SCN5A compound heterozygosity mutation in Brugada syndrome: Functional consequences and the implication for pharmacological treatment

• Published in: Life sciences (1973) 2021-08, Vol.278, p.119646-119646, Article 119646
• Main Authors: Joviano-Santos, J.V., Santos-Miranda, A., Neri, E.A., Fonseca-Alaniz, M.H., Krieger, J.E., Pereira, A.C., Roman-Campos, D.
• Format: Article
• Language: English
• Subjects: Brugada syndrome; Cell membranes; Channels; Compound mutation; Drug therapy; Heterozygosity; Immunofluorescence; Impact analysis; In vitro methods and tests; Incubation; Loss-of-function; Mutants; Mutation; Pharmacology; Phenotypes; Quinidine; SCN5A; Sodium channels; Sodium channels (voltage-gated); Sodium current
• ISSN: 0024-3205; 1879-0631
• DOI: 10.1016/j.lfs.2021.119646

SCN5A gene encodes the α-subunit of Nav1.5, mainly found in the human heart. SCN5A variants are the most common genetic alterations associated with Brugada syndrome (BrS). In rare cases, compound heterozygosity is observed; however, its functional consequences are poorly understood. We aimed to analyze the functional impact of de novo Nav1.5 mutations in compound heterozygosity in distinct alleles (G400R and T1461S positions) previously found in a patient with BrS. Moreover, we evaluated the potential benefits of quinidine to improve the phenotype of mutant Na+ channels in vitro. The functional properties of human wild-type and Nav1.5 variants were evaluated using whole-cell patch-clamp and immunofluorescence techniques in transiently expressed human embryonic kidney (HEK293) cells. Both variants occur in the highly conservative positions of SCN5A. Although all variants were expressed in the cell membrane, a significant reduction in the Na+ current density (except for G400R alone, which was undetected) was observed along with abnormal biophysical properties, once the variants were expressed in homozygosis and heterozygosis. Interestingly, the incubation of transfected cells with quinidine partially rescued the biophysical properties of the mutant Na+ channel. De novo compound heterozygosis mutations in SNC5A disrupt the Na+ macroscopic current. Quinidine could partially reverse the in vitro loss-of-function phenotype of Na+ current. Thus, our data provide, for the first time, a detailed biophysical characterization of dysfunctional Na+ channels linked to compound heterozygosity in BrS as well as the benefits of the pharmacological treatment using quinidine on the biophysical properties of Nav1.5.