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Differential induction of gene expression by basic fibroblast growth factor and neuroD in cultured retinal pigment
1Department of Ophthalmology, University of Alabama at Birmingham School of Medicine, USA.
Insights
Basic fibroblast growth factor (bFGF) and NeuroD trigger different gene expressions in embryonic chick retinal pigment epithelial (RPE) cells. bFGF induces RA4 expression, while NeuroD promotes neuronal markers and visinin, with no observed interaction between the factors.
Area of Science:
- Developmental biology
- Cell biology
- Molecular biology
Background:
- Embryonic chick retinal pigment epithelial (RPE) cells can transdifferentiate into neural retina under specific conditions.
- Basic fibroblast growth factor (bFGF) can induce transdifferentiation in intact RPE tissue.
- NeuroD, a transcription factor, can induce RPE cells to produce cells resembling photoreceptors.
Purpose of the Study:
- To investigate if bFGF induces similar transdifferentiation as NeuroD in dissociated embryonic day 6 (E6) RPE cells.
- To determine if there is an interplay between bFGF and NeuroD in cultured E6 RPE cells.
Main Methods:
- Dissociated E6 RPE cells were cultured with or without bFGF.
- Retrovirus expressing NeuroD was added to some cultures.
- Gene expression was analyzed using immunocytochemistry and in situ hybridization.
Main Results:
- bFGF did not induce neuronal markers (visinin, HNK-1/N-CAM, MAP2) but elicited RA4 expression in E6 RPE cells.
- NeuroD induced visinin and neuronal markers, but not RA4.
- Neither bFGF nor NeuroD altered the expression levels induced by the other factor, indicating no synergy or interference.
Conclusions:
- bFGF and NeuroD induce distinct gene expression profiles in cultured embryonic chick RPE cells.
- The two factors act independently, suggesting different molecular pathways for RPE transdifferentiation.
Abstract:
Embryonic chick retinal pigment epithelial (RPE) cells can undergo transdifferentiation upon appropriate stimulation. For example, basic fibroblast growth factor (bFGF) induces intact RPE tissue younger than embryonic day 4.5 (E4.5) to transdifferentiate into a neural retina. NeuroD, a gene encoding a basic helix-loop-helix transcription factor, triggers de novo production of cells that resemble young photoreceptor cells morphologically and express general neuron markers (HNK-1/N-CAM and MAP2) and a photoreceptor-specific marker (visinin) from cell cultures of dissociated E6 RPE (Yan & Wang, 1998). The present study examined whether bFGF will lead to the same transdifferentiation phenomenon as neuroD when applied to dissociated, cultured E6 RPE cells, and whether interplay exists between the two factors under the culture conditions. Dissociated E6 RPE cells were cultured in the presence or absence of bFGF, and with or without the addition of retrovirus expressing neuroD. Gene expression was analyzed with immunocytochemistry and in situ hybridization. Unlike neuroD, bFGF did not induce the expression of visinin, or HNK-1/N-CAM and MAP2. However, bFGF elicited the expression of RA4 immunogenicity; yet, many of these RA4-positive cells lacked a neuronal morphology. Addition of bFGF to neuroD-expressing cultures did not alter the number of visinin-expressing cells; misexpression of neuroD in bFGF-treated cultures did not change the number of RA4-positive cells, suggesting the absence of interference or synergistic interaction between the two factors. Our data indicated that bFGF and neuroD induced the expression of different genes in cultured RPE cells.