Inefficient Sox9 upregulation and absence of Rspo1 repression lead to sex reversal in the B6.XYTIR mouse gonad†

Sry on the Y-chromosome upregulates Sox9, which in turn upregulates a set of genes such as Fgf9 to initiate testicular differentiation in the XY gonad. In the absence of Sry expression, genes such as Rspo1, Foxl2, and Runx1 support ovarian differentiation in the XX gonad. These two pathways antagonize each other to ensure the development of only one gonadal sex in normal development. In the B6.YTIR mouse, carrying the YTIR-chromosome on the B6 genetic background, Sry is expressed in a comparable manner with that in the B6.XY mouse, yet, only ovaries or ovotestes develop. We asked how testicular and ovarian differentiation pathways interact to determine the gonadal sex in the B6.YTIR mouse. Our results showed that (1) transcript levels of Sox9 were much lower than in B6.XY gonads while those of Rspo1 and Runx1 were as high as B6.XX gonads at 11.5 and 12.5 days postcoitum. (2) FOXL2-positive cells appeared in mosaic with SOX9-positive cells at 12.5 days postcoitum. (3) SOX9-positive cells formed testis cords in the central area while those disappeared to leave only FOXL2-positive cells in the poles or the entire area at 13.5 days postcoitum. (4) No difference was found at transcript levels of all genes between the left and right gonads up to 12.5 days postcoitum, although ovotestes developed much more frequently on the left than the right at 13.5 days postcoitum. These results suggest that inefficient Sox9 upregulation and the absence of Rspo1 repression prevent testicular differentiation in the B6.YTIR gonad.

FOXL2 and NR5A1 induce human fibroblasts into steroidogenic ovarian granulosa-like cells

Human granulosa cells in different stages are essential for maintaining normal ovarian function, and granulosa cell defect is the main cause of ovarian dysfunction. To address this problem, it is necessary to induce functional granulosa cells at different stages in vitro. In this study, we established a reprogramming method to induce early- and late-stage granulosa cells with different steroidogenic abilities. We used an AMH-fluorescence-reporter system to screen candidate factors for cellular reprogramming and generated human induced granulosa-like cells (hiGC) by overexpressing FOXL2 and NR5A1. AMH-EGFP+ hiGC resembled human cumulus cells in transcriptome profiling and secreted high levels of oestrogen and progesterone, similar to late-stage granulosa cells at antral or preovulatory stage. Moreover, we identified CD55 as a cell surface marker that can be used to isolate early-stage granulosa cells. CD55+ AMH-EGFP- hiGC secreted high levels of oestrogen but low levels of progesterone, and their transcriptome profiles were more similar to early-stage granulosa cells. More importantly, CD55+ hiGC transplantation alleviated polycystic ovary syndrome (PCOS) in a mouse model. Therefore, hiGC provides a cellular model to study the developmental program of human granulosa cells and has potential to treat PCOS.

A cellular model provides insights into the pathogenicity of the oncogenic FOXL2 somatic variant p.Cys134Trp

BACKGROUND

FOXL2 is a transcription factor expressed in ovarian granulosa cells. A somatic variant of FOXL2 (c.402 C > G, p.Cys134Trp) is the hallmark of adult-type granulosa cell tumours.

METHODS

We generated KGN cell clones either heterozygous for this variant (MUT) or homozygous for the wild-type (WT) allele by CRISPR/Cas9 editing. They underwent RNA-Seq and bioinformatics analyses to uncover pathways impacted by deregulated genes. Cell morphology and migration were studied.

RESULTS

The differentially expressed genes (DEGs) between WT/MUT and WT/WT KGN cells (DEGs-WT/MUT), pointed to several dysregulated pathways, like TGF-beta pathway, cell adhesion and migration. Consistently, WT/MUT cells were rounder than WT/WT cells and displayed a different distribution of stress fibres and paxillin staining. A comparison of the DEGs-WT/MUT with those found when FOXL2 was knocked down (KD) in WT/WT KGN cells showed that most DEGs-WT/MUT cells were not so in the KD experiment, supporting a gain-of-function (GOF) scenario. MUT-FOXL2 also displayed a stronger interaction with SMAD3.

