Transcriptomic Analysis for Differentially Expressed Genes in Ovarian Follicle Activation and Puberty Onset in the Zebrafish

Puberty is a special transition period in sexual maturation, and it has been extensively studied in vertebrates in the past decades. In mammals, the initiation of puberty involves activation of numerous genes; however, there have been few comprehensive reports in small model teleosts such as the zebrafish. In the zebrafish, the onset of puberty in females is marked by the appearance of the first wave of pre-vitellogenic (PV) follicles in the ovary during sexual maturation. Using transcriptomics and real-time qPCR, this study was undertaken to investigate temporal gene expression differences between the primary growth (PG) follicles and pre-vitellogenic (PV) follicles, with particular emphasis on oocyte and follicular cell specific genes as well as several closely associated signaling pathways. Our results showed that totally 1082 genes were significantly upregulated and 530 evidently downregulated during the PG-PV transition, and among them were some well recognized biomarkers such as cyp19a1a, fshr, inha and inhbaa and some novel genes like notch3, amh, gadd45ga and lpl. Further gene ontology analysis showed that egg coat formation and steroid hormone mediated signaling pathway might be critical for follicle activation from PG to PV stage. In addition, KEGG identified several signaling pathways that might play pivotal roles in early folliculogenesis, including phosphatidylinositol signaling system, glycolsaminoglycan biosynthesis, RNA transport, and p53 signaling pathways. Overall, this study reported a comprehensive analysis for biomarker genes and potential pathways involved in PG-PV transition or follicle activation, which also marks female puberty onset in the zebrafish when occurring for the first time in sexual maturation. Overall design: Examination of gene expression patterns in 2 different stage follicles (PG and PV follicles)

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Zhu B, Pardeshi L, Chen Y, Ge W