Defects In Folliculogenesis Research Articles

Genetic evidence for differential functions of figla and nobox in zebrafish ovarian differentiation and folliculogenesis

FIGLA and NOBOX are important oocyte-specific transcription factors. Both figla-/- and nobox-/- mutants showed all-male phenotype in zebrafish due to increased dominance of the male-promoting pathway. The early diversion towards males in these mutants has precluded analysis of their roles in folliculogenesis. In this study, we attenuated the male-promoting pathway by deleting dmrt1, a key male-promoting gene, in figla-/- and nobox-/- fish, which allows a sufficient display of defects in folliculogenesis. Germ cells in figla-/-;dmrt1-/- double mutant remained in cysts without forming follicles. In contrast, follicles could form well but exhibited deficient growth in nobox-/-;dmrt1-/- double mutants. Follicles in nobox-/-;dmrt1-/- ovary could progress to previtellogenic (PV) stage but failed to enter vitellogenic growth. Such arrest at PV stage suggested a possible deficiency in estrogen signaling. This was supported by lines of evidence in nobox-/-;dmrt1-/-, including reduced expression of ovarian aromatase (cyp19a1a) and level of serum estradiol (E2), regressed genital papilla (female secondary sex characteristics), and more importantly the resumption of vitellogenic growth by E2 treatment. Expression analysis suggested Nobox might regulate cyp19a1a by controlling Gdf9 and/or Bmp15. Our discoveries indicate that Figla is essential for ovarian differentiation and follicle formation whereas Nobox is important for driving subsequent follicle development.

Does Baseline Serum Androgen Levels Have an Impact on Ovulation Induction Cycle Outcomes by Using Clomifene Citrate Among Infertile Women with Polycystic Ovary Syndrome? A Retrospective Cohort Study

OBJECTIVE: Hyperandrogenism is one of the diagnostic criteria for polycystic ovary syndrome. Women with polycystic ovary syndrome suffer from infertility due to anovulation. Hyperandrogenism results in follicular arrest at the antral stage during folliculogenesis. baseline intrinsic hyperandrogenism affects the success of ovulation induction or not. The relationship between baseline serum androgen levels and ovulation induction cycle outcomes by using clomifene citrate among infertile women with polycystic ovary syndrome has not been investigated thoroughly. STUDY DESIGN: Ovulation induction cycle outcomes of 35 infertile women diagnosed with polycystic ovary syndrome according to Rotterdam criteria who have received 50-100 mg/day clomifene citrate have been evaluated retrospectively. Menstrual cycle day 2-5 serum levels for gonadotropins, androgens, metabolic parameters, and ovulation induction cycle outcomes have been compared between women who have and have not achieved clinical pregnancy following treatment. RESULTS: Serum basal follicular stimulating hormone, LH, E2, fasting cholesterol, glucose, and HOMA-IR levels were comparable between these two groups of patients. Unlike other serum androgens, baseline serum-free testosterone level is significantly lower for patients who have achieved clinical pregnancy following ovulation induction with clomifene citrate. The baseline serum cut-off level for free testosterone to predict clinical pregnancy was 1.94 pg/ml with 75% sensitivity and 67% specificity rates. CONCLUSION: Lower or higher levels of androgenic milieu within the ovaries result in defective folliculogenesis and ovulation failure. Increased serum levels of free testosterone which is a proxy for ovarian androgen production might be a detrimental factor for clinical pregnancy rates of women with polycystic ovary syndrome by impairing proper folliculogenesis.

Immunopathogenesis of endometriosis - a novel look at an old problem.

