Abstract
Purpose: :
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. Our purpose here was to perform a detailed characterization of the Dp71 localization in the retinal vascular system.
Methods: :
The localization experiments were performed in mouse adult retinas of wild type (wt) and Dp71-null mouse 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 by immuno-fluorescence microscopy 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).
Results: :
On retinal flatmounts of Dp71-null mice, X-Gal staining followed 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 stained with isolectin B4 and H4 antibody, 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/or 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 cells were also positive for H4. H4 labelling in Dp71-null mice was detected only in the outer plexiform layer.
Keywords: retinal glia • blood supply • microscopy: light/fluorescence/immunohistochemistry