Eight novel mutations of the androgen receptor gene in patients with androgen insensitivity syndrome

Clinical, Biochemical, and Molecular Characterization of Indian Children with Clinically Suspected Androgen Insensitivity Syndrome

This study describes the clinical, biochemical, and molecular characteristics of Indian children with 46,XY DSD and suspected androgen insensitivity syndrome (AIS). Fifty children (median age 3.0 years, range 0-16.5 years) with 46,XY DSD and a suspected diagnosis of AIS were enrolled. Sanger sequencing was performed to identify pathogenic variants in the androgen receptor (AR) gene and to study genotype-phenotype correlations. All 5 (100%) patients with CAIS and 14/45 (31%) patients with PAIS had pathogenic/likely pathogenic variants in the AR gene (overall, 14 different variants in 19 patients; 38.8%). There was no significant difference in clinical (cryptorchidism, hypospadias, or external masculinizing score) or biochemical parameters (gonadotropins and testosterone) between patients with or without pathogenic variants. However, patients with AIS were more likely to have a positive family history, be assigned female gender at birth, and present with gynaecomastia at puberty. Three novel pathogenic/likely pathogenic variants, including one splice donor site variant c.2318+1G>A, one frameshift variant p.H790Lfs*40, and one missense variant p.G821E, were identified in 3 patients with CAIS. The missense variant p.G821E was predicted as deleterious, damaging, disease-causing, and likely functionally inactive by in silico analysis and protein modelling study. Two previously not reported pathogenic/likely pathogenic variants, including p.R386H and p.G396R, were identified in patients with PAIS. This study contributes in expanding the spectrum of pathogenic variants in the AR gene in patients with AIS. Only 31% patients with a provisional diagnosis of PAIS had pathogenic variants in the AR gene, suggesting other possible mechanisms or candidate genes may be responsible for such a phenotypic presentation.

Monitoring dynamic cytotoxic chemotherapy response in castration-resistant prostate cancer using plasma cell-free DNA (cfDNA)

Objective

Cell-free DNA (cfDNA) is an attractive cancer biomarker, as it is thought to reflect a component of the underlying genetic makeup of the tumor and is readily accessible in serial fashion. Because chemotherapy regimens are expected to act rapidly on cancer and cfDNA is cleared from the blood within minutes, we hypothesized that cfDNA would reflect immediate effects of treatment. Here, we developed a method for monitoring long cfDNA fragments, and report dynamic changes in response to cytotoxic chemotherapy.

Results

Peripheral blood was obtained from 15 patients with metastatic castration-resistant prostate cancer (CRPC) immediately before and after cytotoxic chemotherapy infusion. cfDNA was extracted and quantified for long interspersed nuclear elements (LINE1; 297 bp) using qPCR. Targeted deep sequencing was performed to quantify the frequency of mutations in exon 8 of the androgen receptor (AR), a mutational hotspot region in CRPC. Single nucleotide mutations in AR exon 8 were found in 6 subjects (6/15 = 40%). Analytical variability was minimized by pooling independent PCR reactions for each library. In 5 patients, tumor-derived long cfDNA levels were found to change immediately after infusion. Detailed analysis of one subject suggests that cytotoxic chemotherapy can produce rapidly observable effects on cfDNA.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4312-2) contains supplementary material, which is available to authorized users.

Investigation of androgen receptor gene mutations in a series of 21 patients with 46,XY disorders of sex development

AIM

Androgen receptor (AR) gene mutations are the leading cause of 46,XY disorders of sex development (DSD) and are associated with varying degrees of androgen insensitivity. The aim of this study is to investigate AR gene mutations in 46,XY DSD patients with normal testosterone secretion, either normal or high testosterone/dihydrotestosterone (T/DHT) ratio and normal SRD5A2 gene analysis, collectively, suggestive of androgen insensitivity syndrome (AIS).

METHODS

We direct sequenced all eight exons of the AR gene in 21 index patients with varying degrees of undervirilization.

