Hereditary Cataract Rat Derived from the Sprague-Dawley Colony

Abstract

Many animal models have been established to explain the mechanism of human cataract development, but none are satisfactory. In 1989, a female Sprague-Dawley rat which developed a spontaneous cataract was found in the colony at Upjohn Pharmaceuticals Limited, Tsukuba Research Laboratory. The cataract was shown to be hereditary by sister-brother matings. Cataracts in rats are classified into two types according to the age of cataract formation, early-onset type and late-onset type. Rats with early-onset cataracts have lens opacification before eye opening, and often also have microphthalmos, microphakia, proptosis, and synechia. Rats with late-onset cataracts start to develop lens opacification from about 7 weeks of age. Abnormally elongated epithelial cells are observed histologically in both cataract types. From our results to date, we hypothesize that this cataract has autosomal intermediate or incomplete dominant inheritance, with early-onset in homozygotes and late-onset in heterozygotes of the gene.