Figure 2.

Gross phenotypes of IKK1^−/−newborn mice. (A) Wild-type newborn mouse (left) and an IKK1^−/− homozygous (right) littermate are shown. The mutant embryos exhibit severe alterations in the overall morphology. Limbs and tail are barely protruding and seem to be shortened. The skin appears translucent and tense. (B,C) A close-up view of a wild-type (B) and mutant (C) head. The mutant embryos lack whiskers, compared with the wild-type embryos. (D) Comparison of E12.5 wild-type (left) and IKK1 (right) mutant embryos. The mutant shows mild phenotypical alterations in morphology of the limb buds, tail and craniofacial region. (E) Bone staining of the embryos shown in A. The mutant skeleton (right) exhibits a few gross alterations. The craniofacial bone structure shows malformation, the tail appears to be shorter, and the bending of the distal limb region is abnormal. However, in contrast to the appearance of a newborn embryo, all long bones of the limbs are formed. (F,G) Ventral view of wild-type (F) and mutant (G) skulls. The skull exhibits a nearly complete fusion of the palate (F; arrowhead), whereas the mutant bilateral palate shelves (arrowhead) remains unfused, allowing the more dorsal lying vomer and presphenoid to be visible (G). (H,I) A ventral view of the ribcage and the sternum of a wild-type skeleton (H) and an IKK1^−/− skeleton (F). The mutant embryo displays a broader sternum and the ribs exhibit a kinky fusion to the sternum and split sternebra 6 (arrowhead). (J) Lower jaw and lower incisors of wild-type (left) and mutant (right) embryos. The morphology of the protruding incisors in mutant jaw appears malformed. (K) A detailed view of the incisors (left, +/+; right , −/−) shows a reduced and distorted mutant incisor.