A shared promoter element regulates the expression of three steroidogenic enzymes

Steroidogenic Factor-1 form and function: From phospholipids to physiology

Steroidogenic Factor-1 (SF-1, NR5A1) is a member of the nuclear receptor superfamily of ligand-regulated transcription factors, consisting of a DNA-binding domain (DBD) connected to a transcriptional regulatory ligand binding domain (LBD) via an unstructured hinge domain. SF-1 is a master regulator of development and adult function along the hypothalamic pituitary adrenal and gonadal axes, with strong pathophysiological association with endometriosis and adrenocortical carcinoma. SF-1 was shown to bind and be regulated by phospholipids, one of the most interesting aspects of SF-1 regulation is the manner in which SF-1 interacts with phospholipids: SF-1 buries the phospholipid acyl chains deep in the hydrophobic core of the SF-1 protein, while the lipid headgroups remain solvent-exposed on the exterior of the SF-1 protein surface. Here, we have reviewed several aspects of SF-1 structure, function and physiology, touching on other transcription factors that help regulate SF-1 target genes, non-canonical functions of SF-1, the DNA-binding properties of SF-1, the use of mass spectrometry to identify lipids that associate with SF-1, how protein phosphorylation regulates SF-1 and the structural biology of the phospholipid-ligand binding domain. Together this review summarizes the form and function of Steroidogenic Factor-1 in physiology and in human disease, with particular emphasis on adrenal cancer.

CRISPR/Cas9-mediated activation of NR5A1 steers female human embryonic stem cell-derived bipotential gonadal-like cells towards a steroidogenic cell fate

The nuclear receptor subfamily 5 group A member 1 (NR5A1), encoding steroidogenic factor 1 (SF-1), has been identified as a critical factor in gonadal development in animal studies. A previous study of ours suggested that upregulation of NR5A1 during early gonadal differentiation in male (46,XY) human pluripotent stem cells steers the cells into a more mature gonadal cell type. However, the detailed role of NR5A1 in female gonadal differentiation has yet to be determined. In this study, by combining the processes of gonadal differentiation and conditional gene activation, we show that NR5A1 induction predominantly upregulates the female gonadal marker inhibin subunit α (INHA) and steroidogenic markers steroidogenic acute regulatory protein (STAR), cytochrome P450 family 11 subfamily A member 1 (CYP11A1), cytochrome P450 family 17 subfamily A member 1 (CYP17A1), hydroxy-delta-5-steroid dehydrogenase (HSD3B2) and hydroxysteroid 17-beta dehydrogenase 1 (HSD17B1). In contrast, NR5A1 induction did not seem to affect the bipotential gonadal markers gata binding protein 4 (GATA4) and Wilms' tumour suppressor 1 (WT1) nor the female gonadal markers r-spondin 1 (RSPO1) and wnt family member 4 (WNT4). Differentially expressed genes were highly associated with adrenal and ovarian steroidogenesis pathways. Moreover, time-series analysis revealed different dynamic changes between male and female induced samples, where continuously upregulated genes in female gonadal differentiation were mostly associated with adrenal steroidogenesis. Thus, in contrast to male gonadal differentiation, NR5A1 is necessary but not sufficient to steer human embryonic stem cell (hESC)-derived bipotential gonadal-like cells towards a more mature somatic, female cell fate. Instead, it seems to direct bipotential gonadal-like cells more towards a steroidogenic-like cell population. The information obtained in this study helps in elucidating the role of NR5A1 in gonadal differentiation of a female stem cell line.

EHD3 positively regulated by NR5A1 participates in testosterone synthesis via endocytosis

AIMS

Increasing evidence has shown that hormone secretion is regulated by endocytosis. Eps15 homology domain-containing protein 3 (EHD3) is an endocytic-trafficking regulatory protein, but whether EHD3 is associated with testosterone secretion is not clear. This work aims to explore the role of EHD3 in testosterone synthesis.

MAIN METHODS

Testosterone concentration was determined by ELISA. The effects of EHD3 on endocytosis were assessed by exosomes tracing assay and Immunofluorescence. Targeting relationship between EHD3 and NR5A1 was verified by chromatin immunoprecipitation (ChIP) and dual luciferase reporter gene assay in Leydig cells. For in vivo assessments, conditional NR5A1 knockout mouse model was established with CRISPR/Cas9 gene targeting technology.

KEY FINDINGS

EHD3 overexpression significantly increased the concentration of testosterone. EHD3 knockdown markedly decreased testosterone synthesis by reducing endocytosis. The activity of the EHD3 promoter was positively regulated by NR5A1, which occupied the conserved sequence "AGGTCA" in the EHD3 promoter. Furthermore, mice with a Leydig cell-specific conditional NR5A1 knockout displayed the blunted levels of EHD3 and clathrin (a key factor for endocytosis), and serum testosterone concentration compared with NR5A1^f/f mice.

SIGNIFICANCE

This study suggests a potential molecular mechanism of testosterone synthesis to fully understand male reproductive health.

Glucocorticoids in T cell development, differentiation and function

Glucocorticoids (GCs) are small lipid hormones produced by the adrenals that maintain organismal homeostasis. Circadian and stress-induced changes in systemic GC levels regulate metabolism, cardiovascular and neural function, reproduction and immune activity. Our understanding of GC effects on immunity comes largely from administration of exogenous GCs to treat immune or inflammatory disorders. However, it is increasingly clear that endogenous GCs both promote and suppress T cell immunity. Examples include selecting an appropriate repertoire of T cell receptor (TCR) self-affinities in the thymus, regulating T cell trafficking between anatomical compartments, suppressing type 1 T helper (T_H1) cell responses while permitting T_H2 cell and, especially, IL-17-producing T helper cell responses, and promoting memory T cell differentiation and maintenance. Furthermore, in addition to functioning at a distance, extra-adrenal (local) production allows GCs to act as paracrine signals, specifically targeting activated T cells in various contexts in the thymus, mucosa and tumours. These pleiotropic effects on different T cell populations during development and immune responses provide a nuanced understanding of how GCs shape immunity.

Transactivation of miR-202-5p by Steroidogenic Factor 1 (SF1) Induces Apoptosis in Goat Granulosa Cells by Targeting TGFβR2

MicroRNAs play key roles during ovary development, with emerging evidence suggesting that miR-202-5p is specifically expressed in female animal gonads. Granulosa cells (GCs) are somatic cells that are closely related to the development of female gametes in mammalian ovaries. However, the biological roles of miR-202-5p in GCs remain unknown. Here, we show that miR-202-5p is specifically expressed in GCs and accumulates in extracellular vesicles (EVs) from large growth follicles in goat ovaries. In vitro assays showed that miR-202-5p induced apoptosis and suppressed the proliferation of goat GCs. We further revealed that miR-202-5p is a functional miRNA that targets the transforming growth factor-beta type II receptor (TGFβR2). MiR-202-5p attenuated TGF-β/SMAD signaling through the degradation of TGFβR2 at both the mRNA and protein level, decreasing p-SMAD3 levels in GCs. Moreover, we verified that steroidogenic factor 1 (SF1) is a transcriptional factor that binds to the promoters of miR-202 and cytochrome P450 family 19 subfamily A member 1 (CYP19A1) through luciferase reporter and chromatin immunoprecipitation (ChIP) assays. That contributed to positive correlation between miR-202-5p and CYP19A1 expression and estradiol (E2) release. Furthermore, SF1 repressed TGFβR2 and p-SMAD3 levels in GCs through the transactivation of miR-202-5p. Taken together, these results suggest a mechanism by which miR-202-5p regulates canonical TGF-β/SMAD signaling through targeting TGFβR2 in GCs. This provides insight into the transcriptional regulation of miR-202 and CYP19A1 during goat ovarian follicular development.

