视网膜眼电图对DMD/BMD携带者的检测价值探讨

目的研究杜氏／贝氏进行性肌营养不良（DMD／BMD）携带者视网膜眼电图（ERG）的改变，探讨ERG对DMD／BMD携带者的诊断意义。方法对22个基因突变类型明确的DMD／BMD家系．用定量PCR法结合系谱分析将家系中女性成员分成肯定携带者和非携带者，对患者和家系女性成员进行详细的眼科检查和ERG检测，并用ERG国际测量标准记录结果。结果22名患者中17名出现异常ERG改变；11名肯定携带者中5名出现ERG异常，14名非携带者无ERG改变，两组无重叠。结论ERG是一项对DMD／BMD诊断非常敏感和特异的检查，而ERG对携带者的诊断也具有一定的临床意义。     

缺失型DMD／BMD患者PCR快速检测的可行性与意义

应用对应于Ｄｙｓｔｒｏｐｈｉｎ基因缺失热区的二对ＰＣＲ引物和一对内对照无关引物，在同一反应体系中扩增，检测６６例ＤＭＤ／ＢＭＤ患者。发现其中２５例存在１７号或４９号外显子缺失，与同时采用ｃＤＮＡ探针杂交检测出的３５例基因缺失相比．检出率达７１．４％。说明该扩增系统能够作为快速筛查缺失型ＤＭＤ／ＢＭＤ患者的有效手段。这对指导合理选用探针，尤其在产前诊断方面，具有重要意义。     

Comparative study on deletions of the dystrophin gene in three Asian populations

The frequency and distribution of deletions of 19 deletion-prone exons clustered in two hot spots in the proximal and central regions of the dystrophin gene were compared in three populations from Singaporean, Japan, and Vietnam. DNA samples obtained from 105 Singaporean, 86 Japanese, and 34 Vietnamese Duchenne muscular dystrophy patients were examined by polymerase chain reaction amplification. Deletions of the examined exons were found in 51.2% of Japanese patients but in 40.0% or less of the Singaporeans and Vietnamese. About two thirds of the deletions were localized in the central region and the remaining deletions were clustered at the proximal region. The most commonly deleted exons at the central deletion hot spot were exon 50 in the Singaporean, exons 49 and 50 in the Japanese, and exon 51 in the Vietnamese population. At the proximal deletion hot spot, the most commonly deleted exons were exons 6 and 8 in the Singaporeans, exons 12 and 17 in the Japanese, and exons 8 and 12 in the Vietnamese. Two cases each from Singapore and Japan had large-scale gross mutations spanning both deletion hot spots. Our results suggest that, although the presence and frequency of the two deletion hot spots may be similar in the three Asian populations analyzed, the distribution and frequency of deletions among the different exons can vary as a result of population-specific intronic sequences that predispose individuals to preferential deletion breakpoints. Received: May 20, 2002 / Accepted: July 1, 2002     

A new intragenic polymorphism detected by the single-strand conformation polymorphism (SSCP) assay in the dystrophin gene.

We have employed the single strand conformation polymorphism (SSCP) technique to examine a group of patients with Duchenne or Becker muscular dystrophy who do not contain deletions detectable by multiplex PCR or Southern/cDNA, in an attempt to identify uncommon mutations within the dystrophin gene. In SSCP analysis, a mutated sequence can be detected as a change of mobility in a nondenaturing polyacrylamide gel. During the course of this investigation, we detected and characterized a new polymorphism at the 3' end of intron 16. The G-to-T base change creates a TaqI restriction site which allows for rapid typing of the polymorphism by restriction digestion and electrophoresis of PCR amplified products. Its localization inside the 5' region of the dystrophin gene and its high heterozygosity makes it a useful and easy tool for rapid carrier and prenatal diagnosis.     

