Figure 1

External phenotype and skeletal and somite defects in cax mutant mice. (A-C) Examples of homozygous mutants demonstrating the variable phenotype in the backcross progeny. (D-G) Skeletal preparations of E15.5 embryos showing that even externally apparently normal mice have skeletal defects (D), and demonstrating various defects such as split vertebrae (asterisks in D, F, G), rib fusions and bifurcations (arrowheads in F), reduced or missing pedicles (arrows in G), and axial truncations (E). White and black boxes in (E) indicate the regions shown enlarged in (F) and (G), respectively. (H, I) Sections of E9.5 cax mutant embryos showing distinct somite borders (indicated by arrowheads) and somites of variable size.