RESULTS

We detected AR gene alterations in five patients. In patients with complete AIS we found p.Val30Met in exon 1 and p.Gly689* in exon 4. One patient with partial AIS had p.Gln712Glu in exon 4. In two patients with partial phenotype, we found common p.Glu213Glu (c.639G>A) SNP, and an additional p.Ile817Ile (c.2451T>C) mutation was found in one of these two patients.

DISCUSSION

Despite the fact that T/DHT ratio is frequently used in diagnosis of AIS, lack of precisely determined cutoffs compromises correct diagnosis. Hence, depending on clinical and biochemical findings solely may delay correct diagnosis. Direct sequence analysis of the AR is essential for precise diagnosis of AIS.

Complete androgen insensitivity syndrome in juveniles and adults with female phenotypes

AIM

To report on six cases of the diagnosis and treatment of patients with complete androgen insensitivity syndrome (CAIS) and a review of the relevant published work.

METHODS

A retrospective analysis was performed on the clinical features, diagnosis and treatment of a total of six patients with CAIS who were admitted to our hospital between September 1985 and June 2012. All surgical patients were examined for sex chromosomes and sex hormone levels pre- and postoperatively, respectively, and underwent lower abdominal B ultrasounds and pathological examinations among other tests.

RESULTS

Five of the patients were treated with castration, one patient aged 5 years was treated conservatively Tissue from surgical resections showed normal testicular tissue that comprised Leydig cells and Sertoli cells, and pathological examinations showed no sign of testicular cancer. Following corrective operations, postoperative complications, such as female secondary sexual characteristics, stagnation and osteoporosis, have not developed. Sex hormone level ratio changed significantly after being treated with castration compared with preoperative levels; mainly testosterone and estrogen decreased significantly (P < 0.05), while luteinizing hormone and follicle-stimulating hormone significantly increased (P < 0.05). However, prolactin did not change significantly (P > 0.05).

CONCLUSION

The study show that removal of the testes in CAIS patients after puberty is safe and reliable. Meanwhile, it is essential to provide a hormone drug after being treated with castration. Further studies are needed to evaluate the safety and the quality of life for CAIS patients.

Understanding nuclear receptors using computational methods

Nuclear receptors (NRs) are important targets for therapeutic drugs. NRs regulate transcriptional activities through binding to ligands and interacting with several regulating proteins. Computational methods can provide insights into essential ligand-receptor and protein-protein interactions. These in turn have facilitated the discovery of novel agonists and antagonists with high affinity and specificity as well as have aided in the prediction of toxic side effects of drugs by identifying possible off-target interactions. Here, we review the application of computational methods toward several clinically important NRs (with special emphasis on PXR) and discuss their use for screening and predicting the toxic side effects of xenobiotics.

A novel mutation F826L in the human androgen receptor in partial androgen insensitivity syndrome; increased NH2-/COOH-terminal domain interaction and TIF2 co-activation

A novel mutation F826L located within the ligand binding domain (LBD) of the human androgen receptor (AR) was investigated. This mutation was found in a boy with severe penoscrotal hypospadias (classified as 46,XY DSD). The AR mutant F826L appeared to be indistinguishable from the wild-type AR, with respect to ligand binding affinity, transcriptional activation of MMTV-luciferase and ARE2-TATA-luciferase reporter genes, protein level in genital skin fibroblasts (GSFs), and sub-cellular distribution in transfected cells. However, an at least two-fold higher NH2-/COOH-terminal domain interaction was found in luciferase and GST pull-down assays. A two-fold increase was also observed for TIF2 (transcription intermediary factor 2) co-activation of the AR F826L COOH-terminal domain. This increase could not be explained by a higher stability of the mutant protein, which was within wild-type range. Repression of transactivation by the nuclear receptor co-repressor (N-CoR) was not affected by the AR F826L mutation. The observed properties of AR F826L would be in agreement with an increased activity rather than with a partial defective AR transcriptional activation. It is concluded that the penoscrotal hypospadias in the present case is caused by an as yet unknown mechanism, which still may involve the mutant AR.

