Mice Null for Frizzled4 (Fzd4−/−) Are Infertile and Exhibit Impaired Corpora Lutea Formation and Function1

Follicle-intrinsic and spatially distinct molecular programs drive follicle rupture and luteinization during ex vivo mammalian ovulation

During ovulation, the apical wall of the preovulatory follicle breaks down to facilitate gamete release. In parallel, the residual follicle wall differentiates into a progesterone-producing corpus luteum. Disruption of ovulation, whether through contraceptive intervention or infertility, has implications for women's health. In this study, we harness the power of an ex vivo ovulation model and machine-learning guided microdissection to identify differences between the ruptured and unruptured sides of the follicle wall. We demonstrate that the unruptured side exhibits clear markers of luteinization after ovulation while the ruptured side exhibits cell death signals. RNA-sequencing of individual follicle sides reveals 2099 differentially expressed genes (DEGs) between follicle sides without ovulation induction, and 1673 DEGs 12 h after induction of ovulation. Our model validates molecular patterns consistent with known ovulation biology even though this process occurs in the absence of the ovarian stroma, vasculature, and immune cells. We further identify previously unappreciated pathways including amino acid transport and Jag-Notch signaling on the ruptured side and glycolysis, metal ion processing, and IL-11 signaling on the unruptured side of the follicle. This study yields key insights into follicle-inherent, spatially-defined pathways that underlie follicle rupture, which may further understanding of ovulation physiology and advance women's health.

SDNOR, a Novel Antioxidative lncRNA, Is Essential for Maintaining the Normal State and Function of Porcine Follicular Granulosa Cells

Increasing evidence shows that lncRNAs, an important kind of endogenous regulator, are involved in the regulation of follicular development and female fertility, but the mechanism remain largely unknown. In this study, we found that SDNOR, a recently identified antiapoptotic lncRNA, is a potential multifunctional regulator in porcine follicular granulosa cells (GCs) through RNA-seq and multi-dimension analyses. SDNOR-mediated regulatory networks were established and identified that SOX9, a transcription factor inhibited by SDNOR, mediates SDNOR's regulation of the transcription of downstream targets. Functional analyses showed that loss of SDNOR significantly impairs GC morphology, inhibits cell proliferation and viability, reduces E2/P4 index, and suppresses the expression of crucial markers, including PCNA, Ki67, CDK2, CYP11A1, CYP19A1, and StAR. Additionally, after the detection of ROS, SOD, GSH-Px, and MDA, we found that SDNOR elevates the resistance of GCs to oxidative stress (OS) and also inhibits OS-induced apoptosis. Notably, GCs with high SDNOR levels are insensitive to oxidative stress, leading to lower apoptosis rates and higher environmental adaptability. In summary, our findings reveal the regulation of porcine GCs in response to oxidative stress from the perspective of lncRNA and demonstrate that SDNOR is an essential antioxidative lncRNA for maintaining the normal state and function of GCs.

Polychlorinated biphenyls alter hepatic m6A mRNA methylation in a mouse model of environmental liver disease

Exposure to polychlorinated biphenyls (PCBs) has been associated with liver injury in human cohorts and with nonalcoholic steatohepatitis (NASH) in mice fed a high fat diet (HFD). N (6)-methyladenosine (m6A) modification of mRNA regulates transcript fate, but the contribution of m6A modification on the regulation of transcripts in PCB-induced steatosis and fibrosis is unknown. This study tested the hypothesis that PCB and HFD exposure alters the levels of m6A modification in transcripts that play a role in NASH in vivo. Male C57Bl6/J mice were fed a HFD (12 wks) and administered a single oral dose of Aroclor1260, PCB126, or Aroclor1260 + PCB126. Genome-wide identification of m6A peaks was accomplished by m6A mRNA immunoprecipitation sequencing (m6A-RIP) and the mRNA transcriptome identified by RNA-seq. Exposure of HFD-fed mice to Aroclor1260 decreased the number of m6A peaks and m6A-containing genes relative to PCB vehicle control whereas PCB126 or the combination of Aroclor1260 + PCB126 increased m6A modification frequency. ∼41% of genes had one m6A peak and ∼49% had 2-4 m6A peaks. 117 m6A peaks were common in the four experimental groups. The Aroclor1260 + PCB126 exposure group showed the highest number (52) of m6A-peaks. qRT-PCR confirmed enrichment of m6A-containing fragments of the Apob transcript with PCB exposure. A1cf transcript abundance, m6A peak count, and protein abundance was increased with Aroclor1260 + PCB126 co-exposure. Irrespective of the PCB type, all PCB groups exhibited enriched pathways related to lipid/lipoprotein metabolism and inflammation through the m6A modification. Integrated analysis of m6A-RIP-seq and mRNA-seq identified 242 differentially expressed genes (DEGs) with increased or reduced number of m6A peaks. These data show that PCB exposure in HFD-fed mice alters the m6A landscape offering an additional layer of regulation of gene expression affecting a subset of gene responses in NASH.

The expression profile of WNT/β-catanin signalling genes in human oocytes obtained from polycystic ovarian syndrome (PCOS) patients

Polycystic ovarian syndrome (PCOS) is a chronic hormonal turmoil that is demonstrated in 2.2-27% of women of pre-menopausal age. This disease is a complex multigenic disorder that results from the interaction between excess androgen expression, genetic susceptibility and environmental influences. PCOS is associated with 40% of female infertility and endometrial cancer. The WNT/β-catenin signalling transduction pathway regulates aspects of cell proliferation, migration and cell fate determination in the tissue along with early embryonic development and controls the proper activation of the female reproductive system, along with regulating hormonal activity in ovarian granulosa cells. In the current study, we investigated the expression profiles of WNT/β-catenin signalling pathway genes (AXIN2, FZD4, TCF4, WNT3, WNT4, WNT5A, WNT7A, WNT1, APC, GSK3B and β-catenin) in a total of 13 oocyte samples. Seven of these samples were from polycystic women and six were from healthy women. The results of this study displayed the absence of expression of AXIN2, FZD4, TCF4, WNT5A, WNT3, WNT4 and WNT7A genes in ovaries from women with PCOS and from healthy women. While APC and β-catenin expression levels were similar in the oocytes of both patients and controls, conversely, WNT1 and GSK3β genes both showed elevated expression in the oocytes of patients with PCOS, therefore suggesting an association between aberrant expression of WNT1 and GSK3β and the pathogenesis of PCOS. The observations of the current study could be helpful to provide evidence regarding the pathogenesis of PCOS and its treatment.

Causal and Candidate Gene Variants in a Large Cohort of Women With Primary Ovarian Insufficiency

CONTEXT

A genetic etiology likely accounts for the majority of unexplained primary ovarian insufficiency (POI).

OBJECTIVE

We hypothesized that heterozygous rare variants and variants in enhanced categories are associated with POI.

DESIGN

The study was an observational study.

SETTING

Subjects were recruited at academic institutions.

PATIENTS

Subjects from Boston (n = 98), the National Institutes of Health and Washington University (n = 98), Pittsburgh (n = 20), Italy (n = 43), and France (n = 32) were diagnosed with POI (amenorrhea with an elevated follicle-stimulating hormone level). Controls were recruited for health in old age or were from the 1000 Genomes Project (total n = 233).

INTERVENTION

We performed whole exome sequencing (WES), and data were analyzed using a rare variant scoring method and a Bayes factor-based framework for identifying genes harboring pathogenic variants. We performed functional studies on identified genes that were not previously implicated in POI in a D. melanogaster model.

MAIN OUTCOME

Genes with rare pathogenic variants and gene sets with increased burden of deleterious variants were identified.

RESULTS

Candidate heterozygous variants were identified in known genes and genes with functional evidence. Gene sets with increased burden of deleterious alleles included the categories transcription and translation, DNA damage and repair, meiosis and cell division. Variants were found in novel genes from the enhanced categories. Functional evidence supported 7 new risk genes for POI (USP36, VCP, WDR33, PIWIL3, NPM2, LLGL1, and BOD1L1).

CONCLUSIONS

Candidate causative variants were identified through WES in women with POI. Aggregating clinical data and genetic risk with a categorical approach may expand the genetic architecture of heterozygous rare gene variants causing risk for POI.

