DAX1: Increasing complexity in the roles of this novel nuclear receptor

An Update on the Genetic Drivers of Corticotroph Tumorigenesis

The genetic landscape of corticotroph tumours of the pituitary gland has dramatically changed over the last 10 years. Somatic changes in the USP8 gene account for the most common genetic defect in corticotrophinomas, especially in females, while variants in TP53 or ATRX are associated with a subset of aggressive tumours. Germline defects have also been identified in patients with Cushing's disease: some are well-established (MEN1, CDKN1B, DICER1), while others are rare and could represent coincidences. In this review, we summarise the current knowledge on the genetic drivers of corticotroph tumorigenesis, their molecular consequences, and their impact on the clinical presentation and prognosis.

A Novel Look at Dosage-Sensitive Sex Locus Xp21.2 in a Case of 46,XY Partial Gonadal Dysgenesis without NR0B1 Duplication

A region of 160 kb at Xp21.2 has been defined as dosage-sensitive sex reversal (DSS) and includes the NR0B1 gene, considered to be the candidate gene involved in XY gonadal dysgenesis if overexpressed. We describe a girl with 46,XY partial gonadal dysgenesis carrying a 297 kb duplication at Xp21.2 upstream of NR0B1 initially detected by chromosomal microarray analysis. Fine mapping of the breakpoints by whole-genome sequencing showed a tandem duplication of TASL (CXorf21), GK and partially TAB3, upstream of NR0B1. This is the first description of an Xp21.2 duplication upstream of NR0B1 associated with 46,XY partial gonadal dysgenesis.

Inhibition of NR5A1 phosphorylation alleviates a transcriptional suppression defect caused by a novel NR0B1 mutation

Context

Mutations in the NR0B1 gene, also well-known as the DAX1 gene, are known to cause congenital adrenal hypoplasia associated with hypogonadotropic hypogonadism. The abnormal NR0B1 protein fails to suppress the transcription of promoters of steroidogenic enzymes, which are also targets of NR5A1 protein, also well-known as Ad4BP/SF-1 protein. Since NR5A1 and NR0B1 have antagonistic effects on steroidogenesis, the loss of function due to NR0B1 mutations may be compensated by inducing loss of function of NR5A1 protein.

Patient

A middle-aged man was diagnosed with congenital adrenal hypoplasia associated with hypogonadotropic hypogonadism and genetic analysis revealed him to have a novel NR0B1 mutation, c.1222C>T(p.Gln408Ter).

Methods

NR0B1 activity was evaluated in CLK1/4 inhibitor-treated 293T cells via immunoblotting and luciferase assays of the STAR promoter.

Results

TG003 treatment suppressed NR5A1 protein function to compensate for the mutant NR0B1 showing inhibited suppression of transcription. Immunoblotting analyses showed that the phosphorylation status of NR5A1 at Ser203 was attenuated by the CLK1/4 inhibitor.

Conclusion

The specific reduction of NR5A1 phosphorylation by a CLK1/4 inhibitor may alleviate developmental defects in patients with NR0B1 mutations.

46,XX DSD: Developmental, Clinical and Genetic Aspects

Differences in sex development (DSD) in patients with 46,XX karyotype occur by foetal or postnatal exposure to an increased amount of androgens. These disorders are usually diagnosed at birth, in newborns with abnormal genitalia, or later, due to postnatal virilization, usually at puberty. Proper diagnosis and therapy are mostly based on the knowledge of normal development and molecular etiopathogenesis of the gonadal and adrenal structures. This review aims to describe the most relevant data that are correlated with the normal and abnormal development of adrenal and gonadal structures in direct correlation with their utility in clinical practice, mainly in patients with 46,XX karyotype. We described the prenatal development of structures together with the main molecules and pathways that are involved in sex development. The second part of the review described the physical, imaging, hormonal and genetic evaluation in a patient with a disorder of sex development, insisting more on patients with 46,XX karyotype. Further, 95% of the etiology in 46,XX patients with disorders of sex development is due to congenital adrenal hyperplasia, by enzyme deficiencies that are involved in the hormonal synthesis pathway. The other cases are explained by genetic abnormalities that are involved in the development of the genital system. The phenotypic variability is very important in 46,XX disorders of sex development and the knowledge of each sign, even the most discreet, which could reveal such disorders, mainly in the neonatal period, could influence the evolution, prognosis and life quality long term.

FXRα modulates leydig cell endocrine function in mouse

The hypothalamic-pituitary axis exert a major control over endocrine and exocrine testicular functions. The hypothalamic-pituitary axis corresponds to a cascade with the Gonadotropin Releasing Hormone secreted by the hypothalamus, which stimulates the synthesis and the release of Luteinizing Hormone (LH) and Follicle Stimulating Hormone by the gonadotropic cells of the anterior pituitary. The LH signaling pathway controls the steroidogenic activity of the Leydig cells via the activation of the luteinizing hormone/choriogonadotropin receptor. In order to avoid a runaway system, sex steroids exert a negative feedback within hypothalamus and pituitary. Testicular steroidogenesis is locally controlled within Leydig cells. The present work reviews some local regulations of steroidogenesis within the Leydig cells focusing mainly on the roles of the Farnesoid-X-Receptor-alpha and its interactions with several orphan members of the nuclear receptor superfamily. Further studies are required to reinforce our knowledge of the regulation of testicular endocrine function, which is necessary to ensure a better understanding of fertility disorders and then proposed an adequate treatment of the diseases.

