Fig. 6. Forced β-catenin expression causes increased epithelial and mesenchymal Wnt activity and upregulation of placode marker genes. (A-D) Vibratome sections of X-gal stained E14 BAT-gal and BAT-gal; Catnb^ex3K14/+ mice indicated increased Wnt activity in mutant skin both in placode epithelium and underlying mesenchyme (B,D) compared with control (A,C). (E-J) By radioactive in situ hybridization, Wnt10b was localized to placode epithelium. (E,F) Sostdc1 was restricted to epithelium flanking the placodes but was absent from the placode, and its expression was more intense in the mutant (G,H). Dkk1 was expressed in mesenchyme underlying the placodes, and was more intense and widespread in the mutant skin (I,J). Arrows indicate hair placodes. Broken lines indicate epithelial-mesenchymal border. Scale bars: 100 µm. (K) Quantitative RT-PCR reveals doubling of Dkk1, Sostdc1 and Shh expression in E13.75 Catnb^ex3K14/+ skin compared with control. Edar expression levels were unaltered in the mutant skin. Data are represented as mean±s.d.