FUNCTIONAL CONSERVATION OF THE WNT SIGNALING PATHWAY REVEALED BY ECTOPIC EXPRESSION OF DROSOPHILA DISHEVELLED IN XENOPUS

Witt genes encode secreted growth factors that exhibit potent effects on both embryonic and postembryonic development in vertebrates and inv ertebrates. Recently, the dishevelled (dsh), shaggy/zeste-white 3, and armadillo genes have been shown to participate in Wnt (wingless; wg) signaling in Drosophila. Vertebrate genes that have sequence similarit ies to all of these Drosophila genes have been identified. To determin e whether these structurally conserved components of insect wg signali ng represent a functionally conserved Wnt signaling pathway in vertebr ates, we investigated the role of Drosophila dsh in Xenopus Wnt signal ing. Xenopus embryos ectopically injected with Drosophila dsh mRNA dev eloped duplicated axes similar to those seen in embryos injected with Wnt mRNAs. The involvement of dsh function in the Wnt signaling pathwa y in Xenopus was demonstrated using two assays which are specifically sensitive to Wnt signaling: synergistic induction of dorsal mesoderm w ith bFGF and the specific induction of a Wnt-responsive reporter gene. These findings support the notion that the intracellular response to the Wnt signal has been conserved during evolution to such an extent t hat its components may be interchanged between distantly related speci es. (C) 1995 Academic Press, Inc.