This review aims to cast a look at endometriosis as a chronic and progressive gynecological disease.Endometriosis-affected tissues show a variety of pathologic features: alterations in cell growth, apoptosis, activation, angiogenesis, cell adhesion, and cytokine production. Fresh endometriotic lesions are associated with induction of an inflammatory reaction represented by overproduction of prostaglandins (PGE2), metalloproteinases (MMP-2, -3, -9), cytokines (IL-1β, IL-8, IFN-γ, TNF-α, MCP-1 and MIF) and adhesive molecules (ICAM-1, VCAM-1) and activation of synthesis of reactive oxygen and nitrogen species. The inflammatory process may lead to defective folliculogenesis by an altered follicular milieu. An increase in the number and change in function of macrophages, T- and B-lymphocytes and reduction of NK cells have been reported. Treg lymphocytes are known to play an extremely important role in controlling and modulating changes in the aberrant immune response in endometriosis. Dysregulation of the immune system results in both increased progression of endometriosis and its severity. In inflammatory conditions the immune cells provide immune defense at the local level – in peritoneal fluid – and could further cause: 1) a decrease of the number of NK CD16+ cells with expression of KIRs and an increase of NK CD57+; 2) increased numbers of CD8+ cells and CD11b– immature dendritic cells; 3) an increase of FoxP3 expression in the regulatory T cell (Treg) population; 4) an increase of macrophages activating T- and B-lymphocytes leading to elevated synthesis of cytokines and/or autoantibodies. We may conclude that endometriosis resembles an immunodependent disease with the autoimmune background and breakdown of immunosuppressive mechanisms. Further immunological investigations may open a new avenue to discover innovative immunomodulatory treatments of endometriosis.

Abnormal early folliculogenesis due to impeded pyruvate metabolism in mouse oocytes†.

Fetal ovarian germ cells show characteristic energy metabolism status, such as enhanced mitochondrial metabolism as well as glycolysis, but their roles in early folliculogenesis are unclear. We show here that inhibition of pyruvate uptake to mitochondria by UK5099 in organ cultures of fetal mouse ovaries resulted in repressed early folliculogenesis without affecting energy production, survival of oocytes, or meiosis. In addition, the abnormal folliculogenesis by UK5099 was partially rescued by α-ketoglutarate and succinate, intermediate metabolites in the TCA cycle, suggesting the importance of those metabolites. The expression of TGFβ-related genes Gdf9 and Bmp15 in ovarian germ cells, which are crucial for folliculogenesis, was downregulated by UK5099, and the addition of recombinant GDF9 partially rescued the abnormal folliculogenesis induced by UK5099. We also found that early folliculogenesis was similarly repressed, as in the culture, in the ovaries of a germ cell-specific knockout of Mpc2, which encodes a mitochondria pyruvate carrier that is targeted by UK5099. These results suggest that insufficient Gdf9 expression induced by abnormal pyruvate metabolism in oocytes results in early follicular dysgenesis, which is a possible cause of defective folliculogenesis in humans.

Implantation failure and embryo loss contribute to subfertility in female mice mutant for chromatin remodeler Cecr2†.

Defects in the maternal reproductive system that result in early pregnancy loss are important causes of human female infertility. A wide variety of biological processes are involved in implantation and establishment of a successful pregnancy. Although chromatin remodelers have been shown to play an important role in many biological processes, our understanding of the role of chromatin remodelers in female reproduction remains limited. Here, we demonstrate that female mice mutant for chromatin remodeler Cecr2 are subfertile, with defects detected at the peri-implantation stage or early pregnancy. Using both a less severe hypomorphic mutation (Cecr2GT) and a more severe presumptive null mutation (Cecr2Del), we demonstrate a clear difference in the severity of the phenotype depending on the mutation. Although neither strain shows detectable defects in folliculogenesis, both Cecr2GT/GT and Cecr2GT/Del dams show defects in pregnancy. Cecr2GT/GT females have a normal number of implantation sites at embryonic day 5.5 (E5.5), but significant embryo loss by E10.5 accompanied by the presence of vaginal blood. Cecr2GT/Del females show a more severe phenotype, with significantly fewer detectable implantation sites than wild type at E5.5. Some Cecr2GT/Del females also show premature loss of decidual tissue after artificial decidualization. Together, these results suggest a role for Cecr2 in the establishment of a successful pregnancy.

Influence of mouse defective zona pellucida in folliculogenesis on apoptosis of granulosa cells and developmental competence of oocytes†.

