Novel CYP17A1 mutation in a Japanese patient with combined 17alpha-hydroxylase/17,20-lyase deficiency

Clinical, biochemical and genetic characteristics of children with congenital adrenal hyperplasia due to 17α-hydroxylase deficiency

Objectives Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder, that could rarely be due to 17 α-hydroxylase deficiency (17αOHD) and/or 17,20 lyase deficiency. Mutation of CYP17A1 gene causes deficiency of glucocorticoids and androgens but excess of mineralocorticoids. Lack of genital ambiguity in most children causes a delay in diagnosis even until puberty. Classical presentation with hypertension and hypokalemia is often not encountered. We intended to study the clinical, biochemical and genetic characteristics of children diagnosed with CAH due to 17αOHD. Methods Three children who were diagnosed with CAH due to 17αOHD in our institute and on follow up were included in this retrospective study. Clinical, biochemical and genetic characteristics of these children were retrieved and studied from electronic medical records. Results Two children were genetic females and one was genetic male, but all three were raised as females. All had hypertension at diagnosis except one but none had hypokalemia. All of them had mutation in the CYP17A1 gene. The two females responded well to oestrogen and progesterone and had adequate estrogenization clinically. Conclusions Even though CAH due to 17αOHD is quite rare, it should be considered while evaluating young individuals with hypogonadism, hypertension with or without hypokalemia. Lack of genital ambiguity and absence of classical signs at presentation does not rule out this not so uncommon condition and warrants follow up.

Functional Identification of Compound Heterozygous Mutations in the CYP17A1 Gene Resulting in Combined 17α-Hydroxylase/17,20-Lyase Deficiency

BACKGROUND

We previously reported a patient with congenital adrenal hyperplasia (CAH) with compound heterozygous mutations in the cytochrome P450 17A1 (CYP17A1) gene. One allele had a p.His373Leu and the other a new p.Glu383fsX36 mutation. The aim of this study was to investigate the functional properties of a new allele present in a compound heterozygote of CYP17A1.

METHODS

To understand how p.His373Leu and p.Glu383fsX36 affect P450c17 enzymatic activity, wild type and mutant CYP17A1 cDNAs were cloned into flag-tagged pcDNA3 vector and introduced into human embryonic kidney cells 293T (HEK293T) cells. Protein expression levels of CYP17A1 were then analyzed. And the activities of 17α-hydroxylase and 17,20-lyase of CYP17A1 were evaluated by measuring the conversion of progesterone to 17α-hydroxyprogesterone and of 17α-hydroxypregnenolone to dehydroepiandrosterone, respectively. In addition a computer model was used to create the three-dimensional structure of the mutant CYP17A1 enzymes.

RESULTS

Production of the p.His373Leu mutant protein was significantly lower than that of the wild type protein, and the p.Glu383fsX36 protein was hardly produced. Similarly the enzymatic activity derived from the p.His373Leu mutant vector was significantly lower than that obtained from the wild type vector, and little activity was obtained from the p.Glu383fsX36 vector. Three-dimensional modeling of the enzyme showed that p.His373 was located in region important for heme-binding and proper folding. Neither the p.His373Leu nor the p.Glu383fsX36 mutant protein formed a heme-binding structure.

CONCLUSION

Enzyme activity measured in both mutants disappeared completely in both 17α-hydroxylase and 17,20-lyase. This result accounts for the clinical manifestations of the patient with the compound heterozygous CYP17A1 mutations.

Association of CYP17A1 Genetic Polymorphisms and Susceptibility to Essential Hypertension in the Southwest Han Chinese Population

Background

The CYP17A1 gene encodes for cytochrome P450 enzyme CYP17A1, which is involved with the steroidogenic pathway including mineralocorticoids. The CYP17A1 polymorphisms might affect enzyme activity, then leading to a state of mineralocorticoid 11-deoxycorticosterone excess characterized by hypertension, suppressed plasma renin activity, and low aldosterone concentrations. The aim of this study was to investigate the contribution of CYP17A1 polymorphisms in inducing the susceptibility to essential hypertension among the Southwest Han Chinese population.

Material/Methods

Eight single nucleotide polymorphisms of CYP17A1 were genotyped in a case-control study for samples by polymerase chain reaction-restriction fragment length polymorphism analysis.

