In the regeneration game, mammals pale before such creatures as salamanders. Humans barely avert complete disappointment, regrowing digit tips if they are severed past the last joint, while salamanders are superheroes, regrowing any structure that can be cut off without killing them. Though the salamander is a stalwart regeneration model, research is expanding into model organisms such as the zebrafish and mouse, which offer broader tools and possibly better translation to clinical medicine. "We want to take advantage of the strength of genetics," says Ken Muneoka of Tulane University in New Orleans, who switched from working on salamanders to digit-tip regeneration in the mouse.
Developmental studies in the salamander have built a solid framework for studying regeneration. Researchers have described, for example, the organization of the cone-shaped blastema from which newly grown structures emerge, and they have implicated molecules such as fibroblast growth factor and retinoic acid in the process.
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