Genetic models meet trophic mechanisms: EGF family members are gliatrophins in Drosophila.

Trophic survival mechanisms are crucial for the determination of cell numbers in the developing vertebrate nervous system, but important neurotrophic factor families such as the neurotrophins have not yet been found in either Drosophila or C. elegans. Two independent studies on distinct glial populations in Drosophila have now shown that their survival is regulated by EGF family members secreted by adjacent neurons. Fly genetics thus promises new insights on trophic signaling mechanisms and confirms that trophic regulation of cell survival is an evolutionarily ancient mechanism for building the nervous system.