Zona pellucida (ZP), which enwraps the oocyte during folliculogenesis, initially forms in the primary follicle and plays an important role in female fertility. Here, we investigated a mouse strain ("mutant mice" for short) carrying two types of ZP defects in folliculogenesis, i.e., ZP thinned (but intact) and ZP cracked, caused by targeted mutation in the Zp1 gene. Using this mutant mouse strain and wild-type mouse as control, we studied the effects of the ZP defects on the development of oocytes and granulosa cells during folliculogenesis. For each ZP defect, we examined the morphology of transzonal projections and apoptosis of granulosa cells in the corresponding growing follicles, as well as the morphology of corresponding ovulated eggs and their abilities to develop into viable individuals. Our results suggested that ZP integrity rather than thickness or porosity is crucial for preventing the ectopia of granulosa cells, maintaining adequate routine bilateral signaling between oocyte and surrounding granulosa cells, and thus for ensuring the survival of granulosa cells and the establishment of the full developmental competence of oocytes. This is the first study to elucidate the effects of different degrees of ZP defects caused by the same gene mutation, on the apoptosis of granulosa cells and developmental competence of oocytes, and to explore the potential mechanisms underlying these effects.

Mitofusin1 in oocyte is essential for female fertility

Mitofusins (Mfn) are the important regulators of mitochondrial organization in mammalian cells; however, their roles during oocyte development remain unknown. In the present study, we generated mice with oocyte-specific knockout of Mfn1 or Mfn2 (Mfn1fl/fl;Zp3-Cre or Mfn2fl/fl;Zp3-Cre). We report that deletion of Mfn1, but not Mfn2, in oocytes leads to female mice sterility, associated with the defective folliculogenesis and impaired oocyte quality. In specific, follicles are arrested at secondary stage in Mfn1fl/fl;Zp3-Cre mice, accompanying with the reduced proliferation of granulosa cells. Moreover, alterations of mitochondrial structure and distribution pattern are readily observed in Mfn1-null oocytes. Consistent with this, mitochondrial activity and function are severely disrupted in oocytes from Mfn1fl/fl;Zp3-Cre mice. In addition, the differentially expressed genes in Mfn1-deleted oocytes are also identified by whole-transcriptome sequencing. In sum, these results demonstrate that Mfn1-modulated mitochondrial function is essential for oocyte development and folliculogenesis, providing a novel mechanism determining female fertility.

Thyrocyte-specific deletion of insulin and IGF-1 receptors induces papillary thyroid carcinoma-like lesions through EGFR pathway activation.

Insulin and insulin-like growth factor (IGF)-1 signaling in the thyroid are thought to be permissive for the coordinated regulation by thyroid-stimulating hormone (TSH) of thyrocyte proliferation and hormone production. However, the integrated role of insulin receptor (IR) and IGF-1 receptor (IGF-1R) in thyroid development and function has not been explored. Here, we generated thyrocyte-specific IR and IGF-1R double knockout (DTIRKO) mice to precisely evaluate the coordinated functions of these receptors in the thyroid of neonates and adults. Neonatal DTIRKO mice displayed smaller thyroids, paralleling defective folliculogenesis associated with repression of the thyroid-specific transcription factor Foxe1. By contrast, at postnatal day 14, absence of IR and IGF-1R paradoxically induced thyrocyte proliferation, which was mediated by mTOR-dependent signaling pathways. Furthermore, we found elevated production of TSH during the development of follicular hyperplasia at 8 weeks of age. By 50 weeks, all DTIRKO mice developed papillary thyroid carcinoma (PTC)-like lesions that correlated with induction of the ErbB pathway. Taken together, these data define a critical role for IR and IGF-1R in neonatal thyroid folliculogenesis. They also reveal an important reciprocal relationship between IR/IGF-1R and TSH/ErbB signaling in the pathogenesis of thyroid follicular hyperplasia and, possibly, of papillary carcinoma.

Vitamin D Receptor TaqI Polymorphism Is Associated With Reduced Follicle Number in Women Utilizing Assisted Reproductive Technologies.

