Type II neuroblast lineage-specific or immature INP-specific depletion of the ligand Delta, as well as neuroblast lineage-specific expression of a dominant negative form of Delta (Dl-DN) that lacks its intracellular domain (Baonza et al., 2000; Flores et al., 2000; Huppert et al., 1997), completely or potently suppressed brain tumor phenotypes caused by vps35 mutations (Figure 3D,E and Figure 3—figure supplement 2E,F). This evidence concerns the gene VPS35 and brain neoplasm.