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). Here, NPTX1 is linked to brain neoplasm.