ATXN3 and Machado-Joseph disease: MJD is caused by a mutation in the exon 10 of the MJD1/ATXN3 gene, located at the chromosome 14, which leads to an extension of the trinucleotide cytosine-adenine-guanine (CAG), coding for the glutamine aminoacid, resulting in a polyglutamine tract expansion in the ataxin-3 protein3–5.