CONCLUSIONS

Our work, aiming at better understanding the GOF scenario, shows that the dysregulated genes and pathways are consistent with this idea. Besides, we propose that GOF might result from an enhanced interaction with SMAD3 that could underlie an ectopic capacity of mutated FOXL2 to bind SMAD4.

ERK1/2-SOX9/FOXL2 axis regulates ovarian steroidogenesis and favors the follicular-luteal transition

Estradiol and progesterone are the primary sex steroids produced by the ovary. Upon luteinizing hormone surge, estradiol-producing granulosa cells convert into progesterone-producing cells and eventually become large luteal cells of the corpus luteum. Signaling pathways and transcription factors involved in the cessation of estradiol and simultaneous stimulation of progesterone production in granulosa cells are not clearly understood. Here, we decipher that phosphorylated ERK1/2 regulates granulosa cell steroidogenesis by inhibiting estradiol and inducing progesterone production. Down-regulation of transcription factor FOXL2 and up-regulation of SOX9 by ERK underpin its differential steroidogenic function. Interestingly, the incidence of SOX9 is largely uncovered in ovarian cells and is found to regulate FOXL2 along with CYP19A1 and STAR genes, encoding rate-limiting enzymes of steroidogenesis, in cultured granulosa cells. We propose that the novel ERK1/2-SOX9/FOXL2 axis in granulosa cells is a critical regulator of ovarian steroidogenesis and may be considered when addressing pathophysiologies associated with inappropriate steroid production and infertility in humans and animals.

Identification of SF-1 and FOXL2 and Their Effect on Activating P450 Aromatase Transcription via Specific Binding to the Promoter Motifs in Sex Reversing Cheilinus undulatus

The giant wrasse Cheilinus undulatus is a protogynous socially hermaphroditic fish. However, the physiological basis of its sex reversal remains largely unknown. cyp19 is a key gender-related gene encoding P450 aromatase, which converts androgens to estrogens. cyp19 transcription regulation is currently unknown in socially sexually reversible fish. We identified NR5A1 by encoding SF-1, and FOXL2 from giant wrasse cDNA and cyp19a1a and cyp19a1b promoter regions were cloned from genomic DNA to determine the function of both genes in cyp19a1 regulation. Structural analysis showed that SF-1 contained a conserved DNA-binding domain (DBD) and a C-terminal ligand-binding domain (LBD). FOXL2 was comprised of an evolutionarily conserved Forkhead domain. In vitro transfection assays showed that SF-1 could upregulate cyp19a1 promoter activities, but FOXL2 could only enhance cyp19a1b promoter transcriptional activity in the HEK293T cell line. Furthermore, HEK293T and COS-7 cell lines showed that co-transfecting the two transcription factors significantly increased cyp19a1 promoter activity. The -120 to -112 bp (5'-CAAGGGCAC-3') and -890 to -872 bp (5'-AGAGGAGAACAAGGGGAG-3') regions of the cyp19a1a promoter were the core regulatory elements for SF-1 and FOXL2, respectively, to regulate cyp19a1b promoter transcriptional activity. Collectively, these results suggest that both FOXL2 and SF-1 are involved in giant wrasse sex reversal.

Functional Divergence of Multiple Duplicated Foxl2 Homeologs and Alleles in a Recurrent Polyploid Fish

