Monitoring measurable residual disease in paediatric acute lymphoblastic leukaemia using immunoglobulin gene clonality based on next-generation sequencing.

BACKGROUND: Assessment of measurable residual disease (MRD) is an essential prognostic tool for B-lymphoblastic leukaemia (B-ALL). In this study, we evaluated the utility of next-generation sequencing (NGS)-based MRD assessment in real-world clinical practice. METHOD: The study included 93 paediatric patients with B-ALL treated at our institution between January 2017 and June 2022. Clonality for IGH or IGK rearrangements was identified in most bone marrow samples (91/93, 97.8%) obtained at diagnosis. RESULTS: In 421 monitoring samples, concordance was 74.8% between NGS and multiparameter flow cytometry and 70.7% between NGS and reverse transcription-PCR. Elevated quantities of clones of IGH alone (P < 0.001; hazard ratio [HR], 22.2; 95% confidence interval [CI], 7.1-69.1), IGK alone (P = 0.011; HR, 5.8; 95% CI, 1.5-22.5), and IGH or IGK (P < 0.001; HR, 7.2; 95% CI, 2.6-20.0) were associated with an increased risk of relapse. Detection of new clone(s) in NGS was also associated with inferior relapse-free survival (P < 0.001; HR, 18.1; 95% CI, 3.0-108.6). Multivariable analysis confirmed age at diagnosis, BCR::ABL1-like mutation, TCF3::PBX1 mutation, and increased quantity of IGH or IGK clones during monitoring as unfavourable factors. CONCLUSION: In conclusion, this study highlights the usefulness of NGS-based MRD as a routine assessment tool for prognostication of paediatric patients with B-ALL.

Comprehensive insights into AML relapse: genetic mutations, clonal evolution, and clinical outcomes.

INTRODUCTION: Acute myeloid leukemia (AML) is a complex hematologic malignancy characterized by uncontrolled proliferation of myeloid precursor cells within bone marrow. Despite advances in understanding of its molecular underpinnings, AML remains a therapeutic challenge due to its high relapse rate and clonal evolution. METHODS: In this retrospective study, we analyzed data from 24 AML patients diagnosed at a single institution between January 2017 and August 2023. Comprehensive genetic analyses, including chromosomal karyotyping, next-generation sequencing, and gene fusion assays, were performed on bone marrow samples obtained at initial diagnosis and relapse. Clinical data, treatment regimens, and patient outcomes were also documented. RESULTS: Mutations in core genes of FLT3, NPM1, DNMT3A, and IDH2 were frequently discovered in diagnostic sample and remained in relapse sample. FLT3-ITD, TP53, KIT, RUNX1, and WT1 mutation were acquired at relapse in one patient each. Gene fusion assays revealed stable patterns, while chromosomal karyotype analyses indicated a greater diversity of mutations in relapsed patients. Clonal evolution patterns varied, with some cases showing linear or branching evolution and others exhibiting no substantial change in core mutations between diagnosis and relapse. CONCLUSIONS: Our study integrates karyotype, gene rearrangements, and gene mutation results to provide a further understanding of AML heterogeneity and evolution. We demonstrate the clinical relevance of specific mutations and clonal evolution patterns, emphasizing the need for personalized therapies and measurable residual disease monitoring in AML management. By bridging the gap between genetics and clinical outcome, we move closer to tailored AML therapies and improved patient prognoses.

Common genes and recurrent causative variants in 957 Asian patients with pediatric epilepsy.

