Six flatworms

Flatworms blasted with radiation thrive after receiving a single transplanted stem cell. Credit: A. Zeng et al./Cell

Stem cells

One special cell can revive a flatworm on the brink of death

Scientists pinpoint the stem cells that bestow the power of regeneration on planaria.

Cut some types of flatworm into bits, and most of those bits can regrow into a whole body. But the identity of the stem cells that give these worms, called planaria, their regenerative capacity has been a mystery for more than a century.

Alejandro Sánchez Alvarado at the Stowers Institute for Medical Research in Kansas City, Missouri, and his colleagues have now solved the puzzle. Studying the planarian Schmidtea mediterranea, the researchers found that the regenerative cells can be distinguished by high expression of a gene called tspan-1. These cells are distributed throughout the worms’ bodies.

When the researchers exposed planaria to heavy doses of radiation, cells expressing tspan-1 survived and eventually replaced the cells that had been killed. The transplant of a single tspan-1-expressing cell was enough to rescue a planarian that had received a lethal dose of radiation.