Gene expression profiling in human age-related nuclear cataract.
OBJECTIVE
To identify genes that are differentially expressed in age-related nuclear cataracts compared to transparent human lenses.


METHODS
Total RNA was extracted from pools of central 5 mm capsulorrhexis epithelial samples microdissected at surgery from eyes with nuclear cataract or from age-matched transparent lenses (post-mortem). mRNA levels in the two samples were compared by hybridization to DNA microarrays (GeneFilter GF211) containing 4,132 known human genes. Only mRNAs consistently modulated over four comparisons were retained for analysis. A subset of the mRNA expression differences thus identified were verified and confirmed by Real-Time RT-PCR. Expressed and modulated genes were categorized according to the Gene Ontology classification.


RESULTS
The data revealed 262 genes that are downregulated and 7 that are upregulated by a factor of 2.5 or more in epithelial samples from cataractous lenses compared with transparent lenses. The highest content of downregulated genes was found in the functional classes "Signal transduction", "Regulation of cell proliferation", and "Protein modification". The "Response to oxidative stress" class was one of the least modulated. Among downregulated genes, we found several mRNAs coding for transcription/translation-related proteins, heat shock proteins 70 and 27, two ubiquitin-conjugating enzymes, two subunits of the cytoskeletal/chaperone protein, tubulin, betaA4-crystallin, and a group of Alzheimer-related proteins, including presenilin 1 and presenilin 2.


CONCLUSIONS
An extensive mRNA downregulation accompanies the development of the nuclear type of human age-related cataract. A few genes and classes of genes more prominently displaying this type of response have been identified. Altogether, the data indicate the tendency, in age-related nuclear cataract, towards a shutdown of de novo RNA and protein biosynthesis rather than an upregulation of cell defense components such as chaperones and various kinds of antioxidative or detoxifying proteins.
Ruotolo
Roberta
R
Dipartimento di Biochimica e Biologia Molecolare, University of Parma, Parma, Italy.
Grassi
Francesca
F
Percudani
Riccardo
R
Rivetti
Claudio
C
Martorana
Davide
D
Maraini
Giovanni
G
Ottonello
Simone
S
D000368:Aged; D000375:Aging / Q000502:physiology*; D002386:Cataract / Q000378:metabolism*; D015536:Down-Regulation; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D007907:Lens Nucleus, Crystalline / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis; D012313:RNA / Q000302:isolation & purification; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D012333:RNA, Messenger; D012313:RNA