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

Targeted long-read sequencing identifies missing pathogenic variant in unsolved 11β-hydroxylase deficiency

BACKGROUND

11β-hydroxylase deficiency (11β-OHD), caused by homozygosity or compound heterozygosity CYP11B1 variants, is the second most common cause of congenital adrenal hyperplasia (CAH). Due to the high degree of sequence identity between CYP11B1 and CYP11B2, chimeric genes, and complex structural variants (SVs), the conventional approach to gene testing for 11β-OHD is facing challenges. The study aimed to clarify the underlying genetic causes of two siblings of a Chinese family with 11β-OHD.

METHODS

Peripheral blood samples and clinical information were collected from subjects and their family members. Sex steroid concentrations were measured using LC-MS/MS. Long-range PCR-based next-generation sequencing (NGS), PCR assay and target long-read sequencing were used to detect the pathogenic variants.

RESULTS

Early onset hypertension, increased serum levels of adrenocorticotropin (ACTH), progesterone, testosterone, and decreased cortisol and potassium were detected in both affected siblings. Long-range PCR-based NGS identified a heterozygous missense variant (NM_000497.4:c.281 C > T, p.P94> L) in CYP11B1 gene in the two siblings. PCR detected no chimeric CYP11B2/CYP11B1 gene. We finally identified a second pathogenic variant in CYP11B1 gene via target long-read sequencing (T-LRS). This novel variant was a deletion-insertion variant and located chr8:143957269-143,957,579 (hg19) with the insertion of 'ACAG' (NM_000497.4:c.954 + 78_980delinsACAG), which was in trans with CYP11B1: c.281 C > T.

CONCLUSIONS

Our study suggests that the integrated long-range PCR-based NGS and T-LRS seem to be the most reliable and accurate method for 11β-OHD genetic diagnosis and carrier sequencing.

Non-classical 11β-hydroxylase deficiency caused by a novel heterozygous mutation: a case report and review of the literature

PURPOSE

11β-hydroxylase deficiency (11β-OHD) constitutes a rare form of congenital adrenal hyperplasia (CAH), typically accounting for ~5-8% of CAH cases. Non-classical 11β-OHD is reported even more rarely and frequently results in misdiagnosis or underdiagnosis due to its mild clinical symptoms.

METHODS

A clinical, biochemical, radiological, and genetic study was conducted on a 9-year-old girl presenting with mild breast development, axillary hair growth, and advanced bone age. Additionally, a comprehensive review and synthesis of the literature concerning 11β-OHD were conducted.

RESULTS

The patient presented with breast enlargement, axillary hair development, and accelerated growth over the past year. Laboratory tests revealed levels of cortisol, luteinizing hormone, testosterone, and progesterone that were below normal. A gonadotropin-releasing hormone (GnRH) stimulation test suggested the possibility of central precocious puberty. Radiologic examination revealed a 2-year advance in bone age, while bilateral adrenal ultrasonography showed no abnormalities. Her mother exhibited hirsutism, while her father's physical examination revealed no abnormalities. Whole-exon genetic testing of the child and her parents indicated a heterozygous mutation of c.905_907delinsTT in exon 5 of the 11β-hydroxylase gene (CYP11B1) in the child and her mother. This mutation resulted in a substitution of aspartic acid with valine at amino acid position 302 of the coding protein. This frameshift resulted in a sequence of 23 amino acids, culminating in a premature stop codon (p.Asp302ValfsTer23). A review of the previous literature revealed that the majority of heterozygous mutations in 11β-OHD were missense mutations, occurring primarily in exons 2, 6, 7, and 8. The most common mutation among 11β-OHD patients was the change of Arg-448 to His (R448H) in CYP11B1. Furthermore, bioinformatics analyses revealed that heterozygous mutation of c.905_907delinsTT had deleterious effects on the function of CYP11B1 and affected the stability of the protein, presumably leading to a partial impairment of enzyme activity. The results of the in vitro functional study demonstrated that the missense mutant (p.Asp302ValfsTer23) exhibited partial enzymatic activity.

CONCLUSIONS

We report a novel heterozygous mutation of CYP11B1 (c.905_907delinsTT), enriching the spectrum of genetic variants of CYP11B1. This finding provides a valuable case reference for early diagnosis of non-classical patients with 11β-OHD.

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.

Clinical analysis of 78 patients with nonclassical 21-hydroxylase deficiency

PURPOSE

Retrospectively analyze the clinical characteristics of patients with nonclassical 21-hydroxylase deficiency (NC21OHD) as well as the relationship between the gene mutations and endocrine hormones. In addition, the relationship between different basal 17-hydroxyprogesterone (17OHP) levels and patients' glucolipid metabolism, hormone levels, pregnancy, and treatment outcomes were examined.

METHODS

Clinical data of 78 females with NC21OHD from January 2012 to July 2022 in the Department of Endocrinology and Metabolism of the Third Affiliated Hospital of Guangzhou Medical University were retrospectively analyzed. Diagnosis was based on the 17OHP level combined with clinical manifestations, imaging, and other endocrine hormones and the cytochrome P450 c21, steroid 21-hydroxylase (CYP21A2) gene.

