多重连接探针扩增方法在假肥大性肌营养不良产前基因诊断中的应用

假肥大性肌营养不良(Duchenne/Becker muscular dystrophy, DMD/BMD)是一种由于DMD基因突变导致的X连锁隐性致死性遗传病。目前没有有效的治疗方法。为建立一种既可以对携带者进行检测又可以进行产前基因诊断的方法, 文章联合应用多重连接探针扩增技术(Multiplex ligation-dependent probe amplification, MLPA)和短串联重复序列(Short tandem repeats , STR)为遗传标记连锁分析的方法对26例有高风险再生育患儿的假肥大性肌营养不良家系的孕妇通过羊水穿刺进行产前基因诊断。26例进行产前基因诊断的羊水标本中有7例诊断为男性患儿, 4例诊断为女性携带者。MLPA可以作为筛查DMD基因缺失和重复突变的首选方法。联合应用MLPA和STR连锁分析, 可以提高假肥大性肌营养不良的产前基因诊断率。     

Detection of deletions by the amplification of exons (multiplex PCR) in Duchenne muscular dystrophy

The polymerase chain reaction is a new powerful method for in vitro cloning of specific regions of DNA. The use of the heat-stable DNA polymerase made the reaction amenable to automation. This method greatly facilitates the detection of mutations which are responsible for Duchenne muscular dystrophy, via DNA amplification of multiple deletions prone exons from the DMD gene.     

Drug discovery for Duchenne muscular dystrophy via utrophin promoter activation screening

Background

Duchenne muscular dystrophy (DMD) is a devastating muscle wasting disease caused by mutations in dystrophin, a muscle cytoskeletal protein. Utrophin is a homologue of dystrophin that can functionally compensate for its absence when expressed at increased levels in the myofibre, as shown by studies in dystrophin-deficient mice. Utrophin upregulation is therefore a promising therapeutic approach for DMD. The use of a small, drug-like molecule to achieve utrophin upregulation offers obvious advantages in terms of delivery and bioavailability. Furthermore, much of the time and expense involved in the development of a new drug can be eliminated by screening molecules that are already approved for clinical use.

Methodology/Principal Findings

We developed and validated a cell-based, high-throughput screening assay for utrophin promoter activation, and used it to screen the Prestwick Chemical Library of marketed drugs and natural compounds. Initial screening produced 20 hit molecules, 14 of which exhibited dose-dependent activation of the utrophin promoter and were confirmed as hits. Independent validation demonstrated that one of these compounds, nabumetone, is able to upregulate endogenous utrophin mRNA and protein, in C2C12 muscle cells.

Conclusions/Significance

We have developed a cell-based, high-throughput screening utrophin promoter assay. Using this assay, we identified and validated a utrophin promoter-activating drug, nabumetone, for which pharmacokinetics and safety in humans are already well described, and which represents a lead compound for utrophin upregulation as a therapy for DMD.     

Duchenne muscular dystrophy.

Progress in understanding the role of dystrophin raises promising hopes for a treatment for Duchenne muscular dystrophy. In addition, great improvements have been made in the ability to diagnose this disease using simple molecular methods.     

Duchenne muscular dystrophy

Summary By a general survey in the hospitals of northeast Italy, Duchenne cases have been located and identified over a 20-year period.In a more restricted area screening for Duchenne carriers has been carried out in affected families. This procedure made possible an exact estimate of the incidence rate, prevalence rate, and mutation rate in a large sample of population. Prevalence rate was found to be 34x10^-6, incidence rate about 28x10^-5, while mutation rate was found lower than 50x10^-6 by the direct method.The discrepancy between the results obtained by the Haldane formula and those obtained by the direct method for the estimate of the mutation rate is discussed.     

Duchenne muscular dystrophy

Summary In an extensive epidemiological survey of Duchenne muscular dystrophy carried out in Venetia (Italy) the incidence was found to be 28.2×10^-5 and female gamete mutation rate was estimated by the direct method between 61 and 35×10^-6. The percentage of isolated cases was 0.54. Indirect and direct estimates of this proportion suggest, however, that only a minor fraction arises from maternal mutation (from 0.11 to 0.18 of the total number of cases). Studies on pedigrees collected in the course of the survey indicate that there is a higher frequency of Duchenne carrier females than normal females in affected sibships. Additional evidence supporting the hypothesis of a reproductive heterozygote advantage and gametic selection is reported.This work was supported by an MDA grant and by funds from the Italian Muscular Dystrophy Assoc. (UILDM)     

Duchenne muscular dystrophy

Summary A segregation analysis on 135 Duchenne families from Venetia (Italy) suggests that the proportion of sporadic cases might be less than expected. Support for this view is also given by an analysis of a pooled sample including 284 additional sibships from comparable studies published previously. Several hypotheses were tested: the maximum likelihood was obtained for a segregation frequency p=0.46 and for a proportion of sporadic cases x=0.227±0.048.Dedicated to Professor G. Montalenti in the occasion of his 80th birthday     

Experience with screening newborns for Duchenne muscular dystrophy in Wales.

