OLIG2 and glioblastoma: The Nestin-tva (Ntv-a) transgenic mice in an Ink4a-Arf-/- Ptenfl/fl background develop Olig2-positive glioblastomas upon PDGF-B expression homologous to human glioblastomas of the proneural subtype with the same histopathology, including pseudopalisading necrosis, microvascular proliferation, and high mitotic activity (65,66).