RESULTS

The age at diagnosis of the 78 patients was 29.1 ± 4.2 years; 83.3% (65/78) of the patients had menstrual abnormalities, 70 patients were of childbearing age, and 97.1% (68/70) had a history of infertility with a median time of infertility of 3.6 years. Moreover, 71.8% (56/78) of the patients had polycystic ovaries, 26.9% (21/78) had hyperandrogenemia manifestations on physical examination, 66.7% (52/78) had adrenal hyperplasia, 32.1% (25/78) had combined dyslipidemia, and 41.0% (32/78) had combined insulin resistance. Pathogenic mutations were detected in 78.2% (61/78) of the patients with both CYP21A2 alleles; 14.1% (11/78) of the patients had only one allele and 7.7% (6/78) had no pathogenic mutations. The levels of total testosterone (TT), progesterone (P) (0 min, 30 min), and 17-OHP (0 min, 30 min, 60 min) in the adrenocorticotropic hormone (ACTH) stimulation test varied between the groups. Furthermore, patients with NC21OHD were divided into 17OHP < 2 ng/ml, 2 ng/ml < 17OHP < 10 ng/ml, and 17OHP ≥ 10 ng/ml groups according to their different basal 17OHP levels. The 17OHP ≥ 10 ng/ml group had significantly higher TT, FT4, basal and post-stimulation progesterone, and 17OHP, net value added of 17-hydroxyprogesterone (△17OHP), net value added of 17-hydroxyprogesterone/net value added of cortisol ratio (△17OHP/△F), the incidence of adrenal hyperplasia, and number of gene mutations compared to those of the 17OHP < 2 ng/ml group (P < 0.05). NC21OHD infertile patients who received low-dose glucocorticoids showed a significant increase in pregnancy and live birth rates, and a significant decrease in miscarriage rate (all P < 0.05).

CONCLUSION

Comprehensive analysis is important as NCCAH diagnoses may be false positive or false negative based on clinical characteristics, hormone levels, and gene detection. Females with NC21OHD showed varying degrees of fertility decline; thus, low doses of glucocorticoid treatment for infertile females with NC21OHD can improve fertility and fertility outcomes.

Congenital Adrenal Hyperplasia-Current Insights in Pathophysiology, Diagnostics, and Management

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders affecting cortisol biosynthesis. Reduced activity of an enzyme required for cortisol production leads to chronic overstimulation of the adrenal cortex and accumulation of precursors proximal to the blocked enzymatic step. The most common form of CAH is caused by steroid 21-hydroxylase deficiency due to mutations in CYP21A2. Since the last publication summarizing CAH in Endocrine Reviews in 2000, there have been numerous new developments. These include more detailed understanding of steroidogenic pathways, refinements in neonatal screening, improved diagnostic measurements utilizing chromatography and mass spectrometry coupled with steroid profiling, and improved genotyping methods. Clinical trials of alternative medications and modes of delivery have been recently completed or are under way. Genetic and cell-based treatments are being explored. A large body of data concerning long-term outcomes in patients affected by CAH, including psychosexual well-being, has been enhanced by the establishment of disease registries. This review provides the reader with current insights in CAH with special attention to these new developments.

Detection of Small CYP11B1 Deletions and One Founder Chimeric CYP11B2/CYP11B1 Gene in 11β-Hydroxylase Deficiency

OBJECTIVE

11β-Hydroxylase deficiency (11β-OHD) caused by mutations in the CYP11B1 gene is the second most common form of congenital adrenal hyperplasia. Both point mutations and genomic rearrangements of CYP11B1 are important causes of 11β-OHD. However, the high degree of sequence identity between CYP11B1 and its homologous gene CYP11B2, presents unique challenges for molecular diagnosis of suspected 11β-OHD. The aim of this study was to detect the point mutation, indel, small deletion of CYP11B1 and chimeric CYP11B2/CYP11B1 gene in a one-tube test, improving the genetic diagnosis of 11β-OHD.

METHODS

Optimized custom-designed target sequencing strategy was performed in three patients with suspected 11β-OHD, in which both the coverage depth of paired-end reads and the breakpoint information of split reads from sequencing data were analysed in order to detect genomic rearrangements covering CYP11B1. Long-range PCR was peformed to validate the speculated CYP11B1 rearrangements with the breakpoint-specifc primers.

RESULTS

Using the optimized target sequencing approach, we detected two intragenic/intergenic deletions of CYP11B1 and one chimeric CYP11B2/CYP11B1 gene from three suspected patients with 11β-OHD besides three pathogenic heterozygous point mutation/indels. Furthermore, we mapped the precise breakpoint of this chimeric CYP11B2/CYP11B1 gene located on chr8:143994517 (hg19) and confirmed it as a founder rearrangement event in the Chinese population.

CONCLUSIONS

Our optimized target sequencing approach improved the genetic diagnosis of 11β-OHD.

