Mutational spectrum of DMD mutations in dystrophinopathy patients: application of modern diagnostic techniques to a large cohort

Abstract

Mutations in the DMD gene, encoding the dystrophin protein, are responsible for the dystrophinopathies Duchenne Muscular Dystrophy (DMD), Becker Muscular Dystrophy (BMD), and X-linked Dilated Cardiomyopathy (XLDC). Mutation analysis has traditionally been challenging, due to the large gene size (79 exons over 2.2 Mb of genomic DNA). We report a very large aggregate data set comprised of DMD mutations detected in samples from patients enrolled in the United Dystrophinopathy Project, a multicenter research consortium, and in referral samples submitted for mutation analysis with a diagnosis of dystrophinopathy. We report 1111 mutations in the DMD gene, including 891 mutations with associated phenotypes. These results encompass 506 point mutations (including 294 nonsense mutations) and significantly expand the number of mutations associated with the dystrophinopathies, highlighting the utility of modern diagnostic techniques. Our data supports the uniform hypermutability of CGA>TGA mutations, establishes the frequency of polymorphic muscle (Dp427m) protein isoforms and reveals unique genomic haplotypes associated with `private' mutations. We note that 60% of these patients would be predicted to benefit from skipping of a single DMD exon using antisense oligonucleotide therapy, and 62% would be predicted to benefit from an inclusive multi-exon skipping approach directed toward exons 45 through 55.

Antisense mediated exon skipping therapy for duchenne muscular dystrophy (DMD)

“…For example, exon 51 skipping therapy, described above, may be feasible only up to 13% of all DMD patients. 26 Including the next common mutations with exon 45, 53, 44 and 2, 10,27,28 would still only enable targeting of 35% of all DMD patients. Analogously, Wood et al estimated that approximately 40% of all patients could be targeted by single exon skipping using the most promising 10 AOs.…”

Splicing mutation of a gene within the Duchenne muscular dystrophy family

“…Three different types of mutation exist: 1) a partial gene deletion (55-65%); 2) a gene duplication (5-15%); and 3) a point mutation (35%). Approximately 70% of PHMD diagnoses result from carrier mothers and 30% of these cases occur as a result of spontaneous mutation (Aartsma-Rus et al, 2006;Flanigan et al, 2009;Takeshima et al, 2010). Both DMD and BMD are characterized by progressive skeletal muscle weakness, muscular dystrophy, Gower's sign, possible intellectual disability, or cardiomyopathy.…”

Multiplex Ligation Dependent Probe Amplification Based Mutation Analysis of Dystrophin Gene in Nepalese Patients with Duchenne Muscular Dystrophy

“…Muscular dystrophy is diagnosed on the basis of clinical examination, raised creatine phosphokinase (CPK) level, muscle biopsy and dystrophin gene mutation analysis. The genetic tests commonly used to identify dystrophin mutations are multiplex polymerase chain reaction (mPCR), multiplex ligation dependent probe amplification (MLPA), single condition amplification/internal primer, and multiplex amplifiable probe hybridization [5]. Mutation analysis of dystrophin gene in DMD/BMD has been performed in several countries [2,3].…”