D610 Nucleic Acids Research, 2010, Vol. 38, Database issue Figure 3. Expression search interface. Over 500 000 gene expression objects can be searched using a variety of criteria. development stages. For both of these screens the gene involved has been determined by aligning the sequences for the probes used with mRNA for Xenbase gene catalog entries. The last source of images is community-submitted images, of which there are currently over 2000. These images are submitted with at least curation of stage and accessions for the sequences used to generate probes. These clone sequences are aligned with mRNAs in our gene catalog to create gene associations. We would like to encourage users to submit their gene expression image data. To this end, there is a submit data button on each Xenbase page where users can upload data ﬁles—this includes an optional template spreadsheet for entering image annotation. The alignment threshold used by Xenbase to align clone sequences from expression experiments (e.g. ESTs) to gene catalog mRNAs is a blast hit with a maximum e-value of 1e 20, a minimum 90% identity and 65% alignment. This methodology does leave the possibility that a single probe may be incorrectly associated with two genes with similar sequences. In these rare cases, a curator chooses the correct assignment. GENE CATALOG The gene catalog remains at the core of Xenbase. In addition to the new literature, interactants and expres- sion tabs described above, several improvements have been made to the gene page summary tab itself. Most signiﬁcantly, the contents of the gene pages have been greatly expanded. New links to additional related data sources include: Ensembl, UniProtKB, Aﬀymetrix and GEO (7). The literature summary section also provides links to papers that speciﬁcally discuss morpholino loss of function data. There are also links to several clone suppliers. Finally, the gene page summary tab now supports laevis gene duplicates (e.g. sox17a). However, so far, only a small number have been identiﬁed. The most important expansion of the gene catalog has been through the growth in the number of gene pages that has grown from an initial set of 1934 human-annotated gene pages to 4705 human-annotated gene pages and 10 833 machine-annotated gene pages. Of the 4705 human-annotated genes, there are 4159 with synteny to other organisms determined via Metazome, our primary method for establishing orthology. Another 546 human- annotated genes have sequence similarity with another