Our current study in HSALR mice shows evidence for fiber type switching in response to damage and shows qualitative differences between HSALR-, DM200-, and MBNL-deficient mouse models that may shed light on differences between mouse models of RNA toxicity and human variants of myotonic dystrophy (i.e., DM1 and DM2). The gene discussed is MBNL1; the disease is myotonic dystrophy type 1.