Steroid 17alpha-hydroxylase deficiency: functional characterization of four mutations (A174E, V178D, R440C, L465P) in the CYP17A1 gene

Generation of human steroidogenic cytochrome P450 enzymes for structural and functional characterization

Six cytochrome P450 enzymes are involved in human steroidogenesis, converting cholesterol to sex steroids, mineralocorticoids, and glucocorticoids. While early work was accomplished with steroidogenic P450 orthologs from more accessible sources, knowledge of basic biochemistry through successful drug design have been greatly facilitated by recombinantly-expressed, highly purified human versions of these membrane proteins. Many membrane proteins are difficult to express and purify and are unstable. Membrane P450 expression in E. coli has been facilitated by modification and/or truncation of the membrane-interacting N-terminus, while metal-affinity resins and histidine-tagging greatly facilitates purification. However, substantial optimization is still frequently required to maintain protein stability. Over time, a generalized three-column purification scheme has been developed and tweaked to generate substantial quantities of fully active, highly purified human cytochrome P450 enzymes that have made possible the application of many structural, biochemical, and biophysical techniques to elucidate the mysteries of these critical human enzymes.

Congenital Adrenal Hyperplasia Due to 17-α-hydroxylase Deficiency: A Case Report

Congenital adrenal hyperplasia, an innate error in adrenal steroid biosynthesis, triggers a wide range of consequences based on the level of enzyme blockade. Due to the various forms of enzyme deficiency and degree of penetration, the clinical features are very variable. In this case report, we present a form of congenital adrenal hyperplasia due to an enzymatic defect of CYP17A1, with a late diagnosis. The recognition of this pathology should occur as early as possible to avoid sequelae, both metabolic and psychological.

The broad phenotypic spectrum of 17α-hydroxylase/17,20-lyase (CYP17A1) deficiency: a case series

CONTEXT

17α-Hydroxylase/17,20-lyase deficiency (17OHD) caused by mutations in the CYP17A1 gene is a rare form of congenital adrenal hyperplasia typically characterised by cortisol deficiency, mineralocorticoid excess and sex steroid deficiency.

OBJECTIVE

To examine the phenotypic spectrum of 17OHD by clinical and biochemical assessment and corresponding in silico and in vitro functional analysis.

DESIGN

Case series.

PATIENTS AND RESULTS

We assessed eight patients with 17OHD, including four with extreme 17OHD phenotypes: two siblings presented with failure to thrive in early infancy and two with isolated sex steroid deficiency and normal cortisol reserve. Diagnosis was established by mass spectrometry-based urinary steroid profiling and confirmed by genetic CYP17A1 analysis, revealing homozygous and compound heterozygous sequence variants. We found novel (p.Gly111Val, p.Ala398Glu, p.Ile371Thr) and previously described sequence variants (p.Pro409Leu, p.Arg347His, p.Gly436Arg, p.Phe53/54del, p.Tyr60IlefsLys88X). In vitro functional studies employing an overexpression system in HEK293 cells showed that 17,20-lyase activity was invariably decreased while mutant 17α-hydroxylase activity retained up to 14% of WT activity in the two patients with intact cortisol reserve. A ratio of urinary corticosterone over cortisol metabolites reflective of 17α-hydroxylase activity correlated well with clinical phenotype severity.

CONCLUSION

Our findings illustrate the broad phenotypic spectrum of 17OHD. Isolated sex steroid deficiency with normal stimulated cortisol has not been reported before. Attenuation of 17α-hydroxylase activity is readily detected by urinary steroid profiling and predicts phenotype severity.

SIGNIFICANCE STATEMENT

Here we report, supported by careful phenotyping, genotyping and functional analysis, a prismatic case series of patients with congenital adrenal hyperplasia due to 17α-hydroxylase (CYP17A1) deficiency (17OHD). These range in severity from the abolition of function, presenting in early infancy, and unusually mild with isolated sex steroid deficiency but normal ACTH-stimulated cortisol in adult patients. These findings will guide improved diagnostic detection of CYP17A1 deficiency.

