Fig. 6. Ephrin-Ad represses MAPK activity. (A) Delta-like expression is lost in both A7.6 (arrows, 80%) or one A7.6 (15%) of the Ciona embryos co-injected with ephrin-Ad MO and torso-FGFR mRNA, suggesting Ephrin-Ad and MAPK pathways function synergistically. Ectopic activation of Delta-like in b-line blastomeres is often observed (arrowheads). (B-E) Treating ephrin-Ad MO-injected embryos with the MEK inhibitor U0126 reverses the repression of A7.6 genes in A7.6 and ectopically activates them in the anterior endoderm. The number of affected embryos/total embryos is shown.