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

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.

The etiology and clinical features of non-CAH primary adrenal insufficiency in children

BACKGROUND

The most common cause of primary adrenal insufficiency (PAI) in children is congenital adrenal hyperplasia; however, other genetic causes occur. There is limited epidemiological and clinical information regarding non-CAH PAI.

METHODS

Data for patients diagnosed from January 2015 to December 2021 at a tertiary hospital in northern China were retrospectively analyzed. We excluded those with CAH, which is the most common pathogenic disease among PAI patients. Next-generation sequencing was used for genetic analysis.

RESULTS

This retrospective study included 16 children (14 males and 2 females) with PAI. A genetic diagnosis was obtained for 14/16 (87.5%) individuals. Pathogenic variants occurred in 6 genes, including ABCD1 (6/16, 37.5%), NR0B1 (4/16, 25.0%), NR5A1/steroidogenic factor-1 (2/16; 12.5%), AAAS (1/16, 6.25%), and NNT (1/16, 6.25%). No genetic cause of PAI diagnosis was found in 2 girls (2/16, 12.5%).

CONCLUSIONS

Causes of PAI in children are diverse and predominantly affect males. Most PAI in children is congenital, and ABCD1 gene defects account for the largest proportion of PAI cases. Whole-exome sequencing is a tool for diagnosis. However, diagnoses are unclear in some cases.

Case Report: A Novel Truncating Variant of NR0B1 Presented With X-Linked Late-Onset Adrenal Hypoplasia Congenita With Hypogonadotropic Hypogonadism

Nuclear receptor subfamily 0 group B member 1 gene (NR0B1) encodes an orphan nuclear receptor that plays a critical role in the development and regulation of the adrenal gland and hypothalamic-pituitary-gonadal axis. In this study, we report a novel mutation in NR0B1 that led to adult-onset adrenal hypoplasia congenita (AHC) and pubertal development failure in a male adult. Clinical examinations revealed hyponatremia, elevated adrenocorticotropic hormone levels, reduced testosterone and gonadotropin levels, and hyper-responses to gonadotropin-releasing hormone and human chorionic gonadotropin stimulation tests. Whole-exome sequencing and Sanger sequencing were performed to identify the potential causes of AHC. Candidate variants were shortlisted based on the X-linked recessive models. Sequence analyses identified a novel hemizygous variant of c.1034delC in exon 1 of NR0B1 at Xp21.2, resulting in a frameshift mutation and premature stop codon formation. The c.1034delC/p.Pro345Argfs*27 in the NR0B1 gene was detected in the hemizygous state in affected males and in the heterozygous state in healthy female family carriers. These results expand the clinical features of AHC as well as the mutation profile of the causative gene NR0B1. Further studies are needed to elucidate the biological effects of the mutation on the development and function of the adrenal gland and the hypothalamic-pituitary-gonadal axis.

Identification and Analysis of a Novel NR0B1 Mutation in Late-Onset Adrenal Hypoplasia Congenita and Hypogonadism

Objective

X-linked adrenal hypoplasia congenita (AHC) is a rare disorder characterized by primary adrenal insufficiency and hypogonadotropic hypogonadism (HHG) caused by mutations of the NR0B1/DAX1 gene. We aimed to search for the presence of any NR0B1/DAX1 gene mutations in a referred patient and to further characterize the phenotypes of the identified mutation.

Case Presentation

Herein, we report a Japanese patient with a novel missense mutation of the NR0B1/DAX1 gene resulting in adult-onset AHC and HHG. The patient was referred with diffuse skin pigmentation at 28 years of age, presented partial adrenal insufficiency and had undiagnosed incomplete HHG. Urological examination revealed severe oligospermia and testicular microlithiasis.

Results

The NR0B1/DAX1 gene mutation was identified by exome sequencing as a novel missense mutation (c.884A>T, p.Leu295His). We conducted in silico modeling of this mutant NR0B1/DAX1 protein (p.Leu295His) which affected the conserved hydrophobic core of the putative ligand-binding domain (LBD). In addition, functional analysis revealed that this mutant showed a decreased ability as a transcriptional repressor to suppress target genes, such as STAR and LHB. Furthermore, this mutant showed functionally impaired repression of steroidogenesis in human adrenocortical H295R cells.

Conclusions

We identified a novel missense mutation of the NR0B1/DAX1 gene in a patient suffering from late-onset AHC and HHG, who presented with oligospermia and testicular microlithiasis. This mutant NR0B1/DAX1 protein was found to have reduced repressor activity, according to in vitro studies, clinically consistent with the patient’s phenotypic features.

