MicroRNA-132 promotes estradiol synthesis in ovarian granulosa cells via translational repression of Nurr1

Abstract

BackgroundEstrogen synthesis is an important function of the mammalian ovary. Estrogen plays important roles in many biological processes, including follicular development, oocyte maturation and endometrial proliferation, and dysfunctions in estrogen synthesis contribute to the development of polycystic ovary syndrome and premature ovarian failure. Classical signaling cascades triggered by follicle-stimulating hormone induce estrogen synthesis via the upregulation of Cyp19a1 in granulosa cells (GCs). This study aimed to determine the effect of microRNA-132 (miR-132) on estradiol synthesis in GCs.MethodsPrimary mouse GCs were collected from ovaries of 21-day-old immature ICR mice through follicle puncture. GCs were cultured and treated with the stable cyclic adenosine monophosphate analog 8-Br-cAMP or transfected with miR-132 mimics, Nurr1-specific small interfering RNA oligonucleotides and Flag-Nurr1 plasmids. Concentrations of estradiol and progesterone in culture medium were determined by an automated chemiluminescence-based assay. Quantitative real time PCR and western blot were performed to identify the effect of miR-132 on Cyp19a1, Cyp11a1 and an orphan nuclear receptor-Nurr1 expression in GCs. Direct suppression of Nurr1 via its 3'-untranslated region by miR-132 were further verified using luciferase reporter assays.ResultsThe expression level of miR-132 in cultured mouse GCs was significantly elevated during 48 h of treatment with 8-Br-cAMP. The synthesis of estradiol increased after the overexpression of miR-132 in mouse GCs. The real-time PCR results demonstrated that miR-132 induced the expression of Cyp19a1 significantly. Nurr1, an orphan nuclear receptor that suppresses Cyp19a1 expression, was found to be a direct target of miR-132. Nurr1 was suppressed by miR-132, as indicated by a luciferase assay and Western blotting. The knockdown of Nurr1 primarily elevated the synthesis of estradiol and partially attenuated the miR-132-induced estradiol elevation, and the ectopic expression of Flag-Nurr1 abrogated the stimulatory effect of miR-132 on estradiol synthesis in mouse GCs.ConclusionsOur findings suggest that miR-132 is involved in the cAMP signaling pathway and promotes estradiol synthesis via the translational repression of Nurr1 in ovarian GCs.

Maternal Recognition of Pregnancy in the Horse: Are MicroRNAs the Secret Messengers?

“…In conformity with our results, pregnancy associated upregulation of miR-132 was also detected in porcine endometrium, it was the only miRNA which was differentially expressed on day 12 in the pig [54]. Expression of miR-132 is associated with increased estradiol synthesis in mouse ovarian granulosa cells [55] and in human granulosa-like tumor cell lines [56], and might influence the process of MRP as such. Moreover, upregulation of miR-132-3p was found in follicular fluid yielding top quality embryos in human [57].…”

Dynamics and role of MicroRNAs during mammalian follicular development

“…Extracellular microvesicles and exosomes in follicular fluid carrying miRNAs as cargo molecules have been detected in bovine (Sohel et al, 2013;Noferesti et al, 2015;Navakanitworakul et al, 2016), equine (da Silveira et al, 2012(da Silveira et al, , 2014(da Silveira et al, , 2015 and human (Xiao et al, 2016). The presence of EVs (microvesicles or exosomes) in follicular fluid may support the notion that they play a significant role in ovarian functions.…”

Roles of microRNAs in mammalian reproduction: from the commitment of germ cells to peri‐implantation embryos

“…miR‐21 plays anti‐apoptotic roles and facilitates the maintenance of GCs, both in vitro and in vivo (Carletti et al, ), while miR‐132 and miR‐212 regulate the differentiation of GCs by targeting C‐terminal binding protein 1 ( Ctbp1 ) (Fiedler et al, ). miR‐132 regulates cyclic adenosine monophosphate (cAMP) signalling and promotes oestradiol production in mouse GCs through translational repression of nuclear receptor related 1 ( Nurr1 ) following upregulation of Cyp19a1 (Wu et al, ), and miR‐122 increases LHCGR mRNA‐binding protein ( Lrbp ) expression by activating Srebp in rat ovaries (Menon et al, ).…”