Laboratory of Marine Biology, Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
Biol Reprod. 2013 Jun 13;88(6):148. doi: 10.1095/biolreprod.112.107292. Print 2013 Jun.
The pituitary gonadotropins (GtHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), are key regulators of gametogenesis in teleosts. However, little is known about the physiological mechanisms by which GtHs regulate asynchronous oocyte development in multiple-spawning marine fishes. We cloned cDNAs encoding GtH receptors (FSHR and LHR) from chub mackerel (Scomber japonicus). FSH and LH were purified by anion-exchange chromatography, gel filtration, and concanavalinA-agarose. When expressed in mammalian cells, FSHR and LHR responded strongly to their own ligands. By separating LH into two subunits by the use of reverse-phase chromatography, we found that the beta-subunit is responsible for signal transduction and the alpha-subunit may be important for holding hormone-receptor complex. In situ hybridization showed that only fshr was expressed in prefollicle and granulosa cells in oocytes at the perinucleolus and cortical alveolus stages, suggesting that FSH is involved in the primary and early secondary growth of oocytes. In ovarian follicles during vitellogenesis, both fshr and lhr were expressed in granulosa and thecal cells, and lhr was strongly expressed during germinal vesicle migration (GVM). Real-time PCR analysis of stage-dependent fshr and lhr expression showed that fshr expression was high in ovarian follicles throughout vitellogenesis and decreased during GVM, whereas lhr expression was low in early vitellogenesis, but increased markedly in the late phase of vitellogenesis, remaining high during GVM. These findings suggest that switching of the expression of FSHR to LHR controls the effects of FSH and/or LH on vitellogenesis and final oocyte maturation via steroid production in granulosa and thecal cells.
垂体促性腺激素（GtHs），卵泡刺激素（FSH）和黄体生成素（LH），是硬骨鱼类配子发生的关键调节剂。然而，对于 GtHs 调节多产卵海洋鱼类异步卵母细胞发育的生理机制知之甚少。我们从鲐鱼（Scomber japonicus）克隆了编码 GtH 受体（FSHR 和 LHR）的 cDNA。通过阴离子交换层析、凝胶过滤和刀豆球蛋白 A-琼脂糖纯化 FSH 和 LH。当在哺乳动物细胞中表达时，FSHR 和 LHR 对其自身配体有强烈反应。通过使用反相色谱法将 LH 分成两个亚基，我们发现β亚基负责信号转导，α亚基可能对保持激素-受体复合物很重要。原位杂交显示，仅在核仁周围和皮质小泡阶段的卵母细胞的前卵泡和颗粒细胞中表达 fshr，表明 FSH 参与卵母细胞的初级和早期次级生长。在卵黄发生期间的卵巢卵泡中，fshr 和 lhr 均在颗粒细胞和膜细胞中表达，并且在生殖泡迁移（GVM）期间 lhr 强烈表达。对阶段依赖性 fshr 和 lhr 表达的实时 PCR 分析表明，fshr 在整个卵黄发生期间在卵巢卵泡中表达较高，并在 GVM 期间降低，而 lhr 在早期卵黄发生中表达较低，但在卵黄发生的后期显著增加，在 GVM 期间保持较高。这些发现表明，FSHR 表达向 LHR 的转换通过颗粒细胞和膜细胞中的类固醇产生控制 FSH 和/或 LH 对卵黄发生和最终卵母细胞成熟的作用。
