Fig. 2. Progressive disruption of segmentation in the Fgfr1^f/f;T-Cre mutant embryos. (A,B) Skeletons stained with Alizarin Red (bone) and Alcian Blue (cartilage). (C-H) Uncx4.1 staining in Fgfr1^f/+;T-Cre control (C,E,G) and Fgfr1^f/f;T-Cre mutant embryos (D,F,H); C and D show whole mounts of E9.5 embryos and E and F are higher magnifications of the somite region at E10.0. (G,H) Sagittal sections through Uncx4.1-stained embryos. The posterior-most Uncx4.1-positive region is shown at the same magnification for both. In the Fgfr1^f/f;T-Cre mutant embryos (H), somites fail to separate and a giant somite spanning over the region normally covering two somites is formed. Arrowheads indicate the boundaries between somites.