Orphan nuclear receptor Nur77 regulates androgen receptor gene expression in mouse ovary

Genome-wide association study (GWAS) identified PCOS susceptibility variants and replicates reported risk variants

BACKGROUND

Genetic predisposition and environmental factors are considered risk factors for polycystic ovary syndrome (PCOS). Genome-wide association studies (GWAS) have been reported from various subpopulations to evaluate SNPs associated with PCOS risk. No PCOS-associated GWAS study has been reported from India so far.

PURPOSE

The current study was conducted to identify the PCOS-susceptible loci among the North Indian population and to validate the significant loci reported by previous GWAS studies.

METHODS

A total of 272 participants with 134 PCOS patients and 138 age-matched healthy controls were recruited. Genomic DNA was isolated and genotyped by using Infinium Global Screening Array v3.0 microchip considering HWE 10e-5 statistically significant.

RESULTS

A total of fifteen markers have been identified as candidate PCOS risk factors. Only two SNPs, namely rs17186366 and rs11171739 have been identified through replication analysis while comparing the previously reported PCOS GWAS data. In-silico analysis was performed to study the functional impact of identified significant genes for gene ontology, pathways related to gene set, and cluster analysis to determine protein-protein interaction among genes or gene products.

CONCLUSION

The study suggests that multiple variants play an important role in PCOS pathogenesis and emphasizes the importance of further genetic studies among Indian subpopulations. The study also validates two previously reported SNPs in the Indian population. What this study adds to clinical work Study summarizes the importance of candidate gene markers validated by replication and in-silico functional study, significantly involved in PCOS pathogenesis in the studied population. These markers can be used in the future as diagnostic markers for clinical phenotype identification.

Targeted deletion of NR2F2 and VCAM1 in theca cells impacts ovarian follicular development: insights into polycystic ovary syndrome?†

Defining features of polycystic ovary syndrome (PCOS) include elevated expression of steroidogenic genes, theca cell androgen biosynthesis, and peripheral levels of androgens. In previous studies, we identified vascular cell adhesion molecule 1 (VCAM1) as a selective androgen target gene in specific NR2F2/SF1 (+/+) theca cells. By deleting NR2F2 and VCAM1 selectively in CYP17A1 theca cells in mice, we documented that NR2F2 and VCAM1 impact distinct and sometimes opposing theca cell functions that alter ovarian follicular development in vivo: including major changes in ovarian morphology, steroidogenesis, gene expression profiles, immunolocalization images (NR5A1, CYP11A1, NOTCH1, CYP17A1, INSL3, VCAM1, NR2F2) as well as granulosa cell functions. We propose that theca cells impact follicle integrity by regulating androgen production and action, as well as granulosa cell differentiation/luteinization in response to androgens and gonadotropins that may underlie PCOS.

Nuclear receptor NURR1 functions to promote stemness and epithelial-mesenchymal transition in prostate cancer via its targeting of Wnt/β-catenin signaling pathway

Dysregulated activation of Wnt/β-catenin signaling pathway is a frequent or common event during advanced progression of multiple cancers. With this signaling activation, it enhances their tumorigenic growth and facilitates metastasis and therapy resistance. Advances show that this signaling pathway can play dual regulatory roles in the control of cellular processes epithelial-mesenchymal transition (EMT) and cancer stemness in cancer progression. Aberrant activation of Wnt/β-catenin signaling pathway is shown to be common in prostate cancer and also castration-resistant prostate cancer (CRPC). However, the transcriptional regulators of this pathway in prostate cancer are still not well characterized. NURR1 (NR4A2) is an orphan nuclear receptor and plays an important role in the development of dopaminergic neurons. Previously, we have shown that NURR1 exhibits an upregulation in isolated prostate cancer stem-like cells (PCSCs) and a xenograft model of CRPC. In this study, we further confirmed that NURR1 exhibited an upregulation in prostate cancer and also enhanced expression in prostate cancer cell lines. Functional and molecular analyses showed that NURR1 could act to promote both in vitro (cancer stemness and EMT) and also in vivo oncogenic growth of prostate cancer cells (metastasis and castration resistance) via its direct transactivation of CTNNB1 (β-catenin) and activation of β-catenin to mediate the activation of Wnt/β-catenin signaling pathway. Moreover, we also demonstrated that NURR1 activity in prostate cancer cells could be modulated by small molecules, implicating that NURR1 could be a potential therapeutic target for advanced prostate cancer management.

