Reproduction Abstracts

Introduction: MicroRNAs interact with multiple mRNAs resulting in their degration and/or translational repression. Embryo diapause is a widespread phenomenon in which temporarily arrest occurred in embryo development. Our previous data showed that the levels of let-7 are relatively high in diapause embryos compared to reactivated embryos by E₂ in mice. However, it is still not clear whether or not let-7 is involved in embryo diapause.

Materials and methods: Firstly, blastocysts electroporated with pre-let7a were cultured for 3-9 days in vitro, and then checked metabolic parameters (such as glucose, lactate et al) and shape of embryos. Secondly, we transferred the embryos cultured in vitro into the uteri of 2-Fl-E₂ induced pseudopregnant mice to confirm whether these embryos are dormant or not. Finally, we applied microarray methods to dectect which genes are mediated the roles of let-7 in embryo dormancy.

Results and discussion: The embryos electroporated with let-7 can still be alive and induce the formation of implantation sites even after the culture for up to Day 13. Further studies showed that the activated embryos changed into diapause state if these embryos were electroporated with let-7. Interestingly, 12.5% of diapause embryos induced by let-7 in vitro developed to term after culture for 4 days (ie Day 8). Survival mechanisms of diapause embryos induced by let-7 are involved in decreasing the apoptosis and cell cycle of embryos. In conclusion, the levels of let-7 are positive correlated with the diapause state of embryos. This study will provide information on understanding difference in embryo dormancy between animals.