OBJECTIVE: We aimed to identify common genes and recurrent causative variants in a large group of Asian patients with different epilepsy syndromes and subgroups. METHODS: Patients with unexplained pediatric-onset epilepsy were identified from the in-house Severance Neurodevelopmental Disorders and Epilepsy Database. All patients underwent either exome sequencing or multigene panels from January 2017 to December 2019, at Severance Children's Hospital in Korea. Clinical data were extracted from the medical records. RESULTS: Of the 957 patients studied, 947 (99.0%) were Korean and 570 were male (59.6%). The median age at testing was 4.91 years (interquartile range, 1.53-9.39). The overall diagnostic yield was 32.4% (310/957). Clinical exome sequencing yielded a diagnostic rate of 36.9% (134/363), whereas the epilepsy panel yielded a diagnostic rate of 29.9% (170/569). Diagnostic yield differed across epilepsy syndromes. It was high in Dravet syndrome (87.2%, 41/47) and early infantile developmental epileptic encephalopathy (60.7%, 17/28), but low in West syndrome (21.8%, 34/156) and myoclonic-atonic epilepsy (4.8%, 1/21). The most frequently implicated genes were SCN1A (n = 49), STXBP1 (n = 15), SCN2A (n = 14), KCNQ2 (n = 13), CDKL5 (n = 11), CHD2 (n = 9), SLC2A1 (n = 9), PCDH19 (n = 8), MECP2 (n = 6), SCN8A (n = 6), and PRRT2 (n = 5). The recurrent genetic abnormalities included 15q11.2 deletion/duplication (n = 9), Xq28 duplication (n = 5), PRRT2 deletion (n = 4), MECP2 duplication (n = 3), SCN1A, c.2556+3A>T (n = 3), and 2q24.3 deletion (n = 3). SIGNIFICANCE: Here we present the results of a large-scale study conducted in East Asia, where we identified several common genes and recurrent variants that varied depending on specific epilepsy syndromes. The overall genetic landscape of the Asian population aligns with findings from other populations of varying ethnicities.

Eif2b3 mutants recapitulate phenotypes of vanishing white matter disease and validate novel disease alleles in zebrafish.

Leukodystrophy with vanishing white matter (VWM), also called Childhood Ataxia with Central Nervous System Hypomyelination, is caused by mutations in the subunits of the eukaryotic translation initiation factor, EIF2B1, EIF2B2, EIF2B3, EIF2B4 or EIF2B5. However, little is known regarding the underlying pathogenetic mechanisms, and there is no curative treatment for VWM. In this study, we established the first EIF2B3 animal model for VWM disease in vertebrates by CRISPR mutagenesis of the highly conserved zebrafish ortholog eif2b3. Using CRISPR, we generated two mutant alleles in zebrafish eif2b3, 10- and 16-bp deletions, respectively. The eif2b3 mutants showed defects in myelin development and glial cell differentiation, and increased expression of genes in the induced stress response pathway. Interestingly, we also found ectopic angiogenesis and increased VEGF expression. Ectopic angiogenesis in the eif2b3 mutants was reduced by the administration of VEGF receptor inhibitor SU5416. Using the eif2b3 mutant zebrafish model together with in silico protein modeling analysis, we demonstrated the pathogenicity of 18 reported mutations in EIF2B3, as well as of a novel variant identified in a 19-month-old female patient: c.503 T > C (p.Leu168Pro). In summary, our zebrafish mutant model of eif2b3 provides novel insights into VWM pathogenesis and offers rapid functional analysis of human EIF2B3 gene variants.

Copy-number analysis by base-level normalization: An intuitive visualization tool for evaluating copy number variations.

Next-generation sequencing (NGS) facilitates comprehensive molecular analyses that help with diagnosing unsolved disorders. In addition to detecting single-nucleotide variations and small insertions/deletions, bioinformatics tools can identify copy number variations (CNVs) in NGS data, which improves the diagnostic yield. However, due to the possibility of false positives, subsequent confirmation tests are generally performed. Here, we introduce Copy-number Analysis by BAse-level NormAlization (CABANA), a visualization tool that allows users to intuitively identify candidate CNVs using the normalized single-base-level read depth calculated from NGS data. To demonstrate how CABANA works, NGS data were obtained from 474 patients with neuromuscular disorders. CNVs were screened using a conventional bioinformatics tool, ExomeDepth, and then we normalized and visualized those data at the single-base level using CABANA, followed by manual inspection by geneticists to filter out false positives and determine candidate CNVs. In doing so, we identified 31 candidate CNVs (7%) in 474 patients and subsequently confirmed all of them to be true using multiplex ligation-dependent probe amplification. The performance of CABANA was deemed acceptable by comparing its diagnostic yield with previous data about neuromuscular disorders. Despite some limitations, we expect CABANA to help researchers accurately identify CNVs and reduce the need for subsequent confirmation testing.

Development and validation of sensitive BCR::ABL1 fusion gene quantitation using next-generation sequencing.

