Myeloproliferative neoplasms (MPNs), a class of blood cancers, typically arise from mutations in the thrombopoietin receptor (MPL), JAK2, or calreticulin that constitutively activate JAK/STAT signaling in hematopoietic stem and progenitor cells (HSPCs) (6–8). The gene discussed is JAK2; the disease is myeloproliferative neoplasm.