MSH2 and Huntington disease: For example, Msh2-/- knockout results in a stabilization of 110–120 (CAG) repeats in the HTT gene in HD mice, and a shift toward contractions of long (CTG) repeats in DM1 mice (Manley et al. 1999; Savouret et al. 2003) Moreover, Msh3-/- cells exhibit the stabilization of long (CAG) tracts and (CTG) tracts in HD and DM1 mice respectively, and a later onset of disease phenotype.