In the cells expressing CUGexp RNA following induction by Cre recombinase, the total expression level of transgene and endogenous DMPK was increased 3.8-fold compared with that of endogenous DMPK and DM1 fibroblasts and to a similar level in DM1 myoblasts (Supplementary Figure S1B). Here, DMPK is linked to myotonic dystrophy type 1.