Fig. 4. Localization of E-cadherin and ß-catenin in embryos lacking the binding partner. (A) E-cadherin is detectable on the blastomere surface of embryos expressing truncated ß-catenin. E-cadherin is visible on the surface of the blastomeres of both the control embryos (+/+) and the embryos expressing truncated ß-catenin (Cre/Ø). E-cadherin is also detectable in the cytoplasm of 2-cell and 4-cell stage embryos expressing truncated ß-catenin. (B) ß-catenin is present in the nucleus of early embryos lacking maternal E-cadherin. ß-catenin was detected in control embryos (+/+) and embryos lacking maternal E-cadherin (Cre/Ø), using the polyclonal ß-catenin antibody recognizing the C terminus of the protein. ß-catenin is visible on the blastomere surface of control zygotes, 2-cell stage embryos and 8-cell stage embryos, with some ß-catenin also visible in the cytoplasm of control zygotes and 2-cell stage embryos. By contrast, ß-catenin is visible in the pronuclei and cytoplasm of zygotes, as well as in the nuclei and cytoplasm of 2-cell stage embryos lacking maternal E-cadherin. Only a small amount of ß-catenin is detectable in 8-cell embryos lacking maternal E-cadherin. (C) Truncated ß-catenin is present in the nucleus of embryos lacking maternal E-cadherin. ß-catenin was detected in control embryos (+/+), and in embryos expressing truncated ß-catenin and lacking maternal E-cadherin (double mutant) embryos (Cre/Ø), using the polyclonal ß-catenin antibody that detects the C-terminal part of the protein. ß-catenin is detected in the pronuclei of control and double-mutant zygotes, on the surface and in the cytoplasm of control 2-cell stage embryos, in the nuclei and cytoplasm of double-mutant 2-cell stage embryos, and on the surface of 4 to 8-cell stage control and double-mutant embryos. Note for B and C, blastomeres of 8-cell stage embryos lacking maternal E-cadherin do not adhere to each other. Consequently all manipulations during the immunostaining process were carried out with extreme caution to maintain blastomeres of embryos in a clump. No fluorescence was detected in embryos where the primary antibody was omitted (data not shown). Scale bars: 10 µm.