GATA-2 functions as a gatekeeper in hematogenic precursor cells. GATA-2 is expressed in endothelial cells in the early stage of angiogenesis, and TG-GFP specifically recapitulated GATA-2 expression in endothelial and/or mesenchymal cells with the potential to undergo hematopoietic differentiation. The high-level expression of GATA-2 in hematogenic precursor cells blocks subsequent differentiation of the cells into hematopoietic lineages. Cells with a light-blue cytoplasm represent endothelial cells. Cells with rhomboid shape and spheroid shape represent mesenchymal and hematopoietic cells, respectively. The blue nuclei and the green cytoplasm represent the cells expressing GATA-2 and TG-GFP, respectively.