scholarly journals Author Correction: Long-QT founder variant T309I-Kv7.1 with dominant negative pattern may predispose delayed afterdepolarizations under β-adrenergic stimulation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Iva Synková ◽  
Markéta Bébarová ◽  
Irena Andršová ◽  
Larisa Chmelikova ◽  
Olga Švecová ◽  
...  
Keyword(s):  
Dominant Negative ◽  
Adrenergic Stimulation ◽  
Long Qt ◽  
Negative Pattern ◽  
Delayed Afterdepolarizations

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

scholarly journals Long-QT founder variant T309I-Kv7.1 with dominant negative pattern may predispose delayed afterdepolarizations under β-adrenergic stimulation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Iva Synková ◽  
Markéta Bébarová ◽  
Irena Andršová ◽  
Larisa Chmelikova ◽  
Olga Švecová ◽  
...  
Keyword(s):  
Calcium Current ◽  
Cell Model ◽  
Dominant Negative ◽  
Qtc Interval ◽  
Adrenergic Stimulation ◽  
Patch Clamp Technique ◽  
Long Qt ◽  
Channel Trafficking ◽  
Whole Cell Patch Clamp ◽  
Delayed Afterdepolarizations

AbstractThe variant c.926C > T (p.T309I) in KCNQ1 gene was identified in 10 putatively unrelated Czech families with long QT syndrome (LQTS). Mutation carriers (24 heterozygous individuals) were more symptomatic compared to their non-affected relatives (17 individuals). The carriers showed a mild LQTS phenotype including a longer QTc interval at rest (466 ± 24 ms vs. 418 ± 20 ms) and after exercise (508 ± 32 ms vs. 417 ± 24 ms), 4 syncopes and 2 aborted cardiac arrests. The same haplotype associated with the c.926C > T variant was identified in all probands. Using the whole cell patch clamp technique and confocal microscopy, a complete loss of channel function was revealed in the homozygous setting, caused by an impaired channel trafficking. Dominant negativity with preserved reactivity to β-adrenergic stimulation was apparent in the heterozygous setting. In simulations on a human ventricular cell model, the dysfunction resulted in delayed afterdepolarizations (DADs) and premature action potentials under β-adrenergic stimulation that could be prevented by a slight inhibition of calcium current. We conclude that the KCNQ1 variant c.926C > T is the first identified LQTS-related founder mutation in Central Europe. The dominant negative channel dysfunction may lead to DADs under β-adrenergic stimulation. Inhibition of calcium current could be possible therapeutic strategy in LQTS1 patients refractory to β-blocker therapy.

scholarly journals Multiphoton Imaging of Ca2+ Instability in Acute Myocardial Slices from a RyR2R2474S Murine Model of Catecholaminergic Polymorphic Ventricular Tachycardia

2021 ◽  
Vol 10 (13) ◽  
pp. 2821
Author(s):  
Giulia Borile ◽  
Tania Zaglia ◽  
Stephan E. Lehnart ◽  
Marco Mongillo
Keyword(s):  
Ventricular Tachycardia ◽  
Single Cells ◽  
Tissue Level ◽  
Catecholaminergic Polymorphic Ventricular Tachycardia ◽  
Polymorphic Ventricular Tachycardia ◽  
Adrenergic Stimulation ◽  
Release Channel ◽  
Multiphoton Imaging ◽  
Delayed Afterdepolarizations ◽  
Multiple Cells

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is a familial stress-induced arrhythmia syndrome, mostly caused by mutations in Ryanodine receptor 2 (RyR2), the sarcoplasmic reticulum (SR) Ca2+ release channel in cardiomyocytes. Pathogenetic mutations lead to gain of function in the channel, causing arrhythmias by promoting diastolic spontaneous Ca2+ release (SCR) from the SR and delayed afterdepolarizations. While the study of Ca2+ dynamics in single cells from murine CPVT models has increased our understanding of the disease pathogenesis, questions remain on the mechanisms triggering the lethal arrhythmias at tissue level. Here, we combined subcellular analysis of Ca2+ signals in isolated cardiomyocytes and in acute thick ventricular slices of RyR2R2474S knock-in mice, electrically paced at different rates (1–5 Hz), to identify arrhythmogenic Ca2+ dynamics, from the sub- to the multicellular perspective. In both models, RyR2R2474S cardiomyocytes had increased propensity to develop SCR upon adrenergic stimulation, which manifested, in the slices, with Ca2+ alternans and synchronous Ca2+ release events in neighboring cardiomyocytes. Analysis of Ca2+ dynamics in multiple cells in the tissue suggests that SCRs beget SCRs in contiguous cells, overcoming the protective electrotonic myocardial coupling, and potentially generating arrhythmia triggering foci. We suggest that intercellular interactions may underscore arrhythmic propensity in CPVT hearts with ‘leaky’ RyR2.

