Here, we sought to identify the direct in vivo role and transcriptional targets of ASCL1 in brain tumors of previously characterized patient‐derived xenograft (PDX)‐GBM (Marian et al., 2010; Marin‐Valencia et al., 2012) and a genetically engineered glioma mouse model (Lin et al., 2004; Zhu et al., 2001). The gene discussed is ASCL1; the disease is glioblastoma.