Testicular microlithiasis in a boy with X-linked adrenal hypoplasia congenita

X-linked adrenal hypoplasia congenita (AHC) is a rare disorder that usually presents clinically as adrenal insufficiency in early infancy. It is caused by mutations in the NR0B1 gene which is located on the short arm of chromosome X (Xp21). The NR0B1 gene plays an important role in normal development and function of both the adrenal and gonadal axes and some patients with the disease can present in adolescence with hypogonadotropic hypogonadism. Testicular microlithiasis is an ultrasonographic finding of unknown etiology that has been associated with several benign conditions such as cryptorchidism, congenital adrenal hyperplasia, varicoceles, and testicular malignancy. We report the case of an 11-year-old boy who was diagnosed at the age of 8 months with X-linked AHC due to adrenal failure and presented testicular microlithiasis during follow-up. To the best of our knowledge, this is the first case of an X-linked AHC patient diagnosed with testicular microlithiasis in follow-up.

A novel de novo frameshift mutation in NR0B1 and low prenatal estriol in adrenal hypoplasia congenita

Mutations in the gene NR0B1 have been associated with several clinical phenotypes of X-linked adrenal hypoplasia congenita (AHC). The degree and onset of adrenal insufficiency and involvement of hypogonadotropic hypogonadism is variable and may not be concordant with the identified mutation. We review a patient with AHC in which prenatal estriol levels were low, presenting with early-onset mineralocorticoid deficiency in the newborn period followed by glucocorticoid deficiency 2 years later. The reported child is hemizygous for a novel mutation that is deemed de novo in the ligand-binding site of the protein (DAX1) expressed by NR0B1. The identified frameshift mutation results in a T407N/fs protein change. Low prenatal estriol levels may represent a sensitive marker of potentially fatal disorders associated with adrenal insufficiency and should be utilized more frequently. Additionally, accurate reporting of mutations in NR0B1 and the associated phenotype are important to eventually establish a genotype-phenotype correlation that may help anticipate guidance in AHC.

Late-onset X-linked adrenal hypoplasia (DAX-1, NR0B1): two new adult-onset cases from a single center

PURPOSE

DAX-1 (NR0B1) is an orphan nuclear receptor, which plays a critical role in development and regulation of the adrenal gland and hypothalamo-pituitary-gonadal axis. Mutations in NR0B1 lead to adrenal hypoplasia congenita (AHC), hypogonadotropic hypogonadism (HH) and azoospermia in men. Presentation is typically with adrenal insufficiency (AI) during infancy or childhood. To date only eight cases/kindreds are reported to have presented in adulthood.

METHODS

We describe two new cases of men with DAX-1 mutations who presented in adulthood and who were diagnosed at a large University Hospital.

RESULTS

Case 1 presented with AI at 19 years. At 38 years he was diagnosed with HH. Detailed history revealed a brother diagnosed with AI at a similar age. Sequencing of the DAX-1 (NR0B1) gene revealed a heterozygous c.775T > C substitution in exon 1, which changes codon 259 from serine to proline (p.Ser259Pro). Case 2 was diagnosed with AI at 30 years. Aged 37 years he presented with HH and azoospermia. He was treated with gonadotropin therapy but remained azoospermic. Testicular biopsy showed maturational arrest and hypospermatogenesis. Analysis of the NR0B1 gene showed a heterozygous c.836C > T substitution in exon 1, resulting in a change of codon 279 from proline to leucine (p.Pro279Leu). This change alters the structure of the repression helix domain of DAX-1 and affects protein complex interactions with NR5A family members.

CONCLUSIONS

We describe two missense mutations within the putative carboxyl-terminal ligand binding domain of DAX-1, presenting with AHC and HH in adulthood, from a single center. DAX-1 mutations may be more frequent in adults than previously recognized. We recommend testing for DAX-1 mutations in all adults with primary AI and HH or impaired fertility where the etiology is unclear.

MANAGEMENT OF ENDOCRINE DISEASE: Regenerative therapies in autoimmune Addison's disease

The treatment for autoimmune Addison's disease (AAD) has remained virtually unchanged in the last 60 years. Most patients have symptoms that are relatively well controlled with exogenous steroid replacement, but there may be persistent symptoms, recurrent adrenal crisis and poor quality of life, despite good compliance with optimal current treatments. Treatment with conventional exogenous steroid therapy is also associated with premature mortality, increased cardiovascular risk and complications related to excessive steroid replacement. Hence, novel therapeutic approaches have emerged in the last decade attempting to improve the long-term outcome and quality of life of patients with AAD. This review discusses the recent developments in treatment innovations for AAD, including the novel exogenous steroid formulations with the intention of mimicking the physiological biorhythm of cortisol secretion. Our group has also carried out a few studies attempting to restore endogenous glucocorticoid production via immunomodulatory and regenerative medicine approaches. The recent advances in the understanding of adrenocortical stem cell biology, and adrenal plasticity will also be discussed to help comprehend the science behind the therapeutic approaches adopted.