Retinoic Acid Antagonizes Testis Development in Mice

Mammalian sex determination depends on a complex interplay of signals that promote the bipotential fetal gonad to develop as either a testis or an ovary, but the details are incompletely understood. Here, we investigated whether removal of the signaling molecule retinoic acid (RA) by the degradative enzyme CYP26B1 is necessary for proper development of somatic cells of the testes. Gonadal organ culture experiments suggested that RA promotes expression of some ovarian markers and suppresses expression of some testicular markers, acting downstream of Sox9. XY Cyp26b1-null embryos, in which endogenous RA is not degraded, develop mild ovotestes, but more important, steroidogenesis is impaired and the reproductive tract feminized. Experiments involving purified gonadal cells showed that these effects are independent of germ cells and suggest the direct involvement of the orphan nuclear receptor DAX1. Our results reveal that active removal of endogenous RA is required for normal testis development in the mouse.

Cloning, characterization and function analysis of DAX1 in Chinese loach (Paramisgurnus dabryanus)

The mechanisms of sex determination and differentiation have not been elucidated in most fish species. In this study, the full-length cDNAs of DAX1 was cloned and characterized in aquaculture fish Chinese loach (Paramisgurnus dabryanus), designated as Pd-DAX1. The cDNA sequence of Pd-DAX1 was 1261 bp, including 795 bp open reading frame (ORF) encoding 264 amino acids. Pd-DAX1 shares highly identical sequence with DAX1 homologues from different species. The expression profiles of Pd-DAX1 in different developmental stages and diverse adult tissues were analyzed by quantitative real-time RT-PCR and in situ hybridization (ISH). Pd-DAX1 was continuously expressed during embryogenesis, with the extensive distribution in the development of the central nervous system. Tissue distribution analysis revealed that Pd-DAX1 expressed widely in adult tissues, with the highest expression level found in testis, moderate level in ovary, showing a sex-dimorphic expression pattern. Pd-DAX1 mainly located in spermatogonia cells, spermatocytes, primary oocytes and previtellogenic oocyte cells, implying that Pd-DAX1 may involve in gametogenesis. These preliminary findings suggest that Pd-DAX1 gene is highly conserved during vertebrate evolution and involved in a wide range of developmental processes including embryogenesis, central nervous system development and gonad development.

Genetics of Cushing's Syndrome

The knowledge on the molecular and genetic causes of Cushing's syndrome (CS) has greatly increased in the recent years. Somatic mutations leading to overactive 3',5'-cyclic adenosine monophosphate/protein kinase A and wingless-type MMTV integration site family/beta-catenin pathways are the main molecular mechanisms underlying adrenocortical tumorigenesis. Corticotropinomas are characterized by resistance to glucocorticoid negative feedback, impaired cell cycle control and overexpression of pathways sustaining ACTH secretion. Recognizing the genetic defects behind corticotroph and adrenocortical tumorigenesis proves crucial for tailoring the clinical management of CS patients and for designing strategies for genetic counseling and clinical screening to be applied in routine medical practice.

DAX1 promotes cervical cancer cell growth and tumorigenicity through activation of Wnt/β-catenin pathway via GSK3β

DAX1 is well known for its fundamental role in several types of cancer, while its biological role in cervical cancer remains largely unexplored. The expression of DAX1 in cervical carcinoma tissue was examined using immunohistochemistry and western blot. The effects of DAX1 silencing on the cell growth, tumor formation, and CSC (cancer stem cell) characteristics were also investigated. DAX1 expressed a gradual increase from normal cervix to high-grade squamous intraepithelial lesions, and consequently to cervical cancer. Silence of DAX1 significantly inhibited the cell growth, tumorigenicity, and tumorsphere formation. Furthermore, the TOP/FOP-Flash reporter assay revealed that Wnt/β-catenin pathway was significantly inactivated in DAX1-silenced cervical cancer cells with the downregulation of Wnt/β-catenin targeting genes, including cyclinD1 and c-myc. Moreover, dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assay confirmed that DAX1 transcriptionally repressed glycogen synthase kinase 3β (GSK3β), an inhibitor of the Wnt/β-catenin pathway, by physically interacting with -666~-444 motif on the GSK3β promoter. Additionally, the blockage of GSK3β by CHIR-99021 resulted in a significant increase of CSC characteristics induced by the silence of DAX1. Our data demonstrated that DAX1 is overexpressed in cervical cancer, and that it promotes cell growth and tumorigenicity through activating Wnt/β-catenin pathway mediated by GSK3β.

Single-Nucleotide Variations of the Human Nuclear Hormone Receptor Genes in 60,000 Individuals

Nuclear hormone receptors (NRs) mediate biologic actions of lipophilic molecules to gene transcription and are phylogenetically and functionally categorized into seven subfamilies and three groups, respectively. Single-nucleotide variations (SNVs) or polymorphisms are genetic changes influencing individual response to environmental factors and susceptibility to various disorders, and are part of the genetic diversification and basis for evolution. We sorted out SNVs of the human NR genes from 60,706 individuals, calculated three parameters (percentage of all variants, percentage of loss-of-function variants, and ratio of nonsynonymous/synonymous variants in their full protein-coding or major domain-coding sequences), and compared them with several valuables. Comparison of these parameters between NRs and control groups identified that NRs form a highly conserved gene family. The three parameters for the full coding sequence are positively correlated with each other, whereas four NR genes are distinct from the others with much higher tolerance to protein sequence-changing variants. DNA-binding domain and N-terminal domain are respectively those bearing the least and the most variation. NR subfamilies based on their phylogenetic proximity or functionality as well as diversity of tissue distribution and numbers of partner molecules are all not correlated with the variation parameters, whereas their gene age demonstrates an association. Our results suggest that the natural selection driving the NR family evolution still operates in humans. Gene age and probably the potential to adapt to various new ligands, but not current functional diversity, are major determinants for SNVs of the human NR genes.

