ATXN3 and juvenile Huntington disease: We expressed expanded polyQ transgenes modeling spinocerebellar ataxia type 1 (SCA1, ATX1.82Q), spinocerebellar ataxia type 2 (SCA2, ATX2.64Q), spinocerebellar ataxia type 3 (SCA3, MJD.78Q), and Huntington’s disease (HD, HTT231NT.128Q) in class IV da neurons41,44,50,52,53.