Vedantham, V. | bioRxiv Science

bioRxiv2023

Single Cell Multi-Omics of an iPSC Model of Human Sinoatrial Node Development Reveals Genetic Determinants of Heart Rate and Arrhythmia Susceptibility

Human model systems for functional genomics of heart rhythm are needed to translate genome wide association studies into biological insight and actionable targets. Here we develop a human induced pluripotent stem cell sinoatrial node system that recapitulated the transcriptional and epigenetic heterogeneity of primary human pacemaker tissue, permitting exploration of heart rhythm-associated single nucleotide polymorphisms (SNPs) in a cell subtype-specific manner. Using self-transcribing active regulatory region sequencing (STARR-seq), we experimentally validated numerous enhancers containing heart rhythm associated variants. We demonstrated the utility of this platform for fine mapping of candidate causal SNPs by identifying an AF-associated variant at the ATXN1 locus that affects signal responsiveness of an enhancer, and a variant at the GNB4 locus that regulates cardiac autonomic sensitivity, leading to a pleiotropic effect on heart rate and atrial fibrillation. Taken together, these data establish a robust human cellular system to explore the mechanistic basis of heart rhythm heritability.

developmental biology↗

bioRxiv2023

Cholecystokinin-A Signaling Regulates Automaticity of Pacemaker Cardiomyocytes and Shortens Sinus Node Recovery Time

AimsThe behavior of pacemaker cardiomyocytes (PCs) in the sinoatrial node (SAN) is modulated by neurohormonal and paracrine factors, many of which signal through G-protein coupled receptors (GPCRs). The aims of the present study are to catalog GPCRs that are differentially expressed in the mammalian SAN and to define the acute physiological consequences of activating the cholecystokinin-A signaling system in isolated PCs. Methods and ResultsUsing bulk and single cell RNA sequencing datasets, we identify a set of GPCRs that are differentially expressed between SAN and right atrial tissue, including several whose roles in PCs and in the SAN have not been thoroughly characterized. Focusing on one such GPCR, Cholecystokinin-A receptor (CCKAR), we demonstrate expression of Cckar mRNA specifically in mouse PCs, and further demonstrate that subsets of SAN fibroblasts and neurons within the cardiac intrinsic nervous system express cholecystokinin, the ligand for CCKAR. Using mouse models, we find that while baseline SAN function is not dramatically affected by loss of CCKAR, the firing rate of individual PCs is slowed by exposure to sulfated cholecystokinin-8 (sCCK-8), the high affinity ligand for CCKAR. The effect of sCCK-8 on firing rate is mediated by reduction in the rate of spontaneous phase 4 depolarization of PCs and is mitigated by activation of beta-adrenergic signaling. Conclusions(1) PCs express many GPCRs whose specific roles in SAN function have not been characterized, (2) Activation of the the cholecystokinin-A signaling pathway regulates PC automaticity.

physiology↗