Dynamics of Germ Cell Development in the Bovine Fetal Ovary

Abstract This study offers a comprehensive description of germ cell development in the bovine ovary across a 95-day period between embryonic days 45–140, corresponding to the critical window between gonadal colonization by primordial germ cells (PGCs) and the establishment of the ovarian follicular reserve. The developmental progression of female germ cells is delineated through the utilization of established and novel bovine germ cell markers such as POU5F1, DAZL, DDX4, PRDM1, SOX17, TFAP2C, cKIT, and CD9. Here we confirm the asynchronous nature of germline development in the bovine, akin to observed in humans. Significant observations include the proliferation and differentiation of oogonia, meiotic entry, and the appearance of the first primordial follicles by day 90. Moreover, the temporal expression patterns of the markers DDX4, DAZL and POU5F1 unveiled distinct phases of germ cell development and transient loss of POU5F1 during oogenesis. Furthermore, our findings highlight the association of cKIT and CD9 as effective markers for sorting germ cells at various developmental stages. This study contributes to improve our comprehension of bovine ovarian development and emphasizes parallels with human germ cell development, thereby establishing a framework for future investigations into fertility preservation and enhancement.