A Open Archive of My F1000 Reviews

Following on from a recent conversation with David Stephens on Twitter about my decision to resign from Faculty of 1000, F1000 has clarified their terms for the submission of evaluations and confirmed that it is permissible to “reproduce personal evaluations on institutional & personal blogs if you clearly reference F1000″.

As such, I am delighted to be able to repost here an Open Archive of my F1000 contributions. Additionally, this post acts in a second capacity as my first contribution to the Research Blogging Network. Hopefully these commentraies will be of interest to some, and should add support to the Altmetrics profiles for these papers through systems like Total Impact.

ResearchBlogging.org

Nelson CE, Hersh BM, & Carroll SB (2004). The regulatory content of intergenic DNA shapes genome architecture. Genome biology, 5 (4) PMID: 15059258

My review: This article reports that genes with complex expression have longer intergenic regions in both D. melanogaster and C. elegans, and introduces several innovative and complementary approaches to quantify the complexity of gene expression in these organisms. Additionally, the structure of intergenic DNA in genes with high complexity (e.g. receptors, specific transcription factors) is shown to be longer and more evenly distributed over 5′ and 3′ regions in D. melanogaster than in C. elegans, whereas genes with low complexity (e.g. metabolic genes, general transcription factors) are shown to have similar intergenic lengths in both species and exhibit no strong differences in length between 5′ and 3′ regions. This work suggests that the organization of noncoding DNA may reflect constraints on transcriptional regulation and that gene structure may yield insight into the functional complexity of uncharacterized genes in compact animal genomes. (@F1000: http://f1000.com/1032936)

ResearchBlogging.org

Li R, Ye J, Li S, Wang J, Han Y, Ye C, Wang J, Yang H, Yu J, Wong GK, & Wang J (2005). ReAS: Recovery of ancestral sequences for transposable elements from the unassembled reads of a whole genome shotgun. PLoS computational biology, 1 (4) PMID: 16184192

My review: This paper presents a novel method for automating the laborious task of constructing libraries of transposable element (TE) consensus sequences. Since repetitive TE sequences confound whole-genome shotgun (WGS) assembly algorithms, sequence reads from TEs are initially screened from WGS assemblies based on overrepresented k-mer frequencies. Here, the authors invert the same principle, directly identifying TE consensus sequences from those same reads containing high frequency k-mers. The method was shown to identify all high copy number TEs and increase the effectiveness of repeat masking in the rice genome. By circumventing the inherent difficulties of TE consensus reconstruction from erroneously assembled genome sequences, and by providing a method to identify TEs prior to WGS assembly, this method provides a new strategy to increase the accuracy of WGS assemblies as well as our understanding of the TEs in genome sequences. (@F1000: http://f1000.com/1031746)

ResearchBlogging.org

Rifkin SA, Houle D, Kim J, & White KP (2005). A mutation accumulation assay reveals a broad capacity for rapid evolution of gene expression. Nature, 438 (7065), 220-3 PMID: 16281035

My review: This paper reports empirical estimates of the mutational input to gene expression variation in Drosophila, knowledge of which is critical for understanding the mechanisms governing regulatory evolution. These direct estimates of mutational variance are compared to gene expression differences across species, revealing that the majority of genes have lower expression divergence than is expected if evolving solely by mutation and genetic drift. Mutational variances on a gene-by-gene basis range over several orders of magnitude and are shown to vary with gene function and developmental context. Similar results in C. elegans [1] provide strong support for stabilizing selection as the dominant mode of gene expression evolution. (@F1000: http://f1000.com/1040157)

References: 1. Denver DR, Morris K, Streelman JT, Kim SK, Lynch M, & Thomas WK (2005). The transcriptional consequences of mutation and natural selection in Caenorhabditis elegans. Nature genetics, 37 (5), 544-8 PMID: 15852004

ResearchBlogging.org

Caspi A, & Pachter L (2006). Identification of transposable elements using multiple alignments of related genomes. Genome research, 16 (2), 260-70 PMID: 16354754

My review: This paper reports an innovative strategy for the de novo detection of transposable elements (TEs) in genome sequences based on comparative genomic data. By capitalizing on the fact that bursts of TE transposition create large insertions in multiple genomic locations, the authors show that detection of repeat insertion regions (RIRs) in alignments of multiple Drosophila genomes has high sensitivity to identify both individual instances and families of known TEs. This approach opens a new direction in the field of repeat detection and provides added value to TE annotations by placing insertion events in a phylogenetic context. (@F1000 http://f1000.com/1049265)

