Primary Rod Research Articles

Retinal Proteome Profiling of Inherited Retinal Degeneration Across Three Different Mouse Models Suggests Common Drug Targets in Retinitis Pigmentosa

Inherited retinal degenerations (IRDs) are a leading cause of blindness among the population of young people in the developed world. Approximately half of IRDs initially manifest as gradual loss of night vision and visual fields, characteristic of retinitis pigmentosa (RP). Due to challenges in genetic testing, and the large heterogeneity of mutations underlying RP, targeted gene therapies are an impractical largescale solution in the foreseeable future. For this reason, identifying key pathophysiological pathways in IRDs that could be targets for mutation-agnostic and disease-modifying therapies (DMTs) is warranted. In this study, we investigated the retinal proteome of three distinct IRD mouse models, in comparison to sex- and age-matched wild-type mice. Specifically, we used the Pde6βRd10 (rd10) and RhoP23H/WT (P23H) mouse models of autosomal recessive and autosomal dominant RP, respectively, as well as the Rpe65-/- mouse model of Leber's congenital amaurosis type 2 (LCA2). The mice were housed at two distinct institutions and analyzed using LC-MS in three separate facilities/instruments following data-dependent and data-independent acquisition modes. This cross-institutional and multi-methodological approach signifies the reliability and reproducibility of the results. The large-scale profiling of the retinal proteome, coupled with invivo electroretinography recordings, provided us with a reliable basis for comparing the disease phenotypes and severity. Despite evident inflammation, cellular stress, and downscaled phototransduction observed consistently across all three models, the underlying pathologies of RP and LCA2 displayed many differences, sharing only four general KEGG pathways. The opposite is true for the two RP models in which we identify remarkable convergence in proteomic phenotype even though the mechanism of primary rod death in rd10 and P23H mice is different. Our data highlights the cAMP and cGMP second-messenger signaling pathways as potential targets for therapeutic intervention. The proteomic data is curated and made publicly available, facilitating the discovery of universal therapeutic targets for RP.

Multirod posterior occipitocervical instrumentation constructs: a biomechanical analysis and initial case series of 10 patients with complex craniocervical pathology

BACKGROUND CONTEXTStabilization of the occipitocervical (OC) junction with posterior instrumentation plays a vital role in addressing a spectrum of pathologies. Due to limited bone surfaces of the occiput and C1 lamina, achieving union across the OC junction is challenging. PURPOSETo explore the biomechanics and a clinical series of patients treated with multirod constructs across the OC junction using a novel occipital plate with single- and dual-headed, modular tulip heads. STUDY DESIGN/SETTINGBiomechanical analysis and retrospective case series. PATIENT SAMPLEAdults at a single institution who underwent posterior cervical multirod constructs across the OC junction. OUTCOME MEASURESOC–C4 range of motion (ROM), maximum von Mises stress on the rods, and adjacent segment ROMs and intradiscal parameters. Patient demographics, revision operations, rod breakages, wound complications. METHODSA validated occiput-cervical finite element (FE) model was used to simulate OC–C4 cervical fixation under multidirectional pure moment loading. A total of 4 rod configurations were simulated: (A) 2-rod-Ti (4.0 mm titanium rods); (B) 2-rod-CoCr (3.5 mm cobalt chrome rods); (C) 3-rods (4.0 mm titanium rods); (D) 4-rods (4.0 mm titanium rods). The aforementioned measures were compared. A retrospective analysis was also performed of adults at a single institution who underwent posterior cervical multirod constructs across the OC junction. RESULTSBiomechanically, lowest primary rod stresses were observed for 3- and 4-rod constructs. Compared to 2-rod-Ti (121.8 MPa), 2-rod-CoCr showed a 43.2% stress increase in the rods, while 3- and 4-rods experienced rod stress reductions of 20% and 23.2%, respectively. No appreciable differences in OC–C4 ROM, C4–5 ROM, and C4–5 discal stresses were found between multirod and 2-rod constructs. Maximum occipital and C4 screw stresses were decreased in multirod constructs compared to 2-rods, with least stresses noted in the 4-rod construct. Maximum plate stresses were slightly increased in the 4-rod construct compared to 2- and 3-rod fixation, though the forces were largely similar among the constructs. Ten patients (average age 66.4±10.6 years; 8 males) were assessed clinically. Nine of the ten operations were for primary stabilization of pathological fractures and associated craniocervical and/or atlantoaxial instability using 4-rods across the OC junction. At an average follow-up time of 1.58±0.5 years (range, 1–2.3 years), there were no instrumentation failures, no adjacent segment failures, and no wound complications. CONCLUSIONSIn this proof-of-concept investigation, multiple rods (3- and 4-rods) across the OC junction using a novel occipital plate with single- and dual-headed, modular tulips was safe and effective in stabilizing the OC junction. Accompanying FE analysis demonstrated that multirod constructs decreased primary rod stresses and had lower stresses on occipital and C4 screws compared to 2-rod constructs, while occipital plate stresses were largely similar. Additional clinical studies are needed to confirm these findings and to determine the ultimate utility of multirod constructs across the OC junction.

