Mutations in the CYP11B1 gene causing congenital adrenal hyperplasia and hypertension cluster in exons 6, 7, and 8

Development of mass spectrometric methods for determination of desoxycorticosterone pivalate and its esterase product in canine serum

Hypoadrenocorticism is a serious condition in dogs that results from autoimmune adrenalitis and depletion of mineralocorticoids and glucocorticoids. Affected dogs respond well to glucocorticoid supplementation and treatment with the synthetic mineralocorticoid desoxycorticosterone pivalate (DOCP). DOCP injected once monthly resolves serum Na/K abnormalities and normalizes water balance, but therapy is expensive. Cost abatement involves prolongation of the 30-day dosage interval or decreasing the 2.2 mg/kg dosage. These approaches are not based on DOCP pharmacokinetics. A full assessment of the practicality of either approach would benefit from understanding drug pharmacokinetics, requiring measurement of DOCP and its esterase product desoxycorticosterone (DOC) in canine serum while avoiding toxic endpoints from overdosing. Mass spectrometric methods were developed including gas chromatography-tandem mass spectrometry of DOCP and DOC-methoxime trimethylsilyl derivatives, an approach sensitive to 2 ng/mL. Greater sensitivity was desired, so liquid chromatography-tandem mass spectrometry (LC-MS/MS) with ESI+ ionization was investigated. Supported liquid extraction was devised for serum with recoveries ∼100%. The LC-MS/MS method was validated for linearity, precision, accuracy and limits of detection (0.029 and 0.019 ng/mL for DOC and DOCP, respectively). A pilot experiment with DOCP-treated hypoadrenocorticism dogs over one-month revealed DOC baseline values as 0.183+/-0.090 ng/mL, which increased to the 1.0 - 2.2 ng/mL range. DOCP was not visible in any samples suggesting 100% conversion. Halving the dosage to 1.1 mg/kg still showed clear increases over the DOC baseline. MS fragmentation involved ring cleavages, dehydrations and double-charged fragments. The methodology was robust and suitable for studying DOC/DOCP pharmacokinetics in future studies of hypoadrenocorticism dogs.

Pulling back the mitochondria's iron curtain

Mitochondrial functionality and cellular iron homeostasis are closely intertwined. Mitochondria are biosynthetic hubs for essential iron cofactors such as iron-sulfur (Fe-S) clusters and heme. These cofactors, in turn, enable key mitochondrial pathways, such as energy and metabolite production. Mishandling of mitochondrial iron is associated with a spectrum of human pathologies ranging from rare genetic disorders to common conditions. Here, we review mitochondrial iron utilization and its intersection with disease.

Novel recurrent mutations and genetic diversity in Sudanese children with adrenal insufficiency

OBJECTIVE

Studies of primary adrenal insufficiency (PAI) in African children are rare, but in Sudan, congenital adrenal hyperplasia (CAH) and triple A syndrome are the most common genetic causes. Differential diagnosis is challenging, especially in resource-limited settings, where presentation can mimic common childhood diseases and facilities for biochemical and genetic testing may be restricted.

DESIGN

Forty-eight patients from 43 families (31 male:17 female) with PAI were included (CAH/triple A excluded). Additional features seen included white matter changes on magnetic resonance imaging, auto-immune features, and/or obesity. Sanger and whole exome sequencing (WES) were employed for diagnosis, confirmation, and segregation with in vitro assays to investigate potential splice defects.

RESULTS

In 21/43 families, a genetic aetiology consistent with non-autoimmune PAI was discovered, and in 3 families, autoimmune regulator (AIRE) mutations were found, indicating an autoimmune origin. In Sudan, adenosine triphosphate (ATP) binding cassette subfamily D member 1 (ABCD1)/nicotinamide nucleotide transhydrogenase (NNT)/AIRE mutations were commonest, including recurrent NNT splice and AIRE deletion mutations. In 2 families, we identified ARSA mutations fitting a diagnosis of metachromatic leucodystrophy (MLD), in which adrenal insufficiency has not previously been described. In the remaining 17 families, no causative gene mutations were found. Putative causal variants for comorbidities were concomitantly detected.

CONCLUSIONS

In this population, WES revealed itself as a useful frontline tool for the differential diagnosis of individuals presenting with adrenal insufficiency, including discrimination between MLD and adrenoleucodystrophy and giving plausible gene defects for additional comorbidities such as obesity. Such genetic diagnoses are crucial to design optimal treatment plans and for genetic counselling in affected individuals and their families.

Conserved genes regulating human sex differentiation, gametogenesis and fertilization

The study of the functional genome in mice and humans has been instrumental for describing the conserved molecular mechanisms regulating human reproductive biology, and for defining the etiologies of monogenic fertility disorders. Infertility is a reproductive disorder that includes various conditions affecting a couple's ability to achieve a healthy pregnancy. Recent advances in next-generation sequencing and CRISPR/Cas-mediated genome editing technologies have facilitated the identification and characterization of genes and mechanisms that, if affected, lead to infertility. We report established genes that regulate conserved functions in fundamental reproductive processes (e.g., sex determination, gametogenesis, and fertilization). We only cover genes the deletion of which yields comparable fertility phenotypes in both rodents and humans. In the case of newly-discovered genes, we report the studies demonstrating shared cellular and fertility phenotypes resulting from loss-of-function mutations in both species. Finally, we introduce new model systems for the study of human reproductive biology and highlight the importance of studying human consanguineous populations to discover novel monogenic causes of infertility. The rapid and continuous screening and identification of putative genetic defects coupled with an efficient functional characterization in animal models can reveal novel mechanisms of gene function in human reproductive tissues.

Identification and functional characterization of compound heterozygous CYP11B1 gene mutations

PURPOSE

11β-Hydroxylase deficiency (11β-OHD) is the second leading cause of congenital adrenal hyperplasia (CAH), a rare autosomal recessive disease caused by mutations in the CYP11B1 gene. We previously reported the case of a male Chinese patient with typical 11β-OHD symptoms. Sanger sequencing revealed that the patient carried a splice-site mutation, c.595+1G>A in the CYP11B1 gene. His mother and sister harbored the heterozygous mutation, c.595+1G>A. Paradoxically, Sanger sequencing did not detect any abnormality in the CYP11B1 gene of his father and brother. Therefore, in this study, we aimed to further explore the exact genetic etiology of 11β-OHD in this pedigree and analyze the functional consequence of the c.595+1G>A mutation.

METHODS

Gemomic DNA was extracted from the peripheral blood leukocytes of the family members and normal control individuals, followed by quantitative real-time polymerase chain reaction (qPCR) to detect the copy number of the target CYP11B1 gene fragment. Mutation analysis was also performed via whole-exome sequencing (WES) followed by Sanger sequencing validation. In vitro minigene assay was also performed to investigate the impact of the c.595+1G>A mutation on pre-mRNA splicing.

RESULTS

qPCR results suggested a heterozygous deletion encompassing position c.595+1 along with flanking exonic and intronic sequences in the CYP11B1 gene of the patient and his father. WES followed by Sanger sequencing verified that the patient carried compound heterozygous mutations in the CYP11B1 gene, including a novel 2840-bp deletion (c.395+661_c.1121+180del) and c.595+1G>A, while his father carried the heterozygous c.395+661_c.1121+180del mutation. No other novel CYP11B1 mutations were found in the rest of the family members. Furthermore, minigene assay revealed that the c.595+1G>A mutation resulted in a 70-bp deletion of exon 3 in the mRNA, and this altered the reading frame at amino acid 176 and created a premature stop codon at amino acid 197.

CONCLUSION

We identified a novel 2840-bp-sized large deletion and confirmed that the c.595+1G>A mutation disrupts normal pre-mRNA splicing. Either mutation could significantly alter the reading frame and abolish CYP11B1 enzyme activity. Therefore, our findings widen the mutation spectrum of CYP11B1 and provide an accurate diagnosis of 11β-OHD at a molecular genetic level.

