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Figure 3. Xhairy2b expression inhibits head formation and represses expression of some trunk and head organizer genes. A′: Uninjected control embryos (A) and 800 pg of Xhairy2b mRNA dorsally injected embryos (A′′) at stage 30. The overexpression of Xhairy2b results in a deficit of the expression of nkx2.4 (A,A′), otx2 (B,B′), and en2 (C,C′) but not that of krox20 (D,D′). Arrowheads indicate the remainder of the expression. E,E′: β-catenin ventrally injected embryo (E) and β-catenin and Xhairy2b coinjected embryo (E′). β-catenin expression induces a secondary axis containing a complete head (arrowhead in E), whereas the coinjection of Xhairy2b and β-catenin induces a secondary axis lacking head structures (arrowhead in E′). F′: Uninjected control embryo (F), 800 pg of Xhairy2b mRNA dorsally injected embryos (F′′), 400 pg of β-catenin mRNA ventrally injected embryos (L), and 400 pg of β-catenin and 800 pg of Xhairy2b mRNA ventrally coinjected embryos (L′′) are shown in vegetal view, dorsal side up at stage 10.5. The expression of Xhex (F,F′), Xdkk1 (G,G′), chordin (I, I′), and Xnot (J,J′) is repressed by Xhairy2b (green arrowheads), whereas that of cerberus (H,H′) and noggin (K,K′) is not affected by Xhairy2b. Light blue staining is coinjected β-gal. These genes are ventrally induced by β-catenin expression (red arrowheads in L). The ectopic expression of Xhex (L′), Xdkk1 (M′), chordin (O′), and Xnot (P′) is repressed by Xhairy2b coexpression with β-catenin (green arrowheads). Meanwhile, the expression of cerberus (N′) and noggin (Q′) is not affected (red arrowheads). |
