A protein that is present mainly in developing embryos gives some adult tissues an exceptional ability to heal.

The protein Lin28a controls growth and development in animals from worms to humans, but it is rarely found in adult tissues in vertebrates.

When researchers led by George Daley at Boston Children's Hospital in Massachusetts engineered mice so that the protein was produced into adulthood, the animals' hair grew faster and puncture wounds in their ears healed more thoroughly. Newborn animals were more likely to regrow the tips of severed digits.

Lin28a represses an anti-growth regulatory program and boosts the production of many metabolic enzymes. In doing so, the researchers say, the protein induces a state that enhances tissue repair.

Cell 155, 778–792 (2013) Footnote 1