THE FRIZZLED GENE OF DROSOPHILA ENCODES A MEMBRANE-PROTEIN WITH AN ODD NUMBER OF TRANSMEMBRANE DOMAINS

The protein encoded by the Drosophila tissue polarity gene, frizzled ( fz), is required for both the intercellular transmission and the intra cellular transduction of a tissue polarity signal. In order to study t he biochemical characteristics of this rare protein, we constructed a hs-fz fusion gene and transferred this to Drosophila tissue culture ce lls and embryos. Cell fractionation experiments and immunostaining exp eriments showed that the Fz protein is an integral membrane protein co ntaining an odd number of transmembrane domains, consistent with previ ous suggestions that it contains seven transmembrane domains. Immunost aining of pupal wings showed that the Fz protein is evenly distributed throughout the wing arguing that the Fz protein does not act as a gra ded morphogen.