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Fig. 7. Teratogenic dose of RA induces anterior shifts in the Cyp26c1
expression domain and the Hoxb1/vHnf1 expression boundary. All
embryos were subjected to a 20 mg/kg dose of RA at E7.5, then analyzed 18
hours later at E8.25 (see Figs
2,
3,
4 for untreated controls).
(B,C,F,H) Lateral view; (G,I) dorsal view; (A) ventral view; (D,E) anterior
view. (A) RARE-lacZ expression is observed to the anterior tip of
some embryos (left embryo), but in other embryos RARE-lacZ expression
is reduced at the anterior tip (upper arrowhead in right embryo).
RARE-lacZ expression in all embryos is greatly reduced posteriorly in
the tailbud (lower arrowheads) when compared with the trunk. (B-C)
Cyp26a1 expression is observed in the tailbud (arrowhead) similar to
untreated embryos (MacLean et al.,
2001), whereas Cyp26c1 expression has been shifted to the
anterior-most region of the embryo (arrowhead). A lateral view shows that most
Cyp26c1 expression is neural, with mesodermal expression being
greatly reduced. (D,E) Comparison of anterior expression patterns of
RARE-lacZ and Cyp26c1 demonstrates that the abnormal domain
of Cyp26c1 expression lies in the region where RARE-lacZ
expression first clears anteriorly. (F,G) The anterior domain of
Hoxb1 expression (arrowhead) has been shifted further anteriorly from
where it should normally reside at r4. (H-I) The anterior border of
vHnf1 expression (arrowhead) has been shifted further anteriorly.
This abnormal anterior border of vHnf1 expression lies posterior to
the abnormal expression domains of Cyp26c1 and Hoxb1.
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