Differential regulation of the von Willebrand factor and Flt-1 promoters in the endothelium of hypoxanthine phosphoribosyltransferase-targeted mice.
An important limitation of standard transgenic assays is that multiple copies of the transgene are inserted randomly into the mouse genome, resulting in line-to-line variation in expression. One way to control for these variables is to target a single copy of the transgene to a defined locus of the mouse genome by homologous recombination. In the present study, we have used such an approach to target the promoters of 2 different genes, namely von Willebrand factor (VWF) and Flt-1, to the hypoxanthine phosphoribosyltransferase (Hprt) gene locus. Consistent with previous findings in standard transgenic animals, we report that the VWF promoter contains information for expression in a subset of endothelial cells in the heart, skeletal muscle, and brain. In contrast, the Flt-1 promoter directs expression in all vascular beds except for the liver. The Flt-1 transgene was active in the endothelium of tumor xenografts, whereas the VWF promoter was not. Under in vitro conditions, conditioned medium from tumor cells resulted in a significant up-regulation of Flt-1 mRNA and promoter activity, but no change in VWF levels. Taken together, these results suggest that (1) Hprt locus targeting is a valuable tool for studying vascular bed-specific gene regulation, (2) the VWF and Flt-1 promoters are regulated by distinct transcriptional mechanisms in the intact endothelium, and (3) tumor angiogenesis results in the differential activation of endothelial cell-specific promoters.
Minami
Takashi
T
Department of Molecular Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
Donovan
Diana J
DJ
Tsai
Jo C
JC
Rosenberg
Robert D
RD
Aird
William C
WC
D000818:Animals; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004622:Embryo, Mammalian; D004730:Endothelium, Vascular / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000235:genetics*; D005260:Female; D005786:Gene Expression Regulation; D007041:Hypoxanthine Phosphoribosyltransferase / Q000172:deficiency / Q000235:genetics*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D018995:Myosin Heavy Chains; D009374:Neoplasms, Experimental / Q000098:blood supply / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000235:genetics; D024501:Nonmuscle Myosin Type IIB; D009928:Organ Specificity; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects; D014407:Tumor Cells, Cultured; D040281:Vascular Endothelial Growth Factor Receptor-1; D014841:von Willebrand Factor / Q000235:genetics*
D017077:Culture Media, Conditioned; D016326:Extracellular Matrix Proteins; D012333:RNA, Messenger; D014841:von Willebrand Factor; D007041:Hypoxanthine Phosphoribosyltransferase; C501163:Flt1 protein, mouse; D040281:Vascular Endothelial Growth Factor Receptor-1; D024501:Nonmuscle Myosin Type IIB; C103815:nonmuscle myosin type IIB heavy chain; D018995:Myosin Heavy Chains