Role of SCN5A coding and non-coding sequences in Brugada syndrome onset: What’s behind the scenes?

AbstractBrugada syndrome (BrS) is a rare inherited cardiac arrhythmia associated with a high risk of sudden cardiac death (SCD) due to ventricular fibrillation (VF). BrS is characterized by coved-type ST-segment elevation in the right precordial leads (V1-V3) in the absence of structural heart disease. This pattern is spontaneous, or is unmasked by intravenous administration of Class I antiarrhythmic drugs. The SCN5A-encoded α-subunit of the NaV1.5 cardiac sodium channel has been linked to BrS, and mutations in SCN5A are identified in 15–30% of BrS cases. Genetic testing of BrS patients generally involves sequencing of protein-coding portions and flanking intronic regions of SCN5A, according to recent international guidelines. This excludes the regulatory untranslated regions (5’UTR and 3’UTR) from the routine genetic testing of BrS patients. We here screened the coding sequence, the flanking intronic regions as well as the 5’ and 3’UTR regions of SCN5A gene and further five candidate genes (GPD1L, SCN1B, KCNE3, SCN4B, and MOG1) in a Tunisian family diagnosed with Brugada syndrome.A new Q1000K mutation was identified on the SCN5A gene along with two common polymorphisms (H558R and D1819). Furthermore, multiple genetic variants were identified on the SCN5A 3’UTR, one of which is predicted to create additional microRNA (miRNAs) binding site for miR-1270. Additionally, we identified the hsa-miR-219a rs107822. No relevant coding sequence variant was identified in the remaining studied candidate genes. Although Q1000K is localized in the conserved binding site of MOG1 which predicts a functional consequence, this new mutation along with the additional variants were differentially distributed among the family members without any clear genotype-phenotype concordance. This gives extra evidences about the complexity of the disease and suggests that the occurrence and prognosis of BrS is most likely controlled by a combination of multiple genetic factors and exposures, rather than a single polymorphism/mutation. Most SCN5A polymorphisms were localized in non-coding regions hypothesizing an impact on the miRNA-target complementarities. In this regard, over-expression of miR-1270 led to a significant decrease of luciferase activity suggesting a direct role regulating SCN5A. Therefore, genetic variants that disrupt its binding affinity to SCN5A 3’UTR and/or its expression might cause loss of normal repression control and be associated to BrS.

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Novel SCN5A p.Val1667Asp Missense Variant Segregation and Characterization in a Family with Severe Brugada Syndrome and Multiple Sudden Deaths

International Journal of Molecular Sciences ◽

10.3390/ijms22094700 ◽

2021 ◽

Vol 22 (9) ◽

pp. 4700

Author(s):

Michelle M. Monasky ◽

Emanuele Micaglio ◽

Giuseppe Ciconte ◽

Ilaria Rivolta ◽

Valeria Borrelli ◽

...

Keyword(s):

Genetic Testing ◽

Family History ◽

Risk Stratification ◽

Brugada Syndrome ◽

Electrophysiological Study ◽

Functional Characterization ◽

The Family ◽

Novel Variant ◽

History Of ◽

Scn5a Gene

Genetic testing in Brugada syndrome (BrS) is still not considered to be useful for clinical management of patients in the majority of cases, due to the current lack of understanding about the effect of specific variants. Additionally, family history of sudden death is generally not considered useful for arrhythmic risk stratification. We sought to demonstrate the usefulness of genetic testing and family history in diagnosis and risk stratification. The family history was collected for a proband who presented with a personal history of aborted cardiac arrest and in whom a novel variant in the SCN5A gene was found. Living family members underwent ajmaline testing, electrophysiological study, and genetic testing to determine genotype-phenotype segregation, if any. Patch-clamp experiments on transfected human embryonic kidney 293 cells enabled the functional characterization of the SCN5A novel variant in vitro. In this study, we provide crucial human data on the novel heterozygous variant NM_198056.2:c.5000T>A (p.Val1667Asp) in the SCN5A gene, and demonstrate its segregation with a severe form of BrS and multiple sudden deaths. Functional data revealed a loss of function of the protein affected by the variant. These results provide the first disease association with this variant and demonstrate the usefulness of genetic testing for diagnosis and risk stratification in certain patients. This study also demonstrates the usefulness of collecting the family history, which can assist in understanding the severity of the disease in certain situations and confirm the importance of the functional studies to distinguish between pathogenic mutations and harmless genetic variants.

