MSH3 and myotonic dystrophy type 1: In mice, several mismatch repair genes, including Msh3, influence the somatic instability of CAG repeats (Dragileva et al., 2009, Schmidt and Pearson, 2016, Tomé et al., 2013) and in humans, naturally occurring MSH3 polymorphisms are associated with instability of the non-coding myotonic dystrophy type 1 CTG repeat in blood DNA (Morales et al., 2016).