Inhibition of FGF-induced alphaA-crystallin promoter activity in lens epithelial explants by TGFbeta.
OBJECTIVE
Fibroblast growth factor (FGF) plays a key role in normal lens biology, and recent studies suggest that transforming growth factor (TGF)-beta is involved in the origin of certain forms of cataract. In the current study, the effects of FGF and TGFbeta on alphaA-crystallin promoter activity were investigated.


METHODS
Rat lens epithelial explants were cultured with or without growth factors after transfecting with the firefly luciferase reporter gene driven by either the mouse alphaA-crystallin promoter region or a control simian virus (SV)40 promoter.


RESULTS
FGF-2, at a concentration that induced lens fiber differentiation, strongly stimulated alphaA-crystallin promoter activity in explants at 3 to 4 days of culture, whereas SV40 promoter control specimens showed no comparable increase. At lower concentrations of FGF, sufficient to induce cell proliferation but not differentiation, there was only a slight increase in alphaA-crystallin promoter activity. Stimulation of alphaA-crystallin promoter activity induced by the fiber-differentiating concentration of FGF was virtually abolished by as little as 25 pg/ml TGFbeta2, but the onset of fiber-specific beta-crystallin accumulation was not prevented at this concentration. Phase-contrast microscopy revealed overt cataractous changes only at concentrations of TGFbeta more than 25 pg/ml.


CONCLUSIONS
The stimulation of alphaA-crystallin promoter activity by FGF is consistent with its role in inducing accumulation of crystallins in explants. The blocking effect of TGFbeta on this process, even at a concentration too low to induce obvious pathologic changes, indicates the potential for TGFbeta to disturb alphaA-crystallin gene expression during early fiber differentiation.
Ueda
Y
Y
Department of Anatomy and Histology and Institute for Biomedical Research, The University of Sydney, Australia.
Chamberlain
C G
CG
Satoh
K
K
McAvoy
J W
JW
D000818:Animals; D002417:Cattle; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003459:Crystallins / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005346:Fibroblast Growth Factors / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D007908:Lens, Crystalline / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D051381:Rats; D013539:Simian virus 40 / Q000235:genetics; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D003459:Crystallins; D016212:Transforming Growth Factor beta; D005346:Fibroblast Growth Factors; D008156:Luciferases; D001616:beta-Galactosidase