Fig. (2) Splicing factor expression in immortalized DM1 cells. (A) Western blot analysis of CUGBP1 and MBNL1 splicing factor proteins in immortalized WT and DM1 fibroblasts, myoblasts and myotubes (with Lamin A/C and β-actin loading controls for nuclear and whole cell lysates, respectively). (B) Localization of DMPK mutant RNA to nuclear foci (highlighted by white arrowheads) via in situ hybridization with a Texas Red-conjugated RNA probe containing 7 CUG repeats ((CUG)7-TR), together with MBNL1 immunostaining (green) and Hoechst counterstaining (blue). Scale bars represent 10µm.