Transcription factor Ajuba regulates stem cell activity in the heart during embryonic development. It is not unusual for babies to be born with congenital heart defects. This is because the development of the heart in the embryo is a process which is not only extremely complex, but also error-prone. Scientists from the Max Planck Institute for Heart and Lung Research in Bad Nauheim have now identified a key molecule that plays a central role in regulating the function of stem cells in the heart. As a result, not only could congenital heart defects be avoided in future, but new ways of stimulating the regeneration of damaged hearts in adults may be opened up.