A major advance in the process of unraveling the molecular bases of SCA1 pathogenesis was achieved by showing that expansion of the polyQ tract is necessary but not sufficient to cause pathology: expanded Atx1 does not produce cerebellar degeneration if it lacks regions other than the polyQ tract such as a nuclear localization signal (NLS) [15] or the AXH domain [14], or if a serine to alanine mutation prevents phosphorylation at residue 776 [16]. Here, ATXN1 is linked to cerebellar degeneration.