Hereditary and Histologic Characteristics of the CF1/b cac Mouse Cataract Model

A substrain of mice originating from the CF1 strain (an outbred colony) reared at Osaka Prefecture University (CF1/b cac mice) develops cataracts beginning at 14 d old. Affected mice were fully viable and fertile and had developed cataracts by 22 d of age. The incidence of cataracts did not differ between male and female mice. Histologically, 14-wk-old CF1/b cac mice showed vacuolated lens epithelial cells, swollen lens fibers, many pyknotic nuclei, and vacuolation of the lens cortex. To elucidate the mode of inheritance, we analyzed heterozygous mutants hybrids generated from CF1/b cac and wildtype BALB/c mice and the offspring of the backcrossed heterozygous mutants. None of the heterozygous mutants was affected, but the ratio of affected to unaffected mice was 1:3 among the offspring of the heterozygous mutants. The initial genomewide screen of 20 affected backcrossed offspring (CF1/b cac × [CF1/b cac × BALB/c]) indicated that the mutant gene resides on chromosome 16. For further mapping, we used affected progeny of CF1/b cac × (CF1/b cac × MSM/Ms) mice. We concluded that the cataracts in CF1/b cac mice are inherited through an autosomal recessive mutation and that the mutant gene is located on mouse chromosome 16 between D16Mit5 and D16Mit92 and between D16Mit92 and D16Mit201. The mapping of the mutant gene of the CF1/b cac mice to mouse chromosome 16 provides the positional information necessary to identify the candidate gene responsible for the CF1/b cac phenotype.