Research Centre for Reproductive Health, Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health, Robinson Institute, University of Adelaide, Adelaide, SA 5005, Australia.
BMC Genomics. 2014 Jan 14;15:24. doi: 10.1186/1471-2164-15-24.
At later stages of folliculogenesis, the mammalian ovarian follicle contains layers of epithelial granulosa cells surrounding an antral cavity. During follicle development granulosa cells replicate, secrete hormones and support the growth of the oocyte. In cattle, the follicle needs to grow > 10 mm in diameter to allow an oocyte to ovulate, following which the granulosa cells cease dividing and differentiate into the specialised cells of the corpus luteum. To better understand the molecular basis of follicular growth and granulosa cell maturation, we undertook transcriptome profiling of granulosa cells from small (< 5 mm; n = 10) and large (> 10 mm, n = 4) healthy bovine follicles using Affymetrix microarrays (24,128 probe sets).
Principal component analysis for the first two components and hierarchical clustering showed clustering into two groups, small and large, with the former being more heterogeneous. Size-frequency distributions of the coefficient of variation of the signal intensities of each probe set also revealed that small follicles were more heterogeneous than the large. IPA and GO enrichment analyses revealed that processes of axonal guidance, immune signalling and cell rearrangement were most affected in large follicles. The most important networks were associated with: (A) Notch, SLIT/ROBO and PI3K signalling, and (B) ITGB5 and extracellular matrix signalling through extracellular signal related kinases (ERKs). Upstream regulator genes which were predicted to be active in large follicles included STAT and XBP1. By comparison, developmental processes such as those stimulated by KIT, IHH and MEST were most active in small follicles. MGEA5 was identified as an upstream regulator in small follicles. It encodes an enzyme that modifies the activity of many target proteins, including those involved in energy sensing, by removal of N-acetylglucosamine from serine and threonine residues.
Our data suggest that as follicles enlarge more genes and/or pathways are activated than are inactivated, and gene expression becomes more uniform. These findings could be interpreted that either the cells in large follicles are more uniform in their gene expression, or that follicles are more uniform or a combination of both and that additional factors, such as LH, are additionally controlling the granulosa cells.
在卵泡发生的后期阶段，哺乳动物的卵巢卵泡包含围绕腔隙的上皮颗粒细胞层。在卵泡发育过程中，颗粒细胞复制、分泌激素并支持卵母细胞的生长。在牛中，卵泡需要生长到 >10mm 直径才能使卵母细胞排卵，之后颗粒细胞停止分裂并分化为黄体的特化细胞。为了更好地理解卵泡生长和颗粒细胞成熟的分子基础，我们使用 Affymetrix 微阵列对来自小(<5mm;n=10)和大(>10mm;n=4)健康牛卵泡的颗粒细胞进行了转录组谱分析(24128 个探针集)。
前两个成分的主成分分析和层次聚类显示聚类为两个组，小和大，前者更具异质性。每个探针集信号强度的变异系数的大小频率分布也表明小卵泡比大卵泡更具异质性。IPA 和 GO 富集分析表明，大卵泡中轴突导向、免疫信号和细胞重排等过程受到的影响最大。最重要的网络与(A)Notch、SLIT/ROBO 和 PI3K 信号以及(B)ITGB5 和细胞外基质信号通过细胞外信号相关激酶(ERKs)有关。预测在大卵泡中活跃的上游调节基因包括 STAT 和 XBP1。相比之下，在小卵泡中，刺激 KIT、IHH 和 MEST 等的发育过程最为活跃。MGEA5 被确定为小卵泡中的上游调节基因。它编码一种通过从丝氨酸和苏氨酸残基上除去 N-乙酰葡萄糖胺来修饰许多靶蛋白活性的酶，包括那些参与能量感应的蛋白。
我们的数据表明，随着卵泡的增大，激活的基因和/或途径比失活的基因和/或途径多，基因表达变得更加均匀。这些发现可以解释为大卵泡中的细胞在基因表达上更加均匀，或者卵泡更加均匀，或者两者兼而有之，并且还存在其他因素，如 LH，额外控制颗粒细胞。
