Drosophila miR-932 modulates hedgehog signaling by targeting its co-receptor Brother of ihog.

Hedgehog (Hh) proteins act as morphogens in a variety of developmental contexts to control cell fates and growth in a concentration-dependent manner. Therefore, secretion, distribution, and reception of Hh proteins must be tightly regulated and deregulation of these processes contributes to numerous human diseases. Brother of ihog (Boi) and its close relative Ihog (Interference hedgehog) are cell surface proteins that act as Hh co-receptors required for Hh signaling response and cell-surface maintenance of Hh protein. MicroRNAs (miRNAs) are a group of widely expressed 21-23 nucleotides non-coding RNAs that repress gene function through interactions with target mRNAs. Here, we have identified a novel miRNA, miR-932, as an important regulator for Boi. We show that overexpression of miR-932 in the wing disc can enhance Hh signaling strength, but reduce its signaling range, a phenotype similar to that of boi knockdown. In both in vivo sensor assay and in vitro luciferase assay, miR-932 can suppress Boi by directly binding to its 3'UTR. Meanwhile, down-regulation of miR-932 by sponge elevates the protein level of Boi, confirming that miR-932 is an in vivo regulator of Boi expression. Further, we demonstrate that miR-932 can block Hh signaling when co-expressed with ihog-RNAi. Moreover, we find that other predicted miRNAs of Boi fail to suppress it as strong as miR-932. Taken together, our data demonstrate that miR-932 can modulate Hh activity by specifically targeting Boi in Drosophila, illustrating the important roles of miRNAs in fine regulation of the Hh signaling pathway.