Partial deficiency of 17α-hydroxylase/17,20-lyase caused by a novel missense mutation in the canonical cytochrome heme-interacting motif

Rare forms of congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders due to pathogenic variants in genes encoding enzymes and cofactors involved in adrenal steroidogenesis. Although 21-hydroxylase, 11β-hydroxylase, 3β-hydroxysteroid dehydrogenase type 2, 17α-hydroxylase/17,20-lyase, P450 oxidoreductase, steroidogenic acute regulatory protein, cholesterol side-chain cleavage enzyme deficiencies are considered within the definition of CAH, the term 'CAH' is often used to refer to '21-hydroxylase deficiency (21OHD)' since 21OHD accounts for approximately 95% of CAH in most populations. The prevalence of the rare forms of CAH varies according to ethnicity and geographical location. In most cases, the biochemical fingerprint of impaired steroidogenesis points to the specific subtypes of CAH, and genetic testing is usually required to confirm the diagnosis. Despite there are significant variations in clinical characteristics and management, most data about the rare CAH forms are extrapolated from 21OHD. This review article aims to collate the currently available data about the diagnosis and the management of rare forms of CAH.

How Is CYP17A1 Activity Altered in Autism? A Pilot Study to Identify Potential Pharmacological Targets

Background: Increasing evidence exists that higher levels of androgens can be found in individuals with autism. Evidence yields to a susceptible role of Cytochrome P450 17A1 (CYP17A1) with its catalyzation of the two distinct types of substrate oxidation by a hydroxylase activity (17-alpha hydroxylase) and C17/20 lyase activity. However, to what extent steps are altered in affected children with autism versus healthy controls remains to be elucidated. Methods: Urine samples from 48 boys with autism (BMI 19.1 ± 0.6 kg/m², age 14.2 ± 0.5 years) and a matched cohort of 48 healthy boys (BMI 18.6 ± 0.3 kg/m², 14.3 ± 0.5 years) as well as 16 girls with autism (BMI 17.5 ± 0.7 kg/m², age 13.8 ± 1.0 years) and a matched cohort of 16 healthy girls (BMI 17.2 ± 0.8 kg/m², age 13.2 ± 0.8 years) were analyzed for steroid hormone metabolites by gas chromatography-mass spectrometry. Results: The activity of 17-alpha Hydroxylase increased by almost 50%, whereas activity of 17/20 Lyase activity increased by around 150% in affected children with autism. Furthermore, the concentration of Cortisol was higher as compared to the average increase of the three metabolites TH-Corticosterone, 5α-TH-Corticosterone and TH-11β-DH-Corticosterone, indicating, in addition, a stimulation by the CRH-ACTH system despite a higher enzymatic activity. Discussion: As it was shown that oxidative stress increases the 17/20-lyase activity via p38α, a link between higher steroid hormone levels and oxidative stress can be established. However, as glucocorticoid as well as androgen metabolites showed higher values in subjects affected with autism as compared to healthy controls, the data indicate, despite higher CYP17A1 activity, the presence of increased substrate availability in line with the Cholesterol theory of autism.

Phenotypic Heterogeneity and Fertility Potential of Patients With 17-Hydroxylase/17,20-lyase Deficiency

CONTEXT

17α-Hydroxylase/17,20-lyase deficiency (17OHD) is caused by a human CYP17A1 gene mutation and has the classical phenotype of hypertension, hypokalemia, sexual infantilism, and primary amenorrhea in females (46,XX) and disorders of sexual development in males (46,XY). To date, few cases of 17OHD have been reported, and the likelihood of pregnancy has rarely been explored.

OBJECTIVE

To study the clinical characteristics, phenotype heterogeneity, genotyping, and the likelihood of pregnancy of patients with 17OHD.

