Transcription factor that acts synergistically with tal1/scl in primitive and definitive hematopoiesis, and in endothelial development. Specifies mesodermal precursors to a hemangioblast cell fate. Hemangioblasts are bipotential precursors of blood and endothelium, and in the absence of hematopoietic induction cues such as gata1, tal1/scl-lmo2-induced haemangioblasts differentiate into endothelial cells. During embryogenesis, expressed in hematopoietic and endothelial precursors, including the two stripes of posterior and anterior lateral plate mesoderm at the 1-somite stage that give rise to the primitive blood. By ets transcription factors including ets1.