Yun Yang

Targeted next-generation sequencing as a comprehensive test for patients with and female carriers of DMD/BMD: a multi-population diagnostic study

Duchenne and Becker muscular dystrophies (DMD/BMD) are the most commonly inherited neuromuscular disease. However, accurate and convenient molecular diagnosis cannot be achieved easily because of the enormous size of the dystrophin gene and complex causative mutation spectrum. Such traditional methods as multiplex ligation-dependent probe amplification plus Sanger sequencing require multiple steps to fulfill the diagnosis of DMD/BMD. Here, we introduce a new single-step method for the genetic analysis of DMD patients and female carriers in real clinical settings and demonstrate the validation of its accuracy. A total of 89 patients, 18 female carriers and 245 non-DMD patients were evaluated using our targeted NGS approaches. Compared with traditional methods, our new method yielded 99.99% specificity and 98.96% sensitivity for copy number variations detection and 100% accuracy for the identification of single-nucleotide variation mutations. Additionally, this method is able to detect partial deletions/duplications, thus offering precise personal DMD gene information for gene therapy. We detected novel partial deletions of exons in nine samples for which the breakpoints were located within exonic regions. The results proved that our new method is suitable for routine clinical practice, with shorter turnaround time, higher accuracy, and better insight into comprehensive genetic information (detailed breakpoints) for ensuing gene therapy.

A comprehensive genetic diagnosis of Chinese muscular dystrophy and congenital myopathy patients by targeted next-generation sequencing.

Muscular dystrophies and congenital myopathies are a large group of heterogeneous inherited muscle disorders. The spectrum of muscular dystrophies and congenital myopathies extends to more than 50 diseases today, even excluding the common forms Duchenne Muscular Dystrophy, Myotonic Dystrophy and Facioscapulohumeral Dystrophy. Unfortunately, even by critical clinical evaluation and muscle pathology, diagnosis is still difficult. To potentially remediate this difficulty, we applied a microarray-based targeted next-generation sequencing (NGS) technology to diagnose these patients. There were 55 consecutive unrelated patients who underwent the test, 36 of which (65%) were found to have a causative mutation. Our result shows the accuracy and efficiency of next-generation sequencing in clinical circumstances and reflects the features and relative distribution of inherited myopathies in the Chinese population.

Analysis of a Chinese pedigree with Zellweger syndrome reveals a novel PEX1 mutation by next-generation sequencing.

BACKGROUNDnAutosomal recessive Zellweger spectrum disorder (ZSD), the main subgroup of the peroxisome biogenesis disorders (PBDs), can be caused by mutations in any of the 13 PEX genes. Zellweger syndrome (ZS) is the most common and severe phenotype in the heterogeneous ZSD. For the large number genes involved, it is difficult to make a precise genetic diagnosis by traditional methods at a time. A combination of enrichment of targeted genes and next-generation sequencing (NGS) would result in both high efficiency and low cost for targeted sequencing of genes of interest.nnnMETHODSnTo identify potential mutations in a Chinese family associated with Zellweger syndrome, 1930kb of all the targeted region of PEX genes were captured and sequenced using NGS. We also performed Sanger sequencing to validate the NGS results.nnnRESULTSnHere, we reported a Chinese patient diagnosed as a severe classic type of PBD based on a clinical investigation. We then performed microarray-based NGS to detect the variants in PEX genes of the whole family. One reported heterozygosis mutation (c.782_783delAA) was identified in the patients father and one novel heterozygosis missense mutation (c.475G>C) was found in the patients mother, the patient inherited both mutations.nnnCONCLUSIONSnThe results proved that the application of target sequence capture using chip and high-throughput NGS is a valuable tool for the molecular diagnosis of peroxisome biogenesis disorders. The accuracy, high-throughput and speed of the method make it suitable for clinical application.