Sex-reversed phenotype in association with two novel mutations c.2494delA and c.T3004C in the ligand-binding domain of the androgen receptor gene

OBJECTIVE

To establish the diagnosis of complete androgen insensitivity syndrome (CAIS) in two patients with characteristic clinical and hormonal findings, relative family history in one of them, and unusual Müllerian remnants in the other.

DESIGN

Case report.

SETTING

Research laboratory in the Department of Medical Genetics at a university children's hospital.

PATIENT(S)

Two patients with 46,XY sex reversal and two maternal aunts of the first patient with the same clinical condition were tested.

INTERVENTION(S)

Bilateral gonadectomy was performed on both patients.

MAIN OUTCOME MEASURE(S)

Genetic counseling, cancer prophylaxis, hormone substitution therapy.

RESULT(S)

Molecular analysis revealed two novel mutations, a frameshift familial (c.2494delA) in patient 1 and a missense sporadic (c.T3004C) in patient 2. The c.2494delA mutation was also detected in two of the three affected maternal aunts of patient 1. Patient 2 presents an unusual persistence of Müllerian structures.

CONCLUSION(S)

Genetic counseling of potential women carriers of androgen receptor (AR) mutations is crucial for the early diagnosis of the affected offspring. The presence of Müllerian remnants, although rare, should not exclude the diagnosis of CAIS. Both identified mutations are novel and provide further evidence for the correlation between specific AR mutations and phenotype.

Comparison of crystal structures of human androgen receptor ligand-binding domain complexed with various agonists reveals molecular determinants responsible for binding affinity

Androgens exert their effects by binding to the highly specific androgen receptor (AR). In addition to natural potent androgens, AR binds a variety of synthetic agonist or antagonist molecules with different affinities. To identify molecular determinants responsible for this selectivity, we have determined the crystal structure of the human androgen receptor ligand-binding domain (hARLBD) in complex with two natural androgens, testosterone (Testo) and dihydrotestosterone (DHT), and with an androgenic steroid used in sport doping, tetrahydrogestrinone (THG), at 1.64, 1.90, and 1.75 A resolution, respectively. Comparison of these structures first highlights the flexibility of several residues buried in the ligand-binding pocket that can accommodate a variety of ligand structures. As expected, the ligand structure itself (dimension, presence, and position of unsaturated bonds that influence the geometry of the steroidal nucleus or the electronic properties of the neighboring atoms, etc.) determines the number of interactions it can make with the hARLBD. Indeed, THG--which possesses the highest affinity--establishes more van der Waals contacts with the receptor than the other steroids, whereas the geometry of the atoms forming electrostatic interactions at both extremities of the steroid nucleus seems mainly responsible for the higher affinity measured experimentally for DHT over Testo. Moreover, estimation of the ligand-receptor interaction energy through modeling confirms that even minor modifications in ligand structure have a great impact on the strength of these interactions. Our crystallographic data combined with those obtained by modeling will be helpful in the design of novel molecules with stronger affinity for the AR.

Sexualmedizinische Aspekte bei Intersexsyndromen

Disorders of somatosexual development that lead to ambiguous genitalia occur in one from 3,000-5,000 newborns. Parents and health care professionals are confronted with a number of crucial questions: to what sex should the child be assigned, what is the appropriate treatment in terms of hormonal and surgical interventions, when and how should these take place, and what impact do they have on the development of gender identity (GI), psychosexual well-being and fertility? This paper reviews the etiology, treatment and outcome in terms of GI and sexual health for the following syndromes: congenital adrenal hyperplasia (CAH), complete and partial androgen insensitivity (cAIS, pAIS), and pure and mixed gonadal dysgenesis (pGD, mGD). Emphasis is focussed on the current discussion involving the timing and extent of genital surgery. Finally, a procedure is introduced that covers the sexual-medical needs of patients, parents and health care professionals.

Novel and Recurrent Mutations in Patients with Androgen Insensitivity Syndromes

BACKGROUND/AIMS

Androgen insensitivity syndrome (AIS) caused by mutations within the androgen receptor gene represents a variety of phenotypes from females with 46,XY karyotype over individuals with ambiguous genitalia to infertile males.

