Antagonist activity of DWnt-4 and wingless in the Drosophila embryonic ventral ectoderm and in heterologous Xenopus assays

Wnt genes encode secreted signalling molecules involved in a number of basi c developmental processes. In Drosophila, wingless and DWnt-4 are two physi cally clustered Wnt genes, which are transcribed in overlapping patterns du ring embryogenesis and, in several instances, are controlled by the same re gulatory molecules. To address the question of the functional relationship of wingless and DWnt-4, we analysed how embryonic cells respond when they a re exposed, simultaneously or not, to the encoded Wnt signals. We show that DWnt-4 has the capacity to antagonise Wingless signalling both in the Dros ophila ventral epidermis and in a heterologous system, the Xenopus embryo. We provide evidence that DWnt-4 inhibits the Wingless/Wnt-1 signalling path way upstream of the activation of transcriptional targets. This is the firs t report that antagonising Wnt signals exist in Drosophila. (C) 1999 Elsevi er Science Ireland Ltd. All rights reserved.