Ageing versus developmental silencing: Answers from the epigenome.

A strong regenerative capacity is a hallmark of youth. From the tadpole's tail to the mammalian brain, young animals of many species can repair or regrow damaged tissues more effectively than older animals. Here, we take a broad perspective on ageing, inclusive of the transition from the developmental processes of embryogenesis through maturation to adulthood, as well as the processes that occur as an animal reaches the end of its lifespan. In some cases, the loss of regenerative capacity occurs once development is complete, and in others it occurs in the latter part of the animal's life. Regardless, the loss of regenerative capacity is caused by a failure to activate genes required for successful regeneration. This, in part, can be attributed to restructuring of the epigenome.