Retention in the Endoplasmic Reticulum as a Mechanism of Dominant-negative Current Suppression in Human Long QT Syndrome

2000 ◽  
Vol 32 (12) ◽  
pp. 2327-2337 ◽  
Author(s):  
Eckhard Ficker ◽  
Adrienne T Dennis ◽  
Carlos A Obejero-Paz ◽  
Pasqualina Castaldo ◽  
Maurizio Taglialatela ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Long Qt Syndrome ◽  
Dominant Negative ◽  
Long Qt ◽  
Negative Current ◽  
Qt Syndrome

scholarly journals Early somatic mosaicism is a rare cause of long-QT syndrome

2016 ◽  
Vol 113 (41) ◽  
pp. 11555-11560 ◽  
Author(s):  
James Rush Priest ◽  
Charles Gawad ◽  
Kristopher M. Kahlig ◽  
Joseph K. Yu ◽  
Thomas O’Hara ◽  
...  
Keyword(s):  
Long Qt Syndrome ◽  
Sodium Current ◽  
Somatic Mosaicism ◽  
Mendelian Inheritance ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Causal Mechanism ◽  
Long Qt ◽  
Gene Panel Testing ◽  
Qt Syndrome

Somatic mosaicism, the occurrence and propagation of genetic variation in cell lineages after fertilization, is increasingly recognized to play a causal role in a variety of human diseases. We investigated the case of life-threatening arrhythmia in a 10-day-old infant with long QT syndrome (LQTS). Rapid genome sequencing suggested a variant in the sodium channel NaV1.5 encoded by SCN5A, NM_000335:c.5284G > T predicting p.(V1762L), but read depth was insufficient to be diagnostic. Exome sequencing of the trio confirmed read ratios inconsistent with Mendelian inheritance only in the proband. Genotyping of single circulating leukocytes demonstrated the mutation in the genomes of 8% of patient cells, and RNA sequencing of cardiac tissue from the infant confirmed the expression of the mutant allele at mosaic ratios. Heterologous expression of the mutant channel revealed significantly delayed sodium current with a dominant negative effect. To investigate the mechanism by which mosaicism might cause arrhythmia, we built a finite element simulation model incorporating Purkinje fiber activation. This model confirmed the pathogenic consequences of cardiac cellular mosaicism and, under the presenting conditions of this case, recapitulated 2:1 AV block and arrhythmia. To investigate the extent to which mosaicism might explain undiagnosed arrhythmia, we studied 7,500 affected probands undergoing commercial gene-panel testing. Four individuals with pathogenic variants arising from early somatic mutation events were found. Here we establish cardiac mosaicism as a causal mechanism for LQTS and present methods by which the general phenomenon, likely to be relevant for all genetic diseases, can be detected through single-cell analysis and next-generation sequencing.

scholarly journals Pharmacological correction of long QT-linked mutations in KCNH2 (hERG) increases the trafficking of Kv11.1 channels stored in the transitional endoplasmic reticulum

2013 ◽  
Vol 305 (9) ◽  
pp. C919-C930 ◽  
Author(s):  
Jennifer L. Smith ◽  
Allison R. Reloj ◽  
Parvathi S. Nataraj ◽  
Daniel C. Bartos ◽  
Elizabeth A. Schroder ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Therapeutic Potential ◽  
Functional Expression ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Delayed Rectifier ◽  
Protein Synthesis Inhibitor ◽  
Missense Mutations ◽  
Long Qt ◽  
Pharmacological Correction

KCNH2 encodes Kv11.1 and underlies the rapidly activating delayed rectifier K+ current ( IKr) in the heart. Loss-of-function KCNH2 mutations cause the type 2 long QT syndrome (LQT2), and most LQT2-linked missense mutations inhibit the trafficking of Kv11.1 channels. Drugs that bind to Kv11.1 and block IKr (e.g., E-4031) can act as pharmacological chaperones to increase the trafficking and functional expression for most LQT2 channels (pharmacological correction). We previously showed that LQT2 channels are selectively stored in a microtubule-dependent compartment within the endoplasmic reticulum (ER). We tested the hypothesis that pharmacological correction promotes the trafficking of LQT2 channels stored in this compartment. Confocal analyses of cells expressing the trafficking-deficient LQT2 channel G601S showed that the microtubule-dependent ER compartment is the transitional ER. Experiments with E-4031 and the protein synthesis inhibitor cycloheximide suggested that pharmacological correction promotes the trafficking of G601S stored in this compartment. Treating cells in E-4031 or ranolazine (a drug that blocks IKr and has a short half-life) for 30 min was sufficient to cause pharmacological correction. Moreover, the increased functional expression of G601S persisted 4–5 h after drug washout. Coexpression studies with a dominant-negative form of Rab11B, a small GTPase that regulates Kv11.1 trafficking, prevented the pharmacological correction of G601S trafficking from the transitional ER. These data suggest that pharmacological correction quickly increases the trafficking of LQT2 channels stored in the transitional ER via a Rab11B-dependent pathway, and we conclude that the pharmacological chaperone activity of drugs like ranolazine might have therapeutic potential.

