Mutant Forkhead L2 (FOXL2) proteins associated with premature ovarian failure (POF) dimerize with wild-type FOXL2, leading to altered regulation of genes associated with granulosa cell differentiation

miR-6881-3p contributes to diminished ovarian reserve by regulating granulosa cell apoptosis by targeting SMAD4

BACKGROUND

In our previous investigation, we revealed a significant increase in the expression of microRNA-6881-3p (miR-6881-3p) in follicular fluid granulosa cells (GCs) from women with diminished ovarian reserve (DOR) compared to those with normal ovarian reserve (NOR). However, the role of miR-6881-3p in the development of DOR remains poorly understood.

OBJECTIVE

This study aimed to elucidate the involvement of miR-6881-3p in the regulation of granulosa cells (GCs) function and the pathogenesis of DOR.

MATERIALS AND METHODS

Initially, we assessed the expression levels of miR-6881-3p in GCs obtained from human follicular fluid in both NOR and DOR cases and explored the correlation between miR-6881-3p expression and clinical outcomes in assisted reproduction technology (ART). Bioinformatic predictions and dual-luciferase reporter assays were employed to identify the target gene of miR-6881-3p. Manipulation of miR-6881-3p expression was achieved through the transfection of KGN cells with miR-6881-3p mimics, inhibitor, and miRNA negative control (NC). Following transfection, we assessed granulosa cell apoptosis and cell cycle progression via flow cytometry and quantified target gene expression through quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot (WB) analysis. Finally, we examined the correlation between target gene expression levels in GCs from NOR and DOR patients and their association with ART outcomes.

RESULTS

Our findings revealed elevated miR-6881-3p levels in GCs from DOR patients, which negatively correlated with ovarian reserve function and ART outcomes. We identified a direct binding interaction between miR-6881-3p and the 3'-untranslated region of the SMAD4. Transfection with miR-6881-3p mimics induced apoptosis in KGN cell. Furthermore, miR-6881-3p expression negatively correlated with both mRNA and protein levels of the SMAD4. The mRNA and protein levels of SMAD4 were notably reduced in GCs from DOR patients, and SMAD4 mRNA expression positively correlated with ART outcomes. In addition, the mRNA levels of FSHR, CYP11A1 were notably reduced after transfection with miR-6881-3p mimics in KGN cell, while LHCGR notably increased. The mRNA and protein levels of FSHR, CYP11A1 were notably reduced in GCs from DOR patients, while LHCGR notably increased.

CONCLUSION

This study underscores the role of miR-6881-3p in directly targeting SMAD4 mRNA, subsequently diminishing granulosa cell viability and promoting apoptosis, and may affect steroid hormone regulation and gonadotropin signal reception in GCs. These findings contribute to our understanding of the pathogenesis of DOR.

Comparative Studies on Duplicated foxl2 Paralogs in Spotted Knifejaw Oplegnathus punctatus Show Functional Diversification

As a member of the forkhead box L gene family, foxl2 plays a significant role in gonadal development and the regulation of reproduction. During the evolution of deuterostome, whole genome duplication (WGD)-enriched lineage diversifications and regulation mechanisms occurs. However, only limited research exists on foxl2 duplication in teleost or other vertebrate species. In this study, two foxl2 paralogs, foxl2 and foxl2l, were identified in the transcriptome of spotted knifejaw (Oplegnathus punctatus), which had varying expressions in the gonads. The foxl2 was expressed higher in the ovary, while foxl2l was expressed higher in the testis. Phylogenetic reconstruction, synteny analysis, and the molecular evolution test confirmed that foxl2 and foxl2l likely originated from the first two WGD. The expression patterns test using qRT-PCR and ISH as well as motif scan analysis revealed evidence of potentially functional divergence between the foxl2 and foxl2l paralogs in spotted knifejaw. Our results indicate that foxl2 and foxl2l may originate from the first two WGD, be active in transcription, and have undergone functional divergence. These results shed new light on the evolutionary trajectories of foxl2 and foxl2l and highlights the need for further detailed functional analysis of these two duplicated paralogs.

Next-generation sequencing of 500 POI patients identified novel responsible monogenic and oligogenic variants

BACKGROUND

Premature ovarian insufficiency refers to the loss of ovarian function before 40 years of age. The etiology is heterogeneous, and genetic factors account for 20-25% of cases. However, how to transform genetic findings to clinical molecular diagnose remains a challenge. To identify potential causative variations for POI, a next generation sequencing panel with 28 known causative genes of POI was designed, and a large cohort of 500 Chinese Han patients was screened directly. Pathogenic evaluation of the identified variants and the phenotype analysis were performed according to monogenic or oligogenic variants.

RESULTS

A total of 14.4% (72/500) of the patients carried 61 pathogenic or likely pathogenic variants in 19 of the genes in the panel. Interestingly, 58 variants (95.1%, 58/61) were firstly identified in patients with POI. FOXL2 harbored the highest occurrence frequency (3.2%, 16/500), among whom presented with isolated ovarian insufficiency instead of blepharophimosis-ptosis-epicanthus inversus syndrome. Moreover, luciferase reporter assay confirmed variant p.R349G, which account for 2.6% of POI cases, impaired the transcriptional repressive effect of FOXL2 on CYP17A1. The novel compound heterozygous variants in NOBOX and MSH4 were confirmed by pedigree haplotype analysis, and digenic heterozygous variants in MSH4 and MSH5 were firstly identified. Furthermore, nine patients (1.8%, 9/500) with digenic or multigenic pathogenic variants presented with delayed menarche, early onset of POI and high prevalence of primary amenorrhea compared with those with monogenic variation(s).