Evolutionary fates of duplicated genes have been widely investigated in many polyploid plants and animals, but research is scarce in recurrent polyploids. In this study, we focused on foxl2, a central player in ovary, and elaborated the functional divergence in gibel carp (Carassius gibelio), a recurrent auto-allo-hexaploid fish. First, we identified three divergent foxl2 homeologs (Cgfoxl2a-B, Cgfoxl2b-A, and Cgfoxl2b-B), each of them possessing three highly conserved alleles and revealed their biased retention/loss. Then, their abundant sexual dimorphism and biased expression were uncovered in hypothalamic-pituitary-gonadal axis. Significantly, granulosa cells and three subpopulations of thecal cells were distinguished by cellular localization of CgFoxl2a and CgFoxl2b, and the functional roles and the involved process were traced in folliculogenesis. Finally, we successfully edited multiple foxl2 homeologs and/or alleles by using CRISPR/Cas9. Cgfoxl2a-B deficiency led to ovary development arrest or complete sex reversal, whereas complete disruption of Cgfoxl2b-A and Cgfoxl2b-B resulted in the depletion of germ cells. Taken together, the detailed cellular localization and functional differences indicate that Cgfoxl2a and Cgfoxl2b have subfunctionalized and cooperated to regulate folliculogenesis and gonad differentiation, and Cgfoxl2b has evolved a new function in oogenesis. Therefore, the current study provides a typical case of homeolog/allele diversification, retention/loss, biased expression, and sub-/neofunctionalization in the evolution of duplicated genes driven by polyploidy and subsequent diploidization from the recurrent polyploid fish.

Transcriptome sequencing revealed that knocking down FOXL2 affected cell proliferation, the cell cycle, and DNA replication in chicken pre-ovulatory follicle cells

Forkhead box L2 (FOXL2) is a single-exon gene encoding a forkhead transcription factor, which is mainly expressed in the ovary, eyelids and the pituitary gland. FOXL2 plays an essential role in ovarian development. To reveal the effects of FOXL2 on the biological process and gene expression of ovarian granulosa cells (GCs), we established stable FOXL2-knockdown GCs and then analysed them using transcriptome sequencing. It was observed that knocking down FOXL2 affected the biological processes of cell proliferation, DNA replication, and apoptosis and affected cell cycle progression. FOXL2 knockdown promoted cell proliferation and DNA replication, decreased cell apoptosis, and promoted mitosis. In addition, by comparing the transcriptome after FOXL2 knockdown, we found a series of DEGs (differentially expressed genes) and related pathways. These results indicated that, through mediating these genes and pathways, the FOXL2 might induce the cell proliferation, cycle, and DNA replication, and play a key role during ovarian development and maintenance.

Non-esterified fatty acids in the ovary: friends or foes?

A majority of common metabolic diseases can result in excessive lipolysis, leading to elevated levels of non-esterified fatty acids (NEFAs) in the body fluids. In females, increased NEFA levels in the follicular fluid markedly alter the functions of intrafollicular cells such as granulosa cells (GCs) and oocytes. Therefore, elevated levels of NEFAs have been suggested to be a significant player of subfertility in females of both human and economically important animal species such as cattle, buffalo, sheep, pig, chicken, and dog. However, the effects imposed by saturated and unsaturated fatty acids (SFAs and UFAs) on ovarian follicles are controversial. The present review emphasizes that SFAs induce apoptosis in granulosa and cumulus cells of ovarian follicles in different species. They further could adversely affect oocyte maturation and developmental competence. Many types of UFAs affect steroidogenesis and proliferation processes and could be detrimental for follicular cells, especially when at elevated concentrations. Interestingly, monounsaturated fatty acids (MUFAs) appear to contribute to the etiology of the polycystic ovarian syndrome (PCOS) as they were found to induce the transcription and translation of the androgenic transcription factor SOX9 while downregulating its estrogenic counterpart FOXL2 in GCs. Overall, this review presents our revised understanding of the effects of different fatty acids on the female reproductive success, which may allow other researchers and clinicians to investigate the mechanisms for treating metabolic stress-induced female infertility.

Maternal Testosterone Excess Contributes to Reproductive System Dysfunction of Female Offspring Mice

Hyperandrogenism is considered 1 of the most important characteristics of polycystic ovary syndrome, which affects more than 10% of females of reproductive age and is a common cause of infertility. In addition to the effects on patients themselves, maternal androgen excess has also been reported to impair the growth and development of offspring. In our current study, we found that maternal testosterone (T) treatment during different gestational stages increased the percentage of atretic follicle and decreased corpus luteum formation in female offspring. In addition, decreased serum estradiol and increased T levels were also observed in female offspring of T-treated mice during late gestational stage. Further studies revealed that Forkhead box protein L2 (FOXL2) and Cytochrome P450 family 19 subfamily a member 1 (CYP19A1) expression in granulosa cells of these female offspring mice were decreased. By using mouse primary granulosa cells and the KGN cell line, we demonstrated that decreasing FOXL2 and CYP19A1 levels in ovarian granulosa cells partially may contribute to disturbed sex hormone synthesis in female offspring of T-treated mice during the late gestational stage. Findings from our current study highlight a critical role of excess maternal T exposure, especially during the late gestational stage, which could further lead to aberrant ovary development and sex hormone synthesis in female offspring.