Targeted Next-Generation Sequencing for Clinical Diagnosis of 561 Mendelian Diseases

Background Targeted next-generation sequencing (NGS) is a cost-effective approach for rapid and accurate detection of genetic mutations in patients with suspected genetic disorders, which can facilitate effective diagnosis. Methodology/Principal Findings We designed a capture array to mainly capture all the coding sequence (CDS) of 2,181 genes associated with 561 Mendelian diseases and conducted NGS to detect mutations. The accuracy of NGS was 99.95%, which was obtained by comparing the genotypes of selected loci between our method and SNP Array in four samples from normal human adults. We also tested the stability of the method using a sample from normal human adults. The results showed that an average of 97.79% and 96.72% of single-nucleotide variants (SNVs) in the sample could be detected stably in a batch and different batches respectively. In addition, the method could detect various types of mutations. Some disease-causing mutations were detected in 69 clinical cases, including 62 SNVs, 14 insertions and deletions (Indels), 1 copy number variant (CNV), 1 microdeletion and 2 microduplications of chromosomes, of which 35 mutations were novel. Mutations were confirmed by Sanger sequencing or real-time polymerase chain reaction (PCR). Conclusions/Significance Results of the evaluation showed that targeted NGS enabled to detect disease-causing mutations with high accuracy, stability, speed and throughput. Thus, the technology can be used for the clinical diagnosis of 561 Mendelian diseases.

Two Novel Mutations in the C-Terminal Region of Centrosomal Protein 290 (CEP290) Result in Classic Joubert Syndrome

Joubert syndrome is a neurologic disorder with a pathognomonic “molar tooth sign” on brain imaging. The purpose of this study was to identify potential mutations in a Chinese patient with Joubert syndrome by targeted massively parallel sequencing. Taking advantage of high-throughput DNA sequencing technologies, 18 Joubert-causing genes of a Chinese patient with classic Joubert syndrome were sequenced at a time, and 2 novel variants in the CEP290 gene (c.7323_7327delAGAAG and c.6012-2A>G) were identified in this patient. Sanger validation showed that 2 variants were inherited from each parents, respectively. Both variants are located in the C-terminal region of the CEP290 protein and are predicted to be deleterious. The results support that the combination of targeted genes enrichment and next-generation sequencing is valuable molecular diagnostic tool and suitable for clinical application.

Characterization of genomic clones using circulating tumor DNA in patients with hepatocarcinoma

Background: Hepatocarcinoma (HCC) is often diagnosed at an advanced stage with poor prognosis. A non-invasive method concerning circulating tumor DNA (ctDNA) has been recognized as a promising biomarker. ctDNA has been widely studied to monitor tumor dynamics and measure tumor burden. However, the results of previous studies for biomarkers for HCC have generally been inconsistent and limited in clinical application. n Methods: HCC usually represent a mixture of different cancer cell clones differing in mutation content, which can be used to monitor important features such as treatment responses. In this study, we used Bayesian cluster with PyClone to identify clonal population structures based on variations from ctDNA of a 4 HCC patients dataset. n Results: As a result, reductions in cellular prevalences of private mutation clusters were observed between preoperative and postoperative plasma samples, which reflected the treatment responses of surgery. We also identified expansion and sharing sub-clonality of initially minor clones in plasma samples after treatment, and located clusters in patients which might be used as actionable targets. n Conclusions: These results provided a more complete picture of the liver cancer pathogenesis. The comparison of preoperative and postoperative plasma samples showed that ctDNA can be used to real-time sampling of clonal evolution in patients with hepatocarcinoma. In addition to dynamic monitoring of disease progression and response to therapy, characterizing of dynamics of genomic clones can be used to determine the benefit of new therapeutics and guide therapy.