CONCLUSIONS

The genetic architecture of POI has been enriched through the targeted gene panel in a large cohort of patients with POI. Specific variants in pleiotropic genes may result in isolated POI rather than syndromic POI, whereas oligogenic defects might have cumulative deleterious effects on the severity of POI phenotype.

Ovarian Reserve and ART Outcomes in Blepharophimosis-Ptosis-Epicanthus Inversus Syndrome Patients With FOXL2 Mutations

Objective

To characterize the status of ovarian reserve and ART outcomes in BPES women and provide informative reference for clinical diagnosis and treatment.

Methods

Twenty-one women with BPES were screened for mutations in the FOXL2 gene and underwent assisted reproductive technology (ART) treatment. Indicators for ovarian reserve and ART outcomes were compared between patients with and without FOXL2 mutations. Additionally, ART outcomes were compared among patients with different subtypes of FOXL2 mutations.

Results

A total of 13 distinct heterozygous variants in the FOXL2 gene were identified in 80.95% of BPES women, including 4 novel mutations with plausible pathogenicity (c.173_175dup, c.481C>T, c.576del and c.675_714del). Compared to non-mutation group, patients with FOXL2 mutations had elevated levels of FSH (P=0.007), decreased AMH levels (P=0.012) and less AFC (P=0.015). They also had worse ART outcomes with large amount of Gn dosage (P=0.008), fewer oocytes (P=0.001), Day3 good quality embryos (P=0.001) and good quality blastocysts (P=0.037), and a higher cancellation rate (P=0.272). High heterogeneity of ART outcomes existed in BPES patients with different FOXL2 mutation types.

Conclusions

BPES patients with FOXL2 mutations had diminished ovarian reserve and adverse ART outcomes. The genotype-reproductive phenotype correlations were highly heterogeneous and cannot be generalized. Genetic counseling for fertility planning and preimplantation or prenatal genetic diagnosis to reduce offspring inheritance are recommended.

Effects of Sex Steroid Receptor Agonists and Antagonists on the Expression of the FOXL2 Transcription Factor and its Target Genes AMH and CYP19A1 in the Neonatal Porcine Ovary

Recently, we have demonstrated that neonatal exposure to androgen and estrogen agonists or antagonists influenced the number of ovarian follicles in piglets. Since the FOXL2 transcription factor is required for proper ovarian follicle formation and activation, the objective of the study was to examine effects of exposure of the neonatal porcine ovary to testosterone propionate (TP; an androgen), flutamide (FLU; an antiandrogen), 4-tert-octylphenol (OP; compound with estrogenic activity), ICI 182,780 (ICI; an antiestrogen), and methoxychlor (MXC; compound with estrogenic, antiestrogenic and antiandrogenic properties) on FOXL2 expression and expression of its target genes, AMH and CYP19A1. Piglets were injected subcutaneously with TP, FLU, OP, ICI, MXC, or corn oil (control) between postnatal days 1 and 10 (n = 4/each group). Ovaries were excised from the 11-day-old piglets and the expression of FOXL2, AMH and CYP19A1 was examined using immunohistochemistry and/or real-time PCR and Western blot. FOXL2 was localized in stroma cells surrounding egg nests and in granulosa cells. TP, OP and MXC increased both FOXL2 and AMH mRNAs, while FLU and ICI decreased CYP19A1 mRNA. The increased FOXL2 protein abundance was found in all examined groups. In addition, TP, OP, ICI and MXC increased AMH protein abundance, while TP, FLU and OP decreased CYP19A1 protein abundance. In conclusion, neonatal exposure to sex steroid receptor agonists and antagonists increased FOXL2 expression at mRNA and/or protein levels and affected FOXL2 target genes in the ovaries of 11-day-old piglets. Therefore, it seems that impaired ovarian folliculogenesis induced by altered steroid milieu during the neonatal development period in pigs may, at least in part, involve FOXL2.

Transcriptional regulation of CYP19A1 expression in chickens: ESR1, ESR2 and NR5A2 form a functional network

Aromatase, encoded by CYP19A1, is responsible for the conversion of androgen to estrogen, which plays a vital role in the development and function of the ovary and functions in many other physiological processes in both sexes. Instead of being expressed in ovarian granulosa cells, as in mammals, CYP19A1 is expressed in chickens in the theca cells of ovarian follicles, and the mechanism of CYP19A1 expression regulation remains unknown. Here, using immunofluorescence and western blotting assay, we first confirmed that CYP19A1 and FOXL2 (Forkheadbox L2) were coexpressed in pre-granulosa cells of female chicken embryonic gonads, while FOXL2 did not affect aromatase expression at embryonic stages. Second, our research showed that CYP19A1, ESR1 (estrogen receptor alpha), ESR2 (estrogen receptor beta) and NR5A2 (liver receptor homologue-1) were coexpressed in the theca cell layers of chicken small yellow follicles. There was cross-talk between CYP19A1 and candidate transcription factors (ESR1, ESR2 and NR5A2), which was identified by generating a reliable theca cell culture model. Using luciferase assays in theca cells and chicken embryonic fibroblast (DF-1) cells, the results suggested that ESR1 and NR5A2 had potential effects on CYP19A1 promoter activity in chickens. Overexpression of ESR1, ESR2 and NR5A2 in chicken embryonic fibroblast (DF-1) cells upregulated the protein expression of CYP19A1, mutually restricted each other and formed a potential regulatory network to coordinate the expression of CYP19A1. To conclude, our results indicated that FOXL2 cannot regulate the expression of CYP19A1 at chicken embryonic stages and after sexual maturity, ESR1, ESR2 and NR5A2 form a functional network to affect the expression of CYP19A1. These results laid a foundation for further research on the transcriptional regulation of chicken aromatase.

