One additional mutation at exon A amplifies thermolability of androgen receptor in a case with complete androgen...

We have previously demonstrated a substitutional mutation (glycine to alanine at position 820) of the androgen receptor (AR) gene in a patient with complete androgen insensitivity syndrome (CAIS). We first examined whether the mutation could lead to a disorder in AR binding activity in in vitro expression experiments. In a luciferase assay, the effect of the mutant AR on a target's gene was definitely impaired. However, the mutant AR had less thermal instability compared to that of the patient's fibroblast cell lines established in a whole-cell binding assay. In order to analyze the cause of the thermal instability, a further analysis of exon A in the AR gene was performed because the previous study had been performed only between exon B and H encoding the DNA-binding domain and the hormone-binding domain. The second mutation (leucine to proline at position 257) was newly identified. In in vitro expression experiments, the AR with both mutations showed marked thermal instability, whereas the AR with a mutation in exon A had no effect on thermal stability. The results show that the N-terminal domain might also play an important role in amplifying or modifying the AR binding activity.