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Tian Wang, Greg Field, Francis Concepcion, Jeannie Chen; The potential for restoration of retinal structure and function following neural remodeling. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1714.
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© ARVO (1962-2015); The Authors (2016-present)
Most blinding disorders in humans are initiated by death of photoreceptor cells. This is followed by retinal remodeling that includes neuronal death, cell migration and rewiring of retinal circuits. How these processes impact therapeutic efforts to restore vision is unclear. To address this issue, we have generated a cyclic-nucleotide gated channel knockout (CNGB1-/-) mouse line that is capable of gene reactivation upon Cre-mediated recombination. CNGB1-/- mice display a slow rate of retinal degeneration and the stereotypic activation of neural remodeling markers during the retinal degeneration process. By inducing CNGB1 protein expression at different degeneration stages, we studied the potential of morphologic and functional recovery after neural remodeling.
The insertion of the LoxP-flanked neomycin cassette by homologous recombination precludes endogenous CNGB1 gene expression and leads to a slow rate of retinal degeneration. The CNGB1-/- mice were bred with CAG-Cre/Esr1* (Jackson lab #004682). The Cre/Esr1* fusion protein can be activated at different ages by tamoxifen (TM) administration to remove the neomycin cassette and restore the expression of CNGB1ΔCaM protein. Phototransduction protein levels were examined by western blots after TM administration. Retinal structures were investigated by light microscopy as well as immunocytochemistry. Functional recovery will be monitored by the electroretinogram and multielectrode array recordings from retinal ganglion cells.
After TM administration on one-month-old CAG-Cre/Esr1*+/CNGB1-/- mice, CNGB1ΔCaM protein expression was restored to similar level as wildtype CNGB1 protein, as were other phototransduction proteins, and photoreceptor cell death was halted. However, Müller cell activation and decrease of the ribbon synaptic markers persists long after CNGB1 gene activation.
Cre-mediated CNGB1ΔCaM expression from the endogenous locus restored expression of other phototransduction proteins and halted photoreceptor cell death. These rescue effects can also be achieved in later stages of retinal degeneration. However, retinal remodeling persists after rescue. The functional consequences of the persistence of retinal remodeling will be investigated.
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