Clinical and molecular characteristics in 15 patients with androgen receptor gene mutations from South China

A variety of mutations in the androgen receptor (AR) gene are linked to androgen insensitivity syndrome (AIS) or sexual development disorder. Here, we studied 15 patients with various degrees of disorders of genital hypoplasia from South China. Clinical data including basal hormone level, phenotype, karyotyping and SRY gene identification were documented. Exons with flanking intronic region of the AR gene were sequenced and analysed for mutations, and a total of eight mutations were identified in the AR gene. Of eight mutations, two novel mutations c.2518G>T (p.Asp840Tyr) and c.1186G>C (p.Gly396Arg) were predicted to be damaging by SIFT and Polyphen2 online software. Previously reported mutations: c.528C>A (p.Ser176Arg), c.1789G>A (p.Ala597Thr), c.2612C>T (p.Ala871Val), c.1752C>A (p.Phe584Leu), c.171_172insCTG (p.57_58insLeu) and c.2659A>G (p.Met887Val) were also detected in our subjects. Most of them are involved in hypospadias, penis dysplasia or other disorders of sexual development. A complete AIS case (p.Phe584Leu) with female phenotype and high serum concentrations of dihydrotestosterone (DHT) was also found. This study presented a wide range of spectrum of AIS (from partial AIS to complete AIS) caused by AR mutations in South China population. It suggests that further study with larger data set need to be performed to elucidate the differences of the phenotypes in our study.     

Novel mutation in the ligand-binding domain of the androgen receptor gene (l790p) associated with complete androgen insensitivity syndrome.

Mutations in the X-linked androgen receptor (AR) gene cause androgen insensitivity syndrome (AIS), resulting in an impaired embryonic sex differentiation in 46,XY genetic men. Complete androgen insensitivity (CAIS) produces a female external phenotype, whereas cases with partial androgen insensitivity (PAIS) have various ambiguities of the genitalia. Mild androgen insensitivity (MAIS) is characterized by undermasculinization and gynecomastia. Here we describe a 2-month-old 46,XY female patient, with all of the characteristics of CAIS. Defects in testosterone (T) and dihydrotestosterone (DHT) synthesis were excluded. Sequencing of the AR gene showed the presence in exon 6 of a T to C transition in the second base of codon 790, nucleotide position 2369, causing a novel missense Leu790Pro mutation in the ligand-binding domain of the AR protein. The identification of a novel AR mutation in a girl with CAIS provides significant information due to the importance of missense mutations in the ligand-binding domain of the AR, which are able to induce functional abnormalities in the androgen binding capability, stabilization of active conformation, or interaction with coactivators.     

Is hypospadias a genetic, endocrine or environmental disease, or still an unexplained malformation?

Hypospadias is one of the most frequent genital malformations in the male newborn and results from an abnormal penile and urethral development. This process requires a correct genetic programme, time- and space-adapted cellular differentiation, complex tissue interactions, and hormonal mediation through enzymatic activities and hormonal transduction signals. Any disturbance in these regulations may induce a defect in the virilization of the external genitalia and hypospadias. This malformation thus appears to be at the crossroads of various mechanisms implicating genetic and environmental factors. The genes of penile development (HOX, FGF, Shh) and testicular determination (WT1, SRY) and those regulating the synthesis [luteinizing hormone (LH) receptor] and action of androgen (5α reductase, androgen receptor) can cause hypospadias if altered. Several chromosomal abnormalities and malformative syndromes include hypospadias, from anterior to penoscrotal forms. More recently, CXorf6 and ATF3 have been reported to be involved. Besides these genomic and hormonal factors, multiple substances found in the environment can also potentially interfere with male genital development because of their similarity to hormones. The proportion of hypospadias cases for which an aetiology is detected varies with the authors but it nevertheless remains low, especially for less severe cases. An interaction between genetic background and environment is likely.     

Isolated micropenis reveals partial androgen insensitivity syndrome confirmed by molecular analysis

