Biology subjects

Chaffiol, A.

Publications and source records attributed to Chaffiol, A..

6 recordsLinked to original sources

bioRxiv2025

Ectopic expression of two cone opsins in mouse RGCs results in opposite responses to light stimulation, likely due to differential G protein activation

Retinitis pigmentosa, a leading cause of inherited blindness, results in photoreceptor degeneration that current optogenetic approaches aim to address through microbial opsin expression in retinal ganglion cells (RGCs). While these microbial proteins restore light sensitivity, their clinical potential remains limited by low light sensitivity and immunogenicity risks. Recent efforts have focused on vertebrate opsins as safer alternatives, with mid-wavelength cone opsin (MW-opsin) demonstrating RGC depolarization via endogenous G-protein signaling. In this study, we reveal a surprising divergence in signaling outcomes of expressing short-wavelength mouse cone opsin (Opn1sw) in RGCs of blind mice. Using multielectrode array recordings and whole-cell patch clamping, we demonstrate that Opn1sw induces membrane hyperpolarization in RGCs - a stark contrast to MW-opsins depolarizing effects. This unexpected inversion suggests differential engagement of intracellular signaling pathways, potentially stemming from distinct G-protein coupling preferences. Comparative analysis of native G-protein expression profiles in RGCs versus cone photoreceptors supports this hypothesis, revealing mismatches that may explain ectopic opsin behavior. Our findings challenge the assumption of conserved opsin signaling across spectral subtypes and cell types, highlighting critical gaps in understanding vertebrate opsin-G protein interactions in non-native cellular environments. This discovery points to the necessity of systematic characterization of opsin signaling networks in target retinal cells, a prerequisite for engineering optimized optogenetic tools that reliably produce desired electrophysiological outcomes. By establishing spectral subtype-dependent signaling divergence, our work redefines parameters for developing next-generation vision restoration therapies.

neuroscience↗

bioRxiv2024

Consequences of neuronal morphology for spatially precise optogenetic stimulation

Single-photon optogenetic stimulation is a crucial tool in neuroscience, enabling precise, cell-type-specific modulation of neuronal circuits. Miniaturization of this technique in the form of fully implantable wide-field stimulator arrays enables interrogation of cortical circuits in long-term experiments and promises to enhance Brain-Machine Interfaces for restoring sensory and motor functions. However, for both basic science and clinical applications, it is essential that this technique achieves the precision needed for selective activation of sensory and motor representations at the single-column level. Yet studies report differing and sometimes conflicting neuronal responses within the stimulated cortical areas. While recurrent network mechanisms contribute to complex responses, here we demonstrate that complexity starts already at the level of neuronal morphology. Simulating optogenetic responses in detailed models of layer-2/3 and layer-5 pyramidal neurons, we accounted for realistic physiological dynamics across different stimulation intensities, including threshold, sustained, and depolarization-block responses. Our findings suggest that the spatial distribution of activated neurons from a single stimulator location at the cortical surface can be inhomogeneous and varies with stimulation intensity and neuronal morphology across layers, potentially explaining the observed response heterogeneity in earlier experiments. We found that activation spreads laterally up to several hundred micrometers from the light source due to neuronal morphology. To enhance precision, we explored two strategies: preferentially somatic expression of channelrhodopsin, which was effective only in layer-5 neurons, and narrowing the stimulating light beam, which improved precision in both layers. Our results indicate that, under the right optical setup, single-column precision of stimulation is achievable, and that optical enhancements to the stimulator may offer more significant precision improvements than genetic modifications targeting the soma.

neuroscience↗

bioRxiv2021

In vivo optogenetic stimulation of the primate retina activates the visual cortex after long-term transfection

