Regulation of Kruppel-like factor 4, 9, and 13 genes and the steroidogenic genes LDLR, StAR, and CYP11A in ovarian granulosa cells

Luteinizing Hormone Surge-Induced Krüppel-like Factor 4 Inhibits Cyp17A1 Expression in Preovulatory Granulosa Cells

Previous in vivo and in vitro studies have demonstrated a dramatic up-regulation of Krüppel-like factor 4 (Klf4) in rat preovulatory granulosa cells (GCs) after LH/hCG treatment and its role in regulating Cyp19A1 expression during the luteal shift in steroidogenesis. In this study, we examined whether Klf4 also mediates the LH-induced repression of Cyp17A1 expression in primary rat preovulatory GCs. In response to LH treatment of GCs in vitro, Cyp17A1 expression declined to less than half of its initial value by 1 h, remaining low for 24 h of culture. Overexpression of Klf4 decreased basal and Sf1-induced Cyp17A1 expressions and increased progesterone secretion. Reduction of endogenous Klf4 by siRNA elevated basal Cyp17A1 expression but did not affect LH-stimulated progesterone production. Overexpression of Klf4 also significantly attenuated Sf1-induced Cyp17A1 promoter activity. On the other hand, mutation of the conserved Sp1/Klf binding motif in the promoter revealed that this motif is not required for Klf4-mediated repression. Taken together, these data indicate that the Cyp17A1 gene may be one of the downstream targets of Klf4, which is induced by LH in preovulatory GCs. This information may help in identifying potential targets for preventing the molecular changes occurring in hyperandrogenic disorders.

Krüppel-like Factor-9 and Krüppel-like Factor-13: Highly Related, Multi-Functional, Transcriptional Repressors and Activators of Oncogenesis

Specificity Proteins/Krüppel-like Factors (SP/KLF family) are a conserved family of transcriptional regulators. These proteins share three highly conserved, contiguous zinc fingers in their carboxy-terminus, requisite for binding to cis elements in DNA. Each SP/KLF protein has unique primary sequence within its amino-terminal and carboxy-terminal regions, and it is these regions which interact with co-activators, co-repressors, and chromatin-modifying proteins to support the transcriptional activation and repression of target genes. Krüppel-like Factor 9 (KLF9) and Krüppel-like Factor 13 (KLF13) are two of the smallest members of the SP/KLF family, are paralogous, emerged early in metazoan evolution, and are highly conserved. Paradoxically, while most similar in primary sequence, KLF9 and KLF13 display many distinct roles in target cells. In this article, we summarize the work that has identified the roles of KLF9 (and to a lesser degree KLF13) in tumor suppression or promotion via unique effects on differentiation, pro- and anti-inflammatory pathways, oxidative stress, and tumor immune cell infiltration. We also highlight the great diversity of miRNAs, lncRNAs, and circular RNAs which provide mechanisms for the ubiquitous tumor-specific suppression of KLF9 mRNA and protein. Elucidation of KLF9 and KLF13 in cancer biology is likely to provide new inroads to the understanding of oncogenesis and its prevention and treatments.

Krüppel-like factor 12 regulates aging ovarian granulosa cell apoptosis by repressing SPHK1 transcription and sphingosine-1-phosphate (S1P) production

Oxidative stress triggered by aging, radiation, or inflammation impairs ovarian function by inducing granulosa cell (GC) apoptosis. However, the mechanism inducing GC apoptosis has not been characterized. Here, we found that ovarian GCs from aging patients showed increased oxidative stress, enhanced reactive oxygen species activity, and significantly decreased expression of the known antiapoptotic factor sphingosine-1-phosphate/sphingosine kinase 1 (SPHK1) in GCs. Interestingly, the expression of Krüppel-like factor 12 (KLF12) was significantly increased in the ovarian GCs of aging patients. Furthermore, we determined that KLF12 was significantly upregulated in hydrogen peroxide-treated GCs and a 3-nitropropionic acid-induced in vivo model of ovarian oxidative stress. This phenotype was further confirmed to result from inhibition of SPHK1 by KLF12. Interestingly, when endogenous KLF12 was knocked down, it rescued oxidative stress-induced apoptosis. Meanwhile, supplementation with SPHK1 partially reversed oxidative stress-induced apoptosis. However, this function was lost in SPHK1 with deletion of the binding region to the KLF12 promoter. SPHK1 reversed apoptosis caused by hydrogen peroxide-KLF12 overexpression, a result further confirmed in an in vitro ovarian culture model and an in vivo 3-nitropropionic acid-induced ovarian oxidative stress model. Overall, our study reveals that KLF12 is involved in regulating apoptosis induced by oxidative stress in aging ovarian GCs and that sphingosine-1-phosphate/SPHK1 can rescue GC apoptosis by interacting with KLF12 in negative feedback.

