Cells keep a memory of their tissue origin during axolotl limb regeneration.

By using an integrated GFP transgene to track the major limb tissues during limb regeneration in the salamander Ambystoma mexicanum (the axolotl), it has been possible to demonstrate that each limb tissue produces a different set of progenitors with restricted potential. Thus, the blastema—the collection of cells that regenerates the diverse tissues of the limb—is composed of a heterogeneous collection of restricted progenitor cells instead of dedifferentiated pluripotent cells, as previously thought.