DESIGN

Genotype analysis was performed by direct sequencing of the CYP17A1 gene and next-generation sequencing in nonclassical patients. In vitro enzyme activity assays and 3-dimensional structure observations were used to assess the function of 3 missense mutations of the CYP17A1 gene. Progestin-primed ovarian stimulation (PPOS) was chosen for ovulation induction in 2 patients.

RESULTS

Eight mutations were identified from 13 patients, including the homozygous mutations p. N395D and p. R496C and compound heterozygous mutations p. Y329fs/p. A421A and p. I332T/p. D487_F489del in 4 nonclassical patients. For the 3 missense mutations, an in vitro functional study showed mild impairment of 17α-hydroxylase activities 15.3-25.0% but residual 17,20-lyase activities 6.6%-9.4%. Two 46,XX females succeeded in pregnancy and delivery by combined PPOS, in vitro fertilization embryo transfer (IVF-ET), and the use of low-dose glucocorticoids.

CONCLUSIONS

Partial 17OHD present nonclassical clinical features, without hypertension and hypokalemia. Successful pregnancy in such 46,XX patients could be attained by the appropriate choice of ovulation induction regimen, precise dose of glucocorticoid to reduce progesterone levels, and the use of IVF-ET.

Genotypic Sex and Severity of the Disease Determine the Time of Clinical Presentation in Steroid 17α-Hydroxylase/17,20-Lyase Deficiency

CONTEXT

Steroid 17α-hydroxylase/17,20-lyase deficiency (17OHD) is characterized by decreased sex steroids and cortisol, and excessive mineralocorticoid action. The clinical symptoms of hypocortisolemia are subtle.

AIM

The clinical, biochemical, and molecular characteristics of patients with 17OHD were evaluated to determine the factors influencing the time of diagnosis and the management.

PATIENTS AND METHODS

Clinical data, steroid profiles by liquid chromatography-tandem mass spectrometry, and Sanger sequencing of the CYP17A1 gene was evaluated in 12 patients with 17OHD diagnosed between 2004 and 2020.

RESULTS

Median age of diagnosis was 13.9 (range: 0.04-29.5) years. Ten of 12 patients had 46,XY karyotype. Except for one boy with partial 17OHD, all patients had female external genitalia hence raised as females. The clinical presentation of 17OHD was earlier (median age: 7 years) in patients, who presented with severe hypertension, atypical genitalia, or positive family history (n = 6, 50%) than those without (median age: 15.3 years; p = 0.0005). The latter group presented with amenorrhea (n = 6, 50%). Steroid profile of patients uniformly showed a typical pattern of 17OHD regardless of the age at diagnosis. Serum gonadotropin concentrations were elevated in patients >12 years (n = 7), normal in pre-adolescents (n = 4), and low in a patient, who had a digenic inheritance of homozygous CYP17A1 and KISS1R mutations.

CONCLUSIONS

Early clinical presentation and diagnosis in 17OHD are associated with symptomatic hypertension in both 46,XX and 46,XY patients or inadequate virilization of external genitalia in 46,XY partial 17OHD. In the absence of these, the clinical presentation is at late pubertal ages at which time amenorrhea and elevated gonadotropins are the hints for diagnosis.

17α-hydroxylase/17,20-lyase deficiency in 46, XY: our experience and review of literature

Context

There are more than 100 pathogenic variants in CYP17A1 that have been identified in patients with 17α-hydroxylase/17,20-lyase deficiency (17OHD).

Objective

We aimed to describe 46,XY patients with 17OHD from our center and review the literature.

Methods

We retrospectively analyzed genetically proven index cases of 17OHD from our 46,XY disorders of sex development cohort and reviewed similar cases from the literature (n = 150). Based on the phenotype, 17OHD probands were classified into combined severe deficiency (n = 128) and combined partial deficiency (n = 16). Additionally, patients with the apparent isolated 17,20-lyase deficiency (n = 7, from 6 families) were noted. Residual enzyme activities with the observed mutant enzymes were divided in 2 categories as < 1% and ≥ 1%, each for hydroxylase and lyase.

