Genome-wide copy number variant analysis in inbred chickens lines with different susceptibility to Marek's disease.
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ABSTRACT:
SUBMITTER: Luo J
PROVIDER: S-EPMC3564982 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Marek’s disease virus (MDV) is an oncovirus causing tumor disease known as Marek’s disease (MD) in chicken. Breeding of chickens genetically resistant to MD is considered a vital augment to better control MD. To find the mechanism underlying the genetic resistance to MD, a genomic structural variation, copy number variation (CNV), was examined in inbred MD-resistant and -susceptible chicken lines by using the comparative genomic hybridization (CGH) technique. A total of 45 copy number variation regions (CNVRs) were found spanning across 3,297,038 bp in length of the chicken genome in 4 lines of chickens. Ten CNVRs were selectively confirmed with quantitative real-time PCR. The comparison between the resistant and susceptible chicken lines revealed 28 differentially presented CNVRs, which are functionally involved in immune response, cell proliferation in midbrain, G-protein coupled receptor signaling pathway, and protein-glutamine gamma-glutamyltransferase activity. Two CNVRs that are related with MD-resistance and –susceptibility were also found transmitted to descendent recombinant congenic lines that differ in susceptibility to MD. A positive correlation was identified between the CNVRs and gene expression, indicating the importance of gene expression dosage in disease resistance. We also found the overlapping between the CNVR region and the Marek’s disease trait related quantitative trait loci (QTLs). In conclusion, our data provided additional information elucidating one of possible mechanisms underlying of genetic resistance to MD. The findings may eventually lead to better strategies for genetic improvement of resistance to MD in poultry. L63: highly resistant to MD; L72: highly susceptible to MD; RCS-L: moderate resistant to MD; RCS-M: moderate susceptible to MD
2012-09-01 | GSE38689 | GEO
Project description:MarekM-bM-^@M-^Ys disease virus (MDV) is an oncovirus causing tumor disease known as MarekM-bM-^@M-^Ys disease (MD) in chicken. Breeding of chickens genetically resistant to MD is considered a vital augment to better control MD. To find the mechanism underlying the genetic resistance to MD, a genomic structural variation, copy number variation (CNV), was examined in inbred MD-resistant and -susceptible chicken lines by using the comparative genomic hybridization (CGH) technique. A total of 45 copy number variation regions (CNVRs) were found spanning across 3,297,038 bp in length of the chicken genome in 4 lines of chickens. Ten CNVRs were selectively confirmed with quantitative real-time PCR. The comparison between the resistant and susceptible chicken lines revealed 28 differentially presented CNVRs, which are functionally involved in immune response, cell proliferation in midbrain, G-protein coupled receptor signaling pathway, and protein-glutamine gamma-glutamyltransferase activity. Two CNVRs that are related with MD-resistance and M-bM-^@M-^Ssusceptibility were also found transmitted to descendent recombinant congenic lines that differ in susceptibility to MD. A positive correlation was identified between the CNVRs and gene expression, indicating the importance of gene expression dosage in disease resistance. We also found the overlapping between the CNVR region and the MarekM-bM-^@M-^Ys disease trait related quantitative trait loci (QTLs). In conclusion, our data provided additional information elucidating one of possible mechanisms underlying of genetic resistance to MD. The findings may eventually lead to better strategies for genetic improvement of resistance to MD in poultry. L63: highly resistant to MD; L72: highly susceptible to MD; RCS-L: moderate resistant to MD; RCS-M: moderate susceptible to MD Red blood cell DNAs were isolated from L63, L72, RCS-L and RCS-M and then labeled with Cy3. DNA from Red Junglefowl was labeled with Cy5 as reference and mixed with Cy3 labeled DNA, then hybridized to the 385K chicken tiling array. The hybridization, normalization and segmentation analysis were performed by NimbleGen Systems Inc. (Madison, USA). A detailed description of their technical specifics can be found on http://www.nimblegen.com/products/lit/lit.html. Briefly, the segments with five or more probes having a mean log2 ratio greater than M-BM-10.5 (0.5_5) were chosen as candidate CNVs.
2012-09-01 | E-GEOD-38689 | biostudies-arrayexpress
Project description:Copy number variation (CNV) is a major source of genome polymorphism that directly contributes to phenotypic variation such as resistance to infectious diseases. Lines 63 and 72 are two highly inbred experimental chicken lines that differ greatly in susceptibility to Marek's disease (MD), and have been used extensively in efforts to identify the genetic and molecular basis for genetic resistance to MD. Using next generation sequencing, we present a genome-wide assessment of CNVs that are potentially associated with genetic resistance to MD.Three chickens randomly selected from each line were sequenced to an average depth of 20×. Two popular software, CNVnator and Pindel, were used to call genomic CNVs separately. The results were combined to obtain a union set of genomic CNVs in the two chicken lines.A total of 5,680 CNV regions (CNVRs) were identified after merging the two datasets, of which 1,546 and 1,866 were specific to the MD resistant or susceptible line, respectively. Over half of the line-specific CNVRs were shared by 2 or more chickens, reflecting the reduced diversity in both inbred lines. The CNVRs fixed in the susceptible lines were significantly enriched in genes involved in MAPK signaling pathway. We also found 67 CNVRs overlapping with 62 genes previously shown to be strong candidates of the underlying genes responsible for the susceptibility to MD.Our findings provide new insights into the genetic architecture of the two chicken lines and additional evidence that MAPK signaling pathway may play an important role in host response to MD virus infection. The rich source of line-specific CNVs is valuable for future disease-related association studies in the two chicken lines.