Partial androgen insensitivity syndrome （PAIS） is the milder variant of androgen receptor （AR） defects. The subtle effects of AR mutations present in a patient with micropenis, peno-scrotal hypospadias, infertility, clitoromegaly and posterior labial fusion. We studied the association of isolated micropenis with the genetic defects resulting in androgen resistance, that is, AR gene defects and 5-α reductase type 2 （SRD5A2） deficiency. We describe two cases of isolated micropenis： one in a 14-year-old boy and the other in a 3-year-old boy who was followed until he was 10 years old. There were no findings of hypospadias, cryptorchidism or gynecomastia in either of these patients. Serum gonadotrophin and androgen levels were obtained and karyotyping was done. Human chorionic gonadotropin （hCG） stimulation testing assessed the functional capacity of the testes. DNA was extracted from peripheral leukocytes, and all exons of the SRD5A2 and AR genes were amplified by polymerase chain reaction and sequenced. In both patients, baseline testosterone （T） level was low and the values were elevated after hCG testing. The sequence of the SRD5A2 gene was normal in patient 1, and a heterozygous polymorphism, V89L, was found in patient 2. Two known mutations, P390S and A870V, were identified in patients 1 and 2, respectively. Mutations in the AR gene can be associated with isolated micropenis without other features of PAIS, such as hypospadias or gynecomastia. This underlines the importance of including AR gene analysis in the evaluation of isolated micropenis with normal plasma T to ensure proper management of the patient and appropriate genetic counseling for the family.     

Functional characterisation of a natural androgen receptor missense mutation (N771H) causing human androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS) is an X-linked disorder due to mutations of androgen receptor (AR) gene. Various AR mutations have been identified, and the characterisation of these mutations greatly facilitates our understanding of AR structure-function. In this study, we have analysed an AR missense mutation (N771H) identified in patients with AIS. Functional analysis of the mutant AR was performed by in vitro mutagenesis-cotransfection assays. Compared to the wild-type AR, the dose-response curve of dihydrotestosterone-induced transactivation activity in the mutant AR was greatly shifted to the right and significantly decreased. However, the maximal efficacy of transactivation activity in the mutant AR was similar to that of the wild type. Receptor binding assay indicated that the mutant AR had an approximately 2.5-fold lower binding affinity to dihydrotestosterone compared to the wild type. Western blot analysis showed that the size and the expression level of mutant AR in transfected cells were comparable to the wild type. These data underscore the importance of asparagine at amino acid position 771 of human AR in normal ligand binding and normal receptor function, and a mutation at this position results in androgen insensitivity in affected subjects.     

Etiological studies of severe or familial hypospadias

PURPOSE: Hypospadias is a congenital anomaly occurring in 1250 to 1830 live male births, of which 20% involve a severe type. The recurrence risk in families is high. In the majority of cases the underlying etiology remains unknown, which hampers further management based on the specific requirements associated with a specific etiology. MATERIALS AND METHODS: In a single center study 63 unselected cases of severe hypospadias were studied for all presently known causes of hypospadias using clinical as well as molecular biological techniques. Also, 16 families with hypospadias were analyzed for possible androgen receptor gene mutations. RESULTS: In 31% of cases of severe hypospadias the underlying etiology was identified. Of these 31% of cases 17% were due to complex genetic syndromes, 9.5% were due to chromosomal anomalies, and 1 involved the vanishing testes syndrome, the androgen insensitivity syndrome and 5alpha-reductase type 2 deficiency, respectively. Based on hormone stimulation tests Leydig cell hypoplasia and disorders of testosterone biosynthesis were suspected in some patients but not confirmed by mutation analysis of the respective genes. Familial hypospadias was due to androgen insensitivity in only 1 family but no other etiologies were identified in this group. CONCLUSIONS: Using patient history, physical examination, karyotyping, hormonal evaluation, including human chorionic gonadotropin testing in prepubertal cases and additional biochemical and molecular genetic evaluation, an etiological diagnosis was made in 31% of cases of severe hypospadias. This diagnosis has implications for further patient treatment. In addition, familial hypospadias is rarely due to the androgen insensitivity syndrome.     

尿道下裂患者雄激素受体基因突变的研究

目的研究国人尿道下裂患者雄激素受体基因突变情况。方法采集92例各型尿道下裂患者外周抗凝血,使用酚氯仿变性法提取基因组DNA,通过PCR扩增DNA测序的方法,检测了雄激素受体2～7外显子全部序列。结果4例患者外周血提取的基因组DNA中具有雄激素受体基因外显子突变,第4外显子1例(664ATT→ACT);第7外显子3例(840CGT→CAT、855CGC→CAC、859CTC→CTA)。结论雄激素受体基因点突变可能是尿道下裂的发病原因之一,但是所占比例仅为43%。     

Phenotype, hormonal profile and genotype of subjects with partial androgen insensitivity syndrome: report of a family with four adult males and one child with disorder of sexual differentiation

There is little information on the molecular basis of intrafamilial and inter-familial phenotypic heterogeneity with the same androgen receptor (AR) mutation in patients with partial androgen insensitivity syndrome. A genetic analysis was performed in a large kindred with ambiguous genitalia and the genotype–phenotype correlations were analysed. The index case was brought for sex assignment. Family history revealed four other affected members who had hypospadias and varying degrees of virilisation. All the affected males had hemizygous mutations in the third exon of the AR gene (A596T). One was also found to have a heterozygous mutation in the fourth exon of the 5 alpha reductase type 2 gene (G196S). This affected male with double mutations was better virilised compared with the other affected members with a single mutation. The degree of virilisation correlated with serum testosterone levels. Gynaecomastia was not present in any of these subjects. It is concluded that the subject with dual gene defects also had higher levels of testosterone and pubertal virilsation. Testosterone levels possibly govern the degree of pubertal virilisation in subjects with A596T gene defects. It is not clear whether the better pubertal virilsation and higher testosterone are in any way causally related to the SRD5A2 gene defect.     