Results

The polymorphisms rs11191548 and rs4919687 were significantly associated with hypertension risk, which was confirmed by systolic and diastolic blood pressure distribution analyses between different genotype groups, and these two polymorphisms were found in linkage disequilibrium. The rs4919687 polymorphism was estimated to cause the destruction of exonic splicing silencer (ESR and Motif 3) sites and to transform the transcription factor AREB6 binding site, respectively, in the bioinformatics analyses. The haplotypes rs4919686A-rs3740397G -rs4919687C-rs743572C-rs11191548C and rs4919686A-rs3740397G-rs4919687T-rs743572C- rs11191548T were found to be susceptible to essential hypertension.

Conclusions

Our findings suggest that the CYP17A1 polymorphisms could be a genetic risk factor for essential hypertension among the Yunnan Han Chinese population, which would have implications for the treatment of this complex disorder.

Diagnostic yield of targeted gene panel sequencing to identify the genetic etiology of disorders of sex development

Disorders of sex development (DSD) vary phenotypically and are caused by a number of genetic etiologies. This study investigated the genetic etiology of DSD patients using targeted exome sequencing of 67 known DSD-associated genes in humans. This study included 37 patients with 46, XY DSD and seven patients with 46, XX DSD. We identified known pathogenic mutations or deletion in nine (20.5%) patients in the AR, CYP17A1, SRD5A1, and DMRT1/2 genes. Novel variants were identified in nine patients (20.5%) in the AR, ATRX, CYP17A1, CHD7, MAP3K1, NR5A1, and WWOX genes. Among them, four patients harbored pathogenic or likely pathogenic variants, while the remaining five patients (11.4%) had variants of uncertain significance. We were able to make a genetic diagnosis in 29.5% of patients with pathogenic or likely pathogenic mutations. Targeted exome sequencing is an efficient tool to improve the diagnostic yield of DSD, despite its phenotypic and genetic heterogeneity.

Androgen-metabolizing enzymes: A structural perspective

Androgen-metabolizing enzymes convert cholesterol, a relatively inert molecule, into some of the most potent chemical messengers in vertebrates. This conversion involves thermodynamically challenging reactions catalyzed by P450 enzymes and redox reactions catalyzed by Aldo-Keto Reductases (AKRs). This review covers the structures of these enzymes with a focus on active site interactions and proposed mechanisms. Due to their role in a number of diseases, particularly in cancer, androgen-metabolizing enzymes have been targets of drug design. Hence we will also highlight how existing knowledge of structure is being used to this end.

Comparisons of Prostate Cancer Inhibitors Abiraterone and TOK-001 Binding with CYP17A1 through Molecular Dynamics

Cytochrome P450 17A1 (CYP17A1) is associated in the steroid hormone biosynthesis in human. As cell proliferation of prostate cancer in response to androgen steroid, an inhibition of CYP17A1 becomes an alternative approach to inhibit biosynthesis of androgen and support treatment of prostate cancer. However, biology-driven inhibitor development of prostate cancer is poorly elucidated. The aims of this study are to address structural differences at atomic-level between CYP17A1 and inhibitors i.e., abiraterone and TOK-001, and further investigate the effect of point mutation of CYP17A1 on the active site stability and the local interactions that are hydrophobic interaction and hydrogen bonding throughout molecular dynamics (MD) simulation. After performing multiple comparisons among four different complexes across CYP17A1 and inhibitors, interestingly TOK-001 oriented toward the active pocket and formed larger volume with I-helix of CYP17A1 than abiraterone, whereas abiraterone showed tighter binding and more active site stability. Considering on the effect of hydrophobic interaction and hydrogen bonding between abiraterone and CYP17A1, the key residues of Phe114, Ile371, Val482, and Asn202 were identified. This contributes into tight binding interactions; however abiraterone is effectively weakened along with the global conformation mobility increased in A105L mutation. Surprisingly, overall conformation of the CYP17A1 remained stable when bound to TOK-001. This basic knowledge can guide future experiments on design of efficient inhibitors for CYP17A1, which provides theoretical basis of androgen-dependent disease therapy.