Disorders of Sex Development: Classification, Review, and Impact on Fertility

In this review, the elements included in both sex determination and sex differentiation are briefly analyzed, exposing the pathophysiological and clinical classification of disorders or anomalies of sex development. Anomalies in sex determination without sex ambiguity include gonadal dysgenesis, polysomies, male XX, and Klinefelter syndrome (dysgenesis and polysomies with a female phenotype; and sex reversal and Klinefelter with a male phenotype). Other infertility situations could also be included here as minor degrees of dysgenesis. Anomalies in sex determination with sex ambiguity should (usually) include testicular dysgenesis and ovotesticular disorders. Among the anomalies in sex differentiation, we include: (1) males with androgen deficiency (MAD) that correspond to those individuals whose karyotype and gonads are male (XY and testes), but the phenotype can be female due to different hormonal abnormalities. (2) females with androgen excess (FAE); these patients have ovaries and a 46,XX karyotype, but present varying degrees of external genital virilization as a result of an enzyme abnormality that affects adrenal steroid biosynthesis and leads to congenital adrenal hyperplasia; less frequently, this can be caused by iatrogenia or tumors. (3) Kallman syndrome. All of these anomalies are reviewed and analyzed herein, as well as related fertility problems.

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome: a comprehensive update

BACKGROUND

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome, also referred to as Müllerian aplasia, is a congenital disorder characterized by aplasia of the uterus and upper part of the vagina in females with normal secondary sex characteristics and a normal female karyotype (46,XX).

MAIN BODY

The diagnosis is often made during adolescence following investigations for primary amenorrhea and has an estimated prevalence of 1 in 5000 live female births. MRKH syndrome is classified as type I (isolated uterovaginal aplasia) or type II (associated with extragenital manifestations). Extragenital anomalies typically include renal, skeletal, ear, or cardiac malformations. The etiology of MRKH syndrome still remains elusive, however increasing reports of familial clustering point towards genetic causes and the use of various genomic techniques has allowed the identification of promising recurrent genetic abnormalities in some patients. The psychosexual impact of having MRKH syndrome should not be underestimated and the clinical care foremost involves thorough counselling and support in careful dialogue with the patient. Vaginal agenesis therapy is available for mature patients following therapeutical counselling and education with non-invasive vaginal dilations recommended as first-line therapy or by surgery. MRKH syndrome involves absolute uterine factor infertility and until recently, the only option for the patients to achieve biological motherhood was through gestational surrogacy, which is prohibited in most countries. However, the successful clinical trial of uterus transplantation (UTx) by a Swedish team followed by the first live-birth in September, 2014 in Gothenburg, proofed the first available fertility treatment in MRKH syndrome and UTx is now being performed in other countries around the world allowing women with MRKH syndrome to carry their own child and achieve biological motherhood.

CONCLUSION

Several advances in research across multiple disciplines have been made in the recent years and this kaleidoscopic review provides a current status of various key aspects in MRKH syndrome and provides perspectives for future research and improved clinical care.

The CYP17A1 gene polymorphisms are associated with hypercholesterolemia in Han Chinese

BACKGROUND

The CYP17A1 gene has been identified to associate with hypertension in Chinese population. However, the association between CYP17A1 polymorphisms and hypertension-related factors is unclear. The present study aimed to investigate the relation between CYP17A1 single nucleotide polymorphisms (SNPs) and serum lipid profiles.

METHODS

In total, 1350 participants were included in the study. Six SNPs in or near CYP17A1 gene were genotyped in a Han Chinese population in two stages.

RESULTS

There was a statistically significant association of rs1004467 (adjusted odds ratio = 0.783, 95% confidence interval = 0.667-0.919, p < 0.05) and rs11191548 (adjusted odds ratio = 0.788, 95% confidence interval = 0.672-0.925, p < 0.05) with hypercholesterolemia after adjustment for potential factors. Additionally, the rs1004467 minor G-allele and the rs11191548 minor C-allele were significantly associated with the lower serum total cholesterol levels (p < 0.05 for all).

