Building limb buds

This workshop on limb development was a highly enjoyable meeting that covered a wide range of topics related to appendage development and evolution. The discussions were vivid, open and stimulating for all participants. It was particularly interesting to see how broadly accepted concepts, such as the morphogen models in the fly and the progress zone model in vertebrates, were re-evaluated on the basis of new evidence presented. Important contributions included intense analyses of the roles of factors important in limb development, such as Wingless (Wg) in the fly and Sonic Hedgehog (Shh) in vertebrates. In addition, the overall view of appendage evolution was significantly expanded by data arising from new animal models such as dogfish and cricket and from the analysis of regulatory regions of genes involved in appendage patterning. Within the limits of this report, we have tried to condense the essentials of the advances presented at this meeting. Limb initiation and identity