If the tail of a salamander is amputated then, amazingly, it completely regenerates. But how is a functional central nervous system reconstituted? On , Tanaka and colleagues identify the neuronal stem cell population that repopulates the regenerating tail of the urodele amphibian, the axolotl. Using cell fate mapping and transplantation techniques, they show that a 500 μm region of the mature spinal cord that abuts the amputated plane generates the neuronal progenitors required for regeneration. They map the progeny of these precursors as the regenerating spinal cord extends. Most progeny remain close to the dorsoventral (D/V) location of the parent cell, but some migrate to occupy multiple D/V positions, thus acquiring different expression profiles and fates. The most distally localised cells in the regenerating tail are molecularly distinct from those in more proximal regions, perhaps indicating that, in this zone, progenitor identity is destabilised or altered. Surprisingly, ventral cells in this region can migrate dorsally and exit the spinal cord into the blastema. The fate of these cells remains to be determined.
