Rapidly cycling stem cells regenerate the intestine independent ofLgr5^highcells

AbstractThe +4 cells in intestinal crypts are DNA damage-resistant and contribute to regeneration. However, their exact identity and the mechanism underlying +4 cell-mediated regeneration remain unclear. Using lineage tracing, we show that cells marked by anMsi1reporter (Msi1+) are enriched at the +4 position in intestinal crypts and exhibit DNA damage resistance. Single-cell RNA sequencing reveals that theMsi1+cells are heterogeneous with the majority being intestinal stem cells (ISCs). The DNA damage-resistant subpopulation ofMsi1+cells is characterized by low-to-negativeLgr5expression and is more rapidly cycling thanLgr5highradio-sensitive crypt base columnar stem cells (CBCs); they enable fast repopulation of the intestinal epithelium independent of CBCs that are largely depleted after irradiation. Furthermore, relative to CBCs,Msi1+cells preferentially produce Paneth cells during homeostasis and upon radiation repair. Together, we demonstrate that the DNA damage-resistantMsi1+cells are rapidly cycling ISCs that maintain and regenerate the intestinal epithelium.