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P. Bolte, U. Janssen-Bienhold, K. Schmidt, R. Weiler; Pannexin2 Expression in the Mouse Retina. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3293.
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Pannexins represent a recently described vertebrate protein family that have been suggested to play a role in gap junctional communication. The membrane topology of pannexin proteins is similar to that of connexin hemichannels but it is not clear whether pannexins simply duplicate connexins’ gap junction functions or play a distinct physiological role. Pannexin1 (Panx1) is known to form hemichannels, connecting the cytoplasm with the extracellular space, but so far no active pannexin2 (Panx2) or pannexin3 hemichannels have been described. Gap junctions are found in every major retinal cell type. Since gap junction proteins have not yet been identified in all coupled retinal cell types, pannexins could play a role as gap junction channels in these connections. Retinal pannexin hemichannels could contribute to metabolic and electrical coupling or to signaling via secondary messengers. Our purpose was to characterize the expression and localization pattern of Panx2 in the mouse retina to provide insights into Panx2 function in the retina.
We used single-cell RT-PCR and fluorescence in situ hybridization (FISH) with a Panx2-specific antisense riboprobe to detect Panx2 on the mRNA level. For localization on the protein level we used electron microscopy and immunofluorescence on retinal cryosections with our newly-generated antibodies against mouse Panx2. We demonstrated the specificity of these antibodies with Western blot and immunohistochemistry on Panx2-transfected HeLa cells.
Using RT-PCR, we found that Panx2 is expressed in photoreceptors, müller cells and horizontal cells in the mouse retina. FISH experiments revealed moderate Panx2 mRNA expression in photoreceptors and ganglion cells. Immunohistochemistry and electron microscopy showed Panx2 immunoreactivity in photoreceptors and horizontal cells. Western blots from mouse retina demonstrated that Panx2 is present exclusively in the membrane fraction.
Panx2 is expressed in the membranes of multiple cell types in the mouse retina, especially in photoreceptors and horizontal cells.
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