Expression of DAX-1, the gene responsible for X-linked adrenal hypoplasia congenita and hypogonadotropic hypogonadism, in the hypothalamic-pituitary-adrenal/gonadal axis

X-linked congenital adrenal hypoplasia: Report of long clinical follow-up and description of a new complex variant in the NR0B1 gene

Adrenal hypoplasia congenita, attributed to NR0B1 pathogenic variants, accounts for more than 50% of the incidence of primary adrenal insufficiency in children. Although more than 250 different deleterious variations have been described, no genotype-phenotype correlation has been defined to date. We report a case of an adopted boy who reported the onset of an adrenal crisis at 2 weeks of age, requiring replacement therapy with mineralocorticoids and glucocorticoids for 4 months. For 3 years, he did well without treatment. At almost 4 years of age, the disorder was restarted. A long follow-up showed the evolution of hypogonadotropic hypogonadism. Molecular studies on NR0B1 revealed a novel and deleterious deletion-insertion-inversion-deletion complex rearrangement sorted in the 5'-3' direction, which is described as follows: (1) deletion of the intergenic region (between TASL and NR0B1 genes) and 5' region, (2) insertion of a sequence containing 37 bp at the junction of the intergenic region of the TASL gene and a part of exon 1 of the NR0B1 gene, (3) inversion of a part of exon 1, (4) deletion of the final portion of exon 1 and exon 2 and beginning of the 3'UTR region, (5) maintenance of part of the intergenic sequence (between genes MAGEB1 and NR0B1, telomeric sense), (6) large posterior deletion, in the same sense. The path to molecular diagnosis was challenging and involved several molecular biology techniques. Evaluating the breakpoints in our patient, we assumed that it was a nonrecurrent rearrangement that had not yet been described. It may involve a repair mechanism known as nonhomologous end-joining (NHEJ), which joins two ends of DNA in an imprecise manner, generating an "information scar," represented herein by the 37 bp insertion. In addition, the local Xp21 chromosome architecture with sequences capable of modifying the DNA structure could impact the formation of complex rearrangements.

Hepatocyte DAX1 Deletion Exacerbates Inflammatory Liver Injury by Inducing the Recruitment of CD4+ and CD8+ T Cells through NF-κB p65 Signaling Pathway in Mice

Fulminant hepatitis is characterized by rapid and massive immune-mediated liver injury. Dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome, gene 1 (DAX1; NR0B1) represses the transcription of various genes. Here, we determine whether DAX1 serves as a regulator of inflammatory liver injury induced by concanavalin A (ConA). C57BL/6J (WT), myeloid cell-specific Dax1 knockout (MKO), and hepatocyte-specific Dax1 knockout (LKO) mice received single intravenous administration of ConA. Histopathological changes in liver and plasma alanine aminotransferase and aspartate aminotransferase levels in Dax1 MKO mice were comparable with those in WT mice following ConA administration. Unlike Dax1 MKO mice, Dax1 LKO mice were greatly susceptible to ConA-induced liver injury, which was accompanied by enhanced infiltration of immune cells, particularly CD4⁺ and CD8⁺ T cells, in the liver. Factors related to T-cell recruitment, including chemokines and adhesion molecules, significantly increased following enhanced and prolonged phosphorylation of NF-κB p65 in the liver of ConA-administered Dax1 LKO mice. This is the first study to demonstrate that hepatocyte-specific DAX1 deficiency exacerbates inflammatory liver injury via NF-κB p65 activation, thereby causing T-cell infiltration by modulating inflammatory chemokines and adhesion molecules. Our results suggest DAX1 as a therapeutic target for fulminant hepatitis treatment.

Adult‑onset X‑linked adrenal hypoplasia congenita caused by a novel mutation in DAX1/NR0B1: A case report and literature review

Adrenal hypoplasia congenita (AHC) is a rare X-linked recessive disease caused by mutations in the nuclear receptor subfamily 0, group B, member 1 (NR0B1) gene, which is also referred to as dosage-sensitive sex-reversal, adrenal hypoplasia congenita, in the critical region of the X chromosome, gene 1 (DAX1). This gene is expressed in the hypothalamus, anterior pituitary and steroidogenic tissues, including the gonads and adrenal cortex. Adult-onset forms of X-linked AHC are a significant cause of concern. In the present study, the case of a 21-year-old male who exhibited adrenal insufficiency and hypogonadotropic hypogonadism was described. The patient initially presented with nausea, vomiting, fatigue and dizziness. The laboratory results demonstrated that the patient had hyponatremia, a low basal cortisol concentration and increased adrenocorticotropic hormone levels. Molecular genetic examination revealed a novel frameshift mutation (c.1005delC, p.V336Cfs*36). Following steroid supplementation, the patient's vomiting, fatigue and dizziness rapidly improved. To the best of our knowledge, the present study was the first case report of adult-onset X-linked AHC with this novel frameshift mutation. Furthermore, the present study highlighted differences in the clinical presentation of adult-onset forms of X-linked AHC. This may therefore alert medical professionals to the need to perform genetic analysis for DAX1 mutations in adolescents and adults with primary adrenal insufficiency and hypogonadotropic hypogonadism.

Case report: Clinical characteristics and treatment of secondary osteoporosis induced by X-linked congenital adrenal dysplasia

OBJECTIVE

To summarize the clinical features and bone complications in a patient from a large family with X-linked congenital adrenocortical hypoplasia (AHC) and evaluate the efficacy of different treatment regimens on the prognosis of secondary osteoporosis caused by AHC at a 5-year follow-up.

METHODS

A large family with AHC was recruited, and the causative gene mutation was identified by Sanger sequencing in the proband. Clinical features as well as radiological examinations and laboratory indices of osteoporosis secondary to AHC were analyzed in this study. Meanwhile, the proband was treated with classical antiresorptive drugs (bisphosphonates) for 2 years and switched to a vitamin K₂ analogue for another 3 years, during which the efficacy of the drugs was evaluated.

RESULTS

The proband was identified as carrying a homozygous insertion mutation (p. Thr193GlyfsX13) in the NR0B1 (nuclear receptor subfamily 0, group B, member 1) gene, resulting in a premature stop codon due to a frameshift mutation. During treatment and follow-up, the proband did not respond well to bisphosphonate and developed atypical femoral fractures. Vitamin K₂ improved clinical symptoms. In terms of bone mineral density (BMD), there is no evidence of any effect of vitamin K₂ on the neck of femur, though some minor effects on spinal BMD cannot be excluded.

CONCLUSIONS

Secondary osteoporosis induced by AHC deserves clinical attention. Unlike in primary osteoporosis, the curative effect of bisphosphonates was unsatisfactory and was more likely to cause atypical femoral fractures in long-term treatment. It is suggested that bone anabolic drugs may be better alternatives.

