Fig. 6. c-myc-deficient ECs exhibit no detectable defects in proliferation, survival, morphology, motility or tube formation. (A) BrdU+ ECs in the dorsal aortae. Cross-sections were stained with anti-CD31 and anti-BrdU antibodies. (B) Fold increases in apoptosis in yolk sac ECs and non-ECs. Cross-sections of Tie2-Cre;c-myc^flox/- (at 10.5 dpc) and Vav-iCre;c-myc^flox/- (at 11.5 dpc) mutant (black bars) and control (white bars) yolk sacs were stained with anti-CD31 and for TUNEL. TUNEL⁺ CD31⁺ or TUNEL⁺ CD31^- cells were quantified. ^**P<0.05; ^*P<0.01 by Student's t-test. Data were collected from four pairs of embryos from two different litters. (C,D) Phalloidin (green), anti-CD31 (red) and DAPI (blue) stained ECs isolated from 10.5 dpc embryos. (E-G) Random movement of cultured ECs from 10.5 dpc embryos monitored by timelapse microscopy. Representative EC migration paths are shown (E) and quantitative analysis demonstrated no significant difference in either the net-path of cell migration (F, P=0.083) or in the average migration speed (G, P=0.090) in two independent experiments. The ANOVA two-tailed test was used in the statistical analysis. (H-K) No detectable defects in EC tube formation. myc^flox/flox ECs were purified from adult vena cava. Cells 48 hours after infection with GFP fusion Cre-expressing adenovirus AdCreGFP or GFP expression control virus AdGFP were plated on Matrigel, and cultures were photographed 20 hours later (H,I). The results from four independent experiments were analyzed by two-tailed t-test (J, P=0.1916). Green, GFP; red, DiI-AcLDL labeled ECs. Genomic DNA PCR analysis demonstrates the deletion of c-myc floxed sequence by AdCreGFP but not AdGFP (K). Scale bar: 10 µm in C,D; 200 µm in H,I.