GFAP and oligodendroglioma: The glioma phenotypes of these various tumors were also confirmed by H&E staining revealing the predominance of pink GFAP+ fibers (arrows) within astrocytoma tumors (Olig2-CKO, Ascl1-OE) or round “fried egg” cells with perinuclear halo (arrowhead), characteristics of oligodendroglioma (Ascl1-CKO) tumors (Fig. 4d, h, l, p, t).