Characterization and Mechanisms of Action of Novel Na
            <sub>V</sub>
            1.5 Channel Mutations Associated With Brugada Syndrome

Calloe, Kirstine; Refaat, Marwan M.; Grubb, Søren; Wojciak, Julianne; Campagna, Joan; Thomsen, Nancy Mutsaers; Nussbaum, Robert L.; Scheinman, Melvin M.; Schmitt, Nicole

doi:10.1161/circep.112.974220

Cited by 40 publications

(24 citation statements)

References 21 publications

(21 reference statements)

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“…The abnormal BrS AP profile was explained by a reduction in I Na and upstroke velocity, a phenotype consistent with the loss of hNa v 1.5 function predicted by SCN5A variants utilizing heterologous expression models (29,33–35). The reduction in I Na is similar to results by Davis et al who studied human iPSC-CMs from subjects with an overlap syndrome with Type 3 Long QT and BrS features and demonstrated reduced I Na current density and upstroke velocity (36).…”

Section: Discussionsupporting

confidence: 64%

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Patient-Specific and Genome-Edited Induced Pluripotent Stem Cell–Derived Cardiomyocytes Elucidate Single-Cell Phenotype of Brugada Syndrome

Liang

Sallam

et al. 2016

Journal of the American College of Cardiology

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187

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Background Brugada Syndrome is a disorder associated with characteristic ECG precordial ST elevation and predisposes afflicted patients to ventricular fibrillation and sudden cardiac death. Despite marked achievements in outlining the organ level pathophysiology of the disorder, the understanding of human cellular phenotype has lagged due to lack of adequate human cellular models of the disorder. Methods and Results We recruited two patients with Type 1 Brugada Syndrome (BrS) carrying two different SCN5A variants and two healthy controls. We generated induced pluripotent stem cells (iPSCs) from their skin fibroblasts by using integration-free Sendai virus. We utilized directed differentiation to create purified populations of iPSC-derived cardiomyocytes (iPSC-CMs). BrS iPSC-CMs showed reductions in inward Na+ current density and reduced maximal upstroke velocity of action potential compared to healthy control iPSC-CMs. Furthermore, BrS iPSC-CMs showed increased burden of triggered activity, abnormal Ca2+ transients, and beating interval variation. Correction of the causative variant by genome editing was performed and resultant iPSC-CMs showed resolution of triggered activity and abnormal Ca2+ transients. Gene expression profiling of iPSC-CMs showed clustering of BrS compared to controls. Furthermore, BrS iPSC-CM gene expression correlated with gene expression from BrS human cardiac tissue gene expression. Conclusions Patient-specific iPSC-CMs are able to recapitulate single cell phenotype features of BrS, including blunted inward sodium current, increased triggered activity and abnormal Ca2+ handling. This novel human cellular model creates future opportunities to further elucidate cellular disease mechanism and identify novel therapeutic targets.

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Section: Discussionsupporting

confidence: 64%

“…Furthermore, the patient had a family history of sudden death in two paternal uncles and a female cousin. Genetic testing revealed a double missense mutation (R620H and R811H) in SCN5A gene domain IIS4, with R811H known to be critical in voltage-dependent gating (Figure 1C, Supplemental Figure 1A, and Supplemental Table 2) (29). …”

Section: Resultsmentioning

confidence: 99%

Patient-Specific and Genome-Edited Induced Pluripotent Stem Cell–Derived Cardiomyocytes Elucidate Single-Cell Phenotype of Brugada Syndrome

Liang

Sallam

et al. 2016

Journal of the American College of Cardiology

Self Cite

187

152

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“…We found that the density of Na + currrent was reduced to ∼60% of the WT Na + current density, and the voltage dependence of inactivation was also shifted towards negative voltages compared to the WT channel. Some research showed that when co-expressing trafficking-deficient BrS SCN5A mutations with WT Na v 1.5 channel (0.5:0.5 in ratio) in heterologous expression systems, it is observed that the Na + current was reduced by about 50% compared to the Na + current produced by expressing only WT Na v 1.5 channel [33][34][35]. Such reduction of Na + current is due to the haploinsufficiency of WT Na v 1.5 channel.…”

