MLPA Application in Clinical Diagnosis of DMD/BMD in Shanghai

The Approach to a Child with Dysmorphic Features: What the Pediatrician Should Know

The advancement of genetic knowledge and the discovery of an increasing number of genetic disorders has made the role of the geneticist progressively more complex and fundamental. However, most genetic disorders present during childhood; thus, their early recognition is a challenge for the pediatrician, who will be also involved in the follow-up of these children, often establishing a close relationship with them and their families and becoming a referral figure. In this review, we aim to provide the pediatrician with a general knowledge of the approach to treating a child with a genetic syndrome associated with dysmorphic features. We will discuss the red flags, the most common manifestations, the analytic collection of the family and personal medical history, and the signs that should alert the pediatrician during the physical examination. We will offer an overview of the physical malformations most commonly associated with genetic defects and the way to describe dysmorphic facial features. We will provide hints about some tools that can support the pediatrician in clinical practice and that also represent a useful educational resource, either online or through apps downloaded on a smartphone. Eventually, we will offer an overview of genetic testing, the ethical considerations, the consequences of incidental findings, and the main indications and limitations of the principal technologies.

Mutation spectrum analysis of DMD gene in Indonesian Duchenne and Becker muscular dystrophy patients

Background

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are allelic disorders caused by mutations in the DMD gene. The full mutation spectrum of the DMD gene in Indonesian patients is currently unknown. Mutation-specific therapies are currently being developed, such as exon skipping or stop codon read-through therapy. This study was conducted with the aim of identifying the mutation spectrum of the DMD gene in Indonesia to guide future development and application of feasible therapeutic strategies.

Methods

This study is a cross sectional study that enrolled 43 male patients with a clinical suspicion of DMD or BMD. Multiplex ligation-dependent probe amplification (MLPA) reaction was performed to screen for the common mutations in the DMD gene.

Results

Out of 43 subjects, deletions accounted for 69.77% (n=30) cases, while duplications were found in 11.63% (n=5) cases. One novel duplication spanning exons 2 to 62 was identified. Deletion mutations clustered around the distal (66.67%) and proximal (26.67%) hot spot regions of the DMD gene while duplication mutations were observed solely at the proximal region. Two false positive cases of single exon deletion detected through MLPA were attributed to sequence mutations affecting primer ligation sites, confirming the need to validate all single exon deletions when using this screening method. Analysis of available maternal DNA samples showed that the rate of de novo mutations (48.15%) appears higher than expected in this population. Out of 31 patients who were classified as DMD based on clinical and genotype characterizations, 60.47% (n=26) of cases were suitable for exon skipping therapy.

Conclusion

This is the first comprehensive study showing the feasibility of implementing the MLPA method for routine screening of DMD patients in Indonesia. This is also the first study showing the potential applicability of exon skipping therapy in the majority of DMD cases in the country.

Embryo-Engineered Nonhuman Primate Models: Progress and Gap to Translational Medicine

Animal models of human diseases are vital in better understanding the mechanism of pathogenesis and essential for evaluating and validating potential therapeutic interventions. As close relatives of humans, nonhuman primates (NHPs) play an increasingly indispensable role in advancing translational medicine research. In this review, we summarized the progress of NHP models generated by embryo engineering, analyzed their unique advantages in mimicking clinical patients, and discussed the remaining gap between basic research of NHP models to translational medicine.

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.

An anti-ADAMTS1 treatment relieved muscle dysfunction and fibrosis in dystrophic mice

Duchenne Muscular Dystrophy (DMD) is caused by mutations in the dystrophin gene, accompanied by aberrant extracellular matrix synthesis and muscle damage. ADAMTS1 metalloproteinase was reported increased in dystrophin-deficient mdx mouse. The aim of this study was to explore the role of ADAMTS1 in muscle function, fibrosis and damage, and respiratory function of mdx mice. 102 DMD patients and their mothers were included in this study. Multiplex ligation dependent probe amplification (MLPA) assay and Next-generation sequencing (NGS) were adopted to do genetic diagnosis. Dystrophin-deficient mdx mice were treated with anti-ADAMTS1 antibody (anti-ADAMTS1) for three weeks. The results showed that ADAMTS1 was increased in gastrocnemius muscle of mdx mice and serum of DMD patients. Anti-ADAMTS1 treatment increased Versican transcription but suppressed versican protein expression. Besides, we found anti-ADAMTS1 improved muscle strength, diaphragm and extensor digitorum longus muscles functions in mdx mice. Meanwhile, muscle fibrosis and damage were attenuated in anti-ADAMTS1 treated dystrophic mice. In summary, anti-ADAMTS1 antibody relieved muscle dysfunction and fibrosis in dystrophic mice. It is suggested that ADAMTS1 is a potential target for developing new biological therapies for DMD.

