DISSECTING THE ROLES OF THE DROSOPHILA EGF RECEPTOR IN EYE DEVELOPMENT AND MAP KINASE ACTIVATION

A new conditional Egfr allele was used to dissect the roles of the rec eptor in eye development and to test two published models. EGFR functi on is necessary for morphogenetic furrow initiation, is not required f or establishment of the founder R8 cell in each ommatidium, but is nec essary to maintain its differentiated state. EGFR is required subseque ntly for recruitment of all other neuronal cells. The initial EGFR-dep endent MAP kinase activation occurs in the furrow but the active kinas e (dp-ERK) is observed only in the cytoplasm for over 2 hours. Similar ly, SEVENLESS-dependent activation results in cytoplasmic appearance o f dp-ERK for 6 hours. These results suggest an additional regulated st ep in this pathway and we discuss models for this.