Development and application of a rat ovarian gene expression database

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.

RUN(X) out of blood: emerging RUNX1 functions beyond hematopoiesis and links to Down syndrome

BACKGROUND

RUNX1 is a transcription factor and a master regulator for the specification of the hematopoietic lineage during embryogenesis and postnatal megakaryopoiesis. Mutations and rearrangements on RUNX1 are key drivers of hematological malignancies. In humans, this gene is localized to the 'Down syndrome critical region' of chromosome 21, triplication of which is necessary and sufficient for most phenotypes that characterize Trisomy 21.

MAIN BODY

Individuals with Down syndrome show a higher predisposition to leukemias. Hence, RUNX1 overexpression was initially proposed as a critical player on Down syndrome-associated leukemogenesis. Less is known about the functions of RUNX1 in other tissues and organs, although growing reports show important implications in development or homeostasis of neural tissues, muscle, heart, bone, ovary, or the endothelium, among others. Even less is understood about the consequences on these tissues of RUNX1 gene dosage alterations in the context of Down syndrome. In this review, we summarize the current knowledge on RUNX1 activities outside blood/leukemia, while suggesting for the first time their potential relation to specific Trisomy 21 co-occurring conditions.

CONCLUSION

Our concise review on the emerging RUNX1 roles in different tissues outside the hematopoietic context provides a number of well-funded hypotheses that will open new research avenues toward a better understanding of RUNX1-mediated transcription in health and disease, contributing to novel potential diagnostic and therapeutic strategies for Down syndrome-associated conditions.

Ovarian transcriptome profile from pre-laying period to broody period of Xupu goose

Xupu goose, a breed from Hunan province, produces high quality and quantity of meat and liver. However, its egg production rate is low, with poor reproductive traits but strong broody performance. These characteristics decrease the economic value of Xupu goose significantly. Here, RNA-seq was used to analyze the transcriptome changes of ovaries of Xupu goose at different stages to explore the molecular mechanism of reproduction from the pre-laying period to the broody period. A total of 258 genes were differentially expressed in the 3 stages. These genes are associated with inflammation, reproduction, mutual recognition and adhesion between cells, and cytoskeleton formation, and so on. In particular, we report, for the first time, the expression patterns of MRP126, serglycin, TXNIP, and FZD2 during the pre-laying, egg-laying, and broody periods of goose ovaries. Functional analysis by GO annotation revealed that GO terms were mainly involved in actin, cell signal transduction and regulation, and cellular components. Three pathways, including focal adhesion (gga04510), ECM-receptor interaction (gga04512), and N-Glycan biosynthesis (gga00510), were significantly enriched in the three groups. These findings provide a basis for further exploration of profiles of goose ovaries to improve egg production of Xupu goose.

The mRNA-destabilizing protein Tristetraprolin targets "meiosis arrester" Nppc mRNA in mammalian preovulatory follicles

C-natriuretic peptide (CNP) and its receptor guanylyl cyclase, natriuretic peptide receptor 2 (NPR2), are key regulators of cyclic guanosine monophosphate (cGMP) homeostasis. The CNP-NPR2-cGMP signaling cascade plays an important role in the progression of oocyte meiosis, which is essential for fertility in female mammals. In preovulatory ovarian follicles, the luteinizing hormone (LH)-induced decrease in CNP and its encoding messenger RNA (mRNA) natriuretic peptide precursor C (Nppc) are a prerequisite for oocyte meiotic resumption. However, it has never been determined how LH decreases CNP/Nppc In the present study, we identified that tristetraprolin (TTP), also known as zinc finger protein 36 (ZFP36), a ubiquitously expressed mRNA-destabilizing protein, is the critical mechanism that underlies the LH-induced decrease in Nppc mRNA. Zfp36 mRNA was transiently up-regulated in mural granulosa cells (MGCs) in response to the LH surge. Loss- and gain-of-function analyses indicated that TTP is required for Nppc mRNA degradation in preovulatory MGCs by targeting the rare noncanonical AU-rich element harbored in the Nppc 3' UTR. Moreover, MGC-specific knockout of Zfp36, as well as lentivirus-mediated knockdown in vivo, impaired the LH/hCG-induced Nppc mRNA decline and oocyte meiotic resumption. Furthermore, we found that LH/hCG activates Zfp36/TTP expression through the EGFR-ERK1/2-dependent pathway. Our findings reveal a functional role of TTP-induced mRNA degradation, a global posttranscriptional regulation mechanism, in orchestrating the progression of oocyte meiosis. We also provided a mechanism for understanding CNP-dependent cGMP homeostasis in diverse cellular processes.

Insufficient Cumulus Expansion and Poor Oocyte Retrieval in Endometriosis-Related Infertile Women

Endometriosis (EMs) is a common cause for female infertility, leading to the need for in vitro fertilization (IVF). In clinics, we found the operative oocyte retrieval to be more or less difficult in women with EMs. We hypothesized that EMs may be involved in the insufficient cumulus expansion that partially explained the lower oocyte retrieval in EMs-related infertile women undergoing assisted reproductive technology (ART). To explore whether the insufficient cumulus expansion exists in EMs-related infertile women and whether there is a possible relationship between the insufficient cumulus expansion and the clinical phenomenon of difficulty in oocyte retrieval. Those infertile women undergoing IVF recorded in our database between January 2013 and October 2017 were included. The expression levels of cumulus expansion-related genes (HAS2/PTGS2/PTX3/TNFAIP6) in the cumulus cells (CCs) from 19 infertile women with EMs and 24 controls were analyzed by real-time PCR. After that, 635 women with EMs-associated infertility (the EMs group) and 4634 women with male factor-associated infertility (the control group) were included in the retrospective analysis. The clinical outcomes were compared between the two groups. The relative mRNA levels of cumulus expansion-related genes were significantly decreased in the CCs from those infertile women with EMs when compared to the control group (all p < 0.05), especially the expression of PTGS2. The mean oocyte retrieval rates (proportion of obtained oocytes in punctured follicles) were (76.33 ± 2.58)% and (71.80 ± 0.58)% (p < 0.01). The mean numbers of flushing times per follicle were 1.11 ± 0.65 and 3.86 ± 1.53 (p < 0.001). The lower expression of cumulus expansion-related genes in CCs suggests the insufficient cumulus expansion in EMs-related infertile women, which partially explains a possible mechanism related to poor oocyte retrieval.

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.

Ovulation: Parallels With Inflammatory Processes

The midcycle surge of LH sets in motion interconnected networks of signaling cascades to bring about rupture of the follicle and release of the oocyte during ovulation. Many mediators of these LH-induced signaling cascades are associated with inflammation, leading to the postulate that ovulation is similar to an inflammatory response. First responders to the LH surge are granulosa and theca cells, which produce steroids, prostaglandins, chemokines, and cytokines, which are also mediators of inflammatory processes. These mediators, in turn, activate both nonimmune ovarian cells as well as resident immune cells within the ovary; additional immune cells are also attracted to the ovary. Collectively, these cells regulate proteolytic pathways to reorganize the follicular stroma, disrupt the granulosa cell basal lamina, and facilitate invasion of vascular endothelial cells. LH-induced mediators initiate cumulus expansion and cumulus oocyte complex detachment, whereas the follicular apex undergoes extensive extracellular matrix remodeling and a loss of the surface epithelium. The remainder of the follicle undergoes rapid angiogenesis and functional differentiation of granulosa and theca cells. Ultimately, these functional and structural changes culminate in follicular rupture and oocyte release. Throughout the ovulatory process, the importance of inflammatory responses is highlighted by the commonalities and similarities between many of these events associated with ovulation and inflammation. However, ovulation includes processes that are distinct from inflammation, such as regulation of steroid action, oocyte maturation, and the eventual release of the oocyte. This review focuses on the commonalities between inflammatory responses and the process of ovulation.