| S-EPMC4619206 | biostudies-literature
Project description:SummaryWe have developed an algorithm to detect copy number variants (CNVs) in homozygous organisms, such as inbred laboratory strains of mice, from short read sequence data. Our novel approach exploits the fact that inbred mice are homozygous at virtually every position in the genome to detect CNVs using a hidden Markov model (HMM). This HMM uses both the density of sequence reads mapped to the genome, and the rate of apparent heterozygous single nucleotide polymorphisms, to determine genomic copy number. We tested our algorithm on short read sequence data generated from re-sequencing chromosome 17 of the mouse strains A/J and CAST/EiJ with the Illumina platform. In total, we identified 118 copy number variants (43 for A/J and 75 for CAST/EiJ). We investigated the performance of our algorithm through comparison to CNVs previously identified by array-comparative genomic hybridization (array CGH). We performed quantitative-PCR validation on a subset of the calls that differed from the array CGH data sets.
| S-EPMC2820678 | biostudies-literature
Project description:Copy number variation (CNV) is a common form of structural variation detected in human genomes, occurring as both constitutional and somatic events. Cytogenetic techniques like chromosomal microarray (CMA) are widely used in analyzing CNVs. However, CMA techniques cannot resolve the full nature of these structural variations (i.e. the orientation and location of associated breakpoint junctions) and must be combined with other cytogenetic techniques, such as karyotyping or FISH, to do so. This makes the development of a next-generation sequencing (NGS) approach capable of resolving both CNVs and breakpoint junctions desirable. Mate-pair sequencing (MPseq) is a NGS technology designed to find large structural rearrangements across the entire genome. Here we present an algorithm capable of performing copy number analysis from mate-pair sequencing data. The algorithm uses a step-wise procedure involving normalization, segmentation, and classification of the sequencing data. The segmentation technique combines both read depth and discordant mate-pair reads to increase the sensitivity and resolution of CNV calls. The method is particularly suited to MPseq, which is designed to detect breakpoint junctions at high resolution. This allows for the classification step to accurately calculate copy number levels at the relatively low read depth of MPseq. Here we compare results for a series of hematological cancer samples that were tested with CMA and MPseq. We demonstrate comparable sensitivity to the state-of-the-art CMA technology, with the benefit of improved breakpoint resolution. The algorithm provides a powerful analytical tool for the analysis of MPseq results in cancer.
| S-EPMC6117203 | biostudies-literature
Project description:Suicide and suicide attempts are complex behaviors that result from the interaction of different factors, including genetic variants that increase the predisposition to suicidal behaviors. Copy number variations (CNVs) are deletions or duplications of a segment of DNA usually larger than one kilobase. These structural genetic changes, although quite rare, have been associated with genetic liability to mental disorders, such as autism, schizophrenia, and bipolar disorder. No genome-wide level studies have been published investigating the potential role of CNVs in suicidal behaviors. Based on single-nucleotide polymorphism array data, we followed the Penn-CNV standards to detect CNVs in 1,608 subjects, comprising 475 suicide and suicide attempt cases and 1,133 controls. Although the initial algorithms determined the presence of CNVs on chromosomes 6 and 12 in seven and eight cases, respectively, compared with none of the controls, visual inspection of the raw data did not support this finding. Furthermore we were unable to validate these findings by CNV-specific real-time polymerase chain reaction. Additionally, rare CNV burden analysis did not find an association between the frequency or length of rare CNVs and suicidal behavior in our sample population. Although our findings suggest CNVs do not play an important role in the etiology of suicidal behaviors, they are not inconsistent with the strong evidence from the literature suggesting that other genetic variants account for a portion of the total phenotypic variability in suicidal behavior.
