This lack of acquired mutations contrasts with our prior WES studies in murine leukemias initiated by NUP98 fusions genes, in which we found spontaneous, acquired mutations of well-known leukemia genes (such as Nras, Kras, Idh1, Jak1/2, and Bcor) in 50% of AML19, 72% of ETP-ALL (L. Goldberg and P.D. Aplan, unpublished), and 100% of B cell precursor ALL19. The gene discussed is IDH1; the disease is acute lymphoblastic leukemia.