FRAT1 promotes the angiogenic properties of human glioblastoma cells via VEGFA

Glioblastoma is a common central nervous system tumor and despite considerable advancements in treatment patient prognosis remains poor. Angiogenesis is a significant prognostic factor in glioblastoma, anti‑angiogenic treatments represent a promising therapeutic approach. Vascular endothelial growth factor A (VEGFA) is a predominant regulator of angiogenesis and mounting evidence suggests that the Wnt signaling pathway serves a significant role in tumor angiogenesis. As a positive regulator of the Wnt/β‑catenin signaling pathway, frequently rearranged in advanced T‑cell lymphomas‑1 (FRAT1) is highly expressed in human glioblastoma and is significantly associated with glioblastoma growth, invasion and migration, as well as poor patient prognosis. Bioinformatics analysis demonstrated that both VEGFA and FRAT1 were highly expressed in most tumor tissues and associated with prognosis. However, whether and how FRAT1 is involved in angiogenesis remains to be elucidated. In the present study, the relationship between FRAT1 and VEGFA in angiogenesis was investigated using the human glioblastoma U251 cell line. Small interfering RNAs (siRNAs) were used to silence FRAT1 expression in U251 cells, and the mRNA and protein expression levels of VEGFA, as well as the concentration of VEGFA in U251 cell supernatants, were determined using reverse transcription‑quantitative PCR, western blotting and ELISA. A tube formation assay was conducted to assess angiogenesis. The results demonstrated that siRNA knockdown significantly decreased the protein expression levels of FRAT1 in U251 cells and markedly decreased the mRNA and protein expression levels of VEGFA. Furthermore, the concentration of VEGFA in the cell supernatant was significantly reduced and angiogenesis was suppressed. These results suggested that FRAT1 may promote VEGFA secretion and angiogenesis in human glioblastoma cells via the Wnt/β‑catenin signaling pathway, supporting the potential use of FRAT1 as a promising therapeutic target in human glioblastoma.

Evaluating the Expression of Wnt Pathway Related Genes in Mouse Vitrified Preantral Follicles: An Experimental Study

Background

Wnt signaling pathway plays critical role in ovarian follicle development. Therefore, the aim of this study was to evaluate the effects of vitrification on the expression of Wnt pathway related genes in preantral follicles (PFs).

Methods

Isolated PFs (n=982) of 14-16 day old female mice (n=45: 15 for each group) were divided into fresh (n=265), toxicity (n=272), and vitrified (n=265). The mRNA levels of Wnt2, Wnt4, Lrp5 and Fzd3 were evaluated by real-time PCR on the 2nd and 6th days of culture period. One-way ANOVA was conducted to analyze the data. Post hoc Tukey's HSD was used for multiple comparisons and p-value less than 0.05 was considered statistically significant.

Results

The developmental parameters of fresh PFs were significantly higher than those of vitrified (p<0.001). There were no differences between fresh and vitrified PFs on the 2nd day of culture (p<0.001). Wnt4 expression levels decreased significantly in vitrified groups compared with fresh ones (p<0.001). Fzd3 and Lrp expression levels increased significantly in vitrified groups compared with those in the fresh group on the 2nd day (p<0.001). On the 6th day of culture period, the expression levels of Wnt2 and Fzd3 increased significantly in vitrified group compared to those of fresh group (p<0.001). Moreover, the expression levels of Wnt4 and Lrp increased significantly in toxicity groups compared to those of the control group (p<0.001).

Conclusion

Vitrification increase the expression levels of Wnt2, Lrp and Fzd3 genes of PFs during in vitro culture.

The Signaling Pathways Involved in Ovarian Follicle Development

The follicle is the functional unit of the ovary, which is composed of three types of cells: oocytes, granulosa cells, and theca cells. Ovarian follicle development and the subsequent ovulation process are coordinated by highly complex interplay between endocrine, paracrine, and autocrine signals, which coordinate steroidogenesis and gametogenesis. Follicle development is regulated mainly by three organs, the hypothalamus, anterior pituitary, and gonad, which make up the hypothalamic-pituitary-gonadal axis. Steroid hormones and their receptors play pivotal roles in follicle development and participate in a series of classical signaling pathways. In this review, we summarize and compare the role of classical signaling pathways, such as the WNT, insulin, Notch, and Hedgehog pathways, in ovarian follicle development and the underlying regulatory mechanism. We have also found that these four signaling pathways all interact with FOXO3, a transcription factor that is widely known to be under control of the PI3K/AKT signaling pathway and has been implicated as a major signaling pathway in the regulation of dormancy and initial follicular activation in the ovary. Although some of these interactions with FOXO3 have not been verified in ovarian follicle cells, there is a high possibility that FOXO3 plays a core role in follicular development and is regulated by classical signaling pathways. In this review, we present these signaling pathways from a comprehensive perspective to obtain a better understanding of the follicular development process.

Nanopore-based full-length transcriptome sequencing of Muscovy duck (Cairina moschata) ovary

Unlike mammals, studies on mechanisms that regulate waterfowl ovulation have been rarely reported. To advance our understanding of the ovulation differences in Muscovy duck, we utilized the Oxford Nanopore Technologies (ONT) to generate transcriptome data from 3 groups of female duck ovaries with ovulation differences (i.e., preovulation [PO], consecutive ovulation [CO], and inconsecutive ovulation [IO]). In this study, the full-length transcriptome data qualitative analysis showed that a total of 24,504 nonredundant full-length transcripts were generated, 19,060 new transcripts were discovered and 14,848 novel transcripts were successfully annotated. For the quantitative analysis, differentially expressed genes (DEGs) between the 3 groups were identified and functional properties were characterized. CTNNB1, IGF1, FOXO3, HSPA2, PTEN and SMC4 may be potential hub genes that regulate ovulation. Adhesion-related pathway, mTOR pathway, TGF-β signaling pathway and FoxO signaling pathway have been considered as important pathways that affect follicular development and ovulation. These results provide a more complete data source of full-length transcriptome for the further study of gene expression and genetics in Muscovy duck. The hub genes and potential mechanisms that affect the ovulation of Muscovy duck have been screened out to provide a scientific basis for breeding work to improve the reproduction performance of Muscovy duck.

Oocyte-secreted factors strongly stimulate sFRP4 expression in human cumulus cells

Secreted frizzled-related protein-4 (SFRP4) belongs to a family of soluble ovarian-expressed proteins that participate in female reproduction, particularly in rodents. In humans, SFRP4 is highly expressed in cumulus cells (CCs). However, the mechanisms that stimulate SFRP4 in CCs have not been examined. We hypothesise that oocyte-secreted factors such as growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) are involved in the regulation of SFRP4. Human CCs were collected from patients undergoing fertility treatments and treated with GDF9 or BMP15 or their combination in the presence of FSH or vehicle. FSH treatment significantly decreased SFRP4 mRNA levels when compared with nontreated cells. However, SFRP4 mRNA levels were increased significantly by GDF9 plus BMP15 in a concentration-dependent manner in the presence or absence of FSH. The combination of GDF9 plus BMP15 also increased SFRP4 protein levels and decreased the activity of the β-catenin/T cell factor-responsive promoter significantly. GDF9 plus BMP15 inhibited steroidogenic acute regulatory protein and LH/hCG receptor stimulation by FSH, while treatment with SFRP4 blocked the stimulatory effect of FSH on these genes. The evidence demonstrates that GDF9 and BMP15 act in coordination to stimulate SFRP4 expression and suggests that SFRP4 mediates the anti-luteinising effects of the oocyte in human CCs.

R-Spondin 2 and WNT/CTNNB1 Signaling Pathways Are Required for Porcine Follicle Development and In Vitro Maturation

The secretion of oocyte-derived paracrine factors, such as R-spondin2, is an essential mechanism for follicle growth by promoting the proliferation and differentiation of cumulus cells around oocytes. In the present study, we aimed to identify the effect of R-spondin2 during follicular development. First, R-spondin2-related factors (R-spondin2, CTNNB1, LGR4, and LGR5) were identified through immunofluorescence in porcine ovarian tissue. CTNNB1 was expressed in ooplasm, and CTNNB1 and LGR4 were expressed in granulosa cells. In addition, R-spondin2, LGR4, and LGR5 were expressed in the theca interna. These results imply that these proteins play a major role in porcine follicular development. In addition, the effects of R-spondin2 on the in vitro maturation process of porcine cumulus oocyte complexes and subsequent embryonic development were confirmed. A treatment of 100 ng/mL R-spondin2 in the in vitro maturation (IVM) process increased nuclear maturation and increased the expression of EGFR mRNA in cumulus cells. The EGFR-ERK signal is essential for oocyte maturation, ovulation, and luteinization. R-spondin2 treatment also increased the expression of CTNNB1 and EGFR in primary cultured cumulus cells. In conclusion, RSPO2 and WNT/CTNNB1 signaling pathways are required for porcine follicle development and are predicted to be involved in the EGFR-ERK signaling pathway.

