An integral program for tissue renewal and regeneration: Wnt signaling and stem cell control

Controlling stem cells and their niches

Adult organs such as the intestines and skin continually renew themselves every few days or weeks. In several mammalian tissues, this renewal relies on Wnt signaling. Clevers et al. review this crucial role in stem cell self renewal. Wnt plays a pivotal role in tissue regeneration even in the earliest animals. Wnt proteins function mainly as short-range signals between adjacent cells. The short-range, spatially-constrained nature of Wnt signals underpins mammalian stem cell niche architecture and tissue self-organization.

Science , this issue [Related article:]10.1126/science.1248012

Abstract

Stem cells fuel tissue development, renewal, and regeneration, and these activities are controlled by the local stem cell microenvironment, the “niche.” Wnt signals emanating from the niche can act as self-renewal factors for stem cells in multiple mammalian tissues. Wnt proteins are lipid-modified, which constrains them to act as short-range cellular signals. The locality of Wnt signaling dictates that stem cells exiting the Wnt signaling domain differentiate, spatially delimiting the niche in certain tissues. In some instances, stem cells may act as or generate their own niche, enabling the self-organization of patterned tissues. In this Review, we discuss the various ways by which Wnt operates in stem cell control and, in doing so, identify an integral program for tissue renewal and regeneration.