OBJECTIVETo study the human dystrophin gene molecular deletion mechanism, we analyzed breakpoint regions within junction fragments of deletion-type patients and investigated whether the dystrophin gene's intron structure might be related to intron instability.

METHODSJunction fragments corresponding to exon 46 and 51 deletions were cloned. The breakpoint regions were sequenced, and the features of introns with available Genebank sequences were analyzed.

RESULTSAn analysis of junction fragment sequences corresponding to exon 46 and 51 deletions showed that all 5' and 3' breakpoints are located within repeat sequences. No small insertions, small deletions, or point mutations are located near the breakpoint junctions. By analyzing the secondary structure of the junction fragments, we demonstrated that all junction fragment breakpoints are located in non-matching regions of single-stranded hairpin loops. A high concentration of repetitive elements is found to be a key feature of many dystrophin introns. In total, 34.8% of the overall dystrophin intron sequences is composed of repeat sequences.

CONCLUSIONRepeat elements in many dystrophin gene introns are the key to their structural bases and reflect intron instability. As a result of the primary DNA sequences, single-stranded hairpin loops form, increasing the instability of the gene, and forming the base for breaks in the DNA. The formation of the single-stranded hairpins can result in reattachment of two different breakpoints, producing a deletion.

Dystrophin ; genetics ; Humans ; Introns ; genetics ; Sequence Deletion

OBJECTIVE: To explore the genetic basis of a Chinese pedigree affected with Becker muscular dystrophy (BMD) with myalgia as the main feature. METHODS: Clinical data of the patients and results of auxiliary examinations were retrospectively analyzed. Multiplex ligation-dependent probe amplification and high-throughput sequencing were used to detect potential variants. Sanger sequencing was used to verify the results. RESULTS: The clinical manifestations of the proband included myalgia and elevated serum creatine kinase, which is similar to another patient from the pedigree. Genetic testing revealed that the two patients both harbored hemizygous deletions of exons 10 to 29 of the DMD gene, for which the mother was a carrier. The same deletion was not found in his father. Based on the guidelines from American College of Medical Genetics and Genomics, the deletion was predicted to be pathogenic (PVS1+PM2+PP1). CONCLUSION Myalgia with elevated serum CK may be atypical clinical manifestations of BMD and may be associated with variants in the rod domain of the DMD gene. The deletion of exons 10 to 29 of the DMD gene probably underlay the BMD in this pedigree.
China ; Dystrophin/genetics* ; Female ; Genetic Testing ; Humans ; Muscular Dystrophy, Duchenne/genetics* ; Myalgia/genetics* ; Pedigree ; Retrospective Studies

OBJECTIVE: To carry out pedigree analysis for a rare child with comorbid X-linked ichthyosis (XLI) and Duchenne muscular dystrophy (DMD). METHODS: Whole exome sequencing (WES) and multiple ligation-dependent probe amplification (MLPA) were used to detect potential deletions in the STS and DMD genes. RESULTS: The proband was found to harbor hemizygous deletion of the STS gene and exons 48 to 54 of the DMD gene. CONCLUSION The child has comorbid XLI and DMD, which is extremely rare.
Child ; Dystrophin/genetics* ; Exons ; Gene Deletion ; Genetic Testing ; Humans ; Ichthyosis/genetics* ; Muscular Dystrophy, Duchenne/genetics* ; Mutation

OBJECTIVETo investigate the clinical and lab features of sibling brother and sister both with Duchenne muscular dystrophy (DMD).

METHODSWe conducted comprehensive clinical and lab investigations including the test of serum enzymes, electromyography (EMG), electrocardiography, color Doppler echocardiography, HE staining of skeletal muscles, immunohistochemical study of dystrophin and utrophin, multiple ligation probe amplification (MLPA) on exon 1-79 of dystrophin gene, and short tandem repeat-poly- merase chain reaction of CA repeats located in dystrophin gene.

RESULTSThese two patients were confirmed to suffer from DMD. They were characterized by typical features of DMD including typical clinical manifestations, increased serum enzymes, EMG presenting myogenic impairment, HE staining presentation belonging to DMD, negative dystrophin in brother, and inconstantly positive on the sarcolemma of sister. Furthermore, no deletion or duplication was found in the 1-79 exons of dystrophin gene. The suffering brother and sister carried the same maternal X chromosome.

CONCLUSIONSCarriers of DMD gene show typical clinical and laboratory manifestations of DMD. Comprehensive examinations should be performed for such carriers.

Dystrophin ; genetics ; Female ; Genetic Linkage ; Heterozygote ; Humans ; Male ; Muscular Dystrophy, Duchenne ; genetics ; metabolism ; physiopathology ; Siblings

OBJECTIVETo explore the correlation between genotypes and phenotypes in Chinese patients with pseudohypertrophic muscular dystrophy.

METHODSPatients with Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) were diagnosed clinically. Multiplex ligation-dependent probe amplification (MLPA) were performed to detect potential DMD gene mutations. The results were analyzed statistically.

RESULTSAmong 280 patients, 238(85.0%) were diagnosed with DMD, 35(12.50%) were diagnosed with BMD and 7(2.5%) were diagnosed with intermediate muscular dystrophin (IMD). Among these, 252(92.31%) were in-frame mutations, and 21(7.69%) were out-of-frame mutations. Twelve patients with DMD have carried in-frame mutations, 9 with BMD have carried frame-shift mutations, and 7 IMD patients have carried frame-shift mutation.

CONCLUSIONMost of the genotypes and phenotypes of DMD have complied with the reading-frame hypothesis. Patients with BMD with frame-shift mutations may facilitate understanding of the pathogenesis of DMD, and provide a theoretical basis for clinical therapy.

