Category Archives: Abstracts

Mitochondrial Transfer Between Inner Retinal Neurons

This abstract was presented today, April 26th at the 2023 Association for Research in Vision and Opthalmology (ARVO) meetings in New Orleans, Louisiana by Selena Wirthlin, Crystal Sigulinsky, James Anderson, and Bryan William Jones.

Full resolution version here.

Intercellular mitochondrial transfer has been reported across a variety of cells and tissues under both physiological and pathological conditions. Such transfer has shown broad therapeutic potential. The effectiveness of this therapy, however, is limited by a lack of understanding of the cellular and molecular mechanisms. Here, the ultrastructural features of mitochondrial transfer between inner retinal neurons discovered through retinal connectomics analysis is shown.

Retinal Connectome 2 (RC2) was built by automated transmission electron microscopy at ultrastructural (2nm/pixel) resolution. RC2 is a 0.25mm diameter volume of retina obtained from a 5-month-old female C57BL/6J mouse. The Viking application was used to visualize and annotate inter- and intracellular features of interest in the connectome.

Exploration of RC2 revealed material transfer between apposing neural processes within the OFF subliminal of the inner plexiform layer. The transferred material can be defined as a mitochondria, confirmed by the presence of crustae. At the transfer site, a short, electron-dense 140-nm diameter tube with a curved cap tightly associated with the inner mitochondrial membrane of one neuritis extends into a vacuole within the apposing neuritis formed by the plasma membranes of the two cells. Thin cytoskeletal components consistent with actin microfilaments extend into the mitochondrion. Morphology and synaptology of the acceptor cell confirm it is an Aii amacrine cell, while preliminary findings suggest the donor cell is a type of ON/OFF ganglion cell.

These findings demonstrate active mitochondrial transfer between different classes of endogenous inner retinal neurons and suggests it may represent an important component of tissue homeostasis in the retina. Features of this transfer differ from previously reported mitochondrial transfer between photoreceptors upon transplantation, which may indicate cell type- or context-dependent differences in the cellular or molecular mechanisms. Our findings demonstrate active mitochondrial transfer between different classes of endogenous inner retinal neurons and suggest it may represent an important component of tissue homeostasis in the retina. Features of this transfer differ from previous reports by the Wallace and Pearson groups of material transfer between photoreceptors upon transplantation through tunneling nanotubes (Ortin- Martinez et al., 2021; Kalargyrou et al., 2021), which may indicate cell type- or context-dependent differences in the cellular or molecular mechanisms. Understanding these mechanisms could serve as a catalyst for development of novel therapeutics for disease in the retina and beyond.

Müller Cell Connectomics In Health And Disease

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.

Species-Specific Connectivity In The Aii Connectome

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

Abstract: Biomedical research relies heavily on animal models to study human disease and develop therapeutics. Understanding the architectural diversity in neural networks between humans and these model species is essential for choosing a relevant study model and interpreting conflicting results. Using comparative connectomics, we sought to map and compare the local neural network architecture of rabbit and mouse retinal Aii amacrine cells. This specialized narrow-field, multistratified, glycinergic interneuron has critical feedforward and feedback roles in both the photopic and scotopic retinal networks spanning the ON and OFF pathways, making it an ideal candidate for investigating species-specific differences in retinal networks. High-resolution, serial-section transmission electron microscopy (TEM) volumes of rabbit (RC1: female, 13- month, Dutch Belted) and mouse (RC2: female, 5-month, C57BL/6J) retinal tissue provided spatially-registered synaptic maps of Aii connectivity at directly comparable resolution and completeness. These reveal that despite species-specific morphologies, gross synaptology and compartmentalization appear conserved. Yet, rabbit and mouse Aii cells diverge in the weighting of their partnerships, most notably in their coupling profiles. Opposing biases in gap junction partnerships and their respective sizing rules indicate a greater relative output by mouse Aii cells to ON pathways than in rabbit. However, a unique topological conformation for a subset of conventional presynapses formed by Aii cell lobular dendrites with species-specific features and prevalence may influence signal output to specific partner classes within the OFF pathway and either nullify or exacerbate this difference in ON/OFF output. Additionally, rabbit Aii cells in RC1 showed greater Aii-Aii coupling than in mouse, which may suggest greater signal-to-noise compensation. Lastly, preliminary data suggest mouse Aii cells receive greater excitatory, but not inhibitory input/feedback from the OFF pathway than in rabbit. Together these data indicate that precise neural circuit architectures diverge between species and require detailed, comprehensive mapping to begin to dissect potential influence on signal flow.

Structural Motifs Of Excitatory Synapses In The Mammalian Retina

This abstract was presented today, April 24th at the 2023 Association for Research in Vision and Opthalmology (ARVO) meetings in New Orleans, Louisiana by Taylor Otterness, Crystal Sigulinsky, James Anderson, and Bryan William Jones.

Full resolution version here.

