Clinical and Molecular Analysis of Four 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.

Identification of a Novel CYP11B2 Variant in a Family with Varying Degrees of Aldosterone Synthase Deficiency

Isolated aldosterone synthase deficiency is a rare autosomal recessive disorder caused by pathogenic variants in CYP11B2, resulting in impaired aldosterone synthesis. We report on a neonate with isolated aldosterone synthase deficiency caused by a novel homozygous CYP11B2 variant Chr8:NM_000498.3:c.400G>A p.(Gly134Arg). The patient presented shortly after birth with severe signs of aldosterone deficiency. Interestingly, segregation analysis revealed that the patient’s asymptomatic father was also homozygous for the CYP11B2 variant. Biochemical evaluation of the father indicated subclinical enzyme impairment, characterized by elevated aldosterone precursors. Apparently, this homozygous variant led to different clinical phenotypes in two affected relatives. In this manuscript we elaborate on the biochemical and genetic work-up performed and describe potential pitfalls in CYP11B2 sequencing due to its homology to CYP11B1.

Deciphering genetic causes for sex differences in human health through drug metabolism and transporter genes

Sex differences have been widely observed in human health. However, little is known about the underlying mechanism behind these observed sex differences. We hypothesize that sex-differentiated genetic effects are contributors of these phenotypic differences. Focusing on a collection of drug metabolism enzymes and transporters (DMET) genes, we discover sex-differentiated genetic regulatory mechanisms between these genes and human complex traits. Here, we show that sex-differentiated genetic effects were present at genome-level and at DMET gene regions for many human complex traits. These sex-differentiated regulatory mechanisms are reflected in the levels of gene expression and endogenous serum biomarkers. Through Mendelian Randomization analysis, we identify putative sex-differentiated causal effects in each sex separately. Furthermore, we identify and validate sex differential gene expression of a subset of DMET genes in human liver samples. We observe higher protein abundance and enzyme activity of CYP1A2 in male-derived liver microsomes, which leads to higher level of an active metabolite formation of clozapine, a commonly prescribed antipsychotic drug. Taken together, our results demonstrate the presence of sex-differentiated genetic effects on DMET gene regulation, which manifest in various phenotypic traits including disease risks and drug responses.

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.

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.