Distribution Of Copy Number Variations Research Articles

The research on association of copy number variation in chromosome 9p21 region with atherothrombotic stroke in the Han Chinese population

Background/purposeThe copy number variants (CNVs) contain more genetic information compared with SNPs. The aim of this study was to elucidate whether the CNVs in Chromosome 9p21 region are associated with increased risk of Atherothrombotic stroke (ATS) in a Han Chinese population. MethodsA case-controlled association study was conducted in which only patients with ATS were enrolled. The CNVs were detected by the method of multiplex competitive amplification. The differences in distribution of CNVs between cases and controls were analyzed using univariate and multivariate logistic regression analysis. Subgroup analyses were also carried out to determine whether the effect of the CNVs was specific to age and gender among the subjects. ResultsA total of 274 ATS patients and 282 health controls were included in the present study. 4 genes (ANRIL, CDKN2A, CDKN2B, and MTAP) including eight gene fragments in all were analyzed for CNV. The results showed that the copied number of most CNV in the 4 genes is two. There was no significant difference of CNV frequency between groups. ConclusionsThe obtained data suggested a negative association between CNV of the four genes and ATS. It is necessary to perform sequencing analyses across the entire 9p21 region for detecting rare or uncommon CNV.

Complement C4A and C4B Gene Copy Number Study in Alzheimer's Disease Patients.

Increasing evidence suggests the importance of neuroinflammation in the pathogenesis of Alzheimer's disease (AD), which is a complex neurodegenerative disorder. Complement activation occurs in the brain of patients with AD and seems to contribute to an important local inflammatory state. Increased expression of the fourth serum complement component 4 (C4) has been observed in AD patients in many studies. This protein has two isoforms, encoded by two genes: C4A and C4B localized to the HLA class III region. These genes exhibit copy number variations (CNVs) and this different gene copy number can influence C4 protein levels. We focalized our attention on these two genes, determining the distribution of CNVs in AD patients, compared with healthy controls, in order to analyse their possible involvement in AD pathogenesis. We investigated 191 AD patients and 300 healthy controls. The C4A and C4B copy numbers were assessed by quantitative PCR (qPCR). The results obtained showed a statistically significant increase in the number of copies for both C4A and C4B in AD patients, compared with healthy controls (p<0,001). The presence of high C4A and C4B copy numbers in AD patients could explain the increased C4 protein expression observed in AD patients, thus highlighting a possible role for C4A and C4B CNVs in the risk of developing AD.

Does copy number variation of APOL1 gene affect the susceptibility to focal segmental glomerulosclerosis?

Background: APOL1 risk variants (G1 and G2) are associated with increased susceptibility to focal segmental glomerulosclerosis (FSGS) in African population. However, the two risk mutations were not found in Chinese FSGS patients. In this study, we explored the association between the copy number variation (CNV) of APOL1 gene and FSGS.Methods: APOL1 copy number variations were detected by quantitative real-time PCR with TaqMan probes and compared between 133 FSGS patients and 123 controls. The association between CNV of APOL1 gene and clinical parameters was also investigated.Results: The distribution of APOL1 CNV did not show significant difference between FSGS patients and controls. The creatinine and proteinuria in the high copy number group (CN ≥ 3) were higher than the other two groups, but the difference was not significant (p > .05). The FSGS pathological types were different among the three groups.Conclusion: There was no significant difference in the distribution of APOL1 gene copy variants between FSGS patients and normal controls, and there was no significant correlation between the APOL1 gene CNV and the FSGS patients’ clinical manifestations. APOL1 CNVs may be not associated with susceptibility to FSGS.

