The AP-2 transcription factor is required for joint formation and cell survival in Drosophila leg development

Flies mutant for the Drosophila homologue of the mammalian transcription fa ctor AP-2 show a severe reduction in leg length and fail to develop joint s tructures. Presumptive joint cells express dAP-2 in response to Notch signa ling. dAP-2 is required for joint cell differentiation and can induce forma tion of supernumerary joints when misexpressed. Although dAP-2 is expressed only in presumptive joint cells, its activity is required to support cell survival in the entire leg segment. Taken together, our data indicate that dAP-2 is an important mediator of Notch activity in leg development.