What is the Expression Atlas?

The Expression Atlas is a database of publicly available gene expression data from ArrayExpress. The data is re-analysed in-house using Bioconductor packages, to detect genes showing interesting expression patterns under the conditions of the original experiment. The Experimental Factor Ontology (EFO) is used to annotate the data and enhance search functionality.

What can I do with the Atlas?

  • Search using any experimental condition(s) (e.g. diabetes or spaceflight) to discover genes that are differentially expressed under that condition.
  • Search using any gene(s), or gene properties, of interest (e.g. BRCA1 or p53 binding) to discover experimental conditions in which that gene is differentially expressed.
  • Search with any combination of the above.



The Experimental Factor Ontology (EFO) provides a systematic description of many experimental variables available in EBI databases, and for external projects such as the NHGRI GWAS catalogue. It combines parts of several biological ontologies, such as anatomy, disease and chemical compounds. The scope of the EFO is to support the annotation, analysis and visualisation of data handled by the EBI's Functional Genomics Team.