Calcitriol, or 1,25-hydroxycholecalciferol, is the active form of vitamin D. It binds and activates vitamin D receptor (VDR). Infertility and defective folliculogenesis have been observed in female vdr-knockout mice; however, whether VDR polymorphisms affect human ovarian responses to controlled ovarian stimulation (COS) remains unclear. We hypothesized that VDR polymorphisms are associated with infertility and COS responses. Thus, we evaluated the association between the TaqI, BsmI, and FokI VDR polymorphisms and ovarian responses in women undergoing COS. In this study, we recruited a control group (n = 121) comprising volunteers with a history of natural conception and a second group of women undergoing COS (n = 70). TaqI, BsmI, and FokI genotyping was performed via restriction fragment length polymorphism analysis or TaqMan qPCR and Sanger sequencing. Intrafollicular 25(OH)D contents were measured in follicular fluid collected from COS patients during oocyte retrieval. Ovarian response parameters were obtained from patient medical records. There were no significant differences in the genotype frequencies of VDR polymorphisms (TaqI, BsmI and FokI) between the control and COS groups. However, the allele frequency of TaqI (C allele) was significantly lower in the COS group than in the control group (p = 0.02). Follicle number but not oocyte number was lower in patients with TaqI polymorphic (TC/CC) genotypes (p = 0.03). Importantly, the ratio between the number of follicles retrieved and intrafollicular estradiol concentrations was higher in patients with the TC/CC TaqI genotypes (p < 0.02). We identified an association between the VDR TaqI polymorphism and reduced follicle number in women undergoing COS, suggesting that VDR signaling affects the ovarian response to stimulation via unknown mechanisms.

Endometriosis, especially mild disease: a risk factor for miscarriages

To investigate the prevalence of miscarriage in women with endometriosis (WwE) compared with disease-free control women (CW). Cross-sectional analysis nested in a retrospective observational study (n = 940). Hospitals and associated private practices. Previously pregnant women (n = 268) within reproductive age in matched pairs. Retrospective analysis of surgical reports and self-administered questionnaires. Rate of miscarriage, subanalysis for fertility status (≤12 vs. >12months' time to conception), endometriosis stages (revised American Society of Reproductive Medicine classification [rASRM] I/II vs. III/IV) and phenotypic localizations (superficial peritoneal, ovarian, and deep infiltrating endometriosis). The miscarriage rate was higher in WwE (35.8% [95% confidence interval 29.6%-42.0%]) compared with CW (22.0% [16.7%-27.0%]); adjusted incidence risk ratio of 1.97 (95% CI 1.41-2.75). This remained significant in subfertile WwE (50.0% [40.7%-59.4%]) vs. CW (25.8% [8.5%-41.2%]) but not in fertile WwE (24.5% [16.3%-31.6%]) vs. CW (21.5% [15.9%-26.8%]). The miscarriage rate was higher in women with milder forms (rASRM I/II 42.1% [32.6%-51.4%] vs. rASRM III/IV 30.8% [22.6%-38.7%], compared with 22.0% [16.7%-27.0%] in CW), and in women with superficial peritoneal endometriosis (42.0% [32.0%-53.9%]) compared with ovarian endometriosis (28.6% [17.7%-38.7%]) and deep infiltrating endometriosis (33.9% [21.2%-46.0%]) compared with CW (22.0% [16.7%-27.0%]). Mild endometriosis, as in superficial lesions, is related to a great extent of inflammatory disorder, possibly leading to defective folliculogenesis, fertilization, and/or implantation, presenting as increased risk of miscarriage. NCT02511626.

Inactivation of Retinoblastoma Protein (Rb1) in the Oocyte: Evidence That Dysregulated Follicle Growth Drives Ovarian Teratoma Formation in Mice.

The origin of most ovarian tumors is undefined. Here, we report development of a novel mouse model in which conditional inactivation of the tumor suppressor gene Rb1 in oocytes leads to the formation of ovarian teratomas (OTs). While parthenogenetically activated ooctyes are a known source of OT in some mutant mouse models, enhanced parthenogenetic propensity in vitro was not observed for Rb1-deficient oocytes. Further analyses revealed that follicle recruitment and growth is disrupted in ovaries of mice with conditional inactivation of Rb1, leading to abnormal accumulation of secondary/preantral follicles. These findings underpin the concept that miscues between the germ cell and somatic compartments cause premature oocyte activation and the formation of OTs. Furthermore, these results suggest that defects in folliculogenesis and a permissive genetic background are sufficient to drive OT development, even in the absence of enhanced parthenogenetic activation. Thus, we have discovered a novel role of Rb1 in regulating the entry of primordial oocytes into the pool of growing follicles and signaling between the oocyte and granulosa cells during the protracted process of oocyte growth. Our findings, coupled with data from studies of other OT models, suggest that defects in the coordinated regulation between growth of the oocyte and somatic components in follicles are an underlying cause of OT formation.

The effects of phthalates on the ovary.

