The Gene Expression Database (GXD) collects and integrates the gene expression information in MGI. All data entered into GXD are reviewed by our team of experienced curators. GXD focuses on endogenous gene expression data in wild-type and mutant mice, including reporter data from knock-in experiments. Currently GXD does not include expression data from other types of transgenic animals, chimeras, animals subjected to treatments, or from cultured material. GXD collects data from publications and data submissions for the following assay types: RNA in situ hybridization; Immunohistochemistry; in situ reporter (knock in); RT-PCR; Northern and Western blots. It is our curatorial policy to annotate expression patterns from publications based solely on what is written in the manuscript; we do not interpret images presented within papers. We are happy to accept more detailed descriptions of expression patterns from authors and will update database entries accordingly. When we have permission from publishers or providers we include images. All images are displayed with citation information and with copyright. Selected sets of RNA-Seq data that are in keeping with GXD's scope have been imported from the Expression Atlas at the EMBL-EBI. We processed these files further and curated the sample metadata.