To functionally test ASCL1's role in gliomagenesis in vivo, we began by characterizing the temporal expression pattern of ASCL1 along with OLIG2, SOX2, and glial lineage markers in brain tumors induced in a mouse model carrying floxed alleles of the tumor suppressor genes Neurofibromin 1 (Nf1) and tumor protein 53 (Tp53) (Nf1F/F;Tp53F/F) (Lin et al., 2004; Zhu et al., 2001). The gene discussed is NF1; the disease is brain neoplasm.