Phthalates are commonly used as plasticizers in the manufacturing of flexible polyvinyl chloride products. Large production volumes of phthalates and their widespread use in common consumer, medical, building, and personal care products lead to ubiquitous human exposure via oral ingestion, inhalation, and dermal contact. Recently, several phthalates have been classified as reproductive toxicants and endocrine-disrupting chemicals based on their ability to interfere with normal reproductive function and hormone signaling. Therefore, exposure to phthalates represents a public health concern. Currently, the effects of phthalates on male reproduction are better understood than the effects on female reproduction. This is of concern because women are often exposed to higher levels of phthalates than men through their extensive use of personal care and cosmetic products. In the female, a primary regulator of reproductive and endocrine function is the ovary. Specifically, the ovary is responsible for folliculogenesis, the proper maturation of gametes for fertilization, and steroidogenesis, and the synthesis of necessary sex steroid hormones. Any defect in the regulation of these processes can cause complications for reproductive and non-reproductive health. For instance, phthalate-induced defects in folliculogenesis and steroidogenesis can cause infertility, premature ovarian failure, and non-reproductive disorders. Presently, there is a paucity of knowledge on the effects of phthalates on normal ovarian function; however, recent work has established the ovary as a target of phthalate toxicity. This review summarizes what is currently known about the effects of phthalates on the ovary and the mechanisms by which phthalates exert ovarian toxicity, with a particular focus on the effects on folliculogenesis and steroidogenesis. Further, this review outlines future directions, including the necessity of examining the effects of phthalates at doses that mimic human exposure.

GDF9 Modulates the Reproductive and Tumor Phenotype of Female Inha-Null Mice1

Intraovarian factors play important roles in coordinating germ cell and somatic cell growth in the ovary. Prior to the onset of gonadotropin stimulation and reproductive cyclicity, follicle development is dependent upon locally produced growth factors, such as the transforming growth factor beta family members inhibin, activin, and GDF9. In the absence of inhibin in prepubertal mice (Inha(-/-)), there are marked alterations in preantral follicle growth, but no evidence of ovarian tumors characteristic of adult Inha-null mice. To ascertain the contribution of GDF9 to the Inha-null phenotype, we analyzed folliculogenesis in postnatal Inha Gdf9 double knockout mice. Deletion of Gdf9 from Inha(-/-) rescues the initial growth defects found at early follicle stages in Inha(-/-) ovaries, but surprisingly enhances the onset of pretumor lesions. The normalization of growth dynamics between granulosa cells and oocytes of Inha Gdf9 double knockout mice is also accompanied by a reduction in levels of the activin/inhibin beta B subunit, Inhbb, which is upregulated in Inha(-/-) ovaries. However, at later ages, Inha Gdf9 double knockout ovaries are similar to Inha(-/-) ovaries, and show upregulation of the activin/inhibin subunits and downregulation of the growth factor, kit ligand, thus resulting in a local environment that is growth-promoting for granulosa cells but growth-inhibitory for oocytes. These data suggest a sequential mechanism of action initiated by GDF9 in the Inha knockout mouse that promotes defective folliculogenesis. These studies thus provide a novel role for GDF9 in causing reproductive defects and suppressing tumor initiation in the Inha(-/-) mouse model.

Ovary-Driven Hyperandrogenemia Does Not Induce Metabolic Disorder.

Obesity, metabolic disorder, and infertility have an intertwined relationship as shown in patients with polycystic ovarian syndrome; however, the causal relationships among them are yet to be determined. Our previous studies showed that a high-fat diet (34% fat)-induced metabolic disorder caused defects in folliculogenesis, ovulation, and corpus luteum formation, eventually resulting in the loss of fertility. In this study, we aimed to determine whether ovarian dysfunction leads to metabolic disorder. A strain of mice that exhibits constant hyperandrogenemia (HA) was subjected to metabolic examination. We generated this HA mouse line by inducing a null mutation in estrogen receptor alpha (ERa or Esr1) gene selectively in the ovarian theca cells (theca specific Esr1 knockout; thEsr1KO). The thEsr1KO (HA) and wild type littermates (control) were housed together at the age of 1.5 months and fed with regular diet, and their weight growth patterns were measured for next 3 months. Until then, no differences in weight growth (22.6±0.6g HA vs. 22.7±0.8g control) and metabolic indices (body fat ratio, glucose tolerance, insulin resistance, food consumption and energy expenditure) were seen between the HA and control mice. The mice were then fed with either regular or high fat diet for next 3 months, followed by measurement of weight growth patterns and metabolic indices. There was no difference in weight between HA (28.9±1.7g) and control mice (31.0±2.1g), but was between the mice fed with high fat diet (32.6±1.6g) and regular diet (25.9±0.5g). Furthermore, no significant differences in metabolic indices were noted between HA and control mice: for example, body fat ratio (37.2±4.1% HA vs. 40.5±2.0% control), food consumption (11.1±0.9g HA vs. 10.8±1.7g control), and energy expenditure (13.8±0.8Kcal HA vs. 13.6±0.7Kcal). In all of the metabolic indices measured, significant differences were seen between high-fat diet group and regular diet groups of mice. Taken together, while metabolic disorder does cause ovarian dysfunction, this study demonstrates that ovary-driven hyperandrogenemia does not induce metabolic disorder.

