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Fig. 4. Wnt repression during neurulation can induce a posterior shift in Krox20 and Engrailed-2 expression. Embryos were injected unilaterally with 300 pg Dex-inducible Wnt-repressing RNA (EnR-LefN-GR755A) at the four-cell stage in two blastomeres (B,D,F). As a tracer, 50 pg of -gal RNA was co-injected. Non-injected (NI) embryos were included as a control (A,C,E). Both injected and control embryos were treated with Dex from late gastrula (st12.5) until st20. The most anterior stripe (*) represents En2 expression, the other 2 show expression of Krox20 in rhombomeres 3 and 5. Expression of Krox20 and Engrailed-2 was frequently shifted to a more posterior position. In contrast, expression of Rx2a (shown in Fast Red staining) was not shifted. Bright field (A-D) and red fluorescent images (E, F) are shown. The injected side is indicated by an arrowhead. The dotted line indicates the dorsal midline. |
