Wouldn't it be amazing if, when we needed to, we could regenerate a limb or heart? Just imagine the benefits this would bring to modern medicine. Yet, this ability does exist — at least, for urodele amphibians such as newts and salamanders, which can regenerate their jaws, lens, retina, limbs and large sections of heart. On page 566, Jeremy Brockes and Anoop Kumar discuss the mechanisms behind this regeneration, which provides crucial information about the reversibility and plasticity of the differentiated state. By studying the regenerative mechanisms of urodeles, we can pinpoint the differences between this species and mammals, which could enable us to understand the evolutionary basis of regeneration. The authors believe that “the urodele strategy — the limited respecification of residual differentiated cells — is so successful that it would be surprising if it were not eventually tried as a therapeutic approach in some contexts of mammalian regeneration”.

Further insights into eukaryotic evolution are provided by Stewart Shuman on page 619. The 5′ cap — which is formed by three enzymatic reactions at the 5′ terminus of nascent messenger RNA — is a feature of eukaryotic mRNA that is absent from bacteria and archaea. Although the capping pathway is conserved in all eukaryotes, the properties of the enzymes in this pathway vary among species, and these differences could provide insights into the evolution of eukaryotes and eukaryotic viruses.

Finally, on page 615, Benjamin Glick considers the evolution of the Golgi apparatus in terms of how it forms in cells. Recent evidence suggests that it can be built from scratch, although there is also an argument that it might form through the addition of new material to a permanent template. So, does the Golgi form de novo or is a template involved?