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

Abstract

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.

Alterations of the Sialylation Machinery in Brugada Syndrome

“…HEK293 (human embryonic kidney 293) cells were cultured in a controlled environment (5% CO 2 , 37 °C) and maintained in an appropriate medium (DMEM/F12) (Euroclone, Milan, Italy) supplemented with 10% FBS, 2 mM L-Glutammine, 100 U/mL, and 100 μg/mL Pen/Strep. Wild-Type SCN5A complementary DNA (cDNA) was subcloned into the pcDNA3.1 plasmid, as previously described [ 49 ]. SCN5A was transiently transfected using Viafect reagent (Promega, Madison, WI, USA) according to the manufacturer’s instructions.…”

Noncoding RNAs and Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes in Cardiac Arrhythmic Brugada Syndrome

“…However, female patients with BrS with arrhythmic events exhibit higher SCN5A mutation rates, and a relationship between gender vs. age at the onset of arrhythmic events and ethnicity [131]. In the majority of patients referred for BrS genetic testing with a single SCN5A mutation (74%), this was localized to the transmembrane region of the channel [127,132].…”

The Mechanism of Ajmaline and Thus Brugada Syndrome: Not Only the Sodium Channel!

“…Although it is generally agreed that variants in the SCN5A gene are involved in BrS, it is important to think of variants even within this gene as individual variants with specific effects, rather than thinking of all SCN5A variants collectively, as some may be benign, while others pathogenic ( 26 ). Along these lines, several studies have sought to understand the effect of specific SCN5A variants ( 37 , 72 – 80 ). It has been recently suggested that variants in the SCN5A gene may actually be prognostic, rather than diagnostic ( 35 , 38 , 39 ).…”