Restoring dystrophin expression in duchenne muscular dystrophy muscle progress in exon skipping and stop codon read through

The identification of the Duchenne muscular dystrophy gene and protein in the late 1980s led to high hopes of rapid translation to molecular therapeutics. These hopes were fueled by early reports of delivering new functional genes to dystrophic muscle in mouse models using gene therapy and stem cell transplantation. However, significant barriers have thwarted translation of these approaches to true therapies, including insufficient therapeutic material (eg, cells and viral vectors), challenges in systemic delivery, and immunological hurdles. An alternative approach is to repair the patient's own gene. Two innovative small-molecule approaches have emerged as front-line molecular therapeutics: exon skipping and stop codon read through. Both approaches are in human clinical trials and aim to coax dystrophin protein production from otherwise inactive mutant genes. In the clinically severe dog model of Duchenne muscular dystrophy, the exon-skipping approach recently improved multiple functional outcomes. We discuss the status of these two methods aimed at inducing de novo dystrophin production from mutant genes and review implications for other disorders.     

Discriminant analysis of ribosomal protein synthesis findings in carrier detection of duchenne muscular dystrophy

Previous studies have shown that in vitro muscle ribosomal protein synthesis (RPS) by monomeric ribosomes (MR) and total polyribosomes (TPR) and collagen synthesis (CS) are significantly increased (P < 0.01) in 47 known carriers of Duchenne muscular dystrophy as compared to 60 age-matched controls. However, there was considerable overlap of the distribution of controls and carriers, particularly for monomeric ribosomal protein synthesis and collagen synthesis. To improve detection of carriers we used discriminant analysis utilizing logs of each measurement as superior to a univariate or bivariate scheme. This study considered four groups: proven carriers (30) (group 1), presumptive carriers (female relatives of Duchenne patients with high serum creatine kinase (CK) levels) (32) (group 2), controls ≥ 20 years old (42) (group 3) and controls < 20 years (36) (group 4).

The effect of parental age on rate of mutation for duchenne muscular dystrophy

The effect of parental age on mutation rates at the Duchenne Muscular Dystrophy (DMD) locus was studied in 514 male probands who constitute two thirds of the known patients in Japan. We were unable to detect an effect of maternal age at birth of proband or maternal grandfather's age at birth of the mother of the proband on the rate of DMD mutations. The result supports an observation on the hemophilia gene.     

Nanopatterned muscle cell patches for enhanced myogenesis and dystrophin expression in a mouse model of muscular dystrophy

Skeletal muscle is a highly organized tissue in which the extracellular matrix (ECM) is composed of highly-aligned cables of collagen with nanoscale feature sizes, and provides structural and functional support to muscle fibers. As such, the transplantation of disorganized tissues or the direct injection of cells into muscles for regenerative therapy often results in suboptimal functional improvement due to a failure to integrate with native tissue properly. Here, we present a simple method in which biodegradable, biomimetic substrates with precisely controlled nanotopography were fabricated using solvent-assisted capillary force lithography (CFL) and were able to induce the proper development and differentiation of primary mononucleated cells to form mature muscle patches. Cells cultured on these nanopatterned substrates were highly-aligned and elongated, and formed more mature myotubes as evidenced by up-regulated expression of the myogenic regulatory factors Myf5, MyoD and myogenin (MyoG). When transplanted into mdx mice models for Duchenne muscular dystrophy (DMD), the proposed muscle patches led to the formation of a significantly greater number of dystrophin-positive muscle fibers, indicating that dystrophin replacement and myogenesis is achievable in vivo with this approach. These results demonstrate the feasibility of utilizing biomimetic substrates not only as platforms for studying the influences of the ECM on skeletal muscle function and maturation, but also to create transplantable muscle cell patches for the treatment of chronic and acute muscle diseases or injuries.     