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.

Steroidogenic Factor 1 (Nr5a1) is Required for Sertoli Cell Survival Post Sex Determination

The elevated level of Steroidogenic Factor 1 (Nr5a1, Sf-1) expression in the male gonadal development pathway, post sex determination, implies a vital role in testis gonadal differentiation. In this study we generated Sertoli cell-specific Nr5a1 KO mice (SC-SF-1^-/-) at E14.5, which coincides with testis development post sex determination, using the Amh-Cre mouse model. Analysis of SC-SF-1^-/- (Sertoli cell specific Nr5a1 knockout) testes demonstrated apoptosis as early as E15. Further analysis revealed that SC-SF-1^-/- gonads displayed lower MDM2 levels resulting in elevated TP53 levels, which we believe may lead to apoptosis of the Sertoli cell population, inferring the possibility that NR5A1 directly regulates MDM2 expression. By E15.5, the Sertoli cell and germ cell population declined in SC-SF-1^-/- mice resulting in the disruption of seminiferous cords with limited cord structure remaining at E18.5. Due to the loss of Sertoli and germ cells, the testis weights of SC-SF-1^-/- mice at 6-weeks were much reduced; however, SC-SF-1^-/- seminal vesicles weights were comparable suggesting intact Leydig cell androgen production. We conclude that NR5A1 regulates the TP53 pathway during development, is essential for fetal Sertoli cell survival and controls the cell cycle of Sertoli cells during differentiation.

A Novel Mutation in the Critical P-Box Residue of Steroidogenic Factor-1 Presenting with XY Sex Reversal and Transient Adrenal Failure

BACKGROUND

Although the importance of steroidogenic factor-1 (SF1, NR5A1) for adrenal development is supported by numerous in vitro and in vivo studies, cases of SF1 deficiency associated with adrenal failure are exceptionally rare. The first human NR5A1 mutation was a heterozygous de novo p.G35E variant identified in a patient with disorder of sex development (DSD) 46,XY and primary adrenal insufficiency. Here we describe another association of the "classic" SF1 phenotype with a novel NR5A1 mutation affecting G35 residue.

METHODS

We describe the clinical characteristics of a phenotypically female patient presenting at 2 months with signs of adrenal insufficiency. DSD 46,XY was diagnosed at 4 years. The NR5A1 gene was analyzed by Sanger sequencing. Minigene splicing and dual luciferase reporter assays were used to characterize effects of the novel mutation on splicing and transcription, respectively.

RESULTS

Sequencing of the NR5A1 gene revealed a de novo heterozygous c.104G>A:p.G35D substitution. The minigene experiments demonstrated that c.104G>A substitution did not affect splicing. However, transactivation activity of the p.G35D mutant was clearly impaired, which was comparable with the effect of the p.G35E mutation.

CONCLUSIONS

The findings stress the importance of G35 residue for adrenal development. The current observation also suggests that some patients with SF1 deficiency may present with transient adrenal failure.

Mutant NR5A1/SF-1 in patients with disorders of sex development shows defective activation of the SOX9 TESCO enhancer

Nuclear receptor subfamily 5 group A member 1/Steroidogenic factor 1 (NR5A1; SF-1; Ad4BP) mutations cause 46,XY disorders of sex development (DSD), with phenotypes ranging from developmentally mild (e.g., hypospadias) to severe (e.g., complete gonadal dysgenesis). The molecular mechanism underlying this spectrum is unclear. During sex determination, SF-1 regulates SOX9 (SRY [sex determining region Y]-box 9) expression. We hypothesized that SF-1 mutations in 46,XY DSD patients affect SOX9 expression via the Testis-specific Enhancer of Sox9 core element, TESCO. Our objective was to assess the ability of 20 SF-1 mutants found in 46,XY DSD patients to activate TESCO. Patient DNA was sequenced for SF-1 mutations and mutant SF-1 proteins were examined for transcriptional activity, protein expression, sub-cellular localization and in silico structural defects. Fifteen of the 20 mutants showed reduced SF-1 activation on TESCO, 11 with atypical sub-cellular localization. Fourteen SF-1 mutants were predicted in silico to alter DNA, ligand or cofactor interactions. Our study may implicate aberrant SF-1-mediated transcriptional regulation of SOX9 in 46,XY DSDs.

Aberrant Global and Jagged-Mediated Notch Signaling Disrupts Segregation Between wt1-Expressing and Steroidogenic Tissues in Zebrafish

Although the zebrafish interrenal tissue has been used as a model for steroidogenesis and genesis of the adrenal gland, its specification and morphogenesis remains largely unclear. In the present study, we explored how the Wilms tumor 1 (WT1)-expressing cells are segregated from the SF-1-expressing steroidogenic cells in the zebrafish model. The interrenal tissue precursors expressing ff1b, the equivalent of mammalian SF-1, were derived from wt1-expressing pronephric primordia in the zebrafish embryo. Through histochemistry and in situ hybridization, we demonstrated that the size of functionally differentiated interrenal tissue was substantially increased on global inhibition of the Notch signaling pathway and was accompanied by a disrupted segregation between the wt1- and ff1b-expressing cells. As the Notch pathway was conditionally activated during interrenal specification, differentiation, but not ff1b expression, of interrenal tissue was drastically compromised. In embryos deficient for Notch ligands jagged 1b and 2b, transgenic reporter activity of wt1b promoter was detected within the steroidogenic interrenal tissue. In conclusion, our results indicate that Jagged-Notch signaling is required (1) for segregation between wt1-expressing cells and differentiated steroidogenic tissue; and (2) to modulate the extent of functional differentiation in the steroidogenic interrenal tissue.

Transcription of CYP19A1 is directly regulated by SF-1 in the theca cells of ovary follicles in chicken

Many studies have suggested the important role of estrogen in ovarian differentiation and development of vertebrates including chicken. Cytochrome P450 aromatase, encoded by CYP19A1, is a key enzyme in estrogen synthesis, but the mechanism of CYP19A1 regulation in chicken remains unknown. Here, we found that CYP19A1 was only expressed in the theca cell layers of chicken ovary follicles. Steroidogenic factor 1 (SF-1, also named as nuclear receptor subfamily 5 group A member 1, NR5A1), a potential regulators, was expressed in both the theca cell layers and granulosa cell layers. Forkheadbox L2 (FOXL2), another potential regulator, was only expressed in the granulosa cell layers. Using luciferase assays in vitro, we found that SF-1 could activate the promoter of CYP19A1 by binding to the nuclear receptor half-site (5'-TCAAGGTCA-3') from -280 to -271 base pairs. FOXL2 did not activate the promoter of chicken CYP19A1 gene in either 293T or DF-1 cells. Overexpression of SF-1 in DF-1 cells upregulated aromatase expression, but FOXL2 could not. Taken together, our results indicated that SF-1 activates CYP19A1 mRNA expression via a conserved binding site in chicken ovary, but FOXL2 may not affect the expression of CYP19A1.

