27,723 research outputs found
Fair Evaluation of Global Network Aligners
Biological network alignment identifies topologically and functionally
conserved regions between networks of different species. It encompasses two
algorithmic steps: node cost function (NCF), which measures similarities
between nodes in different networks, and alignment strategy (AS), which uses
these similarities to rapidly identify high-scoring alignments. Different
methods use both different NCFs and different ASs. Thus, it is unclear whether
the superiority of a method comes from its NCF, its AS, or both. We already
showed on MI-GRAAL and IsoRankN that combining NCF of one method and AS of
another method can lead to a new superior method. Here, we evaluate MI-GRAAL
against newer GHOST to potentially further improve alignment quality. Also, we
approach several important questions that have not been asked systematically
thus far. First, we ask how much of the node similarity information in NCF
should come from sequence data compared to topology data. Existing methods
determine this more-less arbitrarily, which could affect the resulting
alignment(s). Second, when topology is used in NCF, we ask how large the size
of the neighborhoods of the compared nodes should be. Existing methods assume
that larger neighborhood sizes are better.
We find that MI-GRAAL's NCF is superior to GHOST's NCF, while the performance
of the methods' ASs is data-dependent. Thus, the combination of MI-GRAAL's NCF
and GHOST's AS could be a new superior method for certain data. Also, which
amount of sequence information is used within NCF does not affect alignment
quality, while the inclusion of topological information is crucial. Finally,
larger neighborhood sizes are preferred, but often, it is the second largest
size that is superior, and using this size would decrease computational
complexity.
Together, our results give several general recommendations for a fair
evaluation of network alignment methods.Comment: 19 pages. 10 figures. Presented at the 2014 ISMB Conference, July
13-15, Boston, M
JigsawNet: Shredded Image Reassembly using Convolutional Neural Network and Loop-based Composition
This paper proposes a novel algorithm to reassemble an arbitrarily shredded
image to its original status. Existing reassembly pipelines commonly consist of
a local matching stage and a global compositions stage. In the local stage, a
key challenge in fragment reassembly is to reliably compute and identify
correct pairwise matching, for which most existing algorithms use handcrafted
features, and hence, cannot reliably handle complicated puzzles. We build a
deep convolutional neural network to detect the compatibility of a pairwise
stitching, and use it to prune computed pairwise matches. To improve the
network efficiency and accuracy, we transfer the calculation of CNN to the
stitching region and apply a boost training strategy. In the global composition
stage, we modify the commonly adopted greedy edge selection strategies to two
new loop closure based searching algorithms. Extensive experiments show that
our algorithm significantly outperforms existing methods on solving various
puzzles, especially those challenging ones with many fragment pieces
Data-driven network alignment
Biological network alignment (NA) aims to find a node mapping between
species' molecular networks that uncovers similar network regions, thus
allowing for transfer of functional knowledge between the aligned nodes.
However, current NA methods do not end up aligning functionally related nodes.
A likely reason is that they assume it is topologically similar nodes that are
functionally related. However, we show that this assumption does not hold well.
So, a paradigm shift is needed with how the NA problem is approached. We
redefine NA as a data-driven framework, TARA (daTA-dRiven network Alignment),
which attempts to learn the relationship between topological relatedness and
functional relatedness without assuming that topological relatedness
corresponds to topological similarity, like traditional NA methods do. TARA
trains a classifier to predict whether two nodes from different networks are
functionally related based on their network topological patterns. We find that
TARA is able to make accurate predictions. TARA then takes each pair of nodes
that are predicted as related to be part of an alignment. Like traditional NA
methods, TARA uses this alignment for the across-species transfer of functional
knowledge. Clearly, TARA as currently implemented uses topological but not
protein sequence information for this task. We find that TARA outperforms
existing state-of-the-art NA methods that also use topological information,
WAVE and SANA, and even outperforms or complements a state-of-the-art NA method
that uses both topological and sequence information, PrimAlign. Hence, adding
sequence information to TARA, which is our future work, is likely to further
improve its performance
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