Fig. 1. Tie2- and Tie1-Cre mediate efficient deletion of β1 integrins in mouse embryos. Gene deletion analyses of Tie2-Cre (A-D) and Tie1-Cre (E,F) mutants as compared with controls. (A) Genomic PCR analysis of e8.5 embryos demonstrates recombination (rec.) of β1 integrin in embryos carrying Tie2-Cre and two floxed alleles of β1. (B) e8.5 cryosections were stained with anti-CD31 (red), anti-β1 integrin (Ha2/5, green) and DAPI (blue). (C) Collagenase-dissociated e8.5 embryonic cells were plated onto fibronectin and stained with anti-β1 (HMβ1-1, green), anti-β3 integrin (red) and DAPI (blue). Endothelial cell (EC) identity in C was determined by co-staining with anti-CD31 (not shown). (D) Focal contacts in isolated ECs. Bars are means + s.e.m. of two (β1) or three (β3) experiments. ^**P<0.01 by one sample t-test and ^*P<0.05 by Student's t-test. (E) Genomic PCR analysis of e10.5 embryos from Tie1-Cre matings. (F) e9.5 cryosections were stained with anti-CD31 (red), anti-β1 integrin (green) and DAPI (blue). Arrows, primary head veins; arrowheads, β1 integrin-negative endothelium; ys, yolk sac blood islands; a-da, anterior dorsal aortae; p-da, posterior dorsal aortae; nt, neural tube; g, gut; ve, visceral endoderm. Also see Fig. 3F for diagram of embryonic structures. Scale bars: 20 µm.