Fig. 4. Western blot analysis to compare the levels of Sox2 protein in the E15.5 esophagus of mutants with different genotypes and phenotypes. The example shown is typical of three independent experiments. Control sample is from limb bud mesenchyme that does not express Sox2. Quantification showed that the level of Sox2 in Sox2^EGFP/COND mutants without fistula was approximately 18% of wild type (mean of three experiments).