Analysis Of Exome Data Research Articles

The identification of novel gene mutations for degenerative lumbar spinal stenosis using whole-exome sequencing in a Chinese cohort

BackgroundDegenerative lumbar spinal stenosis (DLSS) is a common lumbar disease that requires surgery. Previous studies have indicated that genetic mutations are implicated in DLSS. However, studies on specific gene mutations are scarce. Whole-exome sequencing (WES) is a valuable research tool that identifies disease-causing genes and could become an effective strategy to investigate DLSS pathogenesis.MethodsFrom January 2016 to December 2017, we recruited 50 unrelated patients with symptoms consistent with DLSS and 25 unrelated healthy controls. We conducted WES and exome data analysis to identify susceptible genes. Allele mutations firstly identified potential DLSS variants in controls to the patients’ group. We conducted a site-based association analysis to identify pathogenic variants using PolyPhen2, SIFT, Mutation Taster, Combined Annotation Dependent Depletion, and Phenolyzer algorithms. Potential variants were further confirmed using manual curation and validated using Sanger sequencing.ResultsIn this cohort, the major classification variant was missense_mutation, the major variant type was single nucleotide polymorphism (SNP), and the major single nucleotide variation was C > T. Multiple SNPs in 34 genes were identified when filtered allele mutations in controls to retain only patient mutations. Pathway enrichment analyses revealed that mutated genes were mainly enriched for immune response-related signaling pathways. Using the Novegene database, site-based associations revealed several novel variants, including HLA-DRB1, PARK2, ACTR8, AOAH, BCORL1, MKRN2, NRG4, NUP205 genes, etc., were DLSS related.ConclusionsOur study revealed that deleterious mutations in several genes might contribute to DLSS etiology. By screening and confirming susceptibility genes using WES, we provided more information on disease pathogenesis. Further WES studies incorporating larger DLSS patient cohorts are required to comprehend the genetic landscape of DLSS pathophysiology fully.

The diagnostic efficacy of exome data analysis using fixed neurodevelopmental gene lists: Implications for prenatal setting.

Laboratories performing prenatal exome sequencing (ES) frequently limit analysis to predetermined gene lists. We used a diagnostic postnatal ES cohort to assess how many of the genes diagnosed are not included in a number of select fixed lists used for prenatal diagnosis. Of 601 postnatal ES tests, pathogenic variants related to neurodevelopmental disorders were detected in 138 probands. We evaluated if causative genes were present in the following: (1) Developmental Disorders Genotype-Phenotype database list, (2) a commercial laboratory list for prenatal ES, (3) the PanelApp fetal anomalies panel, and (4) a published list used for prenatal diagnosis by ES (Prenatal Assessment of Genomes and Exomes study). The percentages of cases where the diagnosed gene was not included in the selected four lists were; 11.6%, 17.24%, 23.2%, and 10.9%, respectively. In 13/138 (9.4%) cases, the causative gene was not included in any of the lists; in 4/13 (∼30%) cases noninclusion was explained by a relatively recent discovery of gene-phenotype association. A significant number of genes related to neurocognitive phenotypes are not included in some of the lists used for prenatal ES data interpretation. These are not only genes related to recently discovered disorders, but also genes with well-established gene-phenotype.

The Power of Yeast in Modelling Human Nuclear Mutations Associated with Mitochondrial Diseases.

The increasing application of next generation sequencing approaches to the analysis of human exome and whole genome data has enabled the identification of novel variants and new genes involved in mitochondrial diseases. The ability of surviving in the absence of oxidative phosphorylation (OXPHOS) and mitochondrial genome makes the yeast Saccharomyces cerevisiae an excellent model system for investigating the role of these new variants in mitochondrial-related conditions and dissecting the molecular mechanisms associated with these diseases. The aim of this review was to highlight the main advantages offered by this model for the study of mitochondrial diseases, from the validation and characterisation of novel mutations to the dissection of the role played by genes in mitochondrial functionality and the discovery of potential therapeutic molecules. The review also provides a summary of the main contributions to the understanding of mitochondrial diseases emerged from the study of this simple eukaryotic organism.

A novel homozygous frameshift mutation in the DCC gene in a Pakistani family with autosomal recessive horizontal gaze palsy with progressive scoliosis-2 with impaired intellectual development.

