ATXN3 and Spinocerebellar ataxia type 3: Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph Disease (MJD), is an autosomal dominant neurodegenerative disorder caused by a CAG-trinucelotide repeat expansion within the coding region of the ATXN3 gene (also called the MJD1 gene) [1].