Figure 1. A, B, Target cells of RCAS infection in Ctv-a mice. Arrows denote RCAS-EGFP-infected mouse cells (adjacent to injected RCAS-producing DF-1 cells) double-positive for GFP and (A) NG2 or (B) OLIG2. Scale bars: A, B, top left, 100 μm; A, top right, 50 μm; B, top right, 25 μm. C–I, K-RAS+AKT-induced astrocytic gliomas from OPCs. Loss of Arf or Ink4a-Arf resulted in (C) increased incidence [wild type (wt) vs Ink4a-Arf−/−, p = 0.0172; wt vs Arf−/−, p = 0.0024; Ink4a−/− vs Ink4a-Arf−/−, p = 0.0511; Ink4a−/− vs Arf−/−, p = 0.0096; Arf−/− vs Ink4a-Arf−/−, p not significant], (D) high-grade tumors, and (E) decreased survival (Kaplan-Meier: wt vs Arf−/−, p = 0.002; wt vs Ink4a-Arf−/−, p = 0.0124; Ink4a−/− vs Arf−/−, p = 0.0064; Ink4a−/− vs Ink4a-Arf−/−, p = 0.0271). F, G, H&E stained tumors. H, I, Immunostainings for HA.