A Drosophila Axin homolog, Daxin, inhibits Wnt signaling

The vertebrate Axin protein, the product of the mouse fused gene, binds to beta-catenin to inhibit Wnt signaling. We have identified a homolog of Axin in Drosophila, Daxin. Using double-stranded RNA interference, we generated loss-of-function phenotypes that are similar to overexpression of the Dros ophila Wnt gene wingless (wg). Overexpression of Daxin produces phenotypes similar to loss of wg. In addition, we show that Daxin overexpression can m odify phenotypes elicited by wg and another Drosophila Wnt gene, DWnt-2. Us ing immunoprecipitation of endogenous Daxin protein from embryos we show th at Daxin interacts with Armadillo and Zeste-white 3. The loss-of-function a nd overexpression phenotypes show that Daxin, like its mammalian counterpar t, acts as a negative regulator of wg/Wnt signaling.