Fig. 2.

Localization of BMP4 in rabbit embryonic discs from stage 2 to stage 5 (at 6.2–7.2 dpc). En face view of in situ hybridized embryos (A–D) oriented with the anterior pole to the top and 5-μm Technovit® sections at low (E–G) and high magnification (H–M). Sagittal sections (E, H, I, M) are oriented with the anterior pole to the left and epiblast (e) or dorsal layer (dl) to the top. Transverse sections (F, G, J–L) are aligned with the epiblast to the top. Bars and letters refer to positions of sections shown and in D their length represents that of the transverse section shown in M. Boxes in E–G indicate magnified details shown in H-L; asterisks mark the border of the embryonic disc. e = epiblast, h = hypoblast, t = trophoblast, y = yolk sac epithelium, m = mesoderm, dl = dorsal layer, vl = ventral layer, n = Hensen’s node, ps = primitive streak, and nc = notochordal process. Scale bar: 700 μm (A–D), 100 μm (F, G), 60 μm (E), 40 μm (J–M), and 20 μm (H, I)