Multiple regulatory regions control the expression of Ets-1 in the developing mouse: vascular expression conferred by intron I.

Ets-1, a developmentally-regulated protooncogene, is expressed in multiple tissues during different stages of mouse development and cellular differentiation including high levels in lymphoid organs and endothelium. The putative roles of this DNA-binding protein in lymphoid development and maturation, as well as in angiogenesis and tumor vascularization, suggest that the regulation of Ets-1 may be critical to understanding these important developmental processes. We have cloned the mouse Ets-1 5' flanking region which shows significant homology to the human 5' flanking region, including potential transcription factor binding sites. Various amounts of mouse Ets-1 5' flanking, exon and intron sequences have been fused to the E. coli lacZ reporter gene and introduced into the mouse germline to identify genomic regions which regulate the developmental and tissue-specific expression of Ets-1. The 2.4 kb 5' flanking region of Ets-1 directs lacZ expression to the folding neural tube of embryos at gestational day 8.5 which is identical to the endogenous expression pattern of Ets-1. However, at later times in gestation, up to 5.3 kb of 5' flanking region results only in aberrant expression and is not able to confer lacZ expression in lymphoid or vascular tissues. When the first exon and 9 kb of the first intron are included with 5' flanking sequences, using an enhancer-trap-strategy, lacZ expression is observed in developing vessels, meninges and choroid plexus which correlates to endogenous Ets-1 expression. Further characterization of the vascular-specific element contained within intron I will provide important insights into the mechanisms controlling gene expression during angiogenesis.