Three novel mutations and a de novo deletion mutation of the DAX-1 gene in patients with X-linked adrenal hypoplasia congenita

Translating genomics to the clinical diagnosis of disorders/differences of sex development

The medical and psychosocial challenges faced by patients living with Disorders/Differences of Sex Development (DSD) and their families can be alleviated by a rapid and accurate diagnostic process. Clinical diagnosis of DSD is limited by a lack of standardization of anatomical and endocrine phenotyping and genetic testing, as well as poor genotype/phenotype correlation. Historically, DSD genes have been identified through positional cloning of disease-associated variants segregating in families and validation of candidates in animal and in vitro modeling of variant pathogenicity. Owing to the complexity of conditions grouped under DSD, genome-wide scanning methods are better suited for identifying disease causing gene variant(s) and providing a clinical diagnosis. Here, we review a number of established genomic tools (karyotyping, chromosomal microarrays and exome sequencing) used in clinic for DSD diagnosis, as well as emerging genomic technologies such as whole-genome (short-read) sequencing, long-read sequencing, and optical mapping used for novel DSD gene discovery. These, together with gene expression and epigenetic studies can potentiate the clinical diagnosis of DSD diagnostic rates and enhance the outcomes for patients and families.

X-Linked Adrenal Hypoplasia Congenita in a Boy due to a Novel Deletion of the Entire NR0B1 (DAX1) and MAGEB1-4 Genes

X-linked Adrenal Hypoplasia Congenita (AHC) is caused by deletions or point mutations in the NR0B1 (DAX1) gene. We present a boy with AHC who came at the age of 25 days in a severe state due to prolonged vomiting and progressive dehydration. Laboratory studies showed prominent hyponatremia and hyperkaliemia but not hypoglycemia. Primary adrenal insufficiency was confirmed with low serum cortisol levels and high plasma ACTH levels. Hydrocortisone therapy combined with saline and glucose infusions was started immediately after blood collection. Two exons of the NR0B1 (DAX1) gene were impossible to amplify using the standard PCR method. Array CGH was used to confirm the putative copy-number variation of NR0B1 (DAX1) revealing a novel hemizygous deletion encompassing the entire NR0B1 (DAX1) gene together with the MAGEB genes. This genetic defect was also present in heterozygosity in the patient's mother. We show that NR0B1 (DAX1) gene analysis is important for confirmation of AHC diagnosis and highlights the role of genetic counseling in families with AHC patients, particularly those with X chromosome microdeletions, covering more than NR0B1 (DAX1) alone. We hope that further clinical follow-up of this patient and his family will shed a new light on the role of MAGEB genes.

X-linked adrenal hypoplasia congenita: clinical and follow-up findings of two kindreds, one with a novel NR0B1 mutation

X-linked adrenal hypoplasia congenita typically manifests as primary adrenal insufficiency in the newborn age and hypogonadotropic hypogonadism in males, being caused by mutations in NR0B1 gene. We present the clinical and follow-up findings of two kindreds with NR0B1 mutations. The proband of kindred A had a diagnosis of primary adrenal insufficiency when he was a newborn. Family history was relevant for a maternal uncle death at the newborn age. Beyond 2 year-old steroid measurements rendered undetectable and delayed bone age was noticed. Molecular analysis of NR0B1 gene revealed a previously unreported mutation (c.1084A>T), leading to a premature stop codon, p.Lys362*, in exon 1. His mother and sister were asymptomatic carriers. At 14 year-old he had 3 mL of testicular volume and biochemical surveys (LH < 0.1 UI/L, total testosterone < 10 ng/dL) concordant with hypogonadotrophic hypogonadism. Kindred B had two males diagnosed with adrenal insufficiency at the newborn age. By 3 year-old both siblings had undetectable androgen levels and delayed bone age. NR0B1 molecular analysis identified a nonsense mutation in both cases, c.243C>G; p.Tyr81*, in exon 1. Their mother and sister were asymptomatic carriers. At 14 year-old (Tanner stage 1) hypothalamic-pituitary-gonadal axis evaluation in both males (LH < 0.1UI/L, total testosterone < 10 ng/dL) confirmed hypogonadotropic hypogonadism. In conclusion, biochemical profiles, bone age and an X-linked inheritance led to suspicion of NR0B1 mutations. Two nonsense mutations were detected in both kindreds, one previously unreported (c.1084A>T; p.Lys362*). Mutation identification allowed the timely institution of testosterone in patients at puberty and an appropriate genetic counselling for relatives.

