Ovarian follicle development in Booroola sheep exhibiting impaired bone morphogenetic protein signalling pathway

Abstract

AbstractThe role of bone morphogenetic proteins (BMPs) in the regulation of ovarian function has been extensively investigated but themechanism of regulation is not well understood. The aim of this study was to investigate the effect of mutation in the BMP receptorin Booroola sheep on the number of primordial follicles and rate of follicle recruitment in comparison with that in normal merino sheepin vivo. Whole sheep ovaries at Q1 the time of birth, 1.5 and 5 years old were collected and processed for the follicle quantification, usingcomputerised stereological methods and statistical analyses. At birth, the total number of primordial follicles in Booroola sheep wassignificantly lower than in merino sheep. At 1.5 and 5 years, a reversed pattern in favour of Booroola ewes was seen with significantlymore primordial follicles than merino. In parallel, the rate of primordial follicle recruitment to developing cohort was substantially lowerin Booroola ewes with only 51 and 66% of primordial follicle consumption at 1.5 and 5 years respectively compared to 92 and 97% inmerino ewes. On other hand, the mean numbers of developing primary follicles were smaller in Booroola sheep at the time of birth, yet,Booroola ewes possess more primary follicles than merino at 1.5 years. These findings suggest that attenuation of the intraovariansignalling pathway of BMPs may in fact be a successful means of rationalising follicle consumption, preventing unnecessary loss offollicles from the initial primordial follicle pool, hence increasing reproductive longevity and fertility.