Association betweenTLR7copy number variations and hepatitis B virus infection outcome in Chinese

AIMTo explore whether copy number variations (CNVs) of toll-like receptor 7 (TLR7) are associated with susceptibility to chronic hepatitis B virus (HBV) infection.METHODSThis study included 623 patients (495 males and 128 females) with chronic hepatitis B virus infection (CHB) and 300 patients (135 females and 165 males) with acute hepatitis B virus infection (AHB) as controls. All CHB patients were further categorized according to disease progression after HBV infection (CHB, liver cirrhosis, or hepatocellular carcinoma). Copy numbers of the TLR7 gene were measured using the AccuCopy method. χ2 tests were used to evaluate the association between TLR7 CNVs and infection type. P values, odds ratios, and 95% confidence intervals (CIs) were used to estimate the effects of risk.RESULTSAmong male patients, there were significant differences between the AHB group and CHB group in the distribution of TLR7 CNVs. Low copy number of TLR7 was significantly associated with chronic HBV infection (OR = 0.329, 95%CI: 0.229-0.473, P < 0.001). Difference in TLR7 copy number was also found between AHB and CHB female patients, with low copy number again associated with an increased risk of chronic HBV infection (OR = 0.292, 95%CI: 0.173-0.492, P < 0.001). However, there were no significant differences in TLR7 copy number among the three types of chronic HBV infection (CHB, liver cirrhosis, or hepatocellular carcinoma). In addition, there was no association between TLR7 copy number and titer of the HBV e antigen.CONCLUSIONLow TLR7 copy number is a risk factor for chronic HBV infection but is not associated with later stages of disease progression.

CNV analysis in the Lithuanian population.

BackgroundAlthough copy number variation (CNV) has received much attention, knowledge about the characteristics of CNVs such as occurrence rate and distribution in the genome between populations and within the same population is still insufficient. In this study, Illumina 770 K HumanOmniExpress-12 v1.0 (and v1.1) arrays were used to examine the diversity and distribution of CNVs in 286 unrelated individuals from the two main ethnolinguistic groups of the Lithuanian population (Aukštaičiai and Žemaičiai) (see Additional file 3). For primary data analysis, the Illumina GenomeStudio™ Genotyping Module v1.9 and two algorithms, cnvPartition 3.2.0 and QuantiSNP 2.0, were used to identify high-confidence CNVs.ResultsA total of 478 autosomal CNVs were detected by both algorithms, and those were clustered in 87 copy number variation regions (CNVRs), spanning ~12.5 Mb of the genome (see Table 1). At least 8.6 % of the CNVRs were unique and had not been reported in the Database of Genomic Variants. Most CNVRs (57.5 %) were rare, with a frequency of <1 %, whereas common CNVRs with at least 5 % frequency made up only 1.1 % of all CNVRs identified. About 49 % of non-singleton CNVRs were shared between Aukštaičiai and Žemaičiai, and the remaining CNVRs were specific to each group. Many of the CNVs detected (66 %) overlapped with known UCSC gene regions.ConclusionsThe ethnolinguistic groups of the Lithuanian population could not be differentiated based on CNV profiles, which may reflect their geographical proximity and suggest the homogeneity of the Lithuanian population. In addition, putative novel CNVs unique to the Lithuanian population were identified. The results of our study enhance the CNV map of the Lithuanian population.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-016-0373-6) contains supplementary material, which is available to authorized users.

Influence of ATM-Mediated DNA Damage Response on Genomic Variation in Human Induced Pluripotent Stem Cells.

Genome instability is a potential limitation to the research and therapeutic application of induced pluripotent stem cells (iPSCs). Observed genomic variations reflect the combined activities of DNA damage, cellular DNA damage response (DDR), and selection pressure in culture. To understand the contribution of DDR on the distribution of copy number variations (CNVs) in iPSCs, we mapped CNVs of iPSCs with mutations in the central DDR gene ATM onto genome organization landscapes defined by genome-wide replication timing profiles. We show that following reprogramming the early and late replicating genome is differentially affected by CNVs in ATM-deficient iPSCs relative to wild-type iPSCs. Specifically, the early replicating regions had increased CNV losses during retroviral (RV) reprogramming. This differential CNV distribution was not present after later passage or after episomal reprogramming. Comparison of different reprogramming methods in the setting of defective DDR reveals unique vulnerability of early replicating open chromatin to RV vectors.

Multiply to conquer: Copy number variations at Ppd-B1 and Vrn-A1 facilitate global adaptation in wheat.

