87 research outputs found

    Evidence, Content and Corroboration and the Tree of Life

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    We examine three critical aspects of Popper’s formulation of the ‘Logic of Scientific Discovery’—evidence, content and degree of corroboration—and place these concepts in the context of the Tree of Life (ToL) problem with particular reference to molecular systematics. Content, in the sense discussed by Popper, refers to the breadth and scope of existence that a hypothesis purports to explain. Content, in conjunction with the amount of available and relevant evidence, determines the testability, or potential degree of corroboration, of a statement; content distinguishes scientific hypotheses from metaphysical assertions. Degree of corroboration refers to the relative and tentative confidence assigned to one hypothesis over another, based upon the performance of each under critical tests. Here we suggest that systematists attempt to maximize content and evidence to increase the potential degree of corroboration in all phylogenetic endeavors. Discussion of this “total evidence” approach leads to several interesting conclusions about generating ToL hypotheses

    Mutation of Rubie, a Novel Long Non-Coding RNA Located Upstream of Bmp4, Causes Vestibular Malformation in Mice

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    Background: The vestibular apparatus of the vertebrate inner ear uses three fluid-filled semicircular canals to sense angular acceleration of the head. Malformation of these canals disrupts the sense of balance and frequently causes circling behavior in mice. The Epistatic circler (Ecl) is a complex mutant derived from wildtype SWR/J and C57L/J mice. Ecl circling has been shown to result from the epistatic interaction of an SWR-derived locus on chromosome 14 and a C57L-derived locus on chromosome 4, but the causative genes have not been previously identified. Methodology/Principal Findings: We developed a mouse chromosome substitution strain (CSS-14) that carries an SWR/J chromosome 14 on a C57BL/10J genetic background and, like Ecl, exhibits circling behavior due to lateral semicircular canal malformation. We utilized CSS-14 to identify the chromosome 14 Ecl gene by positional cloning. Our candidate interval is located upstream of bone morphogenetic protein 4 (Bmp4) and contains an inner ear-specific, long non-coding RNA that we have designated Rubie (RNA upstream of Bmp4 expressed in inner ear). Rubie is spliced and polyadenylated, and is expressed in developing semicircular canals. However, we discovered that the SWR/J allele of Rubie is disrupted by an intronic endogenous retrovirus that causes aberrant splicing and premature polyadenylation of the transcript. Rubie lies in the conserved gene desert upstream of Bmp4, within a region previously shown to be important for inner ear expression of Bmp4. We found that the expression patterns of Bmp4 and Rubie are nearly identical in developing inner ears

    Ensemble approach to predict specificity determinants: benchmarking and validation

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    <p>Abstract</p> <p>Background</p> <p>It is extremely important and challenging to identify the sites that are responsible for functional specification or diversification in protein families. In this study, a rigorous comparative benchmarking protocol was employed to provide a reliable evaluation of methods which predict the specificity determining sites. Subsequently, three best performing methods were applied to identify new potential specificity determining sites through ensemble approach and common agreement of their prediction results.</p> <p>Results</p> <p>It was shown that the analysis of structural characteristics of predicted specificity determining sites might provide the means to validate their prediction accuracy. For example, we found that for smaller distances it holds true that the more reliable the prediction method is, the closer predicted specificity determining sites are to each other and to the ligand.</p> <p>Conclusion</p> <p>We observed certain similarities of structural features between predicted and actual subsites which might point to their functional relevance. We speculate that majority of the identified potential specificity determining sites might be indirectly involved in specific interactions and could be ideal target for mutagenesis experiments.</p

    Assessing Performance of Orthology Detection Strategies Applied to Eukaryotic Genomes