[A predictive analysis of the association between clinical phenotypes and genotypes in children with Becker muscular dystrophy/Duchenne muscular dystrophy]

OBJECTIVE

To study the association between clinical phenotypes and genotypes in children with Becker muscular dystrophy (BMD)/Duchenne muscular dystrophy (DMD) so as to provide a theoretical basis for disease management, gene therapy, and prenatal diagnosis.

METHODS

A retrospective analysis was performed for the clinical data and gene detection results of 52 children with BMD/DMD. Multiplex ligation-dependent probe amplification (MLPA) was used to detect the DMD gene. The children with negative results of MLPA were further screened by exon chip capture combined with next-generation sequencing (NGS). The mothers of 20 probands were validated by sequencing.

RESULTS

The pathogenic genes for BMD/DMD were detected in 50 children by MLPA and NGS, with a detection rate of 96%. Among the 52 children, 36 (69%) had gene deletion, 7 (13%) had duplication, and 7 (13%) had micromutation. Among the 43 children with deletion/duplication, 32 had DMD and 11 had BMD; 37 children (86%) met the reading frame rule, among whom 27 (96%) had DMD and 10 (67%) had BMD. All 7 children with micromutation had DMD.

CONCLUSIONS

The reading frame rule has an extremely high predictive value for DMD but a limited predictive value for BMD.

Molecular Analysis-Based Genetic Characterization of a Cohort of Patients with Duchenne and Becker Muscular Dystrophy in Eastern China

Background:

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are common X-linked recessive neuromuscular disorders caused by mutations in dystrophin gene. Multiplex polymerase chain reaction (multiplex PCR) and multiplex ligation-dependent probe amplification (MLPA) are the most common methods for detecting dystrophin gene mutations. This study aimed to contrast the two methods and discern the genetic characterization of patients with DMD/BMD in Eastern China.

Methods:

We collected 121 probands, 64 mothers of probands, and 15 fetuses in our study. The dystrophin gene was detected by multiplex PCR primarily in 28 probands, and MLPA was used in multiplex PCR-negative cases subsequently. The dystrophin gene of the remaining 93 probands and 62 female potential carriers was tested by MLPA directly. In fetuses, multiplex PCR and MLPA were performed on 4 fetuses and 10 fetuses, respectively. In addition, sequencing was also performed in 4 probands with negative MLPA.

Results:

We found that 61.98% of the subjects had genetic mutations including deletions (50.41%) and duplications (11.57%). There were 43.75% of mothers as carriers of the mutation. In 15 fetuses, 2 out of 7 male fetuses were found to be unhealthy and 2 out of 8 female fetuses were found to be carriers. Exons 3–26 and 45–52 have the maximum frequency in mutation regions. In the frequency of exons individually, exon 47 and exon 50 were the most common in deleted regions and exons 5, 6, and 7 were found most frequently in duplicated regions.

Conclusions:

MLPA has better productivity and sensitivity than multiplex PCR. Prenatal diagnosis should be applied in DMD high-risk fetuses to reduce the disease incidence. Furthermore, it is the responsibility of physicians to inform female carriers the importance of prenatal diagnosis.

Novel noncontiguous duplications identified with a comprehensive mutation analysis in the DMD gene by DMD gene-targeted sequencing

Genomic rearrangements, such as intragenic deletions and duplications, are the most prevalent types of mutation in the DMD gene, and DMD mutations underlie Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). Using multiplex ligation dependent probe amplification (MLPA) and DMD gene-targeted sequencing, we performed a molecular characterization of two cases of complex noncontiguous duplication rearrangements that involved inverted duplications. The breakpoint sequences were analyzed to investigate the mechanisms of the rearrangement. The two cases shared the same duplication events (Dup-nml-Dup/inv), and both involved microhomology and small insertions at the breakpoints. Additionally, in case 1, SNP sequencing results indicated that the de novo duplication mutation arose in the allele that originated from the grandfather. This study has identified a novel type of DMD complex rearrangement and provides insight into the molecular basis of this genomic rearrangement.

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.

Distribution of dystrophin gene deletions in a Chinese population

Objective

To describe the deletion patterns and distribution characteristics of the dystrophin gene in a Chinese population of patients with Duchenne muscular dystrophy (DMD) or Becker muscular dystrophy (BMD).

Methods

Patients with DMD/BMD were recruited. Deletions in 19 exons of the dystrophin gene were evaluated using accurate multiplex polymerase chain reaction (PCR).

Result

Multiplex PCR identified deletions in 238/401 (59.4%) patients with DMD/BMD. Of these, 196 (82.4%) were in the distal hotspot, 32 (13.4%) were in the proximal hotspot, five (2.1%) were in both regions and five (2.1%) were in neither hotspot. Deletions were classified into 54 patterns. Exon 49 was the most frequently deleted. The reading frame rule was upheld for 91.9% of cases.

Conclusion

Accurate multiplex PCR for 19 exons is an effective diagnostic tool.