Genetic disorders of nuclear receptors

Following the first isolation of nuclear receptor (NR) genes, genetic disorders caused by NR gene mutations were initially discovered by a candidate gene approach based on their known roles in endocrine pathways and physiologic processes. Subsequently, the identification of disorders has been informed by phenotypes associated with gene disruption in animal models or by genetic linkage studies. More recently, whole exome sequencing has associated pathogenic genetic variants with unexpected, often multisystem, human phenotypes. To date, defects in 20 of 48 human NR genes have been associated with human disorders, with different mutations mediating phenotypes of varying severity or several distinct conditions being associated with different changes in the same gene. Studies of individuals with deleterious genetic variants can elucidate novel roles of human NRs, validating them as targets for drug development or providing new insights into structure-function relationships. Importantly, human genetic discoveries enable definitive disease diagnosis and can provide opportunities to therapeutically manage affected individuals. Here we review germline changes in human NR genes associated with "monogenic" conditions, including a discussion of the structural basis of mutations that cause distinctive changes in NR function and the molecular mechanisms mediating pathogenesis.

Introduction to the 2016 Keith L. Parker Memorial Lecturer: Douglas M. Stocco, Ph.D

Douglas M. (Doug) Stocco is Professor Emeritus at Texas Tech University Health Sciences Center in Lubbock, TX, and is internationally renowned for his work characterizing the steroidogenic acute regulatory protein, StAR. Stocco's laboratory isolated and cloned StAR from mouse Leydig MA-10 cells, collaborated on the demonstration that StAR mutations cause congenital lipoid adrenal hyperplasia, and delineated much of what is known about the intracellular pathways that regulate its production. This work resolved a decades-long quest to identify the mechanism underlying the acute regulation of steroidogenesis.

A 46,XX Ovotesticular Disorder of Sex Development Likely Caused by a Steroidogenic Factor-1 (NR5A1) Variant

BACKGROUND

A variant in steroidogenic factor-1 (SF-1, encoded by the gene NR5A1), p.Arg92Trp, has recently been reported in multiple families with 46,XX ovotesticular or testicular disorders of sex development (DSD). This amino acid change impacts the DNA-binding domain and perturbs gonadal differentiation pathways.

METHODS

Whole-exome sequencing was performed on a 46,XX subject with ovotesticular DSD.

RESULTS

Exome results identified a heterozygous NR5A1 variant, p.Arg92Gln, in the 46,XX ovotesticular DSD proband. This arginine-to-glutamine change has been previously reported in the homozygous state in a 46,XY patient with gonadal and adrenal dysgenesis, though 46,XY and 46,XX heterozygous carriers of this variant have not been previously reported to have any clinical phenotype.

CONCLUSIONS

The NR5A1 p.Arg92Gln variant, which has thus far only been seen in a family with 46,XY DSD, most likely contributes to the ovotesticular DSD in this case. In light of the recent reports of unrelated 46,XX subjects with testicular or ovotesticular DSD with the NR5A1 variant p.Arg92Trp, it appears that other mutations in the DNA binding domain have the potential to impact the factors determining testicular and ovarian differentiation. This case demonstrates the variability of phenotypes with the same genotype and broadens our understanding of the role of SF-1 in gonadal differentiation.

SF-1 deficiency causes lipid accumulation in Leydig cells via suppression of STAR and CYP11A1

Genetic mutations of steroidogenic factor 1 (also known as Ad4BP or Nr5a1) have increasingly been reported in patients with 46,XY disorders of sex development (46,XY disorders of sex development). However, because the phenotype of 46,XY disorders of sex development with a steroidogenic factor 1 mutation is wide-ranging, its precise diagnosis remains a clinical problem. We previously reported the frequent occurrence of lipid accumulation in Leydig cells among patients with 46,XY disorders of sex development with a steroidogenic factor 1 mutation, an observation also reported by other authors. To address the mechanism of lipid accumulation in this disease, we examined the effects of steroidogenic factor 1 deficiency on downstream targets of steroidogenic factor 1 in in vitro and in vivo. We found that lipid accumulation in Leydig cells was enhanced after puberty in heterozygous steroidogenic factor 1 knockout mice compared with wild-type mice, and was accompanied by a significant decrease in steroidogenic acute regulatory protein and CYP11A1 expression. In mouse Leydig cell lines, steroidogenic factor 1 knockdown induced a remarkable accumulation of neutral lipids and cholesterol with reduced androgen levels. Steroidogenic factor 1 knockdown reduced the expression of steroidogenic acute regulatory protein and CYP11A1, both of which are transcriptional targets of steroidogenic factor 1 and key molecules for steroidogenesis from cholesterol in the mitochondria. Knockdown of either steroidogenic acute regulatory protein or CYP11A1 also induced lipid accumulation, and knockdown of both had an additive effect. Our data suggested that lipid accumulation in the Leydig cells of the 46,XY disorders of sex development phenotype with a steroidogenic factor 1 mutation is due, at least in part, to the suppression of steroidogenic acute regulatory protein and CYP11A1, and a resulting increase in unmetabolized cholesterol.

Mouse genotypes drive the liver and adrenal gland clocks

Circadian rhythms regulate a plethora of physiological processes. Perturbations of the rhythm can result in pathologies which are frequently studied in inbred mouse strains. We show that the genotype of mouse lines defines the circadian gene expression patterns. Expression of majority of core clock and output metabolic genes are phase delayed in the C56BL/6J line compared to 129S2 in the adrenal glands and the liver. Circadian amplitudes are generally higher in the 129S2 line. Experiments in dark - dark (DD) and light - dark conditions (LD), exome sequencing and data mining proposed that mouse lines differ in single nucleotide variants in the binding regions of clock related transcription factors in open chromatin regions. A possible mechanisms of differential circadian expression could be the entrainment and transmission of the light signal to peripheral organs. This is supported by the genotype effect in adrenal glands that is largest under LD, and by the high number of single nucleotide variants in the Receptor, Kinase and G-protein coupled receptor Panther molecular function categories. Different phenotypes of the two mouse lines and changed amino acid sequence of the Period 2 protein possibly contribute further to the observed differences in circadian gene expression.

DNA methylation in endometriosis (Review)

Endometriosis is defined by the presence and growth of functional endometrial tissue, outside the uterine cavity, primarily in the ovaries, pelvic peritoneum and rectovaginal septum. Although it is a benign disease, it presents with malignant characteristics, such as invasion to surrounding tissues, metastasis to distant locations and recurrence following treatment. Accumulating evidence suggests that various epigenetic aberrations may play an essential role in the pathogenesis of endometriosis. Aberrant DNA methylation represents a possible mechanism repsonsible for this disease, linking gene expression alterations observed in endometriosis with hormonal and environmental factors. Several lines of evidence indicate that endometriosis may partially be due to selective epigenetic deregulations influenced by extrinsic factors. Previous studies have shed light into the epigenetic component of endometriosis, reporting variations in the epigenetic patterns of genes known to be involved in the aberrant hormonal, immunologic and inflammatory status of endometriosis. Although recent studies, utilizing advanced molecular techniques, have allowed us to further elucidate the possible association of DNA methylation with altered gene expression, whether these molecular changes represent the cause or merely the consequence of the disease is a question which remains to be answered. This review provides an overview of the current literature on the role of DNA methylation in the pathophysiology and malignant evolution of endometriosis. We also provide insight into the mechanisms through which DNA methylation-modifying agents may be the next step in the research of the pharmaceutical treatment of endometriosis.

