Fig. 2. The development of the cecum is abnormal in both Fgf9^-/- and Fgf10^-/- embryos. (A-F) Morphologic comparison of the development of the cecum in WT, Fgf9^-/- and Fgf10^-/- embryos at E12.5, E14.5 and E18.5. (G-I) Hematoxylin and Eosin (H&E) stained sections of E14.5 WT, Fgf9^-/- and Fgf10^-/- cecum. In WT embryos (A-G), the cecum is located at the ileo-colonic junction. (A-C,H) Fgf9^-/- embryos show a normal appearing epithelial tube throughout the small intestine and colon, but no identifiable cecal bud. (D-F,I) Fgf10^-/- embryos develop a mesenchymal bud at the ileo-colonic junction, but no epithelial budding or expansion into cecal mesenchyme was observed. (F) By E18.5, the cecal mesenchymal bud appeared to degenerate in Fgf10^-/- tissue (arrow). Dashed lines indicate the border between the epithelium and mesenchyme in the cecal region. Arrows indicate the position of the cecal tip or the position of the ileo-colonic junction in the absence of a cecum. M, mesenchyme.