Novel mutation in cytochrome P450c17 causes complete combined 17alpha-hydroxylase/17,20-lyase deficiency

A rare intronic mutation in the splice acceptor site of the CYP17A1 gene in a patient with 17α-hydroxylase/17,20-lyase deficiency

Mutations of the CYP17A1 gene could cause complete or partial and combined or isolated 17α-hydroxylase/17,20-lyase deficiency (17OHD), which is characterized by hypertension, hypokalemia, and abnormal development of the genitalia. Most of the mutations are located in the coding sequence, and very few are located in the intronic region. The aim of this study is to investigate the novel intronic CYP17A1 mutation and its possible influence on phenotype. A 30-year-old Chinese female patient (46, XY) was referred to our Urology Department for severe hypertension, hypokalemia and a right adrenal mass. Physical examination revealed a hypertrophic clitoris and blind-ending vagina. Hormone analysis exhibited increased concentrations of ACTH and low levels of cortisol and sexual steroids. Mutation analysis revealed compound heterozygous CYP17A1 mutations, with c.1072C > T (p.Arg358*) in one allele and a novel intronic splicing mutation (c.970-1G > A) in another allele. Bioinformatics software predicted that the novel mutation may activate a cryptic splice site, shifting the reading frame and introducing a premature stop codon. In conclusion, we discovered a novel splicing mutation of the CYP17A1 gene in a Chinese patient with 17OHD. Our study extended the CYP17A1 mutation spectrum and provided valuable information for patient management and genetic counseling.

A Single Nucleotide Polymorphism near the CYP17A1 Gene Is Associated with Left Ventricular Mass in Hypertensive Patients under Pharmacotherapy

Cytochrome P450 17A1 (CYP17A1) catalyses the formation and metabolism of steroid hormones. They are involved in blood pressure (BP) regulation and in the pathogenesis of left ventricular hypertrophy. Therefore, altered function of CYP17A1 due to genetic variants may influence BP and left ventricular mass. Notably, genome wide association studies supported the role of this enzyme in BP control. Against this background, we investigated associations between single nucleotide polymorphisms (SNPs) in or nearby the CYP17A1 gene with BP and left ventricular mass in patients with arterial hypertension and associated cardiovascular organ damage treated according to guidelines. Patients (n = 1007, mean age 58.0 ± 9.8 years, 83% men) with arterial hypertension and cardiac left ventricular ejection fraction (LVEF) ≥ 40% were enrolled in the study. Cardiac parameters of left ventricular mass, geometry and function were determined by echocardiography. The cohort comprised patients with coronary heart disease (n = 823; 81.7%) and myocardial infarction (n = 545; 54.1%) with a mean LVEF of 59.9% ± 9.3%. The mean left ventricular mass index (LVMI) was 52.1 ± 21.2 g/m2.7 and 485 (48.2%) patients had left ventricular hypertrophy. There was no significant association of any investigated SNP (rs619824, rs743572, rs1004467, rs11191548, rs17115100) with mean 24 h systolic or diastolic BP. However, carriers of the rs11191548 C allele demonstrated a 7% increase in LVMI (95% CI: 1%-12%, p = 0.017) compared to non-carriers. The CYP17A1 polymorphism rs11191548 demonstrated a significant association with LVMI in patients with arterial hypertension and preserved LVEF. Thus, CYP17A1 may contribute to cardiac hypertrophy in this clinical condition.

A new compound heterozygous mutation in the CYP17A1 gene in a female with 17α-hydroxylase/17,20-lyase deficiency

BACKGROUND

Congenital adrenal hyperplasia due to 17α-hydroxylase/17,20-lyase deficiency (OMIM #202110) is a rare autosomal recessive disorder, which is caused by mutations of the CYP17A1 gene located on chromosome 10q24.3. It has been reported that the type of mutation of the CYP17A1 gene was associated with the extent of 17α-hydroxylase/17,20-lyase deficiency, and the prevalence of common mutation was different among ethnic groups.