Chimeric Genes Causing 11β-Hydroxylase Deficiency: Implications in Clinical and Molecular Diagnosis

Deficiency of 11β-hydroxylase (11β-OHD) is the second most common cause of congenital adrenal hyperplasia (CAH), accounting for 0.2-8% of all cases. The disease is transmitted as an autosomal recessive trait and the underlying genetic causes of 11β-OHD are primarily small pathogenic variants affecting the CYP11B1 gene coding the 11β-hydroxylase enzyme. However, special events complicate the molecular diagnosis of 11β-OHD such as an unequal crossing over between the CYP11B2 (coding aldosterone synthase enzyme) and CYP11B1 genes. The resulting allele contains a hybrid gene, with a CYP11B2 5'-end and a CYP11B1 3'-end, where the CYP11B1 gene is under the control of the CYP11B2 promoter and thus not responding to the adrenocorticotropin (ACTH) but to angiotensin II and K+. This leads a reduction of cortisol production in 11β-OHD. In particular, CYP11B2/CYP11B1 chimeric genes can be distinguished into two groups depending on the breakpoint site: chimeras with breakpoint after the exon 5 of CYP11B2 preserve the aldosterone synthase activity, the others with breakpoint before exon 5 lose this function. In the last case, a more severe phenotype is expected. The aim of this review was to explore the setting of CYP11B2/CYP11B1 chimeras in 11β-OHD, performing a careful review of clinical literature cases.

Molecular analysis of 12 Chinese patients with 11β-hydroxylase deficiency and in vitro functional study of 20 CYP11B1 missense variants

Steroid 11β-hydroxylase deficiency (11β-OHD) is a rare autosomal recessive disorder caused by pathogenic variants of CYP11B1 gene. This study aimed to perform molecular analysis of a Chinese 11β-OHD series and in vitro functional study of twenty CYP11B1 missense variants. Twelve Chinese patients with clinical diagnosis of 11β-OHD were included in the study to analyze their molecular etiology. Genomic DNA of patients was extracted to be sequenced all coding exons and intronic flanking sequences of CYP11B1. Fourteen missense variants found in 12 patients mentioned above along with 6 missense variants previously reported by our team were evaluated functionally. Amino acid substitutions were analyzed with computational program to determine their effects on the three-dimensional structure of CYP11B1 protein. Clinical characteristics and hormone levels at baseline of the 18 patients carrying 18 missense variants aforementioned were recorded to perform genotype-phenotype correlation. A total of 21 rare variants including 9 novel and 12 recurrent ones were identified in 12 patients, out of which 17 were missense, 2 were nonsense, 1 was a splice site variant, and 1 was a deletion-insertion variant. Results of in vitro functional study revealed that 3 out of 20 missense mutants (p.Leu3Pro, p.Gly267Ser, and p.Ala367Ser) had partial enzyme activity and the other 17 had little enzymatic activity. The impairment degree of enzymatic activity in vitro functional study was also reflected in the severity degree of interaction change between the wild-type/mutant-type amino acid and its adjacent amino acids in three-dimensional model. In conclusion, the addition of 9 novel variants expands the spectrum of CYP11B1 pathogenic variants. Our results demonstrate that twenty CYP11B1 variants lead to impaired 11β-hydroxylase activity in vitro. Visualizing these variants in the three-dimensional model structure of CYP11B1 protein can provide a plausible explanation for the results measured in vitro.

Congenital adrenal hyperplasia caused by compound heterozygosity of two novel CYP11B1 gene variants

BACKGROUND

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder caused by pathogenic variants in seven genes involved in the cortisol and aldosterone biosynthetic pathway. The second most common cause, 11β-hydroxylase deficiency (11βOHD), is attributed to pathogenic variants in the CYP11B1 gene encoding for the enzyme 11β-hydroxylase (11βOH).

CASE PRESENTATION

A 13-year-old girl was referred to the pediatric endocrinologist due to a syncopal episode. She is the third child of non-consanguineous parents. She presented with premature adrenarche at the age of 6 years and menarche at the age of 12 years. On physical examination, her height was 154.5 cm and weight 50 kg, while she presented with acne, hirsutism, clitoromegaly, and normal blood pressure. Laboratory investigation revealed increased androgen levels and poor cortisol response to the ACTH stimulation test. From the family history, the mother was diagnosed with CAH at the age of 10 years and was under treatment with methylprednisolone. Previous molecular investigation of the CYP21A2 gene was negative. Due to the increased androstenedione levels in the index patient, the suspicion of 11βOH was raised, and she was investigated for 11-deoxycortisol, 11-deoxycorticosterone, and CYP11B1 gene pathogenic variants. The patient and her mother were found to be compound heterozygous for two novel variants of the CYP11B1 gene.

CONCLUSION

We present a case of CAH due to compound heterozygosity of two novel pathogenic variants of the CYP11B1 gene, emphasizing the importance of molecular investigation in order to confirm clinical diagnosis and allow proper genetic counseling of the family.

Clinical and Hormonal Profiles Correlate With Molecular Characteristics in Patients With 11β-Hydroxylase Deficiency

BACKGROUND

Given the rarity of 11β-hydroxylase deficiency (11βOHD), there is a paucity of data about the differences in clinical and biochemical characteristics of classic (C-11βOHD) and nonclassic 11βOHD (NC-11βOHD).

OBJECTIVE

To characterize a multicenter pediatric cohort with 11βOHD.

METHOD

The clinical and biochemical characteristics were retrospectively retrieved. CYP11B1 gene sequencing was performed. Seventeen plasma steroids were quantified by liquid chromatography-mass spectrometry and compared to that of controls.

RESULTS

102 patients (C-11βOHD, n = 92; NC-11βOHD, n = 10) from 76 families (46,XX; n = 53) had biallelic CYP11B1 mutations (novel 9 out of 30). Five 46,XX patients (10%) were raised as males. Nineteen patients (19%) had initially been misdiagnosed with 21-hydroxylase deficiency. Female adult height was 152 cm [-1.85 SD score (SDS)] and male 160.4 cm (-2.56 SDS).None of the NC-11βOHD girls had ambiguous genitalia (C-11βOHD 100%), and none of the NC-11βOHD patients were hypertensive (C-11βOHD 50%). Compared to NC-11βOHD, C-11βOHD patients were diagnosed earlier (1.33 vs 6.9 years; P < 0.0001), had higher bone age-to-chronological age (P = 0.04) and lower adult height (-2.46 vs -1.32 SDS; P = 0.05). The concentrations of 11-oxygenated androgens and 21-deoxycortisol were low in all patients. The baseline ACTH and stimulated cortisol were normal in NC-11βOHD. Baseline cortisol; cortisone; 11-deoxycortisol; 11-deoxycorticosterone and corticosterone concentrations; and 11-deoxycortisol/cortisol, 11-deoxycorticosterone/cortisol, and androstenedione/cortisol ratios were higher in C-11βOHD than NC-11βOHD patients (P < 0.05). The 11-deoxycortisol/cortisol ratio >2.2, <1.5, and <0.1 had 100% specificity to segregate C-11βOHD, NC-11βOHD, and control groups.

CONCLUSION

NC-11βOHD can escape from clinical attention due to relatively mild clinical presentation. However, steroid profiles enable the diagnosis, differential diagnosis, and subtyping of 11βOHD.

Compound heterozygosity of a novel Q73X mutation and a known R141X mutation in CYP11B1 resulting in 11β-hydroxylase deficiency in a Chinese boy with congenital adrenal hyperplasia

Steroid 11β-hydroxylase deficiency (11β-OHD), which is caused by mutations of the CYP11B1 gene, is the second leading cause of congenital adrenal hyperplasia (CAH), an autosomal recessive inherited disorder. Here, we report a case of classic 11β-OHD in a Chinese boy characterized by hypertension, penile enlargement, skin pigmentation, and acne. Molecular analysis of CYP11B1 revealed that the patient was compound heterozygous for a c.217C > T (p.Q73X) mutation in exon 1 and a c.421C > T (p.R141X) mutation in exon 3. His parents carried the novel c.217C > T (p.Q73X) mutation and the prevalent c.421C > T (p.R141X) mutation. Furthermore, we identified a novel 217-bp substitution mutation (Q73X) in CYP11B1 that generates a truncated protein without biological activity, which is likely to be pathogenic. Pursuant to the phenotype of the proband and his family, the Q73X mutation is inferred to exacerbate the disease burden of the R141X mutation, a known pathogenic variant. To further explore this possibility, selecting the x-ray structure of human CYP11B2 as a template, we built three-dimensional homologous models of the normal and mutant proteins. In the mutant model, a change from a helix to terminal structure in amino acids 73 and 141 occurred that affected the binding capacity of CYP11B1 with heme and impaired 11β-hydroxylase activity. Taken together, our findings expand the spectrum of known mutations leading to 11β-OHD and provide evidence to study genotype-phenotype concordance, confirm early diagnosis and treatment of 11β-OHD, and prevent most complications.

