外显子跳跃治疗Duchenne型肌营养不良症的研究进展

Duchenne型肌营养不良症是一种致死性肌肉疾病,抗肌萎缩蛋白基因缺陷是导致本病的原因,目前本病尚无特效的疗法.反义寡核苷酸(antisense oligonucleotides,AOs)诱导的外显子跳跃作为一种新的治疗手段具有良好的应用前景.本文主要从外显子跳跃治疗的原理、基础研究及临床研究进行综述.     

Antisense oligonucleotide-mediated exon skipping for Duchenne muscular dystrophy: progress and challenges

Duchenne muscular dystrophy (DMD) is the most common childhood neuromuscular disorder. It is caused by mutations in the DMD gene that disrupt the open reading frame (ORF) preventing the production of functional dystrophin protein. The loss of dystrophin ultimately leads to the degeneration of muscle fibres, progressive weakness and premature death. Antisense oligonucleotides (AOs) targeted to splicing elements within DMD pre-mRNA can induce the skipping of targeted exons, restoring the ORF and the consequent production of a shorter but functional dystrophin protein. This approach may lead to an effective disease modifying treatment for DMD and progress towards clinical application has been rapid. Less than a decade has passed between the first studies published in 1998 describing the use of AOs to modify the DMD gene in mice and the results of the first intramuscular proof of concept clinical trials. Whilst phase II and III trials are now underway, the heterogeneity of DMD mutations, efficient systemic delivery and targeting of AOs to cardiac muscle remain significant challenges. Here we review the current status of AO-mediated therapy for DMD, discussing the preclinical, clinical and regulatory hurdles and their possible solutions to expedite the translation of AO-mediated exon skipping therapy to clinic.     

Theoretic applicability of antisense‐mediated exon skipping for Duchenne muscular dystrophy mutations

Antisense‐mediated exon skipping aiming for reading frame restoration is currently a promising therapeutic application for Duchenne muscular dystrophy (DMD). This approach is mutation specific, but as the majority of DMD patients have deletions that cluster in hotspot regions, the skipping of a small number of exons is applicable to relatively large numbers of patients. To assess the actual applicability of the exon skipping approach, we here determined for deletions, duplications and point mutations reported in the Leiden DMD mutation database, which exon(s) should be skipped to restore the open reading frame. In theory, single and double exon skipping would be applicable to 79% of deletions, 91% of small mutations, and 73% of duplications, amounting to 83% of all DMD mutations. Exon 51 skipping, which is being tested in clinical trials, would be applicable to the largest group (13%) of all DMD patients. Further research is needed to determine the functionality of different in‐frame dystrophins and a number of hurdles has to be overcome before this approach can be applied clinically. Hum Mutat 0, 1–7, 2009. © 2009 Wiley‐Liss, Inc.     

Duchenne型肌营养不良症的细胞治疗

Duchenne型肌营养不良症（Duchenne muscular dystrophy，DMD）表现为进行性肌肉萎缩，是一种致死性、遗传性神经肌肉疾病。尽管对肌肉萎缩的分子机理的研究取得了很大进展，但是仍然不能治愈，细胞治疗是很有前景的一种治疗方法。成肌细胞移植面临的主要限制是注射后细胞分布差，免疫排斥和细胞存活率低；骨髓干细胞移植需要解决横向分化的低效率问题；而肌源性干细胞看来能更有效地再生表达dystrophin的肌纤维。     

Progress in therapy for Duchenne muscular dystrophy

Duchenne muscular dystrophy is a devastating muscular dystrophy of childhood. Mutations in the dystrophin gene destroy the link between the internal muscle filaments and the extracellular matrix, resulting in severe muscle weakness and progressive muscle wasting. There is currently no cure and, whilst palliative treatment has improved, affected boys are normally confined to a wheelchair by 12 years of age and die from respiratory or cardiac complications in their twenties or thirties. Therapies currently being developed include mutation-specific treatments, DNA- and cell-based therapies, and drugs which aim to modulate cellular pathways or gene expression. This review aims to provide an overview of the different therapeutic approaches aimed at reconstructing the dystrophin-associated protein complex, including restoration of dystrophin expression and upregulation of the functional homologue, utrophin.     

Assessment of the feasibility of exon 45–55 multiexon skipping for duchenne muscular dystrophy

Background  

The specific skipping of an exon, induced by antisense oligonucleotides (AON) during splicing, has shown to be a promising therapeutic approach for Duchenne muscular dystrophy (DMD) patients. As different mutations require skipping of different exons, this approach is mutation dependent. The skipping of an entire stretch of exons (e.g. exons 45 to 55) has recently been suggested as an approach applicable to larger groups of patients. However, this multiexon skipping approach is technically challenging. The levels of intended multiexon skips are typically low and highly variable, and may be dependent on the order of intron removal. We hypothesized that the splicing order might favor the induction of multiexon 45–55 skipping.     

