DMPK and myotonic dystrophy type 1: In the LC15 mouse model, which carries 200–400 CTG repeats in the human DMPK gene and is a model for late-onset/adult DM1 phenotypes, ventricular myocytes showed prolonged action potential duration at 90% repolarization due to Ito reduction, which contributes to the prolonged QRS and QTc intervals in this model [90].