Lens development and crystallin distribution of the early onset hereditary cataract in the UPL rat.

The Upjohn Pharmaceuticals Limited (UPL) rat is a new dominant hereditary cataract model with two types of cataract formation, early onset (E-type) and late onset (L-type). In the UPL E-type rat cataracts have formed by the time the eyes open. The E-type rat also develops microphthalmos and buphthalmos. In this study, histological observations of cataract development in the E-type rats were performed during the period of fetal development, at birth and at 1, 3 and 62 weeks of age. In addition, the distribution of alpha- and gamma-crystallins in the developing lens was determined using anti-crystallin antisera. Abnormal elongation of the lens fibers was first observed on the 13th day of gestation. Stratification of lens epithelial cells was present on the 19th day of gestation and this change became more severe with age. There was no alteration in alpha- and gamma-crystallin expression during the fetal period. The continuity between the lens epithelial cells and lens fibers was lost at 3 weeks of age and it was assumed that differentiation of lens epithelial cells had ceased. These findings suggested that development of the UPL rat E-type cataract was related to an early abnormality in lens cell differentiation not involving crystallin expression.