Changes of maternal transcripts in oocytes from persistent follicles in cattle

A high incidence of early embryonic loss is associated with prolonged dominance of follicles. The objective of the present experiment was to determine if persistence of a follicle resulted in alterations in mRNA expression of important genes in the oocyte. Cows were assigned to four groups: growing follicles on day 6 (G0h) or day 8 (G48h) and persistent follicles on day 13 (P0h) or day 15 (P48h) of the estrous cycle (estrus = day 0). All cows were super-stimulated on day 1-4. Cows in G48h, P0h, and P48h groups received 25 mg prostaglandin (PG) F2 alpha on day 6. Cows in P0h and P48h groups received progesterone from CIDR-13 devices on day 5 through 13. Ovaries of cows in G0h, G48h, P0h, and P48h groups were removed on day 6, 8, 13, and 15, respectively. Oocytes were aspirated immediately after colpotomy and denuded of cumulus cells. Quantitative real-time PCR was used to measure the mRNA abundances of 10 selected genes important for early embryogenesis in oocytes obtained from growing and persistent follicles. Relative abundances of MSY2, PARN, and YY1 mRNA (P < 0.05) were significantly lower in oocytes from persistent than from growing follicles. Oocytes from persistent follicles, however, had greater abundances of PAP and elF-4E transcripts (P < 0.05). The data indicate that persistence of a follicle leads to altered abundances of mRNA for genes important for regulation of transcription and protein translation in the oocyte, which could compromise development of early embryos in cows that ovulate a persistent follicle.