Burning the candle at both ends: Intraretinal signaling of intrinsically photosensitive retinal ganglion cells

Intrinsically photosensitive retinal ganglion cells (ipRGCs) are photoreceptors located in the ganglion cell layer. They project to brain regions involved in predominately non-image-forming functions including entrainment of circadian rhythms, control of the pupil light reflex, and modulation of mood and behavior. In addition to possessing intrinsic photosensitivity via the photopigment melanopsin, these cells receive inputs originating in rods and cones. While most research in the last two decades has focused on the downstream influence of ipRGC signaling, recent studies have shown that ipRGCs also act retrogradely within the retina itself as intraretinal signaling neurons. In this article, we review studies examining intraretinal and, in addition, intraocular signaling pathways of ipRGCs. Through these pathways, ipRGCs regulate inner and outer retinal circuitry through both chemical and electrical synapses, modulate the outputs of ganglion cells (both ipRGCs and non-ipRGCs), and influence arrangement of the correct retinal circuitry and vasculature during development. These data suggest that ipRGC function plays a significant role in the processing of image-forming vision at its earliest stage, positioning these photoreceptors to exert a vital role in perceptual vision. This research will have important implications for lighting design to optimize the best chromatic lighting environments for humans, both in adults and potentially even during fetal and postnatal development. Further studies into these unique ipRGC signaling pathways could also lead to a better understanding of the development of ocular dysfunctions such as myopia

Restoration of Vision with Ectopic Expression of Human Rod Opsin

SummaryMany retinal dystrophies result in photoreceptor loss, but the inner retinal neurons can survive, making them potentially amenable to emerging optogenetic therapies. Here, we show that ectopically expressed human rod opsin, driven by either a non-selective or ON-bipolar cell-specific promoter, can function outside native photoreceptors and restore visual function in a mouse model of advanced retinal degeneration. Electrophysiological recordings from retinal explants and the visual thalamus revealed changes in firing (increases and decreases) induced by simple light pulses, luminance increases, and naturalistic movies in treated mice. These responses could be elicited at light intensities within the physiological range and substantially below those required by other optogenetic strategies. Mice with rod opsin expression driven by the ON-bipolar specific promoter displayed behavioral responses to increases in luminance, flicker, coarse spatial patterns, and elements of a natural movie at levels of contrast and illuminance (≈50–100 lux) typical of natural indoor environments. These data reveal that virally mediated ectopic expression of human rod opsin can restore vision under natural viewing conditions and at moderate light intensities. Given the inherent advantages in employing a human protein, the simplicity of this intervention, and the quality of vision restored, we suggest that rod opsin merits consideration as an optogenetic actuator for treating patients with advanced retinal degeneration

Viral Transduction of Human Rod Opsin or Channelrhodopsin Variants to Mouse ON Bipolar Cells Does Not Impact Retinal Anatomy or Cause Measurable Death in the Targeted Cells

From MDPI via Jisc Publications RouterHistory: accepted 2021-12-01, pub-electronic 2021-12-03Publication status: PublishedFunder: Fight for Sight; Grant(s): 5047/5048Funder: Medical Research Council; Grant(s): MR/N012992/1, MR/S026266/1The viral gene delivery of optogenetic actuators to the surviving inner retina has been proposed as a strategy for restoring vision in advanced retinal degeneration. We investigated the safety of ectopic expression of human rod opsin (hRHO), and two channelrhodopsins (enhanced sensitivity CoChR-3M and red-shifted ReaChR) by viral gene delivery in ON bipolar cells of the mouse retina. Adult Grm6Cre mice were bred to be retinally degenerate or non-retinally degenerate (homozygous and heterozygous for the rd1Pde6b mutation, respectively) and intravitreally injected with recombinant adeno-associated virus AAV2/2(quad Y-F) serotype containing a double-floxed inverted transgene comprising one of the opsins of interest under a CMV promoter. None of the opsins investigated caused changes in retinal thickness; induced apoptosis in the retina or in transgene expressing cells; or reduced expression of PKCα (a specific bipolar cell marker). No increase in retinal inflammation at the level of gene expression (IBA1/AIF1) was found within the treated mice compared to controls. The expression of hRHO, CoChR or ReaChR under a strong constitutive promoter in retinal ON bipolar cells following intravitreal delivery via AAV2 does not cause either gross changes in retinal health, or have a measurable impact on the survival of targeted cells