METHODS

We studied 24 patients with AIS by sequencing androgen receptor gene. 19 of the investigated patients were affected by complete androgen insensitivity syndrome (CAIS) and 5 suffered from partial androgen insensitivity syndrome (PAIS).

RESULTS

So far we have detected 12 unreported mutations as well as 9 recurrent mutations (3 recurrent mutations were detected twice) in exons 2-8 of the androgen receptor gene. Three of the novel mutations cause a frameshift with subsequent premature termination and were found in patients with CAIS. These frameshifts were induced by single nucleotide deletion or insertion, or in one case by a 13-bp deletion, respectively. Another premature stop codon found in a CAIS patient results from an already reported nucleotide substitution in exon 5. Furthermore, in a CAIS patient we found a novel duplication of codon 788. All other mutations caused single base substitutions spread through exons 2-8 and were associated with CAIS or PAIS.

CONCLUSIONS

We report a broad spectrum of different mutations within the AR gene leading to various manifestations of AIS. Apart from truncating mutations, a reliable genotype/phenotype correlation cannot be established. Therefore, modifying factors must be effective.

Mutation of histidine 874 in the androgen receptor ligand-binding domain leads to promiscuous ligand activation and altered p160 coactivator interactions

The androgen receptor (AR) signaling pathway is a major therapeutic target in the treatment of prostate cancer. The AR functions as a ligand-activated transcription factor in the presence of the cognate hormone ligands testosterone and dihydrotestosterone (DHT). We have characterized a highly conserved sequence at the C-terminal end of helix 10/11 in the ligand-binding domain (LBD), which is prone to receptor point mutations in prostate cancer. This sequence includes threonine 877 that is involved in hydrogen bonding to the D ring of the steroid molecule and leads to promiscuous ligand activation of the AR when mutated to alanine or serine. A second mutation in this region, H874Y, also results in a receptor protein that has broadened ligand-binding specificity, but retains an affinity for DHT (K(d) = 0.77 nm) similar to that of the wild-type receptor. The structure of the mutant LBD, expressed in Escherichia coli, is not dramatically altered compared with the wild-type AR-LBD in the presence of DHT, but shows a modestly increased sensitivity to protease digestion in the absence of hormone. This mutant AR showed wild-type AR-LBD/N-terminal domain interactions, but significantly enhanced binding and transactivation activity with all three members of the p160 family of coactivator proteins. Together, these phenotypic changes are likely to confer a selective advantage for tumor cells in a low androgen environment resulting from hormone therapy.

Cofactor Hydrogen Bonding onto the Protein Main Chain Is Conserved in the Short Chain Dehydrogenase/Reductase Family and Contributes to Nicotinamide Orientation

Human estrogenic 17beta-hydroxysteroid dehydrogenase (17beta-HSD1), a member of the short chain dehydrogenase/reductase (SDR) family, is responsible for the biosynthesis of all active estrogens. The crystal structures of two C19-steroid ternary complexes (17beta-HSD1-androstanedione-NADP and 17beta-HSD1-androstenedione-NADP) reveal the critical role of Leu149 in regulating the substrate specificity and provide novel insight into the different fates of a conserved glutamate residue in the estrogen-specific proteins upon the binding of the keto and hydroxyl groups of steroids. The whole NADP molecule can be unambiguously defined in the NADP binary complex, whereas both ternary complexes show that the nicotinamide moiety of NADP cannot be located in the density maps. In both ternary complexes, the expected position of carboxamide oxygen of NADP is occupied by a water molecule, which makes a bifurcated hydrogen bond with the O3 of C19-steroid and the main chain nitrogen of Val188. These results demonstrate that the hydrogen bonding interaction between the main chain amide group and the carboxamide group of NAD(P)(H) plays an important role in anchoring the nicotinamide ring to the enzyme. This finding is substantiated by structural analyses of all 33 NAD(P)(H) complexes of different SDR proteins, because 29 structures of 33 show this interaction. This common feature reveals a general mechanism among the SDR family, providing a rational basis for inhibitor design against biologically relevant SDR targets.