Defective folliculogenesis in female mice lacking Vaccinia-related kinase 1

The Vaccinia-related kinase 1(VRK1), which is generally implicated in modulating cell cycle, plays important roles in mammalian gametogenesis. Female infertility in VRK1-deficient mice was reported to be caused by defective meiotic progression in oocyte at postovulatory stage. VRK1 roles in folliculogenesis, however, remain largely unknown. Here, accurate quantification of folliculogenesis is performed by a direct visualization of ‘intact’ ovary in 3-dimensions (3-D) using a synchrotron X-ray microtomography. In VRK1-deficient ovaries, the numbers of pre-antral and antral follicles are significantly reduced by 38% and 46%, respectively, comparing to control. The oocytes volumes in antral and Graffian follicles also decrease by 42% and 37% in the mutants, respectively, indicating defects in oocyte quality at preovulatory stage. Genetic analysis shows that gene expressions related to folliculogenesis are down-regulated in VRK1-deficient ovaries, implying defects in folliculogenesis. We suggest that VRK1 is required for both follicle development and oocyte growth in mammalian female reproduction system.

Association study of four key folliculogenesis genes in polycystic ovary syndrome

Polycystic ovaries and impaired fertility are the result of abnormal folliculogenesis. Our objective was to determine the role of four candidate folliculogenesis genes in the development of polycystic ovary syndrome (PCOS). Women with and without PCOS (335 cases; 198 controls) were genotyped for single nucleotide polymorphisms in GDF9, BMP15, AMH, and AMHR2. Variants in these genes were not associated with PCOS. Certain GDF9 variants were associated with hirsutism scores and parity in PCOS patients. GDF9 may thus serve as a modifier gene. These results suggest that inherited defects in folliculogenesis are not major factors in the genetic susceptibility to PCOS.

TBP2 is essential for germ cell development by regulating transcription and chromatin condensation in the oocyte.

Development of the germline requires consecutive differentiation events. Regulation of these has been associated with germ cell-specific and pluripotency-associated transcription factors, but the role of general transcription factors (GTFs) remains elusive. TATA-binding protein (TBP) is a GTF involved in transcription by all RNA polymerases. During ovarian folliculogenesis in mice the vertebrate-specific member of the TBP family, TBP2/TRF3, is expressed exclusively in oocytes. To determine TBP2 function in vivo, we generated TBP2-deficient mice. We found that Tbp2(-/-) mice are viable with no apparent phenotype. However, females lacking TBP2 are sterile due to defective folliculogenesis, altered chromatin organization, and transcriptional misregulation of key oocyte-specific genes. TBP2 binds to promoters of misregulated genes, suggesting that TBP2 directly regulates their expression. In contrast, TBP ablation in the female germline results in normal ovulation and fertilization, indicating that in these cells TBP is dispensable. We demonstrate that TBP2 is essential for the differentiation of female germ cells, and show the mutually exclusive functions of these key core promoter-binding factors, TBP and TBP2, in the mouse.