Lithium-induced overexpression of β-catenin delays murine palatal shelf elevation by Cdc-42 mediated F-actin remodeling in mesenchymal cells

BACKGROUND

Lithium chloride (LiCl) is widely used for the treatment of manic and other psychotic disorders, but the administration of lithium can result in several congenital defects in the fetus, including cleft palate (Meng, Wang, Torensma, Jw & Bian, 2015) (Szabo, 1970). However, the mechanism of Lithium's action as a developmental toxicant in palatogenesis is not well known.

METHODS

In this study, hematoxylin-eosin and immunofluorescence staining were employed to evaluate the phenotypes and the expression of related markers in the LiCl-treated mice model. The palatal mesenchymal cells were cultured in vitro, and stimulated with LiCl or SKL2000, and co-treated with CASIN. β-catenin protein and other cytoskeleton associated markers were evaluated by Western blotting.

RESULTS

We found that Lithium disrupted palate elevation by increasing the expression of β-catenin in C57BL/6J mice with the high incidence of cleft palate (62.5%). LiCl disturbed the F-actin responsible for cytoskeletal remodeling in mesenchymal cells, which proved to be essential in generating the elevating force during palatal elevation. Additionally, our Western blotting analysis revealed that the overexpression of β-catenin resulted in up-regulation of Cdc42, which mediated the downstream F-actin synthesis.

CONCLUSIONS

We concluded the LiCl-induced β-catenin overexpression delayed murine palatal shelf elevation by disturbing Cdc42 mediated F-actin cytoskeleton synthesis in the palatal mesenchyme.

Conditional deletion of Wntless in granulosa cells causes impaired corpora lutea formation and subfertility

WNT proteins are widely expressed in the murine ovaries. WNTLESS is a regulator essential for all WNTs secretion. However, the complexity and overlapping expression of WNT signaling cascades have prevented researchers from elucidating their function in the ovary. Therefore, to determine the overall effect of WNT on ovarian development, we depleted the Wntless gene in oocytes and granulosa cells. Our results indicated no apparent defect in fertility in oocyte-specific Wntless knockout mice. However, granulosa cell (GC) specific Wntless deletion mice were subfertile and recurred miscarriages. Further analysis found that GC-specific Wntless knockout mice had noticeably smaller corpus luteum (CL) in the ovaries than control mice, which is consistent with a significant reduction in luteal cell marker gene expression and a noticeable increase in apoptotic gene expression. Also, the deletion of Wntless in GCs led to a significant decrease in ovarian HCGR and β-Catenin protein levels. In conclusion, Wntless deficient oocytes had no discernible impact on mouse fertility. In contrast, the loss of Wntless in GCs caused subfertility and impaired CL formation due to reduced LHCGR and β-Catenin protein levels, triggering GC apoptosis.

An induced pluripotent stem cell line (EHTJUi002-A) derived from a neonate with c.678G>A mutation in the gene FZD4 causing exudative vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is an autosomal dominant genetic disease. An induced pluripotent stem cell line (EHTJUi002-A) was generated from umbilical cord blood mononuclear cells (UCBMCs) of a neonate with heterozygous mutation of p.W226X(c.678G>A) in the FZD4 gene. This iPSC model offers a very valuable resource to study the pathological mechanism of FEVR in vitro.

WOMEN IN REPRODUCTIVE SCIENCE: Discovering science and the ovary: a career of joy

My career has been about discovering science and learning the joys of the discovery process itself. It has been a challenging but rewarding process filled with many exciting moments and wonderful colleagues and students. Although I went to college to become a French major, I ultimately stumbled into research while pursuing a Masters Degree in teaching. Thus, my research career began in graduate school where I was studying NAD kinase in the ovary as a possible regulator of steroidogenesis, a big issue in the late 1960s. After a short excursion of teaching in North Dakota, I became a postdoctoral fellow at the University of Michigan, where radio-immuno assays and radio receptor assays had just come on the scene and were transforming endocrinology from laborious bioassays to quantitative science and of course these assays related to the ovary. From there I went to Baylor College of Medicine, a mecca of molecular biology, cloning genes and generating mouse models. It has been a fascinating and joyous journey.

Non-canonical WNT5a regulates Epithelial-to-Mesenchymal Transition in the mouse ovarian surface epithelium

The ovarian surface epithelium (OSE) is a monolayer that covers the ovarian surface and is involved in ovulation by rupturing and enabling release of a mature oocyte and by repairing the wound after ovulation. Epithelial-to-mesenchymal transition (EMT) is a mechanism that may promote wound healing after ovulation. While this process is poorly understood in the OSE, in other tissues wound repair is known to be under the control of the local microenvironment and different growth factors such as the WNT signaling pathway. Among WNT family members, WNT4 and WNT5a are expressed in the OSE and are critical for the ovulatory process. The objective of this study was to determine the potential roles of WNT4 and WNT5a in regulating the OSE layer. Using primary cultures of mouse OSE cells, we found WNT5a, but not WNT4, promotes EMT through a non-canonical Ca2+-dependent pathway, up-regulating the expression of Vimentin and CD44, enhancing cell migration, and inhibiting the CTNNB1 pathway and proliferation. We conclude that WNT5a is a stimulator of the EMT in OSE cells, and acts by suppressing canonical WNT signaling activity and inducing the non-canonical Ca2+ pathway.

SMAD4 activates Wnt signaling pathway to inhibit granulosa cell apoptosis

The TGF-β and Wnt signaling pathways are interrelated in many cell types and tissues, and control cell functions in coordination. Here, we report that SMAD4, a downstream effector of the TGF-β signaling pathway, induces FZD4, a receptor of the Wnt signaling pathway, establishing a novel route of communication between these two pathways in granulosa cells (GCs). We found that SMAD4 is a strong inducer of FZD4, not only initiating FZD4 transcription but also activating FZD4-dependent Wnt signaling and GC apoptosis. Furthermore, we identified the direct and indirect mechanisms by which SMAD4 promotes expression of FZD4 in GCs. First, SMAD4 functions as a transcription factor to directly bind to the FZD4 promoter region to increase its transcriptional activity. Second, SMAD4 promotes production of SDNOR, a novel lncRNA that acts as a sponge for miR-29c, providing another mean to block miR-29c from degenerating FZD4 mRNA. Overall, our findings not only reveal a new channel of crosstalk between the TGF-β and Wnt signaling pathways, SMAD4–FZD4 axis, but also provide new insights into the regulatory network of GC apoptosis and follicular atresia. These RNA molecules, such as miR-29c and lnc-SDNOR, represent potential targets for treatment of reproductive diseases and improvement of female fertility.

APC2 is critical for ovarian WNT signalling control, fertility and tumour suppression

BACKGROUND

Canonical WNT signalling plays a critical role in the regulation of ovarian development; mis-regulation of this key pathway in the adult ovary is associated with subfertility and tumourigenesis. The roles of Adenomatous polyposis coli 2 (APC2), a little-studied WNT signalling pathway regulator, in ovarian homeostasis, fertility and tumourigenesis have not previously been explored. Here, we demonstrate essential roles of APC2 in regulating ovarian WNT signalling and ovarian homeostasis.

METHODS

A detailed analysis of ovarian histology, gene expression, ovulation and hormone levels was carried out in 10 week old and in aged constitutive APC2-knockout (Apc2-/-) mice (mixed background). Statistical significance for qRT-PCR data was determined from 95% confidence intervals. Significance testing was performed using 2-tailed Student's t-test, when 2 experimental cohorts were compared. When more were compared, ANOVA test was used, followed by a post-hoc test (LSD or Games-Howell). P-values of < 0.05 were considered statistically significant.