Human Follicle-Stimulating Hormone ß Subunit Expression Depends on FOXL2 and SMAD4

Follicle-stimulating hormone (FSH), an essential regulator of mammalian fertility, is synthesized by pituitary gonadotrope cells in response to activins. In mice, activins signal via SMAD3, SMAD4, and FOXL2 to regulate transcription of the FSHβ subunit (Fshb) gene. Gonadotrope-specific deletion of Foxl2, alone or in combination with Smad4, renders mice FSH-deficient. Whether human FSHB expression is similarly regulated is not known. Here, we used a combination of transgenic and conditional knockout mouse strains to assess the roles of activins, FOXL2, and SMAD4 in regulation of the human FSHB gene. First, we cultured pituitaries from mice harboring a human FSHB transgene (hFSHB mice) and measured both murine Fshb and human FSHB messenger ribonucleic acid (mRNA) expression in response to exogenous activins or two antagonists of endogenous activin-like signaling (follistatin-288 and SB431542). Both murine Fshb and human FSHB expression were stimulated by activins and reduced by the inhibitors. Next, we analyzed human FSHB expression in hFSHB mice carrying floxed Foxl2 and Smad4 alleles. Cre-mediated ablation of FOXL2 and SMAD4 strongly reduced basal and activin-stimulated murine Fshb and human FSHB expression in cultured pituitaries. Finally, the hFSHB transgene was previously shown to rescue FSH production and fertility in Fshb knockout mice. However, gonadotrope-specific Foxl2/Smad4 knockout females carrying the hFSHB transgene have significantly reduced murine Fshb and human FSHB pituitary mRNA levels and are hypogonadal. Collectively, these data suggest that similar to Fshb regulation in mice, FOXL2 and SMAD4 play essential roles in human FSHB expression.

Effects of Bisphenol A on Foxl2 gene expression and DNA damage in adult viviparous fish Goodeaatripinnis

Bisphenol A (BPA) is an emerging pollutant of global concern. Viviparous fish Goodea atripinnis is endemic to the Central Mexican Plateau where BPA was detected; however, few studies examined the influence of this chemical on native viviparous fish. The effects of BPA (sublethal dose) were determined on DNA integrity and Foxl2 expression in G. atripinnis gonads, and interactions of BPA with FOXL2 protein. Genotoxicity analysis revealed that % comets, at 14 and 28 days and comet tail length (at 14 days) were significantly higher in exposed compared to controls. In general, the % DNA tail was not markedly higher in BPA-treated fish; however, tail moment related to tail length exhibited significant increases in DNA damage. RT-qPCR assays showed Foxl2 overexpression after 14 and 28 days of exposure in females; while in males, Foxl2 was overexpressed after 28 days. In silico analysis demonstrated that BPA interacted with seven residues located in FOXL2 homeodomain. In summary, sublethal BPA doses induced DNA damage and changes in Foxl2 expression in gonadal cells of G. atripinnis, which may adversely affect reproduction in BPA-exposed wild populations. Foxl2 overexpression and BPA-FOXL2 interaction suggested alterations in processes involving Foxl2. Viviparous fish may thus serve as potential non-conventional models for assessing pollutants effects.

Reduced Foxo3a, FoxL2, and p27 mRNA expression in human ovarian tissue in premature ovarian insufficiency

PURPOSE

Previous studies have suggested that deletion of Foxo3a, FoxL2, PTEN, p27, and AMH leads to early exhaustion of the primordial follicle pool and premature ovarian insufficiency (POI) in transgenic mice. Our aim was to assess for the first time, to our knowledge, messenger RNA (mRNA) expression of these genes and AMHR2 in human ovarian tissue from women with POI. We hypothesized that these genes would be underexpressed in POI women compared with healthy controls.

