Abstract 735: Gene Therapy using Fragments of the SCN5A H558R Polymorphism Restores Function of a Brugada Syndrome Mutation
Brugada Syndrome (BrS) is caused by mutations in the cardiac sodium (Na) channel gene. One such mutation is R282H, which produces a loss of function. We demonstrated that coexpressing the SCN5A polymorphism H558R with this BrS mutation restored Na currents to wild type (WT) levels and provided an explanation for the incomplete penetrance of the disease in a family carrying the R282H mutation and the H558R polymorphism. We established that α-α subunit interactions near 558 were required for rescuing the R282H mutation. We therefore hypothesized that we could develop a gene therapy approach to prevent BrS using the H558R polymorphism to rescue the dysfunctional Na channel. Mini cDNA fragments including the major allele (H558) or the polymorphism (H558R) were generated and coexpressed with either Nav1.5 or R282H mutant channels in HEK cells. Coexpressing the major fragment, H558f, with the R282H mutant does not produce any measurable current as expected, since WT channels are incapable of rescuing the R282H mutation (n=12). Interestingly though, when the protein fragment with the polymorphism H558Rf was coexpressed with the R282H mutation, peak current density increased significantly from the undetectable levels of R282H alone (n=14, p<0.001) (Figure⇓). Using immunocytochemistry, we also observed that H558Rf restored trafficking of the R282H mutant to the cell membrane. We developed, using mini cDNA fragments of H558R, a gene therapy approach tailored to specific disease-causing mutants of BrS with the great advantage of not having to use the entire gene. Thus, we show that fragments of genetic polymorphisms are a tool for therapies aimed at rescuing dysfunctional protein channels.