RESULTS

APC2-deficiency resulted in activation of ovarian WNT signalling and sub-fertility driven by intra-ovarian defects. Follicular growth was perturbed, resulting in a reduced rate of ovulation and corpora lutea formation, which could not be rescued by administration of gonadotrophins. Defects in steroidogenesis and follicular vascularity contributed to the subfertility phenotype. Tumour incidence was assessed in aged APC2-deficient mice, which also carried a hypomorphic Apc allele. APC2-deficiency in these mice resulted in predisposition to granulosa cell tumour (GCT) formation, accompanied by acute tumour-associated WNT-signalling activation and a histologic pattern and molecular signature seen in human adult GCTs.

CONCLUSIONS

Our work adds APC2 to the growing list of WNT-signalling members that regulate ovarian homeostasis, fertility and suppress GCT formation. Importantly, given that the APC2-deficient mouse develops tumours that recapitulate the molecular signature and histological features of human adult GCTs, this mouse has excellent potential as a pre-clinical model to study ovarian subfertility and transitioning to GCT, tumour biology and for therapeutic testing.

SFRP4 Is a Negative Regulator of Ovarian Follicle Development and Female Fertility

WNT signaling regulates a variety of ovarian processes, including follicle development, granulosa cell (GC) proliferation and differentiation, steroidogenesis, and ovulation. The secreted frizzled-related proteins (SFRPs) comprise a family of WNT signaling antagonists. Sfrp4 expression was previously reported to be induced in ovarian GCs and cumulus cells in vivo following human chorionic gonadotropin treatment, suggesting that it may play key roles in cumulus expansion, ovulation/luteinization, and corpus luteum (CL) function. In this study, we aimed to define the physiological roles of Sfrp4 in the ovary by gene targeting. Sfrp4-null female mice were found to produce larger litters than did their wild-type littermates. Although previous studies had suggested roles of Sfrp4 in luteal cell survival, no differences in CL formation, morphology, steroidogenesis, involution, or luteal cell apoptosis were found in Sfrp4-null mice. Likewise, cumulus expansion occurred normally in Sfrp4-null mice, with minimal changes in cumulus cell gene expression. Hyperfertility in the Sfrp4-null model was ultimately attributed to decreased antral follicle atresia, leading to an enhanced ovulatory rate. Increased expression of FSH- and LH-responsive genes was found in GCs from Sfrp4-null mice, and GCs isolated from Sfrp4-null mice were found to be hyperresponsive to FSH and LH in vitro. Although Sfrp2 was found to be overexpressed in the GCs of Sfrp4-null mice (suggesting a compensatory mechanism), Sfrp2-null mice had normal fertility and ovulatory rates, and Sfrp2/4 double knockout mice did not differ from Sfrp4-null mice. Taken together, our results suggest that SFRP4 acts to attenuate GC responsiveness to gonadotropins, thereby decreasing follicle survival, ovulatory rate, and fertility.

Wnt Signaling in vascular eye diseases

The Wnt signaling pathway plays a pivotal role in vascular morphogenesis in various organs including the eye. Wnt ligands and receptors are key regulators of ocular angiogenesis both during the eye development and in vascular eye diseases. Wnt signaling participates in regulating multiple vascular beds in the eye including regression of the hyaloid vessels, and development of structured layers of vasculature in the retina. Loss-of-function mutations in Wnt signaling components cause rare genetic eye diseases in humans such as Norrie disease, and familial exudative vitreoretinopathy (FEVR) with defective ocular vasculature. On the other hand, experimental studies in more prevalent vascular eye diseases, such as wet age-related macular degeneration (AMD), diabetic retinopathy (DR), retinopathy of prematurity (ROP), and corneal neovascularization, suggest that aberrantly increased Wnt signaling is one of the causations for pathological ocular neovascularization, indicating the potential of modulating Wnt signaling to ameliorate pathological angiogenesis in eye diseases. This review recapitulates the key roles of the Wnt signaling pathway during ocular vascular development and in vascular eye diseases, and pharmaceutical approaches targeting the Wnt signaling as potential treatment options.

Dynamic Changes in the Global MicroRNAome and Transcriptome Identify Key Nodes Associated With Ovarian Development in Chickens

The analysis of gene expression patterns during ovarian follicle development will advance our understanding of avian reproductive physiology and make it possible to improve laying performance. To gain insight into the molecular regulation of ovarian development, a systematic profiling of miRNAs and mRNAs at four key stages was conducted, using ovarian tissues from hens at 60 days of age (A), 100 days (B), 140 days-not yet laying (C), and 140 days-laying (D). Comparisons of consecutive stages yielded 73 differentially expressed miRNAs (DEMs) (14 for B vs. A, 8 for C vs. B, and 51 for D vs. C) and 2596 differentially expressed genes (DEGs) (51 for B vs. A, 20 for C vs. B, and 2579 for D vs. C). In addition, 174 DEMs (22 for C vs. A, 74 for D vs. A, and 78 for D vs. B) and 3205 DEGs (118 for C vs. A, 2284 for D vs. A, and 2882 for D vs. B) were identified between nonconsecutive stages. Some DEGs are involved in the Wnt and TGF-beta signaling pathways, which are known to affect ovarian development and ovulation. An integrative analysis of the miRNA and mRNA profiles identified 3166 putative miRNA-mRNA regulatory pairs containing 84 DEMs and 1047 DEGs. Functional annotation of the networks provides strong evidence that the miRNA regulatory networks may play vital roles in ovarian development and ovulation. Ten DEMs and 10 genes were validated by real-time quantitative PCR. The candidate miRNA-mRNA pairs gga-miR-200a-3p-SFRP4, gga-miR-101-3p-BMP5, gga-miR-32-5p-FZD4, and gga-miR-458b-5p-CTNNB1 potentially associated with ovarian development.

A Transcriptome-Wide Association Study Among 97,898 Women to Identify Candidate Susceptibility Genes for Epithelial Ovarian Cancer Risk

Large-scale genome-wide association studies (GWAS) have identified approximately 35 loci associated with epithelial ovarian cancer (EOC) risk. The majority of GWAS-identified disease susceptibility variants are located in noncoding regions, and causal genes underlying these associations remain largely unknown. Here, we performed a transcriptome-wide association study to search for novel genetic loci and plausible causal genes at known GWAS loci. We used RNA sequencing data (68 normal ovarian tissue samples from 68 individuals and 6,124 cross-tissue samples from 369 individuals) and high-density genotyping data from European descendants of the Genotype-Tissue Expression (GTEx V6) project to build ovarian and cross-tissue models of genetically regulated expression using elastic net methods. We evaluated 17,121 genes for their cis-predicted gene expression in relation to EOC risk using summary statistics data from GWAS of 97,898 women, including 29,396 EOC cases. With a Bonferroni-corrected significance level of P < 2.2 × 10-6, we identified 35 genes, including FZD4 at 11q14.2 (Z = 5.08, P = 3.83 × 10-7, the cross-tissue model; 1 Mb away from any GWAS-identified EOC risk variant), a potential novel locus for EOC risk. All other 34 significantly associated genes were located within 1 Mb of known GWAS-identified loci, including 23 genes at 6 loci not previously linked to EOC risk. Upon conditioning on nearby known EOC GWAS-identified variants, the associations for 31 genes disappeared and three genes remained (P < 1.47 × 10-3). These data identify one novel locus (FZD4) and 34 genes at 13 known EOC risk loci associated with EOC risk, providing new insights into EOC carcinogenesis.Significance: Transcriptomic analysis of a large cohort confirms earlier GWAS loci and reveals FZD4 as a novel locus associated with EOC risk. Cancer Res; 78(18); 5419-30. ©2018 AACR.

