title: Global regulatory architecture of human, mouse and rat tissue transcriptomes.
abstract: BACKGROUND
  Predicting molecular responses in human by extrapolating results from model organisms requires a precise understanding of the architecture and regulation of biological mechanisms across species.
  
  
  RESULTS
  Here, we present a large-scale comparative analysis of organ and tissue transcriptomes involving the three mammalian species human, mouse and rat. To this end, we created a unique, highly standardized compendium of tissue expression. Representative tissue specific datasets were aggregated from more than 33,900 Affymetrix expression microarrays. For each organism, we created two expression datasets covering over 55 distinct tissue types with curated data from two independent microarray platforms. Principal component analysis (PCA) revealed that the tissue-specific architecture of transcriptomes is highly conserved between human, mouse and rat. Moreover, tissues with related biological function clustered tightly together, even if the underlying data originated from different labs and experimental settings. Overall, the expression variance caused by tissue type was approximately 10 times higher than the variance caused by perturbations or diseases, except for a subset of cancers and chemicals. Pairs of gene orthologs exhibited higher expression correlation between mouse and rat than with human. Finally, we show evidence that tissue expression profiles, if combined with sequence similarity, can improve the correct assignment of functionally related homologs across species.
  
  
  CONCLUSIONS
  The results demonstrate that tissue-specific regulation is the main determinant of transcriptome composition and is highly conserved across mammalian species.
authors.forename: Ajay
authors.initials: A
authors.lastname: Prasad
authors.forename: Suchitra Suresh
authors.initials: SS
authors.lastname: Kumar
authors.forename: Christophe
authors.initials: C
authors.lastname: Dessimoz
authors.forename: Stefan
authors.initials: S
authors.lastname: Bleuler
authors.forename: Oliver
authors.initials: O
authors.lastname: Laule
authors.forename: Tomas
authors.initials: T
authors.lastname: Hruz
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Gruissem
authors.affiliation: Department of Biology, ETH Zurich, 8092 Zurich, Switzerland. phz@nebion.com.
authors.forename: Philip
authors.initials: P
authors.lastname: Zimmermann
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D016678:Genome; D015894:Genome, Human; D006801:Humans; D051379:Mice; D005810:Multigene Family; D020411:Oligonucleotide Array Sequence Analysis; D025341:Principal Component Analysis; D051381:Rats; D013045:Species Specificity; D059467:Transcriptome