Core Binding Factor β Expression in Ovarian Granulosa Cells Is Essential for Female Fertility

Core binding factor β (CBFβ) is a non-DNA-binding partner of all RUNX proteins and critical for transcription activity of CBF transcription factors (RUNXs/CBFβ). In the ovary, the expression of Runx1 and Runx2 is highly induced by the luteinizing hormone (LH) surge in ovulatory follicles, whereas Cbfb is constitutively expressed. To investigate the physiological significance of CBFs in the ovary, the current study generated two different conditional mutant mouse models in which granulosa cell expression of Cbfb and Runx2 was reduced by Cre recombinase driven by an Esr2 promoter. Cbfbgc-/- and Cbfbgc-/- × Runx2gc+/- mice exhibited severe subfertility and infertility, respectively. In the ovaries of both mutant mice, follicles develop normally, but the majority of preovulatory follicles failed to ovulate either in response to human chorionic gonadotropin administration in pregnant mare serum gonadotropin-primed immature animals or after the LH surge at 5 months of age. Morphological and physiological changes in the corpus luteum of these mutant mice revealed the reduced size, progesterone production, and vascularization, as well as excessive lipid accumulation. In granulosa cells of periovulatory follicles and corpora lutea of these mice, the expression of Edn2, Ptgs1, Lhcgr, Sfrp4, Wnt4, Ccrl2, Lipg, Saa3, and Ptgfr was also drastically reduced. In conclusion, the current study provided in vivo evidence that CBFβ plays an essential role in female fertility by acting as a critical cofactor of CBF transcription factor complexes, which regulate the expression of specific key ovulatory and luteal genes, thus coordinating the ovulatory process and luteal development/function in mice.

Occurrence of sulfonated steroids and ovarian expression of steroid sulfatase and SULT1E1 in cyclic cows

Historically sulfonated steroids were primarily considered as inactive metabolites destined for elimination. However, more recently they have been increasingly recognized as precursors for the production of bioactive steroids in target tissues and as functional molecules without preceding hydrolysis. In order to comprehensively characterize their occurrence in cyclic cows and their formation and hydrolysis in bovine ovarian steroidogenesis, ovaries from cyclic cows were screened for the expression of oestrogen sulfotransferase (SULTE1) and steroid sulfatase (STS) by Western blot and immunohistochemistry. Moreover, a broad spectrum of 13 sulfonated steroids was measured applying liquid chromatography-tandem mass spectrometry (LC-MS/MS) in blood samples collected from three cycling heifers during defined stages of the ovarian cycle and in fluid obtained from ovarian follicles of different size. SULT1E1 was undetectable in ovarian tissues. For STS only a weak immunostaining was found predominantly in granulosa cells of larger follicles. However, no specific band occurred in Western blot. In blood, concentrations of all sulfonated steroids investigated were below the limit of quantification (LOQ). In follicular fluid, only cholesterol sulfate was measured in considerable concentrations (328.3 ± 63.8 ng/ml). However, the role of cholesterol sulfate in bovine follicular steroidogenesis remains unclear as concentrations were obviously unrelated to follicular size. The remaining sulfonated steroids investigated were undetectable or only slightly exceeded LOQ in a minor proportion of samples. The results are clearly contrary to a role of sulfonated steroids as important precursors, intermediates or products of bovine ovarian steroidogenesis.

α-SNAP is expressed in mouse ovarian granulosa cells and plays a key role in folliculogenesis and female fertility

The balance between ovarian folliculogenesis and follicular atresia is critical for female fertility and is strictly regulated by a complex network of neuroendocrine and intra-ovarian signals. Despite the numerous functions executed by granulosa cells (GCs) in ovarian physiology, the role of multifunctional proteins able to simultaneously coordinate/modulate several cellular pathways is unclear. Soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (α-SNAP) is a multifunctional protein that participates in SNARE-mediated membrane fusion events. In addition, it regulates cell-to-cell adhesion, AMPK signaling, autophagy and apoptosis in different cell types. In this study we examined the expression pattern of α-SNAP in ovarian tissue and the consequences of α-SNAP (M105I) mutation (hyh mutation) in folliculogenesis and female fertility. Our results showed that α-SNAP protein is highly expressed in GCs and its expression is modulated by gonadotropin stimuli. On the other hand, α-SNAP-mutant mice show a reduction in α-SNAP protein levels. Moreover, increased apoptosis of GCs and follicular atresia, reduced ovulation rate, and a dramatic decline in fertility is observed in α-SNAP-mutant females. In conclusion, α-SNAP plays a critical role in the balance between follicular development and atresia. Consequently, a reduction in its expression/function (M105I mutation) causes early depletion of ovarian follicles and female subfertility.

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.

Granulosa cell endothelin-2 expression is fundamental for ovulatory follicle rupture

Ovulation is dependent upon numerous factors mediating follicular growth, vascularization, and ultimately oocyte release via follicle rupture. Endothelin-2 (EDN2) is a potent vasoconstrictor that is transiently produced prior to follicle rupture by granulosa cells of periovulatory follicles and induces ovarian contraction. To determine the role of Edn2 expression, surgical transplant and novel conditional knockout mice were super-ovulated and analyzed. Conditional knockout mice utilized a new iCre driven by the Esr2 promoter to selectively remove Edn2. Follicle rupture and fertility were significantly impaired in the absence of ovarian Edn2 expression. When ovaries of Edn2KO mice were transplanted in wild type recipients, significantly more corpora lutea containing un-ovulated oocytes were present after hormonal stimulation (1.0 vs. 5.4, p = 0.010). Following selective ablation of Edn2 in granulosa cells, Esr2-Edn2KO dams had reduced oocytes ovulated (3.8 vs. 16.4 oocytes/ovary) and smaller litters (4.29 ± l.02 vs. 8.50 pups/dam). However, the number of pregnancies per pairing was not different and the reproductive axis remained intact. Esr2-Edn2KO ovaries had a higher percentage of antral follicles and fewer corpora lutea; follicles progressed to the antral stage but many were unable to rupture. Conditional loss of endothelin receptor A in granulosa cells also decreased ovulation but did not affect fecundity. These data demonstrate that EDN2-induced intraovarian contraction is a critical trigger of normal ovulation and subsequent fecundity.

The enigmatic role of RUNX1 in female-related cancers - current knowledge & future perspectives

Historically associated with the aetiology of human leukaemia, the runt-related transcription factor 1 (RUNX1) gene has in recent years reared its head in an assortment of epithelial cancers. This review discusses the state-of-the-art knowledge of the enigmatic role played by RUNX1 in female-related cancers of the breast, the uterus and the ovary. The weight of evidence accumulated so far is indicative of a very context-dependent role, as either an oncogene or a tumour suppressor. This is corroborated by high-throughput sequencing endeavours which report different genetic alterations affecting the gene, including amplification, deep deletion and mutations. Herein, we attempt to dissect that contextual role by firstly giving an overview of what is currently known about RUNX1 function in these specific tumour types, and secondly by delving into connections between this transcription factor and the physiology of these female tissues. In doing so, RUNX1 emerges not only as a gene involved in female sex development but also as a crucial mediator of female hormone signalling. In view of RUNX1 now being listed as a driver gene, we believe that greater knowledge of the mechanisms underlying its functional dualism in epithelial cancers is worthy of further investigation.

The transcriptional repressor ICER binds to multiple loci throughout the genome

The events culminating in ovulation are controlled by the cyclical actions of hormones such as Follical Stimulating Hormone (FSH) and Luteinizing Hormone (LH). The secondary messenger, cyclic AMP (cAMP) conveys the intracellular activity of these hormones. It is well established that a family of transcription factors facilitate cAMP mediated gene expression, yet it remains unknown how these factors directly affect ovulation. One of these factors, Inducible cAMP Early Repressor (ICER) has been implicated in the transcriptional regulation of cAMP inducible genes during folliculogenesis and ovulation. In order to better determine the role of ICER in ovarian function we have identified novel targets using a genome-wide approach. Using a modification of the chromatin immunoprecipitation (ChIP) assay we directly cloned and sequenced the immunoprecipitated ICER-associated DNAs from an immortalized mouse granulose cell line (GRMO2). The analysis of the immunoprecipitated DNA fragments has revealed that ICER's binding to DNA has the following distribution; 16% within the promoter region, 31% within an intron, 14% were not within a gene, 6% were within 20 kb of a promoter and 3% were within the 3' end of genes.