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Cardiac sodium channel, its mutations and their spectrum of arrhythmia phenotypes

Journal of Human Growth and Development ◽

10.7322/jhgd.122759 ◽

2016 ◽

Vol 26 (3) ◽

pp. 281 ◽

Cited By ~ 1

Author(s):

Andrés Ricardo Pérez-Riera ◽

Rodrigo Daminello Raimundo ◽

Rodrigo Akira Watanabe ◽

José Luiz Figueiredo ◽

Luiz Carlos de Abreu

Keyword(s):

Sodium Channel ◽

Cardiac Muscle ◽

Heart Function ◽

Heart Diseases ◽

Cardiac Conduction ◽

Activation Process ◽

Α Subunit ◽

Cardiac Sodium Channel ◽

Wide Range ◽

Scn5a Gene

The mechanisms of cellular excitability and propagation of electrical signals in the cardiac muscle are very important functionally and pathologically. The heart is constituted by three types of muscle: atrial, ventricular, and specialized excitatory and conducting fi bers. From a physiological and pathophysiological point of view, the conformational states of the sodium channel during heart function constitute a signifi cant aspect for the diagnosis and treatment of heart diseases. Functional states of the sodium channel (closed, open, and inactivated) and their structure help to understand the cardiac regulation processes. There are areas in the cardiac muscle with anatomical and functional differentiation that present automatism, thus subjecting the rest of the fi bers to their own rhythm. The rate of these (pacemaker) areas could be altered by modifi cations in ions, temperature and especially, the autonomic system. Excitability is a property of the myocardium to react when stimulated. Another electrical property is conductivity, which is characterized by a conduction and activation process, where the action potential, by the all-or-nothing law, travels throughout the heart. Heart relaxation also stands out as an active process, dependent on the energetic output and on specificion and enzymatic actions, with the role of sodium channel being outstanding in the functional process. In the gene mutation aspects that encode the rapid sodium channel (SCN5A gene), this channel is responsible for several phenotypes, such as Brugada syndrome, idiopathic ventricular fibrillation, dilated cardiomyopathy, early repolarization syndrome, familial atrial fibrillation, variant 3 of long QT syndrome, multifocal ectopic ventricular contractions originating in Purkinje arborizations, progressive cardiac conduction defect (Lenègre disease), sudden infant death syndrome, sick sinus syndrome, sudden unexplained nocturnal death syndrome, among other sodium channel alterations with clinical overlapping. Finally, it seems appropriate to consider the “sodium channel syndrome” (mutations in the gene of the α subunit of the sodium channel, SCN5A gene) as a single clinical entity that may manifest in a wide range of phenotypes, to thus have a better insight on these cardiac syndromes and potential outcomes for their clinical treatment.

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Enhanced Classification of Brugada Syndrome–Associated and Long-QT Syndrome–Associated Genetic Variants in the SCN5A -Encoded Na v 1.5 Cardiac Sodium Channel

Circulation Cardiovascular Genetics ◽

10.1161/circgenetics.114.000831 ◽

2015 ◽

Vol 8 (4) ◽

pp. 582-595 ◽

Cited By ~ 60

Author(s):

Jamie D. Kapplinger ◽

John R. Giudicessi ◽

Dan Ye ◽

David J. Tester ◽

Thomas E. Callis ◽

...

Keyword(s):

Sodium Channel ◽

Long Qt Syndrome ◽

Brugada Syndrome ◽

Genetic Variants ◽

Long Qt ◽

Cardiac Sodium Channel ◽

Qt Syndrome

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Role of CACNA1C variants in Brugada syndrome: clinical aspects and genetic testing strategies

European Heart Journal ◽

10.1093/ehjci/ehaa946.3584 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

V Novelli ◽

M Memmi ◽

A Malovini ◽

A Mazzanti ◽

N Liu ◽

...

Keyword(s):

