Single-cell transcriptome analysis reveals CD34 as a marker of human sinoatrial node pacemaker cardiomyocytes [CITE-seq]

The sinoatrial node regulates the heart rate throughout life. Failure of this primary pacemaker results in life-threatening, slow heart rhythm. Despite its important function, the cellular and molecular composition of the human sinoatrial node is not resolved. Particularly, no cell surface marker to identify and isolate sinoatrial node pacemaker cells has been reported. Here we use single-nuclei/cell RNA sequencing of fetal and human pluripotent stem cell-derived sinoatrial node cells and show that they consist of three subtypes of pacemaker cells, including Core Pacemaker, Sinus Venosus, and Transitional Cells. Our study identifies a host of sinoatrial node pacemaker markers including MYH11, BMP4, and the cell surface antigen CD34. We demonstrate that sorting for CD34+ cells from stem cell differentiation cultures enriches for sinoatrial node cells with a functional pacemaker phenotype. This sinoatrial node pacemaker cell surface marker is highly valuable for stem cell-based disease modelling, drug discovery, cell replacement therapies, as well as the delivery of therapeutics to sinoatrial node cells in vivo using antibody-drug conjugates. Overall design: Examining the heterogenity and global transcriptome of the cells present in the endogenous sinoatrial node and human pluripotent stem cell derived sinoatrial node-like pacemaker cells.