BACKGROUND: BCR::ABL1 fusion has significant prognostic value and is screened for chronic myeloid leukemia (CML) disease monitoring as a part of routine molecular testing. To overcome the limitations of the current standard real-time quantitative polymerase chain reaction (RQ-PCR), we designed and validated a next-generation sequencing (NGS)-based assay to quantify BCR::ABL1 and ABL1 transcript copy numbers. METHODS: After PCR amplification of the target sequence, deep sequencing was performed using an Illumina Nextseq 550Dx sequencer and in-house-designed bioinformatics pipeline. The Next-generation Quantitative sequencing (NQ-seq) assay was validated for its analytical performance, including precision, linearity, and limit of detection, using serially diluted control materials. A comparison with conventional RQ-PCR was performed with 145 clinical samples from 77 patients. RESULTS: The limit of detection of the NQ-seq was the molecular response (MR) 5.6 [BCR::ABL1 0.00028% international scale (IS)]. The NQ-seq exhibited excellent precision and linear range from MR 2.0 to 5.0. The IS value from the NQ-seq was highly correlated with conventional RQ-PCR. CONCLUSIONS: We conclude that the NQ-seq is an effective tool for monitoring BCR::ABL1 transcripts in CML patients with high sensitivity and reliability. Prospective assessment of the unselected large series is required to validate the clinical impact of this NGS-based monitoring strategy.

The Genotype-Phenotype Correlation in Human 5α-Reductase Type 2 Deficiency: Classified and Analyzed from a SRD5A2 Structural Perspective.

The phenotype of the 5α-reductase type 2 deficiency (5αRD2) by the SRD5A2 gene mutation varies, and although there have been many attempts, the genotype-phenotype correlation still has not yet been adequately evaluated. Recently, the crystal structure of the 5α-reductase type 2 isozyme (SRD5A2) has been determined. Therefore, the present study retrospectively evaluated the genotype-phenotype correlation from a structural perspective in 19 Korean patients with 5αRD2. Additionally, variants were classified according to structural categories, and phenotypic severity was compared with previously published data. The p.R227Q variant, which belongs to the NADPH-binding residue mutation category, exhibited a more masculine phenotype (higher external masculinization score) than other variants. Furthermore, compound heterozygous mutations with p.R227Q mitigated phenotypic severity. Similarly, other mutations in this category showed mild to moderate phenotypes. Conversely, the variants categorized as structure-destabilizing and small to bulky residue mutations showed moderate to severe phenotypes, and those categorized as catalytic site and helix-breaking mutations exhibited severe phenotypes. Therefore, the SRD5A2 structural approach suggested that a genotype-phenotype correlation does exist in 5αRD2. Furthermore, the categorization of SRD5A2 gene variants according to the SRD5A2 structure facilitates the prediction of the severity of 5αRD2 and the management and genetic counseling of patients affected by it.

Real-world data on prognostic value of measurable residual disease assessment by fragment analysis or next-generation sequencing in multiple myeloma.

Measurable residual disease (MRD) negativity is a strong prognostic indicator in multiple myeloma (MM). However, the optimal use of MRD in daily clinical practice has been hampered by the limited feasibility of MRD testing. Therefore, we examined the clinical relevance of commercially available MRD modalities based on clonality assays by fragment analysis with IdentiClone® (n = 73 patients) and next-generation sequencing (NGS) with LymphoTrack® (n = 116 patients) in newly diagnosed patients with MM who received autologous stem cell transplantation (ASCT). MRD was assessed at the end of induction (pre-ASCT) and/or at 100 days after ASCT (post-ASCT). MRD could not predict survival when assessed by fragment analysis. However, NGS-based MRD negativity at pre- or post-ASCT was beneficial in terms of progression-free and overall survival. Moreover, NGS-based MRD negativity was independently associated with improved progression-free and overall survival, and MRD-positive patients both pre- and post-ASCT had worst outcome. Indeed, initial adverse prognostic features by high-risk cytogenetics could be mitigated upon achieving MRD negativity by NGS. We demonstrate the feasibility and clinical benefit of achieving MRD negativity by commercially available clonality-based MRD assays in MM and support incorporating NGS, but not fragment analysis, to tailor therapeutic strategies in real-world practice.

Analytical and Clinical Validation of Cell-Free Circulating Tumor DNA Assay for the Estimation of Tumor Mutational Burden.