Hamster DAX1: Molecular insights, specific expression, and its role in the Harderian gland

DAX1 plays an essential role in the differentiation and physiology of the Hypothalamic-Pituitary-Adrenal-Gonadal (HPAG) axis during embryogenesis. However, in adult tissues, in addition to the HPAG axis, evidence has not been found for its differential expression and function. We isolated the DAX1 cDNA to analyze its tissue localization and gene expression profiles in male and female hamsters' Harderian glands (HGs), Mesocricetus auratus. The isolated cDNA clone contains 1848 base pairs (bp), and a 1428-bp open reading frame (ORF) encodes a 476 amino acid protein. Sequence alignments and the phylogenetic tree display a relevant percentage of similarity with human (66%), rat (81%), and mouse (84%) sequences. In adult tissues, the mRNA distribution demonstrated that DAX1 is present in testis, ovaries, and male and female HGs. The highest expression profiles were identified in the adrenal glands, where females exhibit higher mRNA levels than males. The sexually dimorphic expression of DAX1 in adrenals suggests that its presence could be associated with regulating, functioning, and maintaining this endocrine tissue. These findings indicate that the DAX1 gene is limitedly expressed in adult tissues. In the HGs, we demonstrate the absence of sexually dimorphic gene expression. Our results suggest that DAX1 might have an additional physiological function outside of the HPAG axis, specifically in the HG, which may be required for the regulation of intracrine steroidogenesis, secretion, and maintenance of exocrine tissue.

nr0b1 (DAX1) loss of function in zebrafish causes hypothalamic defects via abnormal progenitor proliferation and differentiation

The nuclear receptor DAX-1 (encoded by the NR0B1 gene) is presented in the hypothalamic tissues in humans and other vertebrates. Human patients with NR0B1 mutations often have hypothalamic-pituitary defects, but the involvement of NR0B1 in hypothalamic development and function is not well understood. Here, we report the disruption of the nr0b1 gene in zebrafish causes abnormal expression of gonadotropins, a reduction in fertilization rate, and an increase in post-fasting food intake, which is indicative of abnormal hypothalamic functions. We find that loss of nr0b1 increases the number of prodynorphin (pdyn)-expressing neurons but decreases the number of pro-opiomelanocortin (pomcb)-expressing neurons in the zebrafish hypothalamic arcuate region (ARC). Further examination reveals that the proliferation of progenitor cells is reduced in the hypothalamus of nr0b1 mutant embryos accompanying with the decreased expression of genes in the Notch signaling pathway. Additionally, the inhibition of Notch signaling in wild-type embryos increases the number of pdyn neurons, mimicking the nr0b1 mutant phenotype. In contrast, ectopic activation of Notch signaling in nr0b1 mutant embryos decreases the number of pdyn neurons. Taken together, our results suggest that nr0b1 regulates neural progenitor proliferation and maintenance to ensure normal hypothalamic neuron development.

Leydig Cell-Specific DAX1-Deleted Mice Has Higher Testosterone Level in the Testis During Pubertal Development

Testosterone, the male sex hormone, is necessary for the development and function of the male reproductive system. Biosynthesis of testosterone in mammals mainly occurs in testicular Leydig cells. Many proteins such as P450c17, 3β-HSD, and StAR are involved in testicular steroidogenesis. DAX1 is essential for sex development and interacts with nuclear receptors such as steroidogenic factor 1 to inhibit steroidogenesis. In this study, we investigated the role of DAX1 in testicular steroidogenesis in vivo by generating Leydig cell-specific DAX1-knockout mice. Radioimmunoassay revealed that the levels of testosterone and progesterone were higher in Leydig cell-specific DAX1-knockout testes than in the testes from wild-type mice during the first 3-4 weeks of aging. In addition, the expression levels of steroidogenic genes, such as StAR, P450c17, P450scc, and 3β-HSD, were considerably higher in the testes from DAX1-knockout mice. DAX1-deficient mouse testes seemed to attain early puberty with the acceleration of germ cell development. These data suggest that DAX1 regulates the expression of steroidogenic genes, and thereby controls and fine-tunes steroidogenesis during testis development.

A novel stop-loss DAX1 variant affecting its protein-interaction with SF1 precedes the adrenal hypoplasia congenital with rare spontaneous precocious puberty and elevated hypothalamic-pituitary-gonadal/adrenal axis responses

The case study unveils the likely mechanism of a novel stop-loss DAX1 variant preceding the prolonged precocious puberty in the adrenal hypoplasia congenital (AHC) boy. A boy aged five years and nine months initially examined for the primary adrenal insufficiency symptoms. Next-generation sequencing confirmed the X-linked inheritance of a novel stop-loss DAX1 variant: c.1411T>C/p.Ter471Gln associated with AHC in the patient. The patient was subjected to a brief clinical follow-up from 11 to 15.1 years of age. The effect of the mutant-DAX1 variant (p.Ter471Gln) on DAX1-steroidogenic factor 1 (SF1) (protein-protein) interaction was studied by protein-protein docking using the ClusPro-online tool. At 5.9 yrs of age, the patient exhibited precocious puberty with the secondary sexual characteristics of Tanner 2 stage (of 9-14 yrs of age). The patient showed primary adrenal insufficiency with diminished cortisol concentrations at blood serum (25 ng/ml) and urine (3.55 μg/24 h) levels. Upon steroidal exposure, the patient showed normalized serum cortisol levels of 45-61 ng/ml. However, the precocious puberty got prolonged with the increased penis length of 8.5 cm and the bone age of 18 yrs old during the follow-up. The patient showed increased basal serum adrenocorticotropic hormone (110->2000 pg/ml) and follicle-stimulating hormone (18.4-22.3 mIU/ml) concentrations. Following an elevated hypothalamic-pituitary-gonadal axis activity witnessed upon gonarellin stimulation. Protein-protein docking confirmed a weaker interaction between the mutant-DAX1 (p.Ter471Gln) protein and the wild-SF1 protein. Overall, we hypothesize the weakened mutant-DAX1-SF1 (protein-protein) interaction could govern the prolonged precocious puberty augmented with the elevated hypothalamic-pituitary-gonadal/adrenal axis responses via SF1-induced neuronal nitric oxide synthetase activation in the patient.

Report: central diabetes insipidus and schwannoma in a male with X-linked congenital adrenal hypoplasia

BACKGROUND

DAX1 mutations are related to the X-linked form of adrenal hypoplasia congenita (AHC) in infancy and to hypogonadotropic hypogonadism (HH) in puberty. We report a male patient affected by X-linked AHC who presented with central diabetes insipidus and schwannoma in adulthood, which has not been described in association with AHC.

CASE PRESENTATION

A 36-day-old male infant who presented with severe dehydration was admitted to the intensive care unit. His laboratory findings showed hyponatremia, hyperkalemia, hypoglycemia, and metabolic acidosis. After hormonal evaluation, he was diagnosed with adrenal insufficiency, and he recovered after treatment with hydrocortisone and a mineralocorticoid. He continued to take hydrocortisone and the mineralocorticoid after discharge. At the age of 17, he did not show any signs of puberty. On the basis of a GnRH test, a diagnosis of HH was made. At the age of 24, he was hospitalized with thirst, polydipsia and polyuria. He underwent a water deprivation test for polydipsia and was diagnosed with central diabetes insipidus. By quantitative polymerase chain reaction analysis, we identified a hemizygous frameshift mutation in DAX1 (c.543delA).

