in the visceral endoderm (Figure S8A′, Figure S8B′). At subsequent stages, from E7.5 to E13.5, histochemical analysis of whole mounts showed widespread Bptf–β-Geo expression in the developing embryo (Figure S9A, Figure S9B, S9C, S9D, S9E, S9F). This temporal correlation between the earliest stages of Bptf expression and the stages when the mutant phenotype is revealed, suggests that there could be an essential requirement for Bptf as early as E4.5.