Molecular regulation of steroidogenesis in endocrine Leydig cells

Steroid hormones regulate essential physiological processes and inadequate levels are associated with various pathological conditions. Consequently, the process of steroid hormone biosynthesis is finely regulated. In the testis, the main steroidogenic cells are the Leydig cells. There are two distinct populations of Leydig cells that arise during development: fetal and adult Leydig cells. Fetal Leydig cells are responsible for masculinizing the male urogenital tract and inducing testis descent. These cells atrophy shortly after birth and do not contribute to the adult Leydig cell population. Adult Leydig cells derive from undifferentiated precursors present after birth and become fully steroidogenic at puberty. The differentiation of both Leydig cell populations is controlled by locally produced paracrine factors and by endocrine hormones. In fully differentially and steroidogenically active Leydig cells, androgen production and hormone-responsiveness involve various signaling pathways and downstream transcription factors. This review article focuses on recent developments regarding the origin and function of Leydig cells, the regulation of their differentiation by signaling molecules, hormones, and structural changes, the signaling pathways, kinases, and transcription factors involved in their differentiation and in mediating LH-responsiveness, as well as the fine-tuning mechanisms that ensure adequate production steroid hormones.

CYP17A1 gene mutations and hypertension variations found in 46, XY females with combined 17α-hydroxylase/17, 20-lyase deficiency

The aim of this study was to analyze the structural consequences of the mutations in CYP17A1 gene and their relationship with the variations of clinical manifestations in three patients who presented with complete or partial combined 17α-hydroxylase/17,20-lyase deficiency (17OHD). DNA sequences of the coding exons and intron/exon boundaries of the CYP17A1 gene were analyzed for mutations. In silico analysis with computational three-dimensional model of human P450c17 and multiple alignments analysis were performed to evaluate the spatial conformational changes by missense mutations. Five mutations p.S117fs (c.351_352delCT), p.H373L (c.1184 A>T), p.Y329fs (c.985_987delTACinsAA), p.A82D (c.245 C>A) and p.L209P (c.626 T>C) were identified in three patients, respectively. The novel mutation p.S117fs (c.351_352delCT) has not been reported previously. In silico analysis explained the conformational changes by the described mutations, which resulted in different severe 17OHD. Our studies also suggest that molecular data accompanying with in silico analysis of the CYP17A1 gene are much helpful for the diagnosis, management and genetic counseling of 17OHD.

A review of the literature on common CYP17A1 mutations in adults with 17-hydroxylase/17,20-lyase deficiency, a case series of such mutations among Koreans and functional characteristics of a novel mutation

OBJECTIVE

17α-hydroxylase/17,20-lyase deficiency is a rare form of congenital adrenal hyperplasia, characterized by hypertension and sexual infantilism and caused by loss-of-function mutations in CYP17A1. This study investigated the clinical and molecular characteristics of six adults with 17α-hydroxylase/17,20-lyase deficiency and the functional consequences of a novel CYP17A1 mutation.

MATERIALS AND METHODS

Six phenotypic females, three with 46,XY and three with 46,XX karyotypes, presented with primary amenorrhea and hypertension. All had elevated levels of plasma adrenocorticotropic hormone, serum gonadotropin, progesterone, and 11-deoxycorticosterone, and reduced testosterone and dehydroepiandrosterone sulfate (DHEA-S). All coding exons and flanking intronic sequences of CYP17A1 were directly sequenced using genomic DNA. Wild-type and mutant CYP17A1 cDNAs were inserted into the pcDNA3.1/V5-His-P450c17 vector, and transiently expressed in COS-7 cells. This was followed by an assessment of 17α-hydroxylase and 17,20-lyase activities by measuring the conversions of progesterone to 17-hydroxyprogesterone and 17-hydroxypregnenolone to DHEA.

RESULTS

The mutation analysis identified one patient with compound heterozygosity for p.H373L and p.W406L, one with compound heterozygosity for p.H373L and p.A174E, three with compound heterozygosity for p.Y329fs and p.H373L, and one with homozygosity for p.H373L. An in vitro functional analysis of the novel p.W406L mutation revealed a complete loss of 17α-hydroxylase/17, 20-lyase activities.

CONCLUSIONS

p.H373L was the most common mutation among these Korean patients, consistent with the high allele frequency of p.H373L in Chinese and Japanese populations, suggesting possible founder effects in Asian countries. The novel p.W406L mutation caused a complete loss of both catalytic activities, indicating that this amino acid is critical for P450c17 function.

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.

