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A. Rendon, P. Fort, R. Sarig, D. Yaffe, U. Nudel, T. Pannicke, A. Reichenbach, J. Sahel, C. Dalloz; Expression and Clustered Distribution of the Potassium Channel Kir4.1 and Aquaporin 4 in the Retina of Dystrophin Protein Dp71 Null-mice . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4581.
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Purpose: To elucidate the role(s) of dystrophin protein Dp71 in retina we investigated in Dp71 null-mice the effect on dystrophin-associated proteins (DAPs) and on the expression and localization of the two membrane channel proteins, the inwardly rectifying potassium channel Kir4.1 and the aquaporin 4 (AQP4), which are responsible respectively for the control of potassium and water fluxes in Müller cells. Both channels may form clustered complexes with Dp71. Methods: The expression and localization of dystrophins, DAPs, Kir4.1 and AQP4 were determined by Western-blot and immunocytochemistry methods in retinal sections of wild and Dp71-null mice strains with specific antibodies. In double labeling experiments sections were incubated successively with both types of antibodies. All fluorescence specimens were viewed by using a confocal microscope Results: Analysis of dystrophins and DAPs showed that Dp71 was localized around blood vessels, at the inner limiting membrane (ILM) and that Dp71 deficiency results in decrease level of beta-dystroglycan localized in the ILM, without an apparent effect on the other DAPs. Dp71 deficiency was also associated with an impaired clustering of Kir4.1 and AQP4 around blood vessels and at the ILM. By Western-blot we remarked that the absence of Dp71 induced the down-regulation of AQP4 without an effect on the Kir4.1 protein level Conclusions: Our results showed that Dp71 is involved in the stabilization of Kir4.1 potassium channels and AQP4, water channels at specialized membrane areas of Müller cells.
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