Impact of ACTH Signaling on Transcriptional Regulation of Steroidogenic Genes

The trophic peptide hormone adrenocorticotropic (ACTH) stimulates steroid hormone biosynthesis evoking both a rapid, acute response and a long-term, chronic response, via the activation of cAMP/protein kinase A (PKA) signaling. The acute response is initiated by the mobilization of cholesterol from lipid stores and its delivery to the inner mitochondrial membrane, a process that is mediated by the steroidogenic acute regulatory protein. The chronic response results in the increased coordinated transcription of genes encoding steroidogenic enzymes. ACTH binding to its cognate receptor, melanocortin 2 receptor (MC2R), stimulates adenylyl cyclase, thus inducing cAMP production, PKA activation, and phosphorylation of specific nuclear factors, which bind to target promoters and facilitate coactivator protein recruitment to direct steroidogenic gene transcription. This review provides a general view of the transcriptional control exerted by the ACTH/cAMP system on the expression of genes encoding for steroidogenic enzymes in the adrenal cortex. Special emphasis will be given to the transcription factors required to mediate ACTH-dependent transcription of steroidogenic genes.

Transforming growth factor-β1 and diabetic nephropathy

Transforming growth factor-β1 (TGF-β1) is established to be involved in the pathogenesis of diabetic nephropathy. The diabetic milieu enhances oxidative stress and induces the expression of TGF-β1. TGF-β1 promotes cell hypertrophy and extracellular matrix accumulation in the mesangium, which decreases glomerular filtration rate and leads to chronic renal failure. Recently, TGF-β1 has been demonstrated to regulate urinary albumin excretion by both increasing glomerular permeability and decreasing reabsorption in the proximal tubules. TGF-β1 also increases urinary excretion of water, electrolytes and glucose by suppressing tubular reabsorption in both normal and diabetic conditions. Although TGF-β1 exerts hypertrophic and fibrogenic effects in diabetic nephropathy, whether suppression of the function of TGF-β1 can be an option to prevent or treat the complication is still controversial. This is partly because adrenal production of mineralocorticoids could be augmented by the suppression of TGF-β1. However, differentiating the molecular mechanisms for glomerulosclerosis from those for the suppression of the effects of mineralocorticoids by TGF-β1 may assist in developing novel therapeutic strategies for diabetic nephropathy. In this review, we discuss recent findings on the role of TGF-β1 in diabetic nephropathy.

Regulation of Steroidogenesis, Development, and Cell Differentiation by Steroidogenic Factor-1 and Liver Receptor Homolog-1

Steroidogenic factor-1 (SF-1) and liver receptor homolog-1 (LRH-1) belong to the nuclear receptor superfamily and are categorized as orphan receptors. In addition to other nuclear receptors, these play roles in various physiological phenomena by regulating the transcription of target genes. Both factors share very similar structures and exhibit common functions. Of these, the roles of SF-1 and LRH-1 in steroidogenesis are the most important, especially that of SF-1, which was originally discovered and named to reflect such roles. SF-1 and LRH-1 are essential for steroid hormone production in gonads and adrenal glands through the regulation of various steroidogenesis-related genes. As SF-1 is also necessary for the development of gonads and adrenal glands, it is also considered a master regulator of steroidogenesis. Recent studies have clearly demonstrated that LRH-1 also represents another master regulator of steroidogenesis, which similarly to SF-1, can induce differentiation of non-steroidogenic stem cells into steroidogenic cells. Here, we review the functions of both factors in these steroidogenesis-related phenomena.

MicroRNA-764-3p regulates 17β-estradiol synthesis of mouse ovarian granulosa cells by targeting steroidogenic factor-1

Previous studies have reported that microRNA-764-3p (miR-764-3p) is one of the most up-regulated microRNAs (miRNAs) in TGF-β1-stimulated mouse ovarian granulosa cells. However, little is known about the roles and mechanisms of miR-764-3p in granulosa cell function during follicular development. In this study, we found that overexpression of miR-764-3p inhibited 17β-estradiol (E2) synthesis of granulosa cells through directly targeting steroidogenic factor-1 (SF-1). MiR-764-3p inhibited SF-1 by affecting its messenger RNA (mRNA) stability, which subsequently suppressed the expression levels of Cyp19a1 gene (aromatase, a downstream target of SF-1). In addition, SF-1 was involved in regulation of miR-764-3p-mediated Cyp19a1 expression in granulosa cells which contributed, at least partially, to the effects of miR-764-3p on granulosa cell E2 release. These results suggest that miR-764-3p functions to decrease steroidogenesis by targeting SF-1, at least in part, through inactivation of Cyp19a1. Taken together, our data provide mechanistic insights into the roles of miR-764-3p on E2 synthesis. Understanding of potential miRNAs affecting estrogen synthesis will help to diagnose and treat steroid-related diseases.

Transforming growth factor beta1 and aldosterone

PURPOSE OF REVIEW

It is well established that blocking the renin-angiotensin-aldosterone system (RAAS) is effective for the treatment of cardiovascular and renal complications in hypertension and diabetes mellitus. Although the induction of transforming growth factor beta1 (TGFbeta1) by components of the RAAS mediates the hypertrophic and fibrogenic changes in cardiovascular-renal complications, it is still controversial as to whether TGFbeta1 can be a target to prevent such complications. Here, we review recent findings on the role of TGFbeta1 in fluid homeostasis, focusing on the relationship with aldosterone.

RECENT FINDINGS

TGFbeta1 suppresses the adrenal production of aldosterone and renal tubular sodium reabsorption. We have generated mice with TGFbeta1 mRNA expression graded in five steps, from 10 to 300% of normal, and found that blood pressure and plasma volume are negatively regulated by TGFbeta1. Notably, the 10% hypomorph exhibits primary aldosteronism and sodium and water retention due to markedly impaired urinary excretion of water and electrolytes.

SUMMARY

These results identify TGFbeta signalling as an important counterregulatory system against aldosterone. Understanding the molecular mechanisms for the suppressive effects of TGFbeta1 on adrenocortical and renal function may further our understanding of primary aldosteronism, as well as assist in the development of novel therapeutic strategies for hypertension.

Fgfr2 is required for the expansion of the early adrenocortical primordium

The adrenal cortex is a critical steroidogenic endocrine tissue, generated at least in part from intermediate mesoderm of the anterior urogenital ridge. Previous work has pinpointed a minor role of the FGFR2IIIb isoform in expansion and differentiation of the fetal adrenal cortex in mice but did not address the complete role of FGFR2 and FGFR1 signaling in adrenocortical development. Here, we show that a Tbx18(cre) line mediates specific recombination in the coelomic epithelium of the anterior urogenital ridge which gives rise by a delamination process to the adrenocortical primordium. Mice with conditional (Tbx18(cre)-mediated) deletion of all isoforms of Fgfr2 exhibited severely hypoplastic adrenal glands around birth. Cortical cells were dramatically reduced in number but showed steroidogenic differentiation and zonation. Neuroendocrine chromaffin cells were also reduced and formed a cell cluster adjacent to but not encapsulated by steroidogenic cells. Analysis of earlier time points revealed that the adrenocortical primordium was established in the intermediate mesoderm at E10.5 but that it failed to expand at subsequent stages. Our further experiments show that FGFR2 signaling acts as early as E11.5 to prevent apoptosis and enhance proliferation in adrenocortical progenitor cells. FGFR1 signaling does not contribute to early adrenocortical development. Our work suggests that FGFR2IIIb and IIIc isoforms largely act redundantly to promote expansion of the adrenocortical primordium.

