Identification of novel mutations of the DAX-1 gene in patients with X-linked adrenal hypoplasia congenita

Diverse etiologies, diagnostic approach, and management of primary adrenal insufficiency in pediatric age

Primary adrenal insufficiency (PAI) in pediatric age is a rare, but potentially fatal condition caused by diverse etiologies including biochemical defects of steroid biosynthesis, developmental abnormalities of the adrenal gland, or reduced responsiveness to adrenocorticotropic hormone. Compared to adult PAI, pediatric PAI is more often the result of genetic (monogenic, syndromic disorders) than acquired conditions. During the past decade, rare monogenic disorders associated with PAI have helped unravel the underlying novel molecular genetic mechanism. The diagnosis of adrenal insufficiency in children and young infancy is often challenging, usually based on clinical suspicion and endocrine laboratory findings. Pediatric endocrinologists sometimes encounter therapeutic difficulty in finding the balance between undertreatment and overtreatment, determining how to optimize the dose over the patient's lifetime, and maximizing mimicry of normal cortisol secretion with glucocorticoid replacement therapy.

A Novel NR0B1 Gene Mutation Causes Different Phenotypes in Two Male Patients with Congenital Adrenal Hypoplasia

X-linked congenital adrenal hypoplasia is characterised by the acute onset of primary adrenal insufficiency in infancy or early childhood and hypogonadotropic hypogonadism (HH) at puberty, arising from mutations of the nuclear receptor subfamily 0 group B member 1 (NR0B1) gene. This study investigated an extended family with two affected males (patient A: 23 years and patient B: 2 months old) and three carrier females. Sequencing analysis of the NR0B1 gene coding region from the family revealed a novel hemizygous deletion [c.604delT; p.(C202Afs*62)] in the two male patients. Furthermore, the patients' respective mothers and their common grandmother had this heterozygous mutation, but it was not present in the Human Gene Mutation Database. The two male patients showed inconsistent clinical features at onset, particularly in early childhood; however, it is possible that the younger patient will eventually show a delay of puberty, feminisation, and nonspermatogenesis in adulthood, similar to that in the older patient. Identification of a novel NR0B1 mutation in this family is important for the diagnosis and genetic counselling of children with primary adrenal insufficiency and HH, and will be helpful for predicting long-term clinical symptoms.

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.

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.

Two novel DAX1 gene mutations in Chinese patients with X-linked adrenal hypoplasia congenita: clinical, hormonal and genetic analysis

Mutations in the DAX1 gene result in X-linked congenital adrenal hypoplasia (AHC). Affected boys usually present with primary adrenal failure in early infancy or childhood and hypogonadotropic hypogonadism (HH) at puberty. This paper describes the clinical, hormonal, radiological, and genetic characteristics of 2 Chinese patients with X-linked AHC. Primary adrenal insufficiency occurred in the 2 patients during their childhood and HH was recognized at puberty. Genomic DNA was extracted from their peripheral blood leukocytes and coding sequence abnormalities of the DAX1 gene were assessed by PCR and direct sequencing analysis. Genetic analysis of the DAX1 gene revealed 2 novel mutations c.572-575 dupGGGC, p.Thr193Gly,fs,205X and c.773- 774 dupCC, p.Ser259Pro,fs,264X in exon 1, causing frameshifts and yeilding premature stop codons at 205 and 264, respectively. This study identifies 2 novel mutations in the DAX1 gene which can further expand the mutation database and benefit patients in the diagnosis and treatment of AHC.