Core Binding Factor-β Knockdown Alters Ovarian Gene Expression and Function in the Mouse

Core binding factor (CBF) is a heterodimeric transcription factor complex composed of a DNA-binding subunit, one of three runt-related transcription factor (RUNX) factors, and a non-DNA binding subunit, CBFβ. CBFβ is critical for DNA binding and stability of the CBF transcription factor complex. In the ovary, the LH surge increases the expression of Runx1 and Runx2 in periovulatory follicles, implicating a role for CBFs in the periovulatory process. The present study investigated the functional significance of CBFs (RUNX1/CBFβ and RUNX2/CBFβ) in the ovary by examining the ovarian phenotype of granulosa cell-specific CBFβ knockdown mice; CBFβ f/f * Cyp19 cre. The mutant female mice exhibited significant reductions in fertility, with smaller litter sizes, decreased progesterone during gestation, and fewer cumulus oocyte complexes collected after an induced superovulation. RNA sequencing and transcriptome assembly revealed altered expression of more than 200 mRNA transcripts in the granulosa cells of Cbfb knockdown mice after human chorionic gonadotropin stimulation in vitro. Among the affected transcripts are known regulators of ovulation and luteinization including Sfrp4, Sgk1, Lhcgr, Prlr, Wnt4, and Edn2 as well as many genes not yet characterized in the ovary. Cbfβ knockdown mice also exhibited decreased expression of key genes within the corpora lutea and morphological changes in the ovarian structure, including the presence of large antral follicles well into the luteal phase. Overall, these data suggest a role for CBFs as significant regulators of gene expression, ovulatory processes, and luteal development in the ovary.

SNARE-Mediated Cholesterol Movement to Mitochondria Supports Steroidogenesis in Rodent Cells

Vesicular transport involving soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) proteins is known to be responsible for many major cellular activities. In steroidogenic tissues, chronic hormone stimulation results in increased expression of proteins involved in the steroidogenic pathway, whereas acute hormone stimulation prompts the rapid transfer of cholesterol to the inner mitochondrial membrane to be utilized as substrate for steroid hormone production. Several different pathways are involved in supplying cholesterol to mitochondria, but mobilization of stored cholesteryl esters appears to initially constitute the preferred source; however, the mechanisms mediating this cholesterol transfer are not fully understood. To study the potential contribution of SNARE proteins in steroidogenesis, we examined the expression levels of various SNARE proteins in response to hormone stimulation in steroidogenic tissues and cells and established an in vitro mitochondria reconstitution assay system to assess the contribution of various SNARE proteins on cholesterol delivery for steroidogenesis. Our results from reconstitution experiments along with knockdown studies in rat primary granulosa cells and in a Leydig cell line show that soluble N-ethylmaleimide sensitive factor attachment protein-α, synaptosomal-associated protein of 25 kDa, syntaxin-5, and syntaxin-17 facilitate the transport of cholesterol to mitochondria. Thus, although StAR is required for efficient cholesterol movement into mitochondria for steroidogenesis, specific SNAREs participate and are necessary to mediate cholesterol movement to mitochondria.

Prohibitin( PHB) roles in granulosa cell physiology

Ovarian granulosa cells (GC) play an important role in the growth and development of the follicle in the process known as folliculogenesis. In the present review, we focus on recent developments in prohibitin (PHB) research in relation to GC physiological functions. PHB is a member of a highly conserved eukaryotic protein family containing the repressor of estrogen activity (REA)/stomatin/PHB/flotillin/HflK/C (SPFH) domain (also known as the PHB domain) found in diverse species from prokaryotes to eukaryotes. PHB is ubiquitously expressed in a circulating free form or is present in multiple cellular compartments including mitochondria, nucleus and plasma membrane. In mitochondria, PHB is anchored to the mitochondrial inner membrane and forms complexes with the ATPases associated with proteases having diverse cellular activities. PHB continuously shuttles between the mitochondria, cytosol and nucleus. In the nucleus, PHB interacts with various transcription factors and modulates transcriptional activity directly or through interactions with chromatin remodeling proteins. Many functions have been attributed to the mitochondrial and nuclear PHB complexes such as cellular differentiation, anti-proliferation, morphogenesis and maintenance of the functional integrity of the mitochondria. However, to date, the regulation of PHB expression patterns and GC physiological functions are not completely understood.

Multiple functions of syncytiotrophoblast mitochondria

The human placenta plays a central role in pregnancy, and the syncytiotrophoblast cells are the main components of the placenta that support the relationship between the mother and fetus, in apart through the production of progesterone. In this review, the metabolic processes performed by syncytiotrophoblast mitochondria associated with placental steroidogenesis are described. The metabolism of cholesterol, specifically how this steroid hormone precursor reaches the mitochondria, and its transformation into progesterone are reviewed. The role of nucleotides in steroidogenesis, as well as the mechanisms associated with signal transduction through protein phosphorylation and dephosphorylation of proteins is discussed. Finally, topics that require further research are identified, including the need for new techniques to study the syncytiotrophoblast in situ using non-invasive methods.

X-linked lymphocyte regulated gene 5c-like (Xlr5c-like) is a novel target of progesterone action in granulosa cells of periovulatory rat ovaries

Progesterone (P4), acting through its nuclear receptor (PGR), plays an essential role in ovulation by mediating the expression of genes involved in ovulation and/or luteal formation. To identify ovulatory specific PGR-regulated genes, a preliminary microarray analysis was performed using rat granulosa cells treated with hCG ± RU486 (PGR antagonist). The transcript most highly down-regulated by RU486 was an EST (expressed sequence tag) sequence (gb: BI289578.1) that matches with predicted sequence for Xlr5c-like mRNA. Since nothing is known about Xlr5c-like, we first characterized the expression pattern of Xlr5c-like mRNA in the rat ovary. The level of mRNA for Xlr5c-like is transiently up-regulated in granulosa cells of periovulatory follicles after hCG stimulation in PMSG-primed rat ovaries. The transient induction of Xlr5c-like mRNA was mimicked by hCG treatment in cultured granulosa cells from preovulatory ovaries. We further demonstrated that the LH-activated PKA, MEK, PI3K, and p38 signaling is involved in the increase in Xlr5c-like mRNA. The increase in Xlr5c-like mRNA was abolished by RU486. The inhibitory effect of RU486 was reversed by MPA (synthetic progestin), but not by dexamethasone (synthetic glucocorticoid). Furthermore, mutation of SP1/SP3 and PGR response element sites in the promoter region of Xlr5c-like decreased Xlr5c-like reporter activity. RU486 also inhibited Xlr5c-like reporter activity. ChIP assay verified the binding of PGR and SP3 to the Xlr5c-like promoter in periovulatory granulosa cells. Functionally, siRNA-mediated Xlr5c-like knockdown in granulosa cell cultures resulted in reduced levels of mRNA for Snap25, Cxcr4, and Adamts1. Recombinant Xlr5c-like protein expressed using an adenoviral approach was localized predominantly to the nucleus and to a lesser extent to the cytoplasm of rat granulosa cells. In conclusion, this is the first report showing the spatiotemporally regulated expression of Xlr5c-like mRNA by hCG in rat periovulatory ovaries. P4/PGR mediates the LH-induced increase in Xlr5c-like mRNA. In turn, Xlr5c-like is involved in regulating the expression of specific ovulatory genes such as Snap25, Cxcr4, and Adamts1, possibly acting in the nucleus of periovulatory granulosa cells.

A transcriptomal analysis of bovine oviductal epithelial cells collected during the follicular phase versus the luteal phase of the estrous cycle

BACKGROUND

Reproductive success depends on a functional oviduct for gamete storage, maturation, fertilization, and early embryonic development. The ovarian-derived steroids estrogen and progesterone are key regulators of oviductal function. The objective of this study was to investigate luteal and follicular phase-specific oviductal epithelial cell function by using microarray-based transcriptional profiling, to increase our understanding of mRNAs regulating epithelial cell processes, and to identify novel genes and biochemical pathways that may be found to affect fertility in the future.

METHODS

Six normally cycling Angus heifers were assigned to either luteal phase (LP, n = 3) or follicular phase (FP, n = 3) treatment groups. Heifers in the LP group were killed between day 11 and 12 after estrus. Heifers in the FP group were treated with 25 mg PGF2α (Lutalyse, Pfizer, NY) at 8 pm on day 6 after estrus and killed 36 h later. Transcriptional profiling by microarray and confirmation of selected mRNAs by real-time RT-PCR analyses was performed using total RNA from epithelial cells isolated from sections of the ampulla and isthmus collected from LP and FP treatment groups. Differentially expressed genes were subjected to gene ontology classification and bioinformatic pathway analyses.