DAX-1 (NR0B1) and steroidogenic factor-1 (SF-1, NR5A1) in human disease

DAX-1 (NR0B1) and SF-1 (NR5A1) are two nuclear receptor transcription factors that play a key role in human adrenal and reproductive development. Loss of DAX-1 function is classically associated with X-linked adrenal hypoplasia congenita. This condition typically affects boys and presents as primary adrenal insufficiency in early infancy or childhood, hypogonadotropic hypogonadism at puberty and impaired spermatogenesis. Late onset forms of this condition and variant phenotypes are increasingly recognized. In contrast, disruption of SF-1 only rarely causes adrenal insufficiency, usually in combination with testicular dysgenesis. Variants in SF-1/NR5A1 more commonly cause a spectrum of reproductive phenotypes ranging from 46,XY DSD (partial testicular dysgenesis or reduced androgen production) and hypospadias to male factor infertility or primary ovarian insufficiency. Making a specific diagnosis of DAX-1 or SF-1 associated conditions is important for long-term monitoring of endocrine and reproductive function, appropriate genetic counselling for family members, and for providing appropriate informed support for young people.

SF-1 (NR5A1) expression is stimulated by the PKA pathway and is essential for the PKA-induced activation of LIPE expression in Y-1 cells

In the adrenal cortex, corticotropin induces the expression of several genes encoding proteins involved in the synthesis and intracellular transport of steroid hormones via the protein kinase A (PKA) signalling pathway, and this process is mediated by steroidogenic factor-1 (SF-1). This study was designed to elucidate the influence of the PKA and PKC pathways on the expression of the SF-1 gene in mouse adrenocortical cells, line Y-1. It has also been attempted to answer the question whether or not SF-1 plays a role in the PKA-induced expression of LIPE gene encoding hormone-sensitive lipase/cholesteryl esterase, which supplies cholesterol for steroid hormone synthesis. In this study, we found that stimulation of the PKA pathway caused a significant increase in SF-1 expression, and that this effect was abolished by the PKA inhibitor, H89. Decreased SF-1 gene transcript levels were seen with the simultaneous activation of PKA and PKC, suggesting a possible interaction between the PKA and PKC pathways. It was also observed that SF-1 increased the transcriptional activity of the LIPE gene by interacting with the SF-1 response element located in promoter A. Moreover, transient silencing of SF-1 expression with specific siRNAs abolished PKA-stimulated transcription of the LIPE gene, indicating that SF-1 is an important regulator of LIPE expression in Y-1 cells and thus could play a role in the regulation of the cholesterol supply for adrenal steroidogenesis.

Molecular aspects of development and regulation of endometriosis

Endometriosis is a common and painful condition affecting women of reproductive age. While the underlying pathophysiology is still largely unknown, much advancement has been made in understanding the progression of the disease. In recent years, a great deal of research has focused on non-invasive diagnostic tools, such as biomarkers, as well as identification of potential therapeutic targets. In this article, we will review the etiology and cellular mechanisms associated with endometriosis as well as the current diagnostic tools and therapies. We will then discuss the more recent genomic and proteomic studies and how these data may guide development of novel diagnostics and therapeutics. The current diagnostic tools are invasive and current therapies primarily treat the symptoms of endometriosis. Optimally, the advancement of "-omic" data will facilitate the development of non-invasive diagnostic biomarkers as well as therapeutics that target the pathophysiology of the disease and halt, or even reverse, progression. However, the amount of data generated by these types of studies is vast and bioinformatics analysis, such as we present here, will be critical to identification of appropriate targets for further study.

FOXL2 transcriptionally represses Sf1 expression by antagonizing WT1 during ovarian development in mice

Steroidogenic factor 1 (SF1; Ad4BP/NR5A1) plays key roles in gonadal development. Initially, the Sf1 gene is expressed in mouse fetal gonads of both sexes, but later is up-regulated in testes and down-regulated in ovaries. While Sf1 expression is activated and maintained by Wilms tumor 1 (WT1) and LIM homeobox 9 (LHX9), the mechanism of sex-specific regulation remains unclear. We hypothesized that Sf1 is repressed by the transcription factor Forkhead box L2 (FOXL2) during ovarian development. In an in vitro system (TM3 cells), up-regulation of Sf1 by the WT1 splice variant WT1-KTS was antagonized by FOXL2, as determined by quantitative RT-PCR. Using reporter assays, we localized the Sf1 proximal promoter region involved in this antagonism to a 674-bp interval. A conserved FOXL2 binding site was identified in this interval by in vitro chromatin immunoprecipitation. Introducing mutations into this site abolished negative regulation by FOXL2 in reporter assays. Finally, in Foxl2-null mice, Sf1 expression was increased 2-fold relative to wild-type XX fetal gonads. Our results support the hypothesis that FOXL2 negatively regulates Sf1 expression by antagonizing WT1-KTS during early ovarian development in mice.

The role of transforming growth factor β1 in the regulation of blood pressure

Although human association studies suggest a link between polymorphisms in the gene encoding transforming growth factor (TGF) β1 and differing blood pressure levels, a causative mechanism for this correlation remains elusive. Recently we have generated a series of mice with graded expression of TGFβ1, ranging from approximately 10% to 300% compared to normal. We have found that blood pressure and plasma volume are negatively regulated by TGFβ1. Of note, the 10% hypomorph exhibits primary aldosteronism and markedly impaired urinary excretion of water and electrolytes. We here review previous literature highlighting the importance of TGFβ signaling as a natriuretic system, which we postulate is a causative mechanism explaining how polymorphisms in TGFβ1 could influence blood pressure levels.

Fetal adrenal capsular cells serve as progenitor cells for steroidogenic and stromal adrenocortical cell lineages in M. musculus

The lineage relationships of fetal adrenal cells and adrenal capsular cells to the differentiated adrenal cortex are not fully understood. Existing data support a role for each cell type as a progenitor for cells of the adult cortex. This report reveals that subsets of capsular cells are descendants of fetal adrenocortical cells that once expressed Nr5a1. These fetal adrenocortical cell descendants within the adrenal capsule express Gli1, a known marker of progenitors of steroidogenic adrenal cells. The capsule is also populated by cells that express Tcf21, a known inhibitor of Nr5a1 gene expression. We demonstrate that Tcf21-expressing cells give rise to Nr5a1-expressing cells but only before capsular formation. After the capsule has formed, capsular Tcf21-expressing cells give rise only to non-steroidogenic stromal adrenocortical cells, which also express collagen 1a1, desmin and platelet-derived growth factor (alpha polypeptide) but not Nr5a1. These observations integrate prior observations that define two separate origins of adult adrenocortical steroidogenic cells (fetal adrenal cortex and/or the adrenal capsule). Thus, these observations predict a unique temporal and/or spatial role of adult cortical cells that arise directly from either fetal cortical cells or from fetal cortex-derived capsular cells. Last, the data uncover the mechanism by which two populations of fetal cells (fetal cortex derived Gli1-expressing cells and mesenchymal Tcf21-expressing mesenchymal cells) participate in the establishment of the homeostatic capsular progenitor cell niche of the adult cortex.

Methylation of a novel CpG island of intron 1 is associated with steroidogenic factor 1 expression in endometriotic stromal cells

Steroidogenic factor 1 (SF-1), a transcriptional factor essential for estrogen biosynthesis, is undetectable in endometrial stromal cells and aberrantly expressed in endometriotic stromal cells.

OBJECTIVE

We tried to gain further insight into the mechanism for differential SF-1 expression in endometrial and endometriotic stromal cells.