Unraveling the nanostructures and self-assembly behavior of perfluorosulfonic acid in water/ethanol solvent: Effect of EW and side-chain chemistry

The perfluorosulfonic acid (PFSA) ionomers are key materials for proton exchange membranes (PEMs) and catalyst layers (CLs). Their morphology is profoundly influenced by the chain assembly behavior of PFSA in dispersions. Hence, we combine the characterization techniques of dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (Cryo-TEM) to study the nanostructures of PFSA dispersions, and provide a structure model for diverse PFSA ionomers in water/ethanol solvent. It is seen that PFSA ionomers self-assembly into a rod-like particle in dilute dispersion. As the concentration increases, the primary rod aggregates gradually assemble into a swollen- or Gaussian-network structure. Beyond this feature, we see that different PFSA ionomers show different nanostructures in dispersion. For the long-side-chain (LSC) PFSA ionomers, the 800-LSC PFSA tends to form monodisperse rod-like aggregates that is in a highly ordered arrangement with a rod diameter of 3.16 nm and a length of 28.72 nm. As the equivalent weight (EW) increases to 960, the poor solubility of the main chains in water/ethanol solvents leads to the “end-to-end” assemblies of the primary rod particles and dendritic secondary aggregates. The short-side-chain (SSC) PFSA ionomer that shares the same backbone with 960-LSC PFSA exhibit remarkable mono-dispersity and ordered arrangement of rod-like aggregates in water/ethanol solvents due to the strong electrostatic repulsion.

Iliac Accessory Rod Technique for Rod Fracture Prevention in Long Fusion Constructs: 2-Dimensional Operative Video.

Implant-related complications in surgery for adult spinal deformity (ASD) account for roughly $1 billion US health care expenditures over 5 years, with a majority due to primary rod fracture.1,2 Traditional two-rod constructs have demonstrated rod fracture rates of up to 40%, with a median time to fracture of 3 years.3 Current supplementary rod techniques for decreasing rod fractures inadequately address the issue of increased strain across the lumbosacral junction.4 Here, we describe a novel four-rod technique using "iliac accessory rods," designed to mitigate rod fractures by reinforcing osteotomy levels and dispersing biomechanical stress across the lumbosacral junction. Compared with other supplementary rod techniques for ASD, iliac accessory rods anchor to independent iliac bolts.5 The added fixation points across the lumbosacral junction (4 iliac bolts total) substantially offloads stress on primary rods, most of which fracture near the lumbosacral junction.3 Additionally, connecting these rods to primary rods rostrally via side-to-side connectors, above the osteotomy levels, ensures mobile osteotomy segments are reinforced. Presented is a 78-year-old woman with ASD and worsening lower back pain, radiculopathy, and bilateral leg weakness who failed nonoperative management. She underwent T9 to bi-iliac instrumented fusion with L1-S1 posterior column osteotomies, L4-S1 transforaminal lumbar interbody fusions, and bilateral iliac accessory rod fixation. Postoperatively, she recovered well and had improvement in her symptoms. Imaging revealed correction of spinal alignment. The patient consented to the procedure, and the participants and any identifiable individuals consented to publication of his/her image. Institutional Review Board approval was waived because of institutional exemption policy.

