Intestinal stem cell, muscular niche and Wingless signaling.

Stem cells are typically supported by the local tissue microenvironment named niche. Intestinal stem cells (ISCs) in the Drosophila midgut do not seem to be typical: they are scattered along the basement membrane composed of extracellular matrix, and are not associated with any obvious cellular niches. In addition, regulatory mechanisms controlling ISC self-renewal remain unknown. Recently, we have obtained evidence to show that Wingless signaling is critical for ISC self-renewal. Wingless is specifically produced from the underlying circular muscles and is able to traverse through the basement membrane and reach ISCs, where it activates a canonical Wnt signaling pathway to promote ISC self-renewal. Our study reveals a muscular niche for ISCs and Wnt signaling as a conserved mechanism regulating ISC self-renewal from Drosophila to mammals. Here we provide a brief overview of our findings, and discuss future perspectives on the regulatory mechanisms underlying ISC self-renewal and differentiation.