To test whether the confirmed Muscleblind retention in foci was enough to cause splicing misregulation, we studied the percentage of exon retention (“percentage spliced in”, PSI) of the Drosophila formin (Fhos) gene exon 16′, which has a highly conserved ortholog in human, with altered splicing in DM1 patients36. Here, FHOD1 is linked to myotonic dystrophy type 1.