Fig. 3. Noggin and chordin promote Nodal expression around the node, the level of which correlates with Nodal expression in left LPM. (A-D) Ventral views of 4s mouse embryos hybridized with Nodal probe. The node area is boxed. The approximate level of Nodal expression around the node is judged as normal (++), weak (+) or undetectable (-). Arrowheads indicate Nodal expression in LPM. (A) Wild-type embryo. (B-D) Chrd^-/-;Nog^-/- (DKO) embryos showing variable levels of perinodal Nodal expression. (E) Summary of perinodal Nodal expression in non-mutant control (wild type, Chrd^-/-;Nog^+/+ and Chrd^-/-;Nog^+/-) and Chrd^-/-;Nog^-/- embryos. Numbers above bars indicate embryos of a given result among the total assayed. (F) Summary of the relationship between Nodal expression around the node and in LPM of Chrd^-/-;Nog^-/- embryos. (G,H) Wild-type (G) and Chrd^-/-;Nog^-/- (H) nodes at 1s stained for acetylated tubulin, marking cilia. Dashed lines indicate node boundaries. Confocal sections along planes G-a, -b and H-a, -b are shown alongside. Red arrowheads, example cilia. (I) Node cilia density at 1s, comparing wild-type (n=3) and Chrd^-/-;Nog^-/- (n=3) embryos. ^*, significant difference (mean <0.05).