Xenbase Image ID: 146513

Figure 7. SOX7 antagonism of β-catenin signaling and cardiogenic ability. A: Fertilized eggs were injected with RNA encoding either SOX7-GFP (Sx7GFP) or SOX7δC-GFP (Sx7δC-GFP) (0.5 ng/embryo); at stage 9/10 embryo lysates were prepared and immunoprecipitated with a rabbit antiGFP antibody. Immunoprecipitates where analyzed by SDS-PAGE and immunoblot using an rabbit anti-β-catenin antibody. In addition to the immunoglobulin heavy chain (“HC”), we found that β-catenin was co-precipitated with SOX7-GFP (arrow), but that little or no β-catenin associated with the SOX7δC-GFP immunoprecipitation. Immunoblot with antiGFP antibody of embryonic lysates indicated that both SOX7-GFP and SOX7δC-GFP polypeptides accumulated to similar extents (data not shown). B: In an animal cap assay, injection of RNA (0.5 ng/embryo) encoding SOX7δC-GFP failed to induce Nkx2.5, Tbx5, or MHCα expression (animal caps analyzed when control embryos reached stage 25). C: Injection of RNA encoding a mutationally stabilized form of β-catenin (mt-δG-β-catenin) induces the expression of Siamois in animal caps. Fertilized eggs were injected with RNA encoding mt-δG-β-catenin (50 pg/embryo) alone or together with RNAs encoding SOX7-GFP, mt-SOX7δC-VP16, or SOX18β-GFP (500 pg/embryo); animal caps were prepared at stage 8 and analyzed when control embryos reached stage 10/11. β-catenin induced expression of Siamois; both SOX7-GFP and SOX18β-GFP suppressed β-catenin-induced Siamois expression, and induced expression of Xnr2, Xnr4, Cerberus, and Nkx2.5; SOX7-GFP also induced Xnr5 expression. SOX7δC-VP16 failed to suppress β-catenin-induced Siamois expression, but induced Xnr2, Xnr4, Xnr5, Cerberus, and Nkx2.5 expression. D: The SOX7GGG-GFP construct is analogous to the SOX17G3 construct generated and characterized by Sinner et al (2004). In animal caps assayed at stage 25, SOX7GGG-GFP (0.5 ng/embryo) induced the expression of Edd, but not Nkx2.5, Tbx5, MHCα, or TnIc. E: To examine the ability of SOX7-GFP, SOX7GGG-GFP, and SOX18β-GFP to inhibit β-catenin activation of the OT reporter, fertilized eggs were injected with OT and pTK-Renilla DNAs (20 pg each/embryo) together with RNAs encoding mt-δG-β-catenin (50 pg/embryo) and varying amounts of SOX RNAs; animal caps were analyzed when control embryos reached stage 10/11. SOX7-GFP and SOX18β-GFP RNAs inhibited of βcatenin activation of OT; SOX7GGG-GFP was a much less active antagonist of β-catenin in this assay. Image published in: Zhang C et al. (2005) Copyright © 2005. Image reproduced with permission of the Publisher, John Wiley & Sons. Larger Image Printer Friendly View

Return to previous page