The androgen receptor is a member of the nuclear receptor superfamily, and regulates gene expression in response to the steroid hormones testosterone and dihydrotestosterone. Mutations in the receptor have been correlated with a diverse range of clinical conditions, including androgen insensitivity, prostate cancer and spinal bulbar muscular atrophy, a neuromuscular degenerative condition. The latter is caused by expansion of a polyglutamine repeat within the N-terminal domain of the receptor. Thus the androgen receptor is one of a growing number of neurodegenerative disease-associated proteins, including huntingtin (Huntington's disease), ataxin-1 (spinocerebellar ataxia, type 1) and ataxin-3 (spinocerebellar ataxia, type 3), which show expansion of CAG triplet repeats. Although widely studied, the functions of huntingtin, ataxin-1 and ataxin-3 remain unknown. The androgen receptor, which has a well-recognized function in gene regulation, provides a unique opportunity to investigate the functional significance of poly(amino acid) repeats in normal and disease states.
Sequencing analysis of the spinal bulbar muscular atrophy CAG expansion reveals absence of repeat interruptions