Complex Glycerol Kinase Deficiency and Adrenocortical Insufficiency in Two Neonates

Contiguous gene deletions of chromosome Xp21 can lead to glycerol kinase deficiency and severe adrenocortical insufficiency (AI) in a male newborn among other problems. We describe our experience with two such patients who presented with dysmorphic facies, AI, and pseudo-hypertriglyceridemia. Both infants had normal serum 17-hidroxyprogesterone levels, and adrenal glands could not be observed with ultrasonography. Creatine kinase and triglyceride levels were measured to elucidate the etiology of adrenal hypoplasia and were above normal limits in both cases. Both patients required steroid and salt supplementation. They were both found to have Xp21.2 deletions (DMD, NR0B1, GK, IL1RAPL1). We conclude that AI in the context of other genetic abnormalities should prompt chromosomal investigations in the absence of another unifying explanation.

Molecular cloning and characterization of amh and dax1 genes and their expression during sex inversion in rice-field eel Monopterus albus

The full-length cDNAs of amh and dax1 in the hermaphrodite, rice-field eel (Monopterus albus), were cloned and characterized in this study. Multiple sequence alignment revealed Dax1 was well conserved among vertebrates, whereas Amh had a low degree of similarity between different vertebrates. Their expression profiles in gonads during the course of sex inversion and tissues were investigated. The tissue distribution indicated amh was expressed mostly in gonads and was scarcely detectable in other tissues, whereas the expression of dax1 was widespread among the different tissues, especially liver and gonads. amh was scarcely detectable in ovaries whereas it was abundantly expressed in both ovotestis and testis. By contrast, dax1 was highly expressed in ovaries, especially in ♀IV (ovaries in IV stage), but it was decreased significantly in ♀/♂I (ovotestis in I stage). Its expression was increased again in ♀/♂III (ovotestis in III stage), and then decreased to a low level in testis. These significant different expression patterns of amh and dax1 suggest the increase of amh expression and the decline of dax1 expression are important for the activation of testis development, and the high level of amh and a low level of dax1 expression are necessary for maintenance of testis function.

Aetiological coding sequence variants in non-syndromic premature ovarian failure: From genetic linkage analysis to next generation sequencing

Premature ovarian failure (POF) is a frequent pathology affecting 1-1.5% of women under 40 years old. Despite advances in diagnosing and treating human infertility, POF is still classified as being idiopathic in 50-80% of cases, strongly suggesting a genetic origin for the disease. Different types of autosomal and X-linked genetic anomalies can originate the phenotype in syndromic and non-syndromic POF cases. Particular interest has been focused on research into non-syndromic POF causative coding variants during the past two decades. This has been based on the assumption that amino acid substitutions might modify the intrinsic physicochemical properties of functional proteins, thereby inducing pathological phenotypes. In this case, a restricted number of mutations might originate the disease. However, like other complex pathologies, POF might result from synergistic/compensatory effects caused by several low-to-mildly drastic mutations which have frequently been classified as non-functional SNPs. Indeed, reproductive phenotypes can be considered as quantitative traits resulting from the subtle interaction of many genes. Although numerous sequencing projects have involved candidate genes, only a few coding mutations explaining a low percentage of cases have been described. Such apparent failure to identify aetiological coding sequence variations might have been due to the inherent molecular complexity of mammalian reproduction and to the difficulty of simultaneously analysing large genomic regions by Sanger sequencing. The purpose of this review is to present the molecular and cellular effects caused by non-synonymous mutations which have been formally associated, by functional tests, with the aetiology of hypergonadotropic non-syndromic POF. Considerations have also been included regarding the polygenic nature of reproduction and POF, as well as future approaches for identifying novel aetiological genes based on next generation sequencing (NGS).

Orphan nuclear receptors as drug targets for the treatment of prostate and breast cancers

Nuclear receptors (NRs), a family of 48 transcriptional factors, have been studied intensively for their roles in cancer development and progression. The presence of distinctive ligand binding sites capable of interacting with small molecules has made NRs attractive targets for developing cancer therapeutics. In particular, a number of drugs have been developed over the years to target human androgen- and estrogen receptors for the treatment of prostate cancer and breast cancer. In contrast, orphan nuclear receptors (ONRs), which in many cases lack known biological functions or ligands, are still largely under investigated. This review is a summary on ONRs that have been implicated in prostate and breast cancers, specifically retinoic acid-receptor-related orphan receptors (RORs), liver X receptors (LXRs), chicken ovalbumin upstream promoter transcription factors (COUP-TFs), estrogen related receptors (ERRs), nerve growth factor 1B-like receptors, and ‘‘dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1’’ (DAX1). Discovery and development of small molecules that can bind at various functional sites on these ONRs will help determine their biological functions. In addition, these molecules have the potential to act as prototypes for future drug development. Ultimately, the therapeutic value of targeting the ONRs may go well beyond prostate and breast cancers.

Lhx4 deficiency: increased cyclin-dependent kinase inhibitor expression and pituitary hypoplasia

Defects in the Lhx4, Lhx3, and Pitx2 genes can cause combined pituitary hormone deficiency and pituitary hypoplasia in both humans and mice. Not much is known about the mechanism underlying hypoplasia in these mutants beyond generally increased cell death and poorly maintained proliferation. We identified both common and unique abnormalities in developmental regulation of key cell cycle regulator gene expression in each of these three mutants. All three mutants exhibit reduced expression of the proliferative marker Ki67 and the transitional marker p57. We discovered that expression of the cyclin-dependent kinase inhibitor 1a (Cdkn1a or p21) is expanded dorsally in the pituitary primordium of both Lhx3 and Lhx4 mutants. Uniquely, Lhx4 mutants exhibit reduced cyclin D1 expression and have auxiliary pouch-like structures. We show evidence for indirect and direct effects of LHX4 on p21 expression in αT3-1 pituitary cells. In summary, Lhx4 is necessary for efficient pituitary progenitor cell proliferation and restriction of p21 expression.