Androgen signalling in the ovaries and endometrium

Currently, our understanding of hormonal regulation within the female reproductive system is largely based on our knowledge of estrogen and progesterone signalling. However, while the important functions of androgens in male physiology are well known, it is also recognized that androgens play critical roles in the female reproductive system. Further, androgen signalling is altered in a variety of gynaecological conditions, including endometriosis and polycystic ovary syndrome, indicative of regulatory roles in endometrial and ovarian function. Co-regulatory mechanisms exist between different androgens, estrogens, and progesterone, resulting in a complex network of steroid hormone interactions. Evidence from animal knockout studies, in vitro experiments, and human data indicate that androgen receptor expression is cell-specific and menstrual cycle stage-dependent, with important regulatory roles in the menstrual cycle, endometrial biology, and follicular development in the ovaries. This review will discuss the expression and co-regulatory interactions of androgen receptors, highlighting the complexity of the androgen signalling pathway in the endometrium and ovaries, and the synthesis of androgens from additional alternative pathways previously disregarded as male-specific. Moreover, it will illustrate the challenges faced when studying androgens in female biology, and the need for a more in-depth, integrative view of androgen metabolism and signalling in the female reproductive system.

The function of nuclear hormone receptor 4A signaling in the human reproductive system: A review

AIM

This review aims to summarize the research focused upon the functions of nuclear hormone receptor 4A (NR4A) in the human reproductive system. The research questions addressed are to decipher what role the NR4A subfamily plays in the regulation of the human reproductive system and effects upon fertility issues through regulation of the expression of the NR4A subfamily.

METHODS

The electronic database PubMed was searched for studies published before November 2021. Keywords included "NR4A," "trophoblast," "decidualization," "folliculogenesis," "estrogen," "pregnancy," "Leydig cells," "fertility," and "reproductive." Relevant references from retrieved manuscripts and review articles were also searched manually.

RESULTS

NR4A subfamily are involved in trophoblast differentiation, endometrial decidualization, embryo adhesion, secretion of related hormones, and regulation of spontaneous term labor. Besides, many studies have provided strong evidence that they play critical roles in spermatogenesis. Furthermore, Multiple mechanisms can affect the expression of NR4As. Broadly, NR4A family receptors affect the human reproductive system in multiple ways.

CONCLUSIONS

Further research is needed to specifically dissect the functions and regulatory mechanisms of these receptors and their pharmaceutical antagonists and agonists. The connection between the NR4A subfamily and a variety of reproductive disorders needs to be proven experimentally such that further examination of human tissue is required to assess the role of these receptors in human reproductive diseases.

Androgen upregulates NR4A1 via the TFAP2A and ETS signaling networks

Hyperandrogenism is one of the clinical and biochemical characteristics of polycystic ovary syndrome (PCOS). Our previous studies confirmed that nuclear receptor subfamily 4 group A member 1 (NR4A1), as a differentially expressed gene in the ovaries of PCOS patients, was upregulated by increased androgen. However, the potential mechanism of NR4A1 upregulation remains unknown. To elucidate the molecular mechanisms involved in NR4A1 regulation, we cloned and characterized the promoter regions of the NR4A1 gene using a series of truncated promoter plasmids in luciferase reporter assays. We identified two unique core promoters of NR4A1 located within the +1055/+1251 and +3183/+3233 regions relative to the transcription start site. TFAP2A downregulated NR4A1 expression, while five ETS transcription factors, ETS1, ELK1, ERG, FLI1 and SPI1, could upregulate NR4A1 promoter activity in HeLa cells. Of these transcription factors, ETS1 and ELK1 were the most effective ones. Moreover, all six transcription factors were confirmed to interact directly with the NR4A1 promoter. In conclusion, this study presents the first description that TFAP2A and ETS family signaling networks are involved in the androgen-mediated transcriptional regulation of NR4A1, which contributes to the understanding of the molecular mechanisms involved in the TFAP2A-NR4A1 and ETS-NR4A1 signaling networks in PCOS.