Results

We present 4 index cases of 46,XY 17OHD with a complete spectrum of undervirilization and 2 novel variants in CYP17A1. In the review, the combined severe deficiency was the most common form, with more frequent female sex of rearing, hypertension, hypokalemia, suppressed renin, higher plasma corticotropin, lower serum cortisol, and androgens. Immunoassay-measured serum aldosterone was frequently (68.2%) unsuppressed (>5 ng/dL). Elevated serum progesterone had high sensitivity for diagnosis of combined 17OHD, even in combined partial deficiency (83.3%). Among patients with clinical phenotype of combined severe deficiency, 11.5% had partial 17α-hydroxylase and complete 17,20-lyase deficiency (>1%/<1%) and had significantly higher serum cortisol than those with < 1%/<1% activity.

Conclusion

We report the first monocentric case series of Asian Indian 46,XY patients with 17OHD. We propose that a phenotype of severe undervirilization with milder cortisol deficiency may represent a distinct subtype of combined severe 17OHD with residual 17α-hydroxylase activity but severe 17,20-lyase deficiency (>1%/<1%), which needs further validation.

Reproductive endocrine characteristics and in vitro fertilization treatment of female patients with partial 17α-hydroxylase deficiency: Two pedigree investigations and a literature review

BACKGROUND

17α-hydroxylase/17, 20-lyase deficiency (17-OHD) is caused by the mutations of the CYP17A1 gene. The classical phenotype of 17-OHD includes hypertension, hypokalemia, and abnormal sexual development, with partial 17-OHD typically less severe than the complete deficiency. Infertility is always one of the main clinical manifestations of partial 17-OHD. However, to date, the pregnancy potentials of partial 17-OHD female patients have rarely been investigated, and few live-birth cases have been reported among them. Moreover, the reproductive endocrine characteristics of partial 17-OHD female patients have not been completely clarified and the treatment skills of in vitro fertilization and embryo transfer (IVF-ET) have not been well summarized yet.

METHODS

Two Chinese infertile female patients clinically diagnosed as partial 17-OHD were enrolled and their pedigree investigations were performed. Hormones were determined to depict the endocrine conditions of partial 17-OHD female patients. The adrenocorticotropic hormone (ACTH) stimulation test was performed to evaluate the functions of the adrenal cortex. Genotype analysis was conducted by next-generation sequencing (NGS) and Sanger sequencing was used to verify the results. IVF-ET was performed for the treatment of their infertility. Specifically, the progestin-primed ovarian stimulation (PPOS) protocol was chosen for the controlled ovarian hyperstimulation (COH) cycles, and the hormone replacement treatment (HRT) protocol was adopted for the endometrial preparation in frozen-thawed embryo transfer (FET) cycles.

RESULTS

Hormone assays revealed a reduced estradiol (E2) and testosterone (T) level, and an elevated progesterone (P4) level. The classic ACTH stimulating test evidenced a suboptimal response of cortisol to ACTH. Genotype analysis demonstrated that the proband1 carried two variants: c.1459_1467del (p.Asp487_Phe489del)^het and c.995T>C (p.lle332Thr)^het. The proband2 was found to be a homozygote with the mutation of c.1358T>A (p.Phe453Ser)^hom. The two female patients both succeeded in pregnancy and delivery of healthy babies through IVF-ET, with the usage of PPOS, HRT, and low-dose glucocorticoids.

CONCLUSIONS

Partial 17-OHD female patients manifested menstrual cycle disorders and infertility clinically; displayed high P4 and low E2 and T; showed sparse pubic hair in physical examinations; and revealed multiple ovarian cysts in ultrasonic visualization. Moreover, the pregnancy potentials of infertile partial 17-OHD women seemed to increase with the adoption of IVF-ET. Considering the sustained elevated P4 level, PPOS is a feasible protocol for them in COH.

