HEYL and myotonic dystrophy type 1: Compared to healthy control cells, DM1 cells showed lower expression in genes associated to myogenic markers (e.g., MYF5, MYOD1, MYF6, SIX1), extracellular matrix components (e.g., COL1A1, COL1A2, COL3A1, COL5A2, LAMA2, FN1), Notch signaling (e.g., HEYL, RBPJ), and cell cycle (e.g., CENPF, CCNA2, CCNB1, CCNB2, CDK1, MKI67) (Fig. 1b, c and Supplementary Data 1).