Identification of Copy Number Variations in Xiang and Kele Pigs

Xiang and Kele pigs are two well-known local Chinese pig breeds that possess rich genetic resources and have enormous economic and scientific value. We performed a comprehensive genomic analysis of the copy number variations (CNVs) in these breeds. CNVs are one of the most important forms of genomic variation and have profound effects on phenotypic variation. In this study, PorcineSNP60 genotyping data from 98 Xiang pigs and 22 Kele pigs were used to identify CNVs. In total, 172 candidate CNV regions (CNVRs) were identified, ranging from 3.19 kb to 8175.26 kb and covering 80.41 Mb of the pig genome. Approximately 56.40% (97/172) of the CNVRs overlapped with those identified in seven previous studies, and 43.60% (75/172) of the identified CNVRs were novel. Of the identified CNVRs, 82 (47 gain, 33 loss, and two gain-loss events that covered 4.58 Mb of the pig genome) were found only in a Xiang population with a large litter size. In contrast, 13 CNVRs (8 gain and 5 loss events) were unique to a Xiang population with small litter sizes, and 30 CNVRs (14 loss and 16 gain events) were unique to Kele pigs. The CNVRs span approximately 660 annotated Sus scrofa genes that are significantly enriched for specific biological functions, such as sensory perception, cognition, reproduction, ATP biosynthetic processes, and neurological processes. Many CNVR-associated genes, particularly the genes involved in reproductive traits, differed between the Xiang populations with large and small litter sizes, and these genes warrant further investigation due to their importance in determining the reproductive performance of Xiang pigs. Our results provide meaningful information about genomic variation, which may be useful in future assessments of the associations between CNVs and important phenotypes in Xiang and Kele pigs to ultimately help protect these rare breeds.

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.

Adrenocortical growth and cancer

The adrenal gland consists of two distinct parts, the cortex and the medulla. Molecular mechanisms controlling differentiation and growth of the adrenal gland have been studied in detail using mouse models. Knowledge also came from investigations of genetic disorders altering adrenal development and/or function. During embryonic development, the adrenal cortex acquires a structural and functional zonation in which the adrenal cortex is divided into three different steroidogenic zones. Significant progress has been made in understanding adrenal zonation. Recent lineage tracing experiments have accumulated evidence for a centripetal differentiation of adrenocortical cells from the subcapsular area to the inner part of the adrenal cortex. Understanding of the mechanism of adrenocortical cancer (ACC) development was stimulated by knowledge of adrenal gland development. ACC is a rare cancer with a very poor overall prognosis. Abnormal activation of the Wnt/β-catenin as well as the IGF2 signaling plays an important role in ACC development. Studies examining rare genetic syndromes responsible for familial ACT have played an important role in identifying genetic alterations in these tumors (like TP53 or CTNNB1 mutations as well as IGF2 overexpression). Recently, genomic analyses of ACT have shown gene expression profiles associated with malignancy as well as chromosomal and methylation alterations in ACT and exome sequencing allowed to describe the mutational landscape of these tumors. This progress leads to a new classification of these tumors, opening new perspectives for the diagnosis and prognostication of ACT. This review summarizes current knowledge of adrenocortical development, growth, and tumorigenesis.

Role of Orphan Nuclear Receptor DAX-1/NR0B1 in Development, Physiology, and Disease

DAX-1/NR0B1 is an unusual orphan receptor that has a pivotal role in the development and function of steroidogenic tissues and of the reproductive axis. Recent studies have also indicated that this transcription factor has an important function in stem cell biology and in several types of cancer. Here I critically review the most important findings on the role of DAX-1 in development, physiology, and disease of endocrine tissues since the cloning of its gene twenty years ago.

Novel mutations in DAX1 of X-linked adrenal hypoplasia congenita over several generations in one family

OBJECTIVE

X-linked adrenal hypoplasia congenital (AHC) is a rare disorder caused by mutations in DAX1 gene. We report a case of X-linked AHC in a large family to analyze the pathogenesis of this rare disease and to add to our clinical knowledge of it.

METHODS

We describe 3-year-old boy's clinical features and laboratory test results, as well as the patient's nuclear family members' clinical symptoms, especially those with features of adrenal insufficiency. Genomic deoxyribonucleic acid (DNA) was extracted from the patient's and the family members' peripheral blood leukocytes, and the coding region and promoter region of DAX1 were directly sequenced.