DESIGN

We had previously identified a novel CpG island in SF-1, which is located in the downstream intron 1 region. Here, we evaluated the methylation status of this CpG island.

PATIENTS

We obtained the eutopic endometrium from disease-free participants (n = 8) and the walls of cystic endometriosis lesions of the ovaries from another group of participants (n = 8). None of the patients had received any preoperative hormonal therapy.

INTERVENTIONS

Stromal cells were isolated from these 2 types of tissues and subjected to DNA bisulfite treatment and sequence analysis.

RESULTS

The SF-1 messenger RNA (mRNA) levels in endometriotic stromal cells were significantly higher than those in endometrial stromal cells. Bisulfite sequencing showed strikingly increased methylation of a 1-kbp region around the previously identified CpG island in endometriotic cells compared with endometrial cells (P < .001). A strong correlation between SF-1 mRNA levels and percentage methylation of the intron 1 region of the SF-1 gene was observed in endometriotic cells (Spearman correlation coefficient, .96; P < .001).

CONCLUSIONS

Methylation of the intron 1 region of the SF-1 gene is associated with its expression in endometriotic cells. This CpG island therefore plays an important role in regulating SF-1 expression.

Steroidogenic factor-1 and human disease

Steroidogenic factor-1 (SF-1) (Ad4BP, NR5A1) is a nuclear receptor that plays a key role in adrenal and reproductive development and function. Deletion of the gene encoding Sf-1 (Nr5a1) in mice results in severe developmental defects of the adrenal gland and gonad. Consequently, initial work on the potential effects of SF-1 disruption in humans focused on individuals with primary adrenal failure, a 46,XY karyotype, complete gonadal dysgenesis, and Müllerian structures. This is a rare phenotype, but has been reported on two occasions, because of alterations that affect key DNA-binding domains of SF-1. Attention then turned to a potential wider role of SF-1 in human adrenal and reproductive disorders. Although changes in SF-1 only very rarely cause isolated adrenal failure, it is emerging that variations in SF-1 are a surprisingly frequent cause of reproductive dysfunction in humans. In 46,XY disorders of sex development, a spectrum of phenotypes has been reported including severe and partial forms of gonadal (testicular) dysgenesis, hypospadias, anorchia with microphallus, and even male factor infertility. In 46,XX females, alterations in SF-1 are associated with primary ovarian insufficiency. Thus, SF-1 seems be a more significant factor in human reproductive health than was first envisioned, with implications for adults as well as children.

Wnt signaling in ovarian development inhibits Sf1 activation of Sox9 via the Tesco enhancer

Genome analysis of patients with disorders of sex development, and gain- and loss-of-function studies in mice indicate that gonadal development is regulated by opposing signals. In females, the Wnt/β-catenin canonical pathway blocks testicular differentiation by repressing the expression of the Sertoli cell-specific gene Sox9 by an unknown mechanism. Using cell and embryonic gonad culture models, we show that activation of the Wnt/β-catenin pathway inhibits the expression of Sox9 and Amh, whereas mRNA and protein levels of Sry and steroidogenic factor 1 (Sf1), two key transcriptional regulators of Sox9, are not altered. Ectopic activation of Wnt/β-catenin signaling in male gonads led to a loss of Sf1 binding to the Tesco enhancer and absent Sox9 expression that we also observed in wild-type ovaries. Moreover, ectopic Wnt/β-catenin signaling induced the expression of the female somatic cell markers, Bmp2 and Rspo1, as a likely consequence of Sox9 loss. Wnt/β-catenin signaling in XY gonads did not, however, affect gene expression of the steroidogenic Leydig cell Sf1 target gene, Cyp11a1, or Sf1 binding to the Cyp11a1 promoter. Our data support a model in ovary development whereby activation of β-catenin prevents Sf1 binding to the Sox9 enhancer, thereby inhibiting Sox9 expression and Sertoli cell differentiation.

Steroidogenic factor-1 is required for TGF-beta3-mediated 17beta-estradiol synthesis in mouse ovarian granulosa cells

The TGF-β superfamily members are indicated to play key roles in ovarian follicular development, such as granulosa cell proliferation, estrogens, and progesterone production. However, little is known about the roles of TGF-β3 in follicular development. In this study, we found that TGF-β3 was predominantly expressed in granulosa cells of mouse ovarian follicles, and it significantly promoted 17β-estradiol (E(2)) release in a dose-dependent manner. The orphan nuclear receptor steroidogenic factor-1 (SF-1) was required in TGF-β3-induced Cyp19a1 (a key rate-limiting enzyme for estrogen biosynthesis) expression and E(2) release. Additionally, TGF-β3 enhanced the binding of SF-1 to endogenous ovary-specific Cyp19a1 type II promoter, as evidenced by chromatin immunoprecipitation assays. The enhanced effect of SF-1 by TGF-β3 may be mediated through functional interactions between SF-1 and mothers against decapentaplegic homolog (Smad)3 (a mediator of TGF-β signaling pathway), because disruption of the interaction abolished the synergistic effects of SF-1, Smad3, and TGF-β3 on Cyp19a1 mRNA expression. RNA interference and chromatin immunoprecipitation studies also demonstrated that Smad3 was required for SF-1 binding to Cyp19a1 type II promoter and activation of Cyp19a1. Smad3 thus acts as a point of convergence that involves integration of SF-1 and TGF-β signaling in affecting E(2) production. Taken together, our data provide mechanistic insights into the roles of SF-1 in TGF-β3-mediated E(2) synthesis. Understanding of potential cross-points between extracellular signals affecting estrogen production will help to discover new therapeutic targets in estrogen-related diseases.

Aberrant DNA methylation status of endometriosis: epigenetics as the pathogenesis, biomarker and therapeutic target

Endometriosis, a common, benign, estrogen-dependent disease affecting 3-10% of women of reproductive age, is characterized by the ectopic growth of endometrial tissue that is found primarily in the peritoneum, ovaries and rectovaginal septum. Recently, endometriosis has been alternatively described as an immune disease, a genetic disease and a disease caused by exposure to environmental factors, in addition to its usual description as a hormonal disease. In addition, accumulating evidence suggests that various epigenetic aberrations play definite roles in the pathogenesis of endometriosis. Epigenetic alterations reported to date in endometriosis include the genomic DNA methylation of progesterone receptor-B, E-cadherin, homeobox A10, estrogen receptor-β, steroidogenic factor-1 and aromatase. Aberrant expression of DNA methyltransferases, which attach a methyl group to the 5-carbon position of cytosine bases in the CpG island of the promoter region and silence the corresponding gene expression, has also been demonstrated in endometriosis. This review summarizes the recent studies on the aberrant DNA methylation status and aberrant expression of DNA methyltransferases, which regulate DNA methylation, in endometriosis. We also discuss the recent information on the diagnostic and therapeutic implications of epigenetic alterations occurring in endometriosis.