BACKGROUND: Ultra-deep sequencing to detect low-frequency mutations in circulating tumor-derived DNA (ctDNA) increases the diagnostic value of liquid biopsy. The demand for large ctDNA panels for comprehensive genomic profiling and tumor mutational burden (TMB) estimation is increasing; however, few ctDNA panels for TMB have been validated. Here, we designed a ctDNA panel with 531 genes, named TMB500, along with a technical and clinical validation. METHODS: Synthetic reference cell-free DNA materials with predefined allele frequencies were sequenced in a total of 92 tests in 6 batches to evaluate the precision, linearity, and limit of detection of the assay. We used clinical samples from 50 patients with various cancers, 11 healthy individuals, and paired tissue samples. Molecular barcoding and data analysis were performed using customized pipelines. RESULTS: The assay showed high precision and linearity (coefficient of determination, r2 =0.87) for all single nucleotide variants, with a limit of detection of 0.24%. In clinical samples, the TMB500 ctDNA assay detected most variants present and absent in tissues, showing that ctDNA could assess tumor heterogeneity in different tissues and metastasis sites. The estimated TMBs correlated well between tissue and blood, except in 4 cases with extreme heterogeneity that showed very high blood TMBs compared to tissue TMBs. A pilot evaluation showed that the TMB500 assay could be used for disease monitoring. CONCLUSIONS: The TMB500 assay is an accurate and reliable ctDNA assay for many clinical purposes. It may be useful for guiding the treatment of cancers with diverse genomic profiles, estimating TMB in immune therapy, and disease monitoring.

Optical genome mapping identifies clinically relevant genomic rearrangements in prostate cancer biopsy sample.

BACKGROUND: Prostate cancer (PCa) is characterized by complex genomic rearrangements such as the ETS oncogene family fusions, yet the clinical relevance is not well established. While paneled genetic tests of DNA repair genes are recommended in advanced PCa, conventional genomic or cytogenetic tools are not ideal for genome-wide screening of structural variations (SVs) such as balanced translocation due to cost and/or resolution issues. METHODS: In this study, we tested the feasibility of whole-genome optical genomic mapping (OGM), a newly developed platform for genome-wide SV analysis to detect complex genomic rearrangements in consecutive unselected PCa samples from MRI/US-fusion targeted biopsy. RESULTS: We tested ten samples, and nine (90%) passed quality check. Average mapping rate and coverage depth were 58.1 ± 23.7% and 157.3 ± 97.7×, respectively (mean ± SD). OGM detected copy number alterations such as chr6q13 loss and chr8q12-24 gain. Two adjacent tumor samples were distinguished by inter/intra-chromosomal translocations, revealing that they're from the same ancestor. Furthermore, OGM detected large deletion of chr13q13.1 accompanied by inter-chromosomal translocation t(13;20)(q13.1;p13) occurring within BRCA2 gene, suggesting complete loss of function. CONCLUSION: In conclusion, clinically relevant genomic SVs were successfully detected in PCa samples by OGM. We suggest that OGM can complement panel sequencing of DNA repair genes BRCA1/2 or ATM in high-risk PCa.

Applications of molecular barcode sequencing for the detection of low-frequency variants in circulating tumour DNA from hepatocellular carcinoma.

PURPOSE: Liquid biopsy has emerged as a promising tool for minimally invasive and accurate detection of various malignancies. We aimed to apply molecular barcode sequencing to circulating tumour DNA (ctDNA) from liquid biopsies of hepatocellular carcinoma (HCC). STUDY DESIGN: Patients with HCC or benign liver disease were enrolled between 2017 and 2018. Matched tissue and serum samples were obtained from these patients. Plasma cell-free DNA was extracted and subjected to targeted sequencing with ultra-high coverage and molecular barcoding. RESULTS: The study included 143 patients: 102 with HCC, 7 with benign liver tumours and 34 with chronic liver disease. No tier 1/2 or oncogenic mutations were detected in patients with benign liver disease. Among the HCC patients, 49 (48%) had tier 1/2 mutations in at least one gene; detection rates were higher in advanced stages (75%) than in early stages (26%-33%). TERT was the most frequently mutated gene (30%), followed by TP53 (16%), CTNNB1 (14%), ARID2 (5%), ARID1A (4%), NFE2L2 (4%), AXIN1 (3%) and KRAS (1%). Survival among patients with TP53 mutations was significantly worse (p = 0.007) than among patients without these mutations, whereas CTNNB1 and TERT mutations did not affect survival. ctDNA testing combined with α-fetoprotein and prothrombin induced by vitamin K absence-II analyses improved HCC detection, even in early stages. CONCLUSIONS: ctDNA detection using molecular barcoding technology offers dynamic and personalized information concerning tumour biology, such information can guide clinical diagnosis and management. This detection also has the potential as a minimally invasive approach for prognostic stratification and post-therapeutic monitoring.