Expanding genetic spectrum and discriminatory role of steroid profiling by LC-MS/MS in 11β-hydroxylase deficiency

OBJECTIVE

To report clinical, hormonal and structural effects of CYP11B1 pathogenic variations in Indian patients with 11β-hydroxylase deficiency (11βOHD) and find hormonal criteria that accurately distinguish 11βOHD from 21α-hydroxylase deficiency (21OHD).

DESIGN

Retrospective record review of genetically diagnosed patients with 11βOHD.

PATIENTS AND MEASUREMENTS

Clinical features, hormonal parameters at diagnosis (by immunoassay) and recent follow-up of 13 genetically proven 11βOHD patients managed at our centre were retrospectively reviewed. ACTH-stimulated serum adrenal steroids (measured by LC-MS/MS) of 11βOHD were compared with those of simple virilizing and non-classic 21OHD. Structural analysis of the observed pathogenic variations was performed by computational modelling.

RESULTS

Nine (four females) and four (all females) patients had classic and non-classic disease, respectively. All 11βOHD patients had elevated ACTH-stimulated serum 11-deoxycortisol (26.5-342.7 nmol/L) whereas none had elevated serum 17-hydroxyprogesterone (4.2-21.2 nmol/L); both hormonal parameters distinguished 11βOHD from 21OHD with 100% accuracy. ACTH-stimulated serum cortisol, but not 11-deoxycortisol, clearly distinguished classic (<70 nmol/L) from non-classic (>160 nmol/L) disease. Thirteen (eight novel, two recurrent) pathogenic variants were observed. Only missense mutations were observed among patients with non-classic disease. Computational modelling predicted the possible affection of enzyme structure and function for all the observed missense mutations.

CONCLUSIONS

This first Indian study describes 13 11βOHD patients, including four with the rarer non-classic variant. A total of eight novel pathogenic variants were identified in our study, highlighting regional genetic heterogeneity. Measurement of ACTH-stimulated adrenal steroids by LC-MS/MS will help avoid the misdiagnosis of 11βOHD as 21OHD and has potential to distinguish classic from non-classic 11βOHD.

Structural and functional insights into aldosterone synthase interaction with its redox partner protein adrenodoxin

Aldosterone is the major mineralocorticoid in the human body controlling blood pressure and salt homeostasis. Overproduction of aldosterone leads to primary aldosteronism, which is the most common form of secondary hypertension with limited treatment options. Production of aldosterone by cytochrome P450 11B2 (CYP11B2, aldosterone synthase) requires two reduction events with the electrons delivered by the iron/sulfur protein adrenodoxin. Very limited information is available about the structural and functional basis of adrenodoxin/CYP11B2 interaction, which impedes the development of new treatment options for primary aldosteronism. A systematic study was carried out to determine if adrenodoxin interaction with CYP11B2 might also have an allosteric component in addition to electron transfer. Indeed, local increases in adrenodoxin concentration promote binding of the substrate 11-deoxycorticosterone and the inhibitor osilodrostat (LCI699) in the active site-over 17 Å away-as well as enhance the inhibitory effect of this latter drug. The CYP11B2 structure in complex with adrenodoxin identified specific residues at the protein-protein interface interacting via five salt bridges and four hydrogen bonds. Comparisons with cholesterol-metabolizing CYP11A1 and cortisol-producing CYP11B1, which also bind adrenodoxin, revealed substantial structural differences in these regions. The structural and functional differences between different P450 interactions with adrenodoxin may provide valuable clues for an orthogonal treatment approach for primary aldosteronism by specifically targeting the interaction between CYP11B2 and adrenodoxin.

Zebrafish as an emerging model to study gonad development

The zebrafish (Danio rerio) has emerged as a popular model organism in developmental biology and pharmacogenetics due to its attribute of pathway conservation. Coupled with the availability of robust genetic and transgenic tools, transparent embryos and rapid larval development, studies of zebrafish allow detailed cellular analysis of many dynamic processes. In recent decades, the cellular and molecular mechanisms involved in the process of gonad development have been the subject of intense research using zebrafish models. In this mini-review, we give a brief overview of these studies, and highlight the essential genes involved in sex determination and gonad development in zebrafish.

Skeletal maturation in relation to ethnic background in children of school age: The Generation R Study

Ethnicity is a well-established determinant of pediatric maturity, but the underlying genetic and environmental contributions to these ethnic differences are poorly comprehended. We aimed to evaluate the influence of ethnicity on skeletal age (SA), an assessment of pediatric maturation widely used in clinical settings. We included children from the Generation R Study, a multiethnic population-based pregnancy cohort, assessed at a mean age of 9.78 (±0.33) years. SA was evaluated by a trained observer on hand DXA scans using the Greulich and Pyle method. Ethnic background was defined as geographic ancestry (questionnaire-based assessment) (N = 5325) and genetic ancestry (based on admixture analysis) (N = 3413). Associations between the ethnic background and SA were investigated separately in boys and girls, using linear regression models adjusted for age, height and BMI. Based on geographic ancestry, 84% of the children were classified as European, 6% as Asian and 10% as African. Children of European background had on average younger SA than those of Asian or African descent. Asian boys had 0.46 (95% CI 0.26-0.66, p-value < 0.0001) and African boys 0.36 years (95% CI 0.20-0.53, p-value < 0.0001) older SA as compared to European boys. Similarly, Asian girls showed 0.64 (95% CI 0.51-0.77, p-value < 0.0001) and African girls 0.38 years (95% CI 0.27-0.48, p-value < 0.0001) older SA as compared to European girls. A similar pattern was observed in the analysis with genetically-defined ancestry. Furthermore, an increase in the proportion of Asian or African component was associated with older SA in both boys (log[Non-European/European]proportion = 0.10, 95% CI 0.06-0.13, p-value < 0.0001) and girls (log[Non-European/European]proportion = 0.06, 95% CI 0.04-0.08, p-value < 0.0001). In summary, children of Asian and African backgrounds have on average older SA as compared to children of European descent, partially explained by a genetic component.

Hereditary causes of primary aldosteronism and other disorders of apparent excess mineralocorticoid activity

Secondary hypertension is a common condition with a broad differential diagnosis. Identification of the true cause of hypertension can be critical for guiding appropriate management. Here, we review hereditary conditions underlying the most common cause of secondary hypertension, primary aldosteronism, as well as other disorders impacting various levels of mineralocorticoid action. Recently, several pathogenic variants of ion channels have been described as etiologies of familial aldosteronism. Defects in steroid hormone synthesis cause hypertension in 11β-hydroxylase deficiency and 17α-hydroxylase deficiency, two types of congenital adrenal hyperplasia. Inappropriate activation of mineralocorticoid receptors underlies the syndrome of apparent mineralocorticoid excess and constitutive activation of the mineralocorticoid receptor. Finally, Liddle syndrome and pseudohypoaldosteronism type 2 are disorders impacting the function of renal sodium channels, the endpoint of mineralocorticoid action. We discuss the pathophysiology, clinical presentation, diagnosis and management of these low renin hypertension states that ultimately result in apparent excess mineralocorticoid activity.

Monogenic Forms of Hypertension

Essential hypertension is a highly prevalent disease in the general population. Secondary hypertension is characterized by a specific and potentially reversible cause of increased blood pressure levels. Some secondary endocrine forms of hypertension are common (caused by uncontrolled cortisol, aldosterone, or catecholamines production). This article describes rare monogenic forms of hypertension, characterized by electrolyte disorders and suppressed renin-aldosterone axis. They represent simple models for the physiology of renal control of sodium levels and plasma volume, thus reaching a high scientific interest. Furthermore, they could explain some features closer to the essential phenotype of hypertension, suggesting a mechanistically driven personalized treatment.