CONCLUSIONS

We suggest that DAX1 mutations affect a wider variety of endocrine organs than previously known, including the posterior pituitary gland.

Delayed-onset adrenal hypoplasia congenita and hypogonadotropic hypogonadism caused by a novel mutation in DAX1

In this study, we described a male who presented with delayed-onset adrenal hypoplasia congenita (AHC) and mild hypogonadotropic hypogonadism (HHG) without a relevant family history. A novel mutation in the DAX1 (dosage-sensitive sex reversal, congenital adrenal hypoplasia critical region on the X chromosome, gene 1) gene was shown to cause X-linked AHC and HHG. Genetic analysis revealed a novel nonsense mutation, c.154G > T (p.Glu52Term), in the DAX1 gene. Molecular testing demonstrated that the milder phenotype caused by this mutation was due to expression of a partially functional, amino-truncated DAX1 protein generated from an alternate in-frame translation start site (methionine at codon 83). This unusual case revealed a potential mechanism for a novel mutation that resulted in an unusual delayed-onset mild clinical phenotype. It expands the spectrum of adrenal hypoplasia congenita and hypogonadotropic hypogonadism.

Identification of a novel mutation of NR0B1 in a patient with X-linked adrenal hypoplasia and symptomatic treatment

BACKGROUND

X-linked congenital adrenal hypoplasia (X-linked AHC) is characterized by acute onset of primary adrenal insufficiency in infancy or early childhood and hypogonadotropic hypogonadism (HH) at puberty. Mutations in NR0B1, the gene located on Xp21.3 and encoding an orphan nuclear receptor named DAX1, are responsible for this disease.

METHODS

The entire coding region of the NR0B1 gene of a 14-year-old X-linked AHC proband as well as his family members was sequenced. Clinical and endocrine evaluations with symptomatic treatment results were recorded.

RESULTS

DNA sequencing revealed a missense mutation (c.383-384 insA) in exon 1, which resulted in a novel frameshift mutation, thereby resulting in a truncated protein (p.Leu129 Pro fs*137). The therapeutic trail with an observation period of 20 weeks showed an effective improvement in symptoms of hypogonadism with human chorionic gonadotropin (HCG) administration, including a rapid improvement of serum testosterone level, descending of testicles as well as enlargement of testicles and growth of penis.

CONCLUSIONS

Our study identified a novel frameshift mutation of the NR0B1 gene in a proband with X-linked AHC/HH and further expanded the number of NR0B1 mutations reported in the literature. Moreover, the symptomatic treatment observation provided referential evidence in the treatment of X-linked AHC associated hypogonadism and bilateral inguinal cryptorchidism.

Perspectives in Pediatric Pathology, Chapter 22. Testicular Involvement in Systemic Diseases

Normal testicular physiology requires appropriate function of endocrine glands and other tissues. Testicular lesions have been described in disorders involving the hypothalamus-hypophysis, thyroid glands, adrenal glands, pancreas, liver, kidney, and gastrointestinal tract. Testicular abnormalities can also associate with chronic anemia, obesity, and neoplasia. Although many of the disorders that affect the above-mentioned glands and tissues are congenital, acquired lesions may result in hypogonadism in children and adolescents.

A novel DAX-1 mutation in two male siblings presenting with precocious puberty and late-onset hypogonadotropic hypogonadism

Background The DAX-1 gene is associated with X-linked adrenal hypoplasia congenita (AHC). Our objective was to compare the DAX-1 gene sequence of two male siblings exhibiting different clinical manifestations of AHC. Methods Clinical features were analyzed and laboratory data were collected from both siblings. Genomic DNA was extracted from the peripheral blood leukocytes of the siblings and their parents and the DAX-1 gene exons and intron-flanking regions were amplified by the polymerase chain reaction. The DAX-1 gene sequences were compared following sequencing. Results AHC was diagnosed based on a comprehensive review of the clinical presentation and laboratory tests. Gene analysis revealed a nonsense mutation in DAX-1 gene exon 1 (c.192C>G), resulting in a premature termination codon and a truncated 64-amino acid protein product (p.Tyr64X). Conclusions Our report provides evidence that defined point mutations in the DAX-1 gene do not necessarily translate into the same clinical manifestations of AHC, even in patients with the same pedigree.

Phenotypic spectrum of POLR3B mutations: isolated hypogonadotropic hypogonadism without neurological or dental anomalies

BACKGROUND

A constellation of neurodegenerative disorders exists (Gordon Holmes syndrome, 4H leucodystrophy, Boucher-Neuhauser syndrome) in which patients suffer from both neurological disease (typically manifested by ataxia) and reproductive failure (idiopathic hypogonadotropic hypogonadism (IHH)). POLR3B, which encodes the second largest subunit of RNA polymerase III (pol III), and POLR3A, which forms the pol III catalytic centre, are associated with 4H leucodystrophy.

METHODS

Whole exome sequencing was performed on a large cohort of subjects with IHH (n=565). Detailed neuroendocrine studies were performed in some individuals within this cohort.

RESULTS

Four individuals (two of them siblings) were identified with two rare nucleotide variants in POLR3B. On initial evaluation, all subjects were free of neurological disease. One patient underwent treatment with exogenous pulsatile gonadotropin-releasing hormone for 8 weeks which failed to result in normalisation of his sex steroid milieu due to pituitary resistance.

CONCLUSIONS

These findings suggest that the spectrum of phenotypes resulting from POLR3B mutations is wider than previously believed and that POLR3B can be associated exclusively with disorders characterised by abnormal gonadotropin secretion.

X-linked adrenal hypoplasia congenita and hypogonadotropic hypogonadism: Identification and in vitro study of a novel small indel in the NR0B1 gene

DAX1 is an orphan nuclear receptor that has a key role in the development and function of the adrenal and reproductive axes. Mutations in NR0B1, the gene encoding DAX1, result in X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HHG). A Chinese pedigree with X-linked AHC and HHG was investigated in the present study. Sequence analysis identified a novel small indel variant, c.195_207delinsTG, in the NR0B1 gene. To determine the effect of this variant on DAX1 expression, reverse‑transcription quantitative PCR and western blot assays were performed. The mRNA expression levels in carriers of mutant NR0B1 were significantly reduced (62% decrease) compared to those in individuals with wild-type NR0B1 (WT). The c.195_207delinsTG mutation was demonstrated to lead to various truncated DAX1 proteins, including the C‑terminal truncated DAX1, which was only detected in the cytoplasm, and the N‑terminal truncated DAX1, which was present in the cytoplasm and nucleus. A luciferase assay was then performed to assess the repressor function of DAX1 in modulating steroidogenic factor 1 (SF‑1)‑mediated transactivation. WT DAX1 significantly suppressed the SF‑1‑mediated promoter activity of the steroidogenic acute regulatory protein by 35.5±1.9%. In contrast to other known pathogenic mutations which abolish the repressor function of DAX1, the c.195_207delinsTG mutant proxkduced a higher repressor activity, demonstrating a 49.9±2.6% reduction of promoter activity. These findings suggested that the mutation of NR0B1 in X‑linked AHC with HHG enhanced the function of DAX1 to repress SF-1 activation, while DAX1 is expected to have additional roles in the pathological mechanism.