Dystrophin ; genetics ; Exons ; Genetic Association Studies ; Genotype ; Humans ; Muscular Dystrophy, Duchenne ; diagnosis ; genetics ; Mutation ; Phenotype

OBJECTIVETo clarify the nature of a DMD splice acceptor mutation c.2381-3T>C.

METHODSGenomic DNA was extracted from 5 members of a family affected with DMD. For an obligatory carrier, after excluding gross deletion and duplication of the DMD gene with multiplex ligation-dependent probe amplification (MLPA) method, all coding and splice site sequences of the DMD gene were analyzed with Next Generation Sequencing followed by confirmation with targeted Sanger sequencing. Mutations of the carrier were detected in other 4 members. For the splice site mutation, mini-gene was constructed and expressed in vitro to detect the number of transcript and cDNA sequence.

RESULTSA known nonsense mutation (c.8038C>T, p.Arg2680Ter) was identified in the carrier, her sister and the mother. The rest 4 members, except for the mother from the first generation, have all carried the c.2381-3T>C mutation. The latter has been described as a splice site mutation to cause DMD. One of 135 male adults without DMD was also detected to have carried the c.2381-3T>C mutation. No additional transcript was produced by the mini-genes containing c.2381-3T>C mutation.

CONCLUSIONThe c.8038C>T（p.Arg2680Ter）mutation of DMD gene probably underlies the disease in this family. The presence of the c.2381-3T>C mutation in a asymptomatic male and a non-DMD male control, together with the normal in vitro expression of the mini-gene carrying the c.2381-3T>C, strongly suggested that the c.2381-3T>C mutation collected in the Human Gene Mutation Database is a rare SNP without significant pathogenicity.

Dystrophin ; genetics ; Humans ; Male ; Muscular Dystrophy, Duchenne ; genetics ; Mutation ; Polymorphism, Single Nucleotide

Child ; DNA Mutational Analysis ; Dystrophin ; genetics ; Exons ; Humans ; Male ; Muscular Dystrophy, Duchenne ; genetics ; Mutation

OBJECTIVE: To study the correlation of splicing mutations at the 5' end of the DMD gene with their phenotypes. METHODS: DMD gene mutations were analyzed using Multiplex Ligation Probe Amplification (MLPA) and Sanger sequencing. Co-segregation analysis was performed for the pedigrees of the probands. Influence of mutations on protein function was predicted by bioinformatic analysis. RESULTS: Three novel splicing mutations were identified in three patients with different phenotypes. Patient 1 carried a c.31+3insT mutation and presented primarily with dilated cardiomyopathy (XLDC). There was no clinical signs of skeletal myopathy. Bioinformatic analysis predicted that the mutation may inactivate the splicing donor of intron 1 and lead to premature termination of protein translation. Patient 2 carried a c.264_264+4delTGTAA mutation, which led to loss of splicing donor site for intron 4, and manifested Becker muscular dystrophy (BMD). The mutation was predicted to result in skipping of exon 4. The defective protein may still retain most of its function. Patient 3 had Duchenne muscular dystrophy (DMD) and carried a c.832-3C>T mutation which was predicted to decrease the activity of splicing acceptor of intron 8, resulting in usage of alternative acceptor site or retain of intron 8. All related transcripts may cause premature termination of protein translation and complete loss of protein function. The three mutations were all inherited from the mothers of the patients. CONCLUSION Three novel splicing mutations were discovered at the 5' end of DMD gene in three patients with different disease phenotypes. Our study may facilitate understanding of the influence of splicing mutations at the 5' end of the DMD gene on dystrophin function and the correlation between genotypes and phenotypes.
Dystrophin ; genetics ; Humans ; Muscular Dystrophy, Duchenne ; genetics ; Mutation ; Phenotype ; RNA Splicing

Dystrophinopathies, including Duchenne muscular dystrophy, Becker muscular dystrophy and dilated cardiomyopathy, are X-linked recessive genetic disorders due to variants of the dystrophin gene, which can seriously affect quality of life and health. Genetic diagnosis plays a crucial role in their diagnosis, treatment, and prevention. How to rationally select and standardize the use of various genetic techniques is a skill that clinicians must acquire. By compiling expertise of experts from the relevant areas and guidelines published home and abroad, this consensus has provided a guidance from the perspective of genetic diagnosis for the selection of genetic techniques, testing strategies, and detection process for dystrophinopathies.
Humans ; Quality of Life ; Consensus ; Dystrophin/genetics* ; Muscular Dystrophy, Duchenne/therapy* ; Cardiomyopathy, Dilated/genetics* ; Electrocardiography

OBJECTIVETo study the characteristics, location, and amino acid changes of novel mutations of the Dystrophin gene.

METHODSTwelve patients in whom no deletion or duplication of the Dystrophin gene was detected were analyzed with next-generation sequencing. Fifty healthy adult males were recruited as the controls.

RESULTSAll patients were detected with mutations of the Dystrophin gene, which included c.33C>G, c.583C>T, c.1333C>T, c.2593C>T, c.5731A>T, c.7288G>T, c.2803+1G>T, c.10034G>A, c.4289A>G, c.1905_906delAG, c.5017delC, c.5768_5771delAAGA, and c.6261_6262insA. No similar mutations were found among the controls.

CONCLUSIONOur data has enriched the mutation spectrum of the Dystrophin gene and may provide an important basis for genetic diagnosis.

Child ; Child, Preschool ; Dystrophin ; genetics ; High-Throughput Nucleotide Sequencing ; Humans ; Male ; Mutation