ATXN3 and Spinocerebellar ataxia type 3: Spinocerebellar ataxia type 3 (SCA3), also known as Machado–Joseph disease, is a polyglutamine (polyQ) neurodegenerative disorder caused by abnormal (more than 40 repeats) CAG nucleotide repeat expansions in the ataxin-3 (ATXN3) gene, which encodes a protein that is involved in ubiquitin-proteasome system degradation of proteins [27,28].