DECAPENTAPLEGIC RESTRICTS THE DOMAIN OF WINGLESS DURING DROSOPHILA LIMB PATTERNING

SIGNALLING proteins in the BMP-decapentaplegic (dpp), WNT-wingless (wg ) and Shh-hedgehog (hh) families have been implicated in Limb and appe ndage development in both invertebrates and vertebrates(1-3), In Droso phila, dpp protein (Dpp) induces distal outgrowth and patterning of le gs and wings, but the molecular responses to Dpp are not well characte rized(4-9). Analysis of clones mutant for the Dpp receptors encoded by punt or thickveins (tkv) reveals that repression of wg expression is one critical function of Dpp signalling in leg and wing discs. Distal clones that lie on the anterior edge of the anterior-posterior compart ment boundary ectopically express wg and cause pattern abnormalities, suggesting that Dpp represses Hh activation of wg in the distal primor dia of the leg and wing. By repressing Hg expression in the leg, Dpp s ignalling limits the region that responds to high levels of Wg and Dpp to the site of distal outgrowth. Such negative regulatory feedback lo ops between signalling molecules are likely to be critical for limb pa tterning in other species.