Horizontal Gaze Palsy with Progressive Scoliosis-2 with Impaired Intellectual Development (HGPPS2) is a rare congenital disorder characterized by absence of conjugate horizontal eye movements, and progressive scoliosis developing in childhood and adolescence. We report three new patients with HGPPS2 in a consanguineous Pakistani family, presenting varying degrees of progressive scoliosis, developmental delays, horizontal gaze palsy, agenesis of corpus callosum, and absence of cerebral commissures. Analysis of genotyping data identified shared loss of heterozygosity (LOH) region on chromosomes 5p15.33-15.31, 6q11.2-12, and 18q21.1-21.3. A hypothesis-free, unbiased exome data analysis detected an insertion of nucleotide A (c.2399dupA) in exon 16 of the DCC gene. The insertion is predicted to cause frameshift p.(Asn800Lysfs*11). Interestingly, DCC gene is present in the LOH region on chromosome 18. Variant (c.2399dupA) in the DCC gene is considered as the most probable candidate variant for HGPPS2 based on the presence of DCC in the LOH region, previously reported role of DCC in HGPPS2, perfect segregation of candidate variant with the disease, prediction of variant pathogenicity, and absence of variant in variation databases. Sanger Sequencing confirmed the presence of the novel homozygous mutation in all three patients; the parents were heterozygous carriers of the mutation, in accordance with an autosomal recessive inheritance pattern. DCC encodes a netrin-1 receptor protein; its role in the development of the CNS has recently been established. Biallelic DCC mutations have previously been shown to cause HGPPS2. A novel homozygous variant in patients of the reported family extend the genotypic and phenotypic spectrum of HGPPS2.

An Initial Survey of the Performances of Exome Variant Analysis and Clinical Reporting Among Diagnostic Laboratories in China.

Exome sequencing has become an effective diagnostic method for Mendelian disorders. But the quality of services differs widely across laboratories in China, particularly in variant classification, even with the adoption of the ACMG guidelines. As an effort of quality control and improvement for better clinical utilization of exome sequencing, we assessed the exome data analysis and clinical reporting among Chinese laboratories. Five raw datasets of real clinical samples with associated phenotypes were sent to 53 laboratories. The participants independently performed secondary analysis, variant classification, and reporting. The first round of results was used for identifying problems associated with these aspects. Subsequently, we implemented several corrective actions and a training program was designed based on the identified issues. A second round of five datasets were sent to the same participants. We compared the performances in variant interpretation and reporting. A total of 85.7% (42/49) of participants correctly identified all the variants related with phenotype. Many lines of evidence using the ACMG guidelines were incorrectly utilized, which resulted in a large inter-laboratory discrepancy. After training, the evidence usage problems significantly improved, leading to a more consistent outcome. Participants improved their exome data analysis and clinical reporting capability. Targeted training and a deeper understanding of the ACMG guidelines helped to improve the clinical exome sequencing service in terms of consistency and accuracy in variant classification in China.

New Insights on Genetic Diagnostics in Cardiomyopathy and Arrhythmia Patients Gained by Stepwise Exome Data Analysis.

Inherited cardiomyopathies are characterized by clinical and genetic heterogeneity that challenge genetic diagnostics. In this study, we examined the diagnostic benefit of exome data compared to targeted gene panel analyses, and we propose new candidate genes. We performed exome sequencing in a cohort of 61 consecutive patients with a diagnosis of cardiomyopathy or primary arrhythmia, and we analyzed the data following a stepwise approach. Overall, in 64% of patients, a variant of interest (VOI) was detected. The detection rate in the main sub-cohort consisting of patients with dilated cardiomyopathy (DCM) was much higher than previously reported (25/36; 69%). The majority of VOIs were found in disease-specific panels, while a further analysis of an extended panel and exome data led to an additional diagnostic yield of 13% and 5%, respectively. Exome data analysis also detected variants in candidate genes whose functional profile suggested a probable pathogenetic role, the strongest candidate being a truncating variant in STK38. In conclusion, although the diagnostic yield of gene panels is acceptable for routine diagnostics, the genetic heterogeneity of cardiomyopathies and the presence of still-unknown causes favor exome sequencing, which enables the detection of interesting phenotype–genotype correlations, as well as the identification of novel candidate genes.