Haploinsufficiency for Adrenomedullin Reduces Pinopodes and Diminishes Uterine Receptivity in Mice1

Adrenomedullin (AM) is a multifunctional peptide vasodilator that signals through a G-protein-coupled receptor when the receptor, called calcitonin receptor-like receptor (CL), is associated with a receptor activity-modifying protein 2 (RAMP2). We demonstrated previously that haploinsufficieny for each of these genes led to reduced maternal fertility, and that even a modest genetic reduction of AM peptide caused maternal defects in implantation, placentation, and fetal growth. Here, we further demonstrate that Adm(+/-) female mice displayed reduced pregnancy success rates that were not caused by defects in folliculogenesis, ovulation, or fertilization. The poor fertility of Adm(+/-) female mice could not be rescued by transfer of wild-type blastocysts, which suggested an underlying defect in uterine receptivity. In fact, we found that Adm, Calcrl, and Ramp2 gene expressions are tightly and spatiotemporally regulated in the luminal epithelial cells of the uterus during the estrus cycle and the peri-implantation period. RAMP3, which also generates an AM receptor when associated with CL, had a diametrically opposite expression pattern than that of Adm, Calcrl, and Ramp2 and was most robustly induced in the stroma of the uterus. Finally, we discovered that Adm(+/-) female mice have a substantially reduced number of pinopodes on the uterine luminal epithelial surface, which is indicative and possibly causative of the poor uterine receptivity. Taken together, our studies identify a new class of pharmacologically tractable proteins that are involved in establishing uterine receptivity through the regulation of pinopode formation.

Subfertility with Defective Folliculogenesis in Female Mice Lacking Testicular Orphan Nuclear Receptor 4

Testicular orphan nuclear receptor 4 (TR4) plays essential roles for normal spermatogenesis in male mice. However, its roles in female fertility and ovarian function remain largely unknown. Here we found female mice lacking TR4 (TR4-/-) displayed subfertility and irregular estrous cycles. TR4-/- female mice ovaries were smaller with fewer or no preovulatory follicles and corpora lutea. After superovulation, TR4-/- female mice produced fewer oocytes, preovulatory follicles, and corpora lutea. In addition, more intensive granulosa apoptosis was found in TR4-/- ovaries. Functional analyses suggest that subfertility in TR4-/- female mice can be due to an ovarian defect with impaired folliculogenesis rather than a deficiency in pituitary gonadotropins. Molecular mechanism dissection of defective folliculogenesis found TR4 might induce LH receptor (LHR) gene expression via direct binding to its 5' promoter. The consequence of reduced LHR expression in TR4-/- female mice might then result in reduced gonadal sex hormones via reduced expression of enzymes involved in steroidogenesis. Together, our results showed TR4 might play essential roles in normal folliculogenesis by influencing LHR signals. Modulation of TR4 expression and/or activation via its upstream signals or unidentified ligand(s) might allow us to develop small molecule(s) to control folliculogenesis.

Oocyte-Specific Overexpression of Mouse Bone Morphogenetic Protein-15 Leads to Accelerated Folliculogenesis and an Early Onset of Acyclicity in Transgenic Mice

Whereas mutations in the bmp15 gene cause infertility in ewes and women due to defects in folliculogenesis, most defects in female mice lacking bone morphogenetic protein (BMP)-15 are confined to the ovulation process, supportive of the observation that functional mouse BMP-15 is barely detected in oocytes in vivo until after the LH surge. In addition, the mouse BMP-15 proprotein is not processed into the functional mature protein in transfected cells. However, a chimeric protein consisting of the human proregion, human cleavage site, and mouse mature region (termed hhmBMP-15) is processed and the mature protein secreted. To study the role of BMP-15 in folliculogenesis, we generated transgenic mice overexpressing hhmBMP-15, exclusively in oocytes during folliculogenesis and confirmed the overexpression of mouse BMP-15 mature protein. Immature transgenic mice exhibited accelerated follicle growth with decreased primary follicles and an increase in secondary follicles. Granulosa cells of immature mice displayed an increased mitotic index and decreased FSH receptor mRNA expression. Adult mice had normal litter sizes but an increased number of atretic antral follicles. Interestingly, aging mice exhibited an early onset of acyclicity marked by increased diestrus length and early occurrence of constant diestrus. These findings indicate the role of BMP-15 in vivo in promoting follicle growth and preventing follicle maturation, resulting in an early decline in the ovarian reserve of transgenic mice. Therefore, the lack of mouse BMP-15 during early folliculogenesis in the wild-type mice may be relevant to their polyovulatory nature as well as the preservation of ovarian function as the mice age.