Fig. 3.

Overexpression of the miR-310/13 cluster in Drosophila imaginal discs phenocopies Wg loss of function. (A-A′) Dpp-lacZ expression is restricted by Wg to the dorsal compartment of WT Drosophila leg discs (yellow arrowhead in A′). ns^*, non-specific staining. (B-B′) Misexpression of miR-310/13-dsRED using ptc-GAL4 leads to Dpp-lacZ derepression and expansion to the ventral compartment of the leg disc (yellow arrowhead in B′; quantified in supplementary material Fig. S2). Note the expression of miR-310/13 in the ptc expression domain, visualized by dsRED expression in B′. Red arrowheads (A′,B′) indicate mild expansion of the endogenous expression of Dpp-lacZ evident in the dorsal compartment. (C-I′) Effect of misexpression of miR-310/13 on sens, a Wg target gene, and wing patterning/growth of the wing imaginal disc. Sens is expressed in two rows at the dorsoventral boundary of the wing disc and is used as a readout for Wg signaling activity (C). C96-GAL4-driven expression of Axin leads to downregulation of Sens (D, arrowhead), adult wing notching, and depletion of sensory bristles (H,H′, black arrowhead), compared with the WT control (C,G,G′). Misexpression of miR-310/13-dsRED in the C96 domain (note dsRED expression in E) phenocopies Axin overexpression, both in its ability to repress Sens (F, arrowheads) and by causing wing notching in the adult (I,I′, black arrowheads). (J,K) Co-expression of arm lacking a 3′-UTR together with miR-310/13 leads to significant rescue of wing notching and bristle loss, in addition to the formation of ectopic sensory bristles (J) similar to those observed in flies overexpressing Arm alone under C96-GAL4 (K). (G′,J′,K′) Magnification of dorsal wing margins from WT flies (G′), flies that co-express an active form of Arm (Arm^*) and miR-310/13 (J′), and those expressing Arm^* alone (K′). Note that the increase in dorsal sensory wing margin bristles in flies expressing Arm^* alone (K′) is rescued by the co-expression of miR-310/13 (J′). Boxes indicate the regions magnified.