计算机三维重构验证Dystrophin疏水区段与Duchenne型肌营养不良的发病

背景：Duchenne型肌营养不良和Becker型进行性肌营养不良都是dystrophin基因突变所致,但后者临床表型较轻。“阅读框规则”可解释大部分基因型与临床型关系,但累及疏水区段的整码突变也可导致Duchenne型肌营养不良。因此很有必要了解疏水区域在dystrophin中的功能,且这些疏水区段的三维结构及功能在发病机制中所起的具体作用仍未阐明。 目的：通过Kyte&Doolittle平均疏水轮廓分析研究dystrophin的疏水区段。利用swiss-model三维重构dystrophin的疏水区段阐述其在发病机制中所起的作用。 方法：参考莱顿开放数据库(http://www.dmd.nl/)及收集中山大学附属第一医院2002年至2013年确诊Duchenne型进行性肌营养不良或Becker型进行性肌营养不良的缺失型整码突变患者资料共1 038例,分析其临床型与基因型关系。使用bioedit软件计算dystrophin的平均疏水轮廓及利用swiss-model三维重构疏水区段,结合临床型和基因型关系确定dystrophin重要功能区。 结果与结论：dystrophin存在4个疏水区段,分别为肌动蛋白结合区内的Calponin同源区2、中央棒区内的重复区16、第三铰链区和EF手型区。第1,2,4疏水区段是dystrophin糖蛋白复合物中dystrophin与其他糖蛋白的结合区域,其破坏严重影响dystrophin糖蛋白复合物功能,临床症状重。中央棒区在第三铰链区附近断裂后,HⅢ的无规则卷结构不容易与断端重复区的螺旋结构恢复连接。但第三铰链区同时缺失,其两端的重复区较容易重新连接,所以第3疏水区破坏后其临床症状反而较轻。提示dystrophin的疏水区段是其重要功能区,多是dystrophin糖蛋白复合物中dystrophin与相关蛋白的结合部位,在Duchenne型肌营养不良的发病机制中起重要作用。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程全文链接：     

DNA analysis of Duchenne and Becker muscular dystrophy using pERT87 genomic probes and dystrophin cDNA probes

DNA analysis was performed on 19 unrelated Duchenne muscular dystrophy (DMD) families and one Becker muscular dystrophy (BMD) family in Japan to determine their carrier status. The intragenic genomic probe pERT87 with its subclones 87-1, 87-8, and 87-15 were used together with five cDNA probes from the 5 end of the dystrophin gene. The tests with both a high polymorphism information content (P.I.C.) and a high observed P.I.C. were most effective,i.e., pERT87-1/XmnI, pERT87-15/XmnI, pERT87-8/TaqI, and pERT87-8/BstXI. These test combinations were useful in the Japanese population but pERT87-15/TaqI was not, although it was effective in Caucasians. Two additional test combinations of pERT87-1/MspI and pERT87-15/BamHI, were highly useful in detecting restriction fragment length polymorphisms (RFLPs) when other tests were not informative. Carrier status could be determined in 18 out of 20 clients who were at risk for DMD/BMD carrier status from 20 families, similar to the rate of detection in Caucasians. The total detection rate of deletions was 74% with the five cDNA probes. Deletions were concentrated on two hot spots where 92% of all deletions were detected by only two probes, 1-2a and 8. Deletions were detected in two males with DMD who had none of the eight RFLPs tested. Our results emphasize the usefulness of DNA analysis with pERT87 genomic probes and cDNA probes. In addition, an optimum strategy for carrier detection in Japanese DMD/BMD families was proposed.     

Cell-lineage regulated myogenesis for dystrophin replacement: a novel therapeutic approach for treatment of muscular dystrophy

Duchenne muscular dystrophy (DMD) is characterized in skeletal muscle by cycles of myofiber necrosis and regeneration leading to loss of muscle fibers and replacement with fibrotic connective and adipose tissue. The ongoing activation and recruitment of muscle satellite cells for myofiber regeneration results in loss of regenerative capacity in part due to proliferative senescence. We explored a method whereby new myoblasts could be generated in dystrophic muscles by transplantation of primary fibroblasts engineered to express a micro-dystrophin/enhanced green fluorescent protein (muDys/eGFP) fusion gene together with a tamoxifen-inducible form of the myogenic regulator MyoD [MyoD-ER(T)]. Fibroblasts isolated from mdx(4cv) mice, a mouse model for DMD, were efficiently transduced with lentiviral vectors expressing muDys/eGFP and MyoD-ER(T) and underwent myogenic conversion when exposed to tamoxifen. These cells could also be induced to differentiate into muDys/eGFP-expressing myocytes and myotubes. Transplantation of transduced mdx(4cv) fibroblasts into mdx(4cv) muscles enabled tamoxifen-dependent regeneration of myofibers that express muDys. This lineage control method therefore allows replenishment of myogenic stem cells using autologous fibroblasts carrying an exogenous dystrophin gene. This strategy carries several potential advantages over conventional myoblast transplantation methods including: (i) the relative simplicity of culturing fibroblasts compared with myoblasts, (ii) a readily available cell source and ease of expansion and (iii) the ability to induce MyoD gene expression in vivo via administration of a medication. Our study provides a proof of concept for a novel gene/stem cell therapy technique and opens another potential therapeutic approach for degenerative muscle disorders.     

