Science https://doi.org/10.1126/science.aaq0681 (2018)

The axolotl has the remarkable ability to regenerate lost limbs. New appendages develop from an assemblage of cells called the blastema, which accumulates near the amputation point. What those cells are and how they know to start dividing again has been unclear. But newly developed transgenic axolotls are helping to reveal the salamander’s secrets.

The animals were modified to express a fluorescent protein in their connective tissue cells that can be tracked before and after an experimental forelimb amputation. The researchers involved also analyzed the activity of genes in different axolotl cells with single-cell RNA sequencing techniques. Together, the results suggest that connective tissue cells in the uninjured portion of the limb de-differentiate into progenitor cells that then regenerate the missing appendage.