RESULTS

A 3-year-old boy who was diagnosed with X-linked AHC presented with atypical symptoms, and his laboratory test results revealed elevated serum adrenocorticotropic hormone levels (ACTH) and decreased serum cortisol levels. Three novel mutations were detected in the DAX1 coding sequence in this family: a missense mutation (c.376G>A, p.Val126Met), a synonymous mutation (c.498G>A, p.Arg166Arg), and a nonsense mutation (c.1225C>T, p. Gln409X).

CONCLUSIONS

This report describes the familial transmission of AHC over several generations and further expands the number of DAX1 mutations reported in the literature. Early diagnosis and prompt treatment of X-linked AHC are important and may provide a good prognosis.

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.

Genomics in pediatric endocrinology-genetic disorders and new techniques

In the last few years, there have been remarkable advances in the development of new and more sophisticated genetic techniques. These have allowed a better understanding of the molecular mechanisms of genetically determined pediatric endocrine disorders and are paving the way for a radical change in diagnosis and treatment. This article introduces some of these concepts and some of the genetic techniques being used.

Moving toward personalized cell-based interventions for adrenal cortical disorders: part 2--Human diseases and tissue engineering

Transdifferentiation of an individual's own cells into functional differentiated cells to replace an organ's lost function would be a personalized approach to therapeutics. In this two part series, we will describe the progress toward establishing functional transdifferentiated adrenal cortical cells. In this article (Part 2), we describe the disorders of the adrenal cortex, therefore establishing why there is the need for personalized cell-based therapy for individuals with these disorders. We then present our pilot studies of cell transdifferentiation toward an adrenal cortical fate using genes described in the first article of this pair (Part 1).

Moving toward personalized cell-based interventions for adrenal cortical disorders: part 1--Adrenal development and function, and roles of transcription factors and signaling proteins

Transdifferentiation of an individual's own cells into functional differentiated cells to replace an organ's lost function would be a personalized approach to therapeutics. In this two part series, we will describe the progress toward establishing functional transdifferentiated adrenal cortical cells. In this article (Part 1), we describe adrenal development and function, and discuss genes involved in these processess and selected for use in our pilot studies of transdifferentiation that are presented in the second article (Part 2).

Evidence of adrenal failure in aging Dax1-deficient mice

Dosage-sensitive sex reversal, adrenal hypoplasia congenita (AHC) critical region on the X chromosome, gene 1 (Dax1) is an orphan nuclear receptor essential for development and function of the mammalian adrenal cortex and gonads. DAX1 was cloned as the gene responsible for X-linked AHC, which is characterized by adrenocortical failure necessitating glucocorticoid replacement. Contrary to these human data, young mice with genetic Dax1 knockout (Dax1(-/Y)) exhibit adrenocortical hyperfunction, consistent with the historic description of Dax1 as a transcriptional repressor that inhibits steroidogenic factor 1-dependent steroidogenesis. This paradox of molecular function and two apparently opposite phenotypes associated with Dax1 deficiency in mice and humans is compounded by the recent observations that under certain circumstances, Dax1 can serve as a transcriptional activator of steroidogenic factor 1. The recently revealed role of Dax1 in embryonic stem cell pluripotency, together with the observation that its expression in the adult adrenal is restricted to the subcapsular cortex, where presumptive undifferentiated progenitor cells reside, has led us to reexamine the phenotype of Dax1(-/Y) mice in order to reconcile the conflicting mouse and human data. In this report, we demonstrate that although young Dax1(-/Y) mice have enhanced steroidogenesis and subcapsular adrenocortical proliferation, as these mice age, they exhibit declining adrenal growth, decreasing adrenal steroidogenic capacity, and a reversal of their initial enhanced hormonal sensitivity. Together with a marked adrenal dysplasia in aging mice, these data reveal that both Dax1(-/Y) mice and patients with X-linked AHC exhibit adrenal failure that is consistent with adrenocortical subcapsular progenitor cell depletion and argue for a significant role of Dax1 in maintenance of these cells.

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

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

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

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

Adrenocortical stem and progenitor cells: unifying model of two proposed origins

The origins of our understanding of the cellular and molecular mechanisms by which signaling pathways and downstream transcription factors coordinate the specification of adrenocortical cells within the adrenal gland have arisen from studies on the role of Sf1 in steroidogenesis and adrenal development initiated 20 years ago in the laboratory of Dr. Keith Parker. Adrenocortical stem/progenitor cells have been predicted to be undifferentiated and quiescent cells that remain at the periphery of the cortex until needed to replenish the organ, at which time they undergo proliferation and terminal differentiation. Identification of these stem/progenitor cells has only recently been explored. Recent efforts have examined signaling molecules, including Wnt, Shh, and Dax1, which may coordinate intricate lineage and signaling relationships between the adrenal capsule (stem cell niche) and underlying cortex (progenitor cell pool) to maintain organ homeostasis in the adrenal gland.

