Evaluation Of Copy Number Variations Research Articles

Diagnostic yield of the chromosomal microarray analysis in turkish patients with unexplained development delay/ıntellectual disability(ID), autism spectrum disorders and/or multiple congenital anomalies and new clinical findings.

Chromosomal microarray analysis is an essential tool for copy number variants detection in patients with unexplained developmental delay/intellectual disability, autism spectrum disorders, and multiple congenital anomalies. The study aims to determine the clinical significance of chromosomal microarray analysis in this patient group. Another crucial aspect is the evaluation of copy number variants detected in terms of the diagnosis of patients. A Chromosomal microarray analysis was was conducted on a total of 1227 patients and phenotype-associated etiological diagnosis was established in 135 patients. Phenotype-associated copy number variants were detected in 11% of patients. Among these, 77 patients 77 (57%, 77/135) were diagnosed with well-recognized genetic syndromes and phenotype-associated copy number variants were found in 58 patients (42.9%, 58/135). The study was designed to collect data of patients in Kocaeli Derince Training and Research Hospital retrospectively. In our study, we examined 135 cases with clinically significant copy number variability among all patients. In this study, chromosomal microarray analysis revealed pathogenic de novo copy number variants with new clinical features. Chromosomal microarray analysis in the Turkish population has been reported in the largest patient cohort to date.

A cohort study of neurodevelopmental disorders and/or congenital anomalies using high resolution chromosomal microarrays in southern Brazil highlighting the significance of ASD

Chromosomal microarray (CMA) is the reference in evaluation of copy number variations (CNVs) in individuals with neurodevelopmental disorders (NDDs), such as intellectual disability (ID) and/or autism spectrum disorder (ASD), which affect around 3–4% of the world’s population. Modern platforms for CMA, also include probes for single nucleotide polymorphisms (SNPs) that detect homozygous regions in the genome, such as long contiguous stretches of homozygosity (LCSH). These regions result from complete or segmental chromosomal homozygosis and may be indicative of uniparental disomy (UPD), inbreeding, population characteristics, as well as replicative DNA repair events. In this retrospective study, we analyzed CMA reading files requested by geneticists and neurologists for diagnostic purposes along with available clinical data. Our objectives were interpreting CNVs and assess the frequencies and implications of LCSH detected by Affymetrix CytoScan HD (41%) or 750K (59%) platforms in 1012 patients from the south of Brazil. The patients were mainly children with NDDs and/or congenital anomalies (CAs). A total of 206 CNVs, comprising 132 deletions and 74 duplications, interpreted as pathogenic, were found in 17% of the patients in the cohort and across all chromosomes. Additionally, 12% presented rare variants of uncertain clinical significance, including LPCNVs, as the only clinically relevant CNV. Within the realm of NDDs, ASD carries a particular importance, owing to its escalating prevalence and its growing repercussions for individuals, families, and communities. ASD was one clinical phenotype, if not the main reason for referral to testing, for about one-third of the cohort, and these patients were further analyzed as a sub-cohort. Considering only the patients with ASD, the diagnostic rate was 10%, within the range reported in the literature (8–21%). It was higher (16%) when associated with dysmorphic features and lower (7%) for "isolated" ASD (without ID and without dysmorphic features). In 953 CMAs of the whole cohort, LCSH (≥ 3 Mbp) were analyzed not only for their potential pathogenic significance but were also explored to identify common LCSH in the South Brazilians population. CMA revealed at least one LCSH in 91% of the patients. For about 11.5% of patients, the LCSH suggested consanguinity from the first to the fifth degree, with a greater probability of clinical impact, and in 2.8%, they revealed a putative UPD. LCSH found at a frequency of 5% or more were considered common LCSH in the general population, allowing us to delineate 10 regions as potentially representing ancestral haplotypes of neglectable clinical significance. The main referrals for CMA were developmental delay (56%), ID (33%), ASD (33%) and syndromic features (56%). Some phenotypes in this population may be predictive of a higher probability of indicating a carrier of a pathogenic CNV. Here, we present the largest report of CMA data in a cohort with NDDs and/or CAs from the South of Brazil. We characterize the rare CNVs found along with the main phenotypes presented by each patient and show the importance and usefulness of LCSH interpretation in CMA results that incorporate SNPs, as well as we illustrate the value of CMA to investigate CNV in ASD.