lncRNA GCAT1 is involved in premature ovarian insufficiency by regulating p27 translation in GCs via competitive binding to PTBP1

Dysfunction of granulosa cells (GCs) leading to follicle atresia has been extensively studied as a major cause of premature ovarian insufficiency (POI), but the regulatory role of long non-coding RNAs (lncRNAs) in this process is still poorly understood. Here, we show that the lncRNA LINC02690 or GCAT1 (granulosa cell-associated transcript 1) is downregulated in GCs from patients with biochemical POI (bPOI), and we show a significant correlation between downregulated GCAT1 and serum levels of follicle-stimulating hormone and anti-Müllerian hormone. Downregulation of GCAT1 inhibited G1/S cell cycle progression and thus inhibited the proliferation of GCs. Mechanistically, we show that GCAT1 competes with cyclin-dependent kinase inhibitor 1B (CDKN1B) mRNA for polypyrimidine tract-binding protein 1 (PTBP1) binding, and thus decreased GCAT1 might promote PTBP1 binding to CDKN1B mRNA and thereby initiate CDKN1B protein (p27) translation. Together, our results suggest that downregulation of GCAT1 under conditions of bPOI inhibits the proliferation of GCs through PTBP1-dependent p27 regulation, thus suggesting a novel form of lncRNA-mediated epigenetic regulation of GC function that contributes to the pathogenesis of POI.

Pathways Involved in Premature Ovarian Failure: A Systematic Review of Experimental Studies

Premature ovarian failure (POF), which may be undetectable for a long time, is associated with impaired fertility. The mechanisms involved in the pathogenesis of POF as well as the concomitant treatments are still unclear. Although many data exist, mainly produced by the study of transgenic animals under various experimental conditions, they remain fragmented. A systematic review of the pathways involved in premature ovarian failure was conducted. Data extraction was performed from experimental studies until 2019. The molecular processes and their correlation with the follicular developmental stage have been described. Furthermore, the effects in other cells, such as oocytes, granulosa and theca cells have been reported. An overall estimation was conducted.

A novel FOXL2 mutation in two infertile patients with blepharophimosis-ptosis-epicanthus inversus syndrome

BACKGROUND

Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) is a rare, autosomal dominant disease. There are two clinical types of BPES: type I patients have eyelid abnormalities accompanied by infertility in affected females, while type II patients only display eyelid malformations. Previous studies have reported that the forkhead box L2 (FOXL2) gene mutations cause BPES.

PURPOSE

To identify plausible FOXL2 mutation in a Chinese family with BPES and infertility METHODS: Mutational screening of FOXL2 was performed in the affected members and 223 controls. Functional characterization of the novel mutation identified was carried out in vitro by luciferase reporter assay and subcellular localization experiment.

RESULTS

A novel heterozygous mutation c.188 T > A (p.I63N) in FOXL2 was identified in two BPES patients in this family. The mutation abolished the transcriptional repression of FOXL2 on the promoters of CYP19A1 and CCND2 genes, as shown by luciferase reporter assays. However, no dominant-negative effect was observed for the mutation, and it did not impact FOXL2 protein nuclear localization and distribution.

CONCLUSIONS

The mutation c.188 T > A (p.I63N) in FOXL2 might be causative for BPES and infertility in this family and further amplified the spectrum of FOXL2 mutations.

Human placenta-derived mesenchymal stem cells inhibit apoptosis of granulosa cells induced by IRE1α pathway in autoimmune POF mice

Previous studies have shown that the ovarian failure in autoimmune-induced premature ovarian failure (POF) mice could be improved by the transplantation of human placenta-derived mesenchymal stem cells (hPMSCs); however, the protective mechanism of hPMSCs transplantation on ovarian dysfunction remains unclear. Ovarian dysfunction is closely related to the apoptosis of granulosa cells (GCs). To determine the effects of hPMSCs transplantation on GCs apoptosis, an autoimmune POF mice model was established with zona pellucida glycoprotein 3 (ZP3) peptide. It is reported that the inositol-requiring enzyme 1α (IRE1α) and its downstream molecules play a central role in the endoplasmic reticulum (ER) stress-induced apoptosis pathway. So the aim of this study is to investigate whether hPMSCs transplantation attenuated GCs apoptosis via inhibiting ER stress IRE1α signaling pathway. The ovarian dysfunction, follicular dysplasia, and GCs apoptosis were observed in the POF mice. And the IRE1α pathway was activated in ovaries of POF mice, as demonstrated by, increased X-box binding protein 1 (XBP1), up-regulated 78 kDa glucose-regulated protein (GRP78) and caspase-12. Following transplantation of hPMSCs, the ovarian structure and function were significantly improved in POF mice. In addition, the GCs apoptosis was obviously attenuated and IRE1α pathway was significantly inhibited. Transplantation of hPMSCs suppressed GCs apoptosis-induced by ER stress IRE1α signaling pathway in POF mice, which might contribute to the hPMSCs transplantation-mediating ovarian function recovery.

