Research Article

A Systems’ Biology Approach to Study MicroRNA-Mediated Gene Regulatory Networks

Table 1

Overview of the methodology. Key points in each step of the methodology and the main resources for constructing miRNA-mediated gene regulatory networks are given.

Step 1: data retrieval
Regulation typesResources

Transcriptional gene regulationTRED (http://rulai.cshl.edu/cgi-bin/TRED/tred.cgi?process=home): a database that provides an integrated repository for both cis- and transregulatory elements in mammals
TRANSFAC (http://www.gene-regulation.com/pub/databases.html): a database that collects eukaryotic transcriptional regulation, comprising data on TFs, their target genes, and binding sites
The UCSC table browser (http://genome.ucsc.edu/): a popular web-based tool for querying the UCSC Genome Browser annotation tables
HTRIdb (http://www.lbbc.ibb.unesp.br/htri/): an open-access database for experimentally verified human transcriptional regulation interactions
MIR@NT@N (http://maia.uni.lu/mironton.php/): an integrative resource based on a metaregulation network model including TFs, miRNAs, and genes
PuTmiR (http://www.isical.ac.in/~bioinfo_miu/TF-miRNA.php): a database of predicted TFs for human miRNAs
TransmiR (http://202.38.126.151/hmdd/mirna/tf/): a database of validated TF-miRNA interactions
miRGen 2.0 (http://diana.cslab.ece.ntua.gr/mirgen/): a database of miRNA genomic information and regulation

Posttranscriptional gene regulationmiRecords (http://mirecords.biolead.org/): a resource for animal miRNA-target interactions
Tarbase (http://www.microrna.gr/tarbase/): a database that stores detailed information for each miRNA-gene interaction, the experimental validation methodologies, and their outcomes
miRTarBase (http://mirtarbase.mbc.nctu.edu.tw/): a database that collects validated miRNA-target interactions by manually surveying the pertinent literature
miRWalk (http://www.umm.uni-heidelberg.de/apps/zmf/mirwalk/): a comprehensive database that provides information on miRNAs from human, mouse, and rat, on their predicted as well as validated binding sites in target genes

Protein-protein interactionHPRD (http://www.hprd.org/): a centralized platform to visually depict and integrate information pertaining to domain architecture, posttranslational modifications, interaction networks, and disease association for each protein in the human proteome
STRING (http://string-db.org/): a database of known and predicted protein interactions. The interactions include direct (physical) and indirect (functional) associations
MPPI (http://mips.helmholtz-muenchen.de/proj/ppi/): a collection of manually curated high-quality PPI data collected from the scientific literature by expert curators
DIP (http://dip.doe-mbi.ucla.edu/dip/Main.cgi): a catalog of experimentally determined interactions between proteins
IntAct (http://www.ebi.ac.uk/intact/main.xhtml): a platform that provides a database system and analysis tools for molecular interaction data
Reactome (http://www.reactome.org/): an open-source, open access, manually curated, and peer-reviewed pathway database

GO annotationAmigo GO (http://amigo.geneontology.org/cgi-bin/amigo/go.cgi): the official GO browser and search engine
miR2Disease (http://www.mir2disease.org/): a manually curated database that aims at providing a comprehensive resource of miRNA deregulation in various human diseases
miRCancer (http://mircancer.ecu.edu): a miRNA-cancer association database constructed by text mining on the literature
PhenomiR (http://mips.helmholtz-muenchen.de/phenomir/): a database that provides information about differentially expressed miRNAs in diseases and other biological processes
miRGator (http://mirgator.kobic.re.kr/): a novel database and navigator tool for functional interpretation of miRNAs
miRó (http://ferrolab.dmi.unict.it/miro): a web-based knowledge base that provides users with miRNA-phenotype associations in humans

Step 2: network construction and visualization
(i) Visualize regulatory interactions in platforms such as CellDesigner and Cytoscape that support standardized data formats
(ii) Calculate confidence scores for assessing reliability of interactions in gene regulatory networks

Step 3: model construction and calibration
(i) Formulate equations using rate equations
(ii) Fix parameter values using available biological information
(iii) Estimate the other unknown and immeasurable parameter values using optimization methods which can minimize the distance
between model simulations and experimental data such as time course qRT-PCR and western blot data

Step 4: model validation and analysis
(i) Design new experiments and generate new data to verify the calibrated model
(ii) Study complex properties and behavior of the system