Department of Animal and Poultry Science, Virginia Polytechnic and State University, Blacksburg, Virginia, USA.
Biol Reprod. 2020 Apr 15;102(4):784-794. doi: 10.1093/biolre/ioaa015.
From the time oocytes leave quiescence, there are constant microenvironmental influences contributing to development, thus acquiring developmental competence is not a simple, linear phenomenon. During folliculogenesis, oocytes experience many morphological and cytological changes that contribute toward the acquisition of developmental competence, a process defined by an oocyte's ability to progress through folliculogenesis, be fertilized, undergo cleavage, and develop into an embryo. Many factors, such as ovarian follicle size, cow age, and the morphology of the cumulus-oocyte complex, have been extensively investigated to understand this process. In parallel to aiding in the understanding of oocyte biology, these features have been used to characterize an oocyte's ability to achieve competence. In addition, oocytes undergo intense gene transcription and protein translation to accumulate the maternal stores. When the oocyte is fully grown, most genes are transcriptionally inactive, and the chromatin is densely compacted. More recently, RNA profiling has been used to further define the transcriptional parameters that are associated with oocyte development. Here, focusing on cattle, we provide an overview of the experimental models commonly used to understand the underlying biology related to oocyte developmental competence. We compiled public data and showed that cattle oocytes can express over 15 000 protein-coding genes, suggesting a complex transcriptome landscape. Surprisingly, less than 2% of the expressed genes have been linked to developmental competence. The identification of the gene products that contribute to oocyte development, and understanding their biological function, are a vital component of our quest toward defining oocyte developmental competence at the molecular level.
从卵母细胞离开静止期开始，就一直受到不断的微环境影响，从而促进其发育，因此获得发育能力并不是一个简单的线性现象。在卵泡发生过程中，卵母细胞经历了许多形态和细胞学上的变化，这些变化有助于获得发育能力，这个过程是由卵母细胞通过卵泡发生、受精、卵裂和发育成胚胎的能力来定义的。许多因素，如卵巢卵泡大小、牛的年龄和卵丘-卵母细胞复合体的形态，已经被广泛研究，以了解这个过程。在帮助理解卵母细胞生物学的同时，这些特征也被用来描述卵母细胞获得能力的能力。此外，卵母细胞经历强烈的基因转录和蛋白质翻译，以积累母性储存物。当卵母细胞完全成熟时，大多数基因转录不活跃，染色质致密。最近，RNA 谱分析已被用于进一步定义与卵母细胞发育相关的转录参数。在这里，我们以牛为例，概述了常用于了解与卵母细胞发育能力相关的基础生物学的实验模型。我们编译了公共数据，并表明牛卵母细胞可以表达超过 15000 个蛋白质编码基因，这表明存在复杂的转录组景观。令人惊讶的是，只有不到 2%的表达基因与发育能力有关。鉴定出有助于卵母细胞发育的基因产物，并了解它们的生物学功能，是我们在分子水平上定义卵母细胞发育能力的关键组成部分。
