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

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.

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.

A Novel Homozygous Pathogenic Variant in CYP11B1 in a Female Iranian Patient with 11B Hydroxylase Deficiency

Objective

Congenital adrenal hyperplasia (CAH) addresses a number of autosomal recessive disorders characterized by the enzyme defects in steroid hormones biosynthesis. The second common form of CAH is caused by mutations in the CYP11B1 gene. Here, we reveal a novel mutation in the CYP11B1 gene related to the 11βOHD phenotype.

Methods and Results

Sequence analysis of the CYP11B1 gene in a 19-year-old Iranian woman with the 11βOHD phenotype was performed. In silico analysis and molecular docking were done. A novel missense homozygous variant c.1351C > T (p.L451F) in the CYP11B1 gene was identified in the patient and, according to American College of Medical Genetics and Genomics criteria, was categorized as likely pathogenic. Protein docking showed destructive effects of the variant on the CYP11B1 protein-ligand interactions.

Conclusion

This study broadens the CYP11B1 mutation spectrum and introduces the novel p.L451F likely pathogenic variant leading to destructive effects on protein-ligand interactions. Our results provide reliable information for genetic counseling and molecular diagnostics of CAH.

High prevalence of hypertension and target organ damage in patients with 11β-hydroxylase deficiency

BACKGROUND

Prevalence of hypertension and hypertension-mediated organ damage (HMOD) had not been well studied in patients with 11β-hydroxylase deficiency (11β-OHD).

OBJECTIVE

The study was to assess the prevalence and risk factors of hypertension and HMOD in patients with 11β-OHD.

DESIGN

Retrospective cohort analysis in a single medical centre.

PATIENTS

Twenty-eight patients with 11β-OHD were recruited between January 2003 and June 2021, and their diagnosis had been confirmed by Sanger sequencing.

MEASUREMENTS

Blood pressure and clinical indicators for the assessment of HMOD occurrence were collected from the medical records. Medication adherence of antihypertensive drugs and glucocorticoids were determined by the patients' biochemistry. Logistic regression was used to identify factors associated with HMOD.

RESULTS

Prevalence of hypertension and HMOD in the cohort was 100% and 50%, respectively. The kidneys (71.43%) are the organ most commonly damaged by high blood pressure, followed by the heart (64.29%), eyes (57.14%) and brain (21.43%). Risk factors of HMOD were hypokalemia (odds ratio [OR]: 9.16; 95% confidence interval [CI]: 1.634-51.43; p = .012), blood pressure ≥ 180/110 mmHg (OR: 22.0, 95% CI: 3.08-157.34; p = .002) and irregular glucocorticoid use (OR: 3.18, 95% CI: 1.13-8.98; p = .021). Blood pressure ≥ 180/110 mmHg was an independent predictor for HMOD.

CONCLUSION

Hypertension and HMOD are prevalent in patients with 11β-OHD in our study. These findings illustrate the importance of early HMOD evaluation and optimal glucocorticoid medication in 11β-OHD patients.

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.

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.

Clinical and Molecular Analysis of Four Patients With 11β-Hydroxylase Deficiency

Objective: 11β-hydroxylase deficiency (11βOHD) is a rare autosomal recessive disorder caused by mutations in the CYP11B1 gene. It is characterized by virilization, hypertension, and significant final height impairment. In this study, we aim to investigate the clinical and molecular characteristics of four unrelated Chinese patients with 11βOHD disorder. Methods: The clinical information of four 11βOHD patients were carefully reviewed. Genetic analysis was performed using next-generation sequencing (NGS) based panel analysis. NGS coverage depth was analyzed to detect exonic copy-number variants (CNVs) on patient 1. Quantitative PCR (qPCR) was subsequently performed to confirm the CNVs detected from the NGS coverage depth analysis. Results: The mean age of the patients at diagnosis was 4.7 years (range, 2.0-9.3 years). Two genetically female patients (patients 1 and 2) with 11βOHD presented severe virilization of external genitalia and were raised as males. Two genetically male patients (patients 3 and 4) presented precocious puberty. Additionally, patients 1, 3, and 4 presented with hypertension. In patient 4, unilateral adrenal mass was detected and removed at the age of 9 years. Interestingly, the height of patient 4 (174.4 cm, +6.7 SD) wasn't impaired and reached his mid-parental height (173 cm). Three novel variants in the CYP11B1 gene (c.1150_1153del, c.217C>T, and c.400G>C) were identified by NGS. Various bioinformatics tools revealed potential pathogenic effects for the novel variants, and evolutionary-conservation revealed that the novel missense variant affected an amino acid that is highly conserved among species. Furthermore, NGS coverage depth analysis and qPCR identified a novel heterozygous deletion of exons 1-6 in patient 1. Conclusion: Our study expands the spectrum of mutations of the CYP11B1 gene in Chinese population. In addition, We reported the first case of a patient with classical 11βOHD disorder, whose final height wasn't compromised.

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.