Figure 4

Live imaging H2B-EGFP in postimplantation mouse embryos. (a) Lateral view of the embryonic region of an E7.5 embryo (anterior to the left) with box depicting the region imaged in b and double-headed arrow depicting the x-y layering of the z-stack. (b-d) single optical x-y sections of fluorescence overlayed on bright-field images acquired at the same focal plane. Each panel is 60 μm apart from the preceding panel. These panels comprise x-y images in the z-stack depicted in panel a. The different layers of this stage of embryo including the epiblast, mesoderm, visceral endoderm and node can be distinguished on the basis of both position and nuclear morphology. (e-h) projection of a rendered z-stack of (x-y) sections (n = 90) of the dark-field component of the sections taken in the series schematized in a and of the raw data shown in b. (e) 0° rotation, (f) 60° rotation, (g) 120° rotation, and (h) 180° rotation views. (i) low-magnification frontal view of an E11 embryo that has had a transverse cut made to remove the head. The box depicts the region (at the ventral hindbrain and 1^st branchial pouch) subject to laser scanning confocal imaging, with the double-headed arrow depicting the x-y layering of the acquired z-stack. (j) rendered (z-) stack of sections (n = 200, i.e. 400 μm depth) taken through the boxed region. (k) rendered stack of top 50 x-y sections (100 μm depth) taken from the region imaged around the notochord (comprising axial mesoderm and mesenchyme cells). (l) rendered stack of top 50 sections (100 μm depth) taken around the branchial pouch region (comprising endoderm and mesenchyme cells). The sections used to generate the rendered stacks in panels k and l were electronically magnified. Pink arrowheads, mitotic nuclei; yellow arrowheads, pycnotic nuclei; ect, ectoderm, en, endoderm, hf, headfold, mes, mesoderm, noto, notochord.