A Pilot Study of Multiplex Ligation-Dependent Probe Amplification Evaluation of Copy Number Variations in Romanian Children with Congenital Heart Defects.

Congenital heart defects (CHDs) have had an increasing prevalence over the last decades, being one of the most common congenital defects. Their etiopathogenesis is multifactorial in origin. About 10-15% of all CHD can be attributed to copy number variations (CNVs), a type of submicroscopic structural genetic alterations. The aim of this study was to evaluate the involvement of CNVs in the development of congenital heart defects. We performed a cohort study investigating the presence of CNVs in the 22q11.2 region and GATA4, TBX5, NKX2-5, BMP4, and CRELD1 genes in patients with syndromic and isolated CHDs. A total of 56 patients were included in the study, half of them (28 subjects) being classified as syndromic. The most common heart defect in our study population was ventricular septal defect (VSD) at 39.28%. There were no statistically significant differences between the two groups in terms of CHD-type distribution, demographical, and clinical features, with the exceptions of birth length, weight, and length at the time of blood sampling, that were significantly lower in the syndromic group. Through multiplex ligation-dependent probe amplification (MLPA) analysis, we found two heterozygous deletions in the 22q11.2 region, both in patients from the syndromic group. No CNVs involving GATA4, NKX2-5, TBX5, BMP4, and CRELD1 genes were identified in our study. We conclude that the MLPA assay may be used as a first genetic test in patients with syndromic CHD and that the 22q11.2 region may be included in the panels used for screening these patients.

Molecular basis and genetic testing strategies for diagnosing 21-hydroxylase deficiency, including CAH-X syndrome.

Congenital adrenal hyperplasia (CAH) is a group of autosomally recessive disorders that result from impaired synthesis of glucocorticoid and mineralocorticoid. Most cases (~95%) are caused by mutations in the CYP21A2 gene, which encodes steroid 21-hydroxylase. CAH patients manifest a wide phenotypic spectrum according to their degree of residual enzyme activity. CYP21A2 and its pseudogene (CYP21A1P) are located 30 kb apart in the 6q21.3 region and share approximately 98% of their sequences in the coding region. Both genes are aligned in tandem with the C4, SKT19, and TNX genes, forming 2 segments of the RCCX modules that are arranged as STK19-C4A-CYP21A1P-TNXA-STK19B-C4B-CYP21A2-TNXB. The high sequence homology between the active gene and pseudogene leads to frequent microconversions and large rearrangements through intergenic recombination. The TNXB gene encodes an extracellular matrix glycoprotein, tenascin-X (TNX), and defects in TNXB cause Ehlers-Danlos syndrome. Deletions affecting both CYP21A2 and TNXB result in a contiguous gene deletion syndrome known as CAH-X syndrome. Because of the high homology between CYP21A2 and CYP21A1P, genetic testing for CAH should include an evaluation of copy number variations, as well as Sanger sequencing. Although it poses challenges for genetic testing, a large number of mutations and their associated phenotypes have been identified, which has helped to establish genotype-phenotype correlations. The genotype is helpful for guiding early treatment, predicting the clinical phenotype and prognosis, and providing genetic counseling. In particular, it can help ensure proper management of the potential complications of CAH-X syndrome, such as musculoskeletal and cardiac defects. This review focuses on the molecular pathophysiology and genetic diagnosis of 21-hydroxylase deficiency and highlights genetic testing strategies for CAH-X syndrome.

37. Chromosomal microarray in the investigation of ASD: Diagnostic yield of 333 cases

Chromosomal microarray (CMA) is reference in evaluation of copy number variations (CNVs) in patients with autism spectrum disorders (ASD). We discuss the results of CMA performed during 2013-2019 in a series of 333 patients from the south of Brazil, whose clinical features encompassed ASD, with or without intellectual disability (ID) and with or without dysmorphisms (facial and/or congenital malformations). The male/female ratio was ∼4:1. Us 262 males (253 with diagnosis of Autism and 9 of Asperger Syndrome), 59 were had less than 5 years, bellow the diagnostic age for ID (12 dysmorphic).

Evaluation of copy number variants for genetic hearing loss: a review of current approaches and recent findings.

