Similarly, the age of onset and the severity of the progression of SCA1 are both directly linked to the length of the polyQ tract in ataxin-1 [174,175,176], with the length of the polyQ tract exceeding a threshold of 39–44 glutamine residues being associated with the formation of granular or fibrillar intranuclear aggregates of ataxin-1 and eventual cell death [177,178]. This evidence concerns the gene ATXN1 and spinocerebellar ataxia type 1.