AUTHOR=Hu Peng , Liu Shufang , Liu Xinfu , Liu Haijin , Liu Shengcong , Zhuang Zhimeng 

TITLE=The adverse effects of 17β-estradiol immersion during gonadal differentiation on ovarian development of female Takifugu rubripes

JOURNAL=Frontiers in Marine Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1131041

DOI=10.3389/fmars.2023.1131041

ISSN=2296-7745

ABSTRACT=<p>Estrogen exposure during early-life stages has been found to delay ovarian development in female fish, even after a long-term depuration period. However, the mechanisms underlying the disordered ovarian development remain unclear. In this study, the larvae of tiger puffer <italic>Takifugu rubripes</italic> were exposed to 0 (control) and 10 μg/L 17β-estradiol (E2) from 20 to 90 days post-hatch (dph) and maintained in clear seawater until 180 dph. Genetic females collected at 90 and 180 dph were identified by analyzing a sex-associated SNP. Then, the ovarian structure, gonadosomatic index (GSI), the maximum follicle area and the mRNA levels of genes involving in cell cycle (<italic>ckd2</italic>, <italic>ckd4</italic>, <italic>cdk6</italic>, <italic>ccna2</italic>, <italic>ccnd2</italic>, <italic>cdkn1b</italic> and <italic>cdkn2c</italic>), meiosis initiation (<italic>sycp3</italic>, <italic>rec8</italic>, <italic>spo11</italic>, and <italic>dmc1</italic>), follicle formatiaon (<italic>bmp2</italic>, <italic>hnrnpk</italic>, <italic>hmp15</italic>, <italic>gdf9</italic>, <italic>nobox</italic> and <italic>figla</italic>) and apoptosis (<italic>bax</italic> and <italic>bcl-2</italic>) were analyzed between control and E2-exposed females. The results show that, no structure difference in ovaries was observed between control and E2-treated females at 90 dph, but the primary growth follicles in E2-treated females were observed to be fewer in number than control at 180 dph. Both ovarian weight and GSI of E2-treated females were significant lower than the control at 90 and 180 dph, while there was no significant different in the maximum follicle area between control and E2-treated females at neither 90 or 180 dph. Additionally, the E2 exposure suppressed the expression of <italic>sycp3</italic>, <italic>rec8</italic>, <italic>spo11</italic>, <italic>dmc1, bmp2</italic>, <italic>hnrnpk</italic> and <italic>bcl-2</italic> at 90 dph, but the mRNA levels of those genes in E2-treated females showed no significant different with the control at 180 dph. The reduced mRNA levels of <italic>sycp3</italic>, <italic>rec8</italic>, <italic>spo11</italic> and <italic>dmc1</italic> might result in disrupted meiosis, and suppression the expression of <italic>bmp2</italic> and <italic>hnrnpk</italic> affected follicle formation. Then, abnormal meiosis initiation and follicle formation might further promote apoptosis as indicated by the decrease in mRNA levels of <italic>bcl-2</italic>, which ultimately contributed to less number of follicles and low GSI value in E2-treated females.</p>