Long QT syndrome and associated gene mutation carriers in Japanese children: results from ECG screening examinations

2009 ◽  
Vol 117 (12) ◽  
pp. 415-424 ◽  
Author(s):  
Kenshi Hayashi ◽  
Noboru Fujino ◽  
Katsuharu Uchiyama ◽  
Hidekazu Ino ◽  
Kenji Sakata ◽  
...  
Keyword(s):  
Ion Channel ◽  
Long Qt Syndrome ◽  
High Probability ◽  
Dominant Negative ◽  
Carrier Status ◽  
Japanese Children ◽  
Long Qt ◽  
Mutation Carriers ◽  
Qt Intervals ◽  
Qt Syndrome

LQTS (long QT syndrome) is caused by mutations in cardiac ion channel genes; however, the prevalence of LQTS in the general population is not well known. In the present study, we prospectively estimated the prevalence of LQTS and analysed the associated mutation carriers in Japanese children. ECGs were recorded from 7961 Japanese school children (4044 males; mean age, 9.9±3.0 years). ECGs were examined again for children who had prolonged QTc (corrected QT) intervals in the initial ECGs, and their QT intervals were measured manually. An LQTS score was determined according to Schwartz's criteria, and ion channel genes were analysed. In vitro characterization of the identified mutants was performed by heterologous expression experiments. Three subjects were assigned to a high probability of LQTS (3.5≤ LQTS score), and eight subjects to an intermediate probability (1.0< LQTS score ≤3.0). Genetic analysis of these II subjects identified three KCNH2 mutations (M124T, 547–553 del GGCGGCG and 2311–2332 del/ins TC). In contrast, no mutations were identified in the 15 subjects with a low probability of LQTS. Electrophysiological studies showed that both the M124T and the 547–553 del GGCGGCG KCNH2 did not suppress the wild-type KCNH2 channel in a dominant-negative manner. These results demonstrate that, in a random sample of healthy Japanese children, the prevalence of a high probability of LQTS is 0.038% (three in 7961), and that LQTS mutation carriers can be identified in at least 0.038% (one in 2653). Furthermore, large-scale genetic studies will be needed to clarify the real prevalence of LQTS by gene-carrier status, as it may have been underestimated in the present study.

scholarly journals Clinical, genetic and functional analysis of R562S-Kv7.1 mutation associated with long QT syndrome type 1

EP Europace ◽  
2021 ◽  
Vol 23 (Supplement_3) ◽  
Author(s):  
O Svecova ◽  
R Kula ◽  
L Chmelikova ◽  
J Hosek ◽  
I Synkova ◽  
...  
Keyword(s):  
Long Qt Syndrome ◽  
Adrenergic Stimulation ◽  
Long Qt ◽  
Beta Adrenergic ◽  
The Czech Republic ◽  
Whole Cell Patch Clamp ◽  
Life Threatening ◽  
Qt Syndrome ◽  
Iks Channel

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Ministry of Education, Youth and Sports of the Czech Republic Introduction Loss-of-function variants of the KCNQ1 gene are associated with life-threatening arrhythmogenic long QT syndrome type 1 (LQT1). This gene encodes structure of the slow delayed rectifier potassium channel (IKs). Some functional characteristics of the C-terminal KCNQ1 variant c.1686G &gt; C (p.R562S) have been recently described [1]. However, accumulation of the current under beta-adrenergic stimulation, essential for shortening the action potential duration during exercise, have not been tested. Purpose The aim of this study was to analyse clinical and genetic characteristics of the R562S variant in our patients and to investigate impact of the variant on IKs channel function with a special focus on reactivity of the channels on beta-adrenergic stimulation. Methods The clinical diagnosis was established according to ESC Guidelines including QTc analysis at rest and after exercise. The molecular genetics diagnostics followed according to current practices (the massive parallel sequencing since 2016). The biophysical analysis was performed on Chinese hamster ovary cells (CHO) by the whole cell patch clamp technique at 37 °C. CHO cells were transiently transfected with wild type (WT) and/or R562S human IKs channels (KCNQ1/KCNE1/Yotiao, 1:2:4). Cyclic adenosine monophosphate (cAMP, 200 µM) and okadaic acid (OA, 0.2 µM) in the pipette solution were used to simulate the beta-adrenergic stimulation. In the confocal microscopy experiments, expression of Yotiao was omitted and GFP-tagged KCNQ1 was used. Results The variant R562S-Kv7.1 has been identified in 7 heterozygous carriers from 3 putatively unrelated families in the Czech Republic. The genotype was associated with long QT syndrome phenotype (prolonged QTc, symptoms including syncopes and aborted cardiac arrest) in some of the carriers. The basic functional analysis proved that both homozygous and heterozygous R562S channels are expressed on the cell membrane (confocal microscopy) and carry IKs (whole cell patch clamp) which agrees with the recently published data on this variant. Importantly, reactivity on beta-adrenergic stimulation was absent in both homozygous and heterozygous R562S channels (n = 14 and 8, respectively), but present in the wild-type channels (increase by 51.4 ± 11.1 % at 120-s cAMP/OA diffusion; n = 12). Conclusions The R562S-Kv7.1 variant may be a founder LQT1 variant in our region which will be further investigated in the future. This variant impairs response of IKs channel to beta-adrenergic stimulation. Absence of this essential regulation may considerably aggravate the channel dysfunction and, thus, may result in life-threatening arrhythmias in R562S carriers during exercise.

