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Fig. 6. (A–C) Comparison of expression of XHR1 with that of Xotx2 and Xgbx-2 at gastrula stages. (A) A stage 11 embryo was bisected sagittally into two hemispheres and was then hybridized for XHR1 (left panel) or Xotx2 (right panel). Animal is to the top. (A′) Higher magnification of (A). The expression domain of XHR1 does not correspond to that of Xotx2 in the ectoderm. (B, C) Embryos at stages 11 or 11.5 hybridized for XHR1 (left panel), for Xgbx-2 (right panel), and for both (middle panel). All embryos are dorsally viewed, and animal is to the top. (D–F) Possible regulation of XHR1 expression by the Xbra-expressing region. Embryos were injected with mRNA or DNA as indicated together with nβ-gal mRNA (30 pg/embryo) for a lineage tracer. Double in situ hybridization with XHR1 and Xbra probes was performed after nβ-gal staining. (D) Injection of globin mRNA as negative control. (E) Injection of XFD mRNA (60 pg/embryo). Xbra expression was reduced in a nβ-gal-stained region as indicated by an arrowhead. (F) Injection of CSKA-eFGF (10 pg/embryo). In situ staining in nβ-gal-positive region means Xbra expression as indicated by asterisks. Two typical phenotypes are shown. Dotted lines, the boundary between ectoderm and mesoderm that was determined based on the differences in nuclear density of germ layers visualized by DAPI staining (data not shown; see Fig. 5E–G); st., developmental stage; thick arrows, shifted XHR1 expression; thin arrows, XHR1 expression; white asterisks, Xbra expression. |