Multi-tissue integrative analysis of personal epigenomes

Evaluating the impact of genetic variants on transcriptional regulation is a central goal in biological science that has been constrained by reliance on a single reference genome. To address this, we constructed phased, diploid genomes for four cadaveric donors (using long-read sequencing) and systematically charted noncoding regulatory elements and transcriptional activity across more than 25 tissues from these donors. Integrative analysis revealed over a million variants with allele-specific activity, coordinated, locus-scale allelic imbalances, and structural variants impacting proximal chromatin structure. We relate the personal genome analysis to the ENCODE encyclopedia, annotating allele- and tissue-specific elements that are strongly enriched for variants impacting expression and disease phenotypes. These experimental and statistical approaches, and the corresponding EN-TEx resource, provide a framework for personalized functional genomics

Antimicrobial Strategies and Economic Considerations for Polymeric Medical Implants.

Healthcare acquired infections (HAI's) are a worldwide problem that can be exacerbated by surgery and the implantation of polymeric medical devices. The use of polymer based medical devices which incorporate antimicrobial strategies are now becoming an increasingly routine way of trying to prevent the potential for reduce chronic infection and device failure. There are a wide range of potential antimicrobial agents currently being incorporated into such polymers. However, it is difficult to determine which antimicrobial agent provides the greatest infection control. The economics of replacing current methods with impregnated polymer materials further complicates matters. It has been suggested that the use of a holistic system wide approach should to be developed around the implantation of medical devices which minimises the potential risk of infection. However, the use of such different approaches is still being developed. The control of such infections is important for individual patient health and the economic implications for healthcare services

How Does Light Regulate Mood and Behavioral State?

The idea that light affects mood and behavioral state is not new. However, not much is known about the particular mechanisms and circuits involved. To fully understand these, we need to know what properties of light are important for mediating changes in mood as well as what photoreceptors and pathways are responsible. Increasing evidence from both human and animal studies imply that a specialized class of retinal ganglion cells, intrinsically photosensitive retinal ganglion cells (ipRGCs), plays an important role in the light-regulated effects on mood and behavioral state, which is in line with their well-established roles in other non-visual responses (pupillary light reflex and circadian photoentrainment). This paper reviews our current understanding on the mechanisms and paths by which the light information modulates behavioral state and mood

Les échangeurs Na+/H+ exprimés à la membrane plasmique et dans les compartiments intracellulaires (mécanismes moléculaires, fonction et régulation)