Molecular and genetic characterization of partial masculinization in embryonic ovaries grafted into male nude mice

In most of mammalian embryos, gonadal sex differentiation occurs inside the maternal uterus before birth. In several fetal ovarian grafting experiments using male host mice, an experimental switch from the maternal intrauterine to male-host environment gradually induces partial masculinization of the grafted ovaries even under the wild-type genotype. However, either host-derived factors causing or molecular basis underlying this masculinization of the fetal ovaries are not clear. Here, we demonstrate that ectopic appearance of SOX9-positive Sertoli cell-like cells in grafted ovaries was mediated by the testosterone derived from the male host. Neither Sox8 nor Amh activity in the ovarian tissues is essential for such ectopic appearance of SOX9-positive cells. The transcriptome analyses of the grafted ovaries during this masculinization process showed early downregulation of pro-ovarian genes such as Irx3, Nr0b1/Dax1, Emx2, and Fez1/Lzts1 by days 7–10 post-transplantation, and subsequent upregulation of several pro-testis genes, such as Bhlhe40, Egr1/2, Nr4a2, and Zc3h12c by day 20, leading to a partial sex reversal with altered expression profiles in one-third of the total numbers of the sex-dimorphic pre-granulosa and Sertoli cell-specific genes at 12.5 dpc. Our data imply that the paternal testosterone exposure is partially responsible for the sex-reversal expression profiles of certain pro-ovarian and pro-testis genes in the fetal ovaries in a temporally dependent manner.

Increased Krüppel-like factor 12 impairs embryo attachment via downregulation of leukemia inhibitory factor in women with recurrent implantation failure

Recurrent implantation failure (RIF) caused by various etiological factors remains a challenge for fertility clinicians using assisted reproductive technology (ART) worldwide. Dysregulation of leukemia inhibitory factor (LIF) in the endometria of women with RIF is involved in impaired endometrial receptivity and embryo adhesion. However, the mechanism through which LIF expression is regulated in women with RIF is still poorly understood. Our previous study noted that the abnormally increased endometrial Krüppel-like factor 12 (KLF12) in RIF women led to impaired decidualization and embryo implantation. Here, we further found that KLF12 inhibited embryo adhesion in vivo and in vitro by repressing LIF expression. Mechanistically, KLF12 bound to conserved sites (CAGTGGG, −6771 to −6765 and −7115 to −7109) within the LIF promoter region and repressed LIF transcription directly. Exogenous LIF significantly reversed the KLF12-mediated repression of BeWo spheroid adhesion. KLF12 expression was reduced significantly in Ishikawa cells treated with progestogen, which was due to the activation of Akt signaling. These findings may provide novel potential therapeutic regimens for patients with RIF and disrupted endometrial receptivity.

Role of NeuroD1 on the negative regulation of Pomc expression by glucocorticoid

The mechanism of the negative regulation of proopiomelanocortin gene (Pomc) by glucocorticoids (Gcs) is still unclear in many points. Here, we demonstrated the involvement of neurogenic differentiation factor 1 (NeuroD1) in the Gc-mediated negative regulation of Pomc. Murine pituitary adrenocorticotropic hormone (ACTH) producing corticotroph tumor-derived AtT20 cells were treated with dexamethasone (DEX) (1-100 nM) and cultured for 24 hrs. Thereafter, Pomc mRNA expression was studied by quantitative real-time PCR and rat Pomc promoter (-703/+58) activity was examined by luciferase assay. Both Pomc mRNA expression and Pomc promoter activity were inhibited by DEX in a dose-dependent manner. Deletion and point mutant analyses of Pomc promoter suggested that the DEX-mediated transcriptional repression was mediated via E-box that exists at -376/-371 in the promoter. Since NeuroD1 is known to bind to and activate E-box of the Pomc promoter, we next examined the effect of DEX on NeuroD1 expression. Interestingly, DEX dose-dependently inhibited NeuroD1 mRNA expression, mouse NeuroD1 promoter (-2.2-kb) activity, and NeuroD1 protein expression in AtT20 cells. In addition, we confirmed the inhibitory effect of DEX on the interaction of NeuroD1 and E-box on Pomc promoter by chromatin immunoprecipitation (ChIP) assay. Finally, overexpression of mouse NeuroD1 could rescue the DEX-mediated inhibition of Pomc mRNA expression and Pomc promoter activity. Taken together, it is suggested that the suppression of NeuroD1 expression and the inhibition of NeuroD1/E-box interaction may play an important role in the Gc-mediated negative regulation of Pomc.

Increased Krüppel-like factor 12 in recurrent implantation failure impairs endometrial decidualization by repressing Nur77 expression

BACKGROUND

Decidualization is a prerequisite for successful implantation and the establishment of pregnancy. A critical role of impaired decidualization in subfertility has been established. In human endometrial stromal cells (hESCs), Krüppel-like factor 12 (KLF12) and Nur77 are novel regulators of decidualization. We investigated whether KLF12 impaired the decidualization of hESCs in recurrent implantation failure (RIF) patients.

