A contemporary snapshot of intestinal stem cells and their regulation.

Intestinal stem cells (ISCs) marked by Lgr5 are located at the bottom of the epithelial crypt compartment. Canonical Wnt signaling, activated by Wnt/Rspo ligands, determines the stem cell identity of Lgr5 + ISCs and is strictly regulated by the ISC niche. Emerging evidence indicates that both epithelial and stromal compartments provide the requisite Wnt/Rspo ligands, confining the ISC niche to the lower crypt regions of the intestine. Recent studies have also shown that the ISC niche can reprogram differentiated cells to replenish lost ISCs following tissue injury, accounting for the epithelial cell plasticity within the crypt compartment. Here we review these recent advances and discuss the role of canonical Wnt signaling in maintaining homeostasis and effecting cell plasticity following tissue injury in the intestine, which could reveal potential novel therapeutic opportunities in the clinic.