Differential gene expression in male and female rat lenses undergoing cataract induction by transforming growth factor-beta (TGF-beta)

Epidemiologic studies in humans as well as immunohistologic studies in anim als have demonstrated significant sex differences in the propensity to deve lop cataract. Several studies suggest that estrogen may play a protective r ole against cataractogenesis, Indeed, male and ovariectomized female rat le nses have a greater susceptibility to cataract induced by transforming grow th factor-beta (TGF-beta) than do normal female lenses, However, in spite o f the current evidence that estrogen may play a pivotal role in cataractoge nesis, the molecular mechanisms behind this phenomenon are largely undeterm ined. Our study utilized the differential display procedure to examine gene up- and down-regulation in male, normal female and ovariectomized female r at lenses exposed to TGF-beta. Male and normal female rat lenses were cultu red with or without 0.15 ng ml(-1) TGF-beta. Lenses were then harvested, an d total RNA was isolated for analysis by reverse-transcriptase differential display. Differentially expressed mRNAs were subcloned, sequenced and iden tified through GenBank database searches, The original experiment was repea ted with the addition of ovariectomized female TGF-beta (+/-) conditions, a nd all differential patterns of gene expression were verified using Norther n blot and RT-PCR analysis. Screening of approximately 12% of the mRNA popu lation led to the identification of 27 differentially expressed cDNAs. Nota bly, strong gender differences were found in expression levels of gamma B-c rystallin. In addition, proteasome Z subunit was up-regulated in TGF-beta-t reated male and ovariectomized female lenses, but was down-regulated in TGF -beta-treated normal female lenses, This pattern of expression is consisten t with the increased susceptibility of male and ovariectomized lenses to TG F-beta-induced cataract. We conclude that differential display is a useful and expedient method for analysing changes in gene expression in the lens. Structural and functional studies of the genes identified in this study may further elucidate mechanisms underlying the TGF-beta-induced cataract form ation and differential rates of cataractogenesis in males vs females. In pa rticular, our data suggest that the role of proteasome Z subunit in TGF-bet a-induced anterior subcapsular cataract warrants further investigation. (C) 2000 Academic Press.