Publications

Engineering infrared light sensitivity in the blind human retina could restore visual function in patients with regional retinal degeneration. However, current approaches are complex and contain non-human biological components. Using rational protein design we engineered human TRPV1 channels (Δ786-840) with temperature sensitivity shifted from 45 to 41C that enabled near-infrared light-induced heat activation of mammalian cells at close to physiological temperatures. When expressed in ganglion cells of human retinal explants, Δ786-840 TRPV1 generated robust spiking responses to brief near-infrared light-induced temperature transients. Additionally, increasing intensity of radiation evoked graded responses correlating with increasing firing frequencies. Unlike previous approaches that used non-human TRPV1 channels, which risk immune reactions and a multicomponent system that poses barriers to clinical implementation, this single component human-derived approach eliminates immunogenicity concerns, addressing a major challenge to clinical translation, and allow gene delivery using adeno-associated viral vectors.

Stargardt disease is a currently untreatable, inherited neurodegenerative disease that leads to macular degeneration and blindness due to loss-of-function mutations in the ABCA4 gene. We have designed a dual adeno-associated viral vector split-intein adenine base-editing strategy to correct the most common mutation in ABCA4 (c.5882G>A, p.G1961E). We optimized ABCA4 base editing in human models, including retinal organoids, iPSC-derived retinal pigment epithelial (RPE) cells, as well as adult human retinal- and RPE/choroid explants in vitro. The resulting gene therapy vectors achieved high levels of gene correction in mutation-carrying mice and in non-human primates, with an average editing of 37% of photoreceptors and 73% of RPE cells in vivo. The high editing rates in primates make way for precise and efficient gene editing in other neurodegenerative ocular diseases.

Photoreceptor degeneration is an important cause of blindness. Nelidova et al. used tunable, near-infrared sensors to render diseased photoreceptors light sensitive again (see the Perspective by Franke and Vlasits). Gold nanorods capable of detecting infrared light were coupled with an antibody to temperature-sensitive ion channels. When the nanorods absorbed light and converted it into heat, the coupled ion channels were gated by infrared light. In a mouse model of retinal degeneration, these ion channels were successfully targeted to cone photoreceptors, and responses to near infrared light could be detected. In the primary visual cortex, more cells responded to near-infrared stimuli in mice expressing these ion channels than in controls. By changing the length of the gold nanorods, the system could be tuned to different infrared wavelengths.

Human organoids recapitulating the cell-type diversity and function of their target organ are valuable for basic and translational research. We developed light-sensitive human retinal organoids with multiple nuclear and synaptic layers and functional synapses. We sequenced the RNA of 285,441 single cells from these organoids at seven developmental time points and from the periphery, fovea, pigment epithelium and choroid of light-responsive adult human retinas, and performed histochemistry. Cell types in organoids matured in vitro to a stable “developed” state at a rate similar to human retina development in vivo. Transcriptomes of organoid cell types converged toward the transcriptomes of adult peripheral retinal cell types. Expression of disease-associated genes was cell-type-specific in adult retina, and cell-type specificity was retained in organoids. We implicate unexpected cell types in diseases such as macular degeneration. This resource identifies cellular targets for studying disease mechanisms in organoids and for targeted repair in human retinas.

Targeting genes to specific neuronal or glial cell types is valuable for both understanding and repairing brain circuits. Adeno-associated viruses (AAVs) are frequently used for gene delivery, but targeting expression to specific cell types is an unsolved problem. We created a library of 230 AAVs, each with a different synthetic promoter designed using four independent strategies. We show that a number of these AAVs specifically target expression to neuronal and glial cell types in the mouse and non-human primate retina in vivo and in the human retina in vitro. We demonstrate applications for recording and stimulation, as well as the intersectional and combinatorial labeling of cell types. These resources and approaches allow economic, fast and efficient cell-type targeting in a variety of species, both for fundamental science and for gene therapy.