DAX1 Mutations Research Articles

Adrenal Hypoplasia Congenita Presenting as Congenital Adrenal Hyperplasia

We report on a patient with genetically confirmed adrenal hypoplasia congenita (AHC) whose presentation and laboratory abnormalities were consistent with the more common condition, congenital adrenal hyperplasia (CAH). The patient presented with failure to thrive and salt wasting. General appearance showed marked hyperpigmentation and normal male genitalia. He displayed mildly elevated 17-hydroxyprogesterone and markedly elevated 11-deoxycortisol levels at baseline and with ACTH stimulation testing. Results were consistent with 11β-hydroxylase deficiency. He required glucocorticoids and high doses of mineralocorticoids. The marked elevation in 11-deoxycortisol directed our clinical reasoning away from a hypoplastic condition and towards a hyperplasic adrenal condition. Sequencing of the DAX1 gene (named for dosage-sensitive sex reversal (DSS) locus and the AHC locus on the X chromosome) revealed a missense mutation. A review of the literature revealed that elevated 11-deoxycortisol levels have been noted in kindreds with DAX1 mutations, but only when measured very early in life. A mouse model has recently been described that displays elevated 11-deoxycorticosterone levels and evidence for hyperplasia of the zona glomerulosa of the adrenal gland. We conclude that DAX1 testing may be considered in patients with laboratory evidence of 11β-hydroxylase deficiency, especially in those with severe salt wasting.

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

IntroductionX-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 presentationA 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.ConclusionsWe 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.

A novel DAX1/NR0B1 mutation in a patient with adrenal hypoplasia congenita and hypogonadotropic hypogonadism

We report a case of adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HH) due to a novel DAX1 mutation. A 19-month-old boy with hyperpigmentation and failure to thrive came to our service for investigation. Three brothers of the patient had died due to adrenal failure, and a maternal cousin had adrenal insufficiency. Adrenoleukodystrophy was excluded. MRI showed normal pituitary and hypothalamus. Plasma hormone evaluation revealed high ACTH (up to 2,790 pg/mL), and low levels of androstenedione, DHEA-S, 11-deoxycortisol, and cortisol. At 14 years of age the patient was still prepubescent, his weight was 43.6 kg (SDS: -0.87) and his height was 161 cm (SDS: -0.36), with normal body proportions. In the GnRH test, basal and maximum values of LH and FSH were respectively 0.6/2.1 and < 1.0/< 1.0 U/L. Molecular investigation identified a novel mutation that consists of a deletion of codon 372 (AAC; asparagine) in exon 1 of DAX1. This mutation was not found in a study of 200 alleles from normal individuals. Prediction site analysis indicated that this alteration, located in the DAX1 ligand-binding domain, may damage DAX1 protein. We hypothesize that the novel (p.Asp372del) DAX1 mutation might be able to cause a disruption of DAX1 function, and is probably involved in the development of AHC and HH in this patient.

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.

The DAX1 mutation in a patient with hypogonadotropic hypogonadism and adrenal hypoplasia congenita causes functional disruption of induction of spermatogenesis

Hypogonadotropic hypogonadism (HH) associated with adrenal hypoplasia congenita (AHC) is a very rare syndrome caused by mutation of DAX1 (dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome) [19]. The DAX1 is located on the chromosome X (Xp21.3–21.2) and contains two exons. It encodes a 470-amino acid protein which belongs to the nuclear hormone receptor superfamily (called DAX1). DAX1 is expressed in the adrenal cortex, pituitary and hypothalamus, gonadal cells such as Leydig and Sertoli cells, theca and granulosa cells and in germ cells [15, 26]. Patients with HH due to DAX1 mutation exhibited azoospermia [4, 5, 17, 24]. Results of spermatogenesis induction using exogenous gonadotropin are unsatisfactory [4, 17, 24]. However, Frapsauce et al. [5] has recently presented the first birth after successful assisted reproductive technique (ART) using TESE-ICSI in a man with HH and AHC linked to a DAX1 mutation. In this case, long period of gonadotropin treatment allowed for development of few mature spermatozoa obtained from testicular biopsy and used for ICSI [5]. Here, we report clinical and immunohistochemical studies of patient with HH and AHC due to deletion of the second exon of the DAX1 in order to induce spermatogenesis by gonadotropins treatment.