Targeted inactivation of dystrophin gene product Dp71: phenotypic impact in mouse retina

The abnormal retinal neurotransmission observed in Duchenne muscular dystrophy (DMD) patients and in some genotypes of mice lacking dystrophin has been attributed to altered expression of short products of the dystrophin gene. We have investigated the potential role of Dp71, the most abundant C-terminal dystrophin gene product, in retinal electrophysiology. Comparison of the scotopic electroretinograms (ERG) between Dp71-null mice and wild-type (wt) littermates revealed a normal ERG in Dp71-null mice with no significant changes of the b-wave amplitude and kinetics. Analysis of DMD gene products, utrophin and dystrophin-associated proteins (DAPs), showed that Dp71 and utrophin were localized around the blood vessels, in the ganglion cell layer (GCL), and the inner limiting membrane (ILM). Dp71 deficiency was accompanied by an increased level of utrophin and decreased level of beta-dystroglycan localized in the ILM, without any apparent effect on the other DAPs. Dp71 deficiency was also associated with an impaired clustering of two Müller glial cell proteins-the inwardly rectifying potassium channel Kir4.1 and the water pore aquaporin 4 (AQP4). Immunostaining of both proteins decreased around blood vessels and in the ILM of Dp71-null mice, suggesting that Dp71 plays a role in the clustering and/or stabilization of the two proteins. AQP4 and Kir4.1 may also be involved in the regulation of the ischemic process. We found that a transient ischemia resulted in a greater damage in the GCL of mice lacking Dp71 than in wt mice. This finding points at a crucial role played by Dp71 in retinal function.     

Genetic analysis of dystrophin gene for affected male and female carriers with Duchenne/Becker muscular dystrophy in Korea

Duchenne and Becker muscular dystrophy (DMD/BMD) are X-linked recessive disorders caused by mutation in dystrophin gene. We analyzed the results of a genetic test in 29 DMD/BMD patients, their six female relatives, and two myopathic female patients in Korea. As the methods developed, we applied different procedures for dystrophin gene analysis; initially, multiplex polymerase chain reaction was used, followed by multiplex ligation-dependent probe amplification (MLPA). Additionally, we used direct DNA sequencing for some patients who had negative results using the above methods. The overall mutation detection rate was 72.4% (21/29) in DMD/BMD patients, identifying deletions in 58.6% (17/29). Most of the deletions were confined to the central hot spot region between exons 44 and 55 (52.9%, 7/19). The percentage of deletions and duplications revealed by MLPA was 45.5% (5/11) and 27.2% (3/11), respectively. Using the MLPA method, we detected mutations confirming their carrier status in all female relatives and symptomatic female patients. In one patient in whom MLPA revealed a single exon deletion of the dystrophin gene, subsequent DNA sequencing analysis identified a novel nonsense mutation (c.4558G > T; Gln1520X). The MLPA assay is a useful quantitative method for detecting mutation in asymptomatic or symptomatic carriers as well as DMD/BMD patients.     

BvgAS-mediated signal transduction: analysis of phase-locked regulatory mutants of Bordetella bronchiseptica in a rabbit model.

Members of the Bordetella genus alternate between two distinct phenotypic phases in response to changes in their environment. This switch, termed phenotypic modulation, is mediated by the BvgAS sensory transduction system. We developed an animal model based on the interaction of Bordetella bronchiseptica with one of its natural hosts, the rabbit. To investigate the importance of BvgAS signal transduction, we constructed constitutive (RB53) and Bvg- (RB54) phase-locked derivatives of a wild-type strain, RB50. RB50 and RB53, but not RB54, established respiratory infections in B. bronchiseptica-free rabbits with an intranasal 50% infective dose of less than 200 organisms, and the course of the infection closely resembled that observed with naturally infected rabbits. Bacteria were recovered from the nasal cavity, larynx, trachea, and lungs in similar numbers from RB50- and RB53-infected rabbits, yet no pathology was detected by histological examination of lung and tracheal sections. The antibody responses in rabbits inoculated with RB50 or RB53 were quantitatively and qualitatively indistinguishable; high titers of antibodies were generated primarily against Bvg(+)-phase-specific antigens. No response against flagella, a Bvg- phase factor, was detected. Assessment of bacteria associated with alveolar macrophages indicated that only a small percentage of bacteria, if any, appear to be residing within lung macrophages. We also tested the ability of these strains to survive in a nutrient poor environment, conditions which may be encountered within certain niches in the host or in an environmental reservoir. The Bvg- phase was advantageous for growth under these conditions. Our results indicate the Bvg+ phase is sufficient for establishment of respiratory tract infection in the rabbit and the normal BvgAS-mediated response to environmental signals is not required during initial colonization. The Bvg- phase may play a role at later stages of infection, including persistence, transmission, or survival in the environment.     

