Thus, these observations are most consistent with a model wherein a single p53-mutant neural stem cell spontaneously loses Nf1 or acquires other oncogenic mutations, activating Ras-mediated Erk/MAPK signaling pathway and promoting clonal expansion of p-Erk+Olig2+p53Mutant-expressing glioma precursors. The gene discussed is OLIG2; the disease is central nervous system cancer.