RESULTS

Statistical one-way ANOVA using Benjamini-hochberg multiple testing correction for false discovery rate (FDR) and pairwise comparison of epithelial cells in the ampulla of FP versus LP groups revealed 972 and 597 transcripts up- and down-regulated, respectively (P < 0.05). Within epithelial cells of the isthmus in FP versus LP groups, 946 and 817 transcripts were up- and down-regulated, respectively (P < 0.05). Up-regulated genes from both ampulla and isthmus were found to be largely involved in cholesterol biosynthesis and cell cycle pathways, while down-regulated genes were found in numerous inflammatory response pathways.

CONCLUSIONS

Microarray-based transcriptional profiling revealed phase of the cycle-dependent changes in the expression of mRNA within the epithelium of the oviducts' ampulla and isthmus.

Mitochondrial proteases act on STARD3 to activate progesterone synthesis in human syncytiotrophoblast

BACKGROUND

STARD1 transports cholesterol into mitochondria of acutely regulated steroidogenic tissue. It has been suggested that STARD3 transports cholesterol in the human placenta, which does not express STARD1. STARD1 is proteolytically activated into a 30-kDa protein. However, the role of proteases in STARD3 modification in the human placenta has not been studied.

METHODS

Progesterone determination and Western blot using anti-STARD3 antibodies showed that mitochondrial proteases cleave STARD3 into a 28-kDa fragment that stimulates progesterone synthesis in isolated syncytiotrophoblast mitochondria. Protease inhibitors decrease STARD3 transformation and steroidogenesis.

RESULTS

STARD3 remained tightly bound to isolated syncytiotrophoblast mitochondria. Simultaneous to the increase in progesterone synthesis, STARD3 was proteolytically processed into four proteins, of which a 28-kDa protein was the most abundant. This protein stimulated mitochondrial progesterone production similarly to truncated-STARD3. Maximum levels of protease activity were observed at pH7.5 and were sensitive to 1,10-phenanthroline, which inhibited steroidogenesis and STARD3 proteolytic cleavage. Addition of 22(R)-hydroxycholesterol increased progesterone synthesis, even in the presence of 1,10-phenanthroline, suggesting that proteolytic products might be involved in mitochondrial cholesterol transport.

CONCLUSION

Metalloproteases from human placental mitochondria are involved in steroidogenesis through the proteolytic activation of STARD3. 1,10-Phenanthroline inhibits STARD3 proteolytic cleavage. The 28-kDa protein and the amino terminal truncated-STARD3 stimulate steroidogenesis in a comparable rate, suggesting that both proteins share similar properties, probably the START domain that is involved in cholesterol binding.

GENERAL SIGNIFICANCE

Mitochondrial proteases are involved in syncytiotrophoblast-cell steroidogenesis regulation. Understanding STARD3 activation and its role in progesterone synthesis is crucial to getting insight into its action mechanism in healthy and diseased syncytiotrophoblast cells.

Prostate androgen-regulated mucin-like protein 1: a novel regulator of progesterone metabolism

The LH surge reprograms preovulatory follicular cells to become terminally differentiated luteal cells which produce high levels of progesterone and become resistant to apoptosis. PARM1 (prostate androgen regulated mucin-like protein 1) has been implicated in cell differentiation and cell survival in nonovarian cells, but little is known about PARM1 in the ovary. This study demonstrated that the LH surge induced a dramatic increase in Parm1 expression in periovulatory follicles and newly forming CL in both cycling and immature rat models. We further demonstrated that hCG increases Parm1 expression in granulosa cell cultures. The in vitro up-regulation of Parm1 expression was mediated by hCG-activated multiple signaling pathways and transcriptional activation of this gene. Parm1 knockdown increased the viability of cultured granulosa cells but resulted in a decrease in progesterone levels. The inhibitory effect of Parm1 silencing on progesterone was reversed by adenoviral mediated add-back expression of Parm1. Parm1 silencing had little effect on the expression of genes involved in progesterone biosynthesis and metabolism such as Scarb1, Ldlr, Vldlr, Scp2, Star, Cyp11a1, Hsd3b, and Srd5a1, while decreasing the expression of Akr1c3. Analyses of culture media steroid levels revealed that Parm1 knockdown had no effect on pregnenolone levels, while resulting in time-dependent decreases in progesterone and 20α-dihydroprogesterone and accelerated accumulation of 5α-pregnanediol. This study revealed that the up-regulation of Parm1 expression promotes progesterone and 20α-dihydroprogesterone accumulation in luteinizing granulosa cells by inhibiting progesterone catabolism to 5α-pregnanediol. PARM1 contributes to ovulation and/or luteal function by acting as a novel regulator of progesterone metabolism.

Research resource: preovulatory LH surge effects on follicular theca and granulosa transcriptomes

The molecular mechanisms that regulate the pivotal transformation processes observed in the follicular wall following the preovulatory LH surge, are still not established, particularly for cells of the thecal layer. To elucidate thecal cell (TC) and granulosa cell (GC) type-specific biologic functions and signaling pathways, large dominant bovine follicles were collected before and 21 hours after an exogenous GnRH-induced LH surge. Antral GCs (aGCs; aspirated by follicular puncture) and membrane-associated GCs (mGCs; scraped from the follicular wall) were compared with TC expression profiles determined by mRNA microarrays. Of the approximately 11 000 total genes expressed in the periovulatory follicle, only 2% of thecal vs 25% of the granulosa genes changed in response to the LH surge. The majority of the 203 LH-regulated thecal genes were also LH regulated in GCs, leaving a total of 57 genes as LH-regulated TC-specific genes. Of the 57 thecal-specific LH-regulated genes, 74% were down-regulated including CYP17A1 and NR5A1, whereas most other genes are being identified for the first time within theca. Many of the newly identified up-regulated thecal genes (eg, PTX3, RND3, PPP4R4) were also up-regulated in granulosa. Minimal expression differences were observed between aGCs and mGCs; however, transcripts encoding extracellular proteins (NID2) and matrix modulators (ADAMTS1, SASH1) dominated these differences. We also identified large numbers of unknown LH-regulated GC genes and discuss their putative roles in ovarian function. This Research Resource provides an easy-to-access global evaluation of LH regulation in TCs and GCs that implicates numerous molecular pathways heretofore unknown within the follicle.

Ovarian regulation of neuromedin U and its local actions in the ovary, mediated through neuromedin U receptor 2

Neuromedin U (NMU) was originally identified as an anorexigenic peptide that modulates appetite as well as energy homeostasis through the brain-gut axis. Although growing evidence has linked NMU activity with the development of female reproductive organs, no direct expression of and function for NMU in these organs has been pinpointed. Using a superovulated rat model, we found that NMU is directly expressed in the ovary, where its transcript level is tightly regulated by gonadotropins. Ovarian microdissection and immunohistochemical staining showed clearly that NMU is expressed mainly in theca/interstitial cells and to a moderate extent in granulosa cells. Primary cell studies together with reporter assays indicated the Nmu mRNA level in these cells is strongly induced via cAMP signaling, whereas this increase in expression can be reversed by the degradation message residing within its 3'-untranslated region, which recruits cis-acting mRNA degradation mechanisms, such as the gonadotropin-induced zinc finger RNA-binding protein Zfp36l1. This study also demonstrated that NMUR2, but not NMUR1, is the dominant NMU receptor in the ovary, where its expression is restricted to theca/interstitial cells. Treatment with NMU led to induction of the early response c-Fos gene, phosphorylation of extracellular signal-regulated kinase 1/2, and promotion of progesterone production in both developing and mature theca/interstitial cells. Taken as a whole, this study demonstrates that NMU and NMU receptor 2 compose a novel autocrine system in theca/interstitial cells in which the intensity of signaling is tightly controlled by gonadotropins.