Tubeimoside-1 inhibits the proliferation and activation of mouse T lymphocytes through signal transduction pathways

Abstract

Tubeimoside-1 (TBMS1) is one of the important components in Bolbostemma paniculatum (Maxim.) Franque. In the study, its immunosuppressive effects on murine T lymphocyte responses were evaluated in vitro and in vivo. The data showed that TBMS1 inhibited ConA-induced T lymphocyte proliferation, decreased the ratio of CD4⁺/CD8⁺, suppressed IL-2, IFN-γ, IL-4 and IL-6 production and mRNA expression, down-regulate activation of NF-κB, NFAT2 and AP-1 signal transduction pathways in vitro. In addition, administration of TBMS1 significantly inhibited T cell-mediated DTH response in vivo. These findings indicated that TBMS1 inhibits the proliferation and activation of T lymphocytes in mice.     

Determination of Duchenne muscular dystrophy carrier status by single strand conformation polymorphism analysis of deleted regions of the dystrophin locus.

The molecular characterisation of the dystrophin gene, mutations in which are responsible for X linked Duchenne and Becker muscular dystrophies, has led to an array of strategies for the diagnosis of affected subjects and carriers. Initially these were based on blotting and hybridisation technologies but have recently been largely superseded by PCR based techniques which afford greater speed and sensitivity. We describe the use of single strand conformation polymorphism to detect heterozygosity in regions of the dystrophin locus which are deleted in affected males, to determine the carrier status of their female relatives.     

Quantitative Southern blot analysis in the dystrophin gene of Japanese patients with Duchenne or Becker muscular dystrophy: a high frequency of duplications.

Eighty-four unrelated patients with Duchenne or Becker muscular dystrophy in Japan were studied by quantitative Southern blot analysis with dystrophin cDNA probes. We found partial deletions and duplications in 47 (56%) and 12 (14%) cases respectively by HindIII digestion. The duplications were confirmed by BglII digestion and densitometric scanning. The frequency of duplications in this study is significantly higher than those previously reported. This may be because of the small sample number, the racial difference, or our quantitative methods. Our results suggest that attempts to detect duplications are important for a precise diagnosis. Both deletions and duplications clustered at the two hot spots as reported previously. Six cases were exceptions to the 'reading frame hypothesis'. We detected three types of HindIII RFLP. Based on the results of one duplication case, we propose a revised sequential order of exons in the cDNA10 region of the dystrophin gene.     

Carrier detection of Duchenne/Becker muscular dystrophy by analysis of STRs loci linked to the gene of dystrophin in Venezuelan families

The Duchenne/Becker Muscular Dystrophy (DMD/BMD) is an X linked recessive lethal disease. The female carrier will transmit the disease gene to half of her sons and half of her daughters; half of the daughters will be carriers, while half will be normal. Half of the sons will be normal and, on average, half will have the disease. It is of particular relevance to be able to detect carrier status among female relatives of the patients for genetic counseling and prenatal diagnosis. The method of Short Tandem Repeat (STR) sequence polymorphism analysis can determine haplotype at normal status or at risk status and, to establish genetic linkage between the mutated gene and the segregated haplotype. We have analyzed 105 members from 15 unrelated Venezuelan families with one or more siblings affected with DMD/DMB and 7 unrelated males. Of the 105, 37 were male (26 affected and 11 normal) and 68 were female. STR sequences (STR44, STR45, STR49, STR50, STR3'DYS) of the gene of the Dystrophin were amplified by polymerase chain reaction (PCR) to analyze allelic polymorphism in the families. Five of the 15 families (33%) had a deletion of one or several of the exons. Of the 68 females, 27 (39.7%) were carriers, 27 (39.7%) were non-carriers and in 14 cases (20.58%) it was not possible to reach a definitive diagnosis. The definitive diagnosis could be established in 79% of the females. This analysis also shows that the mutation occurred on the grandpaternal X chromosome in one family. Hemizygocity was detected and carrier status ascertained in the mother of other patient and in one family we were able to do prenatal diagnosis. The germinal mosaicism could not be excluded in 3 patients.