Loqusdb: added value of an observations database of local genomic variation

BackgroundExome and genome sequencing is becoming the method of choice for rare disease diagnostics. One of the key challenges remaining is distinguishing the disease causing variants from the benign background variation. After analysis and annotation of the sequencing data there are typically thousands of candidate variants requiring further investigation. One of the most effective and least biased ways to reduce this number is to assess the rarity of a variant in any population. Currently, there are a number of reliable sources of information for major population frequencies when considering single nucleotide variants (SNVs) and small insertion and deletions (INDELs), with gnomAD as the most prominent public resource available. However, local variation or frequencies in sub-populations may be underrepresented in these public resources. In contrast, for structural variation (SV), the background frequency in the general population is more or less unknown mostly due to challenges in calling SVs in a consistent way. Keeping track of local variation is one way to overcome these problems and significantly reduce the number of potential disease causing variants retained for manual inspection, both for SNVs and SVs.ResultsHere, we present loqusdb, a tool to solve the challenge of keeping track of any type of variant observations from genome sequencing data. Loqusdb was designed to handle a large flow of samples and unlike other solutions, samples can be added continuously to the database without rebuilding it, facilitating improvements and additions. We assessed the added value of a local observations database using 98 samples annotated with information from a background of 888 unrelated individuals.ConclusionsWe show both how powerful SV analysis can be when filtering for population frequencies and how the number of apparently rare SNVs/INDELs can be reduced by adding local population information even after annotating the data with other large frequency databases, such as gnomAD. In conclusion, we show that a local frequency database is an attractive, and a necessary addition to the publicly available databases that facilitate the analysis of exome and genome data in a clinical setting.

Identification of novel genetic variants associated with short stature in a Baka Pygmies population

Human growth is a complex trait determined by genetic factors in combination with external stimuli, including environment, nutrition and hormonal status. In the past, several genome-wide association studies (GWAS) have collectively identified hundreds of genetic variants having a putative effect on determining adult height in different worldwide populations. Theoretically, a valuable approach to better understand the mechanisms of complex traits as adult height is to study a population exhibiting extreme stature phenotypes, such as African Baka Pygmies. After phenotypic characterization, we sequenced the whole exomes of a cohort of Baka Pygmies and their non-Pygmies Bantu neighbors to highlight genetic variants associated with the reduced stature. Whole exome data analysis revealed 29 single nucleotide polymorphisms (SNPs) significantly associated with the reduced height in the Baka group. Among these variants, we focused on SNP rs7629425, located in the 5′-UTR of the Hyaluronidase-2 (HYAL2) gene. The frequency of the alternative allele was significantly increased compared to African and non-African populations. In vitro luciferase assay showed significant differences in transcription modulation by rs7629425 C/T alleles. In conclusion, our results suggested that the HYAL2 gene variants may play a role in the etiology of short stature in Baka Pygmies population.

Next generation sequencing exome data analysis aids in the discovery of SNP and INDEL patterns in Parkinson's disease

Whole exome sequencing is an adept method to reveal novel and disease-related SNPs and INDELs as it screen the actionable areas of the genome. We evaluated the exome sequenced datasets of patients with Parkinson's disease (PD) in South African ethnic origin. The primary focus of this study was to discover the SNPs and INDELs patterns responsible for PD. The variant discovery was performed with genome analysis tool kit best practices variant detection pipelines. The SNPs were linked to the genes and categorized based on the filter-based annotation from ANNOVAR. We identified a total of 7955 SNPs and 9952 INDELs in all seven datasets together. A total of 130 missense nsSNPs were prioritized based on its damaging effect predicted from SIFT and Polyphen2 annotation. We noticed a novel nsSNP rs111655870 in gene LRRK2 that shows the mutation of a Leucine to Phenylalanine at position 208 which can alter the protein function. The study also filtered seven nsSNPs in genes NAGA, SULT4A1, MYH8, FLNA, TPM3, ATP13A1, CLN8 that have potentially deleterious effects predicted by various computational tools. This analysis suggested that the above filtered nsSNPs and INDELs have a functional impact and provide the footing for genetic studies related to PD. Further screening of these variations provides deeper insight for molecular mechanism of disease progression.

Centromere protein I (CENPI) is a candidate gene for X-linked steroid sensitive nephrotic syndrome.

