Posts Tagged ‘networks’

Reconciling differential gene expression data with molecular interaction networks

January 28, 2015

Reconciling differential gene expression
w/…#networkshttp://bioinformatics.oxfordjournals.org/content/29/5/622 Propagating this across interactions finds perturbed pathways

This paper basically propagates scores of disease-related highly differentially expressed genes (-log10 p) over human protein interaction network, calculates new scores using four major algorithms (Vanilla, PageRank, GeneMANIA, Heat Kernel), re-ranks genes based on the new scores and then finds enriched pathways among top-ranking genes. Compared with traditional ways by ranking highly differentially expressed genes based on p-values without any network information, the approach not only recovered canonical pathways but also discovered novel ones such as an insulin-mediated glucose transport pathway in Huntington’s disease. The authors also explored differences among four algorithms and identified the top-ranking genes specifically found by particular algorithms. In short, the paper provides a valuable framework for integrating networks and gene expression data. Their analysis for comparing four major algorithms is also helpful.

http://bioinformatics.oxfordjournals.org/content/29/5/622

Distributed Information Processing in Biological and Computational Systems

January 26, 2015

Distributed Info. Processing in Biological & Computational #Systems http://cacm.acm.org/magazines/2015/1/181614-distributed-information-processing-in-biological-and-computational-systems/fulltext Contrasts in strategies to handle node failures

QT:{{"
While both computational and biological systems need to address these similar types of failures, the methods they use to do so differs. In distributed computing, failures have primarily been handled by majority voting methods,37 by using dedicated failure detectors, or via cryptography. In contrast, most biological systems rely on various network topological features to handle failures. Consider for example the use of failure detectors. In distributed computing, these are either implemented in hardware or in dedicated additional software. In contrast, biology implements implicit failure detector mechanisms by relying on backup nodes or alternative pathways. Several proteins have paralogs, that is, structurally similar proteins that in most cases originated from the same ancestral protein (roughly 40% of yeast and human proteins have at least one paralog). In several cases, when one protein fails or is altered, its paralog can automatically take its place24 or protect the cell against the mutation.26 Thus, by preserving backup functionality in the protein interaction.


While we discussed some reoccurring algorithmic strategies used within both types of systems (for example, stochasticity and feedback), there is much more to learn in this regard. From the distributed computing side, new models are needed to address the dynamic aspects of communication (for example, nodes joining and leaving the network, and edges added and being subtracted), which are also relevant in mobile computing scenarios. Further, while the biological systems we discussed all operate without a single centralized controller, there is in fact a continuum in the term “distributed.” For example, hierarchical distributed models, where higher layers “control” lower layers with possible feedback, represent a more structured type of control system than traditional distributed systems without such a hierarchy. Gene regulatory networks and neuronal networks (layered columns) both share such a hierarchical structure, and this structure has been well-conserved across many different species, suggesting their importance to computation. Such models, however, have received less attention in the distributed computing literature.

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BMC Bioinformatics | Abstract | Sensitive detection of pathway perturbations in cancers

December 23, 2014

Sensitive detection of pathway perturbations in #cancers
http://www.biomedcentral.com/1471-2105/13/S3/S9/abstract Differential expression of #pathways (in toto or a sub-part)

** Sensitive detection of pathway perturbations in cancers. Rivera et al. BMC Bioinfo (2014)

In this paper, the authors introduce a new computational method that identifies subsets of pathways that exhibit differential gene expression between cancer and normal tissue. Some previous methods only considered differential expression in sets of genes without considering the structure of interactions between the genes or their protein products. Other previous methods looked at pathway
perturbations, but required all members of a pathway to exhibit differential gene expression in order for the pathway to appear significant. The authors demonstrate the general superiority of their method to these previous methods, as well as the robustness of their method to missing data. The authors also consider future enhancements, such as taking into account the direction of differential expression, using more information on the nature of each gene interaction involved, and using universal protein interaction networks to incorporate data beyond what is found in curated pathway databases.