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.

Vitamin D: Current Challenges between the Laboratory and Clinical Practice

Vitamin D is a micronutrient with pleiotropic effects in humans. Due to sedentary lifestyles and increasing time spent indoors, a growing body of research is revealing that vitamin D deficiency is a global problem. Despite the routine measurement of vitamin D in clinical laboratories and many years of efforts, methods of vitamin D analysis have yet to be standardized and are burdened with significant difficulties. This review summarizes several key analytical and clinical challenges that accompany the current methods for measuring vitamin D. According to an external quality assessment, methods and laboratories still produce a high degree of variability. Structurally similar metabolites are a source of significant interference. Furthermore, there is still no consensus on the normal values of vitamin D in a healthy population. These and other problems discussed herein can be a source of inconsistency in the results of research studies.

Utility of a Commercially Available Blood Steroid Profile in Endocrine Practice

BACKGROUND

A blood steroid profile has recently become available on commercial basis in India. In this study, we report our initial experience with the use of steroid profile in the evaluation of disorders of sex development (DSD) and suspected cases of congenital adrenal hyperplasia (CAH) and discuss the potential scenarios in endocrine practice that may benefit from this steroid profile.

MATERIALS AND METHODS

The study included six subjects. Patient 1 was a 46, XX girl who presented with peripubertal virilization, patient 2 was a girl who presented with normal pubertal development, secondary amenorrhea, and virilization, and patient 3 was a girl who presented with primary amenorrhea and virilization. These three patients were suspected to have CAH but had non-diagnostic serum 17 OH-progesterone levels. Patient 4 and 5 were 46, XY reared as girls who presented with primary amenorrhea alone and primary amenorrhea and virilization, respectively, and sixth subject was a heathy volunteer. All subjects were evaluated with blood steroid profile by Liquid chromatography tandem mass spectrometry (LC-MS/MS).

RESULTS

Patient 1 and 2 were diagnosed to have 11 β-hydroxylase deficiency by using the steroid profile. Patient 3 was suspected to have CAH, but the steroid profile excluded the diagnosis and helped to confirm the diagnosis as polycystic ovary syndrome. In patient 4 and patient 5, although steroid profile ruled out the possibility of steroidogenesis defects, it did not help to reach at the specific diagnosis.

CONCLUSION

The blood steroid profile used in this study is most useful for the diagnosis of 11 β-hydroxylase deficiency. The utility of this test is limited in the evaluation of 46, XY patients with under-virilization.

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.

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.

CDHR1 mutations in retinal dystrophies

We report ophthalmic and genetic findings in patients with autosomal recessive retinitis pigmentosa (RP), cone-rod dystrophy (CRD) or cone dystrophy (CD) harboring potential pathogenic variants in the CDHR1 gene. Detailed ophthalmic examination was performed in seven sporadic and six familial subjects. Mutation screening was done using a customized next generation sequencing panel targeting 105 genes implicated in inherited retinal disorders. In one family, homozygosity mapping with subsequent candidate gene analysis was performed. Stringent filtering for rare and potentially disease causing variants following a model of autosomal recessive inheritance led to the identification of eleven different CDHR1 variants in nine index cases. All variants were novel at the time of their identification. In silico analyses confirmed their pathogenic potential. Minigene assays were performed for two non-canonical splice site variants and revealed missplicing for the mutant alleles. Mutations in CDHR1 are a rare cause of retinal dystrophy. Our study further expands the mutational spectrum of this gene and the associated clinical presentation.

Steroid hormone analysis in diagnosis and treatment of DSD: position paper of EU COST Action BM 1303 'DSDnet'

Disorders or differences in sex development (DSD) comprise a heterogeneous group of conditions with an atypical sex development. For optimal diagnosis, highly specialised laboratory analyses are required across European countries. Working group 3 of EU COST (European Cooperation in Science and Technology) Action BM 1303 'DSDnet' 'Harmonisation of Laboratory Assessment' has developed recommendations on laboratory assessment for DSD regarding the use of technologies and analytes to be investigated. This position paper on steroid hormone analysis in diagnosis and treatment of DSD was compiled by a group of specialists in DSD and/or hormonal analysis, either from participating European countries or international partner countries. The topics discussed comprised analytical methods (immunoassay/mass spectrometry-based methods), matrices (urine/serum/saliva) and harmonisation of laboratory tests. The following positions were agreed upon: support of the appropriate use of immunoassay- and mass spectrometry-based methods for diagnosis and monitoring of DSD. Serum/plasma and urine are established matrices for analysis. Laboratories performing analyses for DSD need to operate within a quality framework and actively engage in harmonisation processes so that results and their interpretation are the same irrespective of the laboratory they are performed in. Participation in activities of peer comparison such as sample exchange or when available subscribing to a relevant external quality assurance program should be achieved. The ultimate aim of the guidelines is the implementation of clinical standards for diagnosis and appropriate treatment of DSD to achieve the best outcome for patients, no matter where patients are investigated or managed.

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.