Within the mammalian retina, the AII amacrine cell is positioned to function during both rod- and cone-mediated vision within most of the parallel pathways that generate retinal output. Therefore, understanding the AII is a critical to comprehending signaling within the inner retina. This proposal comprises two specific aims that will generate insight into the regulation of synaptic input to AIIs and the mechanisms shaping AIIs'outputs both in the normal and in the degenerating retina.
Specific Aim 1 tests the hypothesis that RB - AII synapse serves a dual purpose in rod-mediated visual signaling: under conditions in which the RB pathway is the only means of conveying rod output, the synapse serves as an event detector;at light intensities sufficient to permit rod-mediated signals pass into the cone pathway via rod-cone gap junctions, the synapse serves as an indicator of mean luminance.
Specific Aim 2 tests the hypothesis that altered K channel function generates aberrant oscillatory activity in AIIs of the rd1 mouse retina, a model for the study of human retinitis pigmentosa (RP). Relevance to Public Health: Retinitis pigmentosa (RP), which affects approximately 1 in 4,000 - 5,000 individuals worldwide (and 100,000 patients in the US alone), refers to a collection of retinal diseases in which photoreceptors die (rods followed by cones). The rd1 mouse is an established model of human RP and exhibits aberrant patterned activity in its retinal output. Our preliminary work, which forms the foundation for the proposed work, demonstrates that this activity arises from cellular changes to AIIs specifically. Therefore, the results arising from the proposed studies will provide new information about how the inner retinal circuitry changes following photoreceptor degeneration and may provide insight into treatments that will prevent activity-dependent changes in the visual systems of patients awaiting treatment for blinding diseases.
The aims of this project address three explicit goals of the Retinal Diseases Program in the National Plan for Eye and Vision Research: 1) determining potential threaputic strategies for treatment of retinitis pigmentosa, 2) increasing understanding of post-photoreceptor adaptation (i.e., gain control in neural circuits), and 3) Increasing understanding of how retinal cellular interactions within neural networks generate signals that are interpretable as visual images. 1

Public Health Relevance

In the mammalian retina, signals arising from photoreceptors--rods and cones--are distributed to a series of parallel neural circuits that provide input to ganglion cells (GCs). There are multiple GC 'types' (~15-20);each type encodes a different aspect of the visual scene (e.g., luminance, motion, etc...). To understand how the visual world is encoded as a neural signal, then, the function of these retinal circuits must be understood. It has become evident that a single type of retinal neuron, the AII amacrine cell, participates in signaling through most of these parallel pathways. Therefore, understanding the AII is a critical to comprehending signaling within the retina. This proposal comprises two specific aims that will generate insight into the regulation of synaptic input to AIIs and the mechanisms shaping AIIs'outputs in both the normal and the degenerated retina. 1

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Biology and Diseases of the Posterior Eye Study Section (BDPE)
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Greenwell, Thomas
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University of Maryland College Park
Schools of Earth Sciences/Natur
College Park
United States
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Park, Silvia J H; Pottackal, Joseph; Ke, Jiang-Bin et al. (2018) Convergence and Divergence of CRH Amacrine Cells in Mouse Retinal Circuitry. J Neurosci 38:3753-3766
Graydon, Cole W; Lieberman, Evan E; Rho, Nao et al. (2018) Synaptic Transfer between Rod and Cone Pathways Mediated by AII Amacrine Cells in the Mouse Retina. Curr Biol 28:2739-2751.e3
Demb, Jonathan B; Singer, Joshua H (2016) Mind the Gap Junctions: The Importance of Electrical Synapses to Visual Processing. Neuron 90:207-9
Mortensen, Lena S; Park, Silvia J H; Ke, Jiang-Bin et al. (2016) Complexin 3 Increases the Fidelity of Signaling in a Retinal Circuit by Regulating Exocytosis at Ribbon Synapses. Cell Rep 15:2239-2250
Pallotto, Marta; Watkins, Paul V; Fubara, Boma et al. (2015) Extracellular space preservation aids the connectomic analysis of neural circuits. Elife 4:
Firl, Alana; Ke, Jiang-Bin; Zhang, Lei et al. (2015) Elucidating the role of AII amacrine cells in glutamatergic retinal waves. J Neurosci 35:1675-86
Demb, Jonathan B; Singer, Joshua H (2015) Functional Circuitry of the Retina. Annu Rev Vis Sci 1:263-289
Choi, Hannah; Zhang, Lei; Cembrowski, Mark S et al. (2014) Intrinsic bursting of AII amacrine cells underlies oscillations in the rd1 mouse retina. J Neurophysiol 112:1491-504
Margolis, David J; Gartland, Andrew J; Singer, Joshua H et al. (2014) Network oscillations drive correlated spiking of ON and OFF ganglion cells in the rd1 mouse model of retinal degeneration. PLoS One 9:e86253
Stafford, Benjamin K; Manookin, Michael B; Singer, Joshua H et al. (2014) NMDA and AMPA receptors contribute similarly to temporal processing in mammalian retinal ganglion cells. J Physiol 592:4877-89

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