MLPA based detection of mutations in the dystrophin gene of 180 Polish families with Duchenne/Becker muscular dystrophy.

Duchenne/Becker muscular dystrophy (DMD/BMD) is a recessive, X-linked disorder caused by a mutation in the dystrophin gene. Deletions account for approximately 60-65% of mutations, duplications for 5-10%. The remaining cases are mainly point mutations. According to Monaco theory clinical form of the disease depends on maintaining or disrupting the reading frame. The purpose of the study was to determine frequency and location of deletions and duplications in the dystrophin gene, to determine the compliance between maintaining/disrupting the reading frame and clinical form of the disease and to check the effectiveness of MLPA (multiplex ligation-dependent probe amplification) in the detection of these mutations in hemizygous patients and heterozygous female carriers. The material is composed of combined results of molecular diagnosis carried out in years 2009-2012 in 180 unrelated patients referred with the diagnosis of DMD/BMD tested by use of MLPA. We identified 110 deletions, 22 duplication (in one patient two different duplications were detected) and 2 point mutations. Deletions involved mainly exons 45-54 and 3-21, whereas most duplications involved exons 3-18. The compliance with Monaco theory was 95% for deletions and 76% for duplications. Most of mutations in the dystrophin gene were localized in the hot spots - different for deletions and duplications. MLPA enabled their quick identification, exact localization and determination whether or not they maintained or disrupted the reading frame. MLPA was also effective in detection of deletions and duplications in female carriers.

Two mutations in one dystrophin gene.

BACKGROUND AND PURPOSE: Duchenne/Becker muscular dystrophies (DMD/BMD) lead to progressive irreversible muscle deterioration caused by recessive mutations in the dystrophin encoding gene (Xp21.1). Approximately 60% of mutations are deletions, 10% are duplications and the remaining 30% are point mutations. The aim of the study is to present the rare occurrence of two pathogenic mutations (deletions or duplications) in one allele of the dystrophin gene. MATERIAL AND METHODS: DNA of patients from 1364 DMD/ BMD families was tested. Two techniques - PCR-multiplex and multiplex ligation-dependent probe amplification - were used to search for mutations in the dystrophin gene. RESULTS: Deletion was detected in 648 families and duplication was found in 74 families (analysis in progress). In two families, presence of two mutations in one gene was documented - in the first family two deletions were found (exons 45-49 and 60-61), and in the second family two duplications were detected (exons 2-7 and 50-59). One of the deletions disrupted the reading frame, and the other deletion retained the reading frame. Both duplications also retained the reading frame of the gene but in both families the disease took a severe course (DMD). In the family with two duplications prenatal diagnosis was also carried out, and carriership of both mutations was discovered in the female fetus. CONCLUSIONS: In the analyzed group of DMD/BMD families, the frequency of combined occurrence of two mutations in one gene was 2 per 722 (0.3%). The phenomenon of detected non-contiguous deletions and duplications is presented together with 31 similar cases published so far.

[Detection of rare mutations in the dystrophin gene]. / Wykrywanie rzadkich mutacji w genie dystrofiny.

INTRODUCTION: Duchenne/Becker muscular dystrophies (DMD/BMD) are allelic X-linked, recessive proximal muscle disorders, caused by mutations in the dystrophin gene located in Xp21. DMD occurs with the incidence 1:3500, BMD with the incidence of 1:18,500 new-born males. Approximately about 60% of mutations in the dystrophin gene are deletions, 10%--duplications and 30%--point mutations. AIM: The aim of the study was detection of the mutations: rare deletions, duplications and point mutations in the dystrophin gene in patients diagnosed as DMD/BMD in whom the presence of the most common deletions had previously been excluded. MATERIALS AND METHODS: Molecular analysis was performed using DNA samples isolated from 105 DMD and 10 BMD patients. Detection of rare deletions and duplications was carried out by Multiplex Ligation-dependent Probe Amplification (MLPA). Point mutations were identified by analysis of single strand conformation polymorphism (SSCP) and DNA sequencing. RESULTS: 38 Different mutations were detected: 10 rare deletions, 14 duplications and 14 point mutations and microdeletions. Majority of the detected rare deletions (7 out of 10) and point mutations (11 out of 14) are novel mutations. CONCLUSIONS: Application of MLPA technique allows the detection of small, rare deletions and duplications. Identification of the nature and localization of the mutations may, in the future, help to apply appropriate therapeutic approaches in DMD patients.

[Carrier detection in Duchenne/Becker muscular dystrophy in the families in which the DNA of the affected person is not available]. / Badanie nosicielstwa dystrofii miesniowej Duchenne'a/Beckera przy braku DNA osoby chorej.

INTRODUCTION: Duchenne muscular dystrophy (DMD) is a severe, progressive, X-linked muscular disease, which affects 1 in 3500 male newborns. The course of the other allelic form of the disease (Becker muscular dystrophy--BMD) is milder. Female relatives of affected subjects may carry the mutated gene. AIM OF THE STUDY: The purpose of this study was to detect the carrier among 23 families affected with DMD/BMD, in whom DNA from the deceased affected person was not available. MATERIAL AND METHODS: The analysis of polymorphic sequences within the dystrophin gene was applied. RESULTS: Informative results were obtained in 26 of 39 females examined (66%): 7 females were found to be carriers and 19 noncarriers. In one family the deletion could be detected in the mother and sister of the deceased proband.