Hybrid Approaches: Integration of Gene Expression data into a GEM model


 

Following the introduction of GEM Models and the high-throughput approaches for extracting genome-wide expression pattern of a cell (e.g. DNA microarray, ChIP-Seq and RNA-Seq), the new challenge for a better prediction of the metabolic activities of different cells appeared; how gene expression data can be integrated into GEM models. The conflation of genetic expression data and GEM models leads to a better and deeper understanding of the occurrence of certain changes in gene expression under different conditions.
First, Covert and Palsson addressed this issue by Boolean approach in 2002.

Afterward, different algorithms were developed for tackling this challenge:
2004 - Akesson PMID: 15491858
2008 - GIMME PMID: 18483554
2008 - iMAT PMID: 20823844
2009 - Moxley PMID: 19346491
2009 - E_Flux PMID: 19714220
2010 - PROOM PMID: 20876091
2011 - MADE PMID: 21172910
2011 - tFBAA PMID: 21071808
2012 - Lee PMID: 22713172
2012 - RELATCH PMID: 23013597
2012 - Fang PMID: 23028286
2012 - INIT PMID: 22615553
2012 - TEAM PMID: 23209390
2012 - AdaM PMID: 23194026
2012 - mCADRE PMID: 23234303
2012 - GX_FBA PMID: 23216785
2012 - E_Flux_Modified PMID: 22606312
2013 - FCGs PMID: 23420780
2013 - EXAMO PMID: 23555222
2013 - GIM3E PMID: 23975765
TIGER
a MATLAB Toolbox for Integrating Genome-scale Metabolism, Expression, and Regulation that includes implementations of three algorithms (GIMME, iMAT, and MADE)
PMID: 21943338
Some methods reduce gene expression levels to binary states (such as GIMME, iMAT, and MADE), whereas methods like the E-Flux tries to map gene expression data into a GEM by constraining the maximum possible flux through the reactions.
Recommended review papers for Integration of gene expression data in GEM models:
Integration of expression data in genome-scale metabolic network reconstructions (Link)
Methods for integration of transcriptomic data in genome-scale metabolic models (Link)
Systematic evaluation of methods for integration of transcriptomic data into constraint-based models of metabolism (Link)
A Practical Protocol for Integration of Transcriptomics Data into Genome-Scale Metabolic Reconstructions (Link)