The breadth of mismatch repair proteins involved in modifying disease-associated repeat instability now includes MSH2, MSH3, MSH6, MLH1, MLH3, and PMS2.
MMR proteins can drive expansions of disease-associated repeats, and they can regulate contractions of the expanded repeat.
The spectrum of disease-associated repeats modified by MMR proteins has broadened to include not only CAG/CTG repeats, but also, CGG/CCG and GAA/TTC repeats.
Naturally occurring polymorphic variants of MMR proteins can dramatically affect instability levels of disease-associated repeats.