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Fig. 6. msx1 participates in the early specification of the neural crest. One blastomere of a two-cell stage embryo was injected with 700 pg of msx-GR mRNA (A-E), with 700 pg of HDmsx-GR mRNA (F-J) or with different combinations of both mRNAs (K-P), treated with dexamethasone at stage 12.5. Embryos were fixed at stage 18/19 and the expression of several genes was analyzed. The arrowheads indicate the injected side that contained FLDx (see Materials and methods). Anterior is towards the right. (A-C,F-H) Neural crest markers. (A-C) Notice the expansion of the markers on the side injected with msx-GR. (A) XSlug expression (n=44, 68% of expansion). (B) XSnail expression (n=60; 80% of expansion). (C) foxd3 expression. (n=52, 61% of expansion). (F-H) Note the inhibition in the expression of the neural crest markers injected with HDmsx-GR. (F) XSlug expression (n=57, 65% of inhibition). (G) XSnail expression (n=42, 69% of inhibition). (H) foxd3 expression (n=66, 64% of inhibition). (D) XSox-2 expression in embryos injected with Msx-GR. Note the inhibition in the expression (n=63, 38% of inhibition). (I) XSox2 expression in embryo injected with HDmsx-GR. Note the expansion in the expression the injected side (n=54, 39% of expansion). (E) XK81a expression in embryos injected with Msx-GR. Note the inhibition in the expression (n=57, 28% of inhibition). (J) XK81a expression in embryos injected with HDmsx-GR. Note the expansion in the expression (n=62, 32% of expansion). (K-M) Embryos were injected with 500 pg of HDmsx-GR mRNA and 250 pg of msx-GR (ratio 2:1). Note the partial rescue in the expression of the neural crest markers. (N-P) Embryos were injected with 500 pg of HDmsx-GR mRNA and 500 pg of msx-GR (ratio 1:1). Note the rescue in the expression of the neural crest markers. (G) Summary of the expression of XSlug. The injected and uninjected side was analyzed for each embryo. Number of embryos analyzed for XSlug expression: 215. Note that the strong rescue (73%) was reached with a proportion of 1:1 for the injected mRNAs. Similar values of rescue were obtained for the other neural crest markers (69% for foxd3, total number is 220; 67% for XSnail, total number is 225). |
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Fig. 7. msx1 lies upstream of XSlug and XSnail in the cascade leading to neural crest development. Embryos were injected in one blastomere at the two-cell stage with different combinations of HDmsx-GR and XSlug-GR (A-G) or XSnail-GR (H-N), induced at stage 12 and the expression of the neural crest markers XSlug (A,D,H,K), foxd3 (B,E,I,L) and XSnail (C,F,J,M) was analyzed at stage 18. Anterior is towards the right. The injected side detected by fluorescein staining is indicated by an arrowhead. (A-C) Embryos were injected with 500 pg of HDmsx-GR mRNA and 500 pg of XSlug-GR (ratio 1:1). Note the rescue in the expression of the neural crest markers. (D-F) Embryos were injected with 250 pg of HDmsx-GR mRNA and 750 pg of XSlug-GR (ratio 1:3). Note the rescue in the expression of the neural crest markers. (G) Summary of the expression of XSlug. The injected and uninjected side was analyzed for each embryo. Number of embryos analyzed for XSlug expression is 225. Note that the strong rescue (65%) was reached with a ratio of 1:1 for the injected mRNAs. Similar values of rescue were obtained for the other neural crest markers (72% for foxd3, total number is 225; 68% for XSnail, total number is 235). (H,I) Embryos were injected with 500 pg of HDmsx-GR mRNA and 500 pg of XSnail-GR (proportion of 1:1). Note the rescue in the expression of the neural crest markers. (K-M) Embryos were injected with 250 pg of HDmsx-GR mRNA and 750 pg of XSnail-GR (proportion of 1:3). Note the rescue in the expression of the neural crest markers. (N) Summary of the expression of XSlug. The injected and uninjected side was analyzed for each embryo. Number of embryos analyzed for XSlug expression is 215. Note that the strong rescue (67%) was reached with a ratio of 1:1 for the injected mRNAs. Similar values of rescue were obtained for the other neural crest markers (51% for foxd3, total number is 202; 62% for XSnail, total number is 215). |
