Cell origin and identity in limb regeneration and development.

The occurrence of limb regeneration in adult urodele amphibians raises fundamental questions about the relationship between development and regeneration. The use of monoclonal antibodies as cell markers has provided clear evidence that blastemal cells, the progenitor cells of the regenerate, are not the same as limb bud cells in the embryo. For one of these antibodies the distinction has been traced to the relationship between limb regeneration and the nerve supply. Innervation of the limb bud during development appears to establish nerve-dependent growth control for regeneration. The cell markers have also contributed to the problem of how the blastemal cells arise after amputation, although several important questions remain to be answered.