However, while MSH6 has been shown to be important for expansion in Friedreich ataxia (FRDA) induced pluripotent stem cells (Du et al., 2012), in mouse models of other repeat expansion diseases, it is MSH3 that is important (van den Broek et al., 2002; Foiry et al., 2006; Tome et al., 2013). The gene discussed is MSH6; the disease is Friedreich ataxia.