Coactivation of SF-1-mediated transcription of steroidogenic enzymes by Ubc9 and PIAS1

Steroidogenic factor-1 (SF-1) is a nuclear orphan receptor, which is essential for adrenal development and regulation of steroidogenic enzyme expression. SF-1 is posttranslationally modified by small ubiquitin-related modifier-1 (SUMO-1), thus mostly resulting in attenuation of transcription. We investigated the role of sumoylation enzymes, Ubc9 and protein inhibitors of activated STAT1 (PIAS1), in SF-1-mediated transcription of steroidogenic enzyme genes in the adrenal cortex. Coimmunoprecipitation assays showed that both Ubc9 and PIAS1 interacted with SF-1. Transient transfection assays in adrenocortical H295R cells showed Ubc9 and PIAS1 potentiated SF-1-mediated transactivation of reporter constructs containing human CYP17, CYP11A1, and CYP11B1 but not CYP11B2 promoters. Reduction of endogenous Ubc9 and PIAS1 by introducing corresponding small interfering RNA significantly reduced endogenous CYP17, CYP11A1, and CYP11B1 mRNA levels, indicating that they normally function as coactivators of SF-1. Wild type and sumoylation-inactive mutants of Ubc9 and PIAS1 can similarly enhance the SF-1-mediated transactivation of the CYP17 gene, indicating that the coactivation potency of Ubc9 and PIAS1 is independent of sumoylation activity. Chromatin immunoprecipitation assays demonstrated that SF-1, Ubc9, and PIAS1 were recruited to an endogenous CYP17 gene promoter in the context of chromatin in vivo. Immunohistochemistry and Western blotting showed that SF-1, Ubc9, and PIAS1 were expressed in the nuclei of the human adrenal cortex. In cortisol-producing adenomas, the expression pattern of SF-1 and Ubc9 were markedly increased, whereas that of PIAS1 was decreased compared with adjacent normal adrenals. These results showed the physiological roles of Ubc9 and PIAS1 as SF-1 coactivators beyond sumoylation enzymes in adrenocortical steroidogenesis and suggested their possible pathophysiological roles in human cortisol-producing adenomas.

Steroidogenic factor-1 (SF-1, NR5A1) and human disease

Steroidogenic factor-1 (SF-1, Ad4BP, encoded by NR5A1) is a key regulator of adrenal and reproductive development and function. Based upon the features found in Nr5a1 null mice, initial attempts to identify SF-1 changes in humans focused on those rare individuals with primary adrenal failure, a 46,XY karyotype, complete gonadal dysgenesis and Müllerian structures. Although alterations affecting DNA-binding of SF-1 were found in two such cases, disruption of SF-1 is not commonly found in patients with adrenal failure. In contrast, it is emerging that variations in SF-1 can be found in association with a range of human reproductive phenotypes such as 46,XY disorders of sex development (DSD), hypospadias, anorchia, male factor infertility, or primary ovarian insufficiency in women. Overexpression or overactivity of SF-1 is also reported in some adrenal tumors or endometriosis. Therefore, the clinical spectrum of phenotypes associated with variations in SF-1 is expanding and the importance of this nuclear receptor in human endocrine disease is now firmly established.

Diverse functions of Hedgehog signaling in formation and physiology of steroidogenic organs

Adrenal, testis, and ovary are steroidogenic organs derived from a common primordium that consists of steroidogenic factor 1 (SF1)-positive precursor cells. SF1 not only defines the steroidogenic lineages in these organs but also controls their differentiation. Recent evidence implicates the Hedgehog (Hh) signaling pathway as a downstream regulator of SF1 in the appearance of steroidogenic cells in these organs. The Hh signaling pathway serves as a common crosstalk component, yet has evolved diverse functions in the expansion and differentiation of the steroidogenic cells in a tissue-specific manner. The purpose of this review is to compare and contrast the different roles of Hh signaling in these three organs during development.

Nuclear receptors in Leydig cell gene expression and function

Several signals, such as hormones and signaling molecules, have been identified as important regulators of Leydig cell differentiation and function. Conveying these signals and translating them into a genomic response to ensure an accurate physiological output requires the action of a network of transcription factors, including those belonging to the nuclear receptor superfamily. Nuclear receptors regulate expression of genes important for growth, differentiation, development, and homeostasis. Several nuclear receptors, such as steroid hormone receptors (NR3A and NR3C families), are activated upon ligand binding, whereas others, including members of the NR2C, NR2F, and NR4A families, either do not require a ligand or ligands have yet to be identified. Several nuclear receptors (e.g., NR2F2 and NR5A1) have been shown to play essential roles in Leydig cells, whereas for others (e.g., NR2B1 and NR4A1), the assessment of their function has been precluded by the early embryonic lethality associated with null mice or by redundancy mechanisms by other family members. This is now being overcome with the generation of novel approaches, including Leydig cell-specific knockout models. This review provides an overview of the nuclear receptor family of transcription factors as they relate to Leydig cell gene expression and function.

Minireview: Nuclear receptor-controlled steroid hormone synthesis and metabolism

Steroid hormones are essential in normal physiology whereas disruptions in hormonal homeostasis represent an important etiological factor for many human diseases. Steroid hormones exert most of their functions through the binding and activation of nuclear hormone receptors (NRs or NHRs), a superfamily of DNA-binding and often ligand-dependent transcription factors. In recent years, accumulating evidence has suggested that NRs can also regulate the biosynthesis and metabolism of steroid hormones. This review will focus on the recent progress in our understanding of the regulatory role of NRs in hormonal homeostasis and the implications of this regulation in physiology and diseases.

Steroidogenic factor-1 (SF-1, Ad4BP, NR5A1) and disorders of testis development

Steroidogenic factor-1 (SF-1) (Ad4BP, NR5A1) is a nuclear receptor that regulates many aspects of adrenal and reproductive development and function. Consequently, deletion of the gene (Nr5a1) encoding Sf-1 in XY mice results in impaired adrenal development, complete testicular dysgenesis with Mullerian structures, and female external genitalia. Initial efforts to identify NR5A1 changes in humans focused on 46,XY individuals with combined adrenogonadal failure and Mullerian structures. Although this combination of clinical features is rare, 2 such patients harboring NR5A1 mutations have been described within the past decade. More recently, however, it has emerged that heterozygous loss of function mutations in NR5A1 can be found relatively frequently in children and adults with 46,XY disorders of sex development (DSD) but with apparently normal adrenal function. The phenotypic spectrum associated with these changes ranges from complete testicular dysgenesis with Mullerian structures, through individuals with mild clitoromegaly or genital ambiguity, to severe penoscrotal hypospadias or even anorchia. Furthermore, a non-synonymous polymorphism in NR5A1 may be associated with micropenis or undescended testes within the population. Taken together, these reports suggest that variable loss of SF-1 function can be associated with a wide range of reproductive phenotypes in humans.

A novel mutation in the accessory DNA-binding domain of human steroidogenic factor 1 causes XY gonadal dysgenesis without adrenal insufficiency

OBJECTIVE

Steroidogenic factor 1 (SF1), officially designated NR5A1, is a nuclear receptor that plays key roles in endocrine development and function. Previous reports of human SF1 mutations revealed a spectrum of phenotypes affecting adrenal function and/or gonadal development and sex differentiation. We present the clinical phenotype and functional effects of a novel SF1 mutation.

PATIENT

The patient is a 22-year-old 46, XY Japanese patient who presented with dysgenetic testes, atrophic vasa deferentia and epididymides, lack of Müllerian structures, and clitoromegaly. Endocrine studies revealed normal adrenal function.

RESULTS

Analysis of the SF1 gene revealed compound heterozygosity for a previously described p.G146A polymorphism and a novel missense mutation (p.R84C) in the accessory DNA-binding domain. The father carried the p.G146A polymorphism and the mother had the p.R84C mutation; both were clinically and reproductively normal. Functional studies demonstrated that the p.R84C SF1 had normal nuclear localization but decreased DNA-binding affinity and transcriptional activity compared with wild-type SF1; it did not exhibit any dominant negative activity.

