Résumé :
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Duchenne and Becker muscular dystrophies are X-linked allelic disorders caused due to mutations in the DMD gene. Mutation detection is laborious due to the presence of 79 exons in the DMD gene and carrier analysis complicated due to the heterozygous nature of the X chromosome. The absence of effective treatments has led to develop new approaches for carrier detection and prenatal diagnosis, which are the only ways available to manage and prevent the disease. Several techniques have been tried for carrier analysis using quantitative multiplex PCR (qmPCR), Southern blot, in families where the mutation is identified. Linkage analysis is used in the remainder of the cases without identifiable mutations. Duplication, as well as deletion in carriers is more difficult to quantify. Multiplex Ligation-dependent Probe Amplification (MLPA), a recent technique to detect gene dosage abnormalities, screen for deletions and duplications over the entire length of the gene and has shown to pick up more mutations and useful in carrier analysis. We have studied the carrier status in 13 cases where the patient's mutations were known .Of these 13, 10 were deletions, 2 duplications and 1 point mutation. We used both qmPCR and MLPA to assess the copy number changes and direct sequencing for the case with point mutation. Of the 13 carrier samples, 5 were carrier-negative and 8 were carrier-positive. Both qmPCR and MLPA were useful in picking up copy number changes. However, MLPA was more useful for picking mutations in exons lying outside the hotspot regions, like the exon 2 duplication. In our study we have found five novel deletions and have shown the usefulness of MLPA in picking up rare deletions, duplications and carrier status. This is the first report from India using the technique of MLPA in DMD.
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