Copy number variation of scavenger-receptor cysteine-rich domains within DMBT1 and Crohn's disease.
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ABSTRACT:
SUBMITTER: Polley S
PROVIDER: S-EPMC4851238 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundDMBT1 is a gene that shows extensive copy number variation (CNV) that alters the number of bacteria-binding domains in the protein and has been shown to activate the complement pathway. It lies next to the ARMS2/HTRA1 genes in a region of chromosome 10q26, where single nucleotide variants have been strongly associated with age-related macular degeneration (AMD), the commonest cause of blindness in Western populations. Complement activation is thought to be a key factor in the pathogenesis of this condition. We sought to investigate whether DMBT1 CNV plays any role in the susceptibility to AMD.MethodsWe analysed long-range linkage disequilibrium of DMBT1 CNV1 and CNV2 with flanking single nucleotide polymorphisms (SNPs) using our previously published CNV and HapMap Phase 3 SNP data in the CEPH Europeans from Utah (CEU). We then typed a large cohort of 860 AMD patients and 419 examined age-matched controls for copy number at DMBT1 CNV1 and CNV2 and combined these data with copy numbers from a further 480 unexamined controls.ResultsWe found weak linkage disequilibrium between DMBT1 CNV1 and CNV2 with the SNPs rs1474526 and rs714816 in the HTRA1/ARMS2 region. By directly analysing copy number variation, we found no evidence of association of CNV1 or CNV2 with AMD.ConclusionsWe have shown that copy number variation at DMBT1 does not affect risk of developing age-related macular degeneration and can therefore be ruled out from future studies investigating the association of structural variation at 10q26 with AMD.
| S-EPMC4946147 | biostudies-literature
Project description:The copy number variation in beta-defensin genes on human chromosome 8 has been proposed to underlie susceptibility to inflammatory disorders, but presents considerable challenges for accurate typing on the scale required for adequately powered case-control studies. In this work, we have used accurate methods of copy number typing based on the paralogue ratio test (PRT) to assess beta-defensin copy number in more than 1500 UK DNA samples including more than 1000 cases of Crohn's disease. A subset of 625 samples was typed using both PRT-based methods and standard real-time PCR methods, from which direct comparisons highlight potentially serious shortcomings of a real-time PCR assay for typing this variant. Comparing our PRT-based results with two previous studies based only on real-time PCR, we find no evidence to support the reported association of Crohn's disease with either low or high beta-defensin copy number; furthermore, it is noteworthy that there are disagreements between different studies on the observed frequency distribution of copy number states among European controls. We suggest safeguards to be adopted in assessing and reporting the accuracy of copy number measurement, with particular emphasis on integer clustering of results, to avoid reporting of spurious associations in future case-control studies.
| S-EPMC2989891 | biostudies-other
Project description:BackgroundSingle nucleotide polymorphisms (SNPs) have been used extensively in genetics and epidemiology studies. Traditionally, SNPs that did not pass the Hardy-Weinberg equilibrium (HWE) test were excluded from these analyses. Many investigators have addressed possible causes for departure from HWE, including genotyping errors, population admixture and segmental duplication. Recent large-scale surveys have revealed abundant structural variations in the human genome, including copy number variations (CNVs). This suggests that a significant number of SNPs must be within these regions, which may cause deviation from HWE.ResultsWe performed a Bayesian analysis on the potential effect of copy number variation, segmental duplication and genotyping errors on the behavior of SNPs. Our results suggest that copy number variation is a major factor of HWE violation for SNPs with a small minor allele frequency, when the sample size is large and the genotyping error rate is 0~1%.ConclusionsOur study provides the posterior probability that a SNP falls in a CNV or a segmental duplication, given the observed allele frequency of the SNP, sample size and the significance level of HWE testing.
| S-EPMC2600609 | biostudies-literature
Project description:Background: Crohn’s disease is presently an incurable inflammatory bowel disease. Fistulae are extensions of the intestinal tract that may form connections with other organs. These are a common complication of Crohn’s disease affecting up to 50% of patients with the most common including perianal and rectovaginal fistulae. The dysregulated growth observed in fistulae shares several major characteristics seen in the development of tumours. These similarities include epithelial-to-mesenchymal transition (EMT), invasive cell growth, increased extracellular matrix production and remodelling, up-regulated local expression of growth factors such as IGF-1 and the down-regulation of apoptosis pathways. Although several susceptibility loci have been described within Crohn’s disease there is no individual gene or mutation that identifies susceptibility or the subsequent formation of fistulae within all people. Copy-number variation (CNV) is one mechanism that may explain much of this genetic complexity. CNV may be caused by a variety of mechanisms such as cycles of chromosomal breakage/fusion/bridging that are typical within chronically inflamed tissue. Interestingly CNV shows locus-specific mutation rates between individuals higher than that of SNPs and has been associated with complex Mendelian traits including disease susceptibility. In this current study we performed array comparative genomic hybridisation (aCGH) analysis of active fistulae resected from patients as part of a previous surgical intervention. As the control for comparison we employed tissue taken from the same patient within the same surgery at an uninvolved site of the gastrointestinal tract. This matched control was employed to better investigate CNV specific to the fistula tissue of each individual avoiding complications associated with the large number of CNV present within the healthy population. Major question addressed by the work: What are the differences in genetic copy-number within localised intestinal fistula tissue of individuals with Crohn’s disease compared to healthy intestinal tissue from the same individual?
