Enforced expression of the GATA-2 transcription factor blocks normal hematopoiesis

The zinc finger transcription factor GATA-2 is highly expressed in immature hematopoietic cells and declines with blood cell maturation. To investigat e its role in normal adult hematopoiesis a bicistronic retroviral vector en coding GATA-2 and the green fluorescent protein (GFP) was used to maintain the high levels of GATA-2 that are normally present in primitive hematopoie tic cells. Coexpression of the GFP marker facilitated identification and qu antitation of vector-expressing cells. Bone marrow cells transduced with th e GATA-2 vector expressed GFP as judged by flow cytometry and GATA-2 as ass essed by immunoblot analysis. A 50% to 80% reduction in hematopoietic proge nitor-derived colony formation was observed with GATA-2/GFP-transduced marr ow, compared with marrow transduced with a GFP-containing vector lacking th e GATA-2 cDNA. Culture of purified populations of GATA-2/GFP-expressing and nonexpressing cells confirmed a specific ablation of the colony-forming ab ility of GATA-2/GFP-expressing progenitor cells. Similarly, loss of spleen colony-forming ability was observed for GATA-2/GFP-expressing bone marrow c ells. Despite enforced GATA-2 expression, marrow cells remained viable and were negative in assays to evaluate apoptosis. Although efficient transduct ion of primitive Sca-1(+) Lin(-) cells was observed with the GATA-2/GFP vec tor, GATA-2/GFP-expressing stem cells failed to substantially contribute to the multilineage hematopoietic reconstitution of transplanted mice. Additi onally, mice transplanted with purified, GATA-2/ GFP-expressing cells showe d post-transplant cytopenias and decreased numbers of total and gene-modifi ed bone marrow Sca-1(+) Lin(-) cells. Although Sca-1(+) Lin(-) bone marrow cells expressing the GATA-2/GFP vector were detected after transplantation, no appreciable expansion in their numbers occurred. In contrast, control G FP-expressing Sca-1(+) Lin(-) cells expanded at least 40-fold after transpl antation. Thus, enforced expression of GATA-2 in pluripotent hematopoietic cells blocked both their amplification and differentiation. There appears t o be a critical dose-dependent effect of GATA-2 on blood cell differentiati on in that downregulation of GATA-2 expression is necessary for stem cells to contribute to hematopoiesis in vivo. (C) 1999 by The American Society of Hematology.