Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Research Center of Fishery Resources and Environment, College of Fisheries, Southwest University, Chongqing 400715, China.
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Research Center of Fishery Resources and Environment, College of Fisheries, Southwest University, Chongqing 400715, China.
Comp Biochem Physiol B Biochem Mol Biol. 2022 Feb-Mar;258:110681. doi: 10.1016/j.cbpb.2021.110681. Epub 2021 Oct 21.
Thyroid-stimulating hormone (TSH) is an important glycoprotein in hypothalamic-pituitary-thyroid axis, which plays a crucial role in the synthesis and release of thyroid hormones in vertebrates. Rice field eel, Monopterus albus, a protogynous hermaphroditic fish, which undergoes sex reversal from a functional female to a male, is an ideal model to investigate the regulation of sex differentiation. In this study, we obtained the cDNA sequence of thyroid-stimulating hormone β subunit (tshβ) from rice field eel, which contained a complete open reading frame and encoded a putative protein of 151 amino acids. Multiple alignment of protein sequences showed that tshβ was highly conserved in teleost. The tissue distribution indicated that tshβ showed high expression in the pituitary, moderate expression in the brain region, gonad, intestine and liver, and low expression in other peripheral tissues. During natural sex reversal, the expression of tshβ had no significant difference in the pituitary. Compared to that in the ovary, the expression of tshβ increased significantly in the gonad at late intersexual and male stages. After treatment by different doses of triiodothyronine (T3) (1 μg/g, 10 μg/g and 100 μg/g body weight), serum T3 and free triiodothyronine (FT3) increased sharply, while the expression of tshβ were inhibited significantly in the pituitary. Although T3 had no significant effect on the levels of serum E2, it stimulated the release of serum 11-KT at high-dose group. We also detected the effects of T3 on the expression of gonadal differentiation-related genes in rice field eel. T3 treatment inhibited the expression of foxl2, cyp19a1a and dax1, while stimulated the expression of sox9a1. These results indicate that TSH may be involved in sex differentiation, and THs may play roles in the regulation of male development and sex reversal in rice field eel.
促甲状腺激素（TSH）是下丘脑-垂体-甲状腺轴中的一种重要糖蛋白，在脊椎动物的甲状腺激素合成和释放中起着至关重要的作用。稻田鳗（Monopterus albus）是一种雌雄同体的鱼类，经历从功能性雌性到雄性的性反转，是研究性别分化调控的理想模型。在本研究中，我们从稻田鳗中获得了促甲状腺激素β亚基（tshβ）的 cDNA 序列，该序列包含一个完整的开放阅读框，并编码一个由 151 个氨基酸组成的假定蛋白。蛋白质序列的多重比对表明，tshβ在硬骨鱼中高度保守。组织分布表明，tshβ在垂体中高表达，在脑区、性腺、肠和肝中中度表达，在其他外周组织中低表达。在自然性反转过程中，垂体中 tshβ的表达没有显著差异。与卵巢相比，在性腺的间性和雄性晚期阶段，tshβ的表达显著增加。用不同剂量的三碘甲状腺原氨酸（T3）（1μg/g、10μg/g 和 100μg/g 体重）处理后，血清 T3 和游离三碘甲状腺原氨酸（FT3）急剧增加，而垂体中 tshβ的表达受到显著抑制。尽管 T3 对血清 E2 水平没有显著影响，但它在高剂量组刺激了血清 11-KT 的释放。我们还检测了 T3 对稻田鳗性腺分化相关基因表达的影响。T3 处理抑制了 foxl2、cyp19a1a 和 dax1 的表达，同时刺激了 sox9a1 的表达。这些结果表明 TSH 可能参与性别分化，THs 可能在调控稻田鳗雄性发育和性反转中发挥作用。
