HETEROZYGOUS OIM MICE EXHIBIT A MILD FORM OF OSTEOGENESIS IMPERFECTA

The oim Strain of mice is one of several rodent models that exhibit an osteogenesis imperfecta (OI) phenotype, These mice have a mutation in the gene encoding alpha-2 chain of type I procollagen that prevents p roper assembly of this propeptide with alpha-1 propeptides, Homozygous oim mice experience multiple bone fractures under standard laboratory animal housing conditions and are representative of moderate to sever e forms of OI, Because fractures are not typically experienced by hete rozygous oim mice, they have not been studied extensively, The present studies show that the organization of cortical bone is deficient in h eterozygotes, exhibiting a morphology intermediate to specimens from h omozygotes and wild-type mice, The biomechanical properties of femurs isolated from heterozygous oim mice are also intermediate to homozygot es and wild-type mice when tested in four-point bending, Although it i s not possible to distinguish visually between heterozygous oim and wi ld-type mice, the quality and biomechanical properties of bone in hete rozygotes is significantly reduced by twelve weeks of age, Heterozygou s oim mice are useful as a model for a mild form of OI. (C) 1996 by El sevier Science Inc.