TGFβ signalling in the development of ovarian function

Growth differentiation factor 9 activates the TGF-β pathway in follicle atresia of Muscovy ducks

Muscovy ducks' high broodiness hinders industry growth. Studying broodiness regulation contributes to the theoretical foundation for enhancing reproductive performance in Muscovy ducks. Experiment 1, a total of 18 Muscovy ducks were divided into 2 groups: Laying group (LO) and Broody group (BO). To collect ovaries for morphological and transcriptome analysis. Experiment 2, Primary Muscovy ducks granulosa cells (GC) were isolated and treated with or without GDF9 at appropriate concentrations as indicated. Experiment 3, GC were treated with or without GDF9 in the presence or absence of a receptor inhibitor. The cell viability, cell apoptosis rate and levels of TGF-β pathway were determined. In vivo, there was a gradual disappearance of follicles in the ovaries and accompanied by follicle atrophy and a concentration of cytoplasm in BO group. The transcriptome expression profile revealed a total of 1,185 up-regulated differentially expressed transcripts (DEs) and 1,258 down-regulated DEs in the BO group compared to the LO group. The up-regulated differentially expressed GDF9 is involved in regulating the TGF-β pathway, which is among the top 10 pathways identified through the KEGG pathway analysis (P < 0.05). Additionally, the fluorescence intensity of apoptosis is primarily observed in the granulosa layers of the ovary. Compared to the LO group, the mRNA level of TGF-β pathway and the protein of GDF9 and p-Smad2/3 were increased in ovary of the BO group (P < 0.05). In vitro, GDF9 supplementation demonstrated does-related promotion of GC (P < 0.01). Compared to CTRL group, 12 ng/mL GDF9 supplementation to GC increased the rate of cell apoptosis, the mRNA and protein expression of TGF-β pathway and the apoptosis-related genes. Pretreatment of GC with GDF9-receptor inhibitor largely abrogated the negative function of GDF9 treatment (P < 0.05). In summary, granulosa cell apoptosis leading to follicle atresia in broodiness of Muscovy ducks is associated with GDF9 activation of the TGF-β pathway. This discovery lays a solid foundation for understanding duck follicular development and enhancing egg production in Muscovy ducks.

MicroRNA Transcriptomes Reveal Prevalence of Rare and Species-Specific Arm Switching Events During Zebrafish Ontogenesis

In metazoans, microRNAs (miRNAs) are essential regulators of gene expression, affecting critical cellular processes from differentiation and proliferation, to homeostasis. During miRNA biogenesis, the miRNA strand that loads onto the RNA-induced Silencing Complex (RISC) can vary, leading to changes in gene targeting and modulation of biological pathways. To investigate the impact of these "arm switching" events on gene regulation, we analyzed a diverse range of tissues and developmental stages in zebrafish by comparing 5p and 3p arms accumulation dynamics between embryonic developmental stages, adult tissues, and sexes. We also compared variable arm usage patterns observed in zebrafish to other vertebrates including arm switching data from fish, birds, and mammals. Our comprehensive analysis revealed that variable arm usage events predominantly take place during embryonic development. It is also noteworthy that isomiR occurrence correlates to changes in arm selection evidencing an important role of microRNA distinct isoforms in reinforcing and modifying gene regulation by promoting dynamics switches on miRNA 5p and 3p arms accumulation. Our results shed new light on the emergence and coordination of gene expression regulation and pave the way for future investigations in this field.

BMP8B Activates Both SMAD2/3 and NF-κB Signals to Inhibit the Differentiation of 3T3-L1 Preadipocytes into Mature Adipocytes

Bone morphogenetic protein 8B (BMP8B) has been found to regulate the thermogenesis of brown adipose tissue (BAT) and the browning process of white adipose tissue (WAT). However, there is no available information regarding the role of BMP8B in the process of adipocyte differentiation. Here, we showed that BMP8B down-regulates transcriptional regulators PPARγ and C/EBPα, thereby impeding the differentiation of 3T3-L1 preadipocytes into fully mature adipocytes. BMP8B increased the phosphorylation levels of SMAD2/3, and TP0427736 HCl (SMAD2/3 inhibitor) significantly reduced the ability of BMP8B to inhibit adipocyte differentiation, suggesting that BMP8B repressed adipocyte differentiation through the SMAD2/3 pathway. Moreover, the knockdown of BMP I receptor ALK4 significantly reduced the inhibitory effect of BMP8B on adipogenesis, indicating that BMP8B triggers SMAD2/3 signaling to suppress adipogenesis via ALK4. In addition, BMP8B activated the NF-κB signal, which has been demonstrated to impede PPARγ expression. Collectively, our data demonstrated that BMP8B activates both SMAD2/3 and NF-κB signals to inhibit adipocyte differentiation. We provide previously unidentified insight into BMP8B-mediated adipogenesis.

Bmp4 in Zebrafish Enhances Antiviral Innate Immunity through p38 MAPK (Mitogen-Activated Protein Kinases) Pathway

Bone morphogenetic proteins (BMPs) are a group of structurally and functionally related signaling molecules that comprise a subfamily, belonging to the TGF-β superfamily. Most BMPs play roles in the regulation of embryonic development, stem cell differentiation, tumor growth and some cardiovascular and cerebrovascular diseases. Although evidence is emerging for the antiviral immunity of a few BMPs, more BMPs are needed to determine whether this function is universal. Here, we identified the zebrafish bmp4 ortholog, whose expression is up-regulated through challenge with grass carp reovirus (GCRV) or its mimic poly(I:C). The overexpression of bmp4 in epithelioma papulosum cyprini (EPC) cells significantly decreased the viral titer of GCRV-infected cells. Moreover, compared to wild-type zebrafish, viral load and mortality were significantly increased in both larvae and adults of bmp4-/- mutant zebrafish infected with GCRV virus. We further demonstrated that Bmp4 promotes the phosphorylation of Tbk1 and Irf3 through the p38 MAPK pathway, thereby inducing the production of type I IFNs in response to virus infection. These data suggest that Bmp4 plays an important role in the host defense against virus infection. Our study expands the understanding of BMP protein functions and opens up new targets for the control of viral infection.

Immunolocalization of activin and inhibin at different stages of follicular development in the lizard Sceloporus torquatus

The activins and inhibins are glycoproteins with a role in the follicular development of vertebrates, that are found in follicular fluid and somatic follicular cells, with a different pattern among taxa. The principal function of activin (Act) is to modulate the follicle-stimulating hormone (FSH) synthesis and secretion, whereas inhibin (Inh) downregulates it. Both factors are modulators of intraovarian follicular recruitment, oocyte maturation, cell proliferation, and steroidogenic activity. Our aim was to characterize the immunolocalization of Act and Inh in the ovarian follicles during the reproductive cycle of the lizard Sceloporus torquatus. Act was detected in the granulosa cells and oocyte cortex in the different stages of follicular development. On the other hand, we identified Inh in the oocyte cortex and the cytoplasm of pyriform and small cells of previtellogenic follicles. Also, we found immunoreactivity in the oocyte cortex, theca, and small cells of vitellogenic and preovulatory follicles. Our data provide evidence that Act and Inh have changes related to the stage of follicular development. This dynamic appears to be conserved among vertebrates and is fundamental to ensure an adequate follicular development in this specie.

Bmp8a deletion leads to obesity through regulation of lipid metabolism and adipocyte differentiation

The role of bone morphogenetic proteins (BMPs) in regulating adipose has recently become a field of interest. However, the underlying mechanism of this effect has not been elucidated. Here we show that the anti-fat effect of Bmp8a is mediated by promoting fatty acid oxidation and inhibiting adipocyte differentiation. Knocking out the bmp8a gene in zebrafish results in weight gain, fatty liver, and increased fat production. The bmp8a-/- zebrafish exhibits decreased phosphorylation levels of AMPK and ACC in the liver and adipose tissues, indicating reduced fatty acid oxidation. Also, Bmp8a inhibits the differentiation of 3T3-L1 preadipocytes into mature adipocytes by activating the Smad2/3 signaling pathway, in which Smad2/3 binds to the central adipogenic factor PPARγ promoter to inhibit its transcription. In addition, lentivirus-mediated overexpression of Bmp8a in 3T3-L1 cells significantly increases NOD-like receptor, TNF, and NF-κB signaling pathways. Furthermore, NF-κB interacts with PPARγ, blocking PPARγ's activation of its target gene Fabp4, thereby inhibiting adipocyte differentiation. These data bring a signal bridge between immune regulation and adipocyte differentiation. Collectively, our findings indicate that Bmp8a plays a critical role in regulating lipid metabolism and adipogenesis, potentially providing a therapeutic approach for obesity and its comorbidities.