Structural variation includes a change in copy number, orientation, or location of a part of the genome. Copy number variants (CNVs) are a common cause of genetic hearing loss, comprising nearly 20% of diagnosed cases. While large deletions involving the gene STRC are the most common pathogenic CNVs, a significant proportion of known hearing loss genes also contain pathogenic CNVs. In this review, we provide an overview of currently used methods for detection of CNVs in genes known to cause hearing loss including molecular techniques such as multiplex ligation probe amplification (MLPA) and digital droplet polymerase chain reaction (ddPCR), array-CGH and single-nucleotide polymorphism (SNP) arrays, as well as techniques for detection of CNVs using next-generation sequencing data analysis including targeted gene panel, exome, and genome sequencing data. In addition, in this review, we compile published data on pathogenic hearing loss CNVs to provide an up-to-date overview. We show that CNVs have been identified in 29 different non-syndromic hearing loss genes. An understanding of the contribution of CNVs to genetic hearing loss is critical to the current diagnosis of hearing loss and is crucial for future gene therapies. Thus, evaluation for CNVs is required in any modern pipeline for genetic diagnosis of hearing loss.

The diagnostic yield of whole exome sequencing as a first approach in consanguineous Omani renal ciliopathy syndrome patients.

Background: Whole exome sequencing (WES) is becoming part of routine clinical and diagnostic practice. In the investigation of inherited cystic kidney disease and renal ciliopathy syndromes, WES has been extensively applied in research studies as well as for diagnostic utility to detect various novel genes and variants. The yield of WES critically depends on the characteristics of the patient population. Methods: In this study, we selected 8 unrelated Omani children, presenting with renal ciliopathy syndromes with a positive family history and originating from consanguineous families. We performed WES in affected children to determine the genetic cause of disease and to test the yield of this approach, coupled with homozygosity mapping, in this highly selected population. DNA library construction and WES was carried out using SureSelect Human All Exon V6 Enrichment Kit and Illumina HiSeq platform. For variants filtering and annotation Qiagen Variant Ingenuity tool was used. Nexus copy number software from BioDiscovery was used for evaluation of copy number variants and whole gene deletions. Patient and parental DNA was used to confirm mutations and the segregation of alleles using Sanger sequencing. Results: Genetic analysis identified 4 potential causative homozygous variants each confirmed by Sanger sequencing in 4 clinically relevant ciliopathy syndrome genes, ( TMEM231, TMEM138, WDR19 and BBS9), leading to an overall diagnostic yield of 50%. Conclusions: WES coupled with homozygosity mapping provided a diagnostic yield of 50% in this selected population. This genetic approach needs to be embedded into clinical practise to allow confirmation of clinical diagnosis, to inform genetic screening as well as family planning decisions. Half of the patients remain without diagnosis highlighting the technical and interpretational hurdles that need to be overcome in the future.

The diagnostic yield of whole exome sequencing as a first approach in consanguineous Omani renal ciliopathy syndrome patients

Background: Whole exome sequencing (WES) is becoming part of routine clinical and diagnostic practice. In the investigation of inherited cystic kidney disease and renal ciliopathy syndromes, WES has been extensively applied in research studies as well as for diagnostic utility to detect various novel genes and variants. The yield of WES critically depends on the characteristics of the patient population. Methods: In this study, we selected 8 unrelated Omani children, presenting with renal ciliopathy syndromes with a positive family history and originating from consanguineous families. We performed WES in affected children to determine the genetic cause of disease and to test the yield of this approach, coupled with homozygosity mapping, in this highly selected population. DNA library construction and WES was carried out using SureSelect Human All Exon V6 Enrichment Kit and Illumina HiSeq platform. For variants filtering and annotation Qiagen Variant Ingenuity tool was used. Nexus copy number software from BioDiscovery was used for evaluation of copy number variants and whole gene deletions. Patient and parental DNA was used to confirm mutations and the segregation of alleles using Sanger sequencing. Results: Genetic analysis identified 4 potential causative homozygous variants each confirmed by Sanger sequencing in 4 clinically relevant ciliopathy syndrome genes, ( TMEM231, TMEM138, WDR19 and BBS9), leading to an overall diagnostic yield of 50%. Conclusions: WES coupled with homozygosity mapping provided a diagnostic yield of 50% in this selected population. This genetic approach needs to be embedded into clinical practise to allow confirmation of clinical diagnosis, to inform genetic screening as well as family planning decisions. Half of the patients remain without diagnosis highlighting the technical and interpretational hurdles that need to be overcome in the future.

