A stepwise model system for limb regeneration

Abstract

The amphibian limb is a model that has provided numerous insights into the principles and mechanisms of tissue and organ regeneration. While later stages of limb regeneration share mechanisms of growth control and patterning with limb development, the formation of a regeneration blastema is controlled by early events that are unique to regeneration. In this study, we present a stepwise experimental system based on induction of limb regeneration from skin wounds that will allow the identification and functional analysis of the molecules controlling this early, critical stage of regeneration. If a nerve is deviated to a skin wound on the side of a limb, an ectopic blastema is induced. If a piece of skin is grafted from the contralateral side of the limb to the wound site concomitantly with nerve deviation, the ectopic blastema continues to grow and forms an ectopic limb. Our analysis of dermal cell migration, contribution, and proliferation indicates that ectopic blastemas are equivalent to blastemas that form in response to limb amputation. Signals from nerves are required to induce formation of both ectopic and normal blastemas, and the diversity of positional information provided by blastema cells derived from opposite sides of the limb induces outgrowth and pattern formation. Hence, this novel and convenient stepwise model allows for the discovery of necessary and sufficient signals and conditions that control blastema formation, growth, and pattern formation during limb regeneration. D

Looking proximally and distally: 100 years of limb regeneration and beyond

“…This thickening subsequently regresses. However, if a nerve is deviated into the wound, the thickening is maintained and a blastema-like growth is formed (Endo et al, 2004). This result implies that the AEC can form independently of the nerve, but that maintenance of AEC structure and function is nerve-dependent, an implication that fits the timing of AEC formation and regeneration of axons into the AEC.…”

“…However, when short longitudinal skin strips from three or four limb quadrants were rotated 90 and grafted to the circumference, regeneration took place normally. Furthermore, blastema-like accumulations induced by deviating nerves to limb skin wounds grew only if pieces of skin from opposite circumferential sites met to cover the wound (Endo et al, 2004).…”

Beyond early development: Xenopus as an emerging model for the study of regenerative mechanisms

“…Very recently, a role for noncanonical Wnt signaling has also been demonstrated during tail regeneration. Sugiura et al (2008) developed an accessory tail model similar to the accessory limb model, which has been developed to study axolotl limb regeneration (Endo et al, 2004). In this model, candidate genes can be tested for their ability to induce/regenerate a tail from a dorsal incision through the spinal cord and muscle by filling the incision with an animal cap graft expressing the candidate gene.…”

A Bayesian approach on molecules and behavior: reconsidering phylogenetic and evolutionary patterns of the Salamandridae with emphasis on Triturus newts

“…We furthermore exploit the phylogenetic hypothesis to reconstruct the evolution of courtship traits within the Salamandridae in terms of the degree of body contact, with a focus on the primarily male-mediated Triturus courtship traits (Halliday, '77, '90). With Triturus being a model system in evolutionary ecology (Schmidt and van Buskirk, 2005), limb development and regeneration (Blanco and Alberch, '92; Rienesl and Wagner, '92; Wagner et al, '99;Endo et al, 2004; Wagner, this issue), population and conservation genetics (Jehle et al, 2005a,b), and ethology (Houck and Arnold, 2003), we believe that a robust phylogeny of Triturus is a valuable scientific contribution that will allow the evolution of observed complex traits to be placed within a sound phylogenetic context. …”