Activin A Reduces Porcine Granulosa Cells Apoptosis via ERβ-Dependent ROS Modulation

Unfavorable conditions compromise animal reproduction by altering the ovarian granulosa cells' follicular dynamics and normal physiological function (GCs), eventually resulting in oxidative damage and cell apoptosis. Activin is produced in the GCs and plays a vital role in folliculogenesis. This study investigated the effects of activin A (ACT-A) treatment in vitro on the apoptosis of porcine GCs and the underlying molecular mechanism. We found that ACT-A could attenuate the apoptosis of the GCs and enhance the synthesis of estrogen (E2). ACT-A also enhanced FSH-induced estrogen receptor-β (ERβ) expression, inhibiting ERβ aggravated intracellular accumulation of the reactive oxygen species (ROS) and apoptosis. The E2 levels in the culture medium, the mRNA expression pattern of the apoptosis-related genes (CASPASE 3, BCL2, and BAX), steroidogenesis-related gene (CYP19A1), and cell viability were analyzed to confirm the results. In summary, this study indicated the protective role of ACT-A in apoptosis by attenuating the ROS accumulation through ERβ. These results aim to enhance the follicular functions and improve animal reproductive performance.

Identification and characterization of unique and common lncRNAs and mRNAs in the pituitary, ovary, and uterus of Hu sheep with different prolificacy

LncRNAs are regarded as regulators in various animal reproductive physiological processes. However, the regulation of lncRNAs in the reproductive organ development of Hu sheep with different prolificacy remains unknown. Herein, numerous tissue-unique and -common differentially expressed lncRNAs (DELs) and differentially expressed genes (DEGs), and fecundity-unique DELs and DEGs were identified among different comparison groups at horizontal and vertical levels. Moreover, the tissue-unique and -common, and fecundity-unique female reproduction-associated DEGs and DELs were screened, and the interaction networks were constructed. Furthermore, MSTRG.43442.1 was mainly present in the cytoplasm of tested cells. The key genes ADAMTS1 and DCN were mainly localized in the granulosa cells, pituitary cells and/or endometrial epithelial cells of ovary, pituitary and/or uterus. Overall, this study identified large numbers of unique and common DELs and DEGs in the female reproductive organs of Hu sheep with different prolificacy and provided new insights into understanding the regulation of Hu sheep fecundity.

Extracellular vesicles in reproduction and pregnancy

Extracellular vesicles (EVs) are small, lipid-bound packages that are secreted by all cell types and have been implicated in many diseases, such as cancer and neurodegenerative disorders. Though limited, an exciting new area of EV research focuses on their role in the reproductive system and pregnancy. In males, EVs have been implicated in sperm production and maturation. In females, EVs play a vital role in maintaining reproductive organ homeostasis and pregnancy, including the regulation of folliculogenesis, ovulation, and embryo implantation. During the development and maintenance of a pregnancy, the placenta is the main form of communication between the mother and the developing fetus. To support the developing fetus, the placenta will act as numerous vital organs until birth, and release EVs into the maternal and fetal bloodstream. EVs play an important role in cell-to-cell communication and may mediate the pathophysiology of pregnancy-related disorders such as preeclampsia, gestational diabetes mellitus, preterm birth, and intrauterine growth restriction, and potentially serve as noninvasive biomarkers for these conditions. In addition, EVs may also mediate processes involved in both male and female infertility. Together, the EVs secreted by both the male and female reproductive tracts work to promote reproductive fertility and play vital roles in mediating maternal-fetal crosstalk and pregnancy maintenance.

Ovarian Biomechanics: From Health to Disease

Biomechanics is a physical phenomenon which mainly related with deformation and movement of life forms. As a mechanical signal, it participates in the growth and development of many tissues and organs, including ovary. Mechanical signals not only participate in multiple processes in the ovary but also play a critical role in ovarian growth and normal physiological functions. Additionally, the involvement of mechanical signals has been found in ovarian cancer and other ovarian diseases, prompting us to focus on the roles of mechanical signals in the process of ovarian health to disease. This review mainly discusses the effects and signal transduction of biomechanics (including elastic force, shear force, compressive stress and tensile stress) in ovarian development as a regulatory signal, as well as in the pathological process of normal ovarian diseases and cancer. This review also aims to provide new research ideas for the further research and treatment of ovarian-related diseases.

Expression profiling of ovarian BMP antagonists reveals the potential interaction between TWSG1 and the chordin subfamily in the ovary

The TGF-β superfamily members and their antagonists comprise an indispensable system that controls mammalian ovarian development in a sophisticated manner. In contrast to a plethora of studies on the ovary-expressed TGF-β superfamily members, knowledge regarding their antagonists, including their expression profiles and antagonism preferences, is still lacking. Using quantitative PCR in rats and transcriptomic dataset comparisons in mice and humans, we set out to characterize the relative expression levels of most antagonists in the mammalian ovary. We found that Twsg1 and Nbl1 are the most abundant BMP antagonists expressed in the rodent and human ovaries, respectively. TWSG1 has been reported to have synergistic action with the chordin subfamily, including CHRD and CHRDL1, the genes of which also showed moderate expression in the mammalian ovary. Therefore, their ovarian expression profiles and antagonisms against the ovary-expressed TGF-β superfamily members were further characterized. Bioactivity tests indicated that TWSG1 alone can directly inhibit the signaling of BMP6 or BMP7. In addition, it can further enhance the antagonizing ability of CHRD towards BMP2, BMP4, BMP7 and GDF5, or CHRDL1's antagonism towards BMP2, BMP4, GDF5 and activin A. In combination with their distinct transcript profiles in ovarian compartments, our findings suggest that TWSG1 may work coordinately with CHRD within theca/interstitial shells and also with CHRDL1 in developing granulosa cells; these interactions would modulate the intraovarian functions of the TGF-β superfamily members, such as the control of progesterone production.

Analysis of miRNA expression changes in bovine endometrial stromal cells treated with lipopolysaccharide

After parturition, bovine uterine stromal cells are often exposed to complex bacterial and viral stimuli owing to epithelial cell rupture, resulting in an inflammatory response. In this study, we used an in vitro model to study the response of bovine endometrial stromal cells to inflammatory mediators and the associated regulated microRNAs in response to lipopolysaccharide. Lipopolysaccharide (LPS) is a bacterial wall component in gram-negative bacteria that causes inflammation upon immune recognition, which is used to create in vitro inflammation models. Thus, we used high-throughput RNA sequencing to identify miRNAs that may have an anti-inflammatory role in the LPS-induced inflammatory response. Two groups of bovine uterine cells were treated with phosphate buffer saline (PBS) and LPS, respectively. Compared with the control (PBS) group, the LPS-treated group had 219 differentially expressed miRNAs, of which 113 were upregulated, and 106 were downregulated. Gene ontology enrichment analysis revealed that the target genes of differentially expressed miRNAs were significantly enriched in several activities, such as transferase activity, small molecule binding, and protein binding. Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that the target genes of differential miRNAs were significantly enriched in fluid shear stress and atherosclerosis, MAPK signaling pathway, TNF signaling pathway. By analyzing differentially expressed miRNAs, we found that miR-200c, miR-1247-3p, and let-7b are directly related to the inflammatory response. For instance, miR-200c target genes (MAP3K1, MAP4K3, MAPKAPK5, MAP3K8, MAP3K5) and let-7b target genes (CASP3, IL13, MAPK8, CXCL10) were significantly enriched in the MAPK and IL-17 signaling pathways, respectively. In summary, our research provides insight into the molecular mechanism underlying LPS-induced inflammation in vitro, which may unveil new targets for the treatment of endometritis.

Bmp8a is an essential positive regulator of antiviral immunity in zebrafish

Bone morphogenetic protein (BMP) is a kind of classical multi-functional growth factor that plays a vital role in the formation and maintenance of bone, cartilage, muscle, blood vessels, and the regulation of adipogenesis and thermogenesis. However, understanding of the role of BMPs in antiviral immunity is still limited. Here we demonstrate that Bmp8a is a newly-identified positive regulator for antiviral immune responses. The bmp8a^−/− zebrafish, when infected with viruses, show reduced antiviral immunity and increased viral load and mortality. We also show for the first time that Bmp8a interacts with Alk6a, which promotes the phosphorylation of Tbk1 and Irf3 through p38 MAPK pathway, and induces the production of type I interferons (IFNs) in response to viral infection. Our study uncovers a previously unrecognized role of Bmp8a in regulation of antiviral immune responses and provides a target for controlling viral infection.

Zhang, Liu and colleagues identify the role of Bmp8a in antiviral immunity in zebrafish and provide mechanistic insight into its function. Bmp8a could serve as a future target for investigative studies of antiviral immune responses.