The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders

Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones. Whereas most endocrine texts discuss adrenal, ovarian, testicular, placental, and other steroidogenic processes in a gland-specific fashion, steroidogenesis is better understood as a single process that is repeated in each gland with cell-type-specific variations on a single theme. Thus, understanding steroidogenesis is rooted in an understanding of the biochemistry of the various steroidogenic enzymes and cofactors and the genes that encode them. The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by a single enzyme, P450scc (CYP11A1), but this enzymatically complex step is subject to multiple regulatory mechanisms, yielding finely tuned quantitative regulation. Qualitative regulation determining the type of steroid to be produced is mediated by many enzymes and cofactors. Steroidogenic enzymes fall into two groups: cytochrome P450 enzymes and hydroxysteroid dehydrogenases. A cytochrome P450 may be either type 1 (in mitochondria) or type 2 (in endoplasmic reticulum), and a hydroxysteroid dehydrogenase may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families. The activities of these enzymes are modulated by posttranslational modifications and by cofactors, especially electron-donating redox partners. The elucidation of the precise roles of these various enzymes and cofactors has been greatly facilitated by identifying the genetic bases of rare disorders of steroidogenesis. Some enzymes not principally involved in steroidogenesis may also catalyze extraglandular steroidogenesis, modulating the phenotype expected to result from some mutations. Understanding steroidogenesis is of fundamental importance to understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiological homeostasis.

Identification of novel SRY mutations and SF1 (NR5A1) changes in patients with pure gonadal dysgenesis and 46,XY karyotype

Primary amenorrhea due to 46,XY disorders of sexual development (DSD) is complex with the involvement of several genes. Karyotyping of such patients is important as they may develop dysgerminoma and molecular analysis is important to identify the underlying mechanism and explore the cascade of events occurring during sexual development. The present study was undertaken for the genetic analysis in seven patients from five families presenting with primary amenorrhea and diagnosed with pure gonadal dysgenesis. Karyotyping was done and the patients were screened for underlying changes in SRY, desert hedgehog (DHH), DAX1 (NR0B1) and SF1 (NR5A1) genes, mutations in which are implicated in DSD. All the patients had 46,XY karyotype and two novel SRY mutations were found. In Family 1 (Patient S1.1) a missense mutation c.294G>A was seen, which results in a stop codon at the corresponding amino acid (Trp98X) and in Family 2 (Patients S2.1, S2.2 and S2.3), a missense mutation c.334G>A (Glu112Leu) was identified in all affected sisters. Both mutations were seen to occur in the conserved high mobility group box of SRY gene. One heterozygous change c.427G>A resulting in Glu143Lys in DHH gene in one patient and two heterozygous changes in the intronic region of SF1 (NR5A1) gene (c.244+80G>A+ c.1068-20C>T) in another patient were noted. One individual did not show changes in any of the genes analyzed. These results reiterate the importance of SRY and others, such as SF1 (NR5A1) and DHH, that are involved in the cascade of events leading to sex determination and also their role in sex reversal.

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.

Genomics in pediatric endocrinology--genetic disorders and new techniques

In the last few years, there have been remarkable advances in the development of new and more sophisticated genetic techniques. These have allowed a better understanding of the molecular mechanisms of genetically determined pediatric endocrine disorders and are paving the way for a radical change in diagnosis and treatment. This article introduces some of these concepts and some of the genetic techniques being used.

In search of adrenocortical stem and progenitor cells

Scientists have long hypothesized the existence of tissue-specific (somatic) stem cells and have searched for their location in different organs. The theory that adrenocortical organ homeostasis is maintained by undifferentiated stem or progenitor cells can be traced back nearly a century. Similar to other organ systems, it is widely believed that these rare cells of the adrenal cortex remain relatively undifferentiated and quiescent until needed to replenish the organ, at which time they undergo proliferation and terminal differentiation. Historical studies examining cell cycle activation by label retention assays and regenerative potential by organ transplantation experiments suggested that the adrenocortical progenitors reside in the outer periphery of the adrenal gland. Over the past decade, the Hammer laboratory, building on this hypothesis and these observations, has endeavored to understand the mechanisms of adrenocortical development and organ maintenance. In this review, we summarize the current knowledge of adrenal organogenesis. We present evidence for the existence and location of adrenocortical stem/progenitor cells and their potential contribution to adrenocortical carcinomas. Data described herein come primarily from studies conducted in the Hammer laboratory with incorporation of important related studies from other investigators. Together, the work provides a framework for the emerging somatic stem cell field as it relates to the adrenal gland.

