Exclusion of Mutations in the Dysferlin Alternative Exons 1 of DYSF-v1, 5a, and 40a in a Cohort of 26 Patients

International audienceMutations in the gene encoding dysferlin (DYSF; MIM# 603009, 2p13, GenBank NM\₀03494.2) cause primary dysferlinopathies, which are autosomal recessive muscular dystrophies. DYSF has a large mutational spectrum, and genetic diagnosis is complicated by incomplete mutation detection rates. Recently, novel dysferlin transcripts were characterized by identifying alternative exons 1 of DYSF-v1 (GenBank DQ267935), exon 5a (GenBank DQ976379), and exon 40a (GenBank EF015906). To evaluate the frequency of possible mutations in the newly identified DYSF alternative exons, we screened the corresponding genomic regions for mutations in a cohort of 26 patients, carrying only one mutation undoubtedly considered as disease causing in the 55 canonical DYSF exons. No disease-causing mutation was identified in alternative exons 1 of DYSF-v1, exon 5a, and exon 40a, demonstrating a low frequency of disease-causing mutations in these exons

UMD-DYSF, a novel locus specific database for the compilation and interactive analysis of mutations in the dysferlin gene

International audienceMutations in the dysferlin gene (DYSF) lead to a complete or partial absence of the dysferlin protein in skeletal muscles and are at the origin of dysferlinopathies, a heterogeneous group of rare autosomal recessive inherited neuromuscular disorders. As a step towards a better understanding of the DYSF mutational spectrum, and towards possible inclusion of patients in future therapeutic clinical trials, we set up the Universal Mutation Database for Dysferlin (UMD-DYSF), a Locus-Specific Database developed with the UMD (R) software. The main objective of UMD-DYSF is to provide an updated compilation of mutational data and relevant interactive tools for the analysis of DYSF sequence variants, for diagnostic and research purposes. In particular, specific algorithms can facilitate the interpretation of newly identified intronic, missense- or isosemantic-exonic sequence variants, a problem encountered recurrently during genetic diagnosis in dysferlinopathies. UMD-DYSF v1.0 is freely accessible at www.umd.be/DYSF/. It contains a total of 742 mutational entries corresponding to 266 different disease-causing mutations identified in 558 patients worldwide diagnosed with dysferlinopathy. This article presents for the first time a comprehensive analysis of the dysferlin mutational spectrum based on all compiled DYSF disease-causing mutations reported in the literature to date, and using the main bioinformatics tools offered in UMD-DYSF

Novel ancestral Dysferlin splicing mutation which migrated from the Iberian peninsula to South America

Primary dysferlinopathies are a group of recessive heterogeneous muscular dystrophies. The most common clinical presentations are Miyoshi myopathy and LGMD2B. Additional presentations range from isolated hyperCKemia to severe functional disability. Symptomatology begins in the posterior muscle compartment of the calf and its clinical course progresses slowly in Miyoshi myopathy whereas LGMD2B involves predominantly the proximal muscles of the lower limbs. The age of onset ranges from 13 to 60 years in Caucasians. We present five patients that carry a novel mutation in the exon12/intron12 boundary: c.1180_1180 + 7delAGTGCGTG (r.1054_1284del). We provide evidence of a founder effect due to a common ancestral origin of this mutation, detected in heterozygosity in four patients and in homozygosity in one patient

Migration of an ancestral dysferlin splicing mutation from the Iberian peninsula to South America

Miyoshi myopathy, LGMD2B and DMAT are primary dysferlinopathies that belong to a group of muscular dystrophies inherited in an autosomal recessive mode. Additional presentations range from isolated hyperCKemia to severe functional disability. LGMD2B involves predominantly the proximal muscles of the lower limbs whereas in Miyoshi myopathy the muscles involved are those of the posterior muscle compartment of the calf. DMAT is characterized by anterior tibial muscle weakness which rapidly progresses to the lower and upper proximal muscles. Onset is usually in young adults, but congenital and late-onset forms have also been reported. We present the first Uruguayan patient to have been diagnosed with Miyoshi myopathy and four Portuguese patients that carry a novel mutation in exon12/intron12 boundary: c.1180_1180 + 7delAGTGCGTG (r.1054_1284del) in the DYSF gene. Evidence of a founder effect due to a common ancestral origin of this mutation was detected in heterozygosity in four patients and in homozygosity in one patient. The homozygous patient has no proven inbreeding so it can be inferred that the mutation is identical by descent. All patients shared a common haplotypes block identical in state between markers Cy172-H32 and D2S211. We believe that it derives from a common mutational event which is ancestral because of the recombination between the mutated gene and the telomeric flanking marker D2S2113. As this haplotype is not common among the Portuguese population, it is very unlikely that these mutated DYSF alleles represent recurrent events. This is the sixth founder effect of the DYSF gene to be found in the world so far

A Naturally Occurring Human Minidysferlin Protein Repairs Sarcolemmal Lesions in a Mouse Model of Dysferlinopathy

International audienceDysferlinopathies are autosomal recessive, progressive muscle dystrophies caused by mutations in DYSF, leading to a loss or a severe reduction of dysferlin, a key protein in sarcolemmal repair. Currently, no etiological treatment is available for patients affected with dysferlinopathy. As for other muscular dystrophies, gene therapy approaches based on recombinant adeno-associated virus (rAAV) vectors are promising options. However, because dysferlin messenger RNA is far above the natural packaging size of rAAV, full-length dysferlin gene transfer would be problematic. In a patient presenting with a late-onset moderate dysferlinopathy, we identified a large homozygous deletion, leading to the production of a natural ``minidysferlin'' protein. Using rAAV-mediated gene transfer into muscle, we demonstrated targeting of the minidysferlin to the muscle membrane and efficient repair of sarcolemmal lesions in a mouse model of dysferlinopathy. Thus, as previously demonstrated in the case of dystrophin, a deletion mutant of the dysferlin gene is also functional, suggesting that dysferlin's structure is modular. This minidysferlin protein could be used as part of a therapeutic strategy for patients affected with dysferlinopathies

Clinical heterogeneity and a high proportion of novel mutations in a Chinese cohort of patients with dysferlinopathy

International audienceDysferlinopathies are a group of autosomal recessive muscular dystrophies caused by mutations in the dysferlin gene. This study presents clinical features and the mutational spectrum in the largest cohort of Chinese patients analyzed to date