METHODS

Endometrial tissues and hESCs were collected from RIF patients (n = 34) and fertile controls (n = 30) for in vitro analysis. Primary hESCs isolated from RIF endometrial tissues were used to evaluate the biological functions of KLF12 and Nur77. In addition, their molecular mechanisms were investigated by adenovirus-mediated overexpression. Gene expression regulation was examined by real-time-quantitative PCR (qRT-PCR), immunostaining and luciferase reporter assay. Further, blastocyst-like spheroid (BLS) and blastocyst implantation models were performed to examine the roles of KLF12 and Nur77 during embryo expansion on hESCs.

RESULTS

hESCs from the RIF patients showed a poor decidual response, mainly characterized by decreased decidual prolactin (dPRL) secretion, impaired transformation and limited BLS expansion. In addition, KLF12 expression was increased in endometrial tissues from the RIF patients compared with those from the fertile controls, especially in stromal compartments. The opposite results were observed for Nur77 expression in these tissues. KLF12 repressed hESC decidualization by decreasing Nur77 expression. Mechanistically, KLF12 bound to a conserved site in the Nur77 promoter region. Nur77 overexpression significantly reversed the KLF12-mediated repression of dPRL expression, decidual transformation and BLS/blastocyst expansion.

CONCLUSIONS

KLF12 impairs endometrial decidualization by transcriptionally repressing Nur77, and Nur77 overexpression reverses the poor decidual response of hESCs in RIF patients.

Curcumin improves LPS-induced preeclampsia-like phenotype in rat by inhibiting the TLR4 signaling pathway

INTRODUCTION

Abnormal inflammation mediated by Toll-like receptor 4 (TLR4) signaling pathway contributes to preeclampsia (PE). Because curcumin can inhibit TLR4 signaling pathway, we investigated its effects on a PE rat model.

METHODS

Twenty-one pregnant rats were randomly divided into three groups: 1) seven rats were injected 0.5 μg/kg lipopolysaccharide (LPS) on gestational day (GD) 5 to create a PE model (LPS-treated group), 2) seven rats were injected with a similar dosage of LPS and further treated with curcumin (0.36 mg/kg) (LPS-curcumin-treated group), 3) seven rats received saline (control group). Blood pressure and urinary protein level were observed. Immunostaining and periodic acid-Schiff staining of placenta were conducted. TLR4 and downstream Nuclear Factor-κB (NF-κB) expressions of placenta were analyzed by Western blot and immunohistochemistry. IL-6 and MCP-1 in rat serum and placenta were determined by ELISA and qRT-PCR.

RESULTS

Compared to LPS-treated group, LPS-curcumin-treated group had decreased blood pressure and urinary protein level, similar to control group. Furthermore, deficient trophoblast invasion and spiral artery remodeling induced by LPS were improved by curcumin. Increased TLR4, NF-κB and IL-6, MCP-1 protein expressions in LPS-treated group were significantly decreased after curcumin administration.

DISCUSSION

Curcumin improves the PE-like phenotype in rat model by reducing abnormal inflammation related to TLR4 signaling pathway.

Effects of RXR Agonists on Cell Proliferation/Apoptosis and ACTH Secretion/Pomc Expression

Various retinoid X receptor (RXR) agonists have recently been developed, and some of them have shown anti-tumor effects both in vivo and in vitro. However, there has been no report showing the effects of RXR agonists on Cushing’s disease, which is caused by excessive ACTH secretion in a corticotroph tumor of the pituitary gland. Therefore, we examined the effects of synthetic RXR pan-agonists HX630 and PA024 on the proliferation, apoptosis, ACTH secretion, and pro-opiomelanocortin (Pomc) gene expression of murine pituitary corticotroph tumor AtT20 cells. We demonstrated that both RXR agonists induced apoptosis dose-dependently in AtT20 cells, and inhibited their proliferation at their higher doses. Microarray analysis identified a significant gene network associated with caspase 3 induced by high dose HX630. On the other hand, HX630, but not PA024, inhibited Pomc transcription, Pomc mRNA expression, and ACTH secretion dose-dependently. Furthermore, we provide new evidence that HX630 negatively regulates the Pomc promoter activity at the transcriptional level due to the suppression of the transcription factor Nur77 and Nurr1 mRNA expression and the reduction of Nur77/Nurr1 heterodimer recruiting to the Pomc promoter region. We also demonstrated that the HX630-mediated suppression of the Pomc gene expression was exerted via RXRα. Furthermore, HX630 inhibited tumor growth and decreased Pomc mRNA expression in corticotroph tumor cells in female nude mice in vivo. Thus, these results indicate that RXR agonists, especially HX630, could be a new therapeutic candidate for Cushing’s disease.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Single administration of ultra-low-dose lipopolysaccharide in rat early pregnancy induces TLR4 activation in the placenta contributing to preeclampsia

