The Legwork of Signaling

The fruit fly leg is a complex structure with 10 segments. Studies of Drosophila appendage development have identified several of the components that are needed to establish the dorsal-ventral (DV) and the proximal-distal (PD) axes of the leg. Signaling by wingless (wg) and decapentaplegic (dpp) operate in the developmental program for both of these axes. However, genetics studies by Galindo et al. show that wg and dpp are not sufficient to explain all of the subsequent patterning events in the PD axis. The tarsus segment, an evolutionarily ancient part of the insect leg, is defined by a dpp/wg-independent phase of distalless and dachshund activity combined with a distal gradient of epidermal growth factor receptor-Ras signaling. M. I. Galindo, S. A. Bishop, S. Greig, J. P. Couso, Leg patterning driven by proximal-distal interactions and EGFR signaling. Science 297, 256-259 (2002). [Abstract] [Full Text]