Current mechanisms of primordial follicle activation and new strategies for fertility preservation

Premature ovarian insufficiency (POI) is characterized by symptoms caused by ovarian dysfunction in patients aged <40 years. It is associated with a shortened reproductive lifespan. The only effective treatment for patients who are eager to become pregnant is IVF/Embryo Transfer (ET) using oocytes donated by young women. However, the use of the technique is constrained by the limited supply of oocytes and ethical issues. Some patients with POI still have some residual follicles in the ovarian cortex, which are not regulated by gonadotropin. These follicles are dormant. Therefore, activating dormant primordial follicles (PFs) to obtain high-quality oocytes for assisted reproductive technology may bring new hope for patients with POI. Therefore, this study aimed to explore the factors related to PF activation, such as the intercellular signaling network, the internal microenvironment of the ovary and the environment of the organism. In addition, we discussed new strategies for fertility preservation, such as in vitro activation and stem cell transplantation.

miR-146a-5p Regulated Cell Proliferation and Apoptosis by Targeting SMAD3 and SMAD4

Background: microRNAs (miRNAs) are a small, endogenous non-coding RNAs that are involved in post-transcriptional gene regulation of many biological processes, including embryo implantation and placental development. In our previous study, miR-146a-5p was found expressed higher in the serum exosomes of pregnant sows than non-pregnant. The research on miR-146a-5p has been mainly related to human diseases, but there are few studies on its effects on the reproduction of sows in early pregnancy.

Objective: In this article, our motivation is to study the role of miR-146a-5p in the early pregnancy of sows on the cell proliferetion and apoptosis by targeting SMAD3 and SMAD4.

Methods: Bioinformatics software was used to identify the target genes of miR-146a-5p. The wild-type and mutant-type recombinant plasmids of dual-luciferase reporter with 3'-UTR of Smad3 or 3'-UTR of Smad4 were constructed, and co-transfected in porcine kidney cell (PK-15 cell) with miR-146a-5p mimic, mimic-NC(M-NC), inhibitor and inhibitor-NC(IN-NC), then dual-luciferase activity analysis, qRT-PCR and Western blot were performed to verify the target genes. After the transfection of BeWo choriocarcinoma cell (BeWo cell) with miR-146a-5p mimic, M-NC, inhibitor and IN-NC, the mRNA expression of Caspase-3, BAX and Bcl-2 was measured using qRT-PCR, and the cell proliferation was measured using CCK-8 kit.

Results: The luciferase, mRNA and protein expression of Smad3 in PK-15 cells treated by Smad3-3'-UTR-W co-transfected with miR-146a-5p mimic were significantly lower than that with miR-146a-5p M-NC, and the results of Smad4 were similar to Smad3, but the protein expression had a trend to lower in mimic group. The expression level of Bcl-2 in the miR-146a-5p mimic group was significantly lower than that in the miR-146a-5p M-NC group, but the expression pattern of Caspase-3 was just opposite. The mimic of miR-146a-5p reduced the proliferation of BeWo cells, however the inhibitor increased.

Conclusion: Smad3 and Smad4 are the direct target genes of miR-146a-5p. The expression of Smad3 and Smad4 were affected by the mimic and inhibitor of miR-146a-5p. miR-146a-5p affects cell apoptosis and proliferation by regulating their target genes. This study provided new data to understand the regulation mechanism of early pregnancy in sows.

Human placenta-derived mesenchymal stem cells stimulate ovarian function via miR-145 and bone morphogenetic protein signaling in aged rats

Background

Aging has detrimental effects on the ovary, such as a progressive reduction in fertility and decreased hormone production, that greatly reduce the quality of life of women. Thus, the current study was undertaken to investigate whether human placenta-derived mesenchymal stem cell (hPD-MSC) treatment can restore the decreases in folliculogenesis and ovarian function that occur with aging.

Methods

Acclimatized 52-week-old female SD rats were randomly divided into four groups: single hPD-MSC (5 × 10⁵) therapy, multiple (three times, 10-day intervals) hPD-MSC therapy, control (PBS), and non-treated groups. hPD-MSC therapy was conducted by tail vein injection into aged rats. The rats were sacrificed 1, 2, 3, and 5 weeks after the last injection. hPD-MSC tracking and follicle numbers were histologically confirmed. The serum levels of sex hormones and circulating miRNAs were detected by ELISA and qRT-PCR, respectively. TGF-β superfamily proteins and SMAD proteins in the ovary were detected by Western blot analysis.

Results

We observed that multiple transplantations of hPD-MSCs more effectively promoted primordial follicle activation and ovarian hormone (E₂ and AMH) production than a single injection. After hPD-MSC therapy, the levels of miR-21-5p, miR-132-3p, and miR-212-3p, miRNAs associated with the ovarian reserve, were increased in the serum. Moreover, miRNAs (miR-16-5p, miR-34a-5p, and miR-191-5p) with known adverse effects on folliculogenesis were markedly suppressed. Importantly, the level of miR-145-5p was reduced after single- or multiple-injection hPD-MSC therapy, and we confirmed that miR-145-5p targets Bmpr2 but not Tgfbr2. Interestingly, downregulation of miR-145-5p led to an increase in BMPR2, and activation of SMAD signaling concurrently increased primordial follicle development and the number of primary and antral follicles.

Conclusions

Our study verified that multiple intravenous injections of hPD-MSCs led to improved ovarian function via miR-145-5p and BMP-SMAD signaling and proposed the future therapeutic potential of hPD-MSCs to promote ovarian function in women at advanced age to improve their quality of life during climacterium.

SMAD-dependent signaling mediates morphogenetic protein 6-induced stimulation of connective tissue growth factor in luteinized human granulosa cells†

Connective tissue growth factor (also known as CTGF or CCN2) is a secreted matricellular protein that belongs to the CCN family. With wide-ranging biological activities and tissue expression patterns, CTGF plays a critical role in regulating various cellular functions. In the female reproductive system, CTGF is highly expressed in granulosa cells in growing ovarian follicles and is involved in the regulation of follicular development, ovulation, and luteal function. In the mammalian ovary, bone morphogenetic protein 6 (BMP6) is an important intraovarian modulator of follicular development. In this study, we demonstrated that BMP6 treatment significantly increased the expression of CTGF in both primary and immortalized human granulosa cells. Using both pharmacological inhibitors and Small interfering RNA-mediated knockdown approaches, we showed that ALK2 and ALK3 type I receptors are required for BMP6-induced cellular activities. Furthermore, this effect is most likely mediated by a Sma- and Mad-related protein (SMAD)-dependent pathway. Our studies provide novel insight into the molecular mechanisms by which an intraovarian growth factor affects the production of another factor via a paracrine effect in human granulosa cells.

TGF-β1 promotes vitamin D-induced prostaglandin E2 synthesis by upregulating vitamin D receptor expression in human granulosa-lutein cells

There is increasing evidence showing the importance of vitamin D (Vit D) and its nuclear receptor, the Vit D receptor (VDR), in female reproductive health. Transforming growth factor-β1 (TGF-β1) and its functional receptors are expressed in human oocytes and granulosa cells that participate in follicular development and ovulation. Recently, Sma- and Mad-related protein 3 (SMAD3; a downstream effector of TGF-β1) has been proposed to mediate crosstalk between the Vit D and TGF-β1 signaling pathways, but this relationship has not been fully explored and has yet to be tested in human granulosa-lutein (hGL) cells. In this study, we showed that TGF-β1 significantly promoted the expression of VDR, and this stimulatory effect occurred through the activin receptor-like kinase 5 type I receptor-mediated SMAD3 and ERK1/2 signaling pathways in hGL cells. Additionally, we showed that Vit D increased the expression of cyclooxygenase 2 (COX-2) and the synthesis of prostaglandin E2 (PGE2) in a time- and dose-dependent manner. Furthermore, we demonstrated a synergistic effect of TGF-β1 and Vit D on the expression of COX-2 and synthesis of PGE2, and this effect could be attenuated by silencing the expression of VDR. Our findings indicate that TGF-β1 upregulates the expression of VDR, which promotes Vit D-induced COX-2 expression and subsequent PGE2 production by activating the SMAD3 and ERK1/2 signaling pathways in hGL cells.

Full-length transcriptome sequencing and comparative transcriptomic analysis to uncover genes involved in early gametogenesis in the gonads of Amur sturgeon (Acipenser schrenckii)

BACKGROUND

Sturgeons (Acipenseriformes) are polyploid chondrostean fish that constitute an important model species for studying development and evolution in vertebrates. To better understand the mechanisms of reproduction regulation in sturgeon, this study combined PacBio isoform sequencing (Iso-Seq) with Illumina short-read RNA-seq methods to discover full-length genes involved in early gametogenesis of the Amur sturgeon, Acipenser schrenckii.