The role for runt related transcription factor 2 (RUNX2) as a transcriptional repressor in luteinizing granulosa cells

Transcription factors induced by the LH surge play a vital role in reprogramming the gene expression in periovulatory follicles. The present study investigated the role of RUNX2 transcription factor in regulating the expression of Runx1, Ptgs2, and Tnfaip6 using cultured granulosa cells isolated from PMSG-primed immature rats. hCG or forskolin+PMA induced the transient increase in Runx1, Ptgs2, and Tnfaip6 expression, while the expression of Runx2 continued to increase until 48 h. The knockdown of the agonist-stimulated Runx2 expression increased Runx1, Ptgs2, and Tnfaip6 expression and PGE(2) levels in luteinizing granulosa cells. Conversely, the over-expression of RUNX2 inhibited the expression of these genes and PGE(2) levels. The mutation of RUNX binding motifs in the Runx1 promoter enhanced transcriptional activity of the Runx1 promoter. The knockdown and overexpression of Runx2 increased and decreased Runx1 promoter activity, respectively. ChIP assays revealed the binding of RUNX2 in the Runx1 and Ptgs2 promoters. Together, these novel findings provide support for the role of RUNX2 in down-regulation of Runx1, Ptgs2, and Tnfaip6 during the late ovulatory period to support proper ovulation and/or luteinization.

Ovarian FAM110C (family with sequence similarity 110C): induction during the periovulatory period and regulation of granulosa cell cycle kinetics in rats

FAM110C belongs to a family of proteins that regulates cell proliferation. In the present study, the spatiotemporal expression pattern of FAM110C and its potential role were examined during the periovulatory period. Immature female rats were injected with equine chorionic gonadotropin (eCG) followed by human chorionic gonadotropin (hCG) and ovaries or granulosa cells were collected at various times after hCG administration (n = 3/time point). Expression levels of Fam110c mRNA and protein were highly induced both in intact ovaries and granulosa cells at 8 to 12 h after hCG treatment. In situ hybridization analysis demonstrated Fam110c mRNA expression was induced in theca and granulosa cells at 4 h after hCG, primarily localized to granulosa cells at 8 h and 12 h, and decreased at 24 h after hCG. There was negligible Fam110c mRNA detected in newly forming corpora lutea. In rat granulosa cell cultures, hCG induced expression of Fam110c mRNA was inhibited by RU486, whereas NS398 and AG1478 had no effect, suggesting that Fam110c expression is regulated in part by the progesterone receptor pathway. Promoter activity analysis revealed that an Sp1 site was important for the induction of Fam110c expression by hCG. Overexpression of FAM110C promoted granulosa cells to arrest at the G(1) phase of the cell cycle but did not change progesterone levels. In summary, hCG induces Fam110c mRNA expression in granulosa cells by activation of an Sp1-binding site and the actions of progesterone. Our findings suggest that FAM110C may control granulosa cell differentiation into luteal cells by arresting cell cycle progression.

Decreased expression of extracellular matrix proteins and trophic factors in the amygdala complex of depressed mice after chronic immobilization stress

Background

The amygdala plays an essential role in controlling emotional behaviors and has numerous connections to other brain regions. The functional role of the amygdala has been highlighted by various studies of stress-induced behavioral changes. Here we investigated gene expression changes in the amygdala in the chronic immobilization stress (CIS)-induced depression model.

Results

Eight genes were decreased in the amygdala of CIS mice, including genes for neurotrophic factors and extracellular matrix proteins. Among these, osteoglycin, fibromodulin, insulin-like growth factor 2 (Igf2), and insulin-like growth factor binding protein 2 (Igfbp2) were further analyzed for histological expression changes. The expression of osteoglycin and fibromodulin simultaneously decreased in the medial, basolateral, and central amygdala regions. However, Igf2 and Igfbp2 decreased specifically in the central nucleus of the amygdala. Interestingly, this decrease was found only in the amygdala of mice showing higher immobility, but not in mice displaying lower immobility, although the CIS regimen was the same for both groups.

Conclusions

These results suggest that the responsiveness of the amygdala may play a role in the sensitivity of CIS-induced behavioral changes in mice.

Ovarian expression and regulation of the stromelysins during the periovulatory period in the human and the rat

The matrix metalloproteinases (MMPs) are postulated to facilitate follicular rupture. In the present study, expression of the stromelysins (MMP3, MMP10, MMP11) was analyzed in the periovulatory human and rat ovary. Human granulosa and theca cells were collected from the dominant follicle at various times after human chorionic gonadotropin (hCG). Intact rat ovaries, granulosa cells, and residual tissue (tissue remaining after granulosa cell collection) were isolated from equine CG (eCG)-hCG-primed animals. Mmp10 mRNA was highly induced in human granulosa and theca cells and intact rat ovaries, granulosa cells, and residual tissue. Localization of MMP10 to granulosa and theca cells in both human and rat ovarian follicles was confirmed by immunohistochemistry. Mmp3 mRNA was unchanged in human cells and rat granulosa cells, but increased in intact rat ovaries and residual tissue. Mmp11 mRNA decreased following hCG treatment in human granulosa and theca cells as well as rat granulosa cells. Regulation of Mmp10 in cultured rat granulosa cells revealed that the EGF inhibitor AG1478 and the progesterone receptor antagonist RU486 suppressed the induction of Mmp10 mRNA, whereas the prostaglandin inhibitor NS398 had no effect. Studies on the Mmp10 promoter demonstrated that forskolin plus PMA stimulated promoter activity, which was dependent upon a proximal AP1 site. In conclusion, there are divergent patterns of stromelysin expression associated with ovulation, with a marked induction of Mmp10 mRNA and a decrease in Mmp11 mRNA, yet a species-dependent pattern on Mmp3 mRNA expression. The induction of Mmp10 expression suggests an important role for this MMP in the follicular changes associated with ovulation and subsequent luteinization.

Immunohistochemical Characterization of S100A6 in the Murine Ovary

S100 proteins comprise a large family of Ca(2+)-binding proteins and exhibit a variety of intra- and extracellular functions. Despite our growing knowledge about the biology of S100 proteins in some tissues such as brain and smooth muscle, little is known about S100 proteins in the normal mammalian reproductive tissue. In the present study, we investigated the distribution pattern of S100A6 (alternatively named calcyclin) in the murine ovary by immunohistochemical study using specific antibody. S100A6 was localized substantially in the cytoplasm of luteal cells, with concomitant expression of S100A11, another S100 protein, but not in the other type of cells such as oocytes, follicle epithelial cells (granulosa cells), and cells of stroma including theca interna cells in the murine ovary. S100A6-immunoreactive corpora lutea (CLs) were divided into two types: homogeneously and heterogeneously stained CLs, and possibly they may represent differentiating and mature CL, respectively. Our regression analysis revealed that expression level of S100A6 positively correlated with that of cytochrome P450 11A, a steroidogenic enzyme in the heterogeously stained CL. These results suggested that S100A6 may contribute to differentiation of steroidogenic activity of luteal cells in a synergistic manner with S100A11 by facilitating some shared functions.

Early steps in steroidogenesis: intracellular cholesterol trafficking

Steroid hormones are made from cholesterol, primarily derived from lipoproteins that enter cells via receptor-mediated endocytosis. In endo-lysosomes, cholesterol is released from cholesterol esters by lysosomal acid lipase (LAL; disordered in Wolman disease) and exported via Niemann-Pick type C (NPC) proteins (disordered in NPC disease). These diseases are characterized by accumulated cholesterol and cholesterol esters in most cell types. Mechanisms for trans-cytoplasmic cholesterol transport, membrane insertion, and retrieval from membranes are less clear. Cholesterol esters and "free" cholesterol are enzymatically interconverted in lipid droplets. Cholesterol transport to the cholesterol-poor outer mitochondrial membrane (OMM) appears to involve cholesterol transport proteins. Cytochrome P450scc (CYP11A1) then initiates steroidogenesis by converting cholesterol to pregnenolone on the inner mitochondrial membrane (IMM). Acute steroidogenic responses are regulated by cholesterol delivery from OMM to IMM, triggered by the steroidogenic acute regulatory protein (StAR). Chronic steroidogenic capacity is determined by CYP11A1 gene transcription. StAR mutations cause congenital lipoid adrenal hyperplasia, with absent steroidogenesis, potentially lethal salt loss, and 46,XY sex reversal. StAR mutations initially destroy most, but not all steroidogenesis; low levels of StAR-independent steroidogenesis are lost later due to cellular damage, explaining the clinical findings. Rare P450scc mutations cause a similar syndrome. This review addresses these early steps in steroid biosynthesis.