Novel method of iliac accessory rods for rod fracture prevention in adult deformity surgery: a case series of 82 patients with outcomes and complications.

Primary rod fracture after surgery for adult spinal deformity (ASD) is a leading cause of revision, with recent prospective multicenter fracture rates reported at 11%-14% by 2 years. Consequently, the addition of supplemental rods has been explored to reduce fractures. Here the authors describe their experience with a novel iliac accessory rod technique in which each accessory rod anchors to an independent iliac bolt caudally via lateral connector, and attaches to the primary rod rostrally via side-to-side connector. This retrospective, single-center case series included patients who underwent thoracolumbar/lumbar fusion for ASD between March 2019 and August 2023. Data on baseline demographics, radiographic parameters, surgical characteristics, complications, rod fracture, and revision rates were collected. Paired, 2-tailed t-tests were used to compare pre- and postoperative radiographic outcomes. Rod fracture rates were compared to prior investigations via chi-square goodness of fit testing. The technique for iliac accessory rod placement is described. The study consisted of 82 patients (mean age 66 years, 51% female, 26% with prior fusion) with a median follow-up of 2 years (IQR 28-104 weeks). A total of 50 patients (61%) had ≥ 2-year follow-up. Each surgery involved an average of 4 posterior column osteotomies and 8 segments. Iliac accessory rods were cobalt chromium and were placed bilaterally in 87% of constructs. Postoperative alignment improved significantly in the following parameters: maximum coronal Cobb angle, fractional curve, sagittal vertical axis, lumbar lordosis, thoracic kyphosis, and pelvic incidence to lumbar lordosis mismatch (p < 0.001 for all comparisons). Of 50 patients with ≥ 2-year follow-up, rod fracture occurred in 1 (2.0%), which was incidentally found and required no intervention. The present rod fracture rate was significantly lower than the authors' historically reported institutional rate of 21% for traditional dual-rod constructs, and the 11%-14% reported in recent prospective multicenter studies that used traditional and supplemental rod constructs (p < 0.05 for all comparisons). Reoperation occurred in 12 patients (14.6%); 7 (8.5%) for proximal junctional kyphosis and 5 (6.1%) for wound complication. Here the authors describe their experience with a novel iliac accessory rod technique to prevent rod fracture in patients undergoing surgery for ASD. The 2-year rod fracture rate (2.0%) in this study is significantly lower than the authors' historical dual-rod fracture rate, and other prospective multicenter investigations. Future studies with longer follow-up are needed to determine the durability of this technique.

Ancient origin of the rod bipolar cell pathway in the vertebrate retina.

Vertebrates rely on rod photoreceptors for vision in low-light conditions. The specialized downstream circuit for rod signalling, called the primary rod pathway, is well characterized in mammals, but circuitry for rod signalling in non-mammals is largely unknown. Here we demonstrate that the mammalian primary rod pathway is conserved in zebrafish, which diverged from extant mammals ~400 million years ago. Using single-cell RNA sequencing, we identified two bipolar cell types in zebrafish that are related to mammalian rod bipolar cell (RBCs), the only bipolar type that directly carries rod signals from the outer to the inner retina in the primary rod pathway. By combining electrophysiology, histology and ultrastructural reconstruction of the zebrafish RBCs, we found that, similar to mammalian RBCs, both zebrafish RBC types connect with all rods in their dendritic territory and provide output largely onto amacrine cells. The wiring pattern of the amacrine cells postsynaptic to one RBC type is strikingly similar to that of mammalian RBCs and their amacrine partners, suggesting that the cell types and circuit design of the primary rod pathway emerged before the divergence of teleost fish and mammals. The second RBC type, which forms separate pathways, was either lost in mammals or emerged in fish.

Investigation on Vision System: Digital FPGA Implementation in Case of Retina Rod Cells.

The development of prostheses and treatments for illnesses and recovery has recently been centered on hardware modeling for various delicate biological components, including the nervous system, brain, eyes, and heart. The retina, being the thinnest and deepest layer of the eye, is of particular interest. In this study, we employ the Nyquist-Based Approximation of Retina Rod Cell (NBAoRRC) approach, which has been adapted to utilize Look-Up Tables (LUTs) rather than original functions, to implement rod cells in the retina using cost-effective hardware. In modern mathematical models, numerous nonlinear functions are used to represent the activity of these cells. However, these nonlinear functions would require a substantial amount of hardware for direct implementation and may not meet the required speed constraints. The proposed method eliminates the need for multiplication functions and utilizes a fast, cost-effective rod cell device. Simulation results demonstrate the extent to which the proposed model aligns with the behavior of the primary rod cell model, particularly in terms of dynamic behavior. Based on the results of hardware implementation using the Field-Programmable Gate Arrays (FPGA) board Virtex-5, the proposed model is shown to be reliable, consume 30 percent less power than the primary model, and have reduced hardware resource requirements. Based on the results of hardware implementation using the reconfigurable FPGA board Virtex-5, the proposed model is reliable, uses 30% less power consumption than the primary model in the worth state of the set of approximation method, and has a reduced hardware resource requirement. In fact, using the proposed model, this reduction in the power consumption can be achieved. Finally, in this article, by using the LUT which is systematically sampled (Nyquist rate), we were able to remove all costly operators in terms of hardware (digital) realization and achieve very good results in the field of digital implementation in two scales of network and single neuron.

PRPH2-Related Retinal Dystrophies: Mutational Spectrum in 103 Families from a Spanish Cohort.

PRPH2, one of the most frequently inherited retinal dystrophy (IRD)-causing genes, implies a high phenotypic variability. This study aims to analyze the PRPH2 mutational spectrum in one of the largest cohorts worldwide, and to describe novel pathogenic variants and genotype-phenotype correlations. A study of 220 patients from 103 families recruited from a database of 5000 families. A molecular diagnosis was performed using classical molecular approaches and next-generation sequencing. Common haplotypes were ascertained by analyzing single-nucleotide polymorphisms. We identified 56 variants, including 11 novel variants. Most of them were missense variants (64%) and were located in the D2-loop protein domain (77%). The most frequently occurring variants were p.Gly167Ser, p.Gly208Asp and p.Pro221_Cys222del. Haplotype analysis revealed a shared region in families carrying p.Leu41Pro or p.Pro221_Cys222del. Patients with retinitis pigmentosa presented an earlier disease onset. We describe the largest cohort of IRD families associated with PRPH2 from a single center. Most variants were located in the D2-loop domain, highlighting its importance in interacting with other proteins. Our work suggests a likely founder effect for the variants p.Leu41Pro and p.Pro221_Cys222del in our Spanish cohort. Phenotypes with a primary rod alteration presented more severe affectation. Finally, the high phenotypic variability in PRPH2 hinders the possibility of drawing genotype-phenotype correlations.

Electrical synapses for a pooling layer of the convolutional neural network in retinas.

We have an example of a synergetic effect between neuroscience and connectome via artificial intelligence. The invention of Neocognitron, a machine learning algorithm, was inspired by the visual cortical circuitry for complex cells to be made by combinations of simple cells, which uses a hierarchical convolutional neural network (CNN). The CNN machine learning algorithm is powerful in classifying neuron borderlines on electron micrograph images for automatized connectomic analysis. CNN is also useful as a functional framework to analyze the neurocircuitry of the visual system. The visual system encodes visual patterns in the retina and decodes them in the corresponding cortical areas. The knowledge of evolutionarily chosen mechanisms in retinas may help the innovation of new algorithms. Since over a half-century ago, a classical style of serial section transmission electron microscopy has vastly contributed to cell biology. It is still useful to comprehensively analyze the small area of retinal neurocircuitry that is rich in natural intelligence of pattern recognition. I discuss the perspective of our study on the primary rod signal pathway in mouse and macaque retinas with special reference to electrical synapses. Photon detection under the scotopic condition needs absolute sensitivity but no intricate pattern recognition. This extreme case is regarded as the most simplified pattern recognition of the input with no autocorrelation. A comparative study of mouse and macaque retinas, where exists the 7-fold difference in linear size, may give us the underlying principle with quantitative verification of their adaptational designs of neurocircuitry.

Use of supplemental rod constructs in adult spinal deformity surgery

Operative treatment for adult spinal deformity (ASD) commonly involves long posterior instrumented fusions with primary rods spanning from the base of the construct to the upper instrumented vertebra. Over the past decade, additional supplemental rods have been increasingly utilized to bolster the primary instrumentation and mitigate risk of primary rod fracture/pseudarthrosis at areas of high biomechanical stress (e.g., 3-column osteotomy [3CO], multiple posterior column osteotomies [PCOs], lumbosacral junction). Supplemental rods for 3CO include satellite rods (4-rod technique with 2 deeply recessed short rods independently attached to pedicle screws across the 3CO), accessory rods (attached to primary rods via side-to-side connectors), and delta rods (accessory rods contoured only at the proximal and distal attachments to primary rods). Utilizing more than 4 rods across a 3CO may increase posterior construct stability; however, diminished load transfer to the anterior vertebral column may increase risk of nonunion and instrumentation failure. Similar supplemental rod constructs can be utilized to support multiple PCOs and/or the lumbosacral junction. We generally recommend using bilateral accessory rods for a total of 4 rods to support the lumbosacral junction (2 accessory rods and 2 primary rods). The novel “kickstand rod” can help facilitate coronal correction and/or function as an accessory rod distally anchored to an independent iliac screw; appropriate nomenclature is “iliac accessory rod” in cases without true kickstand distraction. In this narrative review, we aim to (1) provide a brief historical overview of supplemental rod constructs, (2) describe current indications for supplemental rods, and (3) report our results from a longitudinal analysis (2008–2020) of supplemental rod constructs used by International Spine Study Group (ISSG) surgeons.

326-OR: Rod Photoreceptor Contribution to Inflammation and Angiogenesis in Diabetic Retinopathy

Purpose: Rod photoreceptors (rods) are the most numerous and metabolically active retinal cells, and are susceptible to metabolic stress in response to hyperglycemia. Yet the role of rods in diabetic retinopathy (DR) is controversial. This study aims to investigate if rods exposed to high glucose can trigger inflammatory and angiogenic responses in Müller glia (MG) and retinal microvascular endothelial cells (RMEC). Methods: The streptozocin-induced (STZ) model was used at 10 weeks of diabetes. Transcriptomic shifts in rods were analyzed by RNAseq. The mediators produced by rods were analyzed by multiplex ELISA. The effect of rod-produced mediators on RMEC permeability was assessed. Angiogenic responses of RMECs treated with rod-produced mediators were evaluated by proliferation, migration, and tube formation assays. The effect of rods on proangiogenic mediator production by RMECs and MG was evaluated by western blot. Results: Diabetes induced upregulation of transcripts for tnf (3-fold, P=0.006) and il1a (2.2-fold, P=0.001) in rods. Primary rod cultures treated with 25 mM D-glucose (high glucose) produced increased levels of VEGF (2.5-fold, p&amp;lt;0.05), TNF-α (2.4-fold, p&amp;lt;0.05), and IL-6 (2-fold, p&amp;lt;0.05) compared to rods treated with 5 mM D-glucose (normal glucose), or with 25 mM L-glucose (osmotic control). The mediators produced by rods treated with high glucose elicited increased RMEC proliferation (2.5 fold, p&amp;lt;0.001), RMEC migration (2-fold, p&amp;lt;0.001), and RMEC tube lengths (1.9-fold, p&amp;lt;0.001). The rod-produced mediators induced RMEC secretion of matrix metalloproteinase 2 (MMP-2) (8-fold increase, p&amp;lt;0.001) and of MMP-9 (5-fold increase, p&amp;lt;0.001). MG treated with rod-produced mediators increased their production of VEGF (4-fold, p&amp;lt;0.001) and of MMP-9 (5-fold, p&amp;lt;0.001). Conclusion: Rods in hyperglycemic conditions produce mediators that increase RMEC permeability, proliferation, migration, and branching and induce a proangiogenic secretory shift in RMEC and MG. Disclosure I.De la huerta: None. J.M.Poloway: None. V.Reddy: None. J.S.Penn: None. Funding National Institutes of Health (K08EY032620); International Retinal Research Foundation; Knights Templar Eye Foundation

Using optogenetics to dissect rod inputs to OFF ganglion cells in the mouse retina.

Light responses of rod photoreceptor cells traverse the retina through three pathways. The primary pathway involves synapses from rods to ON-type rod bipolar cells with OFF signals reaching retinal ganglion cells (RGCs) via sign-inverting glycinergic synapses. Secondly, rod signals can enter cones through gap junctions. Finally, rods can synapse directly onto cone OFF bipolar cells. To analyze these pathways, we obtained whole cell recordings from OFF-type α RGCs in mouse retinas while expressing channelrhodopsin-2 in rods and/or cones. Optogenetic stimulation of rods or cones evoked large fast currents in OFF RGCs. Blocking the primary rod pathway with L-AP4 and/or strychnine reduced rod-driven optogenetic currents in OFF RGCs by ~1/3. Blocking kainate receptors of OFF cone bipolar cells suppressed both rod- and cone-driven optogenetic currents in OFF RGCs. Inhibiting gap junctions between rods and cones with mecloflenamic acid or quinpirole reduced rod-driven responses in OFF RGCs. Eliminating the exocytotic Ca2+ sensor, synaptotagmin 1 (Syt1), from cones abolished cone-driven optogenetic responses in RGCs. Rod-driven currents were not significantly reduced after isolating the secondary pathway by eliminating Syt1 and synaptotagmin 7 (Syt7) to block synaptic release from rods. Eliminating Syt1 from both rods and cones abolished responses to optogenetic stimulation. In Cx36 KO retinas lacking rod-cone gap junctions, optogenetic activation of rods evoked small and slow responses in most OFF RGCs suggesting rod signals reached them through an indirect pathway. Two OFF cells showed faster responses consistent with more direct input from cone OFF bipolar cells. These data show that the secondary rod pathway supports robust inputs into OFF α RGCs and suggests the tertiary pathway recruits both direct and indirect inputs.

Dopamine differentially affects retinal circuits to shape the retinal code.

Dopamine has long been reported to enhance antagonistic surrounds of retinal ganglion cells (RGCs). Yet, the retina contains many different RGC subtypes and the effects of dopamine can be subtype-specific. Using multielectrode array (MEA) recordings we investigated how dopamine shapes the receptive fields of RGCs in the mouse retina. We found that the non-selective dopamine receptor agonist apomorphine can either increase or decrease RGCs' surround strength, depending on their subtype. We thenused two-photon targeted patch-clamp to target a specific RGC subtype, the transient-Off-αRGC. In line with our MEA recordings, apomorphine did not increase the antagonistic surround of transient-Off-αRGCs but enhanced their responses to Off stimuli in the centre receptive field. Both D1 - and D2 -like family receptor (D1 -R and D2 -R) blockers had the opposite effect and reduced centre-mediated responses, but differently affected transient-Off-αRGC's surround. While D2 -R blocker reduced surround antagonism, D1 -R blocker led to surround activation, revealing On responses to large stimuli. Using voltage-clamp recordings we separated excitatory inputs from Off cone bipolar cells and inhibitory inputs from the primary rod pathway. In control conditions, cone inputs displayed strong surround antagonism, while inputs from the primary rod pathway showed no surround. Yet, the surround activation in the D1 -R blockade originated from the primary rod pathway. Our findings demonstrate that dopamine differentially affects RGC subtypes via distinct pathways, suggesting that dopamine has a more complex role in shaping the retinal code than previously reported. KEY POINTS: Receptive fields of retinal ganglion cells (RGCs) have a centre-surround organisation, and previous work has shown that this organisation can be modulated by dopamine in a light-intensity-dependent manner. Dopamine is thought to enhance RGCs' antagonistic surround, but a detailed understanding of how different RGC subtypes are affected is missing. Using a multielectrode array recordings, clustering analysis and pharmacological manipulations, we found that dopamine can either enhance or weaken antagonistic surrounds, and also change response kinetics, of RGCs in a subtype-specific manner. We performed targeted patch-clamp recordings of one RGC subtype, the transient-Off-αRGC, and identified the underlying circuits by which dopamine shapes its receptive field. Our findings demonstrate that dopamine acts in a subtype-specific manner and can have complex effects, which has implications for other retinal computations that rely on receptive field structure.