Genetic Testing ◽

Brugada Syndrome ◽

Genetic Variants ◽

Clinical Aspects ◽

Functional Evaluation ◽

Discovery Cohort ◽

Functional Studies ◽

Pathogenic Variants ◽

The Impact

Abstract Background Inconsistent data support the role of CACNA1C as a disease-causing gene responsible for Brugada syndrome (BrS). As of today, the only gene consistently linked with BrS is SCN5A. Several CACNA1c genetic variants have been reported in association wirh BrS; however, due to the limited evidence, CACNA1C is not suggested for routine genetic screening for BrS. Purpose In this study, we carried out a systematic screening of CACNA1C gene, including a functional evaluation of the identified variants, in order to determine the yield of screening in a large series of BrS probands and to address the hypothesis that an appropriate clinical selection of patients would substantially improve the yield of genetic testing. Methods and results Overall 564 consecutive patients, referred for BrS genetic testing, were sequenced for CACNA1C gene. Patients were divided in two groups: discovery cohort (n=200 patients) and confirmation cohort (n=363 patients). Furthermore, analysis of the clinical phenotypes of a matched SCN5A positive BrS cohort (n=146) was included for phenotype characterization. In the discovery cohort we identified 11 different genetic variants of whom 2 (18%) were considered as potentially causative based on ACMG guidelines. However, a large proportion (81%) was classified as variants of unknown significance (VUS). Functional evaluation of the identified variants, including pathogenic and VUS, was assessed by patch-clamp and immunofluorescence studies. Re-evaluation of the variants, including functional studies results, indicated an increase of pathogenic or likely pathogenic variants (81%) getting a yield of screening of 5% in the discovery cohort. Results from the confirmation cohort confirmed a low rate of CACNA1C carriers with a yield of screening of 2.2%. Analysing the clinical phenotype of all CACNA1C carriers showed a significantly shorter QTc [371 ms ± 16 ms vs. 399±18 ms; p=0.000004]. Furthermore, the prevalence of CACNA1C variants was highest (12.9%) among patients with a QTc in the lowest quartile (QTc <390 ms). ROC curve showed an AUC of 0.91 for QTc a cut-off of 385 ms, suggesting a high predictive accuracy. Conclusion We confirmed that CACNA1C variants are not a common cause of BrS, with a yield of screening of 2–5%. However, pathogenic variants are more frequent (12.5%) in patients with a shorter QTc, suggesting a genetic testing strategy in this subgroup of BrS patients. Furthermore, our data highlights the impact of robust functional studies to improve variant classification and reduce uncertainties. Funding Acknowledgement Type of funding source: None

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Epigenetic Changes Governing Scn5a Expression in Denervated Skeletal Muscle

International Journal of Molecular Sciences ◽

10.3390/ijms22052755 ◽

2021 ◽

Vol 22 (5) ◽

pp. 2755

Author(s):

David Carreras ◽

Rebecca Martinez-Moreno ◽

Mel·lina Pinsach-Abuin ◽

Manel M. Santafe ◽

Pol Gomà ◽

...

Keyword(s):

Skeletal Muscle ◽

Cardiac Tissue ◽

Mrna Levels ◽

Striated Muscles ◽

Aberrant Expression ◽

Protein Coding ◽

Α Subunit ◽

Super Enhancer ◽

Cardiac Sodium Channel ◽

Scn5a Gene

The SCN5A gene encodes the α-subunit of the voltage-gated cardiac sodium channel (NaV1.5), a key player in cardiac action potential depolarization. Genetic variants in protein-coding regions of the human SCN5A have been largely associated with inherited cardiac arrhythmias. Increasing evidence also suggests that aberrant expression of the SCN5A gene could increase susceptibility to arrhythmogenic diseases, but the mechanisms governing SCN5A expression are not yet well understood. To gain insights into the molecular basis of SCN5A gene regulation, we used rat gastrocnemius muscle four days following denervation, a process well known to stimulate Scn5a expression. Our results show that denervation of rat skeletal muscle induces the expression of the adult cardiac Scn5a isoform. RNA-seq experiments reveal that denervation leads to significant changes in the transcriptome, with Scn5a amongst the fifty top upregulated genes. Consistent with this increase in expression, ChIP-qPCR assays show enrichment of H3K27ac and H3K4me3 and binding of the transcription factor Gata4 near the Scn5a promoter region. Also, Gata4 mRNA levels are significantly induced upon denervation. Genome-wide analysis of H3K27ac by ChIP-seq suggest that a super enhancer recently described to regulate Scn5a in cardiac tissue is activated in response to denervation. Altogether, our experiments reveal that similar mechanisms regulate the expression of Scn5a in denervated muscle and cardiac tissue, suggesting a conserved pathway for SCN5A expression among striated muscles.

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Human SCN5A gene mutations alter cardiac sodium channel kinetics and are associated with the Brugada syndrome

Cardiovascular Research ◽

10.1016/s0008-6363(99)00350-8 ◽

1999 ◽

Vol 44 (3) ◽

pp. 507-517 ◽

Cited By ~ 121

Author(s):

M Rook

Keyword(s):

Sodium Channel ◽

Brugada Syndrome ◽

Gene Mutations ◽

Channel Kinetics ◽

Cardiac Sodium Channel ◽

Scn5a Gene

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Mechanistic insights into the interaction of the MOG1 protein with the cardiac sodium channel Nav1.5 clarify the molecular basis of Brugada syndrome

Journal of Biological Chemistry ◽

10.1074/jbc.ra118.003997 ◽

2018 ◽

Vol 293 (47) ◽

pp. 18207-18217 ◽

Cited By ~ 4

Author(s):

Gang Yu ◽

Yinan Liu ◽

Jun Qin ◽

Zhijie Wang ◽

Yushuang Hu ◽

...