RESULTS

A total of 50.04 G subread bases were generated from two SMRT cells, and herein 164,618 nonredundant full-length transcripts (unigenes) were produced with an average length of 2782 bp from gonad tissues (three testes and four ovaries) from seven 3-year-old A. schrenckii individuals. The number of ovary-specific expressed unigenes was greater than those of testis (19,716 vs. 3028), and completely different KEGG pathways were significantly enriched between the ovary-biased and testis-biased DEUs. Importantly, 60 early gametogenesis-related genes (involving 755 unigenes) were successfully identified, and exactly 50% (30/60) genes of those showed significantly differential expression in testes and ovaries. Among these, the Amh and Gsdf with testis-biased expression, and the Foxl2 and Cyp19a with ovary-biased expression strongly suggested the important regulatory roles in spermatogenesis and oogenesis of A. schrenckii, respectively. We also found the four novel Sox9 transcript variants, which increase the numbers of regulatory genes and imply function complexity in early gametogenesis. Finally, a total of 236,672 AS events (involving 36,522 unigenes) were detected, and 10,556 putative long noncoding RNAs (lncRNAs) and 4339 predicted transcript factors (TFs) were also respectively identified, which were all significantly associated with the early gametogenesis of A. schrenckii.

CONCLUSIONS

Overall, our results provide new genetic resources of full-length transcription data and information as a genomic-level reference for sturgeon. Crucially, we explored the comprehensive genetic characteristics that differ between the testes and ovaries of A. schrenckii in the early gametogenesis stage, which could provide candidate genes and theoretical basis for further the mechanisms of reproduction regulation of sturgeon.

Interaction between growing oocytes and granulosa cells in vitro

BACKGROUND

Oocyte growth is accompanied by follicular development in mammalian ovaries. Since the discovery of two oocyte-derived factors, growth differentiation factor 9 (GDF9), and bone morphogenetic protein 15 (BMP15), knowledge of the bidirectional communication between oocytes and granulosa cells for ovarian function and fertility has been accumulated. In addition, the growth culture system of oocytes has been improved, further promoting the studies on the communication between oocytes and granulosa cells in vitro.

METHODS

We provide an overview of the role of granulosa cells in oocyte growth and the role of oocytes in follicular development along with our recent findings in culture experiments of bovine growing oocytes.

MAIN FINDINGS

Granulosa cells supply nutrients and metabolites through gap junctions to oocytes and secrete paracrine signals to regulate oocytes. Oocytes regulate granulosa cell proliferation and differentiation and induce antrum formation via GDF9 and BMP15.

CONCLUSION

Oocytes actively participate in various aspects of follicular development, including antrum formation via the oocyte-derived factors GDF9 and BMP15, whose synthesis is probably regulated by granulosa cells. In vitro studies will reveal the precise communication loop between oocytes and granulosa cells that facilitates the coordinated development of oocytes and granulosa cells in the follicles.

TGF-β1 sustains germ cell cyst reservoir via restraining follicle formation in the chicken

The transforming growth factor β (TGF-β) superfamily members are important molecules that regulate many ovarian functions under normal physiological and pathological conditions. TGF-β1 and its receptors are highly expressed in the ovarian cells of many species. However, the effect of TGF-β1 on the capacity of the avian germ cell reservoir remains unknown. In this study, 5-day-old chicks were injected with TGF-β1 (2.5, 12.5, and 62.5 μg/kg body weight) for 3 days to assess the effect of TGF-β1 on early follicle development. Morphological analysis showed that treatment with TGF-β1 (12.5 μg/kg) increased the number of germ cell cysts and reduced the number of primordial and growing follicles. The diameter and area of oocytes and follicles were decreased after TGF-β1 treatment. Immunohistochemical staining of the proliferating cell nuclear antigen revealed that the ratios of the positive somatic and granulosa cells were decreased by 16.2% and 2.48%, respectively. Furthermore, more apoptotic cells were observed in the TGF-β1 group than those of the control by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. In addition, we cultured the 5d chicken ovaries for 3 days in vitro and found that treatment with TGF-β1 (10 ng/mL) manifested similar results as the in vivo experiment. However, the negative effect of TGF-β1 on early ovary development was rescued by treatment with a TGF-βR1 inhibitor SD208, resulting in increased expression of steroidogenic enzymes and cell cycle-regulating proteins. In conclusion, TGF-β1 could maintain the germ cell reservoir by restraining follicle activation involving reduced cell proliferation and steroidogenic enzymes gene expression at the early stage of ovarian development.

Morphometric analyses and gene expression related to germ cells, gonadal ridge epithelial-like cells and granulosa cells during development of the bovine fetal ovary

Cells on the surface of the mesonephros give rise to replicating Gonadal Ridge Epithelial-Like (GREL) cells, the first somatic cells of the gonadal ridge. Later germ cells associate with the GREL cells in the ovigerous cords, and the GREL cells subsequently give rise to the granulosa cells in follicles. To examine these events further, 27 bovine fetal ovaries of different gestational ages were collected and prepared for immunohistochemical localisation of collagen type I and Ki67 to identify regions of the ovary and cell proliferation, respectively. The non-stromal cortical areas (collagen-negative) containing GREL cells and germ cells and later in development, the follicles with oocytes and granulosa cells, were analysed morphometrically. Another set of ovaries (n = 17) were collected and the expression of genes associated with germ cell lineages and GREL/granulosa cells were quantitated by RT-PCR. The total volume of non-stromal areas in the cortex increased significantly and progressively with ovarian development, plateauing at the time the surface epithelium developed. However, the proportion of non-stromal areas in the cortex declined significantly and progressively throughout gestation, largely due to a cessation in growth of the non-stroma cells and the continued growth of stroma. The proliferation index in the non-stromal area was very high initially and then declined substantially at the time follicles formed. Thereafter, it remained low. The numerical density of the non-stromal cells was relatively constant throughout ovarian development. The expression levels of a number of genes across gestation either increased (AMH, FSHR, ESR1, INHBA), declined (CYP19A1, ESR2, ALDH1A1, DSG2, OCT4, LGR5) or showed no particular pattern (CCND2, CTNNB1, DAZL, FOXL2, GATA4, IGFBP3, KRT19, NR5A1, RARRES1, VASA, WNT2B). Many of the genes whose expression changed across gestation, were positively or negatively correlated with each other. The relationships between these genes may reflect their roles in the important events such as the transition of ovigerous cords to follicles, oogonia to oocytes or GREL cells to granulosa cells.

Transcriptomic analysis of the red and green light responses in Columba livia domestica

In this study, 108 paired White King pigeons, randomly divided into three compartments were exposed to green light, red light, and white light followed by 15 h of light exposure, for a 6-month period. Three female birds from each group were selected and ovarian stromal tissue was collected. Pigeon reproductive data were also recorded every day. We performed transcriptome assembly on several tissue samples using Illumina Hiseq 2000 and analyzed differentially expressed genes involving follicle development mechanisms. Reproductive data confirmed that exposure to red and green lights improved pigeon reproduction. In total, approximately 158,080 unigenes with an average length of 753 bp were obtained using the Trinity program. Gene ontology, clusters of orthologous groups, and the Kyoto encyclopedia of genes were used to annotate and classify these unigenes. Large numbers of differentially expressed genes were discovered through pairwise comparisons between groups treated with monochromatic light versus white light. Some of these genes are associated with steroid hormone biosynthesis, cell cycle and circadian rhythm. Furthermore, qRT-PCR was used to detect the relative expression levels of randomly selected genes. A total of 17,419 potential simple sequence repeats were also identified. Our study provides insights into potential molecular mechanisms and genes that regulate pigeon reproduction in response to monochromatic light exposure. Our results and data will facilitate a further investigation into the molecular mechanisms behind the effects of red and green lights on follicle development and reproduction in the pigeon.

Bmp4 inhibits goose granulosa cell apoptosis via PI3K/AKT/Caspase-9 signaling pathway

Bone morphogenetic protein 4 (BMP4) has an important role in regulating cellular proliferation, differentiation and apoptosis. It, however, is still unclear as to the mechanisms by which BMP4 regulates the apoptosis of granulosa cells (GCs) in geese. In the present study, there was cloning of the full-length coding sequence of goose BMP4 gene, which consisted of 1212 nucleotides encoding 403 amino acids. Its deduced amino acid sequence comprised one signal peptide, one TGFβ pro-peptide and one mature peptide domain. Results from conducting the quantitative real-time PCR (qPCR) indicated the relative abundances of BMP4 mRNA in geese GCs increased gradually from the relative abundances in pre-hierarchical follicles that were 4 to 6 mm in diameter to that in the fifth largest (F5) follicle and then relative abundances of BMP4 mRNA decreased with further development as the largest (F1) follicle. Results from use of the TUNEL assay indicated that overexpression of the goose BMP4 gene suppressed GC apoptosis and this was confirmed when relative abundances of the CAD, Caspase-9 and Caspase-3 proteins were determined using western blotting. In addition, overexpression of the BMP4 gene induced phosphorylation of AKT, which was inhibited with use of the PI3K inhibitor, LY294002. Co-transfection of BMP4 and LY294002 resulted in increased relative abundances of Caspase-9 and CAD proteins but had no effect on that of Caspase-3. Taken together, these results suggested that expression of the BMP4 gene resulted in a reduction in Caspase-9 protein leading to inhibition of GC apoptosis via the PI3K/AKT signaling pathway in geese.