CONCLUSIONS

The rs1004467 and rs11191548 in the CYP17A1 gene are associated with a decreased risk of hypercholesterolemia and lower serum TC levels in Han Chinese.

Genetic testing of XY newborns with a suspected disorder of sex development

PURPOSE OF REVIEW

The current review focuses on the neonatal presentation of disorders of sex development, summarize the current approach to the evaluation of newborns and describes recent advances in understanding of underlying genetic aetiology of these conditions.

RECENT FINDINGS

Several possible candidate genes as well as other adverse environmental factors have been described as contributing to several clinical subgroups of 46,XY DSDs. Moreover, registry-based studies showed that infants with suspected DSD may have extragenital anomalies and in 46,XY cases, being small for gestational age (SGA), cardiac and neurological malformations are the commonest concomitant conditions.

SUMMARY

Considering that children and adults with DSD may be at risk of several comorbidities a clear aetiological diagnosis will guide further management. To date, a firm diagnosis is not reached in over half of the cases of 46,XY DSD. Whilst it is likely that improved diagnostic resources will bridge this gap in the future, the next challenge to the clinical community will be to show that such advances will result in an improvement in clinical care.

Functional characterization of the G162R and D216H genetic variants of human CYP17A1

Cytochrome P450 17A1 (CYP17A1) is a dual-function enzyme catalyzing reactions necessary for cortisol and androgen biosynthesis. CYP17A1 is a validated drug target for prostate cancer as CYP17A1 inhibition significantly reduces circulating androgens and improves survival in castration-resistant prostate cancer. Germline CYP17A1 genetic variants with altered CYP17A1 activity manifesting as various endocrinopathies are extremely rare; however, characterizing these variants provides critical insights into CYP17A1 protein structure and function. By querying the dbSNP online database and publically available data from the 1000 genomes project (http://browser.1000genomes.org), we identified two CYP17A1 nonsynonymous genetic variants with unknown consequences for enzymatic activity and stability. We hypothesized that the resultant amino acid changes would alter CYP17A1 stability or activity. To test this hypothesis, we utilized a HEK-293T cell-based expression system to characterize the functional consequences of two CYP17A1 variants, D216H (rs200063521) and G162R (rs141821705). Cells transiently expressing the D216H variant demonstrate a selective impairment of 16α-hydroxyprogesterone synthesis by 2.1-fold compared to wild-type (WT) CYP17A1, while no effect on 17α-hydroxyprogesterone synthesis was observed. These data suggest that substrate orientations in the active site might be altered with this amino acid substitution. In contrast, the G162R substitution exhibits decreased CYP17A1 protein stability compared to WT with a near 70% reduction in protein levels as determined by immunoblot analysis. This variant is preferentially ubiquitinated and degraded prematurely, with an enzyme half-life calculated to be ∼2.5 h, and proteasome inhibitor treatment recovers G162R protein expression to WT levels. Together, these data provide new insights into CYP17A1 structure-function and stability mechanisms.

Common variant rs11191548 near the CYP17A1 gene is associated with hypertension and the serum 25(OH) D levels in Han Chinese

The CYP17A1 gene, which encodes17α-hydroxylase and 17,20-lyase, has been identified as a common hypertension susceptibility locus in a European population. However, the association between CYP17A1 polymorphisms and hypertension is unclear in the Chinese population as well as in the role of serum 25(OH) D levels. Six single nucleotide polymorphisms (SNPs) in CYP17A1 were genotyped in two stages in a Han Chinese population, and the serum 25(OH) D levels were measured. Analysis in stage 1 showed that the rs1004467 minor G-allele and rs11191548 minor C-allele in CYP17A1 were significantly associated with a decreased risk of hypertension and higher serum 25(OH) D levels (all P < 0.05). The larger sample in stage 2 also showed that a mutation in rs11191548 was significantly associated with a decreased risk of hypertension (adjusted OR = 0.707, 95% CI: 0.553-0.904, P = 0.006). The rs11191548 minor C-allele was associated with higher serum 25(OH) D levels in hypertensive subjects (βadj ± SEM = 0.094 ± 0.949, P = 0.003) and controls (βadj ± SEM = 0.128 ± 1.025, P < 0.001). In conclusion, the rs11191548 CYP17A1 gene mutation was associated with hypertension and the serum 25(OH) D levels in Han Chinese.

Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents

These pediatric hypertension guidelines are an update to the 2004 "Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents." Significant changes in these guidelines include (1) the replacement of the term "prehypertension" with the term "elevated blood pressure," (2) new normative pediatric blood pressure (BP) tables based on normal-weight children, (3) a simplified screening table for identifying BPs needing further evaluation, (4) a simplified BP classification in adolescents ≥13 years of age that aligns with the forthcoming American Heart Association and American College of Cardiology adult BP guidelines, (5) a more limited recommendation to perform screening BP measurements only at preventive care visits, (6) streamlined recommendations on the initial evaluation and management of abnormal BPs, (7) an expanded role for ambulatory BP monitoring in the diagnosis and management of pediatric hypertension, and (8) revised recommendations on when to perform echocardiography in the evaluation of newly diagnosed hypertensive pediatric patients (generally only before medication initiation), along with a revised definition of left ventricular hypertrophy. These guidelines include 30 Key Action Statements and 27 additional recommendations derived from a comprehensive review of almost 15 000 published articles between January 2004 and July 2016. Each Key Action Statement includes level of evidence, benefit-harm relationship, and strength of recommendation. This clinical practice guideline, endorsed by the American Heart Association, is intended to foster a patient- and family-centered approach to care, reduce unnecessary and costly medical interventions, improve patient diagnoses and outcomes, support implementation, and provide direction for future research.

Perspectives in Pediatric Pathology, Chapter 22. Testicular Involvement in Systemic Diseases

Normal testicular physiology requires appropriate function of endocrine glands and other tissues. Testicular lesions have been described in disorders involving the hypothalamus-hypophysis, thyroid glands, adrenal glands, pancreas, liver, kidney, and gastrointestinal tract. Testicular abnormalities can also associate with chronic anemia, obesity, and neoplasia. Although many of the disorders that affect the above-mentioned glands and tissues are congenital, acquired lesions may result in hypogonadism in children and adolescents.

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.

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.

17-hydroxylase/17,20-lyase deficiency due to a R96Q mutation causing hypertension and poor breast development

Combined17α-hydroxylase/17,20-lyase deficiency is a rare cause of congenital adrenal hyperplasia and hypogonadism. Hypertension and hypokalemia are essential presenting features. We report an Arab family with four affected XX siblings. The eldest presented with abdominal pain and was diagnosed with a retroperitoneal malignant mixed germ cell tumour. She was hypertensive and hypogonadal. One sibling presented with headache due to hypertension while the other two siblings were diagnosed with hypertension on a routine school check. A homozygous R96Q missense mutation in P450c17 was detected in the index case who had primary amenorrhea and lack of secondary sexual characters at 17 years. The middle two siblings were identical twins and had no secondary sexual characters at the age of 14. All siblings had hypokalemia, very low level of adrenal androgens, high ACTH and high levels of aldosterone substrates. Treatment was commenced with steroid replacement and puberty induction with estradiol. The index case had surgical tumor resection and chemotherapy. All siblings required antihypertensive treatment and the oldest remained on two antihypertensive medications 12 years after diagnosis. Her breast development remained poor despite adequate hormonal replacement. Combined 17α-hydroxylase/17,20-lyase deficiency is a rare condition but might be underdiagnosed. It should be considered in young patients presenting with hypertension, particularly if there is a family history of consanguinity and with more than one affected sibling. Antihypertensive medication might continue to be required despite adequate steroid replacement. Breast development may remain poor in mutations causing complete form of the disease.

