Chen Ying, Breen Kelsey, Pepling Melissa E
Department of Biology, Syracuse University, 107 College Place, Syracuse, New York 13244, USA.
J Endocrinol. 2009 Sep;202(3):407-17. doi: 10.1677/JOE-09-0109. Epub 2009 Jun 8.
During mouse embryonic development, oocytes develop in germline cysts, formed by several rounds of cell division followed by incomplete cytokinesis. Shortly after birth, cysts break down and individual oocytes are enclosed by granulosa cells to form primordial follicles. At the same time, two-thirds of the oocytes die by apoptosis with only one-third surviving. We have previously shown that the steroid hormones, estradiol (E(2)), and progesterone as well as the phytoestrogen genistein can inhibit cyst breakdown and primordial follicle assembly. However, the mechanisms by which steroid hormones regulate oocyte cyst breakdown and selective oocyte survival are unknown. Here, we confirmed the expression of estrogen receptor (ER) mRNA and protein in neonatal mouse ovaries using reverse transcriptase-PCR, western blotting, and immunocytochemistry. We then used ER-specific agonists and antagonists to understand the mechanism of estrogen signaling. 4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol, an ER alpha-selective agonist, and 2,3-bis(4-hydroxyphenyl)-propionitrile, an ER beta-selective agonist, both inhibited cyst breakdown in organ culture, suggesting that E(2) can signal through both the receptors to regulate cyst breakdown. ICI 182,780, an ER antagonist, completely blocked E(2)'s action. 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride, an ER alpha-specific antagonist, fully blocked E(2)'s effect on oocyte cyst breakdown and primordial follicle assembly and (R,R)-5,11-diethyl-5,6,11,12-tetrahydro-2,8-chrysenediol, an ER beta-specific antagonist, partially blocked E(2), further supporting the idea that both receptors are involved in estrogen signaling in neonatal oocyte development. E(2) conjugated to BSA, which can only exert effects at the membrane, was able to inhibit cyst breakdown, implying that E(2) could also function through a membrane-bound ER to regulate cyst breakdown.
在小鼠胚胎发育过程中，卵母细胞在生殖系囊肿中发育，这些囊肿由几轮细胞分裂后不完全胞质分裂形成。出生后不久，囊肿破裂，单个卵母细胞被颗粒细胞包裹形成原始卵泡。与此同时，三分之二的卵母细胞通过凋亡死亡，只有三分之一存活。我们之前已经表明，类固醇激素雌二醇（E₂）、孕酮以及植物雌激素染料木黄酮可以抑制囊肿破裂和原始卵泡组装。然而，类固醇激素调节卵母细胞囊肿破裂和选择性卵母细胞存活的机制尚不清楚。在这里，我们使用逆转录聚合酶链反应、蛋白质印迹和免疫细胞化学方法证实了雌激素受体（ER）mRNA和蛋白在新生小鼠卵巢中的表达。然后我们使用ER特异性激动剂和拮抗剂来了解雌激素信号传导的机制。ERα选择性激动剂4,4',4''-(4-丙基-[1H]-吡唑-1,3,5-三基)三苯酚和ERβ选择性激动剂2,3-双(4-羟基苯基)-丙腈在器官培养中均抑制囊肿破裂，这表明E₂可以通过这两种受体发出信号来调节囊肿破裂。ER拮抗剂ICI 182,780完全阻断了E₂的作用。ERα特异性拮抗剂1,3-双(4-羟基苯基)-4-甲基-5-[4-(2-哌啶基乙氧基)苯酚]-1H-吡唑二盐酸盐完全阻断了E₂对卵母细胞囊肿破裂和原始卵泡组装的影响，而ERβ特异性拮抗剂(R,R)-5,11-二乙基-5,6,11,12-四氢-二萘酚部分阻断了E₂的作用，进一步支持了这两种受体都参与新生卵母细胞发育中雌激素信号传导的观点。与牛血清白蛋白结合的E₂只能在膜上发挥作用，它能够抑制囊肿破裂，这意味着E₂也可以通过膜结合的ER发挥作用来调节囊肿破裂。