2014-07-01 | GSE44275 | GEO
Project description:The class A scavenger receptor (cA-SR) family is a group of five evolutionarily related innate immune receptors. The cA-SRs are known for their promiscuous ligand binding; as they have been shown to bind bacteria, such as Streptococcus pneumoniae and Escherichia coli, as well as different modified forms of low-density lipoprotein. Three of the five family members possess a scavenger receptor cysteine-rich (SRCR) domain while the remaining two receptors lack the domain. Previous work has suggested that the macrophage-associated receptor with collagenous structure (MARCO) shares a recent common ancestor with the non-SRCR-containing receptors; however, the origin of the SRCR domain within the cA-SRs remains unknown. We hypothesize that the SRCR domains of the cA-SRs have a common origin that predates teleost fish. Using the newly available sequence data from sea lamprey and ghost shark genome projects, we have shown that MARCO shares a common ancestor with the SRCR-containing proteins. In addition, we explored the evolutionary relationships within the SRCR domain by reconstructing the ancestral SRCR domains of the cA-SRs. We identified a motif that is highly conserved between the cA-SR SRCR domains and the ancestral SRCR domain that consist of WGTVCDD. We also show that the GRAEVYY motif, a functionally important motif within MARCO, is poorly conserved in the other cA-SRs and in the reconstructed ancestral domain. Further, we identified three sites within MARCO's SRCR domain, which are under positive selection. Two of these sites lie adjacent to the conserved WGTVCDD motif, and may indicate a potential biological function for these sites. Together, these findings indicate a common origin of the SRCR domain within the cA-SRs; however, different selective pressures between the proteins may have caused MARCOs SRCR domain to evolve to contain different functional motifs when compared to the other SRCR-containing cA-SRs.
| S-EPMC4491621 | biostudies-literature
Project description:The C57BL/6J strain is one of the most widely used animal models for biomedical research, and individual mice within the strain are often assumed to be genetically identical after more than 70 yr of inbreeding. Using a single nucleotide polymorphism (SNP) genotyping panel, we assessed if copy number variations (CNVs) could be detected within the C57BL/6J strain by comparing relative allele frequencies in first generation (F(1)) progeny of C57BL/6J mice. Sequencing, quantitative PCR, breeding, and array comparative genomic hybridization (CGH) together confirmed the presence of two CNVs. Both CNVs span genes encoded on chromosome 19, and quantitative RT-PCR demonstrated that they result in altered expression of the insulin-degrading enzyme (Ide) and fibroblast growth factor binding protein 3 (Fgfbp3) genes. Analysis of 39 different C57BL/6J breeders revealed that 64% of mice from the Jackson Laboratory colony were heterozygous for the CNV spanning Ide. Homozygotes with and without the duplication were present in concordance with Hardy-Weinberg equilibrium (13% and 23%, respectively), and analysis of archived samples from the C57BL/6J colony suggests that the duplication has rapidly reached a high frequency in the colony since 1994. The identification of two CNVs in the small portion of the genome screened demonstrates that individual mice of highly inbred strains are not isogenic and suggests other CNVs may be segregating within C57BL/6J as well as other carefully maintained inbred strains. These differences can influence interpretations of physiological, biomedical, and behavioral experiments and can be exploited to model CNVs apparent in the human genome.
