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Rupalatha Maddala, Paulo Ferreira, Vasanth Rao; F-Spondin, a Neuronal Guidance Molecule and a Regulator of Amyloid Beta Generation is Expressed Discretely in a Subset of Cone Photoreceptors within the Retina. Invest. Ophthalmol. Vis. Sci. 2014;55(13):722.
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© ARVO (1962-2015); The Authors (2016-present)
F-Spondin, a floor plate enriched multidomain extracellular matrix-associated protein is known to play a critical role in axonal pathfinding and in neuronal migration, differentiation and survival by regulating cell adhesive interactions. Additionally, F-spondin is involved in the regulation of proteolysis of amyloid precursor protein and ApoER2 and generation of amyloid beta. Here we report the discrete distribution profile of F-spondin in the photoreceptor layer of both the mouse and human retina.
F-Spondin expression and distribution profiles in the retinas of mice (C57BL6) were determined by immunoblot, immunofluorescence and RT-PCR analyses. F-spondin colocalization with rhodopsin, cone arrestin, M-opsin, S-opsin and peanut agglutinin was determined using mouse retinal sections and flat mounts. The levels of F-spondin in cone dystrophy and cone-only mouse models were determined in the Ranbp2 coneless (Tg-HRGP-cre:Ranbp2Flox/Flox) and Nrl null mice respectively, using immunoblot and immunofluorescence analyses.
F-spondin exhibits a mosaic pattern and distributes discretely to the outer and inner segments of a subset of peanut agglutinin (PNA) labeled photoreceptor cells (cones) but not to the rhodopsin presenting cells (rod photoreceptors), based on the results of immunofluorescence analysis. Unlike PNA, F-spondin is not localized to the synaptic terminals of photoreceptors. F-spondin appears to colocalize with S-opsin at both the dorsal and ventral regions of mouse retina. Developmentally, F-Spondin expression in the mouse retina coincides with the morphogenesis of photoreceptor outer segments. Compared to wild-type retinas, the retinas of Ranbp2 coneless and Nrl null mice, the levels of F-spondin were decreased and increased, respectively.
Taken together, the observation of novel, discrete and intense co-distribution of F-spondin with cone photoreceptors suggests a critical role for F-spondin in photoreceptor morphogenesis, survival or function.
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