A load driver device for engineering modularity in biological networks : Nature Biotechnology : Nature Publishing Group

December 9, 2014

A load driver device for engineering modularity in…#networks http://www.nature.com/nbt/journal/vaop/ncurrent/full/nbt.3044.html Allows joining components w/o downstream retroactivity

Twitter “Exhaust” Reveals Patterns of Unemployment | MIT Technology Review

December 1, 2014

Social media fingerprints of unemployment, from detecting network components in tweet mining arxiv.org/abs/1411.3140 +
http://www.technologyreview.com/view/532746/twitter-exhaust-reveals-patterns-of-unemployment

Lots of press for an arxiv paper, viz:
Twitter “Exhaust” Reveals Patterns of Unemployment | MIT Technology Review

QT:{{”

So the team analysed the rate at which messages were exchanged between regions using a standard community detection algorithm. This revealed 340 independent areas of economic activity, which largely coincide with other measures of geographic and economic distribution. “This result shows that the mobility detected from geolocated tweets and the communities obtained are a good description of economical areas,” they say.

Finally, they looked at the unemployment figures in each of these regions and then mined their database for correlations with twitter activity.

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Network Legos: Building Blocks of Cellular Wiring Diagrams | Abstract

November 1, 2014

#Network Legos: Building Blocks of Cellular Wiring Diagrams
http://online.liebertpub.com/doi/abs/10.1089/cmb.2007.0139 Active subnets from protein interactions & co-expression

This paper describes a top-down, set-theoretic approach to comparing gene expression network dynamics under multiple conditions. The method takes an input “wiring diagram” of gene interactions as well as gene expression datasets, which are used to derive interaction profiles composed of enriched genes. Sets of these interaction profiles are used to identify statistically significant “network blocks”
representing network modules underlying the various enriched profiles. These blocks are then organized in a directed acyclic graph in order to identify “network legos”, which represent the most fundamental building blocks of the enriched gene expression networks. The authors demonstrate the utility of the method by identifying a differentially enriched pathway in various forms of leukemia and finding common network modules activated by two human cell types in response to different cellular stresses.

http://online.liebertpub.com/doi/abs/10.1089/cmb.2007.0139

Signaling hypergraphs: Trends in Biotechnology

October 9, 2014

Signaling #hypergraphs
http://www.cell.com/trends/biotechnology/abstract/S0167-7799(14)00071-7 Edges from interactions of 2 sets of nodes. Better representation of assemblies & #complexes.

QT:{{”
each edge is defined not by interaction of 2 nodes (as in graphs), but 2 sets of nodes (known as hypernodes in hypergraphs)……The use of hypernodes also represents three concepts better than directed or non-directed graphs: protein complexes, protein assemblies and regulation (especially involving complexes/assemblies).
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Signaling hypergraphs. Ritz et al. (2014) TIB

This opinion paper advocates the use of hypergraphs to complement graph-based signaling network and pathway analyses, where each edge is defined not by interaction of 2 nodes (as in graphs), but 2 sets of nodes (known as hypernodes in hypergraphs). They argue that
hypergraphs is a set-based method that acts like a more general version of a graph. The use of hypernodes also represents three concepts better than directed or non-directed graphs: protein complexes, protein assemblies and regulation (especially involving complexes/assemblies). They propose that hypergraphs can be very useful in situations where the effects of individual proteins might be neglected in graphs but will have a noticeable effect when these proteins are included in protein complexes as hypernodes. They use 3 applications as examples: pathway enrichment, pathway reconstruction, and pathway crosstalk.

1309.6001 Co-evolutionary dynamics in social networks: A case study of Twitter

September 19, 2014

http://arxiv.org/abs/1309.6001

Constructing structural networks of signaling pathways on the proteome scale

September 6, 2014

Structural networks of signaling pathways
http://www.sciencedirect.com/science/article/pii/S0959440X1200070X Prism on IL10 #networks, mapping on Cosmic, disrupting mutations as drivers

PLOS Computational Biology: Target Essentiality and Centrality Characterize Drug Side Effects

August 7, 2014

Target Essentiality… Characterizes Drug Side Effects – much more so than the total number of targets for a #drug
http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.100311