Trajectory of genetic alterations associated with colistin resistance in Acinetobacter baumannii during an in-hospital outbreak of infection.

BACKGROUND: As carbapenem-resistant Acinetobacter baumannii is dominant in clinical settings, the old polymyxin antibiotic colistin has been revived as a therapeutic option. The development of colistin resistance during treatment is becoming a growing concern. OBJECTIVES: To access low- to mid-level colistin-resistant A. baumannii blood isolates recovered from an outbreak in a tertiary care hospital from a national antimicrobial surveillance study. METHODS: The entire bacterial genome was sequenced through long-read sequencing methodology. Quantitative RT-PCR was carried out to determine the level of gene expression. Relative growth rates were determined to estimate fitness costs of each isolate caused by the genetic alterations. RESULTS: The A. baumannii isolates belonged to global clone 2 harbouring two intrinsic phosphoethanolamine transferases. Cumulative alterations continuing the colistin resistance were observed. PmrC overproduction caused by the PmrBA226T alteration was identified in A. baumannii isolates with low-level colistin resistance and an additional PmrCR109H substitution led to mid-level colistin resistance. Truncation of the PmrC enzyme by insertion of ISAba59 was compensated by ISAba10-mediated overproduction of EptA and, in the last isolate, the complete PmrAB two-component regulatory system was eliminated to restore the biological cost of the bacterial host. CONCLUSIONS: During the in-hospital outbreak, a trajectory of genetic modification in colistin-resistant A. baumannii isolates was observed for survival in the harsh conditions imposed by life-threatening drugs with the clear purpose of maintaining drug resistance above a certain level with a reasonable fitness cost.

Chimerism Assay Using Single Nucleotide Polymorphisms Adjacent and in Linkage-Disequilibrium Enables Sensitive Disease Relapse Monitoring after Hematopoietic Stem-Cell Transplantation.

BACKGROUND: Short tandem repeat (STR)-based chimerism analysis has been widely used for chimerism monitoring after hematopoietic stem-cell transplantation (HSCT), but technical artifacts can be problematic. We designed a chimerism assay using single nucleotide polymorphisms (SNPs) adjacent and in linkage-disequilibrium (CASAL), which doubly checked for SNP pairs, and thus could reduce background errors and increase analytical sensitivity. METHODS: CASAL targeted 84 SNP pairs within 10 bp distance and in perfect linkage-disequilibrium. Using undiluted and serially diluted samples, baseline error rates, and linearity was calculated. Clinical performance of CASAL was evaluated in comparison with a conventional STR assay, using 191 posttransplant samples from 42 patients with HSCT. RESULTS: CASAL had ∼10 times lower baseline error rates compared to that of ordinary next-generation sequencing. Limit of detection and quantification of CASAL were estimated to be 0.09 and 0.39%, respectively, with a linear range of 0.1-100%. CASAL correlated well with STR assay (r2 = 0.99) and the higher sensitivity enabled detection of low-level recipient chimerism and earlier prediction of relapse. CONCLUSIONS: CASAL is a simple, analytically sensitive and accurate assay that can be used in clinical samples after HSCT with a higher performance compared to that of traditional assays. It should also be useful in other forensic and archeological testing.

Disparate treatment outcomes according to presence of pathogenic mutations in West syndrome.

