Advances in cardiac involvement in children with Duchenne muscular dystrophy / 国际儿科学杂志

Duchenne muscular dystrophy(DMD)is an X-linked recessive muscular disorder that affects mainly males.With its low incidence, insidious onset, and rapid progression, DMD is characterized by proximal muscle weakness, gastrocnemius hypertrophy, and markedly elevated serum creatine kinase.In addition to severe motor dysfunction, it also causes cardiac involvement in children, mainly manifested as dilated cardiomyopathy and arrhythmias.The mutations of DMD gene lead to the absence of dystrophin, which results in cytoskeletal defects and the impairment of the integrity of myocardial cell membrane.Meanwhile, calcium overload makes the myocytes more susceptible to damage.Exon deletion is the most common type of gene mutations in children with DMD, followed by point mutations, duplications and small insertion or deletion.The relationship among the clinical manifestations, pathogenesis, evaluation of cardiac damage in DMD and its genotype has not been clarified, which still needs further research and exploration, although some advances have been made recently.

Research progress of therapeutic methods to restore dystrophin expression in Duchenne muscular dystrophy / 中华神经科杂志

Duchenne muscular dystrophy (DMD) is a serious and progressive hereditary muscle disease. The DMD gene mutation on the X chromosome causes the loss of dystrophin, causing progressive muscle weakness and muscular atrophy. Most patients die for heart and lung failure. Current gene therapy methods are mainly aimed at restoring the expression of dystrophin, including read-through therapy, exon skipping therapy, vector-mediated gene replacement therapy and gene editing therapy. This article reviews the mechanisms of these different treatments and important advances in clinical research, and analyzes the challenges and application prospects of these treatments.

Targeting knockout of DMD gene exon51 in HEK293T cell based on CRISPR/Cas9 system / 基础医学与临床

Objective To knockout the exon51 of DMD gene in HEK293T cells using the CRISPR/Cas9 system. Methods Design the target sequences of sgRNA and clone them into plasmid PX459 respectively; transfer these plasmids into HEK293T cell and extract the total genome DNA; test the activity of sgRNAs with surveyor assay, choose the most efficient one in each end;construct plasmid PX459-2sgRNA and transfer it into HEK293T cells;check whether the exon51 has been knocked known with PCR and T vector sequencing. Results 50% of HEK293T cells' DMD gene exon51 were knocked out,showing a high gene editing efficiency. Conclusions We successfully establish a platform to target knockout the exon51 of DMD gene and provide an important experimental basis for the treatment of DMD and other genetic diseases.

Deletion and Duplication in the DMD Gene Detected by MLPA / 现代检验医学杂志

Objective To detect exon deletions/duplications in the DMD gene in Duchenne and Becker muscular dystrophy pedigrees using multiplex ligation-dependent probe amplification method,and explore the usefulness of multiplex ligation-dependent probe amplification analysis as a method for genetic diagnostics in patients with Duchenne and Becker muscular dystrophy.Methods Exon deletions/duplications in the DMD gene were analyzed by multiplex ligation-dependent probe amplification for two pedigrees with Duchenne muscular dystrophy and Becker muscular dystrophy.Patients and carriers were diagnosed by multiplex ligation-dependent probe amplification.Results The pedigree with Duchenne muscular dystrophy was caused by DelEx45-50 mutation,while the pedigree with Becker muscular dystrophy was caused by Dup Ex3-4 mutation.Patients and carriers were diagnosed by multiplex ligation-dependent probe amplification method.Conclusion Exon deletions/duplications in the DMD gene can be indicated by probe copies using multiplex ligation-dependent probe amplification method under standard operating procedure.Multiplex ligation-dependent probe amplification should be considered as a rapid and accurate clinical method for an initial mutation analysis of DMD gene with exon deletions/duplications.

Novel Non-contiguous Duplications in the DMD Gene in Five Patients with Duchenne Muscular Dystrophy

BACKGROUND: Muscular dystrophy is an X-linked recessive disorder caused by mutations in the DMD gene. Muscular dystrophy is classified into 2 types; Duchenne muscular dystrophy (DMD), which has severe clinical symptoms, and Becker muscular dystrophy (BMD), which has much milder clinical symptoms. Phenotypic progression to either DMD or BMD can be predicted by analyzing mutations in DMD by using the reading frame rule. METHODS: Of 88 patients with mutations in DMD, which were detected using Multiplex Ligation-dependent Probe Amplification DMD test kit (MRC-Holland, The Netherlands), medical records of 5 patients with non-contiguous duplications were reviewed. These rare non-contiguous duplications in DMD were compared with those reported previously. RESULTS: We identified 3 novel non-contiguous duplications in DMD that included exons 2-7 and 45-51, exons 5-37 and 50-59, and exons 52-53 and 56-61. The 5 patients with these non-contiguous duplications showed the phenotypic features of DMD. Especially, duplication of exons 52-53 and 56-61 was observed in a family, i.e., 2 DMD-affected brothers and their carrier mother. CONCLUSIONS: Prediction of phenotypes associated with complex non-contiguous duplications by using the reading frame rule is difficult because the duplications affect the expression of DMD together. Because most patients with non-contiguous duplications showed the phenotypic features of DMD, the reading frame rule should be interpreted cautiously. This study provides important insights on the non-contiguous duplications in DMD for understanding genotype-phenotype correlations and for developing dystrophin for therapeutic purposes.

Evaluation of Multiplex PCR Assay Using Dual Priming Oligonucleotide System for Detection Mutation in the Duchenne Muscular Dystrophy Gene / 대한진단검사의학회지

BACKGROUND: Exon deletions of Duchenne muscular dystrophy (DMD) gene account for most of the alterations found in DMD and Becker muscular dystrophy (BMD). This study was to evaluate the usefulness of dual priming oligonucleotide multiplex PCR (DPO PCR) in detection of exon deletions of DMD gene. METHODS: Thirty-seven DMD or BMD patients who had known exon deletions detected by conventional multiplex PCR (conventional PCR) and nine control subjects were enrolled in this study. When a discrepancy was shown between the results of conventional PCR and DPO PCR, the multiplex ligation-dependent probe amplification (MLPA) technique was performed as a confirmation test. RESULTS: The same deletions previously identified by conventional PCR in 32 out of 37 subjects were also detected by DPO PCR. For the five subjects (13.5%) showing discrepant results between the conventional PCR and DPO PCR, MLPA was performed and its results were found to correlate better with those of DPO PCR. The discrepancies were due to false positive or false negative results of the conventional PCR. CONCLUSIONS: DPO PCR shows a high agreement of results with the conventional PCR and is considered an adequate method to be used as a primary genetic test for the diagnosis of DMD. Because of an improved accuracy, especially for determining the boundaries of DMD gene deletions, DPO PCR can be very useful as a supplement to the conventional PCR.

A Report On Higher Frequency Of DMD Gene Deletion In The Indian Subcontinent.

Duchenne Muscular Dystrophy (DMD) gene analysis for 25 unrelated patients from Western India using PCR screening for 14 exons and the promoter region was carried out. Intragenic deletions were detected in 18 patients and most of them were located at the 3' hot spot region of the gene indicating that this part of the gene is more deletion prone in the Indian population from Western India as well. The frequency of deletions observed in the present study is 72%.