Visualization of Individual Cell Division History in Complex Tissues

The division potential of individual stem cells and the molecular consequences of successive rounds of proliferation remain largely unknown. Here, we developed an inducible cell division counter (iCOUNT) that reports cell division events in human and mouse tissues in vitro and in vivo. Analysing cell division histories of neural stem/progenitor cells (NSPCs) in the developing and adult brain, we show that iCOUNT can provide novel insights into stem cell behaviour. Further, we used single cell RNA-sequencing (scRNA-seq) of iCOUNT-labelled NSPCs and their progenies from the developing mouse cortex and forebrain-regionalized human organoids to identify molecular pathways that are commonly regulated between mouse and human cells, depending on individual cell division histories. Thus, we developed a novel tool to characterize the molecular consequences of repeated cell divisions of stem cells that allows an analysis of the cellular principles underlying tissue formation, homeostasis, and repair.