The effects of mouse ovarian granulosa cell function and related gene expression by suppressing BMP/Smad signaling pathway

BMP I type receptor inhibitor can selectively inhibit BMP/Smad signaling pathways, mainly by inhibiting the BMP I type receptor activity to prevent phosphorylation of Smad1, Smad5 and Smad9. The aim of the present study was to explore the effects of mouse ovarian granulosa cell function and related gene expression by suppressing BMP/Smad signaling pathway with LDN-193189(A type of BMP I type receptor inhibitor). In this study, we cultivate the original generation of mouse ovarian granular cells then collect cells and cell culture medium after treatment. Cellular localization and expression of Smad9 and P-smad9 proteins was studied by immunofluorescence (IF) in the ovarian granulosa cells of mouse; Related genes mRNA and proteins expression was checked by QRT-PCR and Western blot; Detected the concentration of related hormones by using ELISA kit; finally, the growth of the cells was analyzed by plotting cell growth curve with CCK-8 assay. The results indicate that, suppression of BMP/Smad signaling pathway can inhibit the expression of LHR and FSHR, inhibit cell proliferation and decrease E₂ secretion, the mechanism of action maybe reduce the expression of smad9, at the same time, we found that the feedback regulation of smad9 may affect the expression of FSHR and cell proliferation.

Transcriptomic Analysis for Differentially Expressed Genes in Ovarian Follicle Activation in the Zebrafish

In teleosts, the onset of puberty in females is marked by the appearance of the first wave of pre-vitellogenic (PV) follicles from the pool of primary growth (PG) follicles (follicle activation) in the ovary during sexual maturation. To understand the mechanisms underlying follicle activation and therefore puberty onset, we undertook this transcriptomic study to investigate gene expression profiles in the event. Our analysis revealed a total of 2,027 up-regulated and 859 down-regulated genes during the PG-PV transition. Gene Ontology (GO) analysis showed that in addition to basic cellular functions such as gene transcription, cell differentiation, and cell migration, other biological processes such as steroidogenesis, cell signaling and angiogenesis were also enriched in up-regulated genes; by comparison, some processes were down-regulated including piRNA metabolism, gene silencing and proteolysis. Further Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified a variety of signaling pathways that might play pivotal roles in PG-PV transition, including MAPK, TGF-β, Hedgehog, FoxO, VEGF, Jak-STAT, and phosphatidylinositol signaling pathways. Other pathways of particular interest included endocytosis and glycosaminoglycan biosynthesis. We also analyzed expression changes of genes expressed in different compartments viz. oocytes and follicle cells. Interestingly, most oocyte-specific genes remained unchanged in expression during follicle activation whereas a great number of genes specifically expressed in the follicle cells showed significant changes in expression. Overall, this study reported a comprehensive analysis for genes, biological processes and pathways involved in follicle activation, which also marks female puberty onset in the zebrafish when occurring for the first time in sexual maturation.

BMP Signalling at the Crossroad of Liver Fibrosis and Regeneration

Bone Morphogenetic Proteins (BMPs) belong to the Transforming Growth Factor-β (TGF-β) family. Initially identified due to their ability to induce bone formation, they are now known to have multiple functions in a variety of tissues, being critical not only during development for tissue morphogenesis and organogenesis but also during adult tissue homeostasis. This review focus on the liver as a target tissue for BMPs actions, devoting most efforts to summarize our knowledge on their recently recognized and/or emerging roles on regulation of the liver regenerative response to various insults, either acute or chronic and their effects on development and progression of liver fibrosis in different pathological conditions. In an attempt to provide the basis for guiding research efforts in this field both the more solid and more controversial areas of research were highlighted.

Effect of co-culture canine cumulus and oviduct cells with porcine oocytes during maturation and subsequent embryo development of parthenotes in vitro

In the estrus stage, canine oocytes are surrounded by cumulus cells and undergo maturation in the oviduct for 2-3 days after ovulation. We hypothesized that canine oviduct cells (cOC) and canine cumulus cells (cCC) during this stage might affect the maturation of oocytes and thereby improve subsequent embryo development. Therefore, the objective of this study was to compare the effects of a cOC and cCC co-culture on oocyte in vitro maturation (IVM) and subsequent embryo development, and to analyze the gene expressions in a molecular fashion what co-culture actually gives the specific pathways in which the co-culture cells act to improve maturation and embryo development. The effect of co-culture using cOC and cCC on porcine oocyte IVM was investigated. Thereafter, oocytes were activated using electrical stimulation and embryo developmental competence was estimated. The expression of the genes related to oocyte maturation, embryo development and apoptosis were analyzed. Also, reactive oxygen species (ROS) levels after IVM was analyzed. The IVM rate and embryo development including cleavage, blastocyst formation rates, and total blastocyst cell numbers from cOC group were significantly higher than other groups (P < 0.05). The expression of SMAD2/3 and growth differentiation factor 9 (GDF9) was significantly increased in cOC and oocytes from the cOC group compared with other groups. Moreover, the levels of GDF9, prostaglandin-endoperoxide synthase 2 (PTGS2), WNT3A and matrix metalloproteinase 2 (MMP2) were significantly up-regulated in blastocysts from the cOC group. The concentration of ROS was significantly lower in the supernatant of cOC groups compared with other groups. Also, the expression of BCL2 was significantly increased in porcine cumulus cells and oocytes from cOC group. The present study demonstrated that co-culture with cOC improved in vitro porcine oocyte maturation and subsequent embryo development competence. Also, co-culture with cOC during IVM induces a suitable environment for oocyte maturation by enhancing the mRNA level of SMAD2/3 and GDF9, and for embryo development by elevating the expression level of PTGS2, WNT3A and MMP2. In addition, the decreased ROS level in cOC co-culture could have a beneficial influence on oocyte maturation.

Evolution and conservation of Characidium sex chromosomes

Fish species exhibit substantial variation in the degree of genetic differentiation between sex chromosome pairs, and therefore offer the opportunity to study the full range of sex chromosome evolution. We used restriction-site associated DNA sequencing (RAD-seq) to study the sex chromosomes of Characidium gomesi, a species with conspicuous heteromorphic ZW/ZZ sex chromosomes. We screened 9863 single-nucleotide polymorphisms (SNPs), corresponding to ~1 marker/100 kb distributed across the genome for sex-linked variation. With this data set, we identified 26 female-specific RAD loci, putatively located on the W chromosome, as well as 148 sex-associated SNPs showing significant differentiation (average F_ST=0.144) between males and females, and therefore in regions of more recent divergence between the Z and W chromosomes. In addition, we detected 25 RAD loci showing extreme heterozygote deficiency in females but which were in Hardy-Weinberg equilibrium in males, consistent with degeneration of the W chromosome and therefore female hemizygosity. We validated seven female-specific and two sex-associated markers in a larger sample of C. gomesi, of which three localised to the W chromosome, thereby providing useful markers for sexing wild samples. Validated markers were evaluated in other populations and species of the genus Characidium, this exploration suggesting a rapid turnover of W-specific repetitive elements. Together, our analyses point to a complex origin for the sex chromosome of C. gomesi and highlight the utility of RAD-seq for studying the composition and evolution of sex chromosomes systems in wild populations.

Ovarian transcriptomic analysis of Shan Ma ducks at peak and late stages of egg production

Objective

To assess the differences in ovarian transcriptomes in Shan Ma ducks between their peak and late stages of egg production, and to obtain new transcriptomic data of these egg-producing ducks.

Methods

The Illumina HiSeq 2000 system was used for high throughput sequencing of ovarian transcriptomes from Shan Ma ducks at their peak or late stages of egg production.

