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Restoration of High-Sensitivity and Adapting Vision with a Cone Opsin

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Restoration of High-Sensitivity and Adapting Vision with a Cone Opsin ARTICLE https://doi.org/10.1038/s41467-019-09124-x OPEN Restoration of high-sensitivity and adapting vision with a cone opsin Michael H. Berry 1,2, Amy Holt1, Autoosa Salari1, Julia Veit1,3, Meike Visel1, Joshua Levitz1,7, Krisha Aghi 3, Benjamin M. Gaub3,8, Benjamin Sivyer2,4, John G. Flannery 1,3,5 & Ehud Y. Isacoff1,3,6 Inherited and age-related retinal degenerative diseases cause progressive loss of rod and cone photoreceptors, leading to blindness, but spare downstream retinal neurons, which can 1234567890():,; be targeted for optogenetic therapy. However, optogenetic approaches have been limited by either low light sensitivity or slow kinetics, and lack adaptation to changes in ambient light, and not been shown to restore object vision. We find that the vertebrate medium wavelength cone opsin (MW-opsin) overcomes these limitations and supports vision in dim light. MW- opsin enables an otherwise blind retinitis pigmenotosa mouse to discriminate temporal and spatial light patterns displayed on a standard LCD computer tablet, displays adaption to changes in ambient light, and restores open-field novel object exploration under incidental room light. By contrast, rhodopsin, which is similar in sensitivity but slower in light response and has greater rundown, fails these tests. Thus, MW-opsin provides the speed, sensitivity and adaptation needed to restore patterned vision. 1 Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA. 2 Department of Physiology and Pharmacology, Oregon Health and Sciences University, Portland, OR 97239, USA. 3 Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720, USA. 4 Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, OR 97239, USA. 5 School of Optometry, University of California, Berkeley, CA 94720, USA. 6 Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. 7Present address: Department of Biochemistry, Weill Cornell Medicine, New York, NY 10024, USA. 8Present address: Department of Biosystems Science Engineering, ETH Zürich, Mattenstrasse 26, Basel 8092, Switzerland. Correspondence and requests for materials should be addressed to E.Y.I. (email: [email protected]) NATURE COMMUNICATIONS | (2019) 10:1221 | https://doi.org/10.1038/s41467-019-09124-x | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-019-09124-x nherited retinal diseases (IRDs) lead to the progressive loss of ambient light levels. Strikingly, the light response of MW-opsin in rods and cones, beginning in the peripheral retina and RGCs itself adapts to ambient light, and does so over a con- I 1 underlie blindness in children and adults into middle age . siderable range, normalizing to background luminance. This Age-related macular degeneration (AMD), the leading cause of “built-in” adaptation expands visual function across naturally severe vision loss in people over 50 years of age, also results from encountered variations in lighting, from indoor to outdoor light. loss of photoreceptor cells, but in the central retina, impairing Although optogenetic and chemical therapies for vision highest acuity vision2. IRDs can result from defects in >50 restoration for photoreceptor degenerative disease have been genes3,4, and there are no clear single gene defects that cause under development for more than a decade, none has yet been AMD5, making gene replacement costly or ineffective. Further- shown to restore object vision. We find that novel object more, gene replacement can slow progression but does not help in exploration in an open field environment, under conditions that late stage disease. depend on vision, is restored by MW-opsin, indicating that An alternative approach is to endow light sensitivity to restoration of object vision under natural light. Thus, MW-opsin downstream neurons of the inner retina that survive following provides a unique combination of speed, sensitivity, and lumi- photoreceptor loss6,7, either with synthetic photoswitches, which nance adaptation and restores key aspects of natural vision. MW- actuate native ion channels8–12, or by genetic introduction of a opsin therefore represents a promising new biological prosthetic light-sensitive signaling protein. A number of light-sensitive sig- for patients suffering from degenerative retinal disease. naling proteins have been tested, including two microbial opsins, the ion channel channelrhodopsin and ion pump halorho- dopsin13–18, chemically engineered mammalian receptors19,20 Results and two G-protein coupled receptor (GPCR) opsins that are MW-opsin restores fast and sensitive light responses. Recent native to the retina, rhodopsin of rod photoreceptor cells