microRNA-181 promotes prostate cancer cell proliferation by regulating DAX-1 expression

microRNAs (miRNAs) are a class of short noncoding RNA molecules that have a critical role in the initiation and progression of types of human cancer, including prostate cancer. In the present study, the expression of miR-181 in prostate cancer tissues was evaluated and was demonstrated to be significantly upregulated in prostate cancer tissues compared with that in adjacent normal tissues. The results of in vitro MTT and BrdU incorporation assays, as well as cell-cycle analysis, indicated that miR-181 overexpression markedly promoted the proliferation of LNCaP cells. Furthermore, miR-181 overexpression was found to promote the progression of LNCaP tumor growth in nude mice. Mechanistic studies demonstrated that dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 (DAX-1), a negative regulator of androgen receptor in prostate cancer, was inhibited by miR-181 overexpression. Therefore, the results from the present study suggest that miR-181 functions as a growth-suppressive miRNA during prostate cancer development.

MicroRNA-561 promotes acetaminophen-induced hepatotoxicity in HepG2 cells and primary human hepatocytes through downregulation of the nuclear receptor corepressor dosage-sensitive sex-reversal adrenal hypoplasia congenital critical region on the X chromosome, gene 1 (DAX-1)

One of the major mechanisms involved in acetaminophen (APAP)-induced hepatotoxicity is hepatocyte nuclear factor 4α (HNF4α)-mediated activation of pregnane X receptor (PXR) and constitutive androstane receptor (CAR). In the present study, we investigated the role of miR-561 and its target gene DAX-1 encoding a corepressor of HNF4α in the process of APAP-induced hepatotoxicity. We used both human hepatocellular liver carcinoma cell line (HepG2) cells and primary human hepatocytes in this study and monitored the levels of reactive oxygen species, lactate dehydrogenase, and glutathione. Our bioinformatics study suggests an association between miR-561 and DAX-1, but not HNF4α. Treatment of HepG2 cells with APAP significantly reduced the expression of DAX-1 in a concentration-dependent manner. miR-561 was induced by APAP treatment in HepG2 cells. Transfection of HepG2 cells with an miR-561 mimic exacerbated APAP-induced hepatotoxicity. HNF4α is physically associated with DAX-1 in HepG2 cells. A decreased protein level of DAX-1 by APAP treatment was also enhanced by miR-561 mimic transfection in HepG2 cells and primary human hepatocytes. The basal and APAP-induced expression of PXR and CAR was enhanced by miR-561 mimic transfection; however, transfection of HepG2 cells or primary human hepatocytes with a miR-561 inhibitor or DAX-1 small interfering RNA reversed these effects. Additionally, the chromatin immunoprecipitation assay revealed that recruitment of DAX-1 onto the PXR promoter was inversely correlated with the recruitment of peroxisome proliferator-activated receptor-α coactivator-1α and HNF4α on APAP treatment. These results indicate that miR-561 worsens APAP-induced hepatotoxicity via inhibition of DAX-1 and consequent transactivation of nuclear receptors.

Therapy of adrenal insufficiency: an update

Adrenal insufficiency may be caused by the destruction or altered function of the adrenal gland with a primary deficit in cortisol secretion (primary adrenal insufficiency) or by hypothalamic-pituitary pathologies determining a deficit of ACTH (secondary adrenal insufficiency). The clinical picture is determined by the glucocorticoid deficit, which may in some conditions be accompanied by a deficit of mineralcorticoids and adrenal androgens. The substitutive treatment is aimed at reducing the signs and symptoms of the disease as well as at preventing the development of an addisonian crisis, a clinical emergency characterized by hypovolemic shock. The oral substitutive treatment should attempt at mimicking the normal circadian profile of cortisol secretion, by using the lower possible doses able to guarantee an adequate quality of life to patients. The currently available hydrocortisone or cortisone acetate preparations do not allow an accurate reproduction of the physiological secretion pattern of cortisol. A novel dual-release formulation of hydrocortisone, recently approved by EMEA, represents an advancement in the optimization of the clinical management of patients with adrenal insufficiency. Future clinical trials of immunomodulation or immunoprevention will test the possibility to delay (or prevent) the autoimmune destruction of the adrenal gland in autoimmune Addison's disease.

Molecular cloning and characterization of amh, dax1 and cyp19a1a genes and their response to 17α-methyltestosterone in Pengze crucian carp

The proteins encoded by amh, dax1 and cyp19a1a play important roles in gonad differentiation. Their functions have been far less studied in teleosts. In this study, the full-length cDNAs of amh, dax1 and cyp19a1a were cloned and characterized in a triploid gynogenic fish, the Pengze crucian carp. Their expression profilings in juvenile development, adult tissues and juveniles exposed to 100 ng/L 17α-methyltestosterone (MT) were investigated. Results showed that their putative proteins shared high identities to their counterparts in cyprinid fish species, respectively. The tissue distribution results indicated that amh and cyp19a1a were predominantly expressed in the ovary and dax1 was dominantly expressed in the liver. Gene profiling in the developmental stages showed that all the three target genes had a consistent highest expression at 48 days post hatching (dph). The period of 48 dph appeared to be a key time during the process of the gonad development of Pengze crucian carp. 100 ng/L MT significantly increased the mRNA expression of amh at 2- and 4-week exposures and enhanced dax1 and cyp19a1a at 6-week exposure. The present study indicated that MT could influence the gonad development in Pengze crucian carp by disturbing sex-differentiation associated gene expression. Furthermore, the present study will be of great significance to broaden the understanding of molecular mechanisms of the physiological processes of reproduction in fish.

Cholesterol and male fertility: what about orphans and adopted?