46,XX DSD due to Androgen Excess in Monogenic Disorders of Steroidogenesis: Genetic, Biochemical, and Clinical Features

The term 'differences of sex development' (DSD) refers to a group of congenital conditions that are associated with atypical development of chromosomal, gonadal, or anatomical sex. Disorders of steroidogenesis comprise autosomal recessive conditions that affect adrenal and gonadal enzymes and are responsible for some conditions of 46,XX DSD where hyperandrogenism interferes with chromosomal and gonadal sex development. Congenital adrenal hyperplasias (CAHs) are disorders of steroidogenesis that mainly involve the adrenals (21-hydroxylase and 11-hydroxylase deficiencies) and sometimes the gonads (3-beta-hydroxysteroidodehydrogenase and P450-oxidoreductase); in contrast, aromatase deficiency mainly involves the steroidogenetic activity of the gonads. This review describes the main genetic, biochemical, and clinical features that apply to the abovementioned conditions. The activities of the steroidogenetic enzymes are modulated by post-translational modifications and cofactors, particularly electron-donating redox partners. The incidences of the rare forms of CAH vary with ethnicity and geography. The elucidation of the precise roles of these enzymes and cofactors has been significantly facilitated by the identification of the genetic bases of rare disorders of steroidogenesis. Understanding steroidogenesis is important to our comprehension of differences in sexual development and other processes that are related to human reproduction and fertility, particularly those that involve androgen excess as consequence of their impairment.

Smooth quantile normalization

Between-sample normalization is a critical step in genomic data analysis to remove systematic bias and unwanted technical variation in high-throughput data. Global normalization methods are based on the assumption that observed variability in global properties is due to technical reasons and are unrelated to the biology of interest. For example, some methods correct for differences in sequencing read counts by scaling features to have similar median values across samples, but these fail to reduce other forms of unwanted technical variation. Methods such as quantile normalization transform the statistical distributions across samples to be the same and assume global differences in the distribution are induced by only technical variation. However, it remains unclear how to proceed with normalization if these assumptions are violated, for example, if there are global differences in the statistical distributions between biological conditions or groups, and external information, such as negative or control features, is not available. Here, we introduce a generalization of quantile normalization, referred to as smooth quantile normalization (qsmooth), which is based on the assumption that the statistical distribution of each sample should be the same (or have the same distributional shape) within biological groups or conditions, but allowing that they may differ between groups. We illustrate the advantages of our method on several high-throughput datasets with global differences in distributions corresponding to different biological conditions. We also perform a Monte Carlo simulation study to illustrate the bias-variance tradeoff and root mean squared error of qsmooth compared to other global normalization methods. A software implementation is available from https://github.com/stephaniehicks/qsmooth.

Divergent gender identity in three siblings with 46XX karyotype and severely virilizing congenital adrenal hyperplasia caused by a novel CYP11B1 mutation

OBJECTIVE

To describe conflicting gender identities in three karyotypically female siblings with congenital adrenal hyperplasia (CAH) caused by a novel mutation in the CYP11B1 gene, who were assigned as males at birth and followed up to adulthood.

METHODS

We present 3 siblings (16, 14 and 10 years old) who were born with severe genital virilization and raised as males. Clinical examination showed Prader IV to V external genitalia with a stretched penile length of 7 to 11 cm. Adrenocorticotrophic hormone (ACTH) stimulation test showed a stimulated 11 deoxycortisol (11DOC) level of 12,300-18,700 μg/L (normal 0-5 μg/L). Their karyotypes were 46 XX, and they had normal-sized uterus and ovaries on pelvic ultrasound. DNA was isolated from peripheral leukocytes, and polymerase chain reaction (PCR) and direct sequencing revealed a novel CYP11B1 mutation. This mutation leads to a c.53_54 T insertion (c.53_54insT) with frameshift and truncation at c.115 (codon 39) of CYP11B1.

RESULTS

Psychological evaluation of the oldest sibling suggested a female gender identity, and she declared herself as female, and female sex was re-assigned after 1 year of psychosocial adjustment. Psychological assessment for the 2 younger siblings and a fourth 46XY sibling with the same condition revealed male gender identities, and they continued their lives as males without significant difficulties.

CONCLUSION

Divergent gender identity was observed in three severely masculinized 46XX siblings with CAH who carried the same CYP11B1 mutation and had comparable postnatal and probably prenatal androgen exposure and environmental circumstances. These cases suggest that the basis of gender identity is more complex than chromosomal, biochemical, and genetic constitution.

Insights on the phenotypic heterogenity of 11β-hydroxylase deficiency: clinical and genetic studies in two novel families

PURPOSE

11β-hydroxylase deficiency accounts for 5% of congenital adrenal hyperplasia cases. Diagnosis suspiction is classically based on the association between abnormal virilization, precocious puberty, and hypertension in 46XX or 46XY subjects. We investigated two families with siblings presenting with opposed clinical features, and provided a review of the mechanisms involved in mineralocorticoid-dependent phenotypic heterogeneity.

METHODS

The coding region of the CYP11B1 gene of 4 patients was sequenced and familial segregation was confirmed. Clinical characterization and blood steroid profile were performed.

RESULTS

Family 1 comprised a female and a male siblings who presented in middle childhood with genital ambiguity (Prader II) and precocious puberty, respectively, associated with hypertension. In the second decade of life, the woman had three full-term pregnancies, and then evolved normotensive with no treatment over a 5-year follow up. On the other hand, her brother had hypertensive end-organ damage at age 24. In family 2, a 2.9 year-old boy presented with precocious puberty and hypertension, whereas his 21 days-old sister had genital ambiguity (Prader III) and salt wasting. A homozygous exon 4 splice site mutation was identified (IVS4ds-1G > A; c.799 G > A) in family 1, while a nonsense mutation in exon 6 (p. Q356X; c.1066 C > T) was found in family 2.

CONCLUSION

CYP11B1 mutations were associated with highly variable phenotypes, from mild to severe virilization, and early-onset hypertension or salt wasting. Further analysis of variants in other hypertension-related genes, steroid synthesis and metabolism compensatory pathways, and/or the investigation of chimeric CYP11B genes are needed to clarify the phenotypic heterogeneity in 11β-hydroxylase deficiency.

A Chinese patient with 11β-hydroxylase deficiency due to novel compound heterozygous mutation in CYP11B1 gene: a case report

BACKGROUND

Congenital adrenal hyperplasia (CAH) resulting from steroid 11β-hydroxylase deficiency (11β-OHD) is caused by mutations in the CYP11B1 gene. It is the second major form of CAH associated with hypertension and hypopotassemia. The aim of this study was to provide a genetic analysis of 11β-OHD in a Chinese family.

CASE PRESENTATION

A 19-year-old Chinese man was clinically diagnosed with 11β-OHD. His initial clinical manifestations included precocious puberty, hyperpigmentation, hypertension, and hypopotassemia. The patient had taken an overdose of dexamethasone (0.75 mg/d) for more than 10 years before finally developing iatrogenic Cushing's syndrome. Our aim was to perform a molecular diagnosis of his family. Mutations in the CYP11B1 gene of the patient and his parents were examined using polymerase chain reaction (PCR) resequencing. Additionally, to predict the possible effects of novel mutations on the structure and function of 11β-hydroxylase, these mutations were analyzed by MutationTaster software. Two novel pathogenic mutations were found in the CYP11B1 gene: a heterozygous in-frame insertion deletion mutation c.1440_1447delinsTAAAAG in exon 9 inherited from the father and a heterozygous mutation c.1094_1120delTGCGTGCGGCCCTCAAGGAGACCTTGC (p.364_372del) in exon 6 inherited from the mother.

CONCLUSIONS

A clear genetic diagnosis can be made by analyzing the functional and structural consequences of CYP11B1 gene mutations that lead to 11β-OHD. Because the dosage of glucocorticoid should be adjusted to minimize the risk of iatrogenic Cushing's syndrome, clinical follow-up should be conducted with these patients.

