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FIG. 6. The expression of Na pump a1 subunit protein prior to gastrulation detected with NPSE or NASE antibodies. The relatively high
background apparent in some images stems from inherent autofluorescence of the early Xenopus embryo. (A) Oblique section through
embryo at the 4-cell stage. The cleavage furrow (indicated by arrows) stains intensely for a1 subunit protein. (B) 64-cell stage; outer animal
pole cells. Note stain restricted to lateral and basal regions of the cell. (C) 64-cell stage; animal pole cells lining the blastocoel (blast). (D)
Stage 7, outer animal pole cells. ext, the outside of the embryo. a1 subunit protein is limited to the lateral and basal membranes. (E) Stage
7, animal pole cells facing the blastocoel (blast). (F) Stage 7 deep vegetal pole cells. Note protein stain on all cell surfaces. (G) Stage 9,
part of section through the embryo showing outer animal pole cells and cells facing the blastocoel. Protein stain is absent from the outer
surface, but stain of varying intensity is present on all other cell membranes. ext, external surface of embryo. b, blastocoel facing surface.
(H) Stage 7, antibody stain is abolished in the presence of competing peptide. ext, extraembryonic surface; AP, animal pole cells. Bars in
A, B, D, 25 mm; in remainder, 100 mm. |
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FIG. 5. The spatial distribution of pXen9 RNAs during gastrulation and neurulation. (A) Longitudinal section through the dorsal lip of
an early gastrula (stage 10.5). Note absence of signal in outer layer of dorsal ectoderm behind the dorsal lip, with a sharp boundary between
nonexpressing and expressing cells (arrow). The nonexpressing cells are destined to form the outer layer of the neural plate. DL, dorsal
lip. (B) Embryo at stage 11. The region of nonexpressing dorsal ectoderm cells now extends further back (arrow), paralleling invagination
of the mesoderm. (C, D) Longitudinal sections through dorsal (C) and ventral (D) regions of an embryo at the end of gastrulation (stage
12). Note the lack of expression in the outer layer of the dorsal ectoderm, the putative neural plate. DL, dorsal lip; VL, ventral lip; YP,
yolk plug. (E) Stage 14, transverse section through the neural plate. Note transcript expression is lower in superficial cells than deep cells
of the neural plate (NP). The notochord (no), somites (som), and endoderm cells lining the archenteron show transcript expression. (F)
Stage 17. Expression is most intense in the neural plate (NP) and lateral ectoderm (LE). The notochord (no) and somites (som) now show
more intense expression than endoderm cells lining the expanding archenteron. (G) Stage 22. NT, neural tube; no, notochord; som, somites.
(H) Stage 36. All dorsal structures now show intense expression of Na pump a1 subunit mRNAs. (I) Sense control, stage 17. (J) Stage 36;
expression of collagen mRNAs. Note expression restricted to the notochord and floor plate (FP). (K) Stage 36. Expression of actin mRNAs
is restricted to the somites. Bars, 100 mm for all except H, J where bars are 25 mm. |
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FIG. 7. The expression of a1 subunit protein during gastrulation. (A, B) Sections through the dorsal lip of two embryos at the beginning
of gastrulation. DL, dorsal lip. Note protein stain is limited to cells lining the developing blastopore. (C, D) Sections through two regions
of the yolk plug of a single embryo at stage 12. DL, dorsal lip; YP, yolk plug. Note intense protein stain on the apposing surfaces of
ectoderm and endoderm as cells move through the blastopore. This is particularly clear in C, which shows endoderm cells as they move
into the embryo. Bars, 100 mm. |
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FIG. 8. The expression of a1 subunit protein during neurulation. (A) Stage 13. The rostral notochord (no) begins to stain for a1 subunit
protein. The neural plate (NP) and somites (som) show little stain. (B) Stage 14, rostral. The notochord begins to show prominent staining
for a1 subunit protein. (C) Stage 14, caudal. Notochord staining (no) is absent. There is some patchy staining elsewhere. som, somites.
(D) Stage 17. The deep surface of neural plate cells (NP) stain for a1 subunit protein. The notochord stains intensely and the somites (som)
show only weak and patchy stain. (E) Stage 17. The boundary (arrow) of a1 subunit protein between deep neural plate (NP) and lateral
ectoderm (LE) cells. Part of the intensely stained notochord is visible and the somite (som) shows little stain. (F) Stage 17: an example of
a1 subunit protein expression in floor plate cells lying immediately above the intensely staining notochord. (G) Stage 17. Negative control.
NP, neural plate; no, notochord; som, somite. Bars, 25 mm for F, G; otherwise, 100 mm. |
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FIG. 9. The expression of a1 subunit protein after closure of the neural tube. (A) Stage 22/23. Note intense stain of notochord, floor plate
(FP), and apical surfaces of neural tube cells (NT). som, somites. (B) Enlargement of A to show the region just above the notochord to
further illustrate floor plate (FP) and neurocoel lining stain. NT, neural tube. (C) Ventral region of same section to show pattern of a1
subunit protein expression in the expanding archenteron (arch). The ventral side of the notochord is just visible. The somites (som)
continue to show little expression. (D) Stage 36. The dorsal notochord and ventral region of the neural tube (NT). Note marked expression
along the cell surfaces lining the neurocoel, particularly in the floor plate. (A, C) Bar, 100 mm; (B, D) Bar, 25 mm. |