BackgroundCopy number variation was found to be a frequent type of DNA polymorphism in the human genome often associated with diseases but its importance in crops and the effects on agronomic traits are still largely unknown.ResultsHere, we employed a large worldwide panel of 1110 winter wheat varieties to assess the frequency and the geographic distribution of copy number variants at the Photoperiod-B1 (Ppd-B1) and the Vernalization-A1 (Vrn-A1) loci as well as their effects on flowering time under field conditions. We identified a novel four copy variant of Vrn-A1 and based on the phylogenetic relationships among the lines show that the higher copy variants at both loci are likely to have arisen independently multiple times. In addition, we found that the frequency of the different copy number variants at both loci reflects the environmental conditions in the varieties’ region of origin and based on multi-location field trials show that Ppd-B1 copy number has a substantial effect on the fine-tuning of flowering time.ConclusionsIn conclusion, our results show the importance of copy number variation at Ppd-B1 and Vrn-A1 for the global adaptation of wheat making it a key factor for wheat success in a broad range of environments and in a wider context substantiate the significant role of copy number variation in crops.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-015-0258-0) contains supplementary material, which is available to authorized users.

Connecting Anxiety and Genomic Copy Number Variation: A Genome-Wide Analysis in CD-1 Mice.

Genomic copy number variants (CNVs) have been implicated in multiple psychiatric disorders, but not much is known about their influence on anxiety disorders specifically. Using next-generation sequencing (NGS) and two additional array-based genotyping approaches, we detected CNVs in a mouse model consisting of two inbred mouse lines showing high (HAB) and low (LAB) anxiety-related behavior, respectively. An influence of CNVs on gene expression in the central (CeA) and basolateral (BLA) amygdala, paraventricular nucleus (PVN), and cingulate cortex (Cg) was shown by a two-proportion Z-test (p = 1.6 x 10-31), with a positive correlation in the CeA (p = 0.0062), PVN (p = 0.0046) and Cg (p = 0.0114), indicating a contribution of CNVs to the genetic predisposition to trait anxiety in the specific context of HAB/LAB mice. In order to confirm anxiety-relevant CNVs and corresponding genes in a second mouse model, we further examined CD-1 outbred mice. We revealed the distribution of CNVs by genotyping 64 CD 1 individuals using a high-density genotyping array (Jackson Laboratory). 78 genes within those CNVs were identified to show nominally significant association (48 genes), or a statistical trend in their association (30 genes) with the time animals spent on the open arms of the elevated plus-maze (EPM). Fifteen of them were considered promising candidate genes of anxiety-related behavior as we could show a significant overlap (permutation test, p = 0.0051) with genes within HAB/LAB CNVs. Thus, here we provide what is to our knowledge the first extensive catalogue of CNVs in CD-1 mice and potential corresponding candidate genes linked to anxiety-related behavior in mice.

Global patterns of large copy number variations in the human genome reveal complexity in chromosome organization.

Global patterns of copy number variations (CNVs) in chromosomes are required to understand the dynamics of genome organization and complexity. For this study, analysis was performed using the Affymetrix Genome-Wide Human SNP Array 6.0 chip and CytoScan High-Density arrays. We identified a total of 44 109 CNVs from 1715 genomes with a mean of 25 CNVs in an individual, which established the first drafts of population-specific CNV maps providing a rationale for prioritizing chromosomal regions. About 19 905 ancient CNVs were identified across all chromosomes and populations at varying frequencies. CNV count, and sometimes CNV size, contributed to the bulk CNV size of the chromosome. Population specific lengthening and shortening of chromosomal length was observed. Sex bias for CNV presence was largely dependent on ethnicity. Lower CNV inheritance rate was observed for India, compared to YRI and CEU. A total of 33 candidate CNV hotspots from 5382 copy number (CN) variable region (CNVR) clusters were identified. Population specific CNV distribution patterns in p and q arms disturbed the assumption that CNV counts in the p arm are less common compared to long arms, and the CNV occurrence and distribution in chromosomes is length independent. This study unraveled the force of independent evolutionary dynamics on genome organization and complexity across chromosomes and populations.

Extensive copy-number variation of young genes across stickleback populations.

