Bone Morphogenetic Protein 5 Expression in the Rat Ovary: Biological Effects on Granulosa Cell Proliferation and Steroidogenesis1

De novo assembly, characterization and comparative transcriptome analysis of gonads reveals sex-biased genes in Coreoperca whiteheadi

The wild Coreoperca whiteheadi is considered as the primordial species in sinipercine fish, which has valuable genetic information. Unfortunately, C. whiteheadi was listed as a near-threatened species because of the environmental pollution, over-exploitation and species invasion. Therefore, more genetic information is needed to have a better understanding of gonadal development in C. whiteheadi. Here, the first gonadal transcriptomes analysis of C. whiteheadi was conducted and 277.14 million clean reads were generated. A total of 96,753 unigenes were successfully annotated. By comparing ovary and testis transcriptomes, a total of 21,741 differentially expressed genes (DEGs) were identified, of which 12,057 were upregulated and 9684 were downregulated in testes. Among them, we also identified about 53 differentially expressed sex-biased genes. Subsequently, the expression of twenty-four DEGs were confirmed by real-time fluorescence quantitative PCR. Furthermore, the histological analysis was conducted on ovaries and testes of one-year-old C. whiteheadi. Our results provided basic support for further studies on the function of sex-biased genes and the molecular mechanism of sex determination and reproduction in C. whiteheadi.

Upregulated bone morphogenetic protein 5 enhances proliferation and epithelial-mesenchymal transition process in benign prostatic hyperplasia via BMP/Smad signaling pathway

BACKGROUND

Benign prostatic hyperplasia (BPH) is one of the most common illnesses in aging men. Recent studies found that bone morphogenetic protein 5 (BMP5) is upregulated in BPH tissues, however, the role of BMP5 in the development of BPH has not been examined. The current study aims to elucidate the potential roles of BMP5 and related signaling pathways in BPH.

METHODS

Human prostate cell lines (BPH-1, WPMY-1) and human/rat hyperplastic prostate tissues were utilized. Western blot, quantitative real-time polymerase chain reaction, immunofluorescent staining, and immunohistochemical staining were performed. BMP5-silenced and -overexpressed cell models were generated and then cell cycle progression, apoptosis, and proliferation were determined. The epithelial-mesenchymal transition (EMT) was also quantitated. And rescue experiments by BMP/Smad signaling pathway agonist or antagonist were accomplished. Moreover, BPH-related tissue microarray analysis was performed and associations between clinical parameters and expression of BMP5 were analyzed.

RESULTS

Our study demonstrated that BMP5 was upregulated in human and rat hyperplastic tissues and localized both in the epithelial and stromal compartments of the prostate tissues. E-cadherin was downregulated in hyperplastic tissues, while N-cadherin and vimentin were upregulated. Overexpression of BMP5 enhanced cell proliferation and the EMT process via phosphorylation of Smad1/5/8, while knockdown of BMP5 induced cell cycle arrest at G0/G1 phase and blocked the EMT process. Moreover, a BMP/Smad signaling pathway agonist and antagonist reversed the effects of BMP5 silencing and overexpression, respectively. In addition, BMP5 expression positively correlated with prostate volume and total prostate-specific antigen.

CONCLUSION

Our novel data suggest that BMP5 modulated cell proliferation and the EMT process through the BMP/Smad signaling pathway which could contribute to the development of BPH. However, further studies are required to determine the exact mechanism. Our study also indicated that BMP/Smad signaling may be rediscovered as a promising new therapeutic target for the treatment of BPH.

The Role of BMP Signaling in Female Reproductive System Development and Function

Bone morphogenetic proteins (BMPs) are a group of multifunctional growth factors that belong to the transforming growth factor-β (TGF-β) superfamily of proteins. Originally identified by their ability to induce bone formation, they are now known as essential signaling molecules that regulate the development and function of the female reproductive system (FRS). Several BMPs play key roles in aspects of reproductive system development. BMPs have also been described to be involved in the differentiation of human pluripotent stem cells (hPSCs) into reproductive system tissues or organoids. The role of BMPs in the reproductive system is still poorly understood and the use of FRS tissue or organoids generated from hPSCs would provide a powerful tool for the study of FRS development and the generation of new therapeutic perspectives for the treatment of FRS diseases. Therefore, the aim of this review is to summarize the current knowledge about BMP signaling in FRS development and function.

Characterization of reproductive gene diversity in the endangered Tasmanian devil

Interindividual variation at genes known to play a role in reproduction may impact reproductive fitness. The Tasmanian devil is an endangered Australian marsupial with low genetic diversity. Recent work has shown concerning declines in productivity in both wild and captive populations over time. Understanding whether functional diversity exists at reproductive genes in the Tasmanian devil is a key first step in identifying genes that may influence productivity. We characterized single nucleotide polymorphisms (SNPs) at 214 genes involved in reproduction in 37 Tasmanian devils. Twenty genes contained nonsynonymous substitutions, with genes involved in embryogenesis, fertilization and hormonal regulation of reproduction displaying greater numbers of nonsynonymous SNPs than synonymous SNPs. Two genes, ADAMTS9 and NANOG, showed putative signatures of balancing selection indicating that natural selection is maintaining diversity at these genes despite the species exhibiting low overall levels of genetic diversity. We will use this information in future to examine the interplay between reproductive gene variation and reproductive fitness in Tasmanian devil populations.

