Table 1:

Role of MMR proteins during length instability of (GAA)_n and (CAG)_n repeats

Complex	MMR protein	GAA somatic and non-dividing	GAA intergenerational and replication-models	CAG somatic and non-dividing	CAG intergenerational and replication-models
MutLα MutLγ	MLH1	Promotes expansions Mouse model [143] No effect on expansions Promotes deletions Non-dividing yeast cells [149]	Promotes expansions Mouse model and human cells [116], [143]	Promotes expansions HD mouse model [156] Human HD population [157]	Prevents expansions S. cerevisiae [158]
MutLα	PMS2 (Pms1 in S. cerevisiae)	Prevents expansions Mouse model Non-dividing yeast cells [114], [149] Promotes deletions Non-dividing yeast cells [149]	Prevents expansions Promotes contractions Mouse model [142] Prevents expansions Human cells [116]	Promotes expansions Prevents deletions Mouse model [159]	Prevents expansions S. cerevisiae [158]
MutLγ	MLH3	Prevents expansions Human cells [116]	Prevents expansions Human cells [116]	Promotes expansions HD mouse models and patient derived cells [156], [160]	No effect S. cerevisiae [158]
MutSβ MutSα	MSH2	Promotes expansions Mouse model Human cells [114], [115]	Prevents contractions Mouse model [142] Promotes expansions iPSC GAA expansion model [144], [161]	Promotes expansions Mouse models Human cell model [126], [162], [163]	Promotes expansions S. cerevisiae Mouse model [164], [165] Prevents contractions S. cerevisiae [158]
MutSβ	MSH3	Prevents expansions Promotes deletions Non-dividing yeast cells [149] Promotes expansions Human cells and FRDA fibroblasts [115]	No effect on expansions G0 yeast cells [149] Prevents contractions Mouse model [142]	Promotes expansions Human cell model [126]	Promotes expansions HD mouse model DM1 mouse Human cell lines S. cerevisiae [164], [166–170]
MutSα	MSH6	Promotes expansions Mouse model [114] No effect on expansions and promotes deletions Non-dividing yeast cells [149]	Prevents expansions and contractions Mouse model iPSC model [142], [161] No effect on expansions Human cells [115]	Prevents expansions Human cell model [126]	Prevents contractions HD mouse model [166] Prevents expansions S. cerevisiae [164]