Hedgehog signaling in Drosophila eye and limb development - conserved machinery, divergent roles?

The secreted signaling molecule Hedgehog plays a key role in patterning Drosophila eyes and limbs. Recently, the transmembrane proteins Patched and Smoothened and the Gli protein Cubitus interruptus have been identified as essential components in Hedgehog signal transduction. Progress has also been made in understanding the function of Decapentaplegic (Dpp) in mediating the Hedgehog signal. Although playing only a minor role in the eye, Dpp governs, at long range, the expression of essential genes such as optomotor blind and spalt in the wing.