Epidermal growth factor receptor (Egfr) signalling is a commonly deployed signalling pathway during development that needs to be tightly regulated to prevent inappropriate inductive events. Now, two groups report a novel antagonist of Egfr signalling, adding to the negative regulators of this pathway that are already known. Their findings show that the Drosophila L1-type transmembrane molecule Echinoid (Ed) acts as an Egfr antagonist during fly retinal development and is required for the proper spatial development of R8 photoreceptor cells: in its absence, Egfr signalling is increased during R8 formation, causing isolated R8 photoreceptors to be replaced by groups of 2-3 cells. Spencer and Cagan's findings, on p. 3725, shed light on how Ed might do this: it co-precipitates with Egfr from cultured cells and eye imaginal discs, indicating that Ed might downregulate Egfr by directly binding to it. In addition, the phosphorylation of Ed is promoted by Egfr activity....

You do not currently have access to this content.