Spinocerebellar ataxia type 3 (SCA3), known as Machado-Joseph disease, is one of nine polyglutamine (polyQ) diseases that occurs due to an abnormal expansion of polyglutamine in exon 10 of the ATXN3 gene (Kawaguchi et al., 1994). The gene discussed is ATXN3; the disease is Machado-Joseph disease.