CONCLUSIONS

These results describe the human phenotype that results from compound heterozygosity of the p.G146A polymorphism and a novel p.R84C mutation of SF1, thereby extending the spectrum of human SF1 mutations that impair testis development and sex differentiation in a sex-limited manner while preserving normal adrenal function.

Transcriptional activation of steroidogenic factor-1 by hypomethylation of the 5' CpG island in endometriosis

CONTEXT

Endometriosis is an estrogen-dependent disease. Steroidogenic factor-1 (SF-1), a transcriptional factor essential for activation of multiple steroidogenic genes for estrogen biosynthesis, is undetectable in normal endometrial stromal cells and aberrantly expressed in endometriotic stromal cells.

OBJECTIVE

The objective of the study was to unravel the mechanism for differential SF-1 expression in endometrial and endometriotic stromal cells.

DESIGN

We identified a CpG island flanking the SF-1 promoter and exon I region and determined its methylation patterns in endometrial and endometriotic cells.

SETTING

The study was conducted at Northwestern University.

PATIENTS OR OTHER PARTICIPANTS

Eutopic endometrium from disease-free subjects (n = 8) and the walls of cystic endometriosis lesions of the ovaries (n = 8) were investigated.

INTERVENTION(S)

Stromal cells were isolated from these two types of tissues.

MAIN OUTCOME MEASURE(S)

Measures are mentioned in Results.

RESULTS

SF-1 mRNA and protein levels in endometriotic stromal cells were significantly higher than those in endometrial stromal cells (P < 0.001). Bisulfite sequencing showed strikingly increased methylation in endometrial cells, compared with endometriotic cells (P < 0.001). Demethylation by 5-aza-2'-deoxycytidine increased SF-1 mRNA levels by up to 55.48-fold in endometrial cell (P < 0.05). Luciferase assays showed that the -85/+239 region bearing the CpG island regulated its activity (P < 0.01). Natural or in vitro methylation of this region strikingly reduced SF-1 promoter activity in both cell types (P < 0.01). Chromatin immunoprecipitation assay showed that methyl-CpG-binding domain protein 2 binds to the SF-1 promoter in endometrial but not endometriotic cells.

CONCLUSIONS

This is the first demonstration of methylation-dependent regulation of SF-1 in any mammalian tissue. These findings point to a new mechanism for targeting local estrogen biosynthesis in endometriosis.

Adrenocorticotropic Hormone-Mediated Signaling Cascades Coordinate a Cyclic Pattern of Steroidogenic Factor 1-Dependent Transcriptional Activation

Steroidogenic factor 1 (SF-1) is an orphan nuclear receptor that has emerged as a critical mediator of endocrine function at multiple levels of the hypothalamic-pituitary-steroidogenic axis. Within the adrenal cortex, ACTH-dependent transcriptional responses, including transcriptional activation of several key steroidogenic enzymes within the steroid biosynthetic pathway, are largely dependent upon SF-1 action. The absence of a bona fide endogenous eukaryotic ligand for SF-1 suggests that signaling pathway activation downstream of the melanocortin 2 receptor (Mc2r) modulates this transcriptional response. We have used the chromatin immunoprecipitation assay to examine the temporal formation of ACTH-dependent transcription complexes on the Mc2r gene promoter. In parallel, ACTH-dependent signaling events were examined in an attempt to correlate transcriptional events with the upstream activation of signaling pathways. Our results demonstrate that ACTH-dependent signaling cascades modulate the temporal dynamics of SF-1-dependent complex assembly on the Mc2r promoter. Strikingly, the pattern of SF-1 recruitment and the subsequent attainment of active rounds of transcription support a kinetic model of SF-1 transcriptional activation, a model originally established in the context of ligand-dependent transcription by several classical nuclear hormone receptors. An assessment of the major ACTH-dependent signaling pathways highlights pivotal roles for the MAPK as well as the cAMP-dependent protein kinase A pathway in the entrainment of SF-1-mediated transcriptional events. In addition, the current study demonstrates that specific enzymatic activities are capable of regulating distinct facets of a highly ordered transcriptional response.

Expression analysis of the steroidogenic acute regulatory protein (STAR) gene in developing porcine conceptuses

Steroidogenesis in porcine non-conceptus tissue is regulated by the STAR-dependent transport of cholesterol from the outer to inner mitochondrial membrane. Previous serial analysis of gene expression (SAGE) identified a STAR mRNA transcript in the porcine peri-implantation conceptus during trophectoderm elongation and increased conceptus estrogen synthesis between gestational day 11 and 12. To assess a potential role for STAR in the modulation of conceptus steroidogenesis via cholesterol transport, the conceptus STAR transcript was PCR cloned and temporal expression of mRNA and protein were examined. Northern analysis of day 12 corpora lutea and pig conceptus RNA detected multiple STAR transcripts in both tissues and identified the cloned transcript as the longest variant. The transcript had a 99% similarity to a truncated ovarian STAR transcript. The conceptus STAR transcript was temporally regulated during elongation but trace expression was present in day 6 blastocysts and day 25 conceptuses. Differential regulation of STAR mRNA was concomitant with the presence of the stimulatory transcription factor steroidogenic factor 1, and absence of the inhibitory transcription factor dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1, transcripts. In contrast to peak STAR mRNA expression at the filamentous stage, Western blot analyses revealed STAR protein levels were highest in tubular conceptuses. These data confirm the presence of STAR mRNA and protein during porcine conceptus elongation and suggest regulation of STAR at two levels, transcriptionally, in part, through differential regulation of transcription factors, and post-transcriptionally, evidenced by the disparity of protein to RNA in filamentous conceptuses.

Binding Sites for Transcription Factor SF-1 in Promoter Regions of Genes Encoding Mouse Steroidogenesis Enzymes 3βHSDI and P450c17

Using gel retardation of DNA samples and specific antibodies, binding sites for the transcription factor SF-1 were found in positions -53/-44 and -285/-270 in the promoter region of the mouse Cyp17 gene and in position -117/-108 of the promoter region of the mouse 3betaHSDI gene.

New insights into the regulation of mammalian sex determination and male sex differentiation

In mammals, sex development is a genetically and hormonally controlled process that begins with the establishment of chromosomal or genetic sex (XY or XX) at conception. At approximately 6 to 7 weeks of human gestation or embryonic day e11.5 in the mouse, expression of the Y chromosome-linked sex determining gene called SRY (described in detail in this chapter) then initiates gonadal differentiation, which is the formation of either a testis (male) or an ovary (female). Male sex differentiation (development of internal and external reproductive organs and acquisition of male secondary sex characteristics) is then controlled by three principal hormones produced by the testis: Mullerian inhibiting substance (MIS) or anti-Mullerian hormone (AMH), testosterone, and insulin-like factor 3 (INSL3). In the absence of these critical testicular hormones, female sex differentiation ensues. This sequential, three-step process of mammalian sex development is also known as the Jost paradigm. With the advent of modern biotechnologies over the past decade, such as transgenics, array-based gene profiling, and proteomics, the field of mammalian sex determination has witnessed a remarkable boost in the understanding of the genetics and complex molecular mechanisms that regulate this fundamental biological event. Consequently, a number of excellent reviews have been devoted to this topic. The purpose of the present chapter is to provide an overview of selected aspects of mammalian sex determination and differentiation with an emphasis on studies that have marked this field of study.