PROXIMO-DISTAL SPECIFICATION IN THE WING DISC OF DROSOPHILA BY THE NUBBIN GENE

Mutations in the nubbin (nub) gene have a phenotype consisting of a se vere wing size reduction and pattern alterations, such as transformati ons of distal elements into proximal ones. nub expression is restricte d to the wing pouch cells in wing discs since early larval development . These effects are also observed in genetic mosaics where cell prolif eration is reduced in all wing blade regions autonomously, and transfo rmation into proximal elements is observed in distal clones. Clones lo cated in the proximal region of the wing blade cause in addition nonau tonomous reduction of the whole wing. Cell lineage experiments in a nu b mutant background show that clones respect neither the anterior-post erior nor the dorsal-ventral boundary but that the selector genes have been correctly expressed since early larval development. The phenotyp es of nub el and nub dpp genetic combinations are synergistic and the overexpression of dpp in clones in nub wings does not result in overpr oliferation of the surrounding wild-type cells. We discuss the role of nub in the wing's proximo-distal axis and in the formation of compart ment boundaries.