PT  - JOURNAL ARTICLE
AU  - Alexandra Wiesinger
AU  - Jiuru Li
AU  - Lianne Fokkert
AU  - Priscilla Bakker
AU  - Arie O. Verkerk
AU  - Vincent M. Christoffels
AU  - Gerard J.J. Boink
AU  - Harsha D. Devalla
TI  - A single cell transcriptional roadmap for human pacemaker cell differentiation
AID  - 10.1101/2021.12.28.474383
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.12.28.474383
4099  - http://biorxiv.org/content/early/2021/12/29/2021.12.28.474383.short
4100  - http://biorxiv.org/content/early/2021/12/29/2021.12.28.474383.full
AB  - Each heartbeat is triggered by the sinoatrial node, the natural pacemaker of the heart. Animal models have revealed that pacemaker cells share a common progenitor with the (pro)epicardium, and that the pacemaker cardiomyocytes further diversify into “transitional”, “tail” and “head” subtypes. However, the underlying molecular mechanisms are poorly understood. Here, we studied the differentiation of human induced pluripotent stem cells into pacemaker cardiomyocytes. Single cell RNA sequencing identified the presence of myocardial populations resembling subtypes present in the formed sinoatrial node, and in addition revealed a side population of (pro)epicardial cells. Time-course trajectory analysis uncovered a role for WNT signaling in determining myocardial versus proepicardial cell fate. We experimentally demonstrate that presence of WNT signaling prior to the branching point of a common progenitor enhances proepicardial cell differentiation at the expense of myocardial pacemaker cells. Furthermore, we uncover a role for TGFβ and WNT signaling in differentiation towards transitional and head pacemaker subtypes, respectively. Our findings provide new biological insights into human pacemaker differentiation, open avenues for complex disease modeling and inform regenerative approaches.