Résumé :
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Communication n° 220. Introduction : Dystrophin is a member of the protein family coded by the Duchenne muscular dystrophy gene, which is expressed in muscular and non-muscular tissues. The absence of dystrophin alters the dystrophin-associated protein complex (DAPC), which is involved in the clustering and anchoring of signaling proteins and ion and water channels. Mammalian spermatozoa present only dystrophin Dp71, which forms complexes with b-dystroglycan and a-syntrophin. Objective : The purpose of this study was to explore the effect of the absence of Dp71 on the morphology and membrane distribution of members of the DAPC, ion channels and signaling proteins of spermatozoa, obtained from the dystrophic mutant mice, mdx3cv. Methods. Sperm morphology was examined by phase-contrast microscopy, 1000 spermatozoa (n=5) from each mouse strain were classified and counted. Results : A significant increase in abnormal morphology of the flagella in the absence of Dp71 was observed, 46% of mdx3cv spermatozoa showed normal morphology, 46% presented curved flagella and 8% exhibited twisted form. In contrast, wild type spermatozoa presented 84% of normal flagellar and only 16% had anomalous flagellar form. The anomalous morphology was partially corrected when the plasma membrane was eliminated by detergent treatment. Analysis by immunofluorescence and western blotting showed that, the absence of Dp71 resulted in a dramatic decrease in b-dystroglycan and induced membrane redistribution and an increase in the total level of a-syntrophin, voltage-dependent Na+ (m1) and K+ (KV1.1) channels and neural nitric oxide synthase. The normal amount of the short utrophin (Up71) was also elevated and redistributed in the spermatozoa of mdx3cv mice. Interestingly, the distribution and normal amount of aquaporin 4 and 7 were not altered. Conclusion : Our observations point to a new phenotype associated with the absence of Dp71. Abnormal flagellar structure and altered distribution of ion channels and signaling proteins may be responsible of the fertility problems of mdx3cv mice.
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