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FIG. 4. XCdc42 overexpression affects the localization of mesodermal and neural markers. Four-cell stage embryos were injected in the DMZ with 200 pg of WT XCdc42 mRNA. (A) (a) Expression of chordin at stage 10 in uninjected control (upper) and XCdc42-injected (lower) embryos (vegetal view is shown; dorsal at top). (b) Expression of chordin in uninjected (upper, dorsovegetal view; anterior at top) and XCdc42-injected (lower, vegetal view; dorsal at top) embryos at stage 12. In XCdc42-injected embryos, chordin-expressing cells did not converge toward the dorsal midline and were still localized around the blastopore. (c) The pattern of Xbra expression in uninjected (upper) and XCdc42-injected (lower) embryos at stage 10 (vegetal view; dorsal at top). (d) Expression of Xbra in stage 12 control (upper, dorsovegetal view) and XCdc42-injected (lower, vegetal view; dorsal at top) embryos. Xbra transcripts, which were detectable in the notochordal mesoderm in uninjected control embryos, were absent in XCdc42-injected embryos, indicating the failure of dorsal mesoderm to involute during gastrulation. (e, f) The expression of XmyoD in uninjected (dorsovegetal view) and XCdc42-injected (vegetal view; dorsal at top) embryos at stage 11.5, respectively. In XCdc42-injected embryos, XmyoD remained expressed around the blastopore, but not in the lateral mesoderm. (g) At stage 13, uninjected control embryos had the anterior expression of Otx-2 (dorsal view is shown; anterior at top). (h) In XCdc42-injected embryos at stage 13, the expression of Otx-2 occurred in the dorsal ectoderm (dorsovegetal).
(B) (a, b) In situ hybridization against XmyoD was performed on both uninjected (a) and XCdc42-injected (b) embryos at stage 25. XCdc42-injected embryos failed to close the neural plate, yet retained muscle differentiation. (c, d) As in the uninjected embryo at stage 30 (c), notochord differentiation normally occurred in the XCdc42-injected embryo (d) as assessed by expression of Xnot. |
