Category Archives: Retinal Disease

Inner-Retinal Changes In AMD: Evidence, Mechanisms, and Future Perspectives

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We have a new manuscript out in Progress in Retinal Eye Research, Inner-retinal changes in AMD: Evidence, mechanisms, and future perspectives.

Authors: Matt Trinh , Michael Kalloniatis , Bryan William Jones @bwjones.bsky.social, Glenn C Yiu, Enrico Borrelli, Lisa Nivison-Smith.

Abstract: Age-related macular degeneration (AMD) has traditionally been regarded as a disorder of the outer-retina and choroid, characterised by drusen accumulation, retinal pigment epithelium (RPE) dysfunction, and photoreceptor degeneration. However, increasing evidence of inner-retinal involvement across the AMD spectrum, with structural and functional compromise evident from the early stages of disease, challenges this paradigm. Advances in spatially optimised optical coherence tomography (OCT), OCT angiography (OCTA), and high-resolution histology have revealed neuronal, vascular, and glial alterations within the inner-retina that reshape our understanding of AMD pathogenesis. This review synthesises clinical and experimental evidence on inner-retinal changes in AMD, including layer-specific thinning, microvascular rarefaction, impaired neurovascular coupling, and reactive gliosis. Such changes frequently emerge in early AMD, may precede, parallel, or exacerbate outer-retinal degeneration, and are associated with visual dysfunction not fully explained by photoreceptor loss alone. Importantly, mechanistic interactions between inner- and outer-retinal pathology support a bidirectional model of neurodegeneration, wherein region-specific vulnerability is shaped by perfusion dynamics, metabolic demands, and structural connectivity throughout the retina. Recognition of these processes expands the potential for earlier diagnosis, refined monitoring, and novel therapeutic targeting. By integrating structural, functional, and systemic insights, this review reframes AMD as a multi-layer neurovascular disease and underscores the central role of inner-retinal integrity in future AMD research and management.

Single-Cell Profiling of Trabecular Meshwork Identifies Mitochondrial Dysfunction In a Glaucoma Model That Is Protected By Vitamin B3 Treatment

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We have a new collaborative paper out in eLife: Single-Cell Profiling of Trabecular Meshwork Identifies Mitochondrial Dysfunction In a Glaucoma Model That Is Protected By Vitamin B3 Treatment.

Authors: Nicholas Tolman, Taibo Li, Revathi Balasubramanian, Guorong Li, Rebecca L. Pfeiffer@beccapfeiffer.bsky.social, Violet Bupp-Chickering, Ruth A Kelly, Marina Simón, John Peregrin, Christa Montgomery, Bryan Jones @bwjones.bsky.social, W Daniel Stamer, Jiang Qian, Simon WM John

Abstract: Since the trabecular meshwork (TM) is central to intraocular pressure (IOP) regulation and glaucoma, a deeper understanding of its genomic landscape is needed. We present a multi-modal, single-­ cell resolution analysis of mouse limbal cells (includes TM). In total, we sequenced 9,394 wild-­ type TM cell transcriptomes. We discovered three TM cell subtypes with characteristic signature genes validated by immunofluorescence on tissue sections and whole-­ mounts. The subtypes are robust, being detected in datasets for two diverse mouse strains and in independent data from two institutions. Results show compartmentalized enrichment of critical pathways in specific TM cell subtypes. Distinctive signatures include increased expression of genes responsible for (1) extracellular matrix structure and metabolism (TM1 subtype), (2) secreted ligand signaling to support Schlemm’s canal cells (TM2), and (3) contractile and mitochondrial/metabolic activity (TM3). ATAC-­ sequencing data identified active transcription factors in TM cells, including LMX1B. Mutations in LMX1B cause high IOP and glaucoma. LMX1B is emerging as a key transcription factor for normal mitochondrial function, and its expression is much higher in TM3 cells than other limbal cells. To understand the role of LMX1B in TM function and glaucoma, we single-­ cell sequenced limbal cells from Lmx1bV265D/+mutant mice (2491 TM cells). In Lmx1bV265D/+ mice, TM3 cells were uniquely affected by pronounced mitochondrial pathway changes. Mitochondria in TM cells of Lmx1bV265D/+ mice are swollen with a reduced cristae area, further supporting a role for mitochondrial dysfunction in the initiation of IOP elevation in these mice. Importantly, treatment with vitamin B3 (nicotinamide), which enhances mitochondrial function and metabolic resilience in other contexts, significantly protected Lmx1b mutant mice from IOP elevation.

