T-box transcription factor 3 governs a transcriptional program for the function of the mouse atrioventricular conduction system

Rajiv A Mohan, Fernanda M Bosada, Jan H van Weerd, Karel van Duijvenboden, Jianan Wang, Mathilda T M Mommersteeg, Ingeborg B Hooijkaas, Vincent Wakker, Corrie de Gier-de Vries, Ruben Coronel, Gerard J J Boink, Jeroen Bakkers, Phil Barnett, Bas J Boukens, Vincent M Christoffels

Research output: Contribution to journal/periodicalArticleScientificpeer-review

Abstract

Genome-wide association studies have identified noncoding variants near TBX3 that are associated with PR interval and QRS duration, suggesting that subtle changes in TBX3 expression affect atrioventricular conduction system function. To explore whether and to what extent the atrioventricular conduction system is affected by Tbx3 dose reduction, we first characterized electrophysiological properties and morphology of heterozygous Tbx3 mutant (Tbx3+/-) mouse hearts. We found PR interval shortening and prolonged QRS duration, as well as atrioventricular bundle hypoplasia after birth in heterozygous mice. The atrioventricular node size was unaffected. Transcriptomic analysis of atrioventricular nodes isolated by laser capture microdissection revealed hundreds of deregulated genes in Tbx3 +/- mutants. Notably, Tbx3 +/- atrioventricular nodes showed increased expression of working myocardial gene programs (mitochondrial and metabolic processes, muscle contractility) and reduced expression of pacemaker gene programs (neuronal, Wnt signaling, calcium/ion channel activity). By integrating chromatin accessibility profiles (ATAC sequencing) of atrioventricular tissue and other epigenetic data, we identified Tbx3-dependent atrioventricular regulatory DNA elements (REs) on a genome-wide scale. We used transgenic reporter assays to determine the functionality of candidate REs near Ryr2, an up-regulated chamber-enriched gene, and in Cacna1g, a down-regulated conduction system-specific gene. Using genome editing to delete candidate REs, we showed that a strong intronic bipartite RE selectively governs Cacna1g expression in the conduction system in vivo. Our data provide insights into the multifactorial Tbx3-dependent transcriptional network that regulates the structure and function of the cardiac conduction system, which may underlie the differences in PR duration and QRS interval between individuals carrying variants in the TBX3 locus.

Original languageEnglish
Pages (from-to)18617-18626
Number of pages10
JournalProceedings of the National Academy of Sciences of the United States of America
Volume117
Issue number31
DOIs
Publication statusPublished - 04 Aug 2020

Keywords

  • Animals
  • Arrhythmias, Cardiac
  • Atrioventricular Node/metabolism
  • Calcium Channels, T-Type/genetics
  • Mice
  • Mice, Transgenic
  • Mutation/genetics
  • Ryanodine Receptor Calcium Release Channel/genetics
  • T-Box Domain Proteins/genetics
  • Transcriptome/genetics

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