METHODS

mRNA levels were evaluated by quantitative reverse transcription-polymerase chain reaction and real-time polymerase chain reaction in cortical ovarian tissue obtained by laparoscopy from Caucasian Greek women with POI (n = 5) and healthy women with normal menstruation (n = 6). Morphological analysis of the ovarian biopsies was also performed to assess the presence of primordial or other types of growing follicles.

RESULTS

Ovarian tissue from POI patients showed lower Foxo3a, FoxL2, and p27 mRNA expression compared with controls (p = 0.017, p = 0.017, and p = 0.030, respectively). mRNA expression of AMH, PTEN, and AMHR2 was reduced in ovarian biopsies from POI patients as well. However, these differences were not statistically significant (p = 0.143, p = 0.247, and p = 0.662, respectively). Morphological analysis showed complete lack of follicular structures in all POI biopsies.

CONCLUSIONS

Our findings suggest a possible role of Foxo3a, FoxL2, and p27 in the pathogenesis of human POI, which may prove to be of great diagnostic-therapeutic value. Further larger studies are needed to identify a similar pattern for AMH, PTEN, and AMHR2 and to investigate gene expression at a protein level.

Estrogen regulates forkhead transcription factor 2 to promote apoptosis of human ovarian granulosa-like tumor cells

Granulosa cell tumors of the ovary (GCTs) are the predominant form of ovarian stromal tumors and can lead to abnormally secreted estrogen hormones. Studies have reported that forkhead transcription factor 2 (FOXL2) inhibits estrogen synthesis and its gene mutation can lead to GCTs. We unexpected found that estrogen also regulates the expression level of FOXL2. High-dose estrogen increased the expression of FOXL2 in ovarian-like granulosa (KGN) cells at both the mRNA and protein levels. However, no research has reported on the molecular regulatory mechanism and function between estrogen and FOXL2 in the development of GCTs. In this research, FOXL2 was highly expressed in KGN cells and ovarian stromal tumor tissues. Deletion of FOXL2 increased the estrogen secretion in KGN cells. In turn, high-dose estrogen increased the FOXL2 expression levels. FOXL2 was phosphorylated by GPR30 (G protein coupled receptor)-Protein kinase C (PKC) signaling pathway upon estrogen stimulation. Estrogen inhibited cell migration and proliferation, while promoting cell apoptosis. Deletion of FOXL2 inhibited the influence of estrogen on cell proliferation, migration, and apoptosis. Results suggest that estrogen via regulating FOXL2 suppresses cell proliferation and induces cell apoptosis.

CBX2 is required to stabilize the testis pathway by repressing Wnt signaling

XX and XY fetal gonads are initially bipotential, poised between the ovary and testis fate. Multiple lines of evidence suggest that commitment to testis fate requires the repression of genes associated with ovary fate. It was previously shown that loss of CBX2, the subunit of the Polycomb Repressive Complex 1 (PRC1) that binds H3K27me3 and mediates silencing, leads to ovary development in XY mice and humans. While it had been proposed that CBX2 is an activator of the testis-determining gene Sry, we investigated the alternative possibility that CBX2 has a direct role as a repressor of the antagonistic ovary-promoting pathway. To investigate this possibility, we developed a quantitative genome-wide profile of the repressive histone mark H3K27me3 and its active counterpart H3K4me3 in isolated XY and XX gonadal supporting cells before and after sex determination. We show that testis and ovary sex-determining (SD) genes are bivalent before sex determination, providing insight into how the bipotential state of the gonad is established at the epigenetic level. After sex determination, many SD genes of the alternate pathway remain bivalent, possibly contributing to the ability of these cells to transdifferentiate even in adults. The finding that many genes in the Wnt signaling pathway were targeted for H3K27me3-mediated repression in Sertoli cells led us to test whether deletion of Wnt4 could rescue testis development in Cbx2 mutants. We show that Sry expression and testis development were rescued in XY Cbx2^-/-;Wnt4^-/- mice. Furthermore, we show that CBX2 directly binds the downstream Wnt signaler Lef1, an ovary-promoting gene that remains bivalent in Sertoli cells. Our results suggest that stabilization of the testis fate requires CBX2-mediated repression of bivalent ovary-determining genes, which would otherwise block testis development.

