Stuhlmann Laboratory

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Research

MOLECULAR REGULATION OF VASCULAR SYSTEM DEVELOPMENT

During the development of the mammalian embryo, the circulatory system is the first functional organ system to arise. The vascular system of organs and tissues develops by two distinct processes, vasculogenesis (de novo endothelial cell differentiation) and angiogenesis (formation of new blood vessels by sprouting of preexisting ones). While the importance of three principal families of vascular endothelial growth factors, VEGFs, angiopoietins, and ephrins, and their respective receptors for vasculogenesis and angiogenesis has been demonstrated, little is known about the nature of endothelial-specific transcription factors that coordinate gene regulation during these processes.

Our laboratory is interested in understanding the molecular pathways that control vascular system development using the mouse as a model system. Using retroviral gene trap vectors in mouse embryonic stem (ES) cells, we previously identified a novel gene, Vascular endothelial zinc finger 1, Vezf1. Vezf1is specifically expressed in endothelial cells of the developing vascular system and their mesodermal precursors in the yolk sac blood islands. Three major projects are presently being investigated in the laboratory:

Vezf1: loss- and gain-of-function studies
Based on its early onset and restricted expression, we hypothesize that Vezf1plays an important role during embryonic vasculogenesis and angiogenesis. To test this hypothesis, we have generated gain- and loss-of-function mutations in mouse embryonic stem (ES) cells and mice. Our results indicate that Vezf1acts in a dosage-dependent manner on the growth, remodeling, and integrity of the vasculature. Mutant embryos display a variety of vascular abnormalities and die from extensive hemorrhaging in the head and neck region.

Molecular pathways of Vezf1signaling
We are investigating the molecular pathways in which Vezf1participates. VEZF1 is a zinc finger transcription factor that contains a proline-rich transcriptional activator and forms specific DNA-protein complexes with oligomers corresponding sequences in the IL-3, Flk-1, and Flt-1 promoter. We are characterizing the regulatory elements and interacting proteins in the Vezf1promoter that are necessary and sufficient for endothelial-specific expression. We are also identifying proteins that functionally interact with VEZF1, and target genes that are regulated by Vezf1during vascular development.

Identification and characterization of endothelial stem cells
Another emphasis of our research is to identify endothelial precursors or "endothelial stem cells", both in the whole mouse embryo and during in vitro differentiation of mouse ES cells. We have designed a "knock-in" approach to mark the endogenous Vezf1allele with the green fluorescent protein (GFP). This approach will allow us to isolate GFP-expressing endothelial precursors, and to subsequently examine their potential to differentiate into vascular endothelium and possible other cell lineages when introduced into embryos or adult mice.