One cell lets a planarian regenerate any body part.

Nature shows us how to rebuild body parts from scratch – well, as long as we’re planarians, that is. But still, it’s one specific kind of cell that lets them rebuild their whole bodies from scratch:

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.

You can read the original research here, in Cell.