title: Exon-based mapping of microarray probes: recovering differential gene expression signal in underpowered hypoxia experiment.
abstract: There is an immense collection of underpowered Affymetrix gene array experiments. Although a majority of these experiments generated biologically feasible results, the considerable fraction of assays failed to identify expected transcriptional changes. There is an unused potential of Affymetrix probe-set redundancy for common exonic and UTR regions. We hypothesized that group analysis of multiple probe-sets which hybridize to the same exon or UTR will increase array discriminating power of transcriptional changes. To test this hypothesis, we analyzed Affymetrix mouse probe-sets that share the same exon using blocking feature of the Significance Analysis of Microarrays (SAM). Two-thousand two-hundred one exon-sharing probe-sets targeting 1011 transcripts were identified by mapping 36701 MG-U74v2 probe-sets to genomic alignments of 3,971,086 known mouse transcripts. Using the blocking feature of SAM with an underpowered (two microarrays per experimental condition) mouse hypoxia-induced pulmonary hypertension model, we identified 24 genes that were significantly (FDR<5%) affected by hypoxia but were not detected by regular SAM. The relevance of the four newly identified genes (Mig6, F3, Bmp6, and Ndrg1) to known hypoxia-associated responses was confirmed by PubMatrix; and hypoxia-induced up-regulation of Mig6 expression was validated by real-time RT-PCR. We demonstrated that analysis of exon-sharing probe-sets allowed discovery of additional hypoxia-affected genes in an underpowered array experiment. This method will facilitate re-evaluation of existing underpowered Affymetrix gene expression profiles.
authors.affiliation: Johns Hopkins University, School of Medicine, Baltimore, MD, USA. dgrigor1@jhmi.edu
authors.forename: Dmitry N
authors.initials: DN
authors.lastname: Grigoryev
authors.forename: Shwu-Fan
authors.initials: SF
authors.lastname: Ma
authors.forename: Larissa A
authors.initials: LA
authors.lastname: Shimoda
authors.forename: Roger A
authors.initials: RA
authors.lastname: Johns
authors.forename: Byungkook
authors.initials: B
authors.lastname: Lee
authors.forename: Joe G N
authors.initials: JG
authors.lastname: Garcia
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics; D001483:Base Sequence; D015342:DNA Probes; D005091:Exons; D005786:Gene Expression Regulation; D000860:Hypoxia; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D016415:Sequence Alignment
chemical_list: D020121:5' Untranslated Regions; D015342:DNA Probes