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JD Ochrietor, TP Moroz, PJ Linser; Molecular Diversity of 5A11/Basigin Expression in the Mouse Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3644.
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Purpose: 5A11/Basigin is an Ig-like membrane glycoprotein found on the surface of Müller cells, photoreceptor cells (inner segments), and blood vessels of the mouse retina, as well as the apical and basolateral surfaces of the retinal pigmented epithelium. Gene inactivation in mice results in blindness from eye opening, as measured by electroretinography, with degeneration of the retina that begins at approximately eight weeks of age. Observations by this laboratory indicate that two forms of 5A11/Basigin exist within the mouse retina. Therefore, the goal of these studies was to characterize the molecular diversity of 5A11/Basigin expression within the mouse retina, in an effort to determine a functional role for these molecules. Methods: 5A11/Basigin variants were cloned from a mouse retina cDNA library and the resulting cDNA sequences were aligned with the mouse 5A11/Basigin gene. The translated polypeptides were then characterized using structure prediction and motif alignment programs. Real-time RT-PCR was then used to determine the relative concentration of each 5A11/Basigin transcript within the mouse retina. Results: Two forms of 5A11/Basigin exist within the mouse retina of ∼50kDa (5A11/Basigin) and ∼60kDa (5A11/Basigin2). 5A11/Basigin2 contains an insert from the predicted intron 1 region of the mouse 5A11/Basigin gene. Both forms of 5A11/Basigin are immunoglobulin-like in structure. The 50 kDa protein possesses two predicted extracellular C-2 loops, whereas the 60 kDa protein possesses three. Contrasting with results from previous immunoblotting and Northern blotting analyses, real-time PCR studies suggest that 5A11/Basigin2 mRNA is more abundant than that of 5A11/Basigin. Expression of both forms of 5A11/Basigin transcript appears to be greater during development of the retina than after retinal maturation. Conclusions: These studies indicate that the mouse 5A11/Basigin gene produces at least two splice variations and consists of eight exons, rather than seven, as previously described. Although previous observations characterized 5A11/Basigin2 as a rare gene product relative to 5A11/Basigin, real-time RT-PCR data indicate that this mRNA is more abundant. Expression profiles of 5A11/Basigin and 5A11/Basigin2 transcripts in the mouse retina suggest that these molecules are more highly expressed and hence potentially more important during retinal development than at tissue maturity, further supporting the hypothesis that retinal degeneration is secondary to failed development.
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