Practice question

Axolotl and newt limb regeneration proceeds via epimorphosis requiring wound epidermis, nerve-derived trophic signals, immune modulation. Stump tissues including muscle, dermis, cartilage, Schwann cells undergo dedifferentiation to lineage-restricted progenitors accumulating beneath apical epidermal cap as blastema. These multipotent progenitor cells proliferate driven by FGF8, FGF10, BMP, Wnt signaling, maintain positional memory via Prod1, Meis, Hox gradients, then redifferentiate reconstructing missing limb. Nerve deviation experiments show blastema formation depends on threshold neurotrophic support, demonstrating complex orchestration of growth factors, extracellular matrix remodeling, and re-deployment of developmental programs.