Duplicate genes emerge as copy-number variations (CNVs) at the population level, and remain copy-number polymorphic until they are fixed or lost. The successful establishment of such structural polymorphisms in the genome plays an important role in evolution by promoting genetic diversity, complexity and innovation. To characterize the early evolutionary stages of duplicate genes and their potential adaptive benefits, we combine comparative genomics with population genomics analyses to evaluate the distribution and impact of CNVs across natural populations of an eco-genomic model, the three-spined stickleback. With whole genome sequences of 66 individuals from populations inhabiting three distinct habitats, we find that CNVs generally occur at low frequencies and are often only found in one of the 11 populations surveyed. A subset of CNVs, however, displays copy-number differentiation between populations, showing elevated within-population frequencies consistent with local adaptation. By comparing teleost genomes to identify lineage-specific genes and duplications in sticklebacks, we highlight rampant gene content differences among individuals in which over 30% of young duplicate genes are CNVs. These CNV genes are evolving rapidly at the molecular level and are enriched with functional categories associated with environmental interactions, depicting the dynamic early copy-number polymorphic stage of genes during population differentiation.

Frequency distribution of autoimmunity associated FCGR3B gene copy number in Indian population.

Amongst several human genome variations, copy number variations (CNVs) are considered as an important source of variability contributing to susceptibility to wide range of diseases. Although CNV is scattered for genes throughout the human genome, several of autoimmunity related genes have CN variation and therefore play an important role in susceptibility to autoimmune diseases. The association of the Fc gamma receptor 3B (FCGR3B) gene copy number in autoimmunity is well characterized in various populations studied. The Fc gamma receptor is a low affinity, glycosylphosphatidylinositol-linked receptor for IgG molecule predominantly expressed on human neutrophils. The variable gene copy number of FCGR3B is found to be involved in the impaired clearance of immune complexes, which significantly contribute to the pathogenesis of several autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), type-1 diabetes and others. The FCGR3B copy number ranged from 0 to ≥ 2 copies per diploid genome in other populations, but yet not explored in Indian population. Hence, this study aims to evaluate the variation in the frequency distribution of FCGR3B CNV in Indian population. FCGR3B gene copy number varied significantly when compared to other population of the world. This observation will help us in exploring the potential role of CNV in FCGR3B gene and its association to autoimmune disorders in Indian population.

VCS: Tool for Visualizing Copy Number Variation and Single Nucleotide Polymorphism.

Copy number variation (CNV) or single nucleotide phlyorphism (SNP) is useful genetic resource to aid in understanding complex phenotypes or deseases susceptibility. Although thousands of CNVs and SNPs are currently avaliable in the public databases, they are somewhat difficult to use for analyses without visualization tools. We developed a web-based tool called the VCS (visualization of CNV or SNP) to visualize the CNV or SNP detected. The VCS tool can assist to easily interpret a biological meaning from the numerical value of CNV and SNP. The VCS provides six visualization tools: i) the enrichment of genome contents in CNV; ii) the physical distribution of CNV or SNP on chromosomes; iii) the distribution of log2 ratio of CNVs with criteria of interested; iv) the number of CNV or SNP per binning unit; v) the distribution of homozygosity of SNP genotype; and vi) cytomap of genes within CNV or SNP region.

Copy number variation in Thai population.

Copy number variation (CNV) is a major genetic polymorphism contributing to genetic diversity and human evolution. Clinical application of CNVs for diagnostic purposes largely depends on sufficient population CNV data for accurate interpretation. CNVs from general population in currently available databases help classify CNVs of uncertain clinical significance, and benign CNVs. Earlier studies of CNV distribution in several populations worldwide showed that a significant fraction of CNVs are population specific. In this study, we characterized and analyzed CNVs in 3,017 unrelated Thai individuals genotyped with the Illumina Human610, Illumina HumanOmniexpress, or Illumina HapMap550v3 platform. We employed hidden Markov model and circular binary segmentation methods to identify CNVs, extracted 23,458 CNVs consistently identified by both algorithms, and cataloged these high confident CNVs into our publicly available Thai CNV database. Analysis of CNVs in the Thai population identified a median of eight autosomal CNVs per individual. Most CNVs (96.73%) did not overlap with any known chromosomal imbalance syndromes documented in the DECIPHER database. When compared with CNVs in the 11 HapMap3 populations, CNVs found in the Thai population shared several characteristics with CNVs characterized in HapMap3. Common CNVs in Thais had similar frequencies to those in the HapMap3 populations, and all high frequency CNVs (>20%) found in Thai individuals could also be identified in HapMap3. The majorities of CNVs discovered in the Thai population, however, were of low frequency, or uniquely identified in Thais. When performing hierarchical clustering using CNV frequencies, the CNV data were clustered into Africans, Europeans, and Asians, in line with the clustering performed with single nucleotide polymorphism (SNP) data. As CNV data are specific to origin of population, our population-specific reference database will serve as a valuable addition to the existing resources for the investigation of clinical significance of CNVs in Thais and related ethnicities.