Late-onset adrenal hypoplasia congenita caused by a novel mutation of the DAX-1 gene

Mutation in the orphan nuclear receptor DAX-1 gene causes X-linked adrenal hypoplasia congenita (AHC). Affected male children classically suffer a salt-losing crisis and adrenal insufficiency in their early infancy or, in some rare exceptions, with late-onset subtype. We report here a patient manifesting late-onset adrenal hypoplasia congenita caused by the premature truncation of the C-terminus of the DAX-1 molecule, which is essential for its function as a transcriptional repressor. A 12-year-old boy was referred to us after being afflicted with generalized skin pigmentation for about 3 years, fatigue and headache. Primary adrenal insufficiency was determined on the basis of a low plasma cortisol level (3.9 microg/dl) despite an extremely high ACTH level (1200 pg/ml). Replacement therapy with hydrocortisone and fludorocortisone acetate was initiated soon thereafter. Hypogonadotropic hypogonadism was confirmed at the age of 18 years, at which time sexual infantilism had become apparent. Direct sequencing of the peripheral lymphocyte-derived DNA revealed a novel 1033del13 mutation on the ligand-binding domain of the NR0B1 (DAX-1) gene, which generated a premature stop codon truncating the C-terminus. This mutation was considered de novo since we could not find it in his mother. This case demonstrates that even a truncated protein lacking the major functional domain of DAX-1 can present late-onset and latent adrenal failure.

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.

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.

Adrenal gland development and defects

The network regulating human adrenal development is complex. Studies of patients with adrenal insufficiency due to gene mutations established a central role for transcription factors GLI3, SF1 and DAX1 in the initial steps of adrenal formation. Adrenal differentiation seems to depend on adrenocorticotropic hormone (ACTH) stimulation and signalling, including biosynthesis and action of POMC, PC1, TPIT, MC2R, MRAP and ALADIN, all of which cause adrenocortical hypoplasia when mutated in humans. Studies of knockout mice revealed many more factors involved in adrenal development; however, in contrast to rodents, in humans several of those factors had no adrenal phenotype when mutated (e.g. WT1, WNT4) or, alternatively, human mutations have not (yet) been identified. Tissue profiling of fetal and adult adrenals suggested 69 genes involved in adrenal development. Among them were genes coding for steroidogenic enzymes, transcription and growth factors, signalling molecules, regulators of cell cycle and angiogenesis, and extracellular matrix proteins; however, the exact role of most of them remains to be elucidated.

An amino-terminal DAX1 (NROB1) missense mutation associated with isolated mineralocorticoid deficiency

CONTEXT

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.

OBJECTIVE

The objective was to identify novel clinical phenotypes associated with DAX1 missense mutations.

PATIENTS AND DESIGN

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.

RESULTS

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.

CONCLUSIONS

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.

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

DAX1 (NR0B1) is a nuclear receptor with a characteristic C-terminal ligand binding domain, but an atypical DNA binding domain. Mutations in the DAX1 gene cause adrenal hypoplasia congenita (AHC) establishing its biological importance. Recent studies highlight the complexities of DAX1 regulation and function. There is considerable phenotypic variability in AHC suggesting the existence of DAX1 modifier genes and environmental influences on DAX1 function. The findings of an alternatively spliced DAX1A, more common than DAX1 in all tissues except testis, of DAX1 homodimers, and of DAX1 heterodimers with a number of transcription factor partners including DAX1A and SHP point to an expanded transcription regulatory network under DAX1 control. Model organisms (mice and zebrafish) are being used to identify other DAX1 functions and modifier genes to understand the pathogenesis of AHC and the lack of genotype-phenotype correlation.

Partial defects in transcriptional activity of two novel DAX-1 mutations in childhood-onset adrenal hypoplasia congenita

OBJECTIVE

Mutations in DAX-1, an X-linked gene encoding an orphan nuclear receptor, have been associated with adrenal hypoplasia congenita and hypogonadotropic hypogonadism. Here we describe two novel DAX-1 mutations, Y214X and I361T, associated with childhood-onset primary adrenal failure. We aimed at analysing their effects on protein localization, transcriptional activity and propose a structural-function relationship.

DESIGN

We have directly sequenced the DAX-1 gene from PCR-amplified DNA. The effect of the mutations on protein localization was assessed by immunocytochemistry in transfected cells. The impact of mutations on transcriptional activity was determined by transfection using a StAR promoter-luciferase reporter system.

RESULTS

The mutation Y214X produces a protein lacking the C-terminal half of DAX-1. The other one, I361T, affects a highly conserved amino acid within the putative ligand-binding domain. The mutant Y214X displayed a wild-type subcellular localization while I361T was partially retained in the cytoplasm. Both mutants retained subtantial transcriptional repressive activity, compared to mutants producing early onset adrenal failure. Interestingly, I361T displayed similar in vitro transcriptional repressive activity to the mutant I439S previously described in a case of late-onset AHC. This shows that molecular alterations of DAX-1 leading to similar in vitro activities may result in very different ages of onset of adrenal failure, which suggests that additional genetic and epigenetic factors are important in determining the clinical course of AHC.