scholarly journals The role and mechanism of chaperones Calnexin/Calreticulin in which ALLN selectively rescues the trafficking defective of HERG-A561V mutation

2018 ◽  
Vol 38 (5) ◽  
Author(s):  
Ying Wang ◽  
Tingting Shen ◽  
Peiliang Fang ◽  
Junbo Zhou ◽  
Kenan Lou ◽  
...  
Keyword(s):  
Western Blot ◽  
Protein Trafficking ◽  
Protein Transport ◽  
Dominant Negative ◽  
Mutant Protein ◽  
Patch Clamp Technique ◽  
Long Qt ◽  
Truncated Protein ◽  
Maximal Peak

Long QT (LQT) type 2 (LQT2) is caused by HERG mutation. L539fs/47 encodes a truncated protein, and its mechanisms in HERG mutation are unknown. HERG mutation plasmids were overexpressed in HEK293T cells, respectively, followed by analyzing lysates with Western blot. Transfected HEK293T cells were treated with or without N-acetyl-l-leucyl-l-leucyl-l-norleucinal (ALLN) and Propranolol (Prop) at 24 or 48 h. HERG-WT, HERG-A561V, WT/A561V, HERG-L539fs/47, WT/L539fs/47, and Calnexin (CNX)/Calreticulin (CRT) protein expression and their interactions were detected by Western blot and immunoprecipitation. Each group with HERG currents (Ikr) were detected by Patch-clamp technique. Treated with ALLN, the expression of mature HERG protein and the CNX/CRT protein increased. The interaction of HERG-A561V and WT/A561V protein with the chaperone CNX/CRT increased significantly. The maximum peak currents and tail currents density increased by 70% and 73%, respectively, while maximal peak currents density (24%) and tail currents density (19%) were slight increased in WT-HERG cells. Treated with Prop, the expression and interaction of mature HERG and chaperones CNX/CRT had no difference in each group. The maximal currents and tail currents density were slight increased. CNX/CRT might play a crucial role in the trafficking-deficient process and degradation of HERG-A561V mutant protein, however they had no effect on L539fs/47 HERG due to protein transport deletion. ALLN can restore HERG-A561V mutant protein trafficking process and rescue the dominant negative suppression of WT-HERG.

Neonatal Long QT Syndrome Due to a De Novo Dominant Negative hERG Mutation

2007 ◽  
Vol 16 (4) ◽  
pp. 416-412 ◽  
Author(s):  
Theresa A. Beery ◽  
Kerry A. Shooner ◽  
D. Woodrow Benson
Keyword(s):  
Long Qt Syndrome ◽  
De Novo ◽  
Sinus Bradycardia ◽  
Molecular Genetic ◽  
Ventricular Tachyarrhythmia ◽  
Dominant Negative ◽  
De Novo Mutation ◽  
Long Qt ◽  
Dominant Negative Mutation ◽  
Qt Syndrome

A 4-day-old girl with ventricular tachyarrhythmias, sinus bradycardia, and 2:1 atrioventricular block had prolongation of the QT interval. She was symptomatic with arching, gasping, and cyanosis presumably due to a life-threatening ventricular tachyarrhythmia such as torsades de pointes. Molecular genetic studies indicated a heterozygous, de novo, dominant negative mutation in hERG, a gene that encodes a protein in a potassium ion channel. The parents do not have the mutation. The patient’s clinical scenario was produced by the convergence of 3 events: a de novo mutation occurred in hERG, the mutation was dominant negative, and the action of the mutation resulted in neonatal long QT syndrome. The child was treated aggressively and is doing well at age 6 years.

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