Fig. 4. MAE acts as a positive component of the RTK pathway and loss of mae function inhibits the downregulation of YAN. (A-D) Scanning electron micrographs of adult Drosophila eyes showing that loss of mae dominantly suppresses the rough eye phenotype of Sev-RAS^V12. (E-G) Tangential sections of adult Drosophila eyes. The average number of R7 photoreceptors per ommatidium is indicated below, with n referring to the total number of ommatidia scored. (A,E) Wild-type; (B,F) Sev-RAS^V12/+; (C,G) Sev-RAS^V12/l(2)k06602; (D,H) Sev-RAS^V12/Df(2R)PC4. Confocal images of germband extended embryos double labeled with anti-YAN (I,J, with high magnification of boxed region shown in I',J') and anti-ELAV (I'',J''). (I,I',I'') show that in mae mutants, YAN fails to be downregulated in the CNS (I', bracketed region) and ELAV expression is inhibited (I''). (I,I',I'') l(2)k06602/l(2)k06602; (J,J',J'') wild type.