Fcγ receptor IIIa single-nucleotide polymorphisms and haplotypes affect human IgG binding and are associated with lupus nephritis in African Americans.

To investigate whether the Fcγ receptor IIIa-66L/R/H (FcγRIIIa-66L/R/H) polymorphism influences net effective receptor function and to assess if the FCGR3A combined genotypes formed by FcγRIIIa-66L/R/H and FcγRIIIa-176F/V, as well as copy number variation (CNV), confer risk of developing systemic lupus erythematosus (SLE) and lupus nephritis. FcγRIIIa variants, expressed on A20 IIA1.6 cells, were used in flow cytometry-based human IgG-binding assays. Using Pyrosequencing methodology, FCGR3A single-nucleotide polymorphism and CNV genotypes were determined in a cohort of 1,728 SLE patients and 2,404 healthy controls. The FcγRIIIa-66L/R/H (rs10127939) polymorphism influenced ligand binding capacity in the presence of the FcγRIIIa-176V (rs396991) allele. There was a trend toward an association of the low-binding FcγRIIIa-176F allele with lupus nephritis among African Americans (P = 0.0609) but not among European Americans (P > 0.10). Nephritis among African American patients with SLE was associated with FcγRIIIa low-binding haplotypes containing the 66L/R/H and 176F variants (P = 0.03) and with low-binding genotype combinations (P = 0.002). No association was observed among European American patients with SLE. The distribution of FCGR3A CNV was not significantly different among controls and SLE patients with or without nephritis. FcγRIIIa-66L/R/H influences ligand binding. The low-binding haplotypes formed by 66L/R/H and 176F confer enhanced risk of lupus nephritis in African Americans. FCGR3A CNVs are not associated with SLE or lupus nephritis in either African Americans or European Americans.

Association of TLR7 and TSHR copy number variation with Graves’ disease and Graves’ ophthalmopathy in Chinese population in Taiwan

BackgroundGraves’ disease (GD) and Graves’ ophthalmopathy (GO) are autoimmune disorders, which might be influenced by genetic factors. Copy number variation (CNV) is an important source of genomic diversity in humans, and influences disease susceptibility. This study investigated the association between CNV in the TSHR and TLR7 genes and the development of GD and GO in a Chinese population in Taiwan.MethodsFor this case-control study, sample from 196 healthy controls and 484 GD patients, including 203 patients with GO were studied. CNV was detected by real-time polymerase chain reaction (PCR) using TaqMan™ probes and the relative copy number (CN) was estimated by using the comparative Ct method.ResultsThe differences in the distribution of TSHR CNV in healthy controls and GD patients were statistically significant (p value = 0.01). However, the difference in the distribution of TSHR CNV in the control group and the GO group was not statistically significant (p value = 0.06). For TLR7 CNV, the results were not significantly different when we compared the distribution in healthy controls and GD patients and in healthy controls and GO patients (p values for Fisher’s exact test were 0.13 and 0.09, respectively). However, a lower than normal CNV for TLR7 (CNV < 2 for female and CNV < 1 for male) was found to have a protective effect against the development of GD (odds ratio (OR) = 0.24; 95% confidence interval (CI), 0.07-0.75) after adjusting for age and gender.ConclusionsThese results suggested that TSHR and TLR7 CNV might be associated with susceptibility to GD.

