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JR Hawse, W Zhang, Q Huang, N Sheets, KM Miller, J Horwitz, M Kantorow; Decreased Expression of Ribosomal Proteins in Age-related Human Cataract . Invest. Ophthalmol. Vis. Sci. 2002;43(13):469.
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Purpose: We have previously identified multiple differentially expressed genes between cataract and normal human lenses that function in growth control, Ca++-homeostasis and metal-detoxification pathways. Here, we sought to identify additional differentially expressed genes between cataract and normal lenses. Methods: RNA was isolated from 90 cataract (70% mixed, 20% nuclear, 5% cortical and 2% PSC) and 41 normal lens epithelia and analyzed for differential gene expression by RT-PCR differential display. Transcripts exhibiting altered levels of gene expression were cloned and identified by sequencing. The expression levels of identified clones were confirmed and the expression levels of functionally similar candidate genes were evaluated between cataract and normal lenses by quantitative RT-PCR. The spatial expression patterns of identified genes were also examined in micodissected normal lenses. Results: Multiple transcripts exhibited significant differences in gene expression. One transcript, exhibiting a 5-fold decrease in expression between cataract and normal lenses, was identified as ribosomal protein L21. Three additional ribosomal proteins, L15, L13a, and L7a, also exhibited significantly decreased expression in cataract compared to normal lenses. By contrast, the levels of elongation factor 1 alpha 1 (EF1a1) and initiation factor 4E (eIF4E) were unchanged. Identical levels of RPL21 were detected throughout the normal lens epithelium and high levels were also detected in lens fibers. Conclusions: The data suggest that decreased expression of ribosomal proteins may direct decreased protein synthesis in age-related cataract and they point to protein synthesis pathways as being important for the maintenance of lens transparency.
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