Over the last 15 years, optogenetics has changed fundamental research in neuroscience, and is now reaching toward therapeutic applications. Vision restoration strategies using optogenetics are now at the forefront of these new clinical opportunities. But applications to human patients suffering from retinal diseases leading to blindness rise important concerns on the long-term functional expression of optogenes and the efficient signal transmission to higher visual centers. Here we demonstrate in non-human primates, continued expression and functionality at the retina level [~]20 months after delivery of our construct. We also performed in-vivo recordings of visually evoked potentials in the primary visual cortex of anaesthetized animals. Using synaptic blockers, we isolated the in-vivo cortical activation resulting from the direct optogenetic stimulation of primate retina. In conclusion, our work indicates long-term transgene expression and transmission of the signal generated in the macaque retina to the visual cortex, two important features for future clinical applications.

neuroscience↗

bioRxiv2021

Functional ultrasound imaging of the spreading activity following optogenetic stimulation of the rat visual cortex

Optogenetic stimulation of the primary visual cortex (V1) is a promising therapy for sight restoration, but it remains unclear what total cerebral volume is activated after surface stimulation. In this study, we expressed the red-shifted opsin ChrimsonR in excitatory neurons within V1 in rats, and used the fine spatial resolution provided by functional ultrasound imaging (fUS) over the whole depth of the brain to investigate the brain response to focal surface stimulation. We observed optogenetic activation of a high proportion of the volume of V1. Extracellular recordings confirmed the neuronal origin of this activation. Moreover, neuronal responses were even located in deep layers under conditions of low irradiance, spreading to the LGN and V2, consistent with a normal visual information process. This study paves the way for the use of optogenetics for cortical therapies, and highlights the value of coupling fUS with optogenetics.

neuroscience↗

bioRxiv2020

Optogenetic therapy: High spatiotemporal resolution and pattern recognition compatible with vision restoration in non-human primates

Restoring vision using optogenetics is an ideal medical application because the eye offers a direct window to access and stimulate the pathological area: the retina. Optogenetic therapy could be applied to diseases with photoreceptor degeneration such as retinitis pigmentosa. Here, we select the specific optogenetic construct that is now used in the clinical trial and assess the opsin functional efficacy on non-human primates retinal ganglion cells (RGCs). We chose the microbial opsin ChrimsonR and showed that the vector AAV2.7m8 produced greater transfection in RGCs compared to AAV2, and that ChrimsonR attached to tdTomato (ChR-tdT) is more efficiently expressed than ChrimsonR. The 600 nm light activates the RGCs transfected with the vector AAV2.7m8-ChR-tdT from an irradiance of 1015 photons.cm-2.s-1. Vector doses of 5.1010 and 5.1011 vg/eye transfect up to 7000 RGCs/mm2 in the perifovea, with no significant immune reaction. Furthermore, using a multielectrode array we recorded RGCs responses starting from 1ms stimulus duration. Using the recorded activity we were able to decode stimulus information and estimate a theoretical visual acuity of 20/249, above legal blindness. Altogether, our results pave the way for the ongoing clinical trial with the AAV2.7m8-ChrimsonR-tdT vector for vision restoration in patients affected by retinitis pigmentosa. One Sentence SummaryWe select here the vector and genetic construct best suited to provide vision restoration in patients suffering from retinopathies, we demonstrate temporal resolution compatible with high dynamic visual scenes and a visual acuity above legal blindness.

neuroscience↗

bioRxiv2018

Restoration of visual function by transplantation of optogenetically engineered photoreceptors

A major challenge in the treatment of retinal degenerative diseases, with the transplantation of replacement photoreceptors, is the difficulty in inducing the grafted cells to grow and maintain light sensitive outer segments (OS) in the host retina, which depends on proper interaction with the underlying retinal pigment epithelium (RPE). For a RPE-independent treatment approach, we introduced a hyperpolarizing microbial opsin into photoreceptor precursors from new-born mice, and transplanted them into blind mice lacking the photoreceptor layer. These optogenetically transformed photoreceptors were light responsive and their transplantation lead to the recovery of visual function, as shown by ganglion cell recordings and behavioral tests. Subsequently, we generated cone photoreceptors from human induced pluripotent stem cells (hiPSCs), expressing the chloride pump Jaws. After transplantation into blind mice, we observed light-driven responses at the photoreceptor and ganglion cell level. These results demonstrate that structural and functional retinal repair is possible by combining stem cell therapy and optogenetics.

bioengineering↗