During development, the bipotential fetal gonad can commit to the testis fate or to the ovary fate. Mutation of the epigenetic regulator CBX2 leads to ovary development in XY embryos, suggesting a critical role for chromatin remodeling during sex determination. However, the epigenetic mechanisms that regulate the testis vs. ovary cell-fate decision in the mammalian bipotential gonad are poorly understood. In this study, we developed a genome-wide profile of two histone modifications that play critical roles during development: H3K27me3 (repressive) and H3K4me3 (active). We find that sex-determining genes that are initially co-expressed in XX and XY bipotential gonads are bivalent (marked by both H3K4me3 and H3K27me3) prior to sex determination, poised to engage either the testis or ovary fate. Remarkably, after sex determination, repressed genes that promote the alternate fate remain bivalent. We show that stabilization of the testis fate requires CBX2-mediated repression of bivalent ovary-determining genes, which would otherwise block testis development. Our study provides insight into how the bipotential state of the gonad is established at the epigenetic level, and how the testis fate is stabilized by repression of the ovary fate during sex determination.

Gestational exposure to an epidemiologically defined mixture of phthalates leads to gonadal dysfunction in mouse offspring of both sexes

The increasing concern for the reproductive toxicity of abundantly used phthalates requires reliable tools for exposure risk assessment to mixtures of chemicals, based on real life human exposure and disorder-associated epidemiological evidence. We herein used a mixture of four phthalate monoesters (33% mono-butyl phthalate, 16% mono-benzyl phthalate, 21% mono-ethyl hexyl phthalate, and 30% mono-isononyl phthalate), detected in 1st trimester urine of 194 pregnant women and identified as bad actors for a shorter anogenital distance (AGD) in their baby boys. Mice were treated with 0, 0.26, 2.6 and 13 mg/kg/d of the mixture, corresponding to 0x, 10x, 100x, 500x levels detected in the pregnant women. Adverse outcomes detected in the reproductive system of the offspring in pre-puberty and adulthood included reduced AGD index and gonadal weight, changes in gonadal histology and altered expression of key regulators of gonadal growth and steroidogenesis. Most aberrations were apparent in both sexes, though more pronounced in males, and exhibited a non-monotonic pattern. The phthalate mixture directly affected expression of steroidogenesis as demonstrated in a relevant in vitro model. The detected adversities at exposures close to the levels detected in pregnant women, raise concern on the existing safety limits for early-life human exposures and emphasizes the need for re-evaluation of the exposure risk.

HDAC inhibitors impair Fshb subunit expression in murine gonadotrope cells

Fertility is dependent on follicle-stimulating hormone (FSH), a product of gonadotrope cells of the anterior pituitary gland. Hypothalamic gonadotropin-releasing hormone (GnRH) and intra-pituitary activins are regarded as the primary drivers of FSH synthesis and secretion. Both stimulate expression of the FSH beta subunit gene (Fshb), although the underlying mechanisms of GnRH action are poorly described relative to those of the activins. There is currently no consensus on how GnRH regulates Fshb transcription, as results vary across species and between in vivo and in vitro approaches. One of the more fully developed models suggests that the murine Fshb promoter is tonically repressed by histone deacetylases (HDACs) and that GnRH relieves this repression, at least in immortalized murine gonadotrope-like cells (LβT2 and αT3-1). In contrast, we observed that the class I/II HDAC inhibitor trichostatin A (TSA) robustly inhibited basal, activin A-, and GnRH-induced Fshb mRNA expression in LβT2 cells and in primary murine pituitary cultures. Similar results were obtained with the class I specific HDAC inhibitor, entinostat, whereas two class II-specific inhibitors, MC1568 and TMP269, had no effects on Fshb expression. Collectively, these data suggest that class I HDACs are positive, not negative, regulators of Fshb expression in vitro and that, contrary to earlier reports, GnRH may not stimulate Fshb by inhibiting HDAC-mediated repression of the gene.

