 RAN is an androgen receptor (AR) coactivator (ARA24) that binds differentially with different lengths of polyglutamine within the androgen receptor.Polyglutamine repeat expansion in the AR is linked to spinal and bulbar muscular atrophy (Kennedy's disease).RAN coactivation of the AR diminishes with polyglutamine expansion within the AR, and this weak coactivation may lead to partial androgen insensitivity during the development of spinal and bulbar muscular atrophy.