Growth differentiation factor 9 (gdf9) and bone morphogenetic protein 15 (bmp15) are potential intraovarian regulators of steroidogenesis in Japanese flounder (Paralichthys olivaceus)

Members of transforming growth factor-β (TGF-β) superfamily are vital regulators during the development of fish ovary. However, its intraovarian functions in teleost are still unclear. As members of the TGF-β superfamily, gdf9 and bmp15 are necessary for follicle formation and granulosa cell proliferation. Here in Japanese flounder, quantitative real-time polymerase chain reaction (qRT-PCR) and in situ hybridization (ISH) analysis showed that gdf9 and bmp15 were mainly expressed in oogonia and oocytes, whereas weakly expressed in non-ovarian tissues. Overexpression of single gdf9 and the co-overexpression with bmp15 could up-regulate the expression of most steroidogenic genes, while the overexpression of single bmp15 could down-regulate the expression of most steroidogenic genes. These findings demonstrate that single gdf9 and the combination with bmp15 may act as "activator", while single bmp15 may act as "inhibitor" in the process of steroidogenesis in flounder. This was also verified in negative feedback regulation of gdf9 and bmp15 during hormone treatment. High concentration of human chorionic gonadotropin (hCG) could down-regulate gdf9 and up-regulate bmp15, which were beneficial for the homeostasis of hCG hormone. Besides, knockdown of either gdf9 or bmp15 could significantly down-regulate most steroidogenic genes. This indicated that heterodimer of GDF9:BMP15 might be the most bioactive ligand in gonad development of flounder. Taken together, our study provided a novel recognition that gdf9 and bmp15 could regulate steroidogenesis in teleost through mechanism different from that in mammals.

A Preliminary Study on the Characteristics of microRNAs in Ovarian Stroma and Follicles of Chuanzhong Black Goat during Estrus

microRNAs (miRNAs) play a significant role in ovarian follicular maturity, but miRNA expression patterns in ovarian stroma (OS), large follicles (LF), and small follicles (SF) have been rarely explored. We herein aimed to identify miRNAs, their target genes and signaling pathways, as well as their interaction networks in OS, LF, and SF of Chuanzhong black goats at the estrus phase using small RNA-sequencing. We found that the miRNA expression profiles of LF and SF were more similar than those of OS—32, 16, and 29 differentially expressed miRNAs were identified in OS vs. LF, OS vs. SF, and LF vs. SF, respectively. Analyses of functional enrichment and the miRNA-targeted gene interaction network suggested that miR-182 (SMC3), miR-122 (SGO1), and miR-206 (AURKA) were involved in ovarian organogenesis and hormone secretion by oocyte meiosis. Furthermore, miR-202-5p (EREG) and miR-485-3p (FLT3) were involved in follicular maturation through the MAPK signaling pathway, and miR-2404 (BMP7 and CDKN1C) played a key role in follicular development through the TGF-β signaling pathway and cell cycle; nevertheless, further research is warranted. To our knowledge, this is the first study to investigate miRNA expression patterns in OS, LF, and SF of Chuanzhong black goats during estrus. Our findings provide a theoretical basis to elucidate the role of miRNAs in follicular maturation. These key miRNAs might provide candidate biomarkers for the diagnosis of follicular maturation and will assist in developing new therapeutic targets for female goat infertility.

Gene Expression Profiling in Ovaries and Association Analyses Reveal HEP21 as a Candidate Gene for Sexual Maturity in Chickens

Simple Summary

Chicken meat and egg productions are essential for human beings. Sexual maturity is important for both egg production and meat flavor. It is necessary to elucidate the genetic mechanism of chicken sexual maturity. In current study, we used digital gene expression (DGE) RNA-sequencing analysis to investigate differential expression of genes in pre-pubertal and post-pubertal ovaries in two different sub-breeds of chicken with different onsets of sexual maturity. After the analysis of RNA-sequencing data, numerous differentially expressed genes were found in both comparisons (32 day old, early-sexual-maturity pre-laying hens (P-F-O1) vs. 103 day old early-sexual-maturity laying hens (P-F-O2), and 32 day old late-sexual-maturity pre-laying hens (L-F-O1) vs. 153 day old late-sexual-maturity pre-laying hens (L-F-O2)). With the bioinformatic analysis, hen egg protein 21 kDa (HEP21) was chosen as the candidate gene to conduct following experiment. The variations in HEP21 were screened and association analyses between rs315156783 and reproductive traits were investigated in fifth-generation Ningdu Yellow chickens from a closely bred population. These results demonstrated that HEP21 is a candidate gene for sexual maturity and ovary development in chickens. However, the underlying mechanism of how HEP21 regulates chicken sexual maturity needs further focused studies.

