Kobayashi Tohru, Chiba Ayaka, Sato Tadashi, Myosho Taijun, Yamamoto Jun, Okamura Tetsuro, Onishi Yuta, Sakaizumi Mitsuru, Hamaguchi Satoshi, Iguchi Taisen, Horie Yoshifumi
Laboratory of Molecular Reproductive Biology, Institute for Environmental Sciences, University of Shizuoka, Shizuoka, Shizuoka 422-8526, Japan.
Institute for Science and Technology, Niigata University, Niigata, Niigata 950-2181, Japan.
Aquat Toxicol. 2017 Oct;191:209-218. doi: 10.1016/j.aquatox.2017.08.011. Epub 2017 Aug 22.
Testis-ova differentiation in sexually mature male medaka (Oryzias latipes) is easily induced by estrogenic chemicals, indicating that spermatogonia persist in sexual bipotentiality, even in mature testes in medaka. By contrast, the effects of estrogen on testicular somatic cells associated with testis-ova differentiation in medaka remain unclear. In this study, we focused on the dynamics of sex-related genes (Gsdf, Dmrt1, and Foxl2) expressed in Sertoli cells in the mature testes of adult medaka during estrogen-induced testis-ova differentiation. When mature male medaka were exposed to estradiol benzoate (EB; 800ng/L), testis-ova first appeared after EB treatment for 14days (observed as the first oocytes of the leptotene-zygotene stage). However, the testis remained structurally unchanged, even after EB treatment for 28days. Although Foxl2 is a female-specific sex gene, EB treatment for 7days induced Foxl2/FOXL2 expression in all Sertoli cell-enclosed spermatogonia before testis-ova first appeared; however, Foxl2 was not detected in somatic cells in control testes. Conversely, Sertoli-cell-specific Gsdf mRNA expression levels significantly decreased after EB treatment for 14days, and no changes were observed in DMRT1 localization following EB treatment, whereas Dmrt1 mRNA levels increased significantly. Furthermore, after EB exposure, FOXl2 and DMRT1 were co-localized in Sertoli cells during testis-ova differentiation, although FOXL2 localization was undetectable in Sertoli-cell-enclosed apoptotic testis-ova, whereas DMRT1 remained localized in Sertoli cells. These results indicated for the first time that based on the expression of female-specific sex genes, feminization of Sertoli cells precedes testis-ova differentiation induced by estrogen in mature testes in medaka; however, complete feminization of Sertoli cells was not induced in this study. Additionally, it is suggested strongly that Foxl2 and Gsdf expression constitute potential molecular markers for evaluating the effects of estrogenic chemicals on testicular somatic cells associated with estrogen-induced testis-ova differentiation in mature male medaka.
在性成熟的雄性青鳉（Oryzias latipes）中，雌激素类化学物质很容易诱导精巢-卵母细胞分化，这表明精原细胞即使在成熟精巢中也保持着性双潜能。相比之下，雌激素对青鳉中与精巢-卵母细胞分化相关的睾丸体细胞的影响仍不清楚。在本研究中，我们聚焦于成年青鳉成熟精巢中支持细胞在雌激素诱导的精巢-卵母细胞分化过程中表达的性别相关基因（Gsdf、Dmrt1和Foxl2）的动态变化。当成熟雄性青鳉暴露于苯甲酸雌二醇（EB；800ng/L）时，精巢-卵母细胞在EB处理14天后首次出现（观察到为细线期-偶线期的第一批卵母细胞）。然而，即使在EB处理28天后，精巢的结构仍未改变。尽管Foxl2是雌性特异性性别基因，但在精巢-卵母细胞首次出现之前，EB处理7天会诱导所有支持细胞包裹的精原细胞中Foxl2/FOXL2的表达；然而，在对照精巢的体细胞中未检测到Foxl2。相反，EB处理14天后，支持细胞特异性Gsdf mRNA表达水平显著降低，EB处理后DMRT1的定位未观察到变化，而Dmrt1 mRNA水平显著升高。此外，EB暴露后，在精巢-卵母细胞分化过程中，FOXL2和DMRT1在支持细胞中共定位，尽管在支持细胞包裹的凋亡精巢-卵母细胞中未检测到FOXL2的定位，而DMRT1仍定位在支持细胞中。这些结果首次表明，基于雌性特异性性别基因的表达，在成熟青鳉精巢中，支持细胞的雌性化先于雌激素诱导的精巢-卵母细胞分化；然而，本研究中未诱导支持细胞的完全雌性化。此外，强烈建议Foxl2和Gsdf表达构成评估雌激素类化学物质对与成熟雄性青鳉中雌激素诱导的精巢-卵母细胞分化相关的睾丸体细胞影响的潜在分子标志物。