Non-classical 11β-hydroxylase deficiency caused by compound heterozygous mutations: a case study and literature review

BACKGROUND

11β-hydroxylase deficiency (11OHD) is extremely rare, and reports of non-classical 11OHD are even rarer. Non-classical 11OHD usually presents as premature adrenarche, hyperandrogenism, menstrual disorders, and hypertension. Because the symptoms of non-classical 11OHD are mild, delayed diagnosis or misdiagnosis as polycystic ovary syndrome or primary hypertension is common.

CASE PRESENTATION

This paper introduces a case of a young female patient presenting hypertension and menstrual disorders. Laboratory examination revealed increased androgen levels, mild adrenal hyperplasia, mild left ventricular hypertrophy, and mild sclerosis of the lower limb arteries. 11OHD was confirmed by genetic testing, and the patient was found to carry compound heterozygous mutations in CYP11B1 (c.583 T > C and c.1358G > A). The mutation Y195H is located in exon 3 and has not been reported previously. In silico studies indicated that this mutation may cause reduced enzymatic activity. After treatment with hydrocortisone and spironolactone, blood pressure was brought under good control, and menstruation returned to normal. We also conducted a retrospective review of previously reported cases in the literature (over 170 cases since 1991).

CONCLUSIONS

Early diagnosis of non-classical 11OHD is difficult because its symptoms are mild. The possibility of this disease should be considered in patients with early-onset hypertension, menstrual disorders, and hyperandrogenism to provide early treatment and prevent organ damage due to hypertension and hyperandrogenism. CYP11B1 mutations are known to be race-specific and are concentrated in exons 3 and 8, of which mutations in the former are mostly associated with non-classical 11OHD, whereas mutations in the latter are mostly found in classical 11OHD, characterized by severe loss of enzymatic activity.

Prevalence, clinical characteristics and long-term outcomes of classical 11 β-hydroxylase deficiency (11BOHD) in Turkish population and novel mutations in CYP11B1 gene

Congenital adrenal hyperplasia (CAH) due to 11β-hydroxylase deficiency (11BOHD) is a rare autosomal recessive disorder and the second most common form of CAH.

AIM

To investigate genotype-phenotype correlation and to evaluate clinical characteristics and long-term outcomes of patients with 11BOHD.

METHODS

A total of 28 patients (n = 14, 46,XX; n = 14, 46,XY) with classical 11BOHD from 25 unrelated families were included in this study. Screening of CYP11B1 is performed by Sanger sequencing. Pathogenic features of novel variants are investigated by the use of multiple in silico prediction tools and with family based co-segregation studies. Protein simulations were investigated for two novel coding region alterations.

RESULTS

The age at diagnosis ranged from 6 days to 12.5 years. Male patients received diagnose at older ages than female patients. The rate of consanguinity was high (71.4%). Five out of nine 46,XX patients were diagnosed late (age 2-8.7 years) and were assigned as male due to severe masculinization. Twenty one patients have reached adult height and sixteen were ultimately short due to delayed diagnosis. Two male patients had testicular microlithiasis and 5 (35.7%) patients had testicular adrenal rest tumor during follow up. Four patients (28.6%) had gynecomastia. Mutation analyses in 25 index patients revealed thirteen different mutations in CYP11B1 gene, 4 of which were novel (c.393 + 3A > G, c.428G > C, c.1398 + 2T > A, c.1449_1451delGGT). The most frequent mutations were c.896T > C with 32%, c.954G > A with 16% and c.1179_1180dupGA with 12% in frequency. There was not a good correlation between genotype and phenotype; phenotypic variability was observed among the patients with same mutation.

CONCLUSION

This study presents the high allelic heterogeneity of CYP11B1 mutations in CAH patients from Turkey. Three dimensional protein simulations may provide additional support for the pathogenicity of the genetic alterations. Our results provide reliable information for genetic counseling, preventive and therapeutic strategies for the families.

Monogenic Hypertension in Children: A Review With Emphasis on Genetics

Hypertension (HT) is a public health problem in children particularly related to the epidemic of overweight and obesity. Monogenic forms of HT are important in the differential diagnosis in children presenting with severe or refractory HT, who have a family history of early-onset HT, unusual physical examination findings, and/or characteristic hormonal and biochemical abnormalities. Most genetic defects in these disorders ultimately result in increased sodium transport in the distal nephron resulting in volume expansion and HT. Genetic testing, which is increasingly available, has diagnostic, therapeutic, and predictive implications for families affected by these rare conditions.

A high rate of novel CYP11B1 mutations in Saudi Arabia

Despite ethnic variation, 11 β-hydroxylase deficiency (11β-OHD) has generally been considered the second most common subtype of congenital adrenal hyperplasia (CAH). We report a high rate of novel mutations in this gene (CYP11B1) in patients from Saudi Arabia. We studied 16 patients with 11β-OHD from 8 unrelated families. DNA was isolated from peripheral blood. The 9 exons and exon-intron boundaries of CYP11B1 were PCR-amplified and directly sequenced. The novel mutations were functionally characterized using subcloning, in vitro mutagenesis, cell transfection and 11-deoxycortisol: cortisol conversion assays. Six mutations were found in these 8 unrelated families. Three of these mutations are completely novel and two have just been recently described as novel mutations from the same population. These include a single nucleotide insertion mutation in codon 18 (c.53_54insT) leading to frameshift and truncation in 4 siblings, a novel mutation (c.1343G>C, p.R448P) in 3 unrelated families, a novel mutation (c.1394A>T, p.H465L) in 2 siblings, a novel mutation (c.617G>T, p.G206V) in 1 patient, and a recently described non-sense novel mutation (c.780G>A, p.W260X) in another patient. Out of the 6 mutations described in this report, only one mutation (p.Q356X) was reported previously. In vitro functional testing of the 3 missense and nonsense novel mutations revealed complete loss of the 11 hydroxylase activity. We conclude that 11 β-OHD in Saudi Arabia has a unique genotype with a high rate of novel mutations. The novel p. R448P mutation is the most common mutation in this highly inbred population.

Congenital adrenal hyperplasia due to 11-hydroxylase deficiency-Compound heterozygous mutations of a prevalent and two novel CYP11B1 mutations

11β-hydroxylase deficiency (11β-OHD) occurs in about 5-8% of congenital adrenal hyperplasia (CAH). In this study, we identified three CYP11B1 (encoding Cytochrome P450 11B1) heterozygous mutations: c.1358G>C (p.R453Q), c.1229T>G (p.L410R) and c.1231G>T (p.G411C) in a Chinese CAH patient due to classic 11β-OHD. His parents were healthy and respectively carried the prevalent mutation c.1358G>C (p.R453Q), and the two novel mutations c.1229T>G (p.L410R) and c.1231G>T (p.G411C). In vitro expression studies, immunofluorescence demonstrated that wild type and mutant (L410R and G411C) proteins of CYP11B1 were correctly expressed on the mitochondria, and enzyme activity assay revealed the mutant reduced the 11-hydroxylase activity to 10% (P<0.001) for the conversion of 11β-deoxycortisol to cortisol. Subsequently, three dimensional homology models for the normal and mutant proteins were built by using the x-ray structure of the human CYP11B2 as a template. Interestingly, in the heme binding site I helix, a change from helix to loop in four amino acide took place in the mutant model. In conclusion, this study expands the spectrum of mutations in CYP11B1 causing to 11β-OHD and provides evidence for prenatal diagnosis and genetic counseling. In addition, our results confirm the two novel CYP11B1 mutations led to impaired 11-hydroxylase activity in vitro.

Genetics of Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) refers to a group of autosomal recessive disorders due to single-gene defects in the various enzymes required for cortisol biosynthesis. CAH represents a continuous phenotypic spectrum with more than 95% of all cases caused by 21-hydroxylase deficiency. Genotyping is an important tool in confirming the diagnosis or carrier state, provides prognostic information on disease severity, and is essential for genetic counseling. In this article, the authors provide an in-depth discussion on the genetics of CAH, including genetic diagnosis, molecular analysis, genotype-phenotype relationships, and counseling of patients and their families.

