PBX1 and myeloproliferative disorder: Shepard et al. observed that HSCs in JAK2 mutant myeloproliferative neoplasms harbored defective self-renewal properties, while robust self-renewal capacity and HSC repopulation was noted when BMI1, PBX1 or MEIS1 were overexpressed within mutant myeloproliferative neoplasms43,44.