Development 136, 2695–2703 (2009)

Transplanting a nucleus from a specialized adult cell into an enucleated egg overhauls gene expression in the nucleus, allowing it to direct development into any one of many tissue types. Yet no one is quite sure how.

John Gurdon and his colleagues at the Gurdon Institute in Cambridge, UK, transplanted various nuclei into developing eggs of the frog Xenopus laevis and looked at the expression of muscle genes. The transplanted nuclei expressed many muscle genes, but surprisingly their expression did not rely on the activity of proteins such as MyoD that are normally required for muscle-gene expression. This suggests that the egg cell uses special methods to reprogram nuclei.