CONCLUSIONS

Our results help the understanding of structure-function relationships in the DAX-1 molecule, suggesting that the N-terminal domain is relatively autonomous and add credence to presumed molecular interactions within ligand binding domain of the protein.

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.

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.

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.

IMAGe association and congenital adrenal hypoplasia: no disease-causing mutations found in the ACD gene

The spontaneous mouse mutant adrenocortical dysplasia (acd) is characterized by defects in the adrenals, kidneys, and gonads of adult mutant mice and by caudal dysgenesis and vertebral segmentation defects in acd embryos. This association of defects mirrors those identified in patients with known or suspected abnormalities in adrenocortical development, including adrenal hypoplasia congenita and IMAGe association. The identification of the Acd gene in mice has prompted the study of its human homolog ACD, which has recently been shown to be a regulator of telomere length. Sequencing of ACD in 15 patients revealed no coding mutations, but three novel SNPs were identified.

[Adrenal hypoplasia congenita: four new cases in children]

Adrenal hypoplasia congenita (AHC) is an extremely uncommon disease of early onset. This condition can be lethal in the absence of adapted treatment. Some of these diseases are related to changes in the gene DAX1 that encodes a member of the superfamily of hormone nuclear receptors. It is a transcriptional repressor that is central in the morphogenesis of the adrenals and the gonadic differentiation. Here we report on four cases of X- linked AHC. In the first two familial cases, mutations were identified and mothers were heterozygotes. Abnormally low levels of estriol were evidenced during the pregnancy leading to an early diagnosis and adapted care of the affected male neonates. These children are doing well with a 21-and 20 months follow-up with hormone replacement at the present time. The two last cases corresponded to a contiguous gene syndrome associating AHC to glycerol-kinase deficiency that was revealed respectively at six days and seven years of age by acute adrenal insufficiency.

Inappropriate tall stature and renal ectopy in a male patient with X-linked congenital adrenal hypoplasia due to a novel missense mutation in theDAX-1 gene

Mutations in DAX-1 gene cause congenital adrenal hypoplasia (AHC). We present a male patient affected by X-linked adrenal hypoplasia congenita due to a novel DAX-1 missense mutation. The mutation V287G affects the C-terminal end of the DAX-1 protein which plays an important role in functioning of the receptor. In addition, our patient presented an inappropriate tall stature and renal ectopy, which have not been described in AHC so far.

Adrenal cortical cell transplantation

PURPOSE

The adrenal cortex is a critical component of the hypothalamic-pituitary-adrenal/gonadal axis that coordinates the stress response and maintains homeostasis. The authors hypothesize that adrenal cortical cells can be transplanted in adrenal insufficiency states to regenerate the adrenal cortex.

METHODS

Murine adrenal glands were dissociated into adrenal cortical cells. Cells cultured in a collagen matrix were transplanted under the renal capsule. The implants were retrieved 1, 2, 4, and 8 weeks later. Total RNA was extracted from the retrieved specimens and was analyzed by real-time polymerase chain reaction.

RESULTS

All animals survived the surgical procedure. At implant retrieval, a distinct organoid could be visualized under the renal capsule. The expressions of adrenal-specific markers including Sf1, Dax1, Star, Cyp11a, Cyp11b1, and Cyp21 were detectable in the retrieved specimens up to 8 weeks posttransplantation.

CONCLUSION

Primary adrenal cortical cells retained their gene expressions after heterotopic transplantation. Ex vivo gene transfer followed by adrenal cortical cell transplantation may lead to curative therapy for patients with adrenal insufficiency.

NR0B1A: an alternatively spliced form of NR0B1

The orphan nuclear receptor DAX1 (dosage-sensitive sex reversal-AHC critical region on the X chromosome gene 1), encoded by the NR0B1 gene, plays important roles in the development of the hypothalamic-pituitary-adrenal/gonadal (HPAG) axis as well as in sex determination. Mutations in NR0B1 cause the X-linked cytomegalic form of adrenal hypoplasia congenita (AHC), and associated hypogonadotropic hypogonadism (HH). Over-expression of NR0B1 results in sex reversal in mice and duplication of the 160kb DSS locus in human patients results in a sex-reversed phenotype (XY females). The purpose of these investigations was to determine if alternatively spliced forms of NR0B1 existed. Analysis of expressed sequence tag data predicted a truncated isoform of DAX1. We confirmed the presence of an alternatively spliced form of NR0B1, which we will refer to as NR0B1A, by reverse transcriptase-polymerase chain reaction (RT-PCR), and will refer to the deduced protein isoform as DAX1A. Sequencing of the NR0B1A cDNA revealed slight differences from the recently described splice form, DAX1alpha. NR0B1A is encoded by NR0B1 exon 1 and exon 2A located within the 3385 nt intron between NR0B1 exons 1 and 2. Exon 2A includes 35 nt of coding sequence. NR0B1A encodes a deduced protein sequence, DAX1A, of 400 amino acids compared with 470 amino acids for DAX1. RT-PCR detected expression of NR0B1A in adrenal gland, testis, ovary, and pancreas. The identification of NR0B1A and the deduced DAX1A requires reinterpretation of many previous experiments involving expression and knockout of NR0B1 and DAX1.