A Prospective Screening of Gene Copy Number Variation in Brazilian Admixed Population Sample

Copy number variants (CNVs) represent an important source of variation in the human genome. Some CNVS embedded genes are differently distributed among the human population groups. Therefore, it is important to understand the distribution of CNV within and between populations, especially in those with admixed ancestry, such as the Brazilians. The aim of the study was to investigate the variability of a set of CNV-embedded genes in a sample of the Brazilian population. The CNV-embedded genes were chosen based on data showing that they have differential copy variation distribution between African and Europeans. Four genes (POLR2J4, PCDHB13, NPEPPS and AMY1) were investigated by qPCR in a sample of 96 Brazilians, previously classified by genetic ancestry. The gene AMY1 showed a variable copy numbers in the range of 1 to 8 copies whereas NPEPPS ranged from 1 to 5 copies. A low variability was identified for the POLR2J4 and PCDHB13 genes, showing 2 copies in frequency of 0.875 and 0.917, respectively. Genetic ancestry was not correlated to the number of copies of the AMY1and NPEPPS genes. The results provided an overview of the corresponding frequency of gene copy number variation in a sample of the Brazilian population, serving as reference for further genetic population studies, which may correlate these polymorphisms with other phenotypic features.

Gene copy number variation in Indian population and its implication in health

Objectives Copy number variations (CNV) are important source of human genetic variation, found to be widely prevalent than what was initially predicted. The involvement of CNVs in disease susceptibility and drug response is well reported in other populations but has not been studied to a larger extent in Indian population. The aim of the present study was to evaluate the distribution of copy number variable genes in Indian population and their link, if any, to health, disease and drug response along with development of a comprehensive resource of CNV frequency distribution among different populations. Methods A total of 100 – 280 healthy controls and in variable number of patients from Indian population were genotyped. Genotyping of the copy number (CN) variable genes was carried by PCR-based methodologies (long range PCR, real-time PCR and PRT assay). Results An indicative correlation with disease susceptibility and significant (p < 0.05) difference in the frequency distribution of the CNV variants was observed in our study. MTUS1 deletion variant was found to be significantly (p = 0.0207) associated with a decreased risk to breast cancer. A significant association between CCL3L1 copy number and risk to HIV-1 was also observed. The interethnic comparison of CCL3L1 gene copy number frequency demonstrated significant difference worldwide, being highest in Africans. The common deletion frequency comprising LCE3B and LCE3C genes was found to be highest in European and American populations. The frequency of FCGR3B CN < 2 was found comparatively higher in Indians, Americans and Africans as compared to European Caucasians. Thus, inter-ethnic differences were observed among populations, highlighting varied frequency distribution pattern based on their distinct geographical location. Conclusion This is our first attempt to create a comprehensive map of the frequency distribution of CNVs and its association to disease susceptibility in Indian population. This varied worldwide distribution can thus be relevant from clinical or evolutionary point of view in future.

Genomic copy number variations in glaucomatous neurodegeneration.

Copy number variation (CNV) is one of the major factors contributing to genomic diversity and diseases. It has been shown especially for neurodegenerative diseases that CNVs can play a very important role in genetic predisposition of the disease. Glaucoma is a major neurodegenerative disease causing irreversible vision loss across the globe. We wanted to analyze the impact of CNVs in a genome-wide scale in patients of primary open angle glaucoma (POAG) collected from the West Bengal state of India and reproduce our results in another cohort of Caucasian origin. Genome-wide data was generated on 347 POAG cases and 345 controls on Illumina 660W-Quad arrays and CNVs were called using PennCNV. The CNVs were classified as small ( 100 kb) and analyzed seprately for their involvement in the disease. A publicly available dataset of POAG cohort of 624 cases and 404 controls from Caucasian origin (GLAUGEN study) was used as a validation cohort and genome-wide CNV data of 208 HAPMAP samples was used as global control. We analyzed genome-wide CNV from 1928 samples. For the large CNVs distribution was significantly skewed toward larger size (>1 Mb) in cases compared to controls and this was replicated in the GLAUGEN data. We found that CNVs >1 Mb are enriched for gene rich regions in POAG patients with 125 genes while for controls a similar percentage of large CNVs overlapped with only 5 genes. In 208 HAPMAP samples CNV >1 Mb overlapped with 95 genes. Interestingly, genes found in the patients were unique and did not overlap with controls or HAPMAP samples. Within CNVs of >1 Mb gene-rich large deletions were ~2 fold enriched in patients compared to duplications irrespective of their ethnic background. Such a bias was not observed in the controls. In the smaller CNV range we performed association analysis and identifed novel regions to be under significantly higher CNV in patients’ comapred to controls. Particularly, a CNV encompassing the transcription factor FOXE3 was significantly enriched in patients of both Indian and Caucasian POAG patietns comapred to their respective controls. A sequence analysis of the gene revealed novel missense mutation in the patients. We have shown that genomic CNVs >1 Mb has significantly higher burden in POAG patient’s genome compared to controls irrespective of the population background. We have also identified candidate genes/regions which are uniquely present in POAG cases and absent in controls from all over the world. Our data provide new insights into role of CNV in pathogenesis of POAG.