Individuals with proteinuria in association with hypoalbuminemia, edema, and hyperlipidemia are considered as having nephrotic syndrome (NS). NS is the most common kidney disease seen in the paediatric age group. NS is usually classified into steroid resistant nephrotic syndrome (SRNS) and steroid sensitive nephrotic syndrome (SSNS). More than 58 genes have been identified as a monogenic cause of SRNS, however, the genetic architecture of childhood SSNS remains poorly understood. Here in this study, we performed sequencing of 66 NS candidate genes followed by whole genome SNP genotyping and whole exome sequencing in SSNS families with multiple affected individuals. NS candidate genes sequencing did not identify any pathogenic variant in the known genes. Homozygosity mapping based on an autosomal recessive model failed to detect any shared loss of heterozygosity region in the genome. An unbiased and hypothesis-free exome data analysis identified a missense variant (c.383G>A; p.Arg128Gln) in the CENPI gene. Sanger sequencing of both parents, unaffected and affected individuals confirmed an X-linked inheritance pattern of the variant (c.383G>A) with SSNS phenotype. The variant (c.383G>A) is very rare and is potentially damaging. Collectively, these observations suggest that a specific pathogenic link between SSNS development and alteration in CENPI exists. However, human mutations in CENPI causing SSNS have not been reported hitherto. Identification of genetic defects underlying SSNS will help in understanding the precise aetiology of SSNS and improved management of children with NS.

Exome sequencing reveals novel causes as well as new candidate genes for human globozoospermia.

STUDY QUESTIONCan exome sequencing identify new genetic causes of globozoospermia?SUMMARY ANSWERExome sequencing in 15 cases of unexplained globozoospermia revealed deleterious mutations in seven new genes, of which two have been validated as causing globozoospermia when knocked out in mouse models.WHAT IS KNOWN ALREADYGlobozoospermia is a rare form of male infertility characterised by round-headed sperm and malformation of the acrosome. Although pathogenic variants in DPY19L2 and SPATA16 are known causes of globozoospermia and explain up to 70% of all cases, genetic causality remains unexplained in the remaining patients.STUDY DESIGN, SIZE, DURATIONAfter pre-screening 16 men for mutations in known globozoospermia genes DPY19L2 and SPATA16, exome sequencing was performed in 15 males with globozoospermia or acrosomal hypoplasia of unknown aetiology.PARTICIPANTS/MATERIALS, SETTING, METHODTargeted next-generation sequencing and Sanger sequencing was performed for all 16 patients to screen for single-nucleotide variants and copy number variations in DPY19L2 and SPATA16. After exclusion of one patient with DPY19L2 mutations, we performed exome sequencing for the 15 remaining subjects. We prioritised recessive and X-linked protein-altering variants with an allele frequency of <0.5% in the population database GnomAD in genes with an enhanced expression in the testis. All identified candidate variants were confirmed in patients and, where possible, in family members using Sanger sequencing. Ultrastructural examination of semen from one of the patients allowed for a precise phenotypic characterisation of abnormal spermatozoa.MAIN RESULTS AND ROLE OF CHANCEAfter prioritisation and validation, we identified possibly causative variants in eight of 15 patients investigated by exome sequencing. The analysis revealed homozygous nonsense mutations in ZPBP and CCDC62 in two unrelated patients, as well as rare missense mutations in C2CD6 (also known as ALS2CR11), CCIN, C7orf61 and DHNA17 and a frameshift mutation in GGN in six other patients. All variants identified through exome sequencing, except for the variants in DNAH17, were located in a region of homozygosity. Familial segregation of the nonsense variant in ZPBP revealed two fertile brothers and the patient’s mother to be heterozygous carriers. Paternal DNA was unavailable. Immunohistochemistry confirmed that ZPBP localises to the acrosome in human spermatozoa. Ultrastructural analysis of spermatozoa in the patient with the C7orf61 mutation revealed a mixture of round heads with no acrosomes (globozoospermia) and ovoid or irregular heads with small acrosomes frequently detached from the sperm head (acrosomal hypoplasia).LIMITATIONS, REASONS FOR CAUTIONStringent filtering criteria were used in the exome data analysis which could result in possible pathogenic variants remaining undetected. Additionally, functional follow-up is needed for several candidate genes to confirm the impact of these mutations on normal spermatogenesis.WIDER IMPLICATIONS OF THE FINDINGSOur study revealed an important role for mutations in ZPBP and CCDC62 in human globozoospermia as well as five new candidate genes. These findings provide a more comprehensive understanding of the genetics of male infertility and bring us closer to a complete molecular diagnosis for globozoospermia patients which would help to predict the success of reproductive treatments.STUDY FUNDING/COMPETING INTEREST(S)This study was funded by The Netherlands Organisation for Scientific Research (918–15-667); National Health and Medical Research Council of Australia (APP1120356) and the National Council for Scientific Research (CONICET), Argentina, PIP grant 11220120100279CO. The authors have nothing to disclose.