Clinical, genetic, and structural basis of congenital adrenal hyperplasia due to 11β-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH), resulting from mutations in CYP11B1, a gene encoding 11β-hydroxylase, represents a rare autosomal recessive Mendelian disorder of aberrant sex steroid production. Unlike CAH caused by 21-hydroxylase deficiency, the disease is far more common in the Middle East and North Africa, where consanguinity is common often resulting in identical mutations. Clinically, affected female newborns are profoundly virilized (Prader score of 4/5), and both genders display significantly advanced bone ages and are oftentimes hypertensive. We find that 11-deoxycortisol, not frequently measured, is the most robust biochemical marker for diagnosing 11β-hydroxylase deficiency. Finally, computational modeling of 25 missense mutations of CYP11B1 revealed that specific modifications in the heme-binding (R374W and R448C) or substrate-binding (W116C) site of 11β-hydroxylase, or alterations in its stability (L299P and G267S), may predict severe disease. Thus, we report clinical, genetic, hormonal, and structural effects of CYP11B1 gene mutations in the largest international cohort of 108 patients with steroid 11β-hydroxylase deficiency CAH.

Clinical perspectives in congenital adrenal hyperplasia due to 11β-hydroxylase deficiency

Congenital adrenal hyperplasia due to 11 beta-hydroxylase deficiency is a rare autosomal recessive genetic disorder. It is caused by reduced or absent activity of 11β-hydroxylase (CYP11B1) enzyme and the resultant defects in adrenal steroidogenesis. The most common clinical features of 11 beta-hydroxylase deficiency are ambiguous genitalia, accelerated skeletal maturation and resultant short stature, peripheral precocious puberty and hyporeninemic hypokalemic hypertension. The biochemical diagnosis is based on raised serum 11-deoxycortisol and 11-deoxycorticosterone levels together with increased adrenal androgens. More than 100 mutations in CYP11B1 gene have been reported to date. The level of in-vivo activity of CYP11B1 relates to the degree of severity of 11 beta-hydroxylase deficiency. Clinical management of 11 beta-hydroxylase deficiency can pose a challenge to maintain adequate glucocorticoid dosing to suppress adrenal androgen excess while avoiding glucocorticoid-induced side effects. The long-term outcomes of clinical and surgical management are not well studied. This review article aims to collate the current available data about 11 beta-hydroxylase deficiency and its management.

Novel and prevalent CYP11B1 gene mutations in Turkish patients with 11-β hydroxylase deficiency

11β-Hydroxylase deficiency is the second most frequent type of congenital adrenal hyperplasia and is more common in those of Turkish descent than in other populations. The purpose of this study is to examine the spectrum of CYP11B1 gene mutations in Turkish patients with 11β-hydroxylase deficiency. Twenty-eight patients from 24 families, ages ranging from 0.1 to 7 years, were included in the study. Clinical diagnosis was based on virilization and high levels of 11-deoxycortisol. Twenty-six cases exhibited the classical and 2 cases the non-classical form. Mutation screening of 9 CYP11B1 exons was performed by direct DNA sequence analysis, specifically amplifying CYP11B1 gene fragments while avoiding simultaneous amplification of homologous CYP11B2 gene sequences. Seventeen different mutations were detected, 6 of which are novel (p.Gln189Hisfs*70, p.Glu198Gly, p.Thr318Lys, p.Gly446Ser, IVS8+5G>C and exon 3-5 del). All of the identified mutations resulted in the classical form with severe virilization, except for the p.Gly446Ser mutation, which caused a late-onset type of 11β-hydroxylase deficiency. The c.954G>A;p.Thr318Thr mutation was the most common in our cohort, with an allele frequency of 14.6%.Of the CYP11B1 gene mutations detected, 75% were found in exons 3, 5 and 7 and the half of the mutations were nonsense, splice site, deletion or insertion mutations, causing severe virilization in female patients. The findings are important for genetic counseling and the prenatal diagnosis of Turkish patients with 11β-hydroxylase deficiency.

Congenital adrenal hyperplasia due to 11-beta-hydroxylase deficiency: description of a new mutation, R384X

CASE DESCRIPTION

It is presented the phenotype of a new compound heterozygous mutation of the genes R384X and Q356X encoding the enzyme of 11-beta-hydroxylase.

CLINICAL FINDINGS

Severe virilization, peripheral hypertension, and early puberty.

TREATMENT AND OUTCOME

Managed with hormone replacement therapy (corticosteroid) and antihypertensive therapy (beta-blocker), resulting in the control of physical changes and levels of arterial tension.

CLINICAL RELEVANCE

According to the phenotypic characteristics of the patient, it is inferred that the R384X mutation carries an additional burden on the Q356X mutation, with the latter previously described as a cause of 11-beta-hydroxylase deficiency. The description of a new genotype, as in this case, expands the understanding of the hereditary burden and deciphers the various factors that lead to this pathology as well as the other forms of congenital adrenal hyperplasia (CAH), presenting with a broad spectrum of clinical presentations. This study highlights the importance of a complete description of the patient's CAH genetic profile as well as their parents' genetic profile.

Splicing analysis of CYP11B1 mutation in a family affected with 11β-hydroxylase deficiency: case report

BACKGROUND

Congenital adrenal hyperplasia (CAH) due to steroid 11β-hydroxylase deficiency (11β-OHD) is a rare form of CAH associated with low renin hypertension, hypokalemia, hyperandrogenemia and ambiguous genitalia in affected females. Herein we describe the clinical, hormonal and molecular characteristics of two Uzbekistan siblings with 11β-OHD and analyze the effects of a splicing mutation.

CASE PRESENTATION

A 46,XX girl presented with genital ambiguity and low renin hypertension; her 46,XY brother presented with precocious puberty. Hormonal studies suggested 11β-OHD. Mutation analysis was performed by PCR followed by Sanger sequencing of the entire coding regions and their flanking introns of the CYP11B1 gene. Mutation analysis showed that both patients were compound heterozygous for IVS7 + 1G > A, and c.421C > T. Although the identified mutations have been previously described, this is, to our knowledge, the first report of these mutations in compound heterozygotes. A minigene assay was used to determine the effects of the splicing mutation. The constructs containing either the wild-type or the splice-site mutant CYP11B1 genomic DNA of exons-introns 6-9 were transfected into COS-7 cells; subsequently, RNA splicing was assessed by reversed transcribed-PCR of CYP11B1 complementary DNA. The minigene assay revealed that the IVS7 + 1G > A mutation resulted in two shorter incorrectly spliced products; one skipping the exon 7 and the other skipping the exons 7-8. The c.421C > T mutation leads to the introduction of a premature stop codon at residue 141 (p.R141X). These mutations are expected to code non-functional proteins.

CONCLUSION

Compound heterozygous mutations (IVS7 + 1G > A and p.R141X) in the CYP11B1 gene were found to cause 11β-OHD. The IVS7 + 1G > A mutation causes aberrant splicing of CYP11B1 leading to exon skipping. This finding could facilitate the future novel therapies targeted on splicing modulation to treat human disease.

Improving the diagnosis of 11β-hydroxylase deficiency using home-made MLPA probes: identification of a novel chimeric CYP11B2/CYP11B1 gene in a Sicilian patient

PURPOSE

11β-Hydroxylase deficiency (11OHD) represents the second most common cause of congenital adrenal hyperplasia. It is caused by mutations in the CYP11B1 gene localized about 40 kb from the CYP11B2 gene with which it shares a homology of 95 %. The asymmetric recombination of these two genes is involved both in 11OHD and in glucocorticoid-remediable aldosteronism (GRA). Our objective was to set up an easy and rapid method to detect these hybrid genes and other kinds of deletions, to improve the molecular diagnosis of 11OHD.

METHODS

A set of 8 specific probes for both the CYP11B1 and the CYP11B2 genes to be used for multiplex ligation-dependent probe amplification (MLPA) analysis was designed to detect rearrangements of these genes.

RESULTS

The method developed was tested on 15 healthy controls and was proved to be specific and reliable; it led us to identify a novel chimeric CYP11B2/CYP11B1 gene in one patient that carried the known A306V mutation on the other allele. Specific amplification and sequencing of the hybrid gene confirmed the breakpoint localization in the second intron.

