Annexin V staining showed that Gfi1 KO thymocytes display higher levels of apoptosis, either at baseline or following exposure to IR, compared to WT controls (Supplementary Fig. 1d), consistent with previous results in T-cell lymphoma and T-cell acute lymphoblastic leukemia (T-ALL)4. The gene discussed is GFI1; the disease is acute lymphoblastic leukemia.