ATXN1 and pachyonychia congenita: These data show that V591A and S602D mutations fully ablate the ATXN1-CIC interaction brain-wide, and although this complex is key for SCA1 PC pathology, it is not the sole driver of toxicity in all cell types, as motor incoordination is only partially improved in Atxn1154Q[V591A;S602D]/2Q mice.