Liu Dong Teng, Brewer Michael S, Chen Shixi, Hong Wanshu, Zhu Yong
State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, Fujian Province 361102, People's Republic of China; Department of Biology, East Carolina University, Greenville, NC 27858, United States.
Department of Biology, East Carolina University, Greenville, NC 27858, United States.
Gen Comp Endocrinol. 2017 Jun 1;247:74-86. doi: 10.1016/j.ygcen.2017.01.019. Epub 2017 Jan 19.
The central roles of luteinizing hormone (LH), progestin and their receptors for initiating ovulation have been well established. However, signaling pathways and downstream targets such as proteases that are essential for the rupture of follicular cells are still unclear. Recently, we found anovulation in nuclear progestin receptor (Pgr) knockout (Pgr-KO) zebrafish, which offers a new model for examining genes and pathways that are important for ovulation and fertility. In this study, we examined expression of all transcripts using RNA-Seq in preovulatory follicular cells collected following the final oocyte maturation, but prior to ovulation, from wild-type (WT) or Pgr-KO fish. Differential expression analysis revealed 3567 genes significantly differentially expressed between WT and Pgr-KO fish (fold change⩾2, p<0.05). Among those, 1543 gene transcripts were significantly more expressed, while 2024 genes were significantly less expressed, in WT than those in Pgr-KO. We then retrieved and compared transcriptional data from online databases and further identified 661 conserved genes in fish, mice, and humans that showed similar levels of high (283 genes) or low (387) expression in animals that were ovulating compared to those with no ovulation. For the first time, ovulatory genes and their involved biological processes and pathways were also visualized using Enrichment Map and Cytoscape. Intriguingly, enrichment analysis indicated that the genes with higher expression were involved in multiple ovulatory pathways and processes such as inflammatory response, angiogenesis, cytokine production, cell migration, chemotaxis, MAPK, focal adhesion, and cytoskeleton reorganization. In contrast, the genes with lower expression were mainly involved in DNA replication, DNA repair, DNA methylation, RNA processing, telomere maintenance, spindle assembling, nuclear acid transport, catabolic processes, and nuclear and cell division. Our results indicate that a large set of genes (>3000) is differentially regulated in the follicular cells in zebrafish prior to ovulation, terminating programs such as growth and proliferation, and beginning processes including the inflammatory response and apoptosis. Further studies are required to establish relationships among these genes and an ovulatory circuit in the zebrafish model.
促黄体生成素（LH）、孕激素及其受体在启动排卵过程中的核心作用已得到充分证实。然而，对于卵泡细胞破裂所必需的信号通路和下游靶点，如蛋白酶，仍不清楚。最近，我们在核孕激素受体（Pgr）基因敲除（Pgr-KO）斑马鱼中发现了排卵障碍，这为研究排卵和生育相关的重要基因及通路提供了一个新模型。在本研究中，我们使用RNA测序检测了从野生型（WT）或Pgr-KO鱼中收集的排卵前卵泡细胞中的所有转录本表达情况，这些卵泡细胞是在最终卵母细胞成熟后但排卵前收集的。差异表达分析显示，WT和Pgr-KO鱼之间有3567个基因存在显著差异表达（倍数变化⩾2，p<0.05）。其中，与Pgr-KO相比，WT中有1543个基因转录本表达显著更高，而有2024个基因表达显著更低。然后，我们从在线数据库中检索并比较了转录数据，并进一步鉴定出鱼类、小鼠和人类中661个保守基因，这些基因在排卵动物与未排卵动物中呈现出相似水平的高表达（283个基因）或低表达（387个基因）。首次使用富集图和Cytoscape对排卵相关基因及其涉及的生物学过程和通路进行了可视化。有趣的是，富集分析表明，高表达的基因参与了多个排卵途径和过程，如炎症反应、血管生成、细胞因子产生、细胞迁移、趋化作用、丝裂原活化蛋白激酶（MAPK）、粘着斑和细胞骨架重组。相反，低表达的基因主要参与DNA复制、DNA修复、DNA甲基化、RNA加工、端粒维持、纺锤体组装、核酸转运、分解代谢过程以及核分裂和细胞分裂。我们的结果表明，在斑马鱼排卵前，卵泡细胞中有大量基因（>3000个）受到差异调节，终止了生长和增殖等程序，并启动了包括炎症反应和凋亡在内的过程。需要进一步研究来确定这些基因与斑马鱼模型中的排卵回路之间的关系。
