Mapping dystrophin gene recombinants in Greek DMD/BMD families: low recombination frequencies in the STR region

DMD/BMD prenatal diagnosis and treatment expectation in a single centre in China for 15 years

Objective

DMD/BMD prenatal diagnosis for 931 foetuses.

Background

DMD is the most common fatal X-linked recessive muscular disease. There is no effective clinical treatment method at present. Accurate gene diagnosis and prenatal diagnosis technology are important ways for early detection, early prevention and early treatment.

Methods

A total of 931 prenatal diagnoses were performed for pregnant women with a definite family history of DMD or a history of DMD childbirth between 2005 and 2019. This report may be considered the largest DMD prenatal diagnosis report in a single centre worldwide. Multiple ligation-dependent probe amplification (MLPA) and next-generation sequencing were used in combination. Techniques and short tandem repeat (STR) linkage analysis were used to determine the location of the DMD gene mutation in the pregnant woman and then to detect the DMD gene in the foetuses.

Results

There were 872 families in our study. Among all 931 foetuses, 20.73% (193/931) were males expected to develop DMD and 16.33% (152/931) were female carriers. In addition, gonadal mosaicism was observed in 5 mothers, and gene recombination was identified in three foetuses. The results of the prenatal diagnosis were consistent with the results of the CPK analysis, and the results of the prenatal diagnosis were 100% accurate.

Conclusions

MLPA and Sanger sequencing, when combined with STR linkage analyses, can provide an accurate and rapid prenatal diagnosis. Due to the high de novo rate, prenatal diagnosis and genetic counselling should be given great attention.

Prenatal diagnosis of Duchenne muscular dystrophy in 131 Chinese families with dystrophinopathy

OBJECTIVES

The objective of this study is to report 6-year clinical prenatal diagnosis experience of Duchenne muscular dystrophy (DMD)-affected families evaluated at a single prenatal diagnosis center in China and establish a reliable and rational prenatal diagnosis procedure for DMD families.

METHODS

The prenatal diagnosis data of 146 at-risk pregnancies in 131 DMD families referred to our center from 2010 to 2016 were retrospectively reviewed.

RESULTS

The mutation detection rate of the probands was greater than 99%. In the 131 families, 50 mothers showed negative results during carrier testing, and de novo exon deletions arose in 51.1% of the probands. Of the 146 pregnancies, 91 were male fetuses, 34 of which were affected. Germline mosaicism was identified three times in this cohort, and recombination of the DMD gene was detected in nine cases.

CONCLUSIONS

Accurate genetic diagnosis of the proband is important for preventing recurrence in at-risk families. The present results demonstrate the importance of considering maternal germline mosaicism in the genetic assessment. Prenatal diagnosis should be suggested to the parent with a DMD proband whether carrier testing found the causative mutation in the mother's blood or not. Finally, we have developed a prenatal diagnosis algorithm for dystrophinopathies that combines multiplex ligation-dependent probe amplification, quantitative PCR, sequencing and linkage analyses. © 2017 John Wiley & Sons, Ltd.

Rapid method for targeted prenatal diagnosis of Duchenne muscular dystrophy in Vietnam

OBJECTIVE

Since there is no effective curative treatment for Duchenne muscular dystrophy (DMD), prevention mostly depends on genetic counseling and prenatal diagnosis. About two-thirds of the affected patients have large deletions or duplications, which can be detected by multiplex ligation-dependent amplification (MLPA). The remaining cases include small mutations, which cannot be easily identified by routine techniques. In such cases, linkage analysis may be a useful tool for prenatal diagnosis. Here we compared results obtained from linkage using short tandem repeats (STRs) with those by MLPA and sequencing analysis.

MATERIALS AND METHODS

Eight Vietnamese pregnant women at risk of having a baby with DMD and requesting prenatal diagnosis were recruited in this study. MLPA and direct sequencing were applied to screen large rearrangements and point mutations in the dystrophin gene in the DMD probands and the fetal samples. STR linkage was also performed to analyze fetal mutation status.

RESULTS

By MLPA and sequencing analysis, five DMD patients showed deletions of the dystrophin gene, and no deletions of exons were detected in seven amniotic fluid cell samples; one patient harbored the out-of-frame small deletion of exon 43, which was also found in the fetal sample of this family. STR analysis revealed the transmission of a mutant allele inside each family.

CONCLUSION

Our results suggest that the combination of STR and MLPA could be a rapid, reliable, and affordable detection protocol for determination of the carrier's status and prenatal diagnosis of DMD in a developing country such as Vietnam.

A larger spectrum of intragenic short tandem repeats improves linkage analysis and localization of intragenic recombination detection in the dystrophin gene: an analysis of 93 families from southern Italy

Duchenne/Becker muscular dystrophies (D/BMD) are X-linked recessive disorders resulting from dystrophin gene mutations. Intragenic recombination in the dystrophin gene occurs with a high frequency. Therefore, determination of the location and frequency of recombination improves D/BMD carrier detection and prenatal diagnosis in families in which the disease-causing mutation cannot be detected by most conventional methods. We describe herein a linkage analysis performed using a fast method based on capillary gel electrophoresis of fluorescent-labeled amplified alleles of 15 intragenic short tandem repeats spanning the entire dystrophin gene. On characterization of recombination events in 93 unrelated D/BMD families from southern Italy, we mapped 25 intragenic recombinations out of 273 informative meioses analyzed. The terminal regions of a gene are notoriously challenging for linkage analysis because some recombination events could be missed in case of lack of informativeness of the outermost markers. Many recombination events (10/25) identified in this study were located at the terminal regions of the dystrophin gene, and some were found by typing of several informative short tandem repeats located in these regions. Moreover, about 24% of the recombination events found in this study mapped to the 3' region of the gene, in contrast with the low frequency (4 to 15%) reported by others.