Sequence of the intron/exon junctions of the coding region of the human androgen receptor gene and identification of a point mutation in a family with complete androgen insensitivity.

TLDR

Androgens mediate male sex differentiation through binding to the androgen receptor (AR). The authors isolated the eight coding exons of the AR gene, mapped intron/exon junctions, designed primers, and amplified the gene from 46,XY siblings with complete androgen insensitivity syndrome. A single G→A point mutation in exon G (residue 866) reduced DHT binding affinity but preserved capacity, and this mutation in the steroid‑binding domain explains the ineffective AR protein responsible for complete androgen insensitivity.

Abstract

Androgens act through a receptor protein (AR) to mediate sex differentiation and development of the male phenotype. We have isolated the eight exons in the amino acid coding region of the AR gene from a human X chromosome library. Nucleotide sequences of the AR gene intron/exon boundaries were determined for use in designing synthetic oligonucleotide primers to bracket coding exons for amplification by the polymerase chain reaction. Genomic DNA was amplified from 46,XY phenotypic female siblings with complete androgen insensitivity syndrome. AR binding affinity for dihydrotestosterone in the affected siblings was lower than in normal males, but the binding capacity was normal. Sequence analysis of amplified exons demonstrated within the AR steroid-binding domain (exon G) a single guanine to adenine mutation, resulting in replacement of valine with methionine at amino acid residue 866. As expected, the carrier mother had both normal and mutant AR genes. Thus, a single point mutation in the steroid-binding domain of the AR gene correlated with the expression of an AR protein ineffective in stimulating male sexual development.