Characterization of the androgen receptor (AR) in sexual differntiation to androgen insensitivity syndrome (AIS).

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The molecular basis of AIS was ultimately established by identification of mutations in the gene encoding the AR in individuals with various forms of this syndrome. We report point mutations in the AR gene of testicular feminization syndrome, and Reifenstein syndrome. These point mutations in the hormone binding domain of the AR were responsible for their thermolability in the radioreceptor assay using fibloblast cells derived from genitalia, which were confirmed through transactivation luciferase assay after transfection of the target genes into COS7 cells. The one mutant expression plasmid significantly decreased the transactivation activity in comparison with that of a wild type (58.5%, P<O.05), and two mutants expression plasmid (M807V, and R840H) significantly decreased the reporter gene activity in comparison with that of a wild type (64.5%, P<O.05). Transactivation assay with one of two mutations didn't show any difference of the reporter gene activity from that of a wild type. Although the replacement of one of two hydrophobic aminoacids for hydrophillic amino acid transfected into the one mutant expression plasmid significantly decreased the reporter gene activity in comparison with that of a wild type (34.8%, P<O.05). We suggest that the point mutation generating the replacement of hydrophobic amino acid for hydrophilic one could be one of the major causes for an ambiguous phenotype of genitalia in patients with ALS.We are undergoing differential display assay of the AR to investigate second message of the target gene.