Nuclear receptor 5A (NR5A) family regulates 5-aminolevulinic acid synthase 1 (ALAS1) gene expression in steroidogenic cells

Development of sexual dimorphism of skeletal muscles through the adrenal cortex, caused by androgen-induced global gene suppression

The zona fasciculata (zF) in the adrenal cortex contributes to multiple physiological actions through glucocorticoid synthesis. The size, proliferation, and glucocorticoid synthesis characteristics are all female biased, and sexual dimorphism is established by androgen. In this study, transcriptomes were obtained to unveil the sex differentiation mechanism. Interestingly, both the amount of mRNA and the expressions of nearly all genes were higher in females. The expression of Nr5a1, which is essential for steroidogenic cell differentiation, was also female biased. Whole-genome studies demonstrated that NR5A1 regulates nearly all gene expression directly or indirectly. This suggests that androgen-induced global gene suppression is potentially mediated by NR5A1. Using Nr5a1 heterozygous mice, whose adrenal cortex is smaller than the wild type, we demonstrated that the size of skeletal muscles is possibly regulated by glucocorticoid synthesized by zF. Taken together, considering the ubiquitous presence of glucocorticoid receptors, our findings provide a pathway for sex differentiation through glucocorticoid synthesis.

ALAS1 associated with goat kidding number trait was regulated by the transcription factor ASCL2 to affect granulosa cell proliferation

ALAS1 is a member of the α-oxoamine synthase family, which is the first rate-limiting enzyme for heme synthesis and is important for maintaining intracellular heme levels. In the ovary, ALAS1 is associated with the regulation of ovulation-related mitochondrial P450 cytochromes, steroid metabolism, and steroid hormone production. However, there are few studies on the relationship between ALAS1 and reproductive traits in goats. In this study, a mutation located in the promoter region of ALAS1 (g.48791372C>A) was found to be significantly (p < 0.05) associated with the kidding number of Yunshang black goats. Specifically, the mean kidding number in the first three litters and the kidding numbers of all three litters were significantly (p < 0.05) higher in individuals with the CA genotype or AA genotype than in those with the CC genotype. To further investigate the regulatory mechanism of ALAS1, the expression of ALAS1 in goat ovarian tissues with different genotypes was verified by real-time quantitative PCR. The results showed that the expression of ALAS1 was significantly higher in the ovaries of individuals with AA genotype than those with AC and CC genotypes (p < 0.01), and the expression trend of transcription factor ASCL2 was consistent with ALAS1. Additionally, the ALAS1 g.48791372C>A mutation created a new binding site for the transcription factor ASCL2. The luciferase activity assay indicated that the mutation increased the promoter activity of ALAS1. Overexpression of the transcription factor ASCL2 induced increased expression of ALAS1 in goat granulosa cells (p < 0.05). The opposite trend was shown for the inhibition of ASCL2 expression. The results of real-time quantitative PCR, EdU and Cell Counting Kit-8 assays indicated that the transcription factor ASCL2 increased the proliferation of goat granulosa cells by mediating the expression of ALAS1. In conclusion, the transcription factor ASCL2 positively regulated the transcriptional activity and expression levels of ALAS1, altering granulosa cell proliferation and the kidding number in goats.

YAP/TAZ-TEAD is a novel transcriptional regulator of genes encoding steroidogenic enzymes in rat granulosa cells and KGN cells

Steroidogenesis in ovarian granulosa cells is regulated by the follicle-stimulating hormone (FSH) via transcriptional regulation of its related genes. We herein showed the involvement of the Hippo pathway in this regulation. In KGN granulosa cell, repression of YAP/TAZ activity induced the expression of CYP11A1, HSD3B2, and CYP19A1 in a TEAD-dependent manner without cAMP stimulation. A selective inhibitor of p38 MAP kinase, suppressed YAP/TAZ knockdown-indued the expression of these genes, suggesting this signal could be involved. The expression of these genes was induced by 8Br-cAMP, whereas that of CYR61 and ADATS1, typical YAP/TAZ-TEAD target genes, was suppressed, suggesting that the cellular signaling of cAMP reduced YAP/TAZ-TEAD activity. The constitutively active mutant YAP canceled the FSH- and 8Br-cAMP-mediated induction of these genes in primary rat granulosa and KGN cells, respectively. Moreover, regulation of steroidogenesis-related genes by YAP/TAZ-TEAD was independent of steroidogenic factor 1, a master gene regulator of steroidogenesis. These results suggest that YAP/TAZ-TEAD is a negative regulator of steroidogenesis and that suppression of YAP/TAZ-TEAD activity by FSH is involved in ovarian steroidogenesis.

