A bioengineer has developed synthetic enzymes that can control the behavior of the signaling protein Vg1, which plays a key role in the development of muscle, bone and blood in vertebrate embryos. The team of researchers is using a new approach, called the Synthetic Processing (SynPro) system, in zebrafish to study how Vg1 is formed. By learning the molecular rules of signal formation in a developing animal, researchers aim to engineer mechanisms — such as giving cells new instructions — that could play a role in treating or preventing disease.