Partial androgen insensitivity caused by an androgen receptor mutation at amino acid 907 (Gly-->Arg) that results in decreased ligand binding affinity and reduced androgen receptor messenger ribonucleic acid levels.

Abstract

Androgen insensitivity is an X-linked disorder of sexual differentiation resulting from mutations in the androgen receptor (AR) gene. In this paper, we report the clinical phenotype and molecular analysis of two siblings with severe partial androgen insensitivity due to a novel mutation in the ligand-binding domain of the AR gene. Binding studies using cultured genital skin fibroblasts demonstrated reduced AR affinity and binding capacity. Nucleotide sequence analysis of the AR gene of both siblings revealed a point mutation causing a glycine to arginine amino acid substitution at position 907 within a conserved region of the ligand-binding domain. A silent guanine to adenine substitution was also identified in the protein-coding region of exon 1. Using an expression vector in which the identified mutation was recreated by site-directed mutagenesis, the mutant receptor was found to have a reduced binding affinity (Kd = 3.06 nmol/L) for mibolerone compared with that of normal AR (Kd = 1.71 nmol/L) when expressed in COS-7 cells. In cotransfection experiments using CV-1 cells and a mouse mammary tumor virus-chloramphenicol acetyltransferase reporter system, the concentration of dihydrotestosterone required to induce half-maximal chloramphenicol acetyltransferase gene expression was 50-fold higher in cells transfected with the mutant AR complementary DNA than in cells transfected with normal AR complementary DNA. AR messenger ribonucleic acid levels in genital skin fibroblasts determined by both competitive PCR amplification and ribonuclease protection assay were decreased compared with normal values. Our studies demonstrate the importance of this region of the AR gene in normal AR function and AR gene expression.

Evolution of the Primate Androgen Receptor: A Structural Basis for Disease

“…Blood collections were performed using procedures approved by the participating institutions. Exon 1 was amplified using internal exon primers (Lubahn et al 1989) and subcloned in pGEM-T (Promega) (Choong et al 1996b). Flanking intron primers were used to amplify exons B-H for direct sequencing of PCR products.…”

Mechanisms involved in the progression of androgen-independent prostate cancers: it is not only the cancer cell's fault.

“…In these patients, the withdrawal of androgens may have even induced the clonal outgrowth of prostate cancer cells with increased AR expression. Additionally the AR may be dysfunctional due to mutations, which alter the receptor specificity and binding affinity (Choong et al 1996). Androgen ablation may induce or preferentially select for cells with mutated AR, especially in metastases (Feldman & Feldman 2001).…”

A novel missense mutation in the amino-terminal domain of the human androgen receptor gene in a family with partial androgen insensitivity syndrome causes reduced efficiency of protein translation.

“…The eight exons of the AR gene were amplified by PCR and exons 2-8 were screened for single base mutations by denaturing gradient gel electrophoresis (DGGE). All exons were subsequently subjected to direct sequence analysis using methods described in detail elsewhere (12,13). The nucleotide mutation identified was confirmed in two separate sequencing reactions from two primary amplifications of genomic DNA from subject II-1 and by direct sequencing of DNA from subjects II-4 and II-10.…”