Fig. 5. Mesodermal Tbx1 affects mesodermal but not epithelial Fgf8 expression. (A-D) Whole-mount RNA in situ hybridization with an Fgf8 probe. (A',B') Transverse sections of the E8.5 embryos shown in A and B, respectively. (C',D') Coronal sections of the E9 embryos shown in C and D, respectively. Orange arrows indicate Fgf8 expression in the ectoderm. Pink arrows indicate Fgf8 expression in endoderm. Black arrowheads indicate Fgf8 expression in splanchnic mesoderm/anterior heart field. Scale bar: 100 µm in B,D,D'; 50 µm in B'.