Structures of cytochrome P450 17A1 with prostate cancer drugs abiraterone and TOK-001

Cytochrome P450 17A1 (P450c17) catalyzes the biosynthesis of androgens in humans¹. Since prostate cancer cells proliferate in response to androgen steroids^2,3, CYP17A1 inhibition is a new strategy to prevent androgen synthesis and treat lethal metastatic castration-resistant prostate cancer⁴, but drug development has been hampered by the lack of a CYP17A1 structure. Here we report the only known structures of CYP17A1, which contain either abiraterone, a first-in-class steroidal inhibitor recently approved by the FDA for late-stage prostate cancer⁵, or TOK-001, another inhibitor in clinical trials^4,6. Both bind the heme iron forming a 60° angle above the heme plane, packing against the central I helix with the 3β-OH interacting with N202 in the F helix. Importantly, this binding mode differs substantially from those predicted by homology models or from steroids in other cytochrome P450 enzymes with known structures, with some features more similar to steroid receptors. While the overall CYP17A1 structure provides a rationale for understanding many mutations found in patients with steroidogenic diseases, the active site reveals multiple steric and hydrogen bonding features that will facilitate better understanding of the enzyme’s dual hydroxylase and lyase catalytic capabilities and assist in rational drug design. Specifically, structure-based design is expected to aid development of inhibitors that bind only CYP17A1 and solely inhibit its androgen-generating lyase activity to improve treatment of prostate and other hormone-responsive cancers.

Three novel CYP17A1 gene mutations (A82D, R125X, and C442R) found in combined 17α-hydroxylase/17,20-lyase deficiency

The aim of this study was to analyze the structure and functional consequences of 3 novel mutations (A82D, R125X, and C442R) of the CYP17A1 gene found in 2 patients with combined 17α-hydroxylase/17,20-lyase deficiency (17OHD). Two Chinese 46, XY female patients were diagnosed with 17OHD based on clinical findings and biochemical results. The CYP17A1 gene was analyzed by polymerase chain reaction direct sequencing. An in vitro expression system was performed in HEK293 cells to analyze the mutant P450c17 activity compared with the wild type. Analysis of the CYP17A1 gene sequences in patient 1 showed compound heterozygous mutations A82D (g.417 C > A) in exon 1 and Y329fs (g.4869 T > A, 4871del) in exon 6; DNA sequencing analysis in patient 2 revealed compound heterozygous mutations R125X (g.2045 C > T) in exon 2 and C442R (g.6457 T > C) in exon 8. The mutations A82D, R125X, and C442R have not been reported previously. The functional study demonstrated that the A82D, R125X, and C442R mutations almost completely eliminate enzymatic activity. These results, which indicate that Ala 82 and Cys 442 are crucial for both 17-hydroxylase and 17,20-lyase activities, help define the structure-function relationship of the CYP17A1 gene. The novel mutations A82D, R125X, and C442R further clarify the patients' clinical manifestations of combined 17OHD.

Genetic variations in CYP17A1, CACNB2 and PLEKHA7 are associated with blood pressure and/or hypertension in She ethnic minority of China

OBJECTIVES

Two large-scale genome-wide association studies (GWAs) have identified multiple variants associated with blood pressure (BP) or hypertension. The present study was to investigate whether some variations were associated with BP traits and hypertension or even prehypertension in adult She ethnic minority of China.

METHODS

The population of the present study comprised 4460 (1979 males and 2481 females, respectively) unrelated she ethnic minority based on a cross-sectional study from Ningde City in Fujian province of China. There were 1692 hypertensives, 1600 prehypertensives and 1168 normotensive controls, respectively. We genotyped 7 variants in CYP17A1, PLEKHA7, CACNB2, ATP2B1, TBX3-TBX5, CSK-ULK3 and SH2B3 reported by the previous GWAs on Europeans. All analyses were performed in an additive genetic model.

RESULTS

As the minor allele of rs653178 in/near SH2B3 was very rare with the frequency of 0.018, we excluded this single nucleotide polymorphism (SNP) in the further analyses. Of the other 6 loci, linear regression analyses revealed that rs11191548 in CYP17A1 and rs11014166 in CACNB2 were significantly associated with systolic BP (β = -1.17, P = 0.002 and β = -0.50, P = 0.006, respectively), while only SNP rs11191548 was significantly associated with diastolic BP (β = -0.56, P=0.002) after adjusted by age, sex and BMI. Two variants in CACNB2 and PLEKHA7 were found to be significantly related to hypertension (odds ratios [OR] and (95% confidence interval [CI]): 0.79 (0.65-0.97) and 1.19 (1.01-1.41), respectively) in logistic regression analyses after adjusted by age, sex and BMI. In addition, we found that combined risk alleles of the 6 SNPs increased risk of hypertension in a stepwise fashion (P for trend < 0.001). However, none of the 6 SNPs was significantly associated with BMI or prehypertension status. While logistic analysis showed that subjects with cumulative risk alleles more than 9 had significantly higher risk for prehypertension (adjusted OR: 3.10, P < 0.001) compared with those with risk alleles less than 4.

