Fig. 4. Ci-ephrin-Ad establishes asymmetric fates in A6.3 lineages. (A-D) Upon Ci-ephrin-Ad MO injection, A7.6 group genes are severely downregulated in Ciona embryos. The numbers of embryos showing a complete loss of marker gene expression/total embryos are indicated. Whereas Hand-like, FGF8 and MyTF display an almost complete loss of expression, Delta-like seems to be the most resilient to MO inhibition, with only 40% loss of expression. The remaining 60% embryos show normal or slightly reduced expression in A7.6. (E) When Ci-ephrin-Ad function is inhibited, ectopic dpERK staining is observed in the A7.6 blastomeres of all injected embryos. (F) Brachyury expression is expanded to the A-line neural tissues in MO embryos, as previously shown (Picco et al., 2007). (G) Ectopic expression of the endoderm marker TTF-1 in A7.6 blastomeres of MO-injected embryos. The ectopic expression is variable and is seen on only one side of the embryo shown here. (H) Schematic illustrating that TTF-1 expression (yellow) is expanded into A7.6 of MO-injected embryos. (I,J) Inhibition of Ci-ephrin-Ad function results in transformation of A7.6 mesoderm fate to endoderm fate. In wild-type arrested embryos (J), alkaline phosphatase (AP) activity is observed in endoderm blastomeres. For an unknown reason, the staining is consistently stronger in the anterior endoderm. (I) In Ci-ephrin-Ad MO-injected embryos, AP staining is also observed in A7.6 blastomeres, suggesting a fate transformation from mesoderm to endoderm.