Ala 586 Asp mutation in androgen receptor disrupts transactivation function without affecting androgen binding

To understand the pathogenesis of the androgen insensitivity syndrome.

Familial case study.

Medical and Evolutionary Genetics Laboratory, Centre for Cellular and Molecular Biology, Hyderabad, India.

Two affected sisters and other unaffected family members.

The hormone levels were measured by RIA. Histology was done by standard protocols. DNA isolation and direct DNA sequencing was undertaken for mutation identification. Site-directed mutagenesis was used for incorporation of mutation in the androgen receptor clone. Functional assays were done using COS-1 cell cultures.

Phenotype, hormone levels, DNA mutations, ligand binding, transactivation function of androgen-androgen receptor complex.

The patients exhibited a female phenotype despite the 46,XY chromosome complement. Both of the affected individuals had higher levels of T and LH. C1760A (coding DNA sequence reference) substitution (Ala 586 Asp) in the AR gene was observed in all of the affected individuals. The mutation did not result in a loss of ligand binding but instead in almost complete loss of transactivation function.

The Ala 586 Asp mutation resulted in a complete loss of transactivation function of the androgen-androgen receptor complex but did not affect ligand binding. In vitro assays confirmed the pathogenic nature of this mutation.