IP: Dra. Sara Pagans Lista/ Dr. Guillermo Pérez González

Resumen del proyecto: Brugada syndrome (BrS) is a rare inherited cardiac disorder with high susceptibility to ventricular arrhythmias and sudden cardiac death. Single nucleotide variants (SNVs) in protein-coding regions of cardiac ion channels account for 25-30% of BrS cases. These SNVs are mostly found in the alpha subunit of the cardiac sodium channel gene SCN5A. However, in a large fraction of BrS diagnosed patients, the etiology of the disease is still unknown. In our recent study (Pinsach-Abuin et al, Cell Reports Medicine 2021), we demonstrated that the composition of a haplotype comprising 7-SNVs in the SCN5A-SCN10A locus is associated with different susceptibilities to BrS. Our analysis showed that the most common haplotype in the European population, Hap1, is more frequent in BrS patients than in control individuals, while Hap2 and Hap3 are more common in control individuals. We also showed that Hap1 represents a risk haplotype following a model of recessive inheritance, while Hap2 and Hap3 represent protective haplotypes. These findings represent a change of paradigm in BrS genetics, and suggest that haplotype composition could be used for BrS-risk assessment. Furthermore, the observation that the 7 SNVs lie within an enhancer element suggests that haplotype composition has an impact on cardiac gene expression. On the other hand, we have identified a family with a pathogenic variant, NaV1.5_p.V1525M, related to BrS. Electrophysiological studies in cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CMs), show a dominant negative (DN) effect, observed as a dramatic loss of sodium current (INa). However, the INa was not decreased in hiPSC-CMs carrying the variant together with the protective polymorphism H558R. Therefore, we propose that the DN effect results from dimer formation of V1525M and WT alpha subunits. We postulate that the rescuing effect exerted by the polymorphism H558R results from its interference with dimer formation. To validate these hypotheses, we will perform a comprehensive haplotype analysis of the SCN5A-SCN10A locus in a group of BrS and control individuals using nanopore long-read sequencing. We will also study potential correlations between haplotype composition and cardiac traits. Second, we propose to deconstruct the association between BrS-risk/protection and haplotype composition at a functional level with two complementary approaches: using hiPSC-CMs and performing a cis-eQTL analysis in the GTEx platform with genomic and gene expression data. Third, we propose to examine the role of the polymorphism H558R in channel dimerization. We will study single channel coupled gating and perform a biochemical analysis from hIPSC-CMs carrying the pathogenic variant alone, together with the polymorphism, or none-carriers. And fourth, we will determine the haplotype composition of these hiPSC- CMs and their SCN5A and SCN10A-short (Nav1.8-short) RNA expression levels. We will also assess the role of the Nav1.8-short peptide on Nav1.5 currents in these cells. This approach will allow us to directly assess the possible interactions between protective and deleterious factors in patient-specific cells. We anticipate that this proposal will advance our understanding of the role the SCN5A-SCN10A haplotype in BrS risk and provide new insights into underlying molecular mechanisms of inherited cardiac arrhythmias. Moreover, we predict that this proposal will have an important impact on the diagnosis and management of BrS.

Entidad financiadora: Agencia Estatal de Investigación, Ministerio de Ciencia e Innovación