Fig. 5. N-Tcf-3 inhibits dorsalising but not ventrolateral-promoting Wnt signalling when expressed in Xenopus embryos. (A) N-Tcf-3 construct used in this experiment. The morphology and molecular marker expression of uninjected control embryos are shown (B-F). N-Tcf-3 RNA was injected into the dorsal marginal zone (DMZ, G-K) or the ventral marginal zone (VMZ, L-P) at the two-cell stage and embryos were analysed by morphology at stage 31 (G,L) and molecular marker expression at stage 11 (H-K,M-P). Dorsally injected embryos have a strong ventralised phenotype with reduced dorsal structures (G). Analysis of molecular markers show that there is a repression of dorsal markers (chordin, H) and Xnot (I) (compared with C,D) and ectopic expression of ventral and lateral markers XmyoD (J) and Xpo (K) in the dorsal midline (compared with E,F). Ventrally injected embryos are unaffected by injection of N-Tcf-3 RNA and show the same morphology and molecular marker expression as the control embryos (compare L-P with B-F). (Q) Western blot detecting HA-tagged N-XTcf-3 protein at stages 6 and 10 of development after injection of the RNA at the four-cell stage into the dorsal marginal zone (DMZ) or the ventral marginal zone (VMZ). As a control, uninjected embryos show no N-XTcf-3 protein present; however, injected embryos show comparable levels of protein at stages 6 and 10 with both ventral and dorsal injection of N-XTcf-3 RNA.