An analysis of pre-implantation embryos suggested that Bptf mutants specify a functional primitive endoderm and ICM. The primitive endoderm of Bptf mutant embryos was found to express the primitive endoderm markers Gata6, Lefty1, and Hex1 at comparable levels to wild type controls (Figure 3B). The expression of these markers suggests that Bptf mutants are not defective in the differentiation of the primitive endoderm, the precursor of the visceral endoderm of E5.5 and later stage embryos. Consistent with a functional ICM, we observed normal expression of the pluripotency marker Nanog in Bptf mutants compared to controls (Figure 2B). Taken together, these results indicate that Bptf is not required for the specification of the primitive endoderm and the ICM in E4.5 embryos.
