Heparan Sulfate Proteoglycans in the Stem Cell Niche: Lessons from Drosophila

In addition to the obvious importance of stem cells in regenerative medicine, their unique behaviors and ingenious molecular systems for their control are of particular interest in the context of basic cell biology. Drosophila genetics plays a pivotal role to reveal fundamental principles of stem cell control mechanisms. Namely, in vivo studies using lineage tracing techniques elucidated the cellular and molecular mechanisms of the interactions between stem cells and the extracellular microenvironment. As one of the key components of the stem cell niche, heparan sulfate proteoglycans (HSPGs) have critical functions in regulating stem cell behavior. HSPGs serve as co-receptors for numerous ligands such as fibroblast growth factors, bone morphogenetic proteins, Wnt-related factors, hedgehog, and cytokines, which are all imperative regulators of stem cell behaviors. By modulating and orchestrating these niche factors’ signaling and distribution, HSPGs control the quantity, quality, and activity of stem cells.