RESUMO
The development of the murine embryonic hematopoietic system occurs in spatially and temporally distinct waves, which it is described as three waves so far-primitive hematopoiesis, bipotential erythroid-myeloid progenitors (EMPs) generation and long-lived transplantable hematopoietic stem cells (HSCs) maturation from their precursors and differentiation toward all the adult lineages. The latest point is that HSC-independent hematopoietic lineages are produced in the primitive wave and definitive progenitor wave in the early mammalian embryo, such as primitive erythrocytes or EMPs. The HSC-dependent phase of hematopoietic development produces all the adult lineages derived from HSCs. In this review, the recent studies on the development of hematopoietic cells and HSCs in the yolk sac and aorta-gonad-mesonephron region (AGM) region at cellular and molecular level will be summarized to provide an integrated model of developmental hematopoiesis, although multiple hematopoietic sites are involved in embryonic hematopoiesis. It may offer new insights into the characteristics and its underlying mechanism of hematopoiesis at the early stage of embryogenesis.