Retinal Connectomics: A Review

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We have a new manuscript out of the lab in Volume 10 of the Annual Review of Vision Science titled Retinal Connectomics: A Review by Crystal L. Sigulinsky, Rebecca L. Pfeiffer, and Bryan William Jones. A .pdf is here.

Abstract
The retina is an ideal model for understanding the fundamental rules for
how neural networks are constructed. The compact neural networks of
the retina perform all of the initial processing of visual information be-
fore transmission to higher visual centers in the brain. The field of retinal
connectomics uses high-resolution electron microscopy datasets to map
the intricate organization of these networks and further our understand-
ing of how these computations are performed by revealing the fundamental
topologies and allowable networks behind retinal computations. In this ar-
ticle, we review some of the notable advances that retinal connectomics
has provided in our understanding of the specific cells and the organi-
zation of their connectivities within the retina, as well as how these are
shaped in development and break down in disease. Using these anatomi-
cal maps to inform modeling has been, and will continue to be, instrumental
in understanding how the retina processes visual signals.

NUDC Is Critical For Rod Photoreceptor Function, Maintenance, And Survival

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We have a new manuscript in collaboration with the Gross Lab out of UAB in The FASEB Journal, (PubMed link here): NUDC is critical for rod photoreceptor function, maintenance, and survival. This manuscript is in collaboration with.  Authors are: Mary Anne Garner, Meredith G. Hubbard, Evan R. Boitet, Seth T. Hubbard, Anushree Gade, Guoxin Ying, Bryan W. Jones, Wolfgang Baehr, Alecia K. Gross. The PDF is here.

Abstract: NUDC (nuclear distribution protein C) is a mitotic protein involved in nuclear migration and cytokinesis across species. Considered a cytoplasmic dynein (henceforth dynein) cofactor, NUDC was shown to associate with the dynein motor complex during neuronal migration. NUDC is also expressed in postmitotic vertebrate rod photoreceptors where its function is unknown. Here, we examined the role of NUDC in postmitotic rod photoreceptors by studying the consequences of a conditional NUDC knockout in mouse rods (rNudC−/−). Loss of NUDC in rods led to complete photoreceptor cell death at 6 weeks of age. By 3 weeks of age, rNudC−/− function was diminished, and rhodopsin and mitochondria were mislocalized, consistent with dynein inhibition. Levels of outer segment proteins were reduced, but LIS1 (lissencephaly protein 1), a well-characterized dynein cofactor, was unaffected. Transmission electron microscopy revealed ultrastructural defects within the rods of rNudC−/− by 3 weeks of age. We investigated whether NUDC interacts with the actin modulator cofilin 1 (CFL1) and found that in rods, CFL1 is localized in close proximity to NUDC. In addition to its potential role in dynein trafficking within rods, loss of NUDC also resulted in increased levels of phosphorylated CFL1 (pCFL1), which would purportedly prevent depolymerization of actin. The absence of NUDC also induced an inflammatory response in Müller glia and microglia across the neural retina by 3 weeks of age. Taken together, our data illustrate the critical role of NUDC in actin cytoskeletal maintenance and dynein-mediated protein trafficking in a postmitotic rod photoreceptor.

Modeling Complex Age-Related Eye Disease

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We have a new Progress in Retinal and Eye Research manuscript out in collaboration with my colleagues here at the Moran Eye Center.

Authors: Silke Becker, Zia L’Ecuyer, Bryan W Jones, Moussa A Zouache, Fiona S McDonnell, Frans Vinberg.

Abstract: Modeling complex eye diseases like age-related macular degeneration (AMD) and glaucoma poses significant challenges, since these conditions depend highly on age-related changes that occur over several decades, with many contributing factors remaining unknown. Although both diseases exhibit a relatively high heritability of >50%, a large proportion of individuals carrying AMD- or glaucoma-associated genetic risk variants will never develop these diseases. Furthermore, several environmental and lifestyle factors contribute to and modulate the pathogenesis and progression of AMD and glaucoma.

Several strategies replicate the impact of genetic risk variants, pathobiological pathways and environmental and lifestyle factors in AMD and glaucoma in mice and other species. In this review we will mostly discuss the most commonly available mouse models, which have and will likely continue to improve our understanding of the pathobiology of age-related eye diseases. Uncertainties persist whether small animal models can truly recapitulate disease progression and vision loss in patients, raising doubts regarding their usefulness when testing novel gene or drug therapies. We will elaborate on concerns that relate to shorter lifespan, body size and allometries, lack of macula and a true lamina cribrosa, as well as absence and sequence disparities of certain genes and differences in their chromosomal location in mice.

Since biological, rather than chronological, age likely predisposes an organism for both glaucoma and AMD, more rapidly aging organisms like small rodents may open up possibilities that will make research of these diseases more timely and financially feasible. On the other hand, due to the above-mentioned anatomical and physiological features, as well as pharmacokinetic and -dynamic differences small animal models are not ideal to study the natural progression of vision loss or the efficacy and safety of novel therapies. In this context, we will also discuss the advantages and pitfalls of alternative models that include larger species, such as non-human primates and rabbits, patient-derived retinal organoids, and human organ donor eyes.

Preprint: Neural Circuit Revision in Retinal Remodeling, A Pathoconnectomics Approach

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We have a new preprint out, Neural Circuit Revision in Retinal Remodeling, A Pathoconnectomics Approach.

Authors: Rebecca L Pfeiffer, Jeebika Dahal, Crystal L Sigulinsky, James R Anderson, Isabel A Barrera, Jia-Hui Yang, Olivia Haddadin, Alexis R Houser, Jessica C Garcia, Bryan William Jones

Abstract: The Aii glycinergic amacrine cell (Aii) plays a central role in bridging rod pathways with cone pathways, enabling an increased dynamic range of vision from scotopic to photopic ranges. The Aii integrates scotopic signals via chemical synapses from rod bipolar cells (RodBCs) onto the arboreal processes of Aii ACs, injecting signals into ON-cone bipolar cells (CBbs) via gap junctions with Aiis on the arboreal processes and the waist of the Aii ACs. The CBbs then carry this information to ON and OFF ganglion cell classes. In addition, the Aii is involved in the surround inhibition of OFF cone bipolar cells (CBas) through glycinergic chemical synapses from Aii ACs onto CBas. We have previously shown changes in RodBC connectivity as a consequence of rod photoreceptor degeneration in a pathoconnectome of early retinal degeneration: RPC1. Here, we evaluated the impact of rod photoreceptor degeneration on the connectivity of the Aii to determine the impacts of photoreceptor degeneration on the downstream network of the neural retina and its suitability for integrating therapeutic interventions as rod photoreceptors are lost. Previously, we reported that in early retinal degeneration, prior to photoreceptor cell loss, Rod BCs make pathological gap junctions with Aiis. Here, we further characterize this altered connectivity and additional shifts in both the excitatory drive and gap junctional coupling of Aiis in retinal degeneration, along with discussion of the broader impact of altered connectivity networks. New findings reported here demonstrate that Aiis make additional gap junctions with CBas increasing the number of BC classes that make pathological gap junctional connectivity with Aiis in degenerating retina. In this study, we also report that the Aii, a tertiary retinal neuron alters their synaptic contacts early in photoreceptor degeneration, indicating that rewiring occurs in more distant members of the retinal network earlier in degeneration than was previously predicted. This rewiring impacts retinal processing, presumably acuity, and ultimately its ability to support therapeutics designed to restore image-forming vision. Finally, these Aii alterations may be the cellular network level finding that explains one of the first clinical complaints from human patients with retinal degenerative disease, an inability to adapt back and forth from photopic to scotopic conditions.

UCI Center For Translational Vision Research Talk on Retinal Connectomics and Pathoconnectomics

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Metabolic changes and retinal remodeling in Heterozygous CRX mutant cats (CRXRDY/+)

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We have a new manuscript from the lab in Experimental Eye Research, (PubMed link here). Metabolic changes and retinal remodeling in Heterozygous CRX mutant cats (CRXRDY/+). This manuscript is in collaboration with the Simon Petersen-Jones lab out of Michigan State University.  Authors are: Laurence M. Occelli, Bryan W. Jones @BWJones, Taylor J. Cervantes, and Simon M. Petersen-Jones. The PDF is here.