Identification of hepsin and protein disulfide isomerase A3 as targets of gelatinolytic action in rat ovarian granulosa cells during the periovulatory period

The matrix metalloproteinase (MMP) family is believed to play a role in the ovulatory process because MMP inhibitors block oocyte release. However, little is known about the mechanisms by which the MMPs affect ovulation. The present study investigated the degradomic actions of the gelatinases, MMP2 and MMP9, by identifying gelatinolytic targets in periovulatory granulosa cells. Granulosa cells were collected from immature rats 48 h after equine chorionic gonadotropin treatment and were cultured with human chorionic gonadotropin (hCG) in the absence or presence of a specific MMP2/9 inhibitor ((2R)-2-[(4-biphenylylsulfonyl)amino]-3-phenylpropionic acid) for an additional 24 h. The conditioned media was analyzed for gelatinolytic activity, progesterone, and peptide profiles. Gelatinolytic activity and progesterone were induced in response to hCG; however, there was no difference in progesterone between cells treated with or without the inhibitor. Peptide fragments of proteins altered in the presence of the gelatinase inhibitor were identified by two-dimensional gel electrophoresis and mass spectrometry. Protein disulfide isomerase A3 (PDIA3), which plays a role in protein folding, was identified as a peptide that decreased in the presence of inhibitor while the serine protease hepsin, was found to increase with inhibitor treatment. Subsequent experiments established that PDIA3 and hepsin were targets of MMP2/9 action by cleavage with MMP2 and Western blot analysis, respectively. Additionally, hepsin was identified as a gelatinolytic target in ovarian cancer cells. In the present study, proteomics has identified proteins that may be involved in novel ways in the complex cascades that are mediated by gelatinolytic MMPs during the periovulatory period.

Methodology matters: IVF versus ICSI and embryonic gene expression

The use of assisted reproduction treatment, especially intracytoplasmic sperm injection (ICSI), is now linked to a range of adverse consequences, the aetiology of which remains largely undefined. Our objective of this study was to determine differences in gene expression of blastocysts generated by ICSI as well as ICSI with artificial oocyte activation (ICSI-A) versus the less manipulative IVF, providing fundamental genetic information that can be used to aid in the diagnosis or treatment of those adversely affected by assisted reproduction treatment, as well as stimulate research to further refine these techniques. Murine blastocysts were generated by ICSI, ICSI-A and IVF, and processed for a microarray-based analysis of gene expression. Ten blastocysts were pooled for each procedure and three independent replicates generated. The data were then processed to determine differential gene expression and to identify biological pathways affected by the procedures. In blastocysts derived by ICSI versus IVF, the expression of 197 genes differed (P < 0.01). In blastocysts derived by ICSI-A versus IVF and ICSI-A versus ICSI, the expression of 132 and 65 genes differed respectively (P < 0.01). Procedural-induced changes in genes regulating specific biological pathways revealed some consistency to known adverse consequences. Detailed investigation of procedure-specific dysfunction is therefore warranted.

A role for nuclear factor interleukin-3 (NFIL3), a critical transcriptional repressor, in down-regulation of periovulatory gene expression

The LH surge triggers dramatic transcriptional changes in genes associated with ovulation and luteinization. The present study investigated the spatiotemporal expression of nuclear factor IL-3 (NFIL3), a transcriptional regulator of the basic leucine zipper transcription factor superfamily, and its potential role in the ovary during the periovulatory period. Immature female rats were injected with pregnant mare's serum gonadotropin, treated with human chorionic gonadotropin (hCG), and ovaries or granulosa cells were collected at various times after hCG. Nfil3 mRNA was highly induced both in intact ovaries and granulosa cells after hCG treatment. In situ hybridization demonstrated that Nfil3 mRNA was highly induced in theca-interstitial cells at 4-8 h after hCG, localized to granulosa cells at 12 h, and decreased at 24 h. Overexpression of NFIL3 in granulosa cells inhibited the induction of prostaglandin-endoperoxide synthase 2 (Ptgs2), progesterone receptor (Pgr), epiregulin (Ereg), and amphiregulin (Areg) and down-regulated levels of prostaglandin E2. The inhibitory effect on Ptgs2 induction was reversed by NFIL3 small interfering RNA treatment. In theca-interstitial cells the expression of hydroxyprostaglandin dehydrogenase 15-(nicotinamide adenine dinucleotide) (Hpgd) was also inhibited by NFIL3 overexpression. Data from luciferase assays demonstrated that NFIL3 overexpression decreased the induction of the Ptgs2 and Areg promoter activity. EMSA and chromatin immunoprecipitation analyses indicated that NFIL3 binds to the promoter region containing the DNA-binding sites of cAMP response element binding protein and CCAAT enhancer binding protein-β. In summary, hCG induction of NFIL3 expression may modulate the process of ovulation and theca-interstitial and granulosa cell differentiation by regulating expression of PTGS2, PGR, AREG, EREG, and HPGD, potentially through interactions with cAMP response element binding protein and CCAAT enhancer binding protein-β on their target gene promoters.

Dynamics of the transcriptome in the primate ovulatory follicle

Experiments were designed to evaluate changes in the transcriptome (mRNA levels) in the ovulatory, luteinizing follicle of rhesus monkeys, using a controlled ovulation model that permits analysis of the naturally selected, dominant follicle at specific intervals (0, 12, 24 and 36 h) after exposure to an ovulatory (exogenous hCG) stimulus during the menstrual cycle. Total RNA was prepared from individual follicles (n= 4-8/timepoint), with an aliquot used for microarray analysis (Affymetrix Rhesus Macaque Genome Array) and the remainder applied to quantitative real-time PCR (q-PCR) assays. The microarray data from individual samples distinctly clustered according to timepoints, and ovulated follicles displayed markedly different expression patterns from unruptured follicles at 36 h. Between timepoint comparisons revealed profound changes in mRNA expression profiles. The dynamic pattern of mRNA expression for steroidogenic enzymes (CYP17A, CYP19A, HSD3B2, HSD11B1 and HSD11B2), steroidogenic acute regulatory protein (StAR) and gonadotrophin receptors [LH/choriogonadotrophin receptor (LHCGR), FSH receptor (FSHR)] as determined by microarray analysis correlated precisely with those from blinded q-PCR assays. Patterns of mRNA expression for epidermal-growth-factor-like factors (amphiregulin, epiregulin) and processes [hyaluronan synthase 2 (HAS2), tumor necrosis factor alpha-induced protein 6 (TNFAIP6)] implicated in cumulus-oocyte maturation/expansion were also comparable between assays. Thus, several mRNAs displayed the expected expression pattern for purported theca (e.g. CYP17A), granulosa (CYP19A, FSHR), cumulus (HAS2, TNFAIP6) cell and surface epithelium (HSD11B)-related genes in the rodent/primate pre-ovulatory follicle. This database will be of great value in analyzing molecular and cellular pathways associated with periovulatory events in the primate follicle (e.g. follicle rupture, luteinization, inflammatory response and angiogenesis), and for identifying novel gene products controlling mammalian fertility.

Periovulatory leukocyte infiltration in the rat ovary

Ovulation is preceded by intraovarian inflammatory reactions that occur in response to the preovulatory gonadotropin surge. As a main inflammatory event, leukocytes infiltrate the ovary and release proteolytic enzymes that degrade the extracellular matrix weakening the follicular wall, a required step for follicle rupture. This study aimed to quantitatively measure the infiltrating leukocytes, determine their cell types, and localize infiltration sites in the periovulatory rat ovary. Cycling adult and gonadotropin-stimulated immature rats were used as animal models. Ovaries were collected at five different stages of estrous cycle in the adult rats (diestrus, 1700 h; proestrus, 1500 h; proestrus, 2400 h; estrus, 0600 h; and metestrus, 1700 h) and at five different time points after superovulation induction in the immature rats (pregnant mare's serum gonadotrophin, 0 h; pregnant mare's serum gonadotrophin, 48 h; human chorionic gonadotropin, 6 h; human chorionic gonadotropin, 12 h; and human chorionic gonadotropin, 24 h). The ovaries were either dissociated into a single cell suspension for flow cytometric analysis or fixed for immunohistochemical localization of the leukocytes. Similar numbers of leukocytes were seen throughout the estrous cycle (approximately 500,000/ovary), except proestrus 2400 when 2-fold higher numbers of leukocytes were found (approximately 1.1 million/ovary). A similar trend of periovulatory rise of leukocyte numbers was seen in the superovulation-induced immature rat model, recapitulating a dramatic increase in leukocyte numbers upon gonadotropin stimulation. Both macrophage/granulocytes and lymphocytes were among the infiltrating leukocytes and were localized in the theca and interstitial tissues, where platelet-endothelial cell adhesion molecule-1 and intercellular adhesion molecule-1 may play roles in the transmigration of leukocytes, because their expressions correlates spatiotemporally with the infiltrating leukocytes. In addition, a strong inverse relationship between leukocyte numbers in the ovary and spleen, as well as significant reduction of leukocyte infiltration in the splenectomized rats, were seen, indicating that the spleen may serve as an immediate supplier of leukocytes to the periovulatory ovary.