Screening of a large cohort of blepharophimosis, ptosis, and epicanthus inversus syndrome patients reveals a very strong paternal inheritance bias and a wide spectrum of novel FOXL2 mutations

Blepharophimosis, Ptosis, and Epicanthus inversus Syndrome (BPES) is caused by autosomal dominant mutations in FOXL2. There are two forms of BPES: type I (with primary ovarian insufficiency (POI)) and type II (without POI). Data are presented from a large cohort of 177 BPES probands. Diagnostic testing identified a wide range of mutations in 119 mutation-positive patients (including 38 novel mutations). Although FOXL2 mutations are distributed throughout the gene, over 50% were frameshift mutations within a hotspot region of the gene that can be detected using a single primer pair to provide a cost-effective and rapid screening method. There was a significant proportion of de novo cases in this study, although in 7% there may be undetected parental mosaicism. There was an excess of female compared to male probands and a highly significant bias in the parental original of inherited mutations, with 20/21 found to be paternal in origin (95%). This could be because BPES in a female is more likely to come to clinical attention and because there is a generalised and more widespread clinical effect on fertility, in addition to the established association with POI. This study demonstrates the importance of cascade screening and provides new information on inheritance and parental mosaicism in BPES which will aid genetic counselling and accurate risk management.

FOXL2C134W-Induced CYP19 Expression via Cooperation With SMAD3 in HGrC1 Cells

Germline knockout studies in female mice demonstrated an essential role for forkhead box L2 (FOXL2) in early follicle development, whereas an inducible granulosa cell (GC)-specific deletion of Foxl2 in adults has shown ovary-to-testis somatic sex reprogramming. In women, over 120 different germline mutations in the FOXL2 gene have been shown to cause blepharophimosis/ptosis/epicantus inversus syndrome associated with or without primary ovarian insufficiency. By contrast, a single somatic mutation (FOXL2C134W) accounts for almost all adult-type GC tumors (aGCTs). To test the hypothesis that FOXL2C134W differentially regulates the expression of aGCT markers, we investigated the effect of FOXL2C134W on inhibin B and P450 aromatase expression using a recently established human GC line (HGrC1), which we now show to bear two normal alleles of FOXL2. Neither FOXL2wt nor FOXL2C134W regulate INHBB messenger RNA (mRNA) expression. However, FOXL2C134W selectively displays a 50-fold induction of CYP19 mRNA expression dependent upon activin A. Mechanistically, the CYP19 promoter is activated in a similar way by FOXL2C134W interaction with SMAD3, but not by FOXL2wt. SMAD2 had no effect. Moreover, FOXL2C134W interactions with SMAD3 and with the FOX binding element located at -199 bp upstream of the ATG initiation codon of CYP19 are more sustainable than FOXL2wt. Thus, FOXL2C134W potentiates CYP19 expression in HGrC1 cells via enhanced recruitment of SMAD3 to a proximal FOX binding element. These findings may explain the pathophysiology of estrogen excess in patients with aGCT.

Functional Analysis of a Novel FOXL2 Indel Mutation in Chinese Families with Blepharophimosis-Ptosis-Epicanthus Inversus Syndrome Type I

Background: Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) is an autosomal dominant disease with a low incidence rate. Indel mutations in the forkhead box L2 (FOXL2) gene cause two types of BPES that are distinguished by the presence (type I) or absence (type II) of premature ovarian failure (POF). The purpose of this study was to identify a possible deletion in FOXL2 in Chinese families with BPES and to clarify its relationship with POF.

Methods: An autosomal dominant Chinese BPES family with four generations was enrolled in this study. Peripheral venous blood was collected from all affected patients, and genomic DNA was extracted from leukocytes. The whole coding sequence and nearby 5' untranslated region (UTR) and 3'UTR of the FOXL2 gene were amplified using polymerase chain reaction (PCR) with three sets of overlapping primers, followed by sequencing analyses. The sequencing results were analysed using SeqMan software. Based on the patients' clinical manifestations and analysis of the identified indel mutation, we found that the mutation disturbed interactions between FOXL2 and the StAR gene. Furthermore, through subcellular localisation and functional studies, we observed significant mislocalisation of the mutant protein; the mutant protein was found in the cytoplasm, while the wild-type protein was found in the nucleus. Loss of function was confirmed by transcriptional activity assays, quantitative real-time PCR, and electrophoretic mobility shift assays.

Results: All affected patients presented with clinical features of BPES type I, including small palpebral fissures, ptosis, telecanthus, and epicanthus inversus with POF. A novel FOXL2 heterozygous indel mutation, c.19_95del, a 77-bp deletion that disrupts FOXL2 protein structure, was identified in all affected members of the family. In addition, this indel mutation significantly increased StAR mRNA expression by disrupting the ability of the FOXL2 protein to bind to the StAR promoter and act as a repressor of this gene.

Conclusions: A novel FOXL2 indel mutation was identified in Chinese families with BPES. Our results expand the spectrum of known FOXL2 mutations and provide additional insight into the structure-function relationships of the FOXL2 protein. Furthermore, this novel mutation resulted in the dysfunction of FOXL2 as a transcription factor, blocking its ability to bind to the promoter region of the StAR gene, resulting in POF in the affected patient.

