Fig. 5. Ectopic eye formation due to ectopic eyg and ey expression. (A-D) Misexpression of eyg can induce ectopic eye formation. (A,B) Adult phenotypes resulting from dpp-GAL4-induced UAS-eyg expression. (C,D) dpp>eyg eye-antenna discs double stained for dpp-lacZ (blue) and mAb22C10 (brown). (C) dpp-lacZ is expressed in the morphogenetic furrow (black arrow) and in a small dorsal region in the antennal disc (black arrowhead). Local overgrowth (white arrowheads) almost always occurred in the ventral and dorsal region of the eye disc adjacent to the antenna disc. These were often, but not always, accompanied by ectopic MF and photoreceptor formation (white arrow), frequently in the ventral pole and only occasionally in the dorsal pole. (D) Higher magnification showing that the axons from the ectopic photoreceptor neurons can sometimes correctly sense the direction of Bolwig's nerve (arrow), but sometimes project in the wrong direction (arrowhead). Occasionally multiple MF formation can be seen (not shown). (E-H) Synergistic effect of eyg and ey coexpression. (E,F) dpp>ey. (E) Ectopic eyes occurred at the base of the antennae, wings and multiple spots on the legs. (F) Ectopic MF (dpp-lacZ, blue) and photoreceptors (22C10, brown) can be detected in the antennal disc but not in the eye disc. (G,H) dpp>ey+eyg coexpression. (G) All ectopic eyes were larger than in dpp>ey. (H) Ectopic MF (dpp-lacZ, blue) and photoreceptor (22C10, brown) were enhanced in the antennal disc, and extended more anteriorly in the ventral margin of the eye disc. Multiple sites of ectopic MF formation in the eye disc and in the antenna disc sometimes led to fusion of the eye fields.

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