The myogenic differentiation status of the Ras-driven sarcomas generated in this system depends largely on the cell type transduced, also known as the “cell-of-origin”: Kras; p16p19null satellite cells typically gave rise to RMS, whereas the identical oncogenetic lesions introduced into fibroadipogenic precursors within the MFA cell pool almost always produced sarcomas lacking myogenic differentiation features (non-myogenic sarcomas, NMS) (Hettmer et al., 2011)(Figure 1—figure supplement 1). Here, KRAS is linked to sarcoma.