Fig. 4. Expanded anterior primitive streak derivatives and increased Nodal expression in Lrp 5^+/-;Lrp6^-/- embryos. Whole-mount RNA in situ analysis of marker gene expression in normal and Lrp5^+/-;Lrp6^-/- mutant embryos. Anterior is towards the left in all panels except B, which is an anterolateral view. Embryos in A-D and K-P are between 7.5 dpc and 8.0 dpc stages, whereas embryos in E-J are at 8.5 dpc. (A,B) Analysis of Foxa2 expression. A control embryo (A) shows expression in the axial mesendoderm, which is greatly expanded in the mutant embryo (B). (C,D) Analysis of Hex expression. A control embryo (C) shows expression in the ADE, which is broader in the mutant embryo (D). (E-H) Analysis of Shh expression. Control embryos (E,G) show expression in the axial mesoderm that is greatly (F) or mildly (H) reduced in mutant embryos. (I,J) Analysis of T expression. Control (I) and mutant (J) embryos show expression in the axial mesoderm. (K-P) Analysis of Nodal expression. Control embryos show expression in the primitive streak (K) that is downregulated by the late streak stage (M) and restricted to the node by the headfold stage (O). Mutant embryos (L,N,P) fail to properly downregulate expression in the primitive streak as development proceeds. Photos taken at the same magnification are grouped as follows: A-D; E,F; G-J; K-P.