ATXN2 and spinocerebellar ataxia type 2: Human ataxin-2 (Atx2, also abbreviated to ATXN2) is such a polyQ tract-containing protein (5); expansion of the polyQ tract in Atx2 can trigger protein aggregation that may cause neurodegenerative diseases like spinocerebellar ataxia type 2 (SCA2) (6, 7, 8, 9).