High frequency of pathogenic ACAN variants including an intragenic deletion in selected individuals with short stature.

ContextDefining the underlying etiology of idiopathic short stature (ISS) improves the overall management of an individual.ObjectiveTo assess the frequency of pathogenic ACAN variants in selected individuals.DesignThe single-center cohort study was conducted at a tertiary university children’s hospital. From 51 unrelated patients with ISS, the 16 probands aged between 3 and 18 years (12 females) with advanced bone age and/or autosomal dominant inheritance pattern of short stature were selected for the study. Fifteen family members of ACAN-positive probands were included. Exome sequencing was performed in all probands, and additional copy number variation (CNV) detection was applied in selected probands with a distinct ACAN-associated phenotype.ResultsSystematic phenotyping of the study cohort yielded 37.5% (6/16) ACAN-positive probands, with all novel pathogenic variants, including a 6.082 kb large intragenic deletion, detected by array comparative genomic hybridization (array CGH) and exome data analysis. All variants were co-segregated with short stature phenotype, except in one family member with the intragenic deletion who had an unexpected growth pattern within the normal range (−0.5 SDS). One patient presented with otosclerosis, a sign not previously associated with aggrecanopathy.ConclusionsACAN pathogenic variants presented a common cause of familial ISS. The selection criteria used in our study were suggested for a personalized approach to genetic testing of the ACAN gene in clinical practice. Our results expanded the number of pathogenic ACAN variants, including the first intragenic deletion, and suggested CNV evaluation in patients with typical clinical features of aggrecanopathy as reasonable. Intra-familial phenotypic variability in growth patterns should be considered.

Multiple rare inherited variants in a four generation schizophrenia family offer leads for complex mode of disease inheritance

Schizophrenia is a clinically and genetically heterogeneous neuropsychiatric disorder, with a polygenic basis but identification of the specific determinants is a continuing challenge. In this study, we analyzed a multigenerational family, with all healthy individuals in the first two generations, and four progeny affected with schizophrenia in the subsequent two generations, using whole exome sequencing. We identified five rare protein sequence altering heterozygous variants, in five different genes namely SMARCA5, PDE1B, TNIK, SMARCA2 and FLRT shared among all affected members and predicted to be damaging.Variants in SMARCA5 and PDE1B were inherited from the unaffected father whereas variants in TNIK, SMARCA2 and FLRT1 were inherited from the unaffected mother in all the three affected individuals in the third generation; and notably all these five variants were transmitted by an affected mother to her affected son. Microsatellite based analysis lent a modest linkage support (LOD score of 1.2; θ=0.0 at each variant). Of note, analysis of exome data of an ancestry matched unrelated schizophrenia cohort (n = 350), revealed a total of 16 rare variants (MAF < 0.01) in these five genes. Interestingly, these five genes involved in neurodevelopmental and/or neurotransmitter signaling processes are implicated in the etiology of schizophrenia previously. This study provides good evidence for a likely cumulative contribution of multiple rare variants from disease relevant genes with a threshold effect in disease development and seems to explain the unusual disease transmission pattern generally witnessed in such conditions, but warrants extensive replication efforts in families with similar complex disease inheritance profiles.

