Question

Describe the role of nerves in amphibian regeneration.

Answer 1

The regeneration of limbs in urodele amphibians is a context where the developing
and regenerating peripheral nervous system interacts with the mechanisms of
epimorphic regeneration. After amputation of a limb, there arise at the amputation
plane the blastemal cells which are the progenitor cells of the regenerate. These cells
divide rapidly and subsequently differentiate to give rise to the internal tissues
(cartilage, muscle and connective tissue) of the regenerate. Division of the blastemal
cells requires the presence of nerve axons at the amputation plane, at least during the
initial stages of regeneration. This requirement can be circumvented by allowing a
limb to develop in the absence of a nerve supply (the 'aneurogenic limb'), but the
underlying mechanisms have been unclear. We have derived a monoclonal antibody
called 22/18 that has provided new information about these issues. It is specific for
blastemal cells versus normal tissue in the limb, specific for regeneration versus
development, and specific for blastemal cells that arise after amputation in the
presence of the nervous system versus its absence (in either development or the
aneurogenic limb). The antibody reactivity appears to mark a cell transition involved
in the imposition of nerve-dependent growth control.