脊椎动物卵子发生受类固醇激素严格调控，现有研究主要集中在雌激素、雄激素和孕激素的作用，而糖皮质激素的作用还不清楚。鱼类主要的糖皮质激素是皮质醇，cyp11b2是合成皮质醇和雄激素11-酮基睾酮的关键酶基因。我们在罗非鱼建立了该基因缺失模型，发现XX杂合突变鱼血清皮质醇和雌激素水平降低，虽能正常产卵并与雄鱼受精，但胚胎致死，这种表型能通过皮质醇而非11-酮基睾酮处理XX亲鱼回救，说明亲鱼皮质醇剂量不足是影响卵子质量的根本原因。更为严重的是，XX纯合子血清雌激素水平显著降低、卵黄发生障碍导致不育。本研究拟通过皮质醇、雌激素回救和皮质醇受体基因敲除等，深入分析皮质醇不足和缺失对卵子发生和卵子质量的影响，阐明皮质醇作用的受体和下游信号通路，解析皮质醇和雌激素合成的偶联机制，旨在揭示皮质醇在卵子发生的功能和作用机制。本项目有助于丰富对卵子发生复杂调控网络的认识，对提高经济鱼类卵子质量有潜在应用价值。

Oogenesis is strictly regulated by steroids in vertebrates. Existing studies have been focused on the role of estrogen, progestin and androgen in oogenesis, while the role of glucocorticoids is unclear. Cortisol is the primary glucocorticoid in fish, and cyp11b2 is the key enzyme gene for synthesizing cortisol and androgen 11-ketotestosterone (11-KT). We successfully mutated cyp11b2 by CRISPR/Cas9, and found that the phenotype of cyp11b2+/- and cyp11b2-/- XY fish was normal except delayed spermatogenesis. Unexpectedly, the serum estrogen level of XX heterozygotes decreased. Although cyp11b2+/- XX fish could lay eggs normally, which were fertilized with normal male fish sperm, all the embryos were lethal after two-day development. Interestingly, this could be rescued by exogenous cortisol instead of 11-KT treatment of the cyp11b2+/- fish. cyp11b2-/- XX fish displayed more serious phenotypes including abnormal vitellogenesis and infertility. In this study, we intend to analyze the effects of cortisol deficiency and absence on oocyte quality and oogenesis，study the receptor mediating the function of cortisol in oogenesis and downstream signaling pathway，and investigate the crosstalk between cortisol and estrogen synthesis. The aim of this proposal is to elucidate the role and molecular mechanism of cortisol in oogenesis. Our results will be in theory helpful for understanding the complex regulatory networks of oogenesis, and in application contributes to improvement of the egg quality in farmed fish.