Results

Greater than 93% of the sequencing data had a base quality score (Q score) that was not less than 20 (Q20). From ducks at their peak stage of egg production, 42,782,676 reads were obtained, with 4,307,499,083 bp sequenced. From ducks at their late stage of egg production, 45,316,166 reads were obtained, with 4,562,063,363 bp sequenced. A comparison of the two datasets identified 2,002 differentially expressed genes, with 790 upregulated and 1,212 downregulated. Further analysis showed that 1,645 of the 2,002 differentially expressed genes were annotated in the non-redundant (NR) database, with 646 upregulated and 999 downregulated. Among the differentially expressed genes with annotations in the NR database, 696 genes were functionally annotated in the clusters of orthologous groups of proteins database, involving 25 functional categories. One thousand two hundred four of the differentially expressed genes with annotations in the NR database were functionally annotated in the gene ontology (GO) database, and could be divided into three domains and 56 categories. The three domains were cellular component, molecular function, and biological process. Among the genes identified in the GO database, 451 are involved in development and reproduction. Analysis of the differentially expressed genes with annotations in the NR database against the Kyoto encyclopedia of genes and genomes database revealed that 446 of the genes could be assigned to 175 metabolic pathways, of which the peroxisome proliferator-activated receptor signaling pathway, insulin signaling pathway, fructose and mannose metabolic pathways, gonadotropin releasing hormone signaling pathway and transforming growth factor beta signaling pathway were significantly enriched.

Conclusion

The differences in ovarian transcriptomes in Shan Ma ducks between their peak and late stages of egg production were elucidated, which greatly enriched the ovarian transcriptomic information of egg-producing ducks.

Oocyte-somatic cell interactions in the human ovary-novel role of bone morphogenetic proteins and growth differentiation factors

BACKGROUND

Initially identified for their capability to induce heterotopic bone formation, bone morphogenetic proteins (BMPs) are multifunctional growth factors that belong to the transforming growth factor β superfamily. Using cellular and molecular genetic approaches, recent studies have implicated intra-ovarian BMPs as potent regulators of ovarian follicular function. The bi-directional communication of oocytes and the surrounding somatic cells is mandatory for normal follicle development and oocyte maturation. This review summarizes the current knowledge on the physiological role and molecular determinants of these ovarian regulatory factors within the human germline-somatic regulatory loop.

OBJECTIVE AND RATIONALE

The regulation of ovarian function remains poorly characterized in humans because, while the fundamental process of follicular development and oocyte maturation is highly similar across species, most information on the regulation of ovarian function is obtained from studies using rodent models. Thus, this review focuses on the studies that used human biological materials to gain knowledge about human ovarian biology and disorders and to develop strategies for preventing, diagnosing and treating these abnormalities.

SEARCH METHODS

Relevant English-language publications describing the roles of BMPs or growth differentiation factors (GDFs) in human ovarian biology and phenotypes were comprehensively searched using PubMed and the Google Scholar database. The publications included those published since the initial identification of BMPs in the mammalian ovary in 1999 through July 2016.

OUTCOMES

Studies using human biological materials have revealed the expression of BMPs, GDFs and their putative receptors as well as their molecular signaling in the fundamental cells (oocyte, cumulus/granulosa cells (GCs) and theca/stroma cells) of the ovarian follicles throughout follicle development. With the availability of recombinant human BMPs/GDFs and the development of immortalized human cell lines, functional studies have demonstrated the physiological role of intra-ovarian BMPs/GDFs in all aspects of ovarian functions, from follicle development to steroidogenesis, cell–cell communication, oocyte maturation, ovulation and luteal function. Furthermore, there is crosstalk between these potent ovarian regulators and the endocrine signaling system. Dysregulation or naturally occurring mutations within the BMP system may lead to several female reproductive diseases. The latest development of recombinant BMPs, synthetic BMP inhibitors, gene therapy and tools for BMP-ligand sequestration has made the BMP pathway a potential therapeutic target in certain human fertility disorders; however, further clinical trials are needed. Recent studies have indicated that GDF8 is an intra-ovarian factor that may play a novel role in regulating ovarian functions in the human ovary.

WIDER IMPLICATIONS

Intra-ovarian BMPs/GDFs are critical regulators of folliculogenesis and human ovarian functions. Any dysregulation or variations in these ligands or their receptors may affect the related intracellular signaling and influence ovarian functions, which accounts for several reproductive pathologies and infertility. Understanding the normal and pathological roles of intra-ovarian BMPs/GDFs, especially as related to GC functions and follicular fluid levels, will inform innovative approaches to fertility regulation and improve the diagnosis and treatment of ovarian disorders.

Differential activation of noncanonical SMAD2/SMAD3 signaling by bone morphogenetic proteins causes disproportionate induction of hyaluronan production in immortalized human granulosa cells

Successful fertilization depends upon proper cumulus-oocyte complex (COC) expansion. Synthesized by hyaluronan synthases (HASs), hyaluronan forms the backbone of the COC matrix and plays a critical role in COC expansion. This study investigated the effects and mechanisms of ovarian BMPs on HAS expression and hyaluronan production in human granulosa cells. Treatment with BMP4, BMP6, BMP7 or BMP15 induced differing levels of noncanonical SMAD2/3, but equal levels of canonical SMAD1/5/8, phosphorylation which were mirrored by differing levels of HAS2 up-regulation and hyaluronan production. The effects of BMP4 and BMP15 on HAS2 mRNA were partially reversed by knockdown of SMAD3, and blocked by knockdown of SMAD2+SMAD3 or SMAD4. BMP4-induced SMAD2/3 phosphorylation and HAS2 mRNA up-regulation were mediated by both BMP and activin/transforming growth factor-β type I receptors. Our results suggest differential activation of noncanonical SMAD2/SMAD3 signaling by BMPs causes disproportionate induction of HAS2 expression and hyaluronan production in immortalized human granulosa cells.

BMP4 and BMP7 Suppress StAR and Progesterone Production via ALK3 and SMAD1/5/8-SMAD4 in Human Granulosa-Lutein Cells

Adequate production of progesterone by the corpus luteum is critical to the successful establishment of pregnancy. In animal models, bone morphogenetic protein (BMP) 4 and BMP7 have been shown to suppress either basal or gonadotropin-induced progesterone production, depending on the species examined. However, the effects of BMP4 and BMP7 on progesterone production in human granulosa cells are unknown. In the present study, we used immortalized (SVOG) and primary human granulosa-lutein cells to investigate the effects of BMP4 and BMP7 on steroidogenic acute regulatory protein (StAR) expression and progesterone production and to examine the underlying molecular mechanism. Treatment of primary and immortalized human granulosa cells with recombinant BMP4 or BMP7 decreased StAR expression and progesterone accumulation. In SVOG cells, the suppressive effects of BMP4 and BMP7 on StAR expression were blocked by pretreatment with inhibitors of activin receptor-like kinase (ALK)2/3/6 (dorsomorphin) or ALK2/3 (DMH1) but not ALK4/5/7 (SB-431542). Moreover, small interfering RNA-mediated depletion of ALK3, but not ALK2 or ALK6, reversed the effects of BMP4 and BMP7 on StAR expression. Likewise, BMP4- and BMP7-induced phosphorylation of SMAD 1/5/8 was reversed by treatment with DMH1 or small interfering RNA targeting ALK3. Knockdown of SMAD4, the essential common SMAD for BMP/TGF-β signaling, abolished the effects of BMP4 and BMP7 on StAR expression. Our results suggest that BMP4 and BMP7 down-regulate StAR and progesterone production via ALK3 and SMAD1/5/8-SMAD4 signaling in human granulosa-lutein cells.

Follistatin288 Regulates Germ Cell Cyst Breakdown and Primordial Follicle Assembly in the Mouse Ovary

In mammals, the primordial follicle pool represents the entire reproductive potential of a female. The transforming growth factor-β (TGF-β) family member activin (ACT) contributes to folliculogenesis, although the exact mechanism is not known. The role of FST288, the strongest ACT-neutralizing isoform of follistatin (FST), during cyst breakdown and primordial follicle formation in the fetal mice ovary was assessed using an in vitro culture system. FST was continuously expressed in the oocytes as well as the cuboidal granulosa cells of growing follicles in perinatal mouse ovaries. Treatment with FST288 delayed germ cell nest breakdown, particularly near the periphery of the ovary, and dramatically decreased the percentage of primordial follicles. In addition, there was a dramatic decrease in proliferation of granulosa cells and somatic cell expression of Notch signaling was impaired. In conclusion, FST288 impacts germ cell nest breakdown and primordial follicle assembly by inhibiting somatic cell proliferation.

