Huntington’s disease is caused by a polyQ expansion in huntingtin(HTT) protein, a nucleo-cytoplasmic protein, which has been shownto participate in axonal transport and in calcium signaling regulation.The androgen receptor (AR), the CAG–polyQ repeat expansionof which causes SBMA, is a nuclear receptor, best known for its rolesin male reproductive system. The gene discussed is AR; the disease is Kennedy disease.