Unravelling molecular signatures of oocyte developmental competence in cattle

可持续的养牛生产对于在气候变化造成的粮食短缺的情况下养活不断增加的世界人口以及减少甲烷排放至关重要。生殖生物技术，如体外胚胎生产（IVEP）与胚胎移植（ET）相结合，可以增加单头高遗传价值奶牛的后代数量，大大有助于提高全球粮食安全，大大减少参与养牛系统的奶牛数量，从而减少养牛业的碳足迹。IVEP的效率需要提高，因为在IVEP中使用的卵母细胞中只有15- 40%设法达到准备用于ET的胚胎阶段。受精卵中的非整倍性（染色体数目异常）绝大多数是由于女性减数分裂错误造成的，并显著导致着床失败、自然流产和死胎。对小鼠的研究强调了负责防止卵母细胞非整倍性和其他通常导致胚胎死亡的细胞分裂错误的关键蛋白质的作用。然而，牛卵母细胞在这方面的知识差距很大。因此，该项目旨在阐明候选蛋白质的作用，这些蛋白质极有可能提供牛卵母细胞发育能力的读数。该项目将利用最先进的活细胞成像技术，将荧光转基因显微注射到牛卵母细胞中，以允许真实的时间监测感兴趣的蛋白质，随后分析已知的预后指标（例如纺锤体形态和染色体比对以指示基因组稳定性）。转基因卵母细胞也将受精并允许发育至胚泡阶段（即约150个细胞，用于ET的常见胚胎阶段），其中将分析与胚胎活力相关的几个细胞和分子终点（例如细胞数量和表观遗传标记物，如H3 K27 me 3）。重要的是，不会产生后代（即不进行ET），屠宰场来源的卵巢将用于提取实验用卵母细胞（养牛业的副产品），因此，本项目不需要对动物进行扑杀。本项目将为鉴定牛卵母细胞发育能力的生物标志物提供基础，目的是提高商业牛IVEP的有效应用。此外，考虑到人类和牛之间卵母细胞和早期胚胎生理学的相似性，该牛模型将为人类生殖医学提供相关数据。

Sustainable cattle production is critical to feed an increasing world population under projected food shortages due to climate change, and to alleviate methane emissions. Reproductive biotechnologies such as in vitro embryo production (IVEP) coupled with embryo transfer (ET) can increase the number of offspring from a single high genetic merit cow, contributing substantially to enhancing global food security, vastly decreasing the number of cows involved in cattle production systems, which in turn will reduce the carbon footprint of the cattle industry.However, to achieve wider commercial acceptance, the efficiency of IVEP needs to be improved as only 15-40 % of oocytes used in IVEP manage to achieve an embryonic stage ready for ET. Aneuploidies (abnormal chromosome numbers) in fertilised eggs are overwhelmingly due to errors in female meiosis, and contribute significantly to implantation failure, spontaneous miscarriage and stillbirth. Studies in mice have highlighted the role of key proteins responsible for the prevention of aneuploidies in oocytes and other cell division errors that would ordinarily result in embryonic demise. Yet, there is a substantial knowledge gap in bovine oocytes in this regard. Hence, this project aims to elucidate the role of candidate proteins highly likely to provide a readout of oocyte developmental competence in cattle.The project will utilise state-of-the-art live cell imaging where fluorescent transgenes will be microinjected into bovine oocytes to allow real time monitoring of proteins of interest, followed by analysis of known indicators of prognosis (e.g. spindle morphology and chromosome alignment to indicate genomic stability). Transgenic oocytes will also be fertilised and allowed to develop to the blastocyst stage (i.e. around 150 cells, a common embryonic stage used for ET) where several cellular and molecular endpoints associated embryo viability will be analysed (e.g. cell number and epigenetic markers such as H3K27me3). Importantly, no offspring will be produced (i.e. no ET will be performed) and abattoir-derived ovaries will be used to extract oocytes for the experiments (a by-product from the cattle industry), hence no animals will be culled for the sake of the project.The project will provide the foundations to identify biomarkers of bovine oocyte developmental competence with the long-term aim of improving the efficient application of commercial bovine IVEP. Furthermore, given the similarities in oocyte and early embryo physiology between humans and cattle, this bovine model will provide data of relevance for human reproductive medicine.