Bisphenol A and bisphenol S both disrupt ovine granulosa cell steroidogenesis but through different molecular pathways

BACKGROUND

Ovarian granulosa cells (GC) are essential for the development and maturation of a proper oocyte. GC are sensitive to endocrine disruptors, including bisphenol A (BPA) and its analogue bisphenol S (BPS), plasticisers present in everyday consumer products. BPA exhibits greater binding affinity for the membrane oestrogen receptor (GPER) than for the nuclear oestrogen receptors (ERα and ERβ). Here, we analysed the effects of BPA and BPS on the steroidogenesis of ovine GC in vitro, as well as their early mechanisms of action, the ovine being a relevant model to study human reproductive impairment. Disruption of GC steroidogenesis might alter oocyte quality and consequently fertility rate. In addition, we compared the effects of a specific GPER agonist (G-1) and antagonist (G-15) to those of BPA and BPS. Ewe GC were cultured with BPA or BPS (10 or 50 µM) or G-1 (1 µM) and/or G-15 (10 µM) for 48 h to study steroidogenesis.

RESULTS

Both BPA and BPS (10 µM) altered the secretion of progesterone, however, only BPS (10 µM) affected oestradiol secretion. RNA-seq was performed on GC after 1 h of culture with BPA or BPS (50 µM) or G-1 (10 µM), followed by real-time PCR analyses of differentially expressed genes after 12, 24 and 48 h of culture. The absence of induced GPER target genes showed that BPA and BPS did not activate GPER in GC after 1 h of treatment. These molecules exhibited mainly independent early mechanisms of action. Gene ontology analysis showed that after 1 h of treatment, BPA mainly disrupted the expression of the genes involved in metabolism and transcription, while BPS had a smaller effect and impaired cellular communications. BPA had a transient effect on the expression of CHAC1 (NOTCH signalling and oxidative balance), JUN (linked to MAPK pathway), NR4A1 (oestradiol secretion inhibition), ARRDC4 (endocytose of GPCR) and KLF10 (cell growth, differentiation and apoptosis), while expression changes were maintained over time for the genes LSMEM1 (linked to MAPK pathway), TXNIP (oxidative stress) and LIF (cell cycle regulation) after 12 and 48 h, respectively.

CONCLUSION

In conclusion, although they exhibited similar effects, BPA and BPS impaired different molecular pathways in GC in vitro. New investigations will be necessary to follow the temporal changes of these genes over time, as well as the biological processes involved.

The study of candidate genes in the improvement of egg production in ducks – a review

Duck is the second-largest poultry species aside from chicken. The rate of egg production is a major determinant of the economic income of poultry farmers. Among the reproductive organs, the ovary is a major part of the female reproductive system which is highly important for egg production. Based on the importance of this organ, several studies have been carried out to identify candidate genes at the transcriptome level, and also the expression level of these genes at different tissues or egg-laying conditions, and single nucleotide polymorphism (SNPs) of genes associated with egg production in duck. In this review, expression profile and association study analyses at SNPs level of different candidate genes with egg production traits of duck were highlighted. Furthermore, different studies on transcriptome analysis, Quantitative Trait Loci (QTL) mapping, and Genome Wide Association Study (GWAS) approach used to identify potential candidate genes for egg production in ducks were reported. This review would widen our knowledge on molecular markers that are associated or have a positive correlation to improving egg production in ducks, for the increasing world populace.

Transcriptome-wide N6-methyladenine methylation in granulosa cells of women with decreased ovarian reserve

Background

The emerging epitranscriptome plays an essential role in female fertility. As the most prevalent internal mRNA modification, N6-methyladenine (m6A) methylation regulate mRNA fate and translational efficiency. However, whether m6A methylation was involved in the aging-related ovarian reserve decline has not been investigated. Herein, we performed m6A transcriptome-wide profiling in the ovarian granulosa cells of younger women (younger group) and older women (older group).

Results

m6A methylation distribution was highly conserved and enriched in the CDS and 3’UTR region. Besides, an increased number of m6A methylated genes were identified in the older group. Bioinformatics analysis indicated that m6A methylated genes were enriched in the FoxO signaling pathway, adherens junction, and regulation of actin cytoskeleton. A total of 435 genes were differently expressed in the older group, moreover, 58 of them were modified by m6A. Several specific genes, including BUB1B, PHC2, TOP2A, DDR2, KLF13, and RYR2 which were differently expressed and modified by m6A, were validated using qRT-PCR and might be involved in the decreased ovarian functions in the aging ovary.

Conclusions

Hence, our finding revealed the transcriptional significance of m6A modifications and provide potential therapeutic targets to promote fertility reservation for aging women.

NRF2-mediated signaling is a master regulator of transcription factors in bovine granulosa cells under oxidative stress condition

Transcription factors (TFs) are known to be involved in regulating the expression of several classes of genes during folliculogenesis. However, the regulatory role of TFs during oxidative stress (OS) is not fully understood. The current study was aimed to investigate the regulation of the TFs in bovine granulosa cells (bGCs) during exposure to OS induced by H₂O₂ in vitro. For this, bGCs derived from ovarian follicles were cultured in vitro till their confluency and then treated with H₂O₂ for 40 min. Twenty-four hours later, cells were subjected to various phenotypic and gene expression analyses for genes related to TFs, endoplasmic reticulum stress, apoptosis, cell proliferation, and differentiation markers. The bGCs exhibited higher reactive oxygen species accumulation, DNA fragmentation, and endoplasmic reticulum stress accompanied by reduction of mitochondrial activity after exposure to OS. In addition, higher lipid accumulation and lower cell proliferation were noticed in H₂O₂-challenged cells. The mRNA level of TFs including NRF2, E2F1, KLF6, KLF9, FOS, SREBF1, SREBF2, and NOTCH1 was increased in H₂O₂-treated cells compared with non-treated controls. However, the expression level of KLF4 and its downstream gene, CCNB1, were downregulated in the H₂O₂-challenged group. Moreover, targeted inhibition of NRF2 using small interference RNA resulted in reduced expression of KLF9, FOS, SREBF2, and NOTCH1 genes, while the expression of KLF4 was upregulated. Taken together, bovine granulosa cells exposed to OS exhibited differential expression of various transcription factors, which are mediated by the NRF2 signaling pathway.

