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Fig. 7. Whole-mount in situ analyses
of XNkx-2.3, Xtwist and XMLC2 RNA
expression in Xenopus embryos. For
details on whole-mount procedure and
probes used, see Materials and
Methods. Arrowheads indicate
relevant stained areas. In B, C, the
boundaries of the anterior neural plate
are outlined with a dotted line. cg,
cement gland, h, heart, np, neural
plate, ph, pharyngeal region. (A)
Anterior view of stage 13.5 embryo
hybridized to probe for XNkx-2.3
RNA. Dorsal is at the top. Bluish
staining band above purple-brown
hybridisation signal (arrowhead) is a
result of artefactual trapping of probe
in the archenteron (Harland, 1991).
(B) Anterior view of stage 16 embryo
stained for XNkx-2.3 RNA expression.
Dorsal is at the top. Staining is
observed ventral to the neural folds,
immediately posterior to the cement
gland. (C) Anterior view of stage 16
embryo hybridized to probe for Xtwist.
twist expression can be seen in the
forming cephalic neural crest
(Hopwood et al., 1989). (D) Ventral
view of stage 19 embryo, hybridized
to XNkx-2.3 probe. Anterior is to the
right. Staining is observed in an
anteroventral position. (E) Ventral
view of stage 23 embryo, showing two
areas of staining for XNkx-2.3 just
posterior to the cement gland. The
posterior staining is clearly bilateral
and corresponds to the partially fused
cardiac primordia. Anterior is to the
right. (F) Lateral view of same embryo
as in E. Anterior is to the right. Note
two streaks of staining just caudal to
the cement gland. (G) Ventral view of
stage 27 embryo hybridized to probe
for XNkx-2.3. Anterior is at the top
right. Arrowheads mark the bilateral
staining that corresponds to the
prospective heart region (see H). The
staining also extends further rostral,
abutting the cement gland. (H) Ventral
view of stage 27 embryo, hybridized
to a probe for XMLC2, a marker for
differentiated cardiac mesoderm.
Anterior is to the right. Note that the
bilateral staining here corresponding to
the cardiac mesoderm does not extend
rostrally to the cement gland, as did
the staining shown in G for XNkx-2.3.
(I) Lateral view of stage 26 embryo
stained for XNkx-2.3 RNA expression.
Anterior is to the right, dorsal is at the
top. Arrowheads indicate two regions
of staining, in the heart tube (see J)
and in the pharyngeal region more rostrally. (J) Lateral view of stage 26 embryo stained for XMLC2 expression. Staining is confined in the
heart tube. (K) Lateral view of stage 26 embryo stained for Xtwist expression. Note the heavy staining in the pharyngeal region, whereas there
is no staining in the cardiac region. (L) Lateral view of stage 34 embryo, hybridized to probe for XNkx-2.3. Anterior is to the right, dorsal at the
top. Staining is seen in the looped heart tube and more rostrally in the pharyngeal region. (M) Lateral view of stage 34 embryo, hybridized to
probe for XMLC2. Staining is evident in the looped heart tube. (N) Lateral view of stage 34 embryo, hybridized to probe for Xtwist. Some
staining remains in the pharyngeal region, and is absent from the heart. Embryos shown in I, K-N were cleared in benzyl:benzoate (Harland,
1991) before photographing. |
