Clinical meaning
Androgen Insensitivity Syndrome arises from loss-of-function mutations in the androgen receptor (AR) gene, located on the long arm of the X chromosome at Xq11-12. The AR gene spans over 90 kb and contains 8 exons encoding a 919-amino acid nuclear receptor protein. The AR protein belongs to the nuclear receptor superfamily and contains four functional domains: the N-terminal transactivation domain (NTD, exon 1), the DNA-binding domain (DBD, exons 2-3) containing two zinc finger motifs that bind androgen response elements (AREs) in target gene promoters, the hinge region (exon 4) containing the nuclear localization signal, and the C-terminal ligand-binding domain (LBD, exons 4-8) that binds testosterone and DHT. Over 1,000 distinct AR mutations have been catalogued in the Androgen Receptor Gene Mutations Database. These mutations can be classified by their functional consequence: complete loss of ligand binding (LBD missense mutations disrupting the hydrophobic ligand-binding pocket), impaired DNA binding (DBD mutations affecting zinc finger coordination or ARE recognition), defective nuclear translocation (hinge region mutations), and impaired coactivator recruitment (mutations affecting the AF-1 and AF-2 transactivation surfaces that interact with p160 coactivators such...