Fringe forms a complex with Notch

The Fringe protein of Drosophila and its vertebrate homologues function in boundary determination during pattern formation(1-9). Fringe has been propo sed to inhibit Serrate-Notch signalling but to potentiate Delta-Notch signa lling(10). Here we show that Fringe and Notch form a complex through both t he Lin-Notch repeats and the epidermal growth factor repeats 22-36 (EGF22-3 6) of Notch when they are co-expressed. The Abruptex(59b) (Ax(59b)) and Ax( M1) mutations, which are caused by missense mutations in EGF repeats 24 and 25, respectively, abolish the Fringe-Notch interaction through EGF22-36, w hereas the l(1)N-B mutation in the third Lin-Notch repeat of Notch abolishe s the interaction through Lin-Notch repeats. Ax mutations also greatly affe ct the Notch response to ectopic Fringe in vivo. Results from in vitro prot ein mixing experiments and subcellular colocalization experiments indicate that the Fringe-Notch complex may form before their secretion. These findin gs explain how Fringe acts cell-autonomously to modulate the ligand prefere nce of Notch and why the Fringe-Notch relationship is conserved between phy la and in the development of very diverse structures.