Project description:U87MG is a commonly studied grade IV glioma cell line that has been analyzed in at least 1,700 publications over four decades. In order to comprehensively characterize the genome of this cell line and to serve as a model of broad cancer genome sequencing, we have generated greater than 30x genomic sequence coverage using a novel 50-base mate paired strategy with a 1.4kb mean insert library. A total of 1,014,984,286 mate-end and 120,691,623 single-end two-base encoded reads were generated from five slides. All data were aligned using a custom designed tool called BFAST, allowing optimal color space read alignment and accurate identification of DNA variants. The aligned sequence reads and mate pair information identified 35 interchromosomal translocation events, 1,315 structural variations (>100bp), 191,743 small (<21bp) insertions and deletions (indels), and 2,384,470 single nucleotide variations (SNVs). Among these observations, the known homozygous mutation in PTEN was robustly identified, and genes involved in cell adhesion were overrepresented in the mutated gene list. Data were compared to 219,187 heterozygous single nucleotide polymorphisms assayed by Illumina 1M Duo genotyping array to assess accuracy: 93.83% of all SNPs were reliably detected at filtering thresholds that yield greater than 99.99% sequence accuracy. Protein coding sequences were disrupted predominantly in this cancer cell line due to small indels, large deletions and translocations. In total, 512 genes were homozygously mutated, including 154 by SNVs, 178 by small indels, 145 by large microdeletions and 35 by interchromosomal translocations to reveal a highly mutated cell line genome. Of the small homozygously mutated variants, 8 SNVs and 99 indels were novel events not present in dbSNP. These data demonstrate that routine generation of broad cancer genome sequence is possible outside of genome centers. The sequence analysis of U87MG provides an unparalleled level of mutational resolution compared to any cell line to date. Whole genome sequencing of the U87MG brain cancer cell line using the AB SOLiD3 sequencer and genotyping using the Illumina Human1M-Duov3 DNA Analysis BeadChip

Project description:U87MG is a commonly studied grade IV glioma cell line that has been analyzed in at least 1,700 publications over four decades. In order to comprehensively characterize the genome of this cell line and to serve as a model of broad cancer genome sequencing, we have generated greater than 30x genomic sequence coverage using a novel 50-base mate paired strategy with a 1.4kb mean insert library. A total of 1,014,984,286 mate-end and 120,691,623 single-end two-base encoded reads were generated from five slides. All data were aligned using a custom designed tool called BFAST, allowing optimal color space read alignment and accurate identification of DNA variants. The aligned sequence reads and mate pair information identified 35 interchromosomal translocation events, 1,315 structural variations (>100bp), 191,743 small (<21bp) insertions and deletions (indels), and 2,384,470 single nucleotide variations (SNVs). Among these observations, the known homozygous mutation in PTEN was robustly identified, and genes involved in cell adhesion were overrepresented in the mutated gene list. Data were compared to 219,187 heterozygous single nucleotide polymorphisms assayed by Illumina 1M Duo genotyping array to assess accuracy: 93.83% of all SNPs were reliably detected at filtering thresholds that yield greater than 99.99% sequence accuracy. Protein coding sequences were disrupted predominantly in this cancer cell line due to small indels, large deletions and translocations. In total, 512 genes were homozygously mutated, including 154 by SNVs, 178 by small indels, 145 by large microdeletions and 35 by interchromosomal translocations to reveal a highly mutated cell line genome. Of the small homozygously mutated variants, 8 SNVs and 99 indels were novel events not present in dbSNP. These data demonstrate that routine generation of broad cancer genome sequence is possible outside of genome centers. The sequence analysis of U87MG provides an unparalleled level of mutational resolution compared to any cell line to date.

Project description:Background: DNA in the nucleus of a living cell carries out its functions in the context of a complex, three-dimensional chromatin architecture. Several recently developed methods, each an extension of the chromatin conformation capture (3C) assay, have enabled the genome-wide profiling of chromatin contacts between pairs of loci in yeast, fruit fly, human and mouse. Especially in complex eukaryotes, data generated by these methods, coupled with other genome-wide datasets, demonstrated that non-random chromatin folding correlates strongly with cellular processes such as gene expression and DNA replication. Here we describe a novel assay to map genome-wide chromatin contacts, tethered multiple 3C (TM3C), that involves a simple protocol of restriction enzyme digestion and religation of fragments upon agarose gel beads followed by deep DNA paired-end sequencing. In addition to identifying contacts between pairs of loci, TM3C enables identification of contacts among more than two loci simultaneously. Results: We use TM3C to assay the genome architectures of two human cell lines: KBM7, a near-haploid chronic leukemia cell line, and NHEK, a normal diploid human epidermal keratinocyte cell line. We confirm that the contact frequency maps produced by TM3C exhibit features characteristic of existing genome architecture datasets, including the expected scaling of contact probabilities with genomic distance, as well as a low noise-to-signal ratio between inter- and intrachromosomal contacts. We also confirm that TM3C captures several known cell type-specific contacts, ploidy shifts and translocations, such as Ph+ formation in KBM7. Furthermore, we develop a two-phase mapping strategy that separately maps chimeric subsequences within a single read, allowing us to identify contacts involving three or four loci simultaneously, potentially corresponding to combinatorial regulation events. This mapping strategy also greatly increases the number of distinct binary contacts identified and, therefore, the coverage obtained for a fixed number of mapped reads. We confirm a subset of the triplet contacts involving the IGF2-H19 imprinting control region (ICR) using PCR analysis for KBM7 cells. Assaying the genome architecture of a near-haploid cell line allows us to create 3D models of a human cell line without averaging signal from two homologous copies of a chromosome. Our 3D models of KBM7 show clustering of small chromosomes with each other and large chromosomes with each other, consistent with previous studies of the genome architectures of other human cell lines. Conclusion: TM3C is a simple protocol for ascertaining genome architecture and can be used to identify simultaneous contacts among three or four loci. Application of TM3C to a near-haploid human cell line revealed large-scale features of chromosomal organization and complex chromatin loops that may play a role in regulating reciprocal expression of the IGF2 and H19 genes. Analysis of the spatial organization of two human cell lines (KBM7, a near-haploid chronic leukemia cell line, and NHEK, a normal diploid human epidermal keratinocyte cell line) using tethered multiple 3C (TM3C), a novel and simple protocol for ascertaining genome architecture which can be used to identify simultaneous contacts among three or four loci in addition to binary contacts that can be identified using traditional chromosome conformation capture coupled with next generation sequencing (Hi-C).

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Hi-C analysis of genomic contacts revealed karyotype abnormalities in chicken HD3 cell line

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