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Published on: December 22, 2014
Robust cone-mediated signaling persists late into rod photoreceptor degeneration
Miranda L Scalabrino1, Mishek Thapa1, Lindsey A Chew1
1Department of Neurobiology, Duke University School of Medicine, Durham, United States.
Abstract:
Rod photoreceptor degeneration causes deterioration in the morphology and physiology of cone photoreceptors along with changes in retinal circuits. These changes could diminish visual signaling at cone-mediated light levels, thereby limiting the efficacy of treatments such as gene therapy for rescuing normal, cone-mediated vision. However, the impact of progressive rod death on cone-mediated signaling remains unclear. To investigate the fidelity of retinal ganglion cell (RGC) signaling throughout disease progression, we used a mouse model of rod degeneration (Cngb1). Despite clear deterioration of cone morphology with rod death, cone-mediated signaling among RGCs remained surprisingly robust: spatiotemporal receptive fields changed little and the mutual information between stimuli and spiking responses was relatively constant. This relative stability held until nearly all rods had died and cones had completely lost well-formed outer segments. Interestingly, RGC information rates were higher and more stable for natural movies than checkerboard noise as degeneration progressed. The main change in RGC responses with photoreceptor degeneration was a decrease in response gain. These results suggest that gene therapies for rod degenerative diseases are likely to prolong cone-mediated vision even if there are changes to cone morphology and density.
Insights
Rod photoreceptor degeneration surprisingly preserves cone-mediated vision signaling in retinal ganglion cells. This suggests gene therapies may effectively restore vision even with retinal structure changes.
Area of Science:
- Neuroscience
- Ophthalmology
- Genetics
Background:
- Rod photoreceptor degeneration impacts cone photoreceptors and retinal circuits.
- This can limit visual signaling and the effectiveness of gene therapies for vision restoration.
- The effect of progressive rod loss on cone-mediated signaling is not well understood.
Purpose of the Study:
- To investigate the fidelity of retinal ganglion cell (RGC) signaling during progressive rod degeneration.
- To determine how cone-mediated signaling is affected by the loss of rod photoreceptors.
Main Methods:
- Utilized a mouse model of rod degeneration (Cngb1).
- Recorded retinal ganglion cell (RGC) responses to visual stimuli.
- Analyzed spatiotemporal receptive fields and mutual information.
Main Results:
- Cone-mediated signaling in RGCs remained robust despite cone morphology deterioration.
- Spatiotemporal receptive fields and information transmission were relatively stable until late stages of degeneration.
- RGCs showed higher and more stable information rates for natural movies compared to checkerboard stimuli.
- A decrease in response gain was the primary change in RGC responses.
Conclusions:
- Cone-mediated visual signaling is surprisingly resilient to rod degeneration.
- Gene therapies for rod degenerative diseases may successfully restore cone-mediated vision.
- Retinal ganglion cell function is maintained longer than expected during photoreceptor loss.
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