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Fig. 4. Early genes expressed in the posterior wall of the tail bud. (A,C)
Sagittal sections of stage 30 whole mount in situ hybridisations. Scale bar,
250 mm. (A) Expression of Xbra (dark staining) in the posterior wall and
chordoneural hinge, with highest levels distally. (C) Expression of X-delta-
1 in the posterior wall, with highest levels distally. X-delta-1 transcripts are
absent from the dorsal roof but punctate expression is seen more anteriorly
in the neural tube. (B,D) Schematic diagrams of expression based on the
sections shown in (A,C), respectively. (E,F) Whole mount in situ hybridisations
showing the expression of other genes in the Notch/delta pathway
in the tail bud. (E) X-delta-2 expression is primarily in the most posterior
somite (*) but is also weakly expressed in the posterior wall. As for Xdelta-
1, expression is lacking from the dorsal roof of the tail bud. (F) XNotch-
1 is expressed widely in the tail bud but is excluded from the same
region of the dorsal roof as X-delta-1 and X-delta-2. All figures are
oriented with posterior to the right and dorsal upwards. Abbreviations:
cnh, chordoneural hinge; end, endoderm; nc, notochord; nt, neural tube;
pw, posterior wall. |