Single-Cell Transcriptomic Profiling of Müller Glia in the rd10 Retina.

Müller glia are the principal macroglia of the retina and support retinal neurons both in health and disease. In retinitis pigmentosa (RP), a highly heterogeneous inherited retinal disorder, the most common form of pathology involves primary rod degeneration, followed by secondary cone death. To investigate Müller glia responses to rod degeneration, we performed droplet-based single-cell RNA sequencing in the rd10 mouse model of RP during primary rod degeneration. We confirmed known MG behavior on gliosis, metabolic, and immune functions. Pde6brd10 Müller glia also exhibited an increased expression of histocompatibility complex members, which might arise from a novel immune function of Müller glia in RP. We also describe a possible decrease in glial lipid biogenesis, which might affect degenerating photoreceptors.

Distrofias Hereditarias de Retina en España: tres décadas de estudio epidemiológico, clínico y genético

Inherited Retinal Dystrophies (IRDs) are a group of rare diseases with a prevalence of 1:3000-4000 people. They are genetic, primarily affecting retinal photoreceptors and epithelial pigmentary cells, and lead to neurodegeneration and finally apoptosis. In 2021, we published our global results obtained in our registry at the Fundación Jiménez Díaz University Hospital (Madrid, Spain) from 1991 to August 2019. Now, we aimed to update these results until August 2022. Thus, we conducted a retrospective hospital-based cross-sectional study on 4.794 IRD-affected unrelated families from all the Spanish autonomous communities. Families were classified into three phenotypic categories: a) “NON-RP” for cone-dominated phenotypes, b) “RP” (retinitis pigmentosa) for primary rod involvement, and c) “syndromic IRD” when visual plus extra-ocular symptoms are present. Molecular studies included: single-gene studies, clinical exome, whole exome or whole genome sequencing. Overall, 62% (2962/4794) of the families were genetically characterized, in which 1.997 different likely causative variants (5.064 different alleles) were identified in 188 genes. The most common phenotype encountered was RP (59% of families, 2465/4794). Regarding the types of causative alleles, missenses were the most frequent (51%), followed by truncating (nonsense, frameshift, indels and splicing; 44%), while copy number variations were only 2%. The most recurrently mutated genes were PRPH2, ABCA4 and RS1 in autosomal dominant (AD), autosomal recessive (AR) and X-linked (XL) NON-RP families, respectively; RHO, USH2A and RPGR in AD, AR and XL for non-syndromic RP; and MYO7A, USH2A and BBS1 in syndromic IRD. Pathogenic variants ABCA4:p.Arg1129Leu and USH2A:p.Cys759Phe were the most frequent. Our study provides the overall genetic landscape for IRD in Spain, reporting the largest cohort ever presented and a high number of causal genes involved in these diseases. Furthermore, our findings have important implications for genetic diagnosis and counseling, but also for possible therapeutic management

Overexpression of Rhodopsin or Its Mutants Leads to Energy Metabolism Dysfunction in 661w Cells.

Retinitis pigmentosa (RP) is a heterogeneous group of inherited disorders characterized by photoreceptor degeneration. The rhodopsin gene (RHO) is the most frequent cause of autosomal dominant RP (ADRP), yet it remains unclear how RHO mutations cause heterogeneous phenotypes. Energy failure is a main cause of the secondary cone death during RP progression; however, its role in primary rod death induced by ADRP RHO mutants is unknown. Three RHO missense mutations were chosen from different clinical classes. Wild-type (WT) RHO and its mutants, P23H (class B1), R135L (class A), and G188R (class B2), were overexpressed in 661w cells, a mouse photoreceptor cell line, and their effects on oxidative phosphorylation (OXPHOS) and aerobic glycolysis were compared separately. Here, we report that energy failure is an early event in the cell death caused by overexpression of WT RHO and its mutants. RHO overexpression leads to OXPHOS deficiency, which might be a result of mitochondrial loss. Nonetheless, only in WT RHO and P23H groups, energy stress triggers AMP-activated protein kinase activation and metabolic reprogramming to increase glycolysis. Metabolic reprogramming impairment in R135L and G188R groups might be the reason why energy failure and cell injury are much more severe in those groups. Our results imply that overexpression of RHO missense mutants have distinct impacts on the two energy metabolic pathways, which might be related to their heterogeneous phenotypes.