Abstract

The age of onset of sexual maturity is an important reproductive trait in chickens. In this study, we explored candidate genes associated with sexual maturity and ovary development in chickens. We performed DGE RNA-sequencing analyses of ovaries of pre-laying (P-F-O1, L-F-O1) and laying (P-F-O2, L-F-O2) hens of two sub-breeds of Ningdu Yellow chicken. A total of 3197 genes were identified in the two comparisons, and 966 and 1860 genes were detected exclusively in comparisons of P-F-O1 vs. P-F-O2 and L-F-O1 vs. L-F-O2, respectively. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that genes involved in transmembrane signaling receptor activity, cell adhesion, developmental processes, the neuroactive ligand–receptor interaction pathway, and the calcium signaling pathway were enriched in both comparisons. Genes on these pathways, including growth hormone (GH), integrin subunit beta 3 (ITGB3), thyroid stimulating hormone subunit beta (TSHB), prolactin (PRL), and transforming growth factor beta 3 (TGFB3), play indispensable roles in sexual maturity. As a gene unique to poultry, hen egg protein 21 kDa (HEP21) was chosen as the candidate gene. Differential expression and association analyses were performed. RNA-seq data and qPCR showed that HEP21 was significantly differentially expressed in pre-pubertal and pubertal ovaries. A total of 23 variations were detected in HEP21. Association analyses of single nucleotide polymorphisms (SNPs) in HEP21 and reproductive traits showed that rs315156783 was significantly related to comb height at 84 and 91 days. These results indicate that HEP21 is a candidate gene for sexual maturity in chickens. Our results contribute to a more comprehensive understanding of sexual maturity and reproduction in chickens.

Genome-Wide Runs of Homozygosity, Effective Population Size, and Detection of Positive Selection Signatures in Six Chinese Goat Breeds

Detection of selection footprints provides insight into the evolution process and the underlying mechanisms controlling the phenotypic diversity of traits that have been exposed to selection. Selection focused on certain characters, mapping certain genomic regions often shows a loss of genetic diversity with an increased level of homozygosity. Therefore, the runs of homozygosity (ROHs), homozygosity by descent (HBD), and effective population size (N_e) are effective tools for exploring the genetic diversity, understanding the demographic history, foretelling the signature of directional selection, and improving the breeding strategies to use and conserve genetic resources. We characterized the ROH, HBD, N_e, and signature of selection of six Chinese goat populations using single nucleotide polymorphism (SNP) 50K Illumina beadchips. Our results show an inverse relationship between the length and frequency of ROH. A long ROH length, higher level of inbreeding, long HBD segment, and smaller N_e in Guangfeng (GF) goats suggested intensive selection pressure and recent inbreeding in this breed. We identified six reproduction-related genes within the genomic regions with a high ROH frequency, of which two genes overlapped with a putative selection signature. The estimated pair-wise genetic differentiation (F_ST) among the populations is 9.60% and the inter- and intra-population molecular variations are 9.68% and 89.6%, respectively, indicating low to moderate genetic differentiation. Our selection signatures analysis revealed 54 loci harboring 86 putative candidate genes, with a strong signature of selection. Further analysis showed that several candidate genes, including MARF1, SYCP2, TMEM200C, SF1, ADCY1, and BMP5, are involved in goat fecundity. We identified 11 candidate genes by using cross-population extended haplotype homozygosity (XP-EHH) estimates, of which MARF1 and SF1 are under strong positive selection, as they are differentiated in high and low reproduction groups according to the three approaches used. Gene ontology enrichment analysis revealed that different biological pathways could be involved in the variation of fecundity in female goats. This study provides a new insight into the ROHs patterns for maintenance of within breed diversity and suggests a role of positive selection for genetic variation influencing fecundity in Chinese goat.

Non-canonical cyclic AMP SMAD1/5/8 signalling in human granulosa cells

Development of mammalian ovarian follicles is promoted by the combined action of endocrine cues and paracrine factors. Follicle stimulating hormone (FSH), through the action of cAMP drives follicular growth and development. The oocyte secretes powerful growth factors such as bone morphogenetic protein 15 (BMP15) to regulate granulosa cell proliferation, metabolism, steroidogenesis and differentiation through the activation of SMAD1/5/8. This study investigated the role of the cAMP signalling pathway on SMAD1/5/8 action in human granulosa cells. Cyclic AMP enhanced BMP15-induction of a SMAD1/5/8-specific BRE reporter. Moreover, in the absence of BMP ligand, cAMP also activated SMAD1/5/8-induced BRE activity. Cyclic AMP increased canonical downstream targets of BMP signalling such as inhibitor of differentiation (ID) mRNA expression. The observed effects were not mediated by secretion of BMPs as cAMP did not promote BMP ligand mRNA expression and a BMP extracellular antagonist, the BMP type II receptor ectodomain, did not affect cAMP-induced ID mRNA expression. Finally, the ERK1/2 pathway was shown to be required for the maintenance of cAMP-induced SMAD1/5/8 activity. Together our results suggest a novel and non-canonical pathway for cAMP signalling in human granulosa cells. Cyclic AMP appears to promote SMAD1/5/8 pathway activity intracellularly and has the ability to activate canonical SMAD1/5/8 downstream targets. Our results add another layer of complexity to the interactions between endocrine signalling and oocyte-secreted BMP ligands during folliculogenesis. Given the importance of both cAMP and SMAD1/5/8 pathways in follicular development, these interactions are likely required for the fine-tuning of oocyte paracrine signalling by endocrine stimuli.

