Résumé :
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Dp71 is the most abundant Duchenne Muscular Dystrophy (DMD) gene product expressed in the retina. This protein in the Müller glial cells (MGC) plays a role in regulating the retinal homeostasis by clustering Kir4.1 and AQP4 channels. (see poster of Sene A.) Our purpose here was to perform the study of the Dp71 expression in the retinal vascular system. The experiments were performed in mouse adult retinas of wild type (wt) and Dp71-null mice strains, on transverse sections and retina flatmounts. Direct evaluation of endogenous Dp71 promoter activity was performed by X-Gal staining. Dp71 and specific cell markers of vascular system expression was evaluated after double labelling with a dystrophins antibody (H4), and the following antibodies specific for astrocytes (GFAP), endothelial cells (isolectin B4), MGC (glutamine synthetase) and microglia (Cd11b). On retinal flatmounts of Dp71-null mice, X-Gal staining follows the vascular pattern, suggesting that Dp71 was localized inside and/or around retinal blood vessels. Closer magnification revealed a stain in cells resembling pericytes. On wt retinal flatmounts, H4 staining was localized around blood vessel wall and also in pericytes. This labeling disappeared in Dp71-null mice, suggesting that Dp71 was the only DMD gene product expressed. No H4 labeling was found in microglia or in endothelial cells of wt. On wt retinal sections, immunostaining with the H4, glutamine synthetase and the GFAP antibodies showed that Dp71 was present in the endfeet of MGC and at the internal limiting membrane, but also in astrocytic endfeet surrounding blood vessels. Surprisingly, amacrine neurons were also positive for H4. These results revealed novel cellular expression of Dp71 in the retina. Dp71 is not only present in MGC, but also in astrocytes (as in the brain), pericytes and amacrine neurons. These locations invest Dp71 with a potential broad spectrum of implications in the physiopathology of the retina.
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