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.

Clinical and Genetic Characteristics of 17 α-Hydroxylase/17, 20-Lyase Deficiency: c.985_987delTACinsAA Mutation of CYP17A1 Prevalent in the Chinese Han Population

OBJECTIVE

17 α-hydroxylase/17, 20-lyase deficiency (17-OHD) is a rare recessive hereditary disease that can be attributed to cytochrome P450 17 α-hydroxylase deficiency caused by CYP17A1 gene mutations.

METHODS

A large cohort of 10 Chinese Han patients with 17-OHD from 2012 to 2020 were enrolled. The clinical and biochemical features were investigated, and genetic mutations of CYP17A1 were analyzed by polymerase chain reaction-Sanger sequencing. Karyotype identification and the SRY gene test were also carried out. In silico analysis was used to predict the effects of genetic mutations on the protein function.

RESULTS

All patients were female. Common complaints were hypertension, hypokalemia, and primary amenorrhea. The karyotype was 46, XY, and the SRY gene was detected in 7 patients; the karyotype was XX in the remaining 3 patients. A total of 7 mutations including Y329N, Y329X, Y329Lfs∗, R96W, A82D, S380N, and A487_P489del have been identified in the CYP17A1 gene. The Y329Lfs∗ mutation was found in 9/10 (90%) of patients with a high allele frequency of 70%. In silico prediction showed that a novel variant of c.1139G>A (S380N) occurs at a conserved residue and can cause disease.

CONCLUSION

We presented a detailed description of the clinical and genetic characteristics in Chinese patients with 17-OHD and concluded that Y329Lfs∗ mutation of CYP17A1 is prevalent in the Chinese Han population. Therefore, hotspot screening by polymerase chain reaction-Sanger sequencing for exon 6 of CYP17A1 could contribute to the rapid diagnosis of 17-OHD in China. Genetic counseling based on the genetic diagnosis for at-risk relatives is advised.

Hereditary causes of primary aldosteronism and other disorders of apparent excess mineralocorticoid activity

Secondary hypertension is a common condition with a broad differential diagnosis. Identification of the true cause of hypertension can be critical for guiding appropriate management. Here, we review hereditary conditions underlying the most common cause of secondary hypertension, primary aldosteronism, as well as other disorders impacting various levels of mineralocorticoid action. Recently, several pathogenic variants of ion channels have been described as etiologies of familial aldosteronism. Defects in steroid hormone synthesis cause hypertension in 11β-hydroxylase deficiency and 17α-hydroxylase deficiency, two types of congenital adrenal hyperplasia. Inappropriate activation of mineralocorticoid receptors underlies the syndrome of apparent mineralocorticoid excess and constitutive activation of the mineralocorticoid receptor. Finally, Liddle syndrome and pseudohypoaldosteronism type 2 are disorders impacting the function of renal sodium channels, the endpoint of mineralocorticoid action. We discuss the pathophysiology, clinical presentation, diagnosis and management of these low renin hypertension states that ultimately result in apparent excess mineralocorticoid activity.

A Novel Compound Heterozygous CYP17A1 Variant Causes 17α-Hydroxylase/17, 20-Lyase Deficiency

Background: Congenital adrenal hyperplasia (CAH) encompasses a group of autosomal recessive diseases characterized by enzyme deficiencies, within steroid hormone anabolism, which lead to disorders in cortisol synthesis. The 17α-hydroxylase/17,20-lyase deficiency (17-OHD) is an uncommon form of CAH caused by variants in the CYP17A1 gene.

Aims: We report a novel compound heterozygous CYP17A1 variant and its association with the pathogenesis of 17-OHD.

