title: Probe selection and expression index computation of Affymetrix Exon Arrays.
abstract: BACKGROUND
  There is great current interest in developing microarray platforms for measuring mRNA abundance at both gene level and exon level. The Affymetrix Exon Array is a new high-density gene expression microarray platform, with over six million probes targeting all annotated and predicted exons in a genome. An important question for the analysis of exon array data is how to compute overall gene expression indexes. Because of the complexity of the design of exon array probes, this problem is different in nature from summarizing gene-level expression from traditional 3' expression arrays.
  
  
  RESULTS
  In this manuscript, we use exon array data from 11 human tissues to study methods for computing gene-level expression. We showed that for most genes there is a subset of exon array probes having highly correlated intensities across multiple samples. We suggest that these probes could be used as reliable indicators of overall gene expression levels. We developed a probe selection algorithm to select such a subset of highly correlated probes for each gene, and computed gene expression indexes using the selected probes.
  
  
  CONCLUSIONS
  Our results demonstrate that probe selection improves gene expression estimates from exon arrays. The selected probes can be used in future analyses of other exon array datasets to compute gene expression indexes.
authors.affiliation: Department of Statistics, Stanford University, Stanford, California, United States of America; Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Yi
authors.initials: Y
authors.lastname: Xing
authors.forename: Karen
authors.initials: K
authors.lastname: Kapur
authors.forename: Wing Hung
authors.initials: WH
authors.lastname: Wong
mesh_terms: D000465:Algorithms; D015342:DNA Probes; D003627:Data Interpretation, Statistical; D030541:Databases, Genetic; D005091:Exons; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods / Q000706:statistics & numerical data; D006681:HLA-D Antigens / Q000235:genetics; D006801:Humans; D018960:Hyaluronan Receptors / Q000235:genetics; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods* / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D014018:Tissue Distribution
chemical_list: C497483:CD44 protein, human; D015342:DNA Probes; D006681:HLA-D Antigens; C084245:HLA-DM antigens; D018960:Hyaluronan Receptors