Transcriptional regulation of SCN5A and cardiac conduction by the novel Brugada syndrome associated transcription factor WT1

Brugada syndrome (BrS) is an inherited cardiac arrhythmic disorder caused by conduction slowing primarily affecting the right ventricular (RV) outflow tract (RVOT). A recent genome-wide association study (GWAS) implicated a genomic region in chromosome 11, overlapping the transcription factor WT1, in BrS susceptibility. Here, we investigated the role of WT1 on cardiac conduction using a heterozygous knockout mouse model (Wt1+/-). Transcriptomic analysis revealed increased Scn5a predominantly in Wt1+/- cardiomyocytes located subepicardially in the RV and RVOT without any changes in electrical properties. To unmask an effect on cardiac conduction, we performed optical mapping in a severely challenged setting offered by Scn5a haploinsufficiency, ageing, and exposure to the sodium channel blocker ajmaline and found that diminished Wt1 improved the observed slowed conduction. Examination of human single-nuclei cardiac datasets indicated a strong negative correlation between WT1 and SCN5A expression. In line with this observation, cardiac samples from patients carrying mutations in SCN5A showed increased WT1 protein abundance in histological sections, suggesting that increased WT1, and not loss, is associated with BrS pathophysiology. By deleting the mouse orthologue of a BrS-associated noncoding region (RE) harboring a candidate regulatory element, we established that this RE controls expression of Wt1 specifically in the (sub)epicardium of the RV. Lastly, transient overexpression of WT1 in hiPSC-derived cardiomyocytes resulted in notably reduced sodium current density. Our study thereby identifies the transcription factor WT1 as a novel contributor to the pathophysiology of BrS, at least in part, through SCN5A.