TGFB1 and Duchenne muscular dystrophy: Our results showed that DMD myoblasts, but not healthy ones, have a decreased fusion index when differentiated with CM from TGFβ1–treated myotubes, but myoblasts incubated with CM from TGFβ1–treated and SETDB1 LOF myotubes show a more normal fusion index (Fig. 5, B and C).