Balanced immune responses are essential for the maintenance of successful pregnancy. Aberrant responses of immune system during pregnancy increase the risk of preeclampsia. Toll-like receptor 4 (TLR4) plays a crucial role in the activation of immune system at the maternal-fetal interface. This study aimed to generate a rat model of preeclampsia by lipopolysaccharide (LPS, a TLR4 agonist) administration on gestational day (GD) 5 as rats are subjected to placentation immediately after implantation between GDs 4 and 5, and to assess the contribution of TLR4 signaling to the development of preeclampsia. Single administration of 0.5 μg/kg LPS significantly increased blood pressure of pregnant rats since GD 6 (systolic blood pressure, 124.89 ± 1.79 mmHg versus 119.02 ± 1.80 mmHg, P < 0.05) and urinary protein level since GD 9 (2.02 ± 0.29 mg versus 1.11 ± 0.18 mg, P < 0.01), but barely affected blood pressure or proteinuria of virgin rats compared with those of saline-treated pregnant rats. This was accompanied with adverse pregnancy outcomes including fetal growth restriction. The expression of TLR4 and NF-κB p65 were both increased in the placenta but not the kidney from LPS-treated pregnant rats, with deficient trophoblast invasion and spiral artery remodeling. Furthermore, the levels of inflammatory cytokines were elevated systemically and locally in the placenta from pregnant rats treated with LPS. TLR4 signaling in the placenta was activated, to which that in the placenta of humans with preeclampsia changed similarly. In conclusion, LPS administration to pregnant rats in early pregnancy could elicit TLR4-mediated immune response at the maternal-fetal interface contributing to poor early placentation that may culminate in the preeclampsia-like syndrome.

Mouse GDF9 decreases KITL gene expression in human granulosa cells

Kit ligand (KITL) is an important granulosa cell-derived growth factor in ovarian folliculogenesis, but its expression and function in human granulosa cells are currently poorly understood. Based on studies performed in animal models, it was hypothesised that KITL gene expression in human granulosa cells is regulated by androgens and/or growth differentiation factor 9 (GDF9). We utilised two models of human granulosa cells, the KGN granulosa tumour cell line and cumulus granulosa cells obtained from preovulatory follicles of women undergoing assisted reproduction. Cells were treated with combinations of 5α-dihydrotestosterone (DHT), recombinant mouse GDF9, and the ALK4/5/7 inhibitor SB431542. KITL mRNA levels were measured by quantitative real-time PCR. No change in KITL mRNA expression was observed after DHT treatment under any experimental conditions, but GDF9 treatment resulted in a significant decrease in KITL mRNA levels in both KGN and cumulus cells. The effect of GDF9 was abolished by the addition of SB431542. These results indicate that KITL is not directly regulated by androgen signalling in human granulosa cells. Moreover, this study provides the first evidence that GDF9 negatively regulates KITL gene expression in human granulosa cells providing new information on the regulation of these important growth factors in the human ovary.

Transcriptional profiling of five isolated size-matched stages of human preantral follicles

Little is known of the early stages of human follicular development and the complex processes that regulate follicular growth. To identify genes of potential importance, we analysed follicle-related transcripts in five populations of isolated size-matched human preantral follicles by microarray analysis. Oocyte-specific genes were found to be the most abundant and differentially expressed transcripts and included germ cell transcription factors LHX8 and SOHLH2 which were significantly down-regulated during preantral follicle development. Differentially expressed genes also included transcription factors of NOTCH signalling, IGF2, orphan nuclear receptor LRH-1, and homeobox gene HOXA7, indicating potentially important regulatory roles for these genes during early human folliculogenesis. We also found that FSHR mRNA and protein were present in the earliest stages of preantral follicles, whereas LHR was absent. In conclusion, our data identify specific oocyte and somatic genes in small human follicles that impact early follicle growth, and provide foundation for further analysis of the signalling pathways involved in early human folliculogenesis.