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    Orthology detection is critically important for accurate functional annotation, and has been widely used to facilitate studies on comparative and evolutionary genomics. Although various methods are now available, there has been no comprehensive analysis of performance, due to the lack of a genomic-scale ‘gold standard’ orthology dataset. Even in the absence of such datasets, the comparison of results from alternative methodologies contains useful information, as agreement enhances confidence and disagreement indicates possible errors. Latent Class Analysis (LCA) is a statistical technique that can exploit this information to reasonably infer sensitivities and specificities, and is applied here to evaluate the performance of various orthology detection methods on a eukaryotic dataset. Overall, we observe a trade-off between sensitivity and specificity in orthology detection, with BLAST-based methods characterized by high sensitivity, and tree-based methods by high specificity. Two algorithms exhibit the best overall balance, with both sensitivity and specificity>80%: INPARANOID identifies orthologs across two species while OrthoMCL clusters orthologs from multiple species. Among methods that permit clustering of ortholog groups spanning multiple genomes, the (automated) OrthoMCL algorithm exhibits better within-group consistency with respect to protein function and domain architecture than the (manually curated) KOG database, and the homolog clustering algorithm TribeMCL as well. By way of using LCA, we are also able to comprehensively assess similarities and statistical dependence between various strategies, and evaluate the effects of parameter settings on performance. In summary, we present a comprehensive evaluation of orthology detection on a divergent set of eukaryotic genomes, thus providing insights and guides for method selection, tuning and development for different applications. Many biological questions have been addressed by multiple tests yielding binary (yes/no) outcomes but no clear definition of truth, making LCA an attractive approach for computational biology

    Considerations for determining optimal mouse caging density

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    At the 2006 National Meeting of the American Association of Laboratory Animal Science, a panel discussed the question of what constitutes optimal or acceptable housing density for mice. Though there is a consensus that present guidelines are somewhat arbitrarily defined, scientific research has not yet been able to provide clear recommendations for amending them. Speakers explored the many factors that influence decisions on mouse housing, including regulatory requirements, scientific data and their interpretation, financial considerations and ethical concerns. The panel largely agreed that animal well-being should be the measure of interest in evaluating housing density and that well-being includes not only physical health, but also animals\u27 behavior, productivity and preference

    Depicting the tree of life in museums: guiding principles from psychological research

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    The Tree of Life is revolutionizing our understanding of life on Earth, and, accordingly, evolutionary trees are increasingly important parts of exhibits on biodiversity and evolution. The authors argue that in using these trees to effectively communicate evolutionary principles, museums need to take into account research results from cognitive, developmental, and educational psychology while maintaining a focus on visitor engagement and enjoyment. Six guiding principles for depicting evolutionary trees in museum exhibits distilled from this research literature were used to evaluate five current or recent museum trees. One of the trees was then redesigned in light of the research while preserving the exhibit’s original learning goals. By attending both to traditional factors that influence museum exhibit design and to psychological research on how people understand diagrams in general and Tree of Life graphics in particular, museums can play a key role in fostering 21st century scientific literacy

    Bacterial Toxin–Antitoxin Systems: More Than Selfish Entities?

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    Bacterial toxin–antitoxin (TA) systems are diverse and widespread in the prokaryotic kingdom. They are composed of closely linked genes encoding a stable toxin that can harm the host cell and its cognate labile antitoxin, which protects the host from the toxin's deleterious effect. TA systems are thought to invade bacterial genomes through horizontal gene transfer. Some TA systems might behave as selfish elements and favour their own maintenance at the expense of their host. As a consequence, they may contribute to the maintenance of plasmids or genomic islands, such as super-integrons, by post-segregational killing of the cell that loses these genes and so suffers the stable toxin's destructive effect. The function of the chromosomally encoded TA systems is less clear and still open to debate. This Review discusses current hypotheses regarding the biological roles of these evolutionarily successful small operons. We consider the various selective forces that could drive the maintenance of TA systems in bacterial genomes

    Evolution of protein domain architectures

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    This chapter reviews current research on how protein domain architectures evolve. We begin by summarizing work on the phylogenetic distribution of proteins, as this will directly impact which domain architectures can be formed in different species. Studies relating domain family size to occurrence have shown that they generally follow power law distributions, both within genomes and larger evolutionary groups. These findings were subsequently extended to multi-domain architectures. Genome evolution models that have been suggested to explain the shape of these distributions are reviewed, as well as evidence for selective pressure to expand certain domain families more than others. Each domain has an intrinsic combinatorial propensity, and the effects of this have been studied using measures of domain versatility or promiscuity. Next, we study the principles of protein domain architecture evolution and how these have been inferred from distributions of extant domain arrangements. Following this, we review inferences of ancestral domain architecture and the conclusions concerning domain architecture evolution mechanisms that can be drawn from these. Finally, we examine whether all known cases of a given domain architecture can be assumed to have a single common origin (monophyly) or have evolved convergently (polyphyly). We end by a discussion of some available tools for computational analysis or exploitation of protein domain architectures and their evolution
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