Model of Vegf regulation of embryonic erythroid development through Gata1 modulation. Development of erythropoiesis profiles are shown from progenitor cells to the terminally differentiated erythrocytes or RBCs (gray bars). Alteration of erythroid Vegf levels lead to cell intrinsic effects on Gata1 expression levels and key transcriptional targets. Expression of Gata2 transgene specifically in erythroid cells can overcome both the decrease of Gata1 expression and the block in erythroid cell differentiation, induced by Vegf overexpression. Modulation of Vegf levels within the erythroid lineage can also modulate the environment and indirectly affect developmental erythropoiesis through the altered secretion of growth factors such as paracrine Vegf, Ihh, Epo, and potentially other as yet unidentified factors.