A high-resolution map of segmental DNA copy number variation in the mouse genome.
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ABSTRACT:
SUBMITTER: Graubert TA
PROVIDER: S-EPMC1761046 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Submicroscopic (< 2 Mb) segmental DNA copy number changes are a recently recognized source of genetic variability between individuals. The biological consequences of copy number variants (CNVs) are largely undefined. CNVs have been detected in diverse species, including mice and humans. Published studies in mice have been limited by resolution and strain selection. We chose to study twenty-one well-characterized inbred mouse strains that are the focus of an international effort to measure, catalog, and disseminate phenotype data. We performed comparative genomic hybridization using long oligomer arrays (oligo-aCGH) to characterize CNVs in these strains. This technique increased the resolution of CNV detection by more than an order of magnitude over previous methodologies. The CNVs range in size from 21-2,002 kb. Clustering strains by CNV profile recapitulates aspects of the known ancestry of these strains. Most of the CNVs (77.5%) contain annotated genes. We demonstrate that this technique can identify copy number differences associated with known polymorphic traits. The phenotype of previously uncharacterized strains can be predicted based on their copy number at these loci. Annotation of CNVs in the mouse genome combined with sequence-based analysis provides an important resource that will help define the genetic basis of complex traits. Keywords: array comparative genomic hybridization (aCGH)
2006-11-21 | GSE5805 | GEO
Project description:Submicroscopic (< 2 Mb) segmental DNA copy number changes are a recently recognized source of genetic variability between individuals. The biological consequences of copy number variants (CNVs) are largely undefined. CNVs have been detected in diverse species, including mice and humans. Published studies in mice have been limited by resolution and strain selection. We chose to study twenty-one well-characterized inbred mouse strains that are the focus of an international effort to measure, catalog, and disseminate phenotype data. We performed comparative genomic hybridization using long oligomer arrays (oligo-aCGH) to characterize CNVs in these strains. This technique increased the resolution of CNV detection by more than an order of magnitude over previous methodologies. The CNVs range in size from 21-2,002 kb. Clustering strains by CNV profile recapitulates aspects of the known ancestry of these strains. Most of the CNVs (77.5%) contain annotated genes. We demonstrate that this technique can identify copy number differences associated with known polymorphic traits. The phenotype of previously uncharacterized strains can be predicted based on their copy number at these loci. Annotation of CNVs in the mouse genome combined with sequence-based analysis provides an important resource that will help define the genetic basis of complex traits. 21 strains of mouse were assayed for copy number changes. Seven strains were assayed at least twice. DNA was extracted from tail for all strains. For two strains spleen DNA was also assayed on separate chips. C57BL/6 was used as the reference sample in all experiments.
2006-11-20 | E-GEOD-5805 | biostudies-arrayexpress
Project description:Detailed analyses of the clone-based genome assembly reveal that the recent duplication content of mouse (4.94%) is now comparable to that of human (5.5%), in contrast to previous estimates from the whole-genome shotgun sequence assembly. However, the architecture of mouse and human genomes differs markedly: most mouse duplications are organized into discrete clusters of tandem duplications that show depletion of genes and transcripts and enrichment of long interspersed nuclear element (LINE) and long terminal repeat (LTR) retroposons. We assessed copy number variation of the C57BL/6J duplicated regions within 15 mouse strains previously used for genetic association studies, sequencing and the Mouse Phenome Project. We determined that over 60% of these base pairs are polymorphic among the strains (on average, there was 20 Mb of copy-number-variable DNA between different mouse strains). Our data suggest that different mouse strains show comparable, if not greater, copy number polymorphism when compared to human; however, such variation is more locally restricted. We show large and complex patterns of interstrain copy number variation restricted to large gene families associated with spermatogenesis, pregnancy, viviparity, pheromone signaling and immune response.
