Incorporation of RBP-J-deficient satellite cells (SCs) into adjacent myofibers. (A): Tibialis anterior (TA) muscle cryosection from a RBP-Jcko animal treated daily with EdU for 14 days, beginning at the onset of tamoxifen administration. EdU-labeled myonuclei located beneath the myofiber membrane as delineated by dystrophin staining are highlighted by white arrows. EdU+ve nuclei that are outside the muscle fiber membrane are highlighted by green arrows. (B): Higher power magnification showing a single EdU+ve myonucleus in a cryosection as in panel (A). (C): Quantification of EdU+ve myonuclei, expressed as the absolute number per TA cryosections, from control and RBP-Jcko mice treated as described for panel (A). (**, p < .01). Abbreviations: CKO, conditional knockout; DAPI, 4′,6-diamidino-2-phenylindole; EdU, 5-ethynyl-2′-deoxyuridine; RBP-J, recombining binding protein-J.