Inhibition of YAP/TAZ-TEAD activity induces cytotrophoblast differentiation into syncytiotrophoblast in human trophoblast

During placentation, placental cytotrophoblast (CT) cells differentiate into syncytiotrophoblast (ST) cells and extravillous trophoblast (EVT) cells. In the placenta, the expression of various genes is regulated by the Hippo pathway through a transcription complex, Yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ)-TEA domain transcription factor (TEAD) (YAP/TAZ-TEAD) activity. YAP/TAZ-TEAD activity is controlled by multiple factors and signaling, such as cyclic AMP (cAMP) signaling. cAMP signaling is believed to be involved in the regulation of trophoblast function but is not yet fully understood. Here we showed that YAP/TAZ-TEAD expressions and their activities were altered by cAMP stimulation in BeWo cells, a human choriocarcinoma cell line. The repression of YAP/TAZ-TEAD activity induced the expression of ST-specific genes without cAMP stimulation, and transduction of constitutively active YAP, i.e., YAP-5SA, resulted in the repression of 8Br-cAMP-induced expressions of ST-specific genes in a TEAD-dependent manner. We also investigated the role of YAP/TAZ-TEAD in maintaining CT cells and their differentiation into ST and EVT cells using human trophoblast stem (TS) cells. YAP/TAZ-TEAD activity was involved in maintaining the stemness of TS cells. Induction or repression of YAP/TAZ-TEAD activity resulted in marked changes in the expression of ST-specific genes. Using primary CT cells, which spontaneously differentiate into ST-like cells, the effects of YAP-5SA transduction were investigated, and the expression of ST-specific genes was found to be repressed. These results indicate that the inhibition of YAP/TAZ-TEAD activity, with or without cAMP stimulation, is essential for the differentiation of CT cells into ST cells.

Early transcriptomic response of mouse adrenal gland and Y-1 cells to dexamethasone

Glucocorticoids have short- and long-term effects on adrenal gland function and development. RNA sequencing (RNA-seq) was performed to identify early transcriptomic responses to the synthetic glucocorticoid, dexamethasone (Dex), in vitro and in vivo. In total, 1711 genes were differentially expressed in the adrenal glands of the 1-h Dex-treated mice. Among them, only 113 were also considered differentially expressed genes (DEGs) in murine adrenocortical Y-1 cells treated with Dex for 1 h. Gene ontology analysis showed that the upregulated DEGs in the adrenal gland of the 1-h Dex-treated mice were highly associated with the development of neuronal cells, suggesting the adrenal medulla had a rapid response to Dex. Interestingly, only 4.3% of Dex-responsive genes in the Y-1 cell line under Dex treatment for 1 h were differentially expressed under Dex treatment for 24 h. The heatmaps revealed that most early responsive DEGs in Y-1 cells during 1 h of treatment exhibited a transient response. The expression of these genes under treatment for 24 h returned to basal levels similar to that during control treatment. In summary, this research compared the rapid transcriptomic effects of Dex stimulation in vivo and in vitro. Notably, adrenocortical Y-1 cells had a transient early response to Dex treatment. Furthermore, the DEGs had a minimal overlap in the 1-h Dex-treated group in vivo and in vitro.

Molecular Signatures Correlated With Poor IVF Outcomes: Insights From the mRNA and lncRNA Expression of Endometriotic Granulosa Cells

The outcomes of in vitro fertilization (IVF) for endometriotic women are significantly worse than for patients without ovarian endometriosis (OEM), as shown by fewer retrieved oocytes. However, the exact pathophysiological mechanism is still unknown. Thus, we conducted a prospective study that analyzed mRNA and lncRNA transcriptome between granulosa cells (GCs) from patients with fewer retrieved oocytes due to OEM and GCs from controls with male factor (MF) infertility using an RNA sequencing approach. We found a group of significantly differentially expressed genes (DEGs), including NR5A2, MAP3K5, PGRMC2, PRKAR2A, DEPTOR, ITGAV, KPNB1, GPC6, EIF3A, and SMC5, which were validated to be upregulated and negatively correlated with retrieved oocyte numbers in GCs of patients with OEM, while DUSP1 demonstrated the opposite. The molecular functions of these DEGs were mainly enriched in pathways involving mitogen-activated protein kinase (MAPK) signaling, Wnt signaling, steroid hormone response, apoptosis, and cell junction. Furthermore, we performed lncRNA analysis and identified a group of differentially expressed known/novel lncRNAs that were co-expressed with the validated DEGs and correlated with retrieved oocyte numbers. Co-expression networks were constructed between the DEGs and known/novel lncRNAs. These distinctive molecular signatures uncovered in this study are involved in the pathological regulation of ovarian reserve dysfunction in OEM patients.