The link between cholesterol homeostasis and male fertility has been clearly suggested in patients who suffer from hyperlipidemia and metabolic syndrome. This has been confirmed by the generation of several transgenic mouse models or in animals fed with high cholesterol diet. Next to the alteration of the endocrine signaling pathways through steroid receptors (androgen and estrogen receptors); "orphan" and "adopted" nuclear receptors, such as the Liver X Receptors (LXRs), the Proliferating Peroxisomal Activated Receptors (PPARs) or the Liver Receptor Homolog-1 (LRH-1), have been involved in this cross-talk. These transcription factors show distinct expression patterns in the male genital tract, explaining the large panel of phenotypes observed in transgenic male mice and highlighting the importance of lipid homesostasis and the complexity of the molecular pathways involved. Increasing our knowledge of the roles of these nuclear receptors in male germ cell differentiation could help in proposing new approaches to either treat infertile men or define new strategies for contraception.

Anchoring ethinylestradiol induced gene expression changes with testicular morphology and reproductive function in the medaka

Environmental estrogens are ubiquitous in the environment and can cause detrimental effects on male reproduction. In fish, a multitude of effects from environmental estrogens have been observed including altered courting behavior and fertility, sex reversal, and gonadal histopathology. However, few studies in fish assess the impacts of estrogenic exposure on a physiological endpoint, such as reproduction, as well as the associated morphologic response and underlying global gene expression changes. This study assessed the implications of a 14 day sub-chronic exposure of ethinylestradiol (EE2; 1.0 or 10.0 µg/L EE2) on male medaka fertility, testicular histology and testicular gene expression. The findings demonstrate that a 14 day exposure to EE2 induced impaired male reproductive capacity and time- and dose-dependent alterations in testicular morphology and gene expression. The average fertilization rate/day following the exposure for control, 1.0 and 10.0 µg/L EE2 was 91.3% (±4.4), 62.8% (±8.3) and 28.8% (±5.8), respectively. The testicular morphologic alterations included increased germ cell apoptosis, decreased germinal epithelium and thickening of the interstitium. These changes were highly associated with testicular gene expression changes using a medaka-specific microarray. A pathway analysis of the differentially expressed genes emphasized genes and pathways associated with apoptosis, cell cycle and proliferation, collagen production/extracellular matrix organization, hormone signaling, male reproduction and protein ubiquitination among others. These findings highlight the importance of anchoring global gonadal gene expression changes with morphology and ultimately with tissue/organ function.

Microsatellites with macro-influence in ewing sarcoma

Numerous molecular abnormalities contribute to the genetic derangements involved in tumorigenesis. Chromosomal translocations are a frequent source of these derangements, producing unique fusion proteins with novel oncogenic properties. EWS/ETS fusions in Ewing sarcoma are a prime example of this, resulting in potent chimeric oncoproteins with novel biological properties and a unique transcriptional signature essential for oncogenesis. Recent evidence demonstrates that EWS/FLI, the most common EWS/ETS fusion in Ewing sarcoma, upregulates gene expression using a GGAA microsatellite response element dispersed throughout the human genome. These GGAA microsatellites function as enhancer elements, are sites of epigenetic regulation and are necessary for EWS/FLI DNA binding and upregulation of principal oncogenic targets. An increasing number of GGAA motifs appear to substantially enhance EWS/FLI-mediated gene expression, which has compelling biological implications as these GGAA microsatellites are highly polymorphic within and between ethnically distinct populations. Historically regarded as junk DNA, this emerging evidence clearly demonstrates that microsatellite DNA plays an instrumental role in EWS/FLI-mediated transcriptional regulation and oncogenesis in Ewing sarcoma. This unprecedented role of GGAA microsatellite DNA in Ewing sarcoma provides a unique opportunity to expand our mechanistic understanding of how EWS/ETS fusions influence cancer susceptibility, prognosis and transcriptional regulation.

Damage in brain development by morpholino knockdown of zebrafish dax1

DAX1 is an orphan nuclear receptor and involved in development of steroidogenic organs, which activates transcription of genes involved in steroidogenesis. In this study, we analyzed the function of the zebrafish dax1 during early development of central nervous systems to appear unidentified aspects of DAX1 and decrease confusions concerned with functions of DAX1 in early development of vertebrates. By whole-mount in situ hybridization of embryo at the 32 h post fertilization (hpf), expression of zebrafish dax1 was detected around the forebrain, midbrain, hindbrain, and the extending tail tip. Embryos injected with zebrafish dax1 morpholino antisense nucleotide (MO) exhibited delayed development. When the developmental stage of wild type embryos was at Prim-15 (32 hpf), zebrafish dax1MO injected embryos were at Prim-5 (24 hpf). Concurrently with developmental delay, the MO injected embryos showed high mortality. At 48 hpf, the MO injected embryos exhibited abnormal development in the central nervous systems. The enlarged tectum and the protruded rhombomeres were observed. Moreover, development of central nervous systems, especially midbrain-hindbrain boundary, became narrower. At 5 day post fertilization, the MO injected embryos formed edemas around head, pericardial sac and abdomen. Collectively, our results indicated that the zebrafish dax1 is important for brain development.

100th anniversary of the discovery of the human adrenal fetal zone by Stella Starkel and Lesław Węgrzynowski: how far have we come?

Year 2010 marks a centennial anniversary of the description by Stella Starkel and Lesław Węgrzynowski, Polish students of the Faculty of Medicine, University of Lwów, the fetal zone of the human fetal adrenal gland. In 1911 both, Starkel and Węgrzynowski were graduated from the Faculty of Medicine of Lwow University. The paper appeared in the German Arch. Anat. Physiol. and its original title was "Beitrag zur Histologie der Nebeniere bei Feten und Kindern" ("Contribution to histology of adrenals of fetuses and children"). The studies were performed on 100 adrenal glands obtained from fetuses (from 6th month of gestation) and up to 5-year-old children. They described the fetal zone as a "medullary zone", also as "immature cortex", which undergoes involution in first years of life. To commemorate this discovery, this review aimed to present the most important achievements of studies on the development and involution of the human adrenal fetal zone.