LEARNING POINTS

Endocrine hypertension due to rarer forms of CAH should be considered in children and adolescents, particularly if more than one sibling is affected and in the presence of consanguinity.17α-hydroxylase/17,20-lyase deficiency is a rare form of CAH but might be underdiagnosed.Blood pressure measurement should be carried out in all females presenting with hypogonadism.Anti-hypertensive medications might be required despite adequate steroid replacement.Initial presenting features might vary within affected members of the same family.Adverse breast development might be seen in the complete enzyme deficiency forms of the disease.

Identification of a novel large CYP17A1 deletion by MLPA analysis in a family with classic 17α-hydroxylase deficiency

Steroid 17α-hydroxylase deficiency (17OHD) is a rare form of congenital adrenal hyperplasia caused by mutations in the 17α-hydroxylase ( CYP17A1) gene. CYP17A1 is a key enzyme in the biosynthesis of adrenal and gonadal steroid hormones facilitating both 17α-hydroxylase and 17,20-lyase activities. We characterized a partial CYP17A1 deletion in a Kurdish family with 17OHD by multiplex ligation-dependent probe amplification (MLPA). The index patient presented with amenorrhea and lack of pubertal development. Investigations established the diagnosis of 46,XY disorder of sex development (DSD). She is the daughter of consanguineous parents and has 2 sisters with similar clinical presentation. All patients showed biochemical signs of primary adrenal and gonadal insufficiency. The molecular genetic analysis by PCR suggested a deletion spanning exons 1–6 of the CYP17A1 gene. MLPA analysis confirmed the large partial CYP17A1 deletion in patients and parents in homozygous and heterozygous state, respectively. This is the first report employing MLPA for mutation analysis to detect a deletion of CYP17A1 spanning multiple exons in 3 patients with classic 17OHD. Therefore, it is important to consider large partial CYP17A1 deletions in 17OHD in addition to point mutations in cases where no segregation analysis is possible to determine the correct genotype.

17α-hydroxylase deficiency diagnosed in early infancy caused by a novel mutation of the CYP17A1 gene

BACKGROUND

Mutations of the CYP17A1 gene cause 17α-hydroxylase deficiency (17OHD) resulting in 46,XY disorder of sex development, hypertension, hypokalemia and absent pubertal development. It is a rare, autosomal recessive form of congenital adrenal hyperplasia (CAH).

PATIENT

We report on a neonate with prenatally determined 46,XY karyotype. At 20 weeks of gestation, lack of development of male external genitalia was noticed. A phenotypically female child was born at 41 weeks of gestation.

RESULTS

Postnatal ultrasound revealed testes in both labia majora, an absence of uterus and normal adrenal glands. Steroid hormone analysis in serum revealed low basal levels of cortisol, testosterone and androstenedione in the presence of massively elevated corticosterone at the age of 2 weeks. The urinary steroid profile from spot urine showed excessive excretion of 17-desoxysteroids, decreased glucocorticoid metabolites and absent C19 steroids, thus proving 17OHD. Molecular analysis identified a novel mutation of the CYP17A1 gene: c.896T>A (p.I299N) in exon 5. Substitution with hydrocortisone was started. The child is raised as a girl and is developing well so far.

CONCLUSION

Herein, we report the unusually early diagnosis of a newborn with the rare CAH form of 17OHD allowing an early start of treatment.

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.

Common polymorphism rs11191548 near the CYP17A1 gene is associated with hypertension and systolic blood pressure in the Han Chinese population

