Fig. 4. A-L: Developmental expression profile of Xenopus TK genes.
RNase protection analysis of Xenopus TK genes was performed using 10
p,g of total RNA (2.2 embryo equivalents) from oocytes (VI), unfertilized
eggs (E), and embryos of blastula (st. 5, 8, 9), gastrula (st. 10.5, 12),
neurula (st. 15, 19), tailbud (st. 21, 24), and hatching stage (st. 34). The
expression of ornithine decarboxylase (ODC), and EF-la are included as
controls. ["PI Labeled anti-sense probes were synthesized from the partial
TK cDNAs. The undigested probe and a background control (hybridization
with yeast tRNA) were included in each RNase protection analysis
experiment (not shown). Protected fragments were quantitated using a
Phosphorlmager (Molecular Dynamics), and the number of TK mRNA
molecules per embryo was estimated as described in Experimental Procedures.
The y-axis represents the TK mRNA levels displayed as units of
106 mRNA molecules per embryo.
Fig. 5. Spatial expression of E59 (FGFR-Al), G62, and E30 transcripts
in tailbud Xenopus embryos. Whole-mount in situ hybridizations
were performed on albino Xenopus embryos using digoxigenin-labeled
antisense RNA probes. Hybridization signals were visualized as alkaline
phosphatase chromogenic reaction products. A: Lateral view of a stage
29/30 embryo stained for E59 mRNA expression. E59 transcripts are
detected mainly in the brain, pronephros, and somites. Note also the high
levels of expression in unsegmented somitogenic mesoderm (sm). 9:
Close-up view of A at higher magnification showing details of E59 mRNA
expression in the anterior half of the embryo. Extensive expression is
seen in the fore-, mid-, and hindbrain (fb, mb, and hb). The otic vesicle
(ov) is indicated as a reference point for the posterior limit of the E59
expression in the hindbrain. Staining is also associated with visceral
arches (arrows), the pronephros (pn), and the pronephric duct (pd). C:
Lateral view of a stage 29/30 embryo stained for G62 mRNA. Similar to
E59, G62 transcripts are mainly detected in the brain, pronephroi, and
somites. No expression was detected in unsegmented somitogenic mesoderm
as with E59. D: Close-up view of C at higher magnification. In the
brain, expression of G62 transcripts is seen predominantly in the eye
vesicle (ev), midbrain (mb), and hindbrain (hb). The midbrain/hindbrain
junction (j) is devoid of G62 transcripts. Other areas of expression include
the pronephros (pn), the pronephric duct (pd), and the tissues in the
region of the liver rudiment (Ir). Faint expression is also seen in the
visceral arches (arrows). E: Lateral view of a stage 28 embryo stained for
E30 mRNA expression. Extensive expression of E30 transcripts is seen
in the brain, visceral arches, and at lower levels in somites. F: Close-up
view of E at higher magnification to illustrate staining of the olfactory
placode (op), the wall of the otic vesicle (ov), the forebrain (fb), and
visceral arches (arrows). All embryos were rendered transparent with
Murray's clear prior to hybridization. Anterior ends of embryos are oriented
to the left. Scale bars: A = 288 pm; B = 144 pm; C, E = 225 km;
D, F = 112.5 pm.
Fig. 6. Spatial expression patterns of G56 mRNA in neurula and
tailbud Xenopus embryos. A: Lateral view of a stage 20 embryo. The
expression of G56 mRNA is predominantly associated with the developing
brain, the cement gland anlage (cg), and somites that have undergone
rotation (arrowheads 1-6). B: Dorsal view of a stage 21 embryo
illustrating G56 mRNA expression in somites (arrowheads 1-8), and the
unsegmented somitogenic mesoderm (sm). C: Lateral view of a stage 26
embryo. G56 mRNAs are localized to segmented somites (arrowheads),
and to different parts of the hindbrain (hb). Expression in the cement
gland (cg) has ceased by this stage. D: Dorsal view of a stage 26 embryo
at a higher magnification to illustrate expression of G56 mRNA in the
differentiating somites. G56 mRNAs are present around somite nuclei,
which are aligned vertically in each somite. Thus, the staining appears as
a stripe (arrowheads) in each somite block. Scale bars: A,B,D = 144 pm;
C = 225 pm.
Fig. 7. Neural crest expression of G37 in neurula and tailbud Xenopus
embryos. A: Lateral view of a stage 15 embryo. Arrowheads indicate
staining of cranial neural crest. B: Dorsal view of A. G37 expression is
seen in the most anterior cranial neural crest. Segregation into individual
neural crest segments (arrowheads) has begun. C: Lateral view of a
stage 21 embryo. G37 mRNAs are now found in cranial (m, mandibular
crest; h, hyoid crest; ab, anterior branchial; pb, posterior branchial), and
truncal (1) neural crest segments. The periphery of the eye vesicle (ev) is
populated by mandibular (m) neural crest expressing G37 mRNA.
D: Dorsal view of C to illustrate expression of G37 mRNAs in the posterior
branchial arch segment (pb), and in truncal (1) neural crest. E: Lateral
view of a stage 27 embryo. Expression of G37 mRNAs in all cranial
neural crest segments and in truncal (1) neural crest of the dorsal fin. F:
Close-up view of E at higher magnification to illustrate expression in
cranial and truncal neural crest (see C for labeling). Neural crest derivatives
were labeled according to the nomenclature of Sadaghiani and
Thiebaud (1987). Scale bars: A, B = 160 pm; C, D = 144 pm; E = 225
pm; F = 112.5 pm.
Fig. 8. Whole-mount in situ hybridization analysis of G50 expression
in neurula and early tailbud stage Xenopus embryos. A: Lateral view of a
stage 17 embryo stained for G50 mRNA expression. Transcripts are
detected in two bilateral stripes of cells in the head region (arrowheads),
and diffusely in the posterior end of the embryo. 6: Dorsal view of A at
higher magnification showing in greater detail the localization of G50
mRNAs in premigratory (arrow) and early migratory neural crest cell populations
(arrowhead). C: Lateral view of a stage 21 embryo stained for
Xenopus En-2 to localize the midbrain-hindbrain junction. D: Lateral view
of a stage 21 embryo stained for G50. Expression of G50 mRNAs is seen
in a stripe of cells at the height of the presumptive rhombomere 3, and in
neural crest of the hyoid arch (h). E: Lateral view of a stage 21 embryo
stained for Xenopus Krox-20. Two stripes of cells in the hindbrain corresponding
to the presumptive rhombomeres 3 and 5, and neural crest of
anterior branchial arch (ab) are expressing XKroxPO mRNAs. F Lateral
view of a stage 21 embryo stained simultaneously for G50 and XKroxPO.
Labeling of stained tissues is as in D and E, respectively. The intensity of
the background stain varies with respect to the length of incubation of the
embryos in the chromogenic reaction. Embryos in C and E were developed
for 1 hr, while the other embryos were incubated 16 hr to obtain
optimal staining. The stars in C and F indicate staining artifacts. Scale
bars: A = 160 pm; 0 = 80 pm; C F = 144 pm.
epha2 (EPH receptor A2) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 21, lateral view, anterior left, dorsal up.
pdgfra (platelet-derived growth factor receptor, alpha polypeptide) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 27, lateral view, anterior left, dorsal up.
ptk7 (protein tyrosine kinase 7) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 29 and 30, lateral view, anterior left, dorsal up.
pdgfra (platelet-derived growth factor receptor, alpha polypeptide) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 21, lateral view, anterior left, dorsal up.