Effects of homozygous Cbfa1 mutations on the mouse skeleton

Targeted disruption of the Cbfa1 gene in the homozygous
state (!/!) results in a severe phenotype.
Homozygous mutant mice are small and
die from respiratory failure at birth. In contrast
to normal mice (+/+, 1), the mutant mice (!/!, 2)
completely lack bone development, as shown
by lack of alizarin red staining. Just before birth,
normal +/+ mouse embryos (3) show welldeveloped
bones (stained red) in the upper extremities,
including the clavicles (arrow) and
the tuberositas humeri (circle). Heterozygous
mice (+/!, 4) show severe hypoplasia and reduced
ossification of the long bones. Homozygous
mutant mice (!/!, 5) totally lack any bone
formation, as shown by lack of red staining.