Fig. 6. msx1 participates in the early specification of the neural crest.
One blastomere of a two-cell stage embryo was injected with 700 pg of msx-GR
mRNA (A-E), with 700 pg of HDmsx-GR mRNA (F-J) or with different combinations
of both mRNAs (K-P), treated with dexamethasone at stage 12.5. Embryos were
fixed at stage 18/19 and the expression of several genes was analyzed. The
arrowheads indicate the injected side that contained FLDx (see Materials and
methods). Anterior is towards the right. (A-C,F-H) Neural crest markers. (A-C)
Notice the expansion of the markers on the side injected with msx-GR. (A)
XSlug expression (n=44, 68% of expansion). (B)
XSnail expression (n=60; 80% of expansion). (C)
foxd3 expression. (n=52, 61% of expansion). (F-H) Note the
inhibition in the expression of the neural crest markers injected with
HDmsx-GR. (F) XSlug expression (n=57, 65% of inhibition).
(G) XSnail expression (n=42, 69% of inhibition). (H)
foxd3 expression (n=66, 64% of inhibition). (D)
XSox-2 expression in embryos injected with Msx-GR. Note the
inhibition in the expression (n=63, 38% of inhibition). (I)
XSox2 expression in embryo injected with HDmsx-GR. Note the expansion
in the expression the injected side (n=54, 39% of expansion). (E)
XK81a expression in embryos injected with Msx-GR. Note the inhibition
in the expression (n=57, 28% of inhibition). (J) XK81a
expression in embryos injected with HDmsx-GR. Note the expansion in the
expression (n=62, 32% of expansion). (K-M) Embryos were injected with
500 pg of HDmsx-GR mRNA and 250 pg of msx-GR (ratio 2:1). Note the partial
rescue in the expression of the neural crest markers. (N-P) Embryos were
injected with 500 pg of HDmsx-GR mRNA and 500 pg of msx-GR (ratio 1:1). Note
the rescue in the expression of the neural crest markers. (G) Summary of the
expression of XSlug. The injected and uninjected side was analyzed
for each embryo. Number of embryos analyzed for XSlug expression:
215. Note that the strong rescue (73%) was reached with a proportion of 1:1
for the injected mRNAs. Similar values of rescue were obtained for the other
neural crest markers (69% for foxd3, total number is 220; 67% for
XSnail, total number is 225).