Though often no bigger than an apple seed, planaria are the envy of the animal kingdom. Cut them into a dozen pieces, and each piece will regrow into a full new worm—a remarkable feat of regeneration beyond the ability of most other animals. Now, researchers have pinpointed the cell—and a key protein—that kick-starts this process.

The discovery “is a major breakthrough in the field,” says Ricardo Zayas, a developmental biologist at San Diego State University in California who was not involved with the work.

Researchers have known for decades that a group of unspecialized stem cells called neoblasts help planaria regenerate. But they’ve failed to figure out exactly which type of neoblast works this magic. So Alejandro Sánchez Alvarado, a developmental biologist at the Stowers Institute for Medical Research in Kansas City, Missouri, tapped new techniques for isolating single cells and characterizing their gene activity.  Read more ..