(Downloading may take up to 30 seconds.
If the slide opens in your browser, select File -> Save As to save it.)
Click on image to view larger version.


Figure 4


Fig. 4. A node defect but normal notochordal extension in E8.5 Lp embryos. (A-F) Structure of the node (arrows) in wild-type (A,C,E) and Lp/Lp (B,D,F) embryos at E7.5 (A-D) and E8.5 (E,F). Embryos are homozygous for the cordon bleu (Cobl) gene trap, which expresses ß-gal in the node and its derivatives. At E7.5, whole-mounts (A,B) and sections (C,D) show a closely similar structure and ß-gal-positive cell number in the node of +/+ and Lp/Lp genotypes. By contrast, at E8.5 the ß-gal-positive node appears markedly wider in sections of Lp/Lp embryos than in +/+ littermates (E,F). (G-I) In situ hybridisation for Shh expression at E8.5 (dorsal view of whole-mounts). The node (arrows) is approximately twice as wide in Lp/Lp embryos (I) as in +/+ embryos (G). Lp/+ embryos have a node of intermediate width (H). The notochordal Shh expression domain (arrowheads in G) is also broader in Lp/Lp (between white arrows in I) compared with +/+ and Lp/+. (J-L) Right lateral view of wild-type E7.5 embryos a few minutes after injection of DiI into the node (J), just in front of the node (K) or further in front of the node (L). Arrows indicate position of node. (M-O) After 18 hours culture, node-injected embryos exhibit labelling of the entire midline (bracketed region in M), including the triangular node and notochordal plate (white arrow in M). Injection in front of the node yields midline labelling along variable portions of the midline: either trunk + head (N), head only (O) or trunk only (not shown) depending on the precise position of injection and stage of embryo. The triangular node and notochordal plate is not labelled in these embryos. (P) Labelling in front of the node (as in K) in embryos from Lp/+ x Lp/+ litters yields a range of labelling patterns as in N,O. The number of Lp/Lp embryos with midline extension does not differ significantly from Lp/+ and +/+ littermates. Red dots: DiI-labelled cells. Black triangles: node. Scale bars: in B, 0.1 mm for A,B; in D, 0.1 mm for C,D; in E, 0.2 mm for E,F; in I, 0.2 mm for G-I; in L, 0.2 mm for J-L; in O, 0.2 mm for M-O.