Stem-cell niche self-restricts the signaling range via receptor-ligand degradation

Abstract

Stem-cell niche signaling is short-range in nature, such that only stem cells and not their differentiating progeny experience self-renewing signals 1 . At the apical tip of the Drosophila testes, 8 to 10 germline stem cells (GSCs) surround the hub, the niche signaling center. Microtubule-based nanotubes (MT-nanotubes) formed by GSCs project into the hub cells, serves as the platform for niche signal reception. Here we show that the receptor for Decapentaplegic (Dpp) accumulated on MT-nanotubes is internalized into hub cells together with the Dpp ligand, and both are degraded in the hub cell lysosomes. Perturbation of hub lysosomal function or MT-nanotube formation lead to excess receptor retention within GSCs as well as excess Dpp ligand that diffuses out of the hub. Our results indicate that degradation of the self-renewal ligand/receptor by niche cells specially restrict the niche signal range, and that might be a general feature of stem-cell niche signaling.