Loss of the Atrial Fibrillation-related gene, Zfhx3, Results in Atrial Dilation and Arrhythmias by Disruption of Genes Essential for Cardiovascular Homeostasis
Background: ZFHX3, a gene that encodes a large transcription factor, is the second-most significantly associated locus with AF, but its function in the heart is unknown. This study aims to identify causative genetic variation related to AF at the ZFHX3 locus and examine the impact of Zfhx3 loss on cardiac function in mice. Methods: CRISPR-Cas9 genome editing, chromatin immunoprecipitation, and luciferase assays in pluripotent stem cell-derived cardiomyocytes were used to identify causative genetic variation related to AF at the ZFHX3 locus. Cardiac function was assessed by echocardiography, MRI, electrophysiology studies, calcium imaging, and RNA sequencing in mice with heterozygous and homozygous cardiomyocyte-restricted Zfhx3 deletion (Zfhx3 Het and KO, respectively). Human cardiac single-nucleus ATAC-sequencing data was analyzed to determine which genes in atrial cardiomyocytes are directly regulated by ZFHX3. Results: We found SNP rs12931021 modulates an enhancer regulating ZFHX3 expression, and the AF risk allele is associated with decreased ZFHX3 transcription. We observed a gene-dose response in AF susceptibility withZfhx3KO mice having higher incidence, frequency, and burden of AF thanZfhx3Het and WT mice, with alterations in conduction velocity, atrial action potential duration, calcium handling and the development of atrial enlargement and thrombus, and dilated cardiomyopathy. Zfhx3 loss results in atrial-specific differential effects on genes and signaling pathways involved in cardiac pathophysiology and AF. Conclusions: Our findings implicate ZFHX3 as the causative gene at the 16q22 locus for AF, and cardiac abnormalities caused by loss of cardiac Zfhx3 are due to atrial-specific dysregulation of pathways involved in AF-susceptibility. Together, these data reveal a novel and important role for Zfhx3 in the control of cardiac genes and signaling pathways essential for normal atrial function. Overall design: Total RNA was collected from left and right atria from Zfhx3 Het, KO, and wildtype (control) mice. Next, mRNA-seq libraries were generated and sequenced and differential expression analysis was performed.