Park Eun-Sil, Lind Anna-Karin, Dahm-Kähler Pernilla, Brännström Mats, Carletti Martha Z, Christenson Lane K, Curry Thomas E, Jo Misung
Department of Obstetrics and Gynecology, Chandler Medical Center, University of Kentucky, Lexington, Kentucky 40536-0298, USA.
Mol Endocrinol. 2010 Apr;24(4):846-58. doi: 10.1210/me.2009-0392. Epub 2010 Mar 2.
The LH surge promotes terminal differentiation of follicular cells to become luteal cells. RUNX2 has been shown to play an important role in cell differentiation, but the regulation of Runx2 expression and its function in the ovary remain to be determined. The present study examined 1) the expression profile of Runx2 and its partner CBFbeta during the periovulatory period, 2) regulatory mechanisms of Runx2 expression, and 3) its potential function in the ovary. Runx2 expression was induced in periovulatory granulosa cells of human and rodent ovaries. RUNX2 and core binding factor-beta (CBFbeta) proteins in nuclear extracts and RUNX2 binding to a consensus binding sequence increased after human chorionic gonadotropin (hCG) administration. This in vivo up-regulation of Runx2 expression was recapitulated in vitro in preovulatory granulosa cells by stimulation with hCG. The hCG-induced Runx2 expression was reduced by antiprogestin (RU486) and EGF-receptor tyrosine kinase inhibitor (AG1478), indicating the involvement of EGF-signaling and progesterone-mediated pathways. We also found that in the C/EBPbeta knockout mouse ovary, Runx2 expression was reduced, indicating C/EBPbeta-mediated expression. Next, the function of RUNX2 was investigated by suppressing Runx2 expression by small interfering RNA in vitro. Runx2 knockdown resulted in reduced levels of mRNA for Rgc32, Ptgds, Fabp6, Mmp13, and Abcb1a genes. Chromatin immunoprecipitation analysis demonstrated the binding of RUNX2 in the promoter region of these genes, suggesting that these genes are direct downstream targets of RUNX2. Collectively, the present data indicate that the LH surge-induced RUNX2 is involved in various aspects of luteal function by directly regulating the expression of diverse luteal genes.
促黄体生成素（LH）峰促使卵泡细胞终末分化为黄体细胞。已有研究表明，RUNX2在细胞分化中发挥重要作用，但Runx2在卵巢中的表达调控及其功能仍有待确定。本研究检测了：1）围排卵期Runx2及其伴侣CBFβ的表达谱；2）Runx2表达的调控机制；3）其在卵巢中的潜在功能。在人和啮齿动物卵巢的围排卵期颗粒细胞中诱导Runx2表达。人绒毛膜促性腺激素（hCG）给药后，核提取物中的RUNX2和核心结合因子β（CBFβ）蛋白以及RUNX2与共有结合序列的结合增加。通过用hCG刺激，在体外排卵前颗粒细胞中重现了这种Runx2表达的体内上调。抗孕激素（RU486）和表皮生长因子受体酪氨酸激酶抑制剂（AG1478）可降低hCG诱导的Runx2表达，表明表皮生长因子信号通路和孕酮介导的途径参与其中。我们还发现，在C/EBPβ基因敲除小鼠卵巢中，Runx2表达降低，表明存在C/EBPβ介导的表达。接下来，通过体外小干扰RNA抑制Runx2表达来研究RUNX2的功能。Runx2敲低导致Rgc32、Ptgds、Fabp6、Mmp13和Abcb1a基因的mRNA水平降低。染色质免疫沉淀分析表明RUNX2与这些基因的启动子区域结合，提示这些基因是RUNX2的直接下游靶点。总体而言，目前的数据表明，LH峰诱导的RUNX2通过直接调节多种黄体基因的表达参与黄体功能的各个方面。