Parabens Accelerate Ovarian Dysfunction in a 4-Vinylcyclohexene Diepoxide-Induced Ovarian Failure Model

Parabens are widely used preservatives in basic necessities such as cosmetic and pharmaceutical products. In previous studies, xenoestrogenic actions of parabens were reported in an immature rat model and a rat pituitary cell line (GH3 cells). The relationship between parabens and ovarian failure has not been described. In the present study, the influence of parabens on ovarian folliculogenesis and steroidogenesis was investigated. A disruptor of ovarian small pre-antral follicles, 4-vinylcyclohexene diepoxide (VCD, 40 mg/kg), was used to induce premature ovarian failure (POF). Methylparaben (MP, 100 mg/kg), propylparaben (PP, 100 mg/kg), and butylparaben (BP, 100 mg/kg) dissolved in corn oil were treated in female 8-week-old Sprague-Dawley rat for 5 weeks. Estrus cycle status was checked daily by vaginal smear test. Ovarian follicle development and steroid synthesis were investigated through real-time PCR and histological analyses. Diestrus phases in the VCD, PP, and BP groups were longer than that in the vehicle group. VCD significantly decreased mRNA level of folliculogenesis-related genes (Foxl2, Kitl and Amh). All parabens significantly increased the Amh mRNA level but unchanged Foxl2 and Kitlg acting in primordial follicles. VCD and MP slightly increased Star and Cyp11a1 levels, which are related to an initial step in steroidogenesis. VCD and parabens induced an increase in FSH levels in serum and significantly decreased the total number of follicles. Increased FSH implies impairment in ovarian function due to VCD or parabens. These results suggest that VCD may suppress both formation and development of follicles. In particular, combined administration of VCD and parabens accelerated inhibition of the follicle-developmental process through elevated AMH level in small antral follicles.

Expression analysis of microRNAs and mRNAs in ovarian granulosa cells after microcystin-LR exposure

Microcystin is a cyclic heptapeptide compounds which could cause female mammals' reproductive toxicity. Ovarian granulosa cells (GCs) are essential for the growth and development of follicles. In this study, after mouse granulosa cells (mGCs) treated with microcystin-LR (MC-LR) for 48 h, microRNAs (miRNAs) and mRNAs microarray technology were adopted to detect the expression of miRNAs and mRNAs. The results showed that 125 miRNAs and 283 mRNAs changed significantly, including 50 miRNAs down-regulated (fold change < -1.2), 75 miRNAs up-regulated (fold change > 1.2), 162 mRNAs down-regulated (fold change < -1.15) and 121 mRNAs up-regulated (fold change > 1.15) in treated group compared with the control group. Functional analysis showed that significant changed miRNAs and mRNAs are mainly involved in proliferation, apoptosis, immunity, metabolism and other biological processes of mGCs. By KEGG pathways analysis, we found that differentially expressed miRNAs and mRNAs mainly participated in apoptosis, formation of cancer, proliferation, production of hormones and other related signal pathways. miRNA-gene network analysis indicated that miR-29b-3p, miR-29a-3p, miR-29c-3p, miR-1906, miR-182-5p, growth factor receptor bound protein 2-associated protein 2 (Gab2), FBJ osteosarcoma oncogene (Fos), insulin-like growth factor 1 (Igf1), mannosidase 1, alpha (Man1a) are key miRNAs and genes. The microarray results were validated by real-time fluorescent quantitative PCR (qRT-PCR).

Novel action of FOXL2 as mediator of Col1a2 gene autoregulation

FOXL2 belongs to the evolutionarily conserved forkhead box (FOX) superfamily and is a master transcription factor in a spectrum of developmental pathways, including ovarian and eyelid development and bone, cartilage and uterine maturation. To analyse its action, we searched for proteins that interact with FOXL2. We found that FOXL2 interacts with specific C-terminal propeptides of several fibrillary collagens. Because these propeptides can participate in feedback regulation of collagen biosynthesis, we inferred that FOXL2 could thereby affect the transcription of the cognate collagen genes. Focusing on COL1A2, we found that FOXL2 indeed affects collagen synthesis, by binding to a DNA response element located about 65Kb upstream of this gene. According to our hypothesis we found that in Foxl2(-/-) mouse ovaries, Col1a2 was elevated from birth to adulthood. The extracellular matrix (ECM) compartmentalizes the ovary during folliculogenesis, (with type I, type III and type IV collagens as primary components), and ECM composition changes during the reproductive lifespan. In Foxl2(-/-) mouse ovaries, in addition to up-regulation of Col1a2, Col3a1, Col4a1 and fibronectin were also upregulated, while laminin expression was reduced. Thus, by regulating levels of extracellular matrix components, FOXL2 may contribute to both ovarian histogenesis and the fibrosis attendant on depletion of the follicle reserve during reproductive aging and menopause.

FOXL2 posttranslational modifications mediated by GSK3β determine the growth of granulosa cell tumours

Approximately 97% of patients with ovarian granulosa cell tumours (GCTs) bear the C134W mutation in FOXL2; however, the pathophysiological mechanism of this mutation is unknown. Here we report how this mutation affects GCT development. Sequential posttranslational modifications of the C134W mutant occur where hyperphosphorylation at serine 33 (S33) by GSK3β induces MDM2-mediated ubiquitination and proteasomal degradation. In contrast, S33 of wild-type FOXL2 is underphosphorylated, leading to its SUMOylation and stabilization. This prominent hyperphosphorylation is also observed at S33 of FOXL2 in GCT patients bearing the C134W mutation. In xenograft mice, the S33 phosphorylation status correlates with the oncogenicity of FOXL2, and the inhibition of GSK3β efficiently represses GCT growth. These findings reveal a previously unidentified regulatory mechanism that determines the oncogenic attributes of the C134W mutation via differential posttranslational modifications of FOXL2 in GCT development.