Deletion of FOXL2 by CRISPR promotes cell cycle G0/G1 restriction in KGN cells

Forkhead box L2 (FOXL2), a member of the forkhead family of transcription factors, is important in eyelid and ovary differentiation. Although the function of FOXL2 in organogenesis has been investigated, the detailed mechanisms by which FOXL2 mediates cellular process remain to be fully elucidated. Few FOXL2‑knockout cell lines have been reported, which has limited molecular mechanism investigations. CRISPR is a novel gene editing technique that has been widely used in human genetic diseases. In the present study, FOXL2 was disrupted using clustered regularly interspaced short palindromic repeats (CRISPR), and screening of a stable knockout cell line was performed in human ovarian granulosa KGN cells. Three sites (F404, F425 and F446) around the ATG start codon on the FOXL2 DNA sequence were constructed in a guide RNA lentivirus. Targeting F425 was most efficient, and western blot analysis and DNA sequencing of the resulting cells suggested that both FOXL2 alleles were fully disrupted. In addition, flow cytometry results indicated that the knockout of FOXL2 restricted cell cycle progression at the G0/G1 phase. In addition, the expression levels of cell cycle mediators cyclin D1 and cyclin‑dependent kinase 4 were reduced. These results confirmed that FOXL2 disruption in KGN cells is associated with the cell cycle attenuation.

Conditional Deletion of FOXL2 and SMAD4 in Gonadotropes of Adult Mice Causes Isolated FSH Deficiency

The glycoprotein FSH, a product of pituitary gonadotrope cells, regulates ovarian follicle development in females and spermatogenesis in males. FSH is a heterodimer of the common α gonadotropin subunit and the hormone-specific FSHβ subunit (a product of the Fshb gene). Using a conditional knockout approach (Cre-lox), we previously demonstrated that Fshb expression in mice depends on the transcription factors forkhead box L2 (FOXL2) and SMAD4. Deletion of Foxl2 or Smad4 alone led to FSH deficiency, female subfertility, and oligozoospermia in males. Simultaneous deletion of the two genes yielded a greater suppression of FSH and female sterility. The Cre-driver used previously was first active during embryonic development. Therefore, it is unclear whether FOXL2 and SMAD4 play important roles in the development or adult function of gonadotropes, or both. To address this question, we developed a tamoxifen-inducible Cre-driver line, which enabled Foxl2 and Smad4 gene deletions in gonadotropes of adult mice. After tamoxifen treatment, females with previously demonstrated fertility exhibited profound reductions in FSH levels, arrested ovarian follicle development, and sterility. FSH levels were comparably reduced in males 1 or 2 months after treatment; however, spermatogenesis was unaffected. These data indicate that (1) FOXL2 and SMAD4 are necessary to maintain FSH synthesis in gonadotrope cells of adult mice, (2) FSH is essential for female reproduction but appears to be unnecessary for the maintenance of spermatogenesis in adult male mice, and (3) the inducible Cre-driver line developed here provides a powerful tool to interrogate gene function in gonadotrope cells of adult mice.

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.

Uterine Foxl2 regulates the adherence of the Trophectoderm cells to the endometrial epithelium

BACKGROUND

Forkhead Transcription Factor L2 (FOXL2) is a member of the forkhead family with important roles in reproduction. Recent studies showed that FOXL2 is expressed in human and bovine endometrium and that its levels fluctuate during pregnancy. In this study, we aimed at evaluating the expression and function of FOXL2 in embryo implantation.

METHODS

Mouse uteri at different days of pregnancy were isolated and analyzed for the expression and localization of FOXL2. A lentiviral strategy was further employed to either knockdown or overexpress FOXL2 in non-receptive human endometrial AN3-CA cells and in receptive Ishikawa cells, respectively. These genetically modified cells were compared to cells infected with a control lentivirus to determine the function of FOXL2 in trophectoderm cells adherence to Endometrial Epithelium was associated with the expression of genes known to be involved in acquisition of uterine receptivity.

