Vezf1:A Zn Finger Transcription Factor Restricted to Endothelial Cells and Their Precursors

Abstract

Using retroviral entrapment vectors, we identified a novel mouse gene whose expression is restricted to vascular endothelial cells and their precursors in the yolk sac blood islands. A 3.68-kb cDNA corresponding to the endogenous transcript was isolated using genomic DNA flanking the entrapment vector insertion as a probe. We have named this gene Vezf1 for vascular endothelial zinc finger 1. Vezf1 encodes a protein with a predicted molecular mass of 56 kDa and that contains six putative zinc finger domains and shows high homology to a previously identified human gene, DB1, that is believed to be involved in regulating expression of cytokine genes such as interleukin-3. In situ hybridization analysis revealed the onset of expression in advanced primitive streak-stage embryos being located in the extraembryonic mesodermal component of the visceral yolk sac and in the anteriormost mesoderm of the embryo proper. During head-fold and somite stages, expression was restricted to vascular endothelial cells that arise during both vasculogenesis and angiogenesis. Vezf1-related sequences were found to be highly conserved among higher vertebrate species that have acquired extraembryonic yolk sac membranes during evolution. The Vezf1 locus mapped to the proximal part of mouse chromosome 2, a region which has homology to human chromosome 9q. Vezf1 expression correlates temporally and spatially with the early differentiation of angioblasts into the endothelial cell lineage and the proliferation of endothelial cells of the embryonic vascular system. Thus, Vezf1 may play an important role in the endothelial lineage determination and may have an additional role during later stages of embryonic vasculogenesis and angiogenesis.

Vezf1/DB1 Is an Endothelial Cell-specific Transcription Factor That Regulates Expression of the Endothelin-1 Promoter

“…In contrast, the highly specific interactions identified between Vezf1/DB1 and the ACCCCC motif result in potent trans-activation of the ET-1 promoter. These observations, in conjunction with the overlapping expression pattern of Vezf1/DB1 and ET-1 during development (4,14), makes regulation of ET-1 by Vezf1/DB1 a more plausible physiologic interaction to regulate gene expression in vascular endothelial cells. The ACCCCC sequence characterized in these studies as the Vezf1/DB1-binding site and response element does not exactly correspond to any previously identified transcription factor-binding sites, as determined by searches of the TRANSFAC data base.…”

“…Localizes to the Nucleus-Analysis of primary amino acid sequence of Vezf1/DB1 demonstrates that it contains 6 Cys 2 /His 2 -type zinc finger motifs and a proline-rich region characteristic of transcriptional activation or repression domains (14,15), suggesting that Vezf1/DB1 is likely to function as a transcription factor to regulate endothelial cell-specific genes. As the first step toward determining the function of this protein, we characterized the intracellular localization of Vezf1/DB1.…”

“…Vezf1/DB1 Trans-activates the hET-1 Promoter Maximally in Endothelial Cells-Because the expression of Vezf1/DB1 is restricted to the vascular endothelium (14), we wanted to determine whether its forced expression was sufficient to transactivate the ET-1 promoter in non-endothelial cell types. To test this, we transiently transfected MEC or non-endothelial cell lines (C2C12 and NIH/3T3) with either the wild-type or mutated hET-1 promoter constructs and the Vezf1/DB1 expression plasmid.…”

“…A retroviral trap screen identified a 56-kDa protein expressed specifically in the vascular endothelium, vascular endothelial zinc finger 1 (Vezf1) (14). Vezf1, which is the mouse homologue of a previously identified but incompletely characterized human protein called DB1 (15), is a putative transcription factor that contains 6 Cys 2 /His 2 -type zinc finger motifs, as well as a glutamine-stretch and a proline-rich region characteristic of transcriptional activation or repression domains.…”

“…Vezf1/DB1 is first expressed in the anterior-most mesoderm at day 7.25 post-conception. Expression remains restricted to the vascular endothelium through at least day 13.5 and is detectable in endothelial cells undergoing both angiogenesis and vasculogenesis (14). Vezf1/DB1 is therefore an attractive candidate as a potential transcription factor for mediating endothelial cell-specific gene expression, and is expressed in the correct spatial and temporal sequence during embryogenesis to regulate genes critical for endothelial cell differentiation, cardiovascular development, and/or angiogenesis.…”