Fig. 7. Effects of N-XTcf-3 and N-XTcf-3 RNA on ectopic Wnt signalling. ß-catenin RNA-mediated axis duplication is rescued by N-XTcf-3 and N-XTcf-3, while only N-XTcf-3 can rescue the CSKA Xwnt-8 DNA-mediated effects on dorsal development. (A) Uninjected control embryo. (B) Misexpression of ß-catenin RNA ventrally mimics ectopic Wnt signalling in early blastula stage embryos resulting in a duplicated axis. However, when ß-catenin is misexpressed ventrally in combination with N-XTcf-3 and N-XTcf-3 rescue occurs (C,D). The rescue with N-XTcf-3 (D) does not result in a wild-type phenotype (A) as with N-XTcf-3 (C), as ventral N-XTcf-3 injection affects ventral mesodermal development (compare with Fig. 6L). (E) Injection of ß-catenin and N-XTcf-3 RNA into different but adjoining ventral blastomeres at the four-cell stage does not rescue ß-catenin-mediated axis duplication, confirming that N-XTcf-3 functions cell autonomously. (F) Uninjected control embryo. (G) Misexpression of CSKA Xwnt8 DNA dorsally causes ectopic ventrolateral-promoting Wnt signalling resulting in embryos with reduced dorsal midline structures and expanded lateral structures. (H) When CSKA Xwnt8 is expressed dorsally in combination with N-XTcf-3, no rescue occurs. (I) The CSKA Xwnt-8 DNA-mediated effects on development are rescued when CSKA Xwnt8 is expressed in combination with N-XTcf-3. Co-injection of CSKA Xwnt8 DNA and N-XTcf-3 RNA results in a phenotype (H) that is a combination of the phenotype caused by CSKA Xwnt8 DNA (G) and the one caused by N-XTcf-3 RNA (Fig. 5G). The rescue with N-XTcf-3 (I) does not result in a wild-type phenotype (F), as ventral N-XTcf-3 injection affects dorsal development (compare with Fig. 6G).