Notch genes encode cell surface proteins, which are evolutionary conserved and found in invertebrates like Drosophila melanogaster as well as in all vertebrate species. The transcription factor RBP-J (Rbpsuh) is a primary nuclear mediator of Notch signals. Signals provided by Notch receptors control cell fate decisions, patterning, and they also affect proliferation or the maintenance of progenitor cells. In these Perspectives we highlight the recent findings on the role of Notch/RBP-J signaling in the maintenance of muscle progenitor cells during embryogenesis and in the generation of satellite cells in fetal development.