Joseph B. Kearney

The vascular endothelial growth factor (VEGF) receptor Flt-1 (VEGFR-1) modulates Flk-1 (VEGFR-2) signaling during blood vessel formation.

Mice lacking the vascular endothelial growth factor (VEGF) receptor flt-1 (VEGFR-1) die from vascular overgrowth, caused primarily by aberrant endothelial cell division (Kearney JB, Ambler CA, Monaco KA, Johnson N, Rapoport RG, Bautch VL: Vascular endothelial growth factor receptor Flt-1 negatively regulates developmental blood vessel formation by modulating endothelial cell division. Blood 2002, 99:2397-2407). Because a second high-affinity VEGF receptor, flk-1, produces a positive endothelial proliferation signal, it was logical to ask whether flt-1 affects developmental blood vessel formation by modulating signaling through flk-1. Differentiated embryonic stem cell cultures lacking flt-1 (flt-1-/-) had increased flk-1 tyrosine phosphorylation, indicating that flk-1 signaling is up-regulated in the mutant background. The selective flk-1 inhibitor SU5416 partially rescued the flt-1-/- mutant phenotype, and this rescue was accompanied by a decrease in the relative amount of flk-1 tyrosine phosphorylation. Thus reduced flk-1 signal transduction can partially compensate for the lack of flt-1. The flt-1-/- mutant phenotype was also partially rescued by Flt-1/Fc, a truncated flt-1 that binds and sequesters the VEGF ligand. Taken together, these data show that down-regulation of flk-1 signaling by two different strategies partially rescues the developmental vascular overgrowth seen in the absence of flt-1, and they support a model whereby flt-1 modulates the flk-1 signal at an early point in the pathway.

In Vitro Differentiation of Mouse ES Cells: Hematopoietic and Vascular Development

Publisher Summary Mouse ES cells have been differentiated in vitro since the mid-1980s, and vasculogenesis and hematopoiesis were among the earliest developmental processes studied using this model. Vascular development during mouse ES cell differentiation involves two processes also used in vivo : (1) vasculogenesis, the assembly of mesodermal precursor cells called angioblasts and their differentiation into endothelial cells, and (2) angiogenesis, the expansion of vessels by migration and cell division of endothelial cells in vessels. This chapter describes protocols and assays that together provide a set of tools for quantitative analysis of vascular and hematopoietic parameters during ES cell differentiation. The in situ localization techniques also described here can be adapted to measure other cell biological parameters, such as the number of cytoplasmic extensions emanating from vascular tips. Moreover, it is just the start to utilize the imaging capability of the ES cell differentiation model to answer questions about the dynamic aspects of vascular and hematopoietic development. It is anticipated that these approaches will be combined with genetic and molecular biological tools (i.e., microarray analysis) in the future to provide new insights into vascular and hematopoietic development.

csf1 is required for early embryonic macrophage development: Characterization of the csf1op/csf1op mutation in ES cell-derived macrophages

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The VEGF receptor Flt-1 spatially modulates Flk-1 signaling and blood vessel branching

Kappas et al. 2008. J. Cell Biol. doi:10.1083/jcb.200709114 [OpenUrl][1][Abstract/FREE Full Text][2] [1]: {openurl}?query=rft_id%253Dinfo%253Adoi%252F10.1083%252Fjcb.200709114%26rft_id%253Dinfo%253Apmid%252F18504303%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%