The analysis of clinical manifestations and genetic mutations in Chinese boys with primary adrenal insufficiency

To analyze the clinical manifestations of primary adrenal insufficiency in Chinese boys, to investigate the prevalence of DAX1 and SF1 gene mutations, and to explore the association between gene mutations and clinical manifestations. A total of 25 boys with primary adrenal insufficiency were enrolled. Mutational analysis of the DAX1 and SF1 genes was done by direct sequencing. DAX1 gene mutations were found in 40% (10 of 25) of 46,XY phenotypic boys referred with adrenal insufficiency, and six of these were novel. One SF1 gene mutation was identified. These patients demonstrated diverse clinical presentations. There was no definite association between clinical manifestations and genetic mutations. DAX1 gene mutations are a relatively frequent cause of primary adrenal insufficiency. In contrast, mutation in the SF1 gene is seldom found. There is no definite relationship between gene mutations and clinical manifestations.

Functional effects of DAX-1 mutations identified in patients with X-linked adrenal hypoplasia congenita

Functional effects of DAX-1 mutations identified in patients with X-linked adrenal hypoplasia congenita

Functional effects of DAX-1 mutations identified in patients with X-linked adrenal hypoplasia congenita

X-linked adrenal hypoplasia congenita with hypogonadotropic hypogonadism and adrenal insufficiency is a rare disorder caused by mutations of DAX-1. In this study, we investigated the functional defects of DAX-1 caused by mutations identified in 3 unrelated Korean patients with adrenal hypoplasia congenita. The DAX-1 gene was directly sequenced using genomic DNA isolated from peripheral blood leukocytes. The functional defects of DAX-1 caused by mutations were evaluated using an in vitro promoter assay. After mutagenesis of DAX-1 complementary DNA in the pcDNA3.1 vector, steroidogenic factor 1 and the promoter region of steroidogenic acute regulatory protein ( StAR) genes in pGL4.10[ luc2] were transiently cotransfected into human embryonic kidney 293 cells, followed by luminometry measurements of the luciferase activity of StAR. Mutation analysis of 3 patients revealed p.L386delfsX2, p.W105X, and p.Q252X mutations of the DAX-1 gene. The mutant DAX-1 proteins showed lower repressive activity on the StAR gene promoter when compared with normal DAX-1. Nonsense and frameshift mutations of the DAX-1 gene partially eliminated the ability of DAX-1 to repress the transcription of StAR in an in vitro assay.

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.

Seven NovelDAX1Mutations with Loss of Function Identified in Chinese Patients with Congenital Adrenal Hypoplasia

DAX1 (for dosage-sensitive sex reversal, adrenal hypoplasia congenital critical region on the X chromosome, gene 1; also called NROB1) mutations are responsible for adrenal failure and hypogonadotropic hypogonadism in patients with adrenal hypoplasia congenita (AHC), through a loss of trans-repression of SF-1 (for steroidogenic factor-1)-mediated StAR (for steroidogenic acute regulatory protein) and LHbeta transcriptional activities and a reduction of GnRH expression. The correlation of clinical features with genetic and functional alterations of the gene was investigated in detail in AHC patients. The present study aimed at identifying DAX1 mutations in Chinese AHC patients and investigating the functional defects of detected novel mutations. Nine patients with AHC were recruited from eight families. DAX1 mutations were screened, and the transcriptional activities of the identified mutations were assessed in vitro. DAX1 mutations were detected in all nine patients enrolled in the study, with eight different mutations. Among the latter, seven are novel mutations, including two missense (L262P and C368F), one nonsense (Q222X), and four frame-shift (637delC, 652_653delAC, 973delC, and 774_775insCC) mutations. The functional studies showed that the mutant DAX1 was impaired by nuclear localization, loss of trans-repression of StAR and LHbeta transcriptional activities, and reduction of GnRH expression. These findings provide insight into the molecular events by which DAX1 mutations influence the hypothalamus-pituitary-gonadal and hypothalamus-pituitary-adrenal axis and lead to AHC and hypogonadotropic hypogonadism.

Orphan Nuclear Receptor DAX-1 Acts as a Novel Corepressor of Liver X Receptor α and Inhibits Hepatic Lipogenesis