Bisphenol analogs AF, S and F: Effects on functional characteristics of porcine granulosa cells

In order to replace industrial functions of the restricted endocrine disruptor bisphenol A (BPA), its structural analogs are increasingly employed without adequate assessment of their biological actions. Our study examined effects of the bisphenols AF (BPAF), S (BPS) and F (BPF), on functions of porcine ovarian granulosa cells (GCs) with the focus on viability, steroid production (10^-9-10^-4M), and expression of factors (10^-9-10^-5M) important for the follicle development: vascular endothelial growth factor A (VEGFA), matrix metalloproteinase 9 (MMP9), forkhead box O1 (FOXO1), and aryl hydrocarbon receptor (AHR). Cell viability was not impaired by the bisphenol analogs, except for the highest BPAF concentration (10^-4M). While the lower concentrations of the bisphenols were without effect, each of them reduced follicle-stimulating hormone (FSH)-induced progesterone synthesis at the highest dose. Estradiol synthesis was sensitive to BPS, inhibitory effects of which were manifested from the concentration of 10^-6M. Treatment of GCs with the selected bisphenol concentrations did not result in marked alterations in steroidogenic enzyme expression. Bisphenols did not significantly modulate VEGFA mRNA expression or output either under basal or FSH-stimulated conditions. BPF at 10^-5M increased MMP9 expression in FSH-stimulated cells. FSH upregulated FOXO1 expression, however, none of the bisphenols significantly affected FOXO1 levels either in basal or in FSH-stimulated conditions. AHR mRNA expression remained unchanged after bisphenol treatment. Although the significant effects of BPAF, BPS and BPF appeared only at supraphysiological doses, the results obtained indicate that BPA analogs are not inert with regard to ovarian physiology.

Ovarian transcriptomic analysis of black Muscovy duck at the early, peak and late egg-laying stages

Ovarian development is a complex process involving many genes and pathways. A well-developed ovary is essential for poultry to keep high egg production and egg fertility. In order to better understand the mechanism of egg production performance, a comparative transcriptomic analysis was performed on ovaries of black Muscovy ducks at the early (BE), peak (BP) and late laying (BL) stages. 1683 DEGs were identified from BL-vs-BE, BL-vs-BP and BP-vs-BE, and the up-regulated genes were 41, 835, 260, the down-regulated genes were 60, 255, 730, respectively. Besides, there were 32, 20 and 424 DEGs co-expressed in the two comparison groups, and 11 DEGs were co-expressed in the three comparison groups. HOXA10, HtrA3, StAR, ZP2 and TAT were found to be involved in the regulation of ovarian development were significantly differentially expressed at different laying stages, which helped to regulate ovarian maturation and egg production. Moreover, we discovered several important functional pathways, such as steroid hormone biosynthesis and ovarian steroidogenesis, that appear to be much more active in the BP ovary compared to those of the BE and BL. Furthermore, 17 coding and 244 non-coding new transcripts were detected in the three comparison groups, the gene structures were optimized and the gene annotation informations were improved. These findings will provide a solid foundation on ovarian development in black Muscovy ducks and other poultry animals at different laying stages, and help to understand the complex molecular and cellular mechanisms of ovary.

Deletion of Krüppel-like factor-4 promotes axonal regeneration in mammals

Axonal regeneration plays an important role in functional recovery after nervous system damage. However, after axonal injury in mammals, regeneration is often poor. The deletion of Krüppel-like factor-4 (Klf4) has been shown to promote axonal regeneration in retinal ganglion cells. However, the effects of Klf4 deletion on the corticospinal tract and peripheral nervous system are unknown. In this study, using a mouse model of sciatic nerve injury, we show that the expression of Klf4 in dorsal root ganglion sensory neurons was significantly reduced after peripheral axotomy, suggesting that the regeneration of the sciatic nerve is associated with Klf4. In vitro, dorsal root ganglion sensory neurons with Klf4 knockout exhibited significantly enhanced axonal regeneration. Furthermore, the regeneration of the sciatic nerve was enhanced in vivo following Klf4 knockout. Finally, AAV-Cre virus was used to knockout the Klf4 gene in the cortex. The deletion of Klf4 enhanced regeneration of the corticospinal tract in mice with spinal cord injury. Together, our findings suggest that regulating KLF4 activity in neurons is a potential strategy for promoting axonal regeneration and functional recovery after nervous system injury. This study was approved by the Animal Ethics Committee at Soochow University, China (approval No. SUDA20200316A01).

