Introduction

Brugada syndrome (BrS) is a rare inherited cardiac arrhythmia characterized by an increased risk of sudden death due to ventricular arrhythmias originating from the right ventricle (RV) and its outflow tract. Rare genetic variants in SCN5A gene, which generates the main cardiac sodium current (INa), are involved in only 20% of BrS cases. Genome-wide association studies identified strong polygenic influence of specific common risk haplotypes on BrS occurrence. The present study focuses on the risk allele located in an intronic region of ZFPM2 transcription factor gene, known to be involved in cardiac development but which has not been linked so far to the regulation of cardiac electrical activity.

Objective

To study the role of ZFPM2 risk haplotype in cardiac electrical activity using RV cells differentiated from human induced pluripotent stem cells (hiPSCs).

Method

A locus depicting epigenetic characteristics of distal enhancer, and that includes the ZFPM2 risk haplotype, has been identified using both CHIP-seq and ATAC-seq data. This locus has been precisely CRISPR-deleted (i-ZFPM2) in a control (WT) hiPSC line. Both lines were differentiated into RV cells using a cardioid protocol adapted from Schmidt C. et al (Cell, 2023). Gene expression, voltage clamp and current clamp experiments were conducted on differentiated cells.

Results

Differentiated cells displayed a gene expression profile characteristic of RV tissue. In accordance with the hypothesis that the locus is an enhancer, the expression of ZFPM2 was reduced. Interestingly, the expression of SCN5A was also reduced. Accordingly, the i-ZFPM2 RV cells showed a significant reduction of INa as compared to WT (-61%, p<0.01) with no alteration of biophysical properties of the channel. The amplitude and the dV/dtmax of the action potential were also decreased.

Conclusion

Our results suggest that the investigated region regulates ZFPM2 expression in human RV cells and that ZFPM2 participates in the control of cardiac electrical activity through SCN5A regulation. These data may unveil new mechanisms involved in BrS pathophysiology. Further studies will decipher the precise mechanisms by which this regulation occurs.