FOXD1 and ALDH are evolutionarily conserved genes that contribute to central nervous system tumorigenesis. Glioblastoma shows cellular heterogeneity linked to glioma stem cells (GSC) of the mesenchymal (MES) or proneural subtype. Analysis of the MES-GSC regulatory machinery led to the identification of ALDH1 as a specific marker for MES GSCs that is transcriptionally regulated by FOXD1. Upregulation of Fd59A (Drosophila FoxD1 ortholog) correlates with formation of invasive glial neoplasms. Using immunohistochemistry in Drososphila larval central nervous system, it was found that Fd59A expression is upregulated in glial neoplasms from repoGAL4 UASPTEN^RNAi UASRas^V12 as compared with normal larvae. For details, see article by Cheng and colleagues on page 7219.