Section: Discussionmentioning

confidence: 99%

De Novo Mutation in the SCN5A Gene Associated with Brugada Syndrome

Meng

Yuchi

Zhao

et al. 2015

Cell Physiol Biochem

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Background: Brugada syndrome (BrS) is a genetically determined cardiac electrical disorder, characterized by typical electrocardiography (ECG) alterations, and it is an arrhythmogenic syndrome that may lead to sudden cardiac death. The most common genotype found among BrS patients is caused by mutations in the SCN5A gene, which lead to a loss of function of the cardiac sodium (Na⁺) channel (Na_v1.5) by different mechanisms. Methods: The assay of confocal laser microscopy and western blot were used to identify the expression and location of L812Q at the cell surface. Characterization of Nav1.5 L812Q mutant Na⁺ channels was text by patch-clamp recordings, and the PHYRE2 server was used to build a model for human Nav1.5 channel. Results: Here, we report that a novel missense SCN5A mutation, L812Q, localized in the DII-S4 transmembrane region of the Na_v1.5 channel protein, was identified in an index patient who showed a typical BrS type-1 ECG phenotype. The mutation was absent in the patient's parents and brother. Heterologous expression of the wild-type (WT) and L812Q mutant Na_v1.5 channels in human embryonic kidney cells (HEK293 cells) reveals that the mutation results in a reduction of Na⁺ current density as well as ∼20 mV hyperpolarizing shift of the voltage dependence of inactivation. The voltage dependence of activation and the time course for recovery from inactivation are not affected by the mutation. The hyperpolarizing shift of the voltage dependence of inactivation caused a reduction of the Na⁺ window current as well. In addition, western blot and confocal laser microscopy imaging experiments showed that the mutation causes fewer channel to be expressed at the membrane than WT channel. A large proportion of the mutant channels are retained in the cytoplasm, probably in the endoplasmic reticulum. Conclusion: The decrease of channel expression, hyperpolarizing shift of voltage dependence of inactivation, and a decline of Na⁺ window current caused by L812Q mutation lead to a reduction of Na⁺ current during the upstroke and the repolarization phases of cardiac action potential, which contribute to the development of BrS.

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“…31 Mokimoto et al studied 93 patients with BrS and 102 healthy control subjects during recovery phase from treadmill exercise testing. 32 Twentytwo patients had previous documented VF, 35 had history of syncope alone and 36 were asymptomatic among BrS patients.…”

Section: Augmented St Elevation During Recovery From Exercise In Patimentioning

confidence: 99%

Utility of the Exercise Electrocardiogram Testing in Sudden Cardiac Death Risk Stratification

Refaat

Hotait

Tseng

2014

Ann Noninvasive Electrocardiol

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Background: Sudden cardiac death (SCD) remains a major public health problem. Current established criteria identifying those at risk of sudden arrhythmic death, and likely to benefit from implantable cardioverter defibrillators (ICDs), are neither sensitive nor specific. Exercise electrocardiogram (ECG) testing was traditionally used for information concerning patients' symptoms, exercise capacity, cardiovascular function, myocardial ischemia detection, and hemodynamic responses during activity in patients with hypertrophic cardiomyopathy.Methods: We conducted a systematic review of MEDLINE on the utility of exercise ECG testing in SCD risk stratification.Results: Exercise testing can unmask suspected primary electrical diseases in certain patients (catecholaminergic polymorphic ventricular tachycardia or concealed long QT syndrome) and can be effectively utilized to risk stratify patients at an increased (such as early repolarization syndrome and Brugada syndrome) or decreased risk of SCD, such as the loss of preexcitation on exercise testing in asymptomatic Wolff-Parkinson-White syndrome.Conclusions: Exercise ECG testing helps in SCD risk stratification in patients with and without arrhythmogenic hereditary syndromes.

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Characterization and Mechanisms of Action of Novel Na _V 1.5 Channel Mutations Associated With Brugada Syndrome

Cited by 40 publications

References 21 publications

Patient-Specific and Genome-Edited Induced Pluripotent Stem Cell–Derived Cardiomyocytes Elucidate Single-Cell Phenotype of Brugada Syndrome

Patient-Specific and Genome-Edited Induced Pluripotent Stem Cell–Derived Cardiomyocytes Elucidate Single-Cell Phenotype of Brugada Syndrome

De Novo Mutation in the SCN5A Gene Associated with Brugada Syndrome

Utility of the Exercise Electrocardiogram Testing in Sudden Cardiac Death Risk Stratification

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Characterization and Mechanisms of Action of Novel Na V 1.5 Channel Mutations Associated With Brugada Syndrome

Cited by 40 publications

References 21 publications

Patient-Specific and Genome-Edited Induced Pluripotent Stem Cell–Derived Cardiomyocytes Elucidate Single-Cell Phenotype of Brugada Syndrome

Patient-Specific and Genome-Edited Induced Pluripotent Stem Cell–Derived Cardiomyocytes Elucidate Single-Cell Phenotype of Brugada Syndrome

De Novo Mutation in the SCN5A Gene Associated with Brugada Syndrome

Utility of the Exercise Electrocardiogram Testing in Sudden Cardiac Death Risk Stratification

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Characterization and Mechanisms of Action of Novel Na _V 1.5 Channel Mutations Associated With Brugada Syndrome