CONCLUSIONS

The MLPA kit developed enables the detection of deletions, duplications or chimeric genes and represents an optimal supplement to DNA sequence analysis in patients with 11OHD. In addition, it can also be used to show the presence of the opposite chimaera associated with GRA.

The combination of a novel 2 bp deletion mutation and p.D63H in CYP11B1 cause congenital adrenal hyperplasia due to steroid 11β-hydroxylase deficiency

Deficiency of steroid 11β-hydroxylase activity occurs in 5-8% of patients with congenital adrenal hyperplasia (CAH). The aim of the current study was to identify mutations in the CYP11B1 gene of a patient with CAH due to deficiency of steroid 11β-hydroxylase activity, and to study the functional and structural consequences of these mutations. A molecular genetic analysis of the CYP11B1 gene in this patient and her parents identified a known missense mutation g.5194G>C (p.D63H) and a novel 2 bp deletion mutation (g.9525_9526delCT, corresponding to p.L380V…R420X) in the patient. In vitro expression studies in COS7 cells revealed a decreased 11β-hydroxylase activity in the p.D63H mutant to 2.0±0.8% and in the p.L380V…R420X mutant to 0.2±2.2% for the conversion of 11-deoxycortisol to cortisol. Three dimensional homology models for the normal and mutant proteins were built by using the recently published x-ray structure of the human CYP11B2 as a template. Presumably, the g.9525_9526delCT mutation in CYP11B1 resulted in a truncated protein with a misfolded C-terminal domain that could not efficiently bind heme iron, substrate, and adrenodoxin and had lost its biochemical function. In summary, CAH due to steroid 11β-hydroxylase deficiency can be attributed to both the novel deletion mutation (g.9525_9526delCT, corresponding to p.L380V…R420X) and known missense mutation (g.5194G>C corresponding to p.D63H) in CYP11B1.

Phenotypic, metabolic, and molecular genetic characterization of six patients with congenital adrenal hyperplasia caused by novel mutations in the CYP11B1 gene

Congenital adrenal hyperplasia (CAH) is an autosomal recessive inherited disorder of steroidogenesis. Steroid 11β-hydroxylase deficiency (11β-OHD) due to mutations in the CYP11B1 gene is the second most common form of CAH. In this study, 6 patients suffering from CAH were diagnosed with 11β-OHD using urinary GC-MS steroid metabolomics analysis. The molecular basis of the disorder was investigated by molecular genetic analysis of the CYP11B1 gene, functional characterization of splicing and missense mutations, and analysis of the missense mutations in a computer model of CYP11B1. All patients presented with abnormal clinical signs of hyperandrogenism. Their urinary steroid metabolomes were characterized by excessive excretion rates of metabolites of 11-deoxycortisol as well as metabolites of 11-deoxycorticosterone, and allowed definite diagnosis. Patient 1 carries compound heterozygous mutations consisting of a novel nonsense mutation p.Q102X (c.304C>T) in exon 2 and the known missense mutation p.T318R (c.953C>G) in exon 5. Two siblings (patient 2 and 3) were compound heterozygous carriers of a known splicing mutation c.1200+1G>A in intron 7 and a known missense mutation p.R448H (c.1343G>A) in exon 8. Minigene experiments demonstrated that the c.1200+1G>A mutation caused abnormal pre-mRNA splicing (intron retention). Two further siblings (patient 4 and 5) were compound heterozygous carriers of a novel missense mutation p.R332G (c.994C>G) in exon 6 and the known missense mutation p.R448H (c.1343G>A) in exon 8. A CYP11B1 activity study in COS-1 cells showed that only 11% of the enzyme activity remained in the variant p.R332G. Patient 6 carried a so far not described homozygous deletion g.2470_5320del of 2850 bp corresponding to a loss of the CYP11B1 exons 3-8. The breakpoints of the deletion are embedded into two typical 6 base pair repeats (GCTTCT) upstream and downstream of the gene. Experiments analyzing the influence of mutations on splicing and on enzyme function were applied as complementary procedures to genotyping and provided a rational basis for understanding the clinical phenotype of CAH.

A Greek girl with 11β-hydroxylase deficiency due to compound heterozygosity for two novel mutations in CYP11B1 gene

11β-hydroxylase deficiency (11β-OHD), an autosomal recessive inherited disorder, accounts for 5–8% of congenital adrenal hyperplasia. In Greece, no cases of 11β-OHD have been described so far. The patient presented at the age of 13 months with mild virilization of external genitalia and pubic hair development since the age of 3 months. Hormonal profile showed elevated 11-deoxycortisol, adrenal androgens and ACTH levels. ACTH stimulation test was compatible with 11β-OHD. DNA of the proband and her parents was isolated and genotyped for CYP11B1 gene coding cytochrome P450c11. The girl was found to be compound heterozygous for two CYP11B1 novel mutations, p.Ala386Glu (exon 7), inherited from the father and p.Leu471Argin (exon 9) from the mother. Hydrocortisone supplementation therapy was initiated. Four years after presentation she remains normotensive, her growth pattern is normal and the bone age remains advanced despite adequate suppression of adrenal androgens.

The next 150 years of congenital adrenal hyperplasia

Congenital adrenal hyperplasias (CAH) are a group of autosomal recessive defects in cortisol biosynthesis. Substantial progress has been made since the description of the first report, 150 years ago. This article reviews some of the recent advances in the genetics, diagnosis and treatment of CAH. In addition, we underline the aspects where further progress is required, including, among others, better diagnostic modalities for the mild phenotype and for some of the rare forms of disease, elucidation of epigenetic factors that lead to different phenotypes in patients with identical genotype and expending on treatment options for controlling the adrenal androgen excess.

Identification of seven novel CYP11B1 gene mutations in Chinese patients with 11β-hydroxylase deficiency

Steroid 11β-hydroxylase deficiency (11β-OHD), one of common cause of congenital adrenal hyperplasia (CAH), is an autosomal recessive disorder characterized by virilization, precocious pseudo-puberty, and hypertension. It is caused by CYP11B1 gene mutation. We performed molecular genetic analysis of the CYP11B1 gene in six patients with preliminary clinical diagnosis of 11β-OHD and four patients identified as potential 11β-OHD from a CAH cohort in which CYP21A2 gene mutations consecutively screened. Seven novel CYP11B1 mutations, including p.R454H, p.Q472P, p.Q155X, p.K173X, IVS2-1G>A, R454A fs 573X, and g.2704_g.3154del, and six previously described mutations (p.P94L, p.G267S, p.G379V, p.R448H, p.R454C and p.R141X) were identified. These mutations mainly clustered in exons 3 and 8. Eight of twenty alleles carried mutations occurring at the Arg454 position, which is a mutational hot spot for Han Chinese. The pathogenic nature of novel p.R454H mutation was predicted by protein sequence alignment and in silico analysis. All the identified mutations were responsible for the clinical features observed in these ten unrelated Chinese patients. This study expands the CYP11B1 mutation spectrum and provides evidence for prenatal diagnosis and genetic counseling. Genetic analysis is an alternative approach to help clinicians confirm uncertain 11β-OHD diagnosis, facilitating reasonable steroid replacement.

Pathophysiology, diagnosis, and treatment of mineralocorticoid disorders

The renin-angiotensin-aldosterone system (RAAS) is a major regulator of blood pressure control, fluid, and electrolyte balance in humans. Chronic activation of mineralocorticoid production leads to dysregulation of the cardiovascular system and to hypertension. The key mineralocorticoid is aldosterone. Hyperaldosteronism causes sodium and fluid retention in the kidney. Combined with the actions of angiotensin II, chronic elevation in aldosterone leads to detrimental effects in the vasculature, heart, and brain. The adverse effects of excess aldosterone are heavily dependent on increased dietary salt intake as has been demonstrated in animal models and in humans. Hypertension develops due to complex genetic influences combined with environmental factors. In the last two decades, primary aldosteronism has been found to occur in 5% to 13% of subjects with hypertension. In addition, patients with hyperaldosteronism have more end organ manifestations such as left ventricular hypertrophy and have significant cardiovascular complications including higher rates of heart failure and atrial fibrillation compared to similarly matched patients with essential hypertension. The pathophysiology, diagnosis, and treatment of primary aldosteronism will be extensively reviewed. There are many pitfalls in the diagnosis and confirmation of the disorder that will be discussed. Other rare forms of hyper- and hypo-aldosteronism and unusual disorders of hypertension will also be reviewed in this article.