Clinical and molecular genetic analysis of a Chinese family with congenital X-linked adrenal hypoplasia caused by novel mutation 1268delA in the DAX-1 gene

Congenital X-linked adrenal hypoplasia (AHC) is a rare disease characterized by primary adrenal insufficiency before adolescence and by hypogonadotropic hypogonadism (HHG) during adolescence. In this paper, we present a Chinese family with AHC. Two brothers, misdiagnosed with adrenal insufficiency of unknown etiology at the age of 9, were correctly diagnosed with AHC when delayed puberty, HHG, and testicular defects were observed. We investigated the clinical features and identified the dosage-sensitive sex reversal AHC critical region of the X chromosome gene 1 (DAX-1) mutation in this kindred. Direct sequencing of the DAX-1 gene revealed that the two siblings have a novel mutation (1268delA) of which their mother is a heterozygous carrier. This mutation causes a frameshift and a premature stop codon at position 436, encoding a truncated protein. It is important to increase knowledge of the mutational spectrum in genes related to this disease, linking phenotype to genotype.

Late onset X-linked adrenal hypoplasia congenita with hypogonadotropic hypgonadism due to a novel 4-bp deletion in exon 2 of NR0B1

We report a novel NR0B1 mutation in a patient affected with X-linked adrenal hypoplasia congenita (X-AHC). The proband first presented with a generalized convulsion at 11 years, 4 months. His clinical and biochemical presentations were consistent with adrenal insufficiency. His basal 17-hydroxyprogesterone (17-OHP) level was not high, and the poor response in 17-OHP on ACTH stimulation test excluded congenital adrenal hyperplasia. At 14 years of age, he did not show any signs of puberty, with low levels of LH, FSH, and testosterone and unresponsiveness to lutenizing hormone releasing hormone stimulation test. Direct DNA sequencing revealed that the proband is hemizygous for a novel NR0B1 mutation (c.1177_1180delGGCC, p.Gly393Cysfs*4). The mother is the conductor of the mutation, which is likely pathogenic as the C-terminus truncated protein lacks the activation function-2 (AF2-TA) transactivation domain, which is highly conserved among members of the nuclear receptor superfamily.

Neurologic complications of disorders of the adrenal glands

Disorders of the adrenal glands frequently have secondary neurological manifestations, while some diseases that involve the central nervous system are accompanied by adrenal gland dysfunction. Excessive corticosteroid secretions in primary or secondary Cushing's syndrome causes muscle weakness and behavioral disturbances, such as emotional lability and sometimes depression, while adrenal insufficiency may cause fatigue, weakness, and depression. Adrenoleukodystrophy and adrenoneuromyelopathy are X-linked recessive disorders of the metabolism of very long chain fatty acids that manifest with white matter abnormalities of the brain, myelopathy and/or neuropathy, as well as adrenal insufficiency. Other disorders of the adrenal glands include hyperaldosteroidism, which may cause weakness from hypokalemia. Dysfunction of the adrenal medulla causes excessive or deficient secretion of catecholamines, primarily causing cardiovascular symptoms. This chapter reviews the clinical manifestations and diagnostic aspects and treatment of the various disorders of the adrenal glands. Some of the congenital adrenal diseases are also discussed.

Minireview: role of orphan nuclear receptors in cancer and potential as drug targets

The nuclear orphan receptors for which endogenous ligands have not been identified include nuclear receptor (NR)0B1 (adrenal hypoplasia congenita critical region on chromosome X gene), NR0B2 (small heterodimer partner), NR1D1/2 (Rev-Erbα/β), NR2C1 (testicular receptor 2), NR2C2 (testicular receptor 4), NR2E1 (tailless), NR2E3 (photoreceptor-specific NR [PNR]), NR2F1 chicken ovalbumin upstream promoter transcription factor 1 (COUP-TFI), NR2F2 (COUP-TFII), NR2F6 (v-erbA-related protein), NR4A1 (Nur77), NR4A2 (Nurr1), NR4A3 (Nor1), and NR6A1 (GCNF). These receptors play essential roles in development, cellular homeostasis, and disease including cancer where over- or underexpression of some receptors has prognostic significance for patient survival. Results of receptor knockdown or overexpression in vivo and in cancer cell lines demonstrate that orphan receptors exhibit tumor-specific pro-oncogenic or tumor suppressor-like activity. For example, COUP-TFII expression is both a positive (ovarian) and negative (prostate and breast) prognostic factor for cancer patients; in contrast, the prognostic activity of adrenal hypoplasia congenita critical region on chromosome X gene for the same tumors is the inverse of COUP-TFII. Functional studies show that Nur77 is tumor suppressor like in acute leukemia, whereas silencing Nur77 in pancreatic, colon, lung, lymphoma, melanoma, cervical, ovarian, gastric, and some breast cancer cell lines induces one or more of several responses including growth inhibition and decreased survival, migration, and invasion. Although endogenous ligands for the orphan receptors have not been identified, there is increasing evidence that different structural classes of compounds activate, inactivate, and directly bind several orphan receptors. Thus, the screening and development of selective orphan receptor modulators will have important clinical applications as novel mechanism-based agents for treating cancer patients overexpressing one or more orphan receptors and also for combined drug therapies.

DAX-1, as an androgen-target gene, inhibits aromatase expression: a novel mechanism blocking estrogen-dependent breast cancer cell proliferation

Sexual hormones, estrogens and androgens, determine biological response in a tissue- and gender-specific manner and have a pivotal role in endocrine-mediated tumorigenesis. In situ estrogen production by aromatase is a critical determinant for breast cancer growth and progression. On the contrary, clinical and in vitro studies indicate that androgens have a protective role in mammary carcinogenesis. Here, we demonstrated, in hormone-dependent breast cancer cells, the existence of a functional interplay between the androgen receptor (AR), the orphan nuclear receptor DAX-1 and the aromatase enzyme involved in the inhibition of the estrogen-dependent breast cancer cell proliferation exerted by androgen signaling. Indeed, our results revealed, in MCF-7 cells, that ligand-activated AR induces the expression of the orphan nuclear receptor DAX-1 by direct binding to a newly identified androgen-response-element within the DAX-1 proximal promoter. In turn, androgen-induced DAX-1 is recruited, in association with the corepressor N-CoR, within the SF-1/LRH-1 containing region of the aromatase promoter, thereby repressing aromatase expression and activity. In elucidating a novel mechanism by which androgens, through DAX-1, inhibit aromatase expression in breast cancer cell lines, these findings reinforce the theory of androgen- opposing estrogen-action, opening new avenues for therapeutic intervention in estrogen-dependent breast tumors.

Primary adrenal insufficiency caused by a novel mutation in DAX1 gene

Adrenal hypoplasia congenita (AHC) is a rare disorder. The X-linked form is related to mutations in the DAX1 (NROB1) gene. Here, we report a newborn who had a novel hemizygous frameshift mutation in DAX1(c.543delA) and presented with primary adrenal failure that was initially misdiagnosed as congenital adrenal hyperplasia. This report highlights the value of genetic testing for definite diagnosis in children with primary adrenal failure due to abnormal adrenal gland development, providing the possibility both for presymptomatic, and in cases with a sibling with this condition, for prenatal diagnosis.

