Armadillo/Tcf Induced Apoptosis: Identification of Downstream Components. Y.F. Ahmed , B. Hafler , E. Wieschaus. Dept Molecular Biol, Princeton Univ, Princeton, NJ.

   The Armadillo ( Arm)/Tcf complex is a transcriptional transactivator in the Wingless signal transduction pathway. Negative regulation of Arm/Tcf requires the activity of two Drosophila homologs of the adenomatous polyposis coli (D-APC) tumor suppressor. Inactivation of D-APC has revealed that in addition to known roles in cell fate specification and cell proliferation, Arm/Tcf signaling can also activate apoptotic death, depending on the specific cell type in which the signaling occurs. Thus Arm/Tcf must activate different downstream effectors in different cell types. Our goal is to identify downstream components that respond to Arm/Tcf signaling in differentiated cells by inducing a cell death, rather than cell proliferation or cell fate specification pathway. To identify such components, we are performing genetic modifier screens based on a sensitive D-APC mutant retinal apoptosis defect. Phenotypic characterization of modifier loci will be presented.