Networks

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Networks
Mark B Gerstein
Yale
Slides at
Lectures.GersteinLab.org
(See Last Slide for References
& More Info.)
Do not reproduce without permission
1 (c) Mark Gerstein, 2002, Yale, bioinfo.mbb.yale.edu
Understanding Protein Function on a Genome-scale
through the Analysis of Molecular Networks
The problem: Grappling with
Function on a Genome Scale?
.……
~530
[Dunham et al. Nature (1999)]
•  >25K Proteins in Entire Human Genome
(with alt. splicing)
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2 Lectures.GersteinLab.org
(c) 2009
•  250 of ~530
originally characterized on chr. 22
EF2_YEAST
Traditional single
molecule way to
integrate evidence &
describe function
Descriptive Name:
Elongation Factor 2
Summary sentence
describing function:
This protein promotes the
GTP-dependent
translocation of the
nascent protein chain from
the A-site to the P-site of
the ribosome.
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3 Lectures.GersteinLab.org
(c) 2009
Lots of references
to papers
Some obvious issues in scaling single
molecule definition to a genomic scale
•  Fundamental complexities
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4 Lectures.GersteinLab.org
(c) 2009
◊  Often >2 proteins/function
◊  Multi-functionality:
2 functions/protein
◊  Role Conflation:
molecular, cellular, phenotypic
Some obvious issues in scaling single
molecule definition to a genomic scale
•  Fundamental complexities
◊  Often >2 proteins/function
◊  Multi-functionality:
2 functions/protein
◊  Role Conflation:
molecular, cellular, phenotypic
◊  Starry night (P Adler, ’94)
[Seringhaus et al. GenomeBiology (2008)]
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5 Lectures.GersteinLab.org
(c) 2009
•  Fun terms… but do they scale?....
An Ontology of Naming Pathologies
[Seringhaus et al. GenomeBiology (2008)]
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[Seringhaus et al. GenomeBiology (2008)]
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7 Lectures.GersteinLab.org
(c) 2009
Gene Name Skew
MIPS (Mewes et al.)
GO (Ashburner et al.)
[Seringhaus & Gerstein,
Am. Sci. '08]
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8 Lectures.GersteinLab.org
(c) 2009
Hierarchies & DAGs of
controlled-vocab terms
but still have issues...
Classical KEGG pathway
Same Genes in High-throughput Network
[Seringhaus & Gerstein,
Am. Sci. '08]
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9 Lectures.GersteinLab.org
(c) 2009
Networks (Old & New)
1D: Complete
Genetic Partslist
[Fleischmann et al., Science, 269 :496]
~2D: Bio-molecular
Network
Wiring Diagram
[Jeong et al. Nature, 41:411]
3D: Detailed
structural
understanding of
cellular machinery
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10 Lectures.GersteinLab.org
(c) 2009
Networks occupy a midway point
in terms of level of understanding
Networks as a universal language
Internet
Disease
Spread
Neural Network
[Cajal]
[Krebs]
Protein
Interactions
[Barabasi]
Social Network
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(c) 2009
Food Web
Electronic
Circuit
11 Lectures.GersteinLab.org
[Burch & Cheswick]
Network pathology & pharmacology
Breast
Cancer
Alzheimer’s
Disease
Parkinson’s
Multiple
Sclerosis
Interactome networks
[Adapted from H Yu]
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12 Lectures.GersteinLab.org
(c) 2009
Disease
[NY Times, 2-Oct-05, 9-Dec-08]
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13 Lectures.GersteinLab.org
(c) 2009
Using the
position in
networks to
describe
function
Combining networks forms an ideal
way of integrating diverse
information
Metabolic
pathway
Co-expression
Relationship
Part of the
TCA cycle
Genetic interaction
(synthetic lethal)
Signaling pathways
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14 Lectures.GersteinLab.org
Physical proteinprotein Interaction
(c) 2009
Transcriptional
regulatory
network
Outline: Molecular Networks
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15 Lectures.GersteinLab.org
(c) 2009
•  Why Networks?
