Figure 1.

Disruption of the mouse VE–cadherin locus by homologous recombination. (A) Gene-targeting strategy used to delete part of exon 2 of VE–cadherin gene. Probe A from inside and probe B from outside the recombination locus were used to screen for homologous recombination events. C, ClaI; N, NcoI; P, PvuII; S, SacI; E 2, exon 2 (solid rectangle); neo, phosphoglycerate kinase–neomycin resistance expression cassette (hatched rectangle); tk, phosphoglycerate kinase–HSV thymidine kinase expression cassette (open rectangle). Plasmid sequences are represented by small open boxes. (B) Southern blot analysis of genomic DNA from ES cell clones. Probe A hybridizes to a 3.7- and a 1.5-kb SacI genomic fragment derived from the wild-type and the targeted VE–cadherin alleles, respectively. Probe B hybridizes to a 6- and a 4.4-kb NcoI genomic fragment derived from the wild-type and the targeted loci, respectively. (C) Analysis of wild-type VE–cadherin, β major Globin (βmG), and hypoxanthine phosphoribosyltransferase gene expression in ES-derived, 11-day-old EBs. Total RNA from EBs, collected 11 days after the initiation of vascular differentiation, was submitted to an RT-PCR procedure. Negative control experiments were performed in parallel with RNA samples that were not treated with the RT (not shown). Hypoxanthine phosphoribosyltransferase gene expression was used as a standard.