Key result
Deletion of pacemaker-specific regulatory elements in the SHOX2 and TBX3 loci resulted in selective loss of gene expression in the sinoatrial node and embryonic or neonatal lethality in mice.
Why the study?
Regulatory DNA elements controlling target gene expression in sinoatrial node pacemaker cells have remained undefined.
Identifies essential human pacemaker-specific regulatory elements, including a TBX3 enhancer linked to genetic variants influencing heart rate recovery after exercise.
Enhancer variants may contribute to SAN dysfunction; leaves open validation in human arrhythmia cohorts.
Rationale: The development and function of the pacemaker cardiomyocytes of the sinoatrial node (SAN), the leading pacemaker of the heart, are tightly controlled by a conserved network of transcription factors, including TBX3 (T-box transcription factor 3), ISL1 (ISL LIM homeobox 1), and SHOX2 (short stature homeobox 2). Yet, the regulatory DNA elements (REs) controlling target gene expression in the SAN pacemaker cells have remained undefined. Objective: Identification of the regulatory landscape of human SAN-like pacemaker cells and functional assessment of SAN-specific REs potentially involved in pacemaker cell gene regulation. Methods and Results: We performed Assay for Transposase-Accessible Chromatin using sequencing on human pluripotent stem cell–derived SAN-like pacemaker cells and ventricle-like cells and identified thousands of putative REs specific for either human cell type. We validated pacemaker cell–specific elements in the SHOX2 and TBX3 loci. CRISPR-mediated homozygous deletion of the mouse ortholog of a noncoding region with candidate pacemaker-specific REs in the SHOX2 locus resulted in selective loss of Shox2 expression from the developing SAN and embryonic lethality. Putative pacemaker-specific REs were identified up to 1 Mbp upstream of TBX3 in a region close to MED13L harboring variants associated with heart rate recovery after exercise. The orthologous region was deleted in mice, which resulted in selective loss of expression of Tbx3 from the SAN and (cardiac) ganglia and in neonatal lethality. Expression of Tbx3 was maintained in other tissues including the atrioventricular conduction system, lungs, and liver. Heterozygous adult mice showed increased SAN recovery times after pacing. The human REs harboring the associated variants robustly drove expression in the SAN of transgenic mouse embryos. Conclusions: We provided a genome-wide collection of candidate human pacemaker-specific REs, including the loci of SHOX2 , TBX3 , and ISL1 , and identified a link between human genetic variants influencing heart rate recovery after exercise and a variant RE with highly conserved function, driving SAN expression of TBX3 .
No takes yet. Share an insight, caveat, or question.
Eif et al. (2020) studied Sinoatrial node pacemaker development and function. CRISPR-mediated deletion of pacemaker-specific regulatory elements was evaluated on Gene expression, embryonic viability, and sinoatrial node recovery times. Deletion of pacemaker-specific regulatory elements in the SHOX2 and TBX3 loci resulted in selective loss of gene expression in the sinoatrial node and embryonic or neonatal lethality in mice.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: