Biology subjects

Ganzen, L.

Publications and source records attributed to Ganzen, L..

4 recordsLinked to original sources

bioRxiv2026

Zebrafish Functional Screening of FDA-Approved Drugs for Autosomal Dominant Retinitis Pigmentosa Caused by RHODOPSIN Q344X Mutation

Retinitis Pigmentosa (RP) is a group of inherited retinal degenerations for which most subtypes lack effective drug treatments. This challenge is particularly critical for autosomal dominant (ad) RP, which is often unsuitable for gene replacement therapy. To address this challenge, we screened an FDA-approved compound library using a zebrafish adRP model expressing a human RHODOPSIN transgene with the Q344X mutation. The screen evaluated drug effects on larval visual behavior by assessing the visual-motor response (VMR). Four compounds significantly improved VMR in Q344X zebrafish: amitriptyline, difluprednate, maprotiline, and prednisolone. Further characterization revealed that these hits act through distinct mechanisms, including reducing rod death, promoting rod neogenesis, and enhancing the function of extraocular photoreceptors. Together, these findings demonstrate the potential to repurpose these drugs for adRP caused by the RHO Q344X mutation, providing preclinical candidates and revealing potential targets for future drug development.

neuroscience↗

bioRxiv2024

Retinal bipolar cells borrow excitability from electrically coupled inhibitory interneurons to amplify excitatory synaptic transmission

Bipolar cells (BCs) carry visual information from photoreceptors in the outer retina to retinal ganglion cells (RGCs) in the inner retina. Most BCs lack voltage-gated Na+ (NaV) channels and action potentials. Instead, voltage signals spread passively from input to output synapses. Despite this, we find that blocking NaV channels reduces synaptic output of On-cone bipolar cells (On-CBCs). These cells borrow NaV channel-mediated excitability from electrically coupled A2 amacrine cells to amplify excitatory output, allowing voltage changes to be transmitted more effectively to downstream RGCs in dim light. Because neighboring On-CBCs form electrical synapses onto the same A2 cell, a spatially adjacent group of On-CBCs is more effective than a dispersed set for recruiting A2 cell electrical excitability and driving post-synaptic RGCs. This mechanism filters the neural representation of an image to highlight shapes over spatially uncorrelated stimuli, a sophisticated feature detection property that is well-suited for object recognition.

neuroscience↗

bioRxiv2023

Retinoic acid-dependent loss of synaptic output from bipolar cells impairs visual information processing in inherited retinal degeneration.

In retinitis pigmentosa (RP), rod and cone photoreceptors degenerate, depriving downstream neurons of light-sensitive input, leading to vision impairment or blindness. Although downstream neurons survive, some undergo morphological and physiological remodeling. Bipolar cells (BCs) link photoreceptors, which sense light, to retinal ganglion cells (RGCs), which send information to the brain. While photoreceptor loss disrupts input synapses to BCs, whether BC output synapses remodel has remained unknown. Here we report that synaptic output from BCs plummets in RP mouse models of both sexes owing to loss of voltage-gated Ca2+ channels. Remodeling reduces the reliability of synaptic output to repeated optogenetic stimuli, causing RGC firing to fail at high stimulus frequencies. Fortunately, functional remodeling of BCs can be reversed by inhibiting the retinoic acid receptor (RAR). RAR inhibitors targeted to BCs present a new therapeutic opportunity for mitigating detrimental effects of remodeling on signals initiated either by surviving photoreceptors or by vision-restoring tools. Significance StatementPhotoreceptor degenerative disorders such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD) lead to vision impairment or blindness. Vision mediated by surviving photoreceptors or artificial vision restoration technologies, rely on bipolar cells retaining normal function despite photoreceptor death. We find that in two animal models of RP, synaptic transmission from both rod and cone bipolar cells is severely impaired owing to diminished voltage-gated calcium current, preventing postsynaptic amacrine cells and retinal ganglion cells from properly receiving and encoding visual information. We find that an inhibitor of the retinoic acid receptor restores both the calcium current and synaptic release from bipolar cells. These discoveries about bipolar cells reveal a new functional deficit in blindness and a potential therapeutically important solution.

neuroscience↗

bioRxiv2020

Drug Screening with Zebrafish Visual Behavior Identifies Carvedilol as a Potential Treatment for Retinitis Pigmentosa

Retinitis Pigmentosa (RP) is an incurable inherited retinal degeneration affecting approximately 1 in 4,000 individuals globally. The goal of this work was to identify drugs that can help patients suffering from the disease. To accomplish this, we screened drugs on a zebrafish RP model. This model expresses a truncated human rhodopsin transgene (Tg(rho:Hsa.RH1_Q344X)) causing significant rod degeneration by 7 days post-fertilization (dpf). Consequently, the larvae displayed a deficit in visual motor response (VMR) under scotopic condition. The diminished VMR was leveraged to screen an ENZO SCREEN-WELL(R) REDOX library since oxidative stress is postulated to play a role in RP progression. Our screening identified a beta-blocker, carvedilol, that ameliorated the deficient VMR of the RP larvae and increased their rod number. Carvedilol can act directly on rods as it affected the adrenergic pathway in a rod-like human Y79 cell line. Since carvedilol is an FDA-approved drug, our findings suggest that carvedilol can potentially be repurposed to treat RP patients. Summary StatementThis paper presents the utilization of zebrafish visual behavior, a novel paradigm to screen and identify drugs to treat retinitis pigmentosa, an incurable retinal-degenerative disease.

neuroscience↗