A novel DAX-1 mutation presented with precocious puberty and hypogonadotropic hypogonadism in different members of a large pedigree

Patients with DAX-1 gene mutations on chromosome Xp21 usually present with adrenal hypoplasia congenita and hypogonadotropic hypogonadism. Yet, neither correlation between the type of mutation and the age of onset of the disease nor mechanism of the mutation on puberty is fully understood. Here, we report a novel non-sense p.Gln208X mutation in the amino terminal domain of the DAX-1 gene observed in a large family with three boys presenting with adrenal manifestations at different ages. Furthermore, two boys developed spontaneous puberty that failed to progress at similar ages, whereas the other boy developed precocious puberty at 10 month of age. The unique structure of the DAX-1 gene may explain this phenotypic variability. However, more studies are needed to understand the role of the DAX-1 gene on development of the adrenal gland and hypothalamus-pituitary-gonadal axis.

Duplication of dosage sensitive sex reversal area in a 46, XY patient with normal sex determining region of Y causing complete sex reversal

BACKGROUND

The sex chromosome composition of the primordial gonad, either 46XX or 46XY, determines its differentiation as ovaries or testes. Local hormones secreted by developing gonads and tissue specific transcription factors influence the differentiation of external and internal genital structures. Dosage sensitive sex reversal adrenal hypoplasia congenita critical region (DAX1) on Xp21 is a gene which is expressed in the developing adrenals, gonads, hypothalamus and pituitary gland. Duplication of this area causes dosage sensitive male-to-female sex reversal while mutation or deletion leads to adrenal hypoplasia congenita with hypogonadotropic hypogonadism in affected males.

AIM

To report a case with duplication of the X chromosome segment within the region of Xp21.1-22.2 resulting in 46 XY sex reversal and a literature review on DAX1 and dosage sensitive sex reversal (DSS).

METHODS AND RESULTS

We present the clinical history, physical findings, laboratory, and imaging study results in a newborn baby. This infant was sex assigned as female at birth and had normal female external genitalia. Chromosome analysis was done due to multiple minor malformations and showed a karyotype of 46 Xp+Y. Fluorescent in situ hybridization analysis revealed the duplication in the DSS area.

CONCLUSION

Duplication of the DAX1 gene on the X chromosome with normal sex determining region of Y (SRY) results in 46 XY sex reversal. This was inherited from the mother who had normal ovarian function. Additional problems include growth failure, mental retardation and multiple congenital anomalies. The baby did not have a mutation or deletion of DAX1, which would have caused adrenal insufficiency and hypogonadism.

X-linked congenital adrenal hypoplasia associated with hypospadias in an Egyptian baby: a case report

Introduction

X-linked congenital adrenal hypoplasia is a rare developmental disorder of the human adrenal cortex and is caused by deletion or mutation of the dosage-sensitive sex reversal adrenal hypoplasia congenita critical region of the X chromosome, gene 1 (DAX-1) gene. Most affected children present with failure to thrive, salt wasting and hypoglycemic convulsions in the first months of life. Hypospadias affects approximately one in 250 live male births. Mutations in the mastermind-like domain-containing 1 (MAMLD1) gene have been implicated as one of the causes of hypospadias in children. To the best of our knowledge, an association between congenital adrenal hypoplasia due to a DAX-1 mutation and hypospadias due to mutation of the MAMLD1 gene has not previously been reported in the literature.

Case presentation

A 35-day-old male Egyptian baby was referred to our institution for the evaluation of a two-week history of recurrent vomiting associated with electrolyte imbalance. On examination, our patient was found to have hypotension and dehydration. A genital examination showed distal penile hypospadias with chordee and normal testes. He had hyponatremia, hyperkalemia, hypoglycemia and metabolic acidosis. Endocrinological investigations revealed low levels of cortisol, 17-hydroxyprogesterone and aldosterone, with a high level of adrenocorticotrophic hormone. A provisional diagnosis of congenital adrenal hypoplasia associated with hypospadias was made. A molecular genetics study confirmed the diagnosis of X-linked congenital adrenal hypoplasia due to DAX-1 mutations and hypospadias due to MAMLD1 mutation. He was started on hydrocortisone and fludrocortisone treatment. After three weeks of treatment, his symptoms improved and his blood sugar, sodium, potassium and cortisol levels normalized.

Conclusions

We report the case of an Egyptian baby with an association of congenital adrenal hypoplasia due to DAX-1 mutation and hypospadias due to MAMLD1 mutation. Early diagnosis of this association and determining its optimal treatment are vital in helping to avoid its fatal course.

Ligand-independent actions of the orphan receptors/corepressors DAX-1 and SHP in metabolism, reproduction and disease

DAX-1 and SHP are two closely related atypical orphan members of the nuclear receptor (NR) family that make up the NR0B subfamily. They combine properties of typical NRs and of NR-associated coregulators: both carry the characteristic NR ligand-binding domain but instead of a NR DNA-binding domain they have unique N-terminal regions that contain LxxLL-related NR-binding motifs often found in coregulators. Recent structural data indicate that DAX-1 lacks a ligand-binding pocket and thus should rely on ligand-independent mechanisms of regulation. This might be true, but remains to be proven, for SHP as well. DAX-1 and SHP have in common that they act as transcriptional corepressors of cholesterol metabolism pathways that are related on a molecular level. However, the expression patterns of the two NRs are largely different, with some notable exceptions, and so are the physiological processes they regulate. DAX-1 is mainly involved in steroidogenesis and reproductive development, while SHP plays major roles in maintaining cholesterol and glucose homeostasis. This review highlights the key similarities and differences between DAX-1 and SHP with regard to structure, function and biology and considers what can be learnt from recent research advances in the field. This article is part of a Special Issue entitled 'Orphan Receptors'.

X-linked adrenal hypoplasia congenita: a novel DAX1 missense mutation and challenges for clinical diagnosis in Africa

Adrenal hypoplasia congenita (AHC) is a rare disease. The X-linked form of AHC is caused by deletions or mutations in DAX1 gene and has a variable clinical presentation. To date, no data on X-linked AHC in central Africa are available. Here, we report a Congolese pedigree with several cases of unexplained deaths of male infants. A careful analysis of the pedigree of this family lead to the recognition of an X-linked inheritance pattern, with subsequent confirmation in a female heterozygous carrier of a DAX1 missense mutation c.1274G>T, (p.Arg425Ile).The diagnosis of this condition remains challenging in a developing country, since the manifestations of AHC overlap with those of the much more frequently occurring infections; darkening of the skin is difficult to evaluate and there is a lack of access to routine endocrinological testing. The diagnosis was eventually made based on the family pedigree, evoking an X-linked inheritance pattern. This illustrates the necessity for medical and clinical genetics to be part of the curriculum of medical school in developing countries.

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.