Runx2 in normal tissues and cancer cells: A developing story

The Runx transcription factors are essential for mammalian development, most notably in the haematopoietic and osteogenic lineages. Runx1 and its binding partner, CBFbeta, are frequently targeted in acute leukaemia but evidence is accumulating that all three Runx genes may have a role to play in a wider range of cancers, either as tumour promoters or tumour suppressors. Whilst Runx2 is renowned for its role as a master regulator of bone development we discuss here its expression pattern and putative functions beyond this lineage. Furthermore, we review the evidence that RUNX2 promotes neoplastic development in haematopoietic lineages and in advanced mammary and prostate cancer.

Cellular cholesterol delivery, intracellular processing and utilization for biosynthesis of steroid hormones

Steroid hormones regulate diverse physiological functions such as reproduction, blood salt balance, maintenance of secondary sexual characteristics, response to stress, neuronal function and various metabolic processes. They are synthesized from cholesterol mainly in the adrenal gland and gonads in response to tissue-specific tropic hormones. These steroidogenic tissues are unique in that they require cholesterol not only for membrane biogenesis, maintenance of membrane fluidity and cell signaling, but also as the starting material for the biosynthesis of steroid hormones. It is not surprising, then, that cells of steroidogenic tissues have evolved with multiple pathways to assure the constant supply of cholesterol needed to maintain optimum steroid synthesis. The cholesterol utilized for steroidogenesis is derived from a combination of sources: 1) de novo synthesis in the endoplasmic reticulum (ER); 2) the mobilization of cholesteryl esters (CEs) stored in lipid droplets through cholesteryl ester hydrolase; 3) plasma lipoprotein-derived CEs obtained by either LDL receptor-mediated endocytic and/or SR-BI-mediated selective uptake; and 4) in some cultured cell systems from plasma membrane-associated free cholesterol. Here, we focus on recent insights into the molecules and cellular processes that mediate the uptake of plasma lipoprotein-derived cholesterol, events connected with the intracellular cholesterol processing and the role of crucial proteins that mediate cholesterol transport to mitochondria for its utilization for steroid hormone production. In particular, we discuss the structure and function of SR-BI, the importance of the selective cholesterol transport pathway in providing cholesterol substrate for steroid biosynthesis and the role of two key proteins, StAR and PBR/TSO in facilitating cholesterol delivery to inner mitochondrial membrane sites, where P450scc (CYP11A) is localized and where the conversion of cholesterol to pregnenolone (the common steroid precursor) takes place.

Identification of a novel role for endothelins within the oviduct

Endothelins were first identified as potent vasoactive peptides; however, diversity in the biological function of these hormones is now evident. We have identified a novel role for endothelins: a requirement for these peptides within the oviduct during fertilization and/or early embryo development. In vivo, treatment after ovulation with a dual endothelin receptor antagonist (tezosentan) decreased the number of two-cell embryos that could be collected from within the oviducts. In vitro fertilization experiments showed that gamete viability and their ability to fertilize were not affected by treatment with this antagonist, suggesting that the effect observed in vivo was mediated by the oviduct itself. Expression of mRNA for all three isoforms of the endothelins and both receptor subtypes was detectable within the oviduct. Expression of mRNA for endothelin-3 was regulated by gonadotropins in epithelial cells of the oviduct and increased specifically within the isthmus of this structure. Immunostaining revealed localization of both endothelin receptors A and B to the columnar epithelial cells within the oviduct, suggestive of a local role for endothelins in the regulation of epithelial function and ultimately oviductal secretions. A microarray analysis revealed three likely endothelin-regulated protein networks for future analysis: the TGFbeta, IL-10, and CCAAT/enhancer-binding protein superfamilies. Overall, these results suggest a novel and requisite role for endothelins within the oviduct during fertilization and/or early embryo development.

Expression profiling of cumulus cells reveals functional changes during ovulation and central roles of prostaglandin EP2 receptor in cAMP signaling

To understand the role of prostaglandin (PG) receptor EP2 (Ptger2) signaling in ovulation and fertilization, we investigated time-dependent expression profiles in wild-type (WT) and Ptger2(-/-) cumuli before and after ovulation by using microarrays. We prepared cumulus cells from mice just before and 3, 9 and 14 h after human chorionic gonadotropin injection. Key genes including cAMP-related and epidermal growth factor (EGF) genes, as well as extracellular matrix- (ECM-) related and chemokine genes were up-regulated in WT cumuli at 3 h and 14 h, respectively. Ptger2 deficiency differently affected the expression of many of the key genes at 3 h and 14 h. These results indicate that the gene expression profile of cumulus cells greatly differs before and after ovulation, and in each situation, PGE(2)-EP2 signaling plays a critical role in cAMP-regulated gene expression in the cumulus cells under physiological conditions.

RUNX2 transcription factor regulates gene expression in luteinizing granulosa cells of rat ovaries

The LH surge promotes terminal differentiation of follicular cells to become luteal cells. RUNX2 has been shown to play an important role in cell differentiation, but the regulation of Runx2 expression and its function in the ovary remain to be determined. The present study examined 1) the expression profile of Runx2 and its partner CBFbeta during the periovulatory period, 2) regulatory mechanisms of Runx2 expression, and 3) its potential function in the ovary. Runx2 expression was induced in periovulatory granulosa cells of human and rodent ovaries. RUNX2 and core binding factor-beta (CBFbeta) proteins in nuclear extracts and RUNX2 binding to a consensus binding sequence increased after human chorionic gonadotropin (hCG) administration. This in vivo up-regulation of Runx2 expression was recapitulated in vitro in preovulatory granulosa cells by stimulation with hCG. The hCG-induced Runx2 expression was reduced by antiprogestin (RU486) and EGF-receptor tyrosine kinase inhibitor (AG1478), indicating the involvement of EGF-signaling and progesterone-mediated pathways. We also found that in the C/EBPbeta knockout mouse ovary, Runx2 expression was reduced, indicating C/EBPbeta-mediated expression. Next, the function of RUNX2 was investigated by suppressing Runx2 expression by small interfering RNA in vitro. Runx2 knockdown resulted in reduced levels of mRNA for Rgc32, Ptgds, Fabp6, Mmp13, and Abcb1a genes. Chromatin immunoprecipitation analysis demonstrated the binding of RUNX2 in the promoter region of these genes, suggesting that these genes are direct downstream targets of RUNX2. Collectively, the present data indicate that the LH surge-induced RUNX2 is involved in various aspects of luteal function by directly regulating the expression of diverse luteal genes.

Lack of functional pregnancy-associated plasma protein-A (PAPPA) compromises mouse ovarian steroidogenesis and female fertility

The insulin-like growth factor (IGF) system plays an important role in regulating ovarian follicular development and steroidogenesis. IGF binding proteins (IGFBP) mostly inhibit IGF actions, and IGFBP proteolysis is a major mechanism for regulating IGF bioavailability. Pregnancy-associated plasma protein-A (PAPPA) is a secreted metalloprotease responsible for cleavage of IGFBP4 in the ovary. The aim of this study was to investigate whether PAPPA plays a role in regulating ovarian functions and female fertility by comparing the reproductive phenotype of wild-type (WT) mice with mice heterozygous or homozygous for a targeted Pappa gene deletion (heterozygous and PAPP-A knockout [KO] mice, respectively). When mated with WT males, PAPP-A KO females demonstrated an overall reduction in average litter size. PAPP-A KO mice had a reduced number of ovulated oocytes, lower serum estradiol levels following equine chorionic gonadotropin administration, lower serum progesterone levels after human chorionic gonadotropin injection, and reduced expression of ovarian steroidogenic enzyme genes, compared to WT controls. In PAPP-A KO mice, inhibitory IGFBP2, IGFBP3, and IGFBP4 ovarian gene expression was reduced postgonadotropin stimulation, suggesting some compensation within the ovarian IGF system. Expression levels of follicle-stimulating hormone receptor, luteinizing hormone receptor, and genes required for cumulus expansion were not affected. Analysis of preovulatory follicular fluid showed complete loss of IGFBP4 proteolytic activity in PAPP-A KO mice, demonstrating no compensation for loss of PAPPA proteolytic activity by other IGFBP proteases in vivo in the mouse ovary. Taken together, these data demonstrate an important role of PAPPA in modulating ovarian function and female fertility by control of the bioavailability of ovarian IGF.

