Fig. 3. Nuclear function of ß-catenin in mutant epiblast. Males of the Wnt-reporter line, BAT-gal, were crossed to wild-type or ß-catEx3flox/ß-catEx3flox;cre/+ females to obtain embryos at E5.5 (A,B), E6.5 (C,D), and E7.5 (E,F). In wild type, ß-galactosidase-positive cells can first be detected on the posterior side of the proximal epiblast at E6.5 (C, arrow), and at E7.5 the ß-galactosidase expression domain extended throughout the posterior part of the embryo (E) (Maretto et al., 2003). In contrast, in mutant embryos, ß-galactosidase-positive cells were first found scattered throughout the epiblast at E5.5, and this positive staining became enhanced at E6.5 and E7.5, with no obvious pattern to the staining. Arrow: ß-galactosidase-positive cells in wild-type E6.5 embryos.