Development and function of the human fetal adrenal cortex: a key component in the feto-placental unit

Continuous efforts have been devoted to unraveling the biophysiology and development of the human fetal adrenal cortex, which is structurally and functionally unique from other species. It plays a pivotal role, mainly through steroidogenesis, in the regulation of intrauterine homeostasis and in fetal development and maturation. The steroidogenic activity is characterized by early transient cortisol biosynthesis, followed by its suppressed synthesis until late gestation, and extensive production of dehydroepiandrosterone and its sulfate, precursors of placental estrogen, during most of gestation. The gland rapidly grows through processes including cell proliferation and angiogenesis at the gland periphery, cellular migration, hypertrophy, and apoptosis. Recent studies employing modern technologies such as gene expression profiling and laser capture microdissection have revealed that development and/or function of the fetal adrenal cortex may be regulated by a panoply of molecules, including transcription factors, extracellular matrix components, locally produced growth factors, and placenta-derived CRH, in addition to the primary regulator, fetal pituitary ACTH. The role of the fetal adrenal cortex in human pregnancy and parturition appears highly complex, probably due to redundant and compensatory mechanisms regulating these events. Mounting evidence indicates that actions of hormones operating in the human feto-placental unit are likely mediated by mechanisms including target tissue responsiveness, local metabolism, and bioavailability, rather than changes only in circulating levels. Comprehensive study of such molecular mechanisms and the newly identified factors implicated in adrenal development should help crystallize our understanding of the development and physiology of the human fetal adrenal cortex.

LRH-1 and Nanog regulate Dax1 transcription in mouse embryonic stem cells

Dax1, an atypical orphan nuclear receptor expressed in steroidogenic tissues, has recently been shown to be expressed in mouse embryonic stem (mES) cells and is required for pluripotency. While the mechanisms of transcriptional regulation of Dax1 in steroidogenic organs have been well characterized, those in mES cells have not. Here we report that 500 bp of the Dax1 gene promoter sequence are sufficient to drive expression in mES cells. In steroidogenic tissues, NR5A1 (Sf1) binds to nuclear receptor binding sites within this sequence to regulate Dax1 expression. In mES cells, while NR5A1 (Sf1) is not expressed, NR5A2 (LRH-1) expression is robust. Luciferase assays, EMSA and overexpression/knockdown studies demonstrate that LRH-1 binds the -128 site and regulates Dax1 in mES cells. Predicated on recent work indicating that Nanog binds to the Dax1 intron, we have used chromatin immunoprecipitation experiments (ChIP) to define an intronic site that is bound by Nanog. Overexpression and knockdown of Nanog in mES cells result in alteration of Dax1 expression, and luciferase assays reveal that this sequence can enhance transcription of a Dax1 reporter construct. These data indicate that LRH-1 and Nanog cooperate to regulate Dax1 expression in mES cells.

47, XY, +der(Y),t(X;Y)(p21.1;p11.2): a unique case of XY sex reversal

Translocations involving the short arms of the X and Y chromosomes are rare and can result in a functional disomy of the short arm of the X chromosome, including the dosage-sensitive sex reversal (DSS) locus. A result of such imbalance may be sex reversal with multiple congenital anomalies. We present the clinical and cytogenetic evaluation of a newborn infant with DSS and additional clinical findings of minor facial anomalies, left abdominal mass, 5th finger clinodactyly, and mild hypotonia. The external genitalia appeared to be normal female. The infant had bilateral corneal opacities and findings suggestive of anterior segment dysgenesis. Ultrasonography showed a small uterus with undetectable ovaries, and a left multicystic dysplastic kidney. High-resolution chromosome analysis identified the presence of a derivative Y chromosome, 47,XY, +der(Y)t(X;Y)(p21.1;p11.2), which was confirmed by fluorescence in situ hybridization studies. Array CGH showed a 35.1 Mb copy number gain of chromosome region Xp22.33-p21.1 and a 52.2 Mb copy number gain of Yp11.2-qter, in addition to the intact X and Y chromosomes. Previously reported patients with XY sex reversal have not had DSS with corneal opacities, dysgenesis of the anterior segment of the eye, and unilateral multicystic dysplastic kidney. These findings represent a new form of XY sex reversal due to an Xp duplication.

Dax1 up-regulates Oct4 expression in mouse embryonic stem cells via LRH-1 and SRA

Dax1 (Nr0b1) is an atypical orphan nuclear receptor that has recently been shown to play a role in mouse embryonic stem (mES) cell pluripotency. Here we describe a mechanism by which Dax1 maintains pluripotency. In steroidogenic cells, Dax1 protein interacts with the NR5A nuclear receptor steroidogenic factor 1 (Nr5a1) to inhibit transcription of target genes. In mES cells, liver receptor homolog 1 (LRH-1, Nr5a2), the other NR5A family member, is expressed, and LRH-1 has been shown to interact with Dax1. We demonstrate by coimmunoprecipitation that Dax1 is, indeed, able to form a complex with LRH-1 in mES cells. Because Dax1 was historically characterized as an inhibitor of steroidogenic factor 1-mediated transcriptional activation, we hypothesized that Dax1 would inhibit LRH-1 action in mES cells. Therefore, we examined the effect of Dax1 on the LRH-1-mediated activation of the critical ES cell factor Oct4 (Pou5f1). Chromatin immunoprecipitation localized Dax1 to the Oct4 promoter at the LRH-1 binding site, and luciferase assays together with Dax1 overexpression and knockdown experiments revealed that, rather than repress, Dax1 accentuated LRH-1-mediated activation of the Oct4 gene. Similar to our previously published studies that defined the RNA coactivator steroid receptor RNA activator as the critical mediator of Dax1 coactivation function, Dax1 augmentation of LRH-1-mediated Oct4 activation is dependent upon steroid receptor RNA activator. Finally, utilizing published chromatin immunoprecipitation data of whole-genome binding sites of LRH-1 and Dax1, we show that LRH-1 and Dax1 commonly colocalize at 288 genes (43% of LRH-1 target genes), many of which are involved in mES cell pluripotency. Thus, our results indicate that Dax1 plays an important role in the maintenance of pluripotency in mES cells through interaction with LRH-1 and transcriptional activation of Oct4 and other genes.

