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Fig. 4. Elevation of BMP4 activity by Cv-2. (A-D) Injection of Cv-2 (A), BMP4 (B) or BMP4 plus Cv-2 mRNA (C,D) with fluorescein dextran lineage tracer into a single animal pole blastomere at the 32-cell stage embryo, and Xbra expression detected at stage 10.5. Fluorescein dextran is detected in red, and Xbra in blue, with the normal expression domain around the blastopore lip indicated with a black ellipse. Ectopic BMP4 with or without Cv-2 induces ectopic expression of Xbra, either co-extensive with the normal expression around the blastopore lip (B,C) or as an isolated patch (D). (E) Summary of the effects of BMP4 and Cv-2 injections on the proportion of embryos with ectopic Xbra expression (%, y-axis). For each amount of BMP4 RNA, co-injection of Cv-2 RNA increases the induction of Xbra expression. The number of embryos analysed are indicated at the top of the chart. (F) Injection of BMP4 and/or Cv-2 mRNA at the one-cell stage embryo, followed by excision of animal caps at stage 8-9, and RT-PCR analysis of Xbra transcripts at stage 10.5. Quantitation with a phosphoimager reveals that Xbra expression is fourfold higher in BMP4 plus CV-2 injected animal caps than with BMP-4. Cv-2 alone does not induce Xbra expression. |