| S-EPMC2134784 | biostudies-other
Project description:Background: CrohnM-bM-^@M-^Ys disease is presently an incurable inflammatory bowel disease. Fistulae are extensions of the intestinal tract that may form connections with other organs. These are a common complication of CrohnM-bM-^@M-^Ys disease affecting up to 50% of patients with the most common including perianal and rectovaginal fistulae. The dysregulated growth observed in fistulae shares several major characteristics seen in the development of tumours. These similarities include epithelial-to-mesenchymal transition (EMT), invasive cell growth, increased extracellular matrix production and remodelling, up-regulated local expression of growth factors such as IGF-1 and the down-regulation of apoptosis pathways. Although several susceptibility loci have been described within CrohnM-bM-^@M-^Ys disease there is no individual gene or mutation that identifies susceptibility or the subsequent formation of fistulae within all people. Copy-number variation (CNV) is one mechanism that may explain much of this genetic complexity. CNV may be caused by a variety of mechanisms such as cycles of chromosomal breakage/fusion/bridging that are typical within chronically inflamed tissue. Interestingly CNV shows locus-specific mutation rates between individuals higher than that of SNPs and has been associated with complex Mendelian traits including disease susceptibility. In this current study we performed array comparative genomic hybridisation (aCGH) analysis of active fistulae resected from patients as part of a previous surgical intervention. As the control for comparison we employed tissue taken from the same patient within the same surgery at an uninvolved site of the gastrointestinal tract. This matched control was employed to better investigate CNV specific to the fistula tissue of each individual avoiding complications associated with the large number of CNV present within the healthy population. Major question addressed by the work: What are the differences in genetic copy-number within localised intestinal fistula tissue of individuals with CrohnM-bM-^@M-^Ys disease compared to healthy intestinal tissue from the same individual? Samples were selected from patients presenting with CrohnM-bM-^@M-^Ys Disease fistulae at Eastern Health Department of Gastroenterology and Hepatology (Arnold Street, Box Hill, Victoria, Australia). The 8 samples used in this study were formalin-fixed paraffin-embedded (FFPE) specimens following a surgical intervention to remove fistula tissue. To focus on changes within the individual patient we used tissue taken from the same surgery at an uninvolved region of the intestine as the matched control for CNV analysis.
2014-07-01 | E-GEOD-44275 | biostudies-arrayexpress
Project description:Next-generation sequencing (NGS) technologies offer new opportunities for precise and accurate identification of genomic aberrations, including copy number variations (CNVs). For high-throughput NGS data, using depth of coverage has become a major approach to identify CNVs, especially for whole exome sequencing (WES) data. Due to the high level of noise and biases of read-count data and complexity of the WES data, existing CNV detection tools identify many false CNV segments. Besides, NGS generates a huge amount of data, requiring to use effective and efficient methods. In this work, we propose a novel segmentation algorithm based on the total variation approach to detect CNVs more precisely and efficiently using WES data. The proposed method also filters out outlier read-counts and identifies significant change points to reduce false positives. We used real and simulated data to evaluate the performance of the proposed method and compare its performance with those of other commonly used CNV detection methods. Using simulated and real data, we show that the proposed method outperforms the existing CNV detection methods in terms of accuracy and false discovery rate and has a faster runtime compared to the circular binary segmentation method.
| S-EPMC7278034 | biostudies-literature
Project description:The structure of chalcone synthase (CHS) gene repeats in different alleles of the I (inhibitor) locus in soybean spawns endogenous RNA interference (RNAi) that leads to phenotypic change in seed coat color of this major agronomic crop. Here, we examined CHS gene copy number by digital PCR and single nucleotide polymorphisms (SNPs) through whole genome resequencing of 15 cultivars that varied in alleles of the I locus (I, ii , ik , and i) that control the pattern distribution of pigments in the seed coats. Lines homozygous for the ii allele had the highest copy number followed by the I and ik cultivars which were more related to each other than to the lines with ii alleles. Some of the recessive i alleles were spontaneous mutations, and each revealed a loss of copy number by digital PCR relative to the parent varieties. Amplicon sequencing and whole genome resequencing determined that the breakpoints of several ii to i mutations resulted from nonallelic homologous recombination (NAHR) events between CHS genes located in segmental duplications leading to large 138-kilobase deletions that erase the structure generating the CHS siRNAs along with eight other non-CHS genes. Functional hybrid CHS genes (designated CHS5:1) were formed in the process and represent rare examples of NAHR in higher plants that have been captured by examining spontaneous mutational events in isogenic mutant lines.
| S-EPMC6710647 | biostudies-literature
Project description:In recent years there has been a growing interest in the role of copy number variations (CNV) in genetic diseases. Though there has been rapid development of technologies and statistical methods devoted to detection in CNVs from array data, the inherent challenges in data quality associated with most hybridization techniques remains a challenging problem in CNV association studies.To help address these data quality issues in the context of family-based association studies, we introduce a statistical framework for the intensity-based array data that takes into account the family information for copy-number assignment. The method is an adaptation of traditional methods for modeling SNP genotype data that assume Gaussian mixture model, whereby CNV calling is performed for all family members simultaneously and leveraging within family-data to reduce CNV calls that are incompatible with Mendelian inheritance while still allowing de-novo CNVs. Applying this method to simulation studies and a genome-wide association study in asthma, we find that our approach significantly improves CNV calls accuracy, and reduces the Mendelian inconsistency rates and false positive genotype calls. The results were validated using qPCR experiments.In conclusion, we have demonstrated that the use of family information can improve the quality of CNV calling and hopefully give more powerful association test of CNVs.
| S-EPMC3668900 | biostudies-other