Small mutations in Duchenne/Becker muscular dystrophy in 164 unrelated Polish patients.

In the 164 patients with Duchenne/Becker muscular dystrophy, we found 142 different small mutations including 51 novel mutations not listed in the LOVD, the UMD-DMD, the ClinVar, and the HGMD databases. Among all mutations, nonsense mutations occurred in 45.7%, frameshift mutations in 32.9%, and splicing mutations in 19.5%. Small mutations were distributed throughout the whole dystrophin gene. Splicing mutations were twice more common in BMD patients than in DMD patients. Eighty-two percent of mothers of the males affected with DMD/BMD were found to be carriers of small mutations.

Deletions, not duplications or small mutations, are the predominante new mutations in the dystrophin gene.

Examination of the carrier state was performed in 744 unrelated mothers of the Duchenne muscular dystrophy/Becker muscular dystrophy (DMD/BMD) probands with identified mutations in the dystrophin gene. Owing to that it was possible to assess frequency and type of new mutations in the gene. Contrary to the Japanese observations of Lee et al. published in this journal, we did not find significant differences in the carrier frequency between mothers of DMD and BMD patients. However, we found that new mutations in patients with deletions were significantly more frequent than in those with duplications and small mutations: of 564 unrelated patients with deletions, 236 (41.8%) carried new mutations, the respective values for duplications and small mutations were 21 of 95 patients (22.1%) and 18 of 85 patients (21.2%)-the differences highly significant (P<0.0001).

A rare subclinical or mild type of Becker muscular dystrophy caused by a single exon 48 deletion of the dystrophin gene.

In the material of 227 families with Becker muscular dystrophy (BMD), we found nine non-consanguineous families with 17 male individuals carrying a rare mutation-a single exon 48 deletion of the dystrophin gene-who were affected with a very mild or subclinical form of BMD. They were usually detected thanks to accidental findings of elevated serum creatine phosphokinase (sCPK). A thorough clinical analysis of the carriers, both children (12) and adults (5), revealed in some of them muscle hypotonia (10/17) and/or very mild muscle weakness (9/17), as well as decreased tendon reflexes (6/17). Adults, apart from very mild muscle weakness and calf hypertrophy in some, had no significant abnormalities on neurological assessments and had good exercise tolerance. Parents of the children carriers of the exon 48 deletion are usually unaware of their children being affected, and possibly at risk of developing life-threatening cardiomyopathy. The same concerns the adult male carriers. Therefore, the authors postulate undertaking preventive measures such as cascade screening of the relatives of the probands. Newborn screening programmes of Duchenne muscular dystrophy (DMD)/BMD based on sCPK marked increase may be considered.

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.

Novel point mutations in survival motor neuron 1 gene expand the spectrum of phenotypes observed in spinal muscular atrophy patients.

The aim of our study was to identify point mutations in a group of 606 patients diagnosed for spinal muscular atrophy with excluded biallelic loss of the SMN1 gene. Point missense mutations or small deletions in the SMN1 gene were ultimately identified in 18 patients. Six patients were found to have small deletions, the c.429_435del mutation in 3 cases, the c.431delC mutation in 2 and c.722delC in one. Those mutations, not described previously, were characteristic of patients presenting a severe phenotype. The most frequent missense mutation - p.Thr274Ile, was identified in 9 patients presenting a rather mild phenotype. Three other missense mutations, i.e., p.Ser230Leu, p.Ala111Gly and p.Pro244Leu, were identified in a further 3 SMA3 patients. Mutation p.Pro244Leu, not described so far, was identified in a patient with a mild form of SMA and more distal distribution of muscle weakness. Our results suggest a specific point mutation spectrum in the Polish population. The existence of small deletions not identified thus far could suggest a possible founder effect. In patients with preserved one SMN1 allele without common exon 7 deletion, presenting a mild form of SMA, a special consideration should be given to the p.Thr274Ile mutation.

[Non-invasive prenatal diagnosis of the most common aneuploidies with cell-free fetal DNA in maternal serum--preliminary results]. / Nieinwazyjna diagnostyka prenatalna najczestszych aneuploidii na podstawie plodowego DNA we krwi matki --doniesienie wstepne.

