title: Growing functional modules from a seed protein via integration of protein interaction and gene expression data.
abstract: BACKGROUND
  Nowadays modern biology aims at unravelling the strands of complex biological structures such as the protein-protein interaction (PPI) networks. A key concept in the organization of PPI networks is the existence of dense subnetworks (functional modules) in them. In recent approaches clustering algorithms were applied at these networks and the resulting subnetworks were evaluated by estimating the coverage of well-established protein complexes they contained. However, most of these algorithms elaborate on an unweighted graph structure which in turn fails to elevate those interactions that would contribute to the construction of biologically more valid and coherent functional modules.
  
  
  RESULTS
  In the current study, we present a method that corroborates the integration of protein interaction and microarray data via the discovery of biologically valid functional modules. Initially the gene expression information is overlaid as weights onto the PPI network and the enriched PPI graph allows us to exploit its topological aspects, while simultaneously highlights enhanced functional association in specific pairs of proteins. Then we present an algorithm that unveils the functional modules of the weighted graph by expanding a kernel protein set, which originates from a given 'seed' protein used as starting-point.
  
  
  CONCLUSIONS
  The integrated data and the concept of our approach provide reliable functional modules. We give proofs based on yeast data that our method manages to give accurate results in terms both of structural coherency, as well as functional consistency.
authors.affiliation: Department of Medical Physics, School of Medicine, University of Patras, GR26500 Patras, Greece. imarazi@heart.med.upatras.gr
authors.forename: Ioannis A
authors.initials: IA
authors.lastname: Maraziotis
authors.forename: Konstantina
authors.initials: K
authors.lastname: Dimitrakopoulou
authors.forename: Anastasios
authors.initials: A
authors.lastname: Bezerianos
mesh_terms: D000465:Algorithms; D001185:Artificial Intelligence; D016000:Cluster Analysis; D003196:Computer Graphics; D030562:Databases, Protein; D015870:Gene Expression / Q000502:physiology*; D020869:Gene Expression Profiling / Q000379:methods; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D010363:Pattern Recognition, Automated; D025941:Protein Interaction Mapping / Q000379:methods*; D011506:Proteins / Q000235:genetics* / Q000378:metabolism*; D040901:Proteomics / Q000379:methods; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D049490:Systems Biology / Q000379:methods*
chemical_list: D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins