Bone morphogenetic protein-15 inhibits follicle-stimulating hormone (FSH) action by suppressing FSH receptor expression

Loss of bmp15 function in the seasonal spawner Atlantic salmon results in ovulatory failure

Bone morphogenetic protein 15 (BMP15) is an oocyte-specific growth factor important for successful female reproduction in mammals. While mutations in BMP15/Bmp15 cause ovulatory deficiency and/or infertility in certain mammalian species, loss of bmp15 in zebrafish, a continuous spawner and the only bmp15 knockout model in fish to date, results in complete arrest of follicle development and later female-to-male sex reversal, preventing to examine effects on ovulation/fertilization. Here, we used Atlantic salmon, a seasonal spawner, and generated bmp15 mutants to investigate ovarian development and fertility. Histological and morphometric analyses revealed that in biallelic frameshift (bmp15 fs/fs) mutant ovaries, folliculogenesis started earlier, resulting in an advanced development compared to wild-type (WT) controls, accompanied by a weaker expression of the (early) oocyte-specific factor figla. This precocious ovarian development was followed in bmp15 fs/fs females by enhanced follicle atresia during vitellogenic stages. Although genes involved in steroid synthesis and signaling (star, cyp11b, cyp17a1 and esr1) were dramatically higher in late vitellogenic bmp15 fs/fs mutant ovaries, estradiol-17β plasma levels were lower than in WT counterparts, potentially reflecting compensatory changes at the level of ovarian gene expression. At spawning, bmp15 fs/fs females displayed lower gonado-somatic index values and reduced oocyte diameter, and the majority (71.4%), showed mature non-ovulating ovaries with a high degree of atresia. The remaining (28.6%) females spawned eggs but they either could not be fertilized or, upon fertilization, showed severe malformations and embryonic mortality. Our results show that Bmp15 is required for proper follicle recruitment and growth and later ovulatory success in Atlantic salmon, providing an alternative candidate target to induce sterility in farmed salmon. Moreover, since loss of bmp15 in salmon, in contrast to zebrafish, does not result in female-to-male sex change, this is the first mutant model in fish allowing further investigations on Bmp15-mediated functions in the ovulatory period.

The Roles of GDF-9, BMP-15, BMP-4 and EMMPRIN in Folliculogenesis and In Vitro Fertilization

Growth differentiation factor 9 (GDF-9) contributes to early ovarian development and oocyte survival. Higher concentrations of GDF-9 in follicular fluid (FF) are associated with oocyte nuclear maturation and optimal embryo development. In in vitro fertilization (IVF), GDF-9 affects the ability of the oocyte to fertilize and subsequent embryonic development. Bone morphogenetic protein 15 (BMP-15) is involved in the regulation of ovarian function and affects oocyte development. During IVF, BMP-15 contributes to the formation of competent blastocysts. BMP-15 may play a role in embryo implantation by affecting endometrial receptivity. Bone morphogenetic protein 4 (BMP-4) is involved in the regulation of follicle growth and development and affects granulosa cell (GC) differentiation. In relation to IVF, BMP-4 is important for embryonic development, influences cell fate and differentiation, and plays a role in facilitating embryo-endometrial interactions during the implantation process. Extracellular matrix metalloproteinase inducer (EMMPRIN) is associated with ovulation and follicle rupture, promotes the release of mature eggs, and affects the modification of the extracellular matrix of the follicular environment. In IVF, EMMPRIN is involved in embryo implantation by modulating the adhesive properties of endometrial cells and promotes trophoblastic invasion, which is essential for pregnancy to occur. The purpose of the current article is to review the studies and recent findings of GDF-9, BMP-15, BMP-4 and EMMPRIN as fundamental factors in normal follicular development and in vitro fertilization.

Dynamics of extracellular vesicle uptake by mural granulosa cells in mice

Extracellular vesicles (EVs) play an important role in the development and function of mammalian ovarian follicles. However, the mechanisms by which they are taken up by the follicular granulosa cells remain unclear. In addition, while oocytes play a pivotal role in follicular development, the possible interactions between oocyte-derived paracrine factors (ODPFs) and EV signals are unknown. Therefore, this study aimed to elucidate the mechanism of EV uptake and the effects of ODPFs on EV uptake by follicular somatic mural granulosa cells in mice. Fluorescence-labeled transferrin (TRF) and cholera toxin B (CTB), substrates for clathrin- and caveolae-mediated endocytosis, respectively, were taken up by mural granulosa cells in vitro. Their uptake was inhibited by Pitstop 2 and genistein, inhibitors of clathrin and caveolae pathways, respectively. Mural granulosa cells took up EVs, and this uptake was suppressed by Pitstop 2 and genistein. Moreover, ODPFs promoted the uptake of EVs and CTB, but not TRF, by mural granulosa cells. These results suggest that mural granulosa cells take up EVs through both clathrin- and caveolae-mediated endocytosis and that oocytes may promote caveolae-mediated endocytosis to facilitate the uptake of EVs.

Genome-wide identification, evolution and expression of TGF-β signaling pathway members in mandarin fish (Siniperca chuatsi)

Members of the transforming growth factor β (TGF-β) signaling pathway regulate diverse cellular biological processes in embryonic and tissue development. We took mandarin fish (Siniperca chuatsi) as the research object to identify all members of the TGF-β signaling pathway, measure their expression pattern in the key period post hatching, and further explore their possible role in the process of sex regulation. Herein, we identified eighty-three TGF-β signaling pathway members and located them on chromosomes based on the genome of mandarin fish. TGF-β signaling pathway members were highly conserved since each TGF-β subfamily clustered with orthologs from other species. Transcriptome analysis, qRT-PCR and in situ hybridization demonstrated that most mandarin fish TGF-β signaling pathway members presented stage-specific and/or sex-dimorphic expression during gonadal development, and different members of the TGF-β signaling pathway participated in different stages of gonadal development. Taken together, our results provide new insight into the role of TGF-β signaling pathway members in the sex regulation of mandarin fish.

Macrophage activation drives ovarian failure and masculinization in zebrafish

BMP15 is a conserved regulator of ovarian development and maintenance in vertebrates. In humans, premature ovarian insufficiency is caused by autoimmunity and genetic factors, including mutation of BMP15. The cellular mechanisms underlying ovarian failure caused by BMP15 mutation and immune contributions are not understood. Using zebrafish, we established a causal link between macrophage activation and ovarian failure, which, in zebrafish, causes sex reversal. We define a germline-soma signaling axis that activates macrophages and drives ovarian failure and female-to-male sex reversal. Germline loss of zebrafish Bmp15 impairs oogenesis and initiates this cascade. Single-cell RNA sequencing and genetic analyses implicate ovarian somatic cells that express conserved macrophage-activating ligands as mediators of ovarian failure and sex reversal. Genetic ablation of macrophages or elimination of Csf1Rb ligands, Il34 or Csf1a, delays or blocks premature oocyte loss and sex reversal. The axis identified here provides insight into the cells and pathways governing oocyte and ovary maintenance and potential therapeutic targets to preserve female fertility.

Making a good egg: human oocyte health, aging, and in vitro development

Mammalian eggs (oocytes) are formed during fetal life and establish associations with somatic cells to form primordial follicles that create a store of germ cells (the primordial pool). The size of this pool is influenced by key events during the formation of germ cells and by factors that influence the subsequent activation of follicle growth. These regulatory pathways must ensure that the reserve of oocytes within primordial follicles in humans lasts for up to 50 years, yet only approximately 0.1% will ever be ovulated with the rest undergoing degeneration. This review outlines the mechanisms and regulatory pathways that govern the processes of oocyte and follicle formation and later growth, within the ovarian stroma, through to ovulation with particular reference to human oocytes/follicles. In addition, the effects of aging on female reproductive capacity through changes in oocyte number and quality are emphasized, with both the cellular mechanisms and clinical implications discussed. Finally, the details of current developments in culture systems that support all stages of follicle growth to generate mature oocytes in vitro and emerging prospects for making new oocytes from stem cells are outlined.

Rescue of bmp15 deficiency in zebrafish by mutation of inha reveals mechanisms of BMP15 regulation of folliculogenesis

As an oocyte-specific growth factor, bone morphogenetic protein 15 (BMP15) plays a critical role in controlling folliculogenesis. However, the mechanism of BMP15 action remains elusive. Using zebrafish as the model, we created a bmp15 mutant using CRISPR/Cas9 and demonstrated that bmp15 deficiency caused a significant delay in follicle activation and puberty onset followed by a complete arrest of follicle development at previtellogenic (PV) stage without yolk accumulation. The mutant females eventually underwent female-to-male sex reversal to become functional males, which was accompanied by a series of changes in secondary sexual characteristics. Interestingly, the blockade of folliculogenesis and sex reversal in bmp15 mutant could be partially rescued by the loss of inhibin (inha-/-). The follicles of double mutant (bmp15-/-;inha-/-) could progress to mid-vitellogenic (MV) stage with yolk accumulation and the fish maintained their femaleness without sex reversal. Transcriptome analysis revealed up-regulation of pathways related to TGF-β signaling and endocytosis in the double mutant follicles. Interestingly, the expression of inhibin/activin βAa subunit (inhbaa) increased significantly in the double mutant ovary. Further knockout of inhbaa in the triple mutant (bmp15-/-;inha-/-;inhbaa-/-) resulted in the loss of yolk granules again. The serum levels of estradiol (E2) and vitellogenin (Vtg) both decreased significantly in bmp15 single mutant females (bmp15-/-), returned to normal in the double mutant (bmp15-/-;inha-/-), but reduced again significantly in the triple mutant (bmp15-/-;inha-/-;inhbaa-/-). E2 treatment could rescue the arrested follicles in bmp15-/-, and fadrozole (a nonsteroidal aromatase inhibitor) treatment blocked yolk accumulation in bmp15-/-;inha-/- fish. The loss of inhbaa also caused a reduction of Vtg receptor-like molecules (e.g., lrp1ab and lrp2a). In summary, the present study provided comprehensive genetic evidence that Bmp15 acts together with the activin-inhibin system in the follicle to control E2 production from the follicle, Vtg biosynthesis in the liver and its uptake by the developing oocytes.

Oocyte secreted factors control genes regulating FSH signaling and the maturation cascade in cumulus cells: the oocyte is not in a hurry

PURPOSE

To assess the effects of the oocyte on mRNA abundance of FSHR, AMH and major genes of the maturation cascade (AREG, EREG, ADAM17, EGFR, PTGS2, TNFAIP6, PTX3, and HAS2) in bovine cumulus cells.

METHODS

(1) Intact cumulus-oocyte complexes, (2) microsurgically oocytectomized cumulus-oolema complexes (OOX), and (3) OOX + denuded oocytes (OOX+DO) were subjected to in vitro maturation (IVM) stimulated with FSH for 22 h or with AREG for 4 and 22 h. After IVM, cumulus cells were separated and relative mRNA abundance was measured by RT-qPCR.

RESULTS

After 22 h of FSH-stimulated IVM, oocytectomy increased FSHR mRNA levels (p=0.005) while decreasing those of AMH (p=0.0004). In parallel, oocytectomy increased mRNA abundance of AREG, EREG, ADAM17, PTGS2, TNFAIP6, and PTX3, while decreasing that of HAS2 (p<0.02). All these effects were abrogated in OOX+DO. Oocytectomy also reduced EGFR mRNA levels (p=0.009), which was not reverted in OOX+DO. The stimulatory effect of oocytectomy on AREG mRNA abundance (p=0.01) and its neutralization in OOX+DO was again observed after 4 h of AREG-stimulated IVM. After 22 h of AREG-stimulated IVM, oocytectomy and addition of DOs to OOX caused the same effects on gene expression observed after 22 h of FSH-stimulated IVM, except for ADAM17 (p<0.025).

CONCLUSION

These findings suggest that oocyte-secreted factors inhibit FSH signaling and the expression of major genes of the maturation cascade in cumulus cells. These may be important actions of the oocyte favoring its communication with cumulus cells and preventing premature activation of the maturation cascade.

Stimulatory effects of vasopressin on progesterone production and BMP signaling by ovarian granulosa cells

The aim of the present study was to clarify the effects of arginine vasopressin (AVP) on ovarian steroid production and its functional relationship to the ovarian bone morphogenetic protein (BMP) system. The results showed that AVP treatment significantly increased gonadotropin- and forskolin-induced progesterone synthesis by primary culture of rat granulosa cells and human granulosa cells, respectively. In contrast, estradiol production was not significantly affected by AVP. Treatment with AVP significantly increased forskolin-induced cAMP synthesis by human granulosa cells and mRNA levels of the progesterogenic enzymes CYP11A1 and HSD3B2 in the cells. On the other hand, AVP also enhanced BMP-15-induced phosphorylation of SMAD1/5/9 and ID1 transcription. It was further revealed that the expression levels of BMP receptors, including ALK3, ALK6 and BMPR2, were upregulated by AVP. Collectively, the results indicate that AVP stimulates progesterone production via the cAMP-PKA pathway with upregulation of BMP signaling that inhibits progesterone production, which may lead to fine adjustment of progesterone biosynthesis by granulosa cells.

Review: Role and regulatory mechanism of inhibin in animal reproductive system

Inhibin (INH) is a glycoprotein hormone secreted by the gonads that inhibit the synthesis and secretion of follicle-stimulating hormone (FSH). Increasing evidence indicates that INH plays a significant role in the development of the reproductive system including follicle development, ovulation rate, corpus luteum formation and ablation, steroid hormone synthesis and spermatogenesis, subsequently affecting the reproductive capacity of animals such as litter size and egg production. There are currently three main views on how INH inhibits FSH synthesis and secretion: influencing the activity of adenylate cyclase, the expression of follicle-stimulating hormone receptor or gonadotropin-releasing hormone receptor, and the competition system of inhibin-activin. This review discusses the current findings on the structure, function, and mechanism of action of INH in the reproductive system of animals.

Oxytocin enhances progesterone production with upregulation of BMP-15 activity by granulosa cells

To elucidate the reproductive role of oxytocin (OXT) in ovarian steroidogenesis and its functional interaction with bone morphogenetic proteins (BMPs), the effects of OXT on ovarian steroidogenesis were investigated by utilizing primary culture of rat granulosa cells and human granulosa KGN cells. Here we revealed that the OXT receptor was expressed in both rat and human granulosa cells and that OXT treatment significantly increased follicle-stimulating hormone (FSH)- and forskolin (FSK)-induced progesterone production, but not estradiol production, by rat and human granulosa cells, respectively. In accordance with the effects of OXT on progesterone production, OXT enhanced mRNA expression of CYP11A1 and HSD3B2 induced by FSK in human granulosa cells. Of note, OXT enhanced the phosphorylation of SMAD1/5/9 and the transcription of ID1 induced by BMP-15, but not those induced by BMP-6, in human granulosa cells. It was also revealed that OXT treatment upregulated the expression of BMPR2, a crucial type-II receptor of BMP-15, and enhanced the BMP-15-induced expression of inhibitory SMAD6 by human granulosa cells. Collectively, it was shown that OXT accelerates ovarian progesterone synthesis with upregulation of BMP-15 activity, leading to a fine-tuning of ovarian steroidogenesis (186 words).

Local regulation of antral follicle development and ovulation in monovulatory species

The identification of mutations in the genes encoding bone morphogenetic protein 15 (BMP15) and growth and differentiation factor 9 (GDF9) associated with phenotypes of sterility or increased ovulation rate in sheep aroused interest in the study of the role of local factors in preantral and antral folliculogenesis in different species. An additive mutation in the BMP15 receptor, BMPR1b, which determines an increase in the ovulatory rate, has been introduced in several sheep breeds to increase the number of lambs born. Although these mutations indicate extremely relevant functions of these factors, the literature data on the regulation of the expression and function of these proteins and their receptors are very controversial, possibly due to differences in experimental models. The present review discusses the published data and preliminary results obtained by our group on the participation of local factors in the selection of the dominant follicle, ovulation, and follicular atresia in cattle, focusing on transforming growth factors beta and their receptors. The study of the expression pattern and the functionality of proteins produced by follicular cells and their receptors will allow increasing the knowledge about this local system, known to be involved in ovarian physiopathology and with the potential to promote contraception or increase the ovulation rate in mammals.

Macrophage activation drives ovarian failure and masculinization

In humans, premature ovarian insufficiency (POI) is caused by autoimmunity and genetic factors, such as mutation of BMP15, a key ovarian determining gene. The cellular mechanisms associated with ovarian failure caused by BMP15 mutation and immune contributions to the disorder are not understood. BMP15's role in ovarian follicle development is conserved in vertebrates, including zebrafish. Using zebrafish, we established a causal link between macrophage activation and ovarian failure. We identified a germline-somatic gonadal cell-macrophage axis underlying ovarian atresia. Germline loss of Bmp15 triggers this axis that single-cell RNA sequencing and genetic analyses indicate involves activation of ovarian somatic cells that express conserved macrophage-activating ligands. Genetic ablation of macrophages blocks premature oocyte loss. Thus, the axis identified here represents potential therapeutic targets to preserve female fertility.

Expression Patterns and Gonadotropin Regulation of the TGF-β II Receptor (Bmpr2) during Ovarian Development in the Ricefield Eel Monopterus albus

Bmpr2 plays a central role in the regulation of reproductive development in mammals, but its role during ovarian development in fish is still unclear. To ascertain the function of bmpr2 in ovarian development in the ricefield eel, we isolated and characterized the bmpr2 cDNA sequence; the localization of Bmpr2 protein was determined by immunohistochemical staining; and the expression patterns of bmpr2 in ovarian tissue incubated with FSH and hCG in vitro were analyzed. The full-length bmpr2 cDNA was 3311 bp, with 1061 amino acids encoded. Compared to other tissues, bmpr2 was abundantly expressed in the ovary and highly expressed in the early yolk accumulation (EV) stages of the ovary. In addition, a positive signal for Bmpr2 was detected in the cytoplasm of oocytes in primary growth (PG) and EV stages. In vitro, the expression level of gdf9, the ligand of bmpr2, in the 10 ng/mL FSH treatment group was significantly higher after incubation for 4 h than after incubation for different durations. However, bmpr2 expression in the 10 ng/mL FSH treatment group at 2 h, 4 h and 10 h was significantly lower. Importantly, the expression level of bmpr2 and gdf9 in the 100 IU/mL hCG group had similar changes that were significantly decreased at 4 h and 10 h. In summary, Bmpr2 might play a pivotal role in ovarian growth in the ricefield eel, and these results provide a better understanding of the function of bmpr2 in ovarian development and the basic data for further exploration of the regulatory mechanism of gdf9 in oocyte development.

Toxicological impacts of nanopolystyrene on zebrafish oocyte with insight into the mechanism of action: An expression-based analysis

Many studies have investigated the negative impacts of microplastics on teleost fishes with very little or no evidence of their mechanism of action. This scenario entreats us to investigate the toxicities of nanopolystyrene in zebrafish oocyte with emphasis on the mechanism of action. In the present study, the cellular levels of mRNA transcripts of different genetic markers (such as: sod, gpx, nrf2, inos, ucp2, and atp6 (redox-sensitive markers); nfkβ, tnfα, il-10, ikβ, gdf9, and bmp15 (immune markers); gadd45, rad51, p53 and bcl2 (DNA damage and apoptotic)) have been quantified by real-time PCR after 6 h of incubation of isolated oocyte with different doses of nanopolystyrene viz. P0 (control i.e. no polystyrene in culture medium), P1 (100 ng/ml), and P2 (400 ng/ml). Results showed that both the treatment concentrations of nanopolystyrene induce oxidative stress with % DPPH = 30.75, 31.61, and 32.43% for P0, P1, and P2, respectively. Increase in oxidative stress in oocytes with increasing doses of nanopolystyrene was also observed in TBARS assay with MDA content 0.12 and 0.21 μM for P1 and P2, respectively as compaired to the control 0.08 μM. This increased oxidative stress can regulate the expression pattern (upregulation/downregulation) of selected genes leading to different toxic effects like - oxidative stress, immunotoxicity, and apoptosis in oocytes, which suggests the impairment of reproductive functions by nanopolystyrene.

Excessive follicle-stimulating hormone during ovarian stimulation of cattle may induce premature luteinization of most ovulatory-size follicles†

High follicle-stimulating hormone (FSH) doses during ovarian stimulation are detrimental to ovulatory follicle function and decrease live birth rate in cattle and women. However, the mechanism whereby excessive FSH causes ovarian dysfunction is unknown. This study tested the hypothesis that excessive FSH during ovarian stimulation induces premature luteinization of ovulatory-size follicles. Small ovarian reserve heifers were injected twice daily for 4 days with 70 IU (N = 7 heifers) or 210 IU (N = 6 heifers) Folltropin-V [commercial FSH-enriched preparation of porcine pituitary glands with minor (<1%) luteinizing hormone (LH) contamination, cpFSH]. Ovulatory-size (≥10 mm) follicles were excised from ovaries after the last cpFSH injection and hormone concentrations in follicular fluid (FF) were determined using ELISA. Luteinization was monitored by assessing cumulus cell-oocyte complex (COC) morphology and measuring concentrations of estradiol (E), progesterone (P), and oxytocin (O) in FF. COCs were classified as having compact (cCOC) or expanded (eCOC) cumulus cell layers, and as estrogen-active (E:P in FF ≥1), estrogen-inactive (EI, E:P in FF ≤1 > 0.1), or extreme-estrogen-inactive (EEI, E:P in FF ≤0.1). A high proportion (72%) of ovulatory-size follicles in 210 IU, but not 70 IU, dose heifers displayed eCOCs. The high doses also produced higher proportions of EI or EEI follicles which had lower E:P ratio and/or E but higher P and/or O concentrations compared with the 70 IU dose heifers. In conclusion, excessive cpFSH doses during ovarian stimulation may induce premature luteinization of most ovulatory-size follicles in heifers with small ovarian reserves.

The putative roles of FSH and AMH in the regulation of oocyte developmental competence: from fertility prognosis to mechanisms underlying age-related subfertility

BACKGROUND

Fertility loss during female ageing is associated with increasing basal FSH and decreasing anti-Müllerian hormone (AMH) concentrations, together with compromised oocyte quality, presumably due to increased oxidative stress (OS) and DNA damage, as well as reduced metabolic and meiotic competences. Basal FSH and AMH circulatory concentrations have been broadly utilized as IVF success predictors, regardless of fluctuations in prognostic accuracy; basal FSH and AMH perform better in pre-advanced maternal age (AMA: >35 years) and AMA patients, respectively. The relationships between FSH and AMH intrafollicular levels and IVF outcomes suggest, nevertheless, that both hormones regulate oocyte competence, supporting the hypothesis that changes in FSH/AMH levels cause, at least in part, oocyte quality degradation during ageing. To understand the reasons behind the fluctuations in FSH and AMH prognostic accuracies and to clarify their participation in mechanisms determining oocyte competence and age-related subfertility, a deeper knowledge of the regulation of FSH and AMH intrafollicular signalling during the female reproductive lifespan, and of their effects on the cumulus-oocyte complex, is required.

OBJECTIVE AND RATIONALE

An extensive body of information on the regulation of FSH and AMH intrafollicular availability and signalling, as well as on the control of folliculogenesis and oocyte metabolism, has been accumulated. However, these datasets have been explored within the relatively narrow boundaries of their specific subjects. Given the aforementioned gaps in knowledge and their clinical relevance, herein we integrate clinical and basic data, within a wide biological perspective, aiming to shed light on (i) the reasons for the variability in the accuracy of serum FSH and AMH as fertility markers, and on (ii) the potential roles of these hormones in mechanisms regulating oocyte quality, particularly those associated with ageing.

SEARCH METHODS

The PubMed database encompassing the period between 1960 and 2021 was searched. Principal search terms were FSH, FSH receptor, AMH, oocyte, maternal age, cumulus, transzonal projections (TZPs), actin, OS, redox, reactive oxygen species, mitochondria, DNA damage, DNA repair, aneuploidy, spindle, meiosis, gene expression, transcription, translation, oocyte secreted factors (OSFs), cAMP, cyclic guanosine monophosphate, natriuretic peptide C, growth differentiation factor 9, bone morphogenetic protein 15 and fibroblast growth factor.

OUTCOMES

Our analysis suggests that variations in the accuracy of fertility prognosis reflect a modest association between circulatory AMH levels and oocyte quality as well as increasing basal FSH inter-cycle variability with age. In addition, the basic and clinical data articulated herein support the hypothesis that increased intrafollicular FSH levels, as maternal age advances, may override the physiological protective influences of AMH and OSFs against excessive FSH signalling in cumulus cells. This would result in the disruption of oocyte homeostasis via reduced TZP-mediated transfer of cumulus-derived molecules essential for meiotic competence, gene expression, redox activity and DNA repair.

WIDER IMPLICATIONS

In-depth data analysis, encompassing a wide biological perspective has revealed potential causative mechanisms of age-related subfertility triggered by alterations in FSH/AMH signalling during the female reproductive life. Insights from new mechanistic models arising from this analysis should contribute to advancing our comprehension of oocyte biology in humans and serve as a valuable reference for novel AMA subfertility treatments aimed at improving oocyte quality through the modulation of AMH/FSH action.

Sexual determination in zebrafish

Zebrafish have emerged as a major model organism to study vertebrate reproduction due to their high fecundity and external development of eggs and embryos. The mechanisms through which zebrafish determine their sex have come under extensive investigation, as they lack a definite sex-determining chromosome and appear to have a highly complex method of sex determination. Single-gene mutagenesis has been employed to isolate the function of genes that determine zebrafish sex and regulate sex-specific differentiation, and to explore the interactions of genes that promote female or male sexual fate. In this review, we focus on recent advances in understanding of the mechanisms, including genetic and environmental factors, governing zebrafish sex development with comparisons to gene functions in other species to highlight conserved and potentially species-specific mechanisms for specifying and maintaining sexual fate.

Roles of NR5A1 and NR5A2 in the regulation of steroidogenesis by Clock gene and bone morphogenetic proteins by human granulosa cells

The functional role of the transcription factors NR5A1 and NR5A2 and their interaction with Clock gene and bone morphogenetic proteins (BMPs) were investigated in human granulosa KGN cells. Treatment with BMP-15 and GDF-9 suppressed forskolin (FSK)-induced steroidogenesis as shown by the mRNA expression levels of StAR and P450scc but not the mRNA expression level of P450arom. Of interest, treatment with BMP-15 and GDF-9 also suppressed FSK-induced NR5A2 mRNA expression. Treatment with BMP-15 suppressed NR5A2 mRNA and protein expression but increased Clock mRNA and protein expression levels by granulosa cells. The mRNA expression levels of NR5A1, but not those of NR5A2, were positively correlated with the levels of Clock mRNA, while the mRNA levels of Id-1, the target gene of BMP signaling, were positively correlated with those of NR5A1 but not with those of NR5A2. It was also demonstrated that the mRNA expression levels of NR5A1 were positively correlated with those of P450arom and 3βHSD, whereas the mRNA expression level of NR5A2 was correlated with those of StAR and P450scc. Furthermore, inhibition of Clock gene expression by siRNA attenuated the expression of NR5A1, and the mRNA levels of Clock gene were significantly correlated with those of NR5A1. Collectively, the results suggested a novel mechanism by which Clock gene expression induced by BMP-15 is functionally linked to the expression of NR5A1, whereas NR5A2 expression is suppressed by BMP-15 in granulosa cells. The interaction between Clock NR5A1/NR5A2 and BMP-15 is likely to be involved in the fine-tuning of steroidogenesis by ovarian granulosa cells.

Identification of polymorphism of FecX gene in indigenous sheep of Meghalaya

Fecundity gene such as FecX, govern fertility and litter size in sheep. Selection of animals with the help of molecular markers through identification of polymorphism of fecundity genes is an impactful method of genetic improvement. The present study was carried out to identify the polymorphism of FecX gene in indigenous sheep of Meghalaya. Blood samples were collected from 50 randomly selected ewes from 2 districts of Meghalaya namely, East Khasi Hills and West Khasi Hills. Genomic DNA was extracted from the samples and PCR amplification of FecX gene with specific primer set was done. PCR product size of 141 bp was obtained. Further, digestion of the PCR product with restriction enzyme HinfI through PCR-RFLP technique was conducted to identify the variants in FecX gene. Upon digestion, 2 types of fragment pattern identified, arbitrarily designated as AA and AB genotype, where AA genotype yielded one fragment (141 bp) and AB genotype yielded 2 fragments (100 and 41 bp). Presence of polymorphism can be an important indicator for selection with the help of molecular markers.

Meta-Analysis of Heifer Traits Identified Reproductive Pathways in Bos indicus Cattle

Fertility traits measured early in life define the reproductive potential of heifers. Knowledge of genetics and biology can help devise genomic selection methods to improve heifer fertility. In this study, we used ~2400 Brahman cattle to perform GWAS and multi-trait meta-analysis to determine genomic regions associated with heifer fertility. Heifer traits measured were pregnancy at first mating opportunity (PREG1, a binary trait), first conception score (FCS, score 1 to 3) and rebreeding score (REB, score 1 to 3.5). The heritability estimates were 0.17 (0.03) for PREG1, 0.11 (0.05) for FCS and 0.28 (0.05) for REB. The three traits were highly genetically correlated (0.75-0.83) as expected. Meta-analysis was performed using SNP effects estimated for each of the three traits, adjusted for standard error. We identified 1359 significant SNPs (p-value < 9.9 × 10-6 at FDR < 0.0001) in the multi-trait meta-analysis. Genomic regions of 0.5 Mb around each significant SNP from the meta-analysis were annotated to create a list of 2560 positional candidate genes. The most significant SNP was in the vicinity of a genomic region on chromosome 8, encompassing the genes SLC44A1, FSD1L, FKTN, TAL2 and TMEM38B. The genomic region in humans that contains homologs of these genes is associated with age at puberty in girls. Top significant SNPs pointed to additional fertility-related genes, again within a 0.5 Mb region, including ESR2, ITPR1, GNG2, RGS9BP, ANKRD27, TDRD12, GRM1, MTHFD1, PTGDR and NTNG1. Functional pathway enrichment analysis resulted in many positional candidate genes relating to known fertility pathways, including GnRH signaling, estrogen signaling, progesterone mediated oocyte maturation, cAMP signaling, calcium signaling, glutamatergic signaling, focal adhesion, PI3K-AKT signaling and ovarian steroidogenesis pathway. The comparison of results from this study with previous transcriptomics and proteomics studies on puberty of the same cattle breed (Brahman) but in a different population identified 392 genes in common from which some genes-BRAF, GABRA2, GABR1B, GAD1, FSHR, CNGA3, PDE10A, SNAP25, ESR2, GRIA2, ORAI1, EGFR, CHRNA5, VDAC2, ACVR2B, ORAI3, CYP11A1, GRIN2A, ATP2B3, CAMK2A, PLA2G, CAMK2D and MAPK3-are also part of the above-mentioned pathways. The biological functions of the positional candidate genes and their annotation to known pathways allowed integrating the results into a bigger picture of molecular mechanisms related to puberty in the hypothalamus-pituitary-ovarian axis. A reasonable number of genes, common between previous puberty studies and this study on early reproductive traits, corroborates the proposed molecular mechanisms. This study identified the polymorphism associated with early reproductive traits, and candidate genes that provided a visualization of the proposed mechanisms, coordinating the hypothalamic, pituitary, and ovarian functions for reproductive performance in Brahman cattle.

Involvement of BMP-15 in glucocorticoid actions on ovarian steroidogenesis by rat granulosa cells

To elucidate the impact of glucocorticoids on ovarian steroidogenesis and its molecular mechanism by focusing on bone morphogenetic proteins (BMPs), we examined the effect of dexamethasone (Dex) on estradiol and progesterone synthesis by using primary culture of rat granulosa cells. It was revealed that Dex treatment dose-dependently decreased estradiol production but increased progesterone production induced by follicle-stimulating hormone (FSH) by granulosa cells. In accordance with the effects of Dex on estradiol synthesis, Dex suppressed P450arom mRNA expression and cAMP synthesis induced by FSH. Dex treatment in turn enhanced basal as well as FSH-induced levels of mRNAs encoding the enzymes for progesterone synthesis including P450scc and 3βHSD but not StAR and 20αHSD. Of note, Dex treatment significantly upregulated transcription of the BMP target gene Id-1 and Smad1/5/9 phosphorylation in the presence of BMP-15 among the key ovarian BMP ligands. It was also found that Dex treatment increased the expression level of BMP type-I receptor ALK-6 among the type-I and -II receptors for BMP-15. Inhibitory Smad6/7 expression was not affected by Dex treatment. On the other hand, BMP-15 treatment upregulated glucocorticoid receptor (GR) expression in granulosa cells. Collectively, it was revealed that glucocorticoids elicit differential effects on ovarian steroidogenesis, in which GR and BMP-15 actions are mutually enhanced in granulosa cells.

Differential molecular and hormonal changes in oocytes, granulosa cells and follicular fluid of pregnant and non-pregnant camels

This study aimed to compare the expression of genes regulating follicles development, survival and steroid hormones secretion in oocytes and granulosa cells (GCs) and study the correlation between their expression and follicular fluid (FF) levels of progesterone (P4) in pregnant and non-pregnant camels. In total, 138 ovarian pairs from slaughtered camels were used. Gene expression and hormonal assay were determined using real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. The obtained results revealed that the number of follicles (3-8 mm) was significantly (P < 0.05) lower in pregnant, compared with non-pregnant, camels. P4 level in the FF was significantly (P < 0.05) higher in pregnant, compared with non-pregnant, camels. However, no significant (P > 0.05) difference was noticed in the oestradiol (E2) level. STAR, PTEN, IGF1 and BCL2 mRNA levels were significantly higher in GCs and significantly lower in oocytes of pregnant, compared with non-pregnant, camels. However, follicle-stimulating hormone receptor (FSHR) mRNA level was significantly lower in GCs and oocytes, and the BMP15 mRNA level was significantly lower in oocytes of pregnant, compared with non-pregnant, camels. P4 level in FF was positively correlated with STAR, PTEN, IGF1 and BCL2 mRNA levels in GCs and negatively correlated with BMP15 mRNA levels in oocytes and FSHR mRNA levels in GCs and oocytes of pregnant camels. It could be concluded that pregnancy-induced variations in oocytes and GC expression of BMP15, IGF1, FSHR, STAR, BCL2, and PTEN genes might be associated with a decrease in the number of follicles and an increase in the FF level of P4.

Bone morphogenetic protein 15 supplementation enhances cumulus expansion, nuclear maturation and progesterone production of in vitro-matured bovine cumulus-oocyte complexes

In vitro embryo production (IVP) efficiency is reduced when compared to in vivo. The basic knowledge of bovine in vitro oocyte maturation (IVM) mechanisms provides support to improve in vitro embryo production yields. The present study assessed the effects of bone morphogenetic protein 15 (BMP15), fibroblast growth factor 16 (FGF16) and their combined action on cumulus cells (CC) expansion, oocyte and CC DNA fragmentation, oocyte nuclear maturation, energetic metabolism and progesterone production in bovine IVM. Cumulus-oocyte complexes (COC) were matured in control or supplemented media containing BMP15 (100 ng/ml), FGF16 (10 ng/ml) or BMP15 combined with FGF16; and assessed at 0 and 22 hr of IVM. BMP15 alone or its association with FGF16 enhanced cumulus expansion. BMP15 decreased DNA fragmentation in both CC and oocytes, and improved oocyte nuclear maturation rate. In addition, BMP15 increased CC progesterone production, an effect not previously reported. The present study reinforces previous data pointing to a beneficial influence of BMP15 during IVM, while providing novel evidence that the underlying mechanisms involve increased progesterone production.

FSH Promotes Progesterone Synthesis by Enhancing Autophagy to Accelerate Lipid Droplet Degradation in Porcine Granulosa Cells

Little is known about the molecular relationships among follicle stimulating hormone (FSH), lipid droplet (LD) degradation, and autophagy. In this study, we aimed to investigate the pathway by which FSH regulates autophagy and the potential role of autophagy in progesterone production. Our results revealed that FSH stimulated progesterone production in mammalian follicular granulosa cells (GCs) through a non-canonical pathway. In porcine secondary follicles cultured in vitro, FSH treatment increased the level of the autophagic marker, LC3-II, as well as increased the number of autophagic vacuoles in GCs. The underlying molecular mechanism and biological functions were then investigated in porcine GCs. Our results demonstrated that FSH could upregulate Beclin1 levels in porcine GCs; however, this effect was blocked by LY294002 (a PI3K/AKT inhibitor) and SP600125 (SAPK/JNK inhibitor). Further research confirmed that the transcriptional factor, c-Jun, was phosphorylated by FSH, then translocated into the nucleus from the cytoplasm and bound to the BECLIN1 promoter region, and that LY294002, SP600125, or c-Jun knockdown prevented the increase in Beclin1 levels induced by FSH. Interestingly, inhibition of autophagy using chloroquine or SP600125 decreased progesterone production in porcine GCs treated with FSH, although the expression of StAR and P450scc was not disturbed. Moreover, FSH treatment reduced the average number and size of LDs in porcine GCs, but these effects were eliminated by knocking down the key autophagy genes, ATG5 and BECLIN1; in addition, the effect of FSH on promoting progesterone secretion by the cells was also reduced significantly. Based on the above results, we concluded that FSH promoted progesterone production by enhancing autophagy through upregulation of Beclin1 via the PI3K/JNK/c-Jun pathway to accelerate LD degradation in porcine GCs, independent of the classical steroidogenic pathway.

TGF-β1 stimulates aromatase expression and estradiol production through SMAD2 and ERK1/2 signaling pathways in human granulosa-lutein cells

Estradiol (E2), one of the main steroid hormones secreted by the ovaries, plays an important role in maintaining normal female reproductive function. Ovarian granulosa cells are the main source of E2 production because these cells express aromatase, which is encoded by the CYP19A1 gene and catalyzes the final step in E2 biosynthesis from androgens. Transforming growth factor-beta 1 (TGF-β1) and its receptors are expressed in human granulosa cells, and TGF-β1 expression can be detected in human follicular fluid. To date, TGF-β1 has been shown to regulate various ovarian functions. However, whether aromatase can be regulated by TGF-β1 in human granulosa cells has not been determined. In the present study, we demonstrate that TGF-β1 stimulates aromatase expression in primary human granulosa-lutein cells and in the human ovarian granulose-like tumor cell line, KGN. We used pharmacological inhibitors and small interfering RNA-mediated knockdown approaches to reveal that the SMAD2 and ERK1/2 signaling pathways are involved in TGF-β1-induced aromatase expression and E2 production. These results not only provide important insights into the molecular mechanisms that mediate TGF-β1-induced aromatase expression and E2 production in human granulosa cells but also increase the understanding of the normal physiological roles of TGF-β1 in the ovary.

Effects of oocyte-derived paracrine factors on release of extracellular vesicles by murine mural granulosa cells in vitro

Both oocytes and extracellular vesicles (EV) have emerged as critical regulators of mammalian follicular development; however, the possible interaction between the oocyte‐derived paracrine factor (ODPF) and EV signals has never been examined. Therefore, to explore the possibility of an interaction between oocyte and EV signals, the effects of ODPFs on the biogenesis of EVs as well as the expression levels of transcripts related to EV biogenesis in mural granulosa cells (MGCs) were examined using mice. The results showed that, while oocyte coculture has some effects on the expression levels of transcripts related to EV biogenesis, the number of EV particles present in the conditioned medium were not significantly different between ODPF‐treated and non‐treated MGCs. Therefore, oocytes have no effects on the EV biogenesis by MGCs, at least with respect to the numbers of EV particles.

Quercetin alleviated H2 O2 -induced apoptosis and steroidogenic impairment in goat luteinized granulosa cells

Quercetin (Que) is a natural flavonoid in most plants. Luteinized granulosa cell (LGC) culture is necessary for the study of follicle growth/differentiation. In the present study, we analyzed the role of Que in steroid production and apoptosis in hydrogen peroxide (H2 O2 )-treated goat LGCs. The results showed that treatment with H2 O2 induced apoptosis in goat LGCs, and treatment with Que decreased LGC apoptosis induced by H2 O2 (P < .05), accompanied with the different expressions of BAX, BCL-2, Caspase 3, and Cleaved caspase 3. Meanwhile, the messenger RNA expressions of nuclear factor erythroid 2 like 2 (Nrf2) and its downstream genes were upregulated with H2 O2 +Que treatment, accompanied by the increased cellular viability (P < .05). Furthermore, Que alleviated H2 O2 -induced reduction in the secretion of progesterone (P4 ) (P < .05); however, it had no effect on the secretion of estrogen (E2 ). Simultaneously, the expressions of StAR and P450scc were increased when treated with Que +H2 O2 , compared with the group treated with only H2 O2 (P < .05). In conclusion, it is observed that Que could alleviate the H2 O2 -induced apoptosis and steroidogenic impairment in goat LGCs, which might be mediated by the Nrf2 pathway.

Expression levels of FSHR, IGF1R, CYP11al and HSD3β in cumulus cells can predict in vitro developmental competence of bovine oocytes

The efficiency of in vitro embryo production technologies would be improved by the development of suitable non-invasive biomarkers that allow the selection of good quality cumulus-oocyte complexes (COCs). The present study used whole, single oocyte culture to investigate whether the expression levels of follicle-stimulating hormone receptor (FSHR), insulin-like factor 1 receptor (IGF1R) and three steroidogenesis-related enzymes (CYP11al, CYP19al and HSD3β) in cumulus cells reflected the developmental competence of COCs. Cumulus cells were collected from single COCs before maturation culture and relative mRNA levels were assessed using real-time PCR. The analysis indicated that mRNAs for FSHR, IGF1R, CYP11al and HSD3β were present at higher levels in cumulus cells from COCs that failed to form blastocysts compared with cumulus cells from COCs that formed blastocysts. Moreover, FSHR and IGF1R mRNA levels were positively correlated with those of genes for steroidogenesis-related enzymes. In conclusion, poor developmental competence of COCs was related to higher expression of FSHR, IGF1R, CYP11al and HSD3β in cumulus cells, which may indicate the advanced differentiation of cumulus cells into granulosa cells.

Bone Morphogenetic Protein 15 Knockdown Inhibits Porcine Ovarian Follicular Development and Ovulation

Bone morphogenetic protein 15 (BMP15) is strongly associated with animal reproduction and woman reproductive disease. As a multifunctional oocyte-specific secret factor, BMP15 controls female fertility and follicular development in both species-specific and dosage-sensitive manners. Previous studies found that BMP15 played a critical role in follicular development and ovulation rate in mono-ovulatory mammalian species, especially in sheep and human, but study on knockout mouse model implied that BMP15 possibly has minimal impact on female fertility of poly-ovulatory species. However, this needs to be validated in other poly-ovulatory species. To investigate the regulatory role of BMP15 on porcine female fertility, we generated a BMP15-knockdown pig model through somatic nuclear transfer technology. The BMP15-knockdown gilts showed markedly reduced fertility accompanied by phenotype of dysplastic ovaries containing significantly declined number of follicles, increased number of abnormal follicles, and abnormally enlarged antral follicles resulting in disordered ovulation, which is remarkably different from the unchanged fertility observed in BMP15 knockout mice. Molecular and transcriptome analysis revealed that the knockdown of BMP15 significantly affected both granulosa cells (GCs) and oocytes development, including suppression of cell proliferation, differentiation, and follicle stimulating hormone receptor (Fshr) expression, leading to premature luteinization and reduced estradiol (E2) production in GCs, and simultaneously decreased quality and meiotic maturation of oocyte. Our results provide in vivo evidence of the essential role of BMP15 in porcine ovarian and follicular development, and new insight into the complicated regulatory function of BMP15 in female fertility of poly-ovulatory species.

The role of FSH and TGF-β superfamily in follicle atresia

Most of the mammalian follicles undergo a degenerative process called “follicle atresia”. Apoptosis of granulosa cells is the main characteristic of follicle atresia. Follicle stimulating hormone (FSH) and the transforming growth factor β (TGF-β) superfamily have important regulatory functions in this process. FSH activates protein kinase A and cooperating with insulin receptor substrates, it promotes the PI3K/Akt pathway which weakens apoptosis. Both Smad or non-Smad signaling of the transforming growth factor β superfamily seem to be related to follicle atresia, and the effect of several important family members on follicle atresia is concluded in this article. FSH and TGF-β are likely to mutually influence each other and what we have already known about the possible underlying molecular mechanism is also discussed below.

Trio, a novel high fecundity allele: I. Transcriptome analysis of granulosa cells from carriers and noncarriers of a major gene for bovine ovulation rate

A major gene for bovine ovulation rate has been mapped to a 1.2 Mb region of chromosome 10. Screening of coding regions of positional candidate genes within this region failed to reveal a causative polymorphism, leading to the hypothesis that the phenotype results from differences in candidate gene expression rather than alteration of gene structure. This study tested differences in expression of positional candidate genes in granulosa cells between carriers and noncarriers of the high fecundity allele, as well as characterizing differences in the transcriptomic profile between genotypes. Five carriers and five noncarriers, female descendants of "Trio," a carrier of the high fecundity allele were initially used in an RNA-seq analysis of gene expression. Four of ten samples were contaminated with theca cells, so that six samples were used in the final analysis (three of each genotype). Of 14 973 genes expressed, 143 were differentially expressed (false discovery rate P < 0.05) in carriers versus noncarriers. Among the positional candidate genes, SMAD6 was 6.6-fold overexpressed in the carriers compared to noncarriers (P < 5 × 10-5). This result was replicated in an independent group of 12 females (7 carriers and 5 noncarriers) using quantitative real-time PCR; SMAD6 was 9.3-fold overexpressed in carriers versus noncarriers (P = 1.17 × 10-6). Association of overexpression of SMAD6, an inhibitor of the BMP/SMAD signaling pathway, with high ovulation rate corresponds well with disabling mutations in ligands (BMP15 and GDF9) and a receptor (BMPR1B) of this pathway that cause increased ovulation rate in sheep.

Growth differentiation factor 9 promotes follicle-stimulating hormone-induced progesterone production in chicken follicular granulosa cells

The function of oocyte-derived growth differentiation factor 9 (GDF9) in ovarian follicles has thus far been poorly defined in avian species compared with the defined function in mammals. Our aim here is to investigate the effects of GDF9 on steroidogenesis and on chicken ovarian granulosa cell (GC) mitosis. Primary GCs from both prehierarchical (6-8 mm in diameter, phGCs) and preovulatory follicles (F1-F5, poGCs) were cultured in the presence or absence of the GDF9 protein. The progesterone (P4) levels in the culture medium were then measured by radioimmunoassay (RIA), and the expression levels of steroidogenesis genes were detected by quantitative PCR. We found that GDF9 alone showed no significant effect on the P4 levels by regulating the expression of steroidogenesis genes, such as STAR, CYP11A1 and HSD3B. Further experiments indicated that GDF9 promoted follicle-stimulating hormone (FSH)-induced P4 production and STAR expression. GDF9 also rescued the FSH-induced decrease of FSH receptor (FSHR) expression but had no effect on the forskolin-induced P4, STAR and forskolin-inhibited FSHR expression levels, suggesting that GDF9 might achieve its regulatory role of P4 by enhancing FSHR and STAR expression. In addition, GDF9 also promoted GC cell cycle progression, regulated the gene transcription of related genes, potentiated DNA replication and inhibited apoptosis. Interestingly, these effects differed between the phGCs and the poGCs. To our knowledge, this is the first report that illustrates the function of GDF9 on chicken GCs and the effects on ovarian steroidogenesis. Our findings highlight the regulation of central oocytes on the surrounding granulosa cells and emphasize the interaction between paracrine signals and endocrine hormones on ovarian progesterone production; these findings contribute to the understanding of the development of avian ovarian follicles.

Molecular mechanism of FSHR expression induced by BMP15 in human granulosa cells

PURPOSE

Follicle-stimulating hormone receptor (FSHR) expression in granulosa cells is critical in enabling follicles to achieve accelerated growth. Although FSHR expression has been reported to be epigenetically regulated, the mechanism is unclear. Cooperation between oocytes and granulosa cells is also essential for normal follicular growth. Among oocyte-derived factors, bone morphogenetic protein 15 (BMP15) promotes follicular growth and is suggested to have epigenetic effects. We examined the role of BMP15 in the acquirement of FSHR in human granulosa cells.

METHODS

Immortalized non-luteinized human granulosa (HGrC1) cells were stimulated with trichostatin A (TSA) or BMP15 to analyze FSHR expression, histone modifications, and USF1/2 binding at the FSHR promoter region. Histone acetyl transferase (HAT) activity and phosphorylation of Smad 1/5/8 and p38 MAPK were examined with or without BMP15, SB203580, and LDN193189. CYP19A1 expression and estradiol production were also studied.

RESULTS

TSA and BMP15 induced FSHR mRNA expression in a dose-dependent manner and histone modifications were observed with increased binding of USF1/2. BMP15 increased FSHR protein expression, which was suppressed by LDN193189. BMP15 increased phosphorylation of Smad 1/5/8 and significantly increased HAT activity, which was inhibited by LDN193189, but not by SB203580. BMP15 increased phosphorylation of p38 MAPK and USF1. LDN193189 suppressed BMP15-induced phosphorylation of both p38 MAPK and USF1, whereas SB203580 suppressed the phosphorylation of USF1. BMP15 increased CYP19A1 mRNA expression and estradiol production.

CONCLUSION

BMP15 induced FSHR expression in human granulosa cells through Smad and non-Smad pathways. This mechanism of FSHR induction by BMP15 may be utilized for controlling follicular growth.

Cumulin and FSH Cooperate to Regulate Inhibin B and Activin B Production by Human Granulosa-Lutein Cells In Vitro

The oocyte-secreted factors bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) interact functionally, and it is hypothesized that this interaction may be mediated by formation of a GDF9:BMP15 heterodimer termed cumulin. GDF9 and BMP15 regulate folliculogenesis and ovulation rate and have been shown to regulate inhibin and activin, local regulators of folliculogenesis. The objective of this study was to determine whether cumulin regulates granulosa cell inhibin and activin production and whether this requires cooperation with FSH. Human granulosa-lutein (hGL) cells collected from patients undergoing in vitro fertilization were cultured with or without FSH with various forms of recombinant cumulin (native and cysteine mutants, with or without the prodomains), and cysteine mutant GDF9 or BMP15. Messenger RNA expression of the subunits of inhibins/activins (INHA, INHBA, INHBB) and secretion of inhibin A, inhibin B, and activin B were measured. Mature forms and proforms of cumulin stimulated comparable INHBB mRNA expression and secretion of inhibin B and activin B, whereas GDF9 or BMP15 exhibited no effect. Cumulin, but not GDF9 or BMP15, interacted synergistically with FSH to increase INHBB mRNA and inhibin B expression. FSH markedly stimulated INHA, which encodes the α subunit of inhibin A/B, and suppressed activin B. Cumulin with or without FSH did not significantly alter inhibin A. Together these data demonstrate that cumulin, but not GDF9 or BMP15, exerts paracrine control of FSH-induced regulation of inhibin B and activin B. The prodomains of cumulin may have a minimal role in its actions on granulosa cells.

Follicle development as an orchestrated signaling network in a 3D organoid

The ovarian follicle is the structural and functional unit of the ovary, composed of the female gamete (the oocyte) and supportive somatic cells. Follicles are not only the source of a female's germ cell supply, but also secrete important hormones necessary for proper endocrine function. Folliculogenesis, the growth and maturation of the follicular unit, is a complex process governed by both intrafollicular crosstalk and pituitary-secreted hormones. While the later stages of this process are gonadotropin-dependent, early folliculogenesis appears to be controlled by the ovarian microenvironment and intrafollicular paracrine and autocrine signaling. In vitro follicle culture remains challenging because of the limited knowledge of growth factors and other cytokines influencing early follicle growth. Here we discuss the current state of knowledge on paracrine and autocrine signaling influencing primary follicles as they develop into the antral stage. Given the importance of intrafollicular signaling and the ovarian microenvironment, we reviewed the current engineering approaches for in vitro follicle culture, including 3D systems using natural hydrogels such as alginate and synthetic hydrogels such as poly(ethylene glycol). Our discussion is focused on what drives the proliferation of granulosa cells, development of the thecal layer, and antrum formation-three processes integral to follicle growth up to the antral stage. Further research in this area may reveal the mechanisms behind these complex signaling relationships within the follicle, leading to more successful and physiologically-relevant in vitro culture methods that will translate well to clinical applications.

Modulation of bone morphogenetic protein activity by melatonin in ovarian steroidogenesis

BACKGROUND

Melatonin regulates circadian and seasonal rhythms and the activities of hormones and cytokines that are expressed in various tissues, including the ovary, in which melatonin receptors are expressed. In the ovary, follicular growth occurs as a result of complex interactions between pituitary gonadotropins and autocrine and paracrine factors, including bone morphogenetic proteins (BMPs) that are expressed in the ovary.

METHODS

The effects of melatonin and BMPs on steroidogenesis were examined by using the primary cultures of rat granulosa cells.

MAIN FINDINGS RESULTS

It was shown that melatonin has antagonistic effects on BMP-6 actions in the granulosa cells, suggesting that melatonin is likely to contribute to balancing the biological activity of endogenous BMPs that maintain progesterone production and luteinization in the growing follicles. Similar interactions between melatonin and BMP-smad signaling also were shown in the mechanism of controlling ovarian steroidogenesis by other ligands.

CONCLUSION

A new role of melatonin in the regulation of endocrine homeostasis in relation to BMP activity is introduced in this review.

Multigenerational obesity-induced perturbations in oocyte-secreted factor signalling can be ameliorated by exercise and nicotinamide mononucleotide

STUDY QUESTION

Can maternal and offspring high-fat diet (HFD)-induced changes in mRNA expression levels in mice be ameliorated by interventions in female offspring?

SUMMARY ANSWER

Our results indicate that exercise and nicotinamide mononucleotide (NMN) can ameliorate the negative effects of maternal and post-weaning HFD in female offspring.

WHAT IS KNOWN ALREADY

Maternal and post-weaning HFD can perturb offspring developmental trajectories. As rates of maternal obesity are rising globally, there is a need for effective treatments in offspring to ameliorate the negative effects from a maternal obesogenic environment. Modulation of the nicotinamide adenine dinucleotide (NAD⁺) pathway by exercise and the NAD⁺ precursor NMN has previously been shown to reduce the effects of obesity.

STUDY DESIGN SIZE DURATION

This study consisted of a multigenerational study using C57Bl6 mice. Mice were fed a control (chow) or HFD ad libitum throughout mating, pregnancy and lactation (n = 13-25). Female offspring (n = 72) were then also supplied either a chow or HFD post-weaning. At 9 weeks of age offspring from HFD dams were subjected to exercise on a treadmill for 9 weeks or at 16 weeks of age administered NMN (i.p.) for 2.5 weeks. At 18.5 weeks mice were euthanized and ovaries and cumulus-oocyte complexes (COC) were collected to examine the possibility of ameliorating the negative effects of maternal and post-weaning HFD.

PARTICIPANTS/MATERIALS SETTING METHODS

Ovary and COC mRNA expression was analysed using RT-qPCR. An initial screen of candidate genes was developed to test which molecular pathways may be involved in generating adverse reproductive system effects. For histological analysis, ovarian tissue was fixed in paraformaldehyde and embedded in paraffin and stained with haematoxylin and eosin. The numbers of primordial, primary, secondary and antral follicles were counted.

MAIN RESULTS AND THE ROLE OF CHANCE

In the offspring's COC, maternal obesity increased both growth differentiation factor 9 (Gdf9: 2-fold; P < 0.05, HFD versus chow) and bone morphogenetic protein 15 (Bmp15: 4-fold; P < 0.05, HFD versus chow) mRNA expression levels while exercise and NMN interventions did not regulate Gdf9 and Bmp15 in the same manner. In whole ovary, maternal diet programmed a 25-50% reduction in FSH receptor and sirtuin-3 mRNA expression levels in daughter ovaries (P < 0.05, HFD versus chow). There was a significant interaction between HFD and intervention on the proportion of large preantral and preovulatory follicles (P < 0.05). However, the increase in preovulatory follicles did not translate to increased oocyte yield. NMN administration resulted in reduced body weight in HFD-fed individuals.

LIMITATIONS REASONS FOR CAUTION

It is unclear if the changes in oocyte mRNA expression levels reported here will impact oocyte quality and fertility in offspring. Offspring ovulation rate or fecundity could not be studied here and fertility trials are required to determine if the changes in gene expression do reduce fertility.

WIDER IMPLICATIONS OF THE FINDINGS

Our results demonstrate that maternal and offspring HFD perturbs key signalling pathways that are known to regulate fertility in mice, highlighting the importance of interventions in helping to prevent the declining rates of fertility in the context of the current obesity epidemic.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by grants and fellowships from the National Health and Medical Research Council to R.B.G. (APP1023210, APP1062762, APP1117538) and to M.J.M. and D.A.S. (APP1044295). DAS is a consultant to and inventor on patents licenced to Ovascience, Metrobiotech and GlaxoSmithKline. The other authors declare that there is no conflict of interest.

The Growth of Preantral Follicles and the Impact of Different Supplementations and Circumstances: A Review Study with Focus on Bovine and Human Preantral Follicles

One of the most important concerns cancer survivors face is fertility. Current treatment modalities often result in damage to the reproductive system. Different options have been proposed to preserve the fertility of affected women, and many attempts have been made to improve their chance of childbearing after therapy. Cryopreservation of ovarian tissue and follicles before the onset of cancer treatment and then either transplantation of ovarian tissue or culture of ovarian tissue and individual follicles in vitro is a commonly cited approach. Extensive research is being done to design an optimal condition for the culture of ovarian follicles. Improving follicle culture systems by understanding their actual growth needs might be a crucial step toward fertility preservation in cancer patients. This review article will try to provide a summary of the role of different factors and conditions on growth of human and bovine preantral follicles in vitro.

Comparison of the Oocyte Quality Derived from Two-Dimensional Follicle Culture Methods and Developmental Competence of In Vitro Grown and Matured Oocytes

In vitro follicle growth (IVFG) is an emerging fertility preservation technique, which can obtain fertilizable oocytes from an in vitro culture system in female. This study aimed to compare efficiency of the most widely used two-dimensional follicle culture methods [with or without oil layer (O+ or O- group)]. Preantral follicles were isolated from mice and randomly assigned. Follicles were cultured for 10 days and cumulus-oocyte complexes harvested 16-18 hours after hCG treatment. Follicle and oocyte growth, hormones in spent medium, meiotic spindle localization, expression of reactive oxygen species (ROS), mitochondrial activity, and gene expression were evaluated. In follicle growth, survival, pseudoantral cavity formation, ovulation, and oocyte maturation were also significantly higher in O+ group than O- group. Hormone production was significantly higher in follicles cultured in O+ than O-. There were no significant differences in mRNA expression related to development. On the other hand, the level of ROS was increased while the mitochondrial activity of in vitro grown matured oocyte was less than in vivo matured oocytes. In conclusion, follicle culture with O+ group appears to be superior to the culture in O- group in terms of follicle growth, development, oocyte growth, maturation, and microorganelles in oocyte.

Involvement of Bone Morphogenetic Proteins (BMP) in the Regulation of Ovarian Function

Primordial germ cells migrate to the fetal gonads and proliferate during gestation to generate a fixed complement of primordial follicles, the so-called ovarian reserve. Primordial follicles comprise an oocyte arrested at the diplotene stage of meiosis, surrounded by a layer of pregranulosa cells. Activation of primordial follicles to grow beyond this arrested stage is of particular interest because, once activated, they are subjected to regulatory mechanisms involved in growth, selection, maturation, and ultimately, ovulation or atresia. The vast majority of follicles succumb to atresia and are permanently lost from the quiescent or growing pool of follicles. The bone morphogenetic proteins (BMPs), together with other intraovarian growth factors, are intimately involved in regulation of follicle recruitment, dominant follicle selection, ovulation, and atresia. Activation of primordial follicles appears to be a continuous process, and the number of small antral follicles at the beginning of the menstrual cycle provides an indirect indication of ovarian reserve. Continued antral follicle development during the follicular phase of the menstrual cycle is driven by follicle stimulating hormone (FSH) and luteinizing hormone (LH) in conjunction with many intraovarian growth factors and inhibitors interrelated in a complex web of regulatory balance. The BMP signaling system has a major intraovarian role in many species, including the human, in the generation of transcription factors that influence proliferation, steroidogenesis, cell differentiation, and maturation prior to ovulation, as well as formation of corpora lutea after ovulation. At the anterior pituitary level, BMPs also contribute to the regulation of gonadotrophin production.

