Ataxin 3 (ATX3) is involved in protein ubiquitination, a trinucleotide expansion of this gene (CAG) causes Machado-Joseph disease or spinocerebellar ataxia, although this mutation is associated with neuronal death, so far ATX does not have a well-defined role in brain development33,34. Here, ATXN3 is linked to Machado-Joseph disease.