To determine whether increased expression of Gab2 and/or Pak1 was relevant for AML progression in this model, we prepared retroviral constructs expressing candidate cDNAs (with an IRES-eGFP tag) and transduced them into lineage-depleted, nonleukemic bone marrow cells from WT, Dnmt3aR878H/+ only, Npm1cA/+ only, or Dnmt3aR878H/+× Npm1cA/+ doubly-mutant mice, creating an initial mixture of transduced (GFP+) and nontransduced (GFP–) cells (Figure 2A). The gene discussed is PAK1; the disease is acute myeloid leukemia.