Project description:The zona pellucida plays a crucial role in the process of fertilization to early embryonic development, including cellular arrangement and communication between blastomeres. However, little is known regarding the role of the zona pellucida in pre- and post-implantation embryonic development associated with gene expression. We investigated the effects of the zona pellucida on the development and gene expression of pre- and post-implantation embryos. After the zona pellucida was removed at the 2-cell stage, compaction occurred earlier. In addition, the expression of differentiation-related genes in the inner cell mass (ICM) (Oct4, Sox21) and trophectoderm (TE) (Cdx2, Eomes, and Tfap2c) was significantly altered in both zona free (ZF) morula and blastocyst compared to zona intact embryos. After embryo transfer, the implantation rate and number of live fetuses were lower in ZF embryos than in control embryos, whereas the fetal weight at birth was not different. However, placental weight was significantly increased in ZF embryos. RNA-seq analysis of the placenta showed that a total of 473 differentially expressed genes that significantly influenced the biological process. The present study suggests that zona pellucida removal at the 2-cell stage not only disturbs the expression pattern of ICM/TE-related genes, but affects the post-implantation development of mouse embryos. Overall, this study provides a deeper insight into the role of the zona pellucida during early mouse embryonic development and the viability of post-implantation development. It also provides a valuable basis for future research related to the production of ZF embryos in mammals and the developmental properties of blastomeres.