Fig. 3. Tcfs expressed throughout the DV axis regulate patterning of the neural tube. (A-D) HH stage 18 embryos showing expression of chick TCF1 (A), chick TCF3 (B), chick TCF4 (C) and chick LEF1 (D). (E) In vivo quantitative analysis of the repressors activities of components of the canonical Wnt pathway. Embryos were electroporated with mutant versions of Tcf proteins. Diagram shows schematic representation of DNAs. Graphics show normalized luciferase units. All mutant Tcfs abolished β-catenin-induced luciferase activity. (F-K) Eight hours PE of Tcf3^DN, dorsal Pax7 (F) and Pax6 (G) showed wild-type expression. GFP as a reporter of transgene expression (H). Ectopic expression of ventral Olig2 (I) and Nkx2.2 (J) was induced in cells expressing the transgene (K). (L-U) Twenty-four hours PE of Tcf3^DN, expression of Pax7 (L) and Pax6 (M) was lost in electroporated cells. GFP as a reporter of transgene expression (N). Intermediate genes Dbx1 (O) and Dbx2 (P), and ventral genes Olig2 (Q), Nkx2.2 (R), Foxa2 (S), Nkx6.2 (T) and Nkx6.1 (U) were all dorsally activated.