CASE

A 21-year-old Korean female presented with primary amenorrhea and sexual infantilism, and intermittent hypokalemic episodes. Laboratory test was consistent with hypergonadotropic hypogonadism. The karyotype was 46,XX[20]. Genomic DNA was extracted from peripheral blood leukocytes. All the eight exons of the CYP17A1 gene including flanking regions of introns were amplified by PCR. The mutations of the CYP17A1 gene were detected by direct sequencing. A compound heterozygous mutation was identified; one allele had a missense mutation of c.1118A>T (p.His373Leu), which was reported previously and induced the complete loss of both 17α-hydroxylase/17,20-lyase activity. This mutation has been known to be one of the common mutation types in East Asia. The other allele had a novel 1-bp deletion c.1148delA causing frameshift, premature termination codon (p.Glu383fs) and induced truncated enzymes.

CONCLUSION

Our experience for stepwise clinical, laboratory and molecular approach would be helpful to diagnose these patients accurately and understand the genetic events in 17α-hydroxylase/17,20-lyase deficiency patients.

Molecular study of five Chinese patients with 46XX partial 17a-hydroxylase/17,20-lyase deficiency

CONTEXT

Partial 17a-hydroxylase/17,20 lyase deficiency (17OHD) is a rare subtype of 17OHD caused by CYP17 gene mutations.

OBJECTIVE

Five Chinese 46,XX patients and one family with partial 17OHD were genotyped.

PATIENTS

The five patients derived from different families and one of them had another patient in family. The diagnosis of partial 17OHD was established through clinical and laboratory characteristics in Peking Union Medical College Hospital, China, from 2000 to 2010.

RESULTS

Seven CYP17 gene mutations are identified from these patients. Among them, R449C and L209P are two novel missense mutations. Four patients are found to have a compound heterozygous mutations and one patient has only one mutation. The patients with family history are also found to have parent origin of gene mutations.

CONCLUSION

Two novel missense mutations in CYP1 7 are found in this study. Comparing with previous reports, the different combination of mutations may have various effects on the activities of the 17-hydroxylase and/or17,20-lyase.

CYP17A1 intron mutation causing cryptic splicing in 17α-hydroxylase deficiency

17α-hydroxylase/17, 20-lyase deficiency (17OHD) is an autosomal recessive disease causing congenital adrenal hyperplasia and a rare cause of hypertension with hypokalemia. The CYP17A1 gene mutation leads to 17OHD and its clinical features. We described an 18 y/o female with clinical features of 17α-hydroxylase/17, 20-lyase deficiency and characterized the functional consequences of an intronic CYP17A1 mutation. The coding regions and flanking intronic bases of the CYP17A1 gene were amplified by PCR and sequenced. The patient is a compound heterozygote for the previously described p.R358X and IVS1 +2T>C mutations. A first intron splice donor site mutation was re-created in minigene and full-length expression vectors. Pre-mRNA splicing of the variant CYP17A1 intron was studied in transfected cells and in a transformed lymphoblastoid cell line. When the full-length CYP17A1 gene and minigene containing the intronic mutation was expressed in transfected cells, the majority (>90%) of mRNA transcripts were incorrectly spliced. Only the p.R358X transcript was detected in the EBV-transformed lymphoblastoid cell line. The IVS1 +2T>C mutation abolished most 17α-hydroxylase/17, 20-lyase enzyme activity by aberrant mRNA splicing to an intronic pseudo-exon, causing a frame shift and early termination.

Male pseudohermaphroditism as a cause of secondary hypertension: a case report

Seventeen alpha-hydroxylase deficiency (17OHD) syndrome is a rare genetic disorder of steroid biosynthesis causing decreased production of glucocorticoids and sex steroids and increased synthesis of mineralocorticoid precursors. There are only 130 cases reported worldwide with documented severe 17OHD. Here, we describe the clinical, hormonal, and molecular genetic characteristics of a Turkish patient with 17OHD, who presented to our clinic due to high blood pressure. A 29-year-old girl with 46,XY genotype was admitted to our nephrology clinic due to uncontrolled hypertension and hypokalemia. The diagnosis was suspected because of primary amenorrhea, absence of sexual maturation, hypertension, and hypokalemia. Endocrine investigation revealed low basal levels of all steroid hormones which require 17-hydroxylation for biosynthesis. Plasma concentrations of ACTH, FSH, and LH were elevated. Imaging did not reveal uterus or adnexial structures. The patient's hypertension and hypokalemia resolved after glucocorticoid replacement and treatment with potassium-sparing diuretics. 17OHD is a rare form of congenital adrenal hyperplasia in which defects in the biosynthesis of cortisol and sex steroids result in mineralocorticoid excess, hypokalemic hypertension, and sexual abnormalities such as pseudohermaphroditism in males, and sexual infantilism in females. 17OHD should be suspected in patients with hypokalemic hypertension and lack of secondary sexual development so that appropriate therapy can be implemented.

