New growth factors for imaginal discs

Several families of peptide growth factors are implicated in regulating cell growth and proliferation of vertebrate cells in culture. Genetic studies in Drosophila implicate some of these factors in growth control in vivo. A recent report identifies a new family of growth factors, related to chitinase enzymes, required by Drosophila imaginal disc cells in culture. It will be of interest to determine how such factors relate to size regulation during development.