Résumé :
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Communication n° 295. In the membrane of healthy animals, dystrophin is associated with a complex named dystrophin-glycoprotein complex. This complex seems to be absent in dystrophin-deficient animals or humans Aim : Assess the consequences of dystrophin deficiency on the sarcolemmal distribution and localization of several glycoproteins contained in the dystrophin-glycoprotein complex (DGC). Skeletal muscle cells were extracted from hindlimb muscles of 4-weeks-old healthy and GRMD dogs. Tibial cranial muscle was isolated from healthy and GRMD dog. Three proteins of the DGC (beta Dystroglycan (bDG), beta and gamma Sarcoglycan (bSG, gSG)), dystrophin and utrophin were immunolabeled and visualized with confocal microscope. In frozen sections, the distances between two fluorescents lines were measured. In vitro, the sequence of apparition of the different proteins appeared identical in control and GRMD dog cells: utrophin, bDG, gSG, bSG, and then dystrophin (only in control cells). Only a delay concerning bSG was noted. Dystrophin, that is located on sarcolemma lately, not seemed necessary for the expression and trafficking of the DGC proteins investigated. On GRMD muscle tissue, utrophin, bDG and bSG and gSG were observed on sarcolemma but with a lesser fluorescence intensity and granular labeling, compared with one noted on healthy muscle. Utrophin seemed to substitute dystrophin on the sarcolemma of GRMD dogs as the distances between glycans and utrophin in GRMD dogs or dystrophin in healty ones are similar. Measured distances between bDG and bSG or gSG labeling were different between healthy and GRMD dogs: bDG-bSG distance decreased as bDG-gSG distance increased whereas the distance between bSG and gSG were unchanged. Substitution of dystrophin by utrophin seems not alter the sarcoglycan sub-complex organization but modifies the relationships between dystroglycan and sarcoglycan complex.
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