Genotyping of a Chinese family with 46,XX and 46,XY 17-hydroxylase deficiency

BACKGROUND

17-Hydroxylase deficiency is a rare form of congenital adrenal hyperplasia caused by CYP17A1 gene mutations.

METHOD

A 46,XY and a 46,XX Chinese patients with 17-hydroxylase deficiency in a family and their four generations family members were genotyped by PCR-sequencing method.

RESULTS

Two CYP17 gene mutations were identified from these patients. Among them, IVS1-1G > A was a novel splicing mutation which disrupted the acceptor signal of exon 2 and might create a new exon after exon 1. The indel mutation of TAC329AA was a one-base deletion mutation and one-base change at codon 329 in exon 6.

CONCLUSION

The results confirmed the diagnosis of 17-hydroxylase deficiency in these two patients and their autosome recessive heritage mode. The TAC329AA indel mutation had been identified in several reports of Chinese and Asian, suggesting that codon 329 was an unstable point of the CYP17 gene and this mutation was a prevalent CYP17 mutation in the Asian population. Although the noval mutation IVS1-1G > A founded in this family need more study to know its machinism of interrupting P450c17 function.

A novel communication role for CYP17A1 in the progression of castration-resistant prostate cancer

BACKGROUND

CYP17A1 is currently a target for total androgen blockade in advanced prostate cancer (CaP) patients. After castration, or removal of testicular androgens, CYP17A1 can act as a rate-limiting enzyme in androgen synthesis from cholesterol or other adrenal precursors within the tumor microenvironment ultimately contributing to disease progression. Herein we provide evidence that CYP17A1 could also be a mediator of cell-to-cell communication within the CaP tumor microenvironment.

METHODS

CYP17A1 expression was evaluated by immunohistochemical analysis of human tumor sections and Western blot analysis of CaP patients' serum and exosome isolates. CYP17A1 activity assays were conducted in human serum (and positive control human liver and kidney microsomes) using progesterone as a precursor and an LC-MS endpoint.

RESULTS

These studies revealed that the expression pattern of CYP17A1 is typical of a secretory protein as it is localized to the luminal pole of the cells in exocrine secretory mode. CYP17A1 is expressed in human serum and in fact is elevated in the serum of CaP patients as compared to healthy controls. Serum CYP17A1 activity could not be confirmed, however, verification of CYP17A1 expression in exosomes suggests a role in cell-to-cell communication within the tumor microenvironment.

CONCLUSIONS

CYP17A1 is a crucial enzyme for de novo androgen synthesis within the tumor microenvironment after removal of testicular androgens by castration. We provide evidence for a novel role for CYP17A1 in serum and further reiterate the importance of targeting this enzyme in CaP progression.

Loss of cytochrome P450 17A1 protein expression in a 17alpha-hydroxylase/17,20-lyase-deficient 46,XY female caused by two novel mutations in the CYP17A1 gene

17alpha-Hydroxylase deficiency (17OHD) is a rare form of congenital adrenal hyperplasia caused by mutations in the CYP17A1 gene. This condition shows considerable clinical and biochemical variation. Molecular characterization of novel mutations in the CYP17A1 gene and detailed study of their structural, enzymatic, and clinical consequences are required to fully understand enzyme behavior. Here, we present the first molecular characterization of two novel mutations in CYP17A1 in a 15-year-old female Mexican mestizo 46,XY female with primary amenorrhea and lack of pubertal development and severe hypertension that manifested only after surgery. A complete clinical and biochemical evaluation was compatible with 17OHD. Structural anomalies in the CYP17A1 gene were discovered by direct automated sequencing, which revealed a novel compound heterozygous K110X/R362H mutation that leads to a complete lack of enzyme activity. Immunohistochemical analyses performed to determine protein expression and localization showed that cytochrome P450 17A1 was completely absent in the patient's testicular tissue. Studies of novel mutations, such as those described here, provide important information that allows us to better understand the effect of a given mutation on enzyme function and to observe the impact of the mutation on clinical phenotype.