|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
|
Fig. 4. Whole-mount in situ hybridization show that hab expression becomes
progressively restricted to superficial layers of the blastoderm. (A) Optical
cross-section of 4-cell stage. (B) Hand-section of 30% epiboly stage. Inset,
higher magnification of boxed region showing a radial gradient (arrow) of
hab expression in the epiblast, highest superficially. (C) Medial
sagittal section of shield stage embryo, dorsal to the right. Arrows indicate
the gradient of hab expression on the ventral side and at the animal
pole. Note clearing on dorsal side, except for the thin line of expression in
the EVL. Arrowhead indicates region of intense hab expression in the
forerunner precursors. (D) Animal pole view of shield stage embryo showing
high levels of hab expressed in the EVL, and the intense expression
in the forerunner cells (arrowhead). Inset shows higher power view, showing
nuclei surrounded by rings of hab expression (E) Medial sagittal
section at 70% showing high levels of hab expressed in the anterior
axial hypoblast (thick arrow), the EVL (thin arrow), and the forerunner cells
(arrowhead), and absence of hab expression in the axial epiblast.
(F,F') High magnification views of embryo in E. Hand sections are along
plane indicated by dashed line in E. (F) Lateral transverse section, showing a
radial gradient of hab expression in the epiblast, highest in
superficial layer adjacent to the EVL. At this location, the hypoblast has not
yet moved under the epiblast. The numbers indicate approximate layers.
(F') Dorsal transverse section, showing absence of hab
expression in axial epiblast cells, and strong expression in anterior axial
hypoblast near the level of the prechordal plate. At this stage, the midline
of the neural epithelium is about two cells thick. (G) Medial sagittal section
at 70% over stained to show the expression in the EVL, and the clearing in the
axial epiblast. (H) Optical cross-section of 70% epiboly
habdtv43/dtv43 missense mutant showing raised levels of
hab mRNA found in the blastoderm. Note intense expression in the
forerunner clusters (arrowhead). Curved bracket indicates heightened
expression in the hypoblast. Embryos in H and E are siblings. (I) Optical
cross-section of 70% epiboly habtx230/tx230 nonsense
mutant showing lowered levels of hab mRNA found in the embryo. epi,
epiblast; hyp, hypoblast; YSL, yolk syncytial layer. Numbers indicate cell
layers of the epiblast. Scale bar: 100 µm in C; 20 µm in F,F'; 75
µm in G; 250 µm in all others.
|