Progesterone receptor-induced gene expression in primary mouse granulosa cell cultures

The progesterone receptor (PGR) is induced by luteinizing hormone (LH) in granulosa cells of preovulatory follicles, and the PGR-A isoform is essential for ovulation based on the phenotypes of Pgr isoform-specific knockout mice. Although several genes regulated by PGR-A in vivo have been identified, whether these genes are primary targets of PGR-A or if their expression also depends on other signaling molecules that are induced by the LH surge has not been resolved. Therefore, to identify genes that are either induced or repressed by PGR in the absence of LH-mediated signaling cascades, we infected primary cultures of mouse granulosa cells with either PGR-A or PGR-B adenoviral vectors without or with R-5020 as a PGR ligand. Total RNA was extracted from infected cells at 16 h and analyzed by Affymetrix Mouse 430 2.0 microarrays. PGR-A in the presence or absence of ligand significantly induced approximately 50 genes 2-fold or more (local pooled error test at P <or= 0.01). Fewer and different genes were induced by PGR-B in the absence of ligand. Edn1, Apoa1, and Cited1 were primarily regulated by PGR-A as verified by additional RT-PCR analyses, suppression by the PGR antagonist RU486, and the lack of induction by protein kinase A, protein kinase C, or epidermal growth factor (EGF)-like factors pathways. PGR regulation of these genes was confirmed further by gene expression analyses in hormonally primed Pgr mutant mouse ovaries. Because Edn1, Apoa1, and Cited1 are known to regulate angiogenesis, PGR may affect the neovascularization of follicles that is initiated with ovulation.

Regulation and function of tissue inhibitor of metalloproteinase (TIMP) 1 and TIMP3 in periovulatory rat granulosa cells

In the ovary, the matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinase (TIMPs) have been postulated to regulate extracellular matrix remodeling associated with ovulation. In the present study, we investigated the regulatory mechanisms controlling expression of Timp1 and Timp3 mRNA in periovulatory granulosa cells. Granulosa cells were isolated from immature pregnant mare serum gonadotropin-primed (10 IU) rat ovaries and treated with human chorionic gonadotropin (hCG; 1 IU/ml). At 4 h after hCG treatment, Timp1 expression was highest and then decreased gradually over the remaining 24 h of culture. In contrast, hCG induced a biphasic increase of Timp3 expression at 2 and 16 h. The hCG stimulated expression of Timp1 and Timp3 mRNA was blocked by inhibitors of the protein kinase A (H89), protein kinase C (GF109203), and MAPK (SB2035850) pathways. To further explore Timp1 and Timp3 regulation, cells were cultured with the progesterone receptor antagonist RU486, which blocked the hCG induction of Timp3 expression, whereas the epidermal growth factor receptor tyrosine kinase inhibitor AG1478 blocked the hCG stimulation of both Timp1 and Timp3 expression. The prostaglandin-endoperoxide synthase 2 inhibitor NS-398 had no effect. The potential function of TIMP3 was investigated with Timp3-specific small interfering RNA treatment. Timp3 small interfering RNA resulted in a 20% decrease in hCG-induced progesterone levels and microarray analysis revealed an increase in cytochrome P450 Cyp 17, ubiquitin conjugating enzyme E2T, and heat shock protein 70. IGF binding protein 5, stearyl-CoA desaturase, and annexin A1 were decreased. The differential regulation between Timp1 and Timp3 may correlate with their unique roles in the processes of ovulation and luteinization. For TIMP3, this may include regulating fatty acid synthesis, steroidogenesis, and protein turnover.

Runt-related transcription factor 1 regulates luteinized hormone-induced prostaglandin-endoperoxide synthase 2 expression in rat periovulatory granulosa cells

Runt-related transcription factor 1 (RUNX1), a transcription factor, is transiently induced by the LH surge and regulates gene expression in periovulatory granulosa cells. Potential binding sites for RUNX are present in the 5'-flanking region of the Ptgs2 (prostaglandin-endoperoxide synthase 2) gene. Periovulatory Ptgs2 expression is essential for ovulation. In the present study, we investigated the role of RUNX1 in mediating the LH-induced expression of Ptgs2 in periovulatory granulosa cells. We first determined whether the suppression of Runx1 expression or activity affects Ptgs2 expression using cultured preovulatory granulosa cells isolated from immature rat ovaries primed with pregnant mare serum gonadotropin for 48 h. Knockdown of human chorionic gonadotropin-induced Runx1 expression by small interfering RNA or inhibition of endogenous RUNX activities by dominant-negative RUNX decreased human chorionic gonadotropin or agonist-stimulated Ptgs2 expression and transcriptional activity of Ptgs2 promoter reporter constructs. Results from chromatin immunoprecipitation assays revealed in vivo binding of endogenous RUNX1 to the Ptgs2 promoter region in rat periovulatory granulosa cells. Direct binding of RUNX1 to two RUNX-binding motifs in the Ptgs2 promoter region was confirmed by EMSA. The mutation of these two binding motifs resulted in decreased transcriptional activity of Ptgs2 promoter reporter constructs in preovulatory granulosa cells. Taken together, these findings provide experimental evidence that the LH-dependent induction of Ptgs2 expression results, in part, from RUNX1-mediated transactivation of the Ptgs2 promoter. The results of the present study assign potential significance for LH-induced RUNX1 in the ovulatory process via regulating Ptgs2 gene expression.

Proteomic analysis of the mouse ovary in response to two gonadotropins, follicle-stimulating hormone and luteinizing hormone

Functional and structural changes in the mammalian ovary are coordinately regulated by the pituitary glycoprotein hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), leading to follicular development, ovulation and transformation of follicles into corpus lutea. To investigate protein profiles during these processes of the mouse ovarian cycle, we applied combined methods (two-dimensional gel electrophoresis [2-DE] for separation and visualization of proteins plus matrix laser desorption/ionization time-of-flight mass spectrometry [MALDI-TOF/MS] analysis for protein identification) for comparative proteomic analysis using immature mice at 3 weeks of age. Protein profiles were obtained from proteins extracted from intact ovaries that had been collected from pregnant mare serum gonadotropin (PMSG)/human chorionic gonadotropin (hCG)-primed immature mice at 0 (no PMSG), 24 and 48 h post PMSG, as well as at 10 and 20 h post hCG. The results showed that 1028 common protein spots were found in representative gels that had been separated in the 3 to 11 pH range and the 15-200 kDa range, 253 protein spots (24.6%) of which were differentially expressed (p<0.05) during the mouse ovarian cycle. Of these 253 protein spots, 99 were identified by MALDI-TOF/MS. This comparative proteomic approach to identifying proteins that were potentially involved in the complex process of the ovarian cycle could contribute to our understanding of the molecular basis of functional and structural changes in the ovary in response to gonadotropins. Furthermore, the interesting ovarian proteins identified in this study may eventually serve as diagnostic biomarker candidates of ovarian function.

Characterization of tissue-specific mbu-3 gene expression in the mouse central nervous system

Mbu-3 is a novel mouse brain unigene that was identified by digital differential display. In this study, expression of the gene was chased through developmental stages and the protein product was identified in the brain. The cDNA sequence was 3,995-bp long and contained an ORF of 745 AA. Database searches revealed that the chicken SST273 gene containing LRR- and Ig-domain was an mbu-3 orthologue. Tissue specificity for the gene was examined in embryos and in brains at post-natal and adult stages. During the embryonic stages, mbu-3 was localized to the central nervous system in the brain and spinal cord. In the early post-natal stages, the gene was evenly expressed in the brain. However, with aging, expression was confined to specific regions, particularly the hippocampus. The protein was approximately 95 kDa as determined by Western blot analysis of brain extracts.