Fig. 7. The N-terminal extracellular domain of Xfz3 is unable to inhibit Xfz3 dimerization and activation of the Wnt/ß-catenin pathway in response to overexpression of Xfz3 in Xenopus embryo. Embryos were injected with mRNA encoding Xfz7-myc, Xfz3-HA or a combination of Xfz3-HA and extra3-myc mRNA. (A) RT-PCR analysis of the Wnt/ß-catenin target gene siamois in animal caps cultured to the early gastrula stage. Siamois expression in whole embryo is used as a positive control and in noninjected caps as a negative control. ODC is a loading control. (B) Immunoprecipitation and western blot analysis of protein extracts from injected embryos. Expression of Xfz3-HA is revealed by immunoprecipitation using the anti-HA antibody followed by western blot analysis with the same antibody. The dimeric form of Xfz3-HA (arrow) is detected after injection of Xfz3-HA mRNA alone (lane 2) or in combination with extra3-myc mRNA (lane3). Expression of the extra3-myc protein in co-injected embryos is checked by immunoprecipitation and western blot with the anti-myc antibody (lane 5, arrowhead).