| S-EPMC2574762 | biostudies-literature
Project description:Olfactory receptors (ORs), which are involved in odorant recognition, form the largest mammalian protein superfamily. The genomic content of OR genes is considerably reduced in humans, as reflected by the relatively small repertoire size and the high fraction ( approximately 55%) of human pseudogenes. Since several recent low-resolution surveys suggested that OR genomic loci are frequently affected by copy-number variants (CNVs), we hypothesized that CNVs may play an important role in the evolution of the human olfactory repertoire. We used high-resolution oligonucleotide tiling microarrays to detect CNVs across 851 OR gene and pseudogene loci. Examining genomic DNA from 25 individuals with ancestry from three populations, we identified 93 OR gene loci and 151 pseudogene loci affected by CNVs, generating a mosaic of OR dosages across persons. Our data suggest that approximately 50% of the CNVs involve more than one OR, with the largest CNV spanning 11 loci. In contrast to earlier reports, we observe that CNVs are more frequent among OR pseudogenes than among intact genes, presumably due to both selective constraints and CNV formation biases. Furthermore, our results show an enrichment of CNVs among ORs with a close human paralog or lacking a one-to-one ortholog in chimpanzee. Interestingly, among the latter we observed an enrichment in CNV losses over gains, a finding potentially related to the known diminution of the human OR repertoire. Quantitative PCR experiments performed for 122 sampled ORs agreed well with the microarray results and uncovered 23 additional CNVs. Importantly, these experiments allowed us to uncover nine common deletion alleles that affect 15 OR genes and five pseudogenes. Comparison to the chimpanzee reference genome revealed that all of the deletion alleles are human derived, therefore indicating a profound effect of human-specific deletions on the individual OR gene content. Furthermore, these deletion alleles may be used in future genetic association studies of olfactory inter-individual differences.
| S-EPMC2570968 | biostudies-literature
Project description:The human genome contains numerous blocks of highly homologous duplicated sequence. This higher-order architecture provides a substrate for recombination and recurrent chromosomal rearrangement associated with genomic disease. However, an assessment of the role of segmental duplications in normal variation has not yet been made. On the basis of the duplication architecture of the human genome, we defined a set of 130 potential rearrangement hotspots and constructed a targeted bacterial artificial chromosome (BAC) microarray (with 2,194 BACs) to assess copy-number variation in these regions by array comparative genomic hybridization. Using our segmental duplication BAC microarray, we screened a panel of 47 normal individuals, who represented populations from four continents, and we identified 119 regions of copy-number polymorphism (CNP), 73 of which were previously unreported. We observed an equal frequency of duplications and deletions, as well as a 4-fold enrichment of CNPs within hotspot regions, compared with control BACs (P < .000001), which suggests that segmental duplications are a major catalyst of large-scale variation in the human genome. Importantly, segmental duplications themselves were also significantly enriched >4-fold within regions of CNP. Almost without exception, CNPs were not confined to a single population, suggesting that these either are recurrent events, having occurred independently in multiple founders, or were present in early human populations. Our study demonstrates that segmental duplications define hotspots of chromosomal rearrangement, likely acting as mediators of normal variation as well as genomic disease, and it suggests that the consideration of genomic architecture can significantly improve the ascertainment of large-scale rearrangements. Our specialized segmental duplication BAC microarray and associated database of structural polymorphisms will provide an important resource for the future characterization of human genomic disorders.
| S-EPMC1226196 | biostudies-literature
Project description:Detailed analyses of the clone-based genome assembly reveal that the recent duplication content of mouse (4.94%) is now comparable to that of human (5.5%), in contrast to previous estimates from the whole-genome shotgun sequence assembly. The architecture of mouse and human genomes differ dramatically; most mouse duplications are organized into discrete clusters of tandem duplications that are depleted for genes/transcripts and enriched for LINE1 and LTR retroposons. We assessed copy-number variation of the C57BL/6J duplicated regions within 15 mouse strains used for genetic association studies, sequencing, and the mouse phenome project. We determined that over 60% of these basepairs are polymorphic between the strains (on average 20 Mbp of copy-number variable DNA between different mouse strains). Our data suggest that different mouse strains show comparable, if not greater, copy-number polymorphism when compared to human; however, such variation is more locally restricted. We show large and complex patterns of inter-strain copy-number variation restricted to large gene families associated with spermatogenesis, pregnancy, viviparity, phermone signaling, and immune response. Keywords: comparative genomic hybridization
2008-05-10 | GSE11369 | GEO
Project description:BackgroundArray comparative genomic hybridization (aCGH) to detect copy number variants (CNVs) in mammalian genomes has led to a growing awareness of the potential importance of this category of sequence variation as a cause of phenotypic variation. Yet there are large discrepancies between studies, so that the extent of the genome affected by CNVs is unknown. We combined molecular and aCGH analyses of CNVs in inbred mouse strains to investigate this question.Principal findingsUsing a 2.1 million probe array we identified 1,477 deletions and 499 gains in 7 inbred mouse strains. Molecular characterization indicated that approximately one third of the CNVs detected by the array were false positives and we estimate the false negative rate to be more than 50%. We show that low concordance between studies is largely due to the molecular nature of CNVs, many of which consist of a series of smaller deletions and gains interspersed by regions where the DNA copy number is normal.ConclusionsOur results indicate that CNVs detected by arrays may be the coincidental co-localization of smaller CNVs, whose presence is more likely to perturb an aCGH hybridization profile than the effect of an isolated, small, copy number alteration. Our findings help explain the hitherto unexplored discrepancies between array-based studies of copy number variation in the mouse genome.