Induction of vitellogenesis by glass bottom boat in the female banana shrimp, Fenneropenaeus merguiensis de Man

In shrimp aquaculture, eyestalk ablation is the only technique that is widely used to accelerate ovarian development. Alternative methods for producing improved ovarian development in broodstock are currently being investigated. Several factors involved in the regulation of ovarian development in shrimp have been investigated. Among these factors, growth factors in the transforming growth factor beta (TGF-β) superfamily have been implicated as playing potential roles in the regulation of gonad development. In this work, a member of the TGF-β superfamily known as glass bottom boat (GBB), an ortholog of bone morphogenetic protein (BMP), was investigated to uncover its role in ovarian development in the banana shrimp Fenneropenaeus merguiensis. Full-length cDNA of FmGBB was obtained from transcriptome data. Phylogenetic analysis indicated that the sequence of FmGBB from banana shrimp was similar to those of other arthropods and vertebrate BMP 5/6/7, but was different from those of decapentaplegic proteins and vertebrate BMP 2/4. The FmGBB transcript was found to be widely expressed in shrimp tissues, and its expression in the ovary was dramatically increased in early and late vitellogenic stages during ovarian development and decreased in the mature stage, suggesting its role in vitellogenesis. To study the effects of FmGBB, a soluble recombinant mature FmGBB peptide (His-TF-rgbb) containing both monomers and homodimers was successfully expressed in Escherichia coli. The His-TF-rgbb peptide triggered oocyte proliferation in both cultured ovarian explants and in previtellogenic shrimp upon injection. Interestingly, the injection of His-TF-rgbb into previtellogenic female shrimp stimulated an increase in Vg expression in their ovaries while suppressing production of 20-hydroxyecdysone. Our results suggest the potential role of FmGBB in oocyte proliferation and vitellogenesis; this novel finding can be utilized to stimulate ovarian development in cultured shrimp.

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.

Transcriptional and translational abundance of Bone morphogenetic protein (BMP) 2, 4, 6, 7 and their receptors BMPR1A, 1B and BMPR2 in buffalo ovarian follicle and the role of BMP4 and BMP7 on estrogen production and survival of cultured granulosa cells

BMPs and their receptors modulate the granulosa cell (GC) function in the follicle of domestic animals. Since little is known on BMPs in the buffalo, the present study was aimed to investigate the expression of BMP2, 4, 6, 7 and their receptors BMPR1A, BMPR1B, BMPR2 in the GC and theca cells (TC) of ovarian follicles and the role of BMP4 and BMP7 on buffalo GC. Follicles were classified into four groups based on size and E₂ level in the follicular fluid as follows: (i) Group1(4-6 mm; <0.5 ng/mL) (ii) Group 2 (7-9 mm; 0.5-5 ng/mL) (iii) Group 3 (10-13 mm; 5-40 ng/mL) and (iv) Group 4 (dominant follicle) (>13 mm; >180 ng/mL). The results revealed that except BMP6, BMP2, 4 7 and receptors BMPR1A, BMPR1B and BMPR2 showed a minimum of 1.5-2 fold increase in mRNA expression in the GC of dominant follicle as compared to other follicle classes. In the dominant follicle, a two-fold increase in BMP4 and BMP7 expression was observed in the TC. At 100 ng/mL, the BMP4 and BMP7 either alone or in combination maximally down-regulated CASPASE3 and stimulated the transcripts of PCNA, FSHR and CYP19A1 that was supported by E₂ secretion in the granulosa cell culture suggesting their role in cell survival and E2 production. In conclusion, GC and TC of dominant follicles express BMP 2, 4, 6, 7 and their receptors BMPR1A, BMPR1B and BMPR2. BMP4 and BMP7 stimulate E₂ production and promote GC survival.

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.

XCI-escaping gene KDM5C contributes to ovarian development via downregulating miR-320a

Mechanisms underlying female gonadal dysgenesis remain unclarified and relatively unstudied. Whether X-chromosome inactivation (XCI)-escaping genes and microRNAs (miRNAs) contribute to this condition is currently unknown. We compared 45,X Turner Syndrome women with 46,XX normal women, and investigated differentially expressed miRNAs in Turner Syndrome through plasma miRNA sequencing. We found that miR-320a was consistently upregulated not only in 45,X plasma and peripheral blood mononuclear cells (PBMCs), but also in 45,X fetal gonadal tissues. The levels of miR-320a in PBMCs from 45,X, 46,XX, 46,XY, and 47,XXY human subjects were inversely related to the expression levels of XCI-escaping gene KDM5C in PBMCs. In vitro models indicated that KDM5C suppressed miR-320a transcription by directly binding to the promoter of miR-320a to prevent histone methylation. In addition, we demonstrated that KITLG, an essential gene for ovarian development and primordial germ cell survival, was a direct target of miR-320a and that it was downregulated in 45,X fetal gonadal tissues. In conclusion, we demonstrated that downregulation of miR-320a by the XCI-escaping gene KDM5C contributed to ovarian development by targeting KITLG.

