A large deletion/insertion-induced frameshift mutation of the androgen receptor gene in a family with a familial complete androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS) is an X-linked recessive genetic disorder with a normal 46, XY karyotype caused by abnormality of the androgen receptor (AR) gene. One Chinese family consisting of the proband and 5 other members with complete androgen insensitivity syndrome (CAIS) was investigated. Mutation analysis by DNA sequencing on all 8 exons and flanking intron regions of the AR gene revealed a unique large deletion/insertion mutation in the family. A 287 bp deletion and 77 bp insertion (c.933_1219delins77) mutation at codon 312 resulted in a frameshift which caused a premature stop (p.Phe312Aspfs*7) of polypeptide formation. The proband's mother and grandmother were heterozygous for the mutant allele. The proband's father, uncle and grandfather have the normal allele. From the pedigree constructed from mutational analysis of the family, it is revealed that the probably pathogenic mutation comes from the maternal side.     

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.     

Differential gene-expression patterns in genital fibroblasts of normal males and 46,XY females with androgen insensitivity syndrome: evidence for early programming involving the androgen receptor

Background  

Androgen insensitivity syndrome (AIS) comprises a range of phenotypes from male infertility to complete feminization. Most individuals with AIS carry germline mutations of the androgen receptor (AR) that interfere with or ablate its function. As genital fibroblasts retain expression of the AR in vitro, we used genital skin fibroblasts from normal males and 46,XY females with complete AIS due to known AR mutations to gain insights into the role of the AR in human genital differentiation.     

L712V mutation in the androgen receptor gene causes complete androgen insensitivity syndrome due to severe loss of androgen function

Inability to respond to the circulating androgens is named as androgen insensitivity syndrome (AIS). Mutations in the androgen receptor (AR) gene are the most common cause of AIS. A cause and effect relationship between some of these mutations and the AIS phenotype has been proven by in vitro studies. Several other mutations have been identified, but need to be functionally validated for pathogenicity. Screening of the AR mutations upon presumptive diagnosis of AIS is recommended. We analyzed a case of complete androgen insensitivity syndrome (CAIS) for mutations in the AR gene. Sequencing of the entire coding region revealed C > G mutation (CTT–GTT) at codon 712 (position according to the NCBI database) in exon 4 of the gene, resulting in replacement of leucine with valine in the ligand-binding domain of the AR protein. No incidence of this mutation was observed in 230 normal male individuals analyzed for comparison. In vitro androgen binding and transactivation assays using mutant clone showed approximately 71% loss of ligand binding and about 76% loss of transactivation function. We conclude that CAIS in this individual was due to L712V substitution in the androgen receptor protein.     

MicroRNAs are mediators of androgen action in prostate and muscle

Androgen receptor (AR) function is critical for the development of male reproductive organs, muscle, bone and other tissues. Functionally impaired AR results in androgen insensitivity syndrome (AIS). The interaction between AR and microRNA (miR) signaling pathways was examined to understand the role of miRs in AR function. Reduction of androgen levels in Sprague-Dawley rats by castration inhibited the expression of a large set of miRs in prostate and muscle, which was reversed by treatment of castrated rats with 3 mg/day dihydrotestosterone (DHT) or selective androgen receptor modulators. Knockout of the miR processing enzyme, DICER, in LNCaP prostate cancer cells or tissue specifically in mice inhibited AR function leading to AIS. Since the only function of miRs is to bind to 3' UTR and inhibit translation of target genes, androgens might induce miRs to inhibit repressors of AR function. In concordance, knock-down of DICER in LNCaP cells and in tissues in mice induced the expression of corepressors, NCoR and SMRT. These studies demonstrate a feedback loop between miRs, corepressors and AR and the imperative role of miRs in AR function in non-cancerous androgen-responsive tissues.     

