ATXN3 and Spinocerebellar ataxia type 3: Spinocerebellar ataxia type 3, also known as Machado–Joseph disease (MJD), is a neurodegenerative disorder caused by a polyglutamine-coding CAG trinucleotide repeat expansion in the MJD domain protease subfamily member ATXN3 (Table 1) [37,50].