OBJECTIVE: It has been known that West syndrome (WS) patients with an unknown etiology have better clinical outcomes than patients with an identified etiology of any kind. However, after the exponential discovery of genes with mutations responsible for developmental and epileptic encephalopathy (DEE), a significant proportion of patients with a previously unknown etiology have been reclassified as having a genetic etiology, requiring reinvestigation of this concept. Therefore, this study investigated clinical outcomes of WS patients with genetic and unknown etiologies. METHODS: Patients diagnosed with WS without structural or metabolic abnormalities were included in this study. The DEE gene panel, comprising 172 genes, was performed for all patients. All patients were treated using the same treatment protocol for vigabatrin and high-dose prednisolone add-on therapy. Favorable responders were defined as patients who were seizure-free and whose electroencephalogram showed Burden of Amplitudes and Epileptiform Discharges scores of 2 or less. RESULTS: Of the 58 patients included in the study, 17 (29.3%) patients had an identified genetic etiology. There was no significant difference in rates of favorable response at 1 and 3 months after treatment, but significantly higher proportions of patients exhibited favorable responses among those with an unknown etiology at long-term follow-up (41.2% vs. 78.0%, p = .006 at 6 months; 29.4% vs. 65.9%, p = .011 at 1 year; 23.5 vs. 65.9%, p = .003 at 2 years). Moreover, the mental, psychomotor, and social age quotients of the patients with an identified genetic etiology were reduced to a significantly greater degree since diagnosis compared with those of the patients with an unknown etiology. SIGNIFICANCE: WS patients with genetic and unknown etiologies did not initially exhibit significantly different response rates to the vigabatrin and high-dose prednisolone add-on treatment. However, patients with a genetic etiology exhibited significantly higher relapse rates and significantly poorer long-term responses.

Copy number variations and multiallelic variants in Korean patients with Leber congenital amaurosis.

Purpose: We comprehensively evaluated the mutational spectrum of Leber congenital amaurosis (LCA) and investigated the molecular diagnostic rate and genotype-phenotype correlation in a Korean cohort. Methods: This single-center retrospective case series included 50 Korean patients with LCA between June 2015 and March 2019. Molecular analysis was conducted using targeted panel-based next-generation sequencing, including deep intronic and regulatory variants or whole exome sequencing. The molecular diagnosis was made based on the inheritance pattern, zygosity, and pathogenicity. Results: Among the 50 patients, 27 patients (54%) were male, and 11 (22%) showed systemic features. Genetic variants highly likely to be causative were identified in 78% (39/50) of cases and segregated into families. We detected two pathogenic or likely pathogenic variants in a gene linked to a recessive trait without segregation analysis in three cases (6.0%). GUCY2D (20%), NMNAT1 (18%), and CEP290 (16%) were the most frequently mutated genes in Korean LCA. Copy number variations were found in three patients, which accounted for 6% of LCA cases. A possible dual molecular diagnosis (Senior-Løken syndrome along with Leigh syndrome, and Joubert syndrome with transposition of the great arteries) was made in two patients (4%). Three of 50 patients were medically or surgically actionable: one patient for RPE65 gene therapy and two patients with WDR19 Senior-Løken syndrome for early preparation for kidney and liver transplantations. Conclusions: This study demonstrated that approximately 4% of patients may have dual molecular diagnoses, and 6% were surgically or medically actionable in LCA. Therefore, accurate molecular diagnosis and careful interpretation of next-generation sequencing results can be of great help in patients with LCA.

Detection of recurrent, rare, and novel gene fusions in patients with acute leukemia using next-generation sequencing approaches.

Identification of gene fusion is an essential part in the management of patients with acute leukemia, not only for diagnosis but also in predicting the treatment outcome and selecting appropriate treatment. Adopting next-generation sequencing (NGS) technology for identification of gene fusion in patients with acute leukemia can be a good alternative to conventional tests. In the present study, the NGS RNA fusion gene panel test was applied to diagnostic samples of patients with acute leukemia to identify fusion genes more efficiently. Among 134 patients with acute leukemia, 53 gene fusions were detected in 52 patients. In addition to the recurrent gene fusions specified in the WHO diagnostic criteria, 11 rare or novel gene fusions were identified. Of those, two were gene fusions associated with Philadelphia-like acute lymphoblastic leukemia (Ph-like ALL), two were novel gene fusions, three were gene fusions with novel partner genes, and six were rare gene fusions from previous reports. We confirmed the clinical utility of the NGS test in identifying clinically significant gene fusions such as gene fusions involving KMT2A that has a large number of partners. Notably, Ph-like ALL-associated gene fusions could be easily identified despite the wide variety of genes involved. The results from the present study may contribute toward a better understanding of the genomic landscape of acute leukemia as well as patient management.

The TECTA mutation R1890C is identified as one of the causes of genetic hearing loss: a case report.

BACKGROUND: Many mutations in the α-tectorin gene (TECTA) have been reported to cause non-syndromic hearing loss (NSHL) in either a dominant or recessive inheritance pattern. Among the identified TECTA mutations, H1400Y has been associated with NSHL in two independent studies. However, its exact role in contributing to genetic hearing loss remains elusive. CASE PRESENTATION: We herein report the whole-exome sequencing of a proband presenting with prelingual, non-progressive, mild-to-moderate hearing loss in a simplex family. By using trio-based whole-exome sequencing, we found two heterozygous mutations of R1890C and H1400Y in the ZP and ZA domains of TECTA, respectively. R1890C, previously reported as a pathogenic autosomal dominant mutation of genetic hearing loss, was found to be inherited in a de novo pattern, causing hearing loss in the proband. By contrast, H1400Y was not segregated in this family, and one family member with normal hearing also carried the H1400Y mutation. CONCLUSION: According to the hearing loss-specific American College of Medical Genetics and Genomics (ACMG) guidelines, we conclude that H1400Y should be disqualified as a cause of genetic hearing loss. True pathogenic variants causing genetic hearing loss should be more deliberately reported in accordance with ACMG guidelines.

Diagnostic application of clinical exome sequencing in Leber congenital amaurosis.

PURPOSE: Leber congenital amaurosis (LCA) is a hereditary retinal dystrophy with wide genetic heterogeneity. Next-generation sequencing (NGS) targeting multiple genes can be a good option for the diagnosis of LCA, and we tested a clinical exome panel in patients with LCA. METHODS: A total of nine unrelated Korean patients with LCA were sequenced using the Illumina TruSight One panel, which targets 4,813 clinically associated genes, followed by confirmation using Sanger sequencing. Patients' clinical information and familial study results were obtained and used for comprehensive interpretation. RESULTS: In all nine patients, we identified pathogenic variations in LCA-associated genes: NMNAT1 (n=3), GUCY2D (n=2), RPGRIP1 (n=2), CRX (n=1), and CEP290 or SPATA7. Six patients had one or two mutations in accordance with inheritance patterns, all consistent with clinical phenotypes. Two patients had only one pathogenic mutation in recessive genes (NMNAT1 and RPGRIP1), and the clinical features were specific to disorders associated with those genes. Six patients were solved for genetic causes, and it remains unclear for three patients with the clinical exome panel. With subsequent targeted panel sequencing with 113 genes associated with infantile nystagmus syndrome, a likely pathogenic allele in CEP290 was detected in one patient. Interestingly, one pathogenic variant (p.Arg237Cys) in NMNAT1 was present in three patients, and it had a high allele frequency (0.24%) in the general Korean population, suggesting that NMNAT1 could be a major gene responsible for LCA in Koreans. CONCLUSIONS: We confirmed that a commercial clinical exome panel can be effectively used in the diagnosis of LCA. Careful interpretation and clinical correlation could promote the successful implementation of clinical exome panels in routine diagnoses of retinal dystrophies, including LCA.

Evaluation of an amplicon-based next-generation sequencing panel for detection of BRCA1 and BRCA2 genetic variants.

The recent advances in the next-generation sequencing (NGS) technology have enabled fast, accurate, and cost-effective genetic testing. Here, we evaluated the performance of a targeted NGS panel for BRCA1/2 sequencing and confirmed its applicability in routine clinical diagnostics. We tested samples from 88 patients using the TruSeq custom panel (Illumina Inc, USA) and a MiSeq sequencer (Illumina) and compared the results to the outcomes of conventional Sanger sequencing. All 1015 sequence variations identified by Sanger sequencing were detected by NGS, except for one missense variant that might have been missed due to a rare mutation on a primer-binding site. One deletion variation, c.1909 + 12delT of BRCA2, was falsely called in all samples due to a homopolymer error. In addition, seven different single-nucleotide substitutions with low variant frequencies (range: 16.2-33.3 %) were falsely called by NGS. In a separate batch, 10 different false-positive variations were found in five samples. The overall sensitivity and positive predictive value of NGS were estimated to be 99.9 and 87.5 %, respectively. The false-positive results could be excluded by setting quality and alternative allele ratio filters and/or by visual inspection using the IGV software. Targeted NGS panel for BRCA1 and BRCA2 showed an excellent agreement with Sanger sequencing results. We therefore conclude that this NGS panel can be used for routine diagnostic method in a clinical genetic laboratory.