Novel WT1 Missense Mutations in Han Chinese Women with Premature Ovarian Failure

Premature ovarian failure (POF) is a heterogeneous disease. Though dozens of candidate genes have been identified for the genetic etiology of POF, it is largely unexplained in majority of patients. Recently, Wt1^+/R394W mice was found to present POF-like phenotype, which indicates that WT1 might be a plausible candidate gene for non-syndromic POF. The coding region of WT1 gene was screened in 384 patients with POF and 6 novel variations were identified, including two missense mutations (p. Pro126Ser in exon1 and p. Arg370His in exon7) and four intronic variants (c.647-27C > T, c.647-13G > C, c.647-13G > A in intron1 and c.950 + 14T > C in intron 4). In vitro experiments showed that both mutant p. Pro126Ser and p. Arg370His repressed the expression of Amh and Cdh1, and induced the expression of Fshr and Cyp19 in mRNA level (P < 0.05). The expression changes of AMH, FSHR, CYP19 and CDH1 were confirmed by western blot. These genes (AMH, FSHR, CYP19 and CDH1) are required for granular cells (GCs) proliferation, differentiation and oocyte-GCs interaction. The novel mutant p. P126S and p. R370H in the WT1 gene potentially impaired GCs differentiation and oocyte-GCs interaction, which might result in loss of follicles prematurely. Therefore, WT1 is a plausible causal gene for POF.

Granulosa cell-derived induced pluripotent stem cells exhibit pro-trophoblastic differentiation potential

Introduction

Human induced pluripotent stem cells (hiPSCs) have been derived from various somatic cell types. Granulosa cells, a group of cells which surround oocytes and are obtained from the (normally discarded) retrieved egg follicles of women undergoing infertility treatment, are a possible cell source for induced pluripotent stem cell (iPSC) generation. Here, we explored the possibility of using human granulosa cells as a donor cell type for iPSC reprogramming, and compared granulosa cell-derived iPSCs (iGRAs) with those derived from other cell sources, to determine the potential ability of iGRA differentiation.

Methods

Granulosa cells were collected from egg follicles retrieved from women undergoing infertility treatment. After short-term culture, the granulosa cells derived from different patients were mixed in culture, and infected with retroviruses encoding reprogramming factors. The resulting iPSC clones were selected and subjected to microsatellite DNA analysis to determine their parental origin. IGRAs were subjected to RT-PCR, immunofluorescence staining, and in vitro and in vivo differentiation assays to further establish their pluripotent characteristics.

Results

Microsatellite DNA analysis was used to demonstrate that hiPSCs with different parental origins can be simultaneously reprogrammed by retroviral transfection of a mixed human granulosa cell population obtained from multiple individuals. The iGRAs resemble human embryonic stem cells (hESCs) in many respects, including morphological traits, growth requirements, gene and marker expression profiles, and in vitro and in vivo developmental propensities. We also demonstrate that the iGRAs express low levels of NLRP2, and differentiating iGRAs possess a biased differentiation potential toward the trophoblastic lineage. Although NLRP2 knockdown in hESCs promotes trophoblastic differentiation of differentiating hESCs, it does not result in exit from pluripotency. These results imply that NLRP2 may play a role in regulating the trophoblastic differentiation of human pluripotent stem cells.

Conclusions

These findings provide a means of generating iPSCs from multiple granulosa cell populations with different parental origins. The ability to generate iPSCs from granulosa cells not only enables modeling of infertility-associated disease, but also provides a means of identifying potential clinical interventions through iPSC-based drug screening.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0005-5) contains supplementary material, which is available to authorized users.

MCM9 mutations are associated with ovarian failure, short stature, and chromosomal instability

Premature ovarian failure (POF) is genetically heterogeneous and manifests as hypergonadotropic hypogonadism either as part of a syndrome or in isolation. We studied two unrelated consanguineous families with daughters exhibiting primary amenorrhea, short stature, and a 46,XX karyotype. A combination of SNP arrays, comparative genomic hybridization arrays, and whole-exome sequencing analyses identified homozygous pathogenic variants in MCM9, a gene implicated in homologous recombination and repair of double-stranded DNA breaks. In one family, the MCM9 c.1732+2T>C variant alters a splice donor site, resulting in abnormal alternative splicing and truncated forms of MCM9 that are unable to be recruited to sites of DNA damage. In the second family, MCM9 c.394C>T (p.Arg132(∗)) results in a predicted loss of functional MCM9. Repair of chromosome breaks was impaired in lymphocytes from affected, but not unaffected, females in both families, consistent with MCM9 function in homologous recombination. Autosomal-recessive variants in MCM9 cause a genomic-instability syndrome associated with hypergonadotropic hypogonadism and short stature. Preferential sensitivity of germline meiosis to MCM9 functional deficiency and compromised DNA repair in the somatic component most likely account for the ovarian failure and short stature.

