 Acute promyelocytic leukemia (APL) is characterized by the t(15;17) translocation that generates the fusion protein promyelocytic leukemia-retinoic acid receptor ? (PML-RARA) in nearly all cases.     ///    "To address this discrepancy, we have generated a system whereby PML-RARA expression is somatically acquired from the mouse Pml locus in the context of Pml haploinsufficiency. "    ///    Multiple prior mouse models of APL constitutively express PML-RARA from a variety of non-Pml loci.     ///    PML-RARA can increase hematopoietic  self-renewal without causing a  myeloproliferative disease in mice..     ///    "Thus, at physiologic doses, PML-RARA primarily acts to increase hematopoietic progenitor self-renewal, expanding a population of cells that are susceptible to acquiring secondary mutations that cause progression to leukemia. "    ///    We found that physiologic PML-RARA expression was sufficient to direct a hematopoietic progenitor self-renewal program in vitro and in vivo. 