In the sea urchin embryo, Wnt/beta-catenin signaling is initially activated in the four micromere cells that form at the vegetal end of the embryo at the 16-cell stage. These cells can be easily isolated in large numbers, and hence this provides us with a system for identifying molecular components that interact with Dsh during the activation of Wnt/beta-catenin signaling in the embryo. Using Dsh co-immunoprecipitation combined with mass spectrometry we have identified several potential partners of Dsh in the sea urchin embryo. We are currently validating these proteins in the lab. We are also carrying out similar experiments in Nematostella in order to better understand how Wnt/beta-catenin is activated during endoderm segregation in this non-bilaterian.