Temporary and reversible meiotic arrest of bovine cumulus-oocyte complexes: in vitro pre-maturation and maturation, and potential effects on epigenetic regulation.

• Grant number: 24/18860-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2025
• End date: March 31, 2026
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Cláudia Lima Verde Leal
• Grantee: José Enrico Monteiro Lo'Buono
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil
• Associated research grant: 21/09886-8 - Epigenetic maturation of the oocyte and totipotence: the potential of the oocyte and its relationship with the ovarian follicular niche, AP.SPEC

Abstract

Epigenetic mechanisms underlying oocyte totipotency and developmental competence remain largely unknown. A better understanding of these fundamental processes offers opportunities for developing novel biotechnologies with benefits for both humans and animals. This study is part of the São Paulo Excellence Chair (SPEC-FAPESP) thematic project "Epigenetic maturation of the oocyte and totipotency - the oocyte's potential and its relationship with the ovarian follicular niche". Current in vitro embryo production (IVP) systems still fail to yield oocytes with high developmental competence after in vitro maturation (IVM), as cumulus-oocyte complexes (COCs) spontaneously resume meiosis upon removal from the follicle. Temporary and reversible meiotic arrest prior to IVM (pre-IVM) could improve the preparation of the female gamete, but the epigenetic effects of such a strategy have not yet been studied. This study aims to investigate pre-IVM as a means of providing additional time for the oocyte to acquire the epigenetic and molecular characteristics that enhance oocyte competence. In Experiment 1, oocytes will undergo pre-IVM followed by IVM, and nuclear maturation (meiotic stage) will be assessed before and after each culture period. In Experiment 2, epigenetic patterns (global DNA methylation and hydroxymethylation) will be evaluated, and in Experiment 3, the expression of imprinted genes will be assessed in the same groups. Each experiment will include a control group subjected only to IVM. We expect to gain new knowledge that will contribute to our understanding of epigenetic regulation in oocytes, providing a basis for improving in vitro embryo production conditions.