•  Network Structure:
Key Positions
◊  Hubs & Bottlenecks
◊  Tops of a Hierachy
•  Networks, Variation & the
Environment
◊  Which pathways change
most with the
environment
Global topological measures
Degree (K )
Path length (L )
5
2
Interaction and expression networks are
Clustering coefficient (C )
1/6
undirected
[Barabasi]
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16 Lectures.GersteinLab.org
(c) 2009
Indicate the gross topological structure of the network
TFs
Regulatory and metabolic networks are
Out-degree
5
directed
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(c) 2009
In-degree
3
17 Lectures.GersteinLab.org
Global
topological
measures for
directed
networks
Targets
Scale-free networks
log(Degree)
Hubs dictate the structure of the network
[Barabasi]
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18 Lectures.GersteinLab.org
(c) 2009
log(Frequency)
Power-law distribution
Hubs tend to be Essential
(c) 2009
Non- Essential
Essential
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19 Lectures.GersteinLab.org
[Yu et al., 2003, TIG]
"hubbiness"
Integrate gene essentiality data with protein
interaction network. Perhaps hubs represent
vulnerable points?
[Lauffenburger, Barabasi]
Relationships extends to "Marginal Essentiality"
(c) 2009
Not important
important
Very important
Essential
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20 Lectures.GersteinLab.org
[Yu et al., 2003, TIG]
"hubbiness"
Marginal essentiality measures relative importance of
each gene (e.g. in growth-rate and condition-specific
essentiality experiments) and scales continuously with
"hubbiness"
Another measure of Centrality:
Betweenness centrality
Betweenness of a node is the number of
shortest paths of pairs of vertices that run
through it -- a measure of information flow.
Freeman LC (1977) Set of measures of centrality based on betweenness.
Sociometry 40: 35–41.
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21 Lectures.GersteinLab.org
(c) 2009
Girvan & Newman (2002) PNAS 99: 7821.
Betweenness centrality -Bottlenecks
George Washington
Bridge
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22 Lectures.GersteinLab.org
(c) 2009
Proteins with high betweenness are defined as
Bottlenecks (top 20%), in analogy to the traffic system
[Yu et al., PLOS CB (2007)]
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23 Lectures.GersteinLab.org
(c) 2009
Bottlenecks
& Hubs
Regulatory networks
Undirected
Directed
[Toenjes, et al, Mol. BioSyst. (2008)]
[Jeong et al, Nature (2001)]
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24 Lectures.GersteinLab.org
Interaction networks
(c) 2009
Different Interactome networks
Bottlenecks are what matters in
regulatory networks
P < 10-20
[Yu et al., PLoS Comput Biol (2007)]
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25 Lectures.GersteinLab.org
(c) 2009
P < 10-4
[Xianglin
Shi ]
[Yu et al., PLoS Comput Biol (2007]
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26 Lectures.GersteinLab.org
(c) 2009
Signaling transduction pathways
are directed
Bottlenecks in signaling pathways
are important
Bottlenecks in
Signal Pathways
Bottlenecks in
Interaction network
[Xianglin
Shi ]
[Yu et al., PLoS Comput Biol (2007)]
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27 Lectures.GersteinLab.org
(c) 2009
P < 0.02
Outline: Molecular Networks
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28 Lectures.GersteinLab.org
(c) 2009
•  Why Networks?
•  Network Structure:
Key Positions
◊  Hubs & Bottlenecks
◊  Tops of a Hierachy
•  Networks, Variation & the
Environment
◊  Which pathways change
most with the
environment
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29 Lectures.GersteinLab.org
(c) 2009
Social
Hierarchy
(c) 2009
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30 Lectures.GersteinLab.org
[Yu et al., PNAS (2006)]
30 (c) Mark Gerstein, 2002, Yale, bioinfo.mbb.yale.edu
Determination of "Level"
in Regulatory Network Hierarchy
with Breadth-first Search
S. cerevisiae
[Yu et al., Proc Natl Acad Sci U S A (2006)]
E. coli
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31 Lectures.GersteinLab.org
(c) 2009
Regulatory Networks have
similar hierarchical structures
Example of Path Through
Regulatory Network
[Yu et al., PNAS (2006)]
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32 Lectures.GersteinLab.org
(c) 2009
Expression of MOT3 is
activated by heme and
oxygen. Mot3 in turn activates
the expression of NOT5 and
GCN4, mid-level hubs. GCN4
activates two specific bottomlevel TFs, Put3 and Uga3,
which trigger the expression of
enzymes in proline and
nitrogen utilization.