ResearchBlogging.org

Simons C, Pheasant M, Makunin IV, & Mattick JS (2006). Transposon-free regions in mammalian genomes. Genome research, 16 (2), 164-72 PMID: 16365385

My review: This paper presents an intriguing analysis of transposon-free regions (TFRs) in the human and mouse genomes, under the hypothesis that TFRs indicate genomic regions where transposon insertion is deleterious and removed by purifying selection. The authors test and reject a model of random transposon distribution and investigate the properties of TFRs, which appear to be conserved in location across species and enriched for genes (especially transcription factors and micro-RNAs). An alternative mutational hypothesis not considered by the authors is the possibility for clustered transposon integration (i.e. preferential insertion into regions of the genome already containing transposons), which may provide a non-selective explanation for the apparent excess of TFRs in the human and mouse genomes. (@F1000: http://f1000.com/1010399)

ResearchBlogging.org

Wheelan SJ, Scheifele LZ, Martínez-Murillo F, Irizarry RA, & Boeke JD (2006). Transposon insertion site profiling chip (TIP-chip). Proceedings of the National Academy of Sciences of the United States of America, 103 (47), 17632-7 PMID: 17101968

My review: This paper demonstrates the utility of whole-genome microarrays for the high-throughput mapping of eukaryotic transposable element (TE) insertions on a genome-wide basis. With an experimental design guided by first computationally digesting the genome into suitable fragments, followed by linker-PCR to amplify TE flanking regions and subsequent hybridization to tiling arrays, this method was shown to recover all detectable TE insertions with essentially no false positives in yeast. Although limited to species with available genome sequences, this approach circumvents inefficiencies and biases associated with the alternative of whole-genome shotgun resequencing to detect polymorphic TEs on a genome-wide scale. Application of this or related technologies (e.g. [1]) to more complex genomes should fill gaps in our understanding of the contribution of TE insertions to natural genetic variation. (@F1000: http://f1000.com/1088573)

References: 1. Gabriel A, Dapprich J, Kunkel M, Gresham D, Pratt SC, & Dunham MJ (2006). Global mapping of transposon location. PLoS genetics, 2 (12) PMID: 17173485

ResearchBlogging.org

Haag-Liautard C, Dorris M, Maside X, Macaskill S, Halligan DL, Houle D, Charlesworth B, & Keightley PD (2007). Direct estimation of per nucleotide and genomic deleterious mutation rates in Drosophila. Nature, 445 (7123), 82-5 PMID: 17203060

My review: This paper presents the first direct estimates of nucleotide mutation rates across the Drosophila genome derived from mutation accumulation experiments. By using DHPLC to scan over 20 megabases of genomic DNA, the authors obtain several fundamental results concerning mutation at the molecular level in Drosophila: SNPs are more frequent than indels; deletions are more frequent than insertions; mutation rates are similar across coding, intronic and intergenic regions; and mutation rates may vary across genetic backgrounds. Results in D. melanogaster contrast with those obtained from mutation accumulation experiments in C. elegans (see [1], where indels are more frequent than SNPs, and insertions are more frequent than deletions), indicating that basic mutation processes may vary across metazoan taxa. (@F1000: http://f1000.com/1070688)

References: 1. Denver DR, Morris K, Lynch M, & Thomas WK (2004). High mutation rate and predominance of insertions in the Caenorhabditis elegans nuclear genome. Nature, 430 (7000), 679-82 PMID: 15295601

ResearchBlogging.org

Katzourakis A, Pereira V, & Tristem M (2007). Effects of recombination rate on human endogenous retrovirus fixation and persistence. Journal of virology, 81 (19), 10712-7 PMID: 17634225

My review: This study shows that the persistence, but not the integration, of long-terminal repeat (LTR) containing human endogenous retroviruses (HERVs) is associated with local recombination rate, and suggests a link between intra-strand homologous recombination and meiotic exchange. This inference about the mechanisms controlling the transposable element (TE) abundance is obtained by demonstrating that total HERV density (full-length elements plus solo LTRs) is not correlated with recombination rate, whereas the ratio of full-length HERVs relative to solo LTRs is. This work relies critically on advanced computational methods to join TE fragments, demonstrating the need for such algorithms to make accurate inferences about the evolution of mobile DNA and to reveal new insights into genome biology. (@F1000: http://f1000.com/1091037)

