This proposal focuses on the analysis of the molecular mechanisms involved in determination of the dorsoventral axis in Xenopus embryos. The Wnt family of secreted proteins are known to specify cell fates and embryonic polarity in many developmental processes, including specification of the dorsoventral polarity in vertebrates. Recent studies point to the cytoplasmic proteins Dishevelled and Axin as the key regulators of the Wnt pathway. Our preliminary results indicate that a novel maternal Xenopus homologue of Axin (Xaxin) is directly regulated by Dishevelled. To further investigate the molecular mechanisms of signal transduction through Axin and Dishevelled, we are using the Xenopus system, in which we plan to combine biochemical analysis with functional embryological studies. Physical interactions of Xaxin and Dishevelled will be analyzed in immunoprecipitaion and subcellular colocalization studies. Specific domains of Xdsh and Xaxin, that are involved in complex formation will be identified and their role in Wnt signal transduction will be evaluated by functional analysis of mutated proteins by microinjections. These studies will assess whether Wnt signaling regulates the interaction of Xdsh and Xaxin. In situ hybridization and immunocytochemistry will be used to assess the distribution of Xaxin RNA and protein in the early embryo and to evaluate whether Xaxin is spatially controlled or post-translationally modified during the specification of the dorsoventral axis. While in the embryo the Wnt pathway is essential for the establishment of the dorsoventral axis in vertebrate embryos, several components of this pathway are known to be deregulated during cancer in humans. Thus, studying the mechanisms of Wnt signal transduction, we hope to get insight into basic questions of axis specification and into molecular mechanisms of cancer.
| Yasunaga, Takayuki; Itoh, Keiji; Sokol, Sergei Y (2011) Regulation of basal body and ciliary functions by Diversin. Mech Dev 128:376-86 |
| Hikasa, Hiroki; Sokol, Sergei Y (2011) Phosphorylation of TCF proteins by homeodomain-interacting protein kinase 2. J Biol Chem 286:12093-100 |
| Hikasa, Hiroki; Ezan, Jerome; Itoh, Keiji et al. (2010) Regulation of TCF3 by Wnt-dependent phosphorylation during vertebrate axis specification. Dev Cell 19:521-32 |
| Choi, Sun-Cheol; Sokol, Sergei Y (2009) The involvement of lethal giant larvae and Wnt signaling in bottle cell formation in Xenopus embryos. Dev Biol 336:68-75 |
| Chia, Ian V; Kim, Min Jung; Itoh, Keiji et al. (2009) Both the RGS domain and the six C-terminal amino acids of mouse Axin are required for normal embryogenesis. Genetics 181:1359-68 |
| Sokol, Sergei Y; Wharton Jr, Keith A (2007) WNTers in La Jolla. Development 134:3393-9 |
