Abstract：
This study aims to explore the roles of three estrogen receptors (Esr1, Esr2, and Gper1) in early differentiation of embryonic gonads of Trachemys scripta. The expression characteristics of the receptor genes were studied first. The Esr1, Esr2, and Gper1 agonists PPT, WAY 200070, and G-1 were respectively injected into the embryos at the male-producing temperature (MPT) before initiation of gonadal differentiation. The sex reversal of the treated embryonic gonads was analyzed in terms of morphological structure of gonads, distribution pattern of germ cells, and expression of key genes and proteins involved in sex differentiation. The expression level of esr1 during the critical stage of sex differentiation was higher than those of esr2 and gper1 (very low expression) and was particularly high in the gonads at the female-producing temperature (FPT). After treatment with PPT, the MPT gonads presented obviously feminized morphology and structure, with the germ cells exhibiting a female distribution pattern. Furthermore, the mRNA expression levels of the key genes (dmrt1, amh, and sox9) for male differentiation were down-regulated significantly, while those of the key genes (foxl2 and cyp19a1) for female differentiation were up-regulated observably. The fluorescent signals of Amh and Sox9 expression almost disappeared, while Foxl2 and Arom were activated to express abundantly, which fully demonstrated the sex reversal of the gonads from male to female (sex reversal rate: 70.27%). However, the MPT gonads treated with WAY 200070 and G-1 still differentiated into testes, and the expression patterns of the key genes and proteins were similar to those in male gonads. The above results demonstrate that activation of Esr1 alone can fully initiate the early female differentiation process of gonads, suggesting that estrogen may induce early ovarian differentiation via Esr1 in Trachemys scripta. The findings provide a basis for further revealing the mechanisms of estrogen regulation in sex determination and differentiation of turtles.
摘要：
本研究旨在探讨三种雌激素受体（Esr1，Esr2和Gper1）在Trachemysscripta胚胎性腺早期分化中的作用。起首研讨了受体基因的表达特征。Esr1，Esr2和Gper1激动剂PPT，在开始性腺分化之前，将WAY200070和G-1分别在雄性产生温度（MPT）下注射到胚胎中。从性腺的形态结构方面分析了处理过的胚胎性腺的性别逆转，生殖细胞的分布模式，以及参与性别分化的关键基因和蛋白质的表达。在性别分化的关键阶段，esr1的表达水平高于esr2和gper1的表达水平（表达非常低），并且在雌性产生温度（FPT）下在性腺中特别高。用PPT治疗后，MPT性腺呈现明显女性化的形态和结构，生殖细胞表现出雌性分布模式。此外，关键基因的mRNA表达水平(dmrt1，amh，和sox9）的雄性分化显着下调，而女性分化的关键基因（foxl2和cyp19a1）则明显上调。Amh和Sox9表达的荧光信号几乎消失，当Foxl2和Arom被激活大量表达时，充分证明了性腺从男性到女性的性别逆转(性别逆转率:70.27%)。然而,用WAY200070和G-1处理的MPT性腺仍然分化为睾丸，关键基因和蛋白质的表达模式与男性性腺相似。以上结果表明，单独激活Esr1可以完全启动性腺的早期雌性分化过程，提示雌激素可能通过Trachemysscripta中的Esr1诱导早期卵巢分化。研究结果为进一步揭示雌激素调节海龟性别决定和分化的机制提供了依据。