Core Binding Factor β Expression in Ovarian Granulosa Cells Is Essential for Female Fertility

Core binding factor β (CBFβ) is a non-DNA-binding partner of all RUNX proteins and critical for transcription activity of CBF transcription factors (RUNXs/CBFβ). In the ovary, the expression of Runx1 and Runx2 is highly induced by the luteinizing hormone (LH) surge in ovulatory follicles, whereas Cbfb is constitutively expressed. To investigate the physiological significance of CBFs in the ovary, the current study generated two different conditional mutant mouse models in which granulosa cell expression of Cbfb and Runx2 was reduced by Cre recombinase driven by an Esr2 promoter. Cbfbgc-/- and Cbfbgc-/- × Runx2gc+/- mice exhibited severe subfertility and infertility, respectively. In the ovaries of both mutant mice, follicles develop normally, but the majority of preovulatory follicles failed to ovulate either in response to human chorionic gonadotropin administration in pregnant mare serum gonadotropin-primed immature animals or after the LH surge at 5 months of age. Morphological and physiological changes in the corpus luteum of these mutant mice revealed the reduced size, progesterone production, and vascularization, as well as excessive lipid accumulation. In granulosa cells of periovulatory follicles and corpora lutea of these mice, the expression of Edn2, Ptgs1, Lhcgr, Sfrp4, Wnt4, Ccrl2, Lipg, Saa3, and Ptgfr was also drastically reduced. In conclusion, the current study provided in vivo evidence that CBFβ plays an essential role in female fertility by acting as a critical cofactor of CBF transcription factor complexes, which regulate the expression of specific key ovulatory and luteal genes, thus coordinating the ovulatory process and luteal development/function in mice.

Transcriptome profiling of bovine ovarian theca cells treated with fibroblast growth factor 9

We reported previously that fibroblast growth factor 9 (FGF9) acts as an antidifferentiation factor, stimulating proliferation of granulosa cells (GCs) and theca cells (TCs) while suppressing hormone-induced steroidogenesis of these cells. How FGF9 acts to simultaneously suppress steroidogenesis and stimulate proliferation remains to be fully elucidated. Thus, this study was undertaken to clarify the effects of FGF9 on the TC transcriptome. Ovaries were obtained from beef heifers at a local abattoir, TCs were isolated from large antral follicles, and cultured with or without 30 ng/mL of FGF9 for 24 h in the presence of LH and IGF-1. After treatment, total RNA was extracted from TC and processed for microarray using Affymetrix GeneChip Bovine Genome Arrays (n = 4/group). Transcriptome analysis comparing FGF9-treated TC with control TC using 1.3-fold cutoff, and a P < 0.05 significance level identified 355 differentially expressed transcripts, with 164 elements upregulated and 191 elements downregulated by FGF9. The ingenuity pathway analysis (IPA) was used to investigate how FGF9 treatment affects molecular pathways, biological functions, and the connection between molecules in bovine TC. The IPA software identified 346 pathways in response to FGF9 in TC involved in several biological functions and unveiled interesting relationships among genes related to cell proliferation (eg, CCND1, FZD5, and MYB), antioxidation/cytoprotection (eg, HMOX1 and NQO1), and steroidogenesis (eg, CYP11A1 and STAR). Overall, genes, pathways, and networks identified in this study painted a picture of how FGF9 may regulate folliculogenesis, providing novel candidate genes for further investigation of FGF9 functions in ovarian follicular development.

WNT Signaling in Cardiac and Vascular Disease

WNT signaling is an elaborate and complex collection of signal transduction pathways mediated by multiple signaling molecules. WNT signaling is critically important for developmental processes, including cell proliferation, differentiation and tissue patterning. Little WNT signaling activity is present in the cardiovascular system of healthy adults, but reactivation of the pathway is observed in many pathologies of heart and blood vessels. The high prevalence of these pathologies and their significant contribution to human disease burden has raised interest in WNT signaling as a potential target for therapeutic intervention. In this review, we first will focus on the constituents of the pathway and their regulation and the different signaling routes. Subsequently, the role of WNT signaling in cardiovascular development is addressed, followed by a detailed discussion of its involvement in vascular and cardiac disease. After highlighting the crosstalk between WNT, transforming growth factor-β and angiotensin II signaling, and the emerging role of WNT signaling in the regulation of stem cells, we provide an overview of drugs targeting the pathway at different levels. From the combined studies we conclude that, despite the sometimes conflicting experimental data, a general picture is emerging that excessive stimulation of WNT signaling adversely affects cardiovascular pathology. The rapidly increasing collection of drugs interfering at different levels of WNT signaling will allow the evaluation of therapeutic interventions in the pathway in relevant animal models of cardiovascular diseases and eventually in patients in the near future, translating the outcomes of the many preclinical studies into a clinically relevant context.

Deletion of RhoA in Progesterone Receptor-Expressing Cells Leads to Luteal Insufficiency and Infertility in Female Mice

Ras homolog gene family, member A (RhoA) is widely expressed throughout the female reproductive system. To assess its role in progesterone receptor-expressing cells, we generated RhoA conditional knockout mice RhoAd/d (RhoAf/f-Pgr-Cre+/-). RhoAd/d female mice had comparable mating activity, serum luteinizing hormone, prolactin, and estradiol levels and ovulation with control but were infertile with progesterone insufficiency, indicating impaired steroidogenesis in RhoAd/d corpus luteum (CL). RhoA was highly expressed in wild-type luteal cells and conditionally deleted in RhoAd/d CL. Gestation day 3.5 (D3.5) RhoAd/d ovaries had reduced numbers of CL, less defined corpus luteal cord formation, and disorganized CL collagen IV staining. RhoAd/d CL had lipid droplet and free cholesterol accumulation, indicating the availability of cholesterol for steroidogenesis, but disorganized β-actin and vimentin staining, indicating disrupted cytoskeleton integrity. Cytoskeleton is important for cytoplasmic cholesterol movement to mitochondria and for regulating mitochondria. Dramatically reduced expression of mitochondrial markers heat shock protein 60 (HSP60), voltage-dependent anion channel, and StAR was detected in RhoAd/d CL. StAR carries out the rate-limiting step of steroidogenesis. StAR messenger RNA expression was reduced in RU486-treated D3.5 wild-type CL and tended to be induced in progesterone-treated D3.5 RhoAd/d CL, with parallel changes of HSP60 expression. These data demonstrated the in vivo function of RhoA in CL luteal cell cytoskeleton integrity, cholesterol transport, StAR expression, and progesterone synthesis, and a positive feedback on StAR expression in CL by progesterone signaling. These findings provide insights into mechanisms of progesterone insufficiency.

Wnt signaling pathway in retinal vascularization

Wnt-signaling, a ubiquitous pathway that directs differentiation, cell polarity, and tissue specificity, has been implicated as an important gene-expression pathway in retinal development. An increasing body of evidence supports the importance of Wnt-signaling, and specifically, norrin-mediated Wnt-signaling in retinal development and retinal maintenance. Gene mutations affecting the Wnt-signaling pathways result in a variety of inherited vitreoretinopathies. Additionally, there is growing evidence that prematurity and associated retinopathy are associated with alterations in the Wnt-signaling pathways. Further investigations may allow for improved diagnoses, management, and therapies in the future.

Germ cell specific overactivation of WNT/βcatenin signalling has no effect on folliculogenesis but causes fertility defects due to abnormal foetal development

All the major components of the WNT signalling pathway are expressed in female germ cells and embryos. However, their functional relevance in oocyte biology is currently unclear. We examined ovaries collected from TCFGFP mice, a well-known Wnt reporter mouse model, and found dynamic changes in the Wnt/βcatenin signalling activity during different stages of oocyte development and maturation. To understand the functional importance of Wnt signalling in oocytes, we developed a mouse model with the germ cell-specific constitutive activation of βcatenin using cre recombinase driven by the DEAD (Asp-Glu-Ala-Asp) box protein 4 (Ddx4) gene promoter. Histopathological and functional analysis of ovaries from these mutant mice (Ctnnb1^ex3cko) showed no defects in ovarian functions, oocytes, ovulation and early embryonic development. However, breeding of the Ctnnb1^ex3cko female mice with males of known fertility never resulted in birth of mutant pups. Examination of uteri from time pregnant mutant females revealed defects in ectoderm differentiation leading to abnormal foetal development and premature death. Collectively, our work has established the role of active WNT/βcatenin signalling in oocyte biology and foetal development, and provides novel insights into the possible mechanisms of complications in human pregnancy such as repeated spontaneous abortion, sudden intrauterine unexpected foetal death syndrome and stillbirth.

Insights into granulosa cell tumors using spontaneous or genetically engineered mouse models

Granulosa cell tumors (GCTs) are rare sex cord-stromal tumors that have been studied for decades. However, their infrequency has delayed efforts to research their etiology. Recently, mutations in human GCTs have been discovered, which has led to further research aimed at determining the molecular mechanisms underlying the disease. Mouse models have been important tools for studying GCTs, and have provided means to develop and improve diagnostics and therapeutics. Thus far, several genetically modified mouse models, along with one spontaneous mouse model, have been reported. This review summarizes the phenotypes of these mouse models and their applicability in elucidating the mechanisms of granulosa cell tumor development.

