Figure 3.

Quantitative vascular phenotype analysis of wild-type^+/+, VE–cadherin mutant heterozygous^+/−, and homozygous^−/− ES cell clone-derived, 11-day-old EBs. Frozen-embedded sections (10-μm thick) of ES cell clone-derived 11-day-old EBs were processed for indirect immunofluorescence using an anti-mouse CD34 rat mAb. Organized (solid rectangle), dispersed (open rectangle), and intermediate (punctuated rectangle) vascular EB phenotypes were counted from at least two independent differentiation experiments for each clones. Clones 4–6 were homozygous null-mutants for the VE–cadherin locus (−/−), clones 2 and 3 remained heterozygous (+/−) after the second round (high concentration) of neomycin selection, and clone 1 was one of the two heterozygous clones obtained from the first round of neomycin selection and from which clones 2–6 were derived. +/+ represents the original CJ7 ES cell population and ri +/+ is a clone with a random integration of the targeting vector with two intact VE–cadherin loci. Similar data have been obtained when vascular phenotypes were quantified with PECAM or MECA-32 distribution analysis.