Conditionally induced apoptosis and ablation of transgenic zebrafish oocytes

Objective To develop a transgenic zebrafish, Danio rerio, line in which oocyte ablation can be conditionally induced, study the characteristics of oocyte ablation, and provide materials for future reproduction studies.

Method The Tol2 transposon system was used to generate a transgenic zebrafish line which expressed nitroreductase (NTR) enzyme under control of the oocyte-specific gene promoter. The effects of metronidazole (Mtz) on appearance of mature females and internal ovary structure were evaluated by regular sampling, continuous observation, dissection and tissue sectioning. Frozen sections stained by TUNEL were used to detect the induced oocyte apoptosis.

Result A transgenic fish line with stable inheritance was obtained and its blastula cells showed specific mCherry fluorescence. Induced by Mtz, the transgenic mature female ovary gradually degenerated and atrophied, and the oocytes progressively ablated. The results indicated NTR expression in the oocytes. TUNEL detection confirmed that Mtz could induce oocyte apoptosis, leading to histological changes in the ovary. Furthermore, the ovarian ablation induced by Mtz was reversible. When the Mtz stress was withdrawn, the oocytes regenerated and the ovary restored its function.

Conclusion The transgenic zebrafish obtained in this study can implement ovarian ablation and regeneration through conditional induction.