Characterization of DM1 patient fibroblasts (PT) transduced with myoD. (A and B) Light microscopy of PT cells cultured in low serum medium for 21 days post-transduction. (A) Non-transduced (NT) PT cells display a fibroblast phenotype, (B) PT cells transduced with myoD display elongated tubular morphology. (D) IF of myogenin in DM1 patient fibroblasts (PT), 12-days post-transduction PT cells express myogenin and exhibit multinuclear morphology, (C) while non-transduced PT cells do not. (E-H) myoD induced myogenesis increase the number of nuclear foci in DM1 patient fibroblasts. (G-H) DM1 patient fibroblasts and (E-F) normal fibroblasts were cultured 10 days in low serum medium following transduction with (E and G) GFP or (F and H) myoD. Cells were analyzed by FISH with a Cy3-labeled (CAG)10 probe (red) targeting the pathogenic CUG repeat expansion of DMPK mRNA. (E-F) Normal fibroblasts (NHDF) displayed no nuclear foci when transduced with GFP or myoD. (G-H) DM1 patient fibroblasts exhibited an increased number of nuclear foci in fibroblasts transduced with myoD relative to GFP transduced fibroblasts. (H) The high number of foci was only observed in myoD transduced fibroblasts with myogenic morphology. (A-B) Original magnification × 400 and (C-H) × 630.