title: Grouping Gene Ontology terms to improve the assessment of gene set enrichment in microarray data.
abstract: BACKGROUND
  Gene Ontology (GO) terms are often used to assess the results of microarray experiments. The most common way to do this is to perform Fisher's exact tests to find GO terms which are over-represented amongst the genes declared to be differentially expressed in the analysis of the microarray experiment. However, due to the high degree of dependence between GO terms, statistical testing is conservative, and interpretation is difficult.
  
  
  RESULTS
  We propose testing groups of GO terms rather than individual terms, to increase statistical power, reduce dependence between tests and improve the interpretation of results. We use the publicly available package POSOC to group the terms. Our method finds groups of GO terms significantly over-represented amongst differentially expressed genes which are not found by Fisher's tests on individual GO terms.
  
  
  CONCLUSIONS
  Grouping Gene Ontology terms improves the interpretation of gene set enrichment for microarray data.
authors.affiliation: Department of Epidemiology and Public Health, Imperial College, Norfolk Place, London W2 1PG, UK. a.m.lewin@imperial.ac.uk
authors.forename: Alex
authors.initials: A
authors.lastname: Lewin
authors.forename: Ian C
authors.initials: IC
authors.lastname: Grieve
mesh_terms: D000465:Algorithms; D003628:Database Management Systems; D030562:Databases, Protein; D020869:Gene Expression Profiling / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods*; D005810:Multigene Family / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D011506:Proteins / Q000145:classification* / Q000235:genetics / Q000378:metabolism*
chemical_list: D011506:Proteins