La famille des échangeurs sodium-proton de mammifères (Na+/H+ Exchangers, NHE) contient 10 membres. Les formes membranaires NHE1-NHE5 sont impliquées dans la régulation du pH intracellulaire, du volume cellulaire, ainsi que dans le transport vectoriel d équivalents acide-base à travers les épithélia. NHE6, 7 et 9 sont localisés dans des compartiments intracellulaires. NHE10 est responsable de la régulation du pH de l'acrosome. Ce travail se concentre sur l isoforme NHE1 exprimée à la membrane plasmique et sur l isoforme intracellulaire NHE7. La première partie de cette thèse étudie les effets du cisplatine, un agent anticancéreux sur NHE1. Cette molécule provoque la mort cellulaire par la formation d'adduits à l'ADN. Chez les patients le cisplatine présente aussi une gamme d effets secondaires à court terme, pour la plupart neurologiques. Ces effets peuvent être si pénibles qu'ils peuvent conduire à l'interruption de l'administration de cisplatine, même si le traitement est efficace sur la tumeur elle-même. Ils sont peu susceptibles d'être liés à l'action génomique du cisplatine, et il a été proposé qu ils pourraient être causés, au moins en partie, par une action sur les membranes cellulaires. Nous avons montré, en utilisant une combinaison de techniques (microscopie électronique, imagerie en temps réel, microscopie de force atomique) que le cisplatine modifie rapidement la morphologie de la membrane cellulaire sans effets significatifs sur l organisation et les propriétés physiques de l actine corticale. Nous avons alors cherché à savoir si cet effet aurait une incidence sur les transporteurs et canaux mécanosensibles très abondants dans le système nerveux et dans les organes impliqués dans mécanosensibilité. Nous avons montré que le cisplatine est un inhibiteur non compétitif de NHE1, et qu'il bloque de façon réversible les canaux Cl- et K+ mécanosensibles VSORC et TREK1, respectivement, avec des constantes d'inhibition similaires. En revanche, des transporteurs et canaux non-mécanosensibles (GLUT1, CFTR et TASK1), sont insensibles au cisplatine. Ce nouveau mécanisme pourrait constituer un dénominateur commun pour les effets secondaires neurologiques du cisplatine. La deuxième partie de ce travail se concentre sur NHE7, un membre hautement conservé des échangeurs des compartiments intracellulaires. Des mutations dans les gènes codant ces transporteurs sont associées à des maladies cognitives et neurodégénératives. Paradoxalement, la fonction précise de ces transporteurs n est pas encore claire, car leur localisation empêche la mesure de leurs caractéristiques fonctionnelles. Le modèle communément accepté est qu ils utilisent le potassium cytoplasmique pour catalyser une fuite de protons hors des compartiments intracellulaires. Par des techniques de génétique somatique cellulaire, nous avons sélectionné une lignée de fibroblastes qui exprime un NHE7 de type sauvage à la membrane plasmique. Cela nous a permis de mesurer pour la première fois sa cinétique, sa sélectivité et ses caractéristiques pharmacologiques. Nous avons ensuite développé une stratégie et des outils pour mesurer son activité in situ en utilisant des sondes fluorescentes qui colocalisent avec cet échangeur dans les compartiments intracellulaires. Cette partie du travail montre pour la première fois que NHE7 possède des caractéristiques uniques qui en font un transporteur électroneutre de protons qui, contrairement à ce qui était supposé, acidifie les compartiments intracellulaires. Son activité se traduit par une accélération du trafic vésiculaire. Ce travail fournit des informations importantes pour comprendre les rôles physiologiques des échangeurs et leur implication dans des maladies neurologiques.NICE-BU Sciences (060882101) / SudocSudocFranceF

Chemogenetic Activation of ipRGCs Drives Changes in Dark-Adapted (Scotopic) Electroretinogram

PURPOSE: The purpose of this study was to investigate the impact of activating melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) on dark-adapted (scotopic) electroretinograms (ERG). METHODS: We used mice (Opn4(Cre/+)) expressing cre recombinase in melanopsin-expressing cells for a targeted gene delivery of a chemogenetic Gq-coupled receptor, hM3Dq, to ipRGCs. Intraperitoneal injection of clozapine N-oxide (CNO) at 5 mg/kg was used for acute activation of hM3Dq and thus excitation of ipRGCs in darkness. Dark-adapted flash ERGs were recorded across a 9-fold range of irradiances from hM3Dq Opn4(Cre/+) and control Opn4(Cre/+) mice before and after intraperitoneal injection of CNO. A- and b-wave amplitudes and implicit times and oscillatory potentials (OPs) were analyzed. Paired-flash stimuli were used to isolate cone-driven responses. RESULTS: Clozapine N-oxide application suppressed a- and b-wave amplitudes of the dark-adapted ERG across the flash intensity range in hM3Dq Opn4(Cre/+) mice compared to control mice. Examination of the normalized irradiance-response functions revealed a shift in b-wave but not a-wave sensitivity. No changes in a- and b-wave implicit times were detected. Total OP amplitudes were also reduced in hM3Dq Opn4(Cre/+) mice compared to controls following CNO administration. The paired-flash method revealed reduction in both the first (rods and cones) and second (cones only) flash response. CONCLUSIONS: Acute and selective activation of ipRGCs modulates the amplitude of both a- and b-waves of the scotopic ERG, indicating that the influence of this ganglion cell class on the retinal physiology extends to the photoreceptors as well as their downstream pathways