Abstract
We have identified Echinoid﹙Ed﹚ as a novel adhesion molecule-like protein that negatively regulates EGFR signaling. ed genetically interacts with several components in the EGFR pathway. Flies of ed mutants produce extra photoreceptors and cone cells. Conversely, ectopic expression of ed in the eye leads to reduction in photoreceptor number. Genetic epistasis experiment showed that ed acts down stream of sina and pnt but upstream of ttk . To understand the expression pattern of Ed, we performed the antibody staining. The result showed that Ed is expressed throughout whole embryogenesis and is located on the cell membrane. During oogenesis, ed is expressed in the follicle cell. Ed is one of the L1 family protein, and overexpression of ed and another L1 family protein Neuroglian（Nrg） reduces the number of cone cells. This result suggested that Ed might interact with Nrg by heterophilic interaction. Overexpression of ed by several GAL4-drivers makes bristle loss, and cell fate transformation. Germ line clones of ed has neurogenic phenotype, and overexpression of ed and Notch has similar phenotype. Otherwise, ed genetically interacts with several components in the Notch pathway. Above all, ed might participate in the Notch pathway and be a positive regulator. Besides these, ed affects R8 formation and might not be a negative regulator in the Torso pathway. Together, these results suggested that ed might be a novel regulator of the EGFR and Notch pathways and plays several functions in Drosophila development.