Transcriptomic profiling of the oocyte-cumulus-granulosa cell complex from estrogen receptor beta knockout mice

Objective: To study the role of estrogen receptor beta in follicle development and maturation and in the response to gonadotropin stimulation aiming at superovulation. Animals: Healthy wild-type and estrogen receptor beta (ER) knockout female mice aged 4 weeks, 7 weeks, and 6 months. analysis. Main Outcomes: Oocyte yield after superovulation, transcriptomic profiling of cumulus cells and oocytes and immunohistochemical analyses. Results: Superovulation of ER knockout (Esr2-KO) mice results in reduced oocyte yield at 6-months of age compared to wild-type (WT) mice. RNA-seq analysis of cumulus cells from superovulated WT and Esr2-KO mice identified genes and pathways associated with among others adhesion, proliferation, Wnt-signaling, and placed ER in bipotential granulosa cell cluster. Loss of ER increased expression of the other estrogen receptors Esr1 and Gper1. Conclusion: Our results show that ER has an important role in regulating ovulation in response to exogenous gonadotropins in 6-month-old mice, but not in younger mice. Our transcriptomic and immunohistochemical observations suggest a dysregulation of the granulosa cell communication and lack of tight coordination between granulosa cell replication and antrum expansion. A significant upregulation of other estrogen receptors supports a compensatory mechanism sustaining fertility during younger age in Esr2-KO mice. Experimental study and transcriptomics analyses研究目的：探究β-雌激素受体（Estrogen Receptor Beta, ERβ）在卵泡发育与成熟过程，以及针对超数排卵的促性腺激素刺激应答中的作用。实验动物：选取健康的野生型（Wild-Type, WT）及β-雌激素受体敲除雌性小鼠，年龄涵盖4周龄、7周龄及6月龄。主要观测指标：超数排卵后的卵母细胞获取量、卵丘细胞与卵母细胞的转录组分析，以及免疫组织化学检测。实验结果：与野生型小鼠相比，6月龄的Esr2基因敲除（Esr2-KO）小鼠经超数排卵后卵母细胞获取量显著降低。对超数排卵后的WT及Esr2-KO小鼠的卵丘细胞进行RNA测序（RNA-seq）分析，鉴定出与黏附、增殖、Wnt信号通路（Wnt-signaling）等相关的基因及信号通路，并明确β-雌激素受体位于双潜能颗粒细胞簇中。β-雌激素受体的缺失会上调其他雌激素受体Esr1与Gper1的表达。研究结论：本研究结果表明，β-雌激素受体在6月龄小鼠中对外源促性腺激素刺激的排卵调控过程中发挥重要作用，但在年轻小鼠中无此功能。本研究的转录组学与免疫组织化学观测结果提示，颗粒细胞间的通讯存在失调，且颗粒细胞增殖与卵泡腔扩张之间缺乏紧密协调。其他雌激素受体的显著上调，表明Esr2-KO小鼠在年轻阶段存在维持生育能力的代偿机制。本研究为实验性研究，包含转录组学分析内容。