Fig. 7. Egfr acts antagonistically to Ed in bristle patterning, but it does not affect the levels of N signaling in proneural clusters. (A-D) Nota of flies expressing in proneural clusters (sca-Gal4 driver) either UAS-Egfr (A), UAS-Egfr plus UAS-ed^ECD (B), UAS-raf^gof (C), or UAS-raf^gof plus UAS-ed^ECD (D). There is a strongly enhanced tufting effect caused by co-expression in B and D. (E,F) Nota of ap-Gal4;UAS-Egfr^DN (E) and ed^1x5/ed^slH8 ap-Gal4;UAS-Egfr^DN (F) flies. The ectopic bristle phenotype of ed^1x5/ed^slH8 mutant flies is partially suppressed by the simultaneous decrease of Egfr function (compare with Fig. 1B). Arrow and arrowhead in F indicates the positions where ADC and PPA bristles are respectively eliminated. (G-I) Accumulation of E(spl)-m8 mRNA in the notum region of a wild-type disc (G) and in discs overexpressing either UAS-ras1^V12 (H) or UAS-aos (I) in proneural clusters (C253-Gal4 driver). No significant differences were observed by comparing discs of similar stages from a total of 22 wild-type, 19 UAS-ras1^V12 and 16 UAS-aos discs examined.