Résumé :
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Dysferlinopathies belong to the heterogeneous group of autosomal recessive muscular dystrophies. Mutations in the gene encoding dysferlin (DYSF) lead to distinct phenotypes, mainly Limb Girdle Muscular Dystrophy type 2B (LGMD2B) and Miyoshi myopathy (MM) Here, we report the results of mutational screening in the largest cohort reported to date. Altogether, 134 patients were included based on clinical suspicion of primary dysferlinopathy and/or dysferlin protein deficiency identified on muscle biopsy samples. Genomic DNA was screened for DYSF mutations using DHPLC analysis, and subsequent sequencing of detected variants, in a routine diagnostic setting. In 89 patients (66%), molecular analysis identified two disease-causing mutations, confirming the diagnosis of primary Dysferlinopathy on a genetic basis. Furthermore, one mutation was identified in 30 patients, without identification of a second deleterious allele. We are currently developing complementary analysis for patients in whom only one or no disease-causing allele could be identified using the genomic screening procedure. Altogether, 64 novel mutations have been identified in this cohort, which corresponds to approximately 25% of all DYSF mutations reported to date. Most of the identified mutations are predicted to produce a truncated protein or one amino-acid substitution, but we also report a high proportion of nonsense mutations as compared to previous series. All mutational and available clinical data from our series, and previous reports in the literature, were included in a novel locus-specific database, the Universal Mutation Database for Dysferlin (UMD-DYSF). This database includes several bioinformatic tools which allow the statistical analysis of mutational data, and the prediction of a pathogenicity score for newly identified intronic, and missense- or isosemantic-exonic sequence variants. The database is therefore a valuable bioinformatic support for genetic diagnosis in Primary Dysferlinopathies. Furthermore, we are currently analysing particular data to determine targeted therapeutical strategies.
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