OCT4/POU5F1 is required for NANOG expression in bovine blastocysts

Significance Studies of mammalian development are mostly performed in the mouse model, where reverse genetics is most advanced. Recent developments in gene editing, including CRISPR-Cas9, facilitated functional studies of specific genes in other mammalian species and revealed important differences (e.g., between human and murine development). In this study, we generated loss-of-function mutations of the OCT4 gene in bovine fibroblasts and produced embryos by nuclear transfer cloning. We demonstrated that, similar to human development but in contrast to mouse development, OCT4 is required for maintaining NANOG-positive epiblast cells in the inner cell mass of blastocysts. Our study outlines a general strategy for dissecting the roles of specific genes in preimplantation development in domestic species.