Growth Arrest Specific-1 (GAS1) Is a C/EBP Target Gene That Functions in Ovulation and Corpus Luteum Formation in Mice

Ovulation and luteinization are initiated in preovulatory follicles by the luteinizing hormone (LH) surge; however, the signaling events that mediate LH actions in these follicles remain incompletely defined. Two key transcription factors that are targets of LH surge are C/EBPalpha and C/EBPbeta, and their depletion in granulosa cells results in complete infertility. Microarray analyses of these mutant mice revealed altered expression of a number of genes, including growth arrest specific-1 (Gas1). To investigate functions of Gas1 in ovulation- and luteinization-related processes, we crossed Cyp19a1-Cre and Gas1^flox/flox mice to conditionally delete Gas1 in granulosa and cumulus cells. While expression of Gas1 is dramatically increased in granulosa and cumulus cells around 12–16 h post-human chorionic gonadotropin (hCG) stimulation in wild-type mice, this increase is abolished in Cebpa/b double mutant and in Gas1 mutant mice. GAS1 is also dynamically expressed in stromal cells of the ovary independent of C/EBPalpha/beta. Female Gas1 mutant mice are fertile, exhibit enhanced rates of ovulation, increased fertility, and higher levels of Areg and Lhcgr mRNA in granulosa cells. The morphological appearance and vascularization of corpora lutea appeared normal in these mutant females. Interestingly, levels of mRNA for a number of genes (Cyp11a1, Star, Wnt4, Prlr, Cd52, and Sema3a) associated with luteinization are decreased in corpora lutea of Gas1 mutant mice as compared with controls at 24 h post-hCG; these differences were no longer detectable by 48 h post-hCG. The C/EBP target Gas1 is induced in granulosa cells and is associated with ovulation and luteinization.

Phylogenetic and Evolutionary Analyses of the Frizzled Gene Family in Common Carp (Cyprinus carpio) Provide Insights into Gene Expansion from Whole-Genome Duplications

In humans, the frizzled (FZD) gene family encodes 10 homologous proteins that commonly localize to the plasma membrane. Besides being associated with three main signaling pathways for cell development, most FZDs have different physiological effects and are major determinants in the development process of vertebrates and. Here, we identified and annotated the FZD genes in the whole-genome of common carp (Cyprinus carpio), a teleost fish, and determined their phylogenetic relationships to FZDs in other vertebrates. Our analyses revealed extensive gene duplications in the common carp that have led to the 26 FZD genes that we detected in the common carp genome. All 26 FZD genes were assigned orthology to the 10 FZD genes of on-land vertebrates, with none of genes being specific to the fish lineage. We postulated that the expansion of the FZD gene family in common carp was the result of an additional whole genome duplication event and that the FZD gene family in other teleosts has been lost in their evolution history with the reason that the functions of genes are redundant and conservation. Through the expression profiling of FZD genes in common carp, we speculate that the ancestral gene was likely capable of performing all functions and was expressed broadly, while some descendant duplicate genes only performed partial functions and were specifically expressed at certain stages of development.

WNT5a is required for normal ovarian follicle development and antagonizes gonadotropin responsiveness in granulosa cells by suppressing canonical WNT signaling

Whereas the roles of the canonical wingless-type MMTV (mouse mammary tumor virus) integration site family (WNT) signaling pathway in the regulation of ovarian follicle growth and steroidogenesis are now established, noncanonical WNT signaling in the ovary has been largely overlooked. Noncanonical WNTs, including WNT5a and WNT11, are expressed in granulosa cells (GCs) and are differentially regulated throughout follicle development, but their physiologic roles remain unknown. Using conditional gene targeting, we found that GC-specific inactivation ofWnt5a(but notWnt11) results in the female subfertility associated with increased follicular atresia and decreased rates of ovulation. Microarray analyses have revealed that WNT5a acts to down-regulate the expression of FSH-responsive genesin vitro, and corresponding increases in the expression of these genes have been found in the GCs of conditional knockout mice. Unexpectedly, we found that WNT5a regulates its target genes not by signalingviathe WNT/Ca(2+)or planar cell polarity pathways, but rather by inhibiting the canonical pathway, causing both β-catenin (CTNNB1) and cAMP responsive element binding (CREB) protein levels to decreaseviaa glycogen synthase kinase-3β-dependent mechanism. We further found that WNT5a prevents follicle-stimulating hormone and luteinizing protein from up-regulating the CTNNB1 and CREB proteins and their target genes, indicating that WNT5a functions as a physiologic inhibitor of gonadotropin signaling. Together, these findings identify WNT5a as a key regulator of follicle development and gonadotropin responsiveness.-Abedini, A., Zamberlam, G., Lapointe, E., Tourigny, C., Boyer, A., Paquet, M., Hayashi, K., Honda, H., Kikuchi, A., Price, C., Boerboom, D. WNT5a is required for normal ovarian follicle development and antagonizes gonadotropin responsiveness in granulosa cells by suppressing canonical WNT signaling.

Joint MiRNA/mRNA expression profiling reveals changes consistent with development of dysfunctional corpus luteum after weight gain

Obese women exhibit decreased fertility, high miscarriage rates and dysfunctional corpus luteum (CL), but molecular mechanisms are poorly defined. We hypothesized that weight gain induces alterations in CL gene expression. RNA sequencing was used to identify changes in the CL transcriptome in the vervet monkey (Chlorocebus aethiops) during weight gain. 10 months of high-fat, high-fructose diet (HFHF) resulted in a 20% weight gain for HFHF animals vs. 2% for controls (p = 0.03) and a 66% increase in percent fat mass for HFHF group. Ovulation was confirmed at baseline and after intervention in all animals. CL were collected on luteal day 7-9 based on follicular phase estradiol peak. 432 mRNAs and 9 miRNAs were differentially expressed in response to HFHF diet. Specifically, miR-28, miR-26, and let-7b previously shown to inhibit sex steroid production in human granulosa cells, were up-regulated. Using integrated miRNA and gene expression analysis, we demonstrated changes in 52 coordinately regulated mRNA targets corresponding to opposite changes in miRNA. Specifically, 2 targets of miR-28 and 10 targets of miR-26 were down-regulated, including genes linked to follicular development, steroidogenesis, granulosa cell proliferation and survival. To the best of our knowledge, this is the first report of dietary-induced responses of the ovulating ovary to developing adiposity. The observed HFHF diet-induced changes were consistent with development of a dysfunctional CL and provide new mechanistic insights for decreased sex steroid production characteristic of obese women. MiRNAs may represent novel biomarkers of obesity-related subfertility and potential new avenues for therapeutic intervention.

The role of WNT signaling in adult ovarian folliculogenesis

Wingless-type mouse mammary tumor virus integration site (WNT) signaling molecules are locally secreted glycoproteins that play important role in regulation of ovarian follicle maturation and steroid production. Components of the WNT signaling pathway have been demonstrated to impact reproductive functions, including embryonic development of the sex organs and regulation of follicle maturation controlling steroidogenesis in the postnatal ovary. Emerging evidence underscores the complexity of WNT signaling molecules in regulation of dynamic changes that occur in the ovary during the reproductive cycle. While disruption in the WNT signaling cascade has been recognized to have deleterious consequences to normal sexual development, more recent studies are beginning to highlight the importance of these molecules in adult ovarian function related to follicle development, corpus luteum formation, steroid production and fertility. Hormonal regulation of WNT genes and expression of members of the WNT signaling network, including WNT ligands, frizzled receptors, and downstream signaling components that are expressed in the postnatal ovary at distinct stages of the estrous cycle suggest a crucial role in normal ovarian function. Similarly, FSH stimulation of T-cell factor-dependent gene expression requires input from β-catenin, a lynchpin molecule in canonical WNT signaling, further indicating β-catenin participation in regulation of follicle maturation. This review will focus on the multiple functions of WNT signaling in folliculogenesis in the adult ovary.

Frizzled-4 Variations Associated with Retinopathy and Intrauterine Growth Retardation: A Potential Marker for Prematurity and Retinopathy

PURPOSE

To present the association between mutations affecting the Wnt-signaling receptor protein (FZD4), inherited vitreoretinopathies, and retinopathy of prematurity (ROP).