DAX-1 (dosage-sensitive sex reversal adrenal hypoplasia congenital critical region on X chromosome, gene 1) is a member of the nuclear receptor superfamily that can repress diverse nuclear receptors and has a key role in adreno-gonadal development. Our previous report has demonstrated that DAX-1 can inhibit hepatocyte nuclear factor 4alpha transactivity and negatively regulate gluconeogenic gene expression (Nedumaran, B., Hong, S., Xie, Y. B., Kim, Y. H., Seo, W. Y., Lee, M. W., Lee, C. H., Koo, S. H., and Choi, H. S. (2009) J. Biol. Chem. 284, 27511-27523). Here, we further expand the role of DAX-1 in hepatic energy metabolism. Transfection assays have demonstrated that DAX-1 can inhibit the transcriptional activity of nuclear receptor liver X receptor alpha (LXRalpha). Physical interaction between DAX-1 and LXRalpha was confirmed Immunofluorescent staining in mouse liver shows that LXRalpha and DAX-1 are colocalized in the nucleus. Domain mapping analysis shows that the entire region of DAX-1 is involved in the interaction with the ligand binding domain region of LXRalpha. Competition analyses demonstrate that DAX-1 competes with the coactivator SRC-1 for repressing LXRalpha transactivity. Chromatin immunoprecipitation assay showed that endogenous DAX-1 recruitment on the SREBP-1c gene promoter was decreased in the presence of LXRalpha agonist. Overexpression of DAX-1 inhibits T7-induced LXRalpha target gene expression, whereas knockdown of endogenous DAX-1 significantly increases T7-induced LXRalpha target gene expression in HepG2 cells. Finally, overexpression of DAX-1 in mouse liver decreases T7-induced LXRalpha target gene expression, liver triglyceride level, and lipid accumulation. Overall, this study suggests that DAX-1, a novel corepressor of LXRalpha, functions as a negative regulator of lipogenic enzyme gene expression in liver.

Role of Seminiferous Tubular Development in Determining the FSH versus LH Responsiveness to GnRH in Early Sexual Maturation

Background: The onset of sexual maturation at puberty is a unique developmental period from a neuroendocrine perspective in that it is characterized by enhanced FSH secretion and FSH responsiveness to exogenous GnRH (vs. LH) from the gonadotrope, yet the mechanism of these dynamics remains unclear. This study aimed to elucidate this phenomenon using a human disease model of GnRH deficiency (idiopathic hypogonadotropic hypogonadism, IHH) in which GnRH input can be experimentally controlled. Methods: 25 GnRH-deficient men were selected for study based upon their baseline testicular volumes (TV) and serum inhibin B (I_B) levels to represent a spectrum of pubertal/testicular development. Subjects underwent: (i) a 12-hour overnight neuroendocrine evaluation for hormonal profiling and determination of endogenous LH secretion pattern, and (ii) a 7-day exposure to a physiologic regimen of exogenous pulsatile GnRH (25 ng/kg every 2 h). Daily measurements of serum testosterone (T) and I_B levels were made and a 2-hour window of frequent blood sampling was monitored to measure LH and FSH following a single i.v. GnRH bolus (25 ng/kg). All subjects were screened for known loci underlying GnRH deficiency and the response to GnRH was tracked according to genotype. Results: Among the entire cohort, no changes were noted in serum T or I_B during the 7 days, thus keeping gonadal feedback relatively constant. However, serum LH and FSH levels increased significantly (p < 0.0001) in the entire cohort. When analyzed by degree of pubertal/testicular development, men with no evidence of prior spontaneous pubertal development (TV ≤3 ml, Group I) showed sharp increases in serum FSH compared to men with some prior evidence of partial puberty (TV >3 ml, Group II, p < 0.0001). Group I exhibited a decreased LH response to GnRH on day 2 compared to day 1 (p < 0.01), which did not recover until day 5 (1–4 vs. 5–7 days, p < 0.0001). Group II displayed robust and equivalent LH responses to GnRH throughout the 7-day study. Genetic studies identified 8 mutations in 4 different loci (DAX1, KAL1, GNRHR, and FGFR1) in this cohort. Conclusions: GnRH-deficient men undergoing GnRH-induced sexual maturation display an inverse relationship between FSH responsiveness to GnRH and baseline testicular size and I_B levels. This observation implies that increasing seminiferous tubule maturity represents the major constraint on FSH responsiveness to GnRH in early puberty. In contrast, LH responsiveness to GnRH correlates directly with duration of GnRH exposure. Attenuated pituitary gonadotropin responses were noted in subjects harboring DAX1 mutations, consistent with known pituitary defects.

