Meeting Abstract
Wnt signaling plays a central role in early metazoan development. A key cytoplasmic component mediating Wnt signaling is the Dishevelled (Dsh) protein. Dsh is considered to be the “hub” of the Wnt signaling pathway, but the mechanisms regulating Dsh “activation” during Wnt signaling remains one of the least understood steps in this pathway. Dsh is highly enriched in a specialized vegetal cortical domain (VCD) of the sea urchin egg and vegetal blastomeres of early embryos. In addition, we found that Dvl is differentially modified at the VCD and in 16-cell stage micromeres. Functional analysis has shown that Dsh activity is essential for the initial activation of canonical Wnt (cWnt) signaling in 16-cell stage micromeres. However, the molecular basis of Dsh asymmetric localization and its activation remain as outstanding questions in the field. Therefore, identification and functional studies of Dsh interacting proteins (DIPs) in 16-cell stage micromeres will advance our understanding of how Dsh is enriched, maintained and activated at the vegetal pole of the sea urchin embryo by its regulatory partners. To identify DIPs in the micromeres, Dsh Co-immunoprecipitation coupled with mass spectrometry was applied to pull down and sequence DIPs. DIPs were then functionally annotated by Blast2GO to determine the enriched gene ontology terms and signaling pathways. Potential DIPs were further characterized by RT-PCR and RNA in situ hybridization. Functional studies will be performed to determine roles of potential DIPs in regulating Dsh activity. This work will provide critical insight into the molecular basis underlying the asymmetric activation of cWnt signaling that leads to the specification of endomesoderm in sea urchins.