Background The single-nucleotide polymorphism (SNP) rs11191548, near the CYP17A1 gene, has been identified as being associated with hypertension and systolic blood pressure (SBP) in genome-wide association studies (GWAS) in a European population. The CYP17A1 gene encodes cytochrome P450c17alpha and plays an important role in the steroidogenic pathway, which includes mineralocorticoids. Methods We investigated the SNP rs11191548 in a case-control study of 1,102 subjects with essential hypertension (EH) and 1,109 normotensive controls. Results The SNP rs11191548 was significantly associated with hypertension in an additive genetic model (genotypes CC vs. TC vs. TT; odds ratio (OR) = 1.27 (95% CI, 1.10-1.47; P = 0.001)). The ORs of the TC vs. TT and CC vs. TT genotypes were 1.34 (95% CI, 1.10-1.63; P = 0.003) and 1.52 (95% CI, 1.10-2.12; P = 0.014), respectively. The risk C-allele was associated with increased SBP (βadj ± SEM = 1.307±0.515; P = 0.011) levels in the controls and decreased plasma renin activity (PRA) (βadj ± SEM = -0.053±0.016; P = 0.001) in the subjects with EH. In a stratified analysis of renin-angiotensin-aldosterone-system (RAAS)-related antagonists, the C-allele was significantly associated with decreased serum potassium (K(+)) (βadj ± SEM = -0.093±0.028; P = 0.001) and PRA (βadj ± SEM = -0.067±0.023; P = 0.003) levels in patients with EH who were not taking RAAS-related antagonists. These results remained statistically significant after correction for multiple corrections. Conclusions The SNP rs11191548, near the CYP17A1 gene, was associated with hypertension and SBP in a Chinese Han population. The rs11191548 polymorphism was also related to lower PRA and K(+) levels, suggesting that it has an effect on the enzymatic activity of CYP17A1.

Rare missense P450c17 (CYP17A1) mutation in exon 1 as a cause of 46,XY disorder of sexual development: implications of breast tissue 'unresponsiveness' despite adequate estradiol substitution

17-Alpha-hydroxylase/17,20-lyase deficiency (17OHD) is a rare autosomal recessive disorder resulting from mutations in the CYP17A1 gene, leading to impaired adrenal and gonadal steroidogenesis. We report for the first time a patient with a missense mutation at codon 96 (R96Q) of the CYP17A1 gene causing a 46,XY disorder of sexual development (DSD) that additionally showed lack of breast development despite highly dosed estradiol replacement treatment. This phenomenon could be attributed to irreversible breast tissue alterations following high serum progesterone levels.

Understanding the genetic aetiology in patients with XY DSD

BACKGROUND

Disorders of sex development (DSD) consist of a wide range of disorders and are commoner in those with an XY karyotype. In over half of these cases who have a 46,XY karyotype and who are raised as boys, the underlying aetiology remains unclear.

AREAS OF AGREEMENT

Identification of the underlying genetic abnormality may predict long-term outcome. However, genetic abnormalities that are associated with XY DSD manifest themselves with a wide range of phenotype. To understand the aetiology as well as the phenotypic variation, there is a need to harness the advanced genetic technology that is now available.

AREAS OF CONTROVERSY

The point at which genetic analysis should be undertaken in the course of investigations is unclear. In addition, there is little agreement on the most effective approach for genetic analysis that will be of clinical benefit to the patient.

AREAS TIMELY FOR DEVELOPING RESEARCH

There is a need to understand and improve the clinical utility of genetic analysis in the clinical setting of the patient with a suspected DSD. This will be even more important when parallel gene sequencing identifies variations in multiple genes.

Genome-wide matching of genes to cellular roles using guilt-by-association models derived from single sample analysis

Background

High-throughput methods that ascribe a cellular or physiological function for each gene product are useful to understand the roles of genes that have not been extensively characterized by molecular or genetic approaches. One method to infer gene function is "guilt-by-association", in which the expression pattern of a poorly characterized gene is shown to co-vary with the expression of better-characterized genes. The function of the poorly characterized gene is inferred from the known function(s) of the well-described genes. For example, genes co-expressed with transcripts that vary during the cell cycle, development, environmental stresses, and with oncogenesis have been implicated in those processes.

