linkstream2 microblog

Long-span PET mapping reveals characteristic patterns of #SVs in… cancer [v norm] genomes, but no MEIs or small events
http://genome.cshlp.org/content/early/2011/04/05/gr.113555.110.abstract

The described study used long paired-end-tags (PET) to analyze and compare SVs in cancer and normal genomes. It determined the prevalence of different types of SVs in normal and cancer sample. Overall, the results are interesting and convincing on a qualitative level; however, for the reasons outlined below, more precise and quantitative delineation of the observed effects is highly desirable.

1) Small sample size of normal genomes (only 2 normal genomes)

2) Validation rate was low (< 77%) for everything except deletions, and for singletons it was even lower. .

3) Long PET is not good for finding smaller events (few kbps). Thus, this analysis missed smaller scale SVs and cancer rearrangements.

4) While there is a discussion about breakpoints and associated repeats, it is not very informative as breakpoint locations were not determined to basepair resolution.

5) No MEI were considered — particularly, no cancer MEI were considered in the analysis, while recently it was found that somatic retrotransposition occurs in cancer (Lee et al., PMID: 22745252)..

Comprehensive long-span paired-end-tag mapping reveals characteristic patterns of structural variations in epithelial cancer genomes –

Hillmer AM, Yao F, Inaki K, Lee WH, Ariyaratne PN, Teo AS, Woo XY, Zhang Z, Zhao H, Ukil L, Chen JP, Zhu F, So JB, Salto-Tellez M, Poh WT, Zawack KF, Nagarajan N, Gao S, Li G, Kumar V, Lim HP, Sia YY, Chan CS, Leong ST, Neo SC, Choi PS, Thoreau H, Tan PB, Shahab A, Ruan X, Bergh J, Hall P, Cacheux-Rataboul V, Wei CL, Yeoh KG, Sung WK, Bourque G, Liu ET, Ruan Y.

Genome Res. 2011 May;21(5):665-75. doi: 10.1101/gr.113555.110. Epub 2011 Apr 5.

Evidence of Abundant Purifying Selection in Humans for Recently Acquired Regulatory Functions
L Ward & M Kellis
http://www.sciencemag.org/content/337/6102/1675.abs

In general we know that conservation across species and within humans are correlated. In this paper the authors focus on emphasize the exceptions to this trend. They show that although only ~5% of the human genome is conserved across mammals, regulatory regions in an additional 4% of the genomes are conserved amongst humans. They also show that some elements are conserved across mammals but lack functional activity from ENCODE data and also do not show purifying selection amongst humans. The authors pinpoint regulatory regions near color vision and nerve-growth genes for that show human-specific constraint. This has been criticized in various publications since there are other genes that are higher up in the authors’ list but harder to explain for lineage-specific constraint.

Mutational landscape and significance across 12 major #cancer types: Common genes mutated in different cancers
http://www.nature.com/nature/journal/v502/n7471/full/nature12634.html

http://www.sciencedaily.com/releases/2013/10/131016132143.htm

Mutational landscape and significance across 12 major cancer types http://www.nature.com/nature/journal/v502/n7471/full/nature12634.html

http://nar.oxfordjournals.org/content/40/D1/D930.long

HaploReg explores functional annotations, such as chromatin states in varied cell types, sequence conservation, regulatory motif
alterations and eQTLs, of linked SNPs or indels within LD block of queried SNPs. The output provides a the guide to develop hypotheses of functional impact of non-coding variants, especially GWAS SNPs. HaploReg is currently limited to known variants (e.g. 1000 Genome variants and dbSNPs) and is unable to deal with private variants.

It look as though the data are now ready for download
http://datasets.pacb.com/2013/Human10x/READS/index.html along with a brief description of the data
http://blog.pacificbiosciences.com/2013/10/data-release-long-read-shotgun.html

BioTechniques – The Myth of the Single Genome
http://www.biotechniques.com/news/The-Myth-of-the-Single-Genome/biotechniques-347272.html

The Myth of the Single #Genome: fetal Y chr left in women + smaller microchimerism in specific tissues
http://www.biotechniques.com/news/The-Myth-of-the-Single-Genome/biotechniques-347272.html MT @xberthet

http://tcga.github.io/
http://tcga.github.io/Roadmap

http://www.ncbi.nlm.nih.gov/pubmed/23925245

Contains a personal-genome like construction for HeLa
with 100X shotgun and then paired ends used for variant discovery and sequencing of pools of fosmid clones for haplotype resolution. Finally, low-freq. somatic and passage variants layered onto this.

Haplotype-resolved genome… of #HeLa: Has mapping of #ENCODE RNA- & chIP-seq against a personal genome
http://dx.doi.org/10.1038/nature12213 via @aemonten

http://www.citeulike.org/user/neils/article/12718324?utm_source=twitterfeed&utm_medium=twitter

Genome Biol. 2012 Dec 13;13(12):R115.

Whole-genome reconstruction and mutational signatures in gastric cancer. Nagarajan N, Bertrand D, Hillmer AM, Zang ZJ, Yao F, Jacques PE, Teo AS, Cutcutache I, Zhang Z, Lee WH, Sia YY, Gao S, Ariyaratne PN, Ho A, Woo XY, Veeravali L, Ong CK, Deng N, Desai KV, Khor CC, Hibberd ML, Shahab A, Rao J, Wu M, Teh M, Zhu F, Chin SY, Pang B, So JB, Bourque G, Soong R, Sung WK, Tean Teh B, Rozen S, Ruan X, Yeoh KG, Tan PB, Ruan Y.

http://www.ncbi.nlm.nih.gov/pubmed/23237666

Some thoughts, much from WC:

Looks like the data is freely available via GEO ID : GSE30833 http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE30833

The article by Nagarajan et al. highlights the authors efforts to utilize de novo genome assembly of gastric cancer genomes to detect not only single nucleotide variants (SNV’s) and short
insertions/deletions (indels), but also larger scale genomic structural variation (SV) that could be signatures of cancer genomes. It is to be applauded that this is a whole genome analysis.

The authors present several interesting findings such as enrichment for C->A and T->A mutations in both cancer genomes, enrichment for C->A and C->T mutations in the H. pylori infected cancer genome (evidence of cytosine specific transcription mediated DNA repair due to deamination), and amplification and deletion of regions on chromosome 12 in the non-H. pylori infected genome.

Although copy number variants (CNV) could potentially be detected by exome sequencing alone, whole genome sequence enables the precise localization of such events, as well as the detection of variation in non-coding regions.

Their methodology relies on combining high-throughput short-read sequencing with longer DNA-PET (paired end tags) in order to construct higher confidence de novo assemblies with longer contiguous regions.