Transcriptome Analysis of the Chicken Follicular Theca Cells with miR-135a-5p Suppressed

As a class of transcription regulators, numerous miRNAs have been verified to participate in regulating ovary follicular development in chickens (Gallus gallus). Previously we showed that gga-miR-135a-5p has significant differential expression between high and low-yield chicken ovaries, and the abundance of gga-miR-135a-5p is significantly higher in follicular theca cells than in granulosa cells. However, the exact role of gga-miR-135a-5p in chicken follicular theca cells is unclear. In this study, primary chicken follicular theca cells were isolated and then transfected with gga-miR-135a-5p inhibitor. Transcriptome sequencing was performed in chicken follicular theca cells with or without transfection. Differentially expressed genes (DEGs) were analyzed using bioinformatics. A dual-luciferase reporter assay was used to verify the target relationship between gga-miR-135a-5p and predicted targets within the DEGs. Compared with the normal chicken follicle theca cells, 953 up-regulated and 1060 down-regulated genes were detected in cells with gga-miR-135a-5p inhibited. The up-regulated genes were significantly enriched in Gene Ontology terms and pathways involved in cell proliferation and differentiation. In chicken follicular theca cells, Krüppel-like factor 4 (KLF4), ATPase phospholipid transporting 8A1 (ATP8A1), and Complexin-1 (CPLX1) were significantly up-regulated when the expression of gga-miR-135a-5p was inhibited. In addition, KLF4, ATP8A1, and CPLX1 confirmed as targets of gga-miR-135a-5p by using a dual-luciferase assay in vitro. The results suggest that gga-mir-135a-5p may involve in proliferation and differentiation in chicken ovarian follicular theca cells by targeting KLF4, ATP8A1, and CPLX1.

LH-induced Transcriptional Regulation of Klf4 Expression in Granulosa Cells Occurs via the cAMP/PKA Pathway and Requires a Putative Sp1 Binding Site

Krüppel-like factor 4 (Klf4) plays an important role in the transition from proliferation to differentiation in a wide variety of cells. Previous studies demonstrated its critical role in the luteal transition of preovulatory granulosa cells (GCs). This study used cultured rat preovulatory GCs to investigate the mechanism by which luteinizing hormone (LH) regulates Klf4 gene expression. Klf4 mRNA and protein were rapidly and transiently induced by LH treatment, reaching peak levels after 45 min and declining to basal levels by 3 h. Pretreatment with the protein synthesis inhibitor cycloheximide had no effect on LH-stimulated Klf4 expression, indicating that Klf4 is an immediate early gene in response to LH. To investigate the signaling pathway involved in LH-induced Klf4 regulation, the protein kinase A (PKA) and protein kinase C (PKC) pathways were evaluated. A-kinase agonists, but not a C-kinase agonist, mimicked LH in inducing Klf4 transcription. In addition, specific inhibitors of A-kinase abolished the stimulatory effect of LH on Klf4 expression. Truncation of a Klf4 expression construct to −715 bp (pKlf4-715/luc) had no effect on transcriptional activity, whereas deletion to −402 bp (pKlf4-402/luc) dramatically reduced it. ChIP analysis revealed in vivo binding of endogenous Sp1 to the −715/−500 bp region and maximal transcriptional responsiveness to LH required the Sp1 binding element at −698/−688 bp, which is highly conserved in mice, rats, and humans. These findings demonstrate that Klf4 is activated by LH via the cAMP/PKA pathway and a putative Sp1 binding element at −698/−688 bp is indispensable for activation and suggest that Klf4 could be a target for strategies for treating luteal phase insufficiency induced by an aberrant response to the LH surge.

Short-term effect of FSH on gene expression in bovine granulosa cells in vitro

In reproduction, FSH is one of the most important hormones, especially in females, because it controls the number of follicles and the rate of follicular growth. Although several studies have examined the follicular response at the transcriptome level, it is difficult to obtain a clear and complete picture of the genes responding to an increase in FSH in an in vivo context because follicles undergo rapid morphological and physical changes during their growth. To help define the transcriptome downstream response to FSH, an in vitro model was used in the present study to observe the short-term (4h) cellular response. Gene expression analysis highlighted a set of novel transcripts that had not been reported previously as being part of the FSH response. Moreover, the results of the present study indicate that the epithelial to mesenchymal transition pathway is inhibited by short-term FSH stimuli, maintaining follicles in a growth phase and preventing differentiation. Modulating gene expression in vitro has physiological limitations, but it can help assess the potential downstream response and begin the mapping of the granulosa cell transcriptome in relation to FSH. This information is a key feature to help discriminate between the effects of FSH and LH, or to elucidate the overlapping of insulin-like growth factor 1 and FSH in the granulosa mitogenic response.

Krüppel-like factor 4 plays a role in the luteal transition in steroidogenesis by downregulating Cyp19A1 expression

