ArrayExpress

Accession Codes

• Full list of four-letter codes
• Secondary accession numbers

Experiments and array designs in ArrayExpress are given unique accession numbers in the format of

• E-XXXX-n for experiments
• A-XXXX-n for array designs

XXXX represents a four letter code and n is a number.

E.g. E-MEXP-568, A-UHNC-18. Some experiments also have secondary accession numbers.

Accessions numbers are generated when sufficient meta-data and data files are provided for a submission. Please refer to our FAQ for more details about obtaining accession number for your data set.

The four letter code in the accession number indicates the data source. The source can be:

• ArrayExpress submission tools: MEXP for MIAMExpress (deprecated since July 2014), MTAB for Annotare, and TABM for Tab2MAGE (deprecated since January 2012).
• Data management tools / submisson pipelines from other research organizations (see full list below).

Note that the 4 letter code does not necessarily tell you which organization performed the experiment or manufactured the array design.

Full list of four-letter codes

Please note that some codes are no longer in active use, i.e. they are not used in accession numbers for new submisisons but are still valid. Some URLs are dead, or point to webpages which are out of maintenance, but are included in the table below for completeness.

Secondary accession numbers

Some experiments or array designs have a secondary accession number which links to another ArrayExpress experiment/array design, or to an external data source. The secondary accession number is shown in the "Links" section on an experiment's page. For example, for experiment E-GEOD-42281:

For array designs, the secondary accession number can be found in the header of the actual design file (in tab-delimited text format), e.g. for array design A-GEOD-9349:

Common reasons for secondary accession numbers

1. Data re-analysis: if the data provided is a re-analysis of another dataset, the accession number of the original experiment will be the secondary accession number
2. NCBI GEO-imported data: experimental data imported from the NCBI Gene Expression Omnibus (GEO) will have the GEO series (prefix "GSE") or data set (prefix "GSD") identifier as the secondary accession number. Similarly, array design will have the GEO platform (prefix "GPL") accession number. The ArrayExpress primary accession and GEO secondary accession for GEO-imported data are intuitively correlated. E.g. GEO accession "GSE12345" would be associated with ArrayExpress accession "E-GEOD-12345" . See also How data is imported from GEO.
3. High-throughput sequencing experiments: they will have a link to the European Nucleotide Archive (ENA) or European Genome-phenome Archive (EGA) where the raw data files (e.g. fastq reads) are kept.