The Effects of Polyadenylation Status on MPFs during in Vitro Porcine Oocyte Maturation

Abstract

Aims: This study aims to clarify the effects of polyadenylation status on M-phase promoting factors (MPFs) during in vitro porcine oocyte maturation. Methods: In this study, porcine follicular oocytes from large follicles (> 5 millimeter (mm)) and small follicles (< 3 mm) were examined at different follicular developmental stages. The polyadenylation of maternal mRNAs was inhibited by the addition of 3′-deoxyadenosine (3′-da) during the germinal vesicle (GV)(0 h), GV breakdown (GVBD)(18 h), metaphase I (MI)(28 h), and metaphase II (MII) (44 h) stages. In addition, the expression levels and poly-(A) tail lengths of the maternal mRNAs Cyclin B1 and cell division cycle 2 (Cdc2) were determined by real-time quantitative PCR. Immunofluorescence was used to assess spindle formation and chromosome alignment in the examined oocytes. Results: In large-follicle oocytes, the effects of inhibiting polyadenylation caused the percentage of mature to be significantly lower for the treated group than for the untreated group (p < 0.01). 3′-da can significantly improve the rate of small oocyte maturation in vitro and inhibits Cdc2 polyadenylation. Cyclin B1 plays a significant role in promoting the maturation of large-follicle oocytes. Polyadenylation contributes to the formation of dominant follicles and facilitates the selection of dominant follicles. However, the inhibition of adenylation affected spindle formation-related propulsion and chromosome alignment in both large- and small-follicle oocytes. The first polar body could not be extruded in certain large follicles. Conclusions: 3′-da can significantly improve the rate of small oocyte maturation in vitro, but it can also affect spindle formation-related propulsion and chromosome alignment.