<i>foxl2l</i> is a germ cell-intrinsic gatekeeper of oogenesis in zebrafish
Zhiqin Ren, 中国科学院种子创新研究院，水生生物研究所，湖北洪山实验室，水产品种创制与高效养殖重点实验室，湖北 武汉 430072，中国, Ye Ding, Naike Su, Chaofan Wang, Lijia He, Houpeng Wang, Mudan He, Yonghua Sun, 海南大学海洋生物与水产学院, 海南 海口 570228, 中国, 中国科学院大学现代农业科学学院, 北京 100049, 中国, 大连海洋大学水产与生命学院, 辽宁 大连 116023, 中国
Abstract
Zebrafish has emerged as a valuable model for investigating germ cell biology and reproduction. The AB strain of zebrafish is proposed to have a polygenic sex determination system and the majority of males develop juvenile ovaries before committing to male fate. In the species with chromosomal sex determination system, it is widely accepted that the gonadal somatic cells play a pivotal role in determining the fate of germ cells. Interestingly, it has been found that the loss of germ cells leads to masculinization in zebrafish, implying that germ cells harbor an intrinsic feminization signal. However, which signal initiates oogenesis in zebrafish remains unclear. In the present study, we identified foxl2l as an oocyte progenitor-specific gene which acts as an indispensable signal for germ cells to enter oogenesis. We first found that the foxl2l-knockout zebrafish bypassed the juvenile ovary stage and exclusively developed into fertile males. Further study revealed that the loss of foxl2l hindered the initiation of oocyte-specific meiosis and obstructed the entry into oogenesis, resulting in premature spermatogenesis during early gonadal development. Furthermore, we showed that while the mutation of the pro-male gene dmrt1 led to fertile female differentiation, simultaneous disruption of foxl2l in dmrt1 mutants resulted in a complete blockage of oogenesis, with a large proportion of germ cells arrested in the state of germline stem cells, highlighting the essential role of foxl2l in oogenesis. Overall, our study revealed the unique function of foxl2l as a germ cell-intrinsic gatekeeper of oogenesis in zebrafish.