HBOS-CNV: A New Approach to Detect Copy Number Variations From Next-Generation Sequencing Data.

Copy number variation (CNV) is a genomic mutation that plays an important role in tumor evolution and tumor genesis. Accurate detection of CNVs from next-generation sequencing (NGS) data is still a challenging task due to artifacts such as uneven mapped reads and unbalanced amplitudes of gains and losses. This study proposes a new approach called HBOS-CNV to detect CNVs from NGS data. The central point of HBOS-CNV is that it uses a new statistic, the histogram-based outlier score (HBOS), to evaluate the fluctuation of genome bins to determine those of changed copy numbers. In comparison with existing statistics in the evaluation of CNVs, HBOS is a non-linearly transformed value from the observed read depth (RD) value of each genome bin, having the potential ability to relieve the effects resulted from the above artifacts. In the calculation of HBOS values, a dynamic width histogram is utilized to depict the density of bins on the genome being analyzed, which can reduce the effects of noises partially contributed by mapping and sequencing errors. The evaluation of genome bins using such a new statistic can lead to less extremely significant CNVs having a high probability of detection. We evaluated this method using a large number of simulation datasets and compared it with four existing methods (CNVnator, CNV-IFTV, CNV-LOF, and iCopyDav). The results demonstrated that our proposed method outperforms the others in terms of sensitivity, precision, and F1-measure. Furthermore, we applied the proposed method to a set of real sequencing samples from the 1000 Genomes Project and determined a number of CNVs with biological meanings. Thus, the proposed method can be regarded as a routine approach in the field of genome mutation analysis for cancer samples.

The diagnostic yield of whole exome sequencing as a first approach in consanguineous Omani renal ciliopathy syndrome patients

Background: Whole exome sequencing (WES) is becoming part of routine clinical and diagnostic practice. In the investigation of inherited cystic kidney disease and renal ciliopathy syndromes, WES has been extensively applied in research studies as well as for diagnostic utility to detect various novel genes and variants. The yield of WES critically depends on the characteristics of the patient population. Methods: In this study, we selected 8 unrelated Omani children, presenting with renal ciliopathy syndromes with a positive family history and originating from consanguineous families. We performed WES in affected children to determine the genetic cause of disease and to test the yield of this approach, coupled with homozygosity mapping, in this highly selected population. DNA library construction and WES was carried out using SureSelect Human All Exon V6 Enrichment Kit and Illumina HiSeq platform. For variants filtering and annotation Qiagen Variant Ingenuity tool was used. Nexus copy number software from BioDiscovery was used for evaluation of copy number variants and whole gene deletions. Patient and parental DNA was used to confirm mutations and the segregation of alleles using Sanger sequencing. Results: Genetic analysis identified 4 potential causative homozygous variants each confirmed by Sanger sequencing in 4 clinically relevant ciliopathy syndrome genes, (TMEM231, TMEM138, WDR19 and BBS9), leading to an overall diagnostic yield of 50%. Conclusions: WES coupled with homozygosity mapping provided a diagnostic yield of 50% in this selected population. This genetic approach needs to be embedded into clinical practise to allow confirmation of clinical diagnosis, to inform genetic screening as well as family planning decisions. Half of the patients remain without diagnosis highlighting the technical and interpretational hurdles that need to be overcome in the future.

Increasing the Clinical Psychiatric Knowledge Base About Pathogenic Copy Number Variation.

Specific copy number variants (CNVs) have been robustly associated with intellectual disability, autism, and schizophrenia. Most of the literature focus has been on documenting the existence of these phenomena. There are few data to guide therapeutic choices for these “orphan” diseases. We call for systematic and longitudinal case reports which, if carefully conducted, may provide crucial initial knowledge to guide therapeutics. We provide a step-by-step overview, a tailored set of consensus criteria for high-quality case reports, and a specific set of learning resources.