DESIGN

Retrospective analysis of prospective samples at a tertiary referral center.

PARTICIPANTS

Patients referred to our practice for management of a variety of pediatric vitreoretinopathies were offered participation in an ophthalmic biobank (421 participants with vitreoretinopathies were included in this study). Full-term healthy infants (n = 98) were recruited to the study as controls.

METHODS

Patients with various vitreoretinopathies were prospectively enrolled in an ophthalmic biobank, approved by the Human Investigation Committee at William Beaumont Hospital. Retrospective genetic analysis of the FZD4 gene was performed (Sanger sequencing). Participants with a diagnosis of familial exudative vitreoretinopathy (FEVR), Norrie disease, Coats' disease, bilateral persistent fetal vasculature, and ROP were reviewed for the presence of a FZD4 variant. Data retrieval included status of retinopathy (including staging when possible), gestational age (GA), birth weight (BW) (when available), and family and birth histories.

MAIN OUTCOME MEASURES

The association of FZD4 variants with the presence of vitreoretinopathy.

RESULTS

The sequence variation p.[P33S(;)P168S] is the most prevalent FZD4 variant and is statistically significant for ROP and FEVR (P = 4.6E-04 and P = 2.4E-03, respectively) compared with full-term newborns (P = 1.7E-01). In addition, infants expressing the sequence variation tended to have significantly lower BWs for respective GA (P = 0.04). This suggests that the FZD4 p.[P33S(;)P168S] variant may be a risk factor for retinopathy and restricted intrauterine growth.

CONCLUSIONS

Testing for FZD4 gene mutations is useful in patients with suspected FEVR and ROP. The relatively high prevalence of the p.[P33S(;)P168S] variant in ROP and intrauterine growth restriction suggests that it also may be a marker for increased risk of developing ROP and preterm birth.

Activation of Gq/11 in the mouse corpus luteum is required for parturition

Mice with a deletion of Gα(q/11) in granulosa cells were previously shown to be subfertile. They also have a reduced ovulatory response due to a deficiency in the ability of the activated LH receptor to fully induce the granulosa cell progesterone receptor. Because this conditional deletion of Gα(q/11) will interfere with the actions of any G protein-coupled receptor that activates G(q/11) in granulosa or luteal cells, we sought to determine whether the actions of other hormones that contribute to fertility were also impaired. We focused our attention on prostaglandin F2 (PGF2)α, because this hormone is known to activate phospholipase C (a prominent Gα(q/11) effector) in luteal cells and because the action of PGF2α on luteal cells is the first step in the murine parturition pathway. Our data show that the conditional deletion of Gα(q/11) from granulosa cells prevents the ability of PGF2α to induce Akr1c18 in luteal cells. Akr1c18 codes for 20α-hydroxysteroid dehydrogenase, an enzyme that inactivates progesterone. The PGF2α-mediated induction of this enzyme towards the end of pregnancy increases the inactivation of progesterone and precipitates parturition in mice. Thus, the conditional deletion of Gαq/11 from granulosa/luteal cells prevents the progesterone withdrawal that occurs at the end of pregnancy and impairs parturition. This novel molecular defect contributes to the subfertile phenotype of the mice with a deletion of Gα(q/11) from granulosa cells.

Lgr4 gene regulates corpus luteum maturation through modulation of the WNT-mediated EGFR-ERK signaling pathway

Luteal-phase insufficiency is one of the major causes of female infertility, but the molecular mechanisms are still largely unknown. Here we found that disruption of Lgr4/Gpr48, the newly identified receptor for R-spondins, greatly reduced female fertility in mice. The expression of Lgr4 was induced specifically in granulosa-lutein cells during luteinization. In Lgr4-deficient female mice, the estrous cycle was prolonged and serum progesterone levels were dramatically downregulated. In Lgr4(-/-) corpora lutea, the expression of key enzymes for steroidogenesis as well as common luteal marker genes was significantly decreased. Additionally, the activity of epidermal growth factor receptor (EGFR)-ERK signaling was attenuated in Lgr4(-/-) granulosa-lutein cells. We found that the maturation of Lgr4(-/-) cells was impaired in cultured primary granulosa cells, but the defect was partially rescued by reactivation of EGFR signaling by heparin-binding EGF-like growth factor treatment. We found that the expression of wingless-type MMTV integration site family (WNT)/catenin (cadherin associated protein), beta 1 (CTNNB1) downstream targets, including matrix metalloproteinase 9, which is a critical matrix metalloproteinase for activation of EGF-like factors, was significantly downregulated in Lgr4(-/-) ovaries. Matrix metalloproteinase 9 inhibitor treatment attenuated human chorionic gonadotropin- but not heparin-binding EGF-like growth factor-induced ERK activation and luteinization in primary granulosa cells. Together, we report that Lgr4 modulates WNT-mediated EGFR-ERK signaling to facilitate corpus luteum maturation and ovarian steroidogenesis to maintain female reproduction.

Wnt/β-catenin signaling regulates follicular development by modulating the expression of Foxo3a signaling components

Wnt signaling is an evolutionarily conserved pathway that regulates cell proliferation, differentiation and apoptosis. To investigate the possible role of Wnt signaling in the regulation of ovarian follicular development, secondary follicles were isolated and cultured in vitro in the presence or absence of its activator (LiCl or Wnt3a) or inhibitor (IWR-1). We have demonstrated that activation of β-catenin signals by activators dramatically suppressed follicular development by increasing granulosa cell apoptosis and inhibiting follicle steroidogenesis. In contrast, inhibition of Wnt signaling by IWR-1 was observed with better developed follicles and increased steroidogenesis. Further studies have shown that the transcription factor Forkhead box O3a (Foxo3a) and its downstream target molecules were modulated by the activators or the inhibitor. These findings provide evidence that Wnt signaling might negatively regulate follicular development potentially through Foxo3a signaling components.

Ovarian LGR5 is critical for successful pregnancy

Leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) is expressed in many organs, including female reproductive organs, and is a stem cell marker in the stomach and intestinal epithelium, hair follicles, and ovarian surface epithelium. Despite ongoing studies, the definitive physiological functions of Lgr5 remain unclear. We utilized mice with conditional deletion of Lgr5 (Lgr5(d/d)) in the female reproductive organs by progesterone receptor-Cre (Pgr(Cre)) to determine Lgr5's functions during pregnancy. Only 30% of plugged Lgr5(d/d) females delivered live pups, and their litter sizes were lower. We found that pregnancy failure in Lgr5(d/d) females was due to insufficient ovarian progesterone (P4) secretion that compromised decidualization, terminating pregnancy. The drop in P4 levels was reflected in elevated levels of P4-metabolizing enzyme 20α-hydroxysteroid dehydrogenase in corpora lutea (CL) inactivated of Lgr5. Of interest, P4 supplementation rescued decidualization failure and supported pregnancy to full term in Lgr5(d/d) females. These results provide strong evidence that Lgr5 is critical to normal CL function, unveiling a new role of LGR5 in the ovary.

Regulation of intestinal stem cells by Wnt and Notch signalling

The mammalian intestine is lined by an epithelial cell layer that is constantly renewed via a population of stem cells that reside in a specialised niche within intestinal crypts. The recent development of tools that permit genetic manipulation and lineage tracing of cells in vivo combined with culture methods in vitro has made the intestine particularly amenable for the study of signals that regulate stem cell function. Both Wnt and Notch signalling are critical regulators of stem cell fate. Gene knockout and transgenic expression analysis combined with meticulous analysis of lineage tracing and molecular characterisation has contributed to the definition of the mechanisms by which these pathways act during normal homeostasis and in disease states.