The transition from granulosa cell (GC) to luteal cell involves a change from estrogen production to predominantly progesterone production. We analyzed the role of Krüppel-like factor 4 (Klf4), a transcriptional repressor used to generate pluripotent cells, in that transition. After luteinizing hormone (LH)/human chorionic gonadotropin treatment of preovulatory follicles, a major but transient increase in Klf4 transcript levels was detected. Therefore, we enquired whether Klf4 is involved in the rapid decline of aromatase, the key estrogen-producing enzyme, using preovulatory GCs obtained from pregnant mare serum gonadotropin-primed immature rat ovaries. Cyp19A1 expression in GCs transfected with FLAG-Klf4 or Klf4-specific siRNA was analyzed by real-time PCR and immunofluorescence staining. Cyp19A1 decreased when Klf4 was overexpressed, and Cyp19A1 and estradiol biosynthesis increased when Klf4 was knocked down. The mechanism by which Klf4 regulates Cyp19A1 expression was investigated using Cyp19A1 promoter-luciferase reporter assays and chromatin immunoprecipitation assays. The results revealed that the steroidogenic factor-1 (SF1)-binding motif, but not the specificity protein 1 (Sp1) binding element or the CACCC motif, was required for Klf4-mediated repression of Cyp19A1 promoter activity. Here we showed that Klf4 suppressed endogenous Cyp19A1 transcript and protein production, and this resulted from direct binding of Klf4 to the SF1 recognition motif in the Cyp19A1 promoter. These findings suggest that Klf4 is a physiologic regulator of Cyp19A1 expression in response to the LH surge in preovulatory GCs and that it has an essential role in the luteal transition in steroidogenesis.

Role of Klf4 in the Regulation of Apoptosis and Cell Cycle in Rat Granulosa Cells during the Periovulatory Period

In the ovary, the luteinizing hormone (LH) surge suppresses the proliferation and induces the luteinization of preovulatory granulosa cells (GCs), which is crucial for the survival of terminally-differentiated GCs. Krüppel-like factor 4 (Klf4) has been shown to play a role in regulating the cell cycle and apoptosis in various cell types. The rapid induction of Klf4 expressions by LH was observed in preovulatory GCs. To evaluate whether Klf4 affects GC proliferation and survival, primary rat GCs were isolated from pregnant mare serum gonadotropin-primed Sprague⁻Dawley rat ovaries and transfected with a Klf4 expression vector or Klf4-specific siRNA, followed by determination of the transcript levels of apoptosis-related and cell cycle-related genes. Cell proliferation, viability, and apoptosis were analyzed by BrdU incorporation, a Cell Counting Kit-8 assay, a bioluminescence caspase 3/7 assay, and flow cytometry. LH treatment increased Klf4 mRNA expression in preovulatory GCs. Transcripts of B-cell lymphoma 2 (Bcl-2) and cell cycle promoters (Cyclin D1 and Cyclin D2) decreased, whereas those of the cell cycle inhibitor, p21, increased. Altering the expression of Klf4 by overexpression or knockdown consistently affected the expression of Bcl-2 and Cyclin D1. In agreement with this, Klf4 overexpression reduced cell viability, increased the fraction of apoptotic cells, and arrested cell cycle progression in G1 phase. We conclude that Klf4 increases the susceptibility of preovulatory GCs to apoptosis by down-regulating Bcl-2, and promotes LH-induced cell cycle exit. It appears to be a key regulator induced by the LH surge that determines the fate of GCs in preovulatory follicles during the luteal transition.

Erythropoietin-producing hepatocellular A7 triggering ovulation indicates a potential beneficial role for polycystic ovary syndrome

Background

The ovulatory dysfunction mechanisms underlying polycystic ovary syndrome (PCOS) are not completely understood. And the roles of EPHA7 and EPHA7-regulated pathway factors in the pathogenesis of anovulation remain to be elucidated.

Methods

We used human granulosa cells (hGCs) of PCOS and non-PCOS patients to measure EPHA7 and other target gene expressions. We performed in vitro experiments in KGN cells to verify the molecular mechanisms. Additionally, we conducted in vivo loss- and gain-of-function studies using EPHA7 shRNA lentivirus and recombinant EPHA7-Fc protein injection to identify the ovulation effects of EPHA7.

Findings

EPHA7 functions as a critically positive upstream factor for the expression of ERK1/2-mediated C/EBPβ. This protein, in turn, induced the expression of KLF4 and then ADAMTS1. Moreover, decreased abundance of EPHA7 was positively correlated with that of its downstream factors in hGCs of PCOS patients. Additionally, a 1-week functional EPHA7 shRNA lentivirus in rat ovaries contributed to decreased numbers of retrieved oocytes, and a 3-week functional lentivirus led to menstrual disorders and morphological polycystic changes in rat ovaries. More importantly, we found that EPHA7 triggered ovulation in rats, and it improved polycystic ovarian changes induced by DHEA in PCOS rats.

Interpretation

Our findings demonstrate a new role of EPHA7 in PCOS, suggesting that EPHA7 is an effective target for the development of innovative medicines to induce ovulation.

Fund

National Key Research and Development Program of China, National Natural Science Foundation, Shanghai Municipal Education Commission--Gaofeng Clinical Medicine, and Shanghai Commission of Science and Technology.

Simultaneous effects of endocrine disruptor bisphenol A and flavonoid fisetin on progesterone production by granulosa cells

In the present study, we aimed to examine effects of different concentrations of the endocrine disruptor Bisphenol A (BPA; 1 nM, 1 μM, 100 μM) and the flavonoid fisetin (1, 10, 25, 50 μM), individually and in combinations, on steroidogenic function of porcine ovarian granulosa cells (GCs) represented by progesterone production. We confirmed that BPA inhibited progesterone production by GCs at the highest concentration. Fisetin reduced gonadotropin-stimulated progesterone synthesis dose-dependently, and in this manner, fisetin impaired progesterone production when added to BPA-treated GCs. The mechanisms of the inhibitory effects of the combinations included a significant down-regulation of the key steroidogenesis-related genes (STAR, CYP11A1, HSD3B). Our findings suggest for the first time that fisetin might interfere with ovarian steroidogenesis, and might not have beneficial but rather aggravating effects in terms of modulating progesterone synthesis altered by high concentrations of BPA.

