Fig. 4

Enhancement of lhx2 expression in a head-specific Six3a- and Six3b-overexpressing embryo by uncaging mRNA for six3a and six3b and severe downregulation of lhx2 expression in a six3-knockdown embryo. (A) six3b and six3a expression in the presumptive forebrain in the 11-hpf embryo (left and right, respectively). (B) A normal pattern of lhx2 expression in the forebrain in the embryo injected with 20 pg of globin mRNA (upper, left) and enhanced lhx2 expressions in the six3b (upper, right), RDsix3b (bottom, left) and six3a mRNA-uncaged embryo (bottom, right) at the 8-somite stage. Scale bar, 100 μm. (C) Similar degrees of enlargement of the head in six3b, RDsix3b and six3a mRNA-uncaged embryos at the 8-somite stage. (D) Dorsal views of lhx2 expression in the forebrain and pax2a expression in the midbrain–hindbrain boundary at the one-somite stage by co-probing for lhx2 and pax2a in an uninjected embryo (upper panel) and marked decrease of lhx2 expression in the six3-knockdown embryo (bottom panel). Arrowheads point to pax2a expression in the developing optic stalk. (E) lhx2 and six3b expression in the six3- and lhx2-knockdown embryos. The upper pairs of pictures show lhx2 and six3b expression in the uninjected embryos. The bottom left picture shows marked decrease of the lhx2 expression in the six3-knockdown embryo. In this experiment, embryos were also probed for myod. Arrowhead points to pax2a expression in the optic stalk. The bottom right picture shows six3b expression in the lhx2-knockdown embryos. Insets in each picture in panel E show the myod expressions of the same embryos, demonstrating that all embryos are at the one-somite stage.