Role of maternal Oct-4 during oogenesis and early embryogenesis in the mouse.

摘要

Oct-4 is a transcription factor that belongs to the POU family. The expression of Oct-4 is found in growing oocytes and in totipotent or pluripotent cells of the early mouse embryo, and is down-regulated in embryos during differentiation events associated with blastocyst implantation and gastrulation. To study the correlation between cell pluripotency and Oct-4 expression, a polyclonal antibody was raised against a unique peptide sequence in the C-terminus of mouse Oct-4. It specifically recognized Oct-4 protein as tested by Western blot and gel mobility shift assays. This antibody was used to measure Oct-4 protein levels during retinoic acid induced differentiation of F9 cells. It was observed that Oct-4 protein was abundant in undifferentiated F9 cells but decreased to levels below detection as the cells differentiated, consistent with changes in levels of expression in early embryos. The role of maternal Oct-4 during oogenesis and early development in the mouse was investigated by a strategy to underexpress Oct-4 in transgenic mice by antisense inhibition. Antisense Oct-4 RNA was expressed under the control of the mouse zona pellucida ZP3 promoter. Oocyte-specific expression of antisense Oct-4 RNA was demonstrated by RT-PCR and by Southern blot analysis. Quantitative RT-PCR revealed that each unfertilized mouse oocyte contained about 800 copies of Oct-4 mRNA. The number was reduced by 69% to 310 in oocytes from transgenic animals. The level of Oct-4 protein in oocytes from transgenic mice was decreased by an average of 53% compared to the value in oocytes of normal mice when measured by immunoprecipitation. The reduced Oct-4 levels had no significant effect on reproductive capacity as measured by oocyte number and litter size in transgenic mice compared to their normal counterparts. However, the transgenic strategy used in this study, with modifications, may be useful for functional analysis of other maternal factors.