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.

Hypogonadotropic hypogonadism in subjects with DAX1 mutations

DAX1 (dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1; also known as NROB1, nuclear receptor subfamily 0, group B, member 1) encodes a nuclear receptor that is expressed in embryonic stem (ES) cells, steroidogenic tissues (gonads, adrenals), the ventromedial hypothalamus (VMH), and pituitary gonadotropes. Humans with DAX1 mutations develop an X-linked syndrome referred to as adrenal hypoplasia congenita (AHC). These boys typically present in infancy with adrenal failure but later fail to undergo puberty because of hypogonadotropic hypogonadism (HHG). The adrenal failure reflects a developmental abnormality in the transition of the fetal to adult zone, resulting in glucocorticoid and mineralocorticoid deficiency. The etiology of HHG involves a combined and variable deficiency of hypothalamic GnRH secretion and/or pituitary responsiveness to GnRH resulting in low LH, FSH and testosterone. Treatment with exogenous gonadotropins generally does not induce spermatogenesis. Animal models indicate that DAX1 also plays a critical role in testis development and function. As a nuclear receptor, DAX1 has been shown to function as a transcriptional repressor, particularly of pathways regulated by other nuclear receptors, such as steroidogenic factor 1 (SF1). In addition to reproductive tissues, DAX1 is also expressed at high levels in ES cells and plays a role in the maintenance of pluripotentiality. Here we review the clinical manifestations associated with DAX1 mutations as well as the evolving information about its function based on animal models and in vitro studies.

ACTH-dependent precocious pseudopuberty in an infant with DAX1 gene mutation

DAX1 gene (Xp21) expression is involved in the development of the hypothalamo-pituitary-gonadal and adrenal axes, and acts as a negative regulator of steroidogenesis. Mutations of this gene determine adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism. We report the case of a 9-month-old boy referred for the study of macrogenitosomia and pubic hair development. He had presented acute adrenal crises in the neonatal period and, later, a clinical picture of peripheral precocious puberty. A mutation in the DAX1 gene was found (Trp291Arg) and a diagnosis of AHC was made. Replacement doses of hydrocortisone (HC) (10 mg/m2/day) failed to produce a feedback inhibition of adrenocorticotropic hormone (ACTH), and testosterone levels remained high. Testosterone and ACTH values normalized after HC was progressively increased to 18 mg/m2/day. In conclusion, peripheral precocious puberty in patients with DAX1 gene mutations appears to be secondary to the stimulus exerted by ACTH on melanocortin receptors in Leydig cells and to the overexpression of testicular steroidogenesis activators by the loss of transcriptional repression.

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.

Sibling cases of Addison's disease caused by DAX-1 gene mutations

We report two sibling cases of Addison's disease without any evidence of sexual precocity, adrenal hyperplasia, or autoimmune disease. The diagnosis of primary adrenocortical insufficiency was made at the age of 5 in the younger brother and at the age of 18 in the elder brother. The younger brother had been inactive during infancy and had diffuse skin pigmentation without abnormal external genitalia, while the elder brother had been healthy until the age of 17 when he noticed skin pigmentation and small testes. Both boys had delayed puberty due to hypogonadotropic hypogonadism. The diagnosis of adrenal hypoplasia congenita (AHC) was established by genetic analysis of DAX-1 gene (dosage-sensitive sex reversal-adrenal hypoplasia gene on the X chromosome, gene 1) with the same single frameshift mutation (305delG). However, yet-uncharacterized epigenetic, nongenetic and/or genetic factors other than the DAX-1 gene may be responsible for the differential onset of AHC in these sibling cases.

Analysis of DAX1 (NR0B1) and steroidogenic factor-1 (NR5A1) in children and adults with primary adrenal failure: ten years' experience

CONTEXT

Primary adrenal failure is a life-threatening condition that can be caused by a range of etiologies, including autoimmune, metabolic, and developmental disorders. The nuclear receptors DAX1 (NR0B1) and steroidogenic factor-1 (SF1/Ad4BP, NR5A1) play an important role in adrenal development and function, and mutations in these transcription factors have been found in patients with adrenal hypoplasia.