Canine X-linked muscular dystrophy as an animal model of Duchenne muscular dystrophy: A review

Canine X-linked muscular dystrophy is a spontaneously occurring, progressive, degenerative myopathy of dogs that is clinically and pathologically similar to Duchenne muscular dystrophy in man. The molecular basis for the disease has been shown to be a lack of dystrophin, the protein product of the Duchenne muscular dystrophy gene. Breeding colonies of dystrophic dogs have been established. This report reviews the findings of genetic, clinical, pathologic, molecular biologic, and immunocytochemical studies of the canine model, and compares the features of the canine disease to those of Duchenne dystrophy in man.     

Canine X-linked muscular dystrophy as an animal model of Duchenne muscular dystrophy: a review.

Canine X-linked muscular dystrophy is a spontaneously occurring, progressive, degenerative myopathy of dogs that is clinically and pathologically similar to Duchenne muscular dystrophy in man. The molecular basis for the disease has been shown to be a lack of dystrophin, the protein product of the Duchenne muscular dystrophy gene. Breeding colonies of dystrophic dogs have been established. This report reviews the findings of genetic, clinical, pathologic, molecular biologic, and immunocytochemical studies of the canine model, and compares the features of the canine disease to those of Duchenne dystrophy in man.     

杜氏进行性肌营养不良的临床实践指南

杜氏进行性肌营养不良(Duchemiemusculardystmphy.DMD)是最常见的X连锁隐性遗传性肌肉变性疾病,在男性新生儿中的发病率约为1/3500。DMD是由于Xp21.2区的抗肌萎缩蛋白基因(dystrop,DMD)突变所致,患者的主要临床表现包括进行性、对称性肌无力。由于呼吸肌和心肌受累,通常在30岁前死亡。通过基因检测,可以为93.1%的患者找到遗传学病因,为早期治疗和指导家庭成员的生育奠定基础,有利于改善患者的生存质量,预防这些家庭再次生育DMD患儿。本指南结合了国内外的相关研究和指南共识,总结了DMD相关的医学遗传学知识和临床处置要点,期望能给予临床工作者帮助,为DMD患者及其家庭提供规范的诊断、治疗和预防。     

Novel synonymous substitution in POMGNT1 promotes exon skipping in a patient with congenital muscular dystrophy

Walker-Warburg syndrome, muscle-eye-brain disease, Fukuyama congenital muscular dystrophy, congenital muscular dystrophy type 1C, and congenital muscular dystrophy type 1D are overlapping clinical entities belonging to a subgroup of the congenital muscular dystrophies (CMD), collectively designated dystroglycanopathies, in which the common underlying defect is hypoglycosylation of alfa-dystroglycan. Currently, six different genes are known to be implicated in these diseases: POMT1, POMT2, POMGNT1, FCMD, FKRP, and LARGE. We report the molecular characterization of a patient presenting clinical features of CMD and reduced immunostaining for alfa-dystroglycan in muscle. Three candidate genes (FCMD, POMT1 and POMGNT1) were analyzed, and a total of 18 sequence variants were detected: 15 polymorphisms in POMT1 [including three unreported single nucleotide polymorphisms (SNPs)], two polymorphisms in FCMD, and the exonic silent mutation c.636C > T in POMGNT1. Expression analysis revealed that this apparently silent mutation compromises correct premessenger RNA (mRNA) splicing, promoting skipping of the entire exon 7, with a consequent frameshift. In silico analysis of this mutation did not predict alterations in the canonical splice sequences, but rather the creation of a new exonic splice silencer. The recognition of such disease-causing elements may contribute to the further understanding of RNA processing and assist mutation screening in routine diagnosis, where such changes may be underestimated. To aid clinical diagnosis, we generated publicly available LOVD-powered Locus Specific Databases for these three genes and recorded all known sequence variants ( http://www.dmd.nl ).     

Pathologic diagnosis of Duchenne muscular dystrophy in an aborted fetus

In a fetus at risk for Duchenne muscular dystrophy and aborted at 21 weeks, an increase in variability in muscle fiber diameter was found in comparison to two control fetuses.     

Multiple mutation in an extended Duchenne muscular dystrophy family.

We have investigated an extended pedigree with three cousins affected by Duchenne muscular dystrophy with apparent transmission through the male line. However, molecular studies have shown that one boy has a de novo duplication, another has a deletion, and the molecular mutation has yet to be defined in the third boy. All three X chromosomes in the affected boys appear to have a different origin. We speculate on the mechanisms by which the Duchenne locus may be particularly prone to mutation in this family and the possible involvement of transposons is discussed. Whatever the mechanism involved, the occurrence of three different mutations in one pedigree is a rare event.