Figure 1. Effects of Ephrin-A1 on EMT in chick cushion explants.

(A) Ephrin-A1-Fc inhibits EMT in chick cushion explants. AV cushion explants were cultured on collagen gel in the presence of 5 µg/ml ephrin-A1 or vehicle control. AV cushion explants were scored for the total number of transformed cells by optically sectioning the collagen gels using Hoffman Optics. The number of explants in each group, total numbers of transformed cells per condition, and the mean number of transformed cells ± SEM, expressed as a percentage of control, were as follows: ephrin-A1 (n=26; 1832; 71 ± 8%), control (n=24; 2370; 100 ± 5%). (B) Ephrin-A1 inhibits endocardial cushion transformation. Adenoviruses expressing ephrin-A1 and GFP, or control GFP only, were injected into the lumen of the chick heart tube at stage 10–12 (top left panel). Embryonic hearts were harvested 24 hours later and ephrin-A1 expression confirmed by western blot analysis (top right panel). AV cushion explants were cultured on collagen gels for 48 hours. GFP expressing cells were scored as epithelial, activated, and transformed. Results for each category, derived from 3 independent experiments, are presented as a percentage of total GFP positive cells ± SEM (bottom panel). Unpaired two-tailed student's t test was used to analyze data. For total explant numbers and total numbers of GFP cells per category, see Table S1.