Novel HLA Typing Method Identifies HLA Alleles Associated with Pediatric ITP

Background: Human leukocyte antigen (HLA) genes on chromosome 6p21 encode the major histocompatibility complex (MHC). MHC molecules are expressed on all nucleated cells and are essential to the immune system's ability to distinguish healthy native cells from foreign or abnormal ones. Specialized antigen presenting cells display MHC molecules loaded with foreign peptides to initiate T cell responses. HLA sequencing variability is critical to function; studies have shown even single allelic changes can alter the ability of MHC molecules to recognize cognate T cell receptors. Given the role of MHC molecules in identifying cells as "self", associations between HLA sequence variation and autoimmunity is a research focus. Like other autoimmune disorders, association between ITP and HLA genes has been investigated. Prior studies are limited by outdated HLA typing methods, genetically homogenous study populations, and lack of validation studies. Preexisting exome data has historically not been used to provide accurate HLA sequencing information given the polymorphic, highly repetitive sequence in this region. This study applied a novel bioinformatics pipeline, xHLA, to an existing set of whole exome sequencing in a cohort of chronic pediatric ITP patients. xHLA, reported by Xie et al. in 2017, yields high-resolution, two field HLA typing for HLA-A, -B, -C, -DQB1, -DPB1, and -DRB1. A prior genetic analysis of chronic ITP patient whole exome data identified a missense variant in BTNL2, a gene which plays a role in peripheral regulatory T cell induction. This variant (rs143211074) is upregulated in chronic ITP versus healthy controls (minor allele frequency= 4.17% in ITP v. 0.54% in controls, p=1.43x10-4). Linkage of rs143211074 and HLA alleles was examined in this study. Methods: Whole exome sequencing data for a cohort of 272 chronic ITP patients was processed using the xHLA method. In order to eliminate sequencing variability related to ethnicity alone, initial analyses were focused on Caucasians only (n=170), using Eigenvectors for principle components analysis. The frequency of individual HLA alleles and HLA haplotypes for Caucasians from the National Marrow Donor Program (NMDP) Be The Match Registry® were compared to the ITP cohort. HLA haplotypes were inferred using the NMDP HaploStats program. A chi-squared test was utilized to compare nonparametric categorical data using GraphPad Prism version 8.0.1 for Windows, GraphPad Software, San Diego, California, USA, www.graphpad.com. A Bonferroni correction was applied and a p-value of &lt;0.05 was statistically significant. Results: 12 HLA alleles had increased frequency in the chronic ITP cohort versus controls. (Table 1) The BTNL2 variant, rs143211074, was found in linkage disequilibrium with the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype. Of the 10 patients heterozygous for the variant allele, 80% had the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype. Both patients homozygous for rs143211074 were also homozygous for the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype. In the entire cohort, this haplotype was identified in 3.63% of ITP patients, and only in 1.27% of controls. Our group recently published that a positive direct antiglobulin test is associated with chronic ITP and need for second line treatments. Of the patients with the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype with DAT testing performed (n=9), 66% had a positive DAT test and 33% had a negative DAT result. Of those without the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype who had DAT testing, 17.2% had a positive DAT and 82.8% had a negative test (p=0.0026). Conclusions: HLA alleles are seen at increased frequency in a cohort of Caucasian chronic ITP patients. The HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype is linked to a variant previously identified in BTNL2. Coupled with prior data suggesting that a positive DAT result is associated with chronic disease and use of second line agents, this presence of the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype may also be linked to refractory disease. Confirmation of the accuracy of the xHLA method in a cohort of patients with both exome data and traditional HLA typing is underway. In the future, a separate cohort of chronic and acute ITP patients will undergo next generation sequencing and have similar HLA typing performed as an independent validation set. Table 1 Disclosures Despotovic: Novartis: Research Funding; Amgen: Research Funding; Dova: Honoraria.

Focal Recurrent Copy Number Alterations Characterize Disease Relapse in High Grade Serous Ovarian Cancer Patients with Good Clinical Prognosis: A Pilot Study.

High grade serous ovarian cancer (HGSOC) retains high molecular heterogeneity and genomic instability, which currently limit the treatment opportunities. HGSOC patients receiving complete cytoreduction (R0) at primary surgery and platinum-based therapy may unevenly experience early disease relapse, in spite of their clinically favorable prognosis. To identify distinctive traits of the genomic landscape guiding tumor progression, we focused on the R0 patients of The Cancer Genome Atlas (TCGA) ovarian serous cystadenocarcinoma (TCGA-OV) dataset and classified them according to their time to relapse (TTR) from surgery. We included in the study two groups of R0-TCGA patients experiencing substantially different outcome: Resistant (R; TTR ≤ 12 months; n = 11) and frankly Sensitive (fS; TTR ≥ 24 months; n = 16). We performed an integrated clinical, RNA-Sequencing, exome and somatic copy number alteration (sCNA) data analysis. No significant differences in mutational landscape were detected, although the lack of BRCA-related mutational signature characterized the R group. Focal sCNA analysis showed a higher frequency of amplification in R group and deletions in fS group respectively, involving cytobands not commonly detected by recurrent sCNA analysis. Functional analysis of focal sCNA with a concordantly altered gene expression identified in R group a gain in Notch, and interferon signaling and fatty acid metabolism. We are aware of the constraints related to the low number of OC cases analyzed. It is worth noting, however, that the sCNA identified in this exploratory analysis and characterizing Pt-resistance are novel, deserving validation in a wider cohort of patients achieving complete surgical debulking.

Genome-wide sequencing in acutely ill infants: genomic medicine’s critical application?

