Oct4 expression in preimplantation stage rabbit embryos. A. Quantitative real time RT-PCR analysis of POU5F1 expression in mouse and B. rabbit preimplantation stage embryos. C. Relative expression level of POU5F1 in ICM and trophoblast portion of rabbit blastocyst. The mean values of gene expression of six individual samples and ± S.E. are shown on the diagrams. For comparison of expression through developmental stages (B), the oocyte level was taken as calibrator, while for comparison of TE and ICM samples (C), the blastocyst level was taken as calibrator. Note the scale of the y-axis differs in the case of the two species. Different letters mark significant differences between values (P < 0.05).