Targeting the hemangioblast with a novel cell type-specific enhancer

Abstract

BackgroundHemangioblasts are known as the common precursors for primitive hematopoietic and endothelial lineages. Their existence has been supported mainly by the observation that both cell types develop in close proximity and by in vitro differentiation and genetic studies. However, more compelling evidence will arise from tracking their cell fates using a lineage-specific marker.ResultsWe report the identification of a hemangioblast-specific enhancer (Hb) located in the cis-regulatory region of chick Cerberus gene (cCer) that is able to direct the expression of enhanced green fluorescent protein (eGFP) to the precursors of yolk sac blood and endothelial cells in electroporated chick embryos. Moreover, we present the Hb-eGFP reporter as a powerful live imaging tool for visualizing hemangioblast cell fate and blood island morphogenesis.ConclusionsWe hereby introduce the Hb enhancer as a valuable resource for genetically targeting the hemangioblast population as well as for studying the dynamics of vascular and blood cell development.

Nkx2.5 marks angioblasts that contribute to hemogenic endothelium of the endocardium and dorsal aorta

“…The mouse Nkx2-5 cardiac enhancer was obtained from Prof. Eric Olson (Lien et al, 1999) and subcloned into the pTK vector for chick expression. To study the relationship between the hemangioblast and the cardiac mesoderm, we obtained a hemangioblast enhancer based on the chick Cerberus gene, that drives expression of GFP (Teixeira et al, 2011). For ectopic expression of Nkx2.5 and Tal1, chick coding sequences were cloned into pCAGG-IRES-GFP, which drives ubiquitous expression in every avian cell (Megason and McMahon, 2002).…”

Hematopoietic Stem Cells

“…It has been proposed that during embryonic development hematopoietic cells arise from a mesodermal progenitor with both endothelial and hematopoietic potential called the hemangioblast [130,131]; reviewed in reference [106]. An alternative theory is that hematopoietic cells originate from a specific type of endothelium designated as hemogenic.…”

Endothelio-hematopoietic relationship: getting closer to the beginnings

“…The first evidence pointing to the existence of the bipotent hemangioblast was obtained when mouse ES cell-derived progenitors were shown to be capable of producing in vitro 'blast' colonies (BL-CFC), comprising both hematopoietic and vascular endothelial cells, in response to growth factors [6,7]. ES cell differentiation has been extensively used to model the stepwise transition of the bipotent hemangioblast to the blood and endothelial lineages, shedding light on surface markers expressed at each stage as well as genetic regulation of this process [4,5,8] (Figure 1A). During hematopoietic differentiation, mouse ES cells first generate the primitive streak mesoderm marked by brachyury expression, followed by quick upregulation of Flk1, which marks the formation of extraembryonic mesoderm and the onset of endothelial specification.…”