Findings

While examining the expression characteristics of several poorly characterized genes, we noted that we could associate each of the genes with a cellular phenotype by correlating individual gene expression changes with gene set enrichment scores from individual samples. We evaluated the effectiveness of this approach using a modest sized gene expression data set (expO) and a compendium of gene expression phenotypes (MSigDBv3.0). We found the transcripts that correlated best with enrichment in mitochondrial and lysosomal gene sets were mostly related to those processes (89/100 and 44/50, respectively). The reciprocal evaluation, ranking gene sets according to correlation of enrichment with an individual gene’s expression, also reflected known associations for prominent genes in the biomedical literature (16/19). In evaluating the model, we also found that 4% of the genome encodes proteins that are associated with small molecule and small peptide signal transduction gene sets, implicating a large number of genes in both internal and external environmental sensing.

Conclusions

Our results show that this approach is useful to infer functions of disparate sets of genes. This method mirrors the biological experimental approaches used by others to associate individual genes with defined gene expression changes. Moreover, the approach can be used beyond discovering genes related to a cellular process to discover meaningful expression phenotypes from a compendium that are associated with a given gene. The effectiveness, versatility, and breadth of this approach make possible its application in a variety of contexts and with a variety of downstream analyses.

A missense mutation in the human cytochrome b5 gene causes 46,XY disorder of sex development due to true isolated 17,20 lyase deficiency

CONTEXT

Isolated 17,20 lyase deficiency is commonly defined by apparently normal 17α-hydroxylase activity but severely reduced 17,20 lyase activity of the bifunctional enzyme cytochrome P450 (CYP) enzyme 17A1 (CYP17A1), resulting in sex steroid deficiency but normal glucocorticoid and mineralocorticoid reserve. Cytochrome b5 (CYB5A) is thought to selectively enhance 17,20 lyase activity by facilitating the allosteric interaction of CYP17A1 with its electron donor P450 oxidoreductase (POR).

OBJECTIVE

We investigated a large consanguineous family including three siblings with 46,XY disorder of sex development (DSD) presenting with isolated 17,20 lyase deficiency.

DESIGN

We investigated the clinical and biochemical phenotype, conducted genetic analyses, and functionally characterized the identified CYB5A mutation in cell-based CYP17A1 coexpression assays.

RESULTS

All three siblings presented with 46,XY DSD, sex steroid deficiency, normal mineralocorticoids and glucocorticoids, and a urine steroid metabolome suggestive of isolated 17,20 lyase deficiency. CYP17A1 and POR sequences were normal, but we detected a homozygous CYB5A missense mutation (g.28,400A→T; p.H44L). Functional in vitro analysis revealed normal CYP17A1 17α-hydroxylase activity but severely impaired 17,20 lyase activity. In silico analysis suggested the disruption of CYB5A heme binding by p.H44L.

CONCLUSION

We have identified the first human CYB5A missense mutation as the cause of isolated 17,20 lyase deficiency in three individuals with 46,XY DSD. Detailed review of previously reported cases with apparently isolated 17,20 lyase deficiency due to mutant CYP17A1 and POR reveals impaired 17α-hydroxylase activity as assessed by steroid metabolome analysis and short cosyntropin testing. This suggests that truly isolated 17,20 lyase deficiency is observed only in individuals with inactivating CYB5A mutations.

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.

Inherited forms of mineralocorticoid hypertension

PURPOSE OF REVIEW

Inherited forms of mineralocorticoid hypertension are a group of monogenic disorders that, although rare, have enlightened our understanding of normal physiology, and subsequent processes implicated in the pathogenesis of 'essential' hypertension. They often present in early life and can be a cause of major morbidity and mortality that can be effectively treated with simple but targeted pharmacological therapy. Interestingly, all the conditions centre on the regulation of sodium transport through its epithelial channel, either directly or through mediators that act via the mineralocorticoid receptor.

RECENT FINDINGS

In recent years, molecular mechanisms of these conditions and their functional consequences have been elucidated. Diagnosis has been facilitated by plasma and urinary biomarkers.

SUMMARY

We provide an overview and diagnostic approach to apparent mineralocorticoid excess, glucocorticoid remediable aldosteronism, familial hyperaldosteronism type 2, Liddle's syndrome, Gordon's syndrome, activating mutations of the mineralocorticoid receptor, generalized glucocorticoid resistance and hypertensive forms of congenital adrenal hyperplasia.