OBJECTIVES: The aim of the study was to present initial results of non-invasive prenatal diagnosis of common aneuploidies of chromosomes 21, 18 and 13 based on cell-free fetal DNA in maternal serum in high-risk patients, and to compare the results with routine karyotyping. MATERIAL AND METHODS: Before the invasive procedure, 10 ml of peripheral blood from 10 patients was collected to isolate cell-free fetal DNA and to perform a non-invasive fetal trisomy test (NIFTY provided by Beijing Genomics Institute, BGI, Shenzen, China). RESULTS: Three out of 10 samples showed an abnormal karyotype in traditional karyotyping. There were 9 conclusive NIFTY results. NIFTY detected 1 out of 2 trisomies 18. The quantity of cell-free fetal DNA in maternal plasma in the second probe with trisomy 18 was unsatisfactory fora conclusive NIFTY result. In 1 case traditional karyotyping revealed mosaicism impossible to detect with NIFTY

[Noninvasive prenatal diagnosis of trisomy 21, 18 and 13 using cell-free fetal DNA]. / Nieinwazyjna diagnostyka prenatalna trisomii 21,18 i 13 z wykorzystaniem wolnego pozakomórkowego DNA plodu.

Trisomy 21, 18 and 13 are the most common trisomies diagnosed in newborns. Screening methods consist of ultrasound and maternal serum markers. High risk for fetal aneuploidies is an indication for routine karyotyping, which requires collection of fetal tissue through amniocentesis or chorionic villous sampling. They are invasive procedures and carry a potential risk of miscarriage. The discovery of cell free fetal DNA (cffDNA) in maternal blood offered new opportunities for noninvasive prenatal diagnosis. The fraction of cell-free fetal DNA in total pool of cell-free DNA in maternal plasma is very low, therefore the analysis of cffDNA is very challenging. The introduction of massive parallel sequencing has enabled the application of noninvasive prenatal testing in the clinical practice and a variety of recent studies have proven its high efficacy in diagnosing common aneuploidies.

Multiplex ligation-dependent probe amplification (MLPA)--new possibilities of prenatal diagnosis.

Multiplex Ligation-dependent Probe Amplification (MLPA) is a relatively new method of molecular diagnosis. It enables a relative quantitative assessment of up to 50 different PCR amplicons in one reaction by the use of a very small amount of examined DNA. Nowadays MLPA is becoming a very helpful tool in prenatal diagnosis and is widely used for the detection of aneuploidies, familial single gene disorders, common microdeletion syndromes, sub-telomeric alterations and identification of marker chromosomes in fetuses. This review demonstrates possible applications of MLPA in prenatal diagnosis.

[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.

[The use of non-typical materials as a source of DNA in post-mortem diagnosis of spinal muscular atrophy]. / Zastosowanie nietypowego zródla DNA w posmiertnej diagnostyce radzeniowego zaniku miesni.

BACKGROUND AND PURPOSE: Patients affected with SMA I usually die in early childhood before the end of the second year of life. Clinical diagnosis is often doubtful--without any molecular verification--and isolated DNA is not available. In such cases predicting the outcome of consecutive pregnancies is not possible. It appears, however, that the families often keep some relics of the diseased child, such as milk teeth, and pieces of umbilical cord; a dried drop of blood used for the Guthrie test in newborn screening may be available. The aim of this study was the post mortem molecular diagnosis of SMA based on samples of DNA isolated from such remnants. MATERIAL AND METHODS: PCR technique was applied to amplify exons 7 and 8 of SMN gene; DraI and DdeI restriction enzymes were used to distinguish SMN1/SMN2 genes. RESULTS: The deletion of the SMN gene was found using DNA isolated from (1) a blot of dried blood, (2) a milk tooth and (3) dried umbilical cord of children who died several years ago without the molecular verification of the suspected SMA. In one case the analysis of DNA obtained from umbilical cord did not confirm the diagnosis of SMA. CONCLUSIONS: Our results showed that biological materials such as those mentioned above may be kept for a long period of time without degradation of DNA, which is still satisfactory for molecular diagnosis of SMA. This is very important for genetic counseling and offering a prenatal test to the families concerned.