Male infertility: no evidence of involvement of androgen receptor gene among Indian men

Spermatogenesis is collaboratively controlled by testosterone and follicle stimulating hormone. Testosterone and its immediate metabolite dihydrotestosterone affect their roles through the androgen receptor (AR). Mutations in the AR gene have been shown to cause partial to complete androgen insensitivity or infertility in otherwise normal males. The dependence of germ cells upon Sertoli and Leydig cells for their differentiation into sperms and deletion studies of the AR gene in animal models indicate a direct or indirect role of the AR gene in spermatogenesis. Although a few studies worldwide have reported AR mutations in male infertility, no similar study has been conducted on Indian populations. Therefore, we undertook this study to look at the contribution of AR mutations in male infertility among Indian men. We have sequenced the complete coding region of the AR gene in a total of 399 infertile samples, comprising 277 azoospermic, 100 oligozoospermic, and 22 oligoteratozoospermic samples. A total of 100 healthy males with proven fertility and the same ethnicity as the experimental group served as controls. Sequence analysis revealed no mutation in any of these samples. Our study suggests that mutations in the AR gene are less likely to cause azoospermia and oligozoospermia; however, it was difficult to rule out its effect in oligoteratozoospermia, as the sample size was small.     

Molecular investigation of mutations in androgen receptor and 5‐alpha‐reductase‐2 genes in 46,XY Disorders of Sex Development with normal testicular development

In this study, we aimed to determine androgen receptor (AR) and SRD5A2 gene mutations in 45 patients characterised by 46,XY Disorders of Sex Differentiation (DSD) signs with normal testicular development referred to the Children's Medical Center from February 2015 to September 2017. Karyotype and sex hormone analyses were performed. Cytogenetic investigation showed that seven patients were 46,XX DSD, six patients were chromosomal DSD and 32 patients were 46,XY DSD. Eight exons of the AR gene and five exons of the SRD5A2 gene were amplified. Two cases were affected with androgen insensitivity syndrome (AIS) (missense mutation on exon 7, position c.3637 G>A: p.R841H and position c.3610 G>A: p.R832Q), one case was affected with 5‐alpha‐reductase deficiency type 2 (missense mutation at c.578A>G: p.N193S on exon 4), and 22 cases (88%) did not demonstrate AIS or 5α‐RD2 gene abnormality. Due to the great impact of these disorders on human lifestyle, evaluation of genes involved can improve genetic counselling and therapeutic management. We focused on the AR and SRD5A2 genes in patients with 46,XY DSDs with normal testicular development referred to the Children's Medical Center from all over the country to eventually culminate in a reliable prenatal diagnosis protocol at this major referral centre giving service to a great number of families with consanguineous marriages.     

男性胎儿5α-还原酶活性和雄激素及其受体的研究

目的 :分析男性胎儿雄激素靶组织外生殖器皮肤的雄激素 (T、DHT)水平、5α 还原酶活性及雄激素受体(AR)配基结合能力 ,探讨其在性别分化成熟中的作用。　方法 :4例孕 16～ 2 0周因意外事件而被迫引产的胎儿 ,取其包皮和阴茎皮肤组织。 10例 4～ 7岁和 2 3例 2 0～ 3 4岁男性因包茎或包皮过长行包皮环切术后的组织 ,制备匀浆 ,经差速超速离心 ,分别制备胞质、核浆和微粒体 3种组份 ,RIA方法测定匀浆中T、DHT水平 ,按作者建立和改良的方法分析 5α 还原酶活性及雄激素受体 (AR)配基结合能力 (B)。　结果 :孕 16～ 2 0周男性胎儿靶组织T为 ( 4 .5 5± 2 .84 )pmol/(mg蛋白·ml) ,DHT为 ( 3 9.12± 17.3 0 )pmol/(mg蛋白·ml) ;5α 还原酶 Ⅰ 型同工酶活性为 ( 162 .15±3 6.94 )pmol/(mg蛋白·3 0min) ,Ⅱ 型同工酶活性为 ( 3 0 7.62± 4 0 .5 5 )pmol/(mg蛋白·3 0min) ;胞质AR的B值为 ( 18.86± 7.62 )fmol/mg蛋白 ,核内AR的B值为 ( 10 8.5 5± 4 9.3 4 )fmol/mg蛋白。各项参数均高于儿童时期 ;除AR外 ,甚至高于成年男子 (P <0 .0 5～ 0 .0 1)。　结论 :胎儿时期雄激素靶组织中具有高水平的雄激素及其受体 ,尤其DHT ,提示雄激素在介导男性外生殖器分化形成和成熟中起重要的调控作用。     

