The identification of these alterations allowed a better classification of leukemia patients in subgroups according to specific genetic lesions (eg, BCR-ABL1 like subgroup), provided new markers for risk-assessment and/or for monitoring minimal residual disease (eg, IKZF1, CRLF2, TP53), and highlighted novel therapeutic approaches (eg, inhibitors of JAK2, HDAC, and NOTCH1). The gene discussed is JAK2; the disease is leukemia.