Abstract: CRX is a transcription factor essential for normal photoreceptor development and survival. The CRXRdy cat has a naturally occurring truncating mutation in CRX and is a large animal model for dominant Leber congenital amaurosis. This study investigated retinal remodeling that occurs as photoreceptors degenerate. CRXRdy/+ cats from 6 weeks to 10 years of age were investigated. In vivo structural changes of retinas were analyzed by fundus examination, confocal scanning laser ophthalmoscopy and spectral domain optical coherence tomography. Histologic analyses including immunohistochemistry for computational molecular phenotyping with macromolecules and small molecules. Affected cats had a cone-led photoreceptor degeneration starting in the area centralis. Initially there was preservation of inner retinal cells such as bipolar, amacrine and horizontal cells but with time migration of the deafferented neurons occurred. Early in the process of degeneration glial activation occurs ultimately resulting in formation of a glial seal. With progression the macula-equivalent area centralis developed severe atrophy including loss of retinal pigmentary epithelium. Microneuroma formation occurs in advanced stages as more marked retinal remodeling occurred. This study indicates that retinal degeneration in the CrxRdy/+ cat retina follows the progressive, phased revision of retina that have been previously described for retinal remodeling. These findings suggest that therapy dependent on targeting inner retinal cells may be useful in young adults with preserved inner retinas prior to advanced stages of retinal remodeling and neuronal cell loss.

Impact of Retinal Degeneration on Response of ON and OFF Cone Bipolar Cells to Electrical Stimulation

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We have a new manuscript from the lab in IEEE, Impact of Retinal Degeneration on Response of ON and OFF Cone Bipolar Cells to Electrical Stimulation. This manuscript is in collaboration with the Lazzi lab out of USC.  The first author, Shayan Farzad, Pragya Kosta, Ege Iseri, Steven T Walston, Jean-Marie C. Bouteiller,  Rebecca L. Pfeiffer @BeccaPfeiffer19, Crystal L. Sigulinsky @CSigulinsky, Jia-Hui Yang, Jessica C. Garcia, James R. Anderson, Bryan W. Jones @BWJones, and Gianluca Lazzi. The PDF is here.

Abstract: In retinal degenerative diseases, such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD), the photoreceptors become stressed and start to degenerate in the early stages of the disease. Retinal prosthetic devices have been developed to restore vision in patients by applying electrical stimulation to the surviving retinal cells. However, these devices provide limited visual perception as the therapeutic interventions are generally considered in the later stages of the disease when only inner retinal layer cells are left. A potential treatment option for retinal degenerative diseases in the early stages can be stimulating bipolar cells, which receive presynaptic signals from photoreceptors. In this work, we constructed computational models of healthy and degenerated (both ON and OFF-type) cone bipolar cells (CBCs) with realistic morphologies extracted from connectomes of the healthy and early-stage degenerated rabbit retina. We examined these cells’ membrane potential and axon terminal calcium current differences when subjected to electrical stimulation. In addition, we investigated how differently healthy and degenerated cells behave with respect to various stimulation parameters, including pulse duration and cells’ distance from the stimulating electrode. The results suggested that regardless of the position of the OFF CBCs in the retina model, there is not a significant difference between the membrane potential of healthy and degenerate cells when electrically stimulated. However, the healthy ON CBC axon terminal membrane potential rising time-constant is shorter (0.29 ± 0.03 ms) than the degenerated cells (0.8 ± 0.07 ms). Moreover, the ionic calcium channels at the axon terminals of the cells have a higher concentration and higher current in degenerated cells (32.24 ± 6.12 pA) than the healthy cells (13.64 ± 2.88 pA) independently of the cell’s position.

Müller Cell Connectomics In Health And Disease

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This talk was presented today, April 25th at the 2023 Association for Research in Vision and Opthalmology (ARVO) meetings in New Orleans, Louisiana by Rebecca Pfeiffer as part of an ARVO Minisymposium Bryan William Jones organized.

Abstract: Muller cells are a critical component of retinal function and rapidly change metabolically and morphologically in retinal disease. Of Muller cell functions, many require close physical relationships between the Muller cell and the synapses of the neurons they support. Despite this required neuro-glial relationship, little is known about the direct contacts between Muller cells and synapses in healthy or diseased retinas. In order to address this, I use a connectomics/pathoconnectomics approach to reconstruct Muller cells and their neighboring synapses. The retinas evaluated are from a healthy rabbit, retinal connectome 1 (RC1), and from the P347L rabbit model of retinitis pigmentosa, retinal pathoconnectome 1 (RPC1). Preliminary data demonstrate an increase in endfoot entanglement in RPC1 when compared with RC1, and direct synaptic contact analysis of both connectomes is ongoing.