Advances in stem cell research for the treatment of primary hypogonadism

In Leydig cell dysfunction, cells respond weakly to stimulation by pituitary luteinizing hormone, and, therefore, produce less testosterone, leading to primary hypogonadism. The most widely used treatment for primary hypogonadism is testosterone replacement therapy (TRT). However, TRT causes infertility and has been associated with other adverse effects, such as causing erythrocytosis and gynaecomastia, worsening obstructive sleep apnoea and increasing cardiovascular morbidity and mortality risks. Stem-cell-based therapy that re-establishes testosterone-producing cell lineages in the body has, therefore, become a promising prospect for treating primary hypogonadism. Over the past two decades, substantial advances have been made in the identification of Leydig cell sources for use in transplantation surgery, including the artificial induction of Leydig-like cells from different types of stem cells, for example, stem Leydig cells, mesenchymal stem cells, and pluripotent stem cells (PSCs). PSC-derived Leydig-like cells have already provided a powerful in vitro model to study the molecular mechanisms underlying Leydig cell differentiation and could be used to treat men with primary hypogonadism in a more specific and personalized approach.

The acyl chains of phosphoinositide PIP3 alter the structure and function of nuclear receptor steroidogenic factor-1

Nuclear receptors are transcription factors that bind lipids, an event that induces a structural conformation of the receptor that favors interaction with transcriptional coactivators. The nuclear receptor steroidogenic factor-1 (SF-1, NR5A1) binds the signaling phosphoinositides PI(4,5)P2 (PIP2) and PI(3,4,5)P3 (PIP3), and our previous crystal structures showed how the phosphoinositide headgroups regulate SF-1 function. However, what role the acyl chains play in regulating SF-1 structure remains unaddressed. Here, we used X-ray crystallography with in vitro binding and functional assays to examine how the acyl chains of PIP3 regulate human SF-1 ligand-binding domain structure and function. Altering acyl chain length and unsaturation regulates apparent binding of all tested phosphoinositides to SF-1. Mass spectrometry-based lipidomics data suggest C16 and C18 phospholipids preferentially associate with SF-1 expressed ectopically in bacteria. We then solved the 2.5 Å crystal structure of SF-1 bound to dioleoyl PIP3(18:1/18:1) to compare it with a matched structure of SF-1 bound to dipalmitoyl PIP3(16:0/16:0). The dioleoyl-bound structure was severely disordered in a specific SF-1 region associated with pathogenic human polymorphisms and within the coactivator-binding region critical for SF-1 function while inducing increased sensitivity to protease digestion in solution. Validating these structural observations, in vitro functional studies showed dioleoyl PIP3 induced 6-fold poorer affinity of a peroxisome proliferator-activated receptor gamma coactivator 1-alpha coactivator peptide for SF-1 compared with dipalmitoyl PIP3. Together, these data suggest the chemical nature of the phosphoinositide acyl chains controls the ordered state of specific, clinically important structural regions in SF-1, regulating SF-1 function in vitro.

Coordination of Multiple Cellular Processes by NR5A1/Nr5a1

The agenesis of the gonads and adrenal gland in revealed by knockout mouse studies strongly suggested a crucial role for Nr5a1 (SF-1 or Ad4BP) in organ development. In relation to these striking phenotypes, NR5A1/Nr5a1 has the potential to reprogram cells to steroidogenic cells, endow pluripotency, and regulate cell proliferation. However, due to limited knowledge regarding NR5A1 target genes, the mechanism by which NR5A1/Nr5a1 regulates these fundamental processes has remained unknown. Recently, newlyestablished technologies have enabled the identification of NR5A1 target genes related to multiple metabolic processes, as well as the aforementioned biological processes. Considering that active cellular processes are expected to be accompanied by active metabolism, NR5A1 may act as a key factor for processes such as cell differentiation, proliferation, and survival by coordinating these processes with cellular metabolism. A complete and definite picture of the cellular processes coordinated by NR5A1/Nr5a1 could be depicted by accumulating evidence of the potential target genes through whole genome studies.

PILOT RESEARCH OF A GENETIC PREDISPOSITION FOR CLINICAL MANIFESTATIONS OF ACUTE INTERMITTENT PORPHYRIA

Introduction.Acute intermittent porphyria (AIP) is the most common and severe form of acute hepatic porphyria. AIP is caused by a deficiency in the third enzyme of the heme biosynthesis system — hydroxymethylbilanine synthase (HMBS) — and has a dominant inheritance type. However, the probability of the clinical manifestation of this condition in carriers of the mutation in the HMBS gene constitutes only 10–20 %. Thi s suggests that the presence of such a mutation can be a necessary but not a sufficient condition for the development of the disease.

