INTERACTIONS BETWEEN WINGLESS AND DFZ2 DURING DROSOPHILA WING DEVELOPMENT

Drosophila Wingless (Wg) is a secreted signaling protein of the Wnt fa mily. Mutations in the wg gene disrupt the patterning of embryonic seg ments and their adult derivatives, Wg protein has been shown in cell c ulture to functionally interact with DFz2, a receptor that is structur ally related to the tissue polarity protein Frizzled (Fz), However, it has not been determined if DFz2 functions in the Wg signaling pathway during fly development. Here ne demonstrate that overexpression of DF z2 increases Wg-dependent signaling to induce ectopic margin bristle f ormation in developing Drosophila wings. Overexpression of a truncated form of DFz2 acts in a dominant-negative manner to block Wg signaling at the wing margin, and this block is rescued by co-expression of ful l-length DFz2 but not full-length Fz. Our results suggest that DFz2 an d not Fz acts in the Wg signaling pathway for wing margin development, However a truncated form of Fz also blocks Wg signaling in embryo and wing margin development, and the truncated form of DFz2 affects ommat idial polarity during eye development. These observations suggest that a single dominant-negative form of Fz or DFz2 can block more than one type of Wnt signaling pathway and imply that truncated proteins of th e Fz family lose some aspect of signaling specificity.