TGFB1 and Duchenne muscular dystrophy: Again, we detected pSMAD3 nuclear accumulation following electrical pacing at a greater extent in DMD iPSCex59X-derived myotubes (3.5 fold) as well as in DMD iPSCex45del, when compared to control myotubes (2.3 fold), indicating that pacing-induced contraction is sufficient to trigger an exacerbated activation of TGFβ/SMAD signaling in DMD myotubes (Fig. 4b and S2C).