The oocyte: the key player in the success of assisted reproduction technologies

Abstract

The ovulation of a mature oocyte at metaphase II of meiosis, with optimal potential to undergo fertilisation by a sperm cell, complete meiosis and sustain the switch to mitotic division, and support early embryo development, involves a protracted and disrupted/delayed series of processes. Many of these are targeted for exploitation in vivo, or recapitulation in vitro, by the livestock industry. Reproductive technologies, including AI, multiple ovulation embryo transfer, ovum pick-up, in vitro embryo production, and oestrus and ovulation synchronisation, offer practitioners and producers the opportunity to produce offspring from genetically valuable dams in much greater numbers than they would normally have in their lifetime, while in vitro oocyte and follicle culture are important platforms for researchers to interrogate the physiological mechanisms driving fertility. The majority of these technologies target the ovarian follicle and the oocyte within; thus, the quality and capability of the recovered oocyte determine the success of the reproductive intervention. Molecular and microscopical technologies have grown exponentially, providing powerful platforms to interrogate the molecular mechanisms which are integral to or affected by ART. The development of the bovine oocyte from its differentiation in the ovary to ovulation is described in the light of its relevance to key aspects of individual interventions, while highlighting the historical timeline.

Roles of Tubulin Concentration during Prometaphase and Ran-GTP during Anaphase ofC. elegansmeiosis

“…Moreover, centrosomes gradually degenerate during oogenesis, and female meiotic spindles in many animal species form without centrosomes (Dumont and Desai, 2012; Gruss, 2018; Heald et al, 1997; Mikeladze-Dvali et al, 2012; Schuh and Ellenberg, 2007). It is well-known that human oocytes, especially from individuals with advanced maternal ages or in vitro fertilizations (IVF) are highly prone to meiotic spindle formation errors, resulting in aneuploid embryos (Angell, 1991; Fair and Lonergan, 2023; Thomas et al, 2021).…”

“…The copyright holder for this preprint (which this version posted April 20, 2024. ; https://doi.org/10.1101/2024.04.19.590357 doi: bioRxiv preprint errors, resulting in aneuploid embryos (Angell, 1991;Fair and Lonergan, 2023;Thomas et al, 2021).…”

Roles of Tubulin Concentration during Prometaphase and Ran-GTP during Anaphase ofCaenorhabditis elegansMeiosis

“…Moreover, centrosomes gradually degenerate during oogenesis, and female meiotic spindles in many animal species form without centrosomes ( Heald et al, 1997 ; Schuh & Ellenberg, 2007 ; Dumont & Desai, 2012 ; Mikeladze-Dvali et al, 2012 ; Gruss, 2018 ). It is well-known that human oocytes, especially from individuals with advanced maternal ages or in vitro fertilizations are highly prone to meiotic spindle formation errors, resulting in aneuploid embryos ( Angell, 1991 ; Thomas et al, 2021 ; Fair & Lonergan, 2023 ).…”