Mutation of the androgen receptor (R840S) in an Egyptian patient with partial androgen insensitivity syndrome: review of the literature on the clinical expression of different R840 substitutions

The X-linked androgen insensitivity syndrome (AIS) encompasses a heterogeneous group of defects in the androgen receptor (AR) that result in varying degrees of undermasculinization. In the current study, we characterize the R840S mutation on exon 7 of the AR ligand-binding domain. The Egyptian patient, who had been reared as female, presented ambiguous genitalia at 6.5 yr. Diagnosis of partial AIS (PAIS) was based on clinical phenotype and laboratory evidence of good testosterone response and normal testosterone/dihydrotestosterone (T/DHT) ratio. The therapeutic response to testosterone depot injections justified reassignment to male sex. To our knowledge, this mutation has been reported only once in two Brazilian brothers with PAIS. Three other mutations of this residue (R840C; R840G, nonconservative; and R840H, conservative) have been reported in patients with PAIS and, when expressed in vitro, they led to subnormal transactivation of a reporter gene. Each of these mutations was associated with a very diverse spectrum of phenotypes. These data highlight the role of the AR ligand-binding pocket (LBP) in the expression of transcriptional activity during prenatal sex differentiation.

Extreme androgen resistance in a kindred with a novel insertion/deletion mutation in exon 5 of the androgen receptor gene

Androgen insensitivy syndrome (AIS) is the most frequent cause of male pseudohermaphroditism resulting from target-organ resistance to androgen action. Individuals bearing the complete form of the disease (CAIS) present a female phenotype and a lack of pubic and axillary hair. In the present study, four 46,XY patients born in two generations from a kindred with a history of AIS were examined for genetic abnormalities in the androgen receptor gene (AR). All eight exons encoding the AR protein were individually amplified from genomic DNA followed by a mutation screening with single-strand conformation polymorphism analysis. Sequencing of the mutant AR revealed a novel insertion/deletion mutation in exon 5. A deletion of 7 bp is replaced by an insertion of 11 nucleotides, which represents a duplication of the adjacent downstream sequence. The mutation g.2640_2646delAGGATGC/2652_2662insTTCGCCCCTGA, results in a frameshift that introduces a premature termination signal TGA, nine codons downstream. Such a rearrangement predicts a truncation of the AR, thereby deleting a large portion of the ligand-binding domain (amino acid position 768-919). Furthermore, although this mutation breaks the translational reading frame starting from codon 760, examination of the complementary DNA suggested that it does not disturb mRNA splicing. These changes have been found in all the patients and appear to account for the observed absence of detectable androgen binding to the AR in cultured fibroblasts and for the CAIS phenotype in the kindred. This disorder represents the first insertion/deletion mutation of the AR that probably arose by a slipped-strand mispairing mechanism.

Different inactivating mutations of the mineralocorticoid receptor in fourteen families affected by type I pseudohypoaldosteronism

We have analyzed the human mineralocorticoid receptor (hMR) gene in 14 families with autosomal dominant or sporadic pseudohypoaldosteronism (PHA1), a rare form of mineralocorticoid resistance characterized by neonatal renal salt wasting and failure to thrive. Six heterozygous mutations were detected. Two frameshift mutations in exon 2 (insT1354, del8bp537) and one nonsense mutation in exon 4 (C2157A, Cys645stop) generate truncated proteins due to premature stop codons. Three missense mutations (G633R, Q776R, L979P) differently affect hMR function. The DNA binding domain mutant R633 exhibits reduced maximal transactivation, although its binding characteristics and ED(50) of transactivation are comparable with wild-type hMR. Ligand binding domain mutants R776 and P979 present reduced or absent aldosterone binding, respectively, which is associated with reduced or absent ligand-dependent transactivation capacity. Finally, P979 possesses a transdominant negative effect on wild-type hMR activity, whereas mutations G633R and Q776R probably result in haploinsufficiency in PHA1 patients. We conclude that hMR mutations are a common feature of autosomal dominant PHA1, being found in 70% of our familial cases. Their absence in some families underscores the importance of an extensive investigation of the hMR gene and the role of precise diagnostic procedures to allow for identification of other genes potentially involved in the disease.