * p < 0.05), QTc interval was shorter (408.2 ± 21.4 vs. 386.8 ± 16.9 ms, ** p < 0.01), and Tp-e/QT was longer (0.22 ± 0.05 vs. 0.28 ± 0.04, *** p < 0.001) in single calcium mutation carriers. Electrophysiological analysis of one mutation, CACNA1C-P817S (c.2449C>T), revealed that the density of whole-cell calcium current (I Ca) was reduced by ~84.61% compared to WT (-3.17 ± 2.53 vs. -20.59 ± 3.60 pA/pF, n = 11 and 15, respectively, ** p < 0.01). Heterozygous expression of mutant channels was associated with a 51.35% reduction of I Ca. Steady-state inactivation was shifted to more negative potentials and significantly accelerated as well. Confocal microscopy revealed trafficking impairment of CACNA1C-P817S (peripheral/central intensity: 0.94 ± 0.10 in WT vs. 0.33 ± 0.12 in P817S, n = 10 and 9, respectively, ** p < 0.01). Conclusions: ERS associated with loss-of-function (LOF) genetic defects in genes encoding the cardiac calcium channel represents a unique clinical entity characterized by decreased heart rate and QTc, as well as increased transmural dispersion of repolarization. In the case of CACNA1C-P817S, impaired trafficking of the channel to the membrane contributes to the LOF.

Dataset Information

Molecular genetic and functional association of Brugada and early repolarization syndromes with S422L missense mutation in KCNJ8.

Publications

Molecular genetic and functional association of Brugada and early repolarization syndromes with S422L missense mutation in KCNJ8.

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