Wang Huizhen, Graham Ian, Hastings Richard, Gunewardena Sumedha, Brinkmeier Michelle L, Conn P Michael, Camper Sally A, Kumar T Rajendra
From the Departments of Molecular and Integrative Physiology.
Flow Cytometry Core Laboratory, University of Kansas Medical Center, Kansas City, Kansas 66160.
J Biol Chem. 2015 Jan 30;290(5):2699-714. doi: 10.1074/jbc.M114.621565. Epub 2014 Dec 18.
Pituitary gonadotropins follicle-stimulating hormone and luteinizing hormone are heterodimeric glycoproteins expressed in gonadotropes. They act on gonads and promote their development and functions including steroidogenesis and gametogenesis. Although transcriptional regulation of gonadotropin subunits has been well studied, the post-transcriptional regulation of gonadotropin subunits is not well understood. To test if microRNAs regulate the hormone-specific gonadotropin β subunits in vivo, we deleted Dicer in gonadotropes by a Cre-lox genetic approach. We found that many of the DICER-dependent microRNAs, predicted in silico to bind gonadotropin β subunit mRNAs, were suppressed in purified gonadotropes of mutant mice. Loss of DICER-dependent microRNAs in gonadotropes resulted in profound suppression of gonadotropin-β subunit proteins and, consequently, the heterodimeric hormone secretion. In addition to suppression of basal levels, interestingly, the post-gonadectomy-induced rise in pituitary gonadotropin synthesis and secretion were both abolished in mutants, indicating a defective gonadal negative feedback control. Furthermore, mutants lacking Dicer in gonadotropes displayed severely reduced fertility and were rescued with exogenous hormones confirming that the fertility defects were secondary to suppressed gonadotropins. Our studies reveal that DICER-dependent microRNAs are essential for gonadotropin homeostasis and fertility in mice. Our studies also implicate microRNAs in gonadal feedback control of gonadotropin synthesis and secretion. Thus, DICER-dependent microRNAs confer a new layer of transcriptional and post-transcriptional regulation in gonadotropes to orchestrate the hypothalamus-pituitary-gonadal axis physiology.
垂体促性腺激素促卵泡激素和促黄体生成素是在促性腺细胞中表达的异源二聚体糖蛋白。它们作用于性腺，促进其发育和功能，包括类固醇生成和配子发生。尽管促性腺激素亚基的转录调控已得到充分研究，但促性腺激素亚基的转录后调控仍未完全了解。为了测试微小RNA是否在体内调节激素特异性促性腺激素β亚基，我们通过Cre-lox基因方法在促性腺细胞中删除了Dicer。我们发现，许多在计算机模拟中预测与促性腺激素β亚基mRNA结合的DICER依赖性微小RNA在突变小鼠的纯化促性腺细胞中受到抑制。促性腺细胞中DICER依赖性微小RNA的缺失导致促性腺激素β亚基蛋白的显著抑制，从而导致异源二聚体激素分泌减少。除了基础水平的抑制外，有趣的是，去势后垂体促性腺激素合成和分泌的诱导增加在突变体中均被消除，这表明性腺负反馈控制存在缺陷。此外，促性腺细胞中缺乏Dicer的突变体生育力严重降低，外源性激素可使其恢复，这证实了生育力缺陷是促性腺激素抑制的继发结果。我们的研究表明，DICER依赖性微小RNA对小鼠促性腺激素稳态和生育力至关重要。我们的研究还表明微小RNA参与了性腺对促性腺激素合成和分泌的反馈控制。因此，DICER依赖性微小RNA在促性腺细胞中赋予了一层新的转录和转录后调控，以协调下丘脑-垂体-性腺轴的生理功能。
