College of Marine Sciences, Ningbo University, Ningbo, Zhejiang, China; College of Animal Science and Technology, Shandong Agricultural University, Taian, Shandong, China.
College of Animal Science and Technology, Shandong Agricultural University, Taian, Shandong, China.
Ecotoxicol Environ Saf. 2021 Jul 1;217:112255. doi: 10.1016/j.ecoenv.2021.112255. Epub 2021 Apr 27.
The aromatase inhibitor letrozole can be found in rivers, effluents, and even drinking water. Studies have demonstrated that letrozole affects various metabolic pathways and may cause reproductive toxicity, especially in fish exposed during development. However, studies on the effect of a low concentration of letrozole at the whole-gonad transcriptomic level in the early stage of fish sexual development have not been investigated. The aim of our study was to explore the potential effects of a low concentration of letrozole on the gonad transcriptome of Nile tilapia at an early stage of sexual development. In this study, 9 dpf (days postfertilization) Nile tilapia were exposed to trace letrozole for 12 days. Letrozole exposure from 9 dpf to 21 dpf persistently altered phenotypic sex development and induced the male-biased sex ratio. The transcriptome results showed that 1173 differentially expressed genes (DEGs) were present in the female control vs 1.5 μg/L letrozole-treated female comparison group and that 1576 DEGs were present in the 1.5 μg/L letrozole-treated female vs male control comparison group. Differentially expressed gene enrichment analysis revealed several crucial pathways, including the drug metabolism-cytochrome P450 pathway, the ErbB-PI3K/Akt/mTOR pathway, and the calcium signalling pathway. Further analysis of these identified DEGs indicated that some key genes correlated with metabolism and epigenetic regulation were significantly affected by letrozole, such as UDP-glucuronosyltransferase (Ugt), glutathione S-transferase omega-1 (Gsto1), lysine-specific demethylase 6bb (Kdm6bb, original name is Kdm6a), jumonji and AT-rich interaction domain containing 2 (Jarid2b, original name is Jarid2), growth arrest and DNA damage inducible gamma (Gadd45g), and chromobox protein 7 (Cbx7). The qRT-PCR validation results for twelve DEGs showed that the Pearson's correlation of the log values between the qPCR and RNA-Seq results was 0.90, indicating the accuracy and reliability of the RNA-Seq results. Our study is the first to report the effect of letrozole on the transcriptome of gonads from fish during early-stage sexual development. These findings will be useful for understanding the toxic effects and molecular mechanisms of letrozole exposure at the early stage of gonad development on the sexual development of aquatic organisms.
芳香酶抑制剂来曲唑存在于河流、污水，甚至饮用水中。研究表明，来曲唑会影响各种代谢途径，可能导致生殖毒性，尤其是在鱼类发育过程中暴露于其中。然而，对于低浓度来曲唑在鱼类性发育早期对整个性腺转录组水平的影响，尚未进行研究。本研究旨在探讨低浓度来曲唑对尼罗罗非鱼早期性腺转录组的潜在影响。在这项研究中，9 天孵化后（pf）的尼罗罗非鱼被暴露于痕量来曲唑中 12 天。从 9 天 pf 到 21 天 pf 持续暴露于来曲唑会改变表型性别发育，并诱导雄性偏性性别比例。转录组结果表明，在雌性对照组与 1.5μg/L 来曲唑处理的雌性对照组相比，有 1173 个差异表达基因（DEGs），在 1.5μg/L 来曲唑处理的雌性组与雄性对照组相比，有 1576 个 DEGs。差异表达基因富集分析显示了几个关键途径，包括药物代谢-细胞色素 P450 途径、ErbB-PI3K/Akt/mTOR 途径和钙信号通路。对这些鉴定出的 DEGs 的进一步分析表明，一些与代谢和表观遗传调控相关的关键基因受到来曲唑的显著影响，如 UDP-葡糖醛酸基转移酶（Ugt）、谷胱甘肽 S-转移酶 omega-1（Gsto1）、赖氨酸特异性去甲基酶 6bb（Kdm6bb，原名 Kdm6a）、组蛋白去甲基化酶 2B（Jarid2b，原名 Jarid2）、生长停滞和 DNA 损伤诱导的 γ（Gadd45g）和染色质盒蛋白 7（Cbx7）。对 12 个 DEGs 的 qRT-PCR 验证结果表明，qPCR 和 RNA-Seq 结果的对数之间的 Pearson 相关系数为 0.90，表明 RNA-Seq 结果的准确性和可靠性。本研究首次报道了来曲唑对鱼类早期性发育阶段性腺转录组的影响。这些发现将有助于了解在性腺发育早期暴露于来曲唑对水生生物性发育的毒性作用和分子机制。
