ATXN1 and spinocerebellar ataxia type 1: Because the normal form of Atxn1 as well as Atxn1 with the expanded CAG repeat are transcribed and translated in the tissues of affected SCA1 patients, and the absence of Atxn1 in the mouse does not lead to any ataxic symptoms or major motor coordination abnormalities [221], the toxic-gain of function exerted by mutant Atxn1 has been suggested.