Fig. 6. The Wnt canonical pathway regulates transcriptional Shh/Gli activity. (A) In vivo quantitative analysis of the transcriptional activities of several components of the Wnt/β-catenin and the Shh/Gli pathways on a Gli-BS reporter. HH stage 11/12 embryos were electroporated with the indicated DNAs. Embryos were assayed 24 hours PE for luciferase activity. The mutant Gli3 protein, Gli3^Act, showed high activity on the reporter; this is partially reduced by co-electroporation of Wnt1/Wnt3a. Wnt1/Wnt3a alone had no transcriptional effect on the Gli-BS reporter. Electroporation of Tcf^DN caused a potent activation of the reporter, activation that was inhibited by either wild-type or TCF^HMG Gli3. (B) Schematic representation of a model for dorsoventral patterning of the spinal cord by antagonistic activities of Shh and Wnt signalling pathways.