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Figure 1 (A–E) Human ski neuralizes Xenopus ectoderm. Explants were cultured until stage 20 for analysis of NCAM expression. (A) Embryos express NCAM only in the central nervous system. Anterior is to the left and dorsal is to the top. (B) Uninjected explants. (C) Explants expressing 500 pg of BF-2 mRNA. (D) Explants expressing 500 pg of human ski mRNA. (E) RT-PCR analysis. Lanes 1 and 2, whole embryo control (stage 20) followed by the RT minus negative control; lane 3, uninjected explants; lanes 4–6, explants injected with increasing amounts of ski mRNA. The elongation factor 1 alpha (EF1α) primers were used to determine RNA recovery. Primers for muscle actin were used to assess mesoderm development. W, whole embryo; RT−, no RT. (F–I) Ski inhibits Xvent2 expression in ectoderm. Ectodermal explants were cultured until the midgastrula stage (stage 10.5). (F) In the embryo, Xvent2 is expressed in the animal cap and the marginal zone (dorsal lip is indicated by the arrow). (G) Uninjected explants. (H) Explants expressing 500 pg of BF-2 mRNA. (I) Explants expressing 500 pg of ski mRNA. (J–M) Ski inhibits Xvent2 expression in the embryo. (J) Control embryos (ventral view) showing Xvent2 expression in the marginal zone (stage 10.5). (K) Embryos injected with 500 pg of ski mRNA; arrowheads point to where Xvent2 expression is inhibited. (L) Control embryos probed for noggin expression. (M) Embryos injected with 500 pg of ski mRNA probed for noggin expression. (N–Q) Ski does not inhibit BMP4 expression in the ectoderm. Explants were cultured until the midgastrula stage (stage 10.5). (N) In the embryo, BMP4 is expressed strongly in the ectoderm and the marginal zone (dorsal lip is indicated by the arrow). (O) Uninjected ectodermal explants. (P) Explants expressing 500 pg of BF-2. (Q) Explants expressing 500 pg of ski. |
