Fig. 2. Wnt patterning activity is mediated by the canonical pathway. (A) Activators of the canonical Wnt pathway (left) generate different transcriptional activities in vivo (centre). Embryos were electroporated with Wnt1/3a, β-catenin^CA, Tcf^VP16 and Wnt4, together with the TopFlash reporter containing HMG-binding sites and normalization plasmid, and assayed 24 hours PE for luciferase activity. Graph shows normalized luciferase units. (B-G) Twenty-four hours PE, β-catenin^CA caused expansion of Pax7 (B) and Pax6 (C) expression in those cells expressing GFP (D), and loss of ventral Olig2 (E) and Nkx2.2 (F) expression in a cell-autonomous way. (G) GFP expression on electroporated cells. (H) Expression of Wnt4 in a HH stage 18 embryo. (I-N) Twenty-four hours PE, Wnt4 produced wild-type expression of Pax7 (I) and Pax6 (J) in cells expressing GFP (K), and wild-type expression of Olig2 (L) and Nkx2.2 (M) in cells expressing GFP (N).