Keyword(s):

Amino Acids ◽

Cell Surface ◽

Sodium Channel ◽

Brugada Syndrome ◽

Molecular Basis ◽

3D Structure ◽

Deletion Analysis ◽

Cardiac Conduction ◽

Α Subunit ◽

Cardiac Sodium Channel

Nav1.5 is the α-subunit of the cardiac sodium channel complex. Abnormal expression of Nav1.5 on the cell surface because of mutations that disrupt Nav1.5 trafficking causes Brugada syndrome (BrS), sick sinus syndrome (SSS), cardiac conduction disease, dilated cardiomyopathy, and sudden infant death syndrome. We and others previously reported that Ran-binding protein MOG1 (MOG1), a small protein that interacts with Nav1.5, promotes Nav1.5 intracellular trafficking to plasma membranes and that a substitution in MOG1, E83D, causes BrS. However, the molecular basis for the MOG1/Nav1.5 interaction and how the E83D substitution causes BrS remains unknown. Here, we assessed the effects of defined MOG1 deletions and alanine-scanning substitutions on MOG1's interaction with Nav1.5. Large deletion analysis mapped the MOG1 domain required for the interaction with Nav1.5 to the region spanning amino acids 146–174, and a refined deletion analysis further narrowed this domain to amino acids 146–155. Site-directed mutagenesis further revealed that Asp-148, Arg-150, and Ser-151 cluster in a peptide loop essential for binding to Nav1.5. GST pulldown and electrophysiological analyses disclosed that the substitutions E83D, D148Q, R150Q, and S151Q disrupt MOG1's interaction with Nav1.5 and significantly reduce its trafficking to the cell surface. Examination of MOG1's 3D structure revealed that Glu-83 and the loop containing Asp-148, Arg-150, and Ser-151 are spatially proximal, suggesting that these residues form a critical binding site for Nav1.5. In conclusion, our findings identify the structural elements in MOG1 that are crucial for its interaction with Nav1.5 and improve our understanding of how the E83D substitution causes BrS.

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Genetic Characteristics and Transcriptional Regulation of Sodium Channel Related Genes in Chinese Patients With Brugada Syndrome

Frontiers in Cardiovascular Medicine ◽

10.3389/fcvm.2021.714844 ◽

2021 ◽

Vol 8 ◽

Author(s):

Ziguan Zhang ◽

Hongwei Chen ◽

Wenbo Chen ◽

Zhenghao Zhang ◽

Runjing Li ◽

...

Keyword(s):

Transcriptional Regulation ◽

Brugada Syndrome ◽

Southern China ◽

Gene Mutations ◽

Northern China ◽

Chinese Patients ◽

Α Subunit ◽

Genetic Characteristics ◽

C Terminus ◽

Scn5a Gene

Objective: To investigate the genetic characteristics and transcriptional regulation of the SCN5A gene of Brugada syndrome (BrS) patients in China.Methods: Using PubMed, Medline, China National Knowledge Internet (CNKI), and Wanfang Database, Chinese patients with BrS who underwent SCN5A gene testing were studied.Results: A total of 27 suitable studies involving Chinese BrS patients who underwent the SCN5A gene test were included. A total of 55 SCN5A gene mutations/variations were reported in Chinese BrS patients, including 10 from southern China and 45 from northern China. Mutations/variations of BrS patients from southern China mostly occurred in the regions of the α-subunit of Nav1.5, including DIII (Domain III), DIV, DIII-DIV, C-terminus regions, and the 3'UTR region. Furthermore, we analyzed the post-transcriptional modifications (PTMs) throughout the Nav1.5 protein encoded by SCN5A and found that the PTM changes happened in 72.7% of BrS patients from southern China and 26.7% from northern China.Conclusions: SCN5A mutations/variations of BrS patients in southern China mostly occurred in the DIII-DIV to C-terminus region and the 3'-UTR region of the SCN5A gene, different from northern China. PTM changes were consistent with the mutation/variation distribution of SCN5A, which might be involved in the regulation of the pathogenesis of BrS patients.

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