Aim.To search for additional genetic factors, which determine the clinical penetrance of AIP using Whole-Exome Sequencing.

Materials and methods.Sequencing of the whole exome was performed using a TruSeqExomeLibraryPrepkit (Illumina) kit by an Illumina HiSeq4000 instrument for 6 women with API with known mutations in the HMBS gene. All the patients suffered from a severe form of the disease. As a reference, a version of the hg19 human genome was used.

Results.No common mutations were found in the examined patients. However, in each patient, functional variations were found in the genes related to detoxification systems, regulation of the heme biosynthesis cascade and expression of delta-aminolevulinic acid synthase (ALAS1) and in genes of proteins regulating nervous system. These variations require further study involving an extended number of patients with AIP manifestations and their relatives, who are asymptomatic carriers of disorders in the gene HMBS.

Conclusions.The results obtained have allowed us to formulate a hypothesis about a possible role of genetic defects in the penetrance of AIP, which determine the development of other neurological pathologies. This is evidenced by the presence of gene pathogenic variations in 5 out of 6 examined patients, defects in which are associated with hereditary myasthenia and muscle atrophy.

ROS-Induced GATA4 and GATA6 Downregulation Inhibits StAR Expression in LPS-Treated Porcine Granulosa-Lutein Cells

LPS is a major endotoxin produced by gram-negative bacteria, and exposure to it commonly occurs in animal husbandry. Previous studies have shown that LPS infection disturbs steroidogenesis, including progesterone production, and subsequently decreases animal reproductive performance. However, little information about the underlying mechanisms is available thus far. In the present study, an in vitro-luteinized porcine granulosa cell model was used to study the underlying molecular mechanisms of LPS treatment. We found that LPS significantly inhibits progesterone production and downregulates the expressions of progesterone synthesis-associated genes (StAR, CYP11A1, and 3β-HSD). Furthermore, the levels of ROS were significantly increased in an LPS dose-dependent manner. Moreover, transcriptional factors GATA4 and GATA6, but not NR5A1, were significantly downregulated. Elimination of LPS-stimulated ROS by melatonin or vitamin C could restore the expressions of GATA4, GATA6, and StAR. In parallel, StAR expression was also inhibited by the knockdown of GATA4 and GATA6. Based on these data, we conclude that LPS impairs StAR expression via the ROS-induced downregulation of GATA4 and GATA6. Collectively, these findings provide new insights into the understanding of reproductive losses in animals suffering from bacterial infection and LPS exposure.

Transcriptional Regulation of Ovarian Steroidogenic Genes: Recent Findings Obtained from Stem Cell-Derived Steroidogenic Cells

Ovaries represent one of the primary steroidogenic organs, producing estrogen and progesterone under the regulation of gonadotropins during the estrous cycle. Gonadotropins fluctuate the expression of various steroidogenesis-related genes, such as those encoding steroidogenic enzymes, cholesterol deliverer, and electronic transporter. Steroidogenic factor-1 (SF-1)/adrenal 4-binding protein (Ad4BP)/NR5A1 and liver receptor homolog-1 (LRH-1) play important roles in these phenomena via transcriptional regulation. With the aid of cAMP, SF-1/Ad4BP and LRH-1 can induce the differentiation of stem cells into steroidogenic cells. This model is a useful tool for studying the molecular mechanisms of steroidogenesis. In this article, we will provide insight into the transcriptional regulation of steroidogenesis-related genes in ovaries that are revealed from stem cell-derived steroidogenic cells. Using the cells derived from the model, novel SF-1/Ad4BP- and LRH-1-regulated genes were identified by combined DNA microarray and promoter tiling array analyses. The interaction of SF-1/Ad4BP and LRH-1 with transcriptional regulators in the regulation of ovarian steroidogenesis was also revealed.

The Orphan Nuclear Receptors Steroidogenic Factor-1 and Liver Receptor Homolog-1: Structure, Regulation, and Essential Roles in Mammalian Reproduction

