Fig. 4.

p120-catenin restricts the domain and level of WNT response in the posterior epiblast. (A–H) WNT reporter gene expression. (A and B) β-Galactosidase staining for the Batgal WNT reporter in E6.5 (A) wild-type and (B) mutant embryos. Posterior to the right. (C and D) Topgal expression in E7.5 (C) wild-type and (D) p120-catenin–null embryos. Posterior view. (E and F) Transverse sections of E7.5 embryos stained for Batgal, (E) wild-type, and (F) p120-catenin mutants; posterior to the right. (G and H) Immunostaining for TCF-Lef:H2B-GFP-reporter expression in transverse sections of E7.5 embryos. The vertical white lines represent the extent of the GFP⁺ domain. (Scale bars, 50 μm.) (I–U) Nuclear β-catenin. (I–T) High-magnification views of immunostained E7.5 embryo sections, showing localization of β-catenin (white) and T (red). Upper panels correspond to the lateral epiblast of (I–K) wild type and (L–N) mutant; Lower panels show the streak of (O–Q) wild type and (R–T) mutant. Note colocalization β-catenin and T in nuclei of cells of the mutant streak. (Scale bar, 8 μm.) (U) Quantitation of fluorescence intensity (FI) of β-catenin in the nuclei of streak and epiblast cells (EPI). In wild-type embryos, the β-catenin FI in the nuclei at the streak was 15.65 $\pm$ 5.57; in contrast, in the mutant streak, the nuclear β-catenin FI was 35.86 $\pm$ 14.94 (P < 0.0001). The mean β-catenin FI in wild-type epiblast nuclei was 15.09 $\pm$ 7.49, whereas in the mutant epiblast was 14.45 $\pm$ 7.30 (P < 0.351). The black bars in the graphic represent the mean + SD.