In most animals, adult stem cells lead a pretty boring life. These sophisticated cells spend much of their time cooling their heels in biological green rooms called "niches," waiting for an SOS cue to replenish damaged or growing tissues. Their infrequent sallies stymie attempts to identify the niches' location in individual tissues and keep scientists from determining how their environment may affect their function.

Enter the sea squirt. Ayelet Voskoboynik, PhD, and her collaborators in the lab of Irving Weissman, MD, capitalized on the colony-living animal's unique ability to completely renew itself once every seven days—no lollygagging allowed. Voskoboynik fluorescently labeled groups of cells from each of the sea squirt's body parts and used time-lapse photography to see which sprang into action to create the new organism.

The findings, published Oct. 9 in Cell Stem Cell, identify a region in the sea squirt, the endostyle, that harbors its hard-working adult stem cell. These cells proliferate and migrate to organs in developing buds in the colony. The researchers plan to investigate how the endostyle niche cells influence the activity of the stem cells—a kind of cross-talk that may mirror what happens in higher organisms.