| S-EPMC4444178 | biostudies-literature
Project description:BackgroundMarek's disease (MD) is a lymphoproliferative disease in chickens caused by Marek's disease virus (MDV) and characterized by T cell lymphoma and infiltration of lymphoid cells into various organs such as liver, spleen, peripheral nerves and muscle. Resistance to MD and disease risk have long been thought to be influenced both by genetic and environmental factors, the combination of which contributes to the observed outcome in an individual. We hypothesize that after MDV infection, genes related to MD-resistance or -susceptibility may exhibit different trends in transcriptional activity in chicken lines having a varying degree of resistance to MD.ResultsIn order to study the mechanisms of resistance and susceptibility to MD, we performed genome-wide temporal expression analysis in spleen tissues from MD-resistant line 63, susceptible line 72 and recombinant congenic strain M (RCS-M) that has a phenotype intermediate between lines 63 and 72 after MDV infection. Three time points of the MDV life cycle in chicken were selected for study: 5 days post infection (dpi), 10dpi and 21dpi, representing the early cytolytic, latent and late cytolytic stages, respectively. We observed similar gene expression profiles at the three time points in line 63 and RCS-M chickens that are both different from line 72. Pathway analysis using Ingenuity Pathway Analysis (IPA) showed that MDV can broadly influence the chickens irrespective of whether they are resistant or susceptible to MD. However, some pathways like cardiac arrhythmia and cardiovascular disease were found to be affected only in line 72; while some networks related to cell-mediated immune response and antigen presentation were enriched only in line 63 and RCS-M. We identified 78 and 30 candidate genes associated with MD resistance, at 10 and 21dpi respectively, by considering genes having the same trend of expression change after MDV infection in lines 63 and RCS-M. On the other hand, by considering genes with the same trend of expression change after MDV infection in lines 72 and RCS-M, we identified 78 and 43 genes at 10 and 21dpi, respectively, which may be associated with MD-susceptibility.ConclusionsBy testing temporal transcriptome changes using three representative chicken lines with different resistance to MD, we identified 108 candidate genes for MD-resistance and 121 candidate genes for MD-susceptibility over the three time points. Genes included in our resistance or susceptibility genes lists that are also involved in more than 5 biofunctions, such as CD8α, IL8, USP18, and CTLA4, are considered to be important genes involved in MD-resistance or -susceptibility. We were also able to identify several biofunctions related with immune response that we believe play an important role in MD-resistance.
| S-EPMC3269463 | biostudies-literature
Project description:Marek's Disease (MD) is a highly contagious pathogenic and oncogenic disease primarily affecting chickens. Chicken Lines 63 and 72, as well as their recombinant congenic strains (RCS) with varied susceptibility to MD, are ideal models to study the complex mechanisms of genetic resistance to MD. In this study, we investigated copy number variation (CNV) in these inbred chicken lines using the Affymetrix Axiom HD 600 K SNP genotyping array. We detected 393 CNV segments across all ten chicken lines, of which 12 CNVs were specifically identified in Line 72. We then assessed genetic structure based on CNV and observed markedly different patterns. Finally, we validated two deletion events in Line 72 and correlated them with genes expression using qPCR and RNA-seq, respectively. Our combined results indicated that these two CNV deletions were likely to contribute to MD susceptibility.
| S-EPMC5454933 | biostudies-literature
Project description:BackgroundMarek's disease (MD) is a neoplastic disease in chickens caused by the MD virus (MDV). Successful vaccine development against MD has resulted in increased virulence of MDV and the understanding of genetic resistance to the disease is, therefore, crucial to long-term control strategies. Also, epigenetic factors are believed to be one of the major determinants of disease response.ResultsHere, we carried out comprehensive analyses of the epigenetic landscape induced by MDV, utilizing genome-wide histone H3 lysine 4 and lysine 27 trimethylation maps from chicken lines with varying resistance to MD. Differential chromatin marks were observed on genes previously implicated in the disease such as MX1 and CTLA-4 and also on genes reported in other cancers including IGF2BP1 and GAL. We detected bivalent domains on immune-related transcriptional regulators BCL6, CITED2 and EGR1, which underwent dynamic changes in both lines as a result of MDV infection. In addition, putative roles for GAL in the mechanism of MD progression were revealed.ConclusionOur results confirm the presence of widespread epigenetic differences induced by MD in chicken lines with different levels of genetic resistance. A majority of observed epigenetic changes were indicative of increased levels of viral infection in the susceptible line symptomatic of lowered immunocompetence in these birds caused by early cytolytic infection. The GAL system that has known anti-proliferative effects in other cancers is also revealed to be potentially involved in MD progression. Our study provides further insight into the mechanisms of MD progression while revealing a complex landscape of epigenetic regulatory mechanisms that varies depending on host factors.
| S-EPMC3505159 | biostudies-literature
Project description:SNP genotyping has emerged as a technology to incorporate copy number variants (CNVs) into genetic analyses of human traits. However, the extent to which SNP platforms accurately capture CNVs remains unclear. Using independent, sequence-based CNV maps, we find that commonly used SNP platforms have limited or no probe coverage for a large fraction of CNVs. Despite this, in 9 samples we inferred 368 CNVs using Illumina SNP genotyping data and experimentally validated over two-thirds of these. We also developed a method (SNP-Conditional Mixture Modeling, SCIMM) to robustly genotype deletions using as few as two SNP probes. We find that HapMap SNPs are strongly correlated with 82% of common deletions, but the newest SNP platforms effectively tag about 50%. We conclude that currently available genome-wide SNP assays can capture CNVs accurately, but improvements in array designs, particularly in duplicated sequences, are necessary to facilitate more comprehensive analyses of genomic variation.
| S-EPMC2759751 | biostudies-literature