Fig. (1) Generation of immortalized DM1 fibroblasts, myoblasts and myotubes. (A) RT-PCR confirmed hTERT expression in immortalized WT and DM1 fibroblasts (hTERT FB), fibroblasts containing the MYOD expression construct before (MYOD FB) and after (Myoblast) doxycycline induction, and following serum starvation-induced differentiation (Myotube), but not in primary fibroblasts (Primary FB). Equal levels of cDNA template were confirmed by amplification of the GAPDH housekeeping gene. (B) Western blot analysis confirmed inducible expression of MYOD upon differentiation of immortalized WT and DM1 cell lines into myotubes. β-actin protein expression was used to ensure equivalent amounts of total protein in each sample. (C) Immunostaining of immortalized WT and DM1 myoblasts and myotubes for markers of early (DESMIN) and late stage (MHC) differentiation (green), with malachite green counterstaining (red). Scale bars represent 10µm.