MicroRNA-145 protects follicular granulosa cells against oxidative stress-induced apoptosis by targeting Krüppel-like factor 4

Oxidative stress-induced follicular granulosa cell (GC) apoptosis plays an essential role in abnormal follicular atresia, which may trigger ovarian dysfunction. To investigate the role of microRNA (miR)-145 in the regulation of GC apoptosis and modulation of the apoptotic pathway in the setting of oxidative stress, we employed an H2O2-induced in vitro model and a 3-nitropropionic acid (NP)-induced in vivo model of ovarian oxidative stress. We demonstrated in vitro that miR-145 expression was significantly down-regulated in KGN cells and mouse granulosa cells (mGCs) treated with H2O2, whereas miR-145 over-expression attenuated H2O2-induced apoptosis in GCs. Moreover, miR-145 protected GCs against H2O2-induced apoptosis by targeting KLF4, which promoted H2O2-induced GC apoptosis via the BAX/BCL-2 pathway. Importantly, decreased miR-145 expression in the in vivo ovarian oxidative stress model promoted apoptosis by up-regulating KLF4 expression, whereas GC-specific miR-145 over-expression attenuated apoptosis by targeting KLF4. In conclusion, miR-145 protects GCs against oxidative stress-induced apoptosis by targeting KLF4.

Human single follicle growth in vitro from cryopreserved ovarian tissue after slow freezing or vitrification

STUDY QUESTION

What is the effect of human ovarian tissue cryopreservation on single follicular development in vitro?

SUMMARY ANSWER

Vitrification had a greater negative effect on growth and gene expression of human ovarian follicles when compared with fresh follicles.

WHAT IS KNOWN ALREADY

For human ovarian cortex cryopreservation, the conventional option is slow freezing while more recently vitrification has been demonstrated to maintain good quality and function of ovarian tissues.

STUDY DESIGN, SIZE, DURATION

Ovarian tissues were collected from 11 patients. For every patient, the ovarian cortex was divided into three samples: Fresh, slow-rate freezing (Slow) and vitrification (Vit). Tissue histology was performed and follicles were isolated for single-cell mRNA analysis and in vitro culture (IVC) in 1% alginate for 8 days.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Follicle morphology was assessed with hematoxylin-eosin analysis. Follicles were individually embedded in alginate (1% w/v) and cultured in vitro for 8 days. Follicle survival and growth were assessed by microscopy. Follicle viability was observed after Calcein-AM and ethidium homodimer-I (Ca-AM/EthD-I) staining. Expression of genes, including GDF9 (growth differentiation factor 9), BMP15 (bone morphogenetic protein 15) and ZP3 (zona pellucida glycoprotein 3) in oocytes and AMH (anti-Mullerian hormone), FSHR (FSH receptor), CYP11A (cholesterol side-chain cleavage cytochrome P450) and STAR (steroidogenic acute regulatory protein) in GCs, was evaluated by single-cell mRNA analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 129 follicles were separated from ovarian cortex (Fresh n = 44; Slow n = 40; Vit n = 45). The percentage of damaged oocytes and granulosa cells was significantly higher in both the Slow and Vit groups, as compared with Fresh control (P< 0.05). The growth of follicles in vitro was significantly delayed in the Vit group compared with the Fresh group (P< 0.05). Both slow freezing (P< 0.05) and vitrification (P< 0.05) down-regulated the mRNA levels of ZP3 and CYP11A compared with Fresh group, while there was no significant difference between the Slow and Vit groups (P> 0.05). Vitrification also down-regulates AMH mRNA levels compared with Fresh group (P< 0.05).

LIMITATIONS, REASONS FOR CAUTION

Only short-term IVC studies (8 days) are reported. Further study should be performed to examine and improve follicular development in a long-term culture system after cryopreservation.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first comparison of gene expression and growth of single human ovarian follicles in vitro after either slow freezing or vitrification. With the decreased gene expression and growth during IVC, damage by cryopreservation still exists and needs to be minimized during the long-term IVC of follicles in the future for eventual clinical application.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by the National Natural Science Foundation of China (31230047, 81571386, 81471508, 31429004 and 81501247), National Natural Science Foundation of Beijing (7142166) and Mega-projects of Science Research for the 12th five-year plan (2012ba132b05). There are no conflicts of interest to declare.

Spatio-Temporal Gene Expression Profiling during In Vivo Early Ovarian Folliculogenesis: Integrated Transcriptomic Study and Molecular Signature of Early Follicular Growth

Background

The successful achievement of early ovarian folliculogenesis is important for fertility and reproductive life span. This complex biological process requires the appropriate expression of numerous genes at each developmental stage, in each follicular compartment. Relatively little is known at present about the molecular mechanisms that drive this process, and most gene expression studies have been performed in rodents and without considering the different follicular compartments.