Post-developmental plasticity of the primary rod pathway allows restoration of visually guided behaviors

The formation of neural circuits occurs in a programmed fashion, but proper activity in the circuit is essential for refining the organization necessary for driving complex behavioral tasks. In the retina, sensory deprivation during the critical period of development is well known to perturb the organization of the visual circuit making the animals unable to use vision for behavior. However, the extent of plasticity, molecular factors involved, and malleability of individual channels in the circuit to manipulations outside of the critical period are not well understood. In this study, we selectively disconnected and reconnected rod photoreceptors in mature animals after completion of the retina circuit development. We found that introducing synaptic rod photoreceptor input post-developmentally allowed their integration into the circuit both anatomically and functionally. Remarkably, adult mice with newly integrated rod photoreceptors gained high-sensitivity vision, even when it was absent from birth. These observations reveal plasticity of the retina circuit organization after closure of the critical period and encourage the development of vision restoration strategies for congenital blinding disorders.

Synaptic inputs to displaced intrinsically-photosensitive ganglion cells in macaque retina

Ganglion cells are the projection neurons of the retina. Intrinsically photosensitive retinal ganglion cells (ipRGCs) express the photopigment melanopsin and also receive input from rods and cones via bipolar cells and amacrine cells. In primates, multiple types of ipRGCs have been identified. The ipRGCs with somas in the ganglion cell layer have been studied extensively, but less is known about those with somas in the inner nuclear layer, the “displaced” cells. To investigate their synaptic inputs, three sets of horizontal, ultrathin sections through central macaque retina were collected using serial block-face scanning electron microscopy. One displaced ipRGC received nearly all of its excitatory inputs from ON bipolar cells and would therefore be expected to have ON responses to light. In each of the three volumes, there was also at least one cell that had a large soma in the inner nuclear layer, varicose axons and dendrites with a large diameter that formed large, extremely sparse arbor in the outermost stratum of the inner plexiform layer. They were identified as the displaced M1 type of ipRGCs based on this morphology and on the high density of granules in their somas. They received extensive input from amacrine cells, including the dopaminergic type. The vast majority of their excitatory inputs were from OFF bipolar cells, including two subtypes with extensive input from the primary rod pathway. They would be expected to have OFF responses to light stimuli below the threshold for melanopsin or soon after the offset of a light stimulus.

Hierarchical partner selection shapes rod-cone pathway specificity in the inner retina

SummaryNeurons form stereotyped microcircuits that underlie specific functions. In the vertebrate retina, the primary rod and cone pathways that convey dim and bright light signals, respectively, exhibit distinct wiring patterns. Rod and cone pathways are thought to be assembled separately during development. However, using correlative fluorescence imaging and serial electron microscopy, we show here that cross-pathway interactions are involved to achieve pathway-specific connectivity within the inner retina. We found that A17 amacrine cells, a rod pathway-specific cellular component, heavily bias their synaptogenesis with rod bipolar cells (RBCs) but increase their connectivity with cone bipolar cells (CBCs) when RBCs are largely ablated. This cross-pathway synaptic plasticity occurs during synaptogenesis and is triggered even on partial loss of RBCs. Thus, A17 cells adopt a hierarchical approach in selecting postsynaptic partners from functionally distinct pathways (RBC>CBC), in which contact and/or synaptogenesis with preferred partners (RBCs) influences connectivity with less-preferred partners (CBCs).

183. The ideal satellite rod configuration spanning a lumbar pedicle subtraction osteotomy: a finite element analysis

183. The ideal satellite rod configuration spanning a lumbar pedicle subtraction osteotomy: a finite element analysis