| S-EPMC2943477 | biostudies-literature
Project description:Detailed analyses of the clone-based genome assembly reveal that the recent duplication content of mouse (4.94%) is now comparable to that of human (5.5%), in contrast to previous estimates from the whole-genome shotgun sequence assembly. The architecture of mouse and human genomes differ dramatically; most mouse duplications are organized into discrete clusters of tandem duplications that are depleted for genes/transcripts and enriched for LINE1 and LTR retroposons. We assessed copy-number variation of the C57BL/6J duplicated regions within 15 mouse strains used for genetic association studies, sequencing, and the mouse phenome project. We determined that over 60% of these basepairs are polymorphic between the strains (on average 20 Mbp of copy-number variable DNA between different mouse strains). Our data suggest that different mouse strains show comparable, if not greater, copy-number polymorphism when compared to human; however, such variation is more locally restricted. We show large and complex patterns of inter-strain copy-number variation restricted to large gene families associated with spermatogenesis, pregnancy, viviparity, phermone signaling, and immune response. Keywords: comparative genomic hybridization Genomic DNA of 14 inbred mouse strains was tested against reference C57BL/6J sample. C57BL/6J DNA sample from another individual was tested as negative control.
2008-05-10 | E-GEOD-11369 | biostudies-arrayexpress
Project description:Accurate and efficient genome-wide detection of copy number variants (CNVs) is essential for understanding human genomic variation, genome-wide CNV association type studies, cytogenetics research and diagnostics, and independent validation of CNVs identified from sequencing based technologies. Numerous, array-based platforms for CNV detection exist utilizing array Comparative Genome Hybridization (aCGH), Single Nucleotide Polymorphism (SNP) genotyping or both. We have quantitatively assessed the abilities of twelve leading genome-wide CNV detection platforms to accurately detect Gold Standard sets of CNVs in the genome of HapMap CEU sample NA12878, and found significant differences in performance. The technologies analyzed were the NimbleGen 4.2 M, 2.1 M and 3×720 K Whole Genome and CNV focused arrays, the Agilent 1×1 M CGH and High Resolution and 2×400 K CNV and SNP+CGH arrays, the Illumina Human Omni1Quad array and the Affymetrix SNP 6.0 array. The Gold Standards used were a 1000 Genomes Project sequencing-based set of 3997 validated CNVs and an ultra high-resolution aCGH-based set of 756 validated CNVs. We found that sensitivity, total number, size range and breakpoint resolution of CNV calls were highest for CNV focused arrays. Our results are important for cost effective CNV detection and validation for both basic and clinical applications.
| S-EPMC3227574 | biostudies-literature
Project description:Genomic copy number alterations are a feature of many human diseases including cancer. We have evaluated the effectiveness of an oligonucleotide array, originally designed to detect single-nucleotide polymorphisms, to assess DNA copy number. We first showed that fluorescent signal from the oligonucleotide array varies in proportion to both decreases and increases in copy number. Subsequently we applied the system to a series of 20 cancer cell lines. All of the putative homozygous deletions (10) and high-level amplifications (12; putative copy number >4) tested were confirmed by PCR (either qPCR or normal PCR) analysis. Low-level copy number changes for two of the lines under analysis were compared with BAC array CGH; 77% (n = 44) of the autosomal chromosomes used in the comparison showed consistent patterns of LOH (loss of heterozygosity) and low-level amplification. Of the remaining 10 comparisons that were discordant, eight were caused by low SNP densities and failed in both lines. The studies demonstrate that combining the genotype and copy number analyses gives greater insight into the underlying genetic alterations in cancer cells with identification of complex events including loss and reduplication of loci.
| S-EPMC327104 | biostudies-literature