DISHEVELLED IS REQUIRED DURING WINGLESS SIGNALING TO ESTABLISH BOTH CELL POLARITY AND CELL IDENTITY

The dishevelled gene of Drosophila is required to establish coherent a rrays of polarized cells and is also required to establish segments in the embryo. Here, we show that loss of dishevelled function in clones , in double heterozygotes with wingless mutants and in flies bearing a weak dishevelled transgene leads to patterning defects which phenocop y defects observed in wingless mutants alone. Further, polarized cells in all body segments require dishevelled function to establish planar cell polarity, and some wingless alleles and dishevelled; wingless do uble heterozygotes exhibit bristle polarity defects identical to those seen in dishevelled alone. The requirement for dishevelled in establi shing polarity is cell autonomous. The dishevelled gene encodes a nove l intracellular protein that shares an amino acid motif with several o ther proteins that are found associated with cell junctions. Clonal an alysis of dishevelled in leg discs provides a unique opportunity to te st the hypothesis that the wingless dishevelled interaction specifies at least one of the circumferential positional values predicted by the polar coordinate model. We propose that dishevelled encodes an intrac ellular protein required to respond to a wingless signal and that this interaction is essential for establishing both cell polarity and cell identity.