For example, the Scn5a gene undergoes a splicing switch to more inclusion of the fetal exon 6A, as well as a reduction in total mRNA expression levels in both DM1 and CUG960 +dox heart tissue (27, 41) (Figure 5, E and F, Figure 6E, and Supplemental Figure 9, E and F). The gene discussed is SCN5A; the disease is myotonic dystrophy type 1.