Diagnostic genome-wide sequencing (exome or genome sequencing and data analysis for high-penetrance disease-causing variants) in acutely ill infants appears to be clinically useful, but the value of this diagnostic test should be rigorously demonstrated before it is accepted as a standard of care. This white paper was developed by the Paediatric Task Team of the Global Alliance for Genomics and Health’s Regulatory and Ethics Work Stream to address the question of how we can determine the clinical value of genome-wide sequencing in infants in an intensive care setting. After reviewing available clinical and ethics literature on this question, we conclude that evaluating diagnostic genome-wide sequencing as a comprehensive scan for major genetic disease (rather than as a large panel of single-gene tests) provides a practical approach to assessing its clinical value in acutely ill infants. Comparing the clinical value of diagnostic genome-wide sequencing to chromosomal microarray analysis, the current evidence-based standard of care, per case of serious genetic disease diagnosed provides a practical means of assessing clinical value. Scientifically rigorous studies of this kind are needed to determine if clinical genome-wide sequencing should be established as a standard of care supported by healthcare systems and insurers for diagnosis of genetic disease in seriously ill newborn infants.

Mechanistic Metabolic Model of Cancer Using DNA Dosages

Background: Among other peculiarities, cancerous tissue is marked by its abnormal energy metabolism. The genetic basis for these metabolic changes is not well understood. We used metabolic modelling to characterize genetic differences between tissues sampled from cancer patients and healthy subjects. Methods: We developed DNA Dosages, a mathematical model and statistical exome data analysis algorithm based on linear programming and a constraint-based model. The algorithm can highlight genetic characteristics of cancer beyond single nucleotide polymorphisms, capturing copy number variations. We applied the algorithm to exome data from studies of three types of malignancy (familial breast cancer, esophageal squamous cell carcinoma, and urothelial bladder cancer). Findings: The DNA Dosages technique revealed that tumour tissue, but also non-tumour tissue in cancer patients shows significant metabolic differences from tissue samples of healthy subjects. Interpretation: Exome analysis with the DNA Dosages approach promises to yield cancer biomarkers as well as to support cancer diagnostics from blood and other non-tumour biopsy samples. Funding Statement: This project was funded by the authors as part of their personal interest in the advancement of science. Declaration of Interests: The authors declare that we have no competing interests. Ethics Approval Statement: Data used in this study are taken from open domain. Ethical committee approvals were taken by the original authors for their respective works.

Abstract 3271: A machine learning approach for somatic mutation discovery

Abstract Variability in the accuracy for somatic mutation detection may affect discovery of alterations and therapeutic management of cancer patients. To address this issue, we developed a somatic mutation discovery method based on machine learning approaches that outperformed other methods using tumor alterations that were experimentally validated (sensitivity of 97% vs 90-99%; positive predictive value of 98% vs 34-92%). Analysis of tumor-normal exome data from 1,376 TCGA samples using this method revealed concordance for 74% of mutation calls but also identified likely false positive and negative changes in TCGA data, including in clinically actionable genes. For melanoma and lung cancer patients treated with immune checkpoint inhibitors, determination of high-quality somatic mutation calls improved mutation load-based predictions of clinical outcome. Integration of high-quality mutation detection in clinical NGS analyses improved the accuracy of test results compared to other clinical sequencing analyses not using these approaches (sensitivity of 100% vs 50-97%; positive predictive value of 100% vs 9-66%). These analyses provide an approach for improved identification of tumor-specific mutations and have important implications for research and clinical management of patients with cancer. Citation Format: Derrick Wood, James White, Andrew Georgiadis, Beth Van Emburgh, Sonya Parpart-Li, Jason Mitchell, Valsamo Anagnostou, Noushin Niknafs, Rachel Karchin, Eniko Papp, Christine McCord, Peter Loverso, David Riley, Luis A. Diaz, Sian Jones, Mark Sausen, Victor E. Velculescu, Samuel Angiuoli. A machine learning approach for somatic mutation discovery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3271.

