Fig. 2. Synergistic activities of Hox, Pbx and Meis factors on element C. Chick embryos were analyzed by X-gal staining after co-electroporation with a lacZ reporter driven by element C and various expression vectors. (A-E) The following expression vectors were used at a concentration of 0.2 µg/µl: (A) empty expression vector, (B) Meis2, (C) Pbx1, (D) Hoxb1, (E) Hoxb9 expression vectors. (F-J) The following expression vectors were used alone or in combination at the indicated concentration: (F) empty expression vector (0.2 µg/µl), (G) Meis2 (0.1 µg/µl), (H) Pbx1 (0.1 µg/µl), (I) Hoxb1 (0.01 µg/µl), (J) Meis2 (0.1 µg/µl), Pbx1 (0.1 µg/µl) and Hoxb1 (0.01 µg/µl) expression vectors. In G-I, total plasmid concentration was brought to 0.2 µg/µl with empty expression vector. ov, otic vesicle.