Genome-wide deserts for copy number variation in vertebrates

Most copy number variations are neutral, but some are deleterious and associated with various human diseases. Copy number variations are distributed non-randomly in vertebrate genomes, and it was recently reported that ohnologs, which are duplicated genes derived from whole genome duplication, are refractory to copy number variations. However, it is unclear what genomic factors affect the deleterious effects of copy number variations and the biological significance of the biased genomic distribution of copy number variations remains poorly understood. Here we show that non-ohnologs neighbouring ohnologs are unlikely to have copy number variations, resulting in ohnolog-rich regions in vertebrate genomes being copy number variation deserts. Our results suggest that the genomic location of ohnologs is a determining factor in the retention of copy number variations and that the dosage-balanced ohnologs are likely to cause the deleterious effects of copy number variations in these regions. We propose that investigating copy number variation of genes in regions that are typically copy number variation deserts is an efficient means to find disease-related copy number variations.

Abstract 3163: ZMAT3, a signature gene for sporadic osteosarcoma.

Abstract Osteosarcoma (OS) is a primary bone malignancy with high incidence in children and young adults. It frequently occurs in patients with strong cancer history (Li-Fraumeni syndrome, retinoblastoma), but the etiology of sporadic OS is still uncertain. The present study is an intensive investigation on susceptibility to sporadic osteosarcoma by genome wide copy number analysis. We evaluated the hypothesis that germline copy number variants (CNVs) could act as a source of genetic susceptibility that may contribute to the development of sporadic osteosarcoma. We analyzed 78 sporadic pediatric OS cases and 2375 controls using Affymetrix SNP 6.0 Array. Two independent methods, Genotyping Console™ (Affymetrix) and Birdsuite (Broad Institute) were employed to call for CNVs. Outliers with large genomic alterations and TP53 mutations were flagged and filtered out. Both bioinformatics methods show similar distribution of CNVs per chromosome, with slightly higher range depicted by Genotyping Console™, with an enriched set of CNVs in the diseased data. Bioinformatics analysis predicts overlap of copy number variable regions with several candidate genes (PIK3CA, STK11, AKT3, ZMAT3, BAI1), for selected samples. We validated these findings by performing real time quantitative PCR experiments that not only verified most of the computational results, but also identified more amplifications, in an extended selection of samples and regions. The most affected candidate gene, showing gain in 66% of osteosarcoma samples tested, is ZMAT3 (Chr. 3q26.32). A very recent method, digital droplet PCR (BioRAD), with very high sensitivity, also confirms qPCR results, although for a smaller number of samples. In addition to calling for CNVs, pathways analyses have been also pursued, to address the hypothesis that disruption of multiple genes from the same pathway in the germline of a particular individual may cause susceptibility for developing osteosarcoma. DAVID software predicted several pathways that are enriched, p53 being one of them. Further investigations by KEGG suggest that several genes, including ZMAT3, are disrupted in the p53 signaling pathway. In order to validate these findings, functional assays on osteosarcoma derived lymphoblastoid cell lines are designed and currently in progress. In all, the current study suggests that ZMAT3 could represent a good candidate signature gene for susceptibility to sporadic osteosarcoma. Citation Format: Cristina Baciu, Rinnat Porat, Margaret Pienkowska, Noa Alon, Jonathan Wasserman, David Malkin. ZMAT3, a signature gene for sporadic osteosarcoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3163. doi:10.1158/1538-7445.AM2013-3163