Molecular Regulation of Adult Hematopoiesis By GATA-2

GATA-2 is a zinc finger-containing transcriptional regulator that plays important roles in embryonic and adult hematopoiesis. Mutations in human GATA2 are associated with myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), as well as immunodeficiency disorders that present with a profound loss of monocytes, dendritic cells and other myeloid lineage populations. Recent work reveals crucial roles for GATA-2 in definitive hematopoietic stem/progenitor cell activity, vascular integrity and lymphatic development. However, the molecular mechanisms by which GATA-2 controls adult hematopoiesis via hematopoietic-cell autonomous functions are largely unknown. To address this question, we generated a tamoxifen-inducible Gata2-deficient mouse strain by breeding Gata2^flox/flox mice with Cre-ER transgenic animals. Following tamoxifen treatment, Cre-ER Gata2^flox/flox mice show a rapid and profound loss of circulating neutrophils, monocytes and lymphocytes, concomitant with development of anemia. These results are consistent with the requirement for GATA-2 in hematopoietic stem/progenitor cells, and may also reflect GATA-2 function in endothelial cells within the vascular niche. To explore hematopoietic-specific GATA-2 activity, we generated bone marrow chimeric mice with hematopoietic-restricted Gata2-deficiency by transplanting Cre-ER Gata2^flox/flox hematopoietic cells into wild type recipients. Cre-ER Gata2^flox/flox bone marrow chimeras show rapid development of cytopenias upon tamoxifen exposure, suggesting a cell autonomous role for GATA-2 in maintaining adult hematopoiesis. Strikingly, hematopoietic progenitor cells rapidly lose c-Kit expression upon inducible Gata2 deletion. Chromatin immunoprecipitation and reporter assays suggest GATA-2 cooperates with C/EBPa in regulating kit transcription. Our study suggests conditional deletion of Gata2 restricted to the hematopoietic compartment provides a model for bone marrow failure associated with MDS and mutant GATA2 human immunodeficiencies that may enable further insight into the molecular network by which GATA-2 mediates definitive hematopoiesis.

Supported by grants from NIH (AI098099) and the MD Anderson Center for Cancer Epigenetics.(SSW) and the MD Anderson Center for Cancer and Inflammation (HSL).