Egfl7^Gt(1-13)Stmn

A gene trap clone, 1-13, displayed strong alkaline phosphatase (AP) reporter gene expression in the extraembryonic mesoderm and in vascular structures of the embryo proper. Using genomic sequences that flank the retroviral integration site to probe an embryonic library, a cDNA clone corresponding to 3' sequences of Vezf1 was identified (J:53033). It was subsequently discovered that this clone comprised a chimeric cDNA that contained Vezf1 sequences at its 5' end and a second open reading frame corresponding to Egfl7. Further comparison of genomic and cDNA sequences revealed that the retroviral insertion in the ES cell clone 1-13 had occurred in the Egfl7 gene (F. Kuhnert and H. Stuhlmann, unpublished observations). This finding suggested that the endothelial-specific expression pattern of the AP reporter gene observed in embryos derived from clone 1-13 (J:53033) reflects the expression of the endogenous Egfl7 gene rather than Vezf1. (J:53033, J:90268)