eLife Assessment
During the development of the unicellular eukaryote Dictyostelium discoideum, cells aggregate into mounds, which then form protrusions called tips, and the tips then become the front of migrating slugs and the top of fruiting bodies. This valuable study identifies a protein called adenosine deaminase-related growth factor (ADGF) as a key regulator of tip formation, and the authors convincingly show that ADGF catalyses the formation of ammonia from adenosine, allowing ammonia to initiate tip formation, and they then elucidate pathways upstream and downstream from ADGF. The authors discuss the intriguing possibility that mammalian ADGF may also regulate development in a similar manner.