CONCLUSIONS

We replicated that variations in CYP17A1, CACNB2 and PLEKHA7 were related to BP traits and/or hypertension in She population. In addition, although we failed to observe single gene associated with prehypertension, we first found that conjoint effect of multiple risk alleles on BP might increase the risk of progressing to prehypertension.

Molecular diagnosis of two families with classic congenital adrenal hyperplasia

We investigated the genetic defects in two families with classic congenital adrenal hyperplasia (CAH). Clinical data and vein blood of the family members were collected, hormonal evaluation, karyotype analysis, ultrasound and CT scans were performed, and a direct-sequencing of PCR products of the candidate genes was used to identify the mutations. In family A, Patients A-II:1 and A-II:2 were found to be in a compound heterozygous state for mutations of p.I172N (g.1004T>A) in exon 4 and IVS2-13A/C>G (g.659A/C>G) in intron 2 in CYP21A2 gene, their father A-I:1 and mother A-I:2 were found to carry a heterozygous mutation of IVS2-13A/C>G (g.659A/C>G) and p.I172N (g.1004T>A) respectively. In family B, Patient B-II:1 was detected to carry only one heterozygous mutation of p.I172N; no other mutations in CYP11B1, CYP17A1 or HSD3B2 genes were detected. Her father B-I:1 carried a heterozygous mutation of p.I172N (g.1004T>A) and her mother B-I:2 was found to be a wild type in all the candidate genes. Obviously, patients A-II:1 and A-II:2 inherited the p.I172N (g.1004T>A)-bearing maternal allele and the IVS2-13A/C>G (g.659A/C>G)-bearing paternal allele. And this kind of compound heterozygous mutations caused simple virilising (SV) CAH. While patient B-II:1, whose phenotype was SV CAH too, was found to carry only one heterozygous mutation of the p.I172N (g.1004T>A)-bearing paternal allele, and needed further studies.

Six new cases confirm the clinical molecular profile of complete combined 17α-hydroxylase/ 17,20-lyase deficiency in Brazil

In 2004, Costa-Santos and cols. reported 24 patients from 19 Brazilian families with 17α-hydroxylase deficiency and showed that p.W406R and p.R362C corresponded to 50% and 32% of CYP17A1 mutant alleles, respectively. The present report describes clinical and molecular data of six patients from three inbred Brazilian families with 17α-hydroxlyse deficiency. All patients had hypogonadism, amenorrhea and hypertension at diagnosis. Two sisters were found to be 46,XY with both gonads palpable in the inguinal region. All patients presented hypergonadotrophic hypogonadism, with high levels of ACTH (> 104 ng/mL), suppressed plasmatic renin activity, low levels of potassium (< 2.8 mEq/L) and elevated progesterone levels (> 4.4 ng/mL). Three of them, including two sisters, were homozygous for p.W406R mutation and the other three (two sisters and one cousin) were homozygous for p.R362C. The finding of p.W406R and p.R362C in the CYP17A1 gene here reported in additional families, confirms them as the most frequent mutations causing complete combined 17α-hydroxylase/17,20-lyase deficiency in Brazilian patients.

Molecular modeling on inhibitor complexes and active-site dynamics of cytochrome P450 C17, a target for prostate cancer therapy

A molecular model for the P450 enzyme cytochrome P450 C17 (CYP17) is presented based on sequence alignments of multiple template structures and homology modeling. This enzyme plays a central role in the biosynthesis of testosterone and is emerging as a major target in prostate cancer, with the recently developed inhibitor abiraterone currently in advanced clinical trials. The model is described in detail, together with its validation, by providing structural explanations to available site-directed mutagenesis data. The CYP17 molecule in this model is in the form of a triangular prism, with an edge of approximately 55 A and a thickness of approximately 37 A. It is predominantly helical, comprising 13 alpha helices interspersed by six 3(10) helices and 11 beta-sheets. Multinanosecond molecular dynamics simulations in explicit solvent have been carried out, and principal components analysis has been used to reveal the details of dynamics around the active site. Coarse-grained methods have also been used to verify low-frequency motions, which have been correlated with active-site gating. The work also describes the results of docking synthetic inhibitors, including the drug abiraterone and the natural substrate pregnenolone, in the CYP17 active site together with molecular dynamics simulations on the complexes.