[Yu et al., PNAS (2006)]
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33 Lectures.GersteinLab.org
(c) 2009
Yeast Regulatory Hierarchy:
the Middle-managers Rule
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34 Lectures.GersteinLab.org
(c) 2009
Yeast Network Similar in Structure
to Government Hierarchy
with Respect to Middle-managers
[Yu et al., PNAS (2006)]
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35 Lectures.GersteinLab.org
(c) 2009
Characteristics of Regulatory
Hierarchy: Middle Managers are
Information Flow Bottlenecks
[Yu et al., PNAS (2006)]
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36 Lectures.GersteinLab.org
(c) 2009
Characteristics of Regulatory
Hierarchy: The Paradox of Influence
and Essentiality
Outline: Molecular Networks
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37 Lectures.GersteinLab.org
(c) 2009
•  Why Networks?
•  Network Structure:
Key Positions
◊  Hubs & Bottlenecks
◊  Tops of a Hierachy
•  Networks, Variation & the
Environment
◊  Which pathways change
most with the
environment
(c) 2009
38 Lectures.GersteinLab.org
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Global Ocean Survey Statistics (GOS)
Rusch, et al., PLOS Biology 2007
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39 Lectures.GersteinLab.org
(c) 2009
6.25 GB of data
7.7M Reads
1 million CPU hours
to process
Expressing
data as
matrices
indexed by
site, env. var.,
and pathway
usage
[Rusch et. al., (2007) PLOS Biology;
Gianoulis et al., PNAS
(inreproduce
press,without
2009]
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permission
(c) 2009
Environmental
Features
40 Lectures.GersteinLab.org
Pathway Sequences
(Community Function)
[ Gianoulis et al., PNAS (in press, 2009) ]
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41 Lectures.GersteinLab.org
(c) 2009
P
a
t
h
w
a
y
s
GPI = a’
+ b’
+c
(c) 2009
+b
+ c’
[ Gianoulis et al., PNAS (in press, 2009) ]
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42 Lectures.GersteinLab.org
UPI = a
Temp
etc
GPI =Chlorophyll
a’
+c
Metabolic
Pathways
Photosynthesis
(c) 2009
b
etc
+ b’ Lipid Metabolism
+ c’
[ Gianoulis et al., PNAS (in press, 2009) ]
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43 Lectures.GersteinLab.org
UPI =Environmental
aFeatures +
a,b
[ Gianoulis et al., PNAS (in press, 2009) ]
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44 Lectures.GersteinLab.org
(c) 2009
The goal of this technique is to interpret cross-variance matrices
We do this by defining a change of basis.
Strength of Pathway co-variation
with environment
Environmentally
variant
[ Gianoulis et al., PNAS (in press, 2009) ]
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45 Lectures.GersteinLab.org
(c) 2009
Environmentally
invariant
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46 Lectures.GersteinLab.org
(c) 2009
Conclusion #1: energy
conversion strategy,
temp and depth
[ Gianoulis et al., PNAS (in press, 2009) ]
(c) 2009
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47 Lectures.GersteinLab.org
[ Gianoulis et al., PNAS (in press, 2009) ]
[ Gianoulis et al., PNAS (in press, 2009) ]
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48 Lectures.GersteinLab.org
(c) 2009
Why is their fluctuation
in amino acid metabolism?
Is there a feature(s) that
underlies those that are
environmentally-variant
as opposed to those which are not?
(c) 2009
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49 Lectures.GersteinLab.org
[ Gianoulis et al., PNAS (in press, 2009) ]
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(c) 2009
50 Lectures.GersteinLab.org
Conclusions
•  Developing Standardized
Descriptions of Protein Function
•  Gene Naming
•  Betweenness is an important global
network statistic
◊  Bottlenecks are more correlated
with essentiality than hubs in
regulatory networks
•  Regulatory Network Hierarchies
◊  Middle managers dominate,
sitting at info. flow bottlenecks
◊  Paradox of influence and
essentiality
◊  Topmost proteins sit at center of
interaction network
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51 Lectures.GersteinLab.org
•  Developed and adapted techniques to
connect quantitative features of
environment to metabolism.
•  Applied to available aquatic datasets, we
identified footprints that were predictive
of their environment (potentially could be
used as biosensor).