Birth after TESE-ICSI in a man with hypogonadotropic hypogonadism and congenital adrenal hypoplasia linked to a DAX-1 (NR0B1) mutation

DAX1/NR0B1 mutations are responsible for X-linked congenital adrenal hypoplasia (AHC) associated with hypogonadotropic hypogonadism (HH). Few data are available concerning testicular function and fertility in men with DAX1 mutations. Azoospermia as well as failure of gonadotrophin treatment have been reported. We induced spermatogenesis in a patient who has a DAX1 mutation (c.1210C>T), leading to a stop codon in position 404 (p.Gln404X). His endocrine testing revealed a low testosterone level at 1.2 nmol/l (N: 12–40) with low FSH and LH levels at 2.1 IU/l (N: 1–5 IU/l) and 0.1 IU/l (N: 1–4 IU/l), respectively. Baseline semen analysis revealed azoospermia. Menotropin (Menopur^®:150 IU, three times weekly) and human chorionic gonadotrophin (1500 IU, twice weekly) were used. After 20 months of treatment, as azoospermia persisted, bilateral multiple site testicular biopsies were performed. Histology revealed severe hypospermatogenesis. Rare spermatozoa were extracted from the right posterior fragment and ICSI was performed. Four embryos were obtained and, after a frozen–thawed single-embryo transfer, the patient's wife became pregnant and gave birth to a healthy boy. We report the first case of paternity after TESE–ICSI in a patient with DAX1 mutation, giving potential hope to these patients to father non-affected children. Furthermore, this case illustrates the fact that patients with X-linked AHC have a primary testicular defect in addition to HH.

Steroidogenic acute regulatory protein expression in the central nervous system

Locally produced neurosteroids are proposed to have many functions in the central nervous system. The identification of the steroidogenic acute regulatory protein in steroid-producing neural cells provides a new tool to understand the sites, regulation, and importance of their synthesis.

Adrenal hypoplasia congenita - an uncommon reason of primary adrenal insufficiency

Adrenal hypoplasia congenita (AHC) is a rare inherited condition characterised by primary adrenal failure and hypogonadotropic hypogonadism. Most cases arise from mutations in the NR0B1 gene (Xp21.3), which encodes an orphan nuclear receptor DAX-1. A 20-year-old patient was recently diagnosed with AHC. Adrenal failure had been recognized and treated since his infancy. During adolescence, gradual decrease in growth velocity and low body mass were noted. Lack of puberty and skeletal immaturity were observed. Serum DHEA-S and testosterone were undetectable. Low gonadotropin levels failed to rise after stimulation. Neither dysfunction of the somatotropic nor pituitary-thyroid axis was found and no hypothalamo-pituitary pathology was visible on MRI. Androgen replacement therapy induced the development of secondary sexual characteristics, remarkably improved patient's growth and advanced his bone age. NR0B1 mutation screening revealed nucleotide transversion C>A, resulting in premature stop codon (Y399X). Same mutation was previously identified in a Scottish family, however, phenotypic differences suggest the role of additional factors modifying the disease course. Although it does not change therapeutic strategy, accurate molecular diagnosis allows genetic counselling in family members. Autoimmunity remains the major cause of adrenal failure; however, other rare conditions should always be considered.

Molecular aspects of steroidogenic factor 1 (SF-1)

Steroidogenic factor 1 (SF-1, also called Ad4BP and NR5A1) is a nuclear receptor with critical roles in steroidogenic tissues, as well as in the brain and pituitary. In particular, SF-1 has emerged as an essential regulator of adrenal and gonadal functions and development. In the last few years, our knowledge on SF-1 has increased considerably at all levels, from the gene to the protein, and on its specific roles in different physiological processes. In this review, we discuss the current understanding on SF-1 with focus on the parameters that control the transcriptional capacity of SF-1 and the mechanisms that ensure proper stage- and tissue-specific expression of the gene encoding SF-1.

The expression of nr0b1, the earliest gene in zebrafish tooth development, is a marker for human tooth and ameloblastoma formation

Zebrafish teeth develop on pharyngeal jaws in the 5th branchial arch, but early tooth development is remarkably similar to mammals (Borday-Birraux et al., Evol Dev 8:130, 2006). Recently, eve1 has been shown to be associated with the primary tooth (4V¹) and early ameloblast development, the enamel organ precursor (Laurenti et al., Dev Dyn 230:727, 2004). dax1 is initially expressed in the 5th branchial arch in zebrafish at approximately 26 h postfertilization (hpf) and colocalizes with eve1 expression at ~48 hpf. Embryos injected with dax1 morpholino show downregulation of eve1 expression. Based on the zebrafish observations, we demonstrated novel DAX1 expression in normal human dental, benign ameloblastoma, and malignant ameloblastoma tissues. The association of NR0B1 and its protein product DAX1 with primary tooth development and ameloblastoma tumorigenesis is an association not previously described.

X-linked congenital adrenal hypoplasia with hypogonadotropic hypogonadism caused by an inversion disrupting a conserved noncoding element upstream of the NR0B1 (DAX1) gene

CONTEXT

X-linked congenital adrenal hypoplasia with hypogonadotropic hypogonadism (AHCH) is known to be caused by coding mutations in the nuclear receptor subfamily 0, group B, member 1 (NR0B1) gene, encoding the transcriptional repressor dosage-sensitive sex-reversal adrenal hypoplasia critical region on the X chromosome protein 1 (DAX1).

OBJECTIVE/PATIENTS

Four males in a family were affected by AHCH. Our aim was to locate the genetic cause of their disease, knowing that they had no mutation in the obvious candidate gene, NR0B1.

DESIGN

Linkage analysis of the X chromosome and mutational screening of conserved noncoding regions upstream of NR0B1 were performed. To functionally characterize the genetic defect, studies of transcription and expression of DAX1 and steroidogenic factor 1 (SF-1) were done.

RESULTS

A 60 Mb inversion on the X chromosome with one of the inversion breakpoints located in a conserved noncoding region 4 kb upstream of NR0B1 was detected. The inversion causes relocation of a putative SF-1 binding site implicated in murine gonadal development. A reporter construct lacking this enhancer element upstream of NR0B1 was unresponsive to SF-1 transcriptional activation. Immunohistochemistry suggested that the inversion leads to SF-1 silencing in the patients' testes both in childhood and in adult life.

CONCLUSION

We report a noncoding mutation causing AHCH, an inversion resulting in a phenotype similar to what is caused by intragenic NR0B1 null mutations. The inversion seems to disrupt and/or relocate regulatory sites crucial in DAX1 expression.

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.

Three cases of congenital adrenal hypoplasia with novel mutations in the (NROB1) DAX-1 gene

Abnormalities in the DAX-1 gene (dosage-sensitive sex reversal-adrenal hypoplasia gene on the X chromosome) are a well-recognized cause of congenital adrenal hypoplasia. DAX-1 is expressed in the adrenal cortex, gonads, hypothalamus and anterior pituitary, which gives rise to the clinical features of this deletion. Presentations are varied but salt-wasting and/or hypoglycaemia are the most common in an infant, with late onset of hypogonadotrophic hypogonadism. Over 80 different mutations in this gene have been identified. We present three unrelated cases with variable clinical presentations, all with novel mutations in the DAX-1 gene.

