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Figure 4. Zic3 overexpression induces neural tissue hyperplasia and ectopic pigment cell expression. A total of 100 pg of Zic3 mRNA (A) was injected into one blastomere of two-cell stage embryos. (A) Uninjected control side (stage 27). (B) Zic3 mRNA injected side (stage 27). Clusters of pigment cells appeared in the anterior region (arrow). (C) Dorsal view of anterior region of the injected embryo (stage 36). (D) Transverse sections of the embryo shown in C. The levels of sections are indicated in C. The injected side was characterized by the hyperplastic neural walls, distorted eye, and unidentified tissue, probably derived from the neural crest (asterisk in D, E, and F, see Results). A total of 100 pg of Zic3 mRNA or control LacZ mRNA was injected into dorsoanimal (G) or ventroanimal (H) two blastomeres of eight-cell stage embryo, and cultured to stage 36 (G), stage 25 (H and I), or stage 20 (J). Lateral view of control LacZ mRNA injected embryos (G and H,Upper) and Zic3 mRNA injected embryos (G and H,Lower). The eye abnormalities were observed in the embryos injected with Zic3 mRNA into dorsal blastomeres (G). Remarkable clusters of ectopic pigment cells appeared in the embryos injected with Zic3 mRNA into ventral blastomeres (H). (I) Higher magnification of the pigment cell clusters in (H). (J) Xtwi expression in the embryos (ventral view) injected with LacZ mRNA (Upper) or Zic3 mRNA (Lower) into ventroanimal two blastomeres at eight-cell stage. The Xtwi expression was observed in the head neural crest of the control embryo (Upper, arrowhead). However, the Zic3 mRNA injection induced the ectopic Xtwi expression (Lower, arrow) near the ectopic clusters of pigment cells (white arrowheads; the brown staining indicates the remnants of the pigments) in the ventral side of embryo. The expansion of the Xtwi expressing cephalic neural crest (Lower, black arrowheads) was also observed in this embryo. |
