Fig. 4.

Impaired vertebral body differentiation in Cv2^−/− 12.5 d.p.c. embryos (anterior, more mature vertebral regions are shown). Sagittal paraffin sections of wild-type (A, C, E, G, I) and Cv2^−/− (B, D, F, H) 12.5 d.p.c. embryos. (A, B) Sections stained with H&E. Boxed areas are shown at higher power in (C, D and E, F). Vertebral bodies (vb) are smaller in the mutant, while the intervertebral discs (ivd) appear to be unaffected.n, notochord. (G, H) pSmad1 is detected at higher levels in the vb at this stage. In Cv2^−/− mutants the area stained for pSmad1 (brackets) is smaller than in the wild-type, reflecting the reduced size of the vertebral body. (I) Detection of CV2 protein by immunohistochemistry in sections counterstained with H&E. CV2 is present in the vb, co-localizing with pSmad1. (J) Summary of the expression of CV2 protein compared to that of Bmp, Tsg, Chd, Chdl-1, Chdl-2 and Tolloid mRNAs and to pSmad1 levels in the anterior vertebral column. At this stage the highest levels of pSmad1 co-localize with CV2 protein in the vb and are complementary to the expression domain of Bmp, Tsg, Chd Chdl-1, Chdl-2 and Tolloid mRNAs in the ivd.