Nuclear receptors are intracellular proteins that act as transcription factors. Proteins with classic nuclear receptor domain structure lacking identified signaling ligands are designated orphan nuclear receptors. Two of these, steroidogenic factor-1 (NR5A1, also known as SF-1) and liver receptor homolog-1 (NR5A2, also known as LRH-1), bind to the same DNA sequences, with different and nonoverlapping effects on targets. Endogenous regulation of both is achieved predominantly by cofactor interactions. SF-1 is expressed primarily in steroidogenic tissues, LRH-1 in tissues of endodermal origin and the gonads. Both receptors modulate cholesterol homeostasis, steroidogenesis, tissue-specific cell proliferation, and stem cell pluripotency. LRH-1 is essential for development beyond gastrulation and SF-1 for genesis of the adrenal, sexual differentiation, and Leydig cell function. Ovary-specific depletion of SF-1 disrupts follicle development, while LRH-1 depletion prevents ovulation, cumulus expansion, and luteinization. Uterine depletion of LRH-1 compromises decidualization and pregnancy. In humans, SF-1 is present in endometriotic tissue, where it regulates estrogen synthesis. SF-1 is underexpressed in ovarian cancer cells and overexpressed in Leydig cell tumors. In breast cancer cells, proliferation, migration and invasion, and chemotherapy resistance are regulated by LRH-1. In conclusion, the NR5A orphan nuclear receptors are nonredundant factors that are crucial regulators of a panoply of biological processes, across multiple reproductive tissues.

High-Throughput Imaging of PPIX Using Confocal Microscopy

Increases in levels of protoporphyrin IX (PPIX; a heme precursor) may be driven by xenobiotic induction of aminolevulinic acid synthase 1 (ALAS1) expression. ALAS1 is the rate-limiting enzyme of heme biosynthesis and may be upregulated to satisfy the increased need for heme in CYP450 enzymes. Therefore, a high-throughput fluorescence spectroscopy method that detects PPIX would enable the screening of drugs that increase ALAS1 through nuclear hormone receptor-mediated induction of transcription that may cause toxicity or even provide utility in the diagnosis or treatment of cancers that have elevated cellular PPIX levels. This chapter describes a high-throughput plate-based imaging technique for determining cellular protoporphyrin levels by using the GE Healthcare InCell 6000 confocal imaging system to detect the presence and location of PPIX in each cell and may be adapted for use with other imaging systems. Laser excitation and a scientific-grade complementary metal oxide semiconductor (CMOS) camera generate short exposure times, decreasing photobleaching in the target cells that may result in inaccurate measurements of PPIX and increasing screening throughput. Nuclear staining was detected by using a laser with 405-nm excitation and 455-nm emission wavelengths, and the presence of PPIX was measured using 405-nm excitation and 706-nm emission wavelengths. Image analysis involving top-hat segmentation on both nuclear and PPIX staining was performed by using the InCell Analyzer Workstation software. This assay may be adapted to screen for PPIX formation, degradation, and transportation effectors. Indeed, the inclusion of PPIX transport inhibition would be expected to further widen the linear range of fluorescence and improve the method.

Transcriptome difference and potential crosstalk between liver and mammary tissue in mid-lactation primiparous dairy cows

Liver and mammary gland are among the most important organs during lactation in dairy cows. With the purpose of understanding both the different and the complementary roles and the crosstalk of those two organs during lactation, a transcriptome analysis was performed on liver and mammary tissues of 10 primiparous dairy cows in mid-lactation. The analysis was performed using a 4×44K Bovine Agilent microarray chip. The transcriptome difference between the two tissues was analyzed using SAS JMP Genomics using ANOVA with a false discovery rate correction (FDR). The analysis uncovered >9,000 genes differentially expressed (DEG) between the two tissues with a FDR<0.001. The functional analysis of the DEG uncovered a larger metabolic (especially related to lipid) and inflammatory response capacity in liver compared with mammary tissue while the mammary tissue had a larger protein synthesis and secretion, proliferation/differentiation, signaling, and innate immune system capacity compared with the liver. A plethora of endogenous compounds, cytokines, and transcription factors were estimated to control the DEG between the two tissues. Compared with mammary tissue, the liver transcriptome appeared to be under control of a large array of ligand-dependent nuclear receptors and, among endogenous chemical, fatty acids and bacteria-derived compounds. Compared with liver, the transcriptome of the mammary tissue was potentially under control of a large number of growth factors and miRNA. The in silico crosstalk analysis between the two tissues revealed an overall large communication with a reciprocal control of lipid metabolism, innate immune system adaptation, and proliferation/differentiation. In summary the transcriptome analysis confirmed prior known differences between liver and mammary tissue, especially considering the indication of a larger metabolic activity in liver compared with the mammary tissue and the larger protein synthesis, communication, and proliferative capacity in mammary tissue compared with the liver. Relatively novel is the indication by the data that the transcriptome of the liver is highly regulated by dietary and bacteria-related compounds while the mammary transcriptome is more under control of hormones, growth factors, and miRNA. A large crosstalk between the two tissues with a reciprocal control of metabolism and innate immune-adaptation was indicated by the network analysis that allowed uncovering previously unknown crosstalk between liver and mammary tissue for several signaling molecules.