“Quadriceps myopathy”: a clinical variant form of becker muscular dystrophy

Summary A 26-year-old male with quadriceps myopathy is presented. He had a family history and only the bilateral quadriceps were wasted, without symptomatic weakness. The specimen of the muscle biopsy showed typical myopathic features without inflammatory reactions. The patchy defect of muscular dystrophin was proved by immunohistochemical study. Dystrophin analysis revealed abnormal 380 kDa dystrophin. Gene deletion was proved at exon 45–48 of Xp21 without frameshift. This case was considered to be a clinical variant form of Becker muscular dystrophy.     

Prednisone can protect against exercise-induced muscle damage

In an experimental animal exercise model we tested whether daily administration of prednisone prevents the development of mechanically induced muscle fibre damage. Six-week-old rats were treated with different doses of prednisone ranging from 1 to 50 mg/kg body weight per day or with placebo, for 8 days. On day 6 of treatment the rats were forced to run for 2 h on a level treadmill. Two days after exercise morphological damage in the soleus muscles was quantified using light microscopy and a semi-automatic image analysis system. Creatine kinase (CK) activity was measured before exercise (day 5) and directly after exercise (day 6). The expression of dystrophin in a placebo group and in a group that received 5 mg prednisone/kg body weight per day with and without performing exercise was studied with Western blotting. The effect of prednisone on fibre type distribution was determined with an antibody against fast myosin and the effect of prednisone on the proliferative activity of muscle satellite cells was studied using bromodeoxyuridine (BrdU) immunohistochemistry. Exercise-induced muscle fibre damage varied in a dose-dependent way. In the placebo group the mean (SEM) damaged muscle fibre area was 4% (1%). The groups that received low doses of prednisone, 1 or 2.5 mg/kg per day, showed a similar level of muscle damage. However, with 5 mg prednisone/kg per day the amount of muscle fibre damage [mean (SEM)] was significantly reduced to 1.4% (0.5%) (P 0.05, Student'st-test). High doses of prednisone had no protective effect. Directly after exercise the CK activity was increased two-fold, except in the group that received 50 mg prednisone/kg body weight per day. No changes in the amount of dystrophin were found after densitometric analysis of the Western blots. Prednisone did not affect the fibre distribution or the labelling index of satellite cells. We conclude that prednisone, given in an appropriate dose, protects muscle fibres against the development of mechanically induced damage, possibly by stabilizing the muscle fibre membranes. This action may explain the beneficial effect of prednisone observed in Duchenne muscular dystrophy patients.     

When a mid-intronic variation of DMD gene creates an ESE site

Duchenne and Becker muscular dystrophy are X-linked allelic disorders caused by mutations in the DMD gene. The majority (65%) of these mutations are intragenic deletions/duplications that often lead to frameshift errors. Among the remaining ones, we find the mid-intronic mutations that usually create cryptic exons by activating potential splice sites. In this report, we identified, in a Becker muscular dystrophy patient, a mid-intronic variation that creates two ESE sites in intron 26 of DMD gene resulting in the insertion of a new cryptic exon in mRNA. Despite the out of frame character of this mutation, we observed the production of a reduced amount of full-size dystrophin which could be explained by the alternation between normal and altered splicing of dystrophin mRNA in this patient.To our knowledge, this is the first case report describing this novel pathogenic mechanism of mid-intronic variations of DMD gene.     

针吸型肌肉活检联合免疫荧光在假肥大型肌营养不良诊断中的应用

目的 探讨应用针吸型肌肉活检结合免疫荧光染色诊断假肥大型肌营养不良症的应用价值及意义。方法 应用针吸型活检术取533例假肥大型肌营养不良症患者(415例DMD, 118例BMD)的肌组织,采用HE染色观察肌细胞形态,免疫荧光染色技术检测抗肌营养不良蛋白, 以2 例正常人的肌细胞作为对照。结果 正常人肌细胞膜上抗肌萎缩蛋白染色阳性,可见沿肌细胞膜分布完整的荧光条带; DMD 患者肌膜染色阴性,肌细胞膜完全不显色; BM D患者染色弱阳性, 可见沿肌细胞膜分布的间断斑片状荧光带。结论 应用针吸型活检术联合免疫荧光染色可以有效的检测抗肌营养不良蛋白的表达, 有助于DMD 和BMD 的确诊及鉴别诊断。