MicroRNAs (miRNAs) are 21- to 24-nucleotide long small noncoding RNAs, which play an important role in follicular atresia and granulosa cell (GC) apoptosis in the mammalian ovary. Here, we report that miR-146b, a conserved and ovary-enriched miRNA, modulates estradiol (E2) secretion, GC apoptosis, and follicular atresia in pigs. Genome-wide analysis and quantitative real-time PCR revealed that miR-146b was significantly upregulated during follicular atresia, and fluorescence-activated cell sorting showed that miR-146b functioned as a proapoptotic factor to induce GC apoptosis. MicroRNA-mRNA network analysis and luciferase reporter assays showed that CYP19A1, the pivotal enzyme for E2 synthesis signaling, was directly targeted by miR-146b. Furthermore, miR-146b interacted with the 3′untranslated region of CYP19A1 to prevent translation, thereby regulating CYP19A1-mediated E2 secretion and GC apoptosis. However, miR-146b was not regulated by the transcription factor SMAD4 or oxidative stress, both of which are critical regulators of CYP19A1. We, thus, conclude that miR-146b is a novel epigenetic factor regulating GC functions, follicular development, and female reproduction.

MicroRNA (miRNA) 是 21 到 24 个核苷酸长的小型非编码 RNA，在哺乳动物卵巢的滤泡闭锁和颗粒细胞 (GC) 凋亡中起重要作用。在这里，我们报告了 miR-146b，一种保守且富含卵巢的 miRNA，可调节猪的雌二醇 (E2) 分泌、GC 细胞凋亡和卵泡闭锁。全基因组分析和实时定量 PCR 显示 miR-146b 在滤泡闭锁期间显着上调，荧光激活细胞分选显示 miR-146b 作为促凋亡因子诱导 GC 细胞凋亡。MicroRNA-mRNA 网络分析和荧光素酶报告基因检测表明，E2 合成信号转导的关键酶 CYP19A1 直接被 miR-146b 靶向。此外，miR-146b 与CYP19A1的 3' 非翻译区相互作用阻止翻译，从而调节 CYP19A1 介导的 E2 分泌和 GC 细胞凋亡。然而，miR-146b 不受转录因子 SMAD4 或氧化应激的调节，这两者都是CYP19A1 的关键调节剂。因此，我们得出结论，miR-146b 是一种新型的表观遗传因子，可调节 GC 功能、卵泡发育和雌性生殖。