胞外基质参与环境雌激素诱导两栖动物雌性化的机制研究

Effects of environmental estrogens on the reproductive systems of animals and humans have received much attention in the field of ecotoxicology and environmental health. Recently, the applicant found that extracellular matrix (ECM) homeostasis was altered in feminizing gonads following exposure to estrogen in Xenopus laevis, a model for studying estrogenic effects. Considering the involvement of basement membrane (a special ECM) in testicular cord formation, we propose that environmental estrogens can change ECM homeostasis, disrupting testicular differentiation and then resulting in gonadal feminization. To prove this hypothesis, we will carry out the following studies: 1) To confirm estrogen receptor-targeted genes involved in ECM homeostasis and reveal the molecular events directly regulated by estrogens; 2) To dissect the effects of a decrease in ECM deposition on normal testicular differentiation and estrogen-caused gonadal feminization and reveal the roles of ECM in gonadal feminization; 3) To investigate the effects of several environmental estrogens on both ECM homeostasis and gonadal feminization, and clarify the relation between ECM homeostasis and feminization to verify the universality of ECM's involvement in gonadal feminization caused by environmental estrogens. The above studies will reveal the mechanisms for gonadal feminization induced by environmental estrogens in amphibians, which will be helpful for developing new methods for assessing estrogenic effects of environmental chemicals.

环境雌激素对动物和人体生殖系统的影响是生态毒理与环境健康领域的重要课题。申请人近期利用非洲爪蛙这一研究环境物质雌激素效应的模式生物，发现雌激素在诱导性腺雌性化过程中明显干扰胞外基质（ECM）稳态。鉴于ECM特化的基底膜参与精巢索形成，申请人提出假设：环境雌激素通过诱导ECM改变，干扰非洲爪蛙精巢的分化，进而导致性腺的雌性化。围绕这一假设本项目拟开展以下工作：1）甄别参与ECM稳态的雌激素受体靶基因，揭示直接受雌激素调控的分子事件；2）通过分析减少ECM沉积的处理对正常精巢分化和E2诱导雌性化结局的影响，揭示ECM在性腺雌性化过程中的作用；3）研究几种环境雌激素对性腺ECM的影响及与雌性化结局的关系，验证ECM参与环境雌激素诱导爪蛙雌性化的普遍性。本项目将在ECM的角度揭示环境雌激素诱导两栖动物雌性化的机制，所发现的受雌激素调控的分子事件可作为早期标记用于测试雌激素效应新方法的开发。

环境雌激素对雄性生殖系统的影响是生态毒理与环境健康领域备受关注的课题。前期研究发现环境雌激素在诱导非洲爪蛙性腺雌性化过程中引起胞外基质（ECM）显著增加，然而雌激素受体（ER）调控ECM的靶基因以及ECM在性腺发生过程中扮演角色尚不清楚。本项目围绕“环境雌激素通过诱导ECM增加，干扰精巢分化，进而导致性腺雌性化”这一假设开展研究。通过ChIP-PCR确证了从转录组中经ERE序列筛选获得的与ECM相关的ER靶基因；通过研究ECM参与非洲爪蛙性腺的发育过程，发现由特化的ECM即基底膜包裹的髓质结可作为发育早期区分雌、雄以及雌性化性腺的关键特征（雄性性腺中存在髓质结，而雌性和雌性化的雄性性腺中没有髓质结）；利用此特征，研究了可疑环境雌激素双酚B（BPB）暴露非洲爪蛙对早期性腺中ECM的改变，并导致晚期的雌性化性结局；基于此，将实验体系扩展到哺乳动物，建立了一套基于哺乳动物的快速评价化学品雄性生殖系统发育毒性的方法，评价了四溴双酚A对小鼠睾丸发育的影响。综合以上，本项目独辟蹊径的从ECM的角度揭示环境雌激素诱导性腺雌性化的机制，建立了雌性化早期事件和晚期结局之间的关系，为后续开发短周期的评价雌激素效应的方法奠定了基础。