Synaptic pathology and therapeutic repair in adult retinoschisis mouse by AAV-RS1 transfer
Jingxing Ou, … , Wei Li, Paul A. Sieving
Jingxing Ou, … , Wei Li, Paul A. Sieving
Published June 22, 2015
Citation Information: J Clin Invest. 2015;125(7):2891-2903. https://doi.org/10.1172/JCI81380.
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Research Article Ophthalmology

Synaptic pathology and therapeutic repair in adult retinoschisis mouse by AAV-RS1 transfer

Abstract

Strategies aimed at invoking synaptic plasticity have therapeutic potential for several neurological conditions. The human retinal synaptic disease X-linked retinoschisis (XLRS) is characterized by impaired visual signal transmission through the retina and progressive visual acuity loss, and mice lacking retinoschisin (RS1) recapitulate human disease. Here, we demonstrate that restoration of RS1 via retina-specific delivery of adeno-associated virus type 8-RS1 (AAV8-RS1) vector rescues molecular pathology at the photoreceptor–depolarizing bipolar cell (photoreceptor-DBC) synapse and restores function in adult Rs1-KO animals. Initial development of the photoreceptor-DBC synapse was normal in the Rs1-KO retina; however, the metabotropic glutamate receptor 6/transient receptor potential melastatin subfamily M member 1–signaling (mGluR6/TRPM1-signaling) cascade was not properly maintained. Specifically, the TRPM1 channel and G proteins Gαo, Gβ5, and RGS11 were progressively lost from postsynaptic DBC dendritic tips, whereas the mGluR6 receptor and RGS7 maintained proper synaptic position. This postsynaptic disruption differed from other murine night-blindness models with an electronegative electroretinogram response, which is also characteristic of murine and human XLRS disease. Upon AAV8-RS1 gene transfer to the retina of adult XLRS mice, TRPM1 and the signaling molecules returned to their proper dendritic tip location, and the DBC resting membrane potential was restored. These findings provide insight into the molecular plasticity of a critical synapse in the visual system and demonstrate potential therapeutic avenues for some diseases involving synaptic pathology.

Authors

Jingxing Ou, Camasamudram Vijayasarathy, Lucia Ziccardi, Shan Chen, Yong Zeng, Dario Marangoni, Jodie G. Pope, Ronald A. Bush, Zhijian Wu, Wei Li, Paul A. Sieving

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Figure 1

Photoreceptor synaptic calcium deficiency and bipolar TRPM1 channel anomaly and hyperpolarized MP in P22 Rs1-KO retinas.

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Photoreceptor synaptic calcium deficiency and bipolar TRPM1 channel anom...
(A–D) RS1 (green); counterstain Gαo (purple), a BC marker. In WT retina, Rs1 is profusely present in the photoreceptor inner segments and OPL. Rs1 is concentrated at the ON-BC dendritic shaft and sparsely present around the cell soma. (E and F) In Rs1-KO retinas at P22, presynaptic RIBEYE (blue) and CaV1.4 (red) are normally distributed as in WT. In contrast to WT retinas (G) where TRPM1 (green) proteins are aggregated at the dendritic tips opposing the presynaptic RIBEYE/CaV1.4 complex (I), the dendritic component of TRPM1 is greatly diminished (H, arrow, and J) in Rs1-KO retinas. (K–L) At P22, mGluR6 (green) is exclusively located at the dendritic tips of the ON-BCs in both WT and Rs1-KO retinas. (M) At P22, measurements with Ca2+-sensitive dye fluo-4 showed that the median [Ca2+]i in Rs1-KO rod spherules was 48% of normalized median WT value (n = 7; ***P < 0.001; Student’s t test). (N) TRPM1 signal intensity at the bipolar dendritic tips was 36% of the whole-cell signal in Rs1-KO retinas, significantly lower than that of over 53% in WT (n = 5; ***P < 0.001; Student’s t test). (O) In line with the TRPM1 defects, the MP of light-exposed RBC is abnormally low in light-exposed Rs1-KO retinas (n = 5; ***P < 0.001; Student’s t test). GCL, ganglion cell layer. Scale bars: 10 μm (B–D); 20 μm (A, E–L). n = 4.