Two Novel CYP11B1 Gene Mutations in Patients from Two Croatian Families with 11 β -Hydroxylase Deficiency

Steroid 11 β -hydroxylase deficiency (11 β -OHD) is the second most common cause of congenital adrenal hyperplasia. Mutations in the CYP11B1 gene, which encodes steroid 11 β -hydroxylase, are responsible for this autosomal recessive disorder. Here, we describe the molecular genetics of two previously reported male siblings in whom diagnosis of 11 β -OHD has been established based on their hormonal profiles displaying high levels of 11-deoxycortisol and hyperandrogenism. Both patients are compound heterozygous for a novel p.E67fs (c.199delG) mutation in exon 1 and a p.R448H (c.1343G>A) mutation in exon 8. We also report the biochemical and molecular genetics data of one new 11 β -OHD patient. Sequencing of the CYP11B1 gene reveals that this patient is compound heterozygous for a novel, previously undescribed p.R141Q (c.422G>A) mutation in exon 3 and a p.T318R (c.953C>G) mutation in exon 5. All three patients are of Croatian (Slavic) origin and there is no self-reported consanguinity in these two families. Results of our investigation confirm that most of the CYP11B1 mutations are private. In order to elucidate the molecular basis for 11 β -OHD in the Croatian/Slavic population, it is imperative to perform CYP11B1 genetic analysis in more patients from this region, since so far only four patients from three unrelated Croatian families have been analyzed.

Gene mutations that promote adrenal aldosterone production, sodium retention, and hypertension

Primary aldosteronism (PA) is the most common form of secondary hypertension, found in about 5% of all hypertension cases, and up to 20% of resistant hypertension cases. The most common forms of PA are an aldosterone-producing adenoma and idiopathic (bilateral) hyperaldosteronism. Rare genetic forms of PA exist and, until recently, the only condition with a known genetic mechanism was familial hyperaldosteronism type 1, also known as glucocorticoid-remediable aldosteronism (FHA1/GRA). FHA type 3 has now been shown to derive from germline mutations in the KCNJ5 gene, which encodes a potassium channel found on the adrenal cells. Remarkably, somatic mutations in KCNJ5 are found in about one-third of aldosterone-producing adenomas, and these mutations are likely to be involved in their pathogenesis. Finally, mutations in the genes encoding an L-type calcium channel (CACNA1D) and in genes encoding a sodium–potassium adenosine triphosphatase (ATP1A1) or a calcium adenosine triphosphatase (ATP2B3) are found in other aldosterone-producing adenomas. These findings provide a working model, in which adenoma formation and/or aldosterone production in many cases derives from increased calcium entry, which drives the pathogenesis of primary aldosteronism.

Congenital adrenal hyperplasia due to 11-beta-hydroxylase deficiency: functional consequences of four CYP11B1 mutations

Congenital adrenal hyperplasia (CAH) is one of the most common autosomal recessive inherited endocrine disease. Steroid 11β-hydroxylase deficiency (11β-OHD) is the second most common form of CAH. The aim of the study was to study the functional consequences of three novel and one previously described CYP11B1 gene mutations (p.(Arg143Trp), p.(Ala306Val), p.(Glu310Lys) and p.(Arg332Gln)) detected in patients suffering from classical and non-classical 11β-OHD. Functional analyses were performed by using a HEK293 cell in vitro expression system comparing wild type (WT) with mutant 11β-hydroxylase activity. Mutant proteins were examined in silico to study their effect on the three-dimensional structure of the protein. Two mutations (p.(Ala306Val) and p.(Glu310Lys)) detected in patients with classical 11β-OHD showed a nearly complete loss of 11β-hydroxylase activity. The mutations p.(Arg143Trp) and p.(Arg332Gln) detected in patients with non-classical 11β-OHD showed a partial functional impairment with approximately 8% and 6% of WT activity, respectively. Functional mutation analysis allows the classification of novel CYP11B1 mutations as causes of classical and non-classical 11β-OHD. The detection of patients with non-classical phenotypes underscores the importance to screen patients with a phenotype comparable to non-classical 21-hydroxylase deficiency for mutations in the CYP11B1 gene in case of a negative analysis of the CYP21A2 gene. As CYP11B1 mutations are most often individual for a family, the in vitro analysis of novel mutations is essential for clinical and genetic counselling.

Two novel mutations in CYP11B1 and modeling the consequent alterations of the translated protein in classic congenital adrenal hyperplasia patients

Mutations in the 11β-hydroxylase (CYP11B1) gene are the second leading cause of congenital adrenal hyperplasia (CAH), an autosomal recessive disorder characterized by adrenal insufficiency, virilization of female external genitalia, and hypertension with or without hypokalemic alkalosis. Molecular analysis of CYP11B1 gene in CAH patients with 11β-hydroxylase deficiency was performed in this study. Cycle sequencing of 9 exons in CYP11B1 was performed in 5 unrelated families with 11β-hydroxylase deficient children. Three-dimensional models for the normal and mutant proteins and their affinity to their known substrates were examined. Analysis of the CYP11B1 gene revealed two novel mutations, a small insertion in exon 7 (InsAG393) and a small deletion in exon 2 (DelG766), and three previously known missense mutations (T318M, Q356X, and R427H). According to docking results, the affinity of the protein to its substrates is highly reduced by these novel mutations. DelG766 has more negative impact on the protein in comparison to InsAG393. The novel mutations, InsAG393 and DelG766, change the folding of the protein and disrupt the enzyme's active site as it was measured in the protein modeling and substrate binding analysis. Molecular modeling and sequence conservation were predictive of clinical severity of the disease and correlated with the clinical diagnosis of the patients.

Ambiguous genitalia and hypertension in a patient with congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is an uncommon condition. Its clinical presentation with hypertension is rare. Deficiency of the steroid 11-beta-hydroxylase accounts for less than 10% of CAH. We report a case of a 19-year-old patient who presents with hypertension with ambiguous genitalia secondary to adrenal steroidogenesis dysfunction. We also discuss the defects in adrenal steroidogenesis and clinical phenotypes of CAH.

Novel homozygous p.Y395X mutation in the CYP11B1 gene found in a Vietnamese patient with 11β-hydroxylase deficiency

CONTEXT

The deficiency of steroid 11β-hydroxylase is caused by mutations in the CYP11B1 gene and is the second major form of congenital adrenal hyperplasia associated with hypertension.

OBJECTIVE

The objective of this study was to screen the CYP11B1 gene for mutations in one Vietnamese male suffering from congenital adrenal hyperplasia.

PATIENT

The patient (46,XY) had congenital adrenal hyperplasia. The clinical manifestations presented precocious puberty, hyper-pigmentation and high blood pressure at 4 years.

RESULTS

The patient was a homozygous carrier of a novel mutation located in exon 7 containing a premature stop codon instead of tyrosine at 395 (p.Y395X).

CONCLUSION

We have identified a novel mutant of the CYP11B1 gene in one Vietnamese family associated with phenotypes of congenital adrenal hyperplasia. The mutant gene p.Y395X produces a truncated form of the polypeptide and abolishes the enzyme activities, leading to a severe phenotype of congenital adrenal hyperplasia.

46,XX DSD: the masculinised female

The 46,XX disorders of sex development (DSDs) cause virilisation or masculinisation of the female foetus. The final common pathway of all 46,XX DSDs is excess dihydrotestosterone (DHT) or potent foreign androgen in the genital tissue during the critical period of sexual differentiation. Whereas the foetal testis is source of androgen in the male, it is the foetal adrenal that produces the DHT precursors in the female. By understanding the principles of human steroid biosynthesis, the pathogenesis of each disorder may be logically deduced, and treatment strategies are rationally constructed. In practice, however, therapies for many of these diseases are fraught with complications and caveats, and current approaches leave much room for improvement. This review discusses these diseases, their pathogenesis and approaches to therapy. We emphasise areas where improved treatments are sorely needed.