BACKGROUND Infertility is linked to depletion of the primordial follicle pool consisting of individual oocytes arrested at the diplotene stage of meiotic prophase I surrounded by granulosa cells. Primordial germ cells, the oocyte precursors, begin to differentiate during embryonic development. These cells migrate to the genital ridge and begin mitotic divisions, remaining connected, through incomplete cytokinesis, in clusters of synchronously dividing oogonia known as germ cell cysts. Subsequently, they enter meiosis, become oocytes and progress through prophase I to the diplotene stage. The cysts break apart, allowing individual oocytes to be surrounded by a layer of granulosa cells, forming primordial follicles each containing a diplotene arrested oocyte. A large number of oocytes are lost coincident with cyst breakdown, and may be important for quality control of primordial follicle formation. Exposure of developing ovaries to exogenous hormones can disrupt cyst breakdown and follicle formation, but it is unclear if hormones affect progression of oocytes through prophase I of meiosis. METHODS Fetal ovaries were treated in organ culture with estradiol, progesterone, or both hormones, labeled for MSY2 or Synaptonemal complex protein 3 (SYCP3) using whole mount immunocytochemistry and examined by confocal microscopy. Meiotic prophase I progression was also followed using the meiotic surface spread technique. RESULTS MSY2 expression in oocytes was reduced by progesterone but not estradiol or the hormone combination. However, while MSY2 expression was upregulated during development it was not a precise marker for the diplotene stage. We also followed meiotic prophase I progression using antibodies against SYCP3 using two different methods, and found that the percent of oocytes at the pachytene stage peaked at postnatal day 1. Finally, estradiol and progesterone treatment together but not either alone in organ culture increased the percent of oocytes at the pachytene stage. CONCLUSIONS We set out to examine the effects of hormones on prophase I progression and found that while MSY2 expression was reduced by progesterone, MSY2 was not a precise diplotene stage marker. Using antibodies against SYCP3 to identify pachytene stage oocytes we found that progesterone and estradiol together delayed progression of oocytes through prophase I.

中文翻译：

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类固醇激素对小鼠减数分裂前期 I 进展影响的分子分析。


背景不孕症与原始卵泡池的耗竭有关，该原始卵泡池由停滞在减数分裂前期I的双线期阶段的单个卵母细胞组成，周围有颗粒细胞。原始生殖细胞（卵母细胞前体）在胚胎发育过程中开始分化。这些细胞迁移到生殖嵴并开始有丝分裂，通过不完全的胞质分裂保持连接，形成同步分裂的卵原细胞簇，称为生殖细胞囊肿。随后，它们进入减数分裂，成为卵母细胞并通过前期 I 进入双线期阶段。囊肿破裂，使单个卵母细胞被一层颗粒细胞包围，形成原始卵泡，每个卵泡含有一个双线期停滞的卵母细胞。大量卵母细胞随着囊肿破裂而丢失，这对于原始卵泡形成的质量控制可能很重要。发育中的卵巢暴露于外源激素会破坏囊肿破裂和卵泡形成，但尚不清楚激素是否会影响卵母细胞在减数分裂前期 I 的进展。方法 在器官培养中用雌二醇、孕酮或两种激素处理胎儿卵巢，使用整体免疫细胞化学标记 MSY2 或联会复合蛋白 3 (SYCP3)，并通过共聚焦显微镜检查。还使用减数分裂表面扩散技术跟踪减数分裂前期 I 进展。结果 孕酮可降低卵母细胞中 MSY2 的表达，但雌二醇或激素组合不会降低卵母细胞中 MSY2 的表达。然而，虽然 MSY2 表达在发育过程中上调，但它并不是双线期阶段的精确标记。 我们还使用两种不同的方法，使用针对 SYCP3 的抗体跟踪减数分裂前期 I 进展，发现粗线期卵母细胞的百分比在出生后第 1 天达到峰值。最后，在器官培养中，雌二醇和黄体酮一起治疗（但单独治疗）不会增加百分比。粗线期卵母细胞。结论 我们着手检查激素对前期 I 进展的影响，发现虽然黄体酮会降低 MSY2 表达，但 MSY2 并不是精确的双线期标记。使用针对 SYCP3 的抗体来识别粗线期卵母细胞，我们发现黄体酮和雌二醇一起延迟卵母细胞通过前期 I 的进展。