Chromosomal alterations of pediatric malignancy in a West Texas population

Background: Comparative genomic hybridization (CGH) microarrays are used forgenome-wide evaluation of copy number variations (CNV) of known prognostic significance;however, unannotated variants of uncertain significance (VUS) are frequently present. Toidentify potentially actionable targets, we retrospectively analyzed VUS loci using CGH datafrom 192 cases of cancer or genetic disorders treated at TTUHSC.Methods: DNA was hybridized onto CytoSure Constitution V3 arrays, scanned with theAgilent microarray D scanner, and analyzed by CytoSure Interpret Software.Results: We found 794 distinct CNVs, the most frequent being 14q32.22 (112rearrangements), 14q11.2 (100), 8p11.2 (98), 15q11.1-q11.2 (83), and 8p23.1 (77). In particular,8p11.22 alterations were found in many pediatric tumors, with gain/loss ratio of 4.7. Linkage ofTACC1, TM2D2, KAT6A and ADAM32 was indicated by a similar 5-year survival rate of 75.3%(n = 253), which was greater than in unaltered cases (62.2%, n = 15,809 cases) in The CancerGenome Atlas database.Conclusion: Knockdown of genes occurring at variants of uncertain significance (VUS)loci may help identify new therapy targets.

MicroRNA-copy number variations in coronary artery disease patients with or without type 2 diabetes mellitus

Background An important cause of Coronary Artery Disease (CAD) is Type 2 Diabetes Mellitus (T2DM). The aim of this study was the evaluation of copy number variations (CNVs) of hsa-miR-93, hsa-miR-122, hsa-miR-192 in CAD patients with or without T2DM. Methods CNVs of three micro-RNAs in 50 CAD patients and 50 non-CAD subjects both with and without diabetes were evaluated by real-time PCR and compared in three comparison groups namely 1, 2 and 3 (including comparison between CAD and non-CAD, diabetic CAD and non-diabetic CAD and between diabetic CAD and diabetic non-CAD subjects, respectively). Results There were significant differences in CNVs of hsa-miR-93 between cases and controls in comparison groups 1 and 3 (p = .0310 and .0232, respectively), for hsa-miR-122 in all comparison groups, and for hsa-miR-192 in comparison group 3 (p = .0181). Conclusion We showed the association of these microRNA-CNVs with CAD, T2DM or both simultaneously.

46. Evaluation of NxClinical for integration of CNV, LOH, and sequence variants for clinical cancer case review

The evaluation of copy number variants (CNVs), loss of heterozygosity (LOH), and sequence variants provides valuable clinical information for the diagnosis and prognosis of both hematologic malignancies and solid tumors. In our laboratories, genomic profiling is typically performed using chromosomal microarray analysis (CMA), Sanger sequencing and next generation sequencing (NGS) assays. The data are analyzed individually with different software tools and then combined in an integrated report.

Integration of genomic copy number variations and chemotherapy-response biomarkers in pediatric sarcoma

BackgroundWhile most pediatric sarcomas respond to front-line therapy, some bone sarcomas do not show radiographic response like soft-tissue sarcomas (rhabdomyosarccomas) but do show 90% necrosis. Though, new therapies are urgently needed to improve survival and quality of life in pediatric patients with sarcomas. Complex chromosomal aberrations such as amplifications and deletions of DNA sequences are frequently observed in pediatric sarcomas. Evaluation of copy number variations (CNVs) associated with pediatric sarcoma patients at the time of diagnosis or following therapy offers an opportunity to assess dysregulated molecular targets and signaling pathways that may drive sarcoma development, progression, or relapse. The objective of this study was to utilize publicly available data sets to identify potential predictive biomarkers of chemotherapeutic response in pediatric Osteosarcoma (OS), Rhabdomyosarcoma (RMS) and Ewing’s Sarcoma Family of Tumors (ESFTs) based on CNVs following chemotherapy (OS n = 117, RMS n = 64, ESFTs n = 25 tumor biopsies).MethodsThere were 206 CNV profiles derived from pediatric sarcoma biopsies collected from the public databases TARGET and NCBI-Gene Expression Omnibus (GEO). Through our comparative genomic analyses of OS, RMS, and ESFTs and 22,255 healthy individuals called from the Database of Genomic Variants (DGV), we identified CNVs (amplifications and deletions) pattern of genomic instability in these pediatric sarcomas. By integrating CNVs of Cancer Cell Line Encyclopedia (CCLE) identified in the pool of genes with drug-response data from sarcoma cell lines (n = 27) from Cancer Therapeutics Response Portal (CTRP) Version 2, potential predictive biomarkers of therapeutic response were identified.ResultsGenes associated with survival and/recurrence of these sarcomas with statistical significance were found on long arm of chromosome 8 and smaller aberrations were also identified at chromosomes 1q, 12q and x in OS, RMS, and ESFTs. A pool of 63 genes that harbored amplifications and/or deletions were frequently associated with recurrence across OS, RMS, and ESFTs. Correlation analysis of CNVs from CCLE with drug-response data of CTRP in 27 sarcoma cell lines, 33 CNVs out of 63 genes correlated with either sensitivity or resistance to 17 chemotherapies from which actionable CNV signatures such as IGF1R, MYC, MAPK1, ATF1, and MDM2 were identified. These CNV signatures could potentially be used to delineate patient populations that will respond versus those that will not respond to a particular chemotherapy.ConclusionsThe large-scale analyses of CNV-drug screening provides a platform to evaluate genetic alterations across aggressive pediatric sarcomas. Additionally, this study provides novel insights into the potential utilization of CNVs as not only prognostic but also as predictive biomarkers of therapeutic response. Information obtained in this study may help guide and prioritize patient-specific therapeutic options in pediatric bone and soft-tissue sarcomas.