A novel mutation in DAX1 (NR0B1) causing X-linked adrenal hypoplasia congenita: clinical, hormonal and genetic analysis

The association of primary adrenal insufficiency and hypogonadotropic hypogonadism is extremely infrequent in daily clinical practice. Differential diagnosis includes X-linked adrenal hypoplasia congenita, a genetic disease characterized by an alteration in the formation of the adrenal glands and the hypothalamus-pituitary-gonadal axis. The gene responsible is DAX1 (NR0B1). The most common form of clinical presentation is neonatal primary adrenal insufficiency and complete hypogonadotropic hypogonadism. Members of a single family often present the same clinical form, although there may be relatives affected with different clinical symptoms. The aim of this study is to characterize clinically and genetically a family affected by different forms of hypogonadotropic hypogonadism and/or primary adrenal insufficiency. We describe a family with three members affected, two adults and a neonate. The way of presentation of the adults was neonatal primary adrenal insufficiency and hypogonadotropic hypogonadism (one complete and another presenting as interrupted puberty). The genetic study revealed a new mutation in DAX1, p.Q76X gene (c.C226T), resulting in a truncated protein of 76 amino acids, the same in all three affected male patients and in the asymptomatic women of the family. These cases further expand the number of DAX1 mutations reported, as well as the description of infrequent forms of presentation of this disease as interrupted puberty.

Dax-1 and Steroid Receptor RNA Activator (SRA) Function as Transcriptional Coactivators for Steroidogenic Factor 1 in Steroidogenesis

The nuclear receptor steroidogenic factor 1 (SF-1) is essential for adrenal development and steroidogenesis. The atypical orphan nuclear receptor Dax-1 binds to SF-1 and represses SF-1 target genes. Paradoxically, however, loss-of-function mutations of Dax-1 also cause adrenal hypoplasia, suggesting that Dax-1 may function as an SF-1 coactivator under some circumstances. Indeed, we found that Dax-1 can function as a dosage-dependent SF-1 coactivator. Both SF-1 and Dax-1 bind to steroid receptor RNA activator (SRA), a coactivator that functions as an RNA. The coactivator TIF2 also associates with Dax-1 and synergistically coactivates SF-1 target gene transcription. A naturally occurring Dax-1 mutation inhibits this transactivation, and the mutant Dax-1-TIF2 complex mislocalizes in living cells. Coactivation by Dax-1 is abolished by SRA knockdown. The expression of the steroidogenic gene products steroidogenic acute regulatory protein (StAR) and melanocortin 2 receptor is reduced in adrenal Y1 cells following the knockdown of endogenous SRA. Similarly, the knockdown of endogenous Dax-1 downregulates the expression of the steroidogenic gene products CYP11A1 and StAR in both H295R adrenal and MA-10 Leydig cells. These findings reveal novel functions of SRA and Dax-1 in steroidogenesis and adrenal biology.

A Phenotypic Spectrum of Sexual Development in Dax1 (Nr0b1)-Deficient Mice: Consequence of the C57BL/6J Strain on Sex Determination1

Nuclear receptor subfamily 0, group B, member 1 (Nr0b1; hereafter referred to as Dax1) is an orphan nuclear receptor that regulates adrenal and gonadal development. Dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene 1 (Dax1) mutations in the mouse are sensitive to genetic background. In this report, a spectrum of impaired gonadal differentiation was observed as a result of crossing the Dax1 knockout on the 129SvIm/J strain onto the C57BL/6J strain over two generations of breeding. Dax1-mutant XY mice of a mixed genetic background (129;B6Dax1(-/Y) [101 total]) developed gonads that were predominantly testislike (n = 61), ovarianlike (n = 27), or as intersex (n = 13). During embryonic development, Sox9 expression in the gonads of 129;B6Dax1(-/Y) mutants was distributed across a wide quantitative range, and a threshold level of Sox9 (>0.4-fold of wild-type) was associated with testis development. Germ cell fate also varied widely, with meiotic germ cells being more prevalent in the ovarianlike regions of embryonic gonads, but also observed within testicular tissue. Ptgds, a gene associated with Sox9 expression and Sertoli cell development, was markedly downregulated in Dax1(-/Y) mice. Stra8, a gene associated with germ cell meiosis, was upregulated in Dax1(-/Y) mice. In both cases, the changes in gene expression also occurred in pure 129 mice but were amplified in the B6 genetic background. Sertoli cell apoptosis was prevalent in 129;B6Dax1(-/Y) gonads. In summary, Dax1 deficiency on a partial B6 genetic background results in further modulation of gene expression changes that affect both Sertoli cell and germ cell fate, leading to a phenotypic spectrum of gonadal differentiation.

