Hematopoietic stem cells (HSCs) emerge during embryogenesis from hemogenic endothelium, but it remains unclear how the HSC lineage is initially established from mesoderm during ontogeny. In Xenopus, the definitive hemangioblast precursors of the HSC lineage have been identified in dorsal lateral plate (DLP) mesoderm, and a transcriptional gene regulatory network (GRN) controlling hemangioblast ...

Endoglin (ENG), an ancillary receptor for several members of the transforming growth factor (TGF)-beta superfamily, has a well-studied role in endothelial function. Here, we report that endoglin also plays an important role early in development at the level of the hemangioblast, an embryonic progenitor of the hematopoietic and endothelial lineages. Eng(-/-), Eng(+/-) and Eng(+/+) mouse embryoni...

The first hematopoietic and endothelial progenitors are derived from a common embryonic precursor termed the hemangioblast. The genetic cascades that regulate the differentiation of the hemangioblast to hematopoietic and endothelial cells are largely unknown. In general, much of embryonic development is coordinately regulated by temporal and spatial expression of transcription factors, such as ...

Recently identified BLast Colony Forming Cells (BL-CFCs) from in vitro differentiated embryonic stem (ES) cells represent the common progenitor of hematopoietic and endothelial cells, the hemangioblast. Access to this initial cell population committed to the hematopoietic lineage provides a unique opportunity to characterize hematopoietic commitment events. Here, we show that BL-CFC expresses t...

We review here the development of the hematopoietic system and its relationship to the endothelium, with a special focus on the characterisation of the hemangioblast, the putative ancestor for endothelial cells and hematopoietic cells. Using the avian model, we have traced in vivo the progeny of embryonic endothelial cells and shown that aortic-born hematopoietic cells (known to generate the de...

BACKGROUND The hemangioblast is a bi-potential precursor cell with the capacity to differentiate into hematopoietic and vascular cells. In mouse E7.0-7.5 embryos, the hemangioblast can be identified by a clonal blast colony-forming cell (BL-CFC) assay or single cell OP9 co-culture. However, the ontogeny of the hemangioblast in mid-gestation embryos is poorly defined. DESIGN AND METHODS The BL...

The hemangioblast is a progenitor cell with the capacity to give rise to both hematopoietic and endothelial progenitors. Currently, the regulatory mechanisms underlying hemangioblast formation are being elucidated, whereas those controllers for the selection of hematopoietic or endothelial fates still remain a mystery. To answer these questions, we screened for zebrafish mutants that have defec...

Primitive hematopoiesis occurs in the yolk sac blood islands during vertebrate embryogenesis, where abundant phosphatidylcholines (PC) are available as important nutrients for the developing embryo. However, whether these phospholipids also generate developmental cues to promote hematopoiesis is largely unknown. Here, we show that lysophosphatidic acid (LPA), a signaling molecule derived from P...

The hematopoietic and endothelial lineages derive from mesoderm and are thought to develop through the maturation of a common progenitor, the hemangioblast. To investigate the developmental processes that regulate mesoderm induction and specification to the hemangioblast, we generated an embryonic stem cell line with the green fluorescent protein (GFP) targeted to the mesodermal gene, brachyury...

Bone morphogenetic protein (BMP) signaling regulates embryonic hematopoiesis via receptor-mediated activation of downstream SMAD proteins, including SMAD1. In previous work, we showed that Smad1 expression is sufficient to enhance commitment of mesoderm to hemangioblast fate. We also found indirect evidence to support a subsequent repressive function for Smad1 in hematopoiesis. To test this hyp...