Roles for scalloped and vestigial in regulating cell affinity and interactions between the wing blade and the wing hinge

The scalloped and vestigial genes are both required for the formation of th e Drosophila wing, and recent studies have indicated that they can function as a heterodimeric complex to regulate the expression of downstream target genes. We have analyzed the consequences of complete loss of scalloped fun ction, ectopic expression of scalloped and ectopic expression of vestigial on the development of the Drosophila wing imaginal disc. Clones of cells mu tant for a strong allele of scalloped fail to proliferate within the wing p ouch, but grow normally in the wing hinge and notum. Cells overexpressing s calloped fail to proliferate in both notal and wing-blade regions of the di sc, and this overexpression induces apoptotic cell death. Clones of cells o verexpressing vestigial grow smaller or larger than control clones, dependi ng upon their distance from the dorsal-ventral compartment boundary. These studies highlight the importance of correct scalloped and vestigial express ion levels to normal wing development. Our studies of vestigial-overexpress ing clones also reveal two further aspects of wing development. First, in t he hinge region vestigial exerts both a local inhibition and a long-range i nduction of wingless expression. These and other observations imply that ve stigial-expressing cells in the wing blade organize the development of surr ounding wing-hinge cells. Second, clones of cells overexpressing vestigial exhibit altered cell affinities. Our analysis of these clones, together wit h studies of scalloped mutant clones, implies that scalloped- and vestigial -dependent cell adhesion contributes to separation of the wing blade from t he wing hinge and to a gradient of cell affinities along the dorsal-ventral axis of the wing. (C) 2000 Academic Press.