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Retinal degeneration in transgenic mice with photoreceptor-specific expression of a dominant-negative fibroblast
P A Campochiaro1, M Chang, M Ohsato
1Wilmer Ophthalmological Institute, Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland 21287-9277, USA.
Abstract:
Mutant cDNAs coding for dominant-negative forms of the fibroblast growth factor receptors 1 (FGFR-1) and 2 (FGFR-2) that lack tyrosine kinase activity were ligated to a 2.2 kb DNA fragment containing the bovine rhodopsin promoter and used to generate transgenic mice. Six independent lines were generated with the FGFR-1 construct, and five were generated with the FGFR-2 construct. Five of the six FGFR-1 mutant lines and all five FGFR-2 mutant lines showed transgene expression in the retina by reverse transcription-PCR. By both in situ hybridization and immunohistochemistry, mutant FGFRs were found to be expressed specifically in photoreceptors of transgene-positive FGFR-1 and FGFR-2 mice. Lines expressing the FGFR-2 mutant showed progressive photoreceptor degeneration; the retinas showed minimal or no abnormalities at 1 month, but by 2 months they showed focal areas of thinning of the outer nuclear layer and disruption of photoreceptors. By 2-4 months, areas of complete loss of photoreceptors were seen. These abnormalities were not seen in control littermates not expressing the transgene. Mice from two FGFR-1 mutant lines showed focal areas of thinning of the outer nuclear layer and numerous photoreceptors with fragmented chromatin, whereas the other FGFR-1 lines showed minimal or no abnormalities. These data indicate that perturbation of FGF signaling in photoreceptors is associated with progressive photoreceptor degeneration, suggesting that one or more of the FGFs may act as a survival factor for photoreceptor cells.
Insights
Fibroblast growth factor (FGF) signaling disruption in photoreceptors causes progressive vision loss. FGFs may be crucial survival factors for these essential eye cells.
Area of Science:
- Ophthalmology
- Genetics
- Cell Biology
Background:
- Fibroblast growth factor receptors (FGFRs) play vital roles in cellular development and function.
- Dysregulation of FGFR signaling is implicated in various diseases.
Purpose of the Study:
- To investigate the role of fibroblast growth factor (FGF) signaling in photoreceptor survival using transgenic mouse models.
- To determine if inhibiting FGFR activity in photoreceptors leads to retinal degeneration.
Main Methods:
- Generated transgenic mice expressing dominant-negative fibroblast growth factor receptors 1 (FGFR-1) and 2 (FGFR-2) in the retina.
- Utilized reverse transcription-PCR, in situ hybridization, and immunohistochemistry to confirm transgene expression and localization.
- Assessed retinal structure and photoreceptor integrity over time in mutant and control mice.
Main Results:
- Transgenic mice expressing dominant-negative FGFR-1 or FGFR-2 specifically in photoreceptors were successfully generated.
- FGFR-2 mutant lines exhibited progressive photoreceptor degeneration, including outer nuclear layer thinning and photoreceptor loss.
- Some FGFR-1 mutant lines also showed signs of photoreceptor damage, such as chromatin fragmentation.
Conclusions:
- Perturbation of FGF signaling in photoreceptor cells is directly linked to progressive photoreceptor degeneration.
- These findings suggest that FGFs act as critical survival factors for photoreceptor cells.
- Targeting FGF signaling pathways may offer therapeutic potential for retinal degenerative diseases.