Leu-676-Pro mutation of the androgen receptor causes complete androgen insensitivity syndrome in a large Hutterite kindred.

A large Manitoba Hutterite kindred with X-linked receptor negative complete androgen insensitivity syndrome (CAIS) was studied. In attempts to identify all carriers of the syndrome in this kindred, using the androgen receptor (AR) cDNA, we have found a novel diagnostic MspI polymorphic pattern, which cosegregates with the disease. This polymorphism was not detected in 79 unrelated X-chromosomes of which 22 were from Hutterite controls. We were able to localize the polymorphism to exon 4, which is known to encode part of the androgen receptor hormone binding domain. A single base substitution (T-->C) was detected, which creates a new MspI site. This novel transition mutation replaces Leu-676 with Pro at a site which is conserved in numerous members of the steroid receptor gene family. Sequencing all 8 exons of the AR revealed the Leu-676-->Pro mutation as the only change in the primary structure of the receptor. Transfection of COS-1 cells with an expression vector of the mutant AR demonstrates that this point mutation of nucleotide 2558 abolishes receptor binding activity. The mutation can easily be detected by MspI digestion of the polymerase chain reaction (PCR) amplified exon 4 product.