OBJECTIVE

Our objective was to investigate the prevalence of DAX1 and SF1 mutations in children and adults with primary adrenal failure of unknown etiology (i.e. not caused by congenital adrenal hyperplasia, adrenoleukodystrophy, or autoimmune disease).

PATIENTS

One hundred seventeen patients were included. Eighty-eight individuals presented in infancy or childhood with adrenal hypoplasia or primary adrenal failure of unknown etiology (n = 64 46,XY phenotypic males; n = 17 46,XY gonadal dysgenesis/impaired androgenization; n = 7 46,XX females). Twenty-nine individuals presented in adulthood with Addison's disease of unknown etiology.

METHODS

Mutational analysis of DAX1 (NR0B1) (including exon 2alpha/1A) and SF1 (NR5A1) was done by direct sequencing.

RESULTS

DAX1 mutations were found in 58% (37 of 64) of 46,XY phenotypic boys referred with adrenal hypoplasia and in all boys (eight of eight) with hypogonadotropic hypogonadism and a family history suggestive of adrenal failure in males. SF1 mutations causing adrenal failure were found in only two patients with 46,XY gonadal dysgenesis. No DAX1 or SF1 mutations were identified in the adult-onset group.

CONCLUSIONS

DAX1 mutations are a relatively frequent cause of adrenal failure in this group of boys. SF1 mutations causing adrenal failure in humans are rare and are more likely to be associated with significant underandrogenization and gonadal dysfunction in 46,XY individuals.

[Gene as a cause of adrenal hypoplasia, hypogonadism and short height novel mutation of DAX-1 gene (pGly168fsX17)]

Various genes play a role in the morphogenesis of the adrenal cortex, among them the DAX-1 gene. We report an 18-year-old man who showed complete adrenal failure in the neonatal period, hypogonadotropic hypogonadism and pathological short stature associated with a mutation of the DAX-1 gene that has not previously been described. The patient was admitted to hospital at the age of 16 days due to salt-losing syndrome with hyperpotassemia. After this episode, he received no treatment for 2 years, when he began to show progressive anorexia, salt avidity, asthenia, cutaneous hyperpigmentation and finally shock, with hypoglycemia, hyponatremia, metabolic acidosis and hyperpotassemia. Puberal development was spontaneous but incomplete. The patient received treatment with testosterone-depot. He reached a definitive testicular volume of 6 ml and pubarche V. His final height is 150 cm (target height 164 cm). Amplification of the DAX-1 gene showed mutation g 2080-2081 insertion in the first position of codon 168, which produces a premature shutdown of protein DAX-1 at position 184.

Mutations in NR0B1 (DAX1) and NR5A1 (SF1) responsible for adrenal hypoplasia congenita

Adrenal hypoplasia congenita (AHC) causes primary adrenal insufficiency due to the failure of development of the adrenal cortex. Clinical and pedigree data indicate that the condition is genetically heterogeneous. The predominant adrenal hypoplasia congenita locus, however, is the NR0B1 gene, at Xp21, encoding the protein DAX1. In this article, we present a compendium of published NR0B1 mutations and polymorphisms, and discuss them in the contexts of known biology and clinical applicability. The recent descriptions of patients with primary adrenal insufficiency due to mutations of NR5A1, which encodes SF1, are also discussed.

Adrenocorticotropin-dependent precocious puberty of testicular origin in a boy with X-linked adrenal hypoplasia congenita due to a novel mutation in the DAX1 gene

Primary adrenal insufficiency is a rare condition in pediatric age, and its association with precocious sexual development is very uncommon. We report a 2-yr-old Brazilian boy with DAX1 gene mutation whose first clinical manifestation was isosexual gonadotropin-independent precocious puberty. He presented with pubic hair, enlarged penis and testes, and advanced bone age. T levels were elevated, whereas basal and GnRH-stimulated LH levels were compatible with a prepubertal pattern. Chronic GnRH agonist therapy did not reduce T levels, supporting the diagnosis of gonadotropin-independent precocious puberty. Testotoxicosis was ruled out after normal sequencing of exon 11 of the LH receptor gene. At age 3 yr he developed clinical and hormonal features of severe primary adrenal insufficiency. The entire coding region of the DAX1 gene was analyzed through direct sequencing. A nucleotide G insertion between nucleotides 430 and 431 in exon 1, resulting in a novel frameshift mutation and a premature stop codon at position 71 of DAX-1, was identified. Surprisingly, steroid replacement therapy induced a clear decrease in testicular size and T levels to the prepubertal range. These findings suggest that chronic excessive ACTH levels resulting from adrenal insufficiency may stimulate Leydig cells and lead to gonadotropin-independent precocious puberty in some boys with DAX1 gene mutations.

