Reproduction Abstracts

In Cdx2-deficient mouse embryos, Oct-4 and Nanog expression are not restricted to the inner cell mass (ICM), and trophectoderm (TE) development is impaired. These results suggest that Cdx2 regulates Oct-4 and Nanog expression in mouse embryos, and plays a key role in TE development. The objective of this study was to investigate the role of CDX2 in the early development of bovine embryos. We attempted CDX2 downregulation in bovine embryos by short interfering RNA (siRNA), and evaluated the effects of CDX2 suppression on developmental competencies and expression of the genes involved in the segregation and function of ICM or TE tissues. Bovine IVF embryos injected with or without siRNA were cultured for 8 days. Gene expressions were evaluated at the morula stage. CDX2 siRNA injected embryos were able to develop to the morula stage. However, the blastocyst developmental rate of CDX2 siRNA-injected embryos (13.1%) was lower (P<0.05) than that of siRNA uninjected or control siRNA-injected embryos (36.6 and 34.4%, respectively) on day 6. On day 8, the embryos downregulated CDX2 were able to form blastocoel. However, the expanded blastocyst formation rate (20.0%) of embryos injected with CDX2 siRNA was lower (P<0.05) than that of control siRNA-injected embryos (33.9%). The CDX2 downregulation resulted in a distinct decrease in GATA3. In contrast, the NANOG expression level in the CDX2 siRNA-injected embryos was higher (P<0.05) than that in control siRNA-injected or siRNA uninjected embryos. Our results suggest that CDX2 is essential for proliferation and functionalization of TE in bovine embryos.