Diffuse intraembryonic hemopoiesis in normal and chimeric avian development

Primitive and definitive erythropoiesis in the yolk sac: a birds eye view

“…Chick/quail and chick/chick chimera studies (Beaupain et al, 1979;Dieterlen-Lievre, 1975;Dieterlen-Lievre et al, 1976;Lassila et al, 1978;Lassila et al, 1982;Martin et al, 1978) and chick/chick parabiotic studies (Metcalf and Moore, 1971;Moore and Owen, 1965; indicated that, at least during the first few days of definitive erythrocyte generation, the source of cells is mainly yolk sac-derived. At about the same time, if not earlier, intraembryonic hematopoietic cells have been observed in association with the dorsal aorta (DieterlenLievre and Martin, 1981;Jaffredo et al, 2003;Jaffredo et al, 2005;Jaffredo et al, 2000;Jaffredo et al, 1998;Jordan, 1916;Nagai and Sheng, 2008;Olah et al, 1988;Pardanaud et al, 1996). A number of questions can be asked, for instance, about whether dorsal aorta-derived hematopoietic cells undergo definitive erythropoiesis either in circulation or in the yolk sac niche; whether yolk sac-derived hematopoietic cells can find their way to the dorsal aorta; and what is the exact type of cells from the yolk sac that contribute to early definitive erythropoiesis.…”

Origins and functions of phagocytes in the embryo

“…The yolk sac hematopoietic cells develop in the splanchnic mesoderm of the yolk sac from the inner cells of the angiogenic clusters (hemangioblasts, also called blood islands) [1][2][3]. Although the hematopoietic progenitors in the yolk sac apparently can differentiate into all hematopoietic lineages when stimulated with appropriate growth factors in vitro, studies with chick/quail chimeras [3,4] indicate that the avian yolk sac blood cells are transitory. Definite blood cells in the chick embryo proper arise not from the yolk sac-derived cells but from the intraembryonic cells originating in the aortic mesoderm.…”

Migratory path of definitive hematopoietic stem/progenitor cells during zebrafish development

“…5 However, the singular hematopoietic origin from yolk sac/VBI is challenged by substantial evidence from experiments with various species that reveals another evolutionary conserved intraembryonic hematopoietic site: the para-aortic splanchnopleurae (pSP) and later referred as aorta-gonad-mesonephros (AGM). [6][7][8][9][10][11] Hence, it is currently believed that yolk sac/VBI mainly supports primitive hematopoiesis, whereas definitive hematopoiesis is autonomously initiated, at least in part, in the pSP/AGM region.…”

“…5 However, the singular hematopoietic origin from yolk sac/VBI is challenged by substantial evidence from experiments with various species that reveals another evolutionary conserved intraembryonic hematopoietic site: the para-aortic splanchnopleurae (pSP) and later referred as aorta-gonad-mesonephros (AGM). [6][7][8][9][10][11] Hence, it is currently believed that yolk sac/VBI mainly supports primitive hematopoiesis, whereas definitive hematopoiesis is autonomously initiated, at least in part, in the pSP/AGM region.The journey of definitive HSPCs is best characterized both temporally and spatially in mice. 4 Although multipotential hematopoietic progenitor cells revealed by in vitro colony assays, injection into yolk sac cavity, transplantation into fetal liver of newborn mice or reconstitution of immunodeficient mice, can be detected in the pSP/AGM region and yolk sac at earlier developmental stages, 12-15 the first definitive HSPCs, defined as cells fully competent to provide long-term reconstitution of irradiated adult recipients, emerge in the pSP/AGM region at embryonic day (E) 10.5.…”