New insights into implication of the SLIT/ROBO pathway in the prehierarchical follicle development of hen ovary

The SLIT/Roundabout (ROBO) pathway is involved in follicle development of mammalian ovary, and 2 secreted hormones activin A and inhibin A have potential roles in modulation of the SLIT/ROBO system, but the related actions remain poorly understood in bird. The aims of the present study were to examine the spatial and temporal expression of the SLIT ligand genes (SLIT1, SLIT2, and SLIT3) and their receptor ROBO1, ROBO2, ROBO3, and ROBO4 genes in various-sized prehierarchical follicles during hen ovary development and the effects of activin A and inhibin A on the expression of these genes in the cultured hen follicles. Our result demonstrated that the transcripts of the 3 SLIT genes were highly expressed in the developing follicles and expression patterns of the SLIT transcripts were different from those of ROBO genes detected by real-time quantitative reverse transcriptase PCR. Both SLIT and ROBO transcripts were predominantly expressed in oocytes and granulosa cells from the prehierarchichal follicles examined by in situ hybridization. The localization for SLIT and ROBO proteins was revealed by immunohistochemistry similar to the spatial distribution of their transcript. In cultured follicles (4 to 8 mm in diameter), the expression levels of SLIT and ROBO members are hormonally regulated by activin A (10 ng/mL) and/or inhibin A (20 ng/mL) after treatment for 24 h. However, the expression of only SLIT2, SLIT3, and ROBO3 mRNA presented a directly opposite response to activin A and inhibin A hormones. These results indicate that SLIT/ROBO pathway is implicated in the prehierarchical follicular development of the hen ovary by an intrafollicular autocrine and/or paracrine action, and is influenced by activin A and inhibin A hormones.

Form-deprivation myopia induces decreased expression of bone morphogenetic protein-2, 5 in guinea pig sclera

AIM

To identify the presence of various bone morphogenetic proteins (BMPs) and their receptors in normal sclera of human, rat and guinea pigs, and to determine whether their expression changed with form-deprivation myopia (FDM) in guinea pig sclera.

METHODS

The expression of BMPs and BMP receptors were detected using reverse transcription polymerase chain reaction (RT-PCR) and immunofluorescence. Two-week-old guinea pigs were monocularly form-deprived with a translucent lens. After fourteen days induction of FDM, total RNA was isolated and subjected to RT-PCR to examine the changes of BMPs and BMP receptors in tissues from the posterior sclera. Western blotting analysis was used to investigate their changes in protein levels.

RESULTS

Human sclera expressed mRNAs for BMP-2, -4, -5, -7, -RIA, -RIB and BMP-RII. Conversely, rat sclera only expressed mRNA for BMP-7 and BMP-RIB, while the expression of BMPs and BMP receptors in guinea pigs were similar to that of humans. Human sclera also expresses BMP-2, -4, -5,-7 in protein level. Fourteen days after the induction of myopia, significant decreased expressions for BMP-2 and BMP-5 in the posterior sclera of FDM-affected eyes (P<0.05 vs internal control eyes).

CONCLUSION

Various BMPs were expressed in human and guinea pig sclera. In the posterior sclera, expressions of BMP-2 and BMP-5 significantly decreased in FDM eyes. This finding indicates that various BMPs as components of the scleral cytokines regulating tissue homeostasis and provide evidence that alterations in the expression of BMP-2 and BMP-5 are associated with sclera remodeling during myopia induction.

The bone morphogenetic protein system and the regulation of ovarian follicle development in mammals

The bone morphogenetic protein (BMP) family consists of several growth factor proteins that belong to the transforming growth factor-β (TGF-β) superfamily. BMPs bind to type I and type II serine-threonine kinase receptors, and transduce signals through the Smad signalling pathway. BMPs have been identified in mammalian ovaries, and functional studies have shown that they are involved in the regulation of oogenesis and folliculogenesis. This review summarizes the role of the BMP system during formation, growth and maturation of ovarian follicles in mammals.

Cloning and spatio-temporal expression of bone morphogenetic proteins-2,-4 gene during ovarian development in New Zealand white rabbit

In the transforming growth factor-β(TGF-β) superfamily, bone morphogenetic proteins (BMPs) are one of the largest subfamily, among which BMP-2 and BMP-4 are the most powerful molecules in biological activities. They have been shown to be involved in follicle development of ovary in mammals. However, whether these factors are involved in folliculogenesis in rabbit is still unknown. This study was performed to determine the relationships between ovarian development and the expression of BMP (BMP-2,-4) mRNAs in rabbit. Ovaries were removed from different development stages of rabbits (30-, 60-, 120-, 180-day age and 6-day encyesis), and method of RT-PCR was used for the cloning. The relative transcript levels of BMP-2,-4 genes were measured by real-time quantitative PCR, with GAPDH as an internal control. Known from the results, the BMP-2,-4 genes showed similar but also different expression patterns during ovarian development; they both increased significantly (p < 0.05) in the ovary on 60-day compared with 120-day and 6-day encyesis, and the expression of BMP-2 was always higher than that of BMP-4. The expression law of BMP-2,-4 genes presented in this study may lay the theoretical foundation for the study of BMPs' biological function.