PCR-RFLP of bone morphogenetic protein 15 (BMP15/FecX) gene as a candidate for prolificacy in sheep

Bone morphogenetic protein 15 (BMP15/FecX) gene is considered one of the major genes and a candidate marker for the reproduction in farm animals, especially sheep. The present study aimed to detect the genetic polymorphisms of BMP15 gene in sheep using PCR-RFLP technique. In the present study, 115 ewes were assigned into high and low prolificacy categories according to their reproductive history. In high prolific group (n = 20), ewes produced twins more than single births. In the low prolific type (n = 95), the ewes produced single births more than twins. DNA was extracted from blood samples of all ewes, subjected to PCR-RFLP analysis and confirmed by sequence analysis. The PCR products of 356 bp size were cut with HinƒI restriction enzyme. Three digested fragments of 70, 117 and 169 bp were obtained in both types of sheep. All animals were homozygous with CC genotype. In conclusion, the accessible findings did not detect any mutation in FecX gene in sheep, regardless their prolificacy. Therefore, further attempts are necessary to detect other SNP for BMP-15 gene in Egyptian sheep breeds.

Positive selection drives the evolution of endocrine regulatory bone morphogenetic protein system in mammals

The rapid evolution of reproductive proteins might be driven by positive Darwinian selection. The bone morphogenetic protein family is the largest within the transforming growth factor (TGF) superfamily. A little have been known about the molecular evolution of bone morphogenetic proteins exhibiting potential role in mammalian reproduction. In this study we investigated mammalian bone morphogenetic proteins using maximum likelihood approaches of codon substitutions to identify positive Darwinian selection in various species. The proportion of positively selected sites was tested by different likelihood models for individual codon, and M8 were found to be the best model. The percentage of positively elected sites under M8 are 2.20% with ω = 1.089 for BMP2, 1.6% with ω = 1.61 for BMP 4 0.53% for BMP15 with ω = 1.56 and 0.78% for GDF9 with ω = 1.93. The percentage of estimated selection sites under M8 is strong statistical confirmation that divergence of bone morphogenetic proteins is driven by Darwinian selection. For the proteins, model M8 was found significant for all proteins with ω > 1. To further test positive selection on particular amino acids, the evolutionary conservation of amino acid were measured based on phylogenetic linkage among sequences. For exploring the impact of these somatic substitution mutations in the selection region on human cancer, we identified one pathogenic mutation in human BMP4 and one in BMP15, possibly causing prostate cancer and six neutral mutations in BMPs. The comprehensive map of selection results allows the researchers to perform systematic approaches to detect the evolutionary footprints of selection on specific gene in specific species.

Interaction of Melatonin and BMP-6 in Ovarian Steroidogenesis

The bone morphogenetic protein (BMP) system in the ovary plays a physiological role as a luteinization inhibitor in growing follicles. BMP-6 secreted from oocytes and granulosa cells can exert an inhibitory effect on follicle-stimulating hormone (FSH) actions by suppressing adenylate cyclase activity downstream of the FSH receptor. The inhibition of FSH-induced progesterone production by BMP-6 is impaired by melatonin treatment in granulosa cells. Intracellular Smad signaling induced by BMP-6 is suppressed by melatonin, suggesting that melatonin has a regulatory role in BMP receptor signaling in granulosa cells. Since the expression of BMP-6 in granulosa cells is increased in patients with polycystic ovary syndrome, melatonin may play an important role in the maintenance of progesterone production by suppressing BMP-6 signaling, leading to the preservation of ovarian function.

Dose and administration protocol for FSH used for ovarian stimulation affect gene expression in sheep cumulus–oocyte complexes

The present study evaluated the effect of four ovarian stimulation protocols on the follicular population and molecular status of cumulus–oocyte complexes (COCs). Twelve Santa Inês ewes (in a cross-over design) received 80 or 120 mg FSH alone in a multiple-dose (MD80 and MD120) regimen or in combination with 300 IU equine chorionic gonadotrophin (eCG) in a one-shot (OS80 and OS120) protocol. The follicular population, COC recovery rate, mean COCs per ewe and the rate of brilliant Cresyl blue-positive (BCB+) COCs were similar among treatments (P > 0.05). The expression of markers of oocyte competence (ZAR1, zygote arrest 1; MATER, maternal antigen that embryo requires; GDF9, growth differentiation factor 9; BMP15, bone morphogenetic protein 15; Bcl-2, B-cell lymphoma 2; BAX, Bcl-2 associated X protein) and the steroidogenic pathway (ERα, oestrogen receptor α; LHr, LH receptor; FSHr, FSH receptor; STAR, steroidogenic acute regulatory protein) was affected by stimulation. Specifically, the expression of markers of the steroidogenic pathway was reduced with increasing FSH dose in the OS protocol. FSH at a dose of 80 mg reduced the expression of FSHr and ERα in the OS versus MD protocol. Conversely, in MD protocol, only LHr was affected by increasing FSH dose. In conclusion, 80 mg FSH in the MD or OS protocol was sufficient to promote the development of multiple follicles and obtain fully grown (BCB+) oocytes. The MD protocol may be more appropriate for the production of better-quality oocytes.

Repertoire of bone morphogenetic proteins and growth/differentiation factors in ovary of the Indian wall lizard (Hemidactylus flaviviridis) with emphasis on differential expression and gonadotropic regulation of bmp15 and gdf9

Analysis of ovarian transcriptome of Indian wall lizard demonstrates the existence of several bone morphogenetic proteins (bmp1, 2, 3, 3b, 7, 8, 15) and growth/differentiation factors (gdf5, 9) for the first time in reptilian ovary. The characterization of putative full-length/partial protein sequences of BMPs (BMP2, 3, 3b, 7, 15) and GDF9 showed high homology of their TGF-β domain with that of other vertebrates while BMP1 bore homology to zinc-dependent metalloprotease. Phylogenetic analyses showed clustering of BMPs and GDF9 from wall lizards with that of squamates lying in close proximity to chelonia, crocodilia and aves. This study also correlates the expression of ovarian bmp15 and gdf9 with folliculogenesis. Level of bmp15 dramatically increased with the onset of follicular growth in early recrudescence and attained peak during late recrudescence whereas gdf9 sharply decreased during recrudescence as compared to regression. Nonetheless, expression of these growth factors decreased appreciably with the formation of vitellogenic follicle during breeding phase. Ovarian expression of bmp15 and gdf9 appeared to be regulated by gonadotropin as bmp15 considerably increased while gdf9 decreased in parallel to follicular development after administration of 3 injections of FSH. Expression of both the growth factors declined with the prolongation of treatment that led to formation of early/late vitellogenic follicle. Our in vitro study revealed stimulatory effect of FSH on expression of bmp15 and gdf9 in early growing, previtellogenic and early vitellogenic follicles. In light of in vitro results, FSH-induced in vivo decline in gene expression seems to be due to some other FSH-induced factor.

Survey of mutations in prolificacy genes in Santa Ines and Morada Nova sheep

ABSTRACT Polymorphisms in the BMP-15 gene related to Galway (FecXG) and Inverdale (FecXI) and in the BMPR-1B gene known as Booroola (FecB) mutations were investigated using the Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (PCR-RFLP) method, on sheep from the breeds Santa Inês (n= 574) and Morada Nova (n=282). DNA was extracted and amplified through PCR with specific primers that introduced a restriction site in association with the mutation. The PCR products were submitted to endonucleases. The experiment found no FecXG and FecXI mutations. Six samples of animals with multiple offspring/birth history presented polymorphism for FecB similar to control samples, but this pattern was not confirmed by nucleotide sequencing. Although the absence of these mutations in the studied breeds, other factors related to prolificacy should be investigated to explain the inherent prolificity mechanisms.

BMP15 regulates the inhibin/activin system independently of ovulation rate control in sheep

Polymorphisms in the gene encoding bone morphogenetic protein 15 (BMP15) have been associated with multiple ovulations in sheep. As BMP15 regulates inhibin expression in rodents, we assumed that the ovarian inhibin/activin system could mediate part of the effect of BMP15 mutations in the regulation of ovulation rate in sheep. To answer this question, we have studied the effects of two natural loss-of-function mutations of BMP15 on the expression of components of this system. The FecX^R and the FecX^Gr mutations, when present respectively in Rasa Aragonesa ewes at the heterozygous state and in Grivette ewes at the homozygous state, were associated with a twofold increase in ovulation rate. There were only small differences between mutant and wild-type ewes for mRNA expression of INHA, INHBA, ACVR1B, ACVR2A, FST or TGFBR3 in granulosa cells and inhibin A or activin A concentrations in follicular fluid. Moreover, the effects of mutations differed between breeds. In cultures of granulosa cells from wild-type ewes, BMP15, acting alone or in synergy with GDF9, stimulated INHA, INHBA and FST expression, but inhibited the expression of TGFBR3 Activin A did not affect INHBA expression, but inhibited the expression of ACVR2A also. The complexity of the inhibin/activin system, including positive and antagonistic elements, and the differential regulation of these elements by BMP15 and activin can explain that the effects of BMP15 mutations differ when present in different genetic backgrounds. In conclusion, the ovarian inhibin/activin system is unlikely to participate in the increase of ovulation rate associated with BMP15 mutations in sheep.