男性不育的遗传学病因研究进展

许多非梗阻性无精子症和严重少精子症患者的病因尚不清楚。据估计,其中约有30%的患者是由于染色体畸变或基因突变等遗传学因素引起的。男性不育的遗传学病因有染色体畸变、Y染色体微缺失和基因突变等,其中Klinefelter综合征和Y染色体微缺失最为常见。与男性不育相关的基因突变包括囊性纤维化跨膜介导的调节子(CFTR)基因、雄激素受体(AR)基因、胰岛素样因子3(INSL3)基因和富含亮氨酸重复序列的G蛋白偶联受体8(LGR8)基因。CFTR基因突变可导致囊性纤维化、输精管缺如和梗阻性无精子症。AR基因突变会引起雄激素不敏感综合征和生精损伤。INSL3和LGR8基因突变则与睾丸下降异常和隐睾相关。Meta分析显示,仅有3个遗传多态性与男性不育显著相关,即AZFc区部分缺失、雄激素受体(AR)基因(CAG)n长度和亚甲基四氢叶酸还原酶(MTHFR)基因多态性。本文主要综述了男性不育常见的遗传学病因以及与男性不育相关的遗传多态性研究进展。     

Low incidence of androgen receptor gene mutations in human prostatic tumors using single strand conformation polymorphism analysis

It is possible that structural changes of the androgen receptor (AR) contribute to the insensitivity of prostatic carcinomas to endocrine therapy. We have isolated DNA from 58 human prostate tumor specimens (31 carcinomas pretreatment, 13 carcinomas after relapse to hormonal therapy, and 14 benign prostatic hyperplasia), three established human prostate carcinoma cell lines and two transplantable human prostatic carcinoma xenografts. Twelve pairs of oligonucleotide primers were used to amplify the majority of the coding region of the AR gene and the products screened for mutations using single-strand conformation polymorphism (SSCP) techniques. In one tumor sample a cystosine to guanine transition in exon F which leads to substitution of glutamic acid for the wild type glutamine at position 798 of the ligand binding domain was detected. The same mutation was also found in the patient's genomic DNA and as been described in a patient with partial androgen insensitivity syndrome. Intronic mutations were detected in two of the benign prostatic hyperplasia samples, and a silent mutation at nucleotide 995 was found to be present in eight poorly differentiated carcinomas, one BPH specimen, as well as in the cell line DU145 (18% of the samples studied). In agreement with most of the literature, these studies indicate that AR mutations are rare both prior to therapy and even in androgen relapsed tumors. © 1996 Wiley-Liss, Inc.     

DHEA Administration Activates Local Bioactive Androgen Metabolism in Cancellous Site of Tibia of Ovariectomized Rats

It is not known whether local androgen metabolism is involved in the mechanisms underlying the dehydroepiandrosterone (DHEA) administration-induced improvement of bone mineral density (BMD) in an estrogen-deficiency state. The aim of the present study was to clarify whether DHEA administration would improve local androgen metabolism and BMD in cancellous site of tibia of ovariectomized (OVX) rats. Twenty-two female rats, 6 weeks old, were randomized into three groups: sham-operated rats, OVX control rats, and OVX rats that received DHEA treatment. DHEA was administered intraperitoneally at 20 mg/kg body weight for 8 weeks. The concentrations of free testosterone and dihydrotestosterone (DHT) in cancellous site of tibia did not change as a result of ovariectomy, while the DHT concentration increased following DHEA administration. We revealed that DHEA administration improved the reduction of 17β- and 3β-hydroxysteroid dehydrogenases and clearly reversed the reduction of 5α-reductase types 1 and 2 and androgen receptor in the cancellous site of tibia of OVX rats. DHEA administration suppressed estrogen deficiency relative to the decrease in the cancellous BMD, which was positively associated with local DHT concentration. These findings indicate that DHEA administration enhances local bioactive androgen metabolism in the cancellous tibia of young OVX rats, suggesting that local DHT may play a part in the DHEA administration-induced improvement of cancellous BMD.