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Fig. 5. Expression pattern of X-dll3 and 4 in sections of
Xenopus tadpoles, after whole-mount in situ hybridization.
Serial sections through the brain of a stage 37 tadpole
after in situ hybridization with a X-dll3 probe (A-E) or an
X-dll4 probe (F-G). The plane of sectioning and the A-P
level of the sections shown is approximately the same
between A-E and F-G and is indicated by arrowheads in
T, superimposed on whole-mount in situ hybridization of
a stage 37 brain with X-dll3. For definition of the A-P and
D-V axis see Fig. 6. In A and F, an arrowhead points to
the dorsal limit of expression in the telencephalon. In B
and C, arrowheads point to the ‘segment-like’ expression
of x-dll3 in the ventral thalamus. The upper arrowhead
marks the sulcus medius (unlabelled) that separates the
dorsal from the ventral thalamus. Note however, that
expression continues ventrally in more posterior sections,
into the anterior hypothalamus (B,C and D for X-dll3, and
G, H and I for X-dll4). In E and J, arrowheads point to
restricted punctate expression in the posterior
hypothalamus. (N,S) Sections that also show the restricted
expression of X-dll3 (N) and X-dll4 (S) in the posterior
hypothalamus at a level more posterior to that shown in E
and J, and at slightly older embryos (stage 39). The
sections shown in E, J, N and S, pass though the punctate
‘line’ of expression that is indicated by an arrow in T and
by arrowheads in O. (O) Parasagittal section though a
stage 37 brain hybridized with x-dll3 (the same result was
obtained with X-dll4; data not shown) In O also note that
there is non-expressing ‘band’ of tissue between the
telencephalon and diencephalon (unlabelled), which is
presumably the tel-diencephalic boundary. Although Xdll3
and X-dll4 appear to have the same A-P and D-V
limits of expression within the neural ectoderm, they
differ in that X-dll3 is expressed more medially than Xdll4,
as can be seen by comparing the mediolateral limit of
expression (arrow) between B (X-dll3) and G (X-dll4), or
between C (X-dll3) and H (X-dll4). They also differ in
their expression in the sense organs in that X-dll3 is
expressed in the olfactory placode (A and B), the otic
vesicle (K) but not in the eye (L), while X-dll4 is not
expressed in the olfactory placode (F,G), and the otic
vesicle (P), but is expressed in the eye (arrowhead in Q).
Both genes are expressed in the branchial arch neural
crest, shown in M for X-dll3 and R for X-dll4, but X-dll3
is expressed strongly only in the distal part and shows a
sharp proximodistal boundary (indicated by arrows in M).
Note that the neural crest envelopes a core of nonexpressing
mesodermally derived muscle cells.
Abbreviations: ch, optic chiasma; cg, cement gland; ddi,
dorsal diencephalon; di, diencephalon; dt, dorsal
telencephalon; Et, epithalamus; e, eye; Ht, hypothalamus;
hy, hypophysis; Tv, ventral thalamus; Td, dorsal
thalamus; me, mesencephalon; m, muscle; nc, neural
crest; on, optic nerve; op, olfactory placode; os, optic
stalk; ov, otic vesicle; ph, pharynx; vdi, ventral
diencephalon; vt, ventral telencephalon. |