Evaluation of copy-number variants as modifiers of breast and ovarian cancer risk for BRCA1 pathogenic variant carriers

Genome-wide studies of patients carrying pathogenic variants (mutations) in BRCA1 or BRCA2 have reported strong associations between single-nucleotide polymorphisms (SNPs) and cancer risk. To conduct the first genome-wide association analysis of copy-number variants (CNVs) with breast or ovarian cancer risk in a cohort of 2500 BRCA1 pathogenic variant carriers, CNV discovery was performed using multiple calling algorithms and Illumina 610k SNP array data from a previously published genome-wide association study. Our analysis, which focused on functionally disruptive genomic deletions overlapping gene regions, identified a number of loci associated with risk of breast or ovarian cancer for BRCA1 pathogenic variant carriers. Despite only including putative deletions called by at least two or more algorithms, detection of selected CNVs by ancillary molecular technologies only confirmed 40% of predicted common (>1% allele frequency) variants. These include four loci that were associated (unadjusted P<0.05) with breast cancer (GTF2H2, ZNF385B, NAALADL2 and PSG5), and two loci associated with ovarian cancer (CYP2A7 and OR2A1). An interesting finding from this study was an association of a validated CNV deletion at the CYP2A7 locus (19q13.2) with decreased ovarian cancer risk (relative risk=0.50, P=0.007). Genomic analysis found this deletion coincides with a region displaying strong regulatory potential in ovarian tissue, but not in breast epithelial cells. This study highlighted the need to verify CNVs in vitro, but also provides evidence that experimentally validated CNVs (with plausible biological consequences) can modify risk of breast or ovarian cancer in BRCA1 pathogenic variant carriers.

GenomeCAT: a versatile tool for the analysis and integrative visualization of DNA copy number variants

BackgroundThe analysis of DNA copy number variants (CNV) has increasing impact in the field of genetic diagnostics and research. However, the interpretation of CNV data derived from high resolution array CGH or NGS platforms is complicated by the considerable variability of the human genome. Therefore, tools for multidimensional data analysis and comparison of patient cohorts are needed to assist in the discrimination of clinically relevant CNVs from others.ResultsWe developed GenomeCAT, a standalone Java application for the analysis and integrative visualization of CNVs. GenomeCAT is composed of three modules dedicated to the inspection of single cases, comparative analysis of multidimensional data and group comparisons aiming at the identification of recurrent aberrations in patients sharing the same phenotype, respectively. Its flexible import options ease the comparative analysis of own results derived from microarray or NGS platforms with data from literature or public depositories. Multidimensional data obtained from different experiment types can be merged into a common data matrix to enable common visualization and analysis. All results are stored in the integrated MySQL database, but can also be exported as tab delimited files for further statistical calculations in external programs.ConclusionsGenomeCAT offers a broad spectrum of visualization and analysis tools that assist in the evaluation of CNVs in the context of other experiment data and annotations. The use of GenomeCAT does not require any specialized computer skills. The various R packages implemented for data analysis are fully integrated into GenomeCATs graphical user interface and the installation process is supported by a wizard. The flexibility in terms of data import and export in combination with the ability to create a common data matrix makes the program also well suited as an interface between genomic data from heterogeneous sources and external software tools. Due to the modular architecture the functionality of GenomeCAT can be easily extended by further R packages or customized plug-ins to meet future requirements.

