Wingless signaling: The inconvenient complexities of life

Nature is a home handywoman. Constrained by evolution, she does the job with the tools at hand, using a screwdriver for a hammer if necessary. This is well illustrated by the way particular cell signaling systems, such as that mediated by Wingless (Wg) in Drosophila and its Wnt homologs in vertebrates, direct diverse developmental decisions. The Wg/Wnt signaling system has been the subject of intense research in recent years, which has led to a snapshot of the machinery that transduces Wg/Wnt signals inside target cells. This machinery is neither elegant nor simple, but consists rather of a complex set of interacting proteins that were cobbled together by evolution. This is rather unfortunate for biologists, who as a rule prefer simple models, such as the current model of Wg/Wnt signaling which is illustrated in Figure 1 [1].