NCBI Summary:
This gene encodes a member of the steroid-thyroid hormone-retinoid receptor superfamily. The encoded protein may act as a transcription factor. Mutations in this gene have been associated with disorders related to dopaminergic dysfunction, including Parkinson disease, schizophernia, and manic depression. Misregulation of this gene may be associated with rheumatoid arthritis. Alternatively spliced transcript variants have been described, but their biological validity has not been determined. [provided by RefSeq, Jul 2008]
General function
DNA binding, Transcription factor
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Cellular localization
Nuclear
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Ovarian function
Ovulation, Steroid metabolism
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Expression regulated by
LH
Comment
MicroRNA-132 promotes estradiol synthesis in ovarian granulosa cells via translational repression of Nurr1. Wu S et al. (2015) Estrogen 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. Primary 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. The 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. Our 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.//////////////////
The Orphan Nuclear Receptors NURR1 and NGFI-B Modulate Aromatase Gene Expression in Ovarian Granulosa Cells: a Possible Mechanism for Repression of Aromatase Expression upon Luteinizing Hormone Surge Wu Y, et al .
Ovarian granulosa cells play pivotal roles in many aspects of ovary functions including folliculogenesis and steroidogenesis. In response to follicle stimulating hormone (FSH) and LH (LH), the elevation of intracellular cyclic AMP (cAMP) level in granulosa cells leads to activation of multiple ovarian genes. Here we report findings from a genome-wide study of the cAMP-responsive gene expression profiles in a human granulosa-like tumor cell line, KGN. The study identified 140 genes that are either activated or repressed by 2-fold or greater following stimulation by the adenylyl cyclase activator forskolin. The induction patterns of some cAMP-responsive genes were further analyzed by quantitative real time PCR. Consistent with previous observations, the LH-responsive genes such as the nuclear receptor 4A subfamily (NURR1, NGFI-B, and NOR-1) were rapidly but transiently induced, whereas the FSH-responsive gene CYP19 encoding aromatase was induced in a delayed fashion. Interestingly, ectopic expression of NURR1 or NGFI-B severely attenuated the cAMP-responsive activation of the ovary-specific aromatase promoter. Reduction of the endogenous NURR1 or NGFI-B by small interfering RNA (siRNA) significantly elevated aromatase gene expression. The cis-elements responsible for NURR1/NGFI-B-mediated repression were mapped to the minimal aromatase promoter sequence that confers cAMP-responsiveness. Furthermore, the DNA-binding domain of NURR1 was required for the repression. Taken together, these results strongly suggest a causal relationship between the rapid decline of aromatase mRNA and induction of NR4A expression that concomitantly occur upon LH surge at the later stages of ovarian follicular development.
Ovarian localization
Granulosa
Comment
Rapid effects of luteinizing hormone on gene expression in the mural granulosa cells of mouse periovulatory follicles. Carletti M et al. Luteinizing hormone (LH) acts on periovulatory granulosa cells by activating the PKA pathway as well as other cell signaling cascades to increase the transcription of specific genes necessary for ovulation and luteinization. Collectively, these cell signaling responses occur rapidly (within minutes), however, presently no high throughput studies have reported changes before 4 h after the LH surge. To identify early response genes that are likely critical for initiation of ovulation and luteinization, mouse granulosa cells were collected before and 1 h after hCG. Fifty-seven gene transcripts were significantly (p<0.05) upregulated and 3 downregulated following hCG. Twenty-four of these transcripts were known to be expressed after the LH/hCG surge at later time points, while 36 were unknown to be expressed by periovulatory granulosa cells. Temporal expression of several transcripts, including the transcription factors Nr4a1, Nr4a2, Egr1, Egr2, Btg1, and Btg2, and the EGF-like ligands Areg and Ereg, were analyzed by quantitative RT-PCR, and their putative roles in granulosa cell function are discussed. Epigen (Epgn), another member of the family of EGF-like ligands, was identified for the first time in granulosa cells as rapidly induced by LH/hCG. We demonstrate that Epgn initiates cumulus expansion, similar to the other EGF-receptor ligands Areg and Ereg. These studies illustrate that a number of changes in gene expression occur in vivo in response to LH, and that many of the differentially expressed genes are transcription factors that we would predict in turn modulate granulosa cell gene expression to ultimately impact the processes of ovulation and luteinization.