Indeed, the expression of the MBNL1 transcript isoform including exon 5, which regulates protein nuclear localization, and the MBNL1 transcript isoform including exon 8 (but excluding exons 7 and 9), which regulates protein self-dimerization, were increased in DM1-1300 iPSC-CMs compared to the CTRL iPSC-CMs (Fig. 2B). Here, MBNL1 is linked to myotonic dystrophy type 1.