VASCULAR ENDOTHELIAL-CELL LINEAGE-SPECIFIC PROMOTER IN TRANSGENIC MICE

Vascular endothelial cells play essential roles in the function and de velopment of the cardiovascular system. However, due to the lack of li neage-specific markers suitable for molecular and biochemical analyses , very little is known about the molecular mechanisms that regulate en dothelial cell differentiation. We report the first vascular endotheli al cell lineage-specific (including angioblastic precursor cells) 1.2 kb promoter in transgenic mice. Moreover, deletion analysis of this pr omoter region in transgenic embryos revealed multiple elements that ar e required for the maximum endothelial cell lineage-specific expressio n. This is a powerful molecular tool that will enable us to identify f actors and cellular signals essential for the establishment of vascula r endothelial cell lineage. It will also allow us to deliver genes spe cifically into this cell type in vivo to test specifically molecules t hat have been implicated in cardiovascular development. Furthermore, w e have established embryonic stem (ES) cells from the blastocysts of t he transgenic mouse that carry the 1.2 kb promoter-LacZ reporter trans gene. These ES cells were able to differentiate in vitro to form cysti c embryoid bodies (CEB) that contain endothelial cells determined by P ECAM immunohistochemistry. However, these in vitro differentiated endo thelial cells did not express the LacZ reporter gene. This indicates t he lack of factors and/or cellular interactions which are required to induce the expression of the reporter gene mediated by this 1.2 kb pro moter in this in vitro differentiation system. Thus this system will a llow us to screen for the putative inducers that exist in vivo but not in vitro. These putative inducers are presumably important for in viv o differentiation of vascular endothelial cells.