Stem Cells and Their Niches: Integrated Units ThatMaintain Drosophila Tissues

摘要

The genetic analysis of four distinct Drosophila stem cells and their niches has revealed principles of stem cell biology thatare likely to apply widely. A stem cell and its niche act together as integral parts of a system that supplies replacement cellswhen and where they are needed within a tissue. Stem cell/niche units are highly regulated and continue to operate despite theperiodic turnover and replacement of all of their component cells. To successfully respond to tissue needs, these units receiveand process a wide range of local and systemic information. A stem cell alone would be no more use at this task than an iso-lated neuron. It is only when integrated into a system of multiple interacting cells (the niche) that stem cells achieve the capac-ity to serve as the fundamental units of tissue homeostasis and repair.