Fig. 2. Chordin and noggin are both required for correct heart looping and expression of left-side determinants. (A-C) Arrows indicate laterality of heart looping from left ventricle to outflow tract. Dashed lines outline hearts. (A) E9.0 wild-type (WT) mouse embryo showing normal rightward heart looping. (B) E9.0 Chrd^-/-;Nog^-/- (DKO) embryo showing no directional looping of the heart. (C) E9.0 Chrd^-/-;Nog^-/- embryo showing reversed, leftward looping. (D) Summary of cardiac looping at E9.5 in various genotypes, each investigated in >20 embryos. (E-H) Embryos subjected to WMISH at 5s. WMISH for Nodal probe in wild type (E) and Chrd^-/-;Nog^-/- (F) and for Lefty2 in wild type (G) and Chrd^-/-;Nog^-/- (H). (I) Summary of expression patterns of the L-R asymmetric markers Nodal, Lefty2 and Pitx2 in Chrd^-/-;Nog^-/- embryos. The percentages and numbers of embryos in each class are shown.