Biology subjects

Boukens, B. J.

Publications and source records attributed to Boukens, B. J..

3 recordsLinked to original sources

bioRxiv2025

The Brugada syndrome associated gene WT1 impacts on SCN5A expression and cardiac conduction

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.

genetics↗

bioRxiv2022

An atrial fibrillation-associated regulatory region modulates cardiac Tbx5 levels and arrhythmia susceptibility

Heart development and rhythm control are highly Tbx5 dosage-sensitive. TBX5 haploinsufficiency causes congenital conduction disorders, whereas increased expression levels of TBX5 in human heart samples has been associated with atrial fibrillation. We deleted the conserved mouse orthologues of two independent AF-associated genomic regions in the Tbx5 locus, one intronic (RE(int)-/-) and one downstream of Tbx5 (RE(down)-/-). In both lines we observed a modest (30%) increase of Tbx5 in the postnatal atria. To gain insight into the effects of slight dosage increase in vivo, we investigated the atrial transcriptional, epigenetic and electrophysiological properties of both lines. We observed induction of genes involved in development, ion transport and conduction, increased action potential duration and increased susceptibility to atrial arrhythmias. We identified an AF-associated variant in the human intronic regulatory region that increases transcriptional activity. Expression of the AF-associated transcription factor Prrx1 was induced in RE(int)-/- cardiomyocytes. We found that some of the transcriptional and functional changes in the atria caused by increased Tbx5 expression were normalized when reducing cardiac Prrx1 expression in RE(int)-/- mice, indicating an interaction between these two AF genes. We conclude that modest increases in expression of dose-dependent transcription factors, caused by common regulatory variants, significantly impact on the cardiac gene regulatory network and disease susceptibility.

molecular biology↗

bioRxiv2020

The mechanism underlying J-waves and T-waves in the electrocardiogram of mice and zebra finches

Brief cardiac cycles are required to achieve high heart rates as seen in endothermic animals. A main determinant of the cardiac cycle is the repolarization phase of the cardiac action potential, which is visible in the ECG as a T-wave. In mammals with high heart rates - such as rodents - the repolarization phase is short and the ECG is characterized by a positive deflection following the QRS-complex, the J-wave. It is unclear whether birds with high heart rates show similar ECG characteristics. Here we study cardiac repolarization and the ECG in the zebra finch which has high heart rates. In ex vivo hearts of zebra finch (N=5) and mouse (N=5), pseudo-ECGs and optical action potentials were measured. In both species, total ventricular activation was fast with QRS durations shorter than 10ms. Ventricular activation progressed from the left to the right ventricle in zebra finch whereas the activation pattern was apex-to-base in mouse. In both species, phase 1 early repolarization followed the activation front, causing a positive J-wave in the pseudo-ECG. In zebra finch, late repolarization was directed from the right ventricle to the left ventricle, whereas late repolarization was directed opposite in mouse. Accordingly, on the zebra finch ECG, the J-wave and the T-wave have the same direction, whereas in the mouse the J-wave and the T-wave are discordant. Our findings demonstrate early repolarization and the associated J-wave are not restricted to mammals and that they also occur within birds. Early repolarization may have evolved by convergence in association with high heart rates. Summary statementZebra finches are small birds with high heart rates. Similar to small rodents, the zebra finch ECG contains a J-wave, which is caused by early repolarization

physiology↗