Abstract 2072: Genomic studies of Brazilian patients with hepatoblastoma: Insight into somatic mutations using whole-exome sequencing

Abstract Hepatoblastomas (HB) are embryonal tumors of the liver with histological features that resemble different stages of liver differentiation. The identification of molecular pathways involved in HB development can expand the understanding of the connections between disruption of normal differentiation and cancer. Exome sequencing (244K Agilent SureSelect Target Enrichment) analysis was performed for 6 HBs matched with their non tumoral liver tissues (fresh frozen tissues). Bioinformatic analysis of exome data identified somatic variants in 69 genes which were chosen for validation using a target sequencing panel (SureSelectXT Target Enrichment System for Illumina Paired-End Sequencing Library). The gene panel was composed of the detected 69 genes and other 48 genes related with HB or cancer, and it was used to investigated additional 13 HB samples as a validation group. 60% of the patients were male, and the mean age at diagnosis was 36 months. 13% of this cohort presented pulmonary metastasis. All patients received pre-surgery chemotherapy (SIOPEL and COG protocol). Results: A total of 71 somatic rare coding mutations (missense and loss-of-function) were validated in 53 genes considering the entire HB group. The somatic analysis reveals pathogenic mutations in the CTNNB1 gene and a recurrent missense mutation in the CX3CL1 gene; the role of these mutations was explored by IHQ studies of their proteins as well as by gene expression analysis by RT-PCR. We also used results from Illumina 450k to evaluated the methylation levels of CX3CL1 and CX3CR1 genes. Methylation values for CpG sites in each sample were measured as β-and CpG sites were grouped into categories, promoter (1stExon; 5'UTR; TSS1500; TSS200) or gene body, information provided by Illumina, based on UCSC data (GRhC 37). The methylation level of each category was obtained by averaging the β-values of all CpGs mapped in the category for each gene, followed by Wilcoxon test correction by calculating the false discovery rate (FDR). Conclusion: Most investigated HBs carry few potentially pathogenic genetic mutations (≤ 5 mutations). This observed low frequency of somatic mutations is a result similar to previous studies. The proposed explanation is based on the fact that pediatric tumors would originate from precursor cells with pluripotent characteristics; therefore, such tumors may require fewer mutations than adult solid tumors to develop. The congenital HB case of our cohort is discrepant from this scenario since a relatively high number of somatic mutations were found compared to the HB group. To our knowledge, this is the first comprehensive genomic characterization of Brazilian HBs. Next steps include expanding the casuistry of exome sequenced tumors, including two cases of HB associated with Hirschprung disease. Grants: FAPESP (2016/04785-0; 2017/11212-0), FAPESP (2013/08028-1), CNPq (141625/2016-3). Citation Format: Talita F. Aguiar, Tatiane Rodrigues, Maria Prates, Fernanda Aparecida dos Santos, Gustavo Fernandes, Cecília Maria Lima da Costa, Isabela Werneck da Cunha, Monica Cypriano, Silvia Regina Caminada de Toledo, Jorge Estefano S. de Souza, Eugênia Valadares, Raquel Borges, Vicente Odone, Israel Tojal, Dirce Carraro, Carla Rosenberg, Ana C.V. Krepischi. Genomic studies of Brazilian patients with hepatoblastoma: Insight into somatic mutations using whole-exome sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2072.

Exome-wide somatic mutation characterization of small bowel adenocarcinoma.

Small bowel adenocarcinoma (SBA) is an aggressive disease with limited treatment options. Despite previous studies, its molecular genetic background has remained somewhat elusive. To comprehensively characterize the mutational landscape of this tumor type, and to identify possible targets of treatment, we conducted the first large exome sequencing study on a population-based set of SBA samples from all three small bowel segments. Archival tissue from 106 primary tumors with appropriate clinical information were available for exome sequencing from a patient series consisting of a majority of confirmed SBA cases diagnosed in Finland between the years 2003–2011. Paired-end exome sequencing was performed using Illumina HiSeq 4000, and OncodriveFML was used to identify driver genes from the exome data. We also defined frequently affected cancer signalling pathways and performed the first extensive allelic imbalance (AI) analysis in SBA. Exome data analysis revealed significantly mutated genes previously linked to SBA (TP53, KRAS, APC, SMAD4, and BRAF), recently reported potential driver genes (SOX9, ATM, and ARID2), as well as novel candidate driver genes, such as ACVR2A, ACVR1B, BRCA2, and SMARCA4. We also identified clear mutation hotspot patterns in ERBB2 and BRAF. No BRAF V600E mutations were observed. Additionally, we present a comprehensive mutation signature analysis of SBA, highlighting established signatures 1A, 6, and 17, as well as U2 which is a previously unvalidated signature. Finally, comparison of the three small bowel segments revealed differences in tumor characteristics. This comprehensive work unveils the mutational landscape and most frequently affected genes and pathways in SBA, providing potential therapeutic targets, and novel and more thorough insights into the genetic background of this tumor type.