Mutation analysis of the dystrophin gene in Southern French DMD or BMD families: from Southern blot to protein truncation test

Abstract

Data from 6 years of experience in molecular diagnosis of Duchenne (DMD) and Becker (BMD) muscular dystrophy in Southern France are reported. DMD and BMD patients have been extensively analyzed for deletions and for point mutations in the dystrophin gene. By scanning the whole coding sequence as reverse-transcribed from lymphocytes or muscular RNA by the protein truncation test, we have reached a minimum of an 86% detection rate for point mutations responsible for DMD; these mutations consist of nonsense, frameshifting, and splicing mutations. Four of 12 small alterations identified in our sample are novel and described in this study. We also present an improved protocol for the automated detection of fluorescently labeled duplex polymerase chain reactions of six known intragenic microsatellites (Dys II, TG 15, STRs 44, 45, 49, and 50). Accurate sizing of the alleles at each locus was performed, and we elucidated the sequence of several repeat units. Allele frequencies at each of the six microsatellite loci and at one restriction fragment length polymorphism site (intron 16/TaqI) were defined in a sample of normal, DMD, and BMD X chromosomes from Southern France. The determination of the grandparental origin of either deletions or point mutations revealed differences depending on the type of the mutation, with most of the deletions occurring in oogenesis and most of the point mutations occurring in spermatogenesis.

Aminoglycoside antibiotics restore dystrophin function to skeletal muscles of mdx mice

“…However, given that there is no treatment for DMD and that the use of gentamicin in humans is already well established, this new and potentially very exciting treatment should be readily tested in appropriate patients. This may be up to 15% of all DMD patients (29).…”

Direct estimates of human per nucleotide mutation rates at 20 loci causing mendelian diseases

“…Mutations were compiled from several studies which screened all DMD exons [Gardner et al, 1995;Whittock et al, 1997;Tuffery et al, 1998;Tuffery-Giraud et al, 1999;Fajkusova et al, 2001]. In such studies, the detection rate is close to 100%.…”

Severe cognitive impairment in DMD: obvious clinical evidence for Dp71 isoform point mutations screening

“…All are translation termination mutations. Four of them are mutations of an arginine CGA codon corresponding to mutations at CpG sites, which are preferential sites for nonsense mutations 17 and have already been described 18,19 (Leiden Muscular Dystrophy pages, web information). The fifth is a mutation in the splice donor site of intron 66.…”

“…Among 19 point mutations reported to date in the Dp71 region in DMD patients with a known cognitive phenotype, 16 were indeed found in mentally retarded patients. 14,15,18,19,[21][22][23][24][25][26][27][28] Only three mutations were found in patients of normal intelligence. 14,27,29 Two were located in exon 74 which is alternatively spliced in brain dystrophin isoforms, 30 and one in exon 79 which corresponds to the 3' untranslated region.…”