Factors regulating the bovine, caprine, rat and human ovarian aromatase promoters in a bovine granulosa cell model

The ovarian promoter of the primate and rodent genes encoding cytochrome P450 aromatase (CYP19A1) are robustly responsive to forskolin in luteinized cell models, whereas the ruminant ovarian promoter is minimally active. We explored this discrepancy by investigating the activity of the bovine ovarian promoter in two bovine granulosa cell models, luteinizing and non-luteinizing cells in vitro. In non-luteinizing cells, both FSH and IGF1 increased abundance of transcripts derived from the ovarian promoter. Comparison of the activity of promoters of several species in response to transcription factors (forskolin, NR5A2, FOXL2) in luteinizing cells demonstrated that a rat ovarian promoter-luciferase reporter was regulated mainly by forskolin (18-fold increase over basal expression) and addition of NR5A2 or FOXL2 had no further effect. Activity of a human promoter was significantly increased by NR5A2 plus forskolin (153-fold) compared with forskolin alone (71-fold over basal); addition of FOXL2 did not significantly increase promoter activity. Forskolin alone provoked minor activation of caprine and bovine promoter reporters (3-fold over basal), and addition of NR5A2 increased activity (7- to 11-fold). When forskolin, NR5A2 and FOXL2 treatments were combined, the activity of the caprine and bovine promoters increased to 20- and 34-fold, respectively. These data suggest that a major reason why CYP19A1 is not expressed in luteinized cells (and the corpus luteum) of ruminants may be the stimulatory effect of FOXL2, which does not appear to be the case in the human and rat.

FOXL2: a central transcription factor of the ovary

Forkhead box L2 (FOXL2) is a gene encoding a forkhead transcription factor preferentially expressed in the ovary, the eyelids and the pituitary gland. Its germline mutations are responsible for the blepharophimosis ptosis epicanthus inversus syndrome, which includes eyelid and mild craniofacial defects associated with primary ovarian insufficiency. Recent studies have shown the involvement of FOXL2 in virtually all stages of ovarian development and function, as well as in granulosa cell (GC)-related pathologies. A central role of FOXL2 is the lifetime maintenance of GC identity through the repression of testis-specific genes. Recently, a highly recurrent somatic FOXL2 mutation leading to the p.C134W subtitution has been linked to the development of GC tumours in the adult, which account for up to 5% of ovarian malignancies. In this review, we summarise data on FOXL2 modulators, targets, partners and post-translational modifications. Despite the progresses made thus far, a better understanding of the impact of FOXL2 mutations and of the molecular aspects of its function is required to rationalise its implication in various pathophysiological processes.

Wnt4, a pleiotropic signal for controlling cell polarity, basement membrane integrity, and antimüllerian hormone expression during oocyte maturation in the female follicle

Wnt4 is a key signal that channels the developmental fate of the indifferent mammalian gonad toward the ovary, but whether Wnt4 has later roles during ovary development remains unknown. To investigate this, we inactivated the Wnt4 gene by crossing Amhr2Cre and doxycycline-inducible Rosa(rtTA)-knock-in Cre mice with mice carrying a floxed Wnt4 allele and used a novel Wnt4(mCherry)-knock-in mouse. In these models, ovarian folliculogenesis was compromised, and female fertility was severely reduced, and Wnt4 deficiency eventually led to premature ovarian failure. These anomalies were associated with cell polarity defects in the follicle. Within the follicle, laminin and type IV collagen assembled ectopic basement membrane-like structures, the cell adherens junction components N-cadherin and β-catenin lost their polarized expression pattern, and expression of the gap junction protein connexin 43 was reduced by ~30% when compared with that of the controls. Besides these changes, expression of antimüllerian hormone (Amh) was inhibited in the absence of Wnt4 signaling in vivo. Consistent with this, Wnt4 signaling up-regulated Amh gene expression in KK1 cells in vitro. Thus, Wnt4 signaling is necessary during maturation of the ovarian follicles, where it coordinates expression of Amh, cell survival, and polarized organization of the follicular cells.

foxl2 and foxl3 are two ancient paralogs that remain fully functional in teleosts

FOXL2 is a forkhead transcription factor involved in mammalian development and regulation of reproduction. Two foxl2 paralogs, foxl2a and foxl2b, have been described in various teleost species and were considered as fish-specific duplicates. Here, we report the isolation and characterization of foxl2a (foxl2) and foxl2b (foxl3) in European sea bass (Dicentrarchus labrax), together with the identification of these two genes in non-teleost genomes. Phylogenetic and synteny analyses indicate that these paralogs originated from an ancient genome duplication event that happened long before the teleost specific duplication. While foxl2/foxl2a has been maintained in most vertebrate lineages, foxl2b, which we propose to rename as foxl3, was repeatedly lost in tetrapods. Gonadal expression patterns of the sea bass genes point to a strong sexual dimorphism, and the mRNA levels of foxl2 in ovary and foxl3 in testis vary significantly during the reproductive cycle. When overexpressed in cultured ovarian follicular cells, foxl2 and foxl3 produced functional transcription factors able to control the expression of reproduction-related genes. Taken together, these data suggest that Foxl2 may play a conserved role in ovarian maturation, while Foxl3 could be involved in testis physiology.

