Advances in the Pathogenic Research of Female Carriers with Symptomatic Duchenne Muscular Dystrophy / 现代生物医学进展

DMD/BMD is a X-linked recessive hereditary disease.It predominantly affects males.While female carriers do not have symptoms,due to their inactive X chromosome make it present mosaic.Recently,more and more papers reported that a clinically significant proportion of DMD/BMD female carriers have symptoms.They presented variable degrees of symptoms.But the mechanism of the pathogencity is still not clear.Most of the research considered that the dominating reason is the skewed X inactivation.It means that the predominant expression of the DMD mutant allele make the normal one have weak expression,thus no function dystrophin proteins could be generate,manifested as DMD/BMD.In this paper,we mainly summarized the relationship between skewed X inactivation and pathogenicity of the symptomatic DMD female carriers.

Clinical Usefulness of Molecular Diagnosis in Dystrophin Gene Mutations Using the Multiplex Ligation-dependent Probe Amplification (MLPA) Method

BACKGROUND: Duchenne/Becker muscular dystrophy (DMD/BMD), which is the most common X-linked muscular dystrophy, is caused by mutations in the dystrophin gene. These mutations comprise deletions in approximately 55~65% of patients, duplications in 5~10%, and point mutations or small insertion/deletions in the remainder. Unfortunately, current diagnostic assays for dystrophin do not accurately detect duplication mutations or female carriers. In this study we employed multiplex ligation-dependent probe amplification (MLPA) analysis to detect deletions or duplications of the dystrophin gene in patients with DMD/BMD, and in potential female carriers. METHODS: A total of 41 subjects was recruited for this study, comprising 35 male DMD/BMD patients, 1 female patient with Turner syndrome, and 5 females with a family history of DMD/BMD. The MLPA method was employed to determine the copy number of each of the 79 exons of the dystrophin gene in the 41 subjects. RESULTS: MLPA analysis for dystrophin was informative in 71.4% (25/35) of patients with DMD/BMD patients, identifying deletions in 60.0% (21/35) and duplications in 11.4% (4/35). MLPA analysis showed the presence of a deletion of the DMD gene in one female patient with Turner syndrome. Of the five female patients with a family history of DMD/BMD, this assay revealed exon deletion in one and duplications in one. CONCLUSIONS: The reported findings reveal that the MLPA method is a powerful tool for detecting duplications and female carriers, as well as DMD gene deletions. MLPA should be considered the method of choice for an initial genetic analysis of DMD/BMD patients.

Deletional mutations of dystrophin gene and carrier detection in eastern India.

Objective. To determine the pattern of deletions of the dystrophin gene, the major class of mutations among the Duchenne and Becker muscular dystrophy patients of eastern India and to analyze the carrier frequency of the female members of the proband’s family. Methods. Deletional mutations occurring in patients have been characterized by multiplex polymerase chain reaction. Carrier state of mothers and sisters of probands were analyzed by either of two methods: 1) typing polymorphic short tandem repeat markers in or around the regions of deletion, by radioactive polymerase chain reaction and 2) quantitative real time amplification of the region of deletion. Results. Deletions were detected in 67 (62.04%) out of 108 male patients, about 76.12% of these being localized in the central hot spot region of the gene, i.e., between exon 42 to exon 53 and 17.91% at the proximal hot spot i.e., between exon 1 to exon 20. In the present study were found 43 types of deletions, out of which 25 (58%) were new deletions, which were not described earlier among the Indian patients. Distribution pattern of deletions in different hot spot regions has been compared with that of other countries and statistical analysis reveals significant difference between countries (p<0.001). Correlation of the pattern of deletion with clinical phenotype of patients has been discussed. Interesting case of germline mosaicism and its implications in counseling has also been discussed. Conclusion. About half the mothers of affected probands were not carriers of the deletion, underscoring the need to use real time techniques for carrier detection.

Diagnosis of Duchenne/Becker Muscular Dystrophy: Clinical and Moleculargenetic Characteristics / 대한소아신경학회지

PURPOSE: Duchenne/Becker muscular dystrophy (DMD/BMD) is an X-linked recessive disease caused by the mutation of dystrophin gene. Since the majority of mutations are deletions, recent diagnosis is made by the moleculargenetic tools. The authors summarized the clinical characteristics, and analyzed the moleculargenetic and immunohistochemical characteristics of DMD/BMD. METHODS: We reviewed the clinical and laboratory findings of 69 patients diagnosed as DMD/BMD from 1989 to 2000. Multiplex PCR using 26 primer sets was performed on 34 cases, and immunohistochemical staining using dystrophin antibody was done on 5 cases. Mutation profile and phenotype-genotype relationship were analyzed. RESULTS: 1) Mean age of onset was 3 years and 6 months. The presenting symptoms were motor weakness of the lower extremities, incidentally found elevated hepatic enzyme level, abnormal gait and motor developmental delay. Forty one percent had history of motor developmental delay, and most patients showed pseudohypertrophic calf muscles. Mean serum creatine kinase level was 11,232IU/L, and 44% revealed abnormal electrocardiogram. 2) All of the 63 cases showed typical histological findings of muscular dystrophy. Of the 5 cases with immunohistochemical staining, 2 showed complete (DYS1, 2 and 3) and 3 showed partial (DYS3) absence pattern. 3) Of the 34 cases on which multiplex PCR was performed, 14 showed deletions, and 11 of them had deletions between exon 44 and 55. CONCLUSION: Since the deletions were detected in less than 50% of the patients with multiplex PCR, tools for dystrophin protein expression must be combined for the correct diagnosis. Considering the invasiveness of muscle biopsy, we conclude immunohistochemistry should be followed in the cases with negative results in multiplex PCR, although moleculargenetic study is the primary diagnostic tool.

Detection of Duchenne and Becker muscular dystrophy patients by DNA microarray / 临床神经病学杂志

Objective To explore the efficient method in detection of DMD/BMD patients.Methods 18 deletion-prone exon fragments of DMD gene were amplified via molecular cloning. They were used as probes and were spotted on the slides treated with APES and poly-lysine together by manual operation to make microarray. In addition, fragments of ?-actin were used as positive contrast and those of pUC 19/EcoR I were used as negative. 30 DMD/BMD patients were detected for deletion in DMD gene with the microarray and 5 healthy people were done as normal control. Parts of the results were compared with PCR method.Results Different exon fragment deletion of DMD/BMD gene was detected in 21 patients by DNA microarray, and 10 of them were confirmed by PCR analysis.Conclusion DNA microarray assay is a convenient ,accurate and sensitive method in diagnosis of DMD/BMD patient.