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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.
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