Kim Hyun, Yamanouchi Keitaro, Matsuwaki Takashi, Nishihara Masugi
Department of Veterinary Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
J Reprod Dev. 2012;58(2):254-9. doi: 10.1262/jrd.11-118o. Epub 2012 Jan 25.
The Ski protein is implicated in the proliferation/differentiation of a variety of cells. We previously reported that the Ski protein is present in granulosa cells of atretic follicles, but not in preovulatory follicles, suggesting that Ski has a role in apoptosis of granulosa cells. However, granulosa cells cannot only undergo apoptosis but can alternatively differentiate into luteal cells. It is unknown whether Ski is expressed and has a role in granulosa cells undergoing luteinization. Thus, the aim of the present study was to determine the localization of the Ski protein in the rat ovary during luteinization to examine if Ski might play a role in this process. In order to examine the Ski protein expression during the progression of luteinization, follicular growth was induced in immature female rats by administration of equine chorionic gonadotropin, and luteinization was induced by human chorionic gonadotropin treatment to mimic the luteinizing hormone (LH) surge. While no Ski-positive granulosa cells were present in the preovulatory follicle, Ski protein expression was induced in response to the LH surge and was maintained after formation of the corpus luteum (CL). Although the Ski protein is absent from the granulosa cells of the preovulatory follicle, its mRNA (c-ski) was expressed, and the level of c-ski mRNA was unchanged even after the LH surge. The combined results demonstrated that Ski protein expression is induced in granulosa cells upon luteinization, and suggested that its expression is regulated posttranscriptionally.
Ski蛋白与多种细胞的增殖/分化有关。我们之前报道过，Ski蛋白存在于闭锁卵泡的颗粒细胞中，而在排卵前卵泡中不存在，这表明Ski在颗粒细胞凋亡中起作用。然而，颗粒细胞不仅会发生凋亡，还可以分化为黄体细胞。目前尚不清楚Ski在正在黄体化的颗粒细胞中是否表达以及是否发挥作用。因此，本研究的目的是确定黄体化过程中Ski蛋白在大鼠卵巢中的定位，以检查Ski是否可能在这一过程中发挥作用。为了研究黄体化过程中Ski蛋白的表达情况，通过给未成熟雌性大鼠注射马绒毛膜促性腺激素诱导卵泡生长，并用人绒毛膜促性腺激素处理诱导黄体化，以模拟促黄体生成素（LH）高峰。虽然排卵前卵泡中不存在Ski阳性颗粒细胞，但Ski蛋白表达在LH高峰刺激下被诱导，并在黄体（CL）形成后维持。尽管排卵前卵泡的颗粒细胞中不存在Ski蛋白，但其mRNA（c-ski）有表达，并且即使在LH高峰后c-ski mRNA水平也没有变化。综合结果表明，颗粒细胞在黄体化时诱导Ski蛋白表达，并提示其表达是在转录后水平受到调控。
