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Expression of a truncated FGF receptor results in defective lens development in transgenic mice
M L Robinson1, L A MacMillan-Crow, J A Thompson
1Department of Cell Biology, Baylor College of Medicine, Houston, TX 77030, USA.
Abstract:
Members of the fibroblast growth factor (FGF) family are thought to initiate biological responses through the activation of cell surface receptors which must dimerize to transmit an intracellular signal. Mammalian lens epithelial cells respond to exogenous extracellular FGF, either in tissue culture or in transgenic mice, by initiating fiber cell differentiation. The role of FGF signalling in normal lens development was evaluated by lens-specific synthesis of a kinase-deficient FGF receptor type I (FGFR1) in transgenic mice. This truncated FGF receptor is thought to act as a dominant negative protein by heterodimerization with endogenous FGF receptors. The presence of transgenic mRNA in the lens was confirmed by in situ hybridization and by polymerase chain reaction amplification of reverse transcribed lens RNA (RT-PCR). The presence of transgenic protein was determined by Western blotting with antibodies to an extracellular domain of FGFR1. Three of four transgenic families expressing the truncated FGF receptor exhibited lens defects ranging from cataracts to severe microphthalmia. While the microphthalmic lenses displayed a normal pattern of differentiation-specific crystallin expression, the lens epithelial cells were reduced in number and the lens fiber cells displayed characteristics consistent with the induction of apoptosis. Our results support the view that FGF receptor signalling plays an essential role in normal lens biology.
Insights
Fibroblast growth factor receptor (FGFR) signaling is crucial for normal lens development. Inhibiting FGFR1 in mice caused severe lens defects, including cataracts and microphthalmia, indicating FGFR signaling
Area of Science:
- Ophthalmology
- Developmental Biology
- Cell Signaling
Background:
- Fibroblast growth factors (FGFs) mediate biological responses via cell surface receptors that dimerize to signal intracellularly.
- FGF signaling influences mammalian lens epithelial cells, promoting fiber cell differentiation.
Purpose of the Study:
- To investigate the role of FGF signaling in normal lens development.
- To evaluate the effects of inhibiting Fibroblast Growth Factor Receptor type I (FGFR1) signaling in vivo.
Main Methods:
- Generated transgenic mice with lens-specific expression of a kinase-deficient FGFR1, acting as a dominant-negative inhibitor.
- Confirmed transgenic mRNA presence using in situ hybridization and RT-PCR.
- Verified transgenic protein expression via Western blotting.
Main Results:
- Three of four transgenic mouse lines exhibited significant lens abnormalities, including cataracts and microphthalmia.
- Microphthalmic lenses showed reduced lens epithelial cells and signs of apoptosis in fiber cells.
- Differentiation-specific crystallin expression remained normal in affected lenses.
Conclusions:
- FGF receptor signaling is essential for maintaining normal lens cell populations and preventing apoptosis during development.
- Disruption of FGFR signaling leads to severe ocular developmental defects.