A D320K mutation was introduced into exon 6 and an FRT flanked neo cassette was inserted in intron 6 via homologous recombination. Flp mediated recombination removed the neo cassette. The mutation in exon 6 disrupts binding to VEGF without disrupting AP-SEMA3A binding. Western blot analysis indicates protein expression level is similar to wild-type controls at E14.5 in the lung and in the adult heart, brain, lung and kidney. (J:218050)