VEGFR-3 neutralization inhibits ovarian lymphangiogenesis, follicle maturation, and murine pregnancy

Lymphatic vessels surround follicles within the ovary, but their roles in folliculogenesis and pregnancy, as well as the necessity of lymphangiogenesis in follicle maturation and health, are undefined. We used systemic delivery of mF4-31C1, a specific antagonist vascular endothelial growth factor receptor 3 (VEGFR-3) antibody to block lymphangiogenesis in mice. VEGFR-3 neutralization for 2 weeks before mating blocked ovarian lymphangiogenesis at all stages of follicle maturation, most notably around corpora lutea, without significantly affecting follicular blood angiogenesis. The numbers of oocytes ovulated, fertilized, and implanted in the uterus were normal in these mice; however, pregnancies were unsuccessful because of retarded fetal growth and miscarriage. Fewer patent secondary follicles were isolated from treated ovaries, and isolated blastocysts exhibited reduced cell densities. Embryos from VEGFR-3-neutralized dams developed normally when transferred to untreated surrogates. Conversely, normal embryos transferred into mF4-31C1-treated dams led to the same fetal deficiencies observed with in situ gestation. Although no significant changes were measured in uterine blood or lymphatic vascular densities, VEGFR-3 neutralization reduced serum and ovarian estradiol concentrations during gestation. VEGFR-3-mediated lymphangiogenesis thus appears to modulate the folliculogenic microenvironment and may be necessary for maintenance of hormone levels during pregnancy; both of these are novel roles for the lymphatic vasculature.

Changes in granulosa cells' gene expression associated with increased oocyte competence in bovine

One of the challenges in mammalian reproduction is to understand the basic physiology of oocyte quality. It is believed that the follicle status is linked to developmental competence of the enclosed oocyte. To explore the link between follicles and competence in cows, previous research at our laboratory has developed an ovarian stimulation protocol that increases and then decreases oocyte quality according to the timing of oocyte recovery post-FSH withdrawal (coasting). Using this protocol, we have obtained the granulosa cells associated with oocytes of different qualities at selected times of coasting. Transcriptome analysis was done with Embryogene microarray slides and validation was performed by real-time PCR. Results show that the major changes in gene expression occurred from 20 to 44  h of coasting, when oocyte quality increases. Secondly, among upregulated genes (20-44  h), 25% were extracellular molecules, highlighting potential granulosa signaling cascades. Principal component analysis identified two patterns: one resembling the competence profile and another associated with follicle growth and atresia. Additionally, three major functional changes were identified: (i) the end of follicle growth (BMPR1B, IGF2, and RELN), involving interactions with the extracellular matrix (TFPI2); angiogenesis (NRP1), including early hypoxia, and potentially oxidative stress (GFPT2, TF, and VNN1) and (ii) apoptosis (KCNJ8) followed by iii) inflammation (ANKRD1). This unique window of analysis indicates a progressive hypoxia during coasting mixed with an increase in apoptosis and inflammation. Potential signaling pathways leading to competence have been identified and will require downstream testing. This preliminary analysis supports the potential role of the follicular differentiation in oocyte quality both during competence increase and decrease phases.

Oocyte-derived R-spondin2 promotes ovarian follicle development

R-spondin proteins are adult stem cell growth factors capable of stimulating gut development by activating LGR4, 5, and 6 receptors to promote Wnt signaling. Although multiple Wnt ligands and cognate Frizzled receptors are expressed in the ovary, their physiological roles are unclear. Based on bioinformatic and in situ hybridization analyses, we demonstrated the exclusive expression of R-spondin2 in oocytes of ovarian follicles. In cultured somatic cells from preantral follicles, R-spondin2 treatment (ED50: 3 ng/ml) synergized with Wnt3a to stimulate Wnt signaling. In cultured ovarian explants from prepubertal mice containing preantral follicles, treatment with R-spondin2, similar to follicle stimulating hormone, promoted the development of primary follicles to the secondary stage. In vivo administration of an R-spondin agonist stimulated the development of primary follicles to the antral stage in both immature mice and gonadotropin releasing hormone antagonist-treated adult mice. Subsequent treatment with gonadotropins allowed the generation of mature oocytes capable of undergoing early embryonic development and successful pregnancy. Furthermore, R-spondin agonist treatment of immune-deficient mice grafted with human cortical fragments stimulated the development of primary follicles to the secondary stage. Thus, oocyte-derived R-spondin2 is a paracrine factor essential for primary follicle development, and R-spondin agonists could provide a new treatment regimen for infertile women with low responses to the traditional gonadotropin therapy.

Activation of the canonical WNT signaling pathway promotes ovarian surface epithelial proliferation without inducing β-catenin/Tcf-mediated reporter expression

BACKGROUND

In response to activation of the canonical WNT signaling pathway, β-catenin cooperates with Lef/Tcf (lymphoid enhancer factor/T-cell factor) transcription factors to drive expression of Wnt target genes. The canonical WNT signaling pathway is involved in development, wound repair, and tumorigenesis. Studies examining the involvement of the canonical WNT signaling pathway in the development of ovarian surface epithelium (OSE) and ovarian carcinogenesis, however, have recently begun to emerge. In this study, we investigated the modulation of β-catenin and β-catenin/Tcf-signaling activity within the OSE using responsive transgenic mice and examined the response of primary OSE cells and ovarian cancer cell lines to activation of the canonical WNT signaling pathway.

RESULTS

β-catenin was localized to the lateral membrane of the ovarian epithelium. Stimulation of primary OSE cells in vitro with LiCl or Wnt3a led to GSK-3β inhibition and stabilization of β-catenin but failed to induce β-catenin/Tcf-mediated lacZ expression. Furthermore, E-cadherin expression was downregulated and the proliferative potency of OSE cells increased. Of four ovarian cancers cell lines screened, only the HEY cell line demonstrated induction of luciferase reporter upon canonical WNT stimulation.

CONCLUSIONS

These observations suggest that in ovarian adenocarcinoma, dysregulated WNT signaling may not always be indicative of β-catenin/Tcf-mediated transcriptional activity.

FZD1 regulates cumulus expansion genes and is required for normal female fertility in mice

WNT4 is required for normal ovarian follicle development and female fertility in mice, but how its signal is transduced remains unknown. Fzd1 encodes a WNT receptor whose expression is markedly induced in both mural granulosa cells and cumulus cells during the preovulatory period, in a manner similar to Wnt4. To study the physiological roles of FZD1 in ovarian physiology and to determine whether it serves as receptor for WNT4, Fzd1-null mice were created by gene targeting. Whereas rare Fzd1(-/-) females were sterile because of uterine fibrosis and ovarian tubulostromal hyperplasia, most were subfertile, producing ≈1 fewer pup per litter on average relative to controls. Unlike WNT4-deficient mice, ovaries from Fzd1(-/-) mice had normal weights, numbers of follicles, steroid hormone production, and WNT4 target gene expression levels. Microarray analyses of granulosa cells from periovulatory follicles revealed few genes whose expression was altered in Fzd1(-/-) mice. However, gene expression analyses of cumulus-oocyte complexes (COCs) revealed a blunted response of both oocyte (Zp3, Dppa3, Nlrp5, and Bmp15) and cumulus (Btc, Ptgs2, Sema3a, Ptx3, Il6, Nts, Alcam, and Cspg2) genes to the ovulatory signal, whereas the expression of these genes was not altered in WNT4-deficient COCs from Wnt4(tm1.1Boer/tm1.1Boer);Tg (CYP19A1-cre)1Jri mice. Despite altered gene expression, cumulus expansion appeared normal in Fzd1(-/-) COCs both in vitro and in vivo. Together, these results indicate that Fzd1 is required for normal female fertility and may act in part to regulate oocyte maturation and cumulus cell function, but it is unlikely to function as the sole ovarian WNT4 receptor.

β-Catenin/Tcf signaling in murine oocytes identifies nonovulatory follicles

WNTS are secreted glycoprotein molecules that signal through one of three signaling pathways. The best-characterized pathway involves stabilization of the multifunctional protein β-catenin, which in concert with members of the T-cell factor (Tcf) family activates specific gene transcription. We have examined putative Wnt/β-catenin in the murine ovary using transgenic mice harboring a reporter construct that activates β-galactosidase (lacZ) expression in response to β-catenin/Tcf binding (TopGal mice). Primordial and primary follicles did not stain for lacZ, and the proportion of β-catenin/Tcf signaling oocytes was lower than that of nonsignaling oocytes throughout estrous cycle. β-Catenin/Tcf signaling oocytes were observed in follicles from the secondary stage of development and their proportion increased with follicular maturation (secondary follicles, 20%; early antral and antral follicles, 70%). In contrast, the majority (>90%) of ovulated oocytes did not stain for lacZ. As the oocyte possesses components for WNT signal transduction, our data suggest that β-catenin/Tcf signaling is involved in the development of follicular ovulatory capability and identifies nonovulatory follicles.