Fig. 7. Delta1 expression is upregulated by Xiro1 and down
regulated by Snail. (A,B) Two-cell embryos were injected in one
blastomere with 1 ng HDGREnR (A) or with 1 ng HDGR (B) mRNA.
The embryos were treated with dexomethasone at stage 12 and the expression of
Delta1 was analyzed by in situ hybridization at stage 17. The
injected side was visualized by alkaline phosphatase-mediated FITC
immunodetection. (A) HDGREnR produces a moderate expansion of
Delta1 expression in the neural crest region (arrowhead), whereas
HDGR leads to a complete inhibition of Delta1 expression in
the crest region (B; arrowhead). (C-E) Animal caps taken from stage 9 embryos
were cultured until the equivalent of stage 18, and the expression of
Delta1 was analyzed by in situ hybridization. (C) In control animal
caps, no expression of Delta1 could be detected. (D,E) In animal caps
taken from embryos injected with 1 ng Xiro3 mRNA, Delta1
expression was observed in 87% of the caps (n=57). (E) Higher
magnification of the animal cap shown in D. (F) RT-PCR to analyze
Delta1 and H4 mRNA. Arrowheads in D,E indicate
Delta1-expressing cells. Left panel, control embryo and PCR in the
absence of reverse transcriptase; right panel, mRNA taken from a control
animal cap, a cap injected with 1 ng Xiro3 mRNA, or a cap co-injected
with 1 ng Xiro3 mRNA and 0.7 ng Xsnail mRNA. (G)
Quantification of data shown above in F. Note the increase in Delta1
mRNA produced by Xiro3, and the complete inhibition produced by
Xsnail. (H-J) Two-cell embryos were injected in one blastomere with
0.7 ng dnSnail mRNA. The embryos were treated with dexomethasone at
stage 12, and the expression of Delta1 was analyzed by in situ
hybridization at stage 17. The injected side was visualized by alkaline
phosphatase-mediated FITC inmunodetection. (H) Delta1 expression is
upregulated in the neural crest region. (I,J) Higher magnification of the
neural crest region indicated by the box in H, where the staining was stronger
on the injected (J) than on the uninjected side (I). Arrow, uninjected side;
arrowhead, injected side. Each experiment was performed at least twice with a
minimum of 52 embryos. The effect seen in each experiment was observed in at
least 65% of embryos.