•  Strong correlation exists between a
community’s energy conversion
strategies and its environmental
parameters (e.g. temperature and
chlorophyll).
•  Suggest that limiting amounts of cofactor
can (partially) explain increased import
of amino acids in nutrient-limited
conditions.
(c) 2009
Conclusions: Networks Dynamics
across Environments
TopNet – an automated web tool
Normal website + Downloaded code (JAVA)
+ Web service (SOAP) with Cytoscape plugin
[Yu et al., NAR (2004); Yip et al. Bioinfo. (2006);
Similar tools include Cytoscape.org, Idekar, Sander et al]
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52 Lectures.GersteinLab.org
(c) 2009
(vers. 2 :
"TopNet-like
Yale Network Analyzer")
MS
MG
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(c) Mark Gerstein, 2002, (c)
Yale,
5353Lectures.GersteinLab.org
2009bioinfo.mbb.yale.edu
Acknowledgements
TopNet.GersteinLab.org
MS
MG
Do not reproduce without permission
(c) Mark Gerstein, 2002,(c)
Yale,
5454
Lectures.GersteinLab.org
2009 bioinfo.mbb.yale.edu
Acknowledgements
TopNet.GersteinLab.org
MS
MG
Do not reproduce without permission
(c) Mark Gerstein, 2002, (c)
Yale,
5555Lectures.GersteinLab.org
2009bioinfo.mbb.yale.edu
Acknowledgements
TopNet.GersteinLab.org
P Bork, J Raes
Acknowledgements
Job opportunities currently
TopNet.GersteinLab.org
for postdocs & students
MS
J Korbel
A Paccanaro
S Teichmann M Babu
N Luscombe
M Seringhaus
H Yu
MG
Y Xia
K Yip
T Gianoulis
P Kim
J Lu
S Douglas
P Cayting
P Patel
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(c) Mark Gerstein, 2002, (c)
Yale,
5656Lectures.GersteinLab.org
2009bioinfo.mbb.yale.edu
A Sboner
Source:
Gerstein & Douglas.
PLoS Comp. Bio. 3:e80
(2007)
PubNet.GersteinLab.org
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57 Lectures.GersteinLab.org
(c) 2009
RNAi:
Birth of a
Field in
the
Literature
Culmin
-ating in
the 2006
Nobel
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58 Lectures.GersteinLab.org
(c) 2009
Extra
Types of Networks
Interaction networks
Nodes: proteins or genes
Edges: interactions
[Horak, et al, Genes & Development, 16:3017-3033]
[DeRisi, Iyer, and Brown, Science, 278:680-686]
[Jeong et al, Nature, 41:411]
Metabolic networks
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59 Lectures.GersteinLab.org
(c) 2009
Regulatory networks
More Information on this Talk
TITLE: Understanding Protein Function on a Genome-scale through the Analysis of Molecular Networks
SUBJECT:
Networks
DESCRIPTION:
PERMISSIONS: This Presentation is copyright Mark Gerstein, Yale University, 2008. Please read permissions statement at
http://www.gersteinlab.org/misc/permissions.html . Feel free to use images in the talk with PROPER acknowledgement (via citation to
relevant papers or link to gersteinlab.org).
.
PHOTOS & IMAGES. For thoughts on the source and permissions of many of the photos and clipped images in this presentation see
kwpotppt , that can be easily
queried from flickr, viz: http://www.flickr.com/photos/mbgmbg/tags/kwpotppt .
http://streams.gerstein.info . In particular, many of the images have particular EXIF tags, such as
Do not reproduce without permission
60 Lectures.GersteinLab.org
(Paper references in the talk were mostly from Papers.GersteinLab.org. The above topic list can be easily
cross-referenced against this website. Each topic abbrev. which is starred is actually a papers “ID” on the
site. For instance,
the topic pubnet* can be looked up at http://papers.gersteinlab.org/papers/pubnet )
(c) 2009
National Academy of Engineering, Meeting at Columbia U, 2009.04.14,
14:00-14:30; [I:NAECU] (Short networks talk, incl. the following
topics: why networks w. amsci*, funnygene*, bottleneck*, nethierarchy*,
metagenomics*, tyna* + topnet*, & pubnet* . Fits into 30’ w. 5’
questions. PPT works on mac & PC and has many photos w. EXIF tag
kwtimewemet .)

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