Fig. 5. Analysis of convergent extension and neural plate closure after overexpression of Xror2 constructs. mRNA (1 ng/embryo) of globin (A,G), Xror2 (B,B',H), Xror2-3I (C,I), Xror2-TM (D,J) or Xror2-KR (E,K) as indicated was injected together with nß-gal mRNA (20 pg/embryo) for a tracer into one blastomere on the dorsoanimal and right side at the four-cell stage, and subjected to ß-gal staining (red). (A-F) Stage 13 embryos; dor, dorsal view; pos, posterior view; a, archenteron; b, blastocoel. (G-K) Stage 18 embryos (dorsal view; anterior is upwards). (A) Globin-expressing control embryos and a section. As a result of normal convergent extension, nß-galpositive cells were restrictedly distributed along the midline in the trunk region (see also G). (B,B') Xror2-expressing embryos (and section in B) with and without open yolk plug, respectively. nß-gal-stained cells were laterally expanded on the right side of both mesoderm and ectoderm layers as a result of the inhibition of convergent extension. (C) Xror2-3I-expressing embryos showing weaker phenotypes than did wild type. (D) Xror2-TM-expressing embryos. nß-gal-stained cells were laterally expanded, and condensation of pigmented cells was observed in nß-gal-positive regions of ectoderm, as indicated by the arrow and arrowhead, each of which show the corresponding position in a whole embryo (second panel from the left) and in sections (third or fourth panel). When nß-gal-positive cells were laterally expanded, the archenteron was not formed (B,D). (E) Xror2-KR-expressing embryo and section showing normal-looking cell movements. (F) Globin-expressing embryos with open yolk plug. In a few embryos that had open yolk plugs as a result of overexpressing globin, nß-gal-positive cells still converged to the midline. (G) Globin-expressing embryos at stage 18. nß-gal-positive cells were restrictedly distributed along the midline in the trunk region. (H) Xror2-expressing embryos which failed to close the neural plate in nß-gal-positive regions (white arrows). Right panel, higher magnification. (I) Xror2-3I-expressing embryos showing weaker phenotypes than those of wild-type Xror2-expressing embryos. (J) Xror2-TM-expressing embryos. Expression of Xror2-TM resulted in neural groove-like formation with pigmented cells (white arrowheads). Right panel shows a higher magnification. (K) Xror2-KR-expressing embryos. Xror2-KR does not have apparent phenotypes, similar to globin control.

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