Induction of steroidogenic cells from adult stem cells and pluripotent stem cells [Review]

Steroid hormones are mainly produced in adrenal glands and gonads. Because steroid hormones play vital roles in various physiological processes, replacement of deficient steroid hormones by hormone replacement therapy (HRT) is necessary for patients with adrenal and gonadal failure. In addition to HRT, tissue regeneration using stem cells is predicted to provide novel therapy. Among various stem cell types, mesenchymal stem cells can be differentiated into steroidogenic cells following ectopic expression of nuclear receptor (NR) 5A subfamily proteins, steroidogenic factor-1 (also known as adrenal 4 binding protein) and liver receptor homolog-1, with the aid of cAMP signaling. Conversely, these approaches cannot be applied to pluripotent stem cells, such as embryonic stem cells and induced pluripotent stem cells, because of poor survival following cytotoxic expression of NR5A subfamily proteins. However, if pluripotent stem cells are first differentiated through mesenchymal lineage, they can also be differentiated into steroidogenic cells via NR5A subfamily protein expression. This approach offers a potential suitable cells for future regenerative medicine and gene therapy for diseases caused by steroidogenesis deficiencies. It represents a powerful tool to investigate the molecular mechanisms involved in steroidogenesis. This article highlights our own and current research on the induction of steroidogenic cells from various stem cells. We also discuss the future direction of their clinical application.

11-Ketotestosterone Is a Major Androgen Produced in Human Gonads

CONTEXT

11-ketotestosterone (11-KT) is a novel class of active androgen. However, the detail of its synthesis remains unknown for humans.

OBJECTIVE

The objective of this study was to clarify the production and properties of 11-KT in human. Design, Participants, and Methods: Expression of cytochrome P450 and 11β-hydroxysteroid dehydrogenase types 1 and 2 (key enzymes involved in the synthesis of 11-KT) were investigated in human gonads. The production of 11-KT was investigated in Leydig cells. Plasma concentrations of testosterone and 11-KT were measured in 10 women and 10 men of reproductive age. Investigation of its properties was performed using breast cancer-derived MCF-7 cells.

RESULTS

Cytochrome P450 and 11β-hydroxysteroid dehydrogenase types 1 and 2 were detected in Leydig cells and theca cells. Leydig cells produced 11-KT, and relatively high levels of plasma 11-KT were measured in both men and women. There was no sexual dimorphism in the plasma levels of 11-KT, even though testosterone levels were more than 20 times higher in men than in women. It is noteworthy that the levels of testosterone and 11-KT were similar in women. In a luciferase reporter system, 11-KT activated human androgen receptor-mediated transactivation. Conversely, 11-KT did not activate estrogen receptor-mediated transactivation in aromatase-expressed MCF-7 cells, whereas testosterone did following conversion to estrogen. 11-KT did not affect the estrogen/estrogen receptor -mediated cell proliferation of MCF-7 cells. Furthermore, it significantly inhibited cell proliferation when androgen receptor was transfected into MCF-7 cells.

CONCLUSIONS

The current study indicates that 11-KT is produced in the gonads and represents a major androgen in human. It can potentially serve as a nonaromatizable androgen.

Identification of novel steroidogenic factor 1 (SF-1)-target genes and components of the SF-1 nuclear complex

Steroidogenic factor 1 (SF-1) is a master regulator of adrenal and reproductive development and function. Although SF-1 was identified as a transcriptional regulator for steroid metabolic enzymes, it has been shown that SF-1 also regulates other genes that are involved in various cellular processes. Previously, we showed that introduction of SF-1 into mesenchymal stem cells resulted in the differentiation of these cells to the steroidogenic lineage. By using this method of differentiation, we performed comprehensive analyses to identify the novel SF-1-target genes and components of the SF-1 nuclear complex. Genome-wide analyses with promoter tiling array and DNA microarray identified 10 genes as novel SF-1-target genes including glutathione S-transferase A family, 5-aminolevulinic acid synthase 1 and ferredoxin reductase. Using SF-1 immuno-affinity chromatography of nuclear proteins followed by MS/MS analysis, we identified 24 proteins including CCAAT/enhancer-binding protein β as components of SF-1 nuclear complex. In this review, we will describe novel roles of the newly identified genes for steroidogenesis.