Nuclear receptor DAX1 in human prostate cancer: a novel independent biological modulator

The orphan nuclear receptor DAX1 (dosage-sensitive sex reversal-AHC critical region on the X chromosome gene 1; NR0B1) has been known for its various roles in human development, specifically sex determination and steroidogenesis. Its expression has been reported in endocrine and sex steroid-dependent neoplasms such as human adrenocortical, pituitary, endometrial, and ovarian tumors. Prostate cancer is also sex steroid-dependent tumor in which androgens play important roles in the pathogenesis and development via androgen receptor (AR). DAX1 is also reported to repress AR activity in human prostate cancer cell line (LNCaP) but its biological roles have remained unclear in the human prostate cancer. The aim of this study is to examine the expression of DAX1 in human prostate cancer using immunohistochemistry in order to evaluate its possible biological and/or clinical significance. In this study, we examined the DAX1 immunoreactivity in human prostate cancer obtained from surgery (n = 40), and correlated the findings with clinicopathological features of the patients. Twenty-one cases were defined as positive cases for DAX1 immunoreactivity (53%). Immunoreactivity for DAX1 was inversely and significantly correlated with Gleason score (P<0.05). However, DAX1 immunoreactivity was not significantly correlated with the status of sex steroid receptors we examined. DAX1 immunoreactivity is considered a new biological modulator of human prostate cancer, but independent to the status of sex steroid receptors in human prostate cancer tissues.

DAX-1A (NR0B1A) expression levels are extremely low compared to DAX-1 (NR0B1) in human steroidogenic tissues

The orphan nuclear receptor DAX-1 (dosage-sensitive sex reversal-AHC critical region on the X chromosome gene 1; NR0B1) is known for its role in human development, specifically sex determination and steroidogenesis. Several recent publications have described an alternatively spliced form of DAX-1 called DAX-1A ( NR0B1A). DAX-1A is encoded by exons 1 and 2A of DAX-1, with exon 2A located within the DAX-1 intron 1. DAX-1A expression has been observed in several tissues, including adrenal gland, ovary, and testis. Transfection studies have further shown that DAX-1A has an inhibitory effect on DAX-1, suggesting a role for DAX-1A in the regulation of adrenal and gonadal differentiation/function. However, the relative level of DAX-1 versus DAX-1A transcripts still remains unclear. Herein, we developed and performed quantitative real-time RT-PCR to measure DAX-1 and DAX-1A mRNA expression levels in H295R human adrenal carcinoma cell lines, human adult and fetal adrenal glands, corpus luteum, testis, whole pre- and postmenopausal ovaries, ovarian follicles, placenta, liver, and kidney. These mRNA expression levels were quantified using DAX-1 and DAX-1A standard curves. In addition, Western blotting analysis was performed to examine both DAX-1 and DAX-1A protein levels in H295R cells, adrenal glands, corpus luteum, and liver. Both DAX-1 and DAX-1A mRNA were detected in all samples of H295R cells, human fetal and adult adrenals, testis, ovary, ovarian follicles, and corpus luteum. However, DAX-1 mRNA levels were significantly higher (> 37-fold) than that seen for DAX-1A (p<0.01). DAX-1A mRNA expression levels were undetectable in human liver, placenta, and kidney. Western blotting analysis results demonstrated that DAX-1 protein was predominantly expressed in H295R cells, human adult adrenal, and corpus luteum. These results suggest that in comparison to DAX-1A, DAX-1 is, by far, the predominant mRNA isoform found in human adrenal glands and gonads.

Clinical and genetic analysis of a Korean patient with late-onset X-linked adrenal hypoplasia congenita and hypogonadotropic hypogonadism: identification of a novel mutation in the NR0B1 gene

Adrenal hypoplasia congenita (AHC) is caused by mutations in the NR0B1 gene on chromosome Xp21.3-p21.2. It manifests as X-linked primary adrenal failure in early infancy or childhood and as hypogonadotropic hypogonadism (HHG) at puberty. Although studies of AHC patients and mutations in the NR0B1 gene have been reported throughout the world, there has previously been only one other case report from Korea. We encountered a 23-year old Korean male with delayed-onset AHC/HHG who had been previously diagnosed with adrenal insufficiency of unknown aetiology at age 13 years. Delayed puberty and incomplete HHG were observed. Direct sequencing of the NR0B1 gene revealed the patient to have a novel insertion mutation (c.959_960insT; Leu321ProfsX68). Although AHC is believed to be rare, it should be considered in a differential diagnosis of patients showing late-onset primary adrenal insufficiency.

Seminiferous tubule function in delayed-onset X-linked adrenal hypoplasia congenita associated with incomplete hypogonadotrophic hypogonadism

OBJECTIVE

X-linked adrenal hypoplasia congenita (AHC, OMIM 300200) due to mutations in the DAX-1 gene is frequently associated to hypogonadotrophic hypogonadism (HHG, OMIM 238320). Clinical variants with delayed-onset have been recognized. The objective of this study is to assess Sertoli cell function throughout pubertal development in patients with childhood-onset AHC due to stop mutations in the DAX-1 gene.

DESIGN

Observational follow-up study of gonadotrophin pulsatility pattern, and serum levels of antimüllerian hormone and inhibin B through pubertal development in these patients.

PATIENTS

Three patients belonging to two families with AHC were included in this study.

MEASUREMENTS

The gonadotrophic pattern, serum inhibin B and antimüllerian hormone were determined in relation to clinical Tanner stage of pubertal development.

RESULTS

One patient showed a marked elevation in serum FSH concomitantly with low inhibin B and antimüllerian hormone levels, indicating a primary testicular dysfunction. The other two patients showed a gonadotrophic pattern of HHG, and their serum levels of inhibin B and antimüllerian hormone also reflected a moderate primary testicular dysfunction. The three patients were azoospermic.

CONCLUSIONS

These cases give further insight into the clinical spectrum of phenotypes of the hypothalamic-pituitary-gonadal axis in patients with variants in hypogonadism associated with childhood-onset X-linked AHC due to DAX-1 mutations.

LXXLL motifs and AF-2 domain mediate SHP (NR0B2) homodimerization and DAX1 (NR0B1)-DAX1A heterodimerization

Small heterodimer partner (SHP; NR0B2) is an unusual orphan member of the nuclear receptor superfamily that functions as a corepressor of other nuclear receptors through heterodimeric interactions. Mutations in SHP are associated with mild obesity and insulin resistance. The protein domain structure of SHP is similar to Dosage-sensitive sex reversal adrenal hypoplasia congenita (AHC) critical region on the X chromosome, gene 1 (DAX1; NR0B1). Mutations in DAX1 cause AHC with associated hypogonadotropic hypogonadism. DAX1A is an alternatively spliced isoform of DAX1 that lacks the last 80 amino acids of the DAX1 C-terminal repressor domain and is replaced by a novel 10-amino acid motif. We have previously shown homodimerization of SHP and DAX1 individually, heterodimerization of DAX1 with SHP, and heterodimerization of DAX1 with DAX1A. In these studies, we investigated the domains and residues of SHP involved in SHP homodimerization and DAX1-SHP heterodimerization and also further characterized DAX1-DAX1 homodimerization and DAX1-DAX1A heterodimerization. We showed involvement of the SHP LXXLL motifs and AF-2 domain in SHP homodimerization and DAX1-SHP heterodimerization. We demonstrated redundancy of the LXXLL motifs in DAX1 homodimerization. While DAX1A subcellular localization is mostly cytoplasmic, DAX1-DAX1A heterodimers existed in the nucleus, suggesting differential functions for DAX1A in each compartment. We showed that the AF-2 domain of DAX1 is involved in DAX1-DAX1A heterodimerization. These results indicate that NR0B family members use similar mechanisms for homodimerization as well as heterodimerization. These resemble coactivator-receptor interactions that may have potential functional consequences for molecular mechanisms of the NR0B family.

