Hypericin repairs misregulated splicing events associated with myotonic dystrophy in type 1 myoblast lines

Myotonic dystrophy is associated with the molecular event of misregulated splicing of a subset of RNAs, which contribute to some of the disease phenotypes. One of the misregulated splicings that leads to one of the disorder’s phenotypes is insulin resistance (IR). Other misregulated splicing events considered in this study included Sarcoplasmic Endoplasmic Reticulum ATPase 1 (SERCA1), and muscleblind protein isoforms 1 and 2 (MBNL1 and MBNL2). Assays based on the above splicing events were designed for reverse transcription (RT-PCR) analysis and applied to myotonic dystrophy type 1 (DM1) myoblasts derived from differentiated fibroblasts to test for a compound that could reverse misregulated splicing in the cultures. Reverse Transcribed PCR methods quantified by the Genescan genetic analyser were utilised for the study. In this study, hypericin, a protein kinase C inhibitor, was observed to affect a slight reversal of misregulated splicing associated with the disorder in the insulin receptor (IR) by enhancing the relative proportion of the muscle signalling type (IR-B) in myotonic dystrophy type 1 myoblasts. Additionally, hypericin increased the proportion of the skeletal muscle isoform (SERCA1a) in DM1 myoblast cultures compared with mock control (DMSO-treated) (p=0.002). Furthermore, hypericin treatment was also observed to correct missplicing in MBNL1 and MBNL2 by reducing the proportion of isoforms containing exon 7. In this study, hypericin treatment corrected splicing abnormalities in all splicing assays performed in DM1 myoblasts. Taken together, the results indicate that hypericin may have therapeutic potential in the DM1 cell model used in this study.