Fig. 4

DUX4c is immunodetected in hypotrophic regenerating myofibers. The FSHD muscle sections were treated as in Fig. 3 with immunodetection of developmental myosin heavy chain (dMyHC, green), a regeneration marker, DUX4c (red) and laminin-α2 (purple), observed by confocal microscopy. dMyHC was detected in either (A) angular or (B) round hypotrophic fibers. (A) Upper panel: a muscle section area with one regenerating myofiber and its magnified 3D reconstruction. Bottom panels: three different focal depths of A using a 0.25 μm step in the Z axis (25 images in total). B Close to the round myofiber with punctuated dMyHC staining, two large nuclei present next to their periphery (at one or both sides) intense dots of dMyHC and of laminin-α2, suggesting they are included in activated satellite cells (SCs). DUX4c is detected in two close nuclei present in distinct cells (arrowhead), and also in the SC cytoplasm (arrows). An enlarged field of this cluster of regenerating cells is presented at Fig. S8A where the indicated nucleus (#) can be observed