Results

We used RNA-seq technology to explore the sheep transcriptome during early ovarian follicular development in the two main compartments: oocytes and granulosa cells. We documented the differential expression of 3,015 genes during this phase and described the gene expression dynamic specific to these compartments. We showed that important steps occurred during primary/secondary transition in sheep. We also described the in vivo molecular course of a number of pathways. In oocytes, these pathways documented the chronology of the acquisition of meiotic competence, migration and cellular organization, while in granulosa cells they concerned adhesion, the formation of cytoplasmic projections and steroid synthesis. This study proposes the involvement in this process of several members of the integrin and BMP families. The expression of genes such as Kruppel-like factor 9 (KLF9) and BMP binding endothelial regulator (BMPER) was highlighted for the first time during early follicular development, and their proteins were also predicted to be involved in gene regulation. Finally, we selected a data set of 24 biomarkers that enabled the discrimination of early follicular stages and thus offer a molecular signature of early follicular growth. This set of biomarkers includes known genes such as SPO11 meiotic protein covalently bound to DSB (SPO11), bone morphogenetic protein 15 (BMP15) and WEE1 homolog 2 (S. pombe)(WEE2) which play critical roles in follicular development but other biomarkers are also likely to play significant roles in this process.

Conclusions

To our knowledge, this is the first in vivo spatio-temporal exploration of transcriptomes derived from early follicles in sheep.

The Krüppel-like factors in female reproductive system pathologies

Female reproductive tract pathologies arise largely from dysregulation of estrogen and progesterone receptor signaling, leading to aberrant cell proliferation, survival, and differentiation. The signaling pathways orchestrated by these nuclear receptors are complex, require the participation of many nuclear proteins serving as key binding partners or targets, and involve a range of paracrine and autocrine regulatory circuits. The members of the Krüppel-like factor (KLF) family of transcription factors are ubiquitously expressed in reproductive tissues and have been increasingly implicated as critical co-regulators and integrators of steroid hormone actions. Herein, we explore the involvement of KLF family members in uterine pathology, describe their currently known molecular mechanisms, and discuss their potential as targets for therapeutic intervention.

The reproductive phenotype of mice null for transcription factor Krüppel-like factor 13 suggests compensatory function of family member Krüppel-like factor 9 in the peri-implantation uterus

The ovarian hormones estrogen and progesterone promote uterine receptivity and successful pregnancy through their cognate receptors functioning in concert with context-dependent nuclear coregulators. Previously, we showed that the transcription factor Krüppel-like factor (KLF) 9 is a progesterone receptor (PGR) coactivator in the uterus and that mice null for Klf9 exhibit subfertility and reduced progesterone sensitivity. The highly related family member KLF13 displays increased expression in uteri of pregnant and nonpregnant Klf9 null mice and similarly regulates PGR-mediated transactivation in endometrial stromal cells. However, a uterine phenotype with loss of Klf13 has not been reported. In the present study, we demonstrate that Klf13 deficiency in mice did not compromise female fertility and pregnancy outcome. Klf13 null females had litter sizes, numbers of implanting embryos, uterine morphology, and ovarian steroid hormone production comparable to those of wild-type (WT) counterparts. Further, pregnant WT and Klf13 null females at Day Postcoitum (DPC) 3.5 had similar uterine Pgr, estrogen receptor, and Wnt-signaling component transcript levels. Nuclear levels of KLF9 were higher in Klf13 null than in WT uteri at DPC 3.5, albeit whole-tissue KLF9 protein and transcript levels did not differ between genotypes. The lack of a similar induction of nuclear KLF9 levels in uteri of virgin Klf13((-/-)) mice relative to WT uteri was associated with lower stromal PGR expression. In differentiating human endometrial stromal cells, coincident KLF9/KLF13 knockdown by small interfering RNA targeting reduced decidualization-associated PRL expression, whereas KLF9 and KLF13 knockdowns alone reduced transcript levels of WNT4 and BMP2, respectively. Results suggest that KLF9 and KLF13 functionally compensate in peri-implantation uterus for pregnancy success.

Oocyte-somatic cells interactions, lessons from evolution

Background

Despite the known importance of somatic cells for oocyte developmental competence acquisition, the overall mechanisms underlying the acquisition of full developmental competence are far from being understood, especially in non-mammalian species. The present work aimed at identifying key molecular signals from somatic origin that would be shared by vertebrates.

Results

Using a parallel transcriptomic analysis in 4 vertebrate species - a teleost fish, an amphibian, and two mammals - at similar key steps of developmental competence acquisition, we identified a large number of species-specific differentially expressed genes and a surprisingly high number of orthologous genes exhibiting similar expression profiles in the 3 tetrapods and in the 4 vertebrates. Among the evolutionary conserved players participating in developmental competence acquisition are genes involved in key processes such as cellular energy metabolism, cell-to-cell communications, and meiosis control. In addition, we report many novel molecular actors from somatic origin that have never been studied in the vertebrate ovary. Interestingly, a significant number of these new players actively participate in Drosophila oogenesis.

Conclusions

Our study provides a comprehensive overview of evolutionary-conserved mechanisms from somatic origin participating in oocyte developmental competence acquisition in 4 vertebrates. Together our results indicate that despite major differences in ovarian follicular structure, some of the key players from somatic origin involved in oocyte developmental competence acquisition would be shared, not only by vertebrates, but also by metazoans. The conservation of these mechanisms during vertebrate evolution further emphasizes the important contribution of the somatic compartment to oocyte quality and paves the way for future investigations aiming at better understanding what makes a good egg.