Association of genetic polymorphisms and autoimmune Addison's disease

Autoimmune Addison's disease (AAD) is a complex genetic disease that results from the interaction of a predisposing genetic background with as yet unknown environmental factors. The disease is marked by the appearance of circulating autoantibodies against steroid 21-hydroxylase. Mutations of the autoimmune regulator gene are responsible for the so-called autoimmune polyendocrine syndrome type I (APS I), of which AAD is a major disease component. Among genetic factors for isolated AAD and APS II, a major role is played by HLA class II genes: HLA-DRB1 0301-DQA1 0501-DQB1 0201 and DRB1 04-DQA1 0301-DQB1 0302 are positively, and RB1 0403 is negatively, associated with a genetic risk for AAD. The MHC class I chain-related gene A allele 5.1 is strongly and positively associated with AAD. Other gene polymorphisms contributing to genetic risk for AAD are MHC2TA, the gene coding for class II transactivator, the master regulator of class II expression, cytotoxic T lymphocyte antigen-4, PTPN22 and the vitamin D receptor.

Retinoic acid-induced nNOS expression depends on a novel PI3K/Akt/DAX1 pathway in human TGW-nu-I neuroblastoma cells

Neuronal nitric oxide synthase (nNOS)-derived nitric oxide (NO) acts as a neurotransmitter and intracellular signaling molecule in the central and peripheral nervous system. NO regulates multiple processes like neuronal development, plasticity, and differentiation and is a mediator of neurotoxicity. The nNOS gene is highly complex with 12 alternative first exons, exon 1a-1l, transcribed from distinct promoters, leading to nNOS variants with different 5'-untranslated regions. Transcriptional control of the nNOS gene is not understood in detail. To investigate regulation of nNOS gene expression by retinoic acid (RA), we used the human neuroblastoma cell line TGW-nu-I as a model system. We show that RA induces nNOS transcription in a protein synthesis-dependent fashion. We identify the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway and the atypical orphan nuclear receptor DAX1 (NR0B1) as critical mediators involved in RA-induced nNOS gene transcription. RA treatment increases DAX1 expression via PI3K/Akt signaling. Upregulation of DAX1 expression in turn induces nNOS transcription in response to RA. These results identify nNOS as a target gene of a novel RA/PI3K/Akt/DAX1-dependent pathway in human neuroblastoma cells and stress the functional importance of the transcriptional regulator DAX1 for nNOS gene expression in response to RA treatment.

Identification of a novel mutation in DAX1/NR0B1A gene in two siblings with severe clinical presentation of adrenal hypoplasia congenita

OBJECTIVE: To search for mutations in DAX1/NR0B1A gene in siblings to establish the molecular etiology of the adrenal hypoplasia congenita (AHC), a rare potentially life-threatening disorder. CASE REPORT: We describe two siblings who presented with salt-wasting syndrome in the newborn period and received hormonal replacement for primary adrenal insufficiency. A diagnostic hypothesis of AHC was suspected because the children maintained, during hormonal treatment, low plasma 17-OH progesterone (17-OHP) and androgens, despite high ACTH levels. RESULTS: DAX1 gene was studied by molecular analysis, which showed a mutation, confirming the diagnosis in the siblings and a heterozygous state in the mother. Direct sequencing of DAX1 revealed an insertion of an adenine base (c1382-1383 A ins), which lead to a pMet461Asp substitution. CONCLUSION: A novel frameshift mutation of DAX1 gene, which established the molecular etiology of the AHC in the siblings, was identified. Obtaining a precise genetic diagnosis of this adrenal disorder, which, sometimes, cannot be confirmed only by clinical aspects, may have important implications for the long-term management of the disease.

Closing the gap: inverting the genetics curriculum to ensure an informed public

Over the past 20 years, the focus of national efforts to improve K-12 science education has ranged from curriculum and professional development of teachers to the adoption of science standards and high-stakes testing. In spite of this work, students in the United States continue to lag behind their peers in other countries. This underperformance is true for genetics, as well as for science and math in general, and is particularly worrisome given the accelerating need for scientists and engineers in our increasingly technology-driven economy. A scientifically literate public is essential if citizens are to engage effectively with policymakers on issues of scientific importance. Perhaps nowhere is this conjunction more personally meaningful than in human genetics and medicine. Rapid changes in our field have the potential to revolutionize healthcare, but the public is ill prepared to participate in this transformation. One potential solution is to modernize the genetics curriculum so that it matches the science of the 21(st) century. This paper highlights changes in human genetics that support a curricular reorganization, outlines the problems with current genetics instruction, and proposes a new genetics curriculum.