RESULTS

We report that FOXL2 is expressed in both, the luminal epithelium and the myometrium of the mouse uterus and that its expression declines prior to implantation. We found that endometrial cells expressing low FOXL2 levels, either endogenous or genetically manipulated, were associated with a higher attachment rate of mouse blastocysts or human Jeg3 spheroids and mouse blastocysts. In accordance, low-FOXL2 levels were associated with changes in the expression level of components of the Wnt/Fzd and apoptotic pathways, both of which are involved in uterine receptivity. Furthermore, FOXL2 expression was inversely correlated with G-protein signaling protein 2 (Rgs2) and cytokine expression.

CONCLUSIONS

These results suggest that FOXL2 interferes with embryo attachment. Better understanding of the function of FOXL2 in the uterus would possibly suggest novel strategies for treatment of infertility attributed to repeated implantation failure.

Estrogen alters gonadal soma-derived factor (Gsdf)/Foxl2 expression levels in the testes associated with testis-ova differentiation in adult medaka, Oryzias latipes

Testis-ova differentiation in sexually mature male medaka (Oryzias latipes) is easily induced by estrogenic chemicals, indicating that spermatogonia persist in sexual bipotentiality, even in mature testes in medaka. By contrast, the effects of estrogen on testicular somatic cells associated with testis-ova differentiation in medaka remain unclear. In this study, we focused on the dynamics of sex-related genes (Gsdf, Dmrt1, and Foxl2) expressed in Sertoli cells in the mature testes of adult medaka during estrogen-induced testis-ova differentiation. When mature male medaka were exposed to estradiol benzoate (EB; 800ng/L), testis-ova first appeared after EB treatment for 14days (observed as the first oocytes of the leptotene-zygotene stage). However, the testis remained structurally unchanged, even after EB treatment for 28days. Although Foxl2 is a female-specific sex gene, EB treatment for 7days induced Foxl2/FOXL2 expression in all Sertoli cell-enclosed spermatogonia before testis-ova first appeared; however, Foxl2 was not detected in somatic cells in control testes. Conversely, Sertoli-cell-specific Gsdf mRNA expression levels significantly decreased after EB treatment for 14days, and no changes were observed in DMRT1 localization following EB treatment, whereas Dmrt1 mRNA levels increased significantly. Furthermore, after EB exposure, FOXl2 and DMRT1 were co-localized in Sertoli cells during testis-ova differentiation, although FOXL2 localization was undetectable in Sertoli-cell-enclosed apoptotic testis-ova, whereas DMRT1 remained localized in Sertoli cells. These results indicated for the first time that based on the expression of female-specific sex genes, feminization of Sertoli cells precedes testis-ova differentiation induced by estrogen in mature testes in medaka; however, complete feminization of Sertoli cells was not induced in this study. Additionally, it is suggested strongly that Foxl2 and Gsdf expression constitute potential molecular markers for evaluating the effects of estrogenic chemicals on testicular somatic cells associated with estrogen-induced testis-ova differentiation in mature male medaka.

Oleic acid induces down-regulation of the granulosa cell identity marker FOXL2, and up-regulation of the Sertoli cell marker SOX9 in bovine granulosa cells

During negative energy balance, the concentration of different fatty acids, especially of oleic acid (OA) increases in the follicular fluid of cattle. Previously, we showed that OA induced morphological, physiological and molecular changes in cultured bovine granulosa cells. In our present study we analyzed effects of OA on the expression of markers for granulosa and Sertoli cell identity, FOXL2 and SOX9, respectively, in addition to effects on the FOXL2 regulated genes ESR2, FST, PTGS2 and PPARG. The results showed that OA down-regulated FOXL2, ESR2, FST and PPARG but up-regulated PTGS2 and SOX9. From these data we conclude that OA can compromise granulosa cell functionality and may initiate trans-differentiation processes in bovine granulosa cells. This novel mechanism may be causally involved in postpartum fertility problems of lactating dairy cows.