In tumor-prone Rb/p107−/− eyes, all differentiating cells exhibit abnormal division, causing apoptosis of most neurons, and while ectopically dividing amacrine and horizontal interneurons as well as Müller glia survive, nascent tumors arise from the amacrine lineage, generating RB in around half of Rb/p107−/− eyes (Chen et al., 2004). Here, RBL1 is linked to neoplasm.