DAX-1 (Dosage-Sensitive Sex Reversal-Adrenal Hypoplasia Congenita Critical Region on the X-Chromosome, Gene 1) Selectively Inhibits Transactivation But Not Transrepression Mediated by the Glucocorticoid Receptor in a LXXLL-Dependent Manner

The glucocorticoid receptor (GR) mediates virtually all actions of glucocorticoids, and the nature and magnitude of a cell's response to these steroids are determined primarily by hormone concentration and GR signaling capacity. DAX-1 (dosagesensitive sex reversal-adrenal hypoplasia congenita critical region on the X-chromosome, gene 1) is an orphan nuclear receptor that functions as a corepressor, and deletion or mutation of DAX-1 causes a decrease in glucocorticoid production. However it is unclear whether DAX-1 also alters GR function as a transcription factor. Here, we demonstrate that DAX-1 acts as a novel selective GR modulator. It specifically inhibits ligand-dependent GR transactivation with little effect on GR-mediated transrepression. As demonstrated by coimmunoprecipitation and glutathione- S-transferase pull-down assays, DAX-1 physically interacts with GR, but this interaction does not influence either ligand-induced GR nuclear translocation or subsequent GR association with glucocorticoid-responsive elements. Instead, DAX-1 competes with coactivators such as GR-interacting protein 1 for binding to the receptor. Specifically, suppression of GR transactivation is mediated by the N-terminal half of DAX-1, and in particular the LXXLL motifs. Thus we demonstrate that DAX-1 directly modulates GR signaling in addition to affecting glucocorticoid hormone levels.

XX Maleness and XX True Hermaphroditism inSRY-Negative Monozygotic Twins: Additional Evidence for a Common Origin

Differentiation of testicular tissue in 46,XX individuals is seen either in XX males, the majority of them with SRY gene, or in individuals, usually SRY(-), with ovotesticular disorder of sex development (OT-DSD). Although they are sporadic cases, there are some reports on familial recurrence, including coexistence of XX maleness and OT-DSD in the same family. We report on a case of SRY(-) 46,XX monozygotic twins with genital ambiguity. Hormonal evaluation included testosterone, FSH, and LH measurements. SRY gene was investigated by PCR and two-step PCR in peripheral leukocytes and gonadal tissues, respectively. Direct DNA sequencing of the DAX-1 coding sequence was performed. Real-time PCR for SOX9 region on chromosome 17 was obtained. Both twins had a 46,XX karyotype. Twin A had a 1-cm phallus with chordee, penoscrotal hypospadias, and palpable gonads. Serum levels of FSH (2.34 mIU/ml), LH (8.8 mIU/ml), and testosterone (1.6 ng/ml) were normal, and biopsies revealed bilateral testes. Twin B had a 0.5-cm phallus, perineal hypospadias, no palpable gonad on the right, and a left inguinal hernia. Hormonal evaluation revealed high FSH (8.2 mIU/ml) and LH (15 mIU/ml) and low testosterone (0.12 ng/ml). Upon herniotomy, a right testis (crossed ectopia) and a small left ovotestis were found. SRY gene was absent in both peripheral leukocytes and gonadal tissue samples. Neither DAX-1 mutations nor SOX9 duplication was identified. This case provides evidence that both XX maleness and XX OT-DSD are different manifestations of the same disorder of gonadal development.

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.

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

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. Observational follow-up study of gonadotrophin pulsatility pattern, and serum levels of antimüllerian hormone and inhibin B through pubertal development in these patients. Three patients belonging to two families with AHC were included in this study. The gonadotrophic pattern, serum inhibin B and antimüllerian hormone were determined in relation to clinical Tanner stage of pubertal development. 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. 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.

An Amino-Terminal DAX1 (NROB1) Missense Mutation Associated with Isolated Mineralocorticoid Deficiency

Mutations in DAX1 (dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome gene 1; NR0B1) cause X-linked adrenal hypoplasia congenita, a disease characterized by primary adrenal failure, testicular dysgenesis, and gonadotropin deficiency. Most DAX1 mutations are deletions, nonsense, or frameshift mutations that markedly impair its transcriptional activity. Missense mutations have been restricted to the carboxy-terminal domain and are associated with more variable clinical phenotypes. The objective was to identify novel clinical phenotypes associated with DAX1 missense mutations. We investigated the genetic basis of isolated mineralocorticoid deficiency in a patient who carries a unique missense mutation (W105C) in the amino-terminal region of DAX1. The W105C DAX1 mutation in the proband was present in three asymptomatic hemizygous males, but it was not detected in the general population. Using in vitro studies of DAX1 expression and function in transfected cells, we demonstrate that the mutant DAX1 protein exhibits mild loss of function, whether studied for genes it represses or for genes it activates. Structure-function studies suggest that the W105C and other mutations in the aminoterminus are compensated by the presence of repeated LXXLL motifs that mediate DAX1 interactions with other proteins. We describe the first missense mutation in the aminoterminus of DAX1 and conclude that mutations in this region may be partially compensated by redundant functional domains. Mild DAX1 mutations may be a cause of isolated mineralocorticoid deficiency.