Find GEO datasets
Find GEO public dataset relevant to your research
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The NCBI GEO database stores curated gene expression DataSets, as well as original Series and Platform records in the Gene Expression Omnibus (GEO) repository. Enter search terms to locate experiments of interest. DataSet records contain additional resources including cluster tools and differential expression queries.
Quick introduction to GEO datasets
- Full GEO documentation page http://www.ncbi.nlm.nih.gov/geo/info/
- GEO main dataset search page http://www.ncbi.nlm.nih.gov/gds/
Search for relevant datasets by keyword
In this short example, we look for mouse experiments related to 'innate immunity'. Type in relevant keywords to restrict the findings to something biologically relevant. Inspect the results of each search until you are satisfied.
If you are interested in specific technologies, take the opportunity to restrict your search to your favorite(s) using the 'Study Type' filter
First select types that are relevant to your needs
Select one or more technologies to filter the results to that type(s) [clicking again clears a selection]
You can add additional filters to the left menu, allowing you to further refine your search in order to better evaluate the supporting data (e.g. sample count)
We often wish to analyze data in a tissue-specific context, this is possible after selecting the tissue filter in the left menu, to restrict the search to experiments for which tissue annotation is available (the scientists who did the experiment have mentioned the tissue they used in the experiment description).
Select a winner and proceed
The GSE14675 dataset seems to fit to the selected biological focus and is selected.
Click the link: Identification of Hedgehog Signaling and Novel Transcription Factors Involved in Regulation of Systemic Response to LPS to inspect the annotations associated with this data in order to choose samples to be used for the next step.
Get more info from the publication
The page also links to Pubmed when the GEO data was part of a publication.
Downloading the original paper  is often a good idea. It allows reading what was deduced from this data and make sure there is no hidden information that would make this dataset unfit for our aims.
Note that you can also download the data. GEO offers microarray data in two formats:
- a set of CEL files containing the raw data
- a single Series Matrix (.txt) file containing the normalized data for all samples. Many software packages to analyze microarray data, like GEO2R and the CLC Main Workbench start from these files.
Link Out to GEO2R and perform differential expression analysis online
Lower in the dataset page, a link to GEO2R allows proceeding with online differential expression analysis.
The GEO2R page opens with sample descriptions organized in a table.
Each column header of the table can be clicked to re-sort this table according to annotation and group samples. We can also see that several organs are available (remember that we asked tissues to be represented in the datasets) as well as several mouse genetic backgrounds. If you have reasons to prefer one or the other, it is now possible.
We are now ready to apply GEO2R to some or all samples. The use of GEO2R and post-processing in [RStudio] are detailed in follow-up tutorials on this wiki.
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