Transcriptional regulation of genes related to progesterone production

Steroid hormones are synthesized from cholesterol in various tissues, mainly in the adrenal glands and gonads. Because these lipid-soluble steroid hormones immediately diffuse through the cells in which they are produced, their secretion directly reflects the activity of the genes related to their production. Progesterone is important not only for luteinization and maintenance of pregnancy, but also as a substrate for most other steroids. Steroidogenic acute regulatory protein (STAR), cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), and 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4) isomerase (3β-HSD) are well-known proteins essential for progesterone production. In addition to them, glutathione S-transferase A1-1 and A3-3 are shown to exert Δ(5)-Δ(4) isomerization activity to produce progesterone in a cooperative fashion with 3β-HSD. 5-Aminolevulinic acid synthase 1, ferredoxin 1, and ferredoxin reductase also play a role in steroidogenesis as accessory factors. Members of the nuclear receptor 5A (NR5A) family (steroidogenic factor 1 and liver receptor homolog 1) play a crucial role in the transcriptional regulation of these genes. The NR5A family activates these genes by binding to NR5A responsive elements present within their promoter regions, as well as to the elements far from their promoters. In addition, various NR5A-interacting proteins including peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), nuclear receptor subfamily 0, group B, member 1 (DAX-1), and CCAAT/enhancer-binding proteins (C/EBP) are involved in the transcription of NR5A target genes and regulate the transcription either positively or negatively under both basal and tropic hormone-stimulated conditions. In this review, we describe the transcriptional regulation of genes related to progesterone production.

Dexamethasone acutely down-regulates genes involved in steroidogenesis in stallion testes

In rodents, livestock and primate species, a single dose of the synthetic glucocorticoid dexamethasone acutely lowers testosterone biosynthesis. To determine the mechanism of decreased testosterone biosynthesis, stallions were treated with 0.1mg/kg dexamethasone 12h prior to castration. Dexamethasone decreased serum concentrations of testosterone by 60% compared to saline-treated control stallions. Transcriptome analyses (microarrays, northern blots and quantitative PCR) of testes discovered that dexamethasone treatment decreased concentrations of glucocorticoid receptor alpha (NR3C1), alpha actinin 4 (ACTN4), luteinizing hormone receptor (LHCGR), squalene epoxidase (SQLE), 24-dehydrocholesterol reductase (DHCR24), glutathione S-transferase A3 (GSTA3) and aromatase (CYP19A1) mRNAs. Dexamethasone increased concentrations of NFkB inhibitor A (NFKBIA) mRNA in testes. SQLE, DHCR24 and GSTA3 mRNAs were predominantly expressed by Leydig cells. In man and livestock, the GSTA3 protein provides a major 3-ketosteroid isomerase activity: conversion of Δ(5)-androstenedione to Δ(4)-androstenedione, the immediate precursor of testosterone. Consistent with the decrease in GSTA3 mRNA, dexamethasone decreased the 3-ketosteroid isomerase activity in testicular extracts. In conclusion, dexamethasone acutely decreased the expression of genes involved in hormone signaling (NR3C1, ACTN4 and LHCGR), cholesterol synthesis (SQLE and DHCR24) and steroidogenesis (GSTA3 and CYP19A1) along with testosterone production. This is the first report of dexamethasone down-regulating expression of the GSTA3 gene and a very late step in testosterone biosynthesis. Elucidation of the molecular mechanisms involved may lead to new approaches to modulate androgen regulation of the physiology of humans and livestock in health and disease.

C/EBPβ (CCAAT/enhancer-binding protein β) mediates progesterone production through transcriptional regulation in co-operation with SF-1 (steroidogenic factor-1)

CCAAT/enhancer-binding protein β (C/EBPβ) was identified as a component of the SF-1 nuclear complex. C/EBPβ regulates expression of progesterone production-related genes (STAR, CYP11A1 and HSD3B2) by co-operation with SF-1. Our findings reveal a novel molecular mechanism of progesterone production.

Differentiation of mesenchymal stem cells into gonad and adrenal steroidogenic cells

Hormone replacement therapy is necessary for patients with adrenal and gonadal failure. Steroid hormone treatment is also employed in aging people for sex hormone deficiency. These patients undergo such therapies, which have associated risks, for their entire life. Stem cells represent an innovative tool for tissue regeneration and the possibility of solving these problems. Among various stem cell types, mesenchymal stem cells have the potential to differentiate into steroidogenic cells both in vivo and in vitro. In particular, they can effectively be differentiated into steroidogenic cells by expressing nuclear receptor 5A subfamily proteins (steroidogenic factor-1 and liver receptor homolog-1) with the aid of cAMP. This approach will provide a source of cells for future regenerative medicine for the treatment of diseases caused by steroidogenesis deficiencies. It can also represent a useful tool for studying the molecular mechanisms of steroidogenesis and its related diseases.