The ability of mouse nuclear transfer embryonic stem cells to differentiate into primordial germ cells

Nuclear transfer embryonic stem cells (ntESCs) show stem cell characteristics such as pluripotency but cause no immunological disorders. Although ntESCs are able to differentiate into somatic cells, the ability of ntESCs to differentiate into primordial germ cells (PGCs) has not been examined. In this work, we examined the capacity of mouse ntESCs to differentiate into PGCs in vitro. ntESCs aggregated to form embryoid bodies (EB) in EB culture medium supplemented with bone morphogenetic protein 4(BMP4) as the differentiation factor. The expression level of specific PGC genes was compared at days 4 and 8 using real time PCR. Flow cytometry and immunocytochemical staining were used to detect Mvh as a specific PGC marker. ntESCs expressed particular genes related to different stages of PGC development. Flow cytometry and immunocytochemical staining confirmed the presence of Mvh protein in a small number of cells. There were significant differences between cells that differentiated into PGCs in the group treated with Bmp4 compared to non-treated cells. These findings indicate that ntESCs can differentiate into putative PGCs. Improvement of ntESC differentiation into PGCs may be a reliable means of producing mature germ cells.

Oocyte-derived Smad4 is not required for development of the oocyte or the preimplantation embryo

The generation of a competent egg requires complex molecular interactions between the oocyte and the ovary, and transforming growth factor β (TGF-β) is a major signaling pathway. Smad4 is a central regulator of the TGF-β signaling pathway as it mediates gene expression triggered by activation of TGF-β receptors. Deletion of Smad4 in granulosa cells disrupts follicle development; however, the role of Smad4 in the oocyte has not been confirmed. Furthermore, the role of Smad4 in embryo development has not been confirmed because previous studies of Smad4(del/del) embryos were generated from heterozygous parents, and thus it is possible that maternal transcripts rescue development before embryonic day 6.5 (E6.5) when Smad4(del/del) embryos die. To determine the role of TGF-β signaling in oocyte and embryo development, mice with oocyte-specific deletion of Smad4 were studied. Fertility was evaluated in Mutant (Smad4(F/F):ZP3Cre) and CONTROL (Smad4(F/F)) females mated continuously with control males during a 6-month period. Surprisingly, Mutant females were fertile with the same litter size (Mutants, 9.23 ± 0.4; CONTROLs, 9.42 ± 0.4) and interlitter period as CONTROLs. Ovulation rate induced using a superovulation regime did not differ between CONTROLs and Mutants at both 6 weeks and 6 months. Embryo development was assessed at E6.5 using CONTROL and Mutant females mated with heterozygous males. Development of Smad4(del/del) embryos at E6.5 was retarded consistent with previous studies of embryos generated from heterozygous parents indicating that there is no rescue of preimplantation development by maternal transcripts. The numbers of implanted embryos at 6.5 dpc also did not differ (

CONTROL

9.1 ± 0.4; Mutant: 7.0 ± 0.9). However, only 26.3% of E6.5 embryos carried by Mutant females were Smad4(del/del) compared with the expected ratio of 50%. Since litter size was not decreased, this indicates that either the number of Smad4(del) sperm fertilizing the oocytes is reduced or implantation of Smad4(del/del) embryos is suboptimal. In summary, we have shown that Smad4 in the oocyte, and thus TGF-β signaling, is not required for oocyte or follicle development, ovulation, fertilization, preimplantation development, or implantation.

Expression and localization of Smad2 and Smad4 proteins in the porcine ovary

The objective of the present study was to investigate the temporal and spatial expression of Smad2 and Smad4 proteins, the downstream signaling molecules of the transforming growth factor beta (TGF-β) superfamily, in the porcine ovary. Cellular localization of Smad2 and Smad4 proteins was examined using immunohistochemistry. The specificity of the antibodies was examined using Western blot assay. Western blot analyses demonstrated that 52kDa Smad2 and 60kDa Smad4 proteins were expressed in the porcine ovary. Immunohistochemistry revealed that Smad2 and Smad4 were widely expressed in the porcine ovary, mainly localized in the oocyte, granulosa and thecal cells at different stages of folliculogenesis. Within the primordial and primary follicles, Smad2 and Smad4 showed strong staining in oocytes and follicular cells. In the antral follicle, strong staining was observed in oocytes, granulosa and theca cells. These findings suggest that Smad2 and Smad4 may be a key regulator of follicular development and growth of oocytes in the porcine ovary.

A comprehensive transcriptomic analysis of infant and adult mouse ovary

Ovary development is a complex process involving numerous genes. A well-developed ovary is essential for females to keep fertility and reproduce offspring. In order to gain a better insight into the molecular mechanisms related to the process of mammalian ovary development, we performed a comparative transcriptomic analysis on ovaries isolated from infant and adult mice by using next-generation sequencing technology (SOLiD). We identified 15,454 and 16,646 transcriptionally active genes at the infant and adult stage, respectively. Among these genes, we also identified 7021 differentially expressed genes. Our analysis suggests that, in general, the adult ovary has a higher level of transcriptomic activity. However, it appears that genes related to primordial follicle development, such as those encoding Figla and Nobox, are more active in the infant ovary, whereas expression of genes vital for follicle development, such as Gdf9, Bmp4 and Bmp15, is upregulated in the adult. These data suggest a dynamic shift in gene expression during ovary development and it is apparent that these changes function to facilitate follicle maturation, when additional functional gene studies are considered. Furthermore, our investigation has also revealed several important functional pathways, such as apoptosis, MAPK and steroid biosynthesis, that appear to be much more active in the adult ovary compared to those of the infant. These findings will provide a solid foundation for future studies on ovary development in mice and other mammals and help to expand our understanding of the complex molecular and cellular events that occur during postnatal ovary development.

Molecular players involved in temperature-dependent sex determination and sex differentiation in Teleost fish

The molecular mechanisms that underlie sex determination and differentiation are conserved and diversified. In fish species, temperature-dependent sex determination and differentiation seem to be ubiquitous and molecular players involved in these mechanisms may be conserved. Although how the ambient temperature transduces signals to the undifferentiated gonads remains to be elucidated, the genes downstream in the sex differentiation pathway are shared between sex-determining mechanisms. In this paper, we review recent advances on the molecular players that participate in the sex determination and differentiation in fish species, by putting emphasis on temperature-dependent sex determination and differentiation, which include temperature-dependent sex determination and genetic sex determination plus temperature effects. Application of temperature-dependent sex differentiation in farmed fish and the consequences of temperature-induced sex reversal are discussed.

Transforming growth factor-β signaling participates in the maintenance of the primordial follicle pool in the mouse ovary

Physiologically, only a few primordial follicles are activated to enter the growing follicle pool each wave. Recent studies in knock-out mice show that early follicular activation depends on signaling from the tuberous sclerosis complex, the mammalian target of rapamycin complex 1 (mTORC1), phosphatase and tensin homolog deleted on chromosome 10, and phosphatidylinositol 3-kinase (PI3K) pathways. However, the manner in which these pathways are normally regulated, and whether or not TGF-β acts on them are poorly understood. So, this study aims to identify whether or not TGF-β acts on the process. Ovary organ culture experiments showed that the culture of 18.5 days post-coitus (dpc) ovaries with TGF-β1 reduced the total population of oocytes and activated follicles, accelerated oocyte growth was observed in ovaries treated with TGF-βR1 inhibitor 2-(5-chloro-2-fluorophenyl)pteridin-4-yl]pyridin-4-yl-amine (SD208) compared with control ovaries, the down-regulation of TGF-βR1 gene expression also activated early primordial follicle oocyte growth. We further showed that there was dramatically more proliferation of granulosa cells in SD208-treated ovaries and less proliferation in TGF-β1-treated ovaries. Western blot and morphological analyses indicated that TGF-β signaling manipulated primordial follicle growth through tuberous sclerosis complex/mTORC1 signaling in oocytes, and the mTORC1-specific inhibitor rapamycin could partially reverse the stimulated effect of SD208 on the oocyte growth and decreased the numbers of growing follicles. In conclusion, our results suggest that TGF-β signaling plays an important physiological role in the maintenance of the dormant pool of primordial follicles, which functions through activation of p70 S6 kinase 1 (S6K1)/ribosomal protein S6 (rpS6) signaling in mouse ovaries.

FSH in vitro versus LH in vivo: similar genomic effects on the cumulus

The use of gonadotropins to trigger oocyte maturation both in vivo and in vitro has provided precious and powerful knowledge that has significantly increased our understanding of the ovarian function. Moreover, the efficacy of most assisted reproductive technologies (ART) used in both humans and livestock species relies on gonadotropin input, mainly FSH and LH. Despite the significant progress achieved and the huge impact of gonadotropins, the exact molecular pathways of the two pituitary hormones, FSH and LH, still remain poorly understood. Moreover, these pathways may not be the same when moving from the in vivo to the in vitro context. This misunderstanding of the intricate synergy between these two hormones leads to a lack of consensus about their use mainly in vitro or in ovulation induction schedules in vivo. In order to optimize their use, additional work is thus required with a special focus on comparing the in vitro versus the in vivo effects. In this context, this overview will briefly summarize the downstream gene expression pathways induced by both FSH in vitro and LH in vivo in the cumulus compartment. Based on recent microarray comparative analysis, we are reporting that in vitro FSH stimulation on cumulus cells appears to achieve at least part of the gene expression activity after in vivo LH stimulation. We are then proposing that the in vitro FSH-response of cumulus cells have similitudes with the in vivo LH-response.

