The Wnt signaling cascades are regulatory modules which are involved in embryonic patterning, cell differentiation, morphogenesis, and diseases (1 , 2 ). The Wnt pathways are activated when secreted Wnt ligands interact with 7-trans-membrane receptors of the Frizzled (Fz) family. Specific readouts are determined by the ligand/receptor combinations and the cellular context. Here we describe two methods for the analysis of Wnt/Frizzled interactions inXenopusembryos. Physical interaction of ligand and receptor are demonstrated by co-immunoprecipitation assays. The activation of Wnt targets inXenopusanimal cap tissue provides a versatile test system for activating and inhibitory components of the Wnt/ β -catenin pathway.