Transcriptional regulation of steroidogenic genes: STARD1, CYP11A1 and HSD3B

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

E3 ubiquitin ligase RNF31 cooperates with DAX-1 in transcriptional repression of steroidogenesis

Genetic and experimental evidence points to a critical involvement of the atypical mammalian orphan receptor DAX-1 in reproductive development and steroidogenesis. Unlike conventional nuclear receptors, DAX-1 appears not to function as a DNA-bound transcription factor. Instead, it has acquired the capability to act as a transcriptional corepressor of steroidogenic factor 1 (SF-1). The interplay of DAX-1 and SF-1 is considered a central, presumably ligand-independent element of adrenogonadal development and function that requires tight regulation. This raises a substantial interest in identifying its modulators and the regulatory signals involved. Here, we uncover molecular mechanisms that link DAX-1 to the ubiquitin modification system via functional interaction with the E3 ubiquitin ligase RNF31. We demonstrate that RNF31 is coexpressed with DAX-1 in steroidogenic tissues and participates in repressing steroidogenic gene expression. We provide evidence for the in vivo existence of a corepressor complex containing RNF31 and DAX-1 at the promoters of the StAR and CYP19 genes. Our data suggest that RNF31 functions to stabilize DAX-1, which might be linked to DAX-1 monoubiquitination. In conclusion, RNF31 appears to be required for DAX-1 to repress transcription, provides means to regulate DAX-1 in ligand-independent ways, and emerges as a relevant coregulator of steroidogenic pathways governing physiology and disease.

Minireview: latest perspectives on antiinflammatory actions of glucocorticoids

Taking into consideration that glucocorticoid (GC) hormones have been used clinically for over half a century and that more than 20 yr have passed since the cloning of the GC receptor (GR), it is hard to imagine that novel aspects in the molecular mechanism by which GCs mediate their antiinflammatory actions are still being unveiled today. Partly, this is because almost on a daily basis, novel insights arise from parallel fields, e.g. nuclear receptor cofactor and chromatin regulation and their concomitant impact on gene transcription events, eventually leading to a revisitation or refinement of old hypotheses. On the other hand, it does remain striking and puzzling why GCs use different mechanisms in so many different cell types and on many different target genes to elicit an antiinflammatory effect. Meanwhile, the obvious question for the clinic remains: is the separation of GR functionalities through differential ligand design the strategy of choice to avoid most GC-mediated side effects? This minireview aims to highlight some of the latest findings on aspects of the antiinflammatory working mechanisms of GCs.

Ligand induced interaction of thyroid hormone receptor beta with its coregulators

Thyroid hormones exert most of their physiological effects through two thyroid hormone receptor (TR) subtypes, TRalpha and TRbeta, which associate with many transcriptional coregulators to mediate activation or repression of target genes. The search for selective TRbeta ligands has been stimulated by the finding that several pharmacological actions mediated by TRbeta might be beneficial in medical conditions such as obesity, hypercholesterolemia and diabetes. Here, we present a new methodology which employs surface plasmon resonance to investigate the interactions between TRbeta ligand binding domain (LBD) complexes and peptides derived from the nuclear receptor interaction motifs of two of its coregulators, SRC2 and DAX1. The effect of several TRbeta ligands, including the TRbeta selective agonist GC-1 and the TRbeta selective antagonist NH-3, were investigated. We also determined the kinetic rate constants for the interaction of TRbeta-T3 with both coregulators, and accessed the thermodynamic parameters for the interaction with DAX1. Our findings suggest that flexibility plays an important role in the interaction between the receptor and its coregulators, and point out important aspects of experimental design that should be addressed when using TRbeta LBD and its agonists. Furthermore, the methodology described here may be useful for the identification of new TRbeta ligands.

Sex determination and SRY: down to a wink and a nudge?

Sex-determining region Y (Sry) is the crucial gene that initiates male sex determination in most mammals. Although several components of the pathway regulating sexual differentiation have been elucidated, the mechanism of Sry action within this was unclear. However, recent discoveries in cellular, genetic and molecular aspects of gonad development are shedding light on the precise role of SRY in the regulation of Sox9, a crucial downstream target gene. SRY is thought to act synergistically with SF1, a nuclear receptor, through an enhancer of Sox9 to promote Sertoli cell differentiation in mice. In this review, we focus on the regulation of these genes and their interaction with other genes involved in promoting testis or ovary development. We also explore the common features between sex determination in mammals and in other vertebrates that lack Sry.

Zebrafish as a developmental model organism for pediatric research

Zebrafish has many advantages as a model of human pediatric research. Given the physical and ethical problems with performing experiments on human patients, biomedical research has focused on using model organisms to study biologic processes conserved between humans and lower vertebrates. The most common model organisms are small mammals, usually rats and mice. Although these models have significant advantages, they are also expensive to maintain, difficult to manipulate embryonically, and limited for large-scale genetic studies. The zebrafish model nicely complements these deficiencies in mammalian experimental models. The low cost, small size, and external development of zebrafish make it an excellent model for vertebrate development biology. Techniques for large-scale genome mutagenesis and gene mapping, transgenesis, protein overexpression or knockdown, cell transplantation and chimeric embryo analysis, and chemical screens have immeasurably increased the power of this model organism. It is now possible to rapidly determine the developmental function of a gene of interest in vivo, and then identify genetic and chemical modifiers of the processes involved. Discoveries made in zebrafish can be further validated in mammals. With novel technologies being regularly developed, the zebrafish is poised to significantly improve our understanding of vertebrate development under normal and pathologic conditions.

Male-to-female sex reversal associated with an ∼250 kb deletion upstream of NR0B1 (DAX1)

Deletion of the dosage sensitive gene NR0B1 encoding DAX1 on chromosome Xp21.2 results in congenital adrenal hypoplasia (AHC), whereas NR0B1 duplication in 46,XY individuals leads to gonadal dysgenesis and a female phenotype. We describe a 21-year-old 46,XY female manifesting primary amenorrhea, a small immature uterus, gonadal dysgenesis, and notably absent adrenal insufficiency with a submicroscopic (257 kb) deletion upstream of NR0B1. We hypothesize that loss of regulatory sequences may have resulted in position effect up-regulation of DAX1 expression, consistent with phenotypic consequences of NR0B1 duplication. We propose that this genomic region and by extension those surrounding the dosage sensitive SRY, SOX9, SF1, and WNT-4 genes, should be examined for copy-number variation in patients with sex reversal.