(temperature, stimulating protocol, etc.). For the second list, the behavioural assessment of animals with a gene mutation was manually curated and classed, based on a controlled vocabulary and an anatomically based grouping of the behavioural tests. Presently, we have amassed information on a total of 340 genes, many of which show phenotypes, by extracting information from about 600 mouse synaptic plasticity and behavioural studies. Using similar techniques we have also surveyed the human genetics literature looking for associations to dis- ease caused by mutations in synapse genes in our cata- logue. To date, we have curated information on 324 diseases, including 90 nervous system diseases, associated with mutations in about 90 synapse genes, from almost 800 articles. Mutations are classiﬁed as one of about 35 types, such as single nucleotide polymorphism (SNP), insertion, deletion, nonsense and copy number variation (CNV). The Genes to Cognition research programme (29) is currently performing a large-scale study of mice carrying mutations in post-synaptic proteins, with extensive pheno- typing in biochemical, electrophysiological and behav- ioural domains. This data is deposited as it becomes available in G2Cdb. Nucleic Acids Research, 2009, Vol. 37, Database issue D849 WEB INTERFACE Public access to G2Cdb is provided through a web inter- face where users can interactively query and retrieve data. We have integrated the above datasets from disparate knowledge domains so that interrogation by a single text search is possible. Users can rapidly determine if a parti- cular gene is found in brain-signalling complex(es), has been altered and studied in experimental paradigms of learning and memory, and whether a mutation in this gene can be associated with a human disease. As an exam- ple, we can take ‘SAP102’. Searching for this gene returns links to the G2Cdb ‘GeneView’ pages for both the mouse and human genes with their species-speciﬁc links to exter- nal resources. Also (at the time of writing) curated results from two human genetics studies that have linked muta- tions in the gene encoding SAP102 (DLG3) to X-linked mental retardation are retrieved, as is data extracted from a published knockout mouse study reporting electrophy- siological characterization (synaptic transmission, short- and long-term plasticity) and results from a battery of behavioural tests (Figure 1). The website provides an interactive comparison tool called ‘CompareGeneLists’ to fully exploit the growing number of gene lists loaded into G2Cdb. This tool allows users to select two gene lists and discover the Figure 1. Sample screenshots of G2Cdb. Searching for SAP102 (A) returns links to the G2Cdb ‘GeneView’ pages for both the mouse (B) and human genes with their species-speciﬁc links to external resources. Also returned are curated results from two human genetics studies (C) that have linked mutations in the gene encoding SAP102 (DLG3) to X-linked mental retardation (D), as is data extracted from a published knockout mouse study. The gene list comparison tool is also shown, displaying the results of comparing the mouse PSD and PSP datasets (E).