Congenital Osteopetrosis, Mouse

Abstract

Mice which inherit osteopetrosis have several distinguishing features, depending upon the mutation and the background upon which it is expressed. Osteopetrotic mice tend to be smaller than normal littermates and are often runts of the litter. In all mutants, teeth fail to erupt and absence of incisors, the first teeth to erupt at 10 days, identifies the mutant genotype. For gl mice, the emergence of a gray hair coat without the usual yellow (agouti) tips at 7–8 days is diagnostic. Microphthalmic (mi) mice lack all pigment and the absence of retinal pigmentation at birth identifies this genotype (Fig. 299). The skeleton is grossly abnormal in mutants (Fig. 300), lacking the typical flared ends of long bones found in normal littermates (Fig. 301). These latter areas are sites of bone resorption (Fig. 302) not seen in mutants where bone formation predominates (Fig. 303). Thus, pathogenetic possibilities, reduced bone resorption, and increased bone formation (see below) are suggested by even a casual examination of external surfaces of the skeleton (Figs. 301–303). Facial growth is stunted in most mutants, producing a foreshortened snout. Hydrocephalus is occasionally found in op mice. Additional gross features of osteopetrotic mice include abnormal shape and reduced size of the teeth (Fig. 304) and a generalized radiopacity of the skeleton (Figs. 305, 306). Skeletal sclerosis is present at birth and the mutant genotype can be determined radiographically at any time postnatally.