ResearchBlogging.org

Giordano J, Ge Y, Gelfand Y, Abrusán G, Benson G, & Warburton PE (2007). Evolutionary history of mammalian transposons determined by genome-wide defragmentation. PLoS computational biology, 3 (7) PMID: 17630829

My review: This article reports the first comprehensive stratigraphic record of transposable element (TE) activity in mammalian genomes based on several innovative computational methods that use information encoded in patterns of TE nesting. The authors first develop an efficient algorithm for detecting nests of TEs by intelligently joining TE fragments identified by RepeatMasker, which (in addition to providing an improved genome annotation) outputs a global “interruption matrix” that can be used by a second novel algorithm which generates a chronological ordering of TE activity by minimizing the nesting of young TEs into old TEs. Interruption matrix analysis yields results that support previous phylogenetic analyses of TE activity in humans but are not dependent on the assumption of a molecular clock. Comparison of the chronological orders of TE activity in six mammalian genomes provides unique insights into the ancestral and lineage-specific record of global TE activity in mammals. (@F1000: http://f1000.com/1089045)

ResearchBlogging.org

Schuemie MJ, & Kors JA (2008). Jane: suggesting journals, finding experts. Bioinformatics (Oxford, England), 24 (5), 727-8 PMID: 18227119

My review: This paper introduces a fast method for finding related articles and relevant journals/experts based on user input text and should help improve the referencing, review and publication of biomedical manuscripts. The JANE (Journal/Author Name Estimator) method uses a standard word frequency approach to find similar documents, then adds the scores in the top 50 records to produce a ranked list of journals or authors. Using either the abstract or full-text, JANE suggested quite sensible journals and authors in seconds for a manuscript we have in press, while the related eTBLAST method [1] failed to complete while I wrote this review. JANE should prove to be a very useful text mining tool for authors and editors alike. (@F1000: http://f1000.com/1101037)

References: 1. Errami M, Wren JD, Hicks JM, & Garner HR (2007). eTBLAST: a web server to identify expert reviewers, appropriate journals and similar publications. Nucleic acids research, 35 (Web Server issue) PMID: 17452348

ResearchBlogging.org

Pask AJ, Behringer RR, & Renfree MB (2008). Resurrection of DNA function in vivo from an extinct genome. PloS one, 3 (5) PMID: 18493600

My review: This paper reports the first transgenic analysis of a cis-regulatory element cloned from an extinct species. Although no differences were seen in the expression pattern of the collagen (Col2A1) enhancer from the extinct Tasmanian tiger and extant mouse, this work is an important proof of principle for using ancient DNA in the evolutionary analysis of gene regulation. (@F1000: http://f1000.com/1108816)

ResearchBlogging.org

Ginsberg J, Mohebbi MH, Patel RS, Brammer L, Smolinski MS, & Brilliant L (2009). Detecting influenza epidemics using search engine query data. Nature, 457 (7232), 1012-4 PMID: 19020500

My review: A landmark paper in health bioinformatics demonstrating that Google searches can predict influenza trends in the United States. Predicting infectious disease outbreaks currently relies on patient reports gathered through clinical settings and submitted to government agencies such as the CDC. The possible use of patient “self-reporting” through internet search queries offers unprecedented real-time access to temporal and regional trends in infectious diseases. Here, the authors use a linear modeling strategy to learn which Google search terms best correlate with regional trends in influenza-related illness. This model explains flu trends over a 5 year period with startling accuracy, and was able to predict flu trends during 2007-2008 with a 1-2 week lead time ahead of CDC reports. The phenomenal use of crowd-based predictive health informatics revolutionizes the role of the internet in biomedical research and will likely set an important precedent in many areas of natural sciences. (@F1000: http://f1000.com/1127181)

ResearchBlogging.org

Taher L, & Ovcharenko I (2009). Variable locus length in the human genome leads to ascertainment bias in functional inference for non-coding elements. Bioinformatics (Oxford, England), 25 (5), 578-84 PMID: 19168912

