title: Multi-membership gene regulation in pathway based microarray analysis.
abstract: BACKGROUND
  Gene expression analysis has been intensively researched for more than a decade. Recently, there has been elevated interest in the integration of microarray data analysis with other types of biological knowledge in a holistic analytical approach. We propose a methodology that can be facilitated for pathway based microarray data analysis, based on the observation that a substantial proportion of genes present in biochemical pathway databases are members of a number of distinct pathways. Our methodology aims towards establishing the state of individual pathways, by identifying those truly affected by the experimental conditions based on the behaviour of such genes. For that purpose it considers all the pathways in which a gene participates and the general census of gene expression per pathway.
  
  
  RESULTS
  We utilise hill climbing, simulated annealing and a genetic algorithm to analyse the consistency of the produced results, through the application of fuzzy adjusted rand indexes and hamming distance. All algorithms produce highly consistent genes to pathways allocations, revealing the contribution of genes to pathway functionality, in agreement with current pathway state visualisation techniques, with the simulated annealing search proving slightly superior in terms of efficiency.
  
  
  CONCLUSIONS
  We show that the expression values of genes, which are members of a number of biochemical pathways or modules, are the net effect of the contribution of each gene to these biochemical processes. We show that by manipulating the pathway and module contribution of such genes to follow underlying trends we can interpret microarray results centred on the behaviour of these genes.
authors.affiliation: School of Information Systems, Computing and Maths, Brunel University, Uxbridge, UB8 3PH, UK. stelios.pavlidis@brunel.ac.uk.
authors.forename: Stelios P
authors.initials: SP
authors.lastname: Pavlidis
authors.forename: Annette M
authors.initials: AM
authors.lastname: Payne
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Swift