Fig. 8. Lef1 associates with the sox3 promoter in vivo. (A) Western blot of whole-embryo lysates probed with anti-ß-catenin and Lef1 polyclonal antibodies. The Lef1 band is specifically absent in X8 mutants, whereas the positive control ß-catenin band is present. (B) ChIP analysis of whole-embryo lysates shows that the Lef1 antibody can immunoprecipitate DNA fragments containing Lef-binding sites in the upstream regulatory region of sox3, nacre and ngn1. These fragments do not precipitate in controls lacking antibody or chromatin (mock). In lysates from X8 mutants that lack Lef1 protein, the antibody is unable to precipitate these fragments, suggesting that the interaction is specific to Lef1.