The control of sexual differentiation of the reproductive system and brain

This review summarizes current knowledge of the genetic and hormonal control of sexual differentiation of the reproductive system, brain and brain function. While the chromosomal regulation of sexual differentiation has been understood for over 60 years, the genes involved and their actions on the reproductive system and brain are still under investigation. In 1990, the predicted testicular determining factor was shown to be theSRYgene. However, this discovery has not been followed up by elucidation of the actions of SRY, which may either stimulate a cascade of downstream genes, or inhibit a suppressor gene. The number of other genes known to be involved in sexual differentiation is increasing and the way in which they may interact is discussed. The hormonal control of sexual differentiation is well-established in rodents, in which prenatal androgens masculinize the reproductive tract and perinatal oestradiol (derived from testosterone) masculinizes the brain. In humans, genetic mutations have revealed that it is probably prenatal testosterone that masculinizes both the reproductive system and the brain. Sexual differentiation of brain structures and the way in which steroids induce this differentiation, is an active research area. The multiplicity of steroid actions, which may be specific to individual cell types, demonstrates how a single hormonal regulator, e.g. oestradiol, can exert different and even opposite actions at different sites. This complexity is enhanced by the involvement of neurotransmitters as mediators of steroid hormone actions. In view of current environmental concerns, a brief summary of the effects of endocrine disruptors on sexual differentiation is presented.

Two sisters with IMAGe syndrome: cytomegalic adrenal histopathology, support for autosomal recessive inheritance and literature review

Adrenal hypoplasia congenita (AHC) is a rare condition and causes primary adrenal insufficiency. X-linked (OMIM 300200) and autosomal recessive (OMIM 240200) forms are recognized. Recently, an association between Intrauterine growth restriction, Metaphyseal dysplasia, Adrenal hypoplasia congenita, and Genital abnormalities (IMAGe syndrome; OMIM 300290) has been described. We present the clinical features of two sisters with intrauterine growth restriction, AHC, and dysmorphic features. Interesting histopathologic findings of one sister are also presented. We suggest that IMAGe syndrome is the most plausible diagnosis and that autosomal recessive inheritance is likely. We analyzed genes that were postulated candidates for IMAGe syndrome (SF1, DAX-1, and STAR), and no mutations were found. Other cases of IMAGe syndrome are reviewed.

Zebrafish dax1 is required for development of the interrenal organ, the adrenal cortex equivalent

Mutations in the human nuclear receptor, DAX1, cause X-linked adrenal hypoplasia congenita (AHC). We report the isolation and characterization of a DAX1 homolog, dax1, in zebrafish. The dax1 cDNA encodes a protein of 264 amino acids, including the conserved carboxy-terminal ligand binding-like motif; but the amino-terminal region lacks the unusual repeats of the DNA binding-like domain in mammals. Genomic sequence analysis indicates that the dax1 gene structure is conserved also. Whole-mount in situ hybridization revealed the onset of dax1 expression in the developing hypothalamus at approximately 26 h post fertilization (hpf). Later, at about 28 hpf, a novel expression domain for dax1 appeared in the trunk. This bilateral dax1-expressing structure was located immediately above the yolk sac, between the otic vesicle and the pronephros. Interestingly, weak and transient expression of dax1 was observed in the interrenal glands (adrenal cortical equivalents) at approximately 31 hpf. This gene was also expressed in the liver after 3 dpf in the zebrafish larvae. Disruption of dax1 function by morpholino oligonucleotides (MO) down-regulated expression of steroidogenic genes, cyp11a and star, and led to severe phenotypes similar to ff1b (SF1) MO-injected embryos. Injection of dax1 MO did not affect ff1b expression, whereas ff1b MO abolished dax1 expression in the interrenal organ. Based on these results, we propose that dax1 is the mammalian DAX1 ortholog, functions downstream of ff1b in the regulatory cascades, and is required for normal development and function of the zebrafish interrenal organ.

A familial missense mutation in the hinge region of DAX1 associated with late-onset AHC in a prepubertal female

Mutations in the DAX1 (Dosage-sensitive sex reversal-Adrenal hypoplasia congenita (AHC) critical region on the X chromosome gene 1; NR0B1) cause X-linked AHC, a disease characterized by primary adrenal failure in infancy and hypogonadotropic hypogonadism. All known missense mutations impair DAX1 repression of steroidogenic factor 1 (SF1) transactivation and have been localized to the putative ligand binding domain. Here, an asymptomatic father and his late-onset AHC daughter were both shown to share a novel DAX1 mutation (C200W), the first missense mutation identified in the hinge region of DAX1. Using immunohistochemistry we demonstrate that the sub-cellular localization of the C200W mutant DAX1 protein is shifted from the nucleus to the cytoplasm. The disturbed localization of the C200W mutant in transfected cells correlates with impaired transcriptional repression activity. The import defect is relatively mild, retaining 80% of wild-type activity, which may explain the unusually mild phenotype. Import of DAX1 into the nucleus involves a direct interaction with SF1. In vitro assays demonstrate that the C200W mutant retains the ability to functionally interact with SF1, which suggests that SF1-independent interactions of DAX1 could be responsible for the import defect.

Importance of genetic diagnosis of DAX-1 deficiency: example from a large, multigenerational family

BACKGROUND

Inactivating mutations of DAX-1 give rise to the X-linked form of adrenal hypoplasia congenita (AHC). Affected fetuses are at risk of early postnatal Addisonian crisis, but the variable phenotypic expression of DAX-1 insufficiency renders this diagnosis challenging.

METHODS

We describe the familial transmission of AHC over several generations. The proband was diagnosed with adrenal insufficiency at age 3.5 years: molecular analysis revealed a novel, 373-bp deletion including the second exon of DAX-1. Given the familial history of several unexplained deaths in male infants related to the proband via his maternal great-grandmother, we hypothesized that all these boys had been affected with AHC. Another female member of the family being pregnant with a male fetus at the time, we performed DAX-1 analysis on the mother and the newborn. The mother was heterozygous for the deletion, and the newborn hemizygous: he presented an adrenal crisis at 10 days of life, and is now doing well on hormone replacement therapy.

CONCLUSION

The unfortunate deaths of male infants at each generation of this family underlie the importance of early and precise diagnosis of this rare condition, stressing the value of genetic diagnosis in six potential female carriers of this family entering their reproductive years.