Although we apply our best efforts to collect and integrate available interaction data, more data sources remain to be integrated. Importantly, human gene regulatory interactions are currently weakly represented in our database (283 interactions) because on the one hand, such data are rare compared to other interaction types (e.g. protein–protein interactions), and, on the other hand, access to the majority of existing gene regulatory data is mostly limited by license constraints (28, 29). Apart from physical interactions, biochemical reactions and gene regulatory interactions, other relations exist between cellular entities that will be integrated into the database, for example, genetic and epigenetic relationships or relations with respect to experimental co-regulation patterns or to more general co-occurrences. Some of these relations are present e.g. in the STRING database (30) and can be integrated into ConsensusPathDB. Although ConsensusPathDB is currently focused on Homo sapiens, the integration of data from other species is an ongoing issue since it will reveal conserved and species-specific cellular processes on the interaction level.
