Related Experiment Videos
Inhibition of FGF-induced alphaA-crystallin promoter activity in lens epithelial explants by TGFbeta
Y Ueda1, C G Chamberlain, K Satoh
1Department of Anatomy and Histology and Institute for Biomedical Research, The University of Sydney, Australia.
Purpose:
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.
Insights
Fibroblast growth factor (FGF) stimulates alphaA-crystallin promoter activity, crucial for lens biology. Transforming growth factor-beta (TGF-beta) can block this stimulation, potentially disrupting crystallin gene expression during lens development.
Area of Science:
- Ocular biology
- Molecular genetics
- Cell signaling
Background:
- Fibroblast growth factor (FGF) is vital for normal lens development.
- Transforming growth factor-beta (TGF-beta) is implicated in cataract formation.
- AlphaA-crystallin is a key protein in the eye lens.
Purpose of the Study:
- To investigate the effects of FGF and TGF-beta on alphaA-crystallin promoter activity.
- To understand the role of these growth factors in lens biology and cataractogenesis.
Main Methods:
- Rat lens epithelial explants were transfected with a luciferase reporter gene under the alphaA-crystallin promoter.
- Explants were cultured with varying concentrations of FGF and TGF-beta.
- Promoter activity was measured using luciferase assays.
Main Results:
- FGF-2 significantly stimulated alphaA-crystallin promoter activity at concentrations inducing lens fiber differentiation.
- Lower FGF concentrations, promoting proliferation but not differentiation, showed minimal effect.
- TGF-beta2 inhibited FGF-induced alphaA-crystallin promoter activity even at low concentrations.
- Overt cataractous changes were observed only at higher TGF-beta concentrations.
Conclusions:
- FGF's role in stimulating crystallin accumulation is supported by its effect on the alphaA-crystallin promoter.
- TGF-beta can interfere with alphaA-crystallin gene expression during early lens fiber differentiation.
- TGF-beta's inhibitory effect at sub-pathological concentrations highlights its potential to disrupt lens development.