Methods: The patient was assessed for medical history, clinical manifestations, physical examination, laboratory examination, karyotype analysis, and adrenal computed tomography. Mutation screening was conducted using whole-exome sequencing (WES) and Sanger sequencing. The wild-type and mutant CYP17A1 complementary DNAs (cDNAs) were amplified and cloned into a pcDNA3.1(+) vector. These plasmids were transfected transiently into HEK-293T cells. Quantitative PCR and Western blotting analysis were performed to measure the expression level of P450c17. An enzymatic activity assay was conducted to measure the content of 17-hydroxyprogesterone (17-OHP) and dehydroepiandrosterone (DHEA) in medium using liquid chromatography–tandem mass spectrometry (LC-MS/MS).

Results: The proband was characterized by 17-OHD with rhabdomyolysis, hypokalemia, and adrenal insufficiency. Novel compound heterozygous variants of the CYP17A1 gene (c.1304T > C/p.Phe435Ser and c.1228delG/p.Asp410Ilefs*9) were identified. The enzymatic activity assay revealed that this variant resulted in a complete deficiency of 17α-hydroxylase and 17,20-lyase activity. This was consistent with the hormonal characteristics of the proband’s blood.

Conclusions: These results suggest that the compound heterozygous variant of c.1304T > C and c.1228delG of the CYP17A1 gene can lead to 17-OHD. Our findings thus provide a novel insight into the clinical evaluations and molecular basis of 17-OHD.

The CYP79A1 catalyzed conversion of tyrosine to (E)-p-hydroxyphenylacetaldoxime unravelled using an improved method for homology modeling

The vast diversity and membrane-bound nature of plant P450s makes it challenging to study the structural characteristics of this class of enzymes especially with respect to accurate intermolecular enzyme-substrate interactions. To address this problem we here apply a modified hybrid structure strategy for homology modeling of plant P450s. This allows for structural elucidation based on conserved motifs in the protein sequence and secondary structure predictions. We modeled the well-studied Sorghum bicolor cytochrome P450 CYP79A1 catalyzing the first step in the biosynthesis of the cyanogenic glucoside dhurrin. Docking experiments identified key regions of the active site involved in binding of the substrate and facilitating catalysis. Arginine 152 and threonine 534 were identified as key residues interacting with the substrate. The model was validated experimentally using site-directed mutagenesis. The new CYP79A1 model provides detailed insights into the mechanism of the initial steps in cyanogenic glycoside biosynthesis. The approach could guide functional characterization of other membrane-bound P450s and provide structural guidelines for elucidation of key structure-function relationships of other plant P450s.

Steroid 17-hydroxylase and 17,20-lyase deficiencies, genetic and pharmacologic

Steroid 17-hydroxylase 17,20-lyase (cytochrome P450c17, P450 17A1, CYP17A1) catalyzes two major reactions: steroid 17-hydroxylation followed by the 17,20-lyase reactions. The most severe mutations in the cognate CYP17A1 gene abrogate all activities and cause combined 17-hydroxylase/17,20-lyase deficiency (17OHD), a biochemical phenotype that is replicated by treatment with the potent CYP17A1 inhibitor abiraterone acetate. The adrenals of patients with 17OHD synthesize 11-deoxycorticosterone (DOC) and corticosterone but no 19-carbon steroids, similar to the rodent adrenal, and DOC causes hypertension and hypokalemia. Loss of 17,20-lyase activity precludes sex steroid synthesis and leads to sexual infantilism. Rare missense CYP17A1 mutations minimally disrupt 17-hydroxylase activity but cause isolated 17,20-lyase deficiency (ILD), Mutations in the POR gene encoding the required cofactor protein cytochrome P450-oxidoreductase causes a spectrum of disease from ILD to 17OHD combined with 21-hydroxylase and aromatase deficiencies, sometimes including skeletal malformations. Mutations in the CYB5A gene encoding a second cofactor protein cytochrome b₅ also selectively disrupt 17,20-lyase activity and cause the purest form of ILD. The clinical manifestations of these conditions are best understood in the context of the biochemistry of CYP17A1.

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.