Proteomic analysis of the follicular fluid of Tianzhu white yak during diestrus

The aim of this study was to identify differentially expressed proteins in the follicular fluid of Tianzhu white yak during diestrus. Follicles obtained from female yak were divided into four groups according to their diameter: 0–2, 2–4, 4–6 mm, and greater than 6 mm. The follicular fluid was directly aspirated from the follicles and mixed according to follicular size, and two-dimensional gel electrophoresis was carried out on the crude follicular fluid samples. Thirty-four differentially expressed spots were generated from these four sizes of follicles. Fourteen of these spots were analyzed by MALDI-TOF/TOF-MS and identified as: AS3MT, VDP, ANKRD6, C10orf107 protein, MRP4, MAPKAP1, AGO3, profilin-β-actin, SPT2 homolog, AGP, AR, RNF20, obscurin-like-1, and one unnamed protein. These proteins were first reported in follicular fluid, in addition to VDP and AGP. Based on existing knowledge of their function and patterns of expression, we hypothesize that most of these differentially expressed proteins play a role in ovarian follicular growth and development, dominant follicle selection, or follicular atresia and development of oocytes; however, the function of the other differentially expressed proteins in reproduction remains ambiguous.

FSH modulates the expression of inhibin-alpha and the secretion of inhibins via orphan nuclear receptor NUR77 in ovarian granulosa cells

It has been previously reported that follicle-stimulating hormone (FSH) regulates the expression of inhibin-alpha in human granulosa cells, but the precise molecular pathway remains unknown. In the present study, we investigated the role of the orphan nuclear receptor, NUR77, in both the transcriptional regulation of the inhibin α-subunit gene and the secretion of inhibins. Our results showed that in a human granulosa cell tumor-derived cell line (KGN) and in human granulosa-lutein cells (hGL), FSH induced the expression of NUR77 and inhibin-alpha, although inhibin-alpha expression did not increased following FSH treatment if NUR77 was knocked down. Furthermore, simply overexpressing or reducing NUR77 levels affected inhibin-alpha expression, while NUR77 overexpression improved the secretion of inhibin A and B from human granulosa cells. In addition, chromatin immunoprecipitation-PCR, avidin-biotin-conjugated DNA precipitation, and luciferase reporter assays confirmed that NUR77 directly regulated the transcription of the inhibin-alpha gene through the specific NGFI-B response element located within its promoter. In the ovarian granulosa cells of the Nur77 knockout mice, the mRNA levels of inhibin-alpha were decreased relative to wild-type mice. These data indicate a role of NUR77 in the regulation of inhibin-alpha in ovarian granulosa cells.

MicroRNA-133b stimulates ovarian estradiol synthesis by targeting Foxl2

Forkhead L2 (Foxl2) is expressed in ovarian granulosa cells and participates in steroidogenesis by transcriptionally regulating target genes such as steroidogenic acute regulatory protein (StAR) and CYP19A1. In this study, a direct link between microRNA-133b (miR-133b) and Foxl2-mediated estradiol release in granulosa cells was established. miR-133b was involved in follicle-stimulating hormone (FSH)-induced estrogen production. Luciferase assays confirmed that miR-133b was bound to the 3' untranslated region (3'UTR) of Foxl2 mRNA. Consistent with this finding, miR-133b overexpression reduced the Foxl2 levels. Furthermore, miR-133b inhibited Foxl2 binding to the StAR and CYP19A1 promoter sequences. These results demonstrate that miR-133b down-regulates Foxl2 expression in granulosa cells by directly targeting the 3'UTR, thus inhibiting the Foxl2-mediated transcriptional repression of StAR and CYP19A1to promote estradiol production.

Krüppel-like factor 12 negatively regulates human endometrial stromal cell decidualization

Members of the KLFs family of transcription factors play roles in maternal endometrium development during embryo implantation. However, the specific role of KLF12 in endometrium development has not yet been described. In this study, we showed that KLF12 expression in human endometrial stromal cells (HESCs) was significantly decreased after decidualization stimulated by 8-Br-cAMP and medroxyprogesterone acetate (MPA). The adenovirus-mediated overexpression of KLF12 in HESCs significantly repressed the expression and secretion of decidualization biomarker genes and their products decidual prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1) induced by 8-Br-cAMP and MPA. Moreover, CHIP and luciferase reporter assays demonstrated that KLF12 bound to a CAGTGGG element within the decidual prolactin promoter and decreased decidual PRL promoter (dPRL/-2000Luc) activation in a sequence-specific manner. Taken together, these findings suggest KLF12 is a negative regulator of human endometrial stromal cell decidualization.