Role of anti-Müllerian hormone and bone morphogenetic proteins in the regulation of FSH sensitivity

The ovary is under control of the hypothalamus and pituitary through the glycoprotein hormones LH and FSH. These hormones undergo a cyclic variation which results in the selection of the species-specific number of follicles that will ovulate during the cycle. Where LH is the main ovulatory hormone and regulator of corpus luteum function, FSH plays an essential role in the cyclic recruitment of the follicles. Within the microenvironment of the ovary, growth factors affect this dominant control of FSH by regulating the FSH sensitivity of individual follicles. In this review we discuss the role of anti-Müllerian hormone (AMH) and bone morphogenetic proteins (BMPs) in this process.

BMP15 suppresses progesterone production by down-regulating StAR via ALK3 in human granulosa cells

In addition to somatic cell-derived growth factors, oocyte-derived growth differentiation factor (GDF)9 and bone morphogenetic protein (BMP)15 play essential roles in female fertility. However, few studies have investigated their effects on human ovarian steroidogenesis, and fewer still have examined their differential effects or underlying molecular determinants. In the present study, we used immortalized human granulosa cells (SVOG) and human granulosa cell tumor cells (KGN) to compare the effects of GDF9 and BMP15 on steroidogenic enzyme expression and investigate potential mechanisms of action. In SVOG cells, neither GDF9 nor BMP15 affects the mRNA levels of P450 side-chain cleavage enzyme or 3β-hydroxysteroid dehydrogenase. However, treatment with BMP15, but not GDF9, significantly decreases steroidogenic acute regulatory protein (StAR) mRNA and protein levels as well as progesterone production. These suppressive effects, along with the induction of Sma and Mad-related protein (SMAD)1/5/8 phosphorylation, are attenuated by cotreatment with 2 different BMP type I receptor inhibitors (dorsomorphin and DMH-1). Furthermore, depletion of activin receptor-like kinase (ALK)3 using small interfering RNA reverses the effects of BMP15 on SMAD1/5/8 phosphorylation and StAR expression. Similarly, knockdown of ALK3 abolishes BMP15-induced SMAD1/5/8 phosphorylation in KGN cells. These results provide evidence that oocyte-derived BMP15 down-regulates StAR expression and decreases progesterone production in human granulosa cells, likely via ALK3-mediated SMAD1/5/8 signaling. Our findings suggest that oocyte may play a critical role in the regulation of progesterone to prevent premature luteinization during the late stage of follicle development.

Regulation and 3 dimensional culture of tertiary follicle growth

It has been revealed that multiple cohorts of tertiary follicles develop during some animal estrous cycle and the human menstrual cycle. To reach developmental competence, oocytes need the support of somatic cells. During embryogenesis, the primordial germ cells appear, travel to the gonadal rudiments, and form follicles. The female germ cells develop within the somatic cells of the ovary, granulosa cells, and theca cells. How the oocyte and follicle cells support each other has been seriously studied. The latest technologies in genes and proteins and genetic engineering have allowed us to collect a great deal of information about folliculogenesis. For example, a few web pages (http://www.ncbi.nlm.nih.gov; http://mrg.genetics.washington.edu) provide access to databases of genomes, sequences of transcriptomes, and various tools for analyzing and discovering genes important in ovarian development. Formation of the antrum (tertiary follicle) is the final phase of folliculogenesis and the transition from intraovarian to extraovian regulation. This final step coordinates with the hypothalamic-pituitary-ovarian axis. On the other hand, currently, follicle physiology is under intense investigation, as little is known about how to overcome women's ovarian problems or how to develop competent oocytes from in vitro follicle culture or transplantation. In this review, some of the known roles of hormones and some of the genes involved in tertiary follicle growth and the general characteristics of tertiary follicles are summarized. In addition, in vitro culture of tertiary follicles is also discussed as a study model and an assisted reproductive technology model.