Statistical Models for the Analysis and Design of Digital Polymerase Chain Reaction (dPCR) Experiments.

Statistical methods for the analysis and design of experiments using digital PCR (dPCR) have received only limited attention and have been misused in many instances. To address this issue and to provide a more general approach to the analysis of dPCR data, we describe a class of statistical models for the analysis and design of experiments that require quantification of nucleic acids. These models are mathematically equivalent to generalized linear models of binomial responses that include a complementary, log-log link function and an offset that is dependent on the dPCR partition volume. These models are both versatile and easy to fit using conventional statistical software. Covariates can be used to specify different sources of variation in nucleic acid concentration, and a model's parameters can be used to quantify the effects of these covariates. For purposes of illustration, we analyzed dPCR data from different types of experiments, including serial dilution, evaluation of copy number variation, and quantification of gene expression. We also showed how these models can be used to help design dPCR experiments, as in selection of sample sizes needed to achieve desired levels of precision in estimates of nucleic acid concentration or to detect differences in concentration among treatments with prescribed levels of statistical power.

Genetic Evaluation of Copy Number Variations, Loss of Heterozygosity, and Single-Nucleotide Variant Levels in Human Embryonic Stem Cells With or Without Skewed X Chromosome Inactivation.

Human embryonic stem cells (hESCs) exhibiting skewed X chromosome inactivation (XCI) have been reported. The copy number variations (CNVs), loss of heterozygosity (LOH), or single-nucleotide variant (SNV) events in those epigenetically distinct cells remain unknown, and whether such genetic abnormalities will influence the XCI status of hESCs is unclear. In this study, three hESCs with skewed XCI, three with random XCI, and two male hESC lines at different passages were analyzed for CNVs and LOH levels using a high-resolution genotyping microarray. Whole-exome sequencing was used to investigate the potentially damaging SNVs. On average, 17.6 CNVs and 5.3 cases of LOH were identified in the skewed hESCs, which were similar to the rates observed in random hESCs. Five recurrent CNV regions were uniquely identified in the skewed hESCs, but all of them were considered polymorphisms. With the exception of a nongenic CNV, no additional CNVs were detected on the X chromosome in the skewed hESCs. Although the XCI status in two hESC lines was observed to be changed from random to skewed, no significant CNV difference was identified before and after the XCI change. SNV analysis indicated that normal alleles are maintained for most genes within copy-neutral LOH regions. Three types of expression patterns were observed in heterozygous alleles, and the damaging SNVs in skewed hESCs favored the expression of the wild-type alleles. In conclusion, in the present study, we did not find genetic differences in the CNV and LOH levels between hESCs with and without skewed XCI. Wild-type allele expression in the presence of damaging SNVs on the X chromosome in skewed hESCs might alleviate adverse effects in those hESCs.

Evaluation of copy number variation and gene expression in neurofibromatosis type-1-associated malignant peripheral nerve sheath tumours.

BackgroundNeurofibromatosis type-1 (NF1) is a complex neurogenetic disorder characterised by the development of benign and malignant tumours of the peripheral nerve sheath (MPNSTs). Whilst biallelic NF1 gene inactivation contributes to benign tumour formation, additional cellular changes in gene structure and/or expression are required to induce malignant transformation. Although few molecular profiling studies have been performed on the process of progression of pre-existing plexiform neurofibromas to MPNSTs, the integrated analysis of copy number alterations (CNAs) and gene expression is likely to be key to understanding the molecular mechanisms underlying NF1-MPNST tumorigenesis. In a pilot study, we employed this approach to identify genes differentially expressed between benign and malignant NF1 tumours.ResultsSPP1 (osteopontin) was the most differentially expressed gene (85-fold increase in expression), compared to benign plexiform neurofibromas. Short hairpin RNA (shRNA) knockdown of SPP1 in NF1-MPNST cells reduced tumour spheroid size, wound healing and invasion in four different MPNST cell lines. Seventy-six genes were found to exhibit concordance between CNA and gene expression level.ConclusionsPathway analysis of these genes suggested that glutathione metabolism and Wnt signalling may be specifically involved in NF1-MPNST development. SPP1 is associated with malignant transformation in NF1-associated MPNSTs and could prove to be an important target for therapeutic intervention.Electronic supplementary materialThe online version of this article (doi:10.1186/s40246-015-0025-3) contains supplementary material, which is available to authorized users.