School of Animal Sciences, Virginia Polytechnic Institute and State University, 175 W Campus Dr, Blacksburg, VA, 24061, USA.
Department of Animal Science, University of Tennessee, Knoxville, TN, USA.
Reprod Biol Endocrinol. 2022 Aug 13;20(1):119. doi: 10.1186/s12958-022-00994-3.
Cytoplasmic and nuclear maturation of oocytes, as well as interaction with the surrounding cumulus cells, are important features relevant to the acquisition of developmental competence.
Here, we utilized Brilliant cresyl blue (BCB) to distinguish cattle oocytes with low activity of the enzyme Glucose-6-Phosphate Dehydrogenase, and thus separated fully grown (BCB positive) oocytes from those in the growing phase (BCB negative). We then analyzed the developmental potential of these oocytes, mitochondrial DNA (mtDNA) copy number in single oocytes, and investigated the transcriptome of single oocytes and their surrounding cumulus cells of BCB positive versus BCB negative oocytes.
The BCB positive oocytes were twice as likely to produce a blastocyst in vitro compared to BCB- oocytes (P < 0.01). We determined that BCB negative oocytes have 1.3-fold more mtDNA copies than BCB positive oocytes (P = 0.004). There was no differential transcript abundance of genes expressed in oocytes, however, 172 genes were identified in cumulus cells with differential transcript abundance (FDR < 0.05) based on the BCB staining of their oocyte. Co-expression analysis between oocytes and their surrounding cumulus cells revealed a subset of genes whose co-expression in BCB positive oocytes (n = 75) and their surrounding cumulus cells (n = 108) compose a unique profile of the cumulus-oocyte complex.
If oocytes transition from BCB negative to BCB positive, there is a greater likelihood of producing a blastocyst, and a reduction of mtDNA copies, but there is no systematic variation of transcript abundance. Cumulus cells present changes in transcript abundance, which reflects in a dynamic co-expression between the oocyte and cumulus cells.
卵母细胞的细胞质和核成熟，以及与周围卵丘细胞的相互作用，是与获得发育能力相关的重要特征。
在这里，我们利用亮甲酚蓝（BCB）来区分牛卵母细胞中葡萄糖-6-磷酸脱氢酶活性较低的卵母细胞，从而将完全成熟的（BCB 阳性）卵母细胞与处于生长阶段的卵母细胞（BCB 阴性）分开。然后，我们分析了这些卵母细胞的发育潜力、单个卵母细胞中线粒体 DNA（mtDNA）的拷贝数，并研究了 BCB 阳性和 BCB 阴性卵母细胞的单个卵母细胞及其周围卵丘细胞的转录组。
BCB 阳性卵母细胞在体外产生囊胚的可能性是 BCB-卵母细胞的两倍（P<0.01）。我们确定 BCB 阴性卵母细胞的 mtDNA 拷贝数比 BCB 阳性卵母细胞多 1.3 倍（P=0.004）。卵母细胞中表达的基因的转录丰度没有差异，但是，根据卵母细胞的 BCB 染色，在 172 个基因在卵丘细胞中表现出差异转录丰度（FDR<0.05）。卵母细胞与其周围卵丘细胞之间的共表达分析显示，一组基因在 BCB 阳性卵母细胞（n=75）及其周围卵丘细胞（n=108）中的共表达构成了卵丘-卵母细胞复合体的独特特征。
如果卵母细胞从 BCB 阴性转变为 BCB 阳性，那么产生囊胚的可能性更大，mtDNA 拷贝数减少，但转录丰度没有系统变化。卵丘细胞的转录丰度发生变化，这反映了卵母细胞和卵丘细胞之间的动态共表达。