Identification and regulation of bone morphogenetic protein antagonists associated with preantral follicle development in the ovary

The TGFβ superfamily comprises several bone morphogenetic proteins (BMP) capable of exerting gonadotropin-independent effects on the development of small preantral follicles. In embryonic tissues, BMP concentration gradients, partly formed by antagonistic factors, are essential for establishing phenotypic fate. By examining the expression of candidate genes whose protein products are known to interact with BMP ligands, we set out to determine which antagonists would most likely contribute toward regulation of paracrine signaling during early follicle development. Juvenile mouse ovaries of 4, 8, 12, and 21 d of age enriched with follicles at successive developmental stages were used to assess changes in candidate gene transcripts by quantitative RT-PCR. Although some antagonists were found to be positively associated with the emergence of developing follicles (Nog, Htra1, Fst, Bmper, Vwc2), two (Sostdc1, Chrd) showed a corresponding reduction in expression. At each age, twisted gastrulation homolog 1 (Twsg1), Htra1, Nbl1, and Fst were consistently highly expressed and localization of these genes by in situ hybridization, and immunohistochemistry further highlighted a clear pattern of expression in granulosa cells of developing follicles. Moreover, with the exception of Nbl1, levels of these antagonists did not change in preantral follicles exposed to FSH in vitro, suggesting regulation by local factors. The presence of multiple antagonists in the juvenile ovary and their high level of expression in follicles imply the actions of certain growth factors are subject to local modulation and further highlights another important level of intraovarian regulation of follicle development.

Dynamic expression of bone morphogenetic protein 4 in reproductive organs of female mice

Various members of the bone morphogenetic protein (BMP) family have been shown to regulate mammalian follicular development by affecting granulosa cell proliferation and steroidogenesis. In situ hybridization studies have shown expression of BMPR1A, BMPR1B, and BMPR2 in the granulosa cells and oocyte of most of the follicles in the ovary, suggesting that these cells have the capacity to respond to BMP signaling. Although much is known about BMP4 signaling, its expression pattern in the female reproductive tract (FRT) is still unclear. The objective of the current study was to characterize the expression of BMP4 and its downstream target proteins (pSMAD1/5/8) in the FRT. In the ovary, BMP4 protein was detected in all the stages of follicular development. Staining for pSMAD1/5/8 was observed in granulosa cells and oocytes of all the stages of follicular development including primordial follicles, suggesting that these follicles are responsive to autocrine/paracrine BMP signaling. In the uterus, BMP4 and pSMAD1/5/8 staining was observed in all three compartments and strongest expression was observed during the estrus phase. BMP4- and pSMAD1/5/8-specific staining was also observed in oviductal epithelium. Different forms (apparent MW: 50, 35, and 15  kDa) of BMP4 were detected in mouse ovary by western blot analysis. In conclusion, these results have defined BMP4 and pSMAD1/5/8 protein expression in the mouse FRT and highlighted the importance of BMP4 in folliculogenesis.

Does bone morphogenetic protein 6 (BMP6) affect female fertility in the mouse?

Bone morphogenetic protein 6 (BMP6) is a transforming growth factor beta superfamily member produced by mammalian oocytes as well as other cell types. Despite well-characterized effects of recombinant BMP6 on granulosa cells in vitro, the function of BMP6 in vivo has been ill-defined. Therefore, the effects of genetic deletion of the Bmp6 gene on female mouse fertility were assessed. The mean litter size of Bmp6(-/-) females was reduced by 22% (P < 0.05) compared to Bmp6(+/+) controls. Not only did Bmp6(-/-) females naturally ovulate 24% fewer eggs, but competence of in vitro-matured oocytes to complete preimplantation development after fertilization in vitro was decreased by 50%. No apparent effect of Bmp6 deletion on either the morphology or the dynamics of follicular development was apparent. Nevertheless, levels of luteinizing hormone (LH)/human chorionic gonadotropin (hCG)-induced transcripts, which encode proteins required for cumulus expansion (HAS2, PTGS2, PTX3, and TNFAIP6), and of epidermal growth factor-like peptides (AREG, BTC, and EREG) were lower in Bmp6(-/-) mice than in controls after administration of a reduced dose of hCG (1 IU) in vivo. LH receptor (Lhcgr) transcript levels were not significantly lower in Bmp6(-/-) granulosa cells, suggesting that BMP6 is required for processes downstream of LH receptors. To assess whether another oocyte-derived BMP, BMP15, could have BMP6-redundant functions in vivo, the fertility of Bmp15/Bmp6 double mutants was assessed. Fertility was not significantly reduced in double-homozygous mutants compared with that in double-heterozygous controls. Therefore, BMP6 promotes normal fertility in female mice, at least in part, by enabling appropriate responses to LH and normal oocyte quality. Thus, Bmp6 probably is part of the complex genetic network that determines female fertility.

Transcriptional regulation of steroidogenic genes: STARD1, CYP11A1 and HSD3B

Expression of the genes that mediate the first steps in steroidogenesis, the steroidogenic acute regulatory protein (STARD1), the cholesterol side-chain cleavage enzyme, cytochrome P450scc (CYP11A1) and 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (HSD3B), is tightly controlled by a battery of transcription factors in the adrenal cortex, the gonads and the placenta. These genes generally respond to the same hormones that stimulate steroid production through common pathways such as cAMP signaling and common actions on their promoters by proteins such as NR5A and GATA family members. However, there are distinct temporal, tissue and species-specific differences in expression between the genes that are defined by combinatorial regulation and unique promoter elements. This review will provide an overview of the hormonal and transcriptional regulation of the STARD1, CYP11A1 and specific steroidogenic HSD3B genes in the adrenal, testis, ovary and placenta and discuss the current knowledge regarding the key transcriptional factors involved.

