An estrogen receptor repressor induces cataract formation in transgenic mice

Despite the high prevalence of age-related cataracts, there are currently no known therapies to delay or prevent their occurrence. Studies in humans and rodent models suggest that estrogen may provide protection against age-related cataracts. The discovery of ocular estrogen receptors (ERs) indicates that estrogen protection may result from direct interactions with its receptors in the eye, instead an indirect consequence from effects on another tissue. Studies in our transgenic mouse model validate the concept that estrogen is beneficial for the eye. These mice express ERΔ3, a dominant-negative form of ERα that inhibits ERα function. In the ERΔ3 transgenic mice, cortical cataracts spontaneously form in ERΔ3 females after puberty and progress with age. The cataracts initiate in the equatorial region of the lens where the epithelial cells differentiate into elongating fiber cells. Cataract formation can be prevented if the females are ovariectomized before, but not after, sexual maturity. Both male and female ERΔ3 mice develop cataracts after neonatal treatment with the potent estrogen diethylstilbestrol (DES). The incidence of spontaneous and DES-induced cataracts in ERΔ3 mice is 100%, yet these cataracts are absent from the wild-type mice. These data suggest that repression of estrogen action induces cortical cataract formation because estrogen is required to activate the ERΔ3 repressor. Evidence of DES-induced cataracts in the ERΔ3 males as well as the females suggests that estrogen is important in lens physiology in both sexes. The ERΔ3 mice provide a powerful model for assessing the role of estrogen in maintaining the transparency of the lens.