Cells do not relive youth

Afew cells in the imaginal disc of the fly larva have the exceptional ability to transdeterminate (TD)—that is, to change fate—upon injury and regeneration. For example, injured leg precursors may form a wing instead. TD cells have many stem cell–like qualities. As stem cell multipotency is thought to be characteristic of “young” cells, it has been suggested that TD is preceded by cellular rejuvenation. Now, research from Anne Sustar and Gerold Schubiger (University of Washington, Seattle, WA) shows that no such fountain of youth is necessary. Instead, cells first adopt an unusual cell cycle profile before TD.Using injuries or ectopic expression of Wg (a Wnt mitogen that induces TD) and a wing-specific reporter, the authors isolated transdetermining cells from imaginal discs. Young cells normally cycle more...