Krüppel-like factors 4 and 5: unity in diversity

Krüppel-like factors (Klf) 4 and 5 belong to a family of zinc finger-containing transcription factors that share homology with the Drosophila gene Krüppel. They regulate proliferation and differentiation of a wide variety of cells and have been linked to tumorigenesis. Their most striking role so far has turned out to be their ability to reprogram/ maintain embryonic stem cell fate. In this review, the data available in the field regarding their role in proliferation and differentiation and their coupling to carcinogenesis are summarized. The emphasis is on their context dependence and how they might be able to regulate diverse transcriptional outputs from the genome.

Gene expression profiling of preovulatory follicle in the buffalo cow: effects of increased IGF-I concentration on periovulatory events

The preovulatory follicle in response to gonadotropin surge undergoes dramatic biochemical, and morphological changes orchestrated by expression changes in hundreds of genes. Employing well characterized bovine preovulatory follicle model, granulosa cells (GCs) and follicle wall were collected from the preovulatory follicle before, 1, 10 and 22 h post peak LH surge. Microarray analysis performed on GCs revealed that 450 and 111 genes were differentially expressed at 1 and 22 h post peak LH surge, respectively. For validation, qPCR and immunocytochemistry analyses were carried out for some of the differentially expressed genes. Expression analysis of many of these genes showed distinct expression patterns in GCs and the follicle wall. To study molecular functions and genetic networks, microarray data was analyzed using Ingenuity Pathway Analysis which revealed majority of the differentially expressed genes to cluster within processes like steroidogenesis, cell survival and cell differentiation. In the ovarian follicle, IGF-I is established to be an important regulator of the above mentioned molecular functions. Thus, further experiments were conducted to verify the effects of increased intrafollicular IGF-I levels on the expression of genes associated with the above mentioned processes. For this purpose, buffalo cows were administered with exogenous bGH to transiently increase circulating and intrafollicular concentrations of IGF-I. The results indicated that increased intrafollicular concentrations of IGF-I caused changes in expression of genes associated with steroidogenesis (StAR, SRF) and apoptosis (BCL-2, FKHR, PAWR). These results taken together suggest that onset of gonadotropin surge triggers activation of various biological pathways and that the effects of growth factors and peptides on gonadotropin actions could be examined during preovulatory follicle development.

WNT4 is required for normal ovarian follicle development and female fertility

To study the role of WNT4 in the postnatal ovary, a mouse strain bearing a floxed Wnt4 allele was created and mated to the Amhr2(tm3(cre)Bhr) strain to target deletion of Wnt4 to granulosa cells. Wnt4(flox/-);Amhr2(tm3(cre)Bhr/+) mice had reduced ovary weights and produced smaller litters (P<0.05). Serial follicle counting demonstrated that Wnt4(flox/-);Amhr2(tm3(cre)Bhr/+) mice were born with a normal ovarian reserve and maintained normal numbers of small follicles until puberty but had only 25.2% of the normal number of healthy antral follicles. Some Wnt4(flox/-);Amhr2(tm3(cre)Bhr/+) mice had no antral follicles or corpora lutea and underwent premature follicle depletion. RT-PCR analyses of Wnt4(flox/-);Amhr2(tm3(cre)Bhr/+) granulosa cells and cultured granulosa cells that overexpress WNT4 demonstrated that WNT4 regulates the expression of Star, Cyp11a1, and Cyp19, steroidogenic genes previously identified as downstream targets of the WNT signaling effector CTNNB1. Decreased serum progesterone levels were found in immature, gonadotropin-treated Wnt4(flox/-);Amhr2(tm3(cre)Bhr/+) mice (P<0.05). WNT4- and CTNNB1-overexpressing cultured granulosa cells were analyzed by microarray for alterations in gene expression, which showed that WNT4 regulates additional genes involved in late follicle development via the WNT/CTNNB1 signaling pathway. Together, these data indicate that WNT4 is required for normal antral follicle development and may act by regulating granulosa cell functions including steroidogenesis.

Regulation of the human HBA genes by KLF4 in erythroid cell lines

KLF1/EKLF and related Krueppel-like factors (KLFs) are variably implicated in the regulation of the HBB-like globin genes. Prompted by the observation that four KLF sites are distributed in the human alpha-globin gene (HBA) promoter, we investigated if KLFs could also act to modulate the expression of the HBA genes. Among the KLFs tested, only KLF4/GKLF bound specifically to three out of four alpha-globin KLF sites. The occupancy of the same sites by KLF4 in vivo was confirmed by chromatin immunoprecipitation assays with KLF4-specific antibodies. In luciferase reporter assays in MEL cells, high levels of the wild type HBA promoter, but not mutated promoters bearing point mutations that disrupted KLF4-DNA binding, were transactivated by over-expression of KLF4. In K562 cells, induced KLF4 expression with a Tet-off regulated cassette stimulated the expression of the endogenous HBA genes. In a complementary assay in the same cell line, knocking down KLF4 with lentiviral delivered sh-RNAs caused a parallel decrease in the transcription of the HBA genes. All experiments combined support a regulatory role of KLF4 in the control of HBA gene expression.

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.