β-catenin transcriptional activity and expression of Nanog are required for Bra expression and associated EMT. (A) Bra expression in E14-Tg2A, β-catenin−/− and β-cateninΔC cells differentiated in Act and Chi. Hoechst stain is on the left-hand side. (B) Time evolution of the distribution of Bra expression in cells as in (A). β-catenin transcriptional activity is required for Bra expression. See text for details. (C) Live imaging of β-catenin mutants in Act/Chi. (D) Individual cell velocities (μm/h), and the average velocity profile for each cell line (indicated by colours) in Act/Chi. (E) The distribution of velocities over time. Scale bars denote 50 μm. Act, activin A; AFU, arbitrary fluorescence units; β-cat, β-catenin; Bra, brachyury; Chi, chiron CHIR99021; EMT, epithelial-to-mesenchymal transition; Vel., velocity; WT, wild type.