Fig. 5. Xiro1 participates in the induction of neural crest cells. Two-cell embryos were injected in one blastomere with 1 ng of the inducible forms of a repressor of Xiro1 (HDGREnR) (A,D,G,J), an activator form of Xiro1 (HDGRE1A) (B,E,H,K), or with a dominant-negative form of Xiro1 (HDGR) (C,F,I,L). The embryos were treated with dexomethasone at stage 12, and the expression of Xslug, Bmp4, Xmsx1 and Hairy2A was analyzed by in situ hybridization. The injected side was visualized by Myc inmunostaining, or alkaline phosphatase-mediated FITC inmunostaining, and is indicated with an arrowhead. (A-C) Xslug expression. (A) An expansion of the Xslug expressing neural crest domain is observed. (B,C) Xslug expression is reduced on the injected side. (D-F) Bmp4 expression. (D) A repression of Bmp4 in the neural fold domain is indicated by the bracket. (E,F) The levels of Bmp4 transcripts are augmented on the injected side and an expansion in the expression domain is also observed. Note that in F, the expression indicated by two small brackets on the uninjected side is transformed into a single big bracket on the injected side. Scale bar: 85 µm. (G-I) Xmsx1 expression. (G) Note the expanded Xmsx1 expression domain. (H,I) A reduction in the expression of Xmsx1 can be seen in the neural fold region. (J-L) Hairy2A expression. (J) An expanded domain of Hairy2A expression is observed in the neural fold, whereas Hairy2A expression is inhibited by the injection of HDGRE1A and HDGR (K,L). Each experiment was performed at least twice with a minimum of 42 embryos. The effect seen in each experiment was observed in at least 65% of embryos.