and studies have established that vertebrate rhodopsin, found in rod melanopsin of intrinsically photosensitive retinal ganglion cells21– outer segments, may be used ectopically to control G-coupled 25. These light-gated systems, when delivered to the surviving signaling in cultured cells, RGCs and ON bipolar cells, but runs neurons of the blind retina using adeno-associated viruses down with repeated stimulation and deactivates slowly30,31,21,22, (AAVs), restore light sensitivity, transmission of light-driven raising concern that it may not support vision of natural scenes activity to higher order visual centers in the brain, and both because of movement of the observer and surrounding objects or innate and learned visually guided behaviors. However, each of saturation and possibly photo-bleaching of the chromophore these approaches encounters a significant limitation. The under photopic lighting conditions. We wondered if another microbial opsins and the chemically engineered receptors have vertebrate opsin would have faster kinetics while maintaining fast kinetics (~50–200 ms) and follow high frequency modulation similar light-sensitivity to rhodopsin. We turned to a mammalian of light (~20 Hz) but have a low sensitivity to light (requiring cone opsin, MW-opsin, whose activation of the tetrameric GIRK1 intensities of very bright outdoor light). The sensitivity is so low (F137S) G protein-coupled inward-rectifier potassium channel in that a clinical trial for channelrhodopsin requires intensifying HEK293 cells we found to decay 8-fold more rapidly and recover goggles26,27, risking retinal photo-toxicity28,29. In contrast, ecto- more completely than rhodopsin (Fig. 1a–c). pic expression of rhodopsin and melanopsin are extremely sen- We tested MW-opsin in the retina of the rd1 mouse, which sitive to light (responding to indoor light), but so slow (seconds to has a mutation in the PDE-6-β gene, resulting in progressive tens of seconds)21–24 that they may not support patterned vision loss of rod and cone photoreceptor cells. MW-opsin under given eye motion and movement of the subject and of visual control of the human synapsin promoter (hSyn-1), with a yellow objects. Moreover, the systems tested to date operate over a fluorescent (YFP) C-terminal tag for tracking expression, was relatively narrow range of intensities. In contrast, normal pho- packaged in AAV2/2(4YF) and injected intravitreally at post- toreception combines speed with high sensitivity and adaptation natal day 45–60 (Fig. 1d, e). Retinas isolated 4–8weekslater that permits a sharp intensity-response curve to shift over 9 showed expression to be pan-retinal, with a transfection rate of orders of magnitude. The sensitivity and adaptation emerge from 45 ± 19% (SD) and localized to the soma and dendritic layers of the properties of G-protein signaling pathway of photoreceptor ON-RGCs and OFF-RGCs (Fig. 1f, g and Supplementary Fig. 1), cells that both amplifies and modulates the light response. Our consistent with previous studies32 and similar to expression of goal was to overcome the shortcomings of current vision rhodopsin under identical parameters (Supplementary Fig. 2). restoration approaches by searching for a GPCR that could Retinas were mounted on a multi-electrode array (MEA), with provide fast, sensitive and adapting light responses to surviving the RGC layer in contact with the electrodes, to test for light- cells of the blind retina. evoked activity. Due to complete photoreceptor degeneration in Cone opsins are G-protein coupled receptors of cone outer animals ≥3-months-old33,nolight-evokedresponsewas segments in the vertebrate retina. Like the rhodopsin of rods, detected in the retina of control rd1 littermates (Fig. 1h), with cone opsins are highly sensitive and adapt to light over many the exception of a few RGCs which displayed slow responses orders of magnitude. While rods dominate the periphery of the characteristic of intrinsically photosensitive RGCs34.Incon- retina and play a major role in vision under low light conditions, trast, retinas from MW-opsin rd1 animals displayed robust cones are densely arrayed in the fovea, where they mediate high light-evoked increases in firing rate, consisting of a large fast, acuity central vision, in both indoor and outdoor light. transient component and a small (~30% in size) slow We find that, when virally delivered to retinal ganglion cells component (Fig. 2a, Supplementary Fig. 3). Responses across (RGCs), medium wavelength cone opsin (MW-opsin) is as sensitive retina were normalized using the Light Response Index (LRI = to light as rhodopsin under physiological stimulation parameters, (peak firing rate in the light—average firing rate in dark)/peak but displays 10-fold faster kinetics. MW-opsin restores
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