Connectivity within the nervous system is precise and disruptions lead to degraded performance and disease, yet the rules that govern connectivity remain unknown. Recent efforts reveal that different types of cone bipolar cells in the neural retina show preferences in the selection and frequency of presynaptic structure types used for signal transmission. However, it is not yet known how these differences are related to the quantity or type of postsynaptic partner. We used Retinal Connectome 1 (RC1) to analyze the synaptic output of rabbit CBb6 cells, a type of ON cone bipolar cell that forms excitatory synapses via diverse presynaptic structure types, to identify patterns in how these cells interact with their postsynaptic partners.

RC1 is a 0.25 mm diameter volume sampled from mid-peripheral retina of a 13 month old female Dutch-Belted rabbit, serially sectioned at 70 nm, and imaged at ultrastructural resolution (2nm/px) using transmission electron microscopy. Postsynaptic partners of CBb6 cell 6156’s presynaptic structures were annotated using the Viking Viewer for Connectomics. Statistical analyses were conducted in Microsoft Excel and investigated further with 3D rendering and graph visualization of connectivity.

The factors tracked for comparison included presynaptic structure type, target number, and postsynaptic partner type. Multiribbon synapses of CBb6 cell 6156 trended towards having a greater number of output partners, with a greater proportion of dyads than monads. Despite this, triads and quadrads were only found opposing single ribbon synapses. As the different presynaptic structure types may differ in the strength of neurotransmitter release (ribbonless < single ribbon < multiribbon), these findings are inconsistent with scaling of output to the number of postsynaptic targets. Both amacrine cells (AC) and ganglion cells (GC) are postsynaptic partners of 6156. However, single ribbon and ribbonless structures appear biased towards AC only targets, while multiribbon synapses appear biased toward mixed AC and GC targets.

Target type relationships appear more important than the number of targets in determining presynaptic structure type in CBb6. Future efforts will examine size differences of postsynaptic structures and presynaptic ribbon size, and even compare across bipolar cell classes, in order to provide further insight on the connectivity rules underlying excitatory synapses.

Dynein Dysregulation Due to the Absence of NUDC leads to Mitochondrial Mislocalization and Dysfunction in Rod Photoreceptors

This abstract was presented today, May 4th at the 2022  Association for Research in Vision and Opthalmology (ARVO) meetings in Denver, Colorado by Hailey Levi @drpepperis100, Meredith Hubbard, Mary Anne Garner, TJ Hollingsworth, Ke Jiang, Nat Nelson, Anushree Gade, Drue Benefield, Guoxin Ying, Wolfgang Baehr, Bryan Jones@BWJones, Anand Swaroop, Glenn Rowe, and Alecia Gross @alecia144g.

Proteomic changes in the lens of a congenital cataract mouse model lead to reduced levels of glutathione and taurine

This abstract was presented today, May 4th at the 2022  Association for Research in Vision and Opthalmology (ARVO) meetings in Denver, Colorado by Sheldon Rowan @SheldonRowan, Eloy Bejarano, Elizabeth Whitcomb, Rebecca Pfeiffer @BeccaPfeiffer19, Kristie Rose, Kevin Schey, Bryan Jones @BWJones, Allen Taylor.

Purpose: Congenital cataracts develop through multiple mechanisms, but often lead to common endpoints, including protein aggregation, impaired fiber cell differentiation, and absence of fiber cell denucleation. It is now apparent that other metabolic abnormalities associate with cataractogenesis, including reductions in levels of amino acids, glutathione, and taurine. Here, we analyze the proteome and metabolome of mice expressing a mutant ubiquitin protein (K6W-Ub) to determine the molecular mechanisms underlying formation of its congenital cataract.

Methods: C57BL/6J wild-type or cataractous K6W-Ub transgenic mouse lenses were dissected at E15.5, P1, or P30 and proteins were analyzed via MS-based tandem-mass-tag (TMT) quantitative proteomics. Small molecules were spatially quantified using computational molecular phenotyping (CMP), a tool that enables acquisition of free amino acid fingerprints for every cell in the lens. Validation of proteomics findings was also performed using Western blot analysis and immunohistochemistry.

Results: Proteomic analyses revealed pathways that were altered during lens differentiation, by expression of K6W-Ub, or both. Prominent pathways included glutathione metabolism; glycolysis/gluconeogenesis; and glycine, serine, and threonine metabolism. Within the glutathione metabolism pathway, GSTP1 and GGCT were most strongly downregulated by K6W-Ub. Other consistently downregulated proteins were PGAM2, GAMT, and HMOX1. Proteins that were upregulated by K6W-Ub expression belonged to pathways related to lysosome, autophagy, Alzheimer’s disease, and glycolysis/gluconeogenesis. Analysis of the metabolome via CMP revealed statistically significant decreases in taurine and glutathione and smaller decreases in glutamate, glutamine, aspartate, and valine in all ages of K6W-Ub lenses. Lens metabolites were spatially altered in the cataractous K6W-Ub lens.

Conclusions: K6W-Ub expressing lenses replicate many congenital cataract phenotypes and are useful disease models. The large reductions in levels of taurine and glutathione may be general signatures of cataract development, as human cataracts also have reduced glutathione and taurine. Key roles for amino acid metabolism and glycolysis/gluconeogenesis in cataractogenesis are emerging. Together our data point toward potential common metabolic/proteomic signatures of cataracts.

ARVO Mini-Symposium: Pathoconnectomics in Retinal Degeneration

Lab PI, Bryan Jones delivered a talk at the ARVO 2022 mini-symposium on Pathoconnectomics in Retinal Degeneration.

Abstract: Connectomics has demonstrated that synaptic networks and their topologies are precise and directly correlate with physiology and behavior. The next extension of connectomics is pathoconnectomics: to map neural network synaptology and circuit topologies corrupted by neurological disease in order to identify robust targets for therapeutics. The retina is ideal for pathoconnectomics approaches, and reveals common rules of how neural systems are wired, and how they break in neurodegenerative disease.

Coupling architecture of the retinal Aii/ON cone bipolar cell network and alteration in degeneration

This poster was presented today, July 28th at the 2019 International Gap Junction Conference in Victoria, Canada by Crystal L. Sigulinsky, Rebecca L. PfeifferJames R. Anderson, Christopher Rapp, Jeebika Dahal, Jessica C Garcia, Jia-Hui Yang, Daniel P. Emrich, Hope Morrison, Kevin D. Rapp, Carl B. Watt, Mineo Kondo, Hiroko Terasaki, Robert E. Marc and Bryan W. Jones.

Almost full resolution version here.


Crystal L Sigulinsky1, Rebecca L Pfeiffer1, James R. Anderson1, Christopher N. Rapp1, Jeebika Dahal1, Jessica C Garcia1, Jia-Hui Yang1, Daniel P. Emrich1, Hope Morrison1, Kevin D. Rapp1, Carl B. Watt1, Mineo Kondo2, Hiroko Terasaki3, Robert E. Marc1, Bryan W. Jones1
1Moran Eye Center/ Ophthalmology, University of Utah, Salt Lake City, Utah, United States; 2Mie University, Tsu, Japan; 3Nagoya University, Nagoya-shi, Japan;


Background and aim:
Gap junctions are prevalent throughout the neural retina, with expression by every major neuronal class and at every level of signal processing. Yet, the functional roles and expressing cells/participating networks for many remain unknown. Spontaneous network spontaneous hyperactivity observed during retinal degeneration contributes to visual impairment and requires gap junctional coupling in the Aii amacrine cell/ON cone bipolar cell (CBC) network.  However, it remains unclear whether this hyperactivity reflects changes in the underlying circuitry or dysfunction of the normative circuitry. Here, we used connectomics-based mapping of retinal circuitry to 1) define the coupling architecture of the Aii/ON CBC network in healthy adult rabbit retina using connectome RC1 and 2) evaluate changes in coupling motifs in RPC1, a pathoconnectome from a rabbit retinal degeneration model.


RC1 and RPC1 are connectomes built by automated transmission electron microscopy at ultrastructural (2 nm/pixel) resolution. RC1 is a 0.25 mm diameter volume of retina from a 13-month old, light adapted female Dutch Belted rabbit. RPC1 is a 0.07 mm diameter volume of degenerate retina from a transgenic P347L model of autosomal dominant retinitis pigmentosa (10-months old, male, New Zealand White background) presenting with ~50% rod loss. ON CBCs, Aii amacrine cells, and their coupling partners were annotated using the Viking application. Coupling motifs and features were explored with 3D rendering and network graph visualization. Gap junctions were validated by 0.25 nm resolution recapture with goniometric tilt when necessary.


Complete reconstruction of 37 ON CBCs in RC1 yielded 1339 gap junctions and revealed pervasive in- and cross-class coupling motifs among ON CBCs that produce complex network topologies within the coupled Aii network. Robust rulesets underlie class-specific coupling profiles with specificity defined beyond geometric opportunity. These coupling profiles enabled classification of all 145 ON CBCs contained within RC1 into 7 distinct classes. In RPC1, two ON CBC classes appear to retain their class-specific coupling profiles, accepting and rejecting specific combinations of Aii and ON CBC class partnerships. However, aberrant partnerships exist, including both loss of motifs and acquisition of novel ones.


Gap junctions formed by ON CBCs are prominent network components, with specificity rivaling that of chemical synapses. These gap junctions not only subserve canonical signal transfer for night vision, but also extensive coupling within and across the parallel processing streams. Clearly aberrant morphological and synaptic changes exist in RPC1, including changes in the coupling specificity of both Aii and ON CBCs. Thus, circuit topology is altered prior to complete loss of rods, with substantial implications for therapeutic interventions for blinding diseases that depend upon the surviving retinal network.