RAG2 and acute lymphoblastic leukemia: Another central oncogene associated with T-ALL is NOTCH1. rag2-driven expression of the Notch1 intracellular domain (ICN1) causes constitutive activation of Notch signaling in T cells, eventually leading to the development of T-ALL in zebrafish (Blackburn et al., 2012; Chen et al., 2007).