Mutation analysis of androgen receptor gene: Multiple uses for a single test

Androgen receptor gene mutations are one of the leading causes of disorders of sex development (DSD) exhibited by sexual ambiguity or sex reversal. In this study, 2 families with patients whom diagnosed clinically as androgen insensitivity syndrome (AIS) were physically and genetically examined. This evaluation carried out by cytogenetic and molecular analysis including karyotype and sequencing of SRY and AR genes. In family 1, two brothers and their mother were hemizygous and heterozygous respectively for c.2522G > A variant, while one of their healthy brother was a completely normal hemizygote. Family 2 assessment demonstrated the c.639G > A (rs6152) mutation in two siblings who were reared as girls. The SRY gene was intact in all of the study's participants.     

Androgen insensitivity in forty-nine patients: classification based on clinical and androgen receptor phenotypes

Androgen receptor binding was studied in genital skin fibroblasts from 49 patients with androgen insensitivity syndrome (AIS) classified as complete (CAIS) or partial (PAIS) based on the clinical phenotype. The majority (64%) of CAIS and a minority (7%) of PAIS patients were receptor negative. Only 3 receptor-positive AIS cell strains of 30 studied failed to show an increase in specific receptor binding after prolonged androgen exposure in vitro. The gene coding for the androgen receptor in such patients appears intact.     

Prenatal prediction of androgen insensitivity syndrome using exon 1 polymorphism of the androgen receptor gene.

Exon 1 polymorphism of the androgen receptor (AR) gene is characterized by a (CAG)n(CAA) repeat at position 172 following the translation start codon. The aim of this study was to determine whether AR gene exon 1 polymorphism could be used to perform prenatal diagnosis in high risk families with complete or partial androgen insensitivity syndrome. After enzymatic amplification of a 1 kilobase exon 1 fragment, each DNA was simultaneously digested by MspI and PstI restriction enzymes. After electrophoresis on a 15% electrophoresis on a 15% acrylamide gel or a 6% Nusieve gel, we measured the size of the obtained fragments and determined the number of CAG repeats since a 282 basepair fragment corresponds to 21 CAG. We previously showed that the number of CAG repeats within the AR gene exon 1 in 23 families with complete or partial androgen insensitivity syndrome was 19 +/- 4. By this method, we detected heterozygosity in 50% of the mothers. We present here 2 exclusion prenatal diagnoses using exon 1 polymorphism of the AR gene. Family A presented a boy with a severe form of partial androgen insensitivity syndrome. The mother had 2 uncles with ambiguous genitalia. In family B, the affected child had a complete androgen insensitivity syndrome. In both families, analysis of the AR gene exon 1 polymorphism of the trophoblastic DNA showed the presence of the normal maternal X chromosome. The parents decided to carry on the gestation. In family A, the newborn had normal male external genitalia. In family B, sonography confirmed the presence of normal male external genitalia. These data suggest that exon 1 polymorphism of the AR gene could be prenatally used to predict androgen insensitivity syndrome.     

Phenotypic heterogeneity associated with identical mutations in residue 870 of the androgen receptor

BACKGROUND/AIMS: Mutations in the androgen receptor (AR) gene result in an X-linked recessive form of male pseudohermaphroditism known as the androgen-insensitivity syndrome (AIS). The alterations most frequently observed are missense or nonsense point mutations in exons 4-8 of the AR gene that affect the steroid-binding domain of the receptor in subjects with various degrees of androgen resistance. Despite the increasing number of AR mutations identified, a reliable genotype-phenotype correlation has not been established and individuals with the same molecular defect may exhibit different phenotypes. Here, we studied a patients with an AIS characterized by bilateral gynecomastia, normal male external genitalia, and normal sperm counts. METHODS: Exon-specific polymerase chain reaction, single-stranded conformational polymorphism, and sequencing analysis of the subject's AR gene were performed in addition to hormone-binding assays in skin fibroblasts from the patient. RESULTS: A point mutation at codon 870 of the AR, changing alanine to valine, was detected. CONCLUSION: As AR missense mutations changing alanine 870 to valine have been previously described in 3 unrelated patients showing severe AIS phenotypes, we conclude that phenotypic heterogeneity associated to identical mutations in the AR gene is probably due to individual functional differences in AR coregulator molecules.