Novel sex-determining genes in fish and sex chromosome evolution

Although the molecular mechanisms underlying many developmental events are conserved across vertebrate taxa, the lability at the top of the sex-determining (SD) cascade has been evident from the fact that four master SD genes have been identified: mammalian Sry; chicken DMRT1; medaka Dmy; and Xenopus laevis DM-W. This diversity is thought to be associated with the turnover of sex chromosomes, which is likely to be more frequent in fishes and other poikilotherms than in therian mammals and birds. Recently, four novel candidates for vertebrate SD genes were reported, all of them in fishes. These include amhy in the Patagonian pejerrey, Gsdf in Oryzias luzonensis, Amhr2 in fugu and sdY in rainbow trout. These studies provide a good opportunity to infer patterns from the seemingly chaotic picture of sex determination systems. Here, we review recent advances in our understanding of the master SD genes in fishes.

Inhibins and activins in blood: predictors of female reproductive health?

Inhibins A and B are gonadal factors which are important in fertility. Their use as predictors of female reproductive health has centred on their application to ovarian cancer, Anorexia Nervosa, Down Syndrome and preeclampsia. Inhibin B also provides an index of the endocrine feedback relationship between the ovary and pituitary particularly when the ovarian follicle reserve is low. These applications are relevant in monitoring the onset of the menopause transition, ovarian recovery following chemotherapy and disturbances in pubertal development. Currently, these applications have only found widespread use in Down Syndrome and ovarian cancer. Activins, on the other hand, appear to have a limited application.

The potential role of microRNAs in regulating gonadal sex differentiation in the chicken embryo

Differential gene expression regulates tissue morphogenesis. The embryonic gonad is a good example, where the developmental decision to become an ovary or testis is governed by female- or male-specific gene expression. A number of genes have now been identified that control gonadal sex differentiation. However, the potential role of microRNAs (miRNAs) in ovarian and testicular pathways is unknown. In this review, we summarise our current understanding of gonadal differentiation and the possible involvement of miRNAs, using the chicken embryo as a model system. Chickens and other birds have a ZZ/ZW sex chromosome system, in which the female, ZW, is the heterogametic sex, and the male, ZZ, is homogametic (opposite to mammals). The Z-linked DMRT1 gene is thought to direct testis differentiation during embryonic life via a dosage-based mechanism. The conserved SOX9 gene is also likely to play a key role in testis formation. No master ovary determinant has yet been defined, but the autosomal FOXL2 and Aromatase genes are considered central. No miRNAs have been definitively shown to play a role in embryonic gonadal development in chickens or any other vertebrate species. Using next generation sequencing, we carried out an expression-based screen for miRNAs expressed in embryonic chicken gonads at the time of sexual differentiation. A number of miRNAs were identified, including several that showed sexually dimorphic expression. We validated a subset of miRNAs by qRT-PCR, and prediction algorithms were used to identify potential targets. We discuss the possible roles for these miRNAs in gonadal development and how these roles might be tested in the avian model.

Hyal-1 but not Hyal-3 deficiency has an impact on ovarian folliculogenesis and female fertility by altering the follistatin/activin/Smad3 pathway and the apoptotic process

Ovarian follicle development is a process regulated by various endocrine, paracrine and autocrine factors that act coordinately to promote follicle growth. However, the vast majority of follicles does not reach the pre-ovulatory stage but instead, undergo atresia by apoptosis. We have recently described a role for the somatic hyaluronidases (Hyal-1, Hyal-2, and Hyal-3) in ovarian follicular atresia and induction of granulosa cell apoptosis. Herein, we show that Hyal-1 but not Hyal-3 null mice have decreased apoptotic granulosa cells after the induction of atresia and an increased number of retrieved oocytes after stimulation of ovulation. Furthermore, young Hyal-1 null mice had a significantly higher number of primordial follicles than age matched wild-type animals. Recruitment of these follicles at puberty resulted in an increased number of primary and healthy preantral follicles in Hyal-1 null mice. Consequently, older Hyal-1 deficient female mice have prolonged fertility. At the molecular level, immature Hyal-1 null mice have decreased mRNA expression of follistatin and higher levels of phospho-Smad3 protein, resulting in increased levels of phospho-Akt in pubertal mice. Hyal-1 null ovarian follicles did not exhibit hyaluronan accumulation. For Hyal-3 null mice, compensation by Hyal-1 or Hyal-2 might be related to the lack of an ovarian phenotype. In conclusion, our results demonstrate that Hyal-1 plays a key role in the early phases of folliculogenesis by negatively regulating ovarian follicle growth and survival. Our findings add Hyal-1 as an ovarian regulator factor for follicle development, showing for the first time an interrelationship between this enzyme and the follistatin/activin/Smad3 pathway.

The effects of FSH and activin A on follicle development in vitro

Numerous studies have reported on the roles of activins in gonadal regulation; however, little is known about their specific roles in early folliculogenesis. Ovarian follicular growth was investigated in 10-day cultures of day 4 postnatal whole ovaries treated with activin A (ActA; 50 ng/ml), with or without FSH (100 ng/ml) in vitro. We hypothesized that treatment with ActA±FSH would affect rates of growth and atresia in follicles. None of the treatments affected primordial follicle activation, and antral follicles were not observed after 10 days in culture. Primordial follicle numbers from all treatment groups were ∼20% of those in day 4 fresh ovaries, indicating that activation had occurred. In the presence of ActA, preantral follicle numbers increased significantly (P<0.0001). ActA alone decreased the proportion of atretic follicles in the primary and preantral classes, whereas the combined treatment of ActA+FSH increased the proportion of atretic preantral oocytes. Real-time PCR analysis revealed that follistatin, FSH receptor, and activin βA and βB subunits were all expressed at significantly higher levels in the ActA-only treated group but not in the ActA+FSH group. Here, we report novel findings supporting the role of FSH in primordial follicle survival through an action on apoptosis and a stimulatory role of ActA in the primordial to primary and preantral stages of follicle development, suggesting an inhibitory action of activin on oocyte apoptosis.

The relationship between Evi-1 expression and mouse ovarian follicular development

The ecotropic viral integration site-1 (Evi-1) is a transcription factor with two sets of zinc finger domains. It is an important regulator of the transforming growth factor beta superfamily. In the present study, we investigated the spatiotemporal expression patterns of Evi-1 using immunohistochemistry in ovaries from neonatal mice, gonadotropin-induced immature mice and mice in estrous cycle. Positive staining for Evi-1 was detected in the cytoplasm of oocytes. In postnatal mice, a high level of Evi-1 immunostaining was found from day 1 to 6, an intermediate level from day 10 to 16 and a low level on day 23. After gonadotropin treatment, Evi-1 was mainly expressed in small follicles and exhibited a very low level in large antral follicles. During the estrous cycle, the expression of Evi-1 was higher in diestrus and estrus than in proestrus and metestrus. Real-time PCR was performed to examine the relationship between Evi-1 mRNA and ovulation related genes (Ptgs2, Tnfaip6, Has2, Cd44, C1qbp). At 4 h after hCG treatment, Evi-1 mRNA was down-regulated whereas ovulation related genes were up-regulated. Overall, the results indicate that Evi-1 is expressed in a stage-specific manner during ovarian follicular development and may be involved in early follicle development.

Altered gonadal expression of TGF-β superfamily signaling factors in environmental contaminant-exposed juvenile alligators

Environmental contaminant exposure can influence gonadal steroid signaling milieus; however, little research has investigated the vulnerability of non-steroidal signaling pathways in the gonads. Here we use American alligators (Alligator mississippiensis) hatched from field-collected eggs to analyze gonadal mRNA transcript levels of the activin-inhibin-follistatin gene expression network and growth differentiation factor 9. The eggs were collected from Lake Woodruff National Wildlife Refuge, a site with minimal anthropogenic influence, and Lake Apopka, a highly contaminated lake adjacent to a former EPA Superfund site. The hatchling alligators were raised for 13 months under controlled conditions, thus limiting differences to embryonic origins. Our data reveal sexually dimorphic mRNA expression in 13-month-old alligator gonads similar to patterns established in vertebrates with genetic sex determination. In addition, we observed a relationship between lake of origin and mRNA expression of activin/inhibin subunits α and βB, follistatin, and growth differentiation factor 9. Our study suggests that embryonic exposure to environmental contaminants can affect future non-steroidal signaling patterns in the gonads of a long-lived species.