Targeted next-generation sequencing as a comprehensive test for Mendelian diseases: a cohort diagnostic study

With the development of next generation sequencing, more and more common inherited diseases have been reported. However, accurate and convenient molecular diagnosis cannot be achieved easily because of the enormous size of disease causing mutations. In this study, we introduced a new single-step method for the genetic analysis of patients and carriers in real clinical settings. All kinds of disease causing mutations can be detected at the same time in patients with Mendelian diseases or carriers. First, we evaluated this technology using YH cell line DNA and 9 samples with known mutations. Accuracy and stability of 99.80% and 99.58% were achieved respectively. Then, a total of 303 patients were tested using our targeted NGS approaches, 50.17% of which were found to have deleterious mutations and molecular confirmation of the clinical diagnosis. We identified 219 disease causing mutations, 43.84% (96/219) of which has never been reported before. Additionally, we developed a new deleteriousness prediction method for nonsynonymous SNVs, and an automating annotation and diagnosis system for Mendelian diseases, thus greatly assisting and enhancing Mendelian diseases diagnosis and helping to make a precise diagnosis for patients with Mendelian diseases.

Application of an improved targeted next generation sequencing method to diagnose non‑syndromic mental retardation in one step: A case report

The genetic basis of congenital mental retardation includes chromosomal anomalies and single gene mutations. In addition to chromosome microarray analysis, next‑generation sequencing (NGS) and Sanger sequencing have additionally been applied to identify single gene mutations. However, no methods exist to identify the cause of an anomaly in one step. The present study applied an improved targeted NGS method to diagnose an 8‑year‑old Chinese Han female with mental retardation in one step. The microdeletion 17p11.2 was successfully detected by the improved targeted NGS and no single gene mutations were identified. The same microdeletion was verified using low coverage whole‑genome sequencing. Fertility guidance was also given to the patients parents. In the present study, an improved targeted NGS method was applied to diagnose non‑syndromic mental retardation of unknown cause in one step. This improved method has the potential to be developed into a screening panel for the effective diagnosis of genetic abnormalities in non‑syndromic mental retardation and other congenital anomalies.

Identification of a disease-causing mutation in a Chinese patient with retinitis pigmentosa by targeted next-generation sequencing

Purpose To identify disease-causing mutations in a Chinese patient with retinitis pigmentosa (RP). Methods A detailed clinical examination was performed on the proband. Targeted next-generation sequencing (NGS) combined with bioinformatics analysis was performed on the proband to detect candidate disease-causing mutations. Sanger sequencing was performed on all subjects to confirm the candidate mutations and assess cosegregation within the family. Results Clinical examinations of the proband showed typical characteristics of RP. Three candidate heterozygous mutations in 3 genes associated with RP were detected in the proband by targeted NGS. The 3 mutations were confirmed by Sanger sequencing and the deletion (c.357_358delAA) in PRPF31 was shown to cosegregate with RP phenotype in 7 affected family members, but not in 3 unaffected family members. Conclusions The deletion (c.357_358delAA) in PRPF31 was the disease-causing mutation for the proband and his affected family members with RP. To our knowledge, this is the second report of the deletion and the first report of the other 2 mutations in the Chinese population. Targeted NGS combined with bioinformatics analysis proved to be an effective molecular diagnostic tool for RP.

Targeted next generation sequencing reveals a novel intragenic deletion of the LAMA2 gene in a patient with congenital muscular dystrophy.

Mutations in the LAMA2 gene cause laminin α‑2 (merosin)‑deficient congenital muscular dystrophies, which are autosomal recessive muscle disorders. Laminin α‑2 is widely expressed in the basement membrane of skeletal muscle, the myotendinous junctions and extra‑synaptically at neuromuscular synapses. In the present study, target next‑generation sequencing was used for mutation detection, and polymerase chain reaction (PCR) analysis and Sanger sequencing were used in the identification of small deletions. Subsequently, quantitative PCR (qPCR) was performed to characterize the identified deletion encompassing exon five of the LAMA2 gene. Two causative mutations were identified using target region sequencing which provided the additional information required to facilitate clinical diagnosis. One heterozygous mutation (p. Lys682LysfsX22) was identified and confirmed by Sanger sequencing, and another heterozygous mutation (Exon5del) was found and validated by qPCR. Co‑segregation analysis indicated that the Exon5del mutation originated from the probands mother and the previously reported frameshift mutation (p. Lys682LysfsX22) was inherited from the probands father. To the best of our knowledge, the present study was the first to report an entire exon five deletion in the LAMA2 gene.