Requirement of the transcription factor USF1 in bovine oocyte and early embryonic development

Abstract

Upstream stimulating factor 1 (USF1) is a basic helix–loop–helix transcription factor that specifically binds to E-box DNA motifs, knowncis-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 thatUSF1mRNA 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 ofUSF1in germinal vesicle stage oocytes did not affect meiotic maturation or cumulus expansion, but caused significant changes in mRNA abundance for genes associated with oocyte developmental competence. Furthermore, siRNA-mediated depletion ofUSF1in presumptive zygote stage embryos demonstrated thatUSF1is required for early embryonic development to the blastocyst stage. A similar (USF2) yet unique (TWIST2) expression pattern during oocyte and early embryonic development for related E-box binding transcription factors known to cooperatively bind USF1 implies a potential link to USF1 action. This study demonstrates that USF1 is a maternally derived transcription factor required for bovine early embryonic development, which also functions in regulation ofJY1, GDF9, andFSTgenes associated with oocyte competence.