Comparative Study of the Effects of an SCN5A Mutation within a Family Diagnosed with Brugada Syndrome using iPS-CM

Abstract

Brugada Syndrome (BrS) is a cardiac arrhythmogenic disease that predisposes to sudden cardiac death. It is associated with mutations in the SCN5A gene, encoding the cardiac sodium channel alpha subunit (NaV1.5). We investigated a mutation in the SCN5A gene (c. 4573 G>A; NaV1.5_p.V1525M), associated to BrS. Our objective was to analyze the differences in the sodium current (INa) properties among induced pluripotent stem cell-derived cardiomyocytes (iPS-CM) from three members of a family with two heterozygous carriers and one non-carrier of the mutation. Dermal fibroblasts from the three family members were reprogrammed to iPSc and further differentiated to beating iPS-CM monolayers. INa was studied using the whole-cell patch clamp technique. A total loss of INa was observed in a high percentage of the cells recorded from both mutation carriers (62% n=53 and 54% n=37, respectively). In the remaining cells, with measurable INa, we observed a 77.3% (n=19) and an 82% (n=13) reduction in INa density, compared to the non-carrier individual (n=13). Recovery from inactivation time constant was increased only in one of the two mutation carriers. We confirmed that SCN5A expression was comparable in the three family members’ iPS-CM by qPCR. In addition, we studied the mutation in tsA201 cells transfected to heterozygously express mutation (NaV1.5V1525M/WT). INa reduction in NaV1.5V1525M/WT was 24.3% of the tsA201 expressing NaV1.5WT/WT (n=28 and 23, respectively). tsA201 cells expressing NaV1.5V1525M/WT did not recapitulate the total loss of INa observed in iPS-CM. Overall, our results strongly suggest that the mutation NaV1.5_p.V1525M could cause BrS in this family. Moreover, it demonstrates the importance of the use of physiologically relevant models to elucidate the role of NaV1.5 mutations in arrhythmogenic diseases.