Fig. 4. mRNA injection of Smed-βcatenin1 but not Smed-βcatenin2 induces a secondary axis in Xenopus embryos. (A,B) Xenopus embryos injected with Smed-βcatenin1 (A) or Smed-βcat2 RNA (B), showing Otx2 (forebrain, red arrow), Krox20 (rhombomeres 3 and 5, green arrows) and Cad3 (spinal cord, white arrows) expression, along with muscle staining with the antibody 12/101 (brown signal). A schematic representation of the structure of each β-catenin is shown under the corresponding image. GSK3-binding domain and adhesion domains are shown with red and blue boxes, respectively. (C-H) Neurula (C-F) and tailbud (G,H) stage embryos injected with GFP-tagged constructs for both Schmidtea mediterranea β-catenins. (I,J) Smed-βcatenin1 but not Smed-βcatenin2 is found preferentially in the cell nucleus. (K) Quantification of the secondary axis obtained after each Smed-βcatenin injection (Xenopus β-catenin was used as a control).