Exposure to chemical cocktails before or after conception--- the effect of timing on ovarian development

Exposure of female fetuses to environmental chemicals (ECs) during pregnancy results in a disturbed ovarian adult phenotype. We investigated the influence of pre- and/or post-conception exposure to low-level mixtures of ECs on the structure and function of the fetal ovine ovary. We examined ovarian morphology, expression of oocyte and granulosa cell-specific genes and proteome. Female fetuses were collected at day 110 of gestation, from dams exposed continuously until, and after mating, by grazing in pastures treated with sewage sludge as a fertiliser (TT) or in control fields treated with inorganic fertiliser (CC). In addition, in a cross-over design, fetal ovaries were collected from dams maintained on sludge pastures up to the time of mating but then transferred to control pastures (TC) and, reciprocally, those transferred from control to treated pastures at mating (CT). On examination, the proportion of type 1a follicles (activating primordial follicles) was significantly lower in animals from the CT groups compared with CC and TT groups (P<0.05). Of the 23 ovarian gene transcripts studied, 14 were altered in the ovaries of exposed fetuses (CT, TC, and TT) relative to controls, with the largest number of changes observed in cross-exposure pattern groups (CT or TC). Continuous EC exposure (TT) produced fewer transcript alterations and only two genes (INHBA and GSN) presented differential profiles between CC and TT. Fetal ovarian proteome analysis (2-DE gels) showed, across all exposure groups, 86 differentially expressed protein spots compared to controls. Animals in the CT group exhibited the highest number (53) while TC and TT presented the same number of affected protein spots (42). Fetal ovarian proteins with altered expression included MVP (major vault protein) and several members of the heat-shock family (HSPA4L, HSP90AA1 and HSF1). The present findings indicate that continuous maternal EC exposure before and during gestation, are less deleterious for fetal ovarian development than a change in maternal EC exposure between pre and post-conception. The pathways by which the ovary responds to this chemical stress were common in TT, CT, TC exposed foetuses. In addition to the period of pregnancy, the pre-conception period appears also as crucial for conditioning long-term effects of EC exposure on ovarian development and primordial follicle reserve and hence future fertility.

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.

Impaired fertility and FSH synthesis in gonadotrope-specific Foxl2 knockout mice

Impairments in pituitary FSH synthesis or action cause infertility. However, causes of FSH dysregulation are poorly described, in part because of our incomplete understanding of mechanisms controlling FSH synthesis. Previously, we discovered a critical role for forkhead protein L2 (FOXL2) in activin-stimulated FSH β-subunit (Fshb) transcription in immortalized cells in vitro. Here, we tested the hypothesis that FOXL2 is required for FSH synthesis in vivo. Using a Cre/lox approach, we selectively ablated Foxl2 in murine anterior pituitary gonadotrope cells. Conditional knockout (cKO) mice developed overtly normally but were subfertile in adulthood. Testis size and spermatogenesis were significantly impaired in cKO males. cKO females exhibited reduced ovarian weight and ovulated fewer oocytes in natural estrous cycles compared with controls. In contrast, ovaries of juvenile cKO females showed normal responses to exogenous gonadotropin stimulation. Both male and female cKO mice were FSH deficient, secondary to diminished pituitary Fshb mRNA production. Basal and activin-stimulated Fshb expression was similarly impaired in Foxl2 depleted primary pituitary cultures. Collectively, these data definitively establish FOXL2 as the first identified gonadotrope-restricted transcription factor required for selective FSH synthesis in vivo.

Mouse forkhead L2 maintains repression of FSH-dependent genes in the granulosa cell

The forkhead transcription factor forkhead box L2 (FOXL2) is expressed in granulosa cells of small and medium follicles in the mouse ovary.Foxl2female knockout mice exhibit primordial follicle depletion and primary ovarian failure, but evidence from adult female conditionalFoxl2knockout mice suggests that FOXL2 may also play a significant role in maintenance of ovarian differentiation at stages beyond the primordial follicle and initial wave of folliculogenesis. We previously showed that human FOXL2 functions as a transcriptional repressor of several key genes involved in granulosa cell proliferation and differentiation, including steroidogenic acute regulatory protein (STAR), P450aromatase (CYP19A1(CYP19)), P450scc (CYP11A1(CYP11A)), and cyclin D2 (CCND2). To elucidate the role of mouse FOXL2, we determined its role in transcriptional regulation in Chinese hamster ovary (CHO) cells and then confirmed our findings in mouse granulosa cells. We found that mouse FOXL2 represses the activities of the mouseStar,Cyp19a1,Cyp11a1promoters in CHO cells, but may not repress theCcnd2promoter, and identified the minimal mouseStar,Cyp19a1, andCyp11a1promoter regions responsive to FOXL2 regulation. We then knocked downFoxl2in mouse granulosa cells using siRNA, which resulted in significantly increased expression levels of mouseStar,Cyp19a1, andCyp11a1but notCcnd2. To increaseFoxl2expression levels, we generated a mouseFoxl2lentiviral construct and used it to infect mouse granulosa cells. Following lentiviral infection, the expression levels of mouseStar,Cyp19a1, andCyp11a1, but notCcnd2, decreased significantly. These data confirm that mouse FOXL2 functions as a transcriptional repressor of key granulosa cell genes that influence ovarian development.

Minireview: roles of the forkhead transcription factor FOXL2 in granulosa cell biology and pathology

The forkhead transcription factor (FOXL2) is an essential transcription factor in the ovary. It is important in ovarian development and a key factor in female sex determination. In addition, FOXL2 plays a significant role in the postnatal ovary and follicle maintenance. The diverse transcriptional activities of FOXL2 are likely attributable to posttranslational modifications and binding to other key proteins involved in granulosa cell function. Mutations of FOXL2 lead to disorders of ovarian function ranging from premature follicle depletion and ovarian failure to unregulated granulosa cell proliferation leading to tumor formation. Thus, FOXL2 is a key regulator of granulosa cell function and a master transcription factor in these cells.