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Upstream stimulating factor 1 (USF1) is a basic helix–loop–helix transcription factor that specifically binds to E-box DNA motifs, known cis-elements of key oocyte expressed genes essential for oocyte and early embryonic development. However, the functional and regulatory role of USF1 in bovine oocyte and embryo development is not understood. In this study, we demonstrated that USF1 mRNA is maternal in origin and expressed in a stage specific manner during the course of oocyte maturation and preimplantation embryonic development. Immunocytochemical analysis showed detectable USF1 protein during oocyte maturation and early embryonic development with increased abundance at 8–16-cell stage of embryo development, suggesting a potential role in embryonic genome activation. Knockdown of USF1 in germinal vesicle stage oocytes did not affect meiotic maturation or cumulus expansion, but …