OBJECTIVES--To assess the acceptability of screening newborn boys for Duchenne muscular dystrophy. DESIGN--Screening is offered on the basis of informed consent in response to an information sheet entitled "A new test for baby boys--Do you want it?" The programme includes a prospective long term evaluation of family responses to early diagnosis and a comparison of their experiences and perceptions with those families who have undergone the later traditional clinical diagnosis. SETTING--All maternity units throughout Wales. Samples obtained through screening programme for phenylketonuria and congenital hypothyroidism. SUBJECTS--Those families whose son had a positive screening test. MAIN OUTCOME MEASURES--Creatine kinase activity. Venous blood test to confirm positive result. Molecular genetic mutation analysis. Muscle biopsy and dystrophin analysis. Qualitative measure of satisfaction among affected families. RESULTS--34,219 Boys have been screened and nine affected families have been identified. Eight families were very positive about the programme. Three chose not to complete the diagnostic process. CONCLUSION--The programme should continue to permit a full evaluation of the issues involved and should serve as a model for other initiatives within the community for genetic disease.     

Fluorescent multiplex linkage analysis and carrier detection for Duchenne/Becker muscular dystrophy.

We have developed a fast and accurate PCR-based linkage and carrier detection protocol for families of Duchenne muscular dystrophy (DMD)/Becker muscular dystrophy (BMD) patients with or without detectable deletions of the dystrophin gene, using fluorescent PCR products analyzed on an automated sequencer. When a deletion is found in the affected male DMD/BMD patient by standard multiplex PCR, fluorescently labeled primers specific for the deleted and nondeleted exon(s) are used to amplify the DNA of at-risk female relatives by using multiplex PCR at low cycle number (20 cycles). The products are then quantitatively analyzed on an automatic sequencer to determine whether they are heterozygous for the deletion and thus are carriers. As a confirmation of the deletion data, and in cases in which a deletion is not found in the proband, fluorescent multiplex PCR linkage is done by using four previously described polymorphic dinucleotide sequences. The four (CA)n repeats are located throughout the dystrophin gene, making the analysis highly informative and accurate. We present the successful application of this protocol in families who proved refractory to more traditional analyses.     

Deletion mutations in Duchenne muscular dystrophy (DMD) in Western Saudi children

Duchenne and Becker muscular dystrophy (DMD and BMD) are caused, in the majority of cases, by deletions in the dystrophin gene (DMD). The disease is an X-linked neuromuscular diseases typically caused by disrupting (DMD) or non-disrupting (BMD) the reading frame in the dystrophin (DMD) gene. In the present study, amplifications of the genomic DNAs of unrelated 15 Saudi DMD males were carried out using multiplex polymerase chain reaction (PCR) for nine-hotspot regions of exons 4, 8, 12, 17, 19, 44, 45, 48 and 51. We detected six Saudi patients having deletions in a frequency of 40%. The frequency of deletions in exon 51 (20%) was the most common deletion frequently associated with our Saudi sample males. Exons 19, 45, and 48 were present in a frequency of 6.7% each. All deletions were recognized as an individual exonic deletions, while no gross deletion where detected. Finally, the molecular deletions in the Saudi males was expected to be characterized by a moderate frequency among different populations due to the geographical KSA region, which it is in the crossroad of intense migrations and admixture of people coming from continental Asia, Africa, and even Europe. In conclusion, attempts to include an extra DNA samples might reflect a valid vision of the deletions within the high frequency deletion regions (HFDR’s) in the DMD gene mutations in KSA.     

Hypokalemia complicating Duchenne muscular dystrophy

Although patients with Duchenne muscular dystrophy (DMD) have been shown to have decreased total body potassium levels, serum potassium levels have generally been though to be within normal limits. We report two siblings with DMD noted to be hypokalemic in conjunction with a respiratory illness. Hypokalemia may have exacerbated the pre-existing pulmonary insufficiency in these patients. The literature concerning hypokalemia and DMD is reviewed, and recommendations for the closer monitoring of serum potassium levels in patients with DMD are presented.