Nuclear receptor Dax-1 represses the transcriptional cooperation between GATA-4 and SF-1 in Sertoli cells

A crucial step in mammalian sex differentiation is the regression of the Müllerian ducts in males. This is achieved through the action of Müllerian inhibiting substance (MIS), a key hormone produced by fetal Sertoli cells. Proper spatiotemporal expression of the MIS gene requires the concerted action of several transcription factors that include Sox9, SF-1, WT-1, GATA-4, and Dax-1. Indeed, SF-1 contributes to MIS gene expression by transcriptionally cooperating with other factors such as GATA-4 and WT-1. Dax-1 is coexpressed with SF-1 in many tissues, including the gonads, where it acts as a negative modulator of SF-1-dependent transcription. We now report that Dax-1 can repress MIS transcription in Sertoli cells by disrupting transcriptional synergism between GATA-4 and SF-1. Dax-1-mediated repression of GATA-4/SF-1 synergism did not involve direct repression of GATA-dependent transactivation, but rather, it occurred through a direct protein-protein interaction with DNA-bound SF-1. It is interesting that SF-1, Dax-1, and GATA factors are coexpressed in several tissues such as the pituitary, the adrenals, and the gonads. Because we have shown that other GATA family members also have the ability to synergize with SF-1, Dax-1 repression of GATA/SF-1 synergism may represent an important mechanism for fine-tuning the regulation of SF-1-dependent genes in multiple target tissues.

A novel mutation in DAX1 causes delayed-onset adrenal insufficiency and incomplete hypogonadotropic hypogonadism

Mutations in the DAX1 gene cause X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HHG). In affected boys, primary adrenal insufficiency occurs soon after birth or during early childhood; HHG is recognized at the expected time of puberty. In this report, we describe the novel phenotype of a man who presented with apparently isolated adrenal insufficiency at 28 years of age. Examination revealed partial pubertal development and undiagnosed incomplete HHG. Gonadotropin therapy did not improve his marked oligospermia, suggesting a concomitant primary testicular abnormality. Genomic analysis revealed a novel missense mutation, I439S, in DAX1. The mutant DAX-1 protein was studied for its ability to function as a transcriptional repressor of target genes. Consistent with the patient's mild clinical phenotype, the I439S mutation conferred intermediate levels of repressor activity of DAX-1 when compared with mutations associated with classic AHC. This unique case extends the clinical spectrum of AHC to include delayed-onset primary adrenal insufficiency in adulthood and milder forms of HHG. Furthermore, in accordance with findings in Ahch (Dax1) knockout mice, the clinical features in this patient suggest that DAX-1 function is required for spermatogenesis in humans, independent of its known effects on gonadotropin production.

Mutational analysis of DAX1 in patients with hypogonadotropic hypogonadism or pubertal delay

Although delayed puberty is relatively common and often familial, its molecular and pathophysiologic basis is poorly understood. In contrast, the molecular mechanisms underlying some forms of hypogonadotropic hypogonadism (HH) are clearer, following the description of mutations in the genes KAL, GNRHR, and PROP1. Mutations in another gene, DAX1 (AHC), cause X-linked adrenal hypoplasia congenita and HH. Affected boys usually present with primary adrenal failure in infancy or childhood and HH at the expected time of puberty. DAX1 mutations have also been reported to occur with a wider spectrum of clinical presentations. These cases include female carriers of DAX1 mutations with marked pubertal delay and a male with incomplete HH and mild adrenal insufficiency in adulthood. Given this emerging phenotypic spectrum of clinical presentation in men and women with DAX1 mutations, we hypothesized that DAX1 might be a candidate gene for mutation in patients with idiopathic sporadic or familial HH or constitutional delay of puberty. Direct sequencing of DAX1 was performed in 106 patients, including 85 (80 men and 5 women) with sporadic HH or constitutional delay of puberty and patients from 21 kindreds with familial forms of these disorders. No DAX1 mutations were found in these groups of patients, although silent single nucleotide polymorphisms were identified (T114C, G498A). This study suggests that mutations in DAX1 are unlikely to be a common cause of HH or pubertal delay in the absence of a concomitant history of adrenal insufficiency.