[Signal transduction of BMP/Smad and its relationship with mammalian folliculogenesis]

BMPs belong to the transforming growth factor-b superfamily. BMPs have been proved to have extensive biological functions in mammals, including growth regulation, cell proliferation and differentiation. More and more evidence has shown that BMPs play a key role in fertility, especially in folliculogenesis in female mammals. Smad proteins are intra-cellular signaling transduction molecules of BMP family, which can transduce the BMP signal from the cell membrane to the nucleus. In this review, BMPs, BMP/Smad-related signal transduction and the regulation of BMP activity were summarized, and the regulatory roles of BMP/Smad signal transduction pathway in folliculogenesis were discussed.

Search for the genes involved in oocyte maturation and early embryo development in the hen

Background

The initial stages of development depend on mRNA and proteins accumulated in the oocyte, and during these stages, certain genes are essential for fertilization, first cleavage and embryonic genome activation. The aim of this study was first to search for avian oocyte-specific genes using an in silico and a microarray approaches, then to investigate the temporal and spatial dynamics of the expression of some of these genes during follicular maturation and early embryogenesis.

Results

The in silico approach allowed us to identify 18 chicken homologs of mouse potential oocyte genes found by digital differential display. Using the chicken Affymetrix microarray, we identified 461 genes overexpressed in granulosa cells (GCs) and 250 genes overexpressed in the germinal disc (GD) of the hen oocyte. Six genes were identified using both in silico and microarray approaches. Based on GO annotations, GC and GD genes were differentially involved in biological processes, reflecting different physiological destinations of these two cell layers. Finally we studied the spatial and temporal dynamics of the expression of 21 chicken genes. According to their expression patterns all these genes are involved in different stages of final follicular maturation and/or early embryogenesis in the chicken. Among them, 8 genes (btg4, chkmos, wee, zpA, dazL, cvh, zar1 and ktfn) were preferentially expressed in the maturing occyte and cvh, zar1 and ktfn were also highly expressed in the early embryo.

Conclusion

We showed that in silico and Affymetrix microarray approaches were relevant and complementary in order to find new avian genes potentially involved in oocyte maturation and/or early embryo development, and allowed the discovery of new potential chicken mature oocyte and chicken granulosa cell markers for future studies. Moreover, detailed study of the expression of some of these genes revealed promising candidates for maternal effect genes in the chicken. Finally, the finding concerning the different state of rRNA compared to that of mRNA during the postovulatory period shed light on some mechanisms through which oocyte to embryo transition occurs in the hen.

TGF-β superfamily members and ovarian follicle development

In recent years, exciting progress has been made towards unravelling the complex intraovarian control mechanisms that, in concert with systemic signals, coordinate the recruitment, selection and growth of follicles from the primordial stage through to ovulation and corpus luteum formation. A plethora of growth factors, many belonging to the transforming growth factor-β (TGF-β ) superfamily, are expressed by ovarian somatic cells and oocytes in a developmental, stage-related manner and function as intraovarian regulators of folliculogenesis. Two such factors, bone morphogenetic proteins, BMP-4 and BMP-7, are expressed by ovarian stromal cells and/or theca cells and have recently been implicated as positive regulators of the primordial-to-primary follicle transition. In contrast, evidence indicates a negative role for anti-Mullerian hormone (AMH, also known as Mullerian-inhibiting substance) of pre-granulosa/granulosa cell origin in this key event and subsequent progression to the antral stage. Two other TGF-β superfamily members, growth and differentiation factor-9 (GDF-9) and BMP-15 (also known as GDF-9B) are expressed in an oocyte-specific manner from a very early stage and play key roles in promoting follicle growth beyond the primary stage; mice with null mutations in the gdf-9 gene or ewes with inactivating mutations in gdf-9 or bmp-15 genes are infertile with follicle development arrested at the primary stage. Studies on later stages of follicle development indicate positive roles for granulosa cell-derived activin, BMP-2, -5 and -6, theca cell-derived BMP-2, -4 and -7 and oocyte-derived BMP-6 in promoting granulosa cell proliferation, follicle survival and prevention of premature luteinization and/or atresia. Concomitantly, activin, TGF-β and several BMPs may exert paracrine actions on theca cells to attenuate LH-dependent androgen production in small to medium-size antral follicles. Dominant follicle selection in monovular species may depend on differential FSH sensitivity amongst a growing cohort of small antral follicles. Changes in intrafollicular activins, GDF-9, AMH and several BMPs may contribute to this selection process by modulating both FSH- and IGF-dependent signalling pathways in granulosa cells. Activin may also play a positive role in oocyte maturation and acquisition of developmental competence. In addition to its endocrine role to suppress FSH secretion, increased output of inhibin by the selected dominant follicle(s) may upregulate LH-induced androgen secretion that is required to sustain a high level of oestradiol secretion during the pre-ovulatory phase. Advances in our understanding of intraovarian regulatory mechanisms should facilitate the development of new approaches for monitoring and manipulating ovarian function and improving fertility in domesticated livestock, endangered species and man.