The Adrenal

During the past 15 years, considerable progress has been made in our understanding of the genetic basis of adrenal development and function. More than 30 single gene disorders have now been identified that can affect the hypothalamic-pituitary-adrenal axis in humans (fig. 1, 2; table 1). This review highlights recent advances in the molecular pathology of: (1) adrenal hypoplasia, (2) adrenal destruction, (3) disorders of adrenal steroidogenesis, (4) adrenal steroid resistance and (5) activation of the adrenal axis/tumorigenesis. Characterizing the molecular basis and natural history of these conditions is providing fascinating insight into adrenal development and function and can help to focus treatment and counselling of patients appropriately. However, ongoing translation of research findings into clinical practice is needed if patient care is to be influenced significantly.

Urogenital and caudal dysgenesis in adrenocortical dysplasia (acd) mice is caused by a splicing mutation in a novel telomeric regulator

Adrenocortical dysplasia (acd) is a spontaneous autosomal recessive mouse mutant with developmental defects in organs derived from the urogenital ridge. In surviving adult mutants, adrenocortical dysplasia and hypofunction are predominant features. Adults are infertile due to lack of mature germ cells, and 50% develop hydronephrosis due to ureteral hyperplasia. We report the identification of a splice donor mutation in a novel gene, which is the mouse ortholog of a newly discovered telomeric regulator. This gene (Acd) has recently been characterized as a novel component of the TRF1 protein complex that controls telomere elongation by telomerase. Characterization of Acd transcripts in mutant animals reveals two abnormal transcripts, consistent with a splicing defect. Expression of a wild-type Acd transgene in acd mutants rescues the observed phenotype. Most mutants die within 1-2 days of life on the original genetic background. Analysis of these mutant embryos reveals variable, yet striking defects in caudal specification, limb patterning and axial skeleton formation. In the tail bud, reduced expression of Wnt3a and Dll1 correlates with phenotypic severity of caudal regression. In the limbs, expression of Fgf8 is expanded in the dorsal-ventral axis of the apical ectodermal ridge and shortened in the anterior-posterior axis, consistent with the observed loss of anterior digits in older embryos. The axial skeleton of mutant embryos shows abnormal vertebral fusions in cervical, lumbar and caudal regions. This is the first report to show that a telomeric regulator is required for proper urogenital ridge differentiation, axial skeleton specification and limb patterning in mice.

Near-miss apparent SIDS from adrenal crisis

OBJECTIVE

Adrenal crisis from salt-losing congenital adrenal hyperplasia (CAH) typically occurs in the first 2 weeks of life. We evaluated 3 infants with adrenal crisis who presented at 6 to 8 months of age with near-miss sudden infant death syndrome (SIDS).

SUBJECTS

Three 46,XY phenotypic female infants presented near death at 6 to 8 months of age with adrenal crisis and unmeasurable steroid hormones consistent with congenital lipoid adrenal hyperplasia (lipoid CAH).

METHODS

We sequenced genes potentially causing this phenotype: steroidogenic acute regulatory protein (StAR), the cholesterol side-chain cleavage enzyme, adrenodoxin reductase, adrenodoxin, and steroidogenic factor 1 (SF1). Site-directed mutagenesis and functional assays were performed for the missense mutation.

RESULTS

Hormonal values showed complete absence of adrenal and gonadal steroids. Patient 1 was a compound heterozygote for missense mutation R140P and an mRNA splice donor site mutation in the StAR gene. The R140P mutation was wholly inactive in vitro. Patient 2 was homozygous for a 7 base pair StAR deletion causing a frameshift. No mutations were found in Patient 3, suggesting a novel disease.

CONCLUSIONS

Although genetic disorders of steroidogenesis typically present in the first month of life, some defects, especially those in StAR, can present in mid-infancy, when adrenal hyperplasias are rarely considered. Adrenal insufficiency is a subtle disorder that may cause cardiovascular collapse, causing unexplained infant death that resembles SIDS.