Transcriptional regulation of human ferredoxin reductase through an intronic enhancer in steroidogenic cells

Ferredoxin reductase (FDXR, also known as adrenodoxin reductase) is a mitochondrial flavoprotein that transfers electrons from NADPH to mitochondrial cytochrome P450 enzymes, mediating the function of an iron-sulfur cluster protein, ferredoxin. FDXR functions in various metabolic processes including steroidogenesis. It is well known that multiple steroidogenic enzymes are regulated by a transcription factor steroidogenic factor-1 (SF-1, also known as Ad4BP). Previously, we have shown that SF-1 transduction causes human mesenchymal stem cell differentiation into steroidogenic cells. Genome-wide analysis of differentiated cells, using a combination of DNA microarray and promoter tiling array analyses, showed that FDXR is a novel SF-1 target gene. In this study, the transcriptional regulatory mechanism of FDXR was examined in steroidogenic cells. A chromatin immunoprecipitation assay revealed that a novel SF-1 binding region was located within intron 2 of the human FDXR gene. Luciferase reporter assays showed that FDXR transcription was activated through the novel SF-1 binding site within intron 2. Endogenous SF-1 knockdown in human adrenocortical H295R and KGN cells decreased FDXR expression. In H295R cells, strong binding of two histone markers of active enhancers, histones H3K27ac and H3K4me2, were detected near the SF-1 binding site within intron 2. Furthermore, the binding of these histone markers was decreased concurrent with SF-1 knockdown in H295R cells. These results indicated that abundant FDXR expression in these steroidogenic cells was maintained through SF-1 binding to the intronic enhancer of the FDXR gene.

Human glutathione S-transferase A (GSTA) family genes are regulated by steroidogenic factor 1 (SF-1) and are involved in steroidogenesis

Steroidogenic factor 1 (SF-1) is a master regulator for steroidogenesis. In this study, we identified novel SF-1 target genes using a genome-wide promoter tiling array and a DNA microarray. SF-1 was found to regulate human glutathione S-transferase A (GSTA) family genes (hGSTA1-hGSTA4), a superfamily of detoxification enzymes clustered on chromosome 6p12. All hGSTA genes were up-regulated by transduction of SF-1 into human mesenchymal stem cells, while knockdown of endogenous SF-1 in H295R cells down-regulated all hGSTA genes. Chromatin immunoprecipitation assays, however, revealed that SF-1 bound directly to the promoters of hGSTA3 and weakly of hGSTA4. Chromosome conformation capture assays revealed that the coordinated expression of the genes was based on changes in higher-order chromatin structure triggered by SF-1, which enables the formation of long-range interactions, at least between hGSTA1 and hGSTA3 gene promoters. In steroidogenesis, dehydrogenation of the 3-hydroxy group and subsequent Δ(5)-Δ(4) isomerization are thought to be enzymatic properties of 3β-hydroxysteroid dehydrogenase (3β-HSD). Here, we demonstrated that, in steroidogenic cells, the hGSTA1 and hGSTA3 gene products catalyze Δ(5)-Δ(4) isomerization in a coordinated fashion with 3β-HSD II to produce progesterone or Δ(4)-androstenedione from their Δ(5)-precursors. Thus, hGSTA1 and hGSTA3 gene products are new members of steroidogenesis working as Δ(5)-Δ(4) isomerases.

A novel isoform of liver receptor homolog-1 is regulated by steroidogenic factor-1 and the specificity protein family in ovarian granulosa cells

Liver receptor homolog-1 (LRH-1) is a member of the nuclear receptor 5A (NR5A) subfamily. It is expressed in granulosa cells of the ovary and is involved in steroidogenesis and ovulation. To reveal the transcriptional regulatory mechanism of LRH-1, we determined its transcription start site in the ovary using KGN cells, a human granulosa cell tumor cell line. 5'-rapid amplification of cDNA ends PCR revealed that human ovarian LRH-1 was transcribed from a novel transcription start site, termed exon 2o, located 41 bp upstream of the reported exon 2. The novel LRH-1 isoform was expressed in the human ovary but not the liver. Promoter analysis and an EMSA indicated that a steroidogenic factor-1 (SF-1) binding site and a GC box upstream of exon 2o were required for promoter activity, and that SF-1 and specificity protein (Sp)-1/3 bind to the respective regions in ovarian granulosa cells. In KGN cells, transfection of SF-1 increased ovarian LRH-1 promoter activity and SF-1-dependent reporter activity was further enhanced when peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) was cotransfected. In Drosophila SL2 cells, Sp1 was more effective than Sp3 in enhancing promoter activity, and co-transfection of the NR5A-family synergistically increased activity. Infection with adenoviruses expressing SF-1 or PGC-1α induced LRH-1 expression in KGN cells. These results indicate that the expression of human LRH-1 is regulated in a tissue-specific manner, and that the novel promoter region is controlled by the Sp-family, NR5A-family and PGC-1α in ovarian granulosa cells in a coordinated fashion.