FIG. 3.

Zygotic ODC is expressed in blastocysts but is dispensable for blastocyst formation. (A) Representative genotypic analysis of E3.5 embryos from ODC^+/− breedings. DNA from individual blastocysts was isolated as described in Materials and Methods, and primers were used to amplify fragments from the wild-type and/or ODC mutant allele in each sample. ODC^−/− embryos were found at nearly an expected Mendelian ratio (21%). (B) Phase-contrast photographs of wild-type (left panel) and ODC-null (right panel) blastocysts. ODC-deficient blastocysts appear morphologically normal. (C) Expression of zygotic ODC, as detected by LacZ staining. An intense signal is observed in both the ICM and the TE of an ODC-deficient blastocyst. (D) A similar pattern of ODC expression (green) was detected with an ODC-specific antibody in a wild-type blastocyst. Blastocysts were also stained with propidium iodide (red), which detects DNA. Wt, wild type; Het., heterozygous.