Variant Intronic Enhancer Controls SCN10A-short Expression and Heart Conduction

Abstract

Background: Genetic variants in SCN10A , encoding the neural voltage-gated sodium channel NaV1.8, are strongly associated with atrial fibrillation, Brugada syndrome, cardiac conduction velocities and heart rate. The cardiac function of SCN10A has not been resolved, however, and diverging mechanisms have been proposed. Here, we investigated the cardiac expression of SCN10A and the function of a variant-sensitive intronic enhancer previously linked to the regulation of SCN5A , encoding the major essential cardiac sodium channel NaV1.5. Methods: The expression of SCN10A was investigated in mouse and human hearts. Using CRISPR/Cas9 genome editing, the mouse intronic enhancer was disrupted, and mutant mice were characterized by transcriptomic and electrophysiological analyses. The association of genetic variants at SCN5A-SCN10A enhancer regions and gene expression were evaluated by GWAS SNP mapping and expression QTL analysis. Results: We found that cardiomyocytes of the atria, sinoatrial node and ventricular conduction system express a short transcript comprising the last 7 exons of the gene ( Scn10a-short ). Transcription occurs from an intronic enhancer-promoter complex, while full length Scn10a transcript was undetectable in the human and mouse heart. Expression QTL analysis revealed that the genetic variants in linkage disequilibrium with genetic variant rs6801957 in the intronic enhancer associate with SCN10A transcript levels in the heart. Genetic modification of the enhancer in the mouse genome led to reduced cardiac Scn10a-short expression in atria and ventricles, reduced cardiac sodium current in atrial cardiomyocytes, atrial conduction slowing and arrhythmia, while expression of Scn5a , the presumed enhancer target gene, remained unaffected. In patch-clamp transfection experiments, expression of Scn10a-short -encoded NaV1.8-short increased NaV1.5-mediated sodium current. We propose that non-coding genetic variation modulates transcriptional regulation of Scn10a-short in cardiomyocytes that impacts on NaV1.5-mediated sodium current and heart rhythm. Conclusions: Genetic variants in and around SCN10A modulate enhancer function and expression of a cardiac-specific SCN10A-short transcript. We propose that non-coding genetic variation modulates transcriptional regulation of a functional C-terminal portion of NaV1.8 in cardiomyocytes that impacts on NaV1.5 function, cardiac conduction velocities and arrhythmia susceptibility.

Cavβ1 regulates T cell expansion and apoptosis independently of voltage-gated Ca2+ channel function

“…The alternative exon usage of human CACNA1I and CACNA1H as well as mouse Cacna1f in T cells we demonstrate here has not been reported before. Of note, Man et al recently reported that human and mouse cardiomyocytes do not express full-length transcripts of the neuronal voltage-gated sodium channel Nav1.8 ( Scn10a ), but instead express a short transcript ( Scn10a-short ) comprising only the last 7 exons 76 . Transcription of this short variant occurred from an intronic enhancer-promoter complex.…”

Clinical Characteristics, Genetic Findings and Arrhythmic Outcomes of Patients with Catecholaminergic Polymorphic Ventricular Tachycardia from China: A Systematic Review

“…In contrast, although the expert panel did not identify SCN10A as a causative mutation of CPVT, SCN10A variants were reported in patients with multiple mutations, in addition to patients with BrS [ 52 , 95 ]. Basic studies have also shown that SCN10A variants affect the myocardial sodium current and therefore affect the arrhythmogenic susceptibility of the patient [ 96 , 97 ]. As the SCN10A variant has not been previously detected in a CPVT patient, further study is needed to elucidate the complex causative relationship between genetic mutations and the CPVT phenotype.…”

Cardiogenetics: the role of genetic testing for inherited arrhythmia syndromes and sudden death

“…Other genes have been implicated in BrS, although they remain disputed for diagnostic purposes (table 1). 29 SCN10A encodes a neuronal sodium channel pore subunit Na V 1.8 with expression in intracardiac neuronal tissue, and possibly cardiomyocytes 30. A common variant with loss of function has been associated with BrS 31.…”

“…A common variant with loss of function has been associated with BrS 31. Mechanistic effects of SCN10A variants could, however, be related to consequent altered expression of SCN5A, or altered expression of a Na V 1.5-interacting shortened SCN10A transcript protein Na V 1.8-short 30…”