My review: This paper raises the important observation that differences in the length of genes can bias their functional classification using the Gene Ontology, and provides a simple method to correct for this inherent feature of genome architecture. A basic observation of genome biology is that genes differ widely in their size and structure within and between species. Understanding the causes and consequences of this variation in gene structure is an open challenge in genome biology. Previously, Nelson and colleagues [1] have shown, in flies and worms, that the length of intergenic regions is correlated with the regulatory complexity of genes and that genes from different Gene Ontology (GO) categories have drastically different lengths. Here, Taher and Ovcharenko confirm this observation of functionally non-random gene length in the human genome, and discuss the implications of this feature of genome organization on analyses that employ the GO for functional inference. Specifically, these authors show that random selection of noncoding DNA sequences from the human genome leads to the false inference of over- and under-representation of specific GO categories that preferentially contain longer or shorter genes, respectively. This finding has important implications for the large number of studies that employ a combination of gene expression microarrays and GO enrichment analysis, since gene expression is largely controlled by noncoding DNA. The authors provide a simple method to correct for this bias in GO analyses, and show that previous reports of the enrichment of “ultraconserved” noncoding DNA sequences in vertebrate developmental genes [2] may be a statistical artifact. (@F1000: http://f1000.com/1157594)

References: 1. Nelson CE, Hersh BM, & Carroll SB (2004). The regulatory content of intergenic DNA shapes genome architecture. Genome biology, 5 (4) PMID: 15059258

2. Bejerano G, Pheasant M, Makunin I, Stephen S, Kent WJ, Mattick JS, & Haussler D (2004). Ultraconserved elements in the human genome. Science (New York, N.Y.), 304 (5675), 1321-5 PMID: 15131266

ResearchBlogging.org

Hindorff LA, Sethupathy P, Junkins HA, Ramos EM, Mehta JP, Collins FS, & Manolio TA (2009). Potential etiologic and functional implications of genome-wide association loci for human diseases and traits. Proceedings of the National Academy of Sciences of the United States of America, 106 (23), 9362-7 PMID: 19474294

My review: This article introduces results from human genome-wide association studies (GWAS) into the realm of large-scale functional genomic data mining. These authors compile the first curated database of trait-associated single-nucleotide polymorphisms (SNPs) from GWAS studies (http://www.genome.gov/gwastudies/) that can be mined for general features of SNPs underlying phenotypes in humans. By analyzing 531 SNPs from 151 GWAS studies, the authors discover that trait-associated SNPs are predominantly in non-coding regions (43% intergenic, 45% intronic), but that non-synonymous and promoter trait-associated SNPs are enriched relative to expectations. The database is actively maintained and growing, and currently contains 3943 trait-associated SNPs from 796 publications. This important resource will facilitate data mining and integration with high-throughput functional genomics data (e.g. ChIP-seq), as well as meta-analyses, to address important questions in human genetics, such as the discovery of loci that affects multiple traits. While the interface to the GWAS catalog is rather limited, a related project (http://www.gwascentral.org/) [1] provides a much more powerful interface for searching and browsing data from the GWAS catalog. (@F1000: http://f1000.com/8408956)

References: 1. Thorisson GA, Lancaster O, Free RC, Hastings RK, Sarmah P, Dash D, Brahmachari SK, & Brookes AJ (2009). HGVbaseG2P: a central genetic association database. Nucleic acids research, 37 (Database issue) PMID: 18948288

ResearchBlogging.org

Tamames J, & de Lorenzo V (2010). EnvMine: a text-mining system for the automatic extraction of contextual information. BMC bioinformatics, 11 PMID: 20515448

My review: This paper describes EnvMine, an innovative text-mining tool to obtain physico-chemical and geographical information about environmental genomics samples. This work represents a pioneering effort to apply text-mining technologies in the domain of ecology, providing novel methods to extract the units and variables of physico-chemical entities, as well as link the location of samples to worldwide geographic coordinates via Google Maps. Application of EnvMine to full-text articles in the environmental genomics database envDB {1} revealed very high system performance, suggesting that information extracted by EnvMine will be of use to researchers seeking meta